EA004900B1 - Metallo aluminophosphate molecular sieve with cubic crystal morphology and methanol to olefin process using the sieve - Google Patents

Abstract

1. A catalyst for converting methanol to light olefins comprising a crystalline metallo aluminophosphate molecular sieve having an empirical chemical composition on an anhydrous basis expressed by the formula: (ELxAlyPz)O2 where EL is a metal selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and mixtures thereof, "x" is the mole fraction of EL and has a value of at least 0.005, "y" is the mole fraction of Al and has a value of at least 0.01, "z" is the mole fraction of P and has a value of at least 0.01 and x + y + z = 1, the molecular sieve characterized in that it has predominantly a plate crystal morphology, wherein the average smallest crystal dimension is at least 0.1 micron and has an aspect ratio no greater than 5. 2. The catalyst of Claim 1 where the EL metal is selected from the group consisting of silicon, magnesium, cobalt and mixtures thereof. 3. The catalyst of Claim 2 where the EL metal is silicon and the molecular sieve has the crystal structure of SAPO-34. 4. The catalyst of any one of claims 1 to 3 where catalyst comprises a metal aluminophosphate molecular sieve and an inorganic oxide binder selected from the group consisting of alumina, silica, aluminum phosphate, silica alumina and mixtures thereof. 5. The catalyst of any one of claims 1 to 4 where the molecular sieve is present in an amount from about 10 to about 90 weight percent of the catalyst. 6. The catalyst of any one of claims 1 to 5 where the aluminophosphate has a metal (EL) content from about 0.005 to about 0.05 mole fraction. 7. A process for converting methanol to light olefin comprising contacting the methanol with the catalyst of any one of claims 1 to 6 at conversion conditions. 8. The process of claim 7 where the conversion conditions are a temperature of about 300 degree C to about 600 degree C, a pressure of about 0 kPa to about 17224 kPa and a weight hourly space velocity of about 1 to about 100 hr<-1>.

Description

The technical field to which the invention relates.

This invention relates to a catalyst containing EPARO, and to a method for converting methanol to light olefins using this catalyst.

The level of technology

The limited supply and increasing cost of crude oil initiated the search for alternative ways to produce hydrocarbon products. One such method is the conversion of methanol to hydrocarbons, especially to light olefins (the term light olefins means C ₂ -C ₄ olefins). The interest in the method of converting methanol to olefins is due to the fact that methanol can be obtained from coal or natural gas to form synthesis gas, which is then processed to produce methanol.

Methods for converting methanol to light olefins are well known in the art. Initially, aluminosilicates or zeolites were used as catalysts necessary for the implementation of such a transformation. For example, see US Pat. Nos. 4,238,631, 4,328,384 and 4,423,274. These patents also describe the deposition of coke on zeolites in order to increase the selectivity for light olefins and to minimize the formation of C ₅ + by-products. The effect of coke is associated with a decrease in the pore diameter of the zeolite.

It is also known in the art that silico-aluminophosphates (8APO) can be used to catalyze the conversion of methanol to olefins. Thus, in US patent 4,499,327 it is reported that many molecular sieves of the 8APO family can be used to convert methanol to olefins, with preferred 8APOs being those whose pore size allows adsorbing xenon (kinetic diameter 4.0 A), but small enough to exclude isobutane adsorption (kinetic diameter 5.0 A). A particularly preferred silicoaluminophosphate is 8APO-34.

US Pat. No. 4,752,651 describes the use of non-zeolitic molecular sieves (NCMs), including EFAR and MeAPO molecular sieves, to catalyze the conversion of methanol to olefins.

The effect of molecular sieve particle size on activity is also noted in US Patent 5,126,308. This document states that molecular sieves in which 50% of the particles have a size less than 1.0 micron and no more than 10% of the particles have a size greater than 2.0 microns, have increased activity and / or durability. In addition, this document states that limiting the silicon content to 0.005 to 0.05 mole fraction also improves the catalytic properties of the molecular sieve.

Applicants have found that molecular sieves having the empirical formula (ЕЬ _x А1 _at Р ₂ ) О ₂ (in the subsequent ЕЬАРО), in which ЕЬ is a metal selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel , manganese, chromium and their mixtures, and x, y and ζ are molar fractions of EH, A1 and P, respectively, and possess predominantly lamellar crystal morphology, the average smallest crystal size being at least 0.1 μm, and their dimensional ratio (length to diameter ratio) less than or equal to 5, allow to obtain an increased amount of ethylene relative to propylene. This increased selectivity is a very desirable characteristic of a catalyst for converting methanol to olefins. This crystal morphology is achieved by controlling the content of the metal (Eb) in the molecular sieve and the time of crystallization during the synthesis of the molecular sieve.

Summary of Invention

As indicated above, the present invention relates to a catalyst containing EBALO, and to a method for converting methanol to light olefins using this catalyst. Accordingly, the invention in one embodiment relates to a method for converting methanol to light olefins, comprising contacting methanol with a crystalline metalloaluminophosphate molecular sieve having an anhydrous chemical composition, expressed by the empirical formula (1T, A1, P,) O, in which HB is a metal selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and their mixtures, x is the mole fraction of HB and has a value of at least 0.005 It has a mole fraction of A1 and has a value of at least 0.01, ζ is the mole fraction of P and has a value of at least 0.01, moreover, x + y + преимущественно, which has a predominantly lamellar morphology of crystals, the average smallest the crystals is at least 0.1 μm, and their dimensional ratio is less than or equal to 5.

In another embodiment, the invention relates to a catalyst for converting methanol to light olefins, comprising a crystalline metalloaluminophosphate molecular sieve having a chemical composition in an anhydrous state, expressed by the formula (EB _x Al) O2, in which EB is a metal selected from the group consisting of from silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and their mixtures, x is the mole fraction of EH and has a value of at least

0.005, y is the mole fraction of A1 and has a value of at least 0.01, ζ is the mole fraction of P and has a value of at least 0.01, and χ + γ + = 1, having a morphology of crystals, and the smallest average crystal size is at least 0.1 μm.

These and other objects and embodiments of the invention will become apparent after a detailed description of the invention.

Detailed Description of the Invention

An essential feature of the method according to the invention is the ELARO molecular sieve. This metalloaluminophosphate molecular sieve has the structure of a three-dimensional microporous skeleton of the tetrahedral A1O ₂ , PO ₂ and EBO ₂ blocks. Usually EHLRO has an empirical formula (EH _x A ^) O2, in which EH is a metal selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and their mixtures, x is the mole fraction of EH and has a value of at least 0.005, y is the mole fraction of A1 and has a value of at least 0.01, ζ is the mole fraction of P and has a value of at least 0.01, and x + y + . When EB is a mixture of metals, x represents the total amount of the mixture of metals present. Preferred metals (EB) are silicon, magnesium and cobalt, most preferred is silicon.

The preparation of various EHLROs is well known in the art and can be found in US patents: 4,554,143 (EEPARO), 4,440,871 (8APO), 4,853,197 (MARO, MpARO, ΖηARO, CoAPO), 4793984 (SARO), 4752651 and 4310440. Usually ELLRO molecular sieves synthesized by hydrothermal crystallization from a reaction mixture containing sources of reactive metals Eb, aluminum, phosphorus and a matrix agent. Sources of reactive EB are metal salts, such as chlorides and nitrates. When HB is silicon, the preferred source is fumed, colloidal or precipitated silica. Preferred reactive sources of aluminum and phosphorus are pseudo-boehmite alumina and phosphoric acid. Preferred matrix agents are amines and quaternary ammonium compounds. A particularly preferred matrix agent is tetraethylammonium hydroxide (TEOH).

The reaction mixture is placed in a pressurized pressure vessel, which is optionally lined with an inert plastic material, such as polytetrafluoroethylene, and heated under autogenous pressure at a temperature between 50 and 250 ° C, preferably between 100 and 200 ° C, for a time sufficient to produce crystals molecular sieve Typically, this time varies from 1 to 120 hours, preferably from 24 to 48 hours. The target product is isolated in any convenient way, such as centrifugation or filtration.

The ELARO molecular sieves according to the present invention advantageously have a lamellar crystal morphology. The term preferably means more than 50% of the crystals. Preferably, at least 70% of the crystals, most preferably at least 90% of the crystals, have a lamellar morphology. The term "lamellar morphology" means that the crystals have the appearance of rectangular plates. It is important that the size ratio be less than or equal to 5. The term “size ratio” is defined as the ratio of the largest crystal size to its smallest size. The preferred morphology that is included in the definition of the plates is cubic morphology. The term "cubic morphology" means not only those crystals in which all sizes are the same, but also those in which the size ratio is less than or equal to 2. In addition, it is necessary that the average smallest crystal size be at least 0.1 μm, preferably at least 0.2 microns.

As shown in the examples, the morphology of the crystals and the average size of the smallest crystals are determined by examining the ELARO molecular sieves using scanning electron microscopy (SEM) with crystal measurements, in order to determine the average size of the smallest crystal size.

Not based on any particular theory, the authors believe that the minimum thickness of the crystals is required in order for the diffusion path for desorbed ethylene and propylene molecules to be long enough to provide different behavior for these two molecules. Since ethylene is a more valuable product, it is possible to maximize the formation of ethylene by adjusting the size of the crystals. As will be shown in the examples, when the smallest crystal size is less than 0.1 μm, the ratio of ethylene to propylene (C2 = / C3 =) is about 1.2, while with the smallest size of crystals more than 0.1 μm The ratio C2 = / C3 = is 1.4. This provides increased ethylene production.

Usually, EPARO synthesized using the method described above may contain some amount of organic matrix agent in the pores. In order to ensure the catalytic activity of EPARO, it is necessary to remove the matrix agent from the pores by heating the EPARO powder in an oxygen-containing atmosphere at a temperature of approximately 200 to 700 ° C to remove the matrix agent, which usually requires several hours.

In one of the preferred embodiments of the invention, the content of the metal Eb varies from 0.005 to 0.05 mole fraction. If HB is more than one metal, then the total concentration of all metals is from 0.005 to 0.05 mole fraction. A particularly preferred embodiment is a variant in which HB is silicon (usually denoted by 8). In the present invention, any 8 ° can be used, which are described in US Pat. No. 4,440,871. Of the specific crystallographic structures described in this patent, the type 34 structure is preferred, i.e. 8ΆΡΟ-34. The structure of 8ΆΡΟ-34 differs in that it adsorbs xenon, but does not adsorb isobutane, whence it follows that the mouth of the pore is about 4.2 A.

The molecular sieve ΕΕΑΡΟ according to the invention can be used in its pure form, or it can be mixed with a binding agent and molded to form such as extrudates, pellets, spheres, etc. Examples of binders that can be used include aluminum oxide, silicon dioxide, aluminophosphate, aluminosilicate, etc. When using a bonding agent, the amount of ΕΕΑΡΟ that is contained in the final product varies from 10 to 90 wt.% and preferably from 30 to 70 wt.%.

The conversion of methanol to light olefins is carried out by contacting methanol with a catalyst ΕΕΑΡΟ under the conditions of conversion, as a result of which the desired light olefins are formed. Methanol can be in the liquid or vapor phase, the vapor phase is preferred. The contact of the methanol with the catalyst can be carried out in continuous or batch mode, continuous mode is preferred. The time of contact of methanol with the catalyst should be sufficient to convert methanol into the desired products - light olefins. When the method is carried out in a batch mode, the contact time varies from about 0.001 to 1 hour, preferably from about 0.01 to 1.0 hour. With decreasing temperature, a longer contact time is used, while with increasing temperature a shorter contact time is used. In addition, when carrying out the process in continuous mode, the weight volumetric feed rate (FOTS) based on methanol can vary from about 1 to 1000 h ^-1 , preferably from about 1 to 100 h ^-1 .

In order to obtain light olefins at a sufficiently high rate, the process usually must be carried out at elevated temperatures. Thus, the process should be carried out at a temperature of from 300 to 600 ° C, preferably from 400 to 550 ° C and most preferably from 450 to 525 ° C. The process can be carried out in a very wide range of pressures, including autogenous pressure. Thus, the pressure can vary from about 0 to about 1724 kPa, and preferably from 34 to 345 kPa.

Methanol feeds may optionally be diluted with an inert diluent in order to more efficiently convert methanol to olefins. Examples of diluents that can be used are helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water vapor, paraffinic hydrocarbons, such as methane, aromatic hydrocarbons, such as benzene, toluene, and mixtures thereof. The amount of diluent used can vary over a wide range and is usually from 5 to 90 mol.% In terms of raw materials, preferably from 25 to 75 mol.%.

The actual configuration of the reaction zone can be any that is well known in the art for a catalytic reaction chamber. You can use a single reaction zone or several zones arranged in series or in parallel. In such reaction zones, methanol feedstock passes through a layer containing catalyst ΕΕΑΡΟ. When using multiple reaction zones, one or more catalysts ΕΕΑΡΟ can be sequentially applied to obtain the desired product mixture. Instead of a fixed bed, you can use a dynamic bed system, for example, a fluidized bed or a moving bed. In such a dynamic system, it is easier to carry out, if necessary, catalyst regeneration ΕΕΑΡΟ. If regeneration is required, the catalyst ΕΕΑΡΟ can be continuously introduced as a moving layer into the regeneration zone, where it can be regenerated using a technique such as oxidation in an oxygen-containing atmosphere in order to remove carbon materials.

The following examples are presented only to illustrate the invention, and they are not intended to undesirably limit the general broad scope of the invention as defined by the appended claims.

Example 1. A number of molecular sieves 8ΑΡΟ are prepared according to the following procedure. In a container, 85% orthophosphoric acid is mixed with water. Silica sol and an aqueous solution (35 wt.%) Of tetraethylammonium hydroxide (GTEA) are added to this mixture. At the end, alumina is added in the form of pseudoboehmite along with water and primed zeolite 8ΑΡΟ-34, and all components are mixed. The resulting mixtures have the composition given below in table. 1, in the form of molar ratios of oxides.

Ί

Table 1

The composition of the reaction mixture for zeolites 8APO Sample name Reaction time, h TEON 5Yu ₂ αι ₂ ο ₂ PrGo ₅ H ₂ O BUT 48 1.0 0.10 1.0 1.0 35 AT 48 1.0 0.10 1.0 1.0 35 WITH 48 1.0 0.10 1.0 1.0 45 B 24 1.0 0.10 1.0 1.0 45 E 36 1.0 0.15 1.0 1.0 40 R 48 1.0 0.20 1.0 1.0 45

The mixture is then placed in a steel reactor under pressure, which is equipped with a turbine stirrer. The mixture is stirred and heated to 100 ° C for 6 hours, kept at 100 ° C for 6 hours, then heated to 175 ° C for 3 hours and kept at this temperature for a reaction time of 24, 36 and 48 hours. Finally, the reaction mixture is cooled to ambient temperature, the solid product is isolated by centrifugation and washed with water. All products were analyzed and found to be 8APO-34 molecular sieve.

Example 2. For the catalysts obtained in example 1, assess the degree of conversion of methanol to olefins in the pilot installation with a fixed catalyst bed. For testing use 4 g of the sample in the form of agglomerates with a size of 20-40 mesh. Before testing, each sample was calcined in air in a muffle furnace at 650 ° C for 2 hours and then pretreated in the reactor, heated to 400 ° C for 1 hour in a nitrogen atmosphere. The pretreated sample is then contacted with a raw material containing methanol and water in a molar ratio of 1 / 0.44 at 435 ° C, an overpressure of 35 kPa (5 psi) and a GVO of methanol 2.5 h ^-1 . The composition of the effluent stream is determined using an integrated gas chromatograph after 30 minutes of work in the stream in order to determine the initial conversion and selectivity. First, all the catalysts show complete conversion of methanol, then the degree of conversion decreases with increasing operating time in the stream, since the catalyst is deactivated. In tab. 2 shows the selectivity values for ethylene and propylene and the ethylene / propylene product ratio with a conversion rate of the raw material of 99% for each catalyst.

Table 2 The effect of crystal size on the formation of ethylene and propylene

Sample name The smallest average size, microns Crystal morphology Selectivity for C2 ° + C3 ⁼ ,% C2 ⁼ / C3 ⁼ BUT 0.07 Thin plates 82.4 1.17 AT 0.08 Plates 79.2 1.18 WITH 0.09 Thin plates 82.2 1.25 B 0.13 Plates 80,8 1.40 E 0.17 Plates 81.2 1.41 R 0.58 Cubic 78.7 1.48

The average smallest crystallite size is determined by measuring 20 typical crystallites in one or several micrographs taken using a scanning electron microscope at a magnification of 30,000. These data indicate that when the smallest crystal size exceeds 0.1 µm and the morphology of the crystals is lamellar, increased amounts of ethylene. In addition, it is noted that when the morphology of the crystals is cubic and the smallest crystal size exceeds 0.2 μm, the highest ethylene yield can be obtained. It is noted that when the smallest crystal size is less than 0.1 μm, poor results are obtained (the yield of propylene increases) despite the fact that the morphology of the crystals is lamellar.

Claims (8)

CLAIM 1. The catalyst for the conversion of methanol into light olefins, which contains a crystalline metalaluminophosphate molecular sieve having an empirical chemical composition in an anhydrous state, expressed by the formula (E1 „L1..P.) O _; . in which E represents a metal selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and mixtures thereof, x is a mole fraction of E and has a value of at least 0.005, y is a mole fraction A1 and has a value equal to at least 0.01, ζ is the molar fraction P and has a value equal to at least 0.01, and x + y + ζ ^ Σ, and having a predominantly plate-like morphology of crystals, with the smallest average the crystal size is at least 0.1 μm and the crystals are dimensionally the ratio of not more than 5. 2. The catalyst according to claim 1, in which the metal E is selected from the group consisting of silicon, magnesium, cobalt and mixtures thereof. 3. The catalyst according to claim 2, in which the metal Eb is silicon and the molecular sieve has a crystal structure of 8APO-34. 4. The catalyst according to any one of claims 1 to 3, in which the catalyst contains a metal-aluminum phosphate molecular sieve and a binder, which is an inorganic oxide selected from the group consisting of alumina, silicon dioxide, aluminophosphate, aluminosilicate and mixtures thereof. 5. The catalyst according to any one of claims 1 to 4, in which the molecular sieve is present in an amount of about 10-90 wt.% Based on the catalyst. 6. The catalyst according to any one of claims 1 to 5, in which the aluminophosphate has an Eb metal content of about 0.005-0.05 mole fractions. 7. A method of converting methanol to light olefins, comprising contacting methanol with a catalyst according to any one of claims 1 to 6 under conversion conditions. 8. The method according to claim 7, in which the conversion conditions are a temperature of about 300600 ° C, a pressure of about 0-1724 kPa and a weighted space feed rate of about 1-100 h ^-1 .