CN106140268A - Preparing propylene by methanol transformation silica zeolite catalyst and preparation method thereof - Google Patents

Abstract

The preparation method of the catalyst for the conversion of methanol to propylene comprises the following steps: (1) treating the all-silicon molecular sieve in lye, the concentration of the lye is 0.005-0.5mol/L, and the mass ratio of the molecular sieve to the solution is 1:1- 1:50; preferably, the concentration of lye is 0.01-0.2mol/L, and the mass ratio of molecular sieve to solution is 1:5-1:30; (2) Step (1) The all-silicon molecular sieve after alkali treatment is directly dried or after ion exchange, then filter and dry; (3) the all-silicon molecular sieve in step (2) is compressed into particles after being dried and roasted to obtain a catalyst for methanol conversion to propylene; or the all-silicon molecular sieve after step (2) is roasted and The binder is mixed and kneaded, extruded, dried and calcined to obtain a catalyst for methanol conversion to propylene. The prepared catalyst has high methanol conversion activity, good propylene selectivity and high stability.

Description

All-silicon molecular sieve catalyst for methanol conversion to propylene and preparation method thereof

technical field

The invention relates to the field of petrochemical industry, in particular to an all-silicon molecular sieve catalyst for converting methanol into propylene.

Background technique

Propylene is the most demanded and widely used basic organic chemical raw material in the petrochemical industry. At present, the production of propylene mainly comes from light hydrocarbon cracking and catalytic cracking processes. Due to the increasing shortage of global oil resources and the uncertainty of the market, the traditional propylene production route will inevitably be adjusted to the direction of diversification of raw materials. Among them, methanol to propylene from natural gas or coal is the most promising process route to replace the petroleum route. Natural gas or coal to methanol technology has reached maturity, the key to the feasibility of this process is the development of methanol or dimethyl ether to propylene process and catalyst.

The reaction of converting methanol into olefins includes two reactions: converting methanol into dimethyl ether and converting methanol or dimethyl ether into olefins. Methanol is first dehydrated at a lower temperature (150-350°C) to generate dimethyl ether, and then methanol is combined with di The equilibrium mixture of methyl ether continues to be converted into low-carbon olefins mainly composed of propylene at 420-500 °C, and the generated low-carbon olefins are further generated through polycondensation, cyclization, dehydrogenation, alkylation, and hydrogen transfer reactions to generate alkanes, Aromatics and higher olefins. Therefore, inhibiting the formation of by-products and improving the activity and stability of catalysts are the key points for the development of MTP catalysts.

HZSM-5 molecular sieve is the first choice for methanol to propylene catalyst because of its suitable pore size and wide range adjustable silicon to aluminum ratio. The MTP technology of German Lurgi Company uses Cd and Zn modified ZSM-5 series catalysts provided by Southern Chemical Company to develop a fixed-bed methanol-to-propylene process, but its single-pass propylene carbon-based yield is only about 40%. In addition, the FMTP process developed by Tsinghua University uses a fluidized bed reactor system, and the catalyst is an interphase SAPO molecular sieve with a mixed structure of CHA and AEI, and its single-pass propylene carbon-based yield is also lower than 45%. So far, the existing ZSM-5 catalyst still has the key problems of low propylene selectivity and propylene/ethylene ratio, and high yield of by-products. Among them, the low P/E also results in higher separation costs of ethylene and propylene.

It is generally believed that the conversion of methanol to B acid catalyzes the reaction, and the acid sites of B acid are mainly derived from the bridging hydroxyl group in the molecular sieve, that is, SiOHAl. However, in the process of methanol conversion to propylene, in order to improve the selectivity of propylene, it is generally necessary to carry out certain post-treatment operations on molecular sieves, so as to realize the modulation of acid sites. Chinese patent applications CN 200710039068.0, CN 200710043956.X and CN 200610117872.1 are treated with ammonium solution or acid solution, and then treated with steam and acid solution to prepare methanol conversion to propylene catalyst, which solves the problem of low catalyst P/E ratio and catalyst hydrothermal stability The problem of poor performance, but the process steps are various, which is not conducive to industrial promotion. There is also a catalyst prepared by combining Ce and dilute nitric acid, but its catalytic life is short. Or use rare earth elements La and P, Mg, or use elements Zr and P, or use element W to modify ZSM-5 molecular sieve, and realize the purpose of improving the single-pass selectivity of propylene and the P/E ratio. However, the above-mentioned rare earth or other precious metal elements used for modification are expensive, and the industrialization cost is relatively high. Chinese patent application 201310218415.1 discloses a catalyst for the conversion of methanol to produce gasoline while taking into account the yield of propylene and its preparation method. The ZSM-11 molecular sieve has a hierarchical pore structure of mesopores and micropores and a nanorod plug-in morphology. The aluminum ratio is 30-300, and the evaluation results show that the gasoline conversion rate, propylene yield and P/E are flexible in the ranges of 26.51-66.31%, 8.54-41.35%, and 1.23-5.35, respectively, but the propylene carbon-based yield And the P/E value is relatively low.

Therefore, it is necessary to design and develop a new type of catalyst to further improve the propylene selectivity and P/E ratio, thereby increasing the yield of the target product propylene, reducing the formation of by-products, and reducing energy consumption for separation.

In the reaction of producing low-carbon olefins from syngas, all-silica zeolite (Silicalite-1, Silicalite-2) has shown good performance as a carrier. They not only ensure the effective dispersion of active components, but also have a unique pore structure and weak acidity. It also limits the chain growth and secondary hydrogenation of hydrogenated products and improves the selectivity of C ₂ -C ₄ olefins. All-silicon molecular sieves can also be used as separation membrane materials and used to study the adsorption and desorption properties of p-nitrophenol. At the same time, the generation of defective sites in the all-silicon molecular sieve will form certain acidic sites, thereby exerting certain catalytic activity. The study found that all-silicon molecular sieves with MFI structure showed high reactivity and high amide selectivity in the Beckmann rearrangement reaction (cyclohexanone reacted with hydroxylamine to obtain cyclohexanone oxime and then rearranged to obtain caprolactam). , and the active center of the reaction is the silanol nest on ZSM-5 (J. Catal. 1999, 186: 12-19; J. Phys. Chem. A 2004, 108: 11388-11397). In addition, studies have also shown that the coke generated during the xylene isomerization process mainly exists on the silanol at the defect site in the pores of the molecular sieve, and the presence of the silanol significantly increases the life of the catalyst (Catal.Today 2001,70:227- 241). Recently, some scholars have also found that Silicalite-1 molecular sieve can effectively increase the yield of the target product in the process of cracking 1-butene to propylene, and inhibit the occurrence of side reactions such as hydrogen transfer (ACS Catal.2014, 4, 4205-4214) .

In addition, in order to realize the application of all-silicon molecular sieves in industry, it is necessary to match them with suitable carriers to ensure or improve the higher propylene selectivity and longer catalyst life of the original molecular sieves. Most of them use alumina carrier to meet the requirements of fixed bed catalysts in terms of compressive performance (axial crushing strength is ~100kg/cm ² , radial crushing strength is ~100kg/cm). However, the presence of alumina can cause an increase in methane and coke content, shortening catalyst life. It is an urgent problem to be solved at this stage to find ways to treat existing supports or catalysts to ensure propylene selectivity and catalyst life.

The present invention further broadens the application of the all-silicon molecular sieve through the treatment of the all-silicon molecular sieve. Therefore, the present invention is proposed.

Contents of the invention

One object of the present invention is to provide a catalyst for the high-selectivity conversion of methanol to produce propylene. The catalyst has high methanol conversion activity and good propylene selectivity.

Another object of the present invention is to provide a catalyst preparation method for highly selective conversion of alcohol to propylene. The catalyst obtained by the preparation method has high methanol conversion activity, good propylene selectivity and high stability.

For realizing the purpose of the present invention, adopt following technical scheme:

A catalyst for the highly selective conversion of methanol to propylene, the catalyst comprising an all-silicon molecular sieve, the all-silicon molecular sieve comprising one of all-silicon ZSM-5, all-silicon ZSM-11, all-silicon β, and all-silicon MCM-41 One or several kinds, preferably all-silicon ZSM-5 or all-silicon ZSM-11.

A catalyst for highly selective conversion of methanol to produce propylene, the catalyst comprising all-silicon molecular sieve and phosphorus element, the content of all-silicon molecular sieve is 93.0-99.8wt%, and the phosphorus element accounts for _0.02-7wt % of the weight of the catalyst in terms of _P2O5 , the all-silicon molecular sieve includes one or more of all-silicon ZSM-5, all-silicon ZSM-11, all-silicon β, all-silicon MCM-41, preferably all-silicon ZSM-5 or all-silicon ZSM- 11.

A catalyst for highly selective conversion of methanol to propylene, the catalyst comprising all-silicon molecular sieve, phosphorus element and _Al2O3 , the content of all _- silicon molecular sieve is 20-98wt%, and the phosphorus element accounts for ₂₀ % of the weight of the catalyst in terms of _P2O5 0.02-7wt%, and the binder Al ₂ O ₃ accounts for 1.0-79wt% of the weight of the catalyst.

The all-silicon molecular sieve includes one or more of all-silicon ZSM-5, all-silicon ZSM-11, all-silicon β, and all-silicon MCM-41, preferably all-silicon ZSM-5 or all-silicon ZSM-11 .

Preferably, the content of the all-silicon molecular sieve in the catalyst is 50-95 wt%.

Preferably, the content of phosphorus element calculated as P ₂ O ₅ in the catalyst reaches 0.05-3 wt%.

Preferably, the binder Al ₂ O ₃ accounts for 4.5-49 wt% of the weight of the catalyst.

In the present invention, the all-silicon molecular sieve is a hydrogen-type all-silicon molecular sieve.

Preferably, the all-silicon molecular sieve is subjected to alkali treatment; or the all-silicon molecular sieve is subjected to alkali treatment and ion exchange; or the all-silicon molecular sieve is impregnated with a phosphorus-containing solution; Phosphorus solution impregnation treatment.

Further, the all-silicon molecular sieve has an absorption peak at 3200-3600 cm ^-1 through infrared absorption spectrum analysis. The absorption peak here represents the hydrogen-bonded silicon hydroxyl in the chain or in the silicon nest.

The inventors have found through research that all-silicon molecular sieves exhibit very high propylene selectivity and long catalyst life in methanol conversion. Infrared analysis results show that the active sites are mainly hydrogen-bonded silanol groups with weak acidity. Usually, in the infrared spectrum, the hydroxyl groups at 3740 and 3700 cm ^-1 belong to the terminal silanols on the inner and outer surfaces, and the 3200-3600 cm ^-1 represent hydrogen-bonded silanols in chains or silicon nests. Here, silanols are divided into non-acidic terminal silanols and weakly acidic hydrogen-bonded silanols. In order to improve methanol conversion activity, propylene selectivity and catalyst life, it is necessary to selectively increase the number of hydrogen-bonded silanol groups on molecular sieves.

A method for preparing a catalyst for the conversion of methanol to propylene, comprising the steps of:

(1) All-silicon molecular sieve is processed in lye, and the concentration of lye is 0.005-0.5mol/L;

(2) The all-silicon molecular sieve after alkali treatment in step (1) is directly dried and roasted; or after ion exchange with an acidic solution, then filtered, dried and roasted;

(3) The all-silicon molecular sieve calcined in step (2) is pressed into granules to obtain a catalyst for methanol conversion to propylene;

Alternatively, in step (2), the calcined all-silicon molecular sieve is kneaded with the binder, then extruded, dried and calcined, the calcined catalyst is impregnated with a phosphorus-containing solution, and then dried and calcined after impregnation to obtain methanol conversion to propylene Catalyst; or, step (2) impregnating the all-silicon molecular sieve calcined in a solution containing phosphorus, drying and calcining after impregnation, kneading with an adhesive, extruding, drying and calcining to obtain a catalyst for methanol conversion to propylene.

Further, in the catalyst, the all-silicon molecular sieve is one or more of all-silicon ZSM-5, all-silicon ZSM-11, all-silicon β, and all-silicon MCM-41, preferably all-silicon ZSM-5 or all-silicon Silicon ZSM-11.

In the present invention, the all-silicon molecular sieve is treated with alkali solution at a concentration of 0.005-0.5 mol/L, which can properly produce crystal defects in the all-silicon molecular sieve, and can increase the number of hydrogen-bonded silicon hydroxyl groups per unit molecular sieve. The inventors found that the number of hydrogen-bonded silanol groups on the polymer sieve can effectively improve methanol conversion activity and propylene selectivity.

Further, in step (1), the lye is selected from one or more of ammonia water, sodium hydroxide, potassium hydroxide and lithium hydroxide, preferably ammonia water.

In step (1), the concentration of the lye is 0.01-0.2mol/L.

In step (1), the mass ratio of the molecular sieve to the solution is 1:1-1:50, preferably, the mass ratio of the molecular sieve to the solution is 1:5-1:30.

In step (1), the treatment is carried out at room temperature to 95° C. for 0.1 to 24 hours. Preferably, the temperature for alkali treatment is 50-80° C.; the treatment time is 3 to 10 hours.

The all-silicon molecular sieve is a hydrogen-type all-silicon molecular sieve.

In step (2), when ammonia water is used for the lye, the all-silicon molecular sieve after the lye treatment is suction-filtered and washed to neutrality, and then the filter cake after the suction filtration is dried and roasted, and then the treatment in step (3) is performed.

In step (2), when the alkali adopts lye such as alkali metal hydroxide, the all-silicon molecular sieve after the alkali treatment is suction-filtered and washed to neutrality, then the filter cake after the suction-filtration is dried and roasted, and the filter cake after the roasting is The cake is subjected to ion exchange, and then the ion-exchanged all-silicon molecular sieve is subjected to suction filtration, water washing to neutrality, drying and roasting, and the treatment in step (3) is performed after roasting.

Further, in step (2) or (3), the drying condition is: the temperature is 50-200°C, preferably 80-120°C.

Further, in step (2) or (3), the drying time is 0.5-5 hours, preferably 2-3 hours.

Further, the ion exchange may be a solution of one or more of hydrochloric acid, nitric acid, sulfuric acid, ammonium nitrate, ammonium chloride, ammonium sulfate, and ammonium fluoride, preferably ammonium nitrate solution.

Further, the concentration of the solution used for ion exchange is 0.01-5 mol/L, preferably 0.1-3 mol/L.

Further, during the ion exchange process, the solid-to-liquid mass ratio of the molecular sieve to the solution is 1:5-1:20, preferably 1:5-1:15.

Further, the ion exchange conditions are as follows: the temperature is 60-100°C, preferably 70-90°C; the exchange time is 2-8h, preferably 2-6h.

Further, in the step (3) the method for preparing the catalyst by pressing into particles further includes a treatment process of immersion in a phosphorus-containing solution. Specifically:

Step (2) impregnating the calcined all-silicon molecular sieve with a phosphorus-containing solution, pressing the impregnated all-silicon molecular sieve into catalyst particles, drying and roasting to obtain a catalyst for methanol conversion to propylene; or,

In step (2), the calcined all-silicon molecular sieve is pressed into catalyst particles, then impregnated with a phosphorus-containing solution, dried and calcined after impregnated to obtain a catalyst for methanol conversion to propylene.

In step (3), the impregnation is an incipient wetness impregnation method.

Wherein, the concentration of the phosphorus-containing solution is 0.1-10 wt%, preferably 0.5-5 wt%.

During impregnation, the mass ratio of phosphoric acid or phosphorous ammonium salt solution to molecular sieve is less than 5/1, preferably less than 3/1.

Further, the phosphorus-containing solution includes an aqueous solution of an inorganic compound containing phosphorus, specifically preferably, an aqueous solution of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate or ammonium hydrogen phosphate.

Furthermore, after the impregnation treatment of the phosphorus-containing solution, the phosphorus-containing element in the catalyst accounts for 0.02-7wt% of the weight of the catalyst in terms of P ₂ O ₅ , preferably 0.05-3wt%.

The binder described in step (3) includes but not limited to pseudo-boehmite.

Further, in step (3), the preparation method of all-silicon molecular sieve and adhesive mixed strip extrusion can adopt the method commonly used in this field. In the present invention, preferably, the pseudo-boehmite is mixed with the acid solution to form a gel, and the obtained gel is kneaded with all-silicon molecular sieves, kneaded evenly, and then extruded into strips.

When the catalyst is prepared by the mixed strip extrusion method, the amount of binder pseudo-boehmite can meet the molding conditions. In the present invention, preferably, the mass ratio of all-silicon molecular sieve to Al ₂ O ₃ is 1/ 4 to 98/1, preferably 1/1 to 20/1.

Further, the acid solution includes one or more of nitric acid, hydrochloric acid, sulfuric acid and phosphoric acid, preferably nitric acid.

Further, the concentration of the acid solution is 0.1-15wt%, preferably 1-10wt%; the mass ratio of pseudo-boehmite to the acid solution is 5/1-1/5, preferably 2/1-1/2 .

Further, in steps (2) and (3), the roasting conditions are as follows: the temperature is 500-800°C, preferably 550-700°C; the roasting time is 0.1-10h, preferably 0.5-3h.

Compared with the prior art, the outstanding advantages of the present invention are:

In the present invention, the all-silicon molecular sieve is treated with lye to effectively increase the amount of acidic hydrogen-bonded silicon hydroxyl groups and improve the activity of the catalyst; the phosphorus-containing solution is further used to treat the molecular sieve or the catalyst to passivate the outer surface of the molecular sieve or reduce the concentration of alumina in the catalyst. Acidic, improves propylene selectivity, delays catalyst coking and deactivation. The molecular sieve catalyst prepared by the preparation method of the present invention can increase the number of hydrogen-bonded silicon hydroxyl groups of the molecular sieve without affecting its high-temperature hydrothermal stability, and at the same time, through the treatment of the carrier and the catalyst, the reaction performance of the original molecular sieve can be effectively retained and improved. Applied in the process of producing propylene from methanol, the catalyst has high methanol conversion activity and propylene selectivity, does not have the dealumination phenomenon that the silica-alumina molecular sieve uses in a hydrothermal environment, and the all-silicon molecular sieve has good hydrothermal stability.

Description of drawings

Fig. 1. the infrared spectrogram of the catalyst of the present invention's conversion of methanol to propylene

detailed description

The following is a further detailed description of the all-silicon molecular sieve catalyst for the high-selectivity conversion of methanol to propylene of the present invention and its preparation method. The protection scope of the present application is not limited, and the protection scope is defined by the claims. Certain disclosed specific details provide a thorough understanding of the various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, and with other materials and the like.

Example 1

15 g of all-silicon microporous ZSM-5 molecular sieves were calcined at 550° C. for 4 h. Add 12g of ammonium nitrate and 150g of water to it, treat the above solution in a water bath at 80°C and strong stirring for 2h, suction filter until neutral, dry at 110°C for 2h, then repeat the above operation twice, each time the amount of ammonium nitrate Both are 0.8 times the amount of molecular sieves, and the amount of water is 10 times the mass of molecular sieves. Finally, it is roasted at 550 ° C for 3 hours to become a hydrogen-type all-silicon molecular sieve. After the molecular sieve was pressed into tablets, 1.2 g was taken for micro-reaction evaluation. The ratio of the peak area at 3200-3600cm ^-1 to the peak area at 3740cm ^-1 is 10:21 by infrared detection (Fig. 1a). Evaluation results show that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 45.6%.

In the following examples, unless otherwise specified, the roasting of the molecular sieve powder, the ion exchange and the subsequent roasting process are all consistent with those in Example 1. The H-Zeolite mentioned later refers to the hydrogen molecular sieve after ion exchange.

Example 2

Mix 1.2g of sodium hydroxide and 300g of water into a solution with a concentration of 0.1mol/L, add 10g of all-silicon microporous ZSM-5 molecular sieve to the solution, stir in a water bath at 60°C for 4 hours, and filter until neutral. Dry at 110°C for 3h, then bake at 550°C for 4h. Take 5g of molecular sieve after the above operation, add 4g of ammonium nitrate and 50g of water to it, place the above solution in a water bath at 80°C for 2 hours, repeat the above operation twice, and finally roast at 550°C for 3 hours to obtain the desired hydrogen form All silica molecular sieve. According to infrared detection (Figure 1b), the ratio of the peak area at 3200-3600cm ^-1 to the peak area at 3740cm ^-1 of the molecular sieve is 17:5. The evaluation results show that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 51.7C%.

Example 3

Mix 35g all-silicon microporous H-ZSM-5 molecular sieve and 22.0g pseudo-boehmite evenly, add 15g nitric acid solution (4wt%) to it and knead, extrude with a mold with a diameter of 1.5mm, dry in the air, place Dry at 110°C for 4h, then bake at 600°C for 4h. Dissolve 2.0g of ammonium dihydrogen phosphate in 40g of water, impregnate the solution on the above catalyst by multiple impregnation, dry at 120°C for 1 hour after each impregnation, and finally roast at 600°C for 3 hours to obtain the final product The all-silicon molecular sieve catalyst, the evaluation result of the catalyst shows that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 50.6%.

Example 4

5 g of the all-silicon microporous H-ZSM-5 molecular sieve in Example 1 was pressed into tablets under a pressure of 15 MPa, ground, and the 40-60 mesh catalyst was sieved. Dissolve 0.2g of ammonium dihydrogen phosphate in 10g of water, and impregnate the solution on the above-mentioned catalyst by multiple impregnation methods. After each impregnation, dry at 120°C for 1 hour, and finally bake at 550°C for 3 hours. The catalyst evaluation results show that , the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 50.2%.

Example 5

0.3g of phosphoric acid (85wt%) was dissolved in 10g of water, and this solution was impregnated in 5g of the alkali-treated all-silicon H-ZSM-5 molecular sieve obtained in Example 2 by multiple impregnation methods, and placed at 120°C after each impregnation Dry it for 1 hour, and finally bake it at 550°C for 3 hours, press it into a tablet under a pressure of 15 MPa, grind it, and take a 40-60 mesh catalyst for micro-reflective evaluation. The evaluation results of the catalyst showed that the conversion rate of methanol was 100wt%, and the carbon-based yield of propylene was 52.5%.

Example 6

Add 40g of all-silicon microporous H-ZSM-5 molecular sieve into 400g of 0.05mol/L ammonia solution, treat at 60°C for 1h under stirring conditions, dry at 120°C for 4h, and then calcinate at 550°C for 4h. Mix 35g of the molecular sieve and 22.0g of pseudo-boehmite evenly, add 15g of nitric acid solution (4wt%) to it and knead, extrude with a mold with a diameter of 1.5mm, dry in the air, and dry at 120°C for 4h, then place in the Calcined at 600°C for 4h. Dissolve 1.5g of ammonium dihydrogen phosphate in 30g of water, impregnate the solution on the above catalyst by multiple impregnation, dry at 120°C for 1 hour after each impregnation, and finally roast at 600°C for 3 hours to obtain the final product The all-silicon molecular sieve catalyst, the evaluation result of the catalyst shows that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 51.5%.

Example 7

Add 40g of all-silicon microporous H-ZSM-5 molecular sieve into 1000g of 0.2mol/L potassium hydroxide solution, treat at room temperature for 10h under stirring conditions, dry at 120°C for 4h, and then bake at 550°C for 4h. 64g of ammonium nitrate and 500g of water were added thereto, and the above solution was treated in a 70°C water bath for 4h, the above operation was repeated twice, and finally calcined at 550°C for 3h. Mix 35g of the molecular sieve and 35.0g of pseudo-boehmite evenly, add 15g of nitric acid solution (4wt%) and knead it, extrude it with a mold with a diameter of 1.5mm, dry it in the air, and dry it at 120°C for 4h, then place it in the Calcined at 600°C for 4h. Dissolve 5.2g of ammonium dihydrogen phosphate in 60g of water, impregnate the solution on the above catalyst by multiple impregnation, dry at 120°C for 1 hour after each impregnation, and finally roast at 600°C for 3 hours to obtain the final product The all-silicon molecular sieve catalyst, the evaluation result of the catalyst shows that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 52.2%.

Example 8

29.4g of pseudoboehmite was added with 6g of nitric acid solution (6wt%) to form a gel, then 30g of the molecular sieve obtained by roasting in Example 5 was added and kneaded, extruded with a mold with a diameter of 1.5mm, dried in the air, and dried at 120°C 4h, then baked at 600°C for 4h. The final all-silicon molecular sieve catalyst can be obtained, and the evaluation result of the catalyst shows that the conversion rate of methanol is 100wt%, and the yield of carbon-based propylene is 49.5%.

Comparative example 1

30 g of microporous ZSM-5 molecular sieves with a silicon-aluminum ratio of 38, a cubic shape, and a grain size of 1-2 μm are pressed into tablets. According to infrared detection (Figure 1c), the peak at 3200-3600cm ^-1 of the molecular sieve is not obvious, and the characteristic peak of silicon-aluminum bridge bond hydroxyl at 3610cm ^-1 appears. Catalyst evaluation results show that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 20.3%.

Comparative example 2

Mix 35g all-silicon microporous H-ZSM-5 molecular sieve and 22.0g pseudo-boehmite evenly, add 15g nitric acid solution (4wt%) to it and knead, extrude with a mold with a diameter of 1.5mm, dry in the air, place Dry at 120°C for 4h, then bake at 600°C for 4h. Catalyst evaluation results show that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 40.6%.

Comparative example 3

Mix 35g of microporous H-ZSM-5 molecular sieve (Hebei Pengyu Chemical Co., Ltd.) with a silicon-aluminum ratio of 38, a cubic shape, and a grain size of 1-2 μm and 22.0g of pseudo-boehmite evenly. 15g of nitric acid solution (4wt%) was added and kneaded, extruded into a mold with a diameter of 1.5mm, dried in the air, dried at 120°C for 4h, and then calcined at 600°C for 3h. Dissolve 2.0g of ammonium dihydrogen phosphate in 40g of water, impregnate the solution on the above catalyst by multiple impregnation, dry at 120°C for 1 hour after each impregnation, and finally roast at 600°C for 3 hours to obtain the final product The all-silicon molecular sieve catalyst, the evaluation result of the catalyst shows that the conversion rate of methanol is 100wt%, and the carbon-based yield of propylene is 26.1%.

1. Schedule

Catalyst performance test: use pure methanol with a mass fraction of 99% as raw material to perform performance evaluation on a micro-fixed-bed reaction device, the reaction temperature is 450°C, if it is a catalyst, its loading amount is 2g, if it is a molecular sieve, its loading amount is 1g, the nitrogen flow rate is 21mL/min, the water-alcohol mass ratio is 3:7, and the mass space time is 6h ^-1 . The carbon-based yield of the product is based on the amount of carbon and hydrogen after methanol dehydration.

Table 1. Pure methanol product distribution on embodiment 1-2 molecular sieves

Table 2. Pure methanol product distribution on the catalyst of embodiment 3-7

The results in Table 1 show that the propylene single-pass carbon-based yield of the invented catalyst is greater than 45%, and the P/E ratio is more than 10. The catalyst has undergone multiple reaction regeneration cycles, and the activity and propylene selectivity are basically unchanged, effectively overcoming the existing technology. The catalyst has poor stability and low propylene selectivity.

The results in Table 2 show that when alumina is used as the carrier, the radial strength of the catalyst is above 90N/cm, which meets the requirements of the fixed bed. The reaction results show that when untreated alumina is used as a carrier, although a higher yield of propylene can be achieved, the yield of dry gas and methane and ethylene is higher. After the catalyst is modified by P, the one-way carbon base of propylene The yield increases by about 10 percentage points, the P/E ratio is above 14, and the catalyst stability exceeds 1000h, which effectively overcomes the shortcomings of poor catalyst stability and low propylene selectivity in the prior art. Molecular sieves can also be directly reacted through tableting treatment, and can also obtain higher propylene carbon-based yield and P/E, and the catalyst has higher stability, and better technical results have been achieved.

Claims (11)

1. The preparation method of the catalyst for preparing propylene by methanol conversion comprises the following steps:

(1) treating the all-silicon molecular sieve in alkali liquor, wherein the concentration of the alkali liquor is 0.005-0.5mol/L, and preferably, the concentration of the alkali liquor is 0.01-0.2 mol/L;

(2) directly drying and roasting the all-silicon molecular sieve subjected to alkali treatment in the step (1); or after ion exchange with the acid solution, filtering, drying and roasting;

(3) pressing the calcined all-silicon molecular sieve in the step (2) into particles to obtain a catalyst for preparing propylene by converting methanol; or, kneading the roasted all-silicon molecular sieve in the step (2) with an adhesive, extruding, molding, drying and roasting, impregnating the roasted catalyst with a phosphorus-containing solution, drying and roasting after impregnation to obtain the catalyst for preparing propylene by converting methanol; or, the calcined all-silicon molecular sieve in the step (2) is soaked in a phosphorus-containing solution, dried and calcined after being soaked, kneaded with an adhesive, extruded into strips, molded, dried and calcined to obtain the catalyst for preparing propylene by converting methanol.

2. The preparation method according to claim 1, wherein in the step (1), the alkali treatment is carried out for 0.1-24 h at the temperature of room temperature to 95 ℃, and preferably, the temperature for the alkali treatment is 50-80 ℃; the treatment time is 3-10 h.

3. The preparation method of claim 1 or 2, wherein in the catalyst, the all-silica molecular sieve is one or more of all-silica ZSM-5, all-silica ZSM-11, all-silica beta and all-silica MCM-41, preferably, all-silica ZSM-5 or all-silica ZSM-11;

the ion exchange is selected from one or more solutions of hydrochloric acid, nitric acid, sulfuric acid, ammonium nitrate, ammonium chloride, ammonium sulfate and ammonium fluoride, and preferably ammonium nitrate solution;

the alkali liquor is selected from one or more of ammonia water, sodium hydroxide, potassium hydroxide and lithium hydroxide, preferably ammonia water.

4. The preparation method according to any one of claims 1 to 3, wherein in the step (2), when ammonia water is used as the alkali liquor, the all-silicon molecular sieve treated by the alkali liquor is subjected to suction filtration and washed to be neutral by water, and then a filter cake after suction filtration is dried and roasted to perform the treatment of the step (3);

in the step (2), when alkali is alkali solution such as alkali metal hydroxide, the alkali-treated all-silicon molecular sieve is subjected to suction filtration and water washing to be neutral, then a filter cake after suction filtration is dried and roasted, the roasted filter cake is subjected to ion exchange, then the ion-exchanged all-silicon molecular sieve is subjected to suction filtration, water washing to be neutral, drying and roasting, and the treatment of the step (3) is carried out after roasting.

5. The production method according to any one of claims 1 to 4, wherein in the step (2), the concentration of the solution for ion exchange is 0.01 to 5mol/L, preferably 0.1 to 3 mol/L.

6. The production method according to any one of claims 1 to 5, wherein in the step (2), the conditions for the ion exchange are: the temperature is 60-100 deg.C, preferably 70-90 deg.C.

7. The method according to any one of claims 1 to 6, wherein the step (3) further comprises a process of impregnating with a phosphorus-containing solution, specifically:

impregnating the roasted all-silicon molecular sieve in a phosphorus-containing solution, pressing the impregnated all-silicon molecular sieve into catalyst particles, drying and roasting to obtain a catalyst for preparing propylene by converting methanol; or,

pressing the calcined all-silicon molecular sieve in the step (2) into catalyst particles, then impregnating the catalyst particles with a phosphorus-containing solution, drying and calcining the impregnated catalyst particles after impregnation to obtain a catalyst for preparing propylene by converting methanol; or,

and (3) kneading the roasted all-silicon molecular sieve and an adhesive, extruding, molding, drying, roasting, soaking the roasted catalyst in a phosphorus-containing solution, drying and roasting after soaking to obtain the catalyst for preparing the propylene by converting the methanol.

8. The method according to claim 7, wherein the concentration of the phosphorus-containing solution is 0.1 to 10 wt%, preferably 0.5 to 5 wt%;

the phosphorus-containing solution includes an aqueous solution of an inorganic compound containing phosphorus, and preferably includes an aqueous solution of phosphoric acid, an aqueous solution of ammonium phosphate, an aqueous solution of ammonium dihydrogen phosphate, or an aqueous solution of ammonium hydrogen phosphate.

9. The process according to claim 7 or 8, wherein the phosphorus-containing element in the catalyst is P after the impregnation treatment with the solution containing phosphorus₂O₅0.02-7 wt%, preferably 0.05-3 wt% of the catalyst.

10. The method according to any one of claims 7 to 9, wherein the binder of step (3) comprises pseudoboehmite; all-silicon molecular sieve and Al₂O₃The mass ratio of (A) is 1/4 to 98/1, preferably 1/1 to 20/1.

11. A catalyst for preparing propylene by converting methanol,

the catalyst comprises an all-silicon molecular sieve; or

The catalyst comprises an all-silicon molecular sieve and a phosphorus element, wherein the content of the all-silicon molecular sieve in the catalyst is 93.0-99.8 wt%, and the phosphorus element is P₂O₅Accounting for 0.02-7 wt% of the weight of the catalyst; or

The catalyst comprises an all-silicon molecular sieve, phosphorus and Al₂O₃The content of the all-silicon molecular sieve is 20-98 wt%, and the phosphorus element is P₂O₅0.02-7 wt% of catalyst weight, and adhesive Al₂O₃1.0-79 wt% of the catalyst; preferably, the content of the all-silicon molecular sieve in the catalyst is 50-95 wt%, and P is used₂O₅The content of phosphorus element in the catalyst is 0.05-3 wt%, and the adhesive Al₂O₃Accounting for 4.5-49 wt% of the weight of the catalyst;

the all-silicon molecular sieve comprises one or more of all-silicon ZSM-5, all-silicon ZSM-11, all-silicon beta and all-silicon MCM-41, and preferably all-silicon ZSM-5 or all-silicon ZSM-11.