Theoretical Investigation of the Deactivation of Ni Supported Catalysts for the Catalytic Deoxygenation of Palm Oil for Green Diesel Production

For the first time, a fully comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to predict the selective catalytic deoxygenation of palm oil to produce green diesel over an Ni/ZrO2 catalyst. The modelling results were compared to experimental data, and a very good validation was obtained. It was found that for the Ni/ZrO2 catalyst, the paraffin conversion increased with temperature, reaching a maximum value (>95%) at 300 °C. However, temperatures greater than 300 °C resulted in a loss of conversion due to the fact of catalyst deactivation. In addition, at longer times, the model predicted that the catalyst activity would decline faster at temperatures higher than 250 °C. The CFD model was able to predict this deactivation by relating the catalytic activity with the reaction temperature

Green Diesel: Biomass Feedstocks, Production Technologies, Catalytic Research, Fuel Properties and Performance in Compression Ignition Internal Combustion Engines

The present investigation provides an overview of the current technology related to the green diesel, from the classification and chemistry of the available biomass feedstocks to the possible production technologies and up to the final fuel properties and their effect in modern compression ignition internal combustion engines. Various biomass feedstocks are reviewed paying attention to their specific impact on the production of green diesel. Then, the most prominent production technologies are presented such as the hydro-processing of triglycerides, the upgrading of sugars and starches into C15–C18 saturated hydrocarbons, the upgrading of bio-oil derived by the pyrolysis of lignocellulosic materials and the “Biomass-to-Liquid” (BTL) technology which combines the production of syngas (H2 and CO) from the gasification of biomass with the production of synthetic green diesel through the Fischer-Tropsch process. For each of these technologies the involved chemistry is discussed and the necessary operation conditions for the maximum production yield and the best possible fuel properties are reviewed. Also, the relevant research for appropriate catalysts and catalyst supports is briefly presented. The fuel properties of green diesel are then discussed in comparison to the European and US Standards, to petroleum diesel and Fatty Acid Methyl Esters (FAME) and, finally their effect on the compression ignition engines are analyzed. The analysis concludes that green diesel is an excellent fuel for combustion engines with remarkable properties and significantly lower emissions

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

Catalytic Conversion of Palm Oil to Bio-Hydrogenated Diesel over Novel N-Doped Activated Carbon Supported Pt Nanoparticles

Bio-hydrogenated diesel (BHD), derived from vegetable oil via hydrotreating technology, is a promising alternative transportation fuel to replace nonsustainable petroleum diesel. In this work, a novel Pt-based catalyst supported on N-doped activated carbon prepared from polypyrrole as the nitrogen source (Pt/N-AC) was developed and applied in the palm oil deoxygenation process to produce BHD in a fixed bed reactor system. High conversion rates of triglycerides (conversion of TG > 90%) and high deoxygenation percentage (DeCOx% = 76% and HDO% = 7%) were obtained for the palm oil deoxygenation over Pt/N-AC catalyst at optimised reaction conditions: T = 300 °C, 30 bar of H2, and LHSV = 1.5 h−1. In addition to the excellent performance, the Pt/N-AC catalyst is highly stable in the deoxygenation reaction, as confirmed by the XRD and TEM analyses of the spent sample. The incorporation of N atoms in the carbon structure alters the electronic density of the catalyst, favouring the interaction with electrophilic groups such as carbonyls, and thus boosting the DeCOx route over the HDO pathway. Overall, this work showcases a promising route to produce added value bio-fuels from bio-compounds using advanced N-doped catalysts.This research was funded by the Department of Chemical and Process Engineering of the University of Surrey and the EPSRC grants EP/J020184/2 and EP/R512904/1 as well as the Royal Society Research Grant RSGR1180353. Authors would also like to acknowledge the Ministerio de Economía, Industrial Competitividad of Spain (Project MAT2016-80285-P) and the Chinese Scholarship Council (CSC). L.P.-P. also thanks Comunitat Valenciana for her postdoctoral fellow APOSTD2017. K.P. is grateful for the support of the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. No. 359). The APC was funded by University of Surrey

Theoretical Investigation of the Deactivation of Ni Supported Catalysts for the Catalytic Deoxygenation of Palm Oil for Green Diesel Production

For the first time, a fully comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to predict the selective catalytic deoxygenation of palm oil to produce green diesel over an Ni/ZrO2 catalyst. The modelling results were compared to experimental data, and a very good validation was obtained. It was found that for the Ni/ZrO2 catalyst, the paraffin conversion increased with temperature, reaching a maximum value (>95%) at 300◦CHowever, temperatures greater than 300◦C resulted in a loss of conversion due to the fact of catalyst deactivation. In addition, at longer times, the model predicted that the catalyst activity would decline faster at temperatures higher than 250◦C. The CFD model was able to predict this deactivation by relating the catalytic activity with the reaction temperature

The Effect of WO3 Modification of ZrO2 Support on the Ni-Catalyzed Dry Reforming of Biogas Reaction for Syngas Production

The time-on-stream catalytic performance and stability of 8 wt. % Ni catalyst supported on two commercially available catalytic supports, ZrO2 and 15 wt.% WO3-ZrO2, was investigated under the biogas dry reforming reaction for syngas production, at 750°C and a biogas quality equal to CH4/CO2 = 1.5, that represents a common concentration of real biogas. A number of analytical techniques such as N2 adsorption/desorption (BET method), XRD, H2-TPR, NH3- and CO2-TPD, SEM, ICP, thermal analysis (TGA/DTG) and Raman spectroscopy were used in order to determine textural, structural and other physicochemical properties of the catalytic materials, and the type of carbon deposited on the catalytic surface of spent samples. These techniques were used in an attempt to understand better the effects of WO3-induced modifications on the catalyst morphology, physicochemical properties and catalytic performance. Although Ni dispersion and reducibility characteristics were found superior on the modified Ni/WZr sample than that on Ni/Zr, its dry reforming of methane (DRM) performance was inferior; a result attributed to the enhanced acidity and complete loss of the basicity recorded on this catalyst, an effect that competes and finally overshadows the benefits of the other superior properties. Raman studies revealed that the degree of graphitization decreases with the insertion of WO3 in the crystalline structure of the ZrO2 support, as the ID/IG peak intensity ratio is 1.03 for the Ni/Zr and 1.29 for the Ni/WZr catalyst

Promoting effect of CaO-MgO mixed oxide on Ni/γ-Al2O3 catalyst for selective catalytic deoxygenation of palm oil

The study presented herein examines, for the first time in the literature, the role of CaO-MgO as a modifier of γ-Αl2O3 for Ni catalysts for the production of green diesel through the deoxygenation of palm oil. The characteristics of the catalytic samples were examined by N2 adsorption/desorption, XRD, NH3-TPD, CO2-TPD, H2-TPR, XPS and TEM analysis. The carbon deposited on the catalytic surfaces was characterized by TPO, Raman and TEM/HR-TEM. Experiments were conducted between 300 and 400 °C, at 30 bar. Maximum triglyceride conversion and the yield of the target n–C15–n–C18 paraffins increased with temperature up to 375 °C for both catalysts. Both samples promoted deCO2 and deCO deoxygenation reactions much more extensively than HDO. However, although both catalysts exhibited similar activity at the optimal temperature of 375 °C, the Ni/modAl was more active at lower reaction temperatures, which can be probably understood on the basis of the increased dispersion of Ni on its surface and its lower acidity, which suppressed hydrocracking reactions. Time-on-stream experiments carried out for 20 h showed that the Ni/modAl catalyst was considerably more stable than the Ni/Al, which was attributed to the lower amount and lower crystallinity of the carbon deposits and to the suppression of sintering due to the presence of the CaO-MgO modifiers.KNP is grateful for the support of the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. no. 359). MAG and NDC gratefully acknowledge that this researched was co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» (MIS-5050170). SD is thankful for financial assistance provided by the Research Committee of the University of Western Macedonia (grant number 70277). KP acknowledges 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

Effect of operating parameters on the selective catalytic deoxygenation of palm oil to produce renewable diesel over Ni supported on Al2O3, ZrO2 and SiO2 catalysts

The present work investigated the production of Green Diesel through the deoxygenation of palm oil over Ni catalysts supported on γ-Αl2O3, ZrO2 and SiO2 for a continuous flow fixed bed reactor. A comprehensive experimental study was carried out in order to examine the effects of temperature, pressure, LHSV and H2/oil feed ratio on catalytic activity during short (6 h) and long (20 h) time-on-stream experiments. The catalysts were prepared through the wet impregnation method (8 wt% Ni) and were extensively characterized by N2 adsorption/desorption, XRD, NH3-TPD, CO2-TPD, H2-TPD, H2-TPR, XPS, TEM/HR-TEM and Raman. The characterization of the materials prior to reaction revealed that although relatively small Ni nanoparticles were achieved for all catalysts (4.3 ± 1.6 nm, 6.1 ± 1.8 nm and 6.0 ± 1.8 nm for the Ni/Al2O3, Ni/ZrO2 and Ni/SiO2 catalysts, respectively), NiO was better dispersed on the Ni/ZrO2 catalyst, while the opposite was true for the Ni/SiO2 sample. In the case of Ni/Al2O3, part of Ni could not participate in the reaction due to its entrapment in the NiAl2O4 spinel phase. Regarding performance, although an increase in H2 pressure led to increases in paraffin conversion, the increase of temperature was beneficial only up to a critical value which differed for each catalytic system under consideration (375 °C, 300 °C and 350 °C for the Ni/Al2O3, Ni/ZrO2 and Ni/SiO2 catalysts, respectively). All catalysts favored the deCO2 and deCO deoxygenation paths much more extensively than HDO, irrespective of testing conditions. Time-on-stream experiments showed that all catalysts deactivated after about 6 h, which was attributed to the sintering of the Ni particles and/or their covering by a thin graphitic carbon shell.KNP is grateful for the support of the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. no. 359). MAG and NDC gratefully acknowledge that this researched was co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning” (MIS-5050170). SD is thankful for financial assistance provided by the Research Committee of the University of Western Macedonia (grant number 70277). KP acknowledges the financial support from the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE 2019-233 grant and the support from Khalifa University under the RCII-2018-024.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

Syngas production via the biogas dry reforming reaction over Ni supported on zirconia modified with CeO2 or La2O3 catalysts

Summarization: Concerns over the ever increasing emissions of greenhouse gases, render the dry reforming of biogas (DRM) an important route in mitigating the effects of climate change, as the process consumes methane (CH4) and carbon dioxide (CO2) and produces valuable syngas (H2 and CO), which is useful for gas to liquid (GTL) technologies. Among the various metals explored (e.g., Ni, Co, Pt, Rh,), nickel appears to be the most suitable choice for both technical and economic reasons. It has been demonstrated that nickel sintering and/or carbon deposition (the main drawback of Ni on reforming reactions) can be both minimized via strong nickel–support interactions [1]. Supports commonly play an important role on the surface catalysis of metals through electronic interactions between the support and the active phase. For the present catalytic system, zirconia (ZrO2) is of attracting interest due to its mechanical strength, thermal stability, fracture toughness and hardness and its oxygen ions mobility that can be the origin of strong metal-support interactions [2]. The modification of ZrO2 with ceria (CeO2) and/or lanthana (La2O3), which provides mixed oxides with enhanced oxygen storage capacity and modified basicity, properties that are expected to affect the Ni-catalyzed DRM, is the subject of the present study.Παρουσιάστηκε στο: 21st World Hydrogen Energy Conference 201