An economic analysis of twenty light olefin production pathways

A comprehensive economic analysis of twenty light olefin production pathways has been performed,covering current and promising processes from fossil(petroleum,coal and natural gas)and renewable resources(biomass and CO_(2)).Taking steam cracking of naphtha as the benchmark,this study gives an economic perspective and points out the bottleneck in different olefin production pathways.The assessment indicates that nearly all renewable pathways are economically unattractive currently and the raw material cost accounts for dominant contribution in most pathways,especially in the oil-,natural gas-and CO_(2)-derived pathways.For the ways of methanol-to-olefins and methanol-to-propylene,fossil pathways are cost-competitive according to the date of current Chinese market prices.However,the price of feedstock hydrogen needs to be lowered by 55%to fill the cost gap between CO_(2)-derived pathways and the benchmark.For the ways of oxidative coupling of methane and Fischer-Tropsch synthesis to olefins,fossil pathways enable cost-competitive processes by feedstock price fall,but further process improvement is required to approach benchmark in renewable pathways.Conditionally,a decrease in ethanol price by45%can make ethanol dehydration pathway profitable.In addition,costs can reduce by 4%-23%in different pathways as the production scales expand from 100 to 1000 kt/a,resulting in a change from high cost to economic profit for some of the pathways.The results quantify the need for improvements on feedstock price,scale size and process improvement to achieve competitive production costs.

Anionic polymerization initiated by lithium amides for preparing high molecular weight polyacrylonitrile

Lithium amides have been proved to be effective anionic initiators for the anionic polymerization of acrylonitrile to get high molecular weight polyacrylonitrile in this study. Polyacrylonitrile with weightaverage molecular weight ranging from 1.02 × 10~6 g/mol to 1.23 ×10~6 g/mol (M_w/M_n= 1.9-2.2) could be prepared utilizing lithium amides derived from diisopropylamine, diethylamine, hexamethyldisilazane,dicyclohexylamine, and 2,2,6,6-tetramethylpiperidine as initiators. The polymerization of acrylonitrile proceeded in a homogeneous manner in N,N-di methyl for mamide and insignificant contribution of side reactions was confirmed.