KR20000060916A - Catalytic reforming process with three catalyst zones to produce aromatic-rich product - Google Patents

Abstract

The present invention relates to a process for the catalytic conversion of reformed hydrocarbons, and more particularly, to the production of high aromatics products by catalytically reforming hydrocarbons in the gasoline range.

Description

Catalytic reforming process with three catalytic zones for the production of products with high aromatic content {CATALYTIC REFORMING PROCESS WITH THREE CATALYST ZONES TO PRODUCE AROMATIC-RICH PRODUCT}

The present invention relates to a process for the catalytic conversion of reformed hydrocarbons, and more particularly, to the production of high aromatics products by catalytically reforming hydrocarbons in the gasoline range.

Catalytically reforming hydrocarbon feedstocks in the gasoline range has been practiced in almost all major oil refineries to produce gasoline components or aromatic intermediates in the petrochemical industry that are highly resistant to engine knocking. At present, the demand for aromatics is increasing rapidly than the supply of raw materials for producing aromatics. In addition, due to the upgrading of gasoline and increasing demand for high performance internal combustion engines, which are essential for environmental regulation, the required knocking resistance of gasoline components measured as the "octane" value of gasoline is increasing. Therefore, in order to meet such requirements as the increase in the demand for aromatics and the increase in the required octane number of gasoline, it is often necessary to improve the performance of the catalytic reforming unit used in the refinery field. Such upgrading involves a large number of reaction zones and catalysts, and the application of such upgrading to existing units effectively utilizes existing reforming and catalyst regeneration facilities.

Catalytic reforming processes are commonly used for raw materials with high paraffinic and naphthenic hydrocarbon content, dehydrogenation of naphthenes to aromatics, dehydrocyclization of paraffins, isomerization of paraffins and naphthenes, alkyls Through a variety of reactions including dealkylation of aromatics, hydrocracking paraffins with light hydrocarbons, and formation of coke deposited on the catalyst. As demand for aromatics increased and gasoline essential octane numbers rose, attention was focused on the dehydrocyclization of paraffins, which is less desirable for conventional reforming processes than other aromatics in terms of thermodynamics and mechanics. . Therefore, considerable effort is required to minimize the formation of coke and to promote the dehydrocyclization reaction compared to competitive hydrocarbon reactions to increase the yield of the desired product due to catalytic reforming. The continuous catalytic reforming process, which uses a high activity catalyst and can be carried out under relatively low pressure while continuously regenerating the catalyst, is effective for the dehydrocyclization reaction.

The effects on the paraffin dehydrocyclization process of reforming catalysts containing non-acidic L-zeolites and platinum group metals are known in the art. Processes for producing aromatics from paraffin raffate and naphtha using these reforming catalysts have already been disclosed. However, this dehydrocyclization technology was too slow to develop during intensive, long-term development. Thus, the present invention takes a new approach to complementary use of L-zeolite technology.

Bus US Pat. No. 4,645,586 discloses a large pore zeolite (preferably zeolite L) after contacting a raw material with a bifunctional reforming catalyst containing a metal oxide support and a Group VIII metal. A method of contacting with a zeolite reforming catalyst containing was taught. This patent solves the disadvantages of the prior art by providing a product stream prepared using a conventional first reforming catalyst to a non-acidic, highly selective second catalyst. However, nothing is said about the continuous reforming method.

US Pat. No. 4,985,132 teaches a multi-zone catalyst reforming process using a first catalyst region containing platinum-germanium on a refractory inorganic oxide and a terminal catalyst region, which is a moving bed system involving continuous catalyst regeneration.

U. S. Patent No. 5,190, 638 preferably modifies the feed in a moving bed continuous catalyst regeneration scheme using a catalyst with acid functionality at 100 to 500 psig to provide a partially modified stream, which is then subjected to a second regeneration zone. The method of feeding is taught, but this method does not address the use of non-acidic zeolite catalysts.

It is an object of the present invention to provide a catalytic reforming method with good product yield.

The present invention has been completed based on the fact that the combination of the bifunctional catalytic reforming reaction and the zeolite reforming reaction in a sandwich arrangement significantly improves the yield of aromatics compared to the prior art.

One embodiment of the invention contains a first difunctional catalyst, a non-acidic zeolite and a platinum group metal containing platinum, a metal promoter, a refractory inorganic oxide and a halogen and present in the first catalyst zone and present in the zeolite modified zone. And a catalyst system comprising a zeolite-modifying catalyst, and a catalyst system comprising a platinum, a metal promoter, a refractory inorganic oxide, and a halogen, and a terminal bifunctional catalyst present in the terminal catalyst region, in order to catalytically modify the hydrocarbon raw material. It is about. The first bifunctional reforming catalyst and the terminal bifunctional reforming catalyst are preferably the same catalyst. Optionally, the metal promoter of the first catalyst and the terminal catalyst is selected from the group consisting of Group IVA (IUPAC 14) metals, rhenium and indium. The zeolite reforming catalyst preferably contains non-acidic L-zeolites and platinum.

In one embodiment, the terminal catalyst zone comprises a moving bed system associated with continuous catalyst regeneration. An alternative embodiment of the present invention is a catalytic reforming process in which a continuous reforming portion containing a bifunctional catalyst and a hydrocarbon raw material are continuously treated in a zeolite reforming region containing a zeolite reforming catalyst and then once again in the continuous reforming portion. . Placing zeolite reforming zones as intermediate reactors may increase throughput (or increase) and improve product quality of existing continuous reforming processes.

A broad embodiment of the present invention relates to a catalytic reforming process comprising a sandwich arrangement in the order of a bifunctional reforming catalyst, a zeolite reforming catalyst and a bifunctional reforming catalyst. The present invention provides a first effluent by contacting a hydrocarbon feedstock with a first difunctional catalyst containing a platinum group metal component, a metal promoter, a refractory inorganic oxide, and a halogen component in a first reforming region under a first reforming condition. At least a portion of the first effluent is contacted under a second reforming condition with a zeolite reforming catalyst containing a non-acidic zeolite, an alkali metal component and a metal component of the group of platinum and present in the zeolite reforming zone to obtain an aromatized effluent. And at least a portion of the aromatized effluent are contacted under a terminal reforming condition with a terminal bifunctional reforming catalyst containing a metal component, a metal promoter, a refractory inorganic oxide and a halogen component of the platinum group and present in the terminal reforming region to increase the aromatics content. It provides a catalytic reforming method comprising the step of obtaining a high product. .

Basic arrangements of catalytic reforming processes are known in the art. The hydrocarbon feedstock and the high hydrogen content gas are preheated and fed to a reforming zone which typically contains two or more (usually two to five) reactors in a row. Appropriate heating means are installed between the reactors to compensate for the net endothermic amount of the reaction in each reactor.

The first catalyst region, the intermediate catalyst region and the terminal catalyst region each including the first catalyst, the intermediate catalyst and the terminal catalyst are usually installed in separate reactors, but these catalyst regions may be installed in separate layers in a single reactor. have. Each catalyst zone may be arranged in two or more reactors, and between these reactors may be provided with suitable heating means as described above, for example, the first catalyst zone may be arranged in the first reactor and the terminal catalyst zone may be It can be placed in three reactors. Each catalyst zone may also be separated by one or more reaction zones containing a catalyst composition having a composition different from the catalyst composition of the present invention.

The first catalyst constitutes 10% to 50% of the total catalyst mass in all catalyst zones, the middle catalyst constitutes 20% to 60% and the terminal catalyst constitutes 30% to 70%.

Since the catalyst is housed in a fixed bed system or a moving bed system associated with continuous catalyst regeneration, the catalyst is continuously discharged and recycled and then fed back to the reactor. There are alternatives known to those skilled in the art with regard to catalyst regeneration. For example, (1) in a semi-regeneration unit comprising a fixed bed reactor, maintaining the operational severity by raising the temperature and shutting off the unit for substantially regeneration and reactivation of the catalyst, ( 2) In a swing reactor unit, as the catalyst is deactivated, the individual fixed bed reactors are continuously separated through multiple arrangements, and then the catalysts are regenerated and reactivated in the separated reactors while the remaining reactors remain in the stream. (3) after continuously regenerating and reactivating the catalyst discharged from the moving bed reactor, the reactivated catalyst is returned to the reactor, or (4) using a hybrid system where semi-regeneration and continuous regeneration are performed in the same zone. Way. A preferred embodiment of the present invention is a fixed bed semi-regeneration system or hybrid system of a fixed bed reactor in a semi-regenerating zeolite reforming zone and a moving bed reactor involved in continuous bifunctional catalyst regeneration in a continuous reforming zone. In one embodiment of the hybrid system, a zeolite reforming zone is added to an existing continuous reforming process to enhance the partially modified intermediate stream and / or to improve the quality and throughput of the product obtained in the continuous reforming process.

The hydrocarbon feedstock contains paraffins and naphthenes and may contain aromatics and small amounts of olefins boiling within the gasoline range. Available raw materials include straight-run naphthas, natural gasoline, synthetic naphtha, thermal gasoline, catalytic cracked gasoline, partially modified naphtha or raffinate following extraction of aromatics. The distillation range may be the distillation range of all naphthas having an initial boiling point of typically 40-80 ° C. and a final boiling point of 160-210 ° C., or may be a narrower range with a lower final boiling point. Since the process of the present invention effectively dehydrocyclizes paraffins with aromatics, the process of the present invention enables advantageous treatment of paraffin raw materials, such as naphtha obtained from Middle Eastern crude oil with a final boiling point of 100 to 175 ° C. As an alternative hydrocarbon feedstock, raffinates following extraction of aromatics, which usually contain lower values of C ₆ -C ₈ paraffins which can be converted into valuable BTX aromatics, are preferred.

The hydrocarbon raw material of the present invention contains a small amount of sulfur compound in a mass of less than 10 ppm based on the element. Hydrocarbon feedstocks may contain contaminated feedstocks such as sulfur-containing, nitrogen-containing and oxygen-containing compounds via H ₂ S, NH ₃ and H through conventional pretreatment steps such as hydrotreating, hydrorefining or hydrodesulfurization. It is preferred to prepare from these contaminants by each conversion to ₂ O [these materials can be separated from hydrocarbons by fractionation]. In this conversion process, it would be desirable to use a catalyst known in the art containing an inorganic oxide support and a metal selected from group VIB (IUPAC 6) and group VIII (IUPAC 9-10) of the periodic table {cotton and Wilkinson See Advanced Inorganic Chemistry, John Willy & Sons, 5th ed., 1988. Instead of or in addition to the conventional hydrotreating process, during the pretreatment step, a contact with an adsorbent capable of removing sulfur-containing contaminants and other contaminants may be included. These adsorbents include, but are not limited to, zinc oxide, iron sponge, large surface area sodium, wide surface area alumina, activated carbon and molecular sieves. Excellent results are obtained with nickel / alumina adsorbents. The pretreatment step can provide the zeolite reforming catalyst with a low sulfur content (eg, 1 ppm to 0.1 ppm (100 ppb)) hydrocarbon feedstock disclosed in the prior art as a preferred reforming feedstock.

The pretreatment step can significantly reduce the sulfur content in the hydrocarbon feedstock by mixing a reforming catalyst that is relatively resistant to sulfur with a sulfur adsorbent. A reforming catalyst resistant to sulfur is contacted with the contaminated feed to convert most of the sulfur compounds to provide an H ₂ S containing effluent. The H ₂ S containing effluent is contacted with a sulfur adsorbent (zinc oxide or manganese oxide is advantageous) to remove H ₂ S. As a result, the sulfur content can be lowered to 0.1 ppm or less. It is also within the scope of the present invention to include a pretreatment step in the modification process of the present invention.

The feed may be encountered in the form of upstream, downstream or radial flow with each catalyst in each reactor. Since the reforming process of the present invention is carried out at a relatively low pressure, a radial flow mode is preferred for lowering the pressure in the radial flow reactor.

The first reforming condition comprises a pressure (absolute) of 100 kPa to 6 MPa, preferably a pressure (absolute) of 100 kPa to 1 MPa. Good results were obtained when the operating pressure was 450 kPa or less. Free hydrogen, usually present in gases containing light hydrocarbons, is mixed with the raw materials such that a molar ratio of 0.1 to 10 moles of hydrogen per mole of C ₅ + hydrocarbons is obtained. The space velocity with respect to the volume of the first reforming catalyst is 0.2-20 / hour. The operating temperature is 400 to 560 ° C.

In the first reforming zone, a first effluent stream with a high content of aromatics is produced. Most of the naphthenes contained in the raw materials are converted to aromatics. Paraffins contained in the raw materials are mainly isomerized, hydrocracked and then dehydrogenated, and light paraffins are mainly present in the effluent since heavy paraffins are converted in much larger amounts than hard paraffins.

The refractory support of the first reforming catalyst should be a material that is porous and adsorbable, has a large surface area and is uniform in composition of the components contained therein. Refractory supports encompassed within the scope of the present invention include (1) refractory inorganic oxides such as alumina, silica, titania, magnesia, zirconia, chromia, toria, boria, or mixtures thereof, and (2) natural, which may be acid treated. Or synthetic clays and silicates, (3) synthetic or natural crystalline zeolite aluminosilicates in the hydrogen form or exchanged with metal cations such as FAU, MEL, MFI, MOR, MTW (IUPAC Commission for Zeolite Nomenclature), ( _{4) MgAl 2 O 4, FeAl} 2 O 4, ZnAl 2 O 4, CaAl 2 O 4 , etc. of the spinel, and (5) a refractory containing one or more of a combination of a material selected from at least one of these groups It is a support. The refractory support of the first reforming catalyst preferably contains an inorganic oxide, preferably alumina, with gamma alumina or eta alumina being particularly preferred.

The alumina powder may be molded into any carrier material form known in the art (eg, spherical, extrudates, rods, rings, pellets, tablets or granules). The spherical particles are converted into alumina sol by reacting the alumina powder with a suitable peptizing agent and then dropping a mixture of the resulting sol and gelling agent in an oil bath to form spherical particles of alumina gel, and then known aging and drying. And a calcination step. The extrudate form mixes the alumina powder with water and a suitable peptizing agent (e.g., materials such as nitric acid, acetic acid, aluminum nitrate, etc.) to form an extrudable dough having a burn loss (LOI) of 45-65 mass% at 500 ° C. It is preferable to prepare in such a manner. The resulting dough is extruded through a die of suitable shape and size to form extrudate particles and then dried and calcined by known methods. Alternatively, the extrudate particles can be rolled on a rotating disk to produce spherical particles.

The spherical particles are usually spherical and may be as large as 1.5-3.1 mm (1 / 16-1 / 8 inch) in diameter but about 6.35 mm (1/4 inch). However, in certain regeneration apparatuses, it is preferable to use catalyst particles corresponding to a relatively narrow size range. The preferred diameter of the catalyst particles is 3.1 mm (1/16 inch).

The main component of the first reforming catalyst is at least one platinum group metal, of which the platinum component is preferred. Platinum may be present in the catalyst in the form of compounds such as oxides, sulfides, halides or oxyhalides, in chemical combination with one or more other components of the catalyst composition, or in the form of metal elements. Best results are obtained when substantially all platinum is present in the catalyst in a reduced state. The platinum component usually constitutes 0.01 to 2% by mass, preferably 0.05 to 1% by mass of the catalyst when calculated on the basis of the element.

It is also within the scope of the present invention that the first reforming catalyst contains a metal promoter to modify the effect of the preferred platinum component. Such metal promoters include Group IVA (IUPAC 14) metals, other Group VIII (IUPAC 8-10) metals, rhenium, indium, gallium, zinc, uranium, dysprosium, thallium, and mixtures thereof, among which Group IVA (IUPAC) 14) Metals, rhenium and indium are preferred. Best results are obtained when the first reforming catalyst contains a tin component. Such metal promoters may be incorporated into the catalyst in a catalytically effective amount via any means known in the art.

The first reforming catalyst may contain a halogen component. The halogen component can be fluorine, chlorine, bromine, iodine or mixtures thereof. Of these, chlorine is preferred. The halogen component is usually present in admixture with the inorganic oxide support. The halogen component is preferably well dispersed throughout the catalyst, and may comprise from 0.2 to about 15% by weight of the terminal catalyst, calculated on an elemental basis.

Optional components of the first reforming catalyst are zeolites or crystalline aluminosilicates. However, it is preferable that this catalyst contains substantially no zeolite component. The first reforming catalyst may contain a non-zeolitic molecular sieve, as disclosed in US Pat. No. 4,741,820.

The first reforming catalyst is usually dried at a temperature of 100 to 320 ° C. for 0.5 to 24 hours and then oxidized at a temperature of 300 to 550 ° C. in an air atmosphere for 0.5 to 10 hours. The oxidized catalyst is treated in a substantially anhydrous reducing step for at least 0.5 to 10 hours at a temperature of 300 to 550 ° C. Further details of the preparation and activation methods of embodiments of the first reforming catalyst are disclosed in US Pat. No. 4,677,094.

At least a portion of the first effluent obtained in the first reformed zone feeds into the zeolite reformed zone for selectively forming aromatics. The free hydrogen present in the first effluent is preferably not separated before the first effluent is treated in the zeolite reforming zone, that is, the first reforming zone and the zeolite reforming zone are preferably present in the same hydrogen circuit. . Also included within the scope of the present invention is the addition of the auxiliary naphtha feed to the first effluent present in the zeolite reforming zone to produce the auxiliary reforming product. Any auxiliary naphtha feed has properties that fall within the region described in the hydrocarbon feed but optionally has a lower boiling point, and therefore is more preferred for producing light aromatics than the feed fed to the continuous reforming unit. The first effluent and any auxiliary naphtha feed are in contact with the zeolite reforming catalyst under second reforming conditions in the zeolite reforming zone.

The hydrocarbon feed is contacted with the zeolite reforming catalyst in the zeolite reforming zone to form an aromatized effluent, with the main reaction being the dehydrocyclization of the paraffinic hydrocarbons remaining in the first effluent. The second reforming conditions used in the zeolite reforming zone of the present invention are pressures of 100 kPa to 6 MPa (absolute), preferred ranges of 100 kPa to 1 MPa (absolute), and the outlet pressure of the last reactor is especially 450 kPa or less. desirable. The free hydrogen is supplied to the zeolite reforming zone in an amount sufficient to correspond to a ratio of 0.1 to 10 moles of hydrogen per mole of hydrocarbon raw material, and the ratio is preferably about 6 or more, more preferably about 5 or more. "Free hydrogen" means a molecule H ₂ which is not mixed with a hydrocarbon or other compound. The volume of contained zeolite reforming catalyst corresponds to a liquid hourly space velocity of 1-40 / hour, preferably at least 7 / hour, optionally at least 10 / hour.

The operating temperature, defined as the maximum temperature of the mixed hydrocarbon feedstock, free hydrogen, and any components containing free hydrogen, is usually 260-560 ° C. This temperature is appropriate for the overall results obtained from the continuous reforming zone and the zeolite reforming zone in relation to the yield of aromatics in the product when the chemical preparation of the chemical aromatic material is intended, or the properties such as octane number when the gasoline is the target. Set it to be level. Since zeolite reforming catalysts are particularly effective for the dehydrocyclization of light paraffins, the type of hydrocarbon in the feedstock also influences the determination of temperature. In conventional continuous reforming reactors, naphthenes are usually dehydrogenated to a fairly large extent, thereby concomitantly reducing the temperature across the catalyst bed due to the endotherm of the reaction. To compensate for the inevitable deactivation of the catalyst, the initial reaction temperature is slowly raised during the normal working period. Reactor temperatures in the continuous reforming zone and the zeolite reforming zone are different for each reactor so that the desired product can be obtained in relation to variables such as the proportion of other aromatics and the concentration of non-aromatics. Although the maximum temperature in the zeolite reforming zone is usually lower than the maximum temperature in the first reforming zone, the maximum temperature in the zeolite reforming zone may be further increased depending on the catalyst conditions and the desired product.

The zeolite reforming zone may comprise a single reactor containing a zeolite reforming catalyst, alternatively two or more parallel reactors with valves known in the art to allow for alternative cyclic regeneration. The choice between a single reactor and a parallel circulating reactor depends, in particular, on the reactor volume and the requirement to maintain a constant high yield without interruption. In any case, it is desirable for the reactor in the zeolite reforming zone to have a valve to remove material from the process so that the continuous reforming zone remains in operation even during regeneration or replacement of the zeolite reforming catalyst.

As an alternative embodiment, the zeolite reforming zone includes two or more reactors, and it is also included within the scope of the present invention to install heaters between these reactors to raise the temperature and maintain dehydrocyclization conditions. The main reaction that occurs in the zeolite reforming zone is the reaction of dehydrocyclization of paraffins with aromatic naphthenic dehydrogenation reactions to aromatics, and because the reaction is endothermic, it is lower than the temperature at which the reforming reaction occurs even before sufficient dehydrocyclization reaction occurs. As the reactants may be cooled to temperature, the alternative embodiments described above are advantageous.

The zeolite reforming catalyst contains a non-acidic zeolite, an alkali metal component and a platinum group metal component. Since the zeolite becomes acidic, the selectivity to the aromatics of the finished catalyst is lowered, so the zeolite (preferably LTL or L-zeolite) must be non-acidic. Zeolites have substantially all of the cation exchange sites occupied by non-hydrogen materials to be "non-acidic". The cations occupying the exchangeable cation moiety preferably contain at least one alkali metal, although other cationic materials may also be present. Particularly preferred non acidic L-zeolites are L-zeolites in potassium form.

To provide in a form easy to use in the catalyst of the present invention, L-zeolites are usually mixed with a binder. The art teaches that refractory inorganic oxide binders are suitable. As the binder material of the present invention, at least one of silica, alumina or magnesia is preferable. Amorphous silica is particularly preferred, and superior results are obtained when using white synthetic silica powder precipitated as ultrafine spherical particles from an aqueous solution. The silica binder is preferably non acidic, contains 0.3% by mass of sulfate, and has a BET surface area of 120 to 160 m ² / g.

The L-zeolite and binder can also be mixed by any method known in the art to form the desired catalyst form. For example, the potassium form of L-zeolite and amorphous silica may be mixed in a uniform powder formulation prior to addition of the peptizing agent. An extrudable dough is prepared by adding an aqueous solution containing sodium hydroxide. The dough preferably has a water content of 30-50 mass% so that it may form an extrudate having strength that can withstand the direct calcination process. The resulting dough is extruded through dies of appropriate size and shape to form extrudate particles, which are then dried and calcined by known methods. Alternatively, spherical particles may be shaped using the methods described above for zeolite reforming catalysts.

The alkali metal component is the main component of the zeolite reforming catalyst. One or more alkali metals including lithium, sodium, potassium, rubidium, cesium, and mixtures thereof may be used, and potassium is preferred among them. The alkali metal will suitably occupy all exchangeable cation moieties present in the non-acidic L-zeolite. Surface deposited alkali metals may also be present as described in US Pat. No. 4,619,906.

The platinum group metal component is another major component of the zeolite reforming catalyst, with the platinum component being preferred. Platinum may be present in the form of compounds such as oxides, sulfides, halides or oxyhalides, in chemical combinations with one or more of the other catalyst components in the catalyst, or in the form of metal elements. Best results are obtained when substantially all platinum is present in the catalyst in a reduced state. The platinum component usually constitutes 0.05 to 5 mass%, preferably 0.05 to 2 mass% of the catalyst when calculated on the basis of the element.

It is also within the scope of the present invention that the zeolite catalyst may contain other metal components known to modify the effect of the preferred platinum component. Such metal promoters include Group IVA (IUPAC 14) metals, other Group VIII (IUPAC 8-10) metals, rhenium, indium, gallium, zinc, uranium, dysprosium, thallium and mixtures thereof. Such metal promoters may be incorporated into the catalyst in a catalytically effective amount via any means known in the art.

The final zeolite reforming catalyst is usually dried at a temperature of 100-320 ° C. for 0.5-24 hours and then oxidized at a temperature of 300-550 ° C. (preferably 350 ° C.) in an air atmosphere for 0.5-10 hours. The oxidized catalyst is treated in a substantially anhydrous reduction step for at least 0.5 to 10 hours at a temperature of 300 to 550 ° C. (preferably 350 ° C.). The reduction step should be defined only as long as necessary to reduce the platinum to prevent deactivation of the catalyst, or may be carried out simultaneously with the start up of the device if anhydrous atmosphere is maintained. Further details of methods of making and activating embodiments of zeolite modified catalysts are disclosed in US Pat. No. 4,619,906 and US Pat. No. 4,822,762.

At least a portion of the aromatized effluent obtained from the zeolite reforming zone is contacted with the terminal bifunctional reforming catalyst in the terminal reforming zone to complete the reforming reaction to produce a high content of aromatic material. The free hydrogen present in the first effluent is preferably not separated before the aromatized effluent is treated in the terminal reformed region, that is, the first reformed region, the zeolite modified region and the terminal reformed region are in the same hydrogen cycle. It is preferable to exist.

The aromatized effluent is treated in terminal reforming conditions according to the same parameters as described above for the first reforming conditions. These conditions include an operating pressure of 100 kPa to 6 MPa (absolute), preferably an operating pressure of 100 kPa to 1 MPa (absolute), most preferably an operating pressure of 450 kPa or less. Free hydrogen, which is usually present in gas containing light hydrocarbons, is mixed with the raw materials such that a molar ratio of 0.1 to 10 moles of hydrogen per mole of C ₅ + hydrocarbons is obtained. The space velocity relative to the volume of the first reforming catalyst is between 0.2 and 10 / hour. The operating temperature is 400 to 560 ° C.

The terminal bifunctional reforming catalyst contains the catalyst described above for the first bifunctional reforming catalyst. It is preferred that the first reforming catalyst and the terminal reforming catalyst are the same bifunctional reforming catalyst.

Terminal reforming catalysts are continuously reformed by a continuous catalyst regeneration process. Optionally, continuous reforming occurs in the first reforming zone. The first reforming region and the terminal reforming region may comprise a single continuous reforming portion, and the first effluent is discharged at an intermediate point and treated in the zeolite reforming region to thereby aromatize. Generated effluent, which is treated in the terminal reformed region portion of the continuous reformate.

During the reforming reaction, the catalyst particles are deactivated to the point where they are no longer useful as a result of mechanisms such as coke deposition on the catalyst particles. Such deactivated catalysts must be regenerated and reworked before reuse in the reforming process. According to the continuous reforming process, the regeneration process proceeds for several days to maintain the high catalytic activity of almost the new catalyst, which makes the operation more severe. Moving bed systems have the advantage that the manufacturing process continues while the catalyst is removed or substituted. The catalyst particles are transported by gravity through one or more reactors in the moving bed to the continuous regeneration zone. The continuous catalyst regeneration process is usually carried out by passing the catalyst particles downwardly through the various treatment zones in the regeneration vessel by gravity in the same manner as in the moving bed. Although the movement of the catalyst through the region is shown as continuous, in practice it is semi-continuous because relatively small amounts of catalyst particles move to the dense point in time. For example, one batch per minute can be discharged from the bottom of the reaction zone, and this discharge can take 0.5 minutes. For example, the catalyst particles are one that flows for 0.5 minutes in a period of one minute. Since the reaction zone and the regeneration zone of the present invention are large compared to the batch size, the catalyst bed may be simulated as moving continuously.

In the continuous regeneration zone, the catalyst particles come into contact with a hot oxygen-containing gas stream in the combustion zone to remove coke formed by oxidation. This catalyst is then passed through a drying zone, usually in contact with a hot anhydrous air stream to remove moisture. The anhydrous catalyst is cooled by direct contact with the air stream. Optionally, the catalyst is contacted with a gas containing a halogen component to halogenate in the halogen region located below the combustion zone. Finally, the catalyst particles are reduced by hydrogen-containing gas in the reduction zone to produce reprocessed catalyst particles, which are then transferred to a moving bed reactor. Details of the continuous catalyst regeneration process, particularly related to moving bed reforming processes, are disclosed herein and in US Pat. Nos. 3,647,680, A 3,652,231, A 3,692,496 and A 4,832,921.

The catalyst particles consumed from the continuous reforming portion are first contacted with a hot oxygen-containing gas stream in the regeneration zone to remove coke accumulated on the surface of the catalyst during the reforming reaction. The coke content of the spent catalyst particles is on the order of 20% of the catalyst weight, more typically 5-7%. Coke contains carbon as a main component and a relatively small amount of hydrogen, and is oxidized to carbon monoxide, carbon dioxide and water at a temperature of 450 to 550 ° C. (this temperature can reach 600 ° C. in the local region). Oxygen for combustion of the coke flows into the regeneration gas which usually contains 0.5 to 1.5% by volume of oxygen in the combustion section of the regeneration zone. Flue gas consisting of carbon monoxide, carbon dioxide, water, unreacted oxygen, chlorine, hydrochloric acid, nitrous oxide, sulfur oxides and nitrogen is collected from the combustion section, some of which are discharged from the regeneration zone as flue gas. The remainder is mixed with a small amount of supplemental gas (usually air), usually about 3% of the total gas, to replenish the consumed oxygen and then returned to the combustion section as regeneration gas. Typical combustion section arrangements are shown in US Pat. No. 3,652,231.

As the catalyst particles pass down the combustion section and with this coke removed, the "leakage" point is typically about half the point where less is consumed than all the oxygen delivered. The reforming catalyst particles of the present invention are known to have a large surface area in relation to multiple pores. When the catalyst particles reach the breakthrough point in the bed, the coke remaining on the surface of the particles is buried in the pores, so that the oxidation reaction is made at a much slower rate.

Moisture in the make-up gas discharged from the combustion stage is removed from the small amount of flue gas discharged, thus achieving equilibrium during the regeneration gas loop. The water concentration in the recycle loop is lowered by drying the air constituting the make-up gas and installing a dryer for the gas that circulates the recycle gas loop or by exhausting a large amount of flue gas from the recycle gas stream to lower the equilibrium in the regeneration gas loop. You can

Optionally, the catalyst particles in the combustion zone pass directly through the drying zone, which evaporates moisture from the surface and pores of the particles by contact with the heated gas stream. The gas stream is usually heated to 425-600 ° C. and optionally preheated to increase the amount of moisture that can be absorbed. The dry gas stream preferably contains oxygen, more preferably an oxygen content of about the same or more than air, whereby combustion of the final residue in the coke discharged from the interior pores of the catalyst particles can take place in the drying zone, Excess oxygen not consumed in the drying zone can pass upwards with the flue gas discharged from the combustion zone to replace the oxygen depleted through the combustion reaction. In addition, contacting the catalyst particles with a gas containing a high concentration of oxygen raises the oxidation state of the platinum or other metal contained therein to help restore the overall activity of the catalyst particles. The dry zone is designed to reduce the water content of the catalyst particles to 0.01 parts by weight or less based on the catalyst before the catalyst particles exit the dry zone.

After any drying step, the catalyst particles contact the chlorine containing gas in a separate zone to redisperse the noble metal on the surface of the catalyst. This redispersion process is necessary to reverse the coagulation process of precious metals generated by treatment with high temperature and steam in the combustion zone. The redispersion process is carried out at a temperature of 425-600 ° C, preferably 510-540 ° C. Conditions in which the chlorine concentration in the gas is about 0.01 to 0.2 mole percent and the presence of oxygen are quite advantageous for facilitating the rapid and complete redispersion of platinum group metals to provide redispersed catalyst particles.

The regenerated and redispersed catalyst is converted to the elemental state of the precious metal on the catalyst by contacting with a reducing gas with a high hydrogen content prior to use in catalytic applications. Reduction of the oxidized catalyst is an essential step in most reforming processes, but this step is most often performed immediately before or in the reaction zone, which is not usually seen as part of the apparatus in the reaction zone. The highly oxidized catalyst is reduced at 450-550 ° C., preferably 480-510 ° C., using a relatively pure hydrogen reducing gas to provide a reprocessed catalyst.

Most of the catalyst fed to the zone during the line-out operation of the continuous reforming is the first reforming catalyst regenerated and reprocessed as described above. Some of the catalysts fed to the reforming zone may be first reforming catalysts supplied as supplemental gas, in particular to eliminate losses and miniaturization due to deactivation during the initiation of the reforming process, but the amount of these catalysts is small (usually regeneration). Less than 0.1% per cycle). The first reforming catalyst is a combination having a dual function comprising a metal hydrogenation-dehydrogenation component, preferably a platinum group metal component, on a refractory support (preferably an inorganic oxide providing acid sites for cracking and isomerization). . The first reforming catalyst not only dehydrogenates, but also isomerizes, cracks and dehydrogenates the naphthenes contained in the feed.

A configuration in which the zeolite reforming zone is installed in an existing continuous reforming unit (ie, a facility equipped with a main facility for moving bed reforming units related to continuous catalyst regeneration) is a particularly advantageous embodiment of the present invention. Continuous regeneration reforming units are relatively capital intensive, typically perform fairly harsh reforming processes and include additional facilities for continuous catalyst regeneration. The entire catalyst reforming process offers the advantages of 1 to 3 by laying the zeolite reforming zone which is particularly effective in converting hard paraffins from the first effluent produced by the continuous reforming process.

① increase in toxicities associated with the total yield of aromatics or the octane number of the product

(2) increased throughput of the continuous reformer due to reduced toxicity of the continuous reformer (at least 5%, preferably at least 10%, optionally at least 20%, in some embodiments at least 30%). Such reduced toxicity is achieved by one or more of the operating conditions such as higher space velocity, lower hydrogen / hydrogen ratio and less catalyst circulation in the continuous reforming section. The first effluent discharged from the continuous reforming portion of the first zeolite reforming zone can then be processed to obtain a product of the desired quality.

③ Increased selectivity, reduced toxicities of continuous reforming operations and selective conversion of residual paraffins in the first effluent to aromatics.

The aromatics content in the C ₅ + part of the effluent increases by at least 5 mass% based on the aromatics content of the hydrocarbon feed. The composition of the aromatic material mainly depends on the raw material composition and the operating conditions, and is usually composed of C _{6 to} C ₁₂ aromatic materials.

According to the reforming process of the present invention, a high aromatic content contained in a reformed effluent containing hydrogen and light hydrocarbons is produced. Using techniques and apparatus known in the art, the reformate effluent exiting the terminal reforming zone is usually passed through the cooling zone to the separation zone. In the separation zone, which is usually maintained at 0 ° C. to 65 ° C., the gas with high hydrogen content is separated from the liquid phase. Most of the high hydrogen content stream products are suitable for recycling back to the first reforming zone via suitable compression means, with some of the hydrogen being useful as pure products for use in other petroleum refineries or chemical plants. The liquid phase discharged from the separation zone is usually processed by exiting the fractionation system to control the concentration of light hydrocarbons and to obtain products with high aromatic content.

Example

The following examples are presented to demonstrate the invention and to illustrate certain embodiments of the invention.

A mechanical model was set up and a series of staged reforming processes studied using data from other catalysts produced by pilot equipment and commercial processes. The two catalysts used in this study were bifunctional catalysts ("B") and zeolite catalysts ("Z"), respectively, and their composition (mass%) was as follows.

Catalyst B: 0.376% Pt and 0.25% Ge on the extruded alumina support

Catalyst Z: 0.82% Pt on Silica Bonded Non Acidic L-zeolite

Four reactor systems were used as models, with each catalyst described below being loaded and forming the indicated quantities (mass%) of benzene, toluene and C ₈ aromatics.

First reactor A terminal reactor benzene toluene C₈ Aromatic substances B Z Z B 7.12 23.15 18.41 B Z B B 6.71 21.92 18.35 Z Z B B 6.95 20.78 18.16 Z Z Z B 7.29 22.17 18.07 Z B Z B 6.95 22.44 17.73 B Z B Z 7.13 23.49 17.71 Z Z B Z 7.27 22.42 17.57 B B Z B 8.17 23.16 17.45 Z B B B 7.07 20.93 17.02 B Z Z Z 7.82 24.53 16.93 Z B Z Z 7.48 23.80 16.55 Z Z Z Z 7.93 23.65 16.46 Z B B Z 7.32 22.71 16.40 B B Z Z 8.50 24.55 16.36 B B B B 7.55 21.61 15.95 B B B Z 9.03 23.41 15.81

Sandwich arrangements of bifunctional first and terminal catalysts and intermediate zeolite catalysts are particularly effective for the preparation of C ₈ aromatics, which constitute the largest proportion of modern aromatics.

The process of the present invention provides the advantage that the yield of aromatics is significantly improved over the prior art by carrying out a combination of bifunctional catalytic reforming and zeolite reforming reactions in a sandwich arrangement.

Claims (8)

(a) contacting a hydrocarbon feedstock with a first bifunctional catalyst containing a platinum group metal component, a metal promoter, a refractory inorganic oxide and a halogen component in a first reforming zone under first reforming conditions to provide a first effluent, (b) contacting at least a portion of said first effluent with a zeolite reforming catalyst containing a non-acidic zeolite, an alkali metal component and a platinum group metal component under a second reforming condition in a zeolite reforming zone to provide an aromatized effluent. , And (c) the content of aromatics by contacting a terminal bifunctional reforming catalyst containing a platinum group metal component, a metal promoter, a refractory inorganic oxide and a halogen component with at least a portion of said aromatized effluent under terminal reforming conditions in the terminal reforming region. To give this high product A catalytic reforming method of a hydrocarbon characterized by contacting a hydrocarbon feedstock in a catalyst system comprising at least three sequential catalyst zones, including a high aromatic content product. The method of claim 1 wherein the first bifunctional reforming catalyst and the terminal bifunctional reforming catalyst are the same bifunctional reforming catalyst. 3. The bifunctional reforming catalyst of claim 1 or 2, wherein the first reforming region and the terminal reforming region comprise one continuous reforming portion and the aromatics effluent is in a reactor following the first reforming region on the continuous reforming sequence. Characterized in that it is contacted with. The method of claim 1 or 2, wherein the platinum group metal component of the zeolite reforming catalyst comprises a platinum component and the non-acidic zeolite comprises L-zeolite in potassium form. The method of claim 2, wherein the bifunctional reforming catalyst further comprises a metal promoter consisting of at least one of Group IVA (IUPAC 14) metals, rhenium, indium, or mixtures thereof. The method of claim 1 or 2, wherein the first reforming conditions include a pressure of 100 kPa to 1 MPa, a liquid hourly space velocity of 0.2 to 20 / hour, a molar ratio of hydrogen to C ₅ + hydrocarbons of 0.1 to 10 and 400 to The method is characterized in that the temperature of 560 ℃. The method according to claim 1 or 2, wherein the second reforming condition is a pressure of 100 kPa to 6 MPa, a liquid hourly space velocity of 1 to 40 / hour, and a temperature of 260 to 560 ° C. The process of claim 1 or 2, wherein the end modification conditions are at a pressure of 100 kPa to 1 MPa, a liquid hourly space velocity of 0.2 to 10 / hour, a molar ratio of hydrogen to C ₅ + hydrocarbons of about 0.1 to 10 and 400 to The method is characterized in that the temperature of 560 ℃.