Catalytic co-pyrolysis of waste vegetable oil and high density polyethylene for
hydrocarbon fuel production
In this study, catalytic co pyrolysis of waste vegetable oil and high density
polyethylene (HDPE) for hydrocarbon fuel production was studied using a ZrO2based polycrystalline ceramic foam catalyst. The CHONS contents of waste
vegetable oil and HDPE were determined via ECS 4010 CHONS elemental analyzer.
The fatty acids composition of waste vegetable oil was measured using GC-MS.
Before GC-MS analysis, fatty acids were turned to fatty acids methyl esters by
means of methylation. The co-pyrolysis was carried out under an inert N2
atmosphere in an autoclave had volume of 300 mL. Nitrogen was bubbled into the
reactor at the rate of 100 mL/min for 5 min and then vented, with the purging
process repeated three times. The heating rate of 10 C/min is maintained and kept
at the pyrolysis temperature for 40 min at revolving speed of 80 r/min. HDPE to
waste vegetable oil ratio of 1:1 is selected and the yields of hydro carbon fuel and
bio-char were calculated. Since the components in the pyrolysis products were
complex, mass spectrograms of these compounds were used for analysis. The fuel
properties were determined according to the ASTM methods.
The effects of catalyst loading on the yield and composition of the hydrocarbon fuel
were investigated at 430 C with the HDPE to waste vegetable oil ratio being 1:1
under various catalyst dosages of 0 wt. %, 5 wt. %, 10 wt. %, 15 wt. % and 20 wt. %
but Experimental results indicate that at the catalyst dosage of 15 wt. %, the
proportion of alkanes in the hydrocarbon fuel reached 97.85 wt. %, which improved
the fuel quality. The results indicated that hydrocarbon fuel yield increased while
the bio-char and gas yields decreased with increasing HDPE to waste vegetable oil
ratio. The results indicated that the calorific value of hydrocarbon fuel was higher
than that of biodiesel. Moreover, the density and kinematic viscosity of
hydrocarbon fuel were lower than those of biodiesel. It could be concluded that
hydrocarbon fuel produced from co pyrolysis at 460 C had relatively high
proportions of alkanes and aromatics and low proportions of cycloalkanes, olefins,
and oxygenates and hence was more suitable to be used as a fuel. Therefore,
catalytic co-pyrolysis of waste vegetable oil and HDPE is a promising technology to
produce renewable energy as a substitute of fossil fuels. Also, the hydrocarbon fuel
is probable to be developed into aviation kerosene after further upgrading.