CN112958146B

CN112958146B - MFI molecular sieve nanosheet-loaded zirconium-based catalyst and application thereof in butadiene preparation reaction

Info

Publication number: CN112958146B
Application number: CN201911288832.7A
Authority: CN
Inventors: 郑明远; 李显泉; 庞纪峰; 张涛
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2022-04-19
Anticipated expiration: 2039-12-12
Also published as: CN112958146A

Abstract

The invention provides a catalyst for preparing butadiene through the reaction of ethanol and acetaldehyde and application thereof. The alkali center (A) is one or more of lithium, sodium, potassium, magnesium and calcium. Active components of alkali metal and transition metal zirconium are loaded in the MFI molecular sieve with the nanosheet layer growing in a cross mode of 2-10 nm. The catalyst can realize the reaction of ethanol and acetaldehyde under the reaction conditions of 300-400 ℃ to generate butadiene with high efficiency, high selectivity and high yield. Compared with the existing catalyst for preparing butadiene from ethanol acetaldehyde, the catalyst provided by the invention has the remarkable advantages of good stability and high selectivity.

Description

MFI molecular sieve nanosheet-loaded zirconium-based catalyst and application thereof in butadiene preparation reaction

Technical Field

The invention relates to a catalyst for preparing butadiene through reaction of ethanol and acetaldehyde, a preparation method and application thereof, in particular to an MFI molecular sieve nanosheet-loaded zirconium-based catalyst, preparation thereof and application thereof in preparation of butadiene through reaction of ethanol and acetaldehyde.

Background

Butadiene is an important organic chemical basic raw material, has wide industrial application, and has the second place to ethylene and propylene in the field of petrochemical industry. Butadiene is used as an important organic synthetic monomer and is mainly used for synthesizing industrial products such as styrene-butadiene rubber, nitrile rubber, chloroprene rubber, polybutadiene rubber and the like [ Jianghen, butadiene production application and technical progress, fine chemical raw materials and intermediates, 2008, 3, 16-20 ]. In addition, butadiene, the simplest conjugated diene, is chemically reactive and is capable of undergoing a number of organic chemical reactions, including addition, substitution, polymerization, cyclization, and the like. In addition to the use in the rubber industry, butadiene is a basic material for many other petrochemical products, and can be used in the synthesis of industrial resins, including ABS, SBS, MBS, etc., and also in the production of nylon 66, butanediol, hexanediol, adiponitrile, etc. (Qianbaizhu, Lixiong, technical development and market analysis of butadiene, chemical industry 2015, 11, 33-37).

Since 1920, butadiene production has gone through an ethanol process, a butene or butane dehydrogenation process, and a C4 fractionation process. Soviet Lebedev developed the ethanol one-step synthesis of butadiene in 1928 and subsequently applied to industrial production. The United states Union carbide group company also developed a process route for producing butadiene from ethanol acetaldehyde [ Tanjia, analysis of supply and demand status and development prospects of butadiene at home and abroad, petrochemical technology and economy, 2016, 32, 13-18 ]. In 1943, the technology for producing butadiene by catalytic dehydrogenation of butylene realizes industrial production, and gradually replaces the ethanol method to become the main technology for producing butadiene due to the good economical efficiency of the petroleum route. In 1956, Houdry in the united states succeeded in industrializing the process for the dehydrogenation of butane to butadiene, which, due to the cheap and readily available raw materials, occupied almost the entire market for butadiene production. Subsequently, the PetroTEX company in the United states improves on the catalytic dehydrogenation method of the butylene in 1965, and the oxidative dehydrogenation method of the butylene is industrialized. The technology for producing ethylene by naphtha cracking is developed in a breakthrough manner from the 60 s in the 20 th century, and the method for extracting butadiene as a byproduct from C4 fraction quickly occupies the market. To date, about 97% of the butadiene worldwide comes from this process, with the remainder coming from the butene or butane dehydrogenation process.

The Soviet Union Lebedev makes butadiene by ethanol method for The first time in 1929 and applies to actual production, and The second world war, The method accounts for a great proportion in The production of strategic material synthetic rubber [ S.V.Lebedev, A.O. Yakubicik, The catalytic hydrogenation of catalytic types of unskilled compounds, part IV. The hydrogenation of regulated systems: pipeic acid, J.chem.Soc,1929,220-225 ]. Thereafter, many operational details of the Lebedev process for ethanol production of butadiene are published, but the actual formulation of the catalyst has not been disclosed.

In 1915, Ostromislensky adds acetaldehyde into ethanol raw material, and adopts catalyst with dehydration property to synthesize butadiene [ J.T.Dunn, W.J.Toussaint, Process for making dielleffs, US Patent 2,421,361]. The united carbide company carries out systematic research on a two-step catalytic system, and the binary catalytic systems adopted by the company are tantalum silicon, zirconium silicon and niobium silicon. The first step is dehydrogenation reaction of ethanol with copper as main catalyst, and the second step has the best catalyst system of 2 wt% Ta₂O₅/SiO₂. The reaction temperature is between 325 ℃ and 350 ℃, the feed is 69 wt% ethanol, 24 wt% acetaldehyde and 7 wt% water, the yield of butadiene is 35%, and the selectivity is 67%. Slightly less active in the zirconium-silicon and niobium-silicon systems, 1.6 wt% ZrO₂/SiO₂The selectivity to butadiene was 59%.

From the 50 s to the 70 s, the route for butadiene production using the ethanol process has been slow due to economic constraints. However, after the 70's of the 20 th century, the increasing price of petroleum, the increasing exhaustion of fossil fuels, and the increasing environmental stress have caused the use of renewable resources to be of great concern. Ethanol, a renewable, clean, and non-polluting chemical, is obtained from tubers of some plants (e.g., potatoes, yams, cassava, etc.), grains, sugar cane, and woody plants [ a.m. Shupe, s.liu, Ethanol transfer from hydrosylated hot-water wood extrusions by sugar transfer processes, Biomass and Bioenergy,2012,39, 31-38 ]. In recent years, with the continuous maturity of bioethanol production and purification technologies, the production scale is continuously expanding. In addition to readily fermentable sugars, non-fermentable sugars, lignocellulose, and the like can be used as raw materials. With the increasing demand for bioethanol, more efficient processes based on different biomass sources will be developed. In addition, the other production process of the ethanol, namely the production process of the ethanol prepared from coal, has obvious cost advantage compared with the production process of the ethanol prepared by a fermentation method, and is industrially applied at present. The coal-based ethanol conforms to the national conditions of rich coal, poor oil and more people and less land in China, is an important composition in the field of energy and chemical industry in China, and becomes an important source for increasing the yield of the ethanol. [ Mengye, Baidayu, Likai, etc. ] the research on ethanol production technology and coal-made ethanol technology in our country has progressed [ J ] coal and chemical industry, 2017, 40 (8):21-23 ]. Therefore, the method for producing butadiene by using ethanol as a raw material has wide prospects.

The industrial production of butadiene from ethanol acetaldehyde has been stopped in the last 50 centuries, mainly because the catalyst required by the reaction is easily and rapidly deactivated by carbon deposition, resulting in poor catalyst stability, and because the active ingredient used by the catalyst is Ta, the catalyst cost is high. The invention aims to improve the stability of the reaction for preparing butadiene from ethanol and acetaldehyde, designs a corresponding catalyst, adopts a nanosheet MFI molecular sieve as a carrier, has a special lamellar structure which can obviously improve the stability of the reaction, and adopts cheap metal Zr as an active center so as to greatly reduce the cost of the catalyst.

Disclosure of Invention

The invention aims to provide a catalyst for preparing butadiene from ethanol and acetaldehyde, a preparation method and application thereof, which can realize high-yield and high-selectivity generation of butadiene through catalytic conversion of ethanol and have high stability.

In order to achieve the purpose, the invention adopts the technical scheme that:

a catalyst with magnesium zirconium supported on MFI, said catalyst being represented by the formula a-Zr-MFI. Wherein, zirconium is an active component, A is one of lithium, sodium, potassium, magnesium and calcium; the total loading capacity of the active metal zirconium in the catalyst is 1-30 wt%; the loading amount of A in the catalyst is 0.5-20 wt%, and MFI is MFI molecular sieve carrier with a nano-sheet structure.

Preferably, the carrier MFI is formed by the cross growth of nanosheets, the thickness of the nanosheet is 2-10nm, and the nanosheet has a hierarchical pore structure of micropores and mesopores.

Preferably, the preferred loading of zirconium is in the range of 10 to 24 wt%. The preferred loading of the second metal A is in the range of 0.5 to 5 wt%.

The preparation method of the catalyst comprises the steps of dipping a soluble salt solution of an active component Zr on a carrier, drying at 60-120 ℃, and roasting in an air atmosphere to obtain a sample. Then, a soluble salt solution of the alkali metal center A is soaked in the obtained sample, and the catalyst is obtained by roasting the sample at the air atmosphere after drying at 60-120 ℃. The calcination temperature of the catalyst is between 450 ℃ and 750 ℃. The preferred calcination temperature is 500-600 ℃, and the calcination time is 3-9 hours.

The catalyst is applied to the reaction of preparing butadiene from ethanol and acetaldehyde, the reaction of preparing butadiene from ethanol and acetaldehyde is carried out in a normal-pressure fixed bed reactor, the reaction raw materials are ethanol and acetaldehyde, the mass ratio of the ethanol to the acetaldehyde is 1:1-1:5, and the reaction space velocity range is WHSV (white space velocity) of 0.2-10h^-1Inert gases of nitrogen, argon or the mixture gas thereof are taken as carrier gas, and the space velocity of the carrier gas is 500-10000h^-1The temperature is 200-500 ℃.

The application preferably has the reaction temperature of 300-400 ℃, the amount ratio of ethanol to acetaldehyde is preferably 1:1-1:3, and the reaction space velocity is in the range of WHSV (white space velocity) 0.5-5h^-1The preferred space velocity of the carrier gas is 1000-3000h^-1。

The invention has the following advantages:

(1) compared with the Ta metal catalyst which is industrialized once, the catalyst takes zirconium as an active component, and one of lithium, sodium, potassium, magnesium and calcium as a second component, and has low cost and lower industrialized cost.

(2) Compared with the MFI of a microporous structure and silicon dioxide of a mesoporous structure, the MFI of the nanosheet has the advantages of a microporous structure and a mesoporous structure, has more excellent catalytic performance, can provide diffusion channels for reactants and products while having shape-selective and domain-limiting effects, and enables active centers to be fully utilized, so that the catalytic performance is greatly improved.

(3) The MFI of the nanosheet layer has a large specific surface area, thereby facilitating high dispersion of the active center in the carrier.

(4) The special nanosheet MFI lamellar structure has obvious carbon deposition resistance, so that the reaction stability is improved, and the catalyst utilizing the carrier can keep the reaction stability for more than 100 hours.

(5) The catalytic process has high product yield and selectivity, and the yield of butadiene can reach over 50 percent under optimized reaction conditions. Therefore, the method has good application prospect.

The catalyst is an MFI-type molecular sieve catalyst having a nanosheet structure and containing a base centre (A) and a transition metal Zr oxide. The alkali center (A) is one or more of lithium, sodium, potassium, magnesium and calcium. Active components of alkali metal and transition metal zirconium are loaded in the MFI molecular sieve with the nanosheet layer growing in a cross mode of 2-10 nm. The catalyst can realize the reaction of ethanol and acetaldehyde under the reaction conditions of 300-400 ℃ to generate butadiene with high efficiency, high selectivity and high yield. Compared with the existing catalyst for preparing butadiene from ethanol acetaldehyde, the catalyst provided by the invention has the remarkable advantages of good stability and high selectivity.

The following is a detailed description of the present invention with reference to specific examples.

Drawings

FIG. 1 is a schematic diagram of stability investigation of catalysts of different supports; a. b and c respectively represent 1.2 percent of Mg-16 percent of Zr-MFI, 1.2 percent of Mg-16 percent of Zr-MFI (micropore), and 1.2 percent of Mg-16 percent of Zr-SiO 2;

FIG. 2-1 is an SEM photograph of 1.2 wt% Mg-Zr-MFI;

FIG. 2-2 is a TEM image of 1.2 wt% Mg-Zr-MFI.

Detailed Description

Example 1

Reference [ Wang, Chan. catalytic conversion of ethanol in butadiene over high performance LiZnHf-MFI zeolite nanosheets ], preparation of nanosheet Mg-Zr-MFI catalyst:

and step A, mixing a silicon source, a template agent and water, and stirring at room temperature for 2 hours to prepare gel, wherein the molar composition of the gel is 1 part of tetraethoxysilane, 2 parts of tetrabutyl phosphonium hydroxide and 25 parts of water.

And step B, putting the gel into a hydrothermal kettle, and carrying out hydrothermal crystallization for 5d in an oven at 150 ℃ under self-generated pressure.

And step C, after crystallization is finished, filtering or centrifuging to obtain white powder, drying at 100 ℃ for 8h, and roasting at 550 ℃ for 4h to obtain the MFI molecular sieve carrier with the nanosheet structure.

And D, dissolving zirconium nitrate in water, soaking the zirconium nitrate and the MFI molecular sieve carrier of the multi-level pore nano layer in the same volume, and drying the zirconium nitrate for 8 hours at the temperature of 100 ℃.

And E, roasting the sample obtained in the step D in air at 550 ℃ for 4 hours.

And step F, dissolving magnesium nitrate in water, soaking the magnesium nitrate in the same volume as the sample in the step D, drying the magnesium nitrate at 100 ℃ for 8 hours, and roasting the magnesium nitrate in air at 550 ℃ for 4 hours to obtain the catalyst.

Example 2

Preparing a nano-sheet Zr-Mg-MFI catalyst: the preparation process is similar to that of example 1, except that the order of loading the active centers is different, mainly embodied in that the alkali centers Mg are loaded in step D, and the active centers Zr are loaded in step F.

Example 3

Preparation of nanosheet Zr-Mg-MFI catalyst (co-impregnation): the preparation process is similar to example 1, except that the catalyst is obtained by preparing a solution of soluble salts of Mg and Zr, co-impregnating the solution on an MFI carrier, drying the solution at 100 ℃ for 8 hours and then calcining the solution in air at 550 ℃ for 4 hours.

Example 4

Preparing a nanosheet A-Zr-MFI catalyst: the procedure is similar to example 1, except that in step F the magnesium nitrate is changed to a nitrate solution of A, lithium, sodium, potassium, to obtain A-Zr-MFI catalysts with different base centers.

Example 5

Preparation of microporous A-Zr-MFI catalyst: the preparation procedure is similar to example 1, except that the templating agent used for the preparation of the microporous MFI is tetrabutylammonium hydroxide.

Example 6

A-Zr-SiO₂Preparation of the catalyst: the procedure is analogous to example 1, except that the support is commercially available SiO₂Specific surface area of 480m²The pore size is 2-8 nm.

Example 7

Preparing nano-sheets A _ Zr-MFI with different roasting temperatures: the procedure is analogous to example 1, except that the calcination temperature is 450 ℃,650 ℃,750 ℃.

Example 8

Experiment for the reaction of ethanol and acetaldehyde to prepare butadiene: 1.0g of the catalyst was pelletized and charged to a fixed bed reactor, and the feed was carried into the reactor by means of a pump feed and a carrier gas (flow rate 150 ml/min). The mass ratio of ethanol to acetaldehyde in the reaction mass is 1:1, and the reaction space velocity is WHSV of 2.4h^-1The reaction temperature was 350 ℃.

The method for calculating the reaction conversion rate and selectivity comprises the following steps:

ethanol conversion (%) - (n)_{Ethanol before reaction}-n_{Ethanol remained after the reaction})/n_{Ethanol before reaction}*100％

Acetaldehyde conversion (%) ═ n_{Acetaldehyde before reaction}-n_{Acetaldehyde remaining after the reaction})/n_{Acetaldehyde before reaction}*100％

Total conversion (%) - (n)_{Ethanol and acetaldehyde before reaction}-n_{Ethanol and acetaldehyde remaining after the reaction})/n_{Ethanol and acetaldehyde before reaction}*100％

Butadiene selectivity (%) ═ 2n_{Butadiene in the product}/(n_{Ethanol and acetaldehyde before reaction}-n_{Ethanol and acetaldehyde remaining after the reaction})*100％

Example 9

The catalyst performance of different Zr contents on 1.2 wt% Mg-Zr-MFI catalyst (the catalyst is prepared according to example 3, wherein the Mg loading is unchanged, the Zr content is different in value), and the reaction conditions of ethanol and acetaldehyde are the same as those in example 8.

As can be seen from the table, the Mg-Zr-MFI catalyst of the invention has relatively good catalytic performance when the Zr loading is 8-24%, wherein the loading of the active metal Zr has better effect when the Zr loading is 16%.

Example 10

Comparison of catalyst performances on different supports, (catalyst I, catalyst II, catalyst III prepared as in example 3, example 5, example 6, respectively), ethanol and acetaldehyde reaction conditions were the same as in example 8.

As can be seen from the table, the catalysts of the three different carriers have certain activity, and the comparison shows that the catalytic performance of the catalyst with the nano-sheet MFI as the carrier is obviously superior to that of microporous MFI and commercially available SiO₂A supported catalyst.

Example 11

Comparison of the performances of A-Zr-MFI catalysts containing different alkali metals (catalysts prepared according to example 7, in which both Zr and A loadings are the same), the ethanol and acetaldehyde reaction conditions were the same as in example 8.

As can be seen from the table, the catalyst performance of the present invention, which is composed of the alkali metal active component and Zr, is significantly better than that of the single component catalyst, wherein the catalyst composed of the Mg and Zr active components performs best.

Example 12

Further modified by introducing different loading of base center, (catalyst prepared as in example 3), ethanol and acetaldehyde reaction conditions as in example 8.

As can be seen from the table, Mg catalysts of different loadings all have catalytic activity, with the preferred loading of Mg at the base site being 1.2 wt%.

Example 13

Compared with the catalytic performance of different preparation methods by introducing alkali centers, the reaction conditions of ethanol and acetaldehyde are the same as those of the example 8.

a. Catalyst b in example 1, catalyst c in example 2, and catalyst in example 3

It can be seen from the table that the different preparation methods are active, wherein the catalyst of example 1 has superior catalytic performance compared to the catalysts of examples 2 and 3, indicating that the preparation sequence of introducing the active center Zr first and then carrying out the base modification is more advantageous for this reaction.

Example 14

1.2% Mg-16% Zr-MFI catalytic performances at different temperatures were investigated, the ethanol and acetaldehyde reaction conditions were the same as in example 8.

As can be seen from the table, the catalyst provided by the invention can produce the target product butadiene under the reaction conditions of 250-400 ℃, and the optimal reaction temperature is 350 ℃.

Example 15

1.2% Mg-16% Zr-MFI, under different aldol ratios and space velocities, the ethanol and acetaldehyde reaction conditions were the same as in example 8, except that the space velocity was changed.

As can be seen from the data in the table, the catalyst provided by the invention can produce butadiene as a target product under the reaction conditions of the aldehyde-alcohol ratio ranging from 1:1 to 1:3, and the reaction space velocity WHSV is 1.8h when the aldehyde-alcohol ratio is 1:2^-1When the catalyst is used, a better catalytic effect can be achieved.

Example 16

1.2% Mg-16% Zr-MFI catalytic performances at different calcination temperatures were investigated, the ethanol and acetaldehyde reaction conditions were the same as in example 8.

As can be seen from the table, the catalyst provided by the invention can stably exist under the condition that the roasting temperature is 450 ℃ and 750 ℃, and the optimal roasting temperature for reaction is 550 DEG C

Example 17

Catalyst stability investigation (catalysts IV, V, VI prepared as in examples 3, 5, 6, respectively) under conditions of aldol ratio of 1:2 and reaction space velocity WHSV of 1.8h^-1The temperature was 350 ℃. See fig. 1.

The figure and the table show that the stability of the catalyst with the nano-sheet MFI as the carrier is obviously superior to that of microporous MFI and commercially available SiO within the reaction time of 100h₂A supported catalyst.

In conclusion, the prepared MFI molecular sieve nanosheet-loaded zirconium-based catalyst can be used for preparing butadiene through ethanol-acetaldehyde reaction, has the advantages of high conversion rate, good butadiene selectivity, simple preparation process, low cost and the like, and is easy for industrial production.

Claims

1. A preparation method of an MFI molecular sieve nanosheet-supported zirconium-based catalyst for a reaction of preparing butadiene from ethanol and acetaldehyde is characterized by comprising the following steps: the catalyst is represented by a formula A-Zr-MFI, wherein Zr is an active component, and A is magnesium; the total loading capacity of the active metal zirconium element in the catalyst is 1-30 wt%; the supporting capacity of the element A in the catalyst is 0.5-20 wt%; MFI is an MFI molecular sieve carrier with a nanosheet structure;

the preparation method of the catalyst comprises the following steps:

(1) soaking a soluble salt solution of Zr on the MFI molecular sieve carrier, drying at 60-200 ℃, and roasting in an air atmosphere at the roasting temperature of 350-750 ℃ for 1-9 hours to obtain a prefabricated body;

(2) and then, dipping the soluble salt solution of the active component A on the prefabricated body, drying at 60-200 ℃, and roasting at 350-750 ℃ for 1-9 hours in the air atmosphere to obtain the catalyst.

2. The method of claim 1, wherein: the carrier MFI is formed by the crossed growth of nano-sheet layers and has a microporous and mesoporous hierarchical pore structure.

3. The method of claim 1, wherein: the loading amount of the zirconium element in the catalyst is 10-24 wt%; the supporting amount of the element A in the catalyst is 0.5-5 wt%.

4. The method of claim 1, wherein: the drying temperature in the step (1) and the step (2) is 100-150 ℃, the roasting temperature is 400-650 ℃, and the roasting time is 2-4 hours.

5. Use of a catalyst obtained by the preparation method according to any one of claims 1 to 4 in the preparation of butadiene starting from ethanol and acetaldehyde, characterized in that: the reaction is fixed at normal pressureIn a bed reactor, the mass ratio of acetaldehyde and ethanol is 1:1-1:5, and the reaction space velocity is in the range of WHSV (0.2-10 h)^-1At least one of nitrogen and argon is used as carrier gas, and the space velocity of the carrier gas is 500-^-1The reaction temperature is 200-500 ℃.

6. Use according to claim 5, characterized in that: the reaction temperature is 300-400 ℃, the mass ratio of acetaldehyde to ethanol is 1:1-1:3, and the reaction space velocity range is WHSV of 0.5-5h^-1The space velocity of the carrier gas is 1000-3000h^-1。