Piotr Michorczyk

Activity enhancement of zeolite MCM-22 by interlayer expansion enabling higher Ce loading and room temperature CO oxidation

Layered zeolite precursor MCM-22P can be stabilized as interlayer expanded structure MWW-IEZ with enlarged pores by silylation producing –O–Si(OH)2–O– bridges. It adsorbs two times more cerium than MCM-22 and becomes activated for CO oxidation to CO2 at room temperature. This represents one of the most notable activity enhancements upon modification of layered zeolites.

Framework-substituted cerium MCM-22 zeolite and its interlayer expanded derivative MWW-IEZ

Framework-substituted cerium MCM-22 zeolites were synthesized with both TEOS and solid silica sources. The Si/Al ratio in the gel was 15/1 with two different Si/Ce ratios equal to 100/1 and 30/1. The products showed high Bronsted acid site concentrations, above 700 μmol g−1, that diminished slightly as the Ce content increased. The state of Ce was evaluated by IR and UV-vis spectroscopy. There was no indication of a separate Ce phase and extraframework atoms. Both oxidation states, 3+ and 4+, were present. In contrast to the interlayer expanded form MCM-22-IEZ with Ce exchanged into it, the present MCM-22 did not show oxidation of adsorbed CO. This indicates fundamental differences in the location of Ce, which is outside the framework in the exchanged form. The framework-substituted Ce-MCM-22 became active for CO oxidation after its conversion into the IEZ form and additional exchange of Ce. Textural properties were evaluated by nitrogen adsorption and quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) of hydrocarbons.

Preparation of monolithic catalysts using 3D printed templates for oxidative coupling of methane

3D printed polymer models were applied as templates in order to control channel architectures in monolithic catalysts. The resulting Mn- and Na2WO4-containing monoliths exhibited stable 23–25% methane conversion in the oxidative coupling of methane, with a high selectivity of 67–70% towards C2–C3 hydrocarbons.

In situ UV-Vis DRS evidence of Cr2+ species oxidation by CO2

In situ UV-Vis DRS investigations have revealed that the Cr(2+) species, which dominate on the surface of a CO-reduced Cr/SBA-1 catalyst, can be oxidized by CO(2) at a wide range of temperatures. Such an oxidation is a multistep process proceeding probably via carboxylate intermediates.

Catalytic Behavior of Chromium Oxide Supported on Nanocasting-Prepared Mesoporous Alumina in Dehydrogenation of Propane

Mesoporous alumina with narrow pore size distribution centered in the range of 4.4–5.0 nm and with a specific surface area as high as 270 m2·g−1 was prepared via the nanocasting approach using a CMK-3 carbon replica as a hard template. Based on this support, a series of catalysts containing 1, 5, 10, 20 and 30 wt % of chromium was prepared by incipient wetness impregnation, characterized, and studied in the dehydrogenation of propane to propene (PDH). Cr species in three oxidation states—Cr(III), Cr(V) and Cr(VI)—were found on the oxidized surface of the catalysts. The concentration of these species varied with the total Cr loading. Temperature-programmed reduction (H2-TPR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) studies revealed that Cr(VI) species dominated at the lowest Cr content. An increase in the Cr loading resulted in an appearance of an increasing amount of Cr(III) oxide. UV-Vis-DRS measurements performed in situ during the PDH process showed that at the beginning of the catalytic test Cr(VI) species were reduced to Cr(III) redox species. A crucial role of the redox species in the PDH process over the catalysts with the low Cr content was confirmed. The stability test for the catalyst containing 20 wt % of Cr showed that this sample exhibited the reproducible catalytic performance after the first four regeneration–dehydrogenation cycles. Moreover, this catalyst had higher resistance on deactivation during the PDH process as compared to the reference catalyst with the same Cr loading, but was supported on commercially available alumina.

Influence of Co2 on the Catalytic Performance Of La2O3/CeO2 and CaO/CeO2 Catalysts in the Oxidative Coupling of Methane

In this work the La2O3/CeO2 (33 mol % of La) and CaO/CeO2 (33 mol % of Ca) catalysts were prepared by the impregnation method and characterized by XRD and CO2-TPD. The catalytic properties of the catalysts were tested in the OCM process at 1073 K using the methane/oxygen mixture of the mole ratio 3.7 or 2.5 additionally containing CO2 and helium balance. It was found that in the presence of both catalysts an addition of CO2 enhances the selectivity to the ethylene and ethane and it does not have any negative influence on methane conversion. In the case of the CaO/CeO2 catalyst the promoting effect of CO2 was the highest. When the partial pressure of CO2 equals to 39 kPa the increase in selectivity from 36 to 41% was noted while the conversion of methane equal to 19.4-19.7 %.

Dehydrogenation of propane with CO2 – a new green process for propene and synthesis gas production

Abstract Dehydrogenation of propane in the presence of CO2 was considered as an alternative to commercial dehydrogenation pathway of obtaining propene and the new sources of synthesis gas. Based on thermodynamic calculations and a catalytic tests it was shown that by controlling CO2 concentration in the feed the molar ratio of H2/CO (synthesis gas) in the products mixture can be regulated. Several different pathways of DHP-CO2 process integration with commercialized chemical processes utilized synthesis gas were proposed

Zastosowanie drukowania 3d do modelowania strukturykanałów w monolitycznych katalizatorach dedykowanychdla procesu utleniającego sprzęgania met

Abstract In this work, a new preparation method is proposed to obtain high temperature monolithic structures for catalytic applications. A commercial 3D printer was used to synthesise polymeric templates that were utilised in the designing of channel structures in monolithic catalysts. New materials with manganese and sodium tungstate supported on corundum with macropores of well-defined shapes and sizes were prepared; their catalytic performance was investigated in the process of the oxidative coupling of methane.Zastosowanie drukowania 3d do modelowania struktury kanalow w monolitycznych katalizatorach dedykowanych dla procesu utleniającego sprzegania met

Influence of carbon precursor on porosity, surface composition and catalytic behaviour of CMK-3 in oxidative dehydrogenation of propane to propene

Ordered mesoporous CMK-3 carbon replicas were synthesized by infiltration of mesopores present in a SBA-15 silica template with two different carbon precursors, i.e. sucrose and poly(furfuryl alcohol). The obtained composites were carbonized under an inert gas atmosphere at 550, 650, 750 and 850 °C, and the template was etched with a HF solution. The final carbon replicas were analyzed by various physicochemical techniques, including low-temperature N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and tested as catalysts in the oxidative dehydrogenation of propane (ODP) at 450 °C. Both series of materials differed strongly with respect to their porosity, but showed very similar surface composition determined by XPS. Higher porosity of CMK-3 prepared using the sucrose precursor influenced propane conversion and selectivity to propene. Furthermore, oxygen containing groups (e.g. carbonyl-type) were found to be less sensitive to the type of carbon precursor than to the ODP reaction conditions.

Incorporation of Ti as a Pyramidal Framework Site in the Mono‐Layered MCM‐56 Zeolite and its Oxidation Activity

MWW zeolite MCM‐56 with Al atoms on the surface was functionalized with Ti to produce pyramidal TiOH groups. This was carried out by removal of Al with nitric acid, calcination and treatment with titanium diisopropoxide bis(acetylacetonate) (Ti(acac)2 (i‐propoxide)2, Ti(acac)2OiPr2). Up to 0.7 % Ti was introduced. Using UV‐Vis spectroscopy three types of Ti moieties were identified in the uncalcined materials – tetrahedral in the framework, 5/6‐coordinated Ti on the surface, presumably in the vacated pyramidal sites, and oxide‐like clusters. The presence of TiOH on the surface was indicated by in situ measurement of UV‐Vis spectra during calcination. It showed the band at 290 nm, which disappeared at 500 °C, perhaps due to condensation with silanols. Catalytic oxidation tests were carried out with three samples containing 0.13, 0.36, and 0.70 % Ti and methyl phenyl sulfide and cis‐cyclooctene as model reactants. The study confirmed potential of the TiOH moieties in oxidation catalysis although their final form is not certain. Future studies will include increasing Ti content to enhance catalytic activity and better detection of this type of the Ti site.