CO2 Hydrogenation at Atmospheric Pressure and Low Temperature Using Plasma-Enhanced Catalysis over Supported Cobalt Oxide Catalysts

CO2 is a promising renewable, cheap, and abundant C1 feedstock for producing valuable chemicals, such as CO and methanol. In conventional reactors, because of thermodynamic constraints, converting CO2 to methanol requires high temperature and pressure, typically 250 °C and 20 bar. Nonthermal plasma is a better option, as it can convert CO2 at near-ambient temperature and pressure. Adding a catalyst to such plasma setups can enhance conversion and selectivity. However, we know little about the effects of catalysts in such systems. Here, we study CO2 hydrogenation in a dielectric barrier discharge plasma-catalysis setup under ambient conditions using MgO, γ-Al2O3, and a series of CoxOy/MgO catalysts. While all three catalyst types enhanced CO2 conversion, CoxOy/MgO gave the best results, converting up to 35% of CO2 and reaching the highest methanol yield (10%). Control experiments showed that the basic MgO support is more active than the acidic γ-Al2O3, and that MgO-supported cobalt oxide catalysts improve the selectivity toward methanol. The methanol yield can be tuned by changing the metal loading. Overall, our study shows the utility of plasma catalysis for CO2 conversion under mild conditions, with the potential to reduce the energy footprint of CO2-recycling processes

Butane Dry Reforming Catalyzed by Cobalt Oxide Supported on Ti2AlC MAX Phase

MAX (M(n+1)AX(n)) phases are layered carbides or nitrides with a high thermal and mechanical bulk stability. Recently, it was shown that their surface structure can be modified to form a thin non-stoichiometric oxide layer, which can catalyze the oxidative dehydrogenation of butane. Here, the use of a Ti2AlC MAX phase as a support for cobalt oxide was explored for the dry reforming of butane with CO2, comparing this new catalyst to more traditional materials. The catalyst was active and selective to synthesis gas. Although the surface structure changed during the reaction, the activity remained stable. Under the same conditions, a titania-supported cobalt oxide catalyst gave low activity and stability due to the agglomeration of cobalt oxide particles. The Co3O4/Al(2)O(3)catalyst was active, but the acidic surface led to a faster deactivation. The less acidic surface of the Ti2AlC was better at inhibiting coke formation. Thanks to their thermal stability and acid-base properties, MAX phases are promising supports for CO(2)conversion reactions

Molybdenum Oxide Supported on Ti3AlC2 is an Active Reverse Water−Gas Shift Catalyst

MAX phases are layered ternary carbides or nitrides that are attractive for catalysis applications due to their unusual set of properties. They show high thermal stability like ceramics, but they are also tough, ductile, and good conductors of heat and electricity like metals. Here, we study the potential of the Ti(3)AlC(2 )MAX phase as a support for molybdenum oxide for the reverse water-gas shift (RWGS) reaction, comparing this new catalyst to more traditional materials. The catalyst showed higher turnover frequency values than MoO3/TiO2 and MoO3/Al2O3 catalysts, due to the outstanding electronic properties of the Ti3AlC2 support. We observed a charge transfer effect from the electronically rich Ti3AlC2 MAX phase to the catalyst surface, which in turn enhances the reducibility of MoO3 species during reaction. The redox properties of the MoO3/Ti3AlC2 catalyst improve its RWGS intrinsic activity compared to TiO2- and Al2O3-based catalysts

CuOx/CeO2 catalyst derived from metal organic framework for reverse water-gas shift reaction

Herein, we have studied an alternative route for preparing CuOx/CeO2 catalysts using metal organic frameworks (MOFs) as precursors. Usually, CuOx/CeO2 materials are prepared by wet impregnation of ceria support. In this study, we have impregnated a Cu-MOF with a ceria precursor and then pyrolized the impregnated MOF using different conditions and procedures. The prepared catalysts have been characterized by using a wide range of techniques such as XRD, XPS, Raman, and TPR. We have found that the pyrolysis method determines the dispersion of the oxidized copper species on the ceria surface what, in turn, controls the catalytic activity and selectivity of the catalysts in the reverse water-gas shift (RWGS) reaction. We have compared the behavior of the MOF-derived catalysts against an optimized catalyst prepared by a conventional method (wet impregnation), finding that the MOF-derived catalyst shows better catalytic performance.Financial support from Generalitat Valenciana (project PROMETEOII/2014/004) and MINECO (Project MAT2013-45008-P) is gratefully acknowledged. EVRF also thanks MINECO for his Ramon y Cajal fellow RYC-2012-11427 and the following project MAT2016-81732-ERC

Mixed‐Valence Ce/Zr Metal‐Organic Frameworks: Controlling the Oxidation State of Cerium in One‐Pot Synthesis Approach

The preparation of MOFs including a metal with an easily exchangeable oxidation state, while maintaining the same crystal structure and stability, is of paramount importance for myriad applications. In this work, a new synthesis method is reported that can be used to prepare Ce/Zr‐MOFs (UiO‐66 structure) having only Ce(III), a mixed‐valence Ce(IV)/Ce(III), or only Ce(IV) cations, as desired. The materials are characterized using a large number of techniques, including X‐ray absorption and X‐ray photoelectron spectroscopies.Authors acknowledge financial support by MINECO (Spain) through projects, MAT2017-86992-R and MAT2016-80285-P. EVRF acknowledges MINECO for his Ramón y Cajal fellow RYC-2012-11427. The authors also would like to thank Diamond Light Source (I20-Scanning beamline) for the beamtime given at the proposal SP19114

Highly active and stable Co (Co3O4)_Sm2O3 nano-crystallites derived from Sm2Co7 and SmCo5 intermetallic compounds in NH3 synthesis and CO2 conversion

Intermetallic compounds (IMCs) are interesting materials in the field of heterogeneous catalysis due to their ordered structure and tunable electronic properties. These IMCs can act as precursor to synthesize metal/metal oxide composite catalysts that are more active than just the starting IMCs. In this work, Sm2Co7 and SmCo5 IMCs were used as precursors to prepare highly active and stable Co_SmO, Co_Sm2O3 and Co3O4_Sm2O3 catalysts via controlled modification. Transmission electron microscopy (TEM) demonstrated that Co and Sm2O3 Nano crystallites were formed after the modification of the IMC. IMCs derived Co_SmO and Co_Sm2O3 were stable and active in NH3 synthesis with very low activation energy of 55 and 77 kJ mol−1 respectively. The structural, morphological and surface characterization revealed that a strong metal support interaction existed between Co and Sm2O3 (electronic effect) along with the presence of surface steps and edges of Co nano crystallites (structural effect) that activate the N2 at low temperature (360 °C). Similarly, Co3O4_Sm2O3 derived from the IMC were found to exhibit high CO2 and butane conversion in butane dry reforming at low temperature (550 °C) with excellent stability. The study revealed that the presence of Co3O4 and Sm2O3 active sites in close proximity (geometrical effect) promoted the simultaneous adsorption or activation of butane and CO2. The Co_Sm2O3 and Co3O4_Sm2O3 derived from IMCs exhibited superior catalytic performance in both NH3 synthesis and butane dry reforming compared to similar compositional catalyst synthesized by hydrothermal route. These studies pave the way to potential uses of IMCs as precursors to derive composite metal/metal oxide catalysts that are highly stable and active despite their low surface areas

Highly Active and Stable Co (Co3O4)_Sm2O3 Nano-crystallites Derived from Sm2Co7 and SmCo5 Intermetallic Compounds in NH3 Synthesis and CO2 Conversion

Intermetallic compounds (IMCs) are interesting materials in the field of heterogeneous catalysis due to their ordered structure and tunable electronic properties. These IMCs can act as precursor to synthesize metal/metal oxide composite catalysts that are more active than just the starting IMCs. In this work, Sm2Co7 and SmCo5 IMCs were used as precursors to prepare highly active and stable Co_SmO, Co_Sm2O3 and Co3O4_Sm2O3 catalysts via controlled modification. Transmission electron microscopy (TEM) demonstrated that Co and Sm2O3 Nano crystallites were formed after the modification of the starting IMC. IMCs derived Co_SmO and Co_Sm2O3 were stable and active in NH3 synthesis with very low activation energy of 55 and 77 kJ/mol respectively. The structural, morphological and surface characterization revealed that a strong metal support interaction existed between Co and Sm2O3 (electronic effect) along with the presence of surface steps and edges of Co nano crystallites (structural effect) that activated the N2 at low temperature (360 °C). Similarly, Co3O4_Sm2O3 derived from the IMC were found to exhibit high CO2 and butane conversion in butane dry reforming at low temperature (550 °C) with excellent stability. The study revealed that the presence of Co3O4 and Sm2O3 active sites in close proximity (geometrical effect) promoted the simultaneous adsorption or activation of butane and CO2. The Co_Sm2O3 and Co3O4_Sm2O3 derived from IMCs exhibited superior catalytic performance in both NH3 synthesis and butane dry reforming compared to similar compositional catalyst synthesized by hydrothermal route. These studies pave the way to potential uses of IMCs as precursors to derive composite metal/metal oxide catalysts that are highly stable and active despite their low surface areas

Plasma assisted catalytic conversion of CO\u3csub\u3e2\u3c/sub\u3e and H\u3csub\u3e2\u3c/sub\u3eO Over Ni/Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e in a DBD Reactor

\u3cp\u3eWe present an innovative approach for reacting carbon dioxide and water to give syngas by combining heterogeneous catalysis and non-thermal plasma techniques. This approach utilizes an abundant water and nickel catalyst, and mitigates the thermodynamic penalty by using a Dielectric Barrier Discharge (DBD) plasma reactor. Argon dilution was used in the experiment to reduce the exothermic recombination of hydrogen and oxygen, which is considered as the major hurdle for H\u3csub\u3e2\u3c/sub\u3eO conversion. As a result, the syngas ratio was dramatically improved from 0.07 to 0.86. In addition, the conversions of CO\u3csub\u3e2\u3c/sub\u3e and H\u3csub\u3e2\u3c/sub\u3eO were improved by packing Ni/γ–Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e catalysts into the DBD reactor. The yields of H\u3csub\u3e2\u3c/sub\u3e and CO were up to 13.8% and 5.6% respectively. The conditions for plasma catalysis and the catalyst characterization are presented and discussed.\u3c/p\u3

The role of vacancies in a Ti2CTx MXene-derived catalyst for Butane Oxidative Dehydrogenation

MXenes are a new family of 2D carbides or nitrides that have attracted attention due to their layered structure, tunable surface groups and high electrical conductivity. Here, we report for the first time that Ti 2 CT x MXene catalyses the selective oxidative dehydrogenation of n -butane to butenes and 1,3-butadiene. This catalyst showed higher intrinsic activity compared to commercial TiC and TiO 2 samples in terms of C 4 olefin formation rate. We propose that the stabilisation of structural vacancies and the change in composition (from a carbide to a mixed phase oxide) in the MXene causes its higher catalytic activity. These vacancies can lead to a higher concentration of unpaired electrons in the MXene-derived material, enhancing its nucleophilic properties and favouring the production of olefins.We thank the Netherlands Organization for Scientific Research (NWO) for the grant “Developing novel catalytic materials for converting CO2, methane and ethane to high-value chemicals in a hybrid plasma-catalytic reactor” (China.15.119). EVRF thanks the “Ministerio de Ciencia e innovación” grant (PID2020-116998RB-I00)