Catalytic cracking and deoxygenation of cottonseed oil to yield light olefins over lanthanum-impregnated zeolite catalysts

Abstract

This work investigated the production of renewable hydrocarbons from cottonseed oil using catalytic cracking. In a continuous fixed bed reactor, cottonseed oil was catalytically upgraded to light olefins using HZSM-5 zeolite modified with 6 wt% La. The physicochemical characterization of both catalysts was carried out using XRD, BET, NH₃-TPD, DSC-TGA, and FT-IR techniques. The amount of La doped into the microporous HZSM-5 catalyst was altered to optimize its structure and characteristics. The catalytic behavior of cottonseed oil during its decomposition was investigated using a redesigned HZSM-5 catalyst incorporating a rare-earth metal, i.e., lanthanum, in its lattice. The new synthesized catalyst (6 wt% La/HZSM-5) showed improved characteristics in terms of activity along with a reduced reaction condition compared to those of the HZSM-5 catalyst. A significant decrement in the reaction temperature for high cottonseed oil conversion was observed, and the La-doped catalyst showed considerable activity and anti-coking performance compared to the HZSM-5 catalyst. In a time-on-stream experiment conducted at 500 °C for three hours, the optimized conditions produced the maximum light olefin yield (27 wt%) over 6 wt% La/HZSM-5. Considering several olefinic products, propylene–ethylene is noteworthy, whereas CO, CH₄, and hydrogen are among the main gaseous components of the reaction, as confirmed by GC-FID, GC-TCD, GC-MS, and ¹H NMR studies. The study recorded the effect of operational parameters, including temperature and GHSV (0.038–0.38 h⁻¹), on the yield of different compounds. Hence, the catalytic decomposition of cottonseed by microporous zeolite into valuable chemicals could be promising.