KR940003499B1 - Integrated adsorption process for hydrogen and hydrocarbon recovery using temperature swing step in front of pressure swing step - Google Patents

Abstract

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Description

Integrated adsorption method for recovering hydrogen and hydrocarbons using a warm swing step prior to the pressurized swing step

1 illustrates a flowchart of a process using the method of the present invention.

2 illustrates the method of the present invention applied to a hydrogen consumption method.

3 illustrates the method of the present invention as applied to the hydrogen production method.

* Explanation of symbols for main parts of the drawings

1-12: Line 20-40: Line

51-75: lines 101,102,106: heat exchanger

103 flash chamber 104,107 first adsorption band

105: second adsorption band 201,204,208,210: heat exchanger

202: furnace 203: reactor

205,206,209: first absorption band 207: second absorption band

211: flash chamber 301, 304, 308, 313: heat exchanger

302: furnace 303: reactor

305,310: Flash chamber 307: Compressor

306: deisobutanizer column

309: cooler 311: first adsorption zone

312: second adsorption band

The present invention provides a swing swing and a pressure swing in the adsorption process, more particularly in the separation of light hydrocarbons from a mixture of hydrogen and heavy hydrocarbons and light hydrocarbons. It relates to an integrated method that utilizes both adsorption.

Hydrocarbon conversion processes are often carried out in the presence of hydrogen. This is due to various reasons, such as to assist in the vaporization of hydrocarbons, to provide the hydrogen required for the desired reaction, or to extend the life of the catalyst used in the reaction zone. In most cases, hydrogen is recovered from the reaction zone effluent and recycled. Often this recycle hydrogen stream is purified before returning to the reaction zone. In other modes of operation, hydrogen is recycled only after undergoing another treatment unit or purification step, even if it is not recycled or recycled. This method is most commonly carried out in a method which consumes only a small amount of hydrogen or produces hydrogen. Such methods include, for example, isomerization, alkylation and dealkylation, hydrogenation and dehydrogenation, reforming and mild desulfurization or denitrification.

In general, hydrocarbon conversion processes produce effluents which have to be subsequently separated off hydrocarbon products. Often, hydrocarbon conversion processes produce light hydrocarbons as by-products which must be removed from the process to prevent accumulation. Although it is possible to purify the system for the removal of light hydrocarbons, such measures may be undesirable as they result in the loss of the desired components along with the byproducts. Therefore, it is often desirable to separate light hydrocarbons (eg, up to 4 carbon atoms) from heavy hydrocarbons (eg, up to 5 carbon atoms) and hydrogen in, for example, the purification stream or the top stream of the reactor effluent separator. This kind of separation is necessary for thermal dealkylation of alkylaromatic hydrocarbons, for example, for the production of benzene from toluene. Toluene is often mass produced directly as a byproduct of thermal cracking, extraction, reforming or isomerization processes or directly from petroleum or coal extraction naphtha fractions. However, the toluene market is limited and there is a significant economic incentive to convert toluene to benzene because benzene is needed as a starting material that is the basis for the manufacture of many petrochemicals. Various separation techniques have been proposed for carrying out such separation.

U.S. Patent No. 4,058,452 to Laboda is directed to the dealkylation of aromatic hydrocarbons and the purification of the hydrogen containing feed stream in an absorbent to remove light paraffins and to form a hydrogen rich gas stream to pass this air stream once. A method of passing through a reaction zone on a substrate is disclosed. The gas separated by partial condensation from the reaction zone effluent is passed through a stripper, a stripping medium used to remove this same light paraffin from the liquid used in the absorbent.

A similar kind of separation process is disclosed in US Pat. No. 4,547,205 to Stecy, which describes the recovery of hydrogen and hydrocarbon products with at least 6 carbon atoms from an effluent stream in a hydrocarbon conversion reaction zone. The condensate stream is partially condensed to remove large quantities of heavy hydrocarbons, which are sent to a fractionation zone. The residual vapors are compressed to a fairly high pressure. The vapor is then passed through an automatic refrigeration zone to cool and partially condensed by indirect heat exchange with the flashed fluid. Compounds that are compressed but not yet condensed are transferred to a pressure swing adsorption zone to obtain high purity hydrogen product.

Both the heated swing adsorption (TSA) method and the pressure swing adsorption (PSA) method are generally known in the art as a method for various adsorptive separations. In general, the TSA method utilizes a step of adsorption treatment at low temperature, regeneration with hot purge gas at elevated temperature, and subsequently cooling to adsorption temperature. One of the gas drying methods, which is a general example of the TSA method, is described in US Pat. No. 4,484,933.

The PSA method provides an adsorption method that does not require heat for regeneration. Instead, regeneration is performed by reducing the pressure below the pressure at which adsorption has occurred in the adsorbent bed. PSA methods typically include adsorption at elevated pressures, desorption at low pressures and repressurization to adsorption pressures. These methods often include a purge step at the desorption pressure to increase desorption.

Examples of such PSA treatments are disclosed in US Pat. Nos. 3,430,418 and 3,986,849, which describe in detail with respect to cycling based on the use of multilayer systems. As is commonly known and described in these patents, the contents of which are hereby incorporated by reference in detail, ie, the PSA method, are generally carried out in a sequential processing cycle comprising each system layer of the PSA. This cycle is typically based on releasing void charge gas from the product end of each layer in one or more trending flow depressurization steps at the end of the adsorption step. The gases released in these cycles are typically used for pressure equalization and subsequent purge steps. This layer is subsequently countercurrently depressurized and often purged to remove such gas from the feed end of the bed before desorbing the components in the more selectively adsorbed gas mixture from the adsorbent to depressurize to the adsorption pressure.

PSA methods have been used for purification and bulk separation. Some PSA methods are particularly suitable for providing a single high purity product gas such as hydrogen and exhaust gas, or fuel gas. Other PSA methods have been disclosed to recover one or more product gas. This is often desirable when the feed stream contains two or more target components.

US Pat. No. 4,813,980, issued to Sicar, discloses a PSA method that uses two groups of adsorbent layers connected in series relating to the separation of hydrogen and carbon dioxide from a mixture of methane and other light gases.

In the dehydration and removal of carbon dioxide, specifically in the purification of air and natural gas streams, a mixture of TSA and PSA has been proposed. US Pat. No. 3,738,084 discloses a process for adsorbing water and carbon dioxide using one TSA method in one adsorbent and both PSA and TSA methods in another adsorbent. US Patent No. 3,841,058 discloses a method for purifying natural gas or the like suitable for liquefaction. US Patent No. 4,249,915 discloses the use of both TSA and PSA methods to remove moisture and carbon dioxide from air.

Although integration methods of TSA and PSA have been proposed for the purification of air and light gases, the disclosure of these methods does not have specific instructions for separating light hydrocarbons from mixtures with hydrogen and heavy hydrocarbons. Thus, there has been a need for a method using TSA and PSA techniques to perform this separation.

The present invention provides a method for separating light hydrocarbons from a mixture of hydrogen and heavy hydrocarbons using an integrated method of TSA and PSA. Heavy hydrocarbons are first adsorbed in the TSA stage and light hydrocarbons are subsequently adsorbed in the PSA stage. The hydrogen stream removed as an effluent from the pressurized swing adsorbent is used as a purge gas in desorbing heavy hydrocarbons from the heated swing adsorbent to provide a hydrogen and heavy hydrocarbon containing product stream suitable for recycling to the upstream conversion stage in most cases. do.

One aspect of the present invention provides a TSA and PSA integration method for separating light hydrocarbons from a feed stream containing a mixture of light hydrocarbons and hydrogen and heavy hydrocarbons. This process comprises: a) passing the feed stream through a first adsorption zone having a solid adsorbent maintained at a temperature and pressure sufficient to adsorb at least some of the heavy hydrocarbons and form a first effluent stream comprising hydrogen and light hydrocarbons. B) passing the first effluent stream through a second adsorption zone having a solid sorbent maintained at a temperature and pressure sufficient to adsorb at least a portion of the light hydrocarbons and form a second effluent stream comprising hydrogen; C) heating at least a portion of the second effluent stream to a temperature sufficient to desorb at least a portion of the heavy hydrocarbons from the heavy hydrocarbon rich adsorbent formed in step a), and heating the heated portion to the first adsorption zone. Desorption conditions effective to pass through to form a first desorption effluent stream comprising heavy hydrocarbons and hydrogen Contacting at least a portion of the heavy hydrocarbon rich adsorbent formed in the first adsorption zone and d) sufficient pressure to desorb at least some of the light hydrocarbons from the light hydrocarbon rich adsorbent to form a second desorption effluent comprising light hydrocarbons. Regenerating at least a portion of the light hydrocarbon rich adsorbent formed in step b) by depressurizing.

Another specific aspect of the present invention provides a process for separating an effluent stream from a hydrocarbon conversion process containing hydrogen, hydrocarbons having 1 to 5 carbon atoms and hydrocarbons having at least 6 carbon atoms. This process comprises: a) condensing the liquid condensate stream containing some hydrocarbons having at least 6 carbon atoms and exiting to a temperature sufficient to form a top vapor stream comprising hydrogen, hydrocarbon fractions having 1 to 5 carbon atoms and hydrocarbon fractions having at least 6 carbon atoms. Cooling the water stream, b) adsorbing at least a portion of the hydrocarbon fractions having at least 6 carbon atoms, and maintaining the hydrogen and the hydrocarbon fractions having 1 to 5 carbon atoms at a temperature and pressure sufficient to form a first effluent stream. Passing the upper vapor stream through a first adsorption zone having, c) adsorbing at least a portion of the hydrocarbon fraction having 1 to 5 carbon atoms and maintaining at a temperature and pressure sufficient to form a second effluent stream comprising hydrogen; Passing the first effluent stream through a second adsorption zone having a solidified solid adsorbent Step, d) heating at least a portion of the second effluent to a temperature sufficient to desorb at least a portion of the hydrocarbon fraction having at least 6 carbon atoms from the hydrocarbon fraction rich adsorbent having at least 6 carbon atoms formed in step b) and heating the heated portion; Contacting at least a portion of the carbon 6 or higher hydrocarbon fraction rich adsorbent formed in the first adsorption zone under sufficient desorption conditions to pass through the first adsorption zone to form a first desorption effluent stream comprising at least a portion of the hydrocarbon fraction having 6 or more carbon atoms. And e) desorbing at least a portion of the hydrocarbon fraction having 1 to 5 carbon atoms from the hydrocarbon fraction rich adsorbent having 1 to 5 carbon atoms to form a second desorption effluent comprising at least a portion of the hydrocarbon fraction having 1 to 5 carbon atoms. C) by reducing the pressure to a sufficient pressure Hydrocarbon fractions having a carbon number of 1 to 5 is formed in a step of reproducing at least one portion of the rich absorbent.

The process of the present invention is intended to be carried out on a feed stream consisting of hydrogen, light hydrocarbons and heavy hydrocarbons. The term “light hydrocarbon” includes hydrocarbons having from 1 to about 4 carbon atoms per molecule. The term "heavy hydrocarbon" includes hydrocarbons having about 6 to 20, preferably about 6 to 12, more preferably 6 to 9 carbon atoms per molecule. Hydrocarbons having five carbon atoms per molecule may be classified as light or heavy hydrocarbons, depending on the particular application. In general, heavy hydrocarbons are adsorbed in a heated swing adsorbent, i.e., the first adsorption zone, and light hydrocarbons are adsorbed in a pressurized swing adsorbent, i. It should be understood that it is desirable to adsorb some heavy hydrocarbons in the sieve. In addition, as is known to those skilled in the art, it is evident that a small amount of co-adsorption of certain species is envisaged, specifically that light hydrocarbons are co-sorbed with heavy hydrocarbons in a heated swing adsorbent.

The relative amount of each of the feed stream components is not critical to carrying out the process of the present invention. In general, it is desirable to have sufficient hydrogen to effectively desorb heavy hydrocarbons from the heated swing adsorbent. The molar ratio of hydrogen to heavy hydrocarbons is preferably at least 1, more preferably at least 5 and most preferably at least 10. If desired, less hydrogen can be used and supplemented by increasing the residual amount of adsorbent in the heated swing adsorbent or by increasing the desorption temperature. Such adjustments are known to those skilled in the art and need not be discussed further herein. Typically, the feed stream is cooled and partially condensed before entering the heated swing adsorbent to remove some of the heavy hydrocarbons. This partially condensed feed stream typically contains less than about 5 mole percent heavy hydrocarbons. Typical feed stream compositions suitable for the treatment according to the process of the invention contain about 1 to 20 mol% heavy hydrocarbons, 10 to 70 mol% light hydrocarbons and 20 to 90 mol% hydrogen.

The process of the invention can be carried out using any of the materials in the first and second adsorption zones as suitable adsorption materials so long as the material has the desired selectivity for light and heavy hydrocarbons in the feed stream. Suitable adsorbents known and commercialized in the art include crystalline molecular sieves, activated carbon, activated clay, silica gel, activated alumina and the like. Molecular sieves include, for example, silicoaluminophosphates and aluminophosphates disclosed in US Pat. Nos. 4,440,871, 4,310,440 and 4,567,027, which are incorporated herein by reference in addition to zeolite molecular sieves.

The zeolite molecular sieve in calcined form is represented by the following general formula.

Me ₂ O _n : Al ₂ O ₃ : xSiO: yH ₂ O

Wherein Me is a cation, x is a number from about 2 to infinity, n is a cation value, and y is from about 2 to 10.

Typical known zeolites that can be used include orthogonal zeolite designated zeolite D, clinoptilolite designated zeolite X and zeolite Y, erionite, faujasite, zeolite A And ferrierite, mordenite, designated Zeolite P. Other zeolites suitable for use according to the invention are those which contain a high content of silica, ie, a silica to alumina ratio of more than 10, typically greater than 100. One such silica high content zeolite is silicalite as the term used herein, and silicapolymorph and US Pat. No. 4,073,865 disclosed in US Pat. No. 4,061,724, which is incorporated herein by reference. All of the F-silicalite disclosed in the call is included.

A detailed description of some of the zeolites defined above is described in Zeolite Molecular Sieves (John Wiley and Sons, John Wiley and Sons, New York, 1974), incorporated by reference herein. have. Patents cited in the context of the present invention provide additional information regarding the various known adsorbents used in TSA and PSA processes. These are incorporated by reference and are suitable for use with the embodiments of the present invention.

When using crystalline molecular sieves it is often desirable to agglomerate the molecular sieves with a binder to ensure that the adsorbent has adequate physical properties. Metal oxides, clays, silica, alumina, silica-alumina, silica-zirconia, silica-thorias, silica-berylias, silica-titania, silica-alumina-toria, silica-alumina-zirconia There are a variety of useful synthetic and natural binders, such as mixtures thereof, but clay type binders are preferred. Examples of clays that can be used to aggregate molecular sieves with little change in the adsorption properties of zeolites are attapulgite, kaolin, volclay, sepiolite and polygorskite polygorskite, kaolinite, bentonite, montmorillonite, illite and chlorite. The selection of suitable binders and methods used to aggregate the molecular sieves is generally known to those skilled in the art and need not be described further herein.

The first adsorption zone has at least two adsorbent layers that are thermally cycled between adsorption and regeneration (ie, desorption) steps. It has been found that the temperature and pressure conditions of the adsorption bed and other conditions of the adsorption system are generally suitable for other heating swing method schemes considering feed stream characteristics. To selectively adsorb and remove heavy hydrocarbons during the adsorption step through which the feed stream is passed through the first adsorbent, the temperature of the feed stream is generally maintained at or below 66 ° C. (150 ° F.), preferably to increase the hydrocarbon load. It is maintained at -18 ° to 38 ° C. (0 ° to 100 ° F.), more preferably 4 to 38 ° C. (40 ° to 100 ° F.). Solidification of certain hydrocarbons, such as benzene, may occur at temperatures below -15 ° C (4 ° F). In addition, the pressure in the adsorbent is preferably at least 1 atmosphere (101 kPa), and when the heavy hydrocarbon partial pressure of the feed stream is low, at least 1 atmosphere is used to increase the heavy hydrocarbon pressure on the adsorbent and consequently increase the heavy hydrocarbon load. May be advantageous. Preferably, the pressure in the first adsorption zone is 689-6890 kPa (100-1000 psia). The degree of pressure increase and temperature conditions of at least 1 atmosphere (101 kPa) can be controlled with respect to the feed stream in a manner known in the art such that the action of the vapor phase has the desired efficiency.

In order to lower the equilibrium heavy hydrocarbon load during the regeneration or desorption of the adsorbent bed within the first adsorption zone and to facilitate the desorption and purification of heavy hydrocarbons (and other impurities) from the bed, purge gas is typically Heat to a temperature significantly higher than the temperature. In general, the higher the temperature of the purge gas, the smaller the required amount of purge gas, but experts in the art consider factors such as higher thermal energy losses due to hot water abuse of the adsorbent and unreasonable temperature differences between the inner and outer layers. shall. Desorption temperature for the purposes of the present invention is preferably 38 ℃ to 316 ℃ (100 to 600 ℃). When the adsorbate is sufficiently desorbed within the above temperature range, a temperature of 38 ° to 177 ° C (100 ° to 350 ° F) is more preferable. In contrast, when the adsorbate is difficult to desorb within the above temperature range, a temperature of 149 ° to 316 ° C (300 ° to 600 ° F) is preferred. The heat of the regenerated adsorbent material at the inlet end of the bed during regeneration can be moved forward with the purge gas introduced without heating, so the purge gas need not be heated throughout the hot purge regeneration. Those skilled in the art will readily be able to perform routing calculations in view of any given method for setting appropriate processing conditions. The technicians can also use indirect heating, i.e., heating the coils in the layer instead of or in addition to the purge gas. Cooling the first adsorption zone to adsorption temperature after regeneration uses methods well known to those skilled in the art, such as passing through a cooling stream, ie, a cooled purge gas or through a feed stream. The first adsorption zone can also optionally reduce the pressure there, ie regenerate by the PSA method. This pressure reduction can be carried out before, after or simultaneously with heat regeneration.

Adsorption stage effluent from the first adsorption zone is sent to a second adsorption zone, which consists of at least three adsorbent vessels, each of which is based on the circulation, high pressure adsorption, from Any trend to releasing intermediate pressure levels proceeds with decompression, backflow depressurization to lower desorption pressure and repressurization to higher adsorption pressure using desorbed gas from the feed end of the bed with or without purging the bed Let's do it. Of course, the adsorption circulation in the second adsorption zone may consist of additional steps well known in the PSA technology, ie, trend decompression steps or trend replacement steps as well known in the PSA technology. The term “conutercurrent” means that the direction of gas flow through the adsorption zone, ie the adsorbent bed, is opposite to the direction of feed stream gas flow. Similarly, the term “cocurrent” denotes a co-directional flow with the feed stream gas stream.

While the effluent from the first adsorption zone can be sent directly to the second adsorption zone, in some cases the effluent from the first adsorption zone may be indirectly heat exchanged with the feed stream to the first adsorption zone and the effluent is heated. It is desirable to partially cool the feed stream to the first adsorption zone. The feed stream cooling to the first adsorption zone improves the performance of the heating swing cycle by increasing the temperature change between adsorption and desorption. Preferably, the adsorption zone is maintained at a pressure in the range of 689 to 6890 kPa (100 to 1000 psia) during adsorption and at 101 to 1379 kPa (14.7 to 200 psia) during backflow depressurization. Intermediate Trend In the case of a decompression or equalization step, the pressure at the end of the step will be halfway between adsorption and countercurrent decompression pressure. Preferably, the temperature in the second adsorption zone is between -17.8 ° and 48.9 ° C. (0 to 120 ° F.) over the pressure swing cycle, but may be used at temperatures outside this range depending on the particular separation to be performed.

An important aspect of the TSA and PSA integration methods of the present invention is at least a portion of the second adsorption stage effluent stream, preferably from the second adsorption zone (PSA), for washing off the rich adsorbent during regeneration in the first adsorption zone (TSA). Is to use the whole effluent. This arrangement is particularly useful when the purpose is to remove light hydrocarbons from a feed stream consisting of minority, light, hydrocarbons and heavy hydrocarbons. The second adsorption zone effluent is used to remix the hydrogen stream with heavy hydrocarbons in addition to providing an effective means of regenerating the adsorbent used in the first adsorption zone. In hydrocarbon processing, it is often necessary to exclude the light hydrocarbon fraction, which may otherwise be accumulated. For example, the decomposition gas is constituted.

The method of the present invention will now be described with reference to the drawings illustrating various aspects of the present invention. Those skilled in the art will appreciate these process flow diagrams, which are simplified by omitting many essential process equipment.

1 illustrates a process flow that can be used to separate light hydrocarbons (eg methine) from hydrogen and heavy hydrocarbons (eg benzene). This separation is preferred for the process of producing benzene with toluene by hydrodealkylation (THDA), where hydrogen and toluene are passed through a heating reactor to produce benzene and methanol. US Patent No. 4,058,452 discloses a process for the dealkylation of alkylaromatic hydrocarbons and is incorporated herein by reference. Often, large amounts of hydrogen and methane containing reactor exhaust are purged to prevent the buildup of methane. The process of the invention can be used to remove methanol from this stream.

Referring to FIG. 1, the feed stream containing about 60 mol% hydrogen, 2 mol% benzene and 38 mol% methane is supplied via line 1 at a pressure of 2965 kPa (430 psia) and a temperature of 40 ° C. (104 ° F.). To heat exchanger 101 where it is cooled to 18.3 ° C. (65 ° F.) by indirect heat exchange by adsorption effluent delivered by line 6 and then to quench 102 via line 2. Are sent and further cooled to 4.4 ° C. (40 ° F.). The cooled feed stream is sent to flash chamber 103 via line 3, where the liquid phase containing benzene is recovered via line 4 and the vapor phase consisting of hydrogen, methane and residual benzene is line ( 5) pass.

It is not necessary to cool and flash the feed stream, ie line 1, before passing through the first adsorption zone. However, this cooling may be advantageous because some of the benzene is removed and thus, if not removed, reduces the size of the first adsorption zone where benzene will be adsorbed. This cooling also lowers the temperature of the feed stream to the first adsorption zone, which can increase the temperature difference between adsorption and regeneration, effectively increasing the capacity of the first adsorption zone.

The first adsorption zone has at least two adsorption layers, namely adsorbent layers 104 and 107, each of which contains an adsorbent suitable for adsorbing benzene, i.e. activated carbon, and is more complex for those skilled in the art. It will also be appreciated that more than one adsorbent layer may be used. The first zone adsorption effluent, from which benzene has been removed, is recovered from adsorbent 104 via line 6 and before being sent to second adsorption zone 105 via line 7 to about 34.4 ° C. (94 ° F.). ) Is sent to a heat exchanger 101 as described above which is heated with Optionally, the heating step can be omitted and the effluent is sent directly to the second zone.

The second adsorption zone 105 contains at least three adsorbent layers and may optionally have more adsorbent layers and contains a suitable adsorbent, i.e. activated carbon, for methane adsorption. The effluent of the second adsorption zone, from which methane has been removed, is removed via line 8 and sent to a heat exchanger 106 which heats to a temperature of 121 ° C. (250 ° F.) and passes the first zone via line 9. The adsorbed benzene is desorbed by being sent to the adsorbent 107 to purify the adsorbent 107.

It will be appreciated that the adsorbent 107 is loaded with benzene in the manner described for the adsorbent 104 above. The amount of benzene adsorbed to each adsorbent can be determined by one skilled in the art depending on the purity of the desired product. For example, in some cases, it may be desirable to allow some benzene to elute into the effluent of the first adsorption zone to ensure high purity of the benzene product. In other cases it may be desirable to stop the adsorption step prior to breakthrough of benzene and hold some of the methane in the first adsorption zone. In such cases, those skilled in the art can use the adsorbents in the appropriate combination to achieve the desired result.

The product stream consisting of hydrogen and benzene is recovered from adsorbent 107 via line 11. In the THDA process, for example, this stream can be recycled back to the THDA reactor without further separation and used for further processing. Alternatively, benzene can be separated by conventional methods and hydrogen can be recycled to the reactor. After the desorption of benzene from the adsorbent 107 proceeds, the second band adsorption outflow around the heat exchanger 106 through line 10 to cool the adsorbent 107 to the second band adsorption effluent temperature for a period of time. Switch the water Some further desorption of benzene occurs during this cooling. The determination of when to deliver the purge gas around the heat exchanger 106 to cool the adsorbent 107 is dependent upon considering methods known to those skilled in the art. Finally cooling to the adsorption temperature can be accomplished by passing the cooled feed stream through it during the adsorption step.

Methane adsorbed in the adsorbent bed in the second adsorption zone is desorbed by lowering the pressure to ambient pressure. A series of intermediate trend decompression and equalization steps are used to improve the recovery of hydrogen in the second adsorption zone prior to the final decompression and purification steps. These steps are known in the art and need not be discussed further herein.

FIG. 2 illustrates the process of the present invention incorporated into a dealkylation reaction, ie a thermal hydrodealkylation reaction, as disclosed in U.S. Patent No. 4,058,452, supra. The arrangement illustrated in FIG. 2 is particularly useful when the hydrogen feed stream contains light hydrocarbon impurities such as methane to butane. A feed stream containing alkylaromatic hydrocarbons is introduced into the process via line 20 to combine with hydrogen stream 38 (its source is described below) and past heat exchanger 201 past line 21 for preheating. Sent to). The preheated stream is sent to furnace 202 via line 22 and then to reactor 203 via line 23. The reaction system is described in US Pat. No. 4,058,452, supra.

In general, when using a thermal hydrogenation dealkylation reaction, the reactor is preferably composed of a vertical cylindrical vessel having an inlet at the top. This vessel does not contain any material selected and designed to act as a catalyst. Nevertheless, the materials used in the reactor may exhibit some catalytic activity at the high temperatures used in this zone. It is preferred that the upper 1/2 to 2/3 of the reaction zone is almost empty and the rest of the zone contains means for inhibiting flow (e. G. Insoluble ceramic balls, vertical baffles, etc.). Thermal hydrogenation dealkylation conditions are generally 593 ° to 816 ° C. (1100 ° to 1500 ° F.) or higher and pressures of 2171 to 5619 kPa (300 to 800 psig). The feed stream residence time in the reaction zone should be in the wide range of 4 to 60 seconds, with 12 to 30 seconds being preferred. The hydrocarbon ratio of hydrogen to carbon atoms of 6 or more in the reaction zone is maintained at least 2, preferably 4-8. The reaction zone should be run in a manner that limits the temperature within the reaction zone to increase below 110 ° C. (200 ° F.), preferably within 55.6 ° to 97.2 ° C. (100 to 175 ° F.).

For catalytic hydrogenation dealkylation of alkylaromatics, preferred conditions are pressures of 2717-6890 kPa (300-1000 psig) and temperatures of 482 ° -816 ° C. (900-1500 ° F.). Any catalyst capable of carrying out the desired reaction is suitable for use in the present invention. One suitable catalyst consists of an oxide of a refractory inorganic oxide, preferably a metal of Group VI-B of the periodic table on the alumina (eg chromium, molybdenum or tungsten). Other metals that may be used on the catalyst include those classified as Group VIII of the periodic table, including platinum nickel, curl and cobalt, and also rhenium and manganese. Particularly preferred catalysts consist of chromium composed on alumina having a large surface area in which chromium is present in an amount of 10 to 20% by weight of chromium oxide based on alumina. The feed stream is packed at an hourly liquid space velocity of 0.5 to 5.0 per hour to maintain a hydrogen to hydrocarbon ratio of about 5.1 to 15: 1 in the reaction zone.

The reactor effluent is recovered via line 24 and sent to heat exchanger 201 for partial cooling and to heat exchanger 204 via line 25 for further cooling. The cooled reactor effluent is sent to flash chamber 205 via line 26 where liquid aromatic compounds are recovered via line 39 and consist of hydrogen, hydrocarbons having 1 to 4 carbon atoms and aromatic hydrocarbons. The merchandise is recovered via line 27. The vapor phase is sent via line 27 to the first zone adsorbent 206 in the first adsorption zone where the aromatic hydrocarbons are adsorbed.

The first zone adsorption effluent consisting of hydrogen and hydrocarbons of 1 to 4 carbon atoms is recovered via line 28 and combined with the impure hydrogen stream by line 29. The combined feed stream is passed through line 30 to a second adsorption zone 207 (ie, PSA zone), where the feed stream contains a fuel gas stream containing 1 to 4 carbon atoms that is returned to line 31. And the hydrogen product stream, which is returned to line 32. The hydrogen product stream is sent to heat exchanger 208 to heat to the desired desorption temperature and to adsorbent 209 in the first adsorption zone where desorption is progressing via line 33. Line 34 provides a bypass around heat exchanger 208 to cool adsorbents 206 and 209. The desorption effluent stream from adsorbent 209 is composed of hydrogen and aromatic hydrocarbons which are sent to cooler 210 via line 35 and then through flash chamber 211 via line 36. do. The liquid aromatic product is recovered via line 37 and combined with line 39 to form product line 40. The hydrogen rich stream is recovered via line 38 and combined with the alkylaromatic feedstream, line 20 described herein.

Figure 3 illustrates a flow diagram illustrating the process of the present invention incorporating propane and butane containing feed streams to produce aromatic hydrocarbons via dehydrogenation cyclodimerization reaction. Dehydrogenation cyclodimerization reactions are disclosed in US Pat. No. 4,547,205, which relates to the recovery of hydrogen and hydrocarbons having at least 6 carbon atoms from the effluent stream of the hydrocarbon conversion reaction zone and is incorporated herein by reference.

Referring to FIG. 3, a feed stream containing propane and butane is introduced into the treatment apparatus via line 51 and merged with additional propane and butane from line 60 and its source is defined below. The combined stream is sent to heat exchanger 301 via line 52 and then to furnace 302 via heated line 53. The heated stream is sent to reactor 303 via line 54 where conversion takes place. Details of the reactions are disclosed in US Pat. No. 4,547,205, incorporated herein by reference.

In general, reactor systems are US Pat. Nos. 3,652,231, 3,692,496, 3,706,536, 3,785,963, 3,825,116, 3,839,196, 3,839,197, 3,854,887, 3,856,662 3,918,930, 3,981,824, 4,094,814, 4,110,091, 4,403,909, and a moving bed radial flow multi stage reactor. These patents also describe various aspects of catalyst regeneration systems and moving catalyst bed operations and apparatus. This reactor system has been commercialized and widely used for reforming naphtha fractions. It also describes the dehydrogenation of light paraffins.

Preferred moving bed reactor systems use spherical catalysts. The catalyst is preferably composed of a support material and a metal component deposited thereon. Zeolite supports are presently preferred, with zeolite ZSM-5 being particularly preferred. Preferred metal components are gallium as described in US Pat. No. 4,180,689. The dehydrogenated cyclo dimerization reaction zone is preferably configured at temperatures of 493 ° to 566 ° C (920 ° to 1050 ° F) and pressures up to 793 kPa (100 psig). Hydrogen generation reactions are generally preferably produced by low pressures, with pressures below 586 kPa (70 psig) being particularly preferred.

The reactor effluent, consisting of aromatic hydrocarbons, hydrogen, methane, ethane, propane and butane, is sent to heat exchanger 301 via line 55 where it is partially cooled. The partially cooled reactor effluent is combined with the first zone desorption analogue carried by line 56 and by line 74 (the source of which is described below) and via cooler 304 via line 57. ) And to flash chamber 305 via line 58. The liquid is sent to deisobuta-nizer column 306 via line 59. Hydrocarbon products containing aromatic hydrocarbons are recovered via line 66. The top from column 306 contains propane and butane and is recycled via line 60 to merge with feed stream 51.

Vapor phase from flash chamber 305 is recovered via line 61 and sent to compressor 307 where it is compressed to at least 1379 kPa (200 psig) and sent to heat exchanger 308 via line 62. And partially cooled by an indirect heat exchanger with the first zone adsorption effluent via line 68 described above. The partially cooled stream is sent to cooler 309 via line 63 and then to flash chamber 310 via line 64. The liquid consisting of aromatic hydrocarbons, butane and propane is sent to butane removal unit column 306 via line 65. The vapor layer from the flash chamber 310 is recovered via the line 67 and sent to the adsorbent 311 where adsorption proceeds in the first adsorption zone operated by the TSA method. Alternatively, for example, the vapor layer from flash chamber 305 is sent to adsorbent 311 before compressing line 61.

The adsorption step in the adsorbent layer 311 continues until most of the methane, ethane and hydrogen are eluted from the bed but most of the propane and butane remain in the bed. At this point, the adsorption step ends and the feed stream is directed to another adsorbent in the first adsorption zone. Effluent from the first adsorption zone is sent to heat exchanger 308 as described above via line 68 and then to second adsorption zone 312 operated in a PSA manner via line 69. Is sent. A fuel gas stream containing methane and ethanol is recovered via line 70. The second adsorption zone effluent stream is recovered via line 75 and a portion thereof is recovered via line 71 as hydrogen product. The remainder passes through heat exchanger 313 or alternatively passes through line 72 and through adsorbent 314 in the first adsorption zone where desorption proceeds via line 73. Desorption effluent from the adsorbent 314 merges with line 56, as described above via line 74. In some cases, it may be desirable to separate and recover the aromatic hydrocarbons to prevent recycling of hydrogen instead of recycling the desorption effluent, ie, line 74, to heat exchanger 304 and flash chamber 305. Such modified methods are also included within the scope of the present invention.

It is apparent to one skilled in the art that the method of the present invention can be used in methods other than those described above. For example, in a method for converting syngas to a liquid motor fuel, as described in US Pat. No. 4,579,834, the objective may be to separate light hydrocarbons of 1 to 4 carbon atoms from heavy hydrocarbons of 5 or more carbon atoms and hydrogen. . In a methane conversion process for producing hydrocarbons and hydrogen as also described in US Pat. No. 4,704,888, it may be an objective to separate light hydrocarbons from heavy hydrocarbons and hydrogen. There are also a number of other hydrocarbon conversion methods, such as catalytic reforming of naphtha and dehydrogenation of paraffin, wherein the present invention can be used, for example, within the scope of the following claims.

Claims (6)

a) a first adsorption zone having a solid phase adsorbent maintained at a temperature and pressure sufficient to adsorb at least some of the heavy hydrocarbons and to form a first effluent stream comprising hydrogen and light hydrocarbons; Passing a feed stream through the process, b) adsorbing at least some of the light hydrocarbons and having a solid adsorbent maintained at a temperature and pressure sufficient to form a second effluent stream comprising hydrogen; Passing the first effluent stream through an adsorption zone, c) a temperature sufficient to desorb at least a portion of the second effluent stream, at least a portion of the heavy hydrocarbons from the heavy hydrocarbon rich adsorbent formed in step a) Heating and passing the heated portion through the first adsorption zone for first desorption comprising heavy hydrocarbons and hydrogen Contacting with at least a portion of the heavy hydrocarbon rich adsorbent formed in the first adsorption zone under desorption conditions effective to form an output stream; and d) desorbing at least some of the light hydrocarbons from the light hydrocarbon rich adsorbent to comprise light hydrocarbons. Recoupling at least a portion of the light hydrocarbon rich adsorbent formed in step b) by depressurizing to a pressure sufficient to form a desorption effluent, separating the light hydrocarbons from the light hydrocarbon, hydrogen and heavy hydrocarbon containing feed stream. Adsorption method. The method of claim 1, wherein the temperature of the second adsorption zone in step b) is higher than the temperature of the first adsorption zone in step a). The method of claim 1, wherein the light hydrocarbon is a hydrocarbon having 1 to 5 carbon atoms per molecule and the heavy hydrocarbon is a hydrocarbon having 6 or more carbon atoms per molecule. Condensing the liquid condensate stream comprising a portion of hydrocarbons having at least 6 carbon atoms and cooling the effluent stream to a temperature sufficient to form a top vapor stream comprising hydrogen, hydrocarbon fractions having 1 to 5 carbon atoms and hydrocarbon fractions having at least 6 carbon atoms. Step, b) first adsorption with solid phase adsorbent maintained at a temperature and pressure sufficient to adsorb at least a portion of the hydrocarbon fraction having at least 6 carbon atoms and to form a first effluent stream comprising hydrogen and hydrocarbon fractions having 1 to 5 carbon atoms; Passing the upper vapor stream through the zone, c) adsorbing at least a portion of the hydrocarbon fraction having 1 to 5 carbon atoms and maintaining a solid phase adsorbent maintained at a temperature and pressure sufficient to form a second effluent stream comprising hydrogen. Passing the first effluent stream through a second adsorption zone having (D) heating and warming at least a portion of the second effluent to a temperature sufficient to desorb at least a portion of the hydrocarbon fraction having at least 6 carbon atoms from the hydrocarbon fraction rich at least 6 carbon atoms adsorbent formed in step b); Is passed through the first adsorption zone to form a first desorption effluent stream comprising at least a portion of the hydrocarbon fractions having at least 6 carbon atoms, wherein at least one of the hydrocarbon fractions rich at 6 carbon atoms or more formed in the first adsorption zone is effective under desorption conditions. Contacting a portion and e) a second desorption effluent comprising at least a portion of the hydrocarbon fraction having 1 to 5 carbon atoms by desorbing at least a portion of the hydrocarbon fraction having 1 to 5 carbon atoms from the hydrocarbon fraction rich adsorbent having 1 to 5 carbon atoms. To a pressure sufficient to form Separating an effluent stream containing hydrogen, hydrocarbons of 1 to 5 carbon atoms and hydrocarbons of 6 or more carbon atoms from the hydrocarbon conversion process, which comprises regenerating at least a portion of the hydrocarbon fraction enriched adsorbent having 1 to 5 carbon atoms formed in step c). How to. The method of claim 4, wherein the hydrocarbon fraction having 1 to 5 carbon atoms contains mainly methane and the hydrocarbon fraction having 6 or more carbon atoms contains mainly benzene. The process of claim 1 wherein the ratio of hydrogen to heavy hydrocarbons contained in the stream and passing through the first adsorption zone is from 1: 1 to 10: 1.