Bugrova, Tatiana A.

Corberán, Vicente Cortés

Dutov, Valeriy V.

Mamontov, Grigory V.

Svetlichnyi, Valerii A.

English

Tomsk State University Repository

 CATALYSIS: from Science to Industry 2018 Section 3: Oral presentations  91  Comparison of supported CrOx catalysts in non-oxidative and oxidative dehydrogenation of light alkanes T. Bugrova1, V. Dutov1, V. Svetlichnyi1, V. Cortés Corberán2, G. Mamontov1 1Tomsk State University, Tomsk, Russia 2Institute of Catalysis and Petroleumchemistry, CSIC, Madrid, Spain bugrova.tatiana@gmail.com  A growing demand in the obtaining of high purity olefins requires new technologies of their production in addition to traditional steam and catalytic cracking methods. Olefins are widely used in chemical and pharmaceutical industry to produce a wide range of valuable chemicals. For these purposes, catalytic non-oxidative (DH) and oxidative (ODH) direct dehydrogenation of alkanes into olefins represent wide scientific interest. DH of alkanes is a promising method due to high selectivity toward olefins. In turn, ODH with CO2 as a mild oxidant is also prospective due to possibility of shifting of the dehydrogenation reaction equilibrium and CO2 utilization. Both DH and ODH pathways strongly depend on red-ox properties of support and active component. To date, different types of mixed oxides [1, 2] have been studied as catalysts for these processes. In spite of toxicity of chromium compounds, Cr-containing catalysts remain one of the most active among the catalysts for DH. The use of CrOx as an active component supported on alumina is caused by ability to multiple and reversible oxidation-reduction (CrV/VI↔CrII/III). Supported Cr-containing catalysts also show high activity in ODH-CO2 of propane and isobutane. However, the use of oxide supports for Cr catalysts with active oxygen and red-ox properties is preferable for higher activity and stable operation of the catalyst. Alumina shows poor red-ox ability, while ZrO2, CeO2 and mixed ceria–zirconia oxides are the best candidates as supports for ODH catalysts due to their unique red-ox properties. Thereby, the purpose of the present work is to compare the activity of Cr-containing systems on different supports in non-oxidative and oxidative dehydrogenation of alkanes. γ-Al2O3, CeO2, ZrO2, CexZr(1-x)O2, and γ-Al2O3, modified with ZrO2 and/or CeO2, were used as supports. Cr-containing catalysts with Cr loading corresponding to a monolayer (5 atCr/nm2) were prepared by incipient wetness impregnation of supports using aqueous solution of H2CrO4. The catalysts were dried at 80 °C for 12 h and calcined at 600 °C for 4 h. The catalysts were characterized by low-temperature N2 sorption, XRD, TPR, DRS, RS and tested in DH of isobutane and ODH-CO2 of ethane. According to the results obtained, the state of Cr on the surface is different over different supports. The formation of α-Cr2O3 particles is observed only for the CrOx/CeO2 catalyst. TPR-H2 results show that the CrOx/ZrO2 and CrOx/CexZr(1-x)O2 contain the highest amount of red-ox Cr5+/6+ species. These catalysts are the most active in i-C4H10 dehydrogenation. Thus, mainly chromium state affects on the catalyst activity in DH of isobutane. The modification of γ-Al2O3 by ZrO2 and/or CeO2 leads to an increase of Cr5+/6+ parts and growth of activity in DH of i-C4H10 in comparison with unmodified CrOx/Al2O3 catalyst. However, in the case of ODH-CO2 of ethane the reaction pathway, activity and stability of the catalyst depend on both chromium state and support features (acid-base and red-ox properties) [3]. The CrOx/γ-Al2O3 and CrOx/ZrO2 catalysts exhibited the highest ethylene formation rates, but the reaction followed different pathways. On CrOx/γ-Al2O3 catalyst, ethylene is formed via direct dehydrogenation of ethane accompanied by RWGS, while on CrOx/ZrO2 ethylene is formed via selective ODH. Addition of ZrO2 and/or CeO2 to CrOx/Al2O3 catalyst results in selective ODH. For CrOx/ZrO2/Al2O3 catalyst, ethylene is additionally formed via selective ODH reaction, while non-selective and/or dry reforming reactions take place on CrOx/CeO2/Al2O3 as shown by the higher CO formation rate.  This work was supported by “The Tomsk State University Academic D. I. Mendeleev Fund Program” grant № 8.2.31.2018. The authors thank A. Livanova for XRD studies and Dr. E. Fakhrutdinova for DRS studies.  References 1. Sattler, J.J.H.B.; Ruiz-Martinez, J.; Santillan-Jimenez, E.; Weckhuysen, B.M. Chem. Rev. 2014, 114, 10613-10653. 2. Gartner, C.A.; van Veen, A.C.; Lercher, J. A. ChemCatChem 2013, 5, 3196-3217. 3. Bugrova, T.; Dutov, V.; Svetlichnyi, V.; Cortés Corberán, V.; Mamontov, G. Catal. Today 2018, in press. 

Comparison of supported CrOx catalysts in non-oxidative and oxidative dehydrogenation of light alkanes

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Comparison of supported CrOx catalysts in non-oxidative and oxidative dehydrogenation of light alkanes

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