Conversion of woody oil into bio-oil in a downdraft reactor using a novel silicon carbide foam supported MCM41 composite catalyst

Pyrolysis of soybean soapstock for hydrocarbon bio-oil over a microwave-responsive catalyst in a series microwave system

A novel Silicon carbide (SiC) foam ceramic based ZSM-5/SiC nanowires microwave-responsive catalyst was developed to upgrade the pyrolysis volatiles in a microwave-assisted series system (both the pyrolysis and catalytic systems were heated by microwave). The growth of SiC nanowires was helpful for the ZSM-5 growth on the SiC foam ceramic. Because the specific surface area of SiC foam ceramic was improved. The dielectric properties of the composite catalyst were improved due to the growth of SiC nanowires. Bio-oil composition analysis showed that area percentage of hydrocarbons and aromatic hydrocarbons could reach 80.89% and 40.48% at catalytic temperature of 450 ℃and 500 ℃, respectively. The microwave-responsive composite catalyst had good aromatization performance in microwave-assisted series system due to high dielectric properties and specific surface area. The composite catalyst performed well after five-cycle regeneration, and the hydrocarbon content could still reach 76.40%, which is 80.89% for the original catalyst.

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.

Integrating pyrolysis and ex-situ catalytic reforming by microwave heating to produce hydrocarbon-rich bio-oil from soybean soapstock

The composite catalysts were synthesized with SiC powder and ZSM-5 and were characterized by Brunauer-Emmett-Teller, X-ray diffraction, thermogravimetric analysis, pyridine-infrared spectroscopy, and scanning electron microscopy. The catalysts showed a high heating rate and excellent catalytic performance for pyrolysis vapors, and the product fractional distribution and chemical compositions of bio-oil in a tandem system (microwave pyrolysis and microwave ex-situ catalytic reforming) was examined. Experimental results confirmed the quality of bio-oil produced by the microwave-induced catalytic reforming was better than that product through electric heating. Additionally, 36.94 wt% of bio-oil was obtained using the catalyst with 20%ZSM-5/SiC under the following conditions: feed-to-catalyst ratio, 2:1; pyrolysis temperature, 550 °C; and catalytic temperature, 350 °C. The selectivities of hydrocarbons reached up to 75.88%. After five cycles, the activity of the regenerated composite catalyst was retained at 95% of the original catalyst.