(731a) Catalytic Pyrolysis of Waste Automobile Tires to Low Sulfur Fuels

Energy production and utilization is one of the main drivers of human civilization and until we master how to produce and distribute it efficiently and sustainably, the human civilization will always be threaten for survival. Currently, there are millions of tons of organic materials, which are classified as waste because we do not know how to efficiently utilize them to benefit humankind. A classic example is the so-called waste automobile tires, which are ubiquitous in every country. Disposal of these tires are increasingly becoming a challenge because of limited landfills and fire problems. Improperly disposed waste tires can potentially become the sources of diseases such as malaria fever and zika virus because they become breeding grounds for mosquitoes that carry the disease. The traditional disposal methods such as land filling, road applications, playground applications, direct pyrolysis to produce high sulfur heating fuels, and combustion as tire-derived fuels are becoming inadequate because of pollution problems associated with them and the low cost petroleum crude oil prices currently prevailing. In the USA about 300 million tires are disposed of annually either in landfills, combustion, and other disposal methods. Tire pyrolysis is extensively practiced in several countries especially, China and India where they are used to produce tire pyrolysis oils for heating. These oils contain 1-1.35 wt% sulfur, which make them unsuitable for transportation fuels where the sulfur content is typically below 0.5 %. The sulfur content of these oils can be reduced through various sweetening or desulfurization processes, but these unit operations increase the cost of fuel and thus noncompetitive relative to petroleum derived heating fuels. At the USTAR Bioenergy Center we have developed a sulfur-tolerant catalyst for catalytic pyrolysis that effectively removes over 60 wt% of the sulfur in the pyrolysis oil and also removes the chlorine in the butyl rubber liner. Thus, the pyrolysis oil can be easily upgraded to higher value fuel. In general, most waste tire pyrolysis oils reported in literature contain 0.80 – 1.35 wt% sulfur for atmospheric pyrolysis oil compared to 0.38 wt% that we measured for the oils produced from the tire crumbs used for these studies. The oxygen content of the oil was less than 1%, which meant that the oil will need minimal hydrogenation to remove the residual oxygen. The hydrodeoxygenation of the tire pyrolysis oils also converted the residual sulfur to hydrogen sulfide and hence making the fuel sulfur free. The higher heating value (HHV) of the pyrolysis oil was 42.7 Mg/kg and after hydrotreatment increased to 45.7 MJ/kg. The ASTM D86 distillation of the pyrolysis showed 95% diesel fraction while after hydrotreating the diesel fraction was 55% and gasoline fraction was 35%. Thus, the catalytic tire pyrolysis oil would be suitable a marine diesel fuel because of its low sulfur content and high energy content.