Process of CH4-CO2 reforming over Fe/SiC catalyst under microwave irradiation

Exploring Simultaneous Upgrading and Purification of Biomass−Gasified Gases Using Plasma Catalysis

Tar and substantial CH4 and CO2 are contained in gasified fuels, which pose an obstacle to direct chemical synthesis, and this is a predominant challenge for biomass gasification technology. Herein, a packed−bed dielectric barrier discharge (DBD) reactor was built for simultaneous CH4 dry reforming and tar removal with a La−Ni/γ−Al2O3 catalyst. The interaction between CH4 dry reforming and tar removal in plasma catalysis was investigated. The results indicated that plasma catalysis can achieve high−efficiency simultaneous tar removal and CH4 dry reforming, as indicated by the reactants’ conversion (14% increase for CCH4 and CCO2 at 450 °C in the presence of tar and a 37% increase for the tar removal rate at 360 °C when CH4 and CO2 were introduced), and the mechanism for mutual promotion of CH4 dry reforming and tar removal was elucidated through catalyst characterization results. In addition, a possible reaction mechanism for tar removal via plasma catalysis was proposed. These findings provide valuable insights for simultaneous upgrading and purification of gases generated by biomass gasification.

Highly active and stable cobalt catalysts with a tungsten carbide-activated carbon support for dry reforming of methane: effect of the different promoters

A series of cobalt catalysts decorated with different transition metals were synthesized. The introduction of Y improves the dispersibility of the active metal and its oxygen vacancy content, thereby enhancing its activity and anti-coking ability.

CO2 reduction routes to value-added oxygenates: a review

Energy is a key attribute that is used to evaluate the economic development of any country. The demand for energy is going to rise in developing countries and will be 67% of global use by 2040. The energy surge in these rising economies will be responsible for 60-70% of the global greenhouse gas emissions. The quest for higher energy motivates technological development to curb the climate change occurring with GHG emissions. Carbon dioxide is one of the primary greenhouse gases in the atmosphere. Current work is intended to give an updated review on the different routes of carbon dioxide utilization that are catalytic route, photocatalytic route, electrocatalytic route, microwave plasma route, and biocatalytic route. These routes are capable of converting CO₂ into different valuable products such as formic acid, methanol, and di-methyl ether (DME), which are majorly derived from biomass and/or fossil fuels (coal gasification and/or natural gas). This work investigates the effect of different routes available for the production of value-added products by CO₂ reduction, discusses various challenges that come across the aforementioned routes, and shares views on future scope and research direction to pave new innovative ways of reducing CO₂ from the environment.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

There is an obvious gap between efforts dedicated to the control of chemicophysical and morphological properties of catalyst active phases and the attention paid to the search of new materials to be employed as functional carriers in the upgrading of heterogeneous catalysts. Economic constraints and common habits in preparing heterogeneous catalysts have narrowed the selection of active-phase carriers to a handful of materials: oxide-based ceramics (e.g. Al₂O₃, SiO₂, TiO₂, and aluminosilicates-zeolites) and carbon. However, these carriers occasionally face chemicophysical constraints that limit their application in catalysis. For instance, oxides are easily corroded by acids or bases, and carbon is not resistant to oxidation. Therefore, these carriers cannot be recycled. Moreover, the poor thermal conductivity of metal oxide carriers often translates into permanent alterations of the catalyst active sites (i.e. metal active-phase sintering) that compromise the catalyst performance and its lifetime on run. Therefore, the development of new carriers for the design and synthesis of advanced functional catalytic materials and processes is an urgent priority for the heterogeneous catalysis of the future. Silicon carbide (SiC) is a non-oxide semiconductor with unique chemicophysical properties that make it highly attractive in several branches of catalysis. Accordingly, the past decade has witnessed a large increase of reports dedicated to the design of SiC-based catalysts, also in light of a steadily growing portfolio of porous SiC materials covering a wide range of well-controlled pore structure and surface properties. This review article provides a comprehensive overview on the synthesis and use of macro/mesoporous SiC materials in catalysis, stressing their unique features for the design of efficient, cost-effective, and easy to scale-up heterogeneous catalysts, outlining their success where other and more classical oxide-based supports failed. All applications of SiC in catalysis will be reviewed from the perspective of a given chemical reaction, highlighting all improvements rising from the use of SiC in terms of activity, selectivity, and process sustainability. We feel that the experienced viewpoint of SiC-based catalyst producers and end users (these authors) and their critical presentation of a comprehensive overview on the applications of SiC in catalysis will help the readership to create its own opinion on the central role of SiC for the future of heterogeneous catalysis.

Catalyst Heating Characteristics in the Traveling-Wave Microwave Reactor

Traveling-Wave Microwave Reactor (TMR) presents a novel heterogeneous catalytic reactor concept based on a coaxial waveguide structure. In the current paper, both modeling and experimental studies of catalyst heating in the TMR are presented. The developed 3D multiphysics model was validated from the electromagnetic and heat transfer points of view. Extrudes of silicon carbide (SiC) were selected as catalyst supports and microwave absorbing media in a packed-bed configuration. The packed-bed temperature evolution was in good agreement with experimental data, with an average deviation of less than 10%. Both experimental and simulation results show that the homogeneous temperature distribution is possible in the TMR system. It is envisioned that the TMR concept may facilitate process scale-up while providing temperature homogeneity beyond the intrinsic restrictions of microwave cavity systems.

Pyrolysis, morphology and microwave absorption properties of tobacco stem materials

The recent development of microwave radiation technology has increased the application possibilities of waste tobacco stems (WTSs). In this study, the morphology and microwave absorption properties of tobacco stem materials as well as the pyrolysis of the resultant biomass (BMTS) were studied via thermogravimetry-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and a vector network analysis (VNA). The results show that the BMTS pyrolysis involves four stages in air: dehydration, heat transfer, pyrolysis, and carbonisation, and it involves three stages in N2: moisture evaporation, de-volatilization, and charring. The microwave-assisted expansion of WTSs can improve the pore diameter and total porosity of the expanded tobacco stems (ETSs) and BMTS. The latter is a macroporous material with a total porosity of 78.2% and a probable pore size of 29.5 μm. Its pore size distribution ranges from 10.7 nm to 227 μm. The microwave absorption properties of the WTSs are affected by the moisture content, bulk density, and grain size; the properties can be enhanced by decreasing the grain size and increasing the moisture content and bulk density within the experimental range. The 3 dB bandwidth and amplitude vary by 0.45 MHz and - 0.406 dB per 1% increase in the moisture content of the materials, respectively. Our results demonstrate that tobacco stem materials with different moisture contents and grain sizes should be classified before the expansion or re-drying steps to ensure heating uniformity and product quality during the microwave radiation treatment.

Fe-rich biomass derived char for microwave-assisted methane reforming with carbon dioxide

Microwave-assisted methane reforming with carbon dioxide was dealt with in this work, using a Fe-rich biomass-derived char by one-step preparation. The main factors on the reforming reaction and stability of this catalyst were evaluated, together with a series of characterization on the produced gas and the used char. The char obtained from biomass pyrolysis with Fe₂O₃ addition of 10% exhibited the best performance on dry reforming reaction. A target CH₄ conversion of 95% over this char was realized at 800 °C. Moreover, H₂/CO ratio achieved with this char was prone to approach the stoichiometric value. Compared to CO₂ conversion, CH₄ conversion was more promoted with the increase of CO₂/CH₄ ratio. The variation of CO₂/CH₄ ratio also leaded to a noticeable changes on H₂/CO ratio. More importantly, the selected char presented a satisfied stability, evidenced by the total decrease of 4.8% for CH₄ conversion and 3.1% for CO₂ conversion in the test of 160 min. This was contributed to a depressed in-situ carbon consumption and a moderate deterioration of porous structure. Gaseous products obtained with the appropriate char in a long run had a syngas content of 88.79% and H₂/CO ratio of 0.92 on average.