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 (C 10 -C 20 ) from synthesis gas (CO ? H 2 ) through hydrocracking of wax ([C 21? ) was carried out in a dual-bed reactor. Co/TiO 2 catalyst was used in the first-bed reactor to produce wax from synthesis gas, and a mesoporous Pd-alumina composite catalyst (Pd-Al 2 O 3 ) 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/Al 2 O 3 ) was also examined as a second-bed catalyst. The catalytic performance of PdAl 2 O 3 and Pd/Al 2 O 3 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-Al 2 O 3 and Pd/Al 2 O 3 catalysts in the secondbed reactor served as an efficient catalyst for hydrocracking of wax to middle distillate. Furthermore, Pd-Al 2 O 3 catalyst showed a higher selectivity for middle distillate than Pd/ Al 2 O 3 . The enhanced catalytic performance of Pd-Al 2 O 3 for hydrocracking of wax to middle distillate was due to high Pd dispersion and high Pd surface area. Large medium acidity of Pd-Al 2 O 3 catalyst was also responsible for its high catalytic performance in the hydrocracking of wax to middle distillate.

Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

“…There is about 45 wt% CNTs in the catalyst. The high percentage of CNTs offers large surface area for catalysts anchoring, leading to high and uniform catalysts dispersion, thus improving catalyst selectivity [26].…”

“…The role and importance of catalysts in the hydrocracking processes has been intensely studied [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Generally, the hydrocracking catalysts composed of noble metals or transition metals paired with a mesoporous support have dual functions in the reaction process.…”

“…The most conventional catalysts are NiW, NiMo, and CoMo bimetallic paired on a number of supports, including zeolite, silica-alumina, and alumina [19][20][21][22]. Recently, Pd-based catalysts have also been widely used due to their high activity on hydrocracking sulfur-free heavy hydrocarbons [24][25][26][27]. Besides the catalyst compositions, it was also found that the selectivity of a catalyst highly depends on the support materials and dispersion of metals in the supports [16,26].…”

“…Recently, Pd-based catalysts have also been widely used due to their high activity on hydrocracking sulfur-free heavy hydrocarbons [24][25][26][27]. Besides the catalyst compositions, it was also found that the selectivity of a catalyst highly depends on the support materials and dispersion of metals in the supports [16,26]. Due to specific interaction between metals and supports, different supports can result in distinctive results.…”

Effect of metal loading on activity, selectivity and deactivation behavior of Pd/silica–alumina catalysts in the hydroconversion of n-hexadecane

“…The waxy products of the FTsynthesis are characterized by the absence of sulfur compounds. For this reason, noble metals such as Pt and Pd or PtPd alloys, which would otherwise be poisoned, can be used in hydrocracking catalysts, and provide high selectivity to middle distillate [11][12][13][14][15][16][17][18][19]. Due to the high content of linear paraffins in FT-waxes, the resulting fuels are characterized by a high cetane number (good combustion properties).…”