CN112958146B - A zirconium-based catalyst supported by MFI molecular sieve nanosheets and its application in the preparation of butadiene - Google Patents

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

A kind of MFI molecular sieve nanosheet supported zirconium-based catalyst and its application in the preparation of butadiene reaction

technical field

The present invention relates to a kind of catalyst, preparation method and application for preparing butadiene by reaction of ethanol and acetaldehyde, in particular to a zirconium-based catalyst supported by MFI molecular sieve nanosheets and its preparation and preparing butadiene by reacting ethanol and acetaldehyde ene applications.

Background technique

Butadiene is an important organic chemical basic raw material with a wide range of industrial applications, and its position in the petrochemical field is second only to ethylene and propylene. As an important organic synthesis monomer, butadiene is mainly used to synthesize styrene-butadiene rubber, butadiene rubber, nitrile rubber, neoprene rubber and polybutadiene rubber and other industrial products [Jiang Wen, Butadiene Production Application and Technology Progress, Fine Chemical Raw Materials and Intermediates, 2008, 3, 16-20]. In addition, as the simplest conjugated diene, butadiene has relatively active chemical properties and can undergo many organic chemical reactions, including addition, substitution, polymerization, and cyclization. In addition to being used in the synthetic rubber industry, butadiene is also the basic raw material for many other petrochemical products, and can be used to synthesize industrial resins, including ABS, SBS, MBS, etc., and can also be used to produce nylon 66, butanediol, hexanediol, etc. , Adiponitrile and other products [Qian Bozhang, Li Xiuhong, Technology Progress and Market Analysis of Butadiene, Chemical Industry, 2015, 11, 33-37].

Since 1920, the production of butadiene has undergone the ethanol process, the butene or butane dehydrogenation process and the C4 fraction extraction process. The Soviet Union Lebedev developed a one-step synthesis of butadiene from ethanol in 1928, which was subsequently applied to industrial production. United Carbon Chemical Group Corporation has also developed a process route for the production of butadiene from ethanol acetaldehyde [Tan Jie, Analysis of the supply and demand status and development prospects of butadiene at home and abroad, Petrochemical Technology and Economy, 2016, 32, 13-18] . In 1943, the process of producing butadiene by catalytic dehydrogenation of butene achieved industrial production. Due to the good economy of this oil route at that time, it gradually replaced the ethanol process as the main process for butadiene production. In 1956, the American Houdry Company successfully industrialized the method of dehydrogenation of butane to butadiene. At that time, the method almost occupied the entire market of butadiene production due to the cheap and easy availability of raw materials. Subsequently, the American PetroTEX Company made improvements on the basis of the butene catalytic dehydrogenation method in 1965, and realized the industrialization of the butene oxidative dehydrogenation method. Since the 1960s, the technology of cracking naphtha to produce ethylene has achieved breakthrough development, and the method of extracting by-product butadiene from C4 fraction has quickly occupied the market. To date, about 97% of the world's butadiene comes from this process, with the remainder from butene or butane dehydrogenation.

The Soviet Union Lebedev first produced butadiene through the ethanol method in 1929 and applied it to actual production. In World War II, this method accounted for a large proportion of the production of synthetic rubber for strategic materials [S.V.Lebedev, A.O.Yakubchik, The catalytic Hydrogenation of different types of unsaturated compounds. Part IV. The hydrogenation of conjugated systems: piperic acid, J. Chem. Soc, 1929, 220-225]. Many operational details of the Lebedev process for the production of butadiene from ethanol have since been published, but the actual formulation of the catalyst has never been publicly disclosed.

In 1915, Ostromislensky added acetaldehyde to the ethanol raw material, and used a catalyst with dehydration properties to synthesize butadiene [JTDunn, WJToussaint, Process for making diolefins, US Patent 2,421,361]. Union Carbide has carried out a systematic study on the catalytic system of the two-step method. The binary catalytic system used by them is tantalum-silicon, zirconium-silicon and niobium-silicon. The first step is to dehydrogenate ethanol with copper as the main catalyst. The best catalyst system for the second step is 2wt% Ta ₂ O ₅ /SiO ₂ . The reaction temperature is between 325-350° C., the feeds are 69wt% ethanol, 24wt% acetaldehyde and 7wt% water, the yield of butadiene is 35%, and the selectivity is 67%. The catalytic activity of the zirconium-silicon and niobium-silicon systems is slightly worse, and the selectivity of 1.6wt% ZrO ₂ /SiO ₂ to butadiene is 59%.

From the 1950s to the 1970s, due to economic constraints, the use of ethanol to produce butadiene was slow. However, after the 1970s, the continuous rise of oil prices, the depletion of fossil fuels and the increasing pressure on the environment made the utilization of renewable resources arouse widespread concern. As a renewable, clean and pollution-free chemical, ethanol can be obtained from tubers of some plants (such as potatoes, yams, cassava, etc.), grains, sugarcane, and woody plants [A.M.Shupe, S.Liu, Ethanol fermentation from Hydrolysed hot-water woodextracts by pentose fermenting yeasts, Biomass and Bioenergy, 2012, 39, 31-38]. In recent years, with the continuous maturity of bioethanol production and purification technology, the production scale is constantly expanding. In addition to using easily fermentable sugars as raw materials, non-fermentable sugars and lignocellulose can now be used. As the demand for bioethanol continues to increase, more efficient processes based on different biomass sources will be developed. In addition, another production process of ethanol: the coal-to-ethanol production process has obvious advantages in cost compared with the fermentation-based ethanol production process, and has been industrialized at present. Coal-to-ethanol is in line with my country's national conditions of rich coal and poor oil, more people and less land. It is an important component of my country's energy and chemical industry and will become an important source of new ethanol production capacity. [Meng Ying, Bai Xiaoyu, Li Kai, et al. Research progress of ethanol production technology and coal-to-ethanol technology in my country [J]. Coal and Chemical Industry, 2017, 40 (8): 21-23]. Therefore, using ethanol as raw material to produce butadiene will be a process method with broad prospects.

The industrial production of butadiene from ethanol acetaldehyde was stopped in the 1950s, mainly because the catalyst required for the reaction was easily deactivated quickly due to carbon deposition, resulting in poor catalyst stability, and the active component used in the catalyst was Ta, Catalyst costs are high. The invention aims to improve the stability of the reaction of preparing butadiene from ethanol acetaldehyde and design a corresponding catalyst. The nano-sheet MFI molecular sieve is used as a carrier, and its special lamellar structure may significantly improve the stability of the reaction, and the cheap metal Zr is used. As an active center, the cost of the catalyst can be greatly reduced.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a catalyst, preparation method and application thereof in the reaction of ethanol and acetaldehyde to butadiene, so as to realize the catalytic conversion of ethanol to generate butadiene with high yield and high selectivity, and the catalyst has high stability .

To achieve the above object, the technical scheme adopted in the present invention is:

A magnesium-zirconium-supported catalyst on MFI, the catalyst is represented by the formula A-Zr-MFI. Among them, zirconium is the active component, A is one of lithium, sodium, potassium, magnesium, calcium, and one of them; the total loading of active metal zirconium in the catalyst is 1-30wt%; the loading of A in the catalyst 0.5-20wt%, MFI is an MFI molecular sieve carrier with nanosheet structure.

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

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

In the preparation method of the catalyst, the soluble salt solution of the active component Zr is impregnated on the carrier, dried at 60-120° C., and then calcined in an air atmosphere to obtain a sample. Then, the soluble salt solution of the alkali metal center A was immersed in the sample obtained before, and after drying at 60-120° C., the catalyst was calcined in an air atmosphere to obtain the catalyst. The calcination temperature of the catalyst is between 450-750°C. The preferred calcination temperature is 500-600°C, and the calcination time is 3-9 hours.

The application of the catalyst in the reaction of preparing butadiene from ethanol acetaldehyde, the reaction of preparing butadiene from ethanol acetaldehyde is carried out in a fixed-bed reactor at normal pressure, and the reaction raw materials are ethanol and acetaldehyde, and the mixture of ethanol and acetaldehyde. The ratio of the amount of substances is 1:1-1:5, the reaction space velocity range is WHSV=0.2-10h ^-1 , the inert gas nitrogen, argon or its mixture is used as the carrier gas, and the carrier gas space velocity is 500-10000h ^-1 , the temperature should be 200-500℃.

The preferred reaction temperature of the application is 300-400°C, the ratio of the amount of ethanol and acetaldehyde is preferably 1:1-1:3, the reaction space velocity range is WHSV=0.5-5h ^-1 , the preferred carrier gas space velocity is 1000-3000h ^-1 .

The present invention has the following advantages:

(1) Using zirconium as the active component and adding one of lithium, sodium, potassium, magnesium, and calcium as the second component, the catalyst cost is lower than that of the once industrialized Ta metal catalyst, and the industrialization cost is lower.

(2) Nanosheet MFI has the advantages of microporous and mesoporous structure. Compared with MFI with microporous structure and silica with mesoporous structure, it has more superior catalytic performance. The mesoporous structure provides diffusion channels for reactants and products, allowing the active centers to be fully utilized, thereby greatly improving the catalytic performance.

(3) The MFI of the nanosheet layer has a large specific surface area, which is conducive to the high dispersion of active centers in the carrier.

(4) The special lamellar structure of nanosheet MFI has significant anti-coking ability, thereby improving the stability of the reaction. The catalyst using this kind of carrier can maintain the stability of the reaction for more than 100 hours.

(5) The catalytic process has high product yield and selectivity, and under more optimized reaction conditions, the butadiene yield can reach more than 50%. Therefore, it has a good application prospect.

The catalyst is a molecular sieve catalyst of the MFI type having a nanoplatelet structure and containing a base center (A) and transition metal Zr oxide. The alkali center (A) is lithium, sodium, potassium, magnesium, calcium, one or more of them. Alkali metal and transition metal zirconium active components are supported in MFI molecular sieves with 2-10 nm cross-grown nanosheets. The catalyst can realize the high-efficiency, high-selectivity and high-yield reaction of ethanol and acetaldehyde to generate butadiene under the reaction conditions of 300-400°C. 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.

Further detailed description will be given below through specific embodiments.

Description of drawings

Figure 1 is a schematic diagram of the stability investigation of catalysts with different supports; a, b, and c represent 1.2%Mg-16%Zr-MFI, 1.2%Mg-16%Zr-MFI (microporous), 1.2%Mg-16%, respectively Zr-SiO2;

Figure 2-1 is the SEM image of 1.2wt% Mg-Zr-MFI;

Figure 2-2 is the TEM image of 1.2wt% Mg-Zr-MFI.

Detailed ways

Example 1

Reference [Wang,Chan.Catalytic conversion of ethanol into butadieneover high performance LiZnHf-MFI zeolite nanosheets], preparation of nanosheet Mg-Zr-MFI catalyst:

In step A, the silicon source, the template agent and water are mixed, and stirred at room temperature for 2 hours to prepare a gel. The molar composition of the gel is 1 part of ethyl orthosilicate: 2 parts of tetrabutylphosphorus hydroxide: 25 parts of water.

In step B, the above gel was put into a hydrothermal kettle, and hydrothermally crystallized under autogenous pressure in an oven at 150° C. for 5 d.

Step C, after the crystallization is completed, filter or centrifuge to obtain a white powder, dry at 100° C. for 8 hours, and calcinate at 550° C. for 4 hours to obtain an MFI molecular sieve carrier with a nano-sheet structure.

In step D, zirconium nitrate is dissolved in water, impregnated with an equal volume of the above-mentioned hierarchical porous nano-layer MFI molecular sieve carrier, and dried at 100° C. for 8 hours.

In step E, the sample in step D is calcined in air at 550° C. for 4 hours.

In step F, magnesium nitrate is dissolved in water, impregnated with the same volume as the sample in the above step D, dried at 100° C. for 8 hours, and then calcined in air at 550° C. for 4 hours to obtain the catalyst.

Example 2

Preparation of nanosheet Zr-Mg-MFI catalyst: The preparation process is similar to Example 1, the difference is that the order of active center loading is different, which is mainly reflected in the loading of base center Mg in step D, and the loading of active center Zr in step F.

Example 3

Preparation of nanosheet Zr-Mg-MFI catalyst (co-impregnation): The preparation process is similar to Example 1, the difference is that the soluble salts of Mg and Zr are prepared into a solution, then co-impregnated on the MFI support, and dried at 100 °C for 8 h Then, the catalyst was obtained by calcining in air at 550°C for 4 hours.

Example 4

Preparation of nanosheet A-Zr-MFI catalyst: the preparation process is similar to Example 1, the difference is that in step F, magnesium nitrate is changed to the nitrate solution of A, and A is lithium, sodium, potassium, thereby obtaining different alkali centers. A-Zr-MFI catalyst.

Example 5

Preparation of microporous A-Zr-MFI catalyst: The preparation process is similar to that of Example 1, except that the template used in the preparation of microporous MFI is tetrabutylammonium hydroxide.

Example 6

Preparation of A-Zr-SiO ₂ catalyst: The preparation process is similar to that of Example 1, except that the support is commercially available SiO ₂ , the specific surface area is 480 m ² /g, and the pore size is 2-8 nm.

Example 7

Preparation of nanosheets A_Zr-MFI with different calcination temperatures: The preparation process is similar to Example 1, except that the calcination temperatures are 450°C, 650°C, and 750°C.

Example 8

Experiment of preparing butadiene by the reaction of ethanol and acetaldehyde: 1.0 g of catalyst was granulated and then charged into a fixed-bed reactor, and the raw materials were brought into the reactor by means of pump feed and carrier gas (flow rate of 150 ml/min). . The mass ratio of ethanol and acetaldehyde in the reaction mass was 1:1, the reaction space velocity was WHSV=2.4h ^-1 , and the reaction temperature was 350°C.

Reaction conversion rate and selectivity calculation method:

Ethanol conversion rate (%)=( _{ethanol before} reaction-n _{remaining ethanol after reaction} )/n _{ethanol before reaction} *100%

Acetaldehyde conversion rate (%)=( _{acetaldehyde before n reaction-} n _{remaining acetaldehyde after reaction} )/n _{acetaldehyde before reaction} *100%

Total conversion (%)=(n _{ethanol and acetaldehyde before reaction-} n _{remaining ethanol and acetaldehyde after reaction} )/n _{ethanol and acetaldehyde before reaction} *100%

Butadiene selectivity (%) = 2n _{butadiene in the product} /(n _{ethanol and acetaldehyde before the reaction -} n _{remaining ethanol and acetaldehyde after the reaction} ) * 100%

Example 9

Catalyst performance with different Zr content on 1.2wt% Mg-Zr-MFI catalyst (catalyst was prepared according to Example 3, wherein the loading of Mg was unchanged, and the value of Zr content was different), and the reaction conditions of ethanol and acetaldehyde were the same as those in Example 8 .

It can be seen from the table that the Mg-Zr-MFI catalyst of the present invention has relatively good catalytic performance when the loading of Zr is 8-24%, and the loading of active metal Zr has better performance when the loading of Zr is 16%. Effect.

Example 10

The catalyst performance comparison of different carriers, (catalyst I, catalyst II, and catalyst III were prepared according to Example 3, Example 5, and Example 6, respectively), and the reaction conditions of ethanol and acetaldehyde were the same as those of Example 8.

It can be seen from the table that the catalysts with three different supports have a certain activity. In comparison, it can be seen that the catalytic performance of the catalyst supported by nanosheet MFI is significantly better than that of microporous MFI and commercial _SiO2 . catalyst.

Example 11

Performance comparison of A-Zr-MFI catalysts containing different alkali metals (the catalysts were prepared according to Example 7, wherein Zr and A loadings were the same), and the reaction conditions of ethanol and acetaldehyde were the same as those in Example 8.

It can be seen from the table that the performance of the catalyst composed of basic metal active components and Zr in the present invention is obviously better than that of the single-component catalyst, and the catalyst composed of Mg and Zr active components has the best performance.

Example 12

The base center with different loadings was further introduced for modification, (the catalyst was prepared as in Example 3), and the reaction conditions of ethanol and acetaldehyde were the same as those in Example 8.

It can be seen from the table that Mg catalysts with different loadings have catalytic activity, and the preferred loading of Mg at the base center is 1.2 wt%.

Example 13

Comparing the catalytic performance of the base centers introduced by different preparation methods, the reaction conditions of ethanol and acetaldehyde are the same as those in Example 8.

a. Catalyst b in Example 1, Catalyst c in Example 2, Catalyst in Example 3

It can be seen from the table that different preparation methods are active, and the catalyst in Example 1 has better catalytic performance than the catalysts in Examples 2 and 3, indicating that the preparation sequence of first introducing the active center Zr, and then carrying out the alkali modification is very important. This reaction is more favorable.

Example 14

The catalytic performance of 1.2%Mg-16%Zr-MFI at different temperatures was investigated, and the reaction conditions of ethanol and acetaldehyde were the same as those in Example 8.

It can be seen from the table that the catalyst provided by the present invention can produce the target product butadiene under the reaction conditions of 250-400°C, and the optimum reaction temperature is 350°C.

Example 15

The catalytic performance of 1.2%Mg-16%Zr-MFI at different aldol ratios and space velocities was investigated. The reaction conditions of ethanol and acetaldehyde were the same as those in Example 8, but the space velocity was changed.

As can be seen from the data in the table, the catalyst provided by the invention can produce the target product butadiene under the reaction conditions in which the aldol ratio is in the range of 1:1-1:3, and when the aldol ratio is 1:2, the reaction is empty. When the speed WHSV=1.8h ^-1 , better catalytic effect can be achieved.

Example 16

The catalytic performance of 1.2%Mg-16%Zr-MFI was investigated at different calcination temperatures. The reaction conditions of ethanol and acetaldehyde were the same as those in Example 8.

As can be seen from the table, the catalyst provided by the present invention can stably exist and produce the target product butadiene under the condition that the calcination temperature is 450-750 ℃, and the optimum calcination temperature of the reaction is 550 ℃

Example 17

Catalyst stability was investigated (catalysts IV, V, VI were prepared according to Examples 3, 5, and 6, respectively), and the reaction conditions were aldol ratio of 1:2, reaction space velocity WHSV=1.8h ^-1 , and temperature of 350°C. see picture 1.

It can be seen from the figure and table that the stability of the catalyst supported by nanosheet MFI is obviously better than that of the catalyst supported by microporous MFI and commercial SiO ₂ within the reaction time of 100 h.

In summary, the present invention has prepared a variety of MFI molecular sieve nanosheet-supported zirconium-based catalysts, which can be used for the preparation of butadiene in the reaction of ethanolic acetaldehyde, and have the advantages of high conversion rate, good butadiene selectivity, simple preparation process and low cost. and other advantages, and easy to industrialize production.

Claims (6)

1. a preparation method for the zirconium-based catalyst of the MFI molecular sieve nanosheet load in the reaction of raw materials for preparing butadiene with ethanol and acetaldehyde, is characterized in that: the catalyzer is represented by formula A-Zr-MFI, wherein , Zr is the active component, A is magnesium; the total loading of active metal zirconium element in the catalyst is 1-30wt%; the loading amount of A element in the catalyst is 0.5-20wt%; MFI is a nanosheet structure MFI molecular sieve carrier; The preparation method of the catalyst comprises the following steps: (1) first impregnate the soluble salt solution of Zr on the MFI molecular sieve carrier, after drying at 60-200 ° C, carry out roasting in an air atmosphere, the roasting temperature is 350-750 ° C, and the roasting time is 1-9 hours, get a prefab; (2) The soluble salt solution of active component A is then dipped on the preform, and after drying at 60-200 ℃, calcination is carried out in an air atmosphere, the calcination temperature is 350-750 ℃, and the calcination time is 1-9 hours to obtain the catalyst. 2 . The preparation method according to claim 1 , wherein the carrier MFI is composed of cross-growth of nano-sheet layers, and has a hierarchical pore structure of micropores and mesopores. 3 . 3 . The preparation method according to claim 1 , wherein the loading of zirconium element in the catalyst is 10-24 wt %; the loading of element A in the catalyst is 0.5-5 wt %. 4 . 4. preparation method according to claim 1 is characterized in that: the drying temperature in step (1) and step (2) is 100-150 ℃, the roasting temperature is 400-650 ℃, and the roasting time is 2-4 hours . 5. the application of a catalyst prepared by the preparation method described in any one of claims 1-4 in the reaction of preparing butadiene with ethanol and acetaldehyde as raw materials, it is characterized in that: the reaction is in a fixed bed reaction at normal pressure The ratio of the amount of acetaldehyde and ethanol is 1:1-1:5, the reaction space velocity range is WHSV=0.2-10h ^-1 , and at least one of nitrogen and argon is used as the carrier gas, The carrier gas space velocity is 500-10000h ^-1 and the reaction temperature is 200-500°C. 6. application according to claim 5 is characterized in that: the temperature of described reaction is 300-400 DEG C, the ratio of the amount of acetaldehyde and the amount of ethanol is 1:1-1:3, and the reaction space velocity range is WHSV=0.5-5h ^-1 , carrier gas air velocity is 1000-3000h ^-1 .

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