Yang Wang,Xinbao Li,Pan Li,Xinbo Zhu,Geng Chen,Yingying Zhu
Graphical Acetic acid is a main component of biomass pyrolysis oil. A high yield of hydrogen is obtained through steam reforming of acetic acid over a tungsten-modified Co/Al 2 O 3 catalyst. The interaction between the reactants and the catalyst surface is enhanced. Steam reforming of bio-oil is a promising green hydrogen production technology. Experimental and theoretical calculations have been carried out to study the performance of Co/Al 2 O 3 catalysts doped with tungsten (1–10 wt%) for bio-oil model compound acetic acid steam reforming. The maximum acetic acid conversion of 95.4 % and H 2 yield of 93.5 % were obtained over the 15Co-5W/Al 2 O 3 catalyst under the optimized reaction conditions of temperature=550 °C, steam to carbon ratio=5 and the gas hourly space velocity of 15,780 h −1 . The feeding capacity of the catalyst was improved by 2.3 times by the addition of 5 wt% W compared to that of the non-W-added Co/Al 2 O 3 catalyst. Catalyst characterizations by BET, XRD, H 2 -TPR, XPS, HRTEM, and SEM were performed. The results showed that high activities were maintained over 20 h on the 15Co-5W/Al 2 O 3 catalyst. A little filamentous coke was formed on the spent catalyst surface, and the agglomeration rate of active Co was relatively low. Density functional theory calculations confirmed that the adsorptions of CH 3 COOH and H 2 O on the catalyst were enhanced by the addition of W.
Ceria has absorbed extensive interests in functioning as catalysts for low-temperature (LT) selective catalytic reduction (SCR) of NOx due to its abundant surface oxygen species and salient redox property. The mechanistic interpretations of how such redox property contributes to its LT-SCR activity, however, still remain debated. Here, we use a model tungsten-promoted ceria catalyst (WO 3 /CeO 2 ), known as preeminent in LT-SCR reactions, and combine steady-state kinetic, structural characteristic and in situ spectroscopic experiments with theoretical treatments to reveal the mechanistic connections between NO oxidative activation and LT-SCR turnovers. We show that, compared with NO oxidation to NO 2 , NO oxidative activation to nitrite intermediates is both kinetically and thermodynamically more favorable; surface nitrate species are not detected in the present case, indicating their more difficult formation than nitrites. All these results thus suggest the prevalence of NO activation to nitrites over NO to nitrates or oxidation to NO 2 and subsequent occurrence of fast SCR in the WO 3 /CeO 2 -catalyzed LT-SCR reaction. These findings progress the understanding of LT-SCR reaction mechanism on CeO 2 -based catalysts and convey a detailed perspective of different reaction intermediates and their consequences for LT-SCR turnovers, which may contribute to the rational design of catalysts towards further improved LT-SCR activity.
The increasing demand for sustainable biofuels has driven the development of efficient catalysts for hydrodeoxygenation (HDO) and isomerization of bio-oils. This study investigates the performance of a W-modified unsupported MoNiP catalyst for the hydroisomerization of palm oil to produce low-freezing-point biofuels. The MoNiP-W catalyst was synthesized via a one-pot method and characterized using XRD, BET, XPS, H 2 -TPR, NH 3 -TPD, Py-IR, and TEM-Mapping. Under optimized reaction conditions (360 °C, 3 MPa H 2 pressure, 3 h −1 LHSV, and 300:1 H 2 /oil ratio), the catalyst achieved 100 % palm oil conversion and a C 5 -C 20 isoparaffin selectivity of 70.6 %. A 240-hour stability test revealed that the catalyst maintained a stable isomerization rate of approximately 60 % without significant deactivation. These results demonstrate the potential of W-modified unsupported MoNiP catalysts for the cost-effective and sustainable production of low-freezing-point biofuels. The enhanced activity is attributed to the synergistic effect between Mo, Ni, P, and W, which optimizes the catalyst’s acidity and promotes hydroisomerization reactions.
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