1, 3-propylene glycol PDO production process

Introduction to 1, 3-propylene glycol

1, 3-propylene glycol (PDO) is a kind of polymer material with excellent synthesis properties. 1, 3-propylene glycol is a high-end technology product, and the production technology is currently dominated and controlled by three companies: Shell, Du Pond and Degussa, Germany. They basically do not sell 1, 3-propylene glycol raw materials, and the original technology is not open to the public. Only PTT slices and its downstream products are provided to customers. 1, 3-propylene glycol can be used in the synthesis of plasticizers, detergents, preservatives, emulsifiers, and can also be used in food, cosmetics and pharmaceutical industries. At present, 1, 3-propylene glycol is mainly used in the production of PTT fiber resin products (PTT refers to propylene glycol terephthalate).

1 Propylene process (acrolein process)

Degussa, a German company, developed an industrial route to produce PDO using acrolein as raw material and applied for a patent. The main steps of its production are as follows:

(1) Acrolein is hydrated to obtain 3-hydroxypropanal (HPA):

CH2=CHCHO+H2O→HOCH2CH2CHO;

(2)HPA catalytic hydrogenation to produce PDO:

HPA+H2, HOCH2CH2CH2OH.

To ensure high product yield and quality, several key steps must be strictly controlled. The yield of the product depends on the hydration reaction of acrolein, and the quality of the final product is determined by the hydrogenation effect of HPA. The key technology of this two-step reaction lies in the choice of catalyst.
2 ethylene oxide process

Shell has successfully developed a new process for small-scale industrial PDO production using the ethylene oxide route, which greatly reduces the cost. The reaction steps are as follows:

(1) Ethylene oxide reacts with CO and H2 carbonyl groups to produce HPA under the action of catalyst.

CH2OCH2+CO+2H2→HPA;

(2) PDO was generated from the separated HPA by catalytic hydrogenation.

HPA+H2, HOCH2CH2CH2OH.

The key of ethylene oxide process is the preparation and selection of catalyst. Shell company has done a detailed test on this, and the latest patent shows that the improved cobalt phosphine ligand catalyst and cocatalyst system of ethylene oxide carbonylation to prepare HPA, and then the traditional catalytic hydrogenation method to produce PDO, the yield is very high, which is the so-called ethylene oxide two-step process. The process conditions are: the ethylene oxide, catalyst, cocatalyst and solvent are placed in an autoclave, heated to the appropriate temperature, and CO and H2 are introduced

After a tubular reactor, the reactant and catalyst contact reaction, the temperature is 70~110C, the pressure is 3.45~20.7MPa, the product can be separated by conventional methods.
Microbial fermentation method

DuPont uses carbohydrates such as monosaccharides (such as glucose and fructose) and polysaccharides (such as starch and cellulose) as carbon substrates to prepare 1,3-PDO under appropriate fermentation conditions through contact with a single microorganism of the dehydrase gene. The company has repeatedly claimed that it has made major breakthroughs in technology and will be industrialised in the near future. The production cost of 1,3-PDO is basically the same as that of existing ethylene glycol, which is an important method for the preparation of 1,3-PDO with the lowest production cost and the least pollution. Compared with chemical synthesis, it has the advantages of mild conditions, simple operation, less by-products, low energy consumption and small investment, and is a low-cost green process.