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The influence of isotypic crystal structures on adsorption and diffusion of methane in all-silica LTA, SAS and ITE zeolites is studied. Results obtained with the experimental structures are compared with structure predictions and approximations that are commonly employed. The results indicate that diffusion coefficients are much more affected than Henry coefficients. In fact, orders of magnitude deviations in the diffusivity can be observed and a systematic parameter study finally gives rise to the correlation between structure sensitivity and diffusion-window size. [ABSTRACT FROM PUBLISHER]

• A continuum model is developed to simulate DRM in catalyst pellets. • The preferred pore diameter is 300 nm, and the optimal porosity is 0.51–0.64. • The bidisperse catalyst is 56–175% more active but uses 10–18% less catalyst. • Engineering pore structure is needed in the design of DRM catalyst pellets. Enhancing the utilization and activity of catalytic materials is crucial in designing catalysts for industrial use. This work achieves these performance enhancements in Rh/Al 2 O 3 catalyzed dry reforming of methane (DRM) at the catalyst pellet level, through engineering catalyst pore network structure. A continuum model, describing the coupled mass, heat transfer and reactions, is developed to optimize the monodisperse and bidisperse catalyst pellets under different temperatures, pressures, and CH 4 /CO 2 ratios. The results show that the preferred pore diameter for the monodisperse catalyst and macropore diameter for the bidisperse catalyst are all 300 nm, above which Knudsen diffusion is not important. Besides, the optimal porosities for the monodisperse and bidisperse catalysts are in the ranges of 0.51–0.59 and 0.61–0.64, which is the result of the trade-off between diffusion and reaction. The optimal bidisperse catalyst can be 56–175% more active but uses 10–18% less catalyst materials when compared to the optimal monodisperse catalyst with the same mesopore size, indicating the great advantage of introducing the optimal macroporosity into mesoporous catalyst pellets for DRM. These results should serve to guide the rational design of industrial catalyst pellets. [ABSTRACT FROM AUTHOR]

Climate change, global warming, fossil fuel depletion and rising fuel prices have created great incentives to seek alternative fuel production technologies. CO 2 transformation to value-added products using renewable H 2 has proven to be an emerging solution to enable this goal. In this regard, three different promising processes, namely methane, methanol and hydrocarbon synthesis via CO 2 hydrogenation are thoroughly discussed. In addition, the influential factors affecting process efficiencies such as catalyst design and mechanistic insight, operating conditions as well as reactor types are investigated, with key pathways that dictate catalyst activity and selectivity of the most promising materials described. Furthermore, a brief overview of the reactor configuration and its crucial role in the improving process viability is analyzed. Accordingly, fixed-bed, fluidized-bed, annular and spherical reactors along with H 2 O/H 2 perm-selective membrane reactors are disscussed for hydrocarbon production. In addition, different reactor configurations are compared to assess the best one that is adjustable depending on the reaction mechanism. Consequently, a corrugated-wall dual-type membrane reactor is proposed as an emerging alternative for CO 2 hydrogenation to value-added products. [Display omitted] [ABSTRACT FROM AUTHOR]