Optimizing the oxide support composition in Pr-doped CeO2 towards highly active and selective Ni-based CO2 methanation catalysts

In this study, Ni catalysts supported on Pr-doped CeO2 are studied for the CO2 methanation reaction and the effect of Pr doping on the physicochemical properties and the catalytic performance is thoroughly evaluated. It is shown, that Pr3+ ions can substitute Ce4+ ones in the support lattice, thereby introducing a high population of oxygen vacancies, which act as active sites for CO2 chemisorption. Pr doping can also act to reduce the crystallite size of metallic Ni, thus promoting the active metal dispersion. Catalytic performance evaluation evidences the promoting effect of low Pr loadings (5 at% and 10 at%) towards a higher catalytic activity and lower CO2 activation energy. On the other hand, higher Pr contents negate the positive effects on the catalytic activity by decreasing the oxygen vacancy population, thereby creating a volcano-type trend towards an optimum amount of aliovalent substitution.AIΤ, NDC and MAG acknowledge support of this work by the project “Development of new innovative low carbon energy technologies to improve excellence in the Region of Western Macedonia” (MIS 5047197) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Program “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).Peer reviewe

Continuous selective deoxygenation of palm oil for renewable diesel production over Ni catalysts supported on Al2O3 and La2O3–Al2O3

The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al2O3 and γ-Al2O3 modified with La2O3, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N2 adsorption/desorption, XRD, NH3-TPD, CO2-TPD, H2-TPR, H2-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h−1). The results show that the incorporation of La2O3 in the Al2O3 support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO2-TPD), and despite leading to a drop in surface acidity (NH3-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C15 to n-C18 hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream

Highly selective and stable Ni/La-M (M=Sm, Pr, and Mg)-CeO2 catalysts for CO2 methanation

In the study presented herein, nickel catalysts supported on CeO2 and, for the first time in the literature, on La2O3-Sm2O3-CeO2, La2O3-Pr2O3-CeO2 and La2O3-MgO-CeO2 were prepared and evaluated for the reaction of CO2 methanation. The carriers were prepared through a sol-gel microwave assisted method and the catalysts were obtained following wet impregnation. The physicochemical properties of the catalysts prior to reaction were determined through H2-TPR, H2-TPD, Raman spectroscopy, XRD, CO2-TPD, N2 physisorption-desorption, XPS and TEM. The spent catalysts, after the time-on-stream experiments were further characterised using TEM and TGA. It was shown that the simultaneous incorporation of La3+, Pr3+ and La3+, Sm3+ into the crystal structure of cerium oxide created higher population of oxygen vacant sites. Moreover, the co-presence of La3+, Mg2+ and La3+, Pr3+ into the CeO2 increased the plethos of moderate basic sites. These physicochemical properties increased the rate of CO2 methanation reaction at relatively low temperatures. Furthermore, it is argued that the addition of La3+ stabilized the Ni active sites via the probable formation of a new compound (La-O-Ni) on the catalyst surface or synergetic catalytic centers at the interfacial area improving the catalytic properties (activity and stability). Finally, the catalytic performance tests revealed that the addition of La3+ mainly improved the conversion of CO2 and yield of CH4 for the Ni/La-Mg-Ce and Ni/La-Sm-Ce samples. The rCO2 and XCO2 values at 300 °C followed the order Ni/La-Sm-Ce >> Ni/La-Mg-Ce > Ni/La-Pr-Ce > Ni/Ce.GIS is grateful for financial support by Greece and ESF through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS-5000432), implemented by the State Scholarships Foundation (IKY). MAG is grateful to the Regional Excellence program (MIS 5047197), which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). IVY and NDC are grateful for financial support from the European Union and Greek national funds through the operational program Competitiveness, Entrepreneurship and Innovation, under the call Research-Create-Innovate (Project code: T1EDK-00782). SAK and KP acknowledge the financial support from the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE 2019-233 grant and support by the Khalifa University of Science and Technology under Award No. RC2-2018-024.Peer reviewe

Highly selective and stable nickel catalysts supported on ceria promoted with Sm2O3, Pr2O3 and MgO for the CO2 methanation reaction

The present work reports on the investigation of the catalytic performance for the methanation of CO2 over Ni catalysts based on CeO2, and for the first time, of Ni catalysts supported on binary CeO2-based oxides, namely, Sm2O3-CeO2, Pr2O3-CeO2 and MgO-CeO2. The supports were obtained using the microwave assisted sol-gel method under reflux, while the catalysts were prepared by the wet impregnation method. For the investigation of the morphological, textural, structural and other intrinsic properties of the catalytic materials a variety of characterization techniques were used, i.e., Raman spectroscopy, XRD, N2 physisorption-desorption, CO2-TPD, H2-TPR, H2-TPD, XPS and TEM. Carbon deposition and sintering were investigated using TEM. It was shown that the addition of Sm3+ or Pr3+, incorporated into the lattice of CeO2, generated oxygen vacancies, but the Ni/Pr-Ce catalyst was found to possess more surface oxygen vacancies (e.g. Ce4+-Ov-Pr3+ entities). Moreover, modification of CeO2 using Sm3+ or Pr3+ restricted the agglomeration of nickel active sites and led to the genesis of Lewis basic positions. These characteristics improved the hydrogenation reaction at lower temperature. On the other hand, the addition of Mg2+ resulted at strong metal support interactions reinforcing the resistance of the Ni/Mg-Ce catalyst against sintering. Furthermore, the addition of Sm3+, Pr3+ and Mg2+ cations increased the overall basicity and the moderate adsorption sites and led to the formation of smaller Ni nano particles; these physico-chemical properties enhanced the CO2 methanation reaction. Finally, the activity experiments (WGHSV = 25,000 mL g−1 h−1, H2/CO2 = 4:1, T =350 °C) showed that at lower reaction temperature the Ni/Pr-Ce had the highest catalytic performance in terms of CO2 conversion (54.5%) and CH4 yield (54.5%) and selectivity (100%). The TOF values were found to follow the order Ni/Pr-Ce >> Ni/Mg-Ce > Ni/Sm-Ce > Ni/Ce.GIS is grateful for financial support by Greece and ESF through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS-5000432), implemented by the State Scholarships Foundation (IKY). NDC is grateful to the Research Committee of UOWM for financial support through grant no. 80304. IVY and MAG are grateful for financial support from the European Union and Greek national funds through the operational program Competitiveness, Entrepreneurship and Innovation, under the call Research-Create-Innovate (Project code: T1EDK-00782). SAK, AAK and KP acknowledge the financial support from the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE 2019-233 grant and support by the Khalifa University of Science and Technology under Award No. RC2-2018-024.Peer reviewe

The Effect of Ni Addition onto a Cu-Based Ternary Support on the H₂ Production over Glycerol Steam Reforming Reaction

In the present study, Ni/Ce-Sm-xCu (x = 5, 7, 10 at.%) catalysts were prepared using microwave radiation coupled with sol-gel and followed by wetness impregnation method for the Ni incorporation. Highly dispersed nanocrystallites of CuO and NiO on the Ce-Sm-Cu support were found. Increase of Cu content seems to facilitate the reducibility of the catalyst according to the H2 temperature-programmed reduction (H2-TPR). All the catalysts had a variety of weak, medium and strong acid/basic sites that regulate the reaction products. All the catalysts had very high XC3H8O3 for the entire temperature (400–750 °C) range; from ≈84% at 400 °C to ≈94% at 750 °C. Ni/Ce-Sm-10Cu catalyst showed the lowest XC3H8O3-gas implying the Cu content has a detrimental effect on performance, especially between 450–650 °C. In terms of H2 selectivity (SH2) and H2 yield (YH2), both appeared to vary in the following order: Ni/Ce-Sm-10Cu > Ni/Ce-Sm-7Cu > Ni/Ce-Sm-5Cu, demonstrating the high impact of Cu content. Following stability tests, all the catalysts accumulated high amounts of carbon, following the order Ni/Ce-Sm-5Cu < Ni/Ce-Sm-7Cu < Ni/Ce-Sm-10Cu (52, 65 and 79 wt.%, respectively) based on the thermogravimetric analysis (TGA) studies. Raman studies showed that the incorporation of Cu in the support matrix controls the extent of carbon graphitization deposited during the reaction at hand

Highly selective and stable Ni/La-M (M=Sm, Pr, and Mg)-CeO2 catalysts for CO2 methanation

Summarization: In the study presented herein, nickel catalysts supported on CeO2 and, for the first time in the literature, on La2O3-Sm2O3-CeO2, La2O3-Pr2O3-CeO2 and La2O3-MgO-CeO2 were prepared and evaluated for the reaction of CO2 methanation. The carriers were prepared through a sol-gel microwave assisted method and the catalysts were obtained following wet impregnation. The physicochemical properties of the catalysts prior to reaction were determined through H2-TPR, H2-TPD, Raman spectroscopy, XRD, CO2-TPD, N2 physisorption-desorption, XPS and TEM. The spent catalysts, after the time-on-stream experiments were further characterised using TEM and TGA. It was shown that the simultaneous incorporation of La3+, Pr3+ and La3+, Sm3+ into the crystal structure of cerium oxide created higher population of oxygen vacant sites. Moreover, the co-presence of La3+, Mg2+ and La3+, Pr3+ into the CeO2 increased the plethos of moderate basic sites. These physicochemical properties increased the rate of CO2 methanation reaction at relatively low temperatures. Furthermore, it is argued that the addition of La3+ stabilized the Ni active sites via the probable formation of a new compound (La-O-Ni) on the catalyst surface or synergetic catalytic centers at the interfacial area improving the catalytic properties (activity and stability). Finally, the catalytic performance tests revealed that the addition of La3+ mainly improved the conversion of CO2 and yield of CH4 for the Ni/La-Mg-Ce and Ni/La-Sm-Ce samples. The rCO2 and XCO2 values at 300 °C followed the order Ni/La-Sm-Ce >> Ni/La-Mg-Ce > Ni/La-Pr-Ce > Ni/Ce.Presented on: Journal of Co2 Utilizatio

Towards maximizing conversion of ethane and carbon dioxide into synthesis gas using highly stable Ni-perovskite catalysts

Dry ethane reforming (DER) aims to utilize captured CO2 and ethane, which is found in large quantities in shale gas, towards the production of high-value synthesis gas. During the dry reforming of hydrocarbons, the interaction between the active metal and the underlying support, along with the choice of the operating temperature, are considered to be the main factors influencing a catalyst’s stability and coking resistance. In this work, the DER catalytic performance and stability of Ni-doped perovskite systems is compared with that of a typical impregnated Ni/Al2O3 catalyst. The calcined, reduced and spent catalysts are assessed using the ICP, XRD, N2 physisorption, H2-TPR, CO2-TPD, TEM, HAADF-STEM, EDS Mapping, XPS and TPO techniques. Ni-CaZrO3 (CZNO) consisting of partly exsolved Ni nanoparticles with a strong metal-support interaction is shown to be particularly stable and accumulate only a fraction of the coke that is deposited on the impregnated Ni/Al2O3 catalyst, which suffers from severe and rapid degradation under the reactant stream. By increasing the operating temperature to 750 °C, Ni-CaZrO3 can achieve almost total conversion of ethane and around 90% conversion of carbon dioxide towards synthesis gas, with no apparent loss of catalytic activity.MAG and NDC gratefully acknowledge that this research has been co-financed by the European Union and Greek national funds under the call “Greece – China Call for Proposals for Joint RT&D Projects” (Project code: T7DKI-00388). KP acknowledges the support from Khalifa University through the grant RC2–2018-024.Peer reviewe

Polythiacalixarene-embedded gold nanoparticles for visible-light-driven photocatalytic CO [sub] 2 reduction

[Image: see text] Metal nanoparticles are potent reaction catalysts, but they tend to aggregate, thereby limiting their catalytic efficiency. Their coordination with specific functional groups within a porous structure prevents their aggregation and facilitates the mass flow of catalytic starting materials and products. Herein, we use a thiacalix[4]arene-based polymer as a porous support with abundant docking sites for Au nanoparticles. The sulfur atoms bridging the phenolic subunits of thiacalix[4]arene serve as Lewis basic sites that coordinate Au atoms. Therefore, this approach takes advantage of the functional groups inherent in the monomer and avoids laborious postsynthetic modifications of the polymer. The presented system was tested for visible-light-driven photocatalytic CO(2) reduction, where it showed adequate ability to generate 6.74 μmol g(–1) CO over the course of 4 h, while producing small amounts of the CH(4) product. This study aims to stimulate interest in the design and development of synthetically simpler porous polymer supports for various metal nanoparticles in catalytic and other applications

Highly selective and stable nickel catalysts supported on ceria promoted with Sm2O3, Pr2O3 and MgO for the CO2 methanation reaction

Summarization: The present work reports on the investigation of the catalytic performance for the methanation of CO2 over Ni catalysts based on CeO2, and for the first time, of Ni catalysts supported on binary CeO2-based oxides, namely, Sm2O3-CeO2, Pr2O3-CeO2 and MgO-CeO2. The supports were obtained using the microwave assisted sol-gel method under reflux, while the catalysts were prepared by the wet impregnation method. For the investigation of the morphological, textural, structural and other intrinsic properties of the catalytic materials a variety of characterization techniques were used, i.e., Raman spectroscopy, XRD, N2 physisorption-desorption, CO2-TPD, H2-TPR, H2-TPD, XPS and TEM. Carbon deposition and sintering were investigated using TEM. It was shown that the addition of Sm3+ or Pr3+, incorporated into the lattice of CeO2, generated oxygen vacancies, but the Ni/Pr-Ce catalyst was found to possess more surface oxygen vacancies (e.g. Ce4+-Ov-Pr3+ entities). Moreover, modification of CeO2 using Sm3+ or Pr3+ restricted the agglomeration of nickel active sites and led to the genesis of Lewis basic positions. These characteristics improved the hydrogenation reaction at lower temperature. On the other hand, the addition of Mg2+ resulted at strong metal support interactions reinforcing the resistance of the Ni/Mg-Ce catalyst against sintering. Furthermore, the addition of Sm3+, Pr3+ and Mg2+ cations increased the overall basicity and the moderate adsorption sites and led to the formation of smaller Ni nano particles; these physico-chemical properties enhanced the CO2 methanation reaction. Finally, the activity experiments (WGHSV = 25,000 mL g−1 h−1, H2/CO2 = 4:1, T =350 °C) showed that at lower reaction temperature the Ni/Pr-Ce had the highest catalytic performance in terms of CO2 conversion (54.5%) and CH4 yield (54.5%) and selectivity (100%). The TOF values were found to follow the order Ni/Pr-Ce >> Ni/Mg-Ce > Ni/Sm-Ce > Ni/Ce.Presented on: Applied Catalysis B: Environmenta