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Two methanol‐to‐dimethyl ether (MTD) process scenarios were proposed to develop new MTD processes with improved energy efficiency by recycling water‐containing methanol to the MTD reactor. In both scenarios, a water‐tolerant K‐modified H‐ZSM‐5 was used in the MTD reactor as the methanol dehydration catalyst. Process modeling was implemented by using Aspen Plus to obtain the quantitative energy analysis results. Both scenarios are mainly comprised of a methanol preheating unit, a methanol dehydration unit, a DME separation unit, a methanol separation unit, and a methanol recycling unit. The two modelled scenarios have differing flow paths of the methanol recycle stream. That is, in option 1, after separating DME, a portion of the water‐containing methanol was recycled directly to the MTD reactor without entering the methanol separation unit. Whereas, in option 2, all of the water‐containing methanol was sent to the methanol separation unit. However, the less‐purified methanol was obtained and recycled. The process performance of both proposed scenarios was investigated by varying the recycle ratio or the recycled methanol purity in scenarios 1 and 2, respectively. Compared with the conventional γ‐Al2O3 based MTD process, both of the proposed scenarios were found to be more beneficial in saving both energy and capital cost, which can be seen from the high energy saving rate and smaller equipment size of the separation units in the newly proposed MTD process scenarios 1 and 2. Energy saving of the newly proposed MTD process scenarios was realized by using water‐tolerant K modified HZSM‐5 as the methanol dehydration catalyst and recycling water‐containing methanol to reduce the total heat duty. [ABSTRACT FROM AUTHOR]

In this article, the hydrothermal stability and change in the physicochemical properties of supported cobalt catalysts modified with Zn, P, and Zr have been studied for slurry‐phase Fischer–Tropsch synthesis (FTS) at 230°C and 2.0 MPa. The Co/P/γ‐Al2O3 exhibited weaker interactions between cobalt oxides and alumina support than other catalysts. The support of all the Co catalysts underwent phase transformation of γ‐Al2O3 into boehmite (AlO(OH)) during hydrothermal treatment at 250°C for 12 h, except Co/P/γ‐Al2O3, which was hydrothermally stable in the presence of H2O. The initial CO conversion increased with increasing number of Co surface sites during FTS. However, CO conversion decreased when H2O was cofed, causing a shift in product distribution from C2–C4 to C5+ hydrocarbons. The CO conversion and product distribution were partially reversible at 0–42.7% H2O in the feed stream. The lower adsorption capacity of H2O on the catalysts caused higher CO conversions under H2O‐rich condition. The catalytic activity of Co/P/γ‐Al2O3 was least affected by the co‐fed H2O, while that of Co/Zr/γ‐Al2O3 was strongly influenced by H2O concentration in the feed stream. The Co/P/γ‐Al2O3 did not exhibit phase transformation of γ‐Al2O3 to AlO(OH) during slurry‐phase FTS. [ABSTRACT FROM AUTHOR]

The role of Gd as a coke inhibitor was studied for the methanol-to-hydrocarbons reaction. It was revealed that thin films of gadolinium oxide covered the ZSM-5 crystals and that the Gd atoms that were uniformly dispersed on the surface enhanced the basicity of the parent ZSM-5. These synergetic effects improved the durability of the acidic function and diminished the growth of coke precursors, which resulted in an increased lifetime of the catalyst. [ABSTRACT FROM AUTHOR]

A phosphorous-modified Al2O3 support was prepared by the impregnation method and applied for the preparation of cobalt-based Fischer-Tropsch synthesis (FTS) catalysts (Co/P-Al2O3), which were calcined at different temperatures. The Co/ P-Al2O3 showed a significant increase of thermal stability with a higher catalytic performance without severe deactivation even above a calcination temperature of 600℃ compared with the unmodified Co/Al2O3. These findings are explained by the suppressed cobalt aluminate formation and less pronounced aggregation of cobalt particles. The suppressed aggregation of cobalt particles is attributed to the localized presence of aluminum phosphate by forming a thermally stable metal-phosphorous oxo-species on Al2O3 surfaces thus suppressing the migration of cobalt particles to the outer pore mouths of the support. These effects significantly enhance the catalytic activity with a higher thermal stability of the catalysts. [ABSTRACT FROM AUTHOR]

The influence of carbon-silica hybrid supports on cobalt catalysts in Fischer-Tropsch synthesishas been investigated. Mesoporous carbon-silica hybrid supports were synthesized through a hydrogen-bonding-assisted self-assembly route by loading different amounts of silica (0 to 45 %) as a framework composition with mesoporous carbon. These carbon and hybrid supports were then impregnated with 15 wt. % cobalt and the resulting catalysts were characterized by various physicochemical, gravimetric, and spectroscopic methods. The dispersion of silica in the framework of mesoporous carbon modified the surface chemistry and enhanced the wetting properties of the support. Hence, the dispersion and reducibility of cobalt over the hybrid supports increased compared to those of the carbon-supported catalyst. However, above the optimum silica incorporation of 34 %, the possibility of phase separation and structural transformation of silica at the high carbonization temperature decreased the dispersion and reducibility of the supported Co catalysts. The carbon-supported catalyst showed a quick drop in the activity during the initial stages of the reaction due to the migration of cobalt particles over the hydrophobic and inert support surface. On the contrary, carbon-silica hybrid supports inhibited the mobility of cobalt particles and produced a higher density of active Co0 sites, leading to a higher initial activity. Carbon-silica-supported catalysts with a silica content of up to 34 % were found to exhibit excellent steady state Fischer-Tropsch synthesis activity and C5+ selectivity compared to only carbon and carbon-silica-supported catalyst with >34 % silica incorporation. [ABSTRACT FROM AUTHOR]

Particle dispersion and fluctuations were investigated in a liquid-solid fluidised bed with viscous liquid media by employing the relaxation method based on the stochastic model. The bed expansion or contraction during the transient state was analysed by means of the histogram of pressure drop variation with elapsed time. The relaxation behaviour of the liquid-solid fluidised bed appeared to be heterogeneous followed by homogeneous expansion or contraction. Effects of liquid velocity ( UL), particle size ( dP), liquid viscosity ( µL) and liquid holdup or bed porosity ( εL) on the fluctuating frequency ( F) and dispersion coefficient ( DP) of fluidised solid particles were examined. The values of F and DP increased with an increase in dP but decreased with µL and exhibited local maxima with variations of UL and εL. The flow pattern of solid particles could be changed from uniform or pseudo-homogeneous to turbulent random behaviour with an increase in the liquid velocity and liquid holdup or bed porosity. © 2012 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

A disulfide/thiolate (T2/T−) redox-couple electrolyte, which is a promising iodine-free electrolyte owing to its transparent and noncorrosive properties, requires alternative counter-electrode materials because conventional Pt shows poor catalytic activity in such an electrolyte. Herein, ordered mesoporous tungsten suboxide (m-WO3− x), synthesized by using KIT-6 silica as a hard template followed by a partial reduction, is used as a catalyst for a counter electrode in T2/T−-electrolyte-based dye-sensitized solar cells (DSCs). The mesoporous tungsten suboxide, which possesses interconnected pores of 4 and 20 nm, provides a large surface area and efficient electrolyte penetration into the m-WO3− x pores. In addition to the advantages conferred by the mesoporous structure, partial reduction of tungsten oxide creates oxygen vacancies that can function as active catalytic sites, which causes a high electrical conductivity because of intervalence charge transfer between the W5+ and W6+ ions. m-WO3− x shows a superior photovoltaic performance (79 % improvement in the power conversion efficiency) over Pt in the T2/T− electrolyte. The superior catalytic activity of m-WO3− x is investigated by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization curve analysis. [ABSTRACT FROM AUTHOR]

Our zirconium phosphate (ZrP)-promoted Ru/Co/ZrP/SiO2 catalyst reveals a high catalytic activity and stability during Fischer-Tropsch synthesis. Surface modification with ZrP on SiO2 support with an appropriate amount of phosphorous component prevents cobalt particle aggregation and enhances its stability. These positive effects of ZrP are mainly induced by the spatial confinement of cobalt particles in a thermally stable ZrP matrix, and the catalytic performance was greatly improved when the P/(Zr+P) molar ratio was 0.134 on the CoZrP(0.5) catalyst. [ABSTRACT FROM AUTHOR]

The Cover picture shows that carbon deposition and coke growth are inhibited by the gadolinium effect on the ZSM‐5 surface. In their Communication, S. Kim et al. explain a role and nature of gadolinium as a coke inhibitor when it applied the ZSM‐5 catalyst for methanol‐to‐hydrocarbon reaction. Gadolinium oxide thin films covered the ZSM‐5 crystals, and gadolinium atoms uniformly dispersed on the surface enhanced the basicity of the parent ZSM‐5. These synergetic effects improve durability of the acidic function and diminish growth of coke precursors, resulting in an increased catalyst lifetime. More information can be found in the Communication by S. Kim et al. on page 1567 in Issue 9, 2017 (DOI: 10.1002/cctc.201601559). [ABSTRACT FROM AUTHOR]