Catalytic cracking of polypropylene and polyethylene using zirconium/aluminium oxide-pillared clay

Abstract

Aluminium oxide-pillared clay was prepared by intercalation between ionic precursors and raw clay suspensions with any previous purification and homoionisation of clay prior to pillaring. The intercalated product was calcined at 500 degress celsius for 1h. And then was impregnated with various amounts of zirconium (from 0.0 to 5.0 wt%) by slurry method and calcined at 450 degress celsius for 4h. The basal spacing, the surface area, the aluminium contents and the vibrational of chemical bonds in different environments were determined by XRD, N[subscript 2] -BET, ICP-AES and IR respectively. The synthesized aluminium oxide-pillared clay had a basal spacing and surface area of 16.3 aungstrom and 189 m[superscript 2] g [superscript-1]. The basal spacings of zirconium doped aluminium oxide-pillared clays(zirconium/aluminium oxide-pillared clays) at 15.6 aungstrom were lower than aluminium oxide-pillared clay. Increasing amount of zirconium, the surface area decreased from 188 to 131 m [superscript 2] g [superscript -1]. When compared catalytic cracking reaction between two type of polymer observed that polyethylene more difficult than polypropylene. When aluminium oxide-pillared clay and zirconium/aluminium oxide-pillared clays were used as catalysts, the conversions of both polymers greatly increased compared to that in the absence of a catalyst. The cracking reaction was carried out in a semi-batch reactor with a mixture of catalyst and plastic at 350-450 degress celsius. The effects of reaction temperature, reaction time, type of catalyst and catalyst per plastic ratio were discussed. The activity and selectivity of catalysts modified by impregnation of zirconium were higher than the original clay catalyst. Gaseous and liquidous hydrocarbon products were analysed by GC. The optimal condition for PP cracking was reaction time of 1.0 h, reaction temperature of 380 degress celsius, 2.0wt%zirconium/aluminium oxide-pillared clay as a catalyst and 10.0 wt% catalyst per plastic ratio. The major components of gas fraction were C [subscript 5] + and C [subscript 3] (propene). Liquid fractions were in he range of C [subscript 7] to C [subscript 9] with the boiling point range compared to that of standard gasoline. The optimal condition for PE cracking was reaction time of 1.5 h, reaction temperature of 410 degress Celsius, 2.0 wt%zirconium/aluminium oxide-pillared clay and 10.0 % catalyst per plastic ratio. The major components of gas fractions were C [subscript 5+], C [subscript 4](n-butane), C [subscript 3] (propene), C [subscript 2] (ethane) and C [subscript 1] (methane). Liquid fractions were in he range of C [subscript 7] to C [subscript 10].