Aromatization of palm fatty acid distillate (PFAD) over HZSM-5 catalysts

Abstract

The catalytic reaction of palm fatty acid distillate (PFAD), a by-product from crude palm oil refining process, was investigated over HZSM-5 catalysts to produce petrochemical aromatics. The catalytic reaction was operated in a fixed-bed reactor system at 500 ℃ 1 atm, and WHSV of 5 h⁻¹. By varying SiO₂/AI₂O₃ ratios (23, 30, and 50). HZSM-5 (30) exhibited the highest aromatic yields with significant amount of light paraffins. Although HZSM-5 (23) provided the highest Br0nsted acidity, the hydrocarbons of this catalyst led to the competitive adsorption between intermediate hydrocarbons and water. In order to improve the aromatics yield, Ga and Zn were loaded on HZSM-5 (30) catalysts by incipient wetness impregnation (IWI) method. The presence of Zn and Ga HZSM-5 (30) catalysts preferentially promoted the dehydrogenation activity, resulting in lower light paraffins and higher aromatics yiold. Even though both catalysts enhanced the aromatization activity, the oxygen removal pathways were apparently different. Over HZSM-5 and HZSM-5, the decarbonylation reaction occurred by the presence of strong Br0nsted acid site, resulting in high amount of CO production. On the other hand, Zn/HZSM-5 promoted the decarboxylation reaction, leading to the great amount of CO₂ and H₂ productions.