Commercial production downstream processing

Production of polymers contributes to pollution during synthesis and after use. A polymer produced by microorganisms is already a commercial product (Biopol). Unfortunately, however, cellular synthesis remains limited by the cost of downstream processing and the fact that the synthesis is aqueous-based, and it is impossible to perform the synthesis in the absence of a solvent. Recent research describes an enzyme-catalyzed polymer synthesis in which there is no solvent. This bulk polymerization mirrors conventional synthesis but eliminates the needs for extremes of temperature and corrosive acid catalysts. This represents the first rapid and efficient synthesis of polyesters from bulk polymerization under ambient conditions with very low concentrations of a biocatalyst (Chaudhary et al., 1997). 

Significant effort is underway in the United States to develop and commercialize coal gasification processes for producing gaseous fuels One of the major obstacles in the development of such a process is the presence of undesirable contaminants in the product gas stream. The major contaminant in coal gasification is hydrogen sulfide (H2S), which is toxic, poisonous to downstream catalysts and extremely corrosive in nature. Control of H2S in the fuel gas to a safe level is therefore essential. The H2S removal requirements are even more critical when the fuel gas is used in combined cycle power generation or in fuel cells. 

The reason for this lack of experience in large scale purification is quite simple downstream processing is avoided so as to minimize the production cost of ionic liquids. On a commercial scale separation processes needed for purification can be assumed to be more costly than improvements in the synthesis stage [114],... 

Winkler process, the Koppers-Totzek process, and the Texaco process. Downstream adjustment and treatment of the raw product gases is required when these processes are used to supply feedstock or cofeedstock to a typical low-pressure methanol process operating at 220 to 270°C and 5.066 to 10.132 MPa (50 to 100 atm). A few of the operating details of these and other commercial coal gasification processes are presented here. 

Besides that, fermentation can only be industrially attractive if the process provides highest yields and exhibits an efficient isolation and purification process (downstream processing) with only minimal product losses. Additionally, suitable substrates must be commercially available at low cost. Finally, the generation of flavours by fermentation in bioreactors will only be profitable if the desired product, be it a pure substance or a complex flavour extract, is not obtainable with comparable quality by inexpensive classical techniques. 

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