Improved process for separating normal and isoparaffins

The present invention relates to a process for separating normal paraffins and isoparaffins from a feed stream, containing a mixture of normal paraffins, isoparaffins and aromatic hydrocarbons, to produce a current resulting from normal paraffins, with reduced concentration of aromatic hydrocarbons. as impurities.

Separation methods are known, in particular a method which refers to fixed bed countercurrent operations, commonly referred to as well as simultaneous fixed bed countercurrent operations. All methods refer to the countercurrent simulated in the processes of solid-liquid separation in which a component extracted from the feed stream is separated by selective absorption from a particular absorber and then is found, in a higher concentration, in the feed stream, as a product. separated. In each process there are various areas, representing quantities of the adsorbent material in which individual operations take place; at least three zones are used: an adsorption zone, a purification zone and a desorption zone. In the adsorption zone, the extracted material is adsorbed selectively and probably some of the impurities are adsorbed while the refined materials2 less selectively retained remain, generally, in the interstitial space surrounding the adsorbent. The basic operation that takes place in the purification zone of the adsorbed extracts present in the adsorbent is characterized by the fact that the adsorbent, passing through the purification zone, becomes more concentrated in the extract materials and less concentrated in the refined ones, and in the desorption zone, a desorbent material separates the distilled material adsorbed from the adsorbent.

Another method includes the same steps of the above basic process, but also includes an additional input of current into the purification zone, an input placed between the adsorption zone and the desorption zone. The input stream is a washing agent, a refined type compound (ie, a material that is relatively non-absorbent to an adsorbent) having such a boiling point that it allows distillation to be separated from the refined feed component, which is introduced into the process. to push the refined material found in the interstitial space between the adsorbent particles in the purification zone back into the adsorption zone, which prevents the refined material of hard food30 from passing through the absorption zone into zo70262

PRICE LEI 15.37 na purification and in the desorption area, thereby contaminating the extract product with refined feed material, in another embodiment, the process described above is used to separate the normal paraffins from isoparaffins.

Another process describes a process using the same steps of the basic process and a particular adsorbent for separating aromatic hydrocarbons, in particular aromatic Cs. In the process described, a purification stream comprising the extract material is passed into the purification area; the extract material may be taken either from a process stream output stream, or from the extract material that was separated from the sorbent material in the fraction stream of the extract stream. The purification stream, containing the extract material, moves from the interstitial space between the adsorbent particles any refined materials transported to the purification zone, removes the impurities from the adsorbed feed stream and reduces the amount of the desorbant that normally surrounds the adsorbent particles in the area where they do not purification current is used. In this process, a process for separating paraxylene from a feed stream is described, containing a mixture of aromatic C 1, using the steps of the basic process described above, a particular crystalline aluminosilicate adsorbent and two stages of desorption operation, in which the first desorbing current comes into contact with the adsorbent in the desorption zone, to influence the desorption of paraxylene from the adsorbent and a second desorbing current, which comes in contact with the adsorbent in the desorption zone, in order to push the desorbed paraxile from the interstitial spaces of the adsorbed particles; from the process is separated a current extract.

In another process, the process of separating the paraffin olefins is described, using the same steps of the basic process described above and a particular adsorbent, being again a two-step desorption operation. The process uses two desorbent materials, which enter the desorption area; the first desorbent material contacts the adsorbent in the desorption zone and determines the desorption of impurities in the adsorbent, while the second desorbent is used for the desorption of olefins from the adsorbent contained in the same desorption zone. Two extract streams are separated from the process, one extract current from the extract impurities and one output stream from the olefin extract.

Another process describes a process for the separation of paraffin olefins and uses the same steps of the basic process.

In this process a 4 sorbent material is allowed in two places in the desorption area and two extract streams, a stream of aromatic impurities and desorbent material and a stream of olefins extract, containing olefins and desorbent material.

Another process describes the process for the separation of aromatic hydrocarbons, which uses four work areas and includes the steps: passing an input stream with extract material through the purification zone to influence the desorption and moving the refined material, passing at least a portion of the refined output current, which exits the adsorption zone into the buffer zone, to influence the desorption and the passage of the current of refined entry into the adsorption zone for the displacement of the desorbant from the adsorption zone.

The process of separating normal paraffins and isoparaffins from a mixture of paraffins and aromatic hydrocarbons using a 5A zeolite adsorbent according to the invention removes the above disadvantages by the fact that at the adsorption temperature of 40. .. 250 ° C and pressure of 35.5 kgf / cm² the adsorbent is counter-current with a first desorbent material, chosen from benzene, toluene, ethylbenzene and xylene mixed with 5. . . 100^e/ n I will use a washing agent, isooctane, to carry out the selective adsorption of normal paraffins and a part of aromatic hydrocarbons, contacting the adsorbent with a second desorbent material, consisting of a mixture of pentane and isooctane, for elimination. normal paraffin wax.

An example of embodiment of the invention is given below, and in connection with the figure which represents a general scheme of the process, where an adsorption zone is delimited by the adsorbent located between the input supply current and the refined output current.

In this zone 1, the feed substance in contact with the adsorbent is adsorbed an extract component and a refined stream is discharged; because the main current through zone 1 is from the supply current entering zone 1 to the refined current coming from zone 1, the current in this zone 1 is considered to be the opposite of the input supply currents. Immediately upstream of the fluid flow in zone 1 is a purification zone 2, which is defined by the adsorbent between the output extract current and the input feed stream. The basic operations that take place in zone 2 are the removal of any refined substance from the non-selective empty space of the adsorbent transported in zone 2, by moving the adsorbent in this zone 2 and the desorption of any refined adsorbed substance.

70 362 in the volume with selective pores of the adsorbent or adsorbed on the surface of the adsorbent particles. The purification is accomplished by using a washing agent and a desorbent substance and in some cases, together with a part of the substance in the extract stream, which may contain both extract material and the second desorbent material from zone 3 to the zone 2 at the upper limit of zone 2 in the form of current output extract. The flow of the material in zone 2 is made downwards and in the opposite direction to the current of the extract extract. If we refer to the fluid flowing into zone 2, immediately above this zone is a desorption zone. 3, which is defined by the adsorbent between the desorption input and the extract current output. The function of the desorption zone is to allow the secondary desorbent substance, which passes through this zone 3, to dislocate the normal paraffins, which are adsorbed by the adsorbent during the previous contact with the feed current in the L · zone in a previous cycle of the operation, the flow. the fluid in zone 3 is made in the same direction as that of zones 1 and 2.

In some cases, an adaptation zone 4, defined by the adsorbent between the refined output current and the desorbent input current, can be used optionally, and if used it is placed immediately above the fluid flow in zone 3; zone 4 could be used to conserve the amount of desorbent, used in the desorption stage, if part of the refined current, which is displaced from zone 1, can be passed to zone 4 to move the desorbent material present in this zone 4; outside this zone 4 in the adsorption zone 1. Zone 4 contains sufficient adsorbent, so that the refined material, present in the refined current that comes out of zone 1 and passes into zone 4, can be prevented from passing into zone 3, thus counting the extracted current from the zone.

3. In cases where the fourth working area is not used, the refined current passed from zone 1 to zone 4 must be carefully directed so that the direct flow from zone 1 to zone 3 can be stopped when there is a sufficient amount of refined material present in the refined current passing from zone 1 to zone 3, so that the output stream is not contaminated.

Both working phases, liquid and vapor, can be used in the process of the present invention; otherwise, the liquid working phase is preferred, due to the lower temperatures and slightly improved selectivity. The adsorption conditions include a temperature range from 40 to 250 ° C and a range of pressures from atmospheric pressure to 35 at. The conditions of the first and second desorption include the same temperature and pressure ranges as those used for the first desorption.

In the figure, the four zones are with stationary beds of the adsorbent particles but may, in other cases, consist of series of one or more rooms connected in series; each of the zones, taken individually, can be a room or a series of bunk beds in a column, thus re-creating an area; In some cases, each of the above areas contains the same amount of adsorbent and has the same physical size, and in other cases, some areas may require more adsorbent than others. The net fluid flow moves upward, but in some cases, an area may operate so as to allow fluid flow, for a certain period, in the opposite direction to the net fluid flow. The current of the adsorbent particles can be considered downstream, to simplify the process steps. During fixed bed countercurrent operations, the adsorbent material remains stationary in the individual adsorption area 1, the purification zone 2, the desorption zone 3 and the adaptation zone 4 are displaced by the adsorbent, by blocking the various inputs and outputs of the unidirectional currents, to allow the fluid to flow. flow in the direction of the counter current to the solid adsorbent and to continuously produce refined and extracted current. In most cases, blocking the inputs and outputs of currents along the fixed bed of the adsorbent is done simultaneously and at the same distance along the fixed bed; In other cases, it is desirable for two or more zonal functions to take place in the adsorbent between the input and output currents, before these currents are cut off. Some connecting pipes 5, 6, 7, 8 and 9 ensure the connection of the beds and some input currents 10, 11, 12 and output 13 and 14 supply the zones. The adsorption zone 1 is the adsorbent material placed between the input supply current 10 and the refined output current 13, which is connected to zone 1, by line 6; purification zone 2 is located immediately above the adsorption zone 1, at the common boundary with the adsorption zone 1; the purification zone 2 is located by the adsorbent between the output stream 14 and the feed stream 10, immediately above the purification zone 2 there is the desorption zone 3, which divides the output stream 14 extract at the common boundary with the purification zone 2. desorption 3 is the adsorbent between the output extract current 14 and the input desorbent current 12. Immediately above the desorption zone 3 is the optional adaptation zone 4, which divides the desorbent input current 12 at the common limit with the desorption zone 3, and the refined output current r

at the common boundary with purification zone 2; additional zone 4 is located in the adsorbent between the input desorbent current 12 and the refined output current 13. In some cases, zone 4 is used to prevent contamination of the extracted material by the refined material in zone 1. The end zones 1 and 4 are connected by the connecting pipes 5 and 6, which allow a part of the fluid to flow out of zone 1, through line 5, into zone 4 or zone 3, depending on whether or not the optional zone 4 has been used, or through line 6. allowing a closed loop flow of the fluid. Lines 7, 8 and 9 are other connecting pipes between zones 1 and 2, zones 2 and 3 and zones 3 and 4, to allow continuous flow of fluid from one area into and through the other zones. In particular, the material leaving the adsorption zone 1 through line 6 may pass into line 13 or a portion thereof may be passed through line 6 into area 4. The feed material entering the process through line 10 passes through the connecting pipe. 7 in the adsorption zone 1. In certain cases, a portion of the fluid material leaving the purification zone 2 through line 7 may be mixed with the feed material entering the process through line 10; line 8 is a connecting pipe which, in certain cases, allows a part of the fluid material removed from the desorption zone 3 through line 8 to be diverted into the purification zone 2 by a derivation made by line 8 of line 14. Similarly, line 9 connects the adaptation zone 4 with the desorption zone 3 and a part of the liquid material, which leaves the area% comes into contact with the material entering the process through line 12 of the input desorbent current and to mix with the desorbent. through line 9 in the desorption zone 3, which leads to a reduction of the adsorbent needs in the process from external sources, that is to say it reduces the input current 12. Line 5 may contain a pump or other means of moving the fluid, to initiate and maintain the process flow in a direction from line 6, through line 5, in zone 4. Other pumps or valves attached to the inlets or outlets of lines and lines which connect different areas that control the flow at the entrance, the exit and through the process are not figured: they can be mounted wherever their presence is required.

Input currents passing through various work areas can be connected to high pressure sources or pumping means to induce flow in the process, and the outgoing currents can be regulated by pressure valves, fitted to the outlet to maintain leakage. required pressure. In some cases, unidirectional flow control systems8 can be used on pipes between areas where there is no pumping circuit.

The main operations that take place in zone 1 are; the contact of the adsorbent material and the feed current and the adsorption of a component extract into the selective porous volume of the adsorbent and the adsorption of small quantities of refined component on the surface of the adsorbent particles. In this separation process, the extract component is the normal paraffin, and the refined component that remains attached to the surface of the adsorbent is the aromatic hydrocarbon, in the previous processes these aromatics adsorbed to the surface appear, finally, with impurities in the extract stream. The feed current enters the process through line 10 and, if the general direction of the fluid flow in this area is up, it passes through line 7, along with other materials that can exit from zone 2 through line 7, into zone 1. When the supply current is passed in zone 1, an equal volume of refined material is moved from zone 1 through line 4; some or all of the refined current passing through line 6 can be transported through line 13, and the rest that are not transported in process pass through line 10 in area 3 or 4. The refined output current 13 can be directed to separation circuits, not shown , for separating refined components from desorbent materials. The adsorbent in zone 1 can be considered as passing in the direction of the counter-current of the fluid flow, there is a simulated flow of solids to and from the adsorption zone, when the zones are displaced during a stage of the operating cycle, the adsorbent enters zone 1 and from zones 3 and 4. If zone 4 is not used, then the adsorbent contains desorbent material, present in both the non-selective porous volume and the selective porous volume. In cases where zone 4 is used, then a portion of the refined current may be passed through line 5 in zone 4, to move the desorbent material from the non-selective voids between the adsorbent particles in zone 4, in zone 3, through line 9. The adsorbent then passing from zone 4 to adsorption zone 1 contains, for the most part, desorbent material fixed in the selective porous volume between the particles of the adsorbent which is required by the extract material to be desorbed in zone 1. It is possible to remain desorbent material transported from the selective porous volume, by contacting the adsorbent with a high purity desorbent material, before the adsorbent comes into contact with the feed current at the top of the adsorption zone 1. This characteristic is followed In many systems, because the absence of sorbent in the adsorption zone was found to increase the adsorbent's ability to selectively adsorb and retain the extract. The adsorbent, passing through the adsorption zone 1, from the lower limit of the current to the upper limit relative to the flow of fluid through this area, absorbs extract material from the input feed material; when the adsorbent exits the adsorption zone, it contains extract material and some refined material from the selective porous volume of the adsorbent and some refined material adsorbed on the surface of the particles of the adsorbent material. The material from the non-selective porous volume of the adsorbent is generally a refined material with small amounts of extract material from the feedstock that has not been adsorbed by the adsorbent.

The adsorbent passes into the purification zone 2 and, since it contains refined material from the non-selective porous volume of the adsorbent and adsorbed on the surface of the adsorbent particles, the function of zone 2 is to remove the refined material from the selective volume of the adsorbent and from the surface of the adsorbent particles, such as the adsorbent to leave purification zone 2 at the upper limit, line 14. containing as little refined material as possible it could contaminate the extract stream. These functions are performed in zone 2 of the different nodes; first, a part of the extract stream, a mixture of desorbent and extract material passes into purification zone 2 of zone 3, through line 8, and moves the refined material from the selective porous volume of the adsorbent and removes the refined material from the non-selective porous volume of the adsorbent in upstream in the upstream stream to the refined outlet stream 13. To the purification zone line 11 is connected, through which a mixture containing a washing agent of refined type and primary desorbent material flows; the washing agent completes the washing action of the part of the extract stream which flows in zone 2 of zone 3, through line 5. The washing agent may also allow the transport of the refined feed material from the adsorbent, by reducing the amount of extract current flowing in zone 2; a reduction of the desorbent material, contained as part of the extract stream entering zone 2, increases the adsorbent's ability to adsorb the last traces of extract material from the fluid surrounding the adsorbent in the purification zone. The washing agent, being a refined non-absorbent material, does not increase the load on the adsorbent in zone 1 of the cycle and does not reduce the adsorbent's capacity for adsorption of fresh extract material entering zone 1, through line 6, as is the case with the flow of material10 of the extract. from zone 3 to zone 2, through line 5. The reasonable speeds of the washing agent or of the extract stream only carry relatively small quantities of refined material, which is strongly adsorbed on the surface of the adsorbent particles. While the volume of aromatic hydrocarbons comes out of the process as part of the refined output stream through line 13, a small portion of these aromatics are adsorbed by the adsorbent particles in zone 1, pass with the adsorbent in zone 2, and are adsorbed by the desorbent material in the zone. 3 and appear as impurities in the stream extracting from the process through line 14. For this reason, a first desorbent material mixed with the washing agent is introduced in zone 2, by line 11, by contacting, in zone 2, the adsorbent with the first desorbent material, the aromatic impurities adsorbed on the surface are desorbed from the particles of the adsorbent and pass, with the aid of the washing agent and a portion of the extract current entering zone 2, through line 8, down, through area 2, to the refined output current 5. The first desorbent material is chosen for the desorption of aromatic impurities and not for the desorption of normal paraffin extract material; thus, the adsorbent leaving the process from zone 2 and entering zone 3 contains normal paraffins in the selective porous volume and a very low concentration of aromatic impurities on the surface of the adsorbent particles, although line 11 can be placed anywhere along the adsorbent material. from zone 2, from line 14 of the current output extract, located in the upper part to the line 10 of the supply current, placed in the lower part, it is preferable that line 11 be placed as close to line 14 as possible so that the washing agent and the first desorbent material can flow through most of zone 2. It is possible to adjust the fluid flow through zone 2 by controlling the amount of material entering zone 2 through line 11, material then entering zone 3, through line 8 and the amount of material exiting through the upper part of zone 2 through line 7. The adsorbent leaving the purification zone 2 passes into the desorption zone 3, through the lower edge of the stream 14.

The operation that takes place in the desorption zone 3 consists in the separation of the normal paraffins from the adsorbent, an operation that is carried out by putting in contact the adsorbent, which is now released by the aromas adsorbed to the surface, with a second desorbent material, able to dislodge the paraffins. normal from the selective porous volume of the adsorbent. The input desorbent current, which contains the second desorbent material, passes into the desorption zone 3 through the upper part of the area through lines 12 and 9. At least a portion of the normal desorbed paraffin exits zone 3 in combination with at least the second desorbent material through line 14 of the current extract extract 14; current extract 14 passes through the washing facility, not shown, where the normal paraffins will be separated from the desorbent material, the adsorbent leaving the desorption zone 3 contains desorbent material in the selective porous volume, as in the non-selective one, and passes into the optional zone 4 through the part upper of zone 4, through line 12 of the input desorbent current.

Adaptation zone 4 can be used in this process both to conserve the amount of desorbent used in the process, as well as to prevent contamination of the extract material with the components of the refined material. When working area 4 is used, it is possible that a portion of the refined current exiting through line 13 will be passed into area 4 through lines 5 and 6 to move the desorbent material from the non-selective void space of the adsorbent particles into the area 4, while, simultaneously, the desorbent material is pushed out of zone 4, through line 9, into zone 3. When the desorbent material, which enters the process through line 12, is connected to the pipe 9, which connects the optional zone 4 with the desorption zone 3, the desorbent material which is moved from the adsorbent in zone 4 tends to reduce the demand for desorbent material, which penetrates through line 12 in the process. The solid adsorbent, which leaves area 4 through line 13 of the refined output current, contains, in particular, desorbent material in the selective porous volume and refined material present in the non-selective void space of the adsorbent. In cases where adaptation zone 4 is not used, it is possible to pass a refined part of the current from zone 1, directly to zone 3; it is necessary that the composition of the material which leaves area 1 through line 6 and which passes over line 13 contains mainly refined material. The refined material initially withdrawn from zone 1 contains a high concentration of desorbent material and can be passed through lines 5 and 6 in zone 3. The refined output current flow, which leaves the process through line 13, can be stopped at this time; when the current passing through lines 5 and 6 in zone 3 contains an appreciable amount of refined material, the flow in zone 3, through line 5, is stopped and the refined output current is withdrawn through line 13. while the refined materials are withdrawn through line 13, desorbent material from an outer race may be introduced, through lines 5 and 6, in zone 3,

Input and output lines 13, 10, 11, 14 and 12, during normal operations, carry the respective currents, in order to ensure continuous operation, it is necessary that the individual input and output currents each move in the same direction and , multiple cases, simultaneously. Depending on the incoming and outgoing currents through the adsorbent bed, together with the need for the end zones to be connected, it is possible to continuously influence the individual operations that take place in different areas. When the mentioned areas have been moved with incremental quantities through the stationary adsorbent material, the adsorbent comes into contact with the areas in order of presentation. A cyclical advancement of the input and output currents can be achieved through the fixed bed of adsorbent, by using a distributor system, in which the distributor valves work sequentially, to achieve the movement of the input and output currents in the same direction as the flow. of the fluid, through the bed of the adsorbent, which allows the fluid to flow counter-current to the solid adsorbent.

Another mode of operation that can influence the solid desorbent counter current to the fluid involves the use of a rotary disc valve, in which the inlet and outlet currents are connected to the valve, and the lines of the feed, extract, sorbent, purification and refined lines are directing? in the same direction through the adsorbent bed. Both the distributor variant and the disc valve variant are known in the art.

Some processes describe a type of rotary disc connection, in which the proper advance of the various current inputs and outputs from fixed sources can be smoothed without difficulty.

In many cases, a work area contains too much adsorbent compared to other work areas; for example, in some operations, the buffer zone may contain a small amount of adsorbent compared to the amount required for adsorption and purification areas. It can also be observed that in cases where the desorbent is used for desorption of the extract material from the desorbent, a small amount of adsorbent is required in the desorption zone as compared to the desorbent required in the buffer zone, or in the adsorption zone or in the zone. or in any of them. Since the adsorbent is not required to be placed in a single column, the use of multiple chambers or a series of columns is an object of the invention.

It is not necessary for all input and output currents to be used simultaneously, and in fact, in many cases, some currents may be blocked, while others influence the input and output of the material. The installation used to carry out the invention may also contain several series of individual beds, connected in series by connecting pipes and having mounted on these connecting pipes taps. who can attach it to -.different; currents described above_F alternatively or, periodically removed; from the process to achieve continuous operation. Im in some cases, pipes, connection can be connected to taps. transfer which, during normal operations, does not function as a conduit through which the material enters or exits the process. It has been designed that the current of the output extract and the refined output should. it may pass into different separation means so that the extracted and refined components can be separated from the desorbent materials present in said output streams. The preferred separation means for the separation of currents are the fractionation columns, but also may include solvent extraction means or adsorption separation means.

The size of the plant that realizes the invention can vary from the size of the pilot plant to that of an industrial project, and the flow rate is in the range from a few cm.³ per hour to several thousand, liters per hour.

Another embodiment of the invention does not denote the optimum for the operating conditions, such as temperature, pressure or type of desorbent used. In this example, it is operated with a method with a mobile bed simultaneously in the countercurrent, for separating the normal paraffins with and without the use of the material, desorbent, in various concentrations, in addition to the washing agent, for; determine the effect on the concentrations of aromatics in the normal paraffin product. The installation used in this variant consists of a column with 24 individual beds of adsorbent, connected in series by pipes. The beds contain transfer valves, to which are transferred transfer lines that allow either the entry or exit of the process, according to a predetermined cycle of operations. The installation contains four separate work areas, although the process can be carried out with only three distinct work areas; However, it is not desirable to use three work areas, as this requires modifications to the available installation. in relation to the figure. tracking down from refined output current 13 in zone 1. there are four beds; the refined output current 13 and the input desorbing current, which is the lower limit of zone 1, are the only input and output currents in zone 1. Then, from this downward current to the area are six adsorbent beds, without any other input or output current in the area

2, with the exception of the input desorbent current and the output extract, which define the lower boundary of zone 2. Below .. there are a total of eight adsorbent beds in the purification zone 3; line 3 is an 'adsorbent' bed lower than the extract stream 14 and .in which it participates * in the process-washing agent in addads with the first Desorbent Material. Underneath the line^f there are adsorbent beds,¹ with d drainage outlet, not figured, passing through * zone 3 at the lower limit of the six beds. The bed left in the '$ zone is placed below the wash line and immediately above the lower boundary of the area

3, which is the current of. feed 10. The role of the wash current is to remove the feed components from the line through which the feed passes after current 10 has been moved to its new down position; this prevents contamination of the extract current with the refined current during the following purification operations, when this washing line carries the purification material. Below line 10 are six adsorbent beds in bed 4, the new power supply lines 10 and the refined output power line 13 are the current streams in area 4. Zone # "?! <and 4 are at the opposite ends of the installation were 24 adsorbent beds and are connected 'through a pipe: 13, which is provided with a pump for introducing the material flow In this line the same' direction 'with the supply current. 10; Pipe 13 and pump represent ^ a closed pumping circuit which, in this embodiment,^; it is necessary to introduce the entire fluid flow into the process. Isn't it absolutely necessary for a pumping circuit to be? used, but by accurately measuring the pressure drop along the various inlet and outlet streams, connected to the adsorbent beds, and mounting the flow orientation devices such as control valves, in the connecting pipes of the individual adsorbent beds, is introduced the same fluid flow.

For continuous operation with a mobile bed at the same time it is necessary that. after a period of flow in the process, all the incoming and outgoing currents are transferred at least one adsorbent bed down at the same time; moving the input and output currents from one or more beds downwards is a single stage of the entire cycle of operations. The complete cycle of operations takes place when a sufficient period of operations has taken place in order to place the input and output currents in the initial position at which the cycle of operations began. In all the experiences of this embodiment, the total cycle of operations through the 24 beds, adsorbents and back to the initial position of the currents was 1.1 h, which increased by 2.75 min of flow for each individual period of operations of the 24 total operations that constitute the complete cycle. The complete installation contains 51.3 1 molecular sieves, 54 as adsorbent; the sieves contain about 5.1 1 of selective porous volume and about 30.5 1 of non-selective void volume and have a particle size distribution of about 16 + 40 eyepieces. The feedstock was from Cio - CX hydrocarbon fractions, the composition being shown in table 1.

Table 1

The composition of the feed material

Weight%

<td>n · -Cio</td><td> 2.8</td>

<td>n_C "</td><td> 9.2</td>

<td>N-CH</td><td> 10.3</td>

<td>N-CN</td><td> 10.7</td>

<td>n-C '</td><td> 6,3</td>

<td>N-C15</td><td> 2.8</td>

<td>ⁿC10</td><td> 0.6</td>

<td>n-C₁₇</td><td> 0.1</td>

<td>Total n-paraffin</td><td> 42,7</td>

<td>Volume%</td><td></td>

<td>aromatic </td><td> 7.8</td>

<td>olefin</td><td> 0.0</td>

<td>Paraffin + me</td><td> 92,2</td>

<td> ' . · · ·</td><td> 100.0</td>

The first desorbent material was mixed with the washing agent, isooctaniil; the first desorbent material was loaded in zone 3 in combination with the washing agent dc (at various concentrations). The second desorbent material was pentane, cures loaded in zone 2 in combination with isooctane; a mixture of 50 / .50% volume of normal pentane and ΐ&gt; octane was used. All experiments were carried out at approximately 175 ° C and at a pressure of dc 2 109 kgf / cm². When controlling the operating conditions for various experiences, an important factor was the reflux ratio that appears in different work areas. The reflux ratio in the given area is defined as the liquid flow through the area, from which the non-selective volume of adsorbent passing through the area is subtracted, divided by the volume of the selective pores of adsorbent that crosses the area.

AVO, the non-selective void of adsorbent that runs through the area. In cases where the reflux ratio is a positive number, the net fluid flow in the given area exceeds the non-selective volume of adsorbent entering the area, which allows the liquid flowing into the area to purify any liquid driven by the non-selective volume of adsorbent. In cases where the reflux ratio is a negative number, the amount of liquid present in the non-selective volume of adsorbent passing through the area exceeds the flow rate of the liquid in that area; this means that the liquid captured by the sorbent ad15 in the non-selective voids is not completely eliminated from the adsorbent prior to its passage through the zone. The reflux ratio of the zones of the realized variants was positive, so that, in each zone, there is sufficient liquid from an input current or from the material derived from an output current from an area immediately above the given area, to wash the adsorbent.

2? Four experiments were performed to prove the low concentration of aromatics in the extract product; the results of the four experiences, together with the basic working conditions required to reproduce them, are shown in Table 2.

Table 2

The results of the experiences

<td>The experience</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td>

<td>High current flows utate / h, 16 ° C Power supply</td><td> 1,67</td><td> 1.62</td><td> 1.66</td><td> 1,74</td>

<td>⁴⁰ First desorbent + a- wash bag in sauce 2</td><td> 1,52</td><td> 1,52</td><td> 1,54</td><td> 1,54</td>

<td>The second desorbent ¹isooctane in zone 3</td><td> 8.16</td><td> 8,29</td><td> 8,10</td><td> 8,23</td>

<td>₄_ Reflux reports Zone 2</td><td> 112,5</td><td> 115,2</td><td> 114,8</td><td> 114,7</td>

<td>Zone 4</td><td> 49,1</td><td> 50,0</td><td> 49,8</td><td> 49,8</td>

<td>Xylene percentage in the first desorbent + washing agent</td><td> 0</td><td> 8</td><td> 26</td><td> 44</td>

<td>50 Percent n-paraffin in the extract product</td><td colspan="2"> +99 +99 4</td><td> -99</td><td> 4-99</td>

<td>Net aromatics in the extract product, ppm weight</td><td> 1400</td><td> 1200</td><td> 100</td><td> 100</td>

<td>Extraction efficiency</td><td> 96,0</td><td> 94,5</td><td> 93,5</td><td> 91,5</td>

Reflux report

Fluid flow The non-selective void volume through the adsorbent zone ~ passing through the zone

The volume of selective adsorbent pores passing through the area

Therefore, it can be seen that, in cases where the reflux ratio is zero, the fluid flow through the area is equal to vo. The extraction efficiency is defined as the ratio between the extract material from the extract current and the total extract material

70 162 • from the refined current and the extracted current. For experience 1 the first desorbent material (xylene mixture) was not used, but only the isooctane washing agent in zone 3, the concentration of aromatics in the extract product was 1,400 ppm weight for experience 1. For the other experiences, the mixture of the first desorbent material with the washing agent contains, respectively, 8.26 and 44 ° / o of xylene in the mixture and produces the concentrations of sprays in the extract product, respectively, d £ 1 201), 100 and 100 ppm. weight, thus demonstrating the advantage of the method. Concentrations of aromatics lower than 100 ppm weight may not be quantified more precisely due to the lack of an analytical technique in the low ppm domain. The efficiency of the extraction was affected by the use of a first desorbent material in zone 3, by decreasing the efficiency dc to 96 ° / o in the first experience to 91.5 * 7o in the fourth experience, where 44'Vo xylene was used. Apparently, this is due to the selectivity of the sieve adsorbe nt o

Molecular 5A compared to xylene, the xylenes being adsorbed to the surface, the inner mesh network remaining partially blocked for desorption of the normal paraffin resulting in a decrease in product recovery.

The process according to the invention brings about an improvement in the separation of normal paraffins from a stream containing normal paraffins, isoparaffins and aromatic hydrocarbons. The process uses a countercurrent process scheme with simulated mobile bed, in which at least three zones are modified by means of the mass of the desorbent, to allow the various portions of the mass of the adsorbent to function as adsorption, purification and desorption zones. The improvement consists in the use of two steps for the desorption operation in which 1) a first desorbing material comes into contact with the adsorbent containing paraffins and aromatics normally adsorbed in the purification area and desorption of the aromatics; 2) a second desorbent material comes into contact with the adsorbent which contains paraffins normally adsorbed in the desorption area and makes the desorption of normal paraffins. This improvement results in normal paraffin being obtained, containing small amounts of aromatic hydrocarbons as impurities.

Prior to the present invention, different methods of pretreatment have been used.the feed current or posttreatment of the paraffin product, normal, or both, to completely or partially remove the aromatic impurities. Such methods have. including acid washing and wastewater processes. - The process according to the invention removes the disadvantage of the previous methods by the fact that the concentration of the aromatic purities in the normal paraffin product can be reduced even in the process of separating the normal paraffin, thus eliminating the need to pretreat the feed current or to postpone the product or at least the intensity of some such treatments. The invention has applicability if normal paraffins are to be used as pure materials for the biochemical production of proteins intended for human or animal consumption and where, in addition, aromatic impurities are prohibited.

The process according to the invention provides a process for separating normal paraffin, in which the concentration of aromatic impurities in the feed stream can be reduced in the current resulting from normal paraffin, using a first desorbent material to extract only the aromatic impurities from the surface of the adsorbent before contacting the adsorbent with the second desorbent material for desorption of normal adsorbed paraffin. The normal paraffin product is recovered as a product of high purity and with low concentration of aromatic hydrocarbon impurities. The process, according to the invention, in short, is an improved process for separating normal paraffins from a feed stream, which contains a mixture of normal paraffins and isoparaffins, together with impurities of aromatic hydrocarbons, a process in which an adsorbent comprising zeolite is used. for the selection of the form and consists of the following steps: a) contacting the adsorbent with the current, under the adsorption conditions, to influence the selective adsorption of the normal paraffins and part of the aromatic hydrocarbon impurities by the adsorbent; b) separation of a refined current, comprising less selectively adsorbed isoparaffins from the adsorbent: c) contacting the adsorbent with a desorbent material, under desorption conditions, to influence the desorption of normal paraffins from the adsorbent; d) extraction from the adsorbent of a normal paraffin extract; e) the passage of at least part of the extract current and there the separation, under the conditions of separation of the normal paraffins from the desorbent material, an improvement consisting of the use of two stages in the desorption operation, which, in turn, comprises the steps: I) contacting, under the conditions of the first desorption of the adsorbent with a first desorbent material, to influence the desorption of the impurities of aromatic hydrocarbons in the feed stream; II) extraction from the adsorbent of a first stream extract, as it comprises impurities of aromatic hydrocarbons * which from the feed mixture and desorbent material from the first desorption; III) putting in

702 162 contact, under the conditions of the second desorption, of the adsorbent with the second desorbent material, to influence the desorption of normal paraffins; IV) extraction from the adsorbent of the second stream extract, comprising normal paraffins and desorbent material from the second desorption; V) passing at least part of the second stream extracted by a separation means and there, under the separation conditions, the separation of normal paraffins from the second desorbent material.

In another embodiment, the present invention is an improvement of the process of separating normal paraffins, isoparaffins and aromatic hydrocarbons, a process that uses a shape-selection zeolite and is carried out in the following steps;

a) maintaining the net flow of fluid from a single direction, through an adsorbent column, a column comprising at least three zones with special working functions, being interconnected with the terminal areas of the column, to provide for a continuous connection of the mentioned areas ;

b) maintaining an adsorption zone in the column, an area delimited by the adsorbent located between the power input at the upper limit of the current and the refined output at the lower limit of the zone; c) maintaining a purification zone immediately above the adsorption zone, a purification zone delimited by the adsorbent placed between the output of the extract current at the upper limit of the purification zone and the input of the feed current at the lower limit of the zone, the purification zone having an input current with a washing agent located above the input supply current; d) maintaining a desorption zone immediately above the purification zone, a desorption zone defined by the adsorbent placed between the input sorbent current at the upper boundary of the zone and the outlet extract current at the lower part of the zone; e) passing the feed current through the adsorption zone, under the adsorption conditions, in order to influence the selective adsorption of the normal paraffins and the aromatics by the adsorbent and the separation of the refined current comprising isoparaffins from the area; f) passing a desorbent input current into the desorption zone, under desorption conditions, to perform normal paraffin removal from the area desorbant and separating a current extract extract containing normal paraffin and desorbent material from the area; g) the passage of at least part of the extracted output current through the separation plant and, here, the separation, under the conditions of separation, of the normal paraffins from the desorbent material; h) introducing a washing agent into the purification area;

i) periodically advancing, through the adsorbent column in a direction opposite to the liquid current in the adsorption area of ​​the input feed current, the refined output current, the output extract current, the input desorbent current, to achieve the displacement areas by adsorbent and obtaining extract and refined output currents, where the improvement, consisting of a two-step desorption operation, involves the steps:

I) the passage into the purification zone, in mixing with the washing agent, of a first desorbent material and, therefore, desorbing, in the first desorption conditions, the aromatics of the desorbent; II) extraction from the adsorption area of ​​a refined current, containing feed isoparaffins and aromatic hydrocarbons; III) the passage into the desorption zone of a second desorbent material and, therefore, the desorption, under the second desorption conditions of the normal paraffins in the adsorbent; IV) removal of a stream extract containing normal paraffins and desorbent material from the desorption area; V) the passage of at least part of the extract current through a separation plant and, therefore, separation, under the conditions of separation, of the normal paraffins of the second desorbent material.

Although it is possible by the process of this invention to obtain normal high-purity paraffins (+ 99 ° / o) with very good recoveries (90% or more), it is appreciated that an extract component is never completely adsorbed by an adsorbent nor a refined component is not completely adsorbed by an adsorbent. Therefore, small quantities of the refined component may appear in the extract stream, as well as small quantities of the extract component may appear in the refined stream. The extract and refined currents are then separated from each other by the feed mixture, by the proportion of the concentration of an extract component and of a refined component appearing in the particular current. More specifically, the ratio of the concentration of normal paraffins adsorbed more selectively to the proportion of isoparaffins less adsorbed is lower in the refined current, higher in the feed mixture and higher in the extract stream. Also. the ratio between the concentration of isoparaffins adsorbed less selectively and the concentration of normal paraffins adsorbed more selectively is highest in the refined current, slightly more in the feed mixture and the lowest in the extract current. In a variant of the process presented, there are two streams extract, one containing aromatic ^ dc desorbed food, the first desorbing material and not at all normal paraffins and the second stream containing normal paraffins, desorbant material and a low concentration of aromatic feed.

In another embodiment of the process, there is a stream extract containing normal paraffins, secondary desorbent material and a reduced concentration of feed aromatics, almost all feed aromatics, together with feed isoparaffins and the first desorbent material appear in the refined stream, in particular , in this embodiment, the composition of the extract stream may vary from 100% desorbent material to 100% eomponent extract.

When the adsorbent passes into the working area, its non-selective porous volume and its selective porous volume transport the fluid to this area. The non-selective porous volume is used to determine the amount of fluid that would pass in the same area in the direction of the adsorbent countercurrent, to move the fluid present in the non-selective porous volume. If the flow rate of the fluid passing through the zone is lower than the flow rate of the non-selective porous volume of the adsorbent material passing through the zone, then there is a net entrainment of the fluid in the area by the adsorbent; when this entrainment is of the fluid present in the non-selective porous volume of the adsorbent, it, in several situations, comprises fewer selectively retained feed components.

The selective porous volume of the adsorbent may, in some cases, absorb fragments of refined material from the fluid surrounding the adsorbent, if there is competition between the extract material and the refined material for the adsorbed sites in the selective porous volume. If a large amount of the refined material, compared to the extract, surrounds the adsorbent, the refined material may be adsorbed by the adsorbent.

The feed materials that can be used in the process of the present invention are fractions of hydrocarbons having a range from 6 carbon atoms to 30 atoms) of carbon per molecule. Typically, the range of the carbon number of the hydrocarbon fractions is narrow, from about 3 to 6 carbon numbers, and as a supply current fractions C10 to C15 of oil slope. The feed currents contain normal, isoparaffin and aromatic paraffins in varying but little or no concentrations. Depending on the type of crude oil from which the hydrocarbon fraction is derived and the carbon number range of the fraction, the normal paraffin concentration ranges from 20 to about 60% by volume from the feed stream and the aromatics concentration from about 10 to 30% by volume from the current of 22 laying. There may be more special currents, which have concentrations of only 2 up to 4% of the volume of the supply current; When food aromatics, such as isoparaffins, cannot enter the pores of the adsorbent used in this process, due to their too large transverse diameter, then almost all aromatics reappear in the refined current. In fact, a small part is strongly adsorbed on the surface of the adsorbent particles and finally appears as impurities in the extract product (normal paraffin). Feed aromatics may include monocyclic aromatics, such as benzene or alkylbenzene, indane or alkylindane, and cyclic aromatics, which include biphenyl or acenaphenic naphthalene. Said aromatic impurities can be characterized by the general formula: Cn H2n-j where j, as used in spectrometry, indicates a specific number which, when replaced in the aforementioned empirical formula, can allow a distinct characterization of complex aromatic types ; it has been found that the aromatic hydrocarbons J &lt;s and J12 are more aided by the adsorbent; other types of aromatic hydrocarbons, such as Js or J10, are also strongly adsorbed.

The washing agent should preferably have a boiling point different from the boiling point of the refined component in the feed stream, to be readily separated from the refined stream by the subsequent distillation; thus, in this process, the washing agent may be selected from the higher or lower boiling counterparts of the branched chain or from the cyclic components of the feed material. As a specific example, an agent used in the separation of normal paraffins from the C10 to C15 feedstock is isooctane, which is not adsorbed by the adsorbent and which is separable from the refined components C10 to C15, by distillation. The washing agent is provided at a sufficient rate to equalize the empty space between the particles of the adsorbent, passing through a given point in the process cycle at a given speed of circulation, thereby effectively and continuously removing the entrained material, the main refined components between the particles. the adsorbent being subsequently circulated in the process flow. The refined components far away meet the current of fluid, moving in the opposite direction of the current and are. eventually, eliminated from the circulating fluid phase, by the extraction in the form of refined output current, which is then passed to the refined current separation plant, when the refined components can be recovered. Preferable loading speed of the washing agent in the purification zone

702Λ3 is, at the speed of a current equal to or greater than the velocity of the empty space between the adsorbent particles, a velocity dependent, at any time, on the size of the adsorbent particles, if a mobile or fixed bed process is used and depends on others factors.

The desorbent materials used in the process of this invention can be readily separated from the feed mixture. Both the refined current and the extract current (or currents, in those variants where there are several extract currents) are removed from the adsorbent in mixture with desorbent materials. Without a method of separating these desorbent materials, the purity of the extracted and refined components, if they are to be recovered, will not be too high nor the desorbent materials will be reusable in the process. Therefore, it is proposed that the desorbent materials have distillation points different from those of the feed mixture directed to the adsorbent, which admits only a fraction to be used to separate the refined components from the extract and allows the recovery of the desorbent materials for possible reuse in the process. .

The first desorbent materials used in this process contain aromatic hydrocarbons, which have a different distillation interval from that of the feed mixture, in the variant of the process described, where a washing agent is used, the first desorbent material also preferably has a distillation interval different from that of the washing agent, to allow separation by distillation here. The desorbent materials that can be used in this process may contain aromatics, such as benzene, toluene, xylthene and ethylbenzene isomers. In the example given above, where the normal paraffins were separated from a C10 feed stream at Cu and isooctane was used, as a washing agent, as para-xylene or ethylbenzene. Where a first desorbent mixture is used in addition to a washing agent, the concentration of the first desorbent material in the mixture may be in the range of 5 to about 100% of the total mixing volume; a concentration in zone 15 is preferred. 40% by volume. Since the fraction of the first desorbent material is required to adsorb only aromatic feeds with adsorption surface, it is also important that the first desorbent material contains little or no second desorbant material, avoiding desorption of normal paraffins; it is preferable that the concentration of the second desorbent material, in the first desorbent material, be below 1% of the voM world. The second desorbent material may be any normal paraffin, with a different distillation interval than that of the feed mixture. A second desorbent, consisting of normal pentane, is frequently used, as it is easily separable from the feed materials commonly used in this process. The second desorbent material can be 100% normal paraffin or a lower concentration of normal paraffin, mixed with diluent, the normal paraffin concentration being usually between 40% and 80% of the volume of the mixture. It is important that the second desorbent material contains little or no of the first desorbent material, because the presence of aromatics prevents the desorption of normal paraffins by the second desorbant; it is preferable to concentrate the raw material! desorbent in the second desorbent material of less than 1% by volume.

Proposed solid adsorbents for use contain zeolites of shape selection, usually referred to as molecular sieves. The term "shape selection" refers to the ability of zeolites to separate molecules, according to a model or size, due to the pore having a fixed diameter, in cross section, of the zeolites. Zeolites belong to a group of aluminum silicate crystals, having a frame structure, in which each SiOi or AlOi tetrahedron splits its corners with other tetrahedrons, occurring with all the silicon, aluminum and oxygen atoms in the structure. These crystals have a chemical form in which the ratio (Si + Al): (O) is 1: 2. Of the known types of zeolites, only those with a rigid framework are suitable molecular sieves. When initially formed, zeolite crystals contain water at the intersections defined by the frame; at moderate heating, this water can be expelled and the open intersections are of uniform size and can admit compounds whose critical maximum molecular diameters are not much larger than the minimum diameters of the intersections. Pure molecular sieves? Zeolite, in particular, some synthetic ones, are generally produced in the form of a light powder mass of small crystals. For the use of commercialized products, these zeolite crystals can be mixed with binder materials such as alumina, clay and other materials to form stronger, more wear-resistant particles. The proposed adsorbents for sure use in this process contain zeolites with pore diameters uO of 5A uniform. for example, capazite or molecular type 5A linden. The latter material is thus used in extruded, granular or tablet form and contains pure zeolite 5A and a binder material, such as clay. The adsorbent used in this process is generally in the form of particles with a size in the range of 20 to 40 times the size of the sieve. The adsorbent can be used in the form of a compact fixed bed and from which it is alternatively put in contact with the feed mixture and with the desorbent substances.

In the simplest embodiment, the adsorbent is used as a single fixed bed, in which the process is semi-continuous; In another embodiment, two or more fixed beds may be used, in contact with fixed bed with appropriate separation, so that the feed mixture passes through one or more beds, while the desorbent substances pass through the rest of the beds. The feed mixing current and the desorbent substances may be up or down through the desorbent. Any conventional installation used for fluid-solid contact with a fixed bed can be used. However, systems with countercurrent mobile bed and simulated countercurrent mobile bed have a higher separation efficiency than systems with fixed adsorbent pot and are therefore preferred. In the processes with mobile bed or with simulated mobile bed, adsorption and desorption operations take place continuously with each other, 30 which allows the continuous production of both an extract current and a refined current and the permanent use of feed currents. and disorienting. A better variant of this process uses 35 what is known in the art, ie the system with counter bed simulated in counter current. In such a system there is a progressive movement around an adsorption chamber, which simulates the movement of the adsorbent upward, adsorbent contained in the chamber; only four access lines are active at any one time, the access lines for the input supply current, the intake desorbent current, 45 for the refined output current and for the extract extract current. Simultaneously with this upward movement of the solid desorbent is a movement of the liquid 50 which occupies the empty space of the compact adsorbent bed; thus, the countercurrent contact is maintained, as a pump supplies the liquid stream down to the adsorbent chamber. Since an access point of the active liquid moves through a cycle, that is, from the top of the chamber to the bottom, the circulation pump in the room will move the liquid through various areas, which require different speeds of current. A programmed flow controller can set and regulate these current speeds. The adsorption chamber is actually divided into zones separated by the access points of the active liquid, each of the zones having a different function. In this process variant, it is generally necessary for three work areas to be present in order for the process to take place, although in some cases a fourth area may be used.

The advantages of the present invention consist in that a separation of the normal paraffins is obtained, having a reduced concentration of aromatic hydrocarbons with impurities, obtaining a purity of up to 99.9% and recoveries of over 90%.