Piotr Michorczyk

Bio: Piotr Michorczyk is an academic researcher from Spanish National Research Council. The author has contributed to research in topics: Catalysis & Dehydrogenation. The author has an hindex of 20, co-authored 46 publications receiving 1193 citations.

Activity of chromium oxide deposited on different silica supports in the dehydrogenation of propane with CO2 – A comparative study

Abstract: Four series of chromium oxide-based catalysts containing 0.7–7 wt.% of Cr were prepared by incipient wetness impregnation of conventional amorphous silicas (SiO2-p; SBET = 261 m2 g−1 and SiO2-a; SBET = 477 m2 g−1) and mesoporous siliceous sieves with cubic (SBA-1; SBET = 1181 m2 g−1) and hexagonal (SBA-15; SBET = 750 m2 g−1) pore structure. The combination of different techniques (chemical analysis with Bunsen–Rupp method, ICP, XRD, UV–vis DRS and quantitative/qualitative H2-TPR) in the characterization of the calcined catalysts revealed that the chromium species anchored on the surface of mesoporous supports show structural properties similar to those on the conventional silicas, but a higher dispersion of chromium species could be achieved using mesoporous supports due to their much higher SBET. This reflects in higher content of Cr6+ species stabilized in comparison with conventional silicas. The Cr6+ species was found to be crucial for high activity in the dehydrogenation of propane with CO2 (DHP–CO2). The rate of propene formation increases almost proportionally to the concentration of Cr6+ species in the calcined catalysts. In situ UV–vis DRS measurements during DHP–CO2 process evidences that the Cr6+ species are reduced rapidly (in a stream of CO2 + propane) to Cr3+ and Cr2+ species indicating that the Cr6+ species are rather precursor than active sites, similar as in nonoxidative dehydrogenation of propane (DHP). The reduction of Cr6+ species generates dispersed Cr3+ and Cr2+ sites at the beginning of the DHP–CO2 that participate in nonoxidative pathway of propene formation. In the presence of CO2, Cr3+ and Cr2+ sites, may participate additionally in an alternative oxidative pathway of propene formation and in a consumption of hydrogen produced in the DHP by reverse water-gas shift reaction.

Dehydrogenation of propane to propene over gallium oxide in the presence of CO2

Abstract: The dehydrogenation of propane to propene in the presence of carbon dioxide has been carried out over unpromoted and potassium promoted Ga2O3 catalysts. It was found that carbon dioxide enhance the initial activity of the Ga2O3 catalyst. After 0.2 h of reaction periodic propane conversion and propene selectivity reach 33 and 93%, respectively, while in the presence of argon only 25% conversion and 90% selectivity are achieved under the same condition.

Chromium oxide supported on MCM-41 as a highly active and selective catalyst for dehydrogenation of propane with CO2

Abstract: Incipient wetness technique was used for a preparation of MCM-supported chromium oxide materials with a Cr loading ranging from 0.7 to 13.7 wt%. The obtained samples were characterized by XRD, UV–vis-DRS, H 2 -TPR and BET, and tested as catalysts in dehydrogenation of propane with CO 2 . The catalytic reaction was studied in a flow apparatus at 773–923 K. All the tested catalysts exhibited a good catalytic performance in the dehydrogenation of propane with CO 2 . The best results were achieved over the sample containing 6.8 wt% of Cr. In this case, the selectivity to propene was above 80%, while the conversion of propane increased from 21% (at 773 K) to 62% (at 923 K). The promoting effect of CO 2 on the yield of propene was found for all the studied catalysts. This effect was discussed on the basis of temperature-programmed reaction of CO 2 with H 2 as well as H 2 -TPR experiments after regeneration of the reduced catalyst with pure CO 2 . It was suggested that one of reasons of a higher yield of propene observed in the presence of CO 2 compared to that measured in the absence of CO 2 was coupling of the dehydrogenation of propane with the reverse water–gas shift reaction.

Cobalt-containing BEA zeolite for catalytic combustion of toluene

Abstract: Co-containing HAlBEA zeolite was obtained by conventional wet impregnation of HAlBEA zeolite with an aqueous Co(NO3)2.6 H2O solution, whereas Co-containing SiBEA zeolites were prepared by a two-step post-synthesis method. This approach consists of, in the first step, dealumination of parent BEA zeolite to obtain an aluminium-free SiBEA support and then, in the subsequent step, contact of the obtained material with an aqueous solution of cobalt nitrate. As shown by X-ray diffraction and low-temperature N2 adsorption, the dealumination of BEA zeolite and introduction of cobalt ions did not involve destruction of zeolite structure, and only insignificant blocking of pore system was observed after introduction of high amounts of cobalt. Nevertheless, clear changes in acidity were found by FTIR of pre-adsorbed pyridine after dealumination of parent BEA zeolite and introduction of cobalt ions. The presence of Lewis acid sites resulted in enhanced selectivity to CO and benzene formed as by-products in the toluene combustion. Therefore, SiBEA zeolite was chosen as a support for an introduction of various amounts of Co into the zeolite structure (the intended Co contents of 3.0–9.0 wt%). Depended on the amount of the introduced Co, cobalt was incorporated into the framework of BEA zeolite as isolated mononuclear Co(II) species, small Co(II) oxide clusters and/or Co3O4 crystallites distributed in the whole zeolite structure. The chemical environment and dispersion of cobalt species were studied by transmission electron microscopy (TEM), FTIR of pre-adsorbed NO, UV–vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy (XPS). Temperature-programmed reduction of hydrogen (H2-TPR) was also performed to determine reducibility of the Co-containing SiBEA zeolites. It was confirmed that siliceous SiBEA zeolite was the excellent support of Co3O4, which was in turn recognized as the main active phase in the total oxidation of toluene. The best catalytic performance was achieved over the catalysts containing at least 0.05 mmol of Co in the form of Co3O4 per 1 g of SiBEA zeolite.

Catalytic dehydrogenation of light alkanes on metals and metal oxides.

Abstract: A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.

CO 2 hydrogenation to high-value products via heterogeneous catalysis.

Abstract: Recently, carbon dioxide capture and conversion, along with hydrogen from renewable resources, provide an alternative approach to synthesis of useful fuels and chemicals. People are increasingly interested in developing innovative carbon dioxide hydrogenation catalysts, and the pace of progress in this area is accelerating. Accordingly, this perspective presents current state of the art and outlook in synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols through two leading hydrogenation mechanisms: methanol reaction and Fischer-Tropsch based carbon dioxide hydrogenation. The future research directions for developing new heterogeneous catalysts with transformational technologies, including 3D printing and artificial intelligence, are provided. Carbon dioxide (CO2) capture and conversion provide an alternative approach to synthesis of useful fuels and chemicals. Here, Ye et al. give a comprehensive perspective on the current state of the art and outlook of CO2 catalytic hydrogenation to the synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols.

Mesoporous materials for clean energy technologies

Abstract: Alternative energy technologies are greatly hindered by significant limitations in materials science. From low activity to poor stability, and from mineral scarcity to high cost, the current materials are not able to cope with the significant challenges of clean energy technologies. However, recent advances in the preparation of nanomaterials, porous solids, and nanostructured solids are providing hope in the race for a better, cleaner energy production. The present contribution critically reviews the development and role of mesoporosity in a wide range of technologies, as this provides for critical improvements in accessibility, the dispersion of the active phase and a higher surface area. Relevant examples of the development of mesoporosity by a wide range of techniques are provided, including the preparation of hierarchical structures with pore systems in different scale ranges. Mesoporosity plays a significant role in catalysis, especially in the most challenging processes where bulky molecules, like those obtained from biomass or highly unreactive species, such as CO2 should be transformed into most valuable products. Furthermore, mesoporous materials also play a significant role as electrodes in fuel and solar cells and in thermoelectric devices, technologies which are benefiting from improved accessibility and a better dispersion of materials with controlled porosity.