Issue 41, 2012 - Urea alcohololysis: a green pathway for DMC synthesis

Urea alcoholysis: a green pathway for the synthesis of DMC

The synthesis of dimethyl carbonate (DMC) from urea and methanol not only greatly reduces production costs, and basically does not produce "three wastes" in the entire production process, but also provides new ideas
for product diversification and economic improvement in the urea industry.
The green process of dimethyl carbonate synthesized by urea alcohololysis method successfully developed by Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences has achieved a win-win situation
for all parties in one fell swoop.
At present, the institute has completed technology transfer with an enterprise in Inner Mongolia, and a 20,000-ton urea alcohololysis dimethyl carbonate production line is under
construction.

It is reported that as early as 2000, the Shanxi Institute of Coal Chemical Industry of the Chinese Academy of Sciences proposed a new method
for the direct synthesis of DMC from urea and methanol 。 After that, with the support of the National Science and Technology Support Program "Key Technologies and Demonstration Research of Clean Production and Circular Economy", the important direction project of the Knowledge Innovation Project of the Chinese Academy of Sciences "Key Technologies for the Industrialization of Non-phosgene Route Synthesis MDI" and major enterprises, the research group has solved the key problems such as stable operation of catalysts, material separation, and equipment blockage after years of efforts, and has completed the pilot test of 1,000-ton industrialization, the catalyst has achieved stable operation, and the urea conversion rate has reached 100%.
The one-pass yield of dimethyl carbonate is more than 60%, and the process has reached the international leading level
.
Moreover, the by-product ammonia after the reaction can also be reused in urea production, and there is basically no "three wastes" in
the whole process.

Because of its low toxicity, safe and convenient use and easy transportation, dimethyl carbonate was listed as a non-toxic product in Europe in 1992, and is an environmentally friendly chemical raw material
that meets the requirements of modern clean technology.
Dimethyl carbonate molecules contain functional groups such as carbonyl, methyl and methoxy, with a variety of reactive activities, can replace highly toxic phosgene as carbonylating agent, replace dimethyl sulfate as methylating agent, etc.
, used in medicine, pesticides and solvents and other fields
.
Dimethyl carbonate is an ideal oil additive
due to its high oxygen content (53% oxygen content, 3 times that of MTBE) and appropriate vapor pressure, water resistance and mixing distribution coefficient.
In addition, dimethyl carbonate can also be used as a cleaning oil additive and electrolyte for lithium-ion batteries, and the market potential demand is huge
.

The large-scale production of dimethyl carbonate was developed along with the non-phosgene synthesis process of polycarbonate.

China's dimethyl carbonate product development began in the early 80s of the last century, early production are using domestic self-developed phosgene method, choose to build production lines in existing phosgene production enterprises, single set of equipment scale of 300~500 tons / year, the total domestic production capacity in 1000~1500 tons / year
.
He said: "After the phosgene method is gradually eliminated, the industrial synthesis methods mainly include transesterification method, carbon dioxide direct synthesis method, and methanol oxidative carbonylation method, but the production cost is generally high, all above 6,000 yuan / ton, which limits the large-scale application
of dimethyl carbonate.
" "Currently, 51% of the dimethyl carbonate market consumption is used to synthesize polycarbonate, with a small amount used in the pharmaceutical, pesticide and solvent industries
.
Affected by production costs, dimethyl carbonate has not been widely used
as an oil additive.

To build a dimethyl carbonate production plant of the same scale, the investment in urea alcohololysis method is 1/3 of the current oxidative carbonylation technology, is 1/2 of the transesterification technology, and the production cost of dimethyl carbonate is also expected to be reduced to less than 4000 yuan / ton, with good economic benefits
.
If the production cost is reduced, the potential market demand for dimethyl carbonate will increase
significantly.
Dimethyl carbonate has the best thermal efficiency when adding a mass ratio of 5% to gasoline and a mass ratio of 10% to diesel, and according to this calculation, the potential annual demand for dimethyl carbonate as an oil additive alone is more than
10 million tons.

In addition, at present, China's urea, methanol and synthetic ammonia industries are overcapacity, especially the main consumption area of urea in China is agriculture, which is greatly affected by the season and the demand is unstable
.
The successful development of dimethyl carbonate synthesis technology by urea alcohololysis will also help promote the diversification of products in China's urea industry, improve the economy of the industry, and alleviate the pressure of
overcapacity.

At present, the Shanxi Institute of Coal Chemical Industry of the Chinese Academy of Sciences has successfully applied for 7 national invention patents and 3 international invention patents
in this field.
In the future, while promoting the industrialization of the technology of dimethyl carbonate synthesized by urea alcoholylysis, the institute will focus on strengthening the development and research of a new generation of high-efficiency catalysts and improving the high-efficiency and energy-saving optimization design
of the process.
(Li Ke)