Anhydride esterification hydrogenation method

Maleic anhydride is currently the third-largest anhydride in the world, after phthalic anhydride and acetic anhydride, and it has wide applications in the chemical and pharmaceutical industries. In recent years, the apparent consumption of maleic anhydride in our country has been increasing continuously. Both the production technology and capacity for maleic anhydride in our country have seen significant development, but there are still some issues when compared to the advanced levels abroad. 　　　 Maleic anhydride, also known as fumaric anhydride or anhydrous malic anhydride, is currently the third-largest anhydride in the world, after phthalic anhydride and acetic anhydride. It is primarily used in the production of unsaturated polyester resins (UPR) and alkyd resins. Furthermore, it can also be used to produce a range of important chemical products such as 1,4-butanediol (BDO), γ-butyrolactone (GBL), **furan (THF), maleic acid, fumaric acid, and **anhydrides. It has wide applications in fields such as pesticides, pharmaceuticals, coatings, inks, lubricant additives, paper chemicals, textile finishing agents, food additives, and surfactants. Currently, the industrial methods for producing maleic anhydride can be classified into four categories based on the raw materials used: the benzene oxidation method, the n-butane oxidation method, the C4 olefins method, and the method utilizing by-products of benzene oxidation. Among these, the benzene oxidation method is the most widely used. However, due to limited supplies of benzene, technologies for producing maleic anhydride using C4 olefins and n-butane as raw materials have emerged. Countries with abundant natural gas and associated gas from oil fields, which possess large amounts of n-butane, have seen rapid development in technologies for producing maleic anhydride via n-butane oxidation. This method has now become dominant in maleic anhydride production, accounting for approximately 80% of the world’s total production capacity.

The maleic anhydride esterification hydrogenation method is a process for the esterification of maleic anhydride that was developed by the British company David Process Technology. This method consists of three steps: the esterification of maleic anhydride with ethanol； BDO is obtained by the hydrogenolysis of diethyl succinate ； The reaction products are separated and purified. By adjusting the process conditions, the ratio of BDO, GBL, and THF can be changed. Due to the cost advantages of BDO production using this process, more new plants have been built with this technology in recent years, which represents the main trend in BDO production processes. The main advantage of the David maleic anhydride process route is that by adjusting the process conditions, it is possible to change the yield ratios of 1,4-butanediol, γ-butyrolactone, and **furan. In industrial installations, to maximize the production of 1,4-butanediol, it is possible to rely on the chemical equilibrium between 1,4-butanediol and γ-butyrolactone by recycling γ-butyrolactone until it is exhausted, thereby achieving maximum production of 1,4-butanediol. In addition, the David maleic anhydride process has other advantages as well, such as a high conversion rate of esters, mild reaction conditions, low requirements for the material of the equipment, a low cost of catalysts and a long service life. Both the investment and production costs are low, and there is a wide range of possibilities for adjusting the ratio of 1,4-butanediol to **furan. The n-butane/cyclohexanone process actually combines a gas-phase oxidation method for converting n-butane into cyclohexanone with a cyclohexanone hydrogenation technique; it still uses C4 fractions as raw materials, and the entire process includes cyclohexanone production, maleic acid hydrogenation, and 1,4-butanediol purification. This process only requires hydrogenation and purification to produce 1,4-butanediol; no esterification step is needed, which shortens the entire process, reduces the number of equipment units, and accordingly lowers investment and operation/maintenance costs. It also has relatively low requirements regarding the purity of maleic anhydride. In this process, the catalyst exhibits high selectivity and a long service life, eliminating the need for catalyst replacement; moreover, it produces minimal by-products, allowing almost all maleic anhydride to be converted into 1,4-butanediol. With slight adjustments to the process conditions during hydrogenation, recovery, and purification steps, furan and γ-butyrolactone can also be produced. The production process is: n-butane → maleic anhydride → maleic acid → BDO → high-purity product.

The maleic anhydride esterification hydrogenation method was developed successfully in 1988 by the British company Davy Mckee. The process consists of three basic steps: (1) Maleic anhydride reacts with ethanol to produce monoethyl maleate, which is then esterified into diethyl maleate under the action of a solid acid catalyst； (2) Diethyl succinate is hydrolyzed to 1,4-butanediol under the action of a CuCr catalyst at a reaction temperature of 140–220°C and a reaction pressure of 1.4–4.1 MPa ； (3) Product separation. The newly developed maleic anhydride process involves a rapid reaction between maleic anhydride and methanol in the absence of a catalyst to produce monomethyl succinate, which is then further esterified in a diesterification reactor using weakly acidic ion exchange resin as a catalyst to yield dimethyl succinate. The reaction mechanism is as follows: The diester obtained through esterification is refined, and then it undergoes gas-phase hydrogenation in an adiabatic fixed-bed reactor along with hydrogen. The reaction temperature is maintained between 140 and 200°C, while the pressure is between 4.5 and 5.0 MPa. The catalyst used is a copper catalyst with barium as a promoter; the products of this hydrogenation are further refined using multiple distillation columns to yield 1,4-butanediol and furan products. The new maleic anhydride method employs a heterogeneous maleic anhydride esterification catalyst, avoiding the significant wastewater treatment problems associated with the use of sulfuric acid as a catalyst in earlier methods. This not only increases the yield of diesters but also reduces the requirements regarding the material used for the equipment. Replacing ethanol with methanol reduces the need for esterification and separation equipment. This method uses abundant raw materials, requires minimal investment, and has low production costs; by adjusting the process conditions, the ratio of BDO, GBL, and THF can be changed. Due to the cost advantages of producing BDO using this process, many new plants have been built with this technology in recent years, which represents the main trend in BDO production processes.

The direct hydrogenation method of maleic anhydride (n-butane-maleic anhydride-1,4-butanediol synthesis method): The esterification-hydrogenation method for maleic anhydride is a direct hydrogenation process for maleic anhydride that was developed in the 1970s by Mitsubishi Oil Chemical and Mitsubishi Kasei in Japan. This process features the ability to produce products such as THF and GBL alongside BDO during the hydrogenation of maleic anhydride; by adjusting various process conditions, it is possible to change the composition of the resulting products. This process is a production method that combines the gas-phase oxidation of n-butane to maleic anhydride with the hydrogenation technology for maleic anhydride. Still using the C4 fraction as raw material, the entire process includes maleic anhydride production, maleic acid hydrogenation, and BDO purification. Compared with the maleic anhydride esterification and hydrogenation method, this process directly hydrogenates the aqueous solution of maleic anhydride, which is a product of n-butane oxidation, to BD0, eliminating the steps of maleic anhydride dehydration, purification, and esterification. This reduces the number of main processing steps from 8 to 4, thereby shortening the entire process and decreasing the number of equipment units required. 2.1.4.2 Anhydride Esterification Hydrogenation Method The anhydride esterification hydrogenation method is a process for the esterification of anhydride developed by the British company Davy Process Technology; this method consists of three steps: (1) The reaction of anhydride with ethanol for esterification ； (2) BDO is obtained by hydrohydrogenation of diethyl succinate ； (3) Separation and purification of reaction products. By adjusting the process conditions, the ratio of BDO, GBL, and THF can be changed. Due to the cost advantages of BDO production using this process, more new plants have been built with this technology in recent years, which represents the main trend in BDO production processes. The main advantage of the David maleic anhydride process route is that by adjusting the process conditions, it is possible to change the yield ratios of 1,4-butanediol, γ-butyrolactone (GBL), and **furan (THF). In industrial installations, to maximize the production of 1,4-butanediol, it is possible to rely on the chemical equilibrium between 1,4-butanediol and γ-butyrolactone by recycling γ-butyrolactone until it is exhausted, thereby achieving maximum production of 1,4-butanediol. In addition, the David maleic anhydride process has other advantages as well, such as a high conversion rate of esters, mild reaction conditions, low requirements for the material of the equipment, a low cost of catalysts and a long service life. Both the investment and production costs are low, and there is a wide range of possibilities for adjusting the ratio of 1,4-butanediol to **furan. The n-butane/cyclohexanone process actually combines a gas-phase oxidation method for converting n-butane into cyclohexanone with a cyclohexanone hydrogenation technique; it still uses C4 fractions as raw materials, and the entire process includes cyclohexanone production, maleic acid hydrogenation, and 1,4-butanediol purification. This process only requires hydrogenation and purification to produce 1,4-butanediol; no esterification step is needed, which shortens the entire process, reduces the number of equipment units, and accordingly lowers investment and operation/maintenance costs. It also has relatively low requirements regarding the purity of maleic anhydride. In this process, the catalyst exhibits high selectivity and a long service life, eliminating the need for catalyst replacement; moreover, it produces minimal by-products, allowing almost all maleic anhydride to be converted into 1,4-butanediol. With slight adjustments to the process conditions during hydrogenation, recovery, and purification steps, furan and γ-butyrolactone can also be produced. The production process is as follows: n-butane (air-catalyzed oxidation) → maleic anhydride (full contact with water) → maleic acid (two-step catalytic hydrogenation in the liquid phase) → BDO (distillation for dehydration) → high-purity product. There are many similar materials available online. As for Meike Company: acetylene is first produced via partial oxidation of natural gas, and then BDO is synthesized from acetylenal

Bisphenol A diglycol (BDO), **tetrahydrofuran (THF), and gamma-butyrolactone (GBL) feature highly active production chains in the chemical industry. They are primarily used to manufacture polybutylene terephthalate (PBT), N-methylpyrrolidone, and polytetramethylene ether glycol (PTMEG). These substances have a wide range of applications, and their derivatives are particularly valuable as high-value fine chemical products, being used in solvents, pharmaceuticals, cosmetics, plasticizers, curing agents, pesticides, herbicides, foam synthetic leathers, fibers, engineering plastics, and more. 1,4-Butanediol-derived **furan is traditionally used in various industries as a solvent and chemical raw material. It is mainly used for the production of PTMEG. PTMEG is mainly used in the production of spandex, polyurethane elastomers, and ester-ether copolymer elastomers. The largest market for PTMEG abroad is polyurethane elastomers, followed by spandex and ester-ether copolymer elastomers. The main domestic market for PTMEG is spandex, followed by polyurethane elastomers. There are currently several processes for producing butanediol products; before 1995, products manufactured using the alkyne aldehyde method accounted for about 80% of the total output. With the development of new petrochemical technologies, by 2007 the proportion of the alkyne-aldehyde method had dropped to 40%, while the maleic anhydride method accounted for about 25%. The maleic anhydride process has a shorter route and cheaper raw materials; depending on the operating conditions, it can produce various products, which has led to rapid development of the process for manufacturing 1,4-butanediol using maleic anhydride. There are many production processes for dibutylene glycol, and the industrial processes that have been implemented so far mainly include: A. The Reppe process (that is, the alkyne-aldehyde process using acetylene and formaldehyde as raw materials) ； B. The butadiene process using butadiene as a raw material ； C. Allyl alcohol method using propylene oxide as a raw material ； D. The maleic anhydride esterification hydrogenation method using maleic anhydride as a raw material. A. The Reppe method can be divided into the conventional Reppe method and the modified Reppe method. In the conventional Reppe method, there is no need to separate the catalyst from the product, resulting in low operating costs. However, due to the high partial pressure of acetylene, explosions can occur; as a result, the safety factor required for reactor design is as high as 12–20 times. This leads to large-scale reaction equipment and high costs for the devices, thus resulting in high investment expenses ； Secondly, acetylene tends to polymerize to form polyacetylene, which not only causes the catalyst to become inactive rapidly but also blocks the pipes, thereby shortening the production cycle and reducing production capacity. Due to the many aforementioned drawbacks of the traditional Reppe method, many chemists have made numerous improvements to it, resulting in improved Reppe method production processes. The improved Reppe process typically uses a slurry bed or suspension bed process. The modified Reppe method improves the operating conditions by reducing the operating pressure, thereby enhancing production safety and lowering costs; it is suitable for large-scale industrial production, which boosts the competitiveness of the Reppe method. It is also one of the main technologies used for the production of 1,4-butanediol at present. However, regarding raw materials, there are also drawbacks such as the danger associated with the long-distance transportation of acetylene as a raw material, and the very limited availability of inexpensive acetylene. Since acetylene and formaldehyde are used as raw materials, the Reppe method inevitably has the following problems: 1. There are significant risks associated with the storage and transportation of acetylene ； 2. If the calcium carbide method is used, cheap acetylene can be obtained, but environmental problems are relatively severe ； If acetylene is obtained through other means, it will result in a significant increase in production costs. Furthermore, the Reppe process cannot produce THF as a by-product; to obtain THF, it is necessary to add production facilities for converting BDO into THF, which inevitably increases the associated environmental and economic costs. B. There are two processes for producing 1,4-butanediol from butadiene: the butadiene acetyloxylation method and the butadiene chlorination method. In the acetoxylation method of butadiene, butadiene, acetic acid, and air are first fed continuously into a fixed-bed reactor equipped with a Pd-Te catalyst, where an acetyl oxidation reaction takes place at 6.8 MPa and 70°C. After the reaction products are distilled to separate out acetic acid, 1,4-dioxybutadiene (DAB) is obtained. DAB is then subjected to catalytic hydrogenation to produce 1,4-diacetoxybutane, which is subsequently hydrolyzed to yield 1,4-butanediol. Meanwhile, the semi-hydrolyzed product 1,2-acetoxy-4-hydroxybutane undergoes deacetylation and cyclization to form THF, while ethanol can be reused. The acetyloxylation method for butadiene suffers from severe equipment corrosion, and using corrosion-resistant materials requires significant additional investment. In the chlorination of butadiene, butadiene is subjected to gas-phase chlorination at 260–300°C to produce 3,4-dichlorobut-1-ene and 1,4-dichlorobut-3-ene; these compounds are used in the production of neoprene. 1,4-Dichlorobut-2-ene can be converted into 1,4-butanediol through hydrolysis. The chlorination of butadiene is constrained by the co-production of neoprene, which limits the production of 1,4-butanediol. For large petrochemical companies that have access to cheap and abundant bromine as a raw material, it is certainly cost-effective to use the bromine method for producing 1,4-butanediol. However, China suffers from a shortage of bromine as a raw material, and for regions or companies that do not have this advantage, using the bromine method to produce 1,4-butanediol may not be the best option. This is because the butadiene process has many drawbacks, such as a long production sequence, complex procedures, high investment costs, and substantial expenses for utility services. Currently, internationally, this production method is generally only used in BDO manufacturing facilities located near large petrochemical companies that produce large amounts of butadiene. C. Allyl alcohol method (also known as the propylene oxide method): In this method, propylene oxide is first isomerized to yield allyl alcohol. Allyl alcohol is then subjected to liquid-phase formylation in the presence of an aromatic solvent, a rhodium-based catalyst Rh6(CO)16, and a triphenylphosphine solution, resulting in a solution of 4-hydroxybutyraldehyde. Subsequently, hydrogenation is carried out in the presence of a Raney nickel catalyst to produce 1,4-butanediol. Allyl alcohol, the raw material, is expensive, and using propylene oxide to produce allyl alcohol would lengthen the production process. The allyl alcohol process suffers from low selectivity in the hydroxylation reaction and low overall yield, which results in high pollutant emissions and serious environmental problems. D. Anhydride esterification hydrogenation method (Davy method): The anhydride esterification hydrogenation method was developed by the British company Davy Mckee, which is why it is also known as the Davy method. Its hydrogenation reaction takes place in the gas phase, and the reaction conditions are milder than those of the direct hydrogenation of maleic anhydride. The production of 1,4-butanediol via the maleic anhydride method has many advantages: low investment, low production costs, reduced amounts of waste, and the possibility of co-producing THF and GBL. Its only drawback is its dependence on the supply and price of the raw material, maleic anhydride. The Davy process BDO production technology, ranging from the earliest Mark I process using maleic anhydride + ethanol, and the Mark II process using maleic anhydride + methanol, to the current Mark IV process. It can be mainly divided into three process stages: 1. Succinic anhydride and methanol react through esterification to produce dimethyl maleate ； II. Dimethyl maleate reacts with hydrogen to produce a crude product containing BDO, GBL, and THF ； III. The crude product is purified through distillation to produce BDO, GBL, and THF of finished product quality. This post was last edited by dychem on 2009-2-26 20:42]

The crude product is purified through distillation to produce BDO, GBL, and THF of product quality; distillation is a good method for this

In the product refining section, there are distillations under normal pressure, at increased pressure, and under reduced pressure; generally, depending on the product requirements, there are 5 to 10 distillation columns operating under different conditions. Qualified product composition (wt%): BDO: 99.5%, GBL: 99.5%, THF: 99.9%. For project research, it is better to get in touch with manufacturers for information, or directly commission a design institute to carry out the feasibility study.

I mainly use acetic anhydride for isomerization reactions. I suggest you conduct thorough market research before proceeding

Which expert has anhydride slag to sell? I want to

For the esterification and hydrogenation of maleic anhydride, it depends on what you need to do. What was mentioned above refers to the formation of monomethyl maleate from maleic anhydride and methanol, followed by the formation of dimethyl maleate, and then hydrogenation. Another method is to directly hydrogenate maleic anhydride to produce succinic anhydride, which then serves as a raw material for downstream biodegradable plastics

It’s a 12-year-old post, and it’s become super popular lately