Effect of process mode on product yields and selectivity in the catalytic co-pyrolysis of peanut shells and polypropylene using spent fluid catalytic cracking (FCC) catalyst

Abstract

In this study, mixtures of peanut shells (B) and polypropylene (PP) were co-pyrolyzed in two configurations using spent fluid-catalytic-cracking (sFCC) catalyst. The feed ratio was varied to investigate changes in yields and selectivity. The ex-situ configuration generated a higher-quality liquid, less char and more gas yields (1.3 times on an average) than the in-situ mode. Both the operation modes produced similar aromatic compounds; however, the ex-situ bio-oil had a higher monoaromatic fraction. The ex-situ configuration showed more polycyclic aromatic hydrocarbons at higher B and PP loadings, with a maximum yield of ∼44%C at B: PP ratio of 1:2. The ex-situ mode cracked polypropylene more efficiently to short-chain olefins (<C10). The dominant fractions were C9 and C12 in the in-situ and C9 in the ex-situ mode. Co-pyrolysis improved the net hydrogen content of bio-oil. PP showed better aromatics selectivity than low density polyethylene (LDPE) due to the differences in their branched-chains.