Syntheses, chemical logistics

The second feedstock factor is the use of coal in China. The quantity is vast and the cost is low, both of these positive factors being offset by logistics (it is stranded coal) and concern about the quality of both the feedstock and the impact of the low quality on the environment. Oil has been the feedstock of choice for most of the world since WWII or earlier, except for a few countries, notably South Africa where political factors forced the development of an entire chemical industry based on coal. It has been remarkable to see the development of a chemical industry in China based on coal in perhaps just 10 or 15 years. Coal to olefins (CTO) is a realily there. Synthesis gas is produced from coal and then used to make methanol, which is then converted to olefins (ethylene or propylene). Coal to olefins is happening fast in China, it is happening widely (over three dozen projects are described), and it is likely to be as significant or more significant than the North American shale gas phenomenon. 

Organic solvents are used for a variety of purposes in the chemical industry, e.g. for synthesis of pharmaceuticals, to precipitate materials from aqueous solutions, for cleaning purposes, and for drying of final products. Spent solvents nearly always contain some water. Dehydration is an essential step in their recovery but difficult since most of the more common solvents form azeotropes with water. Final water removal by distillation is then impossible or complicated. Conventional entrainer distillation is not a real option for pharmaceutical or fine-chemical production. The addition and afterwards removal of the entrainer is difficult and the residual concentration will have to be monitored continuously. Furthermore, entrainer distillation systems require a certain minimum capacity to be economical. Quite often this capacity is above the amount of solvent that will have to be treated at a single location. The only solution is then in many cases to ship out the spent solvent and buy fresh one, with all the related problems of logistics and storage. 

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