Syngas chemistry

Whereas near-term appHcation of coal gasification is expected to be in the production of electricity through combined cycle power generation systems, longer term appHcations show considerable potential for producing chemicals from coal using syngas chemistry (45). Products could include ammonia, methanol, synthetic natural gas, and conventional transportation fuels. 

The incorporation of nitrogen-containing substrates into syngas chemistry offers a route to valuable nitrogen compounds. This field has not been explored extensively. By reacting syngas with ammonia the synthesis of acetonitrile is reported with 40 % conversion and 40-45 % selectivity ( ). Other possible reactions are listed... 

Ci chemistry can no longer be equated only with syngas chemistry. Nature s own C02 photosynthesis and bacterial methane conversion are also Ci conversion processes. We are far from approaching these processes for practical synthetic use efficiently. Production of methane from carbon dioxide (similarly to carbon monoxide) and hydrogen is a feasible process (methanation).80 Similarly, reduction of carbon dioxide with hydrogen to methyl alcohol81 can be readily carried out, and the method has been industrially developed ... 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

Carbon monoxide and syngas play important roles in production of several major petrochemical products. Chemistry based on carbon monoxide is the foundation for both polyurethanes and polycarbonates. Syngas chemistry is used for industrial processes producing a wide range of detergent and plasticizer alcohols. Carbon monoxide also finds its way into a broad array of commodity petrochemicals through its use as feedstock for methanol and acetic acid. 

Shell has been involved in syngas chemistry for many years, giving special attention to the options for the conversion of natural gas into more easily transportable liquid hydrocarbons. The first result of this effort has been the Shell Middle Distillate Synthesis (SMDS) plant commissioned in Malaysia in 1993. This plant makes use of cobalt FT catalyst and tubular reactors in the Heavy Paraffin Synthesis unit (HPS). A simplified flow scheme of this plant is presented in Figure 7. 

Methanol/syngas chemistry for acetic acid/anhydride could possibly be extended to some related intermediates, while Fischer-Tropsch products may fit in with detergent requirements (or provide a cracker feedstock). The Mobil methanol-to-gasoline process is potentially attractive for aromatic hydrocarbons. In view of the importance of polyethylene, the direct conversion of syngas or methanol to lower olefins has also received considerable attention, such that many current cracker-based routes could possibly continue. The possibility of fermentation ethanol re-emerging as an intermediate for chemicals is less clear. 

The use of homogeneous transition metal catalysis in syngas chemistry can be seen for various reasons ... 

Braman, K., Oliver, T.A., Raman, V. Bayesian analysis of syngas chemistry models. Cranbust Theory Model. 17, 858-887 (2013)... 

Once syngas and methanol can be produced viably from renewable resources then established synthetic pathways can be used to produce a whole variety of bulk chemical feedstocks (Scheme 6.16). (There is insufficient space to discuss the details here and readers are invited to consult a textbook of industrial chemistry.) By analogy, syngas and/or methanol will become the petroleum feedstock of the future. 

A major reason for the difference between the target and current technology is the chemistry chosen and the way the flow sheet is put together. At present, CTL processes produce syngas (CO and as an intermediate by gasification of coal, and then convert the syngas into hydrocarbons by the Fischer-Tropsch process. The target for this route can also be calculated. 

Chemistry. Partial oxidation of ethanol (POE) involves reaction between ethanol and oxygen with an appropriate 02/Ethanol molar ratio, up to 1.5 over a suitable metal catalyst for the production of H2 and C02 (eqn (18)). The overall reaction may be considered as a combination of partial oxidation to syngas (eqn (19)) coupled with CO oxidation (eqn (20)). The complete oxidation of ethanol will produce a mixture of H20 and C02 with a huge heat release (eqn (21)). 

Indirect syngas conversions/methyl formate chemistry... 

However, based on cost and lack of chemistry, it appears very unlikely that formaldehyde will develop into a major syngas intermediate, such as methanol is and methyl formate could become. 

Syngas and methanol. Methanol is one of the top industrial chemicals today. It is produced on a very large scale from fossil-derived syngas by use of a Cu-Zn-Al-oxide catalyst, however, it can of course also be produced in a similar manner from bio-derived syngas. Methanol (and also syngas) can be used as a feedstock to produce dimethyl ether via catalytic dehydration. However, the chemistry involved in these processes is well-known, and will not be considered here, since it has been extensively dealt with in detail elsewhere. ... 

C. .-Chemistry. A great deal of research has been undertaken on the development of PGM catalysts for the manufacture of chemicals and fuels from syngas, a mixture of CO and H2 obtained from coal gasification (see Coal CONVERSION PROCESSES). 

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