What is the New Methods for Preparation of 1,4-Butanediol (BDO) ?

1,4-Butanediol (BDO) is an important organic and fine chemical raw material that finds wide applications in fields such as pharmaceuticals, chemicals, textiles, papermaking, automotive, and daily chemicals. Its CAS number is 110-63-4 and molecular formula is C4H10O2.BDO can be used to produce tetrahydrofuran (THF), polybutylene terephthalate (PBT), gamma-butyrolactone (GBL), polyurethane resin (PU Resin), coatings, plasticizers, as well as solvents and brighteners in the electroplating industry.

Methods for the preparation of 1,4-butanediol (BDO)

Acetylene method for BDO production

  • Acetylene method

Firstly, acetylene and formaldehyde react under the presence of Cu-Bi catalyst at 98 kPa and 80-95°C to form 1,4-butyne diol. The latter is then subjected to hydrogenation using a skeletal nickel catalyst at 1.372-2.06 MPa and 50-60°C to form 1,4-butenedioate. This is followed by further catalytic hydrogenation using Ni-Cu-Mn/Al2O3 catalyst (at 13.7-20.6 MPa and 120-140°C) to produce 1,4-butanediol. After removal of metal ions using ion exchange resin, the product is purified through distillation to obtain pure BDO.

  • Improved acetylene method

The above process has been modified by developing a catalyst with magnesium silicate as a carrier and the addition of bismuth to suppress copper polymerization reaction. This allows the synthesis of butyne diol under low and safe acetylene partial pressure, eliminating the risk of explosion. In the low-pressure butyne diol synthesis system, a continuous stirred tank reactor is used with the addition of 37% methanol, 12% Cu-2% Bi/magnesium silicate catalyst (metal mass fraction in the catalyst), a reaction temperature of 95°C, acetylene partial pressure of 0.1 MPa, and a pH of 5-6. Inert gas is used as a diluent to minimize the explosion risk by reducing the acetylene partial pressure. The conversion rate of butyne glycol to formaldehyde is 95% with the recovery of butyne alcohol. The theoretical yield of butanediol is 95%. The hydrogenation process is improved by using a two-stage hydrogenation: a 35% solution of butyne glycol and acetic acid flows into a continuous stirred tank reactor together with Ranny Ni catalyst, operating at a temperature of 50-60°C and hydrogen pressure of 1.4-2.0 MPa, resulting in the production of crude BDO vapor containing partially hydrogenated and carbonyl compounds. The crude BDO vapor is then subjected to a second hydrogenation using a fixed-bed reactor filled with Ni-Cu-Mn/silica gel catalyst at a reaction temperature of 120-140°C and hydrogen pressure of 13.8-20.7 MPa. Research by ISP company has found that the silica gel carrier degrades under the conditions of the second-stage high-pressure hydrogenation reaction, causing pressure fluctuations in the reactor. To address this issue, a new catalyst composed of 15% Ni-7% Cu-0.5% Mn/Al is developed, which exhibits high activity, self-stability, and long lifespan under the reaction conditions. The yield of 1,4-butanediol calculated based on acetylene is 93.1%.

Hydrogenation of maleic anhydride to produce BDO

Processes using n-butane as a raw material include Huntsman/Kvaerner method, BPAmcoc/Lurgi Geminox method, and Sisas method. Among them, the Kvaerner process involves the oxidation of n-butane into maleic anhydride (MA) using a vanadium-based catalyst on a fixed bed, followed by the conversion of MA into the corresponding dimethyl maleate (DMM) and further gas-phase hydrogenation/hydrolysis to obtain BDO. MA reacts with excess methanol to produce DMM through esterification using an acidic ion exchange resin catalyst at 70-80°C, with MA conversion rate of 100% and DMM yield of 99%. The gas-phase hydrogenation of DMM uses copper as an initiator at 170-190°C and 4-7 MPa, with a hydrogen/ester feed molar ratio typically ranging from (250-350):1. The crude BDO obtained from hydrogenation has a yield greater than 99% based on DMM. The crude product is subjected to multi-stage continuous distillation to refine BDO, gamma-butyrolactone (GBL), and tetrahydrofuran (THF), with methanol recovered and recycled to the process. The total yield of BDO based on MA is 98%-99%, with butanol (0.1%-0.2%) as the main by-product.

BDO production by butadiene method

 This method involves the acetoxylation reaction of 1,3-butadiene with acetic acid and oxygen to form 1,4-di(acetoxy)-2-butene, which is then hydrogenated and hydrolyzed to obtain BDO. Tetrahydrofuran (THF) is produced as a by-product, and acetic acid is recycled.

BDO production by 1,4-dichlorobutene method

1,4-dichlorobutene is an intermediate product in the production of chlorobutadiene from butadiene. It is used as a raw material and undergoes hydrolysis and hydrogenation to obtain 1,4-butanediol.

BDO synthesis

In a 3L reaction flask equipped with a stirrer, two reflux condensers, and a dropping funnel, fresh metallic sodium (60g, 2.6 mol) is added, followed by the rapid addition of a solution prepared from 1,4-butanedioate diethyl ester (35g, 0.2 mol) and 700 mL anhydrous ethanol. The reaction proceeds vigorously and can be cooled with an ice-water bath if necessary. After the reaction stabilizes, heat the reaction mixture (bath temperature can reach 130°C) to complete the reaction of metallic sodium (approximately 0.5-1 hour). Cool with an ice-water bath, and filter out the precipitated sodium chloride. Add 300g of anhydrous potassium carbonate to the filtrate to remove water and acid. Filter and extract the filter cake twice with hot ethanol. Combine the filtrate and extract, evaporate the ethanol, and allow solid salts to precipitate. Add dry acetone, filter, and evaporate the acetone. Perform vacuum distillation on the residue and collect the fraction at 133-135°C/2.4 kPa to obtain 1,4-butanediol (13g) with a yield of 72%.

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