Hydrodeoxygenation is one of the promising technologies for the transformation of triglycerides into long-chain hydrocarbon fuel commonly known as green diesel. The hydrodeoxygenation (HDO) of rubber seed oil into diesel range (C15-C18) hydrocarbon over non-sulphided bimetallic (Ni-Mo/γ-Al2O3 solid catalysts were studied. The catalysts were synthesized via wet impregnation method as well as sonochemical method. The synthesized catalysts were subjected to characterization methods including FESEM coupled with EDX, XRD, BET, TEM, XPS, NH3-TPD, CO-chemisorption and H2-TPR in order to investigate the effects of ultrasound irradiations on physicochemical properties of the catalyst. All the catalysts were tested for HDO reaction at 350 °C, 35 bar, H2/oil 1000 N (cm3/cm3) and WHSV = 1 h-1 in fixed bed tubular reactor. The catalyst prepared via sonochemical method showed comparatively higher specific surface area, particles in nano-size and uniform distribution of particle on the external surface of the support, higher crystallinity and lower reduction temperature as well as higher concentration of Mo4+ deoxygenating metal species. These physicochemical properties improved the catalytic activity compared to conventionally synthesized catalyst for HDO of rubber seed oil. The catalytic performance of sonochemically synthesized Ni-Mo/γ-Al2O3 catalyst (80.87%) was higher than the catalyst prepared via wet impregnation method (63.3%). The sonochemically synthesized Ni-Mo/γ-Al2O3 catalyst is found to be active, produces 80.87 wt% of diesel range hydrocarbons, and it gives high selectivity for Pentadecane (18.7 wt%), Hexadecane (16.65 wt%), Heptadecane (24.45 wt%) and Octadecane (21.0 wt%). The product distribution revealed that the deoxygenation reaction pathway was preferred. Higher conversion and higher HDO yield in this study are associated mainly with the change in concentration ratio between oxidation states of molybdenum (Mo4+, Mo5+, and Mo6+) on the external surface of the catalyst due to ultrasound irradiation during the synthesis process. Consequently, the application of sonochemically synthesized non-sulphided catalysts favored mainly hydrodeoxygenation of diesel range hydrocarbon.
The catalytic steam reforming of oxygenated hydrocarbons has been holding an interest in scientific societies for the past two decades. The hydrogen production from steam reforming of glycerol, ethanol and other oxygenates such as ethylene glycol and propylene glycol are more suitable choice not just because it can be produced from renewable sources, but it also helps to decrease the transportation fuel price and making it more competitive. In addition, hydrogen itself is a green fuel for the transportation sector. The studies on the production of hydrogen from various reforming technologies revealed a remarkable impact on the environmental and socio-economic issues. Researchers became more focused on glycerol steam reforming (GSR), ethanol steam reforming (ESR) and other oxygenates to investigate the catalyst suitability, their kinetics and challenges for the sustainability of the oil and gas production. In the present work, the authors critically addressed the challenges and strategies for hydrogen production via GSR, ESR and other oxygenates reforming process. This review covers extensively thermodynamic parametric analysis, catalysts developments, kinetics and advancement in the operational process for glycerol, ethanol and few other oxygenates. This detailed investigation only highlights the steam reforming process (SRP) of these oxygenates at the laboratory experimental stage. It was found that from this review, there are many technical issues, which lead to economic challenges. The issues are yet to be addressed and thus, these particular applications require faster accelerations at the pilot scale, taking into the consideration of the current pandemic and economic issues, for a safer and greener environment. Graphical abstract.