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Chinese Journal of Chemical Engineering 2020年第4期28卷 1095-1106页

作者： Xingqiang Zhao Changfeng Yang Mengke Lu Yao Shi Gang Qian Xinggui Zhou Xuezhi Duan State Key Laboratory of Chemical Engineering East China University of Science and Technology130 Meilong RoadShanghai 200237China

In this work,a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction-diffusion behaviors in gas oil hydrodesulfurization(HDS).The non-isothermal reactor model is determined to be reasonable due to non-negligible temperature variation caused by the reaction heat.The reaction rate along the reactor is mainly dominated by the temperature,and the sulfur concentration gradient in the catalyst pellet decreases gradually along the reactor,leading to the increased internal effectiveness factor.For the fixed catalyst bed volume,there exists a compromise between the catalyst reaction rate and effectiveness factor.Under commonly studied catalyst pellet size of 0.8-3 mm and porosity of 0.4-0.8,an optimization of the temperature and catalyst pellet structures is carried out,and the optimized outlet sulfur content decreases to 7.6 wppm better than the commercial level at 0.96 mm of the catalyst pellet size and 0.40 of the catalyst porosity.

关键词： Hydrodesulfurization catalyst pellet Trickle-bed reactor Coupling model Reaction-diffusion behavior

Optimization of catalyst pellet structures and operation conditions for CO methanation

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Chinese Journal of Chemical Engineering 2021年第12期34卷 106-113页

作者： Yiquan Zhao Yao Shi Guanghua Ye Jing Zhang Xuezhi Duan Gang Qian Xinggui Zhou State Key Laboratory of Chemical Engineering School of Chemical EngineeringEast China University of Science and TechnologyShanghai 200237China

A fundamental understanding of the effects of catalyst pellet structures and operation conditions on catalytic performance is crucial for the reactions limited by diffusion mass transfer. In this work, a numerical investigation has been carried out to understand the effect of catalyst pellet shapes(sphere, cylinder, trilobe and tetralobe) on the reaction-diffusion behaviors of CO methanation. The results reveal that the poly-lobe pellets with larger external specific surface area have shorter diffusion path, and thus result in higher effectiveness factors and CO conversion rates in comparison with the spherical and cylindrical pellets. The effects of operating conditions and pore structures on the trilobular catalyst pellet with high performance are further probed. Though lower temperature can contribute to larger effectiveness factors of pellets, it also brings about lower reaction rates, and pressure has little impact on the effectiveness factors of the pellets. The increase in porosity can reduce the pellet internal diffusion limitations effectively and there exists an optimal porosity for the methanation reaction. Finally, the height of the trilobular pellet is optimized under the given geometric volume, and the results demonstrate that the higher the trilobular catalyst, the better the reaction performance within the allowable mechanical strength range.

关键词： CO methanation Numerical simulation catalyst pellet Shape effects Reaction-diffusion behavior

Probing deactivation by coking in catalyst pellets for dry reforming of methane using a pore network model

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Chinese Journal of Chemical Engineering 2023年第3期55卷 293-303页

作者： Yu Wang Qunfeng Zhang Xinlei Liu Junqi Weng Guanghua Ye Xinggui Zhou State Key Laboratory of Chemical Engineering School of Chemical EngineeringEast China University of Science and TechnologyShanghai 200237China

Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.

关键词： Deactivation by coking Dry reforming of methane Pore network model Diffusion limitation catalyst pellet

CFD modeling of reaction and mass transfer through a single pellet: Catalytic oxidative coupling of methane

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Journal of Natural Gas Chemistry 2011年第4期20卷 356-363页

作者： Siavash Seyednejadian Nakisa Yaghobi Ramin Maghrebi Leila Vafajoo Faculty of Chemical Engineering Azad University Tehran South Branch Iran Polymer and Petrochemical Institute

In this study a mathematical model of a small scale single pellet for the oxidative coupling of methane（OCM）over titanite pervoskite is developed.The method is based on a computational fluid dynamics（CFD）code which known as Fluent may be adopted to model the reactions that take place inside the porous catalyst pellet.The steady state single pellet model is coupled with a kinetic model and the intra-pellet concentration profiles of species are provided.Subsequent to achieving this goal,a nonlinear reaction network consisting of nine catalytic reactions and one gas phase reaction as an external program is successfully implemented to CFD-code as a reaction term in solving the equations.This study is based on the experimental design which is conducted in a differential reactor with a Sn/BaTiO3 catalyst（7-8 mesh） at atmospheric pressure,GHSV of 12000 h-1,ratio of methane to oxygen of 2,and three different temperatures of 1023,1048 and 1073 K.The modeling results such as selectivity and conversion at the pellet exit are in good agreement with the experimental data.Therefore,it is suggested that to achieve high yield in OCM process the modeling of the single pellet should be considered as the heart of catalytic fixed bed reactor.

关键词： catalyst pellet oxidative coupling of methane modeling CFD catalytic reactions ethane