Tailored and uniform coatings in microchannel apparatus

(54) Title: SURFACES PROTECTED WITH ALLOY IN MICROCANAL EQUIPMENT AND CATALYSTS, CATALYSTS SUPPORTED IN ALUMINES, INTERMEDIATE CATALYSTS, AND METHODS FOR FORMING CATALYSTS AND MICROCANAL EQUIPMENT (51) Int.CI .: B01J 19/00; C23C 16/04; C23C 10/50 (30) Unionist Priority: 23/03/2004 US 60 / 556,014 (73) Holder (s): VELOCYS, INC.

(72) Inventor (s): YANG, BARRY, L „DALY, FRANCIS, P„ WATSON, JUNKO, M „MAZANEC, TERRY, FITZGERALD, SEAN, P„ JOHNSON, BRADLEY, R „CAO, CHUNSHE, TONKOVICH, ΑΝΝΑ, LEE, ARORA, RAVI, HESSE, DAVID, J „QIU, DONGMING, TAHA, RACHID, RAMLER, JEFFREY, J„ WANG, YONG, LONG, RICHARD, CHIN, YA-HUEI, LI, XIAOHONG

1/50 “SURFACES PROTECTED WITH ALLOY IN MICROCANAL EQUIPMENT AND CATALYSTS, CATALYSTS SUPPORTED IN ALUMINUM, INTERMEDIATE CATALYSTS, AND METHODS FOR FORMING CATALYSTS AND MICROCANAL EQUIPMENT”.

RELATED REQUESTS

According to 35 USC sect. 119 (e), this application claims the priority of Provisional Patent Application No. 60 / 556,014, filed on March 23, 2004.

FIELD OF THE INVENTION

This invention relates to microchannel equipment, catalysts and the method of producing them. The invention also relates to chemical reactions and microchannel chemical reactors.

INTRODUCTION

In recent years there has been tremendous academic and commercial interest in microchannel devices. This interest has grown due to the advantages of microtechnology including reduced price, increased productivity, the possibility of scaling the systems of any desired capacity (ie, adding), increased heat transfer, and increased mass transfer. A review of some of the work involving micro-reactors (a subset of microchannel equipment) was provided by Gavrilidis et al., “Technology And Applications Of Microengineered Reactors”, Trans. IchemE, Vol. 80, Part A, pp 3-30 (Jan. 2002).

Microchannel equipment can be made from a variety of materials including ceramics, plastics and metals. In many orders, process channels in microchannel equipment require a coating or

2/50 coatings on the structural material. Coatings can serve purposes such as absorption, adsorption, corrosion protection, surface wettability for microfluidics and specific catalysts. In some cases, the microchannels are coated with mud or coated by the sun; for example, an oxide coating applied to a ceramic honeycomb. In some cases, sheets of a material are coated and then assembled and bonded to form a multilayer microchannel device.

Since a focus of the present invention includes aluminide coatings, reference should be made to the initial work described by La Croix in US Patent No. 3,944,505. This patent describes a catalytic device made from a stack of expanded metal sheets (such as Inconel). The metal sheets carry a layer of nickel or cobalt aluminide and a layer of alpha alumina on the aluminide, and a catalytic surface on the aluminide. La Croix did not describe how the aluminide layer was formed on the leaves, nor did he provide any data describing the aluminide layer.

Methods for forming aluminide coatings are well known and have been used commercially to coat certain parts of jet engines. Methods for making aluminum halide coatings are described, for example, in US Patent Nos.^the 3,486,927 and 6,332,926.

There have been attempts to apply aluminide coating to internal channels on surfaces of gas turbine airfoils. Rigney et. al, in US Patent No. 6,283,714 reported coating of internal cooling passages of turbine blades with an aluminum coating using a sludge / aluminization process in a box. Rigney et. al also stated that a gas

3/50 aluminum halide could be passed through high temperature refrigeration passages so that a 0.002 inch thick aluminum coating can be deposited in about 4 to 8 hours. Pfaendter et. al. US Patent No. 6,332,926 also suggests the flow of an aluminum coating precursor to deposit aluminum on an internal surface of airfoils.

Howard et. al. in US Patent 5,928,725 entitled “Gas Phase Coating Method and Equipment for Complex Internal Surfaces of Hollow Articles, reviewed state of the art gas phase coating techniques for coating internal surfaces but stressed that prior art methods were ineffective for coating multiple gas passages on modern airfoil surfaces and resulted in non-uniform internal coatings. In the processes described in this patent, the coating gas flow rate is controlled to a different rate in at least two channels. Howard et. al. states that a mixture of coating including aluminum powder, aluminum oxide and aluminum fluoride could be heated to provide a gas coating. This improved method has been reported to result in a 1.5 mm ± 1.0 mm aluminide coating.

As described below, the present invention provides a new microchannel equipment having improved coatings and methods for preparing improved coatings. The invention also includes methods for conducting operations units through microchannel devices with coated microchannels.

SUMMARY OF THE INVENTION

In a first aspect, the invention provides a reactor or separator

4/50 microchannel, comprising: a microchannel complex defined by at least one microchannel wall; and an aluminide layer disposed on at least one microchannel wall. In this aspect as well as in the next aspect, it is important to recognize the character of the invention as a reactor or separator. These functions are integral to the definition of the invention. Preferably, the reactor or separator further comprises an alumina layer disposed on the aluminide layer; and a catalytic material disposed on the alumina layer. The reactor or separator may include a manifold (multiple arrangement) that is connected to at least two microchannels, wherein the manifold comprises a manifold wall that is coated with an aluminide layer. In a preferred embodiment, the reactor or separator is made by laminating sheets together and the aluminide layer is a post-assembly coating. As with all aspects of the invention, the invention can still be described in conjunction with any details of the Detailed Description. In addition, as with all aspects of the invention, the invention includes methods for producing the equipment and methods for conducting chemical processes in the equipment. For example, the invention includes a method of conducting a chemical reaction or separation of a material comprising at least two components in the reactor or separator described above, also comprising:

(a) in which the reactor or separator is a reactor and the reactor further comprises an alumina layer disposed on the aluminide layer; and a catalytic material disposed on the alumina layer, and comprising a step of passing a reagent into a microchannel complex and reacting the reagent in the microchannel complex to form at least one product; or (b) where the reactor or separator is a separator and comprising

5/50 a step of passing a fluid comprising at least two components in a microchannel complex, preferably separating at least one of at least two components within a microchannel complex.

In another aspect, the invention provides a microchannel reactor or separator, comprising: a microchannel defined by at least one microchannel wall; and a post-assembly aluminide coating disposed on at least one microchannel wall. Preferably, the microchannel reactor or separator of claim B, further comprises an alumina layer disposed on the aluminide layer; and a catalytic material disposed on the alumina layer. Again, as an example, the invention includes methods of producing the equipment (such as by applying post-assembly coating) and a method of conducting a chemical reaction or separation of a mixture comprising at least two components in the reactor or separator described above , also comprising:

(a) where the reactor or separator is a reactor and the reactor further comprises an alumina layer disposed on the post-assembly aluminide layer; and a catalytic material disposed on the alumina layer, and comprising a step of passing a reagent through the microchannel complex and reacting the reagent through the microchannel complex to form at least one product; or (b) wherein the reactor or separator is a separator and comprising a step of passing a fluid comprising at least two components in the microchannel, preferably separating at least one of at least two components within a microchannel complex.

In another aspect, the invention provides a catalyst or precursor

6/50 catalyst, comprising: a substrate; an aluminide coating disposed on the substrate; an alumina layer disposed on the aluminide coating, wherein the alumina layer comprises at least 0.1% by weight of a rare earth element or sintering additive, and a catalytic material disposed on the alumina layer. Likewise, the invention includes a method for producing this catalyst or catalyst precursor and methods for conducting chemical reactions on the catalyst. It can be seen that a “substrate can be any catalyst support including a microchannel wall such as in a microchannel reactor.

In another aspect, the invention provides a method for producing a catalyst, comprising: depositing aluminide on a substrate; oxidation of the surface of the aluminide layer to form aluminum needles; and depositing a catalyst material on the alumina needles.

In yet another aspect, the invention provides a method for producing a coated structure, comprising: depositing aluminide on a substrate; exposing the aluminide to an oxidizing agent to form an alumina layer; depositing a sintering additive on the aluminum layer to form an article with an alumina layer with sintering additive; and heating the article with a layer of alumina with a sintering additive.

In another aspect, the invention provides a method for forming a catalyst, comprising: adding a sintering additive to alumina to form an article with an alumina layer with sintering additive; and heating the article with a layer of alumina with a sintering additive; and subsequently depositing a catalytic material.

In another aspect, the invention provides a method for forming a

7/50 microchannel reactor comprising any of the above methods for forming a catalyst. For example, coatings can be applied to a microchannel wall or to a supplement that is added or arranged in a reaction microchannel.

In yet another aspect, the invention provides microchannel equipment, comprising: at least two parallel microchannels, each of which is contiguous by at least 1 cm; a manifold connecting at least two microchannels; wherein the manifold comprises an aluminum coating.

In another aspect, the invention provides a method for forming protected surfaces, comprising: providing an article comprising an aluminide surface; heating the article comprising an aluminide surface to at least about 800 ° C in an inert or reducing atmosphere; and exposing the aluminide surface to an oxidizing gas at a temperature of at least 800 ° C, preferably about 1000 ° C and more preferably in the range of about 1000 to 1100 ° C, to form an oxide layer.

In yet another aspect, the invention provides a method for making microchannel equipment, comprising: placing a supplement in an internal microchannel; and forming an aluminide within the channel and creating a metabolic link between the supplement and a microchannel wall.

Many aspects of the present invention include the passage of gaseous aluminum components over metal surfaces (especially a metal wall of a microchannel) and simultaneously or subsequently reacting with a metal on the substrate to form a metal aluminide surface layer - this process it is called aluminization, perhaps more precisely, aluminidization. The conditions for aluminidization are

8/50 conventionally known for jet engine parts, and conventional steps are not described here. Certain steps such as excluding oxygen, flow control, and passing through manifolds are discussed in more detail below.

In one aspect, the invention provides a method for forming a catalyst comprising the steps of (1) depositing a layer of Al, (2) forming a layer of metal aluminide or a metal alloy; (3) oxidizing the metal aluminide to form an alumina scale (in some embodiments this scale is in the form of alumina needles); (4) optionally modifying the scale (a) by etching with acid or base, and / or adding a rare earth salt to form a modified rare earth alumina, and / or (c) adding sintering additives; (5) optionally coat with a metal oxide sol (or metal oxide sludge); and (6) adding a metal catalyst (typically by impregnation). Preferably sun or metal oxide sludge is a sun alumina (here, sun alumina means a sun that after deposited and heated, forms alumina) or alumina mud. The invention also includes each of the individual steps or any combination thereof. For example, steps (1) and (2), deposition of Al and formation of a metal aluminide can be performed in a single step. As another example, in a preferred aspect, the invention comprises a method for forming a catalyst comprising a step of adding a sintering additive to an alumina support (which may be tablets or an alumina layer on a substrate). In another example, steps (5) and (6), coating with a catalyst precursor sol, and adding a metal catalyst, can be incorporated in a single step. In another embodiment the metal alloy can be previously coated with a metal

9/50 catalytically active before the deposition of the aluminum surface layer in step (1). The invention also includes catalysts and intermediate catalysts formed by the disclosed methods. The invention further includes microchannel equipment that is treated by any of the methods of the invention; for example, the invention includes microchannel equipment that comprises a layer of a nickel aluminide or equipment that is made by oxidizing a nickel aluminide followed by the application of an alumina washcoat (complex solution composed of various chemical elements). The invention also includes the optional coating of pipes, tubes, or other structures attached to the microchannel reactor.

The invention also includes methods for catalytic chemical conversion, such a method comprising a flow of reactive fluid composition in a microchannel, wherein the catalytic composition is present in the microchannel (in a microchannel wall or elsewhere within the microchannel), and reacting the composition reagent fluid to form a desirable product (or products) in the microchannel. The invention further includes methods for catalytic chemical conversion comprising contacting at least one reagent with the catalyst of the invention.

Various embodiments of the invention can provide several advantages. An aluminide layer serves as an aluminum shell as a self-healing if there is excessively any damage to the alumina layer. The aluminide layer can also reduce the formation of coke (in processes susceptible to the formation of coke) and reduce the metal pitting. The corrosive power of a chemical reaction generally depends on both the temperature and the chemical nature of the fluid being processed. Alumina is both thermally and

10/50 chemically stable, and then superior to many other materials.

GLOSSARY OF TERMS USED “Metal aluminide refers to a metallic material containing 10% or more of Metal and 5%, more preferably 10%, or greater of Aluminum (Al) with the sum of Metal and Aluminum being 50% or more. These percentages refer to the percentage of mass. Preferably, a metal aluminide contains 50% or more Metal and 10% or greater Al with the sum of Ni and Al being 80% or more. In embodiments where Metal and Al have undergone significant thermal diffusion, it is expected that the composition of a Metal-AI layer will gradually vary as a function of thickness so that there may not be a distinct line separating the Metal- AI of an alloy substrate containing underlying Metal. The term aluminide ”is used synonymously with metal aluminide. A phase diagram of the NiAI system is shown in Figure 2 of US 5,716,720.

A preferred metal aluminide is nickel aluminide (NiAI). “Nickel aluminide refers to a material containing 10% or more of Ni and 10% or greater of Al with the sum of Ni and Al being 50% or more. These percentages refer to the percentage of mass. Preferably, a nickel aluminide contains 20% or more Ni and 10% or greater Al with the sum of Ni and Al being 80% or more. In embodiments where Ni and Al have undergone significant thermal diffusion, it is expected that the composition of a layer of Ni-AI will gradually vary as a function of thickness so that there may not be a distinct line separating the layer of Ni-AI. AI of an underlying Ni-based substrate.

A “catalyst material” is a material that catalyzes a reaction

Desired 11/50. It is not alumina. A catalyst material "disposed on" a layer can be a physically separated layer (such as a deposited sol layer) or catalyst material disposed within a porous catalyst support layer. "Arranged in or" arranged over "means directly or indirectly with successive layers. In some preferred embodiments, the catalyst material is directly in a thermally formed alumina layer.

A "catalyst metal" is the preferred catalyst material and is a material in metallic form that catalyzes a desired reaction. Catalyst metals can exist as completely reduced metals, or as mixtures of metal and metal oxides, depending on the treatment conditions. Particularly preferred catalyst metals are Pd, Rh and Pt.

A “microchannel complex is equipment that includes one or more of the following characteristics: at least one contiguous microchannel has a curve of at least 45 °, e. some incorporations at least 90 °, in some incorporations a u-curve; a length of 50 cm or more, or a length of 20 cm or more along with a dimension of 2 mm or less, and in some embodiments a length of 50 to 500 cm; at least one microchannel that divides at least 2 sub-microchannels in parallel, in some embodiments 2 to 4 sub-microchannels in parallel; at least 2 adjacent channels, having an adjacent length of at least one cm that are connected by several holes along a common microchannel wall where the area of ​​the holes mounts 20% or less of the area of ​​the microchannel wall in which the holes are located and where each hole is 1.0 mm² or smaller, in some 0.6 mm incorporations² or smaller, in some 0.1 mm incorporations² or

Smaller 12/50 - which is a particularly challenging configuration because a coating must be applied without plugging the holes; or at least two, in some embodiments at least 5, parallel microchannels having a length of at least 1 cm, have openings for an internal manifold, where the manifold includes at least a dimension that is not more than three times the minimum dimension, of parallel microchannels (for example, if one of the parallel microchannels has a height of 1 mm (as the smallest dimension of the set of parallel microchannels), then the manifold should have a height of no more than 3 mm). An integral manifold is part of the assembled device and is not a connecting tube. A microchannel complex is a type of interior microchannel.

A “contiguous microchannel is a microchannel surrounded by a microchannel wall or walls without substantial breaks or openings - meaning that the openings (if present) mount no more than 20% (in some embodiments no more than 5%, and some incorporations without any opening) of the area of ​​the wall or microchannel walls in which the openings are present.

An internal microchannel '' is a microchannel within a device that is surrounded on all sides by a microchannel wall or walls except for entrances and exits, and optionally connecting holes along the length of a microchannel such as a porous or holes such as connection holes between a feed channel and an oxidizing channel. Since it is surrounded by walls, it is not accessible by conventional lithography, conventional physical vapor deposition, or other line coating techniques.

A “supplement” is a component that can be inserted into a

13/50 cane) both before and after assembling the equipment,

A “manifold is a header or footer that connects several microchannels and is integral with the equipment.

"Ni-based" alloys are those whose alloys comprise at least 30%, preferably at least 45% Ni, more preferably at least 50% (by mass). In some preferred embodiments, these alloys also contain at least 5%, preferably at least 10% Cr.

A post-assembly coating is applied to three-dimensional microchannel equipment. This also occurs after the lamination step in a multilayer device made by laminating sheets or after the manufacture of manufactured multilevel equipment such as equipment in which microchannels are drilled into a block. This “post-assembly” coating can be contrasted with equipment made by the process in which sheets are coated and then assembled and bonded or equipment made by coating the sheets and then expanding the sheets to make a three-dimensional structure. For example, a coated sheet which is then expanded may have an uncoated groove wedding. Uncoated surfaces of all types, such as groove edges, may corrode or react under reaction conditions. So, it is advantageous to coat the device after assembly to protect the entire inner surface from corrosion. The post-assembly coating provides advantages such as gap filling and ease of manufacture. In addition, aluminide or another coating may interfere with the diffusion bonding of a coated sheet pile and result in a lower bond since aluminide is not an ideal material for bonding a laminated device and may not meet high mechanical requirements.

14/50 temperature. If an equipment is made by post-assembly coating, it is detectable by observing characteristics such as filling cracks, filling cracks, analyzing elements (for example, composition of the elements of the sheet surfaces versus connected areas). Typically, these characteristics are observed by optical microscopy, electron microscopy or electron microscopy in conjunction with the analysis of the elements. So, for a given equipment, there is a difference between pre-assembled and post-assembled coated devices, and an analysis using well-known analytical techniques can establish whether a coating was applied before or after assembled (or manufactured in the case of microchannels perforated) of the microchannel device.

A “separator” is a type of chemical process equipment that is capable of separating a component or components from a fluid. For example, a device containing an adsorbent, distillation or distillation reactive equipment, etc.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a simplified view of a micro-reactor with a set of reaction micro-channels in a cross-flow relationship with a set of cooling micro-channels.

Fig. 2 is electronic microphotograph point by point of monocrystalline fibers (whiskers) of theta alumina (Θ) formed from NiAI,

Fig. 3 is a photograph of a microchannel device, cut and opened, showing an aluminum channel surface. This surface was on the side of a microchannel that was opposite to one side having holes (jets) and aluminizing gas passed through these holes and stuck to the surface,

15/50 causing jet impact failures.

Fig. 4 shows SEM scanning electron microscopy micrographs of an alumina disc that has been treated with Li-Na-B solution and treated by heating at 900 ° C for one hour. After cooling to room temperature, the alumina powder was sprayed onto a surface of the coated area and the disc was reheated to 900 ° C for one hour. A - an uncoated area of ​​the disc. B - coated area of ​​the disc. C, D - coated area where the powder was applied. In B, C and D, the sintering addition solution reacted with the alumina to create a shiny phase at the granule edges and also bonded alumina powders to the substrate.

Fig. 5 is a schematic illustration of an aluminide-coated substrate.

Fig. 6 is a scanning electron microscope (SEM) micrograph of an alumina surface after the corrosion test exposed to an atmosphere of Η₂Ο 17%, O2 2.5%, CO₂ 23%, N2 balance. for 1000 hours at 960 ° C.

Fig. 7 is a partially expanded view of a multichannel microchannel device in which the inner microchannels have been coated with aluminide.

Figs. 8 and 9 are cross sections of micrographs by scanning electron microscope (SEM) of aluminidized channels within the device of Fig. 7.

Fig. 10a shows a cross section of a scanning electron microscope (SEM) micrograph of an aluminidized corner within a microchannel.

16/50

Fig. 10b illustrates the distances that can be measured to characterize a facing corner.

Fig. 11 shows a cross section of a micrograph by scanning electron microscope (SEM) of an aluminum crack in a corner of a microchannel.

Fig. 12 shows a cross section of a micrograph by scanning electron microscope (SEM) of an aluminum sample of Inconel® 617.

Fig. 13 shows a cross section of a micrograph by scanning electron microscope (SEM) of a coupon (= test sample) of Inconel © 617 that has been aluminidised (left), or exposed to air at 400 ° C for one hour to form some surface oxide prior to the formation of the aluminide layer.

Fig. 14 shows a cross section of a micrograph by scanning electron microscope (SEM) of an Inconel © 617 coupon that was aluminidized in the presence of alumina discs.

DESCRIPTION DET ALHADA

Microchannel Equipment

Microchannel reactors are characterized by the presence of at least one reaction channel having at least one dimension (wall to wall, not counting the catalyst) of 1.0 cm or less, preferably 2.0 mm or less (in some embodiments about 1 , 0 mm or less) and greater than 100 nm (preferably greater than 1 pm), and in some embodiments from 50 to 500 pm. A reaction channel is a channel containing a catalyst. Microchannel equipment is similarly characterized, except that a

17/50 reaction containing the catalyst is not required. Both height and width are substantially perpendicular to the direction of flow of reagents through the reactor. Microchannels are also defined by the presence of at least one input that is distinct from at least one output - microchannels are not merely channels through zeolite or mesoporous materials. The height and / or width of a reaction microchannel is preferably about 2 mm or less, and more preferably 1 mm or less. The length of a reaction channel is typically longer. Preferably, the length of a channel and reaction is greater than 1 cm, in some embodiments greater than 50 cm, in some embodiments greater than 20 cm, and in some embodiments in the range of 1 to 100 cm. The sides of a microchannel are defined by the walls of the reaction channel. These walls are preferably made of a resistant material such as ceramic, an iron-based alloy such as steel, or Ni-, Co-, or Fe- based alloy such as monel. The choice of material for the reaction channel walls may depend on the reaction for which the reactor is intended. In some incorporations, the walls of the reaction chamber are comprised of stainless steel or Inconei® which is durable and has good thermal conductivity. The alloys must have a low sulfur content, and in some incorporations they are subjected to a desulfurization treatment prior to the formation of an aluminum. Typically, the feed channel walls are formed of a material that provides the primary structural support for the microchannel equipment. Microchannel equipment can be produced using known methods (except for the coatings and treatments described here), and in some preferred embodiments they are made by laminating Interleaf plates (also known as “wedges), and preferably where

18/50 shims designed for reaction channels are interleaved with shims designed for heat exchange. Of course, as is conventionally known, "reactors or separators" do not include parts of the jet mechanism. In preferred embodiments, the microchannel equipment does not include jet engine parts. Some microchannel equipment includes at least 10 layers laminated to a device, where each layer contains at least 10 channels; the device may contain other layers with fewer channels.

Fig. 1 is a simplified and schematic view of an incorporation of a microchannel reactor in which the fed reagent passes through a reaction microchannel (bottom) while refrigerant (in a transverse arrangement) flows through an adjacent heat exchanger (top) ). Microchannel reactors preferably include a plurality of microchannel reaction channels and a plurality of adjacent heat exchange microchannels. The plurality of microchannel reaction channels can contain, for example, 2, 10, 100, 1000 or more channels. In preferred embodiments, the microchannels are arranged in parallel layouts of flat microchannels, for example, at least 3 orders of flat microchannels. In some preferred embodiments, multiple microchannel inputs are connected to a common header and / or multiple microchannel outputs are connected to a common footer. During operation, the heat exchange microchannels (if present) contain the flow of heating and / or cooling fluids. Non-limiting examples of this type of known reactor that can be used in the present invention include those of a variety of microcomponent sheet architecture (eg, a laminate with microchannels) exemplified in US Patents 6,200,536 and 6,219,973 (both

19/50 which are incorporated herein by reference). The performance advantages of using this type of reactor architecture for the purposes of the present invention include its relatively high heat and mass transfer rates, and the substantial absence of any explosion limits. Microchannel reactors can combine the benefits of good heat and mass transfer, excellent temperature control, residence time and minimization of by-products. Pressure drops can be low, allowing a high effective transfer rate and the catalyst can be fixed in a very accessible way within the channels, eliminating the need for separation. Furthermore, the use of microchannel reactors can achieve better temperature control, and maintain a relatively more isothermal profile, compared with conventional systems. In some embodiments, the reaction microchannel (or microchannels) contains a volumetric flow path. The term volumetric flow path ”refers to an open path (contiguous volumetric flow region) within the reaction chamber. A contiguous volumetric flow region allows rapid flow of fluid through the reaction chamber without major pressure drops. In some preferred embodiments there is laminar flow in the volumetric flow region. Volumetric flow regions within each reaction channel preferably have a cross-sectional area of ​​5 x 10 '⁸ to 1 x 10 '² m², more preferably 5 x 10 '⁷ to 1x10⁴ m^z. Volumetric flow regions preferably comprise at least 5%, or more preferably at least 50% and in some embodiments, from 30 to 80% of either 1) the internal volume of the reaction chamber, or 2) a cross section of the channel reaction.

In many preferred embodiments, microchannel equipment

20/50 contains multiple microchannels, preferably groups of at least 5, or more preferably at least 10, parallel channels that are connected in a common manifold that is integral to the device (not a subsequently attached tube) where the common manifold includes an accessory or accessories that tends to balance the flow through the channels connected to the manifold. Examples of such manifolds are described in US Patent Application No Ser. 10/695400, deposited on October 27, 2003 which is incorporated herein as if reproduced in its entirety. In this context, "parallel" does not necessarily mean straight, but rather that the channels conform to each other. In some preferred embodiments, a microchannel device includes at least three groups of parallel microchannels where the channel within each group is connected to a common manifold (for example, 4 microchannel groups and 4 manifolds) and preferably where each common manifold includes a accessory or accessories that tends to balance the flow through the channels connected to the manifold. An aluminide coating can be formed in a group of connected microchannels by passing a gas containing aluminum in a manifold, typically, the manifold will also be coated.

Heat exchange fluids can flow through heat transfer microchannels adjacent to the process channels (preferably reaction microchannels), and can be gases or liquids and can include steam, liquid metals, or any other heat exchange fluids - the system can be optimized to have a phase change in the heat exchanger. In some preferred embodiments, multiple layers of heat exchange are interleaved with multiple reaction microchannels. For example, at least 10 heat exchangers interleaved with at least 10 reaction microchannels and preferably

21/50 there are 10 layers of heat exchange microchannel orders interfaced with at least 10 layers of reaction microchannels. Each of these layers can contain simple or straight channels or channels within a layer can have more complex geometries.

Although simple microchannels can be used, the invention has strong particular advantages for equipment with complex geometry microchannels. And in some preferred embodiments, the microchannel equipment includes one or more of the following characteristics: at least one contiguous microchannel has a curve of at least 45 °, in some embodiments at least 90 °, in some embodiments a u-curve; a length of 50 cm or more or a length of 20 cm or more along a dimension of 2 mm or less, and in some embodiments a length of 50 to 200 cm; at least one microchannel that is divided into at least 2 subchannels in parallel, in some embodiments 2 to 4 subchannels in parallel; at least 2 adjacent channels, having an adjacent length of at least one cm that are connected by a plurality of holes along a common microchannel wall where the area of ​​the holes mounts at least 20% or less than the area of ​​the microchannel wall where the holes are located and where each hole is 1.0 mm² or smaller, in some 0.6 mm incorporations² or smaller, in some 0.1 mm incorporations² or less - this is a particularly challenging configuration as the coating must be applied without plugging the holes; or at least two, in some embodiments at least 5, parallel microchannels having a length of at least 1 cm, have openings for an integral manifold, where the manifold includes at least one dimension that is no more than three times the minimum dimension of the parallel microchannels (for

22/50 example, if one of the parallel microchannels had a height of 1 mm (as the smallest dimension in the set of parallel microchannels), then the manifold should have a height of no more than 3 mm). An integral manifold is part of the assembled device and is not a connecting tube. A microchannel complex is a type of internal microchannel. In some equipment, a microchannel contains a u-curve which means that during operation, flow (or at least a portion of the flow) passes in opposite directions within a device and within a contiguous channel (note that a contiguous channel with a u-curve includes separate flows such as a w-curve, however in some preferred embodiments the entire flow within a microchannel passes through the u-curve in the opposite direction in a single microchannel).

In some embodiments, the inventive equipment (or method) includes a catalyst material. The catalyst can define at least a portion of at least one wall of a volumetric flow path. In some preferred embodiments, the surface of the catalyst defines at least one wall of a volumetric flow path through which the mixture passes. During operation, a reagent composition flows through the microchannel, passed and in contact with the catalyst. In some preferred embodiments, a catalyst is provided as a supplement that can be inserted (or removed) into each channel in a single part; it is clear that the supplement would need to be sized to fit within the microchannel. In some embodiments, the height and width of a microchannel defines a transverse area, and this transverse area comprises a porous catalyst material and an open area, where the porous catalyst material occupies 5% to 95% of the transverse area and where the open area occupies 5% to 95% of the transversal area. In

23/50 some incorporations, the open area in the transversal area occupies a contiguous area of ​​5 x 10 '⁸ to 1 x 10 '² m². In some embodiments, a porous catalyst (not including voids within the catalyst) occupies at least 60%, in some embodiments at least 90%, of a cross-sectional area of ​​a microchannel. Alternatively, the catalyst can substantially fill the transverse area of ​​a microchannel (a parallel flow configuration). In another alternative, the catalyst can be supplied as a coating (such as a washcoat) of material within a microchannel reaction channel or channels. The use of a perpendicular flow configuration catalyst can create an advantageous capacity / pressure drop ratio. In a perpendicular flow configuration catalyst, the fluid preferably flows into an opening adjacent to a porous supplement or passes a catalyst wall covering that contacts the microchannel wall (preferably the microchannel wall that contacts the catalyst is in direct thermal contact) with the heat exchanger (preferably a microchannel heat exchanger), and in some embodiments, a refrigerant or heating current contacts the opposite side of the wall that contacts the catalyst).

Other substrates

In preferred embodiments, the inventive equipment, catalysts and methods contain or use an aluminide coating on an internal microchannel. In preferred embodiments, the invention includes an aluminide layer, an alumina layer and a catalyst material coated on an interior microchannel wall. However, in some embodiments, the aluminide-coated microchannel contains a porous catalyst material ”as described below. For example, a porous catalyst material such as

24/50 foam of a porous metal can be coated with an aluminide layer to form a catalyst. In other embodiments, the invention includes a catalyst (or method for making a catalyst) in which an aluminide layer is formed on a substrate (catalyst support) other than a microchannel wall. Then, in some embodiments, the invention includes a substrate, an aluminide coating on the substrate, and a catalyst material on the aluminide (preferably with an alumina layer extending) - the substrate may have a conventional shape such as tablets or rings; in some embodiments the substrate is not a sheet of expanded metal. As in the case of microchannel walls, preferred catalyst supports are preferably formed from a Ni, Co-, or Fe- based superalloy.

A porous catalyst material ”(or porous catalyst) refers to a porous material (which may be a supplement) having a pore volume of 5 to 98%, more preferably 30 to 95% of the total volume of the porous material. At least 20% (more preferably at least 50%) of the volume of the porous material is composed of pores in the size (diameter) range of 0.1 to 300 microns, more preferably 0.3 to 200 microns, and even more preferably from 1 to 100 microns. The distribution of pore volume and pore size is measured by the mercury porosimeter (assuming a cylindrical pore geometry) and nitrogen adsorption. As is known, the mercury porosimeter and nitrogen adsorption are complementary techniques with the mercury porosimeter being more accurate for measuring large pores (greater than 30 nm) and the more accurate nitrogen adsorption for small pores (less than than 50 nm). Pore ​​sizes in the range of about 0.1 to 300

25/50 microns allow the molecules to have a molecular diffusion through the materials under most conditions of gas phase catalysis. The porous material may itself be a catalyst, but more preferably the porous material comprises a support of metal, ceramic, or compound having deposited there a layer or layers of a material or catalyst materials. The porosity can be geometrically regular as in a honeycomb or parallel pore structure, or the porosity can be geometrically tortuous or random. Preferably, a support with large pores is a metal foam or ceramic foam. The catalyst layers, if present, are preferably also porous. The average pore size (average volume) of the catalyst layer (s) is preferably smaller than the average pore size of the support. The average pore sizes in the catalyst layer (s) arranged on the support are preferably classified as 10 '⁹ ma 10 '⁷ m as measured by N2 adsorption by the BET method. More preferably, at least 50% of the volume of the total pore volume is composed of pores in the range of 10 "⁹ ma 10 '⁷ m in diameter. Metal Aluminide Layer

In some embodiments of the invention, at least a portion of at least one inner wall of a microchannel equipment (preferably a micro-reactor) is coated with a layer of a metal aluminide (preferably nickel aluminide (NiAI)). It was surprisingly found that the coating of an alumina wall formed by the oxidation of a nickel aluminide coating (NiAI in the examples) provides superior corrosion resistance compared to the equally thermally formed oxide layer (formed from the substrate without the formation of aluminide) ) or

26/50 a layer of deposited alumina solution. Exceptionally uniform coatings are believed to result from the reaction of solid state alumina deposited on the surface of the gas phase and nickel diffusing from the substrate to the surface. In addition, nickel can be galvanized into a metal that is not rich in nickel, such as stainless steel, to create a reactive surface for the aluminidization process. Nickel aluminide can also be deposited by supplying precursors to both Al and Ni in the vapor phase concurrently or as a mixture. In a relative state, a catalyst or intermediate catalyst is formed on the substrates having such a nickel aluminide surface. Of course, the invention also includes methods for making catalysts or microchannel equipment comprising coating a substrate (preferably a Ni-based alloy) with chemical vapor deposition of aluminum which is converted simultaneously and / or subsequently to an aluminide (such as like Ni Al).

A NiAI layer can be formed by exposing a Ni-based alloy to AICI3 and H₂ at high temperature, preferably at least 700 ° C, in some embodiments of 900 to 1200 ° C. Aluminum is deposited on the surface as a result of the reaction between AICI3 and H2. At temperature, 0 Ni of the substrate would diffuse to the surface and react with the aluminum to form a nickel aluminide surface layer. The Ni source can be 0 Ni on a substrate with Ni-based alloy, an electrolytically galvanized Ni layer, or a vapor deposited Ni layer that can be deposited on a substrate before aluminidization. It is believed that other metal aluminides (such as Co or Fe) can be formed under similar conditions.

27/50

Preferably the aluminidization is carried out with good flow control for the device through a manifold, for example, good control can be obtained by passing the flow through the microchannels through a flow manifold that is integral to the microchannel device. Preferably the aluminidization process is carried out from 100 Torr (2 pounds per square inch absolute, psia) to 35 psia (1800 Torr), more preferably between 400 Torr (8 psia) and 25 psia (1300 Torr).

In preferred embodiments, nickel aluminide contains from 13 to 32% aluminum, more preferably from 20 to 32%, and most preferably still consists of beta-NiAI. If Al falls significantly below 13% by weight% of the level of the primary gamma phase, a negative effect on the quality of the thermally formed alumina scale can be expected.

In some embodiments, the metal aluminide layer has a thickness of 1 to 100 micrometers; in some incorporations a thickness of 5 to 50 micrometers. In some embodiments, the aluminide layer is completely oxidized; however, this is generally not preferred.

The metal surface on which the metal aluminide is formed is preferably substantially free of oxides. Optionally, the surface can be cleaned, polished, or otherwise treated to remove such oxides if any are present.

A reactor can be formed by a catalyst that is arranged as a coating on an Internal wall (where the walls can be single walls or formed walls). Alternatively, or in addition, supplements such as fins, plates, wires, nets, or foams can be inserted into a channel. These supplements can provide surface area and characteristics of

28/50 additional flow effect. An aluminum process can be used to fix the supplements on the wall of a device (such as a reactor); the resulting aluminum layer (or aluminum oxide, or aluminum, or metal aluminide, or a mixture of these) fills some voids and greatly improves the thermal conduction between the supplement and the device wall (such as a reactor wall) .

Thermally Formed Oxide

Aluminide layer of metal, or more preferably NiAI, is heated in the presence of oxygen or other oxidizer to form an aluminum oxide layer. It was surprisingly found that when the surface was heated to the treatment temperature in the absence of O₂ or another oxidant prior to the formation of the oxide at temperature, a significantly improved oxide coating resulted. The oxide layer formed by heating the surface to the treatment temperature in the presence of oxygen showed splinters whereas the layer formed heating the surface from room temperature to the treatment temperature in the absence of oxygen did not. Oxygen can be substantially excluded from the heating step of the heat treatment process.

A convenient and preferred method of excluding oxygen from the surface while heating the surface from room temperature to the treatment temperature involves exposure to hydrogen. Hydrogen effectively reduces the oxidation power of the atmosphere during heating to prevent premature formation of an oxide scale. Other gases that reduce the oxidizing power of the gas, such as NH₃, CO, CH4, hydrocarbons, or the like, or any combination of these can also be used. All

29/50 these reducing gases can be used in combination with inert gases such as N₂, He, Ar, or other inert gases, or combinations of inert gases.

The oxide layer is formed by exposing the surface to an oxidizing atmosphere at or within 100 ° C of the treatment temperature. The oxidizing gas can be air, diluted air, oxygen, CO₂, steam or any mixture of these gases or other gases that have substantial oxidizing power, with or without an inert diluent. The inert diluent can be inert gases such as N₂, He, Ar, or other inert gases, or combination of inert gases. The oxide formation temperature is at least 500 ° C, preferably at least 650 ° C. The surface can be exposed to treatment conditions in stages of different temperatures, different oxidation powers, or both. For example, the surface can be treated at 650 ° C for a time and then heated to 1000 ° C and maintained at 1000 ° C for an additional time. Such controlled and stepped surface treatment can generate a surface structure of a desired morphology, crystalline phase and composition.

Higher oxide coatings result from preheating to about 1000 ° C (in some embodiments to at least 900 ° C) under an inert atmosphere, or preferably, reduction such as an atmosphere containing H₂ (preferably at least 1000 ppm H₂, in some incorporations from 1 to 100% H₂). It has been observed that preheating under a reducing atmosphere produces superior oxide coatings with little or no cracking. This control of preheating conditions is believed to result in superior coatings because it minimizes the formation of nickel oxide. Great care must be taken to select an atmosphere that is really “inert because atmospheres

30/50 conventionally considered inert atmospheres yield inferior results. This is because nickel oxide can theoretically form even at 1O '¹⁰ oxygen atm and chromia at 10 '²¹ oxygen; such extreme levels of purity are not available in commercially offered gases. However, reducing atmospheres are preferred.

Conventional wisdom suggests that the higher the temperature, the faster the oxidation rate. Surprisingly, we found that the oxide formed faster at 1000 ° C than at 1050 ° C. A possible explanation is that the oxide at high temperature may be more dense, thus discouraging a more accelerated formation. The oxide at a lower temperature can be more porous, thus allowing more accelerated oxide formation. On the other hand, very high temperature will promote interdiffusion between the aluminide layer and the substrate, and the aluminide will disappear in the volume of the alloy. Consequently, the thermally formed oxide is conducted in the temperature range of 1000 to 1100 ° C, more preferably 1025 to 1075 ° C. In the presence of excess oxygen, for example, air flow, the oxidation treatment is preferably conducted for 30 to 6000 min, more preferably 60 to 1500 min.

Although it has never been known before about the formation of catalysts, it is known that monocrystalline fibers (whiskers) of theta (Θ) alumina can be formed from NiAI. The monocrystalline fibers (whiskers) of alumina are substantially in the form of sticks or in the form of needles with an expression index of at least 10. An example of these monocrystalline fibers (whiskers) in Inconel is shown in Fig. 2.

It should be recognized that the term “alumina can be used to refer to a material containing aluminum oxides in the presence of metals

Additional 31/50. In the descriptions here, unless specified, the term alumina ”encompasses substantially pure materials (“ consists essentially of alumina) and / or aluminum oxides containing modifiers.

Thinner layers are less likely to crack; however, the thermally formed oxide layer preferably has a thickness of 5 pm or less, more preferably a thickness of 1 pm or less, in some embodiments it has a thickness of 0.1 pm to 0.5 pm. In some preferred embodiments, the articles have an oxide thickness of a thermally formed scale of less than 10 micrometers, and in some embodiments an oxide thickness of a thermally formed scale in the range of about 0.1 to about 5 micrometers . In some embodiments, thicker oxide layers may be useful, such as for a larger surface area catalyst support. In some preferred embodiments, the articles have a washcoat oxide thickness of less than 10 micrometers, and in some embodiments a washcoat oxide thickness in the range of about 1 to about 5 micrometers. Typically, these thicknesses are measured with an optical or electron microscope. Generally, the thermally formed oxide layer can be identified visually; the underlying aluminide layer is metallic in nature and contains no more than 5% by weight of oxygen atoms, washcoat surface layers can be distinguished from the thermally formed oxides by differences in density, porosity or crystalline phase.

The aluminized surface can be modified by adding alkaline earth elements (Be, Mg, Ca, Sr, Ba), rare earth elements (Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb, Lu) or combinations thereof.

32/50

The addition of these elements is followed by a reaction with an oxidation atmosphere to form a mixed oxide scale. When the modifying element is La, for example, the scale contains LaAIOx, lanthanum aluminate. In some embodiments, a stabilized alumina surface can be formed by adding a rare earth element such as La, coated with a layer of sol alumina, then doped with an alkaline earth element such as Ca followed by a heat treatment.

It has been shown that La is effective in increasing the adhesion between the sol alumina coating and the alumina scale. Inconel ® 617 substrate after aluminization and heating treatment was coated with an aqueous solution of La nitrate, followed by drying and calcination in air at 1,000 ° C for 4 hours. This was then coated with alumina sol exposed to the corrosion test environment at 960 ° C for 1000 h. The sol alumina coating resisted well, with no visible signs of damage such as splinters or cracks. In contrast, a similar test with an Inconel ® 617 substrate after aluminization and heat treatment and coated with sol alumina without pretreatment with an aqueous La nitrate solution, showed that most of the sol alumina coating was lost after only 100 test, suggesting insufficient adhesion between alumina sol and alpha alumina scale on aluminide.

The benefit of La as an adhesion promoter is believed to be associated with its reaction with the alpha alumina scale to change the surface to a more chemically active La aluminate. Surface X-ray diffraction (XRD) showed the formation of LaAIO3. Without the addition of La, only alpha alumina and some nickel aluminide background can be detected by XRD. Flow indices

33/50

The alumina-containing layer and alumina layers are preferably formed by reacting a surface with a reagent gas or reagents under dynamic flow conditions. Aluminum can be deposited in a microchannel through the flow of AlClj and H₂ in a microchannel. In a microchannel device, Al can be deposited only in selected channels (such as filling certain channels to exclude aluminum precursors during treatment with CVD). Aluminum can also be applied to selected portions of a microchannel device by controlling relative pressures. For example, in a microchannel device that contains at least two channels separated by a wall and in which the two channels are connected to each other through holes in the wall, AICI3 flows through a first channel while H₂, at a higher pressure, flows through a second channel and through the holes in the first channel.

Static gas treatments can be conducted by filling the desired areas with reactive gases with interim gas pumping if necessary.

It has been found that excessively high flow rates can lead to uneven coatings. An example of this problem can be seen in Fig. 3.

Two flow measures were established to characterize the shear extension and jet compaction. For mechanical shear, the total wall stress (two tangential components and one normal component) was selected as the relevant metric. Likewise, the dynamic pressure, which is equal to the flow moment of the feather jet, was selected as a means of monitoring the effect of the jet compaction on the formation of

34/50 coating.

Computational Fluid Dynamics (CFD) simulations of various device aluminization tests were conducted to contrast with predicted values ​​for wall shear stress and dynamic pressure in regions where treatment was not successful in those regions where the treatment was successfully applied. These simulations used as limit conditions the same temperature, flow rates, current composition, and inlet / outlet flow configuration as used in the aluminization process of the respective device. Comparisons used autopsy results from the aluminized and heat-treated devices. It was determined from these studies that a threshold value could be established for both wall shear stress and dynamic pressure where for flow conditions in which both shear and dynamic pressure were below the threshold values, good treatment should occur; and when the threshold value for any variable has been exceeded, the treatment can be damaged.

Metric Thresholds

The wall shear stress is expressed as ^{τ =}or the product of fluid viscosity μ and the magnitude of the local velocity gradient, expressed in units of force per surface area of ​​the channel wall unit. This amount reflects the magnitude of the molecular frictional forces at the interface between a very thin layer of fluid and the channel wall itself. The dynamic pressure (or equivalently the moment of flow) is given by the expression p =% pu² where p denotes the density of the fluid and the magnitude of the velocity of the local fluid. It is a measure of the strength transmitted by the change in

35/50 moment when a feather jet hits the side of a channel and is also expressed in terms of force per unit area. CFD simulations of a number of combustion test devices were performed to determine if there was any correlation between poor aluminide coating and critical values ​​in both wall shear and dynamic pressure.

Based on the detailed analysis of the tested devices, the following thresholds were established:

Wall Shear Stress: To ensure that resistance forces do not hinder the formation of the aluminization coating, the wall shear stress should not exceed 50 Pa if the aluminization gases are flowing through the jet orifice. The wall shear stress should not exceed 200 Pa if the aluminization gases are not colliding with the wall of a microchannel as through a jet orifice. Dynamic Wall Pressure: To ensure that erosion of the impact moment does not impair the proper formation of the aluminization coating, the dynamic pressure on the wall should not exceed 10 Pa if the aluminization gases are flowing through the jet orifice. Substantially a dynamic pressure on the highest wall is allowed in the absence of a jet orifice. The permissible dynamic pressure on the wall must not exceed 100 Pa if the aluminizing gases are not colliding on the wall of a microchannel as through a jet orifice.

Practical Application

The metrics presented above are used to determine the flow configuration and individual flow index that will infer good aluminization treatment from a fluid point of view. There is usually a combination of

36/50 possible input and output flow paths for a device. CFD predictions are used to determine these combinations of inlet and outlet and individual inlet flow indices that will result in globally maintaining wall shear stress below 5 x 10 '³ PSI and dynamic pressure on the wall below 1 x 10 '³ PSI across the device. The maximum allowable flow rate that meets these two criteria and the associated flow configuration becomes the maximum recommended rate for aluminizing the device based on the measurements developed here. Examples of aluminide coating that result from this orientation have produced aluminide coating without visible defects.

A surprising finding of this invention is that the flow (non-static, see previous discussion of preferred pressures) of aluminization gas at indices below the threshold indices discussed above produced highly uniform defect-free aluminide coatings (less than 10% thickness variation).

Covering (Mask)

The aluminization processes discussed above produce aluminide coatings throughout the channel. However, it is theoretically possible to selectively coat portions of a channel by covering (masking) sections of a channel. This could be done by covering portions of a sheet with refractory material and then laminating the sheet covered in a laminate. After aluminization the coating can be removed, such as by combustion. Possible refractory materials could include Mo, diamond, and graphite. Covering techniques have been mentioned in US Patent No. 6,332,926.

Acid or Base Corrosion

37/50

Adhesion and / or surface area can be increased through acid or base corrosion. It is preferably conducted under moderate conditions in the thermally formed alumina layer. Severe conditions can result in excessive corrosion. As a result, the corrosion step or steps (optional) are conducted at a pH of less than 5 (preferably 0 to 5) or greater than 8 (preferably 8 to 14). Sintering Additives

A sintering additive can be added either as a solution applied on the alumina scale or in a mixture. The purpose of a sintering additive is twofold: 1) locally reduce melting temperatures of the oxide substrate (eg, the oxide scale) to promote diffusion bonds between it and the ceramic particles and 2) create a shiny phase that forms at the edges of the granules and suppresses the oxygen diffusion of subsequent oxidation of the underlying metallic substrate. For alumina layers, sintering additives comprise Na, Li and / or B. Aqueous compositions comprised (or consisting essentially of) of Li or Na borate salts constitute a particularly preferred treatment for an alumina escate. In some preferred embodiments, the invention comprises an oxide layer arranged on a metal substrate where the metal scale comprises metal oxide particles having sintering additives dispersed along the edges of the granules and, preferably, on the surface, sintering can be chosen which are benign or preferred for the desired catalytic processes.

In a preferred embodiment, a sintering additive is applied to the surface of an oxide scale. The resulting surface is then

38/50 treated with a ceramic suspension. In a particularly preferred embodiment, the ceramic suspension comprises a solvent, ceramic particles, a dispersant to prevent particle agglomeration, an organic binder to provide resistance to the ceramic particle film when dried, and a plasticizer to increase the plasticity of the binder. Plasticizers, surfactants, and binders are organic materials that can be readily removed by simple calcination in the air at relatively low temperatures. The resulting article is dried to remove liquid and then heated to elevated temperatures. During this process, the sintering additive locally fuses the ceramic particles at the contact points (with the applied oxide particles) and promotes the diffusional connection between the oxide scale and the ceramic particles. In some of the broader aspects, this process is general and can be applied over any oxide layer that is subsequently treated with an oxide particle composition. Additional coatings with oxide compositions can increase the thickness of the oxide layer and provide support for subsequent application of catalytically active particles. The selection of the appropriate treatment temperatures and / or control of the levels of sintering additives can avoid excessive reduction of surface area in subsequent applied oxide layers.

In some Incorporations, an oxide surface is treated with a sintering additive and then treated by heating. Subsequently, the resulting surface is treated with ceramic particles, (for example, in the form of a powder or suspension). In one test, an alumina disc was treated with a composition made by dissolving 1.66 g of PVA, 3.3 g of U2B4O7 and 7.4 g of Na₂B₄O7 in 83 g of water. The disc was then treated by heating to 900 ° C

39/50 for an hour. The alumina powder was then spread on the disc and the treated disc was again treated by heating at 900 ° C for one hour. The results are shown in Fig. 2 which shows that the treated disc exhibited sintering and adhesion of the alumina powder. Better sintering was observed in the treated area vs. untreated disk, with the formation of a shiny phase at the edges of the granules. The sintering additive or additives must be added in an amount sufficient to achieve its desired purpose. Thus, in some embodiments, sufficient amounts of sintering additives are added in such a way that an increased amount of glossy phase is observed compared to a sample treated in an identical manner without sintering additives. Sintering additives (when used) are preferably present in the coating solutions at least 0.5% by weight. A coating or layer in a coating may have sintering additives in an amount of at least _% by weight, in some embodiments at least 0.5% by weight,% by weight refers to a% by weight in a coating oxide or in a layer within a coating between multiple layers (the multiple layers can be oxide or non-oxide layers). Preferably, the oxide layer containing the sintering additive is alumina.

As shown in Fig, 4, excellent film formation was observed for an Inconel species that was aluminized, heat treated to form an oxide scale, etched with base, coated with a sintering additive solution, and heat treated.

Fig. 5 schematically illustrates an application in which a metal substrate 42 has a first layer of aluminide 44, a layer

40/50 with sintering additive (s) 46, and an alumina layer 48. In preferred embodiments, the outermost layer still comprises an additional catalytically active material 49.

Many suspensions with increased rheological behavior have been prepared and tested. These suspensions contained water as a solvent, aluminum oxide powder 14 to 15% by weight as the ceramic particles, Tergital ® (nonylphenol polyethylene ether) 1.43% by weight as the surfactant, polyethylene glycol (PEG) 0.14 % by weight as the plasticizer and polyvinylpyrrolidone (PVP) 0.20% by weight as the binder. These suspensions exhibited superior coating properties compared to unmodified alumina.

Most commonly, sintering additives can be used in the preparation of thin ceramic films. This type of formulation can be used as a high-temperature adhesive to create complex ceramic shapes, to develop impermeable oxygen barrier thermal coatings, as well as chemical or wear resistant coatings. For example, it could find application in the semiconductor industry where tape casting is used to develop multilayer ceramic modules, the fuel cell industry where ceramic parts are used to develop solid oxide fuel cells , surfaces inside chemical reactors, and / or the automotive industry for chemically resistant, wear resistant coatings. Especially preferred uses of sintering additives are in the formation of ceramic layers in catalysts (typically having another catalyst support layer of larger surface area and a catalytically active material that can be in an additional layer or within the support layer),

41/50 and on the protective surfaces of microchannel equipment.

Other Coating Modifications

Several other modifications can be used to increase the adhesion or other properties of alumina coatings on the alumina scale. An alumina coating can be deposited using sun or alumina sludge.

In some preferred embodiments, instead of a single coating of alumina, multiple coatings of alumina are applied to the surface where at least two of the layers (more preferably at least 4 layers) have graduated properties. For example, a first coating can be calcined at a first temperature (T1) and a calcined coating subsequently deposited at a second lower temperature (T2) resulting in increased surface area graduated coatings. Other graduated layers can be formed through: graduated use of water vapor during calcination; different particle sizes in the coatings (smaller particles can be used for the first coat or coatings thereby increasing the physical contact between the particles and the scale, while larger particles are present in the later coatings); and / or the graded use of stabilizers or binders (where the binders are subsequently burned).

Additives such as rare earth or alkaline earth elements (including La, Ce and / or Pr) can increase the hydrothermal stability of an alumina coating.

Surfactants can be added to the coating solutions. Preferred classes of surfactants include: colloidal, non-ionic, anionic, cationic, and amphoteric, and in some embodiments, surfactants are

42/50 present in at least 0.1% by weight, in some embodiments at least 0.01% by weight, and in some incorporations in the range of 0.01 to 5% by weight. Water soluble polymers such as polyvinyl alcohol! (PVA), polyvinylpyrrolidone, PLE, and Polycup can be added to the coating composition. Polymers can reduce breakage during drying and form additional porosity after firing. The addition of titanium oxide to promote adhesion is another possibility.

Prior to coating, the alumina scale can be treated with rare earth or alkaline earth elements (including Mg or La) (and, optionally, a surfactant such as polyvinyl alcohol) followed by a high temperature treatment to make the surface of the scale more active. for membership. The use of wetting agents and surfactants increases the amount of metal additives that can be added to the alumina surface at each stage of the coating solution.

Catalyst Coatings

Catalysts can be applied using techniques that are known in the art. Impregnation with aqueous salt solutions is preferred. In some embodiments, Pt, Rh, and / or Pd are preferred. It is typically followed by the heating and activation treatment steps as known in the prior art. Salts that form solutions of pH> 0 are preferred.

Reactions

Coated microchannel equipment is useful when used with a surface catalyst and at a high temperature, for example, at temperatures above 500 ° C, in some embodiments 700 ° C or higher, in some

43/50 incorporations 900 ° C or higher.

In some aspects, the invention provides a method for conducting a reaction, comprising: flowing at least one reagent into a microchannel, and reacting this at least one reagent in the presence of a catalyst within a microchannel to form at least one product. In some embodiments, the reaction essentially consists of a reaction selected from: acetylation, addition reactions, alkylation, dealkylation, hydrodesalkylation, reduction alkali, amination, amoxidation, ammonia synthesis, aromatization, arylation, autothermal reform, carbonylation, decarbonylation, reduction carbonylation, carboxylation, reduction carboxylation, reduction copulation, condensation , cracking, hydrocracking, cyclization, cyclooligomerization, dehalogenation, dimerization, epoxidation, esterification, exchange, Fischer-Tropsch, halogenation, hydrohalogenation, homologation, hydration, dehydration, hydrogenation, dehydrogenation, hydrocarboxylation, hydroformylation, hydrogenolysis, hydrometallation, hydrosylation, hydrolysis, hydrotreating (HDS / HDN), isomerization, methylation, demethylation, metathesis, nitration, polymerization, reduction, reforming, water-exchange reaction reverse gas, Sabatier, sulfonation, telomerization, transesterification, trimerization, and water-gas exchange reaction. Combustion is another preferred reaction. Steam reforming of the hydrocarbon is especially preferred (such as steam reforming of methane, ethane or propane). EXAMPLES

Corrosion Protection

Inconel® 617 samples were tested for corrosion with and without the protective aluminide coating. The aluminide-coated sample was made by forming an aluminide layer and heating under a

44/50 H atmosphere₂ and then exposed to air at 1050 ° C. Both samples were tested for corrosion at 960 ° C and 17% water, O₂ 2.5% for 1000 hours. The uncoated sample showed a pitch after 100 hours of testing. In contrast, the aluminide / alumina coated sample did not show any noticeable change after 1000 hours of testing for corrosion. See Fig. 6, which shows no damage to the alumina layer. The granule edges shown in the figures were also present before the corrosion test. Testing for additional corrosion at 4400 hours also showed no damage to the coating. Uniform Coatings in a Multichannel Microchannel Device

A microchannel device (Fig. 7) having 48 sets (4 x 12) of parallel channels, with each set consisting of 5 individual channels. The device is designed for steam reforming of methane (SMR) and contains an integrated combustor (Fuel, Air and Exhaust for combustion and Reagent and Product by SMR). The device is longer than 20 inches (50 cm), making the aluminization circuit longer than 40 inches (1.0 m) (Exhaust connected to Fuel and Air, Product connected to Reagent). The Fuel and Air channels are in communication through an arrangement of jet holes in each pair of channels.

The SMR channels were covered with an argon flow while channels in the combustion circuit were aluminidized. Calculations showed that the flow of aluminizing gas through the microchannels was highly non-uniform with the flow rates in some channels 10 times greater than in others, while the surface area within each microchannel was relatively similar. This difference in flows is due to the complex design of the channels. The CVD steam flow was fed from the exhaust manifold, flowed

45/50 through the exhaust channels, through a curve in u and then in the fuel and air channels and out through the fuel and air manifolds. After aluminidization, the device was opened and several channels were inspected by SEM. Transverse samples were seen at the midpoint of the device (Fig. 8) and close to an end - this end is as close to the beginning of the aluminization circuit (exhaust channel) as to the end of the aluminization circuit (air and fuel channels), Fig., 9.

Based on the SEM data it can be seen that the aluminide coatings were highly uniform both along the length of each channel as well as channel to channel, despite the large difference in the flow rates channel to channel. In each case, the coating thicknesses appeared to be within about 10%.

Additionally, the coatings appeared to be essentially flawless.

Corner Coatings

The inner corners of the microchannel devices were inspected by SEM. These devices were again coated with Inconel® 617 with an aluminide layer. It was surprisingly found that sharp corners (90 ± 20 ° \ well formed coated with aluminide had compliant coatings (see Fig. 10a) with an acute angle at the interface between the interior of the channel (dark area) and the aluminide coating. For the purpose of measuring the coating angle, the coating angle is based on averaging the surface roughness at 100 pm along each edge of the corner. In some preferred embodiments, the coating angle is 90 ± 20 °, in some preferred embodiments 90 ± 10 °. Another measure is the thickness ((d1 +

46/50 d2) / 2) of the coating at the perimeter of the coating corner (see Fig. 10b) based on the extensions (d1 and d2) of the same 100 pm lines used to measure the angle of the coating; preferably this coating thickness at the corner coating perimeter is within 25%, more preferably within 10% of either the average coating thickness (calculated over a microchannel wall, or segment of the microchannel wall, ending at the corner), or within 25%, more preferably within 10% of both the thickness of the midpoint (measured at the midpoint of a microchannel wall, or segment of the microchannel wall, ending at the corner).

The crack filling is shown in Fig. 11. In this example, the Inconel sheets were minted. The coinage process tends to result in slightly curved edges, and these curved edges can result in openings in the corners formed between two laminated sheets. The aluminide coating fills this opening, again this occurs in a manner consistent with the thickness of the coating being uniform with any part in the microchannel to the point that the opening is filled and the coating can no longer form. In other words, the thickness appears to be limited by the distance from the metal substrate.

Multichannel Sol Coated Device

A microchannel test device with 48 sets of channels was prepared with post-assembly coatings and tested. The device was made from sheets of a Ni-based Inconel® superalloy. An aluminide layer was formed over the alloy. Then it was oxidized (as described above) to form an alumina layer. Various coatings based on solutions have been applied. To apply the coatings, the device was oriented in a

47/50 end (the straight microchannels were oriented parallel to gravity), and at each stage, the liquid was added through an entrance located at the bottom (in relation to gravity), in a manifold and above in the microchannels. The liquid level in the manifolds was controlled using a pressure gauge. Then the fluid was drained by gravity and a purge of N₂ removed the remaining liquid from the microchannels. In this example, the thermally formed alumina layer was first treated with a solution containing La, then alumina sol, then a solution containing La, and finally a solution containing Pt. The device was then cut into pieces for analysis. The coatings exhibited excellent adhesion without splintering. Element analyzes were conducted in increments of 100X, 500X and 2000X using dispersive energy spectroscopy (EDS) with excitation energy of 20 kV. Unless otherwise specified, this is the condition (at 100X, or if 100x is greater than the area available, then the largest area available for SEM) that should be used for analyzing elements of any coatings described here (recognizing that some modifications may be necessary if such measurement conditions are impractical for particular systems). As is well known, this technique measures the composition of the surface, as well as some thickness below the surface.

Six channels (two sets of 3 channels) were analyzed. From each set of 3 channels there were 2 channels on one edge of the device and one in the middle. The coatings in the six channels were analyzed at the top and bottom (in relation to gravity during the washcoat application) of the coated section, The% by weight of Pt in each channel is shown below:

<td>Channel No.</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td><td> 6</td>

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<td>Top</td><td> 42</td><td> 38</td><td> 42</td><td> 25</td><td> 28</td><td> 29</td>

<td>Bottom</td><td> 46</td><td> 33</td><td> 41</td><td> 52</td><td>45q</td><td> 61</td>

As can be seen, there is no consistent trend in each microchannel. In the second set of microchannels (4, 5, 6) there seems to have been a problem with filling, drainage, or both. The second set of channels contained about twice as much coating at the bottom of the channel as at the top. It may be that, during the washcoat application stage, the first set of channels drained efficiently, while the second did not. It also appeared to be an effect in which external microchannels contained more coating, perhaps due to slower drainage in these channels. Heating Treatments

Inconel ® 617 coupons have been aluminized and heat treated under a variety of conditions. An aluminum coupon to form the aluminide coating, but not oxidized, is shown in Fig. 12. The aluminide layer was about 30 pm thick and there was an interdiffusion zone between the aluminide layer and the alloy that was about 5 pm. The aluminide layer contained 28 to 31 wt% Al which corresponds to NiAI.

Heat treatment of an aluminidized coupon at 1100 ° C for 100 hours caused the interdiffusion zone to essentially disappear and there was a substantial loss of aluminum from the aluminide layer in the alloy. The treatment of an aluminidized coupon at 1050 ° C for 100 hours showed no loss of the aluminide coating.

Effect of the presence of oxide during the aluminidization process

Fig. 13 shows a comparison between a standard aluminum coupon and a coupon treated by heating in air at 400 ° C for 1 hour to

49/50 deliberately forming some native oxide chromate before being aluminized. A thin dotted line of inclusions in the aluminide is observed in the coupon with native oxide before aluminization. Such a line of inclusions can become a weak point in terms of adhesion. These figures should be taken as a reference when deciding whether an aluminide layer is substantially with or without oxide defects between an aluminide layer and a metal substrate.

Coating defects are also observed in FeCrAIY fins that have been aluminized in the presence of an alumina disc. Fig. 14 shows large voids in the aluminide layer of an Inconel © 617 coupon that was aluminidized in the presence of an alumina disc.

In previous attempts to aluminidize a microchannel device, it was found that the channels closest to the gas inlet (that is, the entrance to the aluminum components) showed the most inclusions while the furthest channels showed less. It is believed to have been caused by surface oxides in the piping or manifolds in the path of aluminum compounds before microchannels. The presence of surface oxide in the pipeline was confirmed by EDS. To avoid these defects, care must be taken to avoid the use of components that have surface oxides in the aluminidization processes, especially surface oxides along the path (that is, the path that carries the aluminum compounds) that leads to a device microchannel. In some preferred techniques, the tubing and / or other fluid pathways are subjected to a treatment to remove (clean) surface oxides, such as by hydrogen treatment, KOH corrosion, electropolishing or micro-brushing. Naturally, before aluminidization,

50/50 microchannels can also be subjected to a treatment to remove surface oxide.

In preferred embodiments, the aluminide layer and the interfaces of the aluminide layer with the alloy substrate and an oxide layer (if present) is preferably substantially without voids or inclusions that are greater than 10 pm, more preferably substantially without voids or inclusions that are greater than 3 pm. “Substantially no voids or inclusions” excludes coatings such as those shown in Fig, 14 and other structures having numerous (that is, more than about 5 large or a single 10 very large) defects of 50 pm in length over a channel, but you should not exclude a structure shown on the left of Fig. 13 that shows a small number of isolated defects.

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