KR20080096675A - Selective conversion of oxygenate to propylene using moving bed technology and a hydrothermally stabilized dual-function catalyst system - Google Patents

Abstract

The average propylene cycle selectivity of an oxygenate to propylene (OTP) process using a dual-function oxygenate conversion catalyst is substantially enhanced by the use of a combination of: 1) moving bed reactor technology in the hydrocarbon synthesis portion of the OTP flow scheme in lieu of the fixed bed technology of the prior art; 2) a hydrothermally stabilized and dual-functional catalyst system comprising a molecular sieve having dual-function capability dispersed in a phosphorus-modified alumina matrix containing labile phosphorus and/or aluminum anions; and 3) a catalyst on-stream cycle time of 400 hours or less. These provisions stabilize the catalyst against hydrothermal deactivation and hold the build-up of coke deposits on the catalyst to a level which does not substantially degrade dual-function catalyst activity, oxygenate conversion and propylene selectivity, thereby enabling maintenance of average propylene cycle yield near or at essentially start-of-cycle levels.

Description

SELECTIVE CONVERSION OF OXYGENATE TO PROPYLENE USING MOVING BED TECHNOLOGY AND A HYDROTHERMALLY STABILIZED DUAL-FUNCTION CATALYST SYSTEM}

The present invention is generally a dual action, preferably used in a hydrocarbon synthesis reaction zone of an oxygenate to propylene (OTP) process operating at relatively high temperatures, preferably by steam diluent, and using mobile phase reactor technology. The present invention relates to the application of hydrothermal stabilization technology on a catalytic catalyst system. Using the hydrothermally stabilized bifunctional catalyst system in conjunction with a mobile phase reactor system in an OTP process promotes catalyst deactivation control not only in on-stream cycles but also on a cycle-to-cycle basis, thereby prolonging the results reported in the prior art. The coke level on the bifunctional catalyst can be maintained at a value that does not significantly reduce the activity and propylene selectivity of the catalyst for a period of time. As a result, the modified OTP process, as well as the initial on-stream catalyst cycle time, over the subsequent cycles, as compared to the average cycle propylene yield obtained with the prior art processes using fixed bed reactor technology and destabilized bifunctional catalyst systems under these conditions. It is possible to greatly improve the average propylene yield that can be achieved by.

Most of the world's petrochemical industry relates to the production of light olefin materials and the subsequent use of such light olefin materials in the production of numerous important chemical products through known chemical reactions such as polymerization, oligopolymerization, alkylation and the like. Light olefins include ethylene, propylene and mixtures thereof. The art has sought a bulk raw material source for supplying the demand for such light olefin materials in addition to petroleum. Oxygenates are of particular interest as they can be produced from widely available materials such as coal, natural gas, recycled plastics, various carbon waste streams derived from industry and various products and by-products derived from agriculture. Techniques for producing methanol and other oxygenates from this type of raw material are well established. Substantially two main techniques are known in the prior art which discuss the conversion of methanol to light olefins (MTO). The first of the MTO processes is described in US 4,387,263, which discloses a methanol conversion technique using a ZSM-5 type catalyst system where recycling of DME byproducts is a problem. US 4,387,263 focused on the DME and methanol scrubbing steps using a solvent to efficiently and effectively recover light olefin values of unreacted methanol and intermediate reactant DME. In order to control the amount of unwanted C ₄ + hydrocarbon product produced by the ZSM-5 type catalyst system, the prior art then uses non-zeolitic molecular sieve catalyst materials. US 5,095,163, US 5,126,308 and US 5,191,141 disclose metal aluminophosphates (ELAPO), more specifically silicoaluminophosphate molecular sieves (SAPO), very preferably SAPO-34. Typical OTO techniques produce a mixture of light olefins, primary ethylene and propylene with various heavy boiling olefins. Typical OTO process technology allows the major olefin product recovered from it to be transferred from ethylene to propylene by varying the conditions maintained in the reaction zone, but the art can provide superior yields of propylene over typical OTO technology. The conversion of oxygenates to propylene (OTP) has been sought for a long time.

The publication US 2003/0139635 A1, published July 24, 2003, describes a method for selectively producing propylene from a feedstock comprising methanol and / or DME. The three reactors comprise the stationary phase of the oxygenate conversion catalyst in a cocurrent arrangement for the oxygenate feed and in a direct current arrangement for the effluent of the first reactor and the second reactor. This publication discloses a pentasil type (ie, ZSM-5 or ZSM-11) dual action OTP catalyst system having an alkali content of less than 380 ppm, a zinc oxide content of less than 0.1 wt%, and a limited amount of cadmium oxide. Is taught. The MTP requires in-system regeneration at Rothaemel et al. "Demonstrating the New Methanol to Propylene (MTP) Process" presented at the ERTC Petrochemical Society held in Paris, France, in March 2003. It is further described that the on-stream portion of the process cycle of 500-700 hours is expected before the conversion activity shows a significant drop. Conventional procedures for replenishment for deactivation during catalytic operation include increasing the average temperature of the reactor with the intention of maintaining the conversion rate of the oxygenate charge in the target range above 94%.

Thus, the challenge addressed by the present invention is to compensate for the low propylene selectivity by increasing the average propylene selectivity of the OTP process over its on-stream cycle time, thereby reducing the need to recycle olefin products other than propylene.

Summary of the Invention

The inventors have found that the hydrothermality of the bifunctional catalyst system used when the overall propylene selectivity is exposed to relatively high temperatures of steam as well as the average coke level and reaction conditions deposited on the OTP conversion catalyst during the on-stream portion of the process cycle. It was recognized as a function of stability. The inventors have discovered a binder or matrix material of prior art bifunctional catalyst systems that can significantly increase hydrothermal stability when used in OTP processes operated in a mobile phase manner. The matrix material is a phosphorus modified alumina matrix containing labile phosphorus and / or aluminum anions. The average propylene selectivity of OTP processes operated in a mobile phase manner can be significantly increased when the bifunctional catalyst comprises molecular sieves, which convert at least a portion of the oxygenate feed to propylene and C ₂ and C ₄ It is known to be capable of interconverting olefins to propylene, and migrate to these molecular sieves and undergo dealumination resulting from exposure to relatively hot steam in both the on-stream and regenerated portions of the OTP process cycle. It is embedded in a matrix material comprising phosphorus modified alumina containing labile phosphorus and / or aluminum anions that can stabilize and / or recover and / or anneal its backbone structure. We have also found that the hydrothermally stabilized bifunctional catalyst of the present invention can be used to significantly improve the performance of prior art fixed bed OTP processes.

The first object of the present invention is the propylene selectivity during the on-stream cycle as well as the cycle-to-cycle loss caused by the regeneration of the prior art fixed bed OTP process when operated with a steam diluent and a steam sensitive dual functional catalyst system. It is to provide a realistic and technically feasible solution to the problem of loss. A second object is to improve the economics of the prior art OTP process, which controls coke deposition on the bifunctional catalyst to maintain oxygenate conversion and propylene selectivity at a higher level than the prior art. A third object is to prevent excessive deactivation by coke deposition of bifunctional OTP catalysts in order to restore catalyst activity to minimize hydrothermal damage and to minimize the severity of the regeneration step required to extend catalyst life. A more general goal is to combine mobile phase technology and hydrothermal stabilization catalyst technology to provide more efficient OTP processes.

The present invention stabilizes hydrothermally, maintaining catalyst performance substantially at or near the onset cycle level in the initial cycle as well as in subsequent cycles to increase the average cycle yield of propylene and minimize oxygen oxide spikes in the product stream. OTP process for selective conversion of oxygenate feeds to propylene using bifunctional catalyst technology and mobile phase technology. In the first step of the process, the oxygenate feed and diluent are contacted with a bifunctional catalyst containing molecular sieve in an amount corresponding to 0.1 to 5 mol of diluent per mol of oxygenate, the molecular sieve being It is known to be able to convert at least a portion to propylene and to convert C ₂ and C ₄ + olefins to C ₃ olefins and is dispersed in a phosphorus modified matrix containing labile phosphorus and / or aluminum anions. This step is carried out in an OTP reaction zone containing one or more fixed or mobile phase reactors operating under oxygenate conversion conditions effective to selectively convert oxygenates to propylene and convert heavy olefins circulated to any ethylene or reactor to propylene. Conduct. The effluent stream is then subjected to a predominant amount of C ₃ olefin product and water by-products and to smaller amounts of C ₂ olefins, C ₄ + olefins, C ₁ -C ₄ + saturated hydrocarbons and small amounts of unreacted oxygenates, by-product oxygenates, Emissions are from the OTP reaction zone containing polyunsaturated hydrocarbons (eg dienes and acetylenic hydrocarbons) and aromatic hydrocarbons. In the second stage, the effluent stream is passed through a separation zone and cooled, the water phase and heavy olefins, heavy saturated hydrocarbons and water fractions containing C ₃ olefin-rich vapor phase fractions, unreacted oxygenates and byproduct oxygenates and It is separated into a liquid hydrocarbon fraction containing small amounts of polyunsaturated hydrocarbons and aromatic hydrocarbons. Subsequently, at least a portion of the water fraction recovered in the separation step is recycled to the oxygenate conversion step to provide at least a portion of the diluent used in the present invention. The vapor phase fraction recovered in the separation step is a fraction rich in C ₂ olefins, a product fraction rich in C ₃ olefins and a fraction rich in first C ₄ + olefins containing a small amount of polyunsaturated hydrocarbons, which are further added in the second separation zone. Are separated. At least a portion of the C ₂ olefin rich fractions may be recovered as product or optionally recycled to the OTP reaction zone. The C ₃ olefin rich product fraction is then recovered as the main product stream and at least a portion of the first C ₄ + olefin rich fraction is fed to any optional hydrotreatment step or recycled directly to the OTP conversion step. Optional hydrotreating steps are designed to selectively convert polyunsaturated compounds contained in a stream rich in C ₄ + olefins to the corresponding olefins, thereby removing coke precursors from the OTP conversion step. Any such catalytic hydrogenation step was converted to olefins corresponding to the highly unsaturated hydrocarbon and the second 1 C ₄ + olefin containing at least a portion, and the hydrogen-rich stream, a metal hydrogenation catalyst, is contained therein, selectively hydrogenated C with _It is carried out by contacting under selective hydrogenation conditions effective to produce a fraction rich in 4+ olefins. At least a portion of the last fraction is then recycled to the OTP conversion step to convert the heavy olefinic material to an additional amount of the desired propylene product.

The invention includes a process for selectively converting an oxygenate feed to propylene, as described above, wherein the bifunctional catalyst is a zeolite-based molecular sieve whose structure corresponds to ZSM-5 or ZSM-11, or whose structure is SAPO. ELAPO molecular sieves corresponding to -34, or a mixture of these materials.

Preferably, the OTP reaction zone contains three or more mobile phase reactors connected in a direct or cocurrent arrangement for the oxygenate and in a direct flow arrangement for the catalyst particle stream therethrough.

The oxygenate feed preferably contains methanol or dimethylether or mixtures thereof. In this embodiment, the process is referred to herein as the conversion of methanol to propylene (MTP) embodiment.

If the liquid hydrocarbon fraction recovered in the first separation step is further separated into a second C ₄ + olefin rich fraction and a naphtha product fraction, a high yield of propylene is obtained and at least of the resulting second C ₄ + olefin rich fraction Some are fed directly into the OTP conversion step or any optional hydrotreatment step, and the resulting hydrotreating product is recycled to the OTP conversion step to convert the heavy olefins to propylene.

Brief description of the drawings

Is a process flow diagram of a preferred embodiment of the present invention.

Definition of terms and conditions

The following terms and conditions are used herein in the following meanings: (1) 'part' of a stream means a preparative portion having the same composition as the entire stream, or a portion obtained by removing components that are readily separable from the entire stream (Eg, if the stream contains hydrocarbons mixed with steam, after most of the concentration of the steam, it contains an aqueous portion and a hydrocarbon portion). (2) A 'top' stream means a pure top stream that is recovered from the particular zone after recycling to any part of any portion for reflux or for other reasons. (3) 'bottom' stream means a pure bottoms stream from a particular zone obtained after recycling any portion for the purpose of reheating and / or reboiling and / or after any phase separation. (4) The term 'light olefin' means ethylene, propylene and mixtures thereof. (5) The term 'heavy olefin' means an olefin having a molecular weight greater than propylene. (6) Representation The 'OTP' process means a process for converting an oxygenate to propylene, and in a preferred embodiment, when the oxygenate is methanol, the OTP process is referred to herein as the MTP process. (7) The term 'oxygenate' means an oxygen substituted aliphatic hydrocarbon having 1 to 10 carbon atoms. (8) The term 'catalyst on-stream cycle time' means the length of time the catalyst particles are exposed to the feed under conversion conditions before exiting the reaction zone for regeneration. (9) The term 'average propylene cycle yield' means the total propylene yield for the catalyst on-stream cycle time divided by the total amount of the oxygenated feed converted during the catalyst on-stream cycle time. (10) The term 'bifunctional' means that the OTP catalyst promotes both the OTP reaction and the olefin interconversion reaction required to convert C ₂ and C ₄ + olefins to propylene. (11) The term 'labile phosphorus and / or aluminum anions' means that one or both of the anions can be easily displaced and / or moved into the structure of the molecular sieve concerned.

Detailed description of the invention

The feedstream charged to the OTP process of the present invention contains at least one oxygenate. The oxygenated feedstock preferably contains one or more oxygen atoms and 1 to 10 carbon atoms, and more preferably 1 to 4 carbon atoms. Suitable oxygenates include lower straight or branched chain alcohols and their unsaturated counterparts. Representative examples of suitable oxygenate compounds include methanol, dimethyl ether (DME), ethanol, diethyl ether, methyl ether, formaldehyde, dimethyl ketone, acetic acid and mixtures thereof. Preferred feedstreams contain methanol or dimethylether and mixtures thereof.

In the OTP conversion step of the present invention, the oxygenate feed is a byproduct hydrocarbon containing propylene and aliphatic moieties such as methane, ethane, ethylene, propane, butylene by contacting the feedstock with the bifunctional OTP catalyst under effective OTP conditions. , Butane (but not limited to), and limited amounts of other high carbon aliphatic are optionally converted by the catalyst. This OTP conversion step also forms small amounts of polyunsaturated hydrocarbons such as dienes and acetylenic hydrocarbons and aromatic hydrocarbons. The presence of diluents is a useful option for maintaining the selectivity of OTP catalysts to produce light olefins, especially propylene. Diluents such as steam can be used to provide specific equipment cost and thermal efficiency benefits, as well as to reduce the partial pressure of the oxidized reactants to increase the selectivity to olefins. It is also possible to apply a phase change of steam and liquid water to benefit from heat transfer between the feedstock and the reactor effluent, and separation of the diluent from the product requires only a simple condensation step to separate the water from the hydrocarbon product.

As mentioned above, the amount of diluent used is in the range of 0.1 to 5 mol, preferably 0.5 to 2 mol, per mol of the oxygenate to lower the partial pressure of the oxygenate to the desired level to produce propylene. All embodiments of the present invention contemplate recycling one or more of certain heavy olefinic by-product streams containing significant amounts of olefins in addition to propylene and saturated hydrocarbons. Thus, the recycle stream feeds the saturated hydrocarbon diluent to the OTP reaction zone, so that the amount of diluent that must be added to the OTP reaction zone to achieve the target molar ratio of diluent to oxygenate is reduced as soon as the OTP reaction zone is initiated. . In the most preferred case of using steam as a diluent, the amount of steam charged to the OTP reaction zone during initiation will be reduced in proportion to the amount of saturated hydrocarbons and other inert materials recycled to the reaction zone.

The conversion conditions applied in the OTP reaction zone according to the invention are carefully chosen to be preferred for producing propylene from oxygenates. An oxygenate conversion temperature range of 350-600 ° C. is effective for the conversion of oxygenates on known oxygenate conversion catalysts. Lower temperatures in the range are preferred to produce propylene, and upper temperatures in the range are preferred to consume propylene to produce ethylene. The inlet temperature into the OTP reaction zone is preferably in the range from 350 to 500 ° C, more preferably in the range from 400 to 500 ° C. The increase in temperature across each OTP reactor is maintained in the range of 10-80 ° C. to minimize hydrothermal deactivation and occurs when the end temperatures of the respective reactors reach levels above those compensated by the present invention. It is desirable to prevent the acceleration of cork deposition. Most known methods for controlling the temperature increase in the reactor zone use multiple phases of the catalyst in separate reactors that cool in-phase or between-phase using appropriate heat exchange means, and / or recycle streams of relative cooling amounts, or Adding a portion of the oxygenate feed and / or diluent used in the region. In the present invention, it is contemplated to apply light and / or heavy olefin interconversion reactions which are moderate endothermic reactions to help control the reactor temperature increase to a particular range. Preferred modes of operation of the present invention provide additional amounts of reactants and diluents by using at least three mobile phase reactors where at least a portion of the phase quenching takes place using a relatively low temperature recycle stream.

The step of converting oxygenates to propylene is advantageously carried out over a wide range of pressures, including inlet voltages between 10.1 kPa and 10.1 MPa, but light olefins such as propylene are known to be prone to formation at low pressure conditions. Therefore, it is desirable to apply an inlet pressure of 101.3 to 304 kPa, with the best results obtained at 136 to 343 kPa.

The contact time of the bifunctional catalyst with the reactant is the sum of the mass of the oxygenate reactant delivered to the OTP conversion zone and the mass of any reactive hydrocarbon material or any recycle stream present in the feed stream being present in the OTP conversion zone. Measurements are generally made in terms of relative hourly space velocity (WHSV) calculated on the basis of hourly mass flow rate divided by mass of bifunctional catalyst. The WHSV in the OTP conversion region is in the range of 0.1 to 100 hours ^-1 , preferably in the range of 0.5 to 20 hours ^-1 , and it is common that the best results are obtained in the range of 0.5 to 10 hours ^-1 .

In the step of converting oxygenates to propylene, it is preferred to use a bifunctional hydrothermally stable catalyst system which retains not only the conversion of oxygenates to propylene but also the interconversion capacity of olefins other than propylene to propylene. Any known catalyst material that possesses the ability to catalyze both reactions is a suitable component for use in the catalyst system of the present invention. Preferred bifunctional catalysts contain molecular sieves as active ingredients, more particularly the molecular sieves have relatively small pores. Preferred small pore molecular sieves have good adsorption capacity (measured by standard McBain-Bakr gravimetric adsorption method using specific adsorptive molecules) and oxygen adsorption (average kinematic diameter 0.346 nm) and insignificant isobutane adsorption (mean kinematic diameter 0.5 nm). It is defined as having at least a portion, preferably a major portion, of the voids having an average effective diameter, which is indicated. The average effective diameter is more preferably characterized by excellent xenon adsorption (average kinetic diameter of 0.4 nm) and minimal isobutane adsorption, excellent n-hexane adsorption (average kinetic diameter of 0.43 nm), and isobutane adsorption. It is most preferable to be characterized by a slight. Minor adsorption of a given adsorbate is less than 3% by weight of the catalyst while good adsorption is an amount above the cut-off value in the test. Certain molecular sieves useful in the present invention have an average effective diameter of voids of less than 5 mm 3. The average effective diameter of the pores of the preferred catalyst is described in its entirety herein by reference. W. Breck, ZEOLITE MOLECULAR SIEVES by John Wiley & Sons, New York (1974). The term 'effective diameter' is sometimes used to mean that the pores are irregularly shaped (eg elliptical) so that the pore dimensions feature molecules that can be adsorbed rather than the actual dimensions. Preferably, the small pore catalyst has a substantially uniform pore structure, for example a pore of substantially uniform size and shape. Suitable bifunctional catalysts can be selected from zeolitic molecular sieves and non-zeolitic molecular sieves.

The zeolitic molecular sieve in calcined form can be represented by the following formula:

Me _{2 / n} O: Al ₂ O ₃ : xSiO ₂ : yH ₂ O

In the above formula, Me is a cation, x is a value of 2 to infinity, n is a cation valence, y is 2 to 100, and more typically a value of 2 to 25.

The zeolites that can be used include chabazite (also called zeolite D), clinoptilolite, erionite, ferrilite, mordenite, zeolite A, zeolite P, ZSM-5, ZSM-11 and MCM-22. Can be mentioned. Zeolites with high silica content (ie, good results when the ratio of framework silica to alumina is greater than 100, typically greater than 150, and the molar ratio of silica to alumina is 150: 1 to 800: 1) desirable. Such highly silica zeolites having a structure of ZSM-5 are silicalites and the term used herein includes both silica polymorphs disclosed in US 4,061,724 and F-silicates disclosed in US 4,073,865. Preferred zeolites for use in the present invention have a structure of ZSM-5 or ZSM-11.

Zeolite-based bifunctional catalysts most preferred for use in the present invention are zeolites having a structural arrangement of ZSM-5 or ZSM-11 disclosed in US 2003 / 0139635A1 and sometimes referred to in the literature as having a 'pentasil' structure. to be. Borosilicate zeolites having a structural arrangement of ZSM-5 or ZSM-11 are disclosed as particularly preferred bifunctional catalysts in US Pat. No. 4,433,188. The use of the dual functionality of the ZSM-5 catalyst system is disclosed in US Pat. No. 4,579,999, in which the conversion zone of methanol to olefins is also filled with a recycle stream containing ethylene and a separate olefin-rich C ₅₊ gasoline stream. Increase the yield of C ₃ -C ₄ olefins in the first stage MTO reaction zone disclosed in. The use of zeolite based catalysts having a mordenite structure arrangement is disclosed in GB-A-2171718.

Non-zeolitic molecular sieves include molecular sieves having a suitable effective pore size and included in the experimental chemical composition represented by the following empirical formula as anhydrides:

(EL _x Al _y P _z ) O ₂

In the above formula, EL is an element selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and mixtures thereof, x is at least 0.005 as the mole fraction of EL, and y is the mole fraction of aluminum. It is 0.01 or more, z is 0.01 or more as a mole fraction of phosphorus, and x + y + z is 1. When EL is a mixture of metals, x means the total amount of elemental mixture present. As the component (EL), silicon, magnesium and cobalt are preferable, and silicon is particularly preferable.

The preparation of various ELAPOs is described in US 5,191,141 (ELAPO); US 4,554,143 (FeAPO); US 4,440,871 (SAPO); US 4,853,197 (MAPO, MnAPO, ZnAPO, CoAPO); US 4,793,984 (CAPO); US 4,752,651 and US 4,310,440. In general, ELAPO molecular sieves are synthesized by hydrothermal crystallization from a reaction mixture containing a reactive source of EL, aluminum, phosphorus and a template. Reactive sources of EL are metal salts such as chloride salts and nitrate salts. When the EL is silicon, the source is preferably fumed silica, colloidal silica or precipitated silica. Preferred reactive sources of aluminum and phosphorus include boehmite like alumina and phosphoric acid. Preferred templates include amines and quaternary ammonium compounds. Particularly preferred template is tetraethylammonium hydroxide (TEAOH). As can be seen from the combination of the teachings of US 4,677,243 and US 4,527,001, the ELAPO material is known to promote both the direct conversion of oxygenates to light olefins and the interconversion of olefins to the desired product olefins. US 6,455,749 specifically teaches the use of silicoaluminophosphate catalysts (SAPOs) as bifunctional catalysts, particularly preferred for SAPO-34. In addition, US 6,455,749 teaches logically clearly both the use of ZSM-5 and SAPO-34 type catalyst systems combined with silica type catalyst systems for use in converting C ₄ olefins to other olefins.

The best results with non-zeolitic catalysts in the present invention can be obtained when using SAPO-34 as a bifunctional catalyst, while the best results with zeolitic materials have a silica to alumina framework molar ratio of 150 to 800: 1. And most preferably with a highly siliceous ZSM-5 or ZSM-11 type material which is from 400: 1 to 600: 1. A particularly preferred embodiment of the present invention is to use a mixture of a non-zeolitic catalyst system and a zeolitic catalyst system. The mixed catalyst embodiment may be carried out using a physical mixture of particles containing zeolitic materials and particles containing non-zeolitic materials, or the catalyst is used to modify the two types of materials into a phosphorus modified aluminum matrix. It can be prepared by mixing to form particles having two components present therein. In either case, the preferred formulations are relative amounts of SAPO-34 and ZSM-5 such that ZSM-5 or ZSM-11 comprise 30 to 95% by weight, particularly preferably 50 to 90% by weight, of the molecular sieve portion of the mixture. Or a mixture of ZSM-11.

A preferred embodiment of the present invention is that the component (EL) content of ELAPO varies from 0.005 to 0.05 mole fraction. When EL is at least one component, the total concentration of all components is from 0.005 to 0.05 mole fraction. Particularly preferred embodiments are those wherein the EL is silicon (commonly referred to as SAPO). SAPOs that may be used in the present invention are described in US 4,440,871; Any of those described in US 5,126,308 and US 5,191,141. Of the particular crystallographic structures described in the '871 patent, SAPO-34 (ie, structure type 34) is preferred. The SAPO-34 structure adsorbs xenon but does not adsorb isobutane, which means that the pore opening is 4.2 kPa. Also preferred are other SAPOs, SAPO-17, disclosed in the '871 patent. The SAPO-17 structure is characterized by adsorbing oxygen, hexane and water but not isobutane, which means that the openings of the pores are greater than 4.3 kPa and less than 5.0 kPa.

Preferred molecular sieve components are introduced or dispersed into a phosphorus modified alumina matrix containing labile phosphorus and / or aluminum anions to form hydrothermally stabilized porous solid particles. The relative amount of molecular sieve relative to the alumina matrix material is preferably set such that the molecular sieve component is present in an amount corresponding to 10 to 75% by weight of the particles in balance with the inherent alumina matrix. Best results are obtained when the molecular sieve portion constitutes 50-70% by weight of the resulting catalyst particles. In order to facilitate the transfer of the resulting bifunctional catalyst to the relevant regeneration zone as well as to the mobile phase reactor, it is highly preferred that the particles are spherical or more nearly spherical in shape. The diameter of the catalyst particles is preferably 0.5-7 mm, with the best results generally being obtained by spherical particles having a diameter of 1.6 mm.

The alumina phosphor modified alumina matrix used in the present invention is to be distinguished from the alumino-phosphate (ie AlPO ₄ ) matrix material presented in the prior art. As described in EP-A-1396481, alumina is very inert and not acidic in nature and does not provide aluminum anions that can realuminize the catalyst. In stark contrast, the phosphorus modified alumina matrix material used in the present invention contains both phosphorus and aluminum anions that are only loosely bound to each other and one or both transfer to the molecular sieve bound to OTP conversion and regeneration conditions or Dispersion may occur. The anion is then restored and annealed to the molecular sieve backbone against known dealmination mechanisms of molecular sieve backbone collapse or modification induced by exposure to steam at a temperature corresponding to the temperature applied in the OTP reaction zone and the regeneration zone. And / or stabilization.

The phosphor modified aluminum matrix material used in the present invention is preferably a hydrogel prepared using the oil drop method according to the teaching of US Pat. No. 4,269,717. Preferred hydrosols are aluminum chloride hydrosols prepared to contain aluminum anions with a weight ratio of chloride anion of 0.7: 1 to 1.5: 1. The molecular sieve component is preferably added to the hydrosol prior to dropping.

A particularly preferred feature of the present invention is the steaming of the molecular sieve powder prior to addition to the phosphorus modified alumina matrix at conditions corresponding to the maximum temperature and steam partial pressure expected to be experienced during OTP application. This pretreatment procedure is carried out for a duration of from 1 hour to 50 hours or more until the silica to alumina ratio in the molecular sieve backbone corresponds to a value in the range of 150: 1 to 800: 1, more preferably 400: 1 to 600: 1. It is desirable to.

The phosphorus content and surface area of the phosphorus modified alumina matrix used in the present invention is preferably set based on the data shown in Table 1.

Phosphorus Modified Alumina Spherical Particle Characteristics Sample One 2 3 4 5 6 7 P weight% 0 1.2 3.3 6.3 15.7 18.5 24.7 Al: P molar ratio ∞ 45: 1 15: 1 7.3: 1 2.3: 1 1.6: 1 1: 1 ΓAl ₂ O ₃ wt% detected by X-ray diffraction 85 75 60 41 4 0 0 Al ₂ O ₃ microcrystal size, Å 40 35 34 32 30 ° 1 ° 1 SA m ² / g 225 275 349 336 322 242 141 PV cc / g 0.51 0.61 0.77 0.75 0.69 0.66 0.91 PD A 91 88 88 89 86 109 258 ABD g / cc 0.75 0.66 0.59 0.58 0.56 0.56 0.45 Skeletal density 3.5 3.38 2.93 2.67 2.48 2.29 ° 1 indicates that the spherical particles are completely amorphous.

When the phosphorus modified aluminum matrix constitutes 25 to 90% by weight, preferably 30 to 50% by weight of the catalyst system of the present invention, the phosphorus content of the matrix should be kept in the range of 10 to 25% by weight, calculated on an elemental basis. Best results are obtained at 15-25 wt%. Referring to Table 1, it can be seen that the phosphorus content range corresponds to a matrix surface area of 140 to 330.5 m ² / g and an Al to P atomic ratio of 1: 1 to 5.3: 1, and the best result is a matrix surface area of 141 to 320 m. ² / g and an Al to P atomic ratio of 1: 1 to 2.7: 1.

10 to 75 wt% of a ZSM-5 or ZSM-1l zeolitic molecular sieve having a molar ratio of silica to an alumina backbone of 150 to 800: 1 and 25 to 90 wt% of a phosphorus modified alumina matrix containing unstable phosphorus and / or aluminum anions A hydrothermal stabilizing composition (COM) of the material comprising with is a very preferred embodiment in the present invention. In another COM embodiment, the present invention includes the COM as defined above wherein the phosphorus content of the matrix is 10-25% by weight of the matrix, calculated on an elemental basis. In a third COM embodiment, the present invention is the above, wherein the alumina and phosphorus content of the material is sufficient to provide a matrix having an aluminum to phosphorus atomic ratio of 1: 1 to 5.3: 1 and a surface area of 140 to 330.5 m ² / g. Contains the first COM defined. The fourth COM embodiment of the present invention includes the COM as defined in any of the preceding COM embodiments for producing COM using the oil drop method. The fifth COM embodiment further comprises adding high silica to alumina ZSM-5 or ZSM-11 molecular sieve to a preferred aluminum chloride hydrosol prepared such that aluminum ions are included in a weight ratio of 0.7: 1 to 1.5: 1 relative to the chloride anion. And the COM defined in the fourth COM embodiment in which the resulting mixture is remnant.

Any optional hydrotreating step of the present invention is a polyunsaturated hydrocarbon such as diene and / or formed in a small amount (i.e., less than 2% by weight of the converted oxygenate feed, typically 0.01-1% by weight) in the OTP conversion step Or is designed to selectively hydrogenate acetylene hydrocarbons. While these polyunsaturated hydrocarbons are not a substantial source of propylene yield loss, we have found that the hydrocarbons are a very important contributor to the coke deposition rate on the bifunctional OTP catalyst. These are coke precursors and tend to concentrate in the heavy olefin byproduct stream recovered in the OTP conversion step. If one or more of the heavy olefin by-product streams are recycled to the OTP conversion stage, the presence of the coke precursor can cause OTP catalyst instability that can cause a significant loss of propylene selectivity. Two or more sources of heavy olefin recycle streams are possible. The first is a fraction enriched in C ₄ + olefins which is subsequently separated from the vapor phase fraction derived from the effluent stream from the OTP conversion stage of the primary effluent cooling and separation stage. The second source is a stream rich in second C ₄ + olefins which is separated from the liquid hydrocarbon fraction recovered in the OTP effluent cooling and separation step. According to a preferred embodiment, at least a portion of one or both of the C + olefin rich streams is subjected to any optional hydrotreatment step to selectively convert the coke precursor to the corresponding olefins. It is a preferred practice to add at least 50%, more preferably at least 70-95%, by weight of any heavy olefin recycle stream to the hydrotreating step. Acetylene is also OTP leak may be present in trace amounts in rich the recovered C ₂ olefin stream from the water stream, dual-functional OTP catalyst it is possible to switch between the ethylene to propylene, and any of the C ₂ olefin recovered for recycle A portion of this rich fraction can be charged to any of the hydrotreatment steps above before recycling to the OTP conversion step. If the amount of acetylene in the C ₂ olefin recycle stream is very high, it is preferred to add at least 50%, more preferably 70% to 95% by weight of the C ₂ olefin-rich recycle stream to the hydrotreatment step. It's running.

Optional hydrotreating steps include contacting at least a portion of the one or more heavy olefin recycle streams and the hydrogen with the metal containing hydrogenation catalyst at selective hydrogenation conditions effective to convert any polyunsaturated hydrocarbons to the corresponding olefins. The catalyst is preferably maintained in the hydroprocessing zone as a stationary phase of catalyst particles, which may be of any suitable form, preferably spherical or cylindrical. It is preferable that the said particle | grain is 1-10 mm in diameter, and / or L-1 is 1-5.

The selective hydrogenation conditions applied to this treatment step are selected from those conditions known to be effective to minimize or prevent the overhydrogenation of the polyunsaturated hydrocarbons to the corresponding olefins and optionally to the full saturated hydrocarbons. The step may be performed at a temperature of 30-250 ° C., 75-150 ° C. for best results; It is typically carried out at a pressure of 101 kPa to 4.05 MPa sufficient to maintain the liquid phase and at a liquid time-space velocity (LHSV) of ¹ to 30 o'clock ^-1 , for best results.

The amount of hydrogen introduced into the treatment step is sufficient to provide 0.8-10 mol, preferably 1-2.5 mol of hydrogen per mol of the polyunsaturated hydrocarbon introduced therein. At least a portion of the hydrogen may be dissolved or mixed in the olefin containing feed stream to the stage, or a portion thereof may be added to the hydrotreatment zone independently of the heavy olefin containing feed stream in rectification or countercurrent.

The hydrogenation catalyst used in any such hydrotreatment step may be any of the known selective hydrogenation catalysts for this application, and is preferably a combination with a catalytically effective amount of a suitable porous carrier material of the metal hydrogenation component. In some cases, an olefin selectivity enhancing component (ie, attenuator) may be added to the catalyst in an amount sufficient to block or substantially prevent any hydrogenation side reactions that produce fully saturated hydrocarbons, such as the corresponding paraffinic hydrocarbons.

The metal hydrogenation component is preferably selected from the group of nickel, palladium, platinum and mixtures thereof, with nickel being preferred. The amount used is preferably sufficient to provide a hydrogenation catalyst containing 0.01 to 5% by weight, preferably 0.05 to 2% by weight, of the metal component calculated on the basis of the metal. At least a significant portion of these metal hydrogenation components are preferably maintained with a hydrogenation catalyst in the metal state, but in some cases metallic compounds such as corresponding metallic oxides and / or sulfides can be used and the results are good.

The optional damping component will be selected from the group consisting of copper, silver, gold, gallium, iridium and mixtures thereof. The amount of damping component added to the hydrogenation catalyst is generally calculated on a metal basis to be an effective amount to produce 0.01 to 2% by weight of the component, and generally 0.01 to 1% by weight yields the best results. When using copper, silver or gold, it is typical that at least a substantial portion of any of these optional damping components will be in the metal state. In contrast, when using gallium or indium, the best results are obtained if a substantial portion of the damping component remains in the oxide state.

Porous carrier materials for the hydrogenation catalyst generally have a surface area of 10 to 50 m ² / g and include the following materials: (1) as silica, silica gel, clays and silicates, including synthetically prepared or naturally occurring , Which may or may not be acid treated, such as clay, kaolin, diatomaceous earth, hull earth, kaolin, bentonite, kigelgur and the like; (2) refractory inorganic oxides such as alumina, titanium oxide, zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafnium oxide, zinc oxide, magnesia, boria, toria, silica-alumina, silica-magnesia, chromium Mia-alumina, alumina-boria, silica-zirconia, and the like; (3) carbon and carbon rich materials such as charcoal; (4) spinels such as zinc aluminate, magnesium aluminate, calcium aluminate, and the like; And (5) a combination of substances from at least one of the above groups. Preferred porous catalysts for use in hydrogenation catalysts are refractory inorganic oxides, with alumina materials yielding the best results.

Suitable alumina materials are crystalline aluminas known as gamma-, eta- and theta-alumina, with gamma- or eta-alumina yielding the best results. In addition, in some embodiments, the alumina carrier material may contain a consumption rate of alkali and / or alkaline earth oxides and / or other known refractory inorganic compounds such as silica, zirconia, magnesia, and the like; However, it is preferred that the catalyst is substantially pure gamma- or eta-alumina. The catalyst preferably has a bulk apparent density of 0.3 to 0.9 g / cc, a surface area characteristic such as an average pore diameter of 20 to 300 mm 3, a pore volume of 0.1 to 1 cc / g, and a surface area of 100 to 500 m ² / g. Generally gamma- used in the form of spherical particles having a diameter of 1 to 10 mm, a bulk apparent density of 0.3 to 0.8 g / cc, a pore volume of 0.4 ml / g and a surface area of 150 to 250 m ² / g. Best results are obtained with the alumina carrier material.

Hydrogenation catalysts can be prepared by any technique known to those skilled in the art of catalyst production. Preferred techniques include preforming the porous carrier material and then adding the metallic component and any attenuator component to the porous support sequentially or simultaneously by impregnation and / or spraying. Available impregnation techniques include vacuum, evaporation, DIP and combinations of these techniques. 'Skin' or 'outer cell' impregnation techniques can be used to concentrate the active ingredient on or near the boundary of the porous support. The impregnated or sprayed porous support is then dried at a temperature of 50-200 ° C. and calcined for 5-100 hours in air, typically at 250-750 ° C. temperature. The resulting catalyst can then be subjected to any reduction step, typically with free hydrogen, at 250-750 ° C. for 1-10 hours.

A very preferred feature of the present invention is the application of mobile phase technology in the OTP conversion step to increase the selectivity of the process for propylene production. The use of mobile phase technology in typical MTO processes is known and described in US Pat. No. 5,157,181.

The mobile phase reaction zone can be configured in a variety of ways, including introducing catalyst particles on top of the OTP reaction zone fed gravity through the entire volume of the reaction zone. The catalyst is contacted with the feedstream in the countercurrent or rectification direction of catalyst movement. Preferably, the feed stream is countercurrent to the catalyst stream, ie the oxygenate feed stream is introduced into the bottom of the reaction zone and withdrawn from the top thereof. This preferred configuration can provide a significant advantage in the OTP conversion reaction, whereby the feedstream is partially contacted with the catalyst, which is partially deactivated during the initial stage of conversion when the driving force is high, and when the driving force is low. This is because it is contacted with a more active catalyst during subsequent steps.

More typical OTP catalyst particles pass through the reaction zone and enter a ring defined by a concentric catalyst retention screen, where the catalyst particles move downward through the ring and exit from the bottom of the OTP reaction zone. The feedstream enters the top or bottom of the reaction zone and generally passes through the ring in the transverse direction of the catalyst flow. With this arrangement the pressure drop across the reaction zone can be lowered and therefore the flow distribution is good.

During the OTP conversion zone circulation, the carbonaceous material, ie coke, is deposited on the catalyst while moving downward through the reaction zone. The carbonaceous deposits act to reduce the number of active sites on the catalyst, affecting the overall degree of conversion and selectivity to propylene. Thus, in the mobile phase embodiment of the OTP conversion step, a portion of the coked catalyst is withdrawn from the OTP reaction zone and regenerated in a regeneration zone that removes at least a portion of the carbonaceous material. In a fixed bed embodiment of an OTP conversion step, the on-stream portion of the process is blocked when the conversion falls to an unacceptable level and the OTP catalyst is regenerated in situ.

Preferably, the carbonaceous material is removed from the catalyst by oxidative regeneration, wherein in the case of mobile phase embodiments, the catalyst exiting from the OTP reactor is at a temperature sufficient to remove a predetermined amount of carbonaceous material from the catalyst by combustion and Contact with an oxygen containing gas stream at a concentration. In a fixed bed embodiment, the oxygen containing gas stream is fed to the OTP reaction zone. Depending on the particular catalyst and conversion, it may be desirable to remove the deposited carbonaceous material considerably, for example, less than 1% by weight, more preferably less than 0.5% by weight. In some cases, it is advantageous to only partially regenerate the catalyst, for example to remove 30 to 80% by weight of the carbonaceous material. The regenerated catalyst preferably contains from 0 to 20%, more preferably from 0 to 10% by weight of the deposited carbonaceous material. This results in carbon combustion with an oxygen containing gas stream containing a relatively large concentration of carbonaceous material (i.e., coke) present on the catalyst which is larger than 1 wt% carbonaceous material on the catalyst and containing oxygen at a relatively low concentration. It is preferred in most cases that cause what happens. The oxygen content is preferably capable of maintaining an initial oxygen level of 0.5 to 2% by volume in the gas in contact with the carbonaceous material containing catalyst by using an inert gas or by recirculating the fuel gas material. By using low concentrations of oxygen, it is possible to prevent the possibility of permanently hydrothermally damaging the molecular sieve catalyst by appropriately regulating the oxidation of the carbonaceous material on the OTP catalyst without excessively high temperatures occurring. The temperature applied during regeneration should be in the range 400-700 ° C., with the best results obtained at 500-650 ° C. The regeneration zone of the mobile phase embodiments of the OTP conversion step is preferably arranged with a mobile phase region similar to the mobile phase configuration applied to the OTP reaction.

The accompanying drawings illustrate the invention in which three mobile phase reaction zones, reactors (1), (2) and (3) are shown in series arrangement in both an oxygenate feed and a flow of hydrothermally stabilized OTP catalyst through the reactor. A schematic diagram of the is shown. The reactor is shown in a vertical cross sectional view where the catalyst is shown flowing through a ring held by a suitable concentric catalyst holding screen. All three reactors are operated by charge into the reactor which flows countercurrently to the descending stream of catalyst particles. All three reactors are operated by an oxygenate feed stream flow that is countercurrent to the movement of catalyst particles from outside the OTP catalyst ring to the central portion where the effluent stream is recovered. The figure shows the flow of the feed material, the intermediate product material and the product material in solid lines and the catalyst flow into and out of the reaction zone in dotted lines. The catalyst is shown to be conveyed by a moving medium, preferably steam, nitrogen or other inert diluent. The catalyst transfer medium is preferably steam because there is a significant amount of steam in the OTP reaction zone.

Hydrothermally stabilized OTP catalysts used in reactors (1), (2) and (3) are derived from a bifunctional catalyst comprising molecular sieves dispersed in a phosphorus modified alumina matrix containing the above-mentioned unstable phosphorus and / or aluminum anions. Is selected. It can be prepared using the 'rubbing' method disclosed in US Pat. No. 4,629,717 and is used as a sphere having an effective diameter of 0.5 to 5 mm, particularly preferably 1.6 mm. The total amount of the OTP catalyst used is preferably split equally among the three OTP reactors.

The number of reaction zones keeps the temperature difference across the individual reactors up to 80 ° C. to increase the propylene yield, thereby preventing the transfer of the yield structure to ethylene, while at the same time exerting the exothermic nature of the conversion of oxygenate to propylene. It is based on maintaining the conversion conditions of the individual reactors with conditions that minimize the formation of coke on the catalyst which accelerates rapidly as the temperature rises at the end of the zone.

During the initiation of the process, hydrocarbon regeneration lines 14, 32, 21 and 22 are blocked at the start of regeneration until sufficient product material is obtained. Similarly, the water dilution recirculation through lines 13, 28 and 29 are blocked and instead an external source of water or steam is connected to line 13 by means not shown just before the connection with line 8 Inject). At initiation, the oxygenate feedstream flows through line 8 to the intersection with line 13, where an appropriate amount of diluent, in the form of water or steam, is mixed so that the ratio of oxygenate to diluent is from 0.1: 1 to 5 : 1, Especially at the time of starting, it becomes 0.5: 1-2: 1. The resulting mixture of oxygenate feed and diluent is then passed through suitable feed and effluent heat exchange and heating means (not shown) to evaporate the resulting steam and to a temperature of 350-475 ° C. and 136-343 kPa. It provides a charge stream for the reactor (1) entering the reactor at a voltage of. Sufficient OTP catalyst is present in the reactors (1), (2) and (3) to provide an hourly weight space velocity (WHSV) of 0.5 to 5 o'clock ^-1 at initiation, and effective WHSV upon initiation of recycling of the heavy olefin hydrocarbon material. Rises to the level of 1 to 10 o'clock ^-1 . The effluent stream from reactor 1 is then withdrawn via line 9 and, through appropriate cooling steps, its temperature is of a value close to the temperature of the charge to reactor 1 via one or more cooling means, not shown. Reduced to temperature, and the resulting cold effluent stream from reactor 1 is charged to reactor 2 via line 9 and again contacted with an appropriate amount of bifunctional catalyst to bring the added amount of oxygenate material into propylene. Effluent streams from reactor 2 were produced which were simultaneously converted and discharged through line 10. The effluent stream from reactor 2 is cooled to a temperature close to the inlet temperature to reactor 1 by appropriate means (not shown) and passed through reactor line 10 to reactor 3 where the stream The silver is contacted with an additional amount of bifunctional catalyst under conditions that lead to further conversion of unreacted oxygenate to propylene and various other byproducts. Take appropriate measures in the design of the flow passages between reactors (1) and (2), and between reactors (2) and (3) to minimize the pressure drop across the reactors, as shown in reactor (1), The temperature difference in the reactors is provided to minimize catalyst coking in reactors 2 and 3 to the same extent as in reactor 1.

The effluent stream from reactor 3 is then discharged through line 11, to liquefy a significant amount of water contained therein through one or more cooling means, such as a feed / effluent exchanger (not shown). Treated with a suitable cooling stage devised and sent to three phase separators, zone 5, wherein the hydrocarbon vapor phase, together with the water phase and the liquid hydrocarbon phase containing a small amount of any unreacted oxygenate exiting the reactor 3 Is formed. As a feature of the present invention is that the activity of the bifunctional catalyst is maintained at or near substantial cycle initial conditions, the amount of unreacted oxygenate delivered to zone 5 is expected to be minimized. The total conversion achieved during the passage of the oxygenate feed through reactors (1), (2) and (3) is expected to be at least 97% of that during the entire cycle.

The aqueous phase from separator 5 is withdrawn via line 13, the drag stream therefrom is taken via line 23 to remove excess water and the resulting pure water stream is passed through line 13 Recycle to the mixture of the oxygenate feed at the confluences of 13) and (8). An additional amount of water is passed through lines 13 and 28 in the case of reactor 2 and in order to cool or adjust the partial pressure of the reactants passing through lines 13 and 29 in the case of reactor 3. May be added to the reactors 2 and 3. Once diluent recycle is initiated, the starting conditions for injection of diluent water are terminated.

Returning to separator 5, the vapor phase formed here is discharged via line 12 and constitutes a charge to fractionation column 6, which acts as a deethanizer and contains a small amount of ethane and some methane and traces of It is engineered to produce an ethylene-rich tower fraction that also contains acetylene. Base fraction comprising the C + ₃ portion of the material to be substantially fed to the column 6, is discharged therefrom through line 15. The drag stream exits line 18 from overhead stream 14 produced in column 6 to regulate the accumulation of C ₁ and C ₂ paraffins in the ethylene recycle loop. Since the drag stream is insufficient to control methane accumulation in the ethylene recycle loop, in such circumstances it is necessary to remove methane from the stream to a point where methane recovery is sufficient to prevent accumulation of significant methane concentrates in the ethylene recycle loop. To this end, any further treatment of the ethylene rich overhead stream is required. Any suitable means for demethanizing the stream is used in any step not shown in the accompanying drawings, including using a demethane column, a methane adsorption zone, a methane-selective membrane zone and other methane separation means. Can be. The amount of drag stream received by line 18 will be 1-15% by volume of the overhead stream flowing through line 14 and will typically comprise 1-10% by volume of the stream. The residue of the overhead stream is then introduced into reactor 1 via lines 14 and 8 according to the accompanying drawings as an ethylene-rich recycle stream. It is within the scope of the present invention to distribute the ethylene-rich recycle stream flowing in line 14 between the three reactor zones, but the inventors have carried the entire amount of the ethylene stream through lines 14 and 8 to the reactor ( In 1), it was confirmed that the results measured by ethylene conversion when this stream was exposed to the maximum amount of acceptable catalyst while flowing through the three reactor zones were superior. If the acetylene content of the stream rich in C ₂ olefins flowing in line 14 is significant, at least a portion of the stream is subjected to hydroprocessing zone 30 by unillustrated means for the purpose of selective hydrogenation of the acetylene-containing ethylene. It is within the scope of the present invention to convert to). The resulting recycled stream enriched in hydrotreated C ₂ olefins is then passed through lines 32 and 8 for reactor 1 and lines 32, 21 and 9 for reactor 2 Can be mixed with the heavy olefin recycle stream via lines (32), (21), (22) and (10) for the reactor (3) and returned to the OTP reaction zone.

Then, the bottom stream from column 6 comprising the C ₃ + material charged to column 6 flows to de-propane column 7 via line 15, in which the C ₃ + stream, the present invention It is subjected to fractional distillation conditions designed to produce a propylene-rich overhead stream that is the main product stream of and contains a small amount of byproduct propane material. The bottom of the stream is very small quantities of butane, pentane, and C ₄ -C ₆ unsaturated hydrocarbon and a C _4, C ₅ and C ₆ C ₄ + olefin-rich mainly containing an olefin-based material with a by-product material from the column (7) One stream, wherein all or most of the bottoms stream is conveyed through line 17 to a selective hydrogenation zone 30 containing a stationary phase of a hydrogenation catalyst comprising from 0.01 to 5% by weight of nickel on a porous alumina support. desirable. In addition, a stream enriched in hydrogen is introduced via line 31 to hydrotreatment zone 30 that contains sufficient hydrogen to provide 0.9-5 mol of hydrogen per mol of polyunsaturated hydrocarbon introduced into zone 30. The stream rich in C ₄ + olefins and the hydrogen stream are then subjected to a nickel containing hydrogenation catalyst and zone (30) under selective hydrogenation conditions effective to convert substantially all of the polyunsaturated hydrocarbons contained in the stream rich in C ₄ + olefins to the corresponding olefins. ) Is contacted. Specific conditions applied in zone 30 include inlet temperatures of 75-150 ° C., pressures of 101 kPa to 405 MPa selected to maintain substantially liquid stream conditions in zone 30, and 1-30 h ^−1. LHSV. The effluent stream exiting zone 30 via line 32 is substantially free of any polyunsaturated hydrocarbons, so the recycle stream thus forms coke formation in the OTP reaction zones (1), (2) and (3). Less likely to accelerate.

The resulting selective hydrogenated C ₄ + olefin-rich recycle stream is then discharged through line 32 and sent to the intersection with line 19 where the drag stream is in the C ₄ + olefin recycle loop. In order to control the accumulation of paraffinic material it is received in an amount of 1 to 15% by volume, preferably 1 to 3% by volume. The residue of C ₄ + material flowing through line 32 is then sent to a connection with line 21, where part of it is withdrawn and the hydrotreated C ₄ + olefin reactants are lines 21 and 22. Through reactors (2) and (3). When the recycle operation begins to facilitate the return of the recycle stream, the recycle line as well as other lines are opened. In contrast to the conditions for the recycle of the ethylene rich stream flowing through the line 14 to the reactor 1, the preferred conditions associated with the recycle of the hydrotreated C ₄ + olefin rich stream through line 32 are the streams. Is divided into three parts and the part is introduced in parallel with the three reactors. The main part is sent to reactor 1, the minor part is sent to reactors 2 and 3, and preferably 60 to 80% by volume of the total amount of the recycle stream enriched in the hydrotreated C ₄ + olefins Flows into reactor 1 through lines 32 and 8, the same portion of 10-20% by volume is fed simultaneously into reactors 2 and 3 for lines 2, 32 and ( Via 21) and (9), the reactor 3 is fed via lines 32, 21, 22 and 10.

As the three recycle streams flowing through lines (13), (14) and (32) rise and circulate, the initiation mode of the present invention is then terminated and the reactor acts as an olefin interconversion catalyst as well as an oxyhydride conversion catalyst. The overall recycle mode of operation is initiated by the phases of the hydrothermally stabilized bifunctional catalyst located at (1), (2) and (3). The order of events in the full recycle mode is that the oxygenate-rich feedstream is introduced into the flow process via line 8, mixed with the ethylene-rich first recycle stream via line 14, and then line 13. ), Where water or steam diluent is added in the amounts described above, and the resulting mixture is then transferred by line 32 to the intersection of line 8, where an additional amount of selectively hydrogenated Allow the treated C ₄ + olefinic material to be added from the charge from reactor 1. The charge mixture is properly heated to an appropriate inlet temperature and then flows into reactor 1 in the manner described above.

After passing through the reactor 1 and thereby crossing the bed of the bifunctional catalyst held in the reactor 1 with the ring space defined by the concentric retention screen described above, the resulting effluent is passed through line 9 Exhausted from reactor 1 and flows to the intersection with lines 28 and 21, where an additional amount of relatively low temperature water diluent is passed through line 21 in an additional amount of relatively low temperature selective hydrogenation. Treated C ₄ + olephine is mixed with the rich recycle stream. Subsequently, after further additional cooling as appropriate to achieve the stated inlet temperature, the resulting mixture is introduced into reactor 2, where it passes over the second ring of the bifunctional catalyst, as shown in the accompanying figures. As can be seen therefrom, the effluent stream exiting through line 10, an additional amount of relatively low temperature water diluent flowing over the ring via line 29 and over the ring through line 22. after relatively produce a low temperature of selective hydrogenation of C ₄ + olefin-rich material to, and the resulting mixture is cooled down to the entrance temperature of the reactor (3) stated above by means which are not shown in the accompanying drawings, the reactor ( Flowing through 3) in contact with an additional amount of the bifunctional catalyst to produce an effluent stream 11, which is subjected to three phases via line 11 after appropriate appropriate quenching and cooling treatments. Li is caused to flow as described above to an area (5).

The amount of hydrothermally stabilized bifunctional catalyst used in reactors (1), (2) and (3) is according to any choice. Reactor 2 when the catalyst flows from reactor 2 to reactor 3 through line 25 and in the reactor 1 through line 26 Although large amounts of catalyst are present in reactors (2) and (3) to compensate for the small amount of deactivation that occurs in the reactors, the catalysts can be operated with substantially the same amount of It is contemplated herein that it is best to operate in such a way that there are approximately 25-30% of the total amount in (2) and (2) and 40-50% by volume in the reactor (3).

Reactors (1), (2) and (3) are initially introduced by hydrothermally stabilized bifunctional catalyst via lines not connected to the lines 24, 25 and 26 and not shown in the accompanying drawings. . When the OTP process is initiated, the catalyst cycle begins after the reactor is aligned to the operating conditions. The catalyst circulates between reactors through catalyst lines 25 and 26 and through regenerator zone 4 through line 27. At least a portion of the coke deposit in the regeneration zone 4 is removed from the coke containing OTP catalyst introduced via line 27 by applying a low degree of oxidation procedure as described above. In addition, an oxygen-containing gas stream containing 0.5 to 2% by volume of oxygen supplied in an amount sufficient to support combustion of most of the coke introduced into the regeneration zone 4 through 27 is regenerated by means not shown. Filled with area 4. The regenerated catalyst is recycled to reactor 1 via line 24, thus completing the catalyst circulation circuit defined by lines 25, 26, 27 and 24. The fuel gas stream exits zone 4 via a line not shown in the accompanying figures.

The present invention is selected such that the flow of hydrothermally stabilized OTP catalysts around this catalytic circuit provides up to 400 hours of OTP catalyst on-stream cycle time to maintain initial cycle conditions or near catalyst activity, oxygenate conversion and propylene selectivity. It is characterized by. On the other hand, the flow rate of the hydrothermally stabilized OTP catalyst particles around the circuit is selected such that the catalyst particle residence time in the reactors (1), (2) and (3) is 400 hours or less before being returned to the zone (4) for regeneration. do.

Recovery to the three phase separator zones 5 is shown in the figures to which liquid hydrocarbon phases formed in these zones are attached, as they exit through line 32. The material is generally boiling in the gasoline range, a gasoline of the invention, which can require additional processing due to containing an unsaturated hydrocarbon of the minor claim 2 C ₄ + olefin is a high-rich recycle stream, and the content of the present olefin-based material Product streams. The preferred option shown in the accompanying figures is that the liquid hydrocarbon phase exiting the separator 5 via line 32 is subjected to an additional fractional distillation step in column 33 to give a second C ₄ + through line 35. An olefin-rich overhead stream is recovered, at least a portion of which may flow through lines 35 and 17 into zone 30 where it is optionally hydrotreated as described above. The resulting hydrotreated stream is then recycled back to reactors (1), (2) and (3) via lines 32, 21 and 22 to provide additional means of conversion of heavy olefins to propylene. do. The bottoms stream of column 33 is also recovered via line 34 and includes an olefin rich gasoline product stream.

Claims (10)

A continuous process for selectively converting an oxygenate feed to propylene, (a) in a reaction zone comprising at least one moving bed reactor in an amount corresponding to the oxygenates and diluent oxygenates to 1 mol per mol diluent 0.1~5, switching at least a portion of oxygenates to olefins and C ₃ C ₂ and Reacting with particles of a bifunctional hydrothermal stabilization catalyst comprising molecular sieves dispersed in a phosphorus modified alumina matrix having the ability to interconvert C ₄ + olefins to C ₃ olefins and containing unstable phosphorus and / or aluminum anions as, the reaction region selected oxygenates conversion conditions and the catalyst-on of less than 400 hours to convert the oxygenates to propylene - by operating in the catalyst circulation rate across the selected reaction region to derive the stream cycle time major amount of C ₃ Olefin products and water by-products and lower amounts of C ₂ olefins, C ₄ + olefins, C ₁ -C ₄ + saturated hydrocarbons and bovine Producing an amount of unreacted oxygenate, byproduct oxygenate, polyunsaturated hydrocarbon and aromatic hydrocarbon; (b) passing the effluent stream through a separation zone where it is cooled and the effluent stream is a vapor phase fraction rich in C ₃ olefins, a water fraction containing unreacted oxygenates and byproduct oxygenates and heavy olefins, heavy saturation Separating into hydrocarbons and liquid hydrocarbon fractions containing small amounts of polyunsaturated and aromatic hydrocarbons; (c) recycling at least a portion of the water fraction recovered in step (b) to step (a) to provide at least a portion of the diluent used herein; (d) separating the vaporous fraction into a C ₂ olefin rich fraction, a C ₃ olefin rich product fraction and a first C ₄ + olefin rich fraction; (e) recycling at least a portion of the olefins contained in the C ₂ olefin rich fraction or the first C ₄ + olefin rich fraction or a mixture of these fractions to step (a); And (f) recovering the coke-containing bifunctional catalyst particles from the reaction zone, oxidizing and regenerating the recovered catalyst particles in a regeneration zone and returning a stream of regenerated catalyst particles to the reaction zone. Continuous method comprising a. The process of claim 1 wherein the oxygenate is methanol or dimethyl ether (DME) or mixtures thereof. The continuous process according to claim 1 or 2, wherein the catalyst contains zeolite-based molecular sieves and / or ELAPO molecular sieves. 4. The process of claim 3, wherein the zeolitic molecular sieve has a structure corresponding to ZSM-5 or ZSM-11, and the ELAPO molecular sieve is an SAPO material having a structure corresponding to SAPO-34. The process of claim 1, wherein the phosphorus modified alumina matrix has an alumina to phosphorus atomic ratio of 1: 1 to 5.3: 1 and a surface area of 140 to 330.5 m ² / g. 6. The process of claim 1 or 5, wherein the phosphorus modified alumina matrix is formed by gelling phosphorus containing aluminum chloride hydrosol having an aluminum to chloride anion weight ratio of 0.7: 1 to 1.5: 1. The process of claim 6, wherein the molecular sieve is dispersed in a hydrosol prior to the gelling step. The process of claim 1, wherein the reaction zone comprises three or more mobile phase reactors connected in a direct current structure with respect to the oxygenate feed and the stream of catalyst particles passing therethrough. Of claim 1 to claim 3 wherein the liquid hydrocarbon fraction separated in step (b) of claim 2 C ₄ + olefin-rich fraction, and is further separation in a naphtha product fraction, C ₂ olefin-rich fraction or the 1 C a continuous method ₄ + olefin-rich fraction or claim 2 C ₄ + olefin-rich fraction, or at least a portion of the olefins contained in the mixture of these fractions is recycled to step (a). The process of claim 9, wherein at least a portion of the fraction enriched in the first C ₄ + olefin or the fraction enriched in the second C ₄ + olefin or a mixture of these fractions is charged with an optional hydrotreating step, wherein the polyunsaturated hydrocarbon is converted to the corresponding olefin. A process of removing coke precursors by contacting hydrogen in the presence of a metal containing hydrogenation catalyst at selective hydrogenation conditions effective to convert to at least a portion of the resulting selectively hydrotreated stream into step (a).

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