Composition of syngas differs because of difference of raw materials used to produce syngas. It usually can’t meet the needs of synthetizing products. For example: raw material of synthetic ammonia gas requires H/N2=3, so nitrogen in the air is needed to introduce into syngas. Production for methanol requires syngas to have ratio of H2/CO = 2 or (H2 - CO2) / (CO+CO2) = 2. For alcohol production, it needs H2/CO = 1; while for production of formic acid, oxalic acid, acetic acid and phosgene, only carbon monoxide is needed. Because of these requirements, components of syngas need to be adjusted. The main method is to use water gas reaction (conversion reaction) to reduce carbon monoxide and improve hydrogen.
Production and application of syngas is very important in the chemical industry. A series of chemical products can be produced from syngas, mainly including:
Ammonia and products made of it.
The most important chemical product made from syngas is ammonia, which is produced by the pressure reaction of hydrogen in syngas and nitrogen in the air. Urea, ammonium salt (such as nitrogen fertilizer and compound fertilizer), nitrate, urotropine, melamine are all made from ammonia, and they are important chemical raw materials.
Methanol and products made of it.
Methanol is the second major product that are made of syngas. It is produced by reaction of carbon monoxide and hydrogen with catalyst. Its use is very extensive:
- Use methanol to produce acetic acid is the main method for acetic acid production;
- Methanol is changed into formaldehyde after oxidative dehydrogenation, and further it can be changed into Urotropine, both of which are important raw materials of polymer chemical industry;
- To produce acetic anhydride by carbonylation of methyl acetate is considered to be the most economical method for the production of acetic anhydride;
- Other products include: use Ethylene glycol diacetate to produce vinyl acetate, use methanol to produce low carbon olefin, use methanol homologation to produce ethanol, and use methanol to synthesize ethylene glycol.
Hydroformylation products.
Hydroformylation products is also called oxo-synthesis products, including products made by Hydroformylation reaction of straight chain and branched chain C2 ~ C17 and syngas. Oxo-synthesis produces aldehyde, and then produces alcohol after further catalytic hydrogenation. They are important raw materials for producing plasticizer.