A membrane apparatus and method of preparing a membrane and a method of producing syngas

The present invention relates to a membrane and a method for producing a membrane, useful in particular, but not exclusively, for the production of synthesis gas used in the conversion of gas into liquids by the Fischer-Tropsch method in the oil and gas extraction industry or for the production of hydrogen used as a fuel.

[0002] While oil production from offshore sources has increased slightly in recent years, there has been a clear increase in the production of natural gas (which consists mainly of methane). Natural gas is often extracted during the extraction of liquid hydrocarbons, such as oil, from the earth and is often undesirable because of the lack of infrastructure to transport gas to land-based places. The lack of infrastructure can be explained by the physical nature of natural gas, which makes it difficult to transport it safely and / or efficiently in its basic gas state. As a result, natural gas is often burned (ignited), which causes economic losses and is a burden on the environment. It would therefore be desirable to either convert natural gas to another substance that can be easily transported or transport natural gas in a liquid state. In this way, by using the rich infrastructure and technology for transporting liquid hydrocarbons already existing in the seabed mining industry, greater profitability for the development of new mining fields will be achieved.

[0003] A method for transporting gas in the form of Liquid Natural Gas (LNG) in specially constructed containers on board vessels adapted for this purpose is known. However, this method has many disadvantages, including the need for expensive pressure equipment, the size of which is difficult to reduce for the needs of smaller production fields, gas losses during transport ("boil-off 'loss due to evaporation), hazards to the ship and crew that occur in transport, associated with high pressure, highly flammable gases and the requirement to reduce LNG pressure on the customer's side, for regasification.

[0004] It is believed that a better way to use natural gas (CH4), produced during the operation of offshore deposits, is to convert it to or in the immediate vicinity of an offshore mining platform to form a synthetic gas (synthesis gas), which in turn can be used to producing gases, liquids and chemicals such as methanol, ammonia, and most importantly, crude oil can easily be pumped through the same pipeline as the oil produced. Syngas consists of a mixture of carbon monoxide (CO) and hydrogen (H2).

[0005] For the reader's information, the conversion of synthesis gas into liquid hydrocarbons is a chain reaction between carbon monoxide and hydrogen on the surface of a heterogeneous catalyst. The catalyst is based on iron or cobalt, and the reaction is highly exothermic. Temperature, pressure and catalyst determine whether a light or heavy synthesis product is produced. For example, at 330 ° C, mainly gasoline and olefins are produced, while at 180 ° C to 250 ° C, mainly diesel and waxes are produced. There are two main types of Fischer-Tropsch reactors. The vertical solid tubular has a catalyst in the pipes that are cooled externally by boiling water under pressure. In large installations, several reactors can be used in parallel, saving energy. Another method uses a slurry reactor in which preheated synthesis gas is introduced into the bottom of the reactor and distributed in a slurry consisting of liquid waxes and catalyst particles. Since the syngas in the form of bubbles travels up through the suspension, it is dispersed and converted into further waxes in the Fischer-Tropsch reaction. The heat generated is removed by the reactor cooling coils, the steam they generate is used in the process. This is shown in Fig. 7, for general information to the reader.

[0006] Thus, if methane (or other gaseous hydrocarbons) can be converted to synthesis gas and then to liquid hydrocarbons, then the transport costs and problems described above will be reduced.

[0007] Synthesis gas can be produced by partial oxidation of methane (although more typically this is done by reacting methane with steam under pressure.) [0008] The main safety problem of partial methane oxidation arises because methane and air (or oxygen) should be fed into reactor at the same time and therefore there is a danger of explosion.

[0009] It is known in the art that a synthesis gas reactor can be used with relatively dense ceramic membranes that carry oxygen (see e.g. WO 98/48921 and WO 01/93987). These membranes generate synthesis gas by avoiding direct contact between the supplied oxygen and the hydrocarbon, but this requires the use of very high temperatures to achieve the necessary oxygen flux. What's more, the density of the membrane means that the membrane must be as thin as possible, which results in brittleness and cracking, reduced performance and reduced working life. [0010] In some cases, the membranes must be so thin that they would not be able to support their own weight and therefore cannot be used in practice.

[0011] Thus, the cost-effective conversion of natural gas (methane) to syngas for converting gas into liquids would be an important economic advance.

[0012] Hydrogen can be used as a clean fuel. However, the amount of hydrogen that can be produced using natural renewable energy sources, such as solar, wind and hydropower, is currently not enough to meet demand. The use of natural gas and / or the production of hydrogen from natural gas is seen as an alternative and most viable solution, at least in the first half of this century [1, 2].

[0013] An example of progress in the widespread use of natural gas is the development of a small cogeneration system using a gas micro-turbine. In addition, fuel cells are to be a highly efficient energy generating system. In addition to installation in vehicles, it is anticipated that fuel cells will also be placed in homes. Domestic use of fuel cells can simultaneously supply hot water and electricity. In order to commercially use stationary fuel cells, it is necessary to develop alternative hydrogen production technology.

[0014] WO98 / 48921 uses a dense membrane, conducting oxygen ions in the methane reforming process, as well described in the literature, the dense membrane cannot be porous in order to achieve the desired gas reforming and air separation function. WO98 / 48921 illustrates two chambers, formed by a dense, non-porous membrane, with an oxidant introduced into one chamber and methane introduced into another. Meanwhile, US5221484 describes catalytic ceramic materials in which the ceramics are porous and not dense, but is not used for reforming gas methane, but for filtering hot gases and catalytic promotion of the reaction of components in one gas stream. The gas passes from one chamber to another and in this way the components of the gas stream react with each other in a way that is possible in the presence of catalysts. However, unlike dense ceramic materials, there is no mention of introducing gas into the second chamber in any way other than through porous ceramic walls. In fact, it is clearly indicated in the claims and drawings that the monolith walls that make up the second chamber are sealed.

[0015] According to a first aspect of the present invention, there is provided a device as defined in claim 1.

[0016] Also described is a method of making a membrane, comprising: providing a support and adding a catalyst to the support.

[0017] The first reactant is activated by passing through the catalyst, during said passage, sufficient energy to react with the second reactant.

[0018] The energy given to the first reactant activates the first reactant molecules without forming ions such as O² [0019] The carrier is adapted to operate at temperatures above 250 ° C.

[0020] Preferably, the membrane initially comprises an inorganic, coarse, porous support. Most preferably, the membrane initially comprises a ceramic, coarse, porous support such as alpha alumina.

[0021] Preferably, the first coating changes the surface of the carrier, and more preferably, the first coating roughs the surface.

[0022] Preferably, the first coating selectively changes the size, and more preferably, the diameter and tortuosity of the pores. Preferably, the first coating is applied by immersing the carrier in a solution that may contain a coating solution, such as a metal oxide solution. In a preferred embodiment, the coating solution contains titanium dioxide (TiO2). Typically, the first coating is applied to the outer surface, which may be the outer cylindrical surface of the carrier.

[0023] The method comprises the step of applying a coating to the second surface of the support, the second surface being the inner surface of the support opening. The second coating comprises a jet controlling layer and is an inorganic porous layer. Preferably, the second coating comprises a gamma alumina layer. Preferably, the second coating is applied by immersing the coating in a solution that may contain a boiling solution.

[0024] In general, the method further comprises the steps of drying and heating / firing the carrier. Typically, the immersion - drying - firing sequence of the second coating may be repeated several times as required.

[0025] The method further includes the step of applying a catalyst to the surface of the membrane. Typically, the catalyst is applied to the pores of the inner membrane opening. Most preferably, the catalyst contains active rhodium. Alternatively, the catalyst may contain nickel. Preferably, the catalyst is applied on this surface by passing an osmotic solution on the first surface, which may be the first side of the membrane, and a cationic or anionic solution of the catalyst precursor on the second surface, which may be the second side of the membrane, so that the catalyst settles on the inner pores of the hole membrane. Preferably, the osmotic solution contains various electrolytes and non-electrolytes in aqueous solution at room temperature. More preferably, the osmotic solution comprises a sucrose solution.

[0026] Preferably, the method further comprises the step of heating the membrane to a relatively high temperature and may include a further step of passing hydrogen through the pores of the membrane so that firing occurs.

[0027] The carrier includes struts to increase the area of ​​the inner surface of the inner hole.

[0028] According to a second aspect of the present invention, there is provided a method for producing synthesis gas as defined in claim 1. 6.

[0029] Preferably, the membrane is a substantially annular cylinder, and more preferably, the first and second chambers are a substantially cylindrical cross-section. More preferably, the side wall of the membrane separates the first and second chambers, the second cylindrical chamber may be in the first cylindrical chamber.

[0030] Preferably, the second cylindrical chamber is defined by an inner opening in the membrane.

[0031] The first reaction substrate passes from the first chamber through the pores formed in the side wall of the membrane to the second chamber.

[0032] Preferably, the first reaction substrate is oxygen and the second reaction substrate is a hydrocarbon. More preferably the second reaction substrate is methane. Typically, the synthesis gas contains carbon monoxide and hydrogen.

[0033] Embodiments of the present invention will be described below by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-sectional view of a carrier of a membrane device in accordance with the present invention;

Fig. 2A is a cross-sectional view showing the carrier of Fig. 1 in more detail;

Fig. 2B is a front view of the carrier of Fig. 2A, showing "O" rings and cross-sectional shape of the carrier;

Fig. 3a is a schematic cross section showing the formation of layers in the membrane of the membrane device of Figs. 2A and 2B;

Fig. 3b is a further schematic cross-sectional view of the membrane device;

Fig. 4 is a synthesis gas temperature / ratio graph showing the optimal temperature needed to obtain the desired synthesis gas ratio;

Fig. 5 is a graph of the gas feed ratio / synthesis gas ratio showing the optimal gas feed ratio needed to obtain the desired synthesis gas ratio; and Fig. 6 is a graph of Vol.%. N 2 / conversion, showing the conversion of CH4 and O2 at 750 ° C;

Fig. 7 is a block diagram showing basic information about the Fischer-Tropsch technology of gas to liquid conversion;

Fig. 8a is a graph showing the effect of temperature on methane conversion rate;

Fig. 8b is a graph showing the effect of reaction temperature on methane conversion rate in fixed bed reactors and membrane reactors;

Fig. 9 is a graph showing the performance of reaction products at low methane conversion rates on a membrane device according to the present invention;

Fig. 10 is a graph showing the yield of various reaction products at high methane conversion rates by changing the constant temperature feed ratio;

Fig. 11 is a graph showing the yield of various reaction products by changing the temperature in a fixed feeding ratio;

Fig. 12 is a graph showing the selectivity of various reaction products in low methane conversion;

Fig. 13 is a graph showing the selectivity of various reaction products when changing the ratio of administration at a constant temperature;

Fig. 14 is a graph showing the selectivities of different reaction products when changing the temperature in a fixed feeding ratio;

Fig. 15 is a graph showing the yield of various reaction products in proportion to nitrogen when administering a nitrogen / oxygen mixture;

Fig. 16 is a graph showing the selectivity of reactions in various products relative to the percentage of nitrogen in the nitrogen / oxygen mixture administered.

Fig. 17 is a graph showing the yield of various reaction products relative to the percentage of carbon dioxide in methane feed; and

Fig. 18 is a graph showing the selectivity of various reaction products relative to the percentage of carbon dioxide in methane feed.

[0034] The membrane device 8, according to the present invention, shown in Fig. 1 comprises a tubular membrane 10 and an outer cylindrical shell 16. In this way two gas flow channels are formed, substantially sealed to each other. The first in the opening 14 of the membrane 10 and the second in the ring 22 between the membrane 10 and the jacket 16.

[0035] The inner opening 14 of the modified membrane 10 may have load-bearing struts 34 as shown in Fig. 2. They increase the structural strength of the modified membrane 10. During operation, the struts 34 also change the way oxygen flows through the sidewall 13 with the membrane 10, reducing the chance that the methane flowing through the inner opening 14 passes directly through the center of the modified inner opening membrane 10 without coming into contact with the surface of the modified membrane 10. The struts 34 also increase the internal surface area per unit volume of the modified membrane 10, and thus increase the possibility of activation, compared to a completely hollow cross section.

[0036] Referring to Fig. 3a, the modified membrane 10 consists of an α-alumina carrier 10, a TiO2 jacket 28 on the outer surface of the carrier 10 and a layer of γ-alumina on the inner side of the α-alumina carrier 10. The Rh particles of the catalyst 12 are embedded in the holes on the inner and outer surfaces of the side wall 13 of the modified membrane 10. [0037] Subsequent layers with increasing pore radii may be placed adjacent the layer 30 of γ-alumina and the layer 28 TiO2.

[0038] Preparation of the membrane 10 will now be described with reference to Figs. 2A, 2B and 3a-3b.

[0039] The process starts with an inorganic (preferably ceramic) coarse, porous carrier 10. Carriers of this type are currently widely available, many different companies currently supply these raw materials, the preferred carrier 10 consists of alpha alumina, a diameter pipe outer 10 mm and inner diameter 7 mm, usually with a pore size between 110 and 180 nm. Carrier 10 comprises a porous central portion 11, which is typically about 300 mm long, and two other non-porous portions 26 approximately 25 mm long at both ends of the membrane 10. End portions 26 are made non-porous by glazing with a sealant such as SiO2 -BaO-CaO at 1100 ° C.

[0040] The jacket 28 is then applied to the outer cylindrical surface of the carrier 10 by immersing the carrier 10 in a substance such as TiO2. This stage of dipping the jacket 28 roughs the outer cylindrical surface of the support 10 and increases the microporosity of the walls of the membrane catalyst 12. (During operation, the rough surface of the jacket 28 forces oxygen particles (not shown) to twist around the unevenness of the jacket 12 and serves to increase the mass transfer of the limiting reagent (oxygen) to the catalytic sites - which results in improved synthesis gas efficiency).

[0041] Next, on the inner surface of the inner carrier hole 14

10. an oxygen flow control layer 30 is applied. This layer 30 is inorganic to allow the membrane 10 to function at high temperatures and may contain a gamma aluminum layer derived from a 0.6 mol / L boon solution (AIO (OH)). The inner surface of the carrier 10 is exposed to a boiling solution by immersion for about 2 minutes. The carrier is then air dried overnight and then heated to 700 - 750 ° C at a rate of 1 ° C / min. To achieve the required thickness of the gamma alumina layer on the substrate 10, it may be necessary to repeat this immersion - drying - firing sequence up to three times.

[0042] The deposition of the catalysts 12 on the support 10 is achieved by means of an osmotic ion exchange process, which will now be described.

Catalyst deposition by osmotic ion exchange:

[0043] Catalyst 12 is produced by cation or anion exchange using RhNO3 or RhCl3.2H2O as precursors in an organic medium (0.2 g / L), respectively, due to the asymmetrical nature of this membrane, as shown in Fig. 3a (e.g. jacket 28 + support 10 + gamma alumina layer 30 (bemite) 30) various methods of introducing catalysts 12 onto support 10 are used. First, the osmosis process involves immersing the outer surface of the partially modified membrane 10 in a 6.0 molar sucrose solution, while the catalyst precursor solution (e.g., RhNO3 or RhCl3.2H2O) flows through the inner hole 14 in the partially modified membrane 10. This configuration is then inverted by immersing the outer surface of the partially modified membrane 10 in the catalyst precursor solution, and the osmotic (sucrose) solution is circulated in the inner hole 14 of the partially modified membrane 10. The membrane 10 is then washed with distilled water and then dried by blowing dry air either through the inner opening of the modified membrane 10 or over the entire outer cylindrical surface.

[0044] Then, firing (which involves heating the modified membrane 10 to a very high temperature followed by passing hydrogen through the modified membrane 10) is carried out at atmospheric pressure at 400 ° C for 2 hours. Metallic (active) Rh (catalyst 12) is obtained by reducing rhodium ions with hydrogen at 400 ° C for 2 hours.

[0045] At this point, the characteristics of the modified membrane 10 can be measured. Measurement can be performed by scanning electron microscopy (SEM) to show the degree of filling of the pore network of the modified membrane 10 and to assess the thickness of the gamma alumina layer 30.

[0046] Alternative materials can be selected. However, it is important that the selected materials have similar coefficients of thermal expansion as neighboring layers. If there is a difference in the thermal expansion coefficients of the active porous layers and the porous support layers, it is preferable to choose such materials as intermediate layers of the porous support having expansion coefficients that gradually change from the value approximate to the value of the active porous layer to the values ​​approximate to the value of the outer layer of the porous support . One way to achieve this is to prepare intermediate layers from a mixture of materials used to form the active porous layer, with the content of this material decreasing in subsequent porous support layers. For example, the porous support layer may contain 75% by weight of the material used to form the active porous layer.

[0047] The above discussion does not preclude the use of equal materials in the active porous layer and the porous support layer. This choice of material eliminates chemical incompatibility and problems of various thermal expansion, but usually involves a reduction in strength and an increase in the cost of the material.

[0048] The number of porous support layers depends on the pore radius of the adjacent active porous layer. It will range from one layer for the pore radius of the active porous layer selected from the upper end of the given range, to four layers for the pore radius selected from the lower limit of the specified range.

[0049] The surface area of ​​a material determines many of its physical and chemical properties, including water retention capacity and reactivity of nutrients and impurities. The BET surface area analyzer can be used to estimate the external specific surface area of ​​a solid by determining the amount of gas that is absorbed under controlled conditions. The BET surface area analyzer is typically used in the routine characterization of various membrane materials and their synthetic mineral analogues important in process engineering systems.

[0050] In the context of the present invention, to evaluate the pore size distribution in a modified membrane 10, and also to indicate the porosity value and pore volume. BET surface analysis by nitrogen adsorption was used. To confirm whether the modification of the membrane 10 forms a continuous gamma aluminum network and the extent of possible damage, X-ray Energy Dispersion Analysis (EDXA) is used. It also determines the elemental composition of the catalysts 12 its relative dispersion. X-ray photoelectron spectroscopy (XPS) is then used for chemical analysis of the modified membrane 10.

[0051] It is recognized that a partial oxidation of methane can occur through two different mechanisms, i.e. direct oxidation of partial or complete oxidation followed by reforming reactions.

[0052] Partial oxidation is required to convert methane to synthesis gas.

CH4 + O2 - CO + H₂ [0053] If complete oxidation would occur, the reaction products would be CO2 and H2O [0054] The operation of the modified membrane 10 in the membrane device 8 will be described below.

[0055] Into the outer hole 22, at one end No. ^ tK ^^ Lniain ^^ nbrr <nKw.eg ^, feed oxygen (O2) is introduced, and to the corresponding end of the inner hole 14 natural gas (which mainly contains methane (CH4)) power supply 20.

[0056] The oxygen partial pressure 18 is maintained at a higher level than that of methane 20, which causes the oxygen to pass through pores (not shown) in the modified membrane 10 from the outer hole 22 to the inner hole 14. By doing so, the oxygen molecules enter contact with the catalyst 12 present in the side wall 13 of the modified membrane 10, which activates oxygen molecules before contacting with methane present in the inner opening of the modified membrane 10. This activation gives the O2 molecules enough energy so that they can react at relatively low temperatures without forming oxygen ions.

[0057] When activated oxygen molecules come into contact with methane molecules, synthesis gas is formed immediately according to the following chemical reaction:

CH4 + O2 * => CO + H catalyst₂.

[0058] The synthesis gas produced leaves the membrane device 8 at the other end of the inner hole 14 due to the natural pressure difference caused by the methane source 20, so that a synthesis gas stream 24 is created. Pneumatic control of the oxygen source flow height 18 allows the use of different methane flow rates feed 20, because the increase in oxygen pressure will result in greater oxygen flow through the pores of the modified membrane 10.

[0059] Under operating conditions, the methane-containing gas stream flows past or through the impregnated catalyst layer 12. The gamma alumina layer 30 on the orifice side 14 increases the reaction between permeating oxygen and methane. Because oxygen molecules have to diffuse into the hole side 14 of the gamma alumina layer 30 and the adjacent porous layer, the gaseous environment of the gamma alumina layer 30 and in the vicinity of the hole is less reducing than in the outer porous layers. As a result, complete or partial oxidation will occur, with some reforming occurring as the gas moves away from the gamma alumina layer, respectively. It is preferred that the pores of the last layer of the porous support are coated with a reforming catalyst, such as Rh, to induce some endothermic reforming of the combustion products flowing through the porous support layer. This promotes the removal of heat from the exothermic oxidation reaction from the surface of the active porous layer.

[0060] The oxygen activity gradient in the porous layer will protect the gamma alumina layer from damage resulting from exposure to very low oxygen partial pressures, which allows greater freedom in the selection of materials for these layers.

[0061] The gas permeability of the modified membrane 10 can be measured by placing the end of the sample of the modified membrane 10 tightly to the ends of the outer shell of the tube 16, with a gasket between them formed by the O-rings 32. A gas connection (not shown) on the outer cylindrical shell 16 is attached to a source of constant pressure. The determined differential pressure used creates a stable gas flow in the side wall 13 of the membrane sample 10 and serves to measure the flow that is proportional to the gas permeability of the modified membrane 10.

[0062] Selectivity for many components can be obtained by measuring the concentration of the individual components in the feed and permeation gas, respectively.

[0063] To determine methane, O2, H2 and CO, reagents and products are analyzed using gas chromatography (GC), online, using 5 m 1/8 inch (3.18 mm) CO2 molecular sieve column will be analyzed using a separate Porapak QS column (RTM). A thermal conductivity detector is also used in this analysis. The resulting water is condensed in an ice trap, then removed, using a Drierite trap (RTM).

[0064] To calibrate the chromatograph, on one side of the modified membrane 10 (e.g. through the outer hole 22) multi-component gas mixtures containing a certain, certain composition of methane, hydrogen, carbon dioxide, carbon monoxide and oxygen were introduced, and the incoming and outgoing streams orifice 14 was analyzed using a thermal conductivity detector (TCD) gas chromatograph.

[0065] Other aspects tested in the membrane 10 tests include temperature performance (Fig. 4), methane flow rate (Fig. 5) and synthesis gas yield and selectivity (Figs. 4 and 6).

[0066] Figs. 9-18 show the various results obtained with such a device. In each case, the methane oxygen conversion values ​​and the yields of hydrogen and carbon monoxide are monitored.

[0067] To test the initial reaction products of the CH4 / O2 fed, the experiments were carried out at low methane conversion rates, and the products were analyzed as described above.

[0068] The feed oxygen flow rate was kept constant at 75ml / min, and the feed methane flow rate varied from 150 to 425ml / min, giving a range of total feed flows from 225 to 500ml / min. The higher overall feed flow rate reduces the contact time of the reactants with the catalyst, thereby reducing methane conversion.

[0069] It can be seen in Fig. 9 that with methane conversion above and below 15%, the CO2 yield increases significantly.

[0070] In contrast, the CO yield increases for conversions below 20%, has a slight decrease in conversion of about 16%, and then increases again. Average CO yield is the highest average yield of any product. The water yield has the same profile as for CO, but for methane conversion about 18% decreases again, deviating from the CO yield. Average water yield is the lowest average yield of any product. The hydrogen yield is a mirror image of the CO yield up to 16% methane conversion, increasing significantly for higher conversion rates.

[0071] In a second experiment, the oxygen feed flow rates varied from 15-75ml / min, while the methane flow was kept constant at 150ml / min, resulting in reactions with total flow rates from 165-225ml / min, as shown in Fig 10. The temperature was 1023.15K. The methane conversion decreases in proportion to the increase in total flow rate, i.e. with a decrease in contact time.

[0072] At higher methane conversion rates, meaning a longer contact time, CO2 efficiency continues to increase to 30% methane conversion, slightly decreases about 15% efficiency, and decreases significantly when methane conversion reaches about 50%. When the methane conversion is over 55%, an insignificant yield of 5% CO2 is found. Thus, the lowest CO2 efficiency occurs at methane conversion above 50%.

[0073] The CO yield will stabilize at around 15% for methane conversion higher than 20%. Water yield stabilizes at 5% for methane conversion from 20% to about 40%, water conversion to almost 10%, with methane conversion at about 50%, again drops to about 5% yield at 55% methane conversion. The hydrogen yield increases to about 18% for methane conversions from 30% to 50%, dropping to 0.16 for higher methane conversions.

[0074] Thus, the contact time (controlled by the feed rate) has no significant effect on the products obtained, but affects the methane conversion factor. An advantage of some embodiments of the present invention is that they can be used at low and high flow rates (giving long and short contact times, respectively), without affecting the resulting products. Longer contact promotes methane conversion and ensures high yields of hydrogen and carbon monoxide as well as a small amount of water and carbon dioxide, with methane conversion of around 50%.

[0075] To achieve this contact time, the total feed flow rate must be lower than 185ml / min for this catalyst load and temperature

1023.15K. Other embodiments of the invention may utilize different power flow rates.

[0076] It is recognized that a partial oxidation of methane can occur through two different mechanisms, ie direct partial oxidation or complete oxidation followed by reforming [3]. To clarify the catalytic mechanism of the membrane reactor used in the present invention, the effect of temperature on methane conversion and product yield was investigated. The results of this analysis are shown in Figs. 4 and 8a.

[0077] Fig. 8a shows the effect of temperature on methane conversion and product performance for a total feed flow rate of 165ml / min (150ml / min methane and 15ml / min oxygen). Fig. 8a shows that all oxygen is consumed. This happens before significant amounts of hydrogen and carbon monoxide are produced. Another important feature is that both methane conversion as well as water yield and hydrogen yield go through a maximum at 750 ° C. This behavior indicates that below 750 ° C, water, carbon monoxide and hydrogen are primary products, carbon dioxide is a parallel side reaction product as shown in Scheme 1.

tb

CH «+ O₌ CO + H_and + H₂ABOUT

<img file="PL1624949T3_D0001.tif" />

CO2

Scheme 1 [0078] Kinetic modeling has shown that the total reaction can also be described using parallel oxidation and full oxidation, according to scheme 1.

[0079] It is believed that above 750 ° C, the total oxidation reaction r2 with a significant increase in water and carbon dioxide will dominate. However, the study of Fig.

8a shows that the carbon dioxide yield shows only a slight increase above 750 ° C, while the yields for water and hydrogen fall above this temperature. This suggests that hydrogen, carbon dioxide and water are consumed according to scheme 2 below.

COj + HaO + H_and -► CH «+ CO

Scheme 2 [0080] Scheme 2 helps explain the decrease in water and hydrogen yield, a modest increase in CO2 yield, and a decrease in methane conversion above 750 ° C.

[0081] An important aspect in the subsequent conversion of synthesis gas to liquid via the Fischer-Tropsch reaction is the ratio of hydrogen: carbon monoxide. The ratio 2/1 is optimal for this transformation. From the analysis of Fig. 4 it can be seen that an optimum temperature of around 750 ° C results in a desired ratio of synthesis gas (H2 / CO) of 2.

[0082] The optimal methane to oxygen administration ratio shown in Fig. 5 is 10, although reasonable results that are relatively close to the desired ratio 2 are also obtained at administration ratios between 2 and 6.

[0083] Fig. 4 is a graph of H2 / CO over the temperature range tested. Optimal gas-liquid conversion is achieved at 750 ° C. Above this temperature, an indicator below 2.0 is obtained, while below 750 ° C, a value above 2.0 is obtained.

[0084] Selectivity is defined as the yields of a given component relative to the amount of methane converted, i.e.

Selectivity x = Capacity x / Conversion CH4 [0085] The selectivity for low and high methane conversion rates is shown in Figures 12 and 13. CO selectivity remains almost constant, with a value of about 0.9. This probably means no secondary reactions for CO with low methane conversion. The hydrogen selectivity decreases to a methane conversion level of 15% and then increases, reaching similar selectivity values ​​as CO.

[0086] The water selectivity profile is a mirror image of hydrogen selectivity, increasing for conversion to 15%, decreasing for higher conversion. For higher methane conversion values, the water selectivity is constant, indicating no secondary reaction to water formation.

[0087] The hydrogen selectivity decreases significantly for methane conversion to 50%, slightly increasing later.

[0088] The CO selectivity decreases to values ​​lower than the H2 selectivity for methane conversion to 45%, then remains the same, which means that with a methane conversion higher than 46%, no CO is formed in any secondary reaction.

[0089] CO2 selectivity decreases as methane conversion increases, it is the least selective gas formed in this reaction.

[0090] It is important to note that the above experimental data were made at different contact times that may affect the selectivity values. Values ​​for constant contact time but changed temperature are shown in Fig. 14.

Impact of variability in the composition of the fed composition on the reactor efficiency [0091] Figures 15 and 16 show efficiency and selectivity, with different amounts of nitrogen added to the fed oxygen. This affects the contact time of the reactants with the catalyst.

[0092] Fig. 15 shows that the CO yield decreases constantly with the addition of nitrogen in the plant. The hydrogen yield decreases to 50% of nitrogen in the oxygen supplied, and then remains constant.

[0093] The selectivity of carbon dioxide and water, as shown in the performance graph, does not depend on the addition of nitrogen in the system. However, the selectivity of carbon monoxide and hydrogen show a continuous decrease after the peak for about 50% vol. nitrogen.

[0094] Water and CO2 yield values ​​do not differ significantly when nitrogen is present or absent, although there is a slight increase in air composition (80% N2).

[0095] Fig. 6 also shows that even when 80% vol. Is administered N2 (and therefore 20% O2) at a temperature of 750 ° C, complete oxygen conversion occurs. The results show that embodiments of the present invention can operate using an air supply instead of supplying pure oxygen, thereby obstructing the need for an oxygen separation installation for this reaction. This clearly reduces both the initial input and operating costs of carrying out the reaction. Thus, an advantage of some embodiments of the invention is that they do not require air separation to produce a synthesis gas with an optimum ratio for further reaction to liquid hydrocarbons by means of a Fischer-Tropsch reaction.

[0096] Unlike nitrogen, the addition of CO2 does not affect the CO yield, but reduces the hydrogen yield while increasing the H2O yield. The results are shown in Figs. 17 and 18.

[0097] The CO and H2 selectivity decreases slightly with a higher proportion of hydrogen with the addition of CO2 in the methane feed.

[0098] Water selectivity is generally constant, but increases slightly for higher amounts of CO2 in the feed gases.

[0099] An advantage of some embodiments of the invention is that oxygen and methane are fed into the device separately, so there is no risk of explosion. Oxygen passes through the modified membrane 10, is activated and reacts when it comes into contact with methane. In this way, it is possible to lower the methane and oxygen ratio in the gas being fed to a ratio more suitable for their reaction. Such a ratio is generally considered to be explosive, but some embodiments of the present invention allow such proportions to be used, without the possibility of an explosion, partly due to the separate administration of oxygen / methane.

[0100] Embodiments of the present invention are advantageous due to the highly dispersed catalyst, which increases its surface and device efficiency.

[0101] Embodiments of the present invention are preferred because of the high degree of oxygen conversion. To illustrate the benefits of operating a membrane reactor in the production of synthesis gas, the effect of reaction temperature on methane conversion over an Ir catalyst was measured in a quartz flow reactor (350-10 mm) with a fixed bed at atmospheric pressure, using 60 mg catalyst, 25 ml / min O2 and temperature range 673-873K. At 873K, the yields of Ir and Rh are about the same. [4] [0102] Experimental data at 900.15 K was collected for the membrane system according to the present invention. Conversion values ​​obtained using a fixed bed flow reactor are significantly lower than those obtained in a membrane reactor due to equilibrium limitations. They have been overcome in a membrane reactor in which 100% oxygen conversion and a methane conversion rate of 41% are achieved. [0103] Because the modified membrane 10 contains catalysts 12 with a high degree of fragmentation, lower reaction temperatures are feasible, which reduces the tendency to coke formation and subsequent deactivation of the catalysts 12. Lack of coke formation optimizes catalyst consumption while maintaining high synthesis gas selectivity. During operation of the membrane device 8, additional catalysts (not shown) may be placed in the inner opening of the modified membrane 10, if necessary to further increase the reaction. These additional catalysts (not shown) are obtained by physically comminuting another sample of the modified membrane 10 to the appropriate particle size and placing these particles into samples for testing or for operation of the device.

[0104] Some embodiments of the present invention are used advantageously to generate hydrogen from, for example, methane. Hydrogen can be used as a fuel and not converted to larger hydrocarbons by Fischer-Tropsch reaction. Some embodiments of the invention are preferred because the partial oxidation method is exothermic and thus reduces energy consumption.

[0105] Some embodiments of the invention are preferred due to the fact that the process is characterized by rapid start-up.

[0106] This is in contrast to steam reforming, which in the production of synthesis gas shows a strongly endothermic reaction and a slow start-up time.

[0107] In this way, some embodiments of the invention provide a catalytic membrane reactor that has been developed and used to produce hydrogen, and especially synthesis gas, under various operating conditions, with total oxygen consumption. At lower feed charge ratios (CH4 / O2), the synthesis gas ratio is well above 2.0 while for higher CH4 / O2 ratios, the synthesis gas ratio is 2.0. Thus, depending on the application, the reactor is flexible enough to be used in the Fischer-Tropsch process to convert natural gas to liquid hydrocarbons. An optimum temperature of 750 ° C has been determined for the conversion of gas into liquids, at which the hydrogen / carbon monoxide ratio is 2.0.

[0108] Modifications and improvements can be made to the above solutions without departing from the scope of the present claims. E.g; [0109] Although the apparatus and method described relate to the production of synthesis gas from the reaction between methane and oxygen, a similar method and apparatus can be used in any light hydrocarbon reaction, e.g., alkane or alkene group members. In addition, the process and apparatus can be used in any reaction that contains two reagents, with restrictions that make it undesirable to mix them prior to the reaction, e.g., flame retardancy.

REFERENCES [0110]

1. 1. Gobina, E., The World Natural Gas Business, BCC, Inc., 2000.

2. 2. Gobina, E., Hydrogen as a Chemical Constituent and as an Energy Source, BCC, Inc. 2002.

3. 3. Prettre, M., C. Eichner, and M. Perrin, Trans. Faraday Society, 1946. 43: p. 335.

4. 4. Nakagawa, K., et al., Partial Oxidation of Methane to Synthesis Gas with Iridium-loaded Titania Catalyst. Chemistry Letters, 1996 p. 10291030.