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

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

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

Selective catalytic deoxygenation of palm oil to produce green diesel over Ni catalysts supported on ZrO2 and CeO2–ZrO2: Experimental and process simulation modelling studies

The selective deoxygenation of palm oil to produce green diesel has been investigated over Ni catalysts supported on ZrO2 (Ni/Zr) and CeO2–ZrO2 (Ni/CeZr) supports. The modification of the support with CeO2 acted to improve the Ni dispersion and oxygen lability of the catalyst, while reducing the overall surface acidity. The Ni/CeZr catalyst exhibited higher triglyceride (TG) conversion and yield for the desirable C15–C18 hydrocarbons, as well as improved stability compared to the unmodified Ni/Zr catalyst, with TG conversion and C15–C18 yield remaining above 85% and 80% respectively during 20 h of continuous operation at 300 oC. The high C17 yields also revealed the dominance of the deCOx (decarbonylation/decarboxylation) pathway. A fully comprehensive process simulation model has been developed to validate the experimental findings in this study, and a very good validation with the experimental data has been demonstrated. The model was then further utilised to investigate the effects of temperature, H2 partial pressure, H2/oil feed ratio and LHSV. The model predicted that maximum triglyceride conversion was attainable at reaction conditions of 300 °C temperature, 30 bar H2 partial pressure, H2/oil of 1000 cm3/cm3 feed ratio and 1.2 h−1 LHSV