Showing papers by "Ajay K. Dalai published in 2020"

A review on subcritical and supercritical water gasification of biogenic, polymeric and petroleum wastes to hydrogen-rich synthesis gas

Abstract: Lignocellulosic feedstocks such as forestry biomass and agricultural crop residues can be utilized to generate biofuels and biochemicals. In addition, a large amount of non-plant residues or biogenic wastes is also generated worldwide that has huge potentials but remains underutilized. Converting these organic waste materials through thermochemical and biochemical processes into biofuels is widely regarded as a remedial approach to address waste management and clean energy problems. One of such thermochemical biomass-to-gas technologies is hydrothermal gasification in the presence of subcritical or supercritical water, which utilizes the unique fluid properties of water to disintegrate effectively the organic wastes into hydrogen-rich syngas. This paper reviews the thermophysical chemistry of subcritical and supercritical water as well as their role in generating syngas from the hydrothermal decomposition of biogenic, polymeric and organic wastes such as municipal solid waste, animal manure, food waste, industrial effluents, sewage sludge, mixed plastics, waste tires and petrochemical wastes. The paper also describes different technologies used for syngas cleaning and conditioning together with gas-to-liquid technology such as Fischer-Tropsch synthesis to produce hydrocarbon fuels. The current progress, challenges and knowledge gaps in the research and development of hydrothermal gasification of biogenic wastes are also discussed.

Subcritical water gasification of lignocellulosic wastes for hydrogen production with Co modified Ni/Al2O3 catalysts

Abstract: Nickel-based catalysts with different supports and cobalt loadings were synthesized for hydrothermal gasification of cellulose at 350 °C. The activity of Ni catalysts was found in the order of Al2O3 > spent bleaching clay ash > SiO2 with H2 yield of 80.6%, 69.0% and 57.0%. When 6 wt. % Co was added, 10Ni-6Co/Al2O3 showed the highest H2 yield of 88.4% i.e., 1.44 times that without Co addition. Catalysts were characterized by NH3-TPD, TPR, XRD, BET and XPS, showing that Ni-Co alloy formation promoted H2 production. Single-factor experiments were conducted to study variables in the presence of 10Ni-6Co/Al2O3 with the selected conditions of 0.5 g biomass and 20 min at 350 °C (achieving 94.9% H2 yield from cellulose) for gasification of rice straw, peanut shell and cotton straw with the increase in H2 yield by 51.4, 76.0 and 67.8 times. Ni-Co/Al2O3 catalysts enhanced hydrothermal gasification of actual agricultural residues.

Catalytic gasification of light and heavy gas oils in supercritical water

Abstract: Canada has the third-largest oil sand reserves in the world as a result of which, it generates considerable amounts of light gas oil and heavy gas oil through petroleum distillation. With the escalating energy demands, it has become essential to explore alternative fuel resources from biomass and petrochemical residues. This study explores the potential of supercritical water gasification to transform light and heavy gas oils to hydrogen-rich syngas through the optimization of process conditions such as temperature (375–675 °C), feed concentration (20–35 wt%) and reaction time (30–75 min). Nickel-supported functionalized carbon nanotubes (10%Ni/FCNT) were synthesized for application in catalytic supercritical water gasification. The functionalization of carbon nanotubes resulted in an increase in their surface area from 108 m2/g (in pristine CNT) to 127 m2/g (in FCNT) and 122 m2/g (in 10%Ni/FCNT). The impregnation of catalytic nickel particles onto carbon nanotubes was confirmed through X-ray diffraction (XDR) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). Fourier-transform infrared (FTIR) spectroscopy of both gas oils revealed the presence of aliphatics, alkyl-aryl ethers and sulfur-containing compounds among several other aromatics. Light gas oil revealed higher hydrogen yields of 3.32 mol/kg compared to that of heavy gas oil (2.79 mol/kg) at optimal process conditions, i.e. 675 °C and 75 min, 20 wt% feed concentration. However, 10%Ni/FCNT enhanced hydrogen yields (4.46 mol/kg), total gas yield (9.22 mol/kg), hydrogen selectivity (94%) and lower heating value (1685 MJ/kg) of product gases obtained from light gas oil in contrast to heavy gas oil. This study indicates a tremendous potential of gas oils for hydrogen generation via hydrothermal gasification.

Synthesis of n-Butyl Levulinate Using Mesoporous Zeolite H-BEA Catalysts with Different Catalytic Characteristics

Abstract: The present work focuses on the utilization of waste biomass for the improvement of key catalytic properties of conventional zeolite H-BEA. In the present endeavor, zeolite H-BEA has been modified using cetyltrimethyl ammonium bromide (CTAB) and rice husk (a waste biomass resource), via desilication post synthetic route, which is not reported so far. The synthesized mesoporous zeolite H-BEA catalysts have been characterized by various characterization techniques such as, SEM, 27Al and 29Si MAS-NMR, wide and low angle XRD, ICP-OES, FT-IR, TGA, NH3-TPD and BET surface area. The resultant mesoporous zeolite materials (MCCK and MCRK) exhibited bimodal porosity as well as improved physicochemical properties, and the utility of these modified zeolites as heterogeneous catalysts has been demonstrated in the production of n-butyl levulinate via levulinic acid (LA) esterification. The catalytic material, which has been modified using CTAB and rice husk, is found to exhibit better catalytic activity towards the synthesis of n-butyl levulinate (95.6%) as compared to other zeolite counterparts under the optimised reaction conditions, which is attributed to its enhanced surface area and lower Si/Al ratio as compared to other catalysts under study.

Physicochemical and Fuel Characteristics of Torrefied Agricultural Residues for Sustainable Fuel Production

Abstract: Torrefaction as a thermal pretreatment was conducted on oat hull, canola hull, and barley straw in a fixed-bed reactor at temperatures in the range of 220–300 °C and residence times of 30-60 min to...

Oxidative desulfurization of heavy gas oil over Ti-TUD-1 supported Keggin-type molybdenum heteropolyacid

Abstract: The authors are thankful to King Abdullah University of Science and Technology (KAUST), Saudi Arabia for providing the financial support for this study through the center partnership funds, Canadian Light Source Inc for the XANES study and Ms. Rosa Do Phuong for assistance in analytical studies.

Effects of promoters (Mn, Mg, Co and Ni) on the Fischer-Tropsch activity and selectivity of KCuFe/mesoporous-alumina catalyst

Abstract: Fischer–Tropsch synthesis (FTS) is one of the promising technologies to produce liquid fuels and fine chemicals from coal, natural gas and biomass. Significant improvements in reactor technology and catalyst development are the focus of research in this area. In this work, the effects of 1.0 wt% promotor such as Mn, Mg, Co and Ni on the FTS activity and selectivity of mesoporous alumina supported KCuFe catalyst were studied. All synthesized promoted catalysts were characterized using BET, XRD, H2-TPR, XPS, TEM and XANES. The FTS reaction was carried out in a fixed bed reactor at 270 °C, 300 psi, 2000 h−1 and H2/CO = 1.25. In this work, the Ni-promoted catalyst showed the highest methane selectivity (∼29 %). The Co-promoted catalyst showed the least Olefins/Paraffins (O/P) ratio and a ∼5% increase in methane selectivity. Mg-promoted catalyst performed average but better than Ni and Co-promoted catalysts. However, Mn-supported catalyst outperformed Mg, Ni and Co-promoted catalysts and resulted in higher C5+ selectivity along with a marginal increase in CO conversion. The ∼5%, 2%, and 2% decline in CO2, CH4 and C2-C4 selectivities were also registered upon the addition of Mn promotor. The improvement in FTS activity and selectivity of Mn-promoted catalyst is related to the increase in iron dispersion and reducibility, as seen during H2-TPR, XPS and XANES analyses. The presence of Mn+3 and Mn+4, as confirmed by Mn 2p XPS and Mn K-edge XANES, indicates that the interaction at the electronic level between manganese and iron has contributed to improved performance. This study concludes that Mn is the most effective promotor for the synthesized mesoporous alumina supported KCuFe catalyst for the FT synthesis process.

Environmental and socioeconomic impact assessment of biofuels from lignocellulosic biomass

Abstract: This chapter highlights the socio-environmental and techno-economic features in commercialization of biofuels production from feedstocks, such as soybean, canola, and green-seed canola oil. Challenges involved in facing the food versus fuel problem associated with most of the agricultural crops have resulted in search of feedstocks, such as lignocellulosic biomass and microalgae as feedstock, for alternate fuels production. This chapter on socio-environmental benefits of biofuels from lignocellulosic biomass presents novelty, robust analysis, and new results with a significant element focusing on recent works in the field of life cycle assessment (LCA) of renewable and sustainable energy. Biofuels production from waste extraction oil and algae are presently gaining attention and globally, focus on commercialization of algae, and waste oil–based biofuels is rising. The information from this chapter can be used by (1) researchers working in the bioenergy sector focusing on the development and commercialization of second- and third-generation biofuels; (2) industries across the globe involved in the LCA of biofuel sector and their growth trends, and (3) legal advisors and policy makers focusing on the environmental carbon balance and ecological development.

A Spotlight on Butanol and Propanol as Next-Generation Synthetic Fuels

Abstract: The exhaustive extraction and prodigious utilization of fossil fuels have led to the large-scale increase in the emissions of greenhouse gases. In addition, the per capita demand of petrochemical resources is escalating due to rapid industrialization and the rising number of vehicles in the transportation sector. There is a growing interest in the development of alternative fuels to reduce the carbon footprint and air pollution caused by the fossil fuels. Biofuels produced from plant residues are carbon neutral and can be produced through biomass-to-liquid and biomass-to-gas conversion technologies. Bioethanol, biopropanol, and biobutanol are some alcohol-based fuels and chemicals that have found multifarious industrial applications. Although bioethanol is blended with gasoline for use as a transportation fuel, it is often criticized over food-versus-fuel debate because of its raw materials being food crops such as corn, sugarcane, and other grains. In addition, butanol and propanol have high potentials over ethanol in replacing gasoline partially or completely due to their advanced fuel properties. This chapter throws light on butanol and propanol as the next-generation synthetic fuels. The aspects discussed in this chapter include their fuel chemistry as well as production technologies from petrochemicals and bio-based feedstocks. The biotechnological developments in the fermentation of lignocellulosic biomass to produce butanol and propanol are provided. The chapter concludes with a note on industrial challenges and future prospects in employing butanol and propanol as commercial biofuels and biochemicals.

Biocrude Oil Production via Hydrothermal Liquefaction of Algae and Upgradation Techniques to Liquid Transportation Fuels

Abstract: Hydrothermal liquefaction of algae is regarded as a favorable thermochemical process to produce biocrude oil from biomass with potential to complement conventional crude oil. This chapter discusses the production of biocrude oil via hydrothermal liquefaction of microalgae. Due to the presence of high protein content in algal species, the catalytic removal of heteroatoms is required to make liquid transportation fuels (biodiesel and biogasoline) from algal biocrude oil. Therefore, different upgradation techniques are explored to remove the heteroatoms using various heterogeneous acid catalysts. Special focus is given to the effects of process parameters on hydrothermal liquefaction and upgradation techniques to escalate biocrude oil yield and liquid transportation fuels.

Mesoporous Adsorbents for Desulfurization of Model Diesel Fuel: Optimization, Kinetic, and Thermodynamic Studies

Abstract: Mesoporous alumina-based adsorbents consisting of a π-electron acceptor complexing agent (2,7-dinitro-9-fluorenone) were synthesized and characterized. Adsorbents were screened for the removal of sulfur compounds from a model ultra-low-sulfur diesel fuel via a charge transfer complex (CTC) mechanism. The sulfur adsorption isotherms and kinetics were examined. The kinetics of sulfur adsorption followed a pseudo-second-order model with the CTC adsorbents. Among the three adsorbents screened, a commercial γ-Al2O3 CTC adsorbent showed the highest desulfurization in a short-run period. The regeneration of spent adsorbent was studied with three different polar solvents, namely chloroform, dichloromethane, and carbon tetrachloride. Dichloromethane was found to be the most suitable solvent for extracting a major portion of sulfur compounds occupied in the pores of the spent adsorbent. γ-Al2O3 CTC adsorbent can be reused after regeneration. Thermodynamic parameters such as Ea, ΔG, ΔH, and ΔS provided a better insight into the adsorption process.

Influence of calcination on physico-chemical properties and Ficher–Tropsch activity of titanosilicate supported cobalt catalysts with different pore sizes

Abstract: Titanosilicate supports of different pore sizes were synthesized by a surfactant-free templating method. Cobalt was loaded by incipient wetness impregnation on the synthesized supports and commercial γ-Al2O3. The Fischer–Tropsch activities of the catalysts were studied with and without prior calcination in a fixed bed reactor at 220 °C, 1.83 MPa and 2000 mLsyngas/mLcatalyst/h after in situ reduction. XANES analysis of the catalysts revealed that after reduction, a greater fraction of the loaded cobalt had been reduced in the calcined catalyst (74 %) compared to the uncalcined catalyst (58 %). Activity studies revealed that the CO conversion and C5+ selectivities of the catalysts with medium pore titanosilicate supports was higher (80 % conversion, 81–85 % selectivity) than the CO conversion by Co/γ-Al2O3 (77 % conversion, 76 % selectivity). Calcination in air increased the liquid product selectivity of all the catalysts towards the diesel fraction from 21–24 % to 25–32 %.

Catalysis for the Production of Sustainable Fuels and Chemicals

Abstract: The emission of green-house gases and environmental concerns have led to recent research in the use of renewable feedstocks derived from biomass, waste oils and fats as a source for fuels and chemicals [...]

Solvent-Free Benzylation of Glycerol by Benzyl Alcohol Using Heteropoly Acid Impregnated on K-10 Clay as Catalyst

Abstract: Value addition to glycerol, the sole co-product in biodiesel production, will lead to reform of the overall biodiesel economy. Different valuable chemicals can be produced from glycerol using heterogeneous catalysis and these valuable chemicals are useful in industries such as cosmetics, pharmaceuticals, fuels, soap, paints, and fine chemicals. Therefore, the conversion of glycerol to valuable chemicals using heterogeneous catalysis is a noteworthy area of research. Etherification of glycerol with alkenes or alcohols is an important reaction in converting glycerol to various value-added chemicals. This article describes reaction of glycerol with benzyl alcohol in solvent-free medium by using a clay supported modified heteropolyacid (HPA), Cs2.5H0.5PW12O40/K-10 (Cs-DTP/K-10) as solid catalyst and its comparison with other catalysts in a batch reactor. Mono-Benzyl glycerol ether (MBGE) was the major product formed in the reaction along with formation of di-benzyl glycerol ether (DBGE). The effects of different parameters were studied to optimize the reaction parameters. This work provides an insight into characterization of Cs2.5H0.5PW12O40/K-10 catalyst by advanced techniques such as surface area measurement, X-ray analysis, ICP-MS, FT-IR, and SEM. Reaction products were characterized and confirmed by using the GCMS method. The kinetic model was developed from an insight into the reaction mechanism. The apparent energy of activation was found to be 18.84 kcal/mol.

Conversion of Glycerol to Value-Added Products

Abstract: The dramatic increase in biodiesel production has increased the oversupply of glycerol as a by-product. Low cost, ready availability, and surplus supply of glycerol is a spectacular opportunity for chemical industry to utilize glycerol as feedstock for production of high-value products. This chapter provides the information about different pathways available for conversion of glycerol into high specialty chemicals. Various approaches and strategies have been developed by researchers to investigate the effects of reaction parameters, i.e., nature and type of catalyst, reaction time, temperature, pressure, and type of solvent, on glycerol conversion and product selectivity. Based on the information provided in this chapter, researchers can select a viable process for the conversion of waste glycerol into valuable commodities.

Process Improvements and Techno-Economic Feasibility of Hydrothermal Liquefaction and Pyrolysis of Biomass for Biocrude Oil Production

Abstract: Biocrude oil production from biomass has gained huge attention globally to complement the conventional fuels and reduce the environmental impact caused by fossil fuels. To produce renewable energy from biomass, several technologies have emerged, such as physical (e.g., drying, pressing, crushing, and pelletization), biochemical (e.g., fermentation and anaerobic digestion), and thermochemical (e.g., pyrolysis, gasification, liquefaction, and combustion) pathways. Among all, thermochemical technologies have gained much attention due to their high-energy content products and process efficiency. The biocrude oil produced from pyrolysis and hydrothermal liquefaction has similar chemical properties to conventional liquid fuels. Therefore, this chapter discusses the current status, challenges, opportunities, recent process developments, and techno-economic feasibility of hydrothermal liquefaction and pyrolysis of biomass for biocrude oil production.

Au/Ce0.5Zr0.5O2 catalysts for hydrogen production via partial oxidation of methanol

Abstract: Effects of ZrO2 addition to the Au/CeO2 and the pretreatment methods of the catalysts on the partial oxidation of methanol (POM) were investigated. ZrO2 addition to Au/CeO2 catalyst led to (i) formation of a Ce0.5Zr0.5O2 solid solution; (ii) enhancement of lattice oxygen reducibility of the Ce0.5Zr0.5O2 support; and (iii) formation of surface Auδ+ (δ = 1 or 3) species coexisting with Au0 nanoparticles. Catalytic evaluation showed that the highest hydrogen selectivity was achieved over Au/Ce0.5Zr0.5O2 at 270 °C. The reductive pretreatment could improve the hydrogen selectivity and methanol conversion as well. At higher reaction temperature Auδ+ clusters in Au/Ce0.5Zr0.5O2 catalyst activated the O‒H bond in the adsorbed CH3‒Oδ−‒Hδ+ due to the interaction between Auδ+ and Oδ−‒Hδ+ of methanol that favors the release of H+ proton, and thus benefits the H2 selectivity enhancement. Some oxygen vacancies in the catalysts evidenced by XPS analysis participated in the formation of active surface oxygen species that promoted CO oxidation to CO2 on Au0 nanoparticles A reaction mechanism of POM involving in the methanol surface adsorption on Auδ+ species, O‒H bond activation, and CO oxidation on Au0 nanoparticles and oxygen defects was proposed.

Impact of synchrotron on alternate fuels sector with special focus on hydrogen energy

Abstract: The global economy is highly dependent on the availability and production of fossil fuels, and over the decades, considerable works have been done on the upgrading of crude oil to obtain fossil fuels. In this chapter, we provide insights into the importance of physicochemical characterization tools, synchrotron-based imaging, and spectroscopic techniques for the design and development of novel catalysts for hydrogen production reactions. Critical parameters during the preparation of catalysts are calcination temperature, metal loading, and the presence/absence of additives such as promoters or chelating agents. The literature on the molecular interpretation for catalytic activity during biohydrogen production reactions is scarce especially in the case of bio-based feedstocks. The application of synchrotron radiation in material science especially for characterization of hydrogen evolution reaction catalysts and molecular mechanistic studies is being focused in recent times. Overall the imaging of catalysts and understanding the reaction mechanism through imaging techniques are gaining importance, and it will be a significant area for future researchers to focus.