| Biography | |
|---|---|
 Prof. Vladislav A. Sadykov Novosibirsk State University, Russia |
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| Title: NANOCOMPOSITE CATALYSTS OF BIOFUELS TRANSFORMATION INTO SYNGAS: DESIGN, REACTION MECHANISM AND PERFORMANCE IN STRUCTURED AND MEMBRANE REACTORS | |
| Abstract:
Transformation of biofuels into syngas via steam/oxysteam reforming is now considered as one of the most important task of catalysis in the energy-related fields. Due to a high reactivity of biofuels a heavy coking is observed leading to the catalyst deactivation. To deal with this phenomenon, active components comprised of complex oxides with a high lattice oxygen mobility (favors efficient gasification of coke precursors) promoted by Ni/Co-based alloys (responsible for fuels molecules activation) are suggested. For achieving a high performance in these reactions, monolithic substrates with a good thermal conductivity are promising for providing an efficient heat supply to the catalyst and prevent emergence of cool/hot zones deteriorating performance. For the renewable/hydrogen energy field, producing syngas and hydrogen from biogas/biofuels using catalytic processes conjugated with reagent (oxygen) and/or products (hydrogen) separation in membrane reactors is a promising approach as well.
This work reviews results of extensive research aimed at design and characterization of such nanocomposite structured catalysts and catalytic membranes performance in transformation of biofuels (biogas, ethanol, acetone, etc). Next basic problems are considered:
1. Atomic-scale factors controlling oxygen mobility and reactivity in complex oxides with perovskite (LnMnCrO), fluorite (LnCeZrO) and spinel (MnCrO) structures (both bulk and loaded on high surface area/mesoporous Mg-alumina, CaTiO3, tialite), their acid/base properties and features of strong interaction with supported metal/alloy nanoparticles (Ni, Co, Ni+Pt, Ni+Ru, etc) as revealed by applying modern diffraction and spectroscopic techniques of nanomaterials structure and surface properties characterization (XRD on synchrotron radiation, EXAFS, TEM with EDX, UV-Vis, Raman, XPS, FTIRS of adsorbed CO, etc), oxygen mobility (oxygen isotope heteroexchange in the flow reactors in temperature-programmed mode) and reactivity (TPR, pulse studies).
2. Effect of the active component composition, specificity of the surface sites and nature of oxidant on basic mechanistic features of biofuels transformation into syngas as elucidated by a complex of transient methods (in situ FTIRS, isotope and chemical transients, pulse microcalorimetry).
3. Design of structured catalysts by supporting optimized active components on heat-conducting substrates (Ni-Al(C) foams, Fe-Cr-alloy corrugated foils, gauzes and microchannel platelets with protective corundum layers, microchannel cermets, SiC monolithic substrates with porous walls, etc).
4. Structured catalysts performance in pilot-scale reactors (including those equipped with the internal heat exchangers) operating on real concentrated feeds and its mathematical modeling.
5. Design of asymmetric supported membrane reactors permeable for oxygen (separated from air to be used as reagent in biofuels oxi-steam/dry reforming in catalytic layers supported on the membrane surface from the fuel side) or hydrogen (to separate it from the products of biofuels steam reforming in catalytic layer supported on the fuel side of membrane). Unique Ni-Al foam substrates with graded porosity were used for design of such membrane reactors.
6. Studies of catalytic membranes performance in real concentrated feeds and their mathematical modeling.
For optimized nanocomposite active components a high mobility and reactivity of strongly bound surface oxygen (heat of adsorption 500-600 kJ/mol O2 in the steady-state) provides realization of step-wise redox mechanism of biofuels transformation with the rate determining stage corresponding to the rupture of C-C bond in activated fuel molecule on the metal site (Ni-Ru alloy nanoparticle, etc) facilitated by the interaction with oxygen species at the metal-support interface.
Optimized structured catalysts provide a high yield of hydrogen (H2 content up to 50%) in the IT range both in steam and autothermal reforming of biofuels at short contact times. Main by-product is CH4 due to cracking, while for alumina-supported active components C2H4 is formed on acid sites. Suppressing acidity by increasing Mg loading and O2 addition to the feed decreases C2H4 content, thus suppressing coking; stable performance was confirmed for more than 100 h time-on-stream. For heat-conducting substrates (Ni-Al foam, microchannel platelets etc.) mathematical modeling demonstrated the absence of any heat- and mass-transfer effects. No spallation or cracking of the active components on metallic substrates was revealed. Reactors equipped with the internal heat exchanger were designed allowing stable and efficient operation in the autothermal mode for the mixture of natural gas and liquid biofuels at feeds inlet temperatures <100oC.
For catalytic oxygen-permeable membrane reactors a high oxygen flux (up to 15 cm3 O2/cm2min) was achieved under air/CH4 (+CO2 + biofuel) feeds gradients at ~ 900 oC, providing a high yield of syngas, thus being promising for the practical application. For catalytic hydrogen-permeable membranes complete EtOH conversion in steam reforming ractions was achieved at ~ 700 oC even at the highest flow rate 10 l/h, and a high hydrogen permeation (≥ 1 ml H2 cm 2 min 1) was revealed. Mathematical modeling revealed absence of any mass transfer effects in porous layers of optimized membranes and provided reliable description of catalytic membrane performance required for up-scaling. Membranes remained robust for up to 300 h time-on-stream without any deterioration of performance or coke deposition. Hence, performance characteristics of these membranes are promising for the practical application.
Support by the Russian Science Foundation (Project 16-13-00112) and Russian -French network GDRI “Catalytic valorization of biomass” (RFBR-CNRS 18-58-16007_a Project) is gratefully acknowledged
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| Biography: Vladislav Sadykov is the head of laboratory at the Boreskov Institute of Catalysis of Siberian Branch of the Academy of Sciences of Russia (Novosibirsk) and Professor of Novosibirsk State University. He has published more than 430 papers, 4 monographs and 7 Chapters in books. He is the member of the Materials Research Society (USA) and American Chemical Society. He received Award of the Russian Federation Government in Science and Technology (1999); Balandin Award of the Russian Academy of Sciences (2007) and Koptyug Award of the National Academy of Sciences of Belarus (2012). He is co-editor of “Catalysis for Sustainable Energy” (de Gruyter Open), member of the Editorial Boards of Applied Catalysis A and Physics of Combustion and Flames. His current research interest includes heterogeneous catalysis of red-ox processes for the energy production (including solid oxide fuel cells), catalytic processes of hydrogen and syngas generation at short contact times, membrane reactors, advanced technologies of nanophase and nanocomposite materials (complex oxides, framework silicates, oxide-ion conductors, nanocomposites with mixed ionic-electronic conductivity) synthesis, solid state ionics (estimation of oxygen mobility by oxygen isotope heteroexchange). He is actively involved in the international collaboration through Framework Projects of European Commission, Era Net Rus Plus and Russian-French Network of laboratories. | |
