Issue 8/2013 - New advances in ethylene glycol production technology

New progress in ethylene glycol production technology

■ Sinopec Shanghai Petrochemical Research Institute Long Xiaofeng Xu Yihan

Ethylene glycol is an important organic chemical raw material
with a wide range of uses.
It is mainly used for the production of polyester monomer, followed by antifreeze, and some are used in the production of fine chemical products, such as surfactants, lubricants, polyurethanes, plasticizers, etc
.
The ethylene glycol production process is divided into oil routes and non-oil routes
.
The oil route is divided into two types: one is the crude oil-naphtha-ethylene route that is currently commonly used, and its production capacity accounts for about 80% of the world's total production capacity; The other is the ethane-ethylene route in the Middle East and Canada, which has about 20% production capacity and is owned
by Anglo-Dutch Shell, SD and Dow.
Due to the long production process and many equipment, the water consumption in the reaction is high, the concentration of ethylene glycol in the product is low, and the energy consumption is large, which directly affects the production cost
of ethylene glycol.
WITH THIS IN MIND, SHELL AND DOW DEVELOPED THE OMEGA PROCESS AND THE METEORTM PROCESS
, RESPECTIVELY.
In the non-oil route, natural gas or coal is used as raw material to synthesize ethylene glycol, first to produce syngas (CO+H2), and then to use syngas to produce ethylene glycol
by direct synthesis or indirect synthesis.
While the traditional process is being improved, various research institutions have launched new process routes, mainly in three aspects: C1 route, ethylene oxide (EO) indirect hydrolysis route, and biological route
.

1.
C1 route foreign R&D institutions mainly focus on the research of formaldehyde method, the main innovation points are formaldehyde condensation/hydrogen transfer to ethylene glycol new route
, high-performance glycolic acid hydrogenation catalyst and synthetic glycolic acid catalyst solidification
.
The California Institute of Technology proposed a new process for formaldehyde to produce ethylene glycol, formaldehyde reacts in the presence of N-heterocyclic carbene catalyst to generate glycolaldehyde, and glycolaldehyde and methanol undergo transfer hydrogenation reaction in the presence of transition metal catalyst to generate ethylene glycol and formaldehyde
.
The advantage of this synthetic route is that the reaction conditions are mild and easy to industrialize
.
Dalian Chemical Institute and BP proposed a multiphase acidic polyoxide catalyst for formaldehyde/CO to glycolic acid, which is insoluble in formaldehyde, glycolic acid and solvents, so the separation is simple, and the activity decreases slowly when reused
.
Eastman Chemical Company proposed a glycolic acid and ester hydrogenation catalyst, which is a homogeneous catalyst containing Ru, which has a short reaction time and high glycol selectivity
.

2.
EO indirect hydrolysis route
Shell proposed two types of process routes: direct esterification of EO reactants and crude esterification
of EO.
The direct esterification process is to directly convert the EO and CO2 generated in the reaction into ethylene carbonate by adding the ethylene carbonate reaction stage to the EO absorption unit, and add bromide-containing substances (brought in by the ethylene carbonate unit) to remove the unit before the unreacted tail gas is recycled back to the EO reaction stage to ensure the safety
of the EO catalyst.
Alternatively, EO and CO2 generated in the reaction are directly converted into ethylene carbonate and hydrolyzed to generate ethylene glycol
.
EO crude esterification process is EO ethylene carbonate production process, which solves the problem that the carbonate esterification activity decreases slower than that of hydrolysis catalyst, thereby reducing the formation
of diethylene glycol and aldehyde by-products.

3.
Biological route
The biological method route mainly includes two types, one is the use of biological fermentation/enzyme catalyst method to prepare ethylene glycol, and the other is the catalytic conversion of biomass (sugar alcohol, starch, cellulose) to generate ethylene glycol
.

The French company Metabolic Explorer proposed a process of biological decarbonylation of glucose to ethylene glycol, using genetically modified microorganisms, with better 2-ketoacid decarbonyl performance, and the yield of ethylene glycol is 0.
5g/g glucose
.
BASF proposes a hydrogenolysis catalyst for the production of ethylene glycol, propylene glycol and glycerol from sugar alcohols, which is easy to handle and replace, has a long life and high
selectivity.
The catalyst is a kind of
metal oxides such as copper oxide, alumina and Fe/W/Mo/Ti.

4.
Domestic technology development trend
At present, China's ethylene glycol manufacturers are mainly concentrated in Sinopec and PetroChina, which are still dominated
by oil routes 。 Shanghai Petrochemical Research Institute has carried out systematic research and development on EO catalytic hydration to ethylene glycol.
Dalian University of Technology conducted experiments on homogeneous acid-base synergistic catalytic reaction system and heterogeneous catalytic reaction system for the preparation of ethylene glycol by EO catalytic hydration, and investigated the catalytic activity, ethylene glycol selectivity and reaction conditions of the catalyst.
The Fujian Institute of Material Structure, Chinese Academy of Sciences, in cooperation with enterprises, has successfully developed a complete set of coal-to-ethylene glycol technology, which is to obtain syngas by coal gasification, and then carbonylation to generate oxalate and further hydrorefine to obtain ethylene glycol
.

The main raw materials of oxalate method are CO, NO, H2, alcohols, etc.
, first N2O3 is generated from NO and O2, and then alcohols are used to react with N2O3 to generate nitrite, and CO and nitrite oxidation coupling under the action of Pd catalyst to obtain dioxalate, oxalate and then catalytic hydrogenation to obtain ethylene glycol
.
This process does not actually consume alcohols and nitrites, but only CO, O2 and H2O to synthesize oxalic acid
.
Among them, the most studied is the use of methanol or ethanol to obtain methyl nitrite or ethyl nitrite and oxidative coupling with CO
.
Domestic Fujian Institute of Physical Structure, Tianjin University, East China University of Science and Technology, Shanghai Coking Co.
, Ltd.
, etc.
have conducted in-depth research
on the carbonylation reaction mechanism.
Among them, Fujian Structural Institute has completed the 10,000-ton industrialization demonstration device of "CO gas phase catalytic synthesis of oxalate and oxalic acid", and has built a 200,000-ton ethylene glycol industrialization plant
in Tongliao, Inner Mongolia.

In 2011, East China University of Science and Technology, Huaihua Group and Shanghai Pujing Chemical cooperated to develop syngas indirect ethylene glycol technology, and built a 1,000-ton pilot plant; In 2011, Sinopec Syngas to Ethylene Glycol pilot plant was completed in Yangtze Petrochemical, with a product purity of 99.
92%, and on August 30, 2012, Sinopec Hubei Fertilizer Branch started construction
of 200,000 tons of syngas to ethylene glycol industrial demonstration plant.
In addition, Japan's Ube Industries, in cooperation with Donghua Engineering Corporation, is promoting the industrialization of syngas to ethylene glycol in China, and in 2012 these projects completed bidding or feasibility demonstration, and some are about to be put into production and
commissioning.

In today's increasingly scarce energy and water resources, while strengthening the development of EO catalytic hydration ethylene glycol technology, China also needs to accelerate the research and development of coal or natural gas to replace petroleum ethylene synthesis process of ethylene glycol, and the current oxalate synthesis method to produce ethylene glycol is the most economical and realistic route
for syngas synthesis of ethylene glycol.
The economic performance and operation effect of the coal-to-ethylene glycol project need to be verified, and it is recommended to build a new coal-to-ethylene glycol plant in the near future to avoid huge losses
.
At the same time, it is recommended to accelerate the research and development of ethylene glycol downstream fine chemical products, gradually change the situation of single ethylene glycol consumption structure in China, and promote the healthy and sustainable development of
China's ethylene glycol industry.

Link: Ethylene glycol market demand is strong domestic supply exceeds demand

In recent years, the demand for ethylene glycol in domestic and foreign markets has maintained a growth trend, and the global consumption of ethylene glycol in 2007 was about 17.
6 million tons, and in 2012, it exceeded 21.
5 million tons, with an average annual growth rate of about 4.
1%.

In 2007, China's ethylene glycol consumption was about 6.
58 million tons, and in 2012, it exceeded 10 million tons, with an average annual growth rate of about 8.
7%.

Due to the strong demand of polyester industry, although China's ethylene glycol production capacity and output are growing, it still cannot meet the growing domestic market demand, and a large number of imports are required every year, and the dependence on foreign countries exceeds 70%.


The production of ethylene glycol in the world is developing rapidly
.
The global ethylene glycol production capacity, output and consumption in 2009~2012 are shown in
Figure 1.
It can be seen from the figure that the production capacity and output of ethylene glycol are steadily increasing year by year, with an output of more than 20 million tons in 2011 and more than 21 million tons
in 2012.
In 2012, the world's ethylene glycol production capacity was concentrated in Asia, the Middle East and North America, and Asian ethylene glycol production capacity accounted for more than
40%.
The Middle East is a major ethylene glycol exporter, accounting for more than
half of world exports.
In the global demand for ethylene glycol production, about 80% of ethylene glycol is used in the polyester field, 11% is used in the production of antifreeze, and the rest is used in lubricants, plasticizers, etc
.
SABIC is the world's largest producer of
ethylene glycol.

Due to the large number of new ethylene glycol production capacity in the Middle East and China in recent years, and the weak demand for raw materials in the market, resulting in an oversupply of global ethylene glycol, ethylene glycol production plants in some countries and regions have been adjusted, converted or shut
down.
Taking 2012 as an example, the production capacity of ethylene glycol showed a growing trend, while its market price fell sharply, and the ethylene glycol market was sluggish
.
However, due to the conversion or shutdown of some plants, the market demand will recover in 2013, the supply of ethylene glycol market will soon become tight, demand will increase steadily, ethylene glycol prices will recover, and the market will not be far
from the trough.

Asia accounts for more than 2/3 of the total global consumption of ethylene glycol, of which China accounts for half of the total consumption in Asia, and is the world's largest
ethylene glycol consumer.
Among them, polyester is the main consumption area of ethylene glycol in China, and its consumption accounts for about
90% of the total domestic consumption.
There are a total of 16 ethylene glycol production enterprises in China, which belong to Sinopec (9), PetroChina (4), CNOOC (1), Liaoning Huajin Chemical and Tongliao Jincoal Chemical
Industry.
China's ethylene glycol consumption, output and import in 2009~2012 are shown in
Figure 2.
It can be seen that although China's ethylene glycol self-sufficiency rate has increased in recent years, it is still less than 30%, and a large number of imports from Saudi Arabia and other countries and regions are required every year, and the import volume is increasing year by year
.