China is making a vigorous development of DMC. (Market Report).

Dimethyl carbonate (DMC) is a new green chemical product starting to arouse great attention both at home and abroad in the recent years. As a product with high added value, it mainly has two applications. One is the extensive use in the synthesis of pharmaceutical, pesticide and perfume intermediates and the other is the use as raw materials in the synthesis of polycarbonate. Its application will surely be extended to the full or partial replacement of chemical substances extremely hazardous to environment and health such as dimethyl sulfate and phosgene. Besides, dimethyl carbonate has good solubility in gasoline and therefore is an ideal lead-free gasoline additive to replace MTBE currently in extensive use. MTBE is also a harmful substance and some places of the United States have already forbidden its use. Products replacing MTBE will be ethanol and dimethyl carbonate.

China has near 20 dimethyl carbonate producers today. Besides some units using the traditional phosgene process, several units using new processes have also been constructed in the recent years but the capacity of each unit is less than 10 000 t/a.

Dimethyl carbonate units not using the phosgene process mostly use the ester exchange process from East China University of Technology. Producers using domestic technology all have stable production and the output in some of them has surpassed the design capacity. For example, the design capacity of Henan Puyang Chlor-alkali Plant, Tangshan Chaoyang Chemical General Plant and Anhui Tongling Jintai Chemical Industrial Co., Ltd. is around 1 000 t/a but the annual output is more than 1 000 tons today. The quality of dimethyl carbonate produced with domestic technology has also fully reached the quality of imports. Producers with good performance are conducting capacity expansion. For example, Tangshan Chaoyang Chemical General Plant has constructed a 5 000 t/a unit in Zhangjiakou (Hebei Xinchaoyang) and the unit already started to produce qualified product in April this year. Hubei Xinglihua Chemical Industrial Co., Ltd., the only dimethyl carbonate producer in China using the methanol oxidative carbonylation pr ocess, has a design capacity of 4 000 t/a and has been making normal production since it was put on stream in early 2001.

The sales at producers is good and the product is in short supply. China already owns dimethyl carbonate production technology with independent intellectual property and the cost is dominant. Dimethyl carbonate therefore still has development space and promising prospect in the international market.

Competition between two synthesis methods

(1) Methanol oxidative carbonylation process

The methanol liquid-phase oxidative carbonylation process developed by Central China University of Technology for dimethyl carbonate synthesis is a cyclic process using cuprous chloride catalyst and tubular reactor. Methanol serves both as reactant and solvent. The reaction temperature is around 150[degrees]C and the reaction pressure is 2.0-3.0MPa. Typical process flow includes methanol oxidative carbonylation and dimethyl carbonate separation. The 4000 t/a unit was completed and put on stream in 2001 and is now making trial production.

(2) Ester exchange process East China University of Technology has made an intensive study of the ester exchange process and developed the technology for the commercial production of dimethyl carbonate through the ester exchange between propylene carbonate and methanol. The technology uses a special separation method (catalytic rectification and azeotropic rectification) to produce high-quality dimethyl carbonate and also byproduct propylene glycol. Several commercial production units with different scales have been constructed and the design of 10 000 t/a units has also been completed. 80% output of dimethyl carbonate in China is produced with the technology developed by ECUT.

In author's opinion the ester exchange process has the following long points:

(1) The two products (dimethyl carbonate and propylene glycol) produced with the process are both in urgent market demand and therefore the input/output effect of the process is better than the carbonylation process.

(2) Compared with the carbonylation process, the ester exchange process has better environmental protection and can reduce the emission of carbon dioxide.

Economic analysis of dimethyl carbonate projects

Large-sized dimethyl carbonate producers such as Tangshan Chaoyang Chemical General Plant and Anhui Tongling Jintai Chemical Industrial Co., Ltd. all use propylene oxide and carbon dioxide as raw materials. They first produce propylene carbonate and then produce dimethyl carbonate through the ester exchange with methanol and also byproduct propylene glycol. Some small-sized producers directly purchase propylene carbonate from the market to produce dimethyl carbonate. The production cost in large-sized producers is of course less than in small-sized producers. Based on the current price of raw materials, the gross profit is RMB3 000 per ton of dimethyl carbonate. The 5 000 t/a dimethyl carbonate project just starting production in Hebei Xinchaoyang Chemical Industrial Co., Ltd. in April this year only has a total investment of RMB2O million and the project surely has a good economic effect.

Urgent market demand of byproduct propylene glycol

Propylene glycol is an excellent solvent with no toxicity and also a main raw material in the production of unsaturated polyester resin and the synthesis of PU, TDI and MDI. There is a supply shortage of propylene glycol in China and more than 60 000 tons has to be imported each year. The import amount was 72 500 tons in 2001. The market price of the product is mainly subject to crude oil price changes. The market price of industrial-grade variety was maintained at RMB6 600-7 500 per ton in 2001.

Table 1

Major Dimethyl Carbonate Producers with a Capacity of Over 1 000 T/A
in China

(t/a)

Producer                             Capacity

Wusong Chemical Plant of Shanghai    1 100
Zhongyuan Group Corp.
Shengju Chemical Plant of Shanghai   2 000
Tianyuan Group Corp.
Tangshan Chaoyang Chemical General   5 000 ester exchange process
Plant                                from ECUT
Hebei Xinchaoyang Chemical           5 000 ester exchange process
Industrial Co., Ltd.                 from ECUT
Anhui Tongling Jintai Chemical       3 500 ester exchange process
Industrial Co., Ltd.                 from ECUT
Henan Puyang Chlor-alkali Plant      1500-2000 ester exchange
                                     process from ECUT
Hubei Xinglihua Chemical Industrial  4 000 methanol oxidative
Co., Ltd.                            carbonylation process from
                                     CCUT

Producer                             Process

Wusong Chemical Plant of Shanghai    phosgene process
Zhongyuan Group Corp.
Shengju Chemical Plant of Shanghai   phosgene process
Tianyuan Group Corp.
Tangshan Chaoyang Chemical General
Plant
Hebei Xinchaoyang Chemical
Industrial Co., Ltd.
Anhui Tongling Jintai Chemical
Industrial Co., Ltd.
Henan Puyang Chlor-alkali Plant

Hubei Xinglihua Chemical Industrial
Co., Ltd.


* Central China University of Technology (CCUT)

** East China University of Technology (ECUT)

Source: CNCIC ChemData