The Role of Solvent and Catalysts on Co-Liquefaction of Coal and Waste

Abstract

It is predictable that liquid fuels will be needed for long distance transport sector for quite some years. Thus, it is imperative to find alternative fuels to reduce the dependency on petroleum derived fuels and to decrease the negative environmental impact. Co-liquefaction of coal and wastes, like plastics, to produce liquid fuels and raw materials for several industries may play an important role in the near future, because it will decrease the problems associated with the dependency of only one raw material and also it will allow taking profit of the suitable properties of each one, while diluting the disadvantageous characteristics of coal. The use of plastics, namely polyethylene (PE) favoured coal liquefaction, as PE macromolecules are easier to break down and to form smaller liquid molecules than coal. To improve the production of liquid compounds by coal liquefaction solvents with different hydrogen donor capabilities were tested, such as: methylnaphthalene and tetralin. Tetralin led to the highest liquid yields and conversion, due to its hydrogen donor capacity. Some commercial available catalysts, like FCC (Fluid Catalytic Cracking) and Co-Mo based were also tried. Coal impregnated with some metals like iron (Fe) and molybdenum (Mo) was also tested. Impregnated coal, especially with Mo showed to have a better performance than the commercial catalysts. Liquid yield obtained during co-liquefaction of coal and PE when coal was impregnated with Mo was around 66 wt%. The use of tetralin allowed increasing this value around 44 %.