Direct forming preparation method and application of methanol-to-olefin catalyst

Abstract

The invention belongs to the technical field of catalyst preparation, and discloses a direct forming preparation method and application of a methanol-to-olefin catalyst. The process flow for preparing the catalyst is simplified, the formed catalyst with an expected shape is directly prepared, the filtering and washing steps in the conventional catalyst production process are avoided, the waste liquid discharge amount is low, and the method is environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and specifically relates to a direct molding preparation method of a methanol to olefin catalyst and application thereof. Background Art

[0002] Low-carbon olefins (ethylene and propylene) are important chemical raw materials and play a pivotal role as important intermediate products in the modern petrochemical industry. Ethylene is mainly used to produce chemical products such as polyethylene, ethylbenzene, ethylene glycol and ethylene oxide. The production capacity and technical level of low-carbon olefins are one of the important indicators of a country's petrochemical development level.

[0003] In 1976, Mobil Oil Company of the United States first used ZSM-5 molecular sieve to conduct research on methanol to olefins (MTO) (Journal of Catalysis, 1977, 47 (2): 249-259). Subsequently, UOP of the United States and Norsk Hydro of Norway further cooperated to develop the UOP / Hydro MTO process on this basis. In addition, the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences successfully developed the DMTO process with independent intellectual property rights and completed the world's first 10,000-ton industrial test in 2006 (ACS Catalysis, 2015, 5 (3): 1922-1938). In 2010, the Shenhua Group's coal-to-olefins project, which used the DMTO technology of the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, achieved the world's first commercial operation, becoming the world's first successful practice of industrial and commercial operation of the coal-to-olefins process route.

[0004] The pore size of the 8-membered ring of SAPO-34 molecular sieve is 3.8Å×3.8Å, and the pore volume is about 0.42 cm 3 / g, its small pore structure can also effectively prevent large molecular HC compounds from entering the pores to form carbon deposits. The SAPO-34 molecular sieve framework is negatively charged because the introduction of Si breaks the charge balance, and the formed Si-OH-Al bond is a proton acidic site. Therefore, the SAPO-34 molecular sieve has both special adsorption properties and proton acidity. This makes it widely used in methanol conversion to olefins (MTO).

[0005] In recent years, with the rapid development of the national economy, the market demand for SAPO-34 molecular sieve has gradually increased. When SAPO-34 molecular sieve is used as a catalyst in actual industrial applications, it is often necessary to make it into finished particles of specific shapes and sizes. The finished product preparation process includes the synthesis of molecular sieve powder and the processing and molding of catalyst particles.

[0006] The synthesis of SAPO-34 molecular sieve powder is industrially carried out by hydrothermal synthesis, which uses water as solvent and mixes materials in a certain ratio to obtain sol. The sol is crystallized at 80-200 °C and under the autogenous pressure of water. After the crystallization, the product is filtered, washed and dried to obtain molecular sieve powder. Then the molecular sieve powder is mixed with additives such as binder, plasticizer, extrusion aid, pore-forming agent to obtain plastic body, and then the catalyst is obtained through kneading, curing, drying and calcination.

[0007] The above method first prepares the molecular sieve powder, then shapes, dries and roasts it. The process is long and complicated. In addition, the hydrothermal crystallization process of the molecular sieve is carried out under high pressure, which poses a safety hazard; the filtering and washing process of the powder produces a large amount of wastewater, causing environmental pollution; the catalyst molding requires the addition of additives such as binders. Due to the introduction of additives, the content of molecular sieve in the finished molecular sieve catalyst is generally 60~80%, and cannot reach 100%, which affects the performance of the molecular sieve.

[0008] In order to solve the above problems, people have done a lot of research on simplifying the molecular sieve molding process and increasing the content of molecular sieve in the molded body.

[0009] The researchers used raw materials with a certain shape to directly produce molecular sieves with the same shape as the raw materials without the need for reshaping, which can simplify the molecular sieve catalyst preparation process.

[0010] Franziska Scheffler et al. prepared a shaped ZSM-5 catalyst using a foam aluminum monolith as raw material. The method placed the foam aluminum monolith in a solution with a molar ratio of Na2O:TPABr:SiO2:H2O=0:423:0.055:1:72.4, and crystallized it at 150 °C for 24 h to obtain a shaped catalyst. The method used the foam aluminum monolith as the aluminum source, and the other raw materials were still in the aqueous solution. The content of ZSM-5 was only 13% (Micropor. Mesopor. Mater., 2004, 67(1):53-9).

[0011] In order to increase the content of molecular sieve in the finished molecular sieve catalyst, researchers have done a lot of work to crystallize the additives such as binders added during the molding process into molecular sieves. For example, patent CN1105906A discloses a method for preparing a zeolite catalyst. The method is to mix ZSM-5 powder and silica binder to form a mixture, further in an organic amine or organic quaternary ammonium base aqueous solution or steam, to obtain an integrated molecular sieve through hydrothermal treatment, and then to obtain a finished catalyst through calcination.

[0012] The above method crystallizes part of the raw materials in the form of integral materials under hydrothermal conditions, and obtains an integral catalyst in one step, which simplifies the preparation process. However, other raw materials still exist in the aqueous solution, and crystallization is still a hydrothermal process, which poses a safety hazard; the reaction raw materials are divided into solid and liquid phases, the reaction process is limited by mass transfer, and the finished product contains unconverted raw materials, and the molecular sieve content is not high. Moreover, although a molded body composed entirely of molecular sieves can be obtained, it is still necessary to synthesize the original molecular sieve powder; the molding process adds a crystallization step, which increases the manufacturing cost. In addition, these methods use integral material shape raw materials, which are limited by the raw material material and have a single shape. At present, the actual finished product shapes of the molded catalyst are rich, including spherical, strip, cylindrical, honeycomb, four-leaf clover, three-leaf clover, external gear, non-porous external gear, plum blossom, porous plum blossom, seven-hole sphere, non-porous sphere, seven-rib wheel, four-hole, four-leaf butterfly, etc. Summary of the invention

[0013] In order to overcome the shortcomings of the prior art, the present invention provides a direct molding preparation method of a methanol to olefins catalyst and its application, which simplifies the process flow of catalyst preparation, directly prepares a shaped catalyst with a desired shape, avoids the filtering and washing steps of the conventional catalyst production process, has low waste liquid discharge, and is environmentally friendly.

[0014] The above object of the present invention is achieved through the following technical scheme: a direct molding preparation method of a methanol to olefins catalyst, comprising the steps of: The pseudo-boehmite, template, silica sol, phosphorus source, ionic liquid and deionized water are mixed to prepare a gel; The gel prepared in step 1 is fed into a material forming system to be processed into a shaped gel having a desired shape; The shaped gel obtained in step 2 is placed in a reaction kettle for crystallization to obtain a shaped SAPO-34 catalyst.

[0015] Furthermore, in step 1, the pseudo-boehmite component is Al2O3, the silica sol component is SiO2, and the phosphorus source component is P2O5.

[0016] Furthermore, in step 1, the template agent is one or both of diethylamine and triethylamine.

[0017] Furthermore, the anion of the ionic liquid in step 1 is Br - ,I - , Cl - 、BF4 - 、NO3 - 、CH3COO - One or more of the following; the cation is an alkyl-substituted imidazolium ion [Rim] + , alkyl-substituted pyridinium ion [Rpy] +, alkyl quaternary ammonium salt ion [NR4] + One or more of the following, R is a C1-C16 alkyl group.

[0018] Furthermore, in step 1, the molar ratio of pseudo-boehmite: template: silica sol: phosphorus source: ionic liquid: deionized water is (0.5-4): (0.1-0.8): (0.8-1.3): (0.4-1): (20-60): (33-78).

[0019] Furthermore, the phosphorus source P2O5 in step 1 comes from one or more of phosphoric acid, diammonium phosphate, diammonium hydrogen phosphate, and triammonium phosphate.

[0020] Furthermore, the material forming system in step 2 is specifically as follows: a conveyor belt, a cavity, and a receiving hopper are connected in sequence, the conveyor belt is controlled by a motor with an operation panel, a box shell is provided outside the cavity, an ultrasonic oscillator is provided at the bottom of the box shell, and a bracket is also provided at the bottom of the box shell.

[0021] Furthermore, the step 2 is specifically as follows: placing the gel on a molding mold and then placing it on a conveyor belt, turning on a motor to convey it to the inside of the cavity, and using an ultrasonic oscillator at the bottom to oscillate the gel until it is uniformly formed, and the formed gel is sent to a receiving hopper.

[0022] Furthermore, the crystallization conditions in step 3 are: crystallization at 180-200° C. for 12-72 hours.

[0023] Another object of the present invention is to protect the application of the above-mentioned methanol to olefins catalyst, specifically to the methanol to light olefins reaction.

[0024] The crystallization process of the present invention is carried out by placing the formed gel in a container, in which a certain amount of water may be placed in advance, but it is not necessary for the water to be in direct contact with the formed gel. The heating method used in the crystallization process is, for example, oil bath heating, oven heating and microwave heating.

[0025] After the crystallization is completed, the molded product prepared by the present invention does not need to be filtered or washed, and maintains the same shape and size as the molded gel. It is completely composed of active metal components and molecular sieves. The molecular sieve framework has a CHA topological structure confirmed by the International Zeolite Association and is completely composed of SAPO-34 molecular sieves.

[0026] To facilitate understanding of the present invention, the term "direct forming" is defined below. The defined terms have the meanings commonly understood by those of ordinary skill in the art to which the present invention relates.

[0027] Unless otherwise specified, "direct molding" in this article refers to the process or step of pre-processing the gel used for synthesizing molecular sieves into a molded gel with a certain shape, size and mechanical strength by compression, extrusion, rotation, spraying, etc., and then directly obtaining a molded molecular sieve with the same shape as the molded gel by heating.

[0028] Compared with the prior art, the present invention has the following beneficial effects: a shaped catalyst is obtained in one step, which simplifies the catalyst preparation process. The shaped body is completely composed of molecular sieves, which increases the amount of active sites per unit volume of the catalyst and can improve its catalytic activity. The method directly obtains a shaped catalyst, avoids the filtering and washing steps in the conventional catalyst production process, has low waste liquid discharge, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Figure 1 It is a schematic diagram of the structure of the material forming system of the present invention; Figure 2 is the XRD spectrum of the sample in Example 1 of the present invention; Figure 3 This is a physical picture of the molded SAPO-34 catalyst in Example 1 of the present invention.

[0030] In the figure, 1. conveyor belt; 2. motor; 3. operation panel; 4. ultrasonic oscillator; 5. bracket; 6. box shell; 7. hopper; 8. cavity. DETAILED DESCRIPTION

[0031] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels. Example 1

[0032] 17.36g of pseudo-boehmite (78.6wt% Al2O3) was placed in a 100ml beaker, 138g of deionized water was added, and the mixture was stirred at room temperature for 30 minutes. 2.67g of 30wt% silica sol was added, and the mixture was stirred at room temperature for 30 minutes. Then, 6.8g of triethylamine was added for 30 minutes. 30.82g of phosphoric acid was added and the stirring was continued. 10.22g of 1-ethyl-3-methylimidazolium bromide ionic liquid was added, and the mixture was stirred until uniform and treated at 90°C and extruded into cylindrical strips. The shaped cylindrical strip gel was placed in a crystallization reactor with a polytetrafluoroethylene reactor liner and crystallized at 200°C for 12h.

[0033] After the crystallization is completed, the crystallization reactor is cooled to room temperature to obtain a molded catalyst, and the molded catalyst is ground into powder. The XRD spectrum analysis shows that the product is SAPO-34. Figure 1 As shown; Figure 2 Physical picture of the formed catalyst. Example 2

[0034] 17.36g of pseudo-boehmite (78.6wt% Al2O3) was placed in a 100ml beaker, 40g of deionized water was added, and the mixture was stirred at room temperature for 30 minutes. 21.36g of 30wt% silica sol was added, and the mixture was stirred at room temperature for 30 minutes. 39.1g of diethylamine was added for 30 minutes, 40.07g of phosphoric acid was added, and stirring was continued. 12.77g of 1-ethyl-3-methylimidazolium bromide ionic liquid was added, and the mixture was stirred until uniform and treated at 90°C, and extruded into cylindrical strips. The shaped cylindrical strip gel was placed in a crystallization reactor with a polytetrafluoroethylene reactor liner and crystallized at 180°C for 72h.

[0035] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a molded catalyst, and the molded catalyst is ground into powder. XRD spectrum analysis shows that the product is SAPO-34. Example 3

[0036] 17.36g of pseudo-boehmite (78.6wt% Al2O3) was placed in a 100ml beaker, 138.35g of deionized water was added, and the mixture was stirred at room temperature for 30 minutes. 13.35g of 30wt% silica sol was added, and the mixture was stirred at room temperature for 30 minutes. Then, 27.2g of triethylamine was added for 30 minutes. 12.33g of phosphoric acid and 6.15g of diammonium phosphate were added, and the stirring was continued. 25.54g of 1-ethyl-3-methylimidazolium bromide ionic liquid was added, and the mixture was stirred until uniform and treated at 90°C, and extruded into cylindrical strips. The shaped cylindrical strip gel was placed in a crystallization reactor with a polytetrafluoroethylene reactor liner, and crystallized at 200°C for 24h.

[0037] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a molded catalyst, and the molded catalyst is ground into powder. XRD spectrum analysis shows that the product is SAPO-34. Example 4

[0038] 17.36g of pseudo-boehmite (78.6wt% Al2O3) was placed in a 100ml beaker, 138.35g of deionized water was added, and the mixture was stirred at room temperature for 30 minutes. 10.68g of 30wt% silica sol was added, and the mixture was stirred at room temperature for 30 minutes. Then, 20.4g of triethylamine was added for 30 minutes. 15.41g of phosphoric acid and 8.83g of diammonium hydrogen phosphate were added, and the stirring was continued. 20.43g of 1-ethyl-3-methylimidazolium bromide ionic liquid was added, and the mixture was stirred until uniform and treated at 90°C, and extruded into cylindrical strips. The shaped cylindrical strip gel was placed in a crystallization reactor with a polytetrafluoroethylene reactor liner and crystallized at 200°C for 48h.

[0039] After the crystallization is completed, the crystallization kettle is cooled to room temperature to obtain a molded catalyst, and the molded catalyst is ground into powder. XRD spectrum analysis shows that the product is SAPO-34. Comparative Example 1

[0040] The methanol to olefins catalyst of Comparative Example 1 was prepared according to the method described in Patent CN105396615A, and the steps were as follows: 18 kg of decationized water, 1.64 kg of acidic silica sol, 4 kg (dry basis) SAPO-34 molecular sieve, 1 kg (dry basis) XF01, 2.5 kg (dry basis) kaolin, 0.2 kg (dry basis) Zn(NO3)2·6H2O and 1 kg (dry basis) pseudo-boehmite were added in sequence into a stirred tank, and after slurrying and dispersion for 120 minutes, 1.3 kg of concentrated phosphoric acid was added, and slurrying was continued for 60 minutes; then the obtained slurry was spray-dried at an inlet temperature of 500°C and an exhaust gas temperature of 180°C to obtain a slurry containing 40 weight parts% SAPO-34, 10 weight parts% XF01, 25 weight parts% kaolin, 10 weight parts% Al2O3, 5 weight parts% SiO2, 2 weight parts% Zn The catalyst containing the additive (calculated as ZnO) and 8 parts by weight % phosphorus additive (calculated as P2O5) is the comparative catalyst.

[0041] The catalysts in Examples 1-4 and Comparative Example 1 were calcined at 600°C for 3h to remove the template. Under normal pressure, a quartz tube fixed bed continuous reaction device was used to evaluate the catalytic performance of the synthesized SAPO-34 molecular sieve sample in the methanol conversion to produce light olefins (MTO) reaction. The specific steps of the MTO reaction evaluation are as follows. The calcined catalyst sample was made into 40-60 mesh particles as a catalyst. About 0.3 g of the catalyst sample was weighed and loaded into a reactor at 550 o C for 1 h in a nitrogen atmosphere and then cooled to 450 o The reaction was carried out at 30 °C with 4.2 mL / min helium as carrier gas. oThe reaction raw materials were introduced into the reactor with methanol at a speed of 3 h. -1 The product distribution was analyzed using an Agilent 7890 online gas chromatograph, and the results are listed in Table 1.

[0042] Table 1 Lifetime and product distribution of different SAPO-34 in MTO reaction

[0043] It can be seen from Table 1 that the shaped catalyst prepared by the present method has higher selectivity for ethylene and propylene than the catalyst of the comparative example, and the shaped catalyst prepared by the present method has a longer service life.

[0044] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A direct molding preparation method for a methanol to olefins catalyst, characterized in that the steps include: S1. The pseudo-boehmite, template, silica sol, phosphorus source, ionic liquid and deionized water are mixed to prepare a gel; S2. The gel prepared in step S1 is processed into a shaped gel having a desired shape by entering a material forming system; S3. Place the shaped gel obtained in step S2 into a reaction kettle for crystallization to obtain a shaped SAPO-34 catalyst.

2. The direct molding preparation method of the methanol to olefins catalyst according to claim 1, characterized in that: In the step S1, the pseudo-boehmite component is Al2O3, the silica sol component is SiO2, and the phosphorus source component is P2O5.

3. The direct molding preparation method of methanol to olefins catalyst according to claim 1, characterized in that: In the step S1, the template agent is one or both of diethylamine and triethylamine.

4. The direct molding preparation method of methanol to olefins catalyst according to claim 1, characterized in that: The anion of the ionic liquid in step S1 is Br - ,I - , Cl - 、BF4 - 、NO3 - 、CH3COO - One or more of the following; the cation is an alkyl-substituted imidazolium ion [Rim] + , alkyl substituted pyridinium ion [Rpy] + 、Alkyl quaternary ammonium salt ion [NR4] + One or more of the following, wherein R is a C1-C16 alkyl group.

5. The direct molding preparation method of methanol to olefins catalyst according to claim 1, characterized in that: In the step S1, the molar ratio of pseudo-boehmite: template: silica sol: phosphorus source: ionic liquid: deionized water is (0.5-4): (0.1-0.8): (0.8-1.3): (0.4-1): (20-60): (33-78).

6. The direct molding preparation method of methanol to olefins catalyst according to claim 2, characterized in that: In step S1, the phosphorus source P2O5 is derived from one or more of phosphoric acid, diammonium phosphate, diammonium hydrogen phosphate, and triammonium phosphate.

7. The direct molding preparation method of methanol to olefins catalyst according to claim 1, characterized in that: The material forming system in step S2 is specifically as follows: a conveyor belt, a cavity, and a receiving hopper are connected in sequence, the conveyor belt is controlled by a motor switch with an operation panel, a box shell is provided outside the cavity, an ultrasonic oscillator is provided at the bottom of the box shell, and a bracket is also provided at the bottom of the box shell.

8. The direct molding preparation method of the methanol to olefins catalyst according to claim 7, characterized in that: The step S2 specifically includes: placing the gel on a forming mold and then placing it on a conveyor belt, turning on a motor to convey it to the inside of the cavity, and using an ultrasonic vibrator at the bottom to vibrate the gel until it is uniformly formed, and the formed gel is sent to a receiving hopper.

9. The direct molding preparation method of methanol to olefins catalyst according to claim 1, characterized in that: The crystallization conditions in step S3 are: crystallization at 180-200° C. for 12-72 hours.

10. Use of the methanol to olefins catalyst prepared as claimed in claim 1, characterized in that: It is specifically used in the reaction of methanol to produce light olefins.

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