Production of Middle Distillate from Synthesis Gas in a Dual-bed Reactor Through Hydrocracking of Wax Over Mesoporous Pd-Al2O3 Composite Catalyst

Abstract

Production of middle distillate (C10–C20) from synthesis gas (CO + H2) through hydrocracking of wax (>C21+) was carried out in a dual-bed reactor. Co/TiO2 catalyst was used in the first-bed reactor to produce wax from synthesis gas, and a mesoporous Pd-alumina composite catalyst (Pd-Al2O3) was used in the second-bed reactor to produce middle distillate through hydrocracking of wax. For comparison, a Pd catalyst supported on mesoporous alumina (Pd/Al2O3) was also examined as a second-bed catalyst. The catalytic performance of Pd-Al2O3 and Pd/Al2O3 for hydrocracking of wax to middle distillate was tested and compared. It was revealed that selectivity for middle distillate in the dual-bed reactor was much higher than that in the first-bed reactor, indicating that both Pd-Al2O3 and Pd/Al2O3 catalysts in the second-bed reactor served as an efficient catalyst for hydrocracking of wax to middle distillate. Furthermore, Pd-Al2O3 catalyst showed a higher selectivity for middle distillate than Pd/Al2O3. The enhanced catalytic performance of Pd-Al2O3 for hydrocracking of wax to middle distillate was due to high Pd dispersion and high Pd surface area. Large medium acidity of Pd-Al2O3 catalyst was also responsible for its high catalytic performance in the hydrocracking of wax to middle distillate.