阅读说明：本技术 一种由乙酸合成丙烯酸的方法 (Method for synthesizing acrylic acid from acetic acid ) 是由 王峰 张志鑫 王业红 李书双 张健 于 2019-11-22 设计创作，主要内容包括：本发明涉及一种丙烯酸的制备方法,具体涉及一种由乙酸溶液为原料,经过氧化-缩合制备丙烯酸。该催化反应在固定床反应器中进行,乙酸溶液经过气化和惰性气氛稀释经过VPO基催化剂,发生碳碳氧化断裂,再经缩合制备丙烯酸。(The invention relates to a preparation method of acrylic acid, in particular to a method for preparing acrylic acid by taking acetic acid solution as a raw material and carrying out oxidation-condensation. The catalytic reaction is carried out in a fixed bed reactor, acetic acid solution is gasified and diluted in inert atmosphere to pass through a VPO-based catalyst, carbon-carbon oxidation fracture occurs, and then acrylic acid is prepared through condensation.)

1. A process for synthesizing acrylic acid from acetic acid, characterized by:

in a fixed bed reactor, acetic acid or an acetic acid solution is gasified and diluted in an oxygen-containing inert atmosphere, and then is catalyzed by a VPO-based catalyst to generate oxidation-condensation to prepare acrylic acid at a certain temperature and under a certain pressure.

2. The method of claim 1, wherein:

the mass fraction of acetic acid in the acetic acid or the acetic acid solution is 50-100%; the solvent is one or more of water, acetonitrile, cyclohexane, benzene, toluene, xylene, dioxane and tetrahydrofuran;

the gasification temperature is 200 ℃ and 400 ℃; the volume fraction of acetic acid in the diluted gas phase is 5-50%;

the oxygen content in the oxygen-containing inert atmosphere is determined according to the acetic acid content in the acetic acid solution, and the ratio of the mole number of the acetic acid to the mole number of the oxygen is ensured to be (2-5);

the oxygen-containing inert atmosphere is N₂One or more of Ar and He; the oxygen-containing inert atmosphere, wherein oxygen is derived from one or two of oxygen and air;

the reaction temperature in the catalysis process is not lower than 280 ℃; the reaction pressure is 0.5 atm-30 atm;

the mass space velocity of the acetic acid is 0.5-5 h^-1。

3. The method of claim 2, wherein:

the mass fraction of acetic acid in the acetic acid solution is 50-90%; the solvent is one or more of water, acetonitrile, cyclohexane, toluene and dioxane;

the gasification temperature is 200-350 ℃; the volume fraction of acetic acid in the diluted gas phase is 5-40%;

the oxygen content in the oxygen-containing inert atmosphere is determined according to the acetic acid content in the acetic acid solution, and the ratio of the mole number of the acetic acid to the mole number of the oxygen is ensured to be (2-4);

the oxygen-containing inert atmosphere is preferably N₂One or two of Ar; wherein the oxygen is derived from air;

the reaction temperature of the catalytic process is 280-450 ℃; the reaction pressure is 0.5 atm-20 atm;

the mass space velocity of the acetic acid is 0.5-3 h^-1。

4. A method according to claim 3, characterized by:

the mass fraction of acetic acid in the acetic acid solution is 50-80%; the solvent is one or more of water, acetonitrile and dioxane;

the gasification temperature is 200 ℃ and 300 ℃; the volume fraction of acetic acid in the diluted gas phase is 5-30%;

the oxygen content in the oxygen-containing inert atmosphere is determined according to the acetic acid content in the acetic acid solution, and the ratio of the mole number of the acetic acid to the mole number of the oxygen is ensured to be (2-3);

the reaction temperature in the catalytic process is 280-400 ℃; the reaction pressure is 0.5 atm-10 atm;

the mass space velocity of the acetic acid is 1-3 h^-1。

5. The method of claim 1, wherein:

the VPO-based catalyst is VPxOy, x is 0.5-3, and y is a suitable value to satisfy the valence states of the respective elements (V and P)

Or the VPO-based catalyst consists of an active component VP_xO_yAn auxiliary agent and a carrier; x is 0.5 to 3, and y is a suitable value satisfying the valence of each element (V and P);

the catalyst comprises an active VPO component and a catalyst component, wherein the active VPO component comprises the following components in percentage by mass: 4 to 50 percent;

the catalyst comprises the following carriers: SiO 2₂,Al₂O₃,SiO₂-Al₂O₃One or more of SiC, MgO, aluminum silicate and magnesium silicate; the mass fraction of the carrier in the catalyst is 50-96%;

the catalyst comprises the following auxiliary agents: one or more oxides of Sc, Y, La, Ti, Nb, Ge, Ta, Mo, W, Bi and Sb; the mass fraction of the auxiliary agent in the catalyst is 0-10%.

6. The method of claim 5, wherein:

the catalyst, wherein the mass fraction of the active VPO component is preferably: 20 to 40 percent;

the catalyst, the preferred carrier is: SiO 2₂,Al₂O₃,SiO₂-Al₂O₃One or more of SiC and MgO; the mass fraction of the carrier in the catalyst is 60-80%;

the catalyst, preferable auxiliaries are: one or more oxides of Sc, La, Ti, Nb, Mo, W, Bi and Sb; the mass fraction of the auxiliary agent in the catalyst is 0-5%.

Technical Field

The invention relates to a method for synthesizing acrylic acid, in particular to a method for preparing acrylic acid by oxidizing acetic acid aqueous solution.

Background

Acrylic acid is an important organic compound that readily polymerizes on its own or with other polymer monomers to form polymers. The polymers are widely applied to the fields of super absorbent materials, dispersing agents, flocculating agents, thickening agents and the like. The synthesis of acrylic acid has attracted considerable attention from the industry and academia due to its important commercial value.

The production method of the acrylic acid mainly comprises the following steps: ethylene process (ethylene, CO and O)₂Reaction), ethylene oxide process (ethylene oxide withCO reaction), ketene method (ketene reacts with formaldehyde), acetylene carbonylation method (Reppe method), chlorohydrin method, cyanoethanol method, propane oxidation method, propylene oxidation method, and acrylonitrile hydrolysis method. Among the above methods, the ethylene process, the ethylene oxide process and the propane oxidation process are still under development, and no large-scale production apparatus is available, and the ketene process, the acetylene carbonylation process, the chlorohydrin process, the cyanoethanol process and the acrylonitrile hydrolysis process have been eliminated due to low efficiency, large consumption and high cost. To date, propylene oxidation is used in all large-scale acrylic acid production facilities in the world. Companies possessing propylene oxidation production technologies mainly include japanese catalytic chemical company, mitsubishi chemical company, BASF company, and ohio standard petroleum Sohio company. With the increasing exhaustion of fossil resources, the cost of producing acrylic acid from propylene as a raw material will gradually increase.

The 20 th century and 70 th era have increased the price of petroleum, and a route for synthesizing acrylic acid from non-petroleum raw materials, namely acetic acid and formaldehyde, has been produced. Both acetic acid and formaldehyde can be generated from methanol, and the methanol is from synthesis gas and has rich raw material sources. With the development of the modern coal chemical industry, the route is widely concerned by researchers.

Among the reported catalysts, VPO-based catalysts are an effective class of catalysts, whose surface is mainly medium-strong Lewis acid sites and basic sites, which synergistically catalyze the process. Mamoru Ai and the like take acetic acid or methyl acetate and formaldehyde as raw materials and utilize V₂O₅-P₂O₅Acrylic acid or methyl acrylate is prepared by aldol condensation of catalysts such as binary acid oxide, vanadium-titanium binary phosphate (V-Ti-P-O) and the like. In recent years, researchers have focused on how to expose more catalytically active sites, with a series of efforts being directed to the preparation of VPO-based catalysts and their catalyzed aldol condensation to acrylic acids and esters. For example, the PEG6000 is used as a template to prepare the VPO catalyst with high specific surface area, or the VPO is loaded on SiO₂SBA-15 and Al₂O₃On the carriers, the concentration of active sites on the surface of the catalyst is effectively improved, so that the yield of target products of acrylic acid and esters thereof is improved. Acidic molecular sieve catalyst such as HZSM-5, HZSM-35 and the like, and Cs/SiO₂Or Cs/SBA-15 or the likeThe catalyst is applied to catalyzing condensation of acetic acid or methyl acetate and formaldehyde to prepare acrylic acid or methyl acrylate, but compared with a VPO catalyst, the catalyst is easier to deposit carbon, and the catalyst needs to be frequently regenerated to maintain the catalytic activity. In addition, acetic acid and acrylic acid on the strong basic catalyst are easy to generate decarboxylation side reaction to generate a large amount of CO_xAnd carbon deposition, which is not favorable for the generation of target products.

Celanese corporation disclosed a combined process of methanol carbonylation to produce acetic acid and reaction of acetic acid with formaldehyde to produce acrylic acid (US20140073812), where acetic acid conversion can reach 50% and acrylic acid selectivity can reach 70%. The advantage of this process is that formaldehyde is easily removed from the crude acrylic acid. BASF corporation discloses a combined process for preparing acetic acid by oxidizing ethanol and preparing acrylic acid by condensing acetic acid and formaldehyde (CN 104817450). The process for preparing acrylic acid by using methanol and acetic acid as raw materials is also protected in the granted patent CN201180054828.X, and a new patent CN201580053093.7 is newly applied to protect the process after the patent right is ended. Eastman discloses a process for preparing acrylic acid from aqueous acetic acid and formaldehyde solutions (US20130237724) in which the mixed oxides of V, Ti and P are used as catalysts and which have a relatively good space-time yield. The southwest institute of chemical engineering design Co., Ltd discloses TiO₂、SiO₂Or the catalyst of active components such as V, Ti, Zr, P and the like loaded by the molecular sieve catalyzes formaldehyde aqueous solution or paraformaldehyde and acetic acid to synthesize acrylic acid (and methyl acrylate), or catalyzes methylal and methyl acetate to synthesize methyl acrylate, and the catalyst has higher activity and selectivity (CN20140795266, CN201210502752 and CN 201210491886). Asahi chemical technology research institute Limited company reported a method for preparing a catalyst for the synthesis of methyl acrylate and co-production of methyl methacrylate from methyl acetate and formaldehyde, wherein SiO is used as the catalyst₂As the catalyst carrier, metal salts of Cs and Zr, and an oxide of Sb (CN201410022889) are also included. A Yangjiang research team, Zhang-Jordan institute of Process engineering, of the Chinese academy of sciences, reports a catalyst for synthesizing acrylic acid from formaldehyde aqueous solution and acetic acid, and a preparation and application method thereof (CN201310566202), wherein the catalyst is prepared from activated carbon and Al₂O₃、SiO₂Or one or more than two of the molecular sieves are used as carriers to load phosphorus pentoxide and one or more than two alkaline earth metal oxides. The Nanjing Daichi-Chongji team reported a VPO catalyst and its application in the preparation of acrylic acid (esters) by reacting acetic acid (esters) with formaldehyde (CN201410103826), in which the active VPO catalyst was prepared by refluxing V in a mixed alcohol solution₂O₅The preparation method comprises the steps of adding polyethylene glycol (PEG6000) as a surfactant, and activating the prepared active catalyst in a butane-air mixed atmosphere of 1.5 percent (volume fraction).

In summary, in the reported literature, two raw materials (acetic acid (ester) and formaldehyde or formaldehyde precursor as raw materials) are used for preparing acrylic acid, but the process of preparing acrylic acid by using only acetic acid solution as raw materials is not reported. The acrylic acid is prepared only by taking the acetic acid solution as the raw material, so that the experimental process is simplified, the formaldehyde solution can be avoided being directly used, and the process is more economic.

Disclosure of Invention

The invention aims to provide a method for synthesizing acrylic acid, which starts from cheap, easily obtained and stable acetic acid solution, and realizes the effective synthesis of acrylic acid by carrying out the oxidative cracking and the self condensation of acetic acid through a proper catalytic system.

The technical scheme is as follows:

a process for synthesizing acrylic acid includes such steps as gasifying acetic acid or its solution, diluting in oxygen-contained inertial atmosphere, oxidizing-condensing by VPO-base catalyst to obtain acrylic acid, and features simple process, low cost and high output rate.

The mass fraction of acetic acid in the acetic acid or the acetic acid solution is 50-100%; the solvent is one or a mixture of water, acetonitrile, cyclohexane, benzene, toluene, xylene, dioxane and tetrahydrofuran;

the gasification temperature is 200 ℃ and 400 ℃; the volume fraction of acetic acid in the diluted gas phase is 5-50%;

the oxygen content in the oxygen-containing inert atmosphere is determined according to the acetic acid content in the acetic acid solution, and the ratio of the mole number of the acetic acid to the mole number of the oxygen is ensured to be (2-5);

inert atmosphere is N₂In Ar, HeOne or a mixture of several of them;

the reaction temperature in the catalysis process is not lower than 280 ℃;

the mass space velocity (mass of acetic acid/mass of catalyst in unit time) of the catalyst is 0.5-5 h^-1；

The reaction pressure of the catalytic process is 0.5 atm-30 atm.

Providing a scheme that:

the mass fraction of acetic acid in the acetic acid solution is 50-90%; the solvent is one or a mixture of water, acetonitrile, cyclohexane, toluene and dioxane;

the gasification temperature is 200-350 ℃; the volume fraction of acetic acid in the gas-diluted phase is 5-40%;

the oxygen content in the oxygen-containing inert atmosphere is determined according to the acetic acid content in the acetic acid solution, and the ratio of the mole number of the acetic acid to the mole number of the oxygen is ensured to be (2-4);

inert atmosphere is N₂And one or a mixture of more of Ar; wherein the oxygen is derived from air;

the reaction temperature of the catalytic process is 280-450 ℃;

the mass space velocity (mass of acetic acid/mass of catalyst in unit time) of the catalyst is 0.5-3 h^-1；

The reaction pressure of the catalytic process is 0.5 atm-20 atm.

Providing a scheme that:

the mass fraction of acetic acid in the acetic acid solution is 50-80%; the solvent is one or a mixture of water, acetonitrile and dioxane;

the gasification temperature is 200 ℃ and 300 ℃; the volume fraction of acetic acid in the diluted gas phase is 5-30%;

the oxygen content in the oxygen-containing inert atmosphere is determined according to the acetic acid content in the acetic acid solution, and the ratio of the mole number of the acetic acid to the mole number of the oxygen is ensured to be (2-3);

inert atmosphere is N₂；

The reaction temperature in the catalytic process is 280-400 ℃;

catalyst mass space velocity (acetic acid per unit time)Mass of (b)/mass of catalyst) is from 1 to 3h^-1；

The reaction pressure of the catalytic process is 0.5 atm-10 atm.

The preparation process of the VPO-based catalyst is as follows:

putting vanadium pentoxide into benzyl alcohol or isobutyl alcohol or a mixed alcohol solution of the benzyl alcohol and the isobutyl alcohol for refluxing, adding 5-15 g of vanadium pentoxide into every 100mL of the alcohol solution, then adding 85% by mass of phosphoric acid and a catalyst carrier (or not) and a catalyst auxiliary agent (or not) for refluxing, adding the phosphoric acid according to the P/V molar ratio of 0.5-3 or simultaneously adding a surfactant, and finally drying, roasting and activating to obtain the VPO catalyst.

The volume ratio of the benzyl alcohol to the isobutanol in the mixed alcohol is 3: 1-1: 3;

the reflux temperature in the alcohol is 120-140 ℃; the reflux time is 3-6 h;

the reflux temperature is 120-140 ℃; the reflux time is 12-24 h;

the surfactant is: PVPK30 (average molecular weight of K30 40000), PVPK150 (average molecular weight 80000), PVPK90 (average molecular weight of 630000), PEG200, PEG2000, PEG 8000; (the concentration is 10-40 mg/mL);

the temperature of the drying process is 100-140 ℃; air-blast drying or vacuum drying;

the drying time is 6-12 h;

the temperature in the roasting process is 400-800 ℃; the atmosphere is air, nitrogen or hydrogen;

the roasting time is 4-12 h; the temperature of the activation process is 400-800 ℃; the atmosphere is a mixed gas of butane and air (the volume fraction of the butane is 0.5-3%); the activation time is 4-24 h;

the carrier of the VPO-based catalyst is: SiO 2₂,Al₂O₃,SiO₂-Al₂O₃One or a mixture of more of SiC, MgO, aluminum silicate and magnesium silicate; during the reflux, it was added.

The auxiliary agent of the VPO-based catalyst is as follows: oxides of Sc, Y, La, Ti, Nb, Ge, Ta, Mo, W, Bi, Sb or mixtures thereof; during the reflux, it was added.

The reactions involved in the present invention can be represented by the following reaction equation:

CH₃COOH+O₂→HCHO+H₂O+CO₂

advantageous technical effects

1. The raw materials of the catalyst used in the invention are cheap and easy to obtain, the preparation process is controllable and easy to operate, and the oxidation-Aldol condensation reaction of the acetic acid solution can be effectively generated;

2. the catalyst has good stability and hydrothermal stability, the reaction process is simple, controllable and easy to operate, and the yield of the acrylic acid can reach 60 percent at most.

3. The acrylic acid is prepared by reacting formaldehyde generated in situ by the oxidative decomposition reaction of acetic acid with acetic acid.

Drawings

FIG. 1 is a gas phase analysis spectrum of the product of example 3, wherein the retention time at 11.47min is the product acrylic acid.

Detailed Description

In order to further explain the present invention in detail, several specific embodiments are given below, but the present invention is not limited to these embodiments.