Debaprasad Shee

Steam reforming of isobutanol for the production of synthesis gas over Ni/γ-Al2O3 catalysts

Bio-isobutanol has received widespread attention as a bio-fuel and a source of chemicals and synthesis gas as part of an integrated biorefinery approach. The production of synthesis gas by steam reforming (SR) of isobutanol was investigated in a down-flow stainless steel fixed-bed reactor (FBR) over Ni/γ-Al2O3 catalysts in the temperature range of 723–923 K. The NiO/γ-Al2O3 catalysts were prepared by the wet impregnation method and reduced in the FBR prior to the reaction. The surface area, metal dispersion, crystalline phase, and reducibility of the prepared catalysts were determined using BET, chemisorption, XRD and TPR, respectively. From the TPR studies, the maximum hydrogen consumption was observed in the temperature range of 748–823 K for all the catalysts. The presence of nickel species was confirmed through the characterization of the catalysts using powder XRD. The time-on-stream (TOS) studies showed that the catalysts remained fairly stable for more than 10 h of TOS. The conversion of carbon to gaseous products (CCGP) was increased by increasing the nickel loading on γ-Al2O3 and the temperature and by decreasing the weight hourly space velocity (WHSV). The hydrogen yield was increased by increasing the nickel loading on γ-Al2O3, the WHSV, the steam-to-carbon mole ratio (SCMR), and the temperature. The selectivity to methane decreased at high reaction temperatures and SCMRs. The selectivity to CO decreased with increasing SCMRs and decreasing temperatures. The work was further extended to the thermodynamic equilibrium analysis of the SR of isobutanol under experimental conditions using Aspen Plus, and the equilibrium results were then compared to the experimental results. A reasonably good agreement was observed between the trends in the equilibrium and the experimental results.

Roles of supports (γ-Al2O3, SiO2, ZrO2) and performance of metals (Ni, Co, Mo) in steam reforming of isobutanol

The production of synthesis gas from bio-isobutanol in an integrated biorefinery is a novel approach for its downstream conversion to hydrocarbon fuels and organic chemicals. The present article provides a systematic examination of the structure–activity correlation of various supported transition metal catalysts, xMS (x mmol metal, M (Ni, Co, and Mo) supported on S (Al, Si, and Zr for γ-Al2O3, SiO2, and ZrO2 respectively)) for steam reforming (SR) of bio-isobutanol. The activity of the catalyst was strongly influenced by metal-support interaction as reflected by metal dispersion, metal crystallite size, and extent of bulk metal/metal oxide. The catalytic activity increased in the order of 4.3NiZr < 4.3NiSi < 4.3NiAl and 4.3MoAl < 4.3CoAl < 4.3NiAl. 7.3CoAl exhibited consistent catalytic activity up to 12 h of time-on-stream. The hydrogen yield was boosted with rise of temperature and steam-to-carbon mole ratio (SCMR) with concurrent drop of selectivity to methane. The selectivity to CO reduced with increasing SCMR and decreasing temperature. Furthermore, spent catalysts were characterized to elucidate the effect of metal and support on the nature of coke formed and chemical transformation of the catalyst during SR.

Kinetics of hydrodeoxygenation of octanol over supported nickel catalysts: a mechanistic study

The hydrodeoxygenation (HDO) of 1-octanol as a model aliphatic alcohol of bio-oil was investigated in a continuous down-flow fixed-bed reactor over γ-Al2O3, SiO2, and HZSM-5 supported nickel catalysts in the temperature range of 488–533 K. The supported nickel catalysts were prepared by incipient wetness impregnation method and characterized by BET, XRD, TPR, TPD, H2 pulse chemisorption, and UV-vis spectroscopy. Characterization of supported nickel (or nickel oxide) catalysts revealed existence of dispersed as well as bulk nickel (or nickel oxide) depending on the extent of nickel loading and the nature of the support. The acidity of γ-Al2O3 supported nickel catalysts decreased with increasing the nickel loading on γ-Al2O3. n-Heptane, n-octane, di-n-octyl ether, 1-octanal, isomers of heptene and octene, tetradecane, and hexadecane were identified as products of HDO of 1-octanol. The C7 hydrocarbons were observed as primary products for catalysts with active metal sites such as γ-Al2O3 and SiO2 supported nickel catalysts. However, C8 hydrocarbons were primarily formed over acidic catalysts such as pure HZSM-5 and HZSM-5 supported nickel catalyst. The 1-octanol conversion increased with increasing nickel loading on γ-Al2O3, and temperature and decreasing pressure and WHSV. The selectivity to products was strongly influenced by temperature, nickel loading on γ-Al2O3, pressure, and types of carrier gases (nitrogen and hydrogen). The selectivity to C7 hydrocarbons was favoured over catalysts with increased nickel loading on γ-Al2O3 at elevated temperature and lower pressure. A comprehensive reaction mechanism of HDO of 1-octanol was delineated based on product distribution under various process conditions over different catalysts.

Hydrodeoxygenation of karanja oil over supported nickel catalysts: influence of support and nickel loading

Production of hydrocarbon transportation fuels from triglycerides is extremely important to reduce dependency on limited fossil fuels. The present article provides a systematic examination of hydrodeoxygenation (HDO) of karanja oil (KO) in a semi-batch reactor over supported (γ-Al2O3, SiO2, and HZSM-5) nickel catalysts. The catalysts were associated with both dispersed and bulk nickel/nickel oxide depending on the extent of nickel loading and nature of the support. Virgin KO is composed of ~76 wt% C18 fatty acids with ~15 wt% oxygen. HDO of KO resulted in a wide range of alkanes (C10–C22) with n-heptadecane being the major one. Transformation of KO into alkanes proceeds through three distinct routes: HDO, catalytic cracking, thermal cracking, or their combination. Highly acidic catalysts (HZSM-5 and Ni/HZSM-5) promote catalytic cracking leading to formation of a large amount of lighter alkanes. The cracking reaction becomes significant over the γ-Al2O3 supported nickel catalyst with ≤15 wt% nickel loading at elevated temperatures. A strong metal–support interaction favored the HDO pathway over the γ-Al2O3 supported nickel catalyst with ≥20 wt% nickel loading. About 80 wt% of KO was converted to the liquid product with physicochemical properties comparable with light diesel oil.

Reaction mechanism and kinetic modeling for the hydrodeoxygenation of triglycerides over alumina supported nickel catalyst

The present work provides a systematic study to delineate the reaction mechanism and develop a mechanistic kinetic model for the hydrodeoxygenation (HDO) of triglycerides (TG) over alumina supported nickel catalyst. The HDO of 1:2 molar mixtures of tripalmitin and tristearin was studied in a batch reactor over a wide range of process conditions. The results showed that TG instantaneously converted to respective fatty acids. The fatty acids further converted to the fatty aldehydes. The fatty aldehydes, then, rapidly converted to alkanes by two parallel reaction pathways. The decarbonylation of fatty aldehyde (RP-I) was the dominating route compared to the reduction of the fatty aldehyde to fatty alcohol followed by its dehydration and hydrogenation (RP-II). A mechanistic kinetic model was developed based on the observed reaction pathway to correlate the experimental results. The rate constants for the conversion of palmitic acid and stearic acid to alkanes were matched closely with each other thereby demonstrating that HDO is independent of fatty acid chain length. The developed kinetic model was further validated using experimental data at various hydrogen-to-nitrogen mole ratios in the gas phase. Furthermore, the rate constants obtained for various catalyst loadings were correlated by a linear equation with zero intercept.

Etherification of Glycerol with Ethanol over Solid Acid Catalysts: Kinetic Study Using Cation Exchange Resin

Abstract The etherification of glycerol with ethanol is a novel process to utilise low-value by-product (glycerol) of the biodiesel industry to produce ethers of glycerol suitable for use as fuel additive or solvent. The etherification of glycerol with ethanol was investigated under the liquid phase in a high pressure batch reactor using two different types of commercial solid acid catalyst (zeolites and strongly acidic cation exchange resin (CER)). The CER showed superior catalytic activity over H-beta zeolite. The diethyl ether was observed as major product at high ethanol-to-glycerol mole ratio. The product selectivity diverted towards ethers of glycerol with decreasing ethanol-to-glycerol mole ratio. Among ethers of glycerol, glycerol monoethyl ether was the major product of the reaction. The reaction mechanism for etherification of glycerol with ethanol was delineated based on experimental observations. The reaction rate increased with increasing catalyst loading and temperature without affecting selectivity to the products significantly. The apparent activation energy of glycerol and ethanol was 25.1 and 26.6 kcal/mol, respectively. An empirical kinetic model was developed to correlate experimental data at different temperatures. The conversion of the reactants calculated from the kinetic model matched reasonably with experimental data.