Production of marine distillate fuel oil from waste polypropylene

Abstract

A semibatch distillative thermolysis of polypropylene waste under 25, 40, 60 and 80 bar was performed. The yield of the resulting products and the distillation characteristics of the liquid thermolysis products depending upon the process conditions have been investigated. It was determined that as the pressure of the thermolysis process increased from 25 to 80 bars, the yield of the liquid product decreased from 74.7 to 62.6 %, whereas the yield of the gaseous product increased by 8.3 to 21.3 %. The liquid product obtained under higher pressure had more flat distillation characteristics, especially the distillate that boils off beyond 40 %, composed of lower molecular mas compounds. In order to assess the potential yield of thermolysis products for the production of the marine distillate fuel, there was set a dependence of the flash point of the liquid fraction upon the light component cut content. According to the ISO 8217:2012 specification, the quality characteristics of the obtained fractions have been investigated. The GC of the lightest liquid fraction (naphta), not suitable for a marine fuel because of a too low frash point, showed the predominance of isoparaffins – a useful feedstock for gasoline production. Carbon residue values of the liquid thermolysis product do not comply with the standard specification because of a significant content of alkenes and alkadienes. The latter at a higher temperature are particularly apt to polymerization, cyclization, and aromatization. During these reactions, carbon residue precursors are formed. The calculated yield of the obtained polypropylene thermolysis liquid fractions compatible with distillate marine fuels of summer and winter grades was 53 % for the ISO-F-DMX category and 41 % for the ISO-F-DMA and ISO-F-DMB categories which are used in the Lithuanian shipping fleet. DOI: http://dx.doi.org/10.5755/j01.ct.63.1.4516