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Effect of pore-size distribution on Ru/ZSM-5 catalyst for enhanced N2 activation to ammonia via dissociative mechanism

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Journal of Rare Earths 2020年第8期38卷 873-882,I0002页

作者： Jihui Cai Congying Wang Yi Liu Jun Ni Bingyu Lin Xiuyun Wang Jianxin Lin Lilong Jiang National Engineering Research Center of Chemical Fertilizer Catalyst Fuzhou UniversityFuzhou 350002China

In the present study,a series of Ru/ZSM-5 catalysts with different pore-size distributions were prepared and investigated for NH3 *** studies indicate that Ru/ZSM-5-Mic with micropore structure exhibits superior NH3 synthesis rate,which is much higher than those of Ru/ZSM-5-Mac(with macroporous structure)and Ru/ZSM-5-Mes(with mesoporous structure)catalysts.A series of TPD experiments demonstrate that pore-size distributions play an important role in N2 adsorption and activation over Ru/***,the addition of La significantly promotes the NH3 synthesis performance over Ru/***,in situ DRIFTS studies indicate that the main intermediate species over Ru/ZSM-5-Mic are-NH2,and most of the surface hydrogen species desorb following the H2O-formation pathway.

关键词： Ru/ZSM-5 La Ammonia synthesis pore-size distribution Reaction pathway Rare earths

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Experimental Study on pore distribution Characters and Convert Rate of CaO

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Journal of Thermal Science 2005年第1期14卷 87-91页

作者： LiJIA YanyanZENG TaoZHANG DepartmentOfPowerEngineeringSchoolofMechanical ElectronicControlEngineeringBeljingJiaotongUniversityBeijing100044China.

During the reaction between calcium sorbents and SO2, calcium sorbents are first calcined and converted into CaO. CaO can be obtained by calcining Ca(OH)2or CaCO3. The porosity of the sorbent is increased because of calcination and is decreased because of sulfurization. In the calcination process H2O or CO2 is escaped from the particles and pores are formed in particles. The reaction or convert rate of CaO is influenced strongly by the pore structure characters. From Ca(OH)2 to CaO the escape velocity of H2O or its mass transfer is one of the key factors influencing the pore forming. During calcination process different healing velocity, different heating time and temperature were suggested. The temperature rising rate and calcining temperature play important role to the pore structure. The convert rates of CaO obtained through different calcining conditions were investigated experimentally. Some interesting results were showed that the calcium utilization of CaO particles is determined not only by the special surface area and total pore volume, but also by pore-size distribution. The main factor influencing the sulfation is the pore diameter distribution at lower sulfation temperature. For higher reaction temperature specific volume is the important reason. But pore-size distribution is strongly influenced by heat flux and temperature in the calcining process.

关键词： pore-size distribution calcine desulfurization.

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A New Model for Soil Consolidation Based on Microstructure

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Journal of Shanghai Jiaotong university(Science) 2011年第1期16卷 78-82页

作者：张季如陶高梁 School of Civil Engineering and Architecture Wuhan University of Technology

This paper introduces a new means to predict consolidation deformation of soil from its *** on a kind of pore-size distribution density function,a fractal model for soil consolidation is *** this model,the relation between macroscopic deformation and microcosmic pore property of soil is *** order to justify this proposed model for soil consolidation,consolidation experiments of soft clay are ***,the microstructure of soft clay unconsolidated and consolidated under every pressure is studied by a scanning electron microscope (SEM).The results show that the proposed model for soil consolidation is valid in predicting consolidation deformation.

关键词： soil consolidation microstructure fractal model pore-size distribution

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Mathematical Modeling for Optimizing the Structural Properties of Catalysts Used for Series Multiple Reactions

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Journal of Applied Mathematics and Physics 2024年第11期12卷 3923-3940页

作者： Violeta Martínez Farhang Shadman Departamento de Ingeniera de Procesos y Ciencias Ambientales Universidad Centroamericana Jos Simen Caas El Salvador San Salvador Department of Chemical and Environmental Engineering University of Arizona Tucson AZ USA

One of the main challenges in the design and operation of catalytic reactors for reactions with multiple paths/steps is the occurrence of undesirable reactions and products. In these cases, two main factors need to be considered in the reactor performance: the “conversion” of the feed and the “selectivity” of the process, which is the conversion split between the desired and the undesired products. In this work, a comprehensive model is developed and used to assess the impact of pore-size distribution (PSD) on both conversion and selectivity in series catalytic reactions. In particular, the evaluation considers the effects of various combinations of micro- and macro-porosity, the potential advantages of radial variation of the porosity in the catalyst pellets, and the effect of pellet size. Results show that, for series reactions, when the formation of the desired product is followed by an undesirable degradation reaction, higher porosity in pellets, particularly in the micro-range, gives higher overall conversion, but lowers selectivity towards the formation of the desired product. Selectivity in these pellets can be improved by using a non-uniform PSD that provides a radial gradient of effective diffusivity in pellets increasing from the center to the outer pellet surface. The pellet size also has a significant effect, and larger pellets show lower selectivity in most cases. In general, conversion and selectivity trends move in opposite directions with changes in PSD and the pore structural properties of pellets. Therefore, finding the optimum design of pellets is an optimization process that requires process modeling. Consequently, selecting the best catalyst properties involves optimization, and the needed tool is a comprehensive mathematical model that takes into account the details of mass transport and reaction kinetics in the catalyst pellets. Our primary objective has been the development of a flexible mathematical model that would be applicable to a wide r

关键词： Series Catalytic Reactions Process Simulation pore-size distribution Selectivity Non-Uniform Catalyst Pellets

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