Full name : Dương Văn Đại
Class : K4
ID Student : CTTT13210111
SELF STUDY 1: CHAPTER 2
1) Interpret production of Ethyleneglycol (EG) from synthesis gas via dimethyl oxalate .
In this process, ethylene glycol is produced from synthesis gas (syngas), a gaseous mixture of carbon monoxide (CO) and hydrogen (H2). CO is first converted to dimethyl oxalate (DMO), which is then hydrogenated to form ethylene glycol.
In the whole process, MN, NO and methanol (ME) recycle and do not lose theoretically. The related reactions are presented as follows:

MN Regeneration : 2𝑁𝑂+0.5
𝑂
2+2𝐶
𝐻
3
𝑂𝐻→2𝐶
𝐻
3
𝑂𝑁𝑂
𝑀𝑁+
𝐻
2
𝑂 (1)

DMO Synthesis : 2𝐶
𝐻
3
𝑂𝑁𝑂+2𝐶𝑂→𝐶
𝐻
3
𝑂𝐶𝑂𝐶𝑂𝑂𝐶
𝐻
3
𝐷𝑀𝑂+2𝑁𝑂 (2)

MEG Production :
𝐶
𝐻
3
𝑂𝐶𝑂𝐶𝑂𝑂𝐶
𝐻
3+4
𝐻
2→𝐶
𝐻
2
𝑂𝐻𝐶
𝐻
2
𝑂𝐻
𝑀𝐸𝐺+ 2𝐶
𝐻
3
𝑂𝐻 (3)

Total : 2𝐶𝑂+0.5
𝑂
2+4
𝐻
2→𝐶
𝐻
2
𝑂𝐻𝐶
𝐻
2
𝑂𝐻
𝑀𝐸𝐺
𝐻
2
𝑂 (4)

MN regeneration can take place without catalyst, while both carbonylation and hydrogenation have to depend on catalysts. In laboratory, we mainly introduce two kinds of catalysts.

Carbonylation process
The CO and H2 in the feed syngas are separated. The recovered CO is fed to the carbonylation reactors along with a recycled stream from the nitrite regeneration section (discussed below) that contains an intermediate (methyl nitrite). Methyl nitrite reacts with CO to produce the intermediate DMO and nitric oxide (NO). The product from the carbonylation reactors is partially condensed, generating a gaseous stream, rich in unconverted CO and NO, and a liquid stream, rich in DMO. The former is directed to the nitrite regeneration section, and the latter is directed to the DMO hydrogenation section.

/(5)


Carbonylation reaction of CO and MN takes place over Pd catalyst.
The catalyst prepared under acid liquid generated low MN conversion, high DMO selectivity, while the catalyst synthesized under basic solution could Increase MN conversion with slightly decreasing DMO selectivity. In view of the product’s yield, basic precursor’s solution is regarded to be more suitable for carbonylation catalyst’s preparation.

Hydrogenation process
The DMO-rich stream is fed to the hydrogenation reactors along with H2 recovered from the syngas feed. DMO reacts with H2 to produce the final product, ethylene glycol and methanol. A few byproducts from undesired side reactions also form. The product stream from the hydrogenation reactors is partially condensed, and the condensate is directed to the purification section. Uncondensed vapor (mostly H2) is compressed and recycled to the hydrogenation reactors.
/(6)
Hydrogenation catalyst is the key during the whole technology to prepare MEG from CO and H2. Current catalyst usually contains some chromium element, which is poisoning to the environment and people’s life. A kind of green and high effective Cu/SiO2 catalyst which performs very well during DMO hydrogenation reaction.
Purification process
The purification system consists of a series of distillation steps to separate fiber-grade ethylene glycol from methanol and other byproducts formed during DMO hydrogenation. Methanol is recovered from an intermediate distillation column and is recycled to the nitrite-regeneration section.
/(7) and (8)
The recovered NO stream from the carbonylation section is mixed with O2 and contacted in a reactive absorber with methanol, which is recycled from the purification section, as well as from a distillation column downstream. These chemicals react to produce methyl nitrite and water. The top product stream from the nitrite reactor is partially condensed to remove most of its water and the resulting methyl-nitrite-rich stream is recycled to the carbonylation section. The reactor bottom product is directed to a water-removal distillation column.
2) Draw block diagram of EG from synthesis gas via dimethyl oxalate.
NO
CO

MN DMO
O2 H2O ME H2


MEG
Product


3) Comment on advantage and disadvantage of hydration, carbonylation and Shell OMEGA technologies.
Hydration
The beneficial effects of increasing the water recycle on MEG yield start to decrease rapidly above water/EO ratios of 10-15. Accordingly, in the design of the economically optimum glycol plant, the improved MEG yields resulting from increasing the water recycle are balanced against increased capital and utility costs.
Carbonylation
The pressure of the process is higher than that of the conventional design so that the diameter of the main unit and pipes is reduced to save costs. Reactors in the heat transfer carbonylation process are very well-suited to the large scale of each production line. The catalyst has better selectivity, higher conversion yield and longer service time.
Shell OMEGA technologies