ACID PROPERTIES OF SILICA-ALUMINA CATALYSTS AND CATALYTIC DEGRADATIONOF POLYETHYLENE

A relationship between the acid strengths and amounts of silica-alumin a catalysts and the compositions of products formed by the catalytic d egradation of polyethylene at 673 K was studied. The acid strengths an d amounts were varied with SiO2/Al2O3 weight ratio in the catalysts. A lthough the resulting products consisted of gases, oils, and wax, the fraction of gases increased, and, inversely, the fraction of oils decr eased, as the acid amounts over the catalysts increased The fraction o f aromatics in the oils was enhanced, however, as the acid amounts ove r the catalysis increased, which was discussed in terms of the acid ty pes: Bronsted and Lewis acids generated on silica-aluminas. Since some inorganic compounds such as MgO, ZnO, TiO2, and carbon are incorporat ed into plastics, the catalytic activities and selectivities of these additives for polyethylene degradation were also discussed.