Anil K. Sinha

Aviation fuel production from lipids by a single-step route using hierarchical mesoporous zeolites†

Hierarchical mesoporous molecular sieves with tunable zeolitic crystallinity, acidity and porosity were tailored to develop a single-step process for hydroconversion of triglycerides and free fatty acids obtained from algae and Jatropha seeds. Ni-W catalyst supported on acidic zeolitic ZSM-5 support with hierarchical structure and intra-crystalline mesoporosity with composition similar to that for typical hydrocracking catalyst could yield 40–45% C9–C15 hydrocarbons and high isomerization selectivity (isomer/n-alkane, i/n ~ 2–6) from Jatropha oil. While Ni-Mo catalysts on the same support furnished 40–50% kerosene range hydrocarbons with i/n ~ 3–13. For algal oil feed hydroconversion using sulfided Ni-Mo catalyst supported on high surface area semi-crystalline ZSM-5, unexpectedly high yield of jet-fuel range hydrocarbons (77%) with moderately high isomerization selectivity (i/n = 2.5) could be obtained.

Hydroprocessing of jatropha oil and its mixtures with gas oil

Hydroprocessing catalysts, sulfided Ni–W/SiO2–Al2O3, Co–Mo/Al2O3 and Ni–Mo/Al2O3 have been developed, and their performances in hydroprocessing of jatropha oil and its mixtures with refinery gas oil compared in terms of, detailed product distribution in order to optimize the catalyst and conditions that can give maximum yield of desired transportation fuel such as diesel or kerosene (jet). C15–C18 hydrocarbon yield (diesel range) is highest (97.9%) over Ni–Mo catalyst, while it is 80.8% over Ni–W catalyst and surprisingly low (49.2%) over Co–Mo catalyst. Jatropha oil with high as well as low free fatty acid (FFA) contents could be hydroprocessed with little observable effect on reactor metallurgy. The isomers to n-paraffins (i/n) ratio is very low and different for the three types of catalysts- nearly 22–36 times higher for the hydrocracking (Ni–W) catalyst than that for the hydrotreating (Ni–Mo) catalyst. The hydrodeoxygenation pathway for oxygen removal from triglyceride is favored over the fresh Ni–Mo and Co–Mo catalysts, while decarboxylation/decarbonylation pathway is favored over the Ni–W catalyst. But, resulfidation of used Ni–Mo catalyst results in decarboxylation/decarbonylation route being slightly more favored. The yield of diesel range (250–380 °C) product during co-processing varied between 88–92% for the Ni–Mo catalyst. Hydrodesulfurization of gas oil is better during co-processing with jatropha oil. The activation energy for overall S-removal is much lower than that for overall O-removal. Densities of the products were also observed to meet the required specification.

An improved high yielding immobilization of vanadium Schiff base complexes on mesoporous silica via azide―alkyne cycloaddition for the oxidation of sulfides

Azide–alkyne [3+2] cycloaddition “click reaction” was found to be a simple yet improved approach for the efficient immobilization of oxo–vanadium(IV) tridentate Schiff base complexes to mesoporous silica via covalent attachment as it occurred under mild reaction conditions and provided high catalyst loading compared to the direct immobilization of oxo–vanadium(IV) tridentate Schiff base complex to 3-chloropropylsilyl functionalized silica support.

Temperature-dependent reaction pathways for the anomalous hydrocracking of triglycerides in the presence of sulfided Co–Mo-catalyst

Kinetic studies and product profiling was done to understand the anomalous cracking of jathropha oil triglycerides in the presence of sulfided Co-Mo/Al(2)O(3) catalyst. At temperatures between 320 and 340 °C, only deoxygenation and oligomerization reactions took place whereas at temperatures above 340 °C, internal conversions between the products and direct conversion to lighter and middle distillates were favored High pressures (80 bar) and H(2)/feed ratios (>1500) were necessary to minimize oligomerization of the products and to increase the lifespan of the catalyst. Lumped kinetic models were validated with experimental results. Activation energies for the formation of lighter (83 kJ/mol) and middle fractions (126 kJ/mol) were higher than those for the heavy (47 kJ/mol) and deoxygenated (47 kJ/mol) products. Jatropha oil triglycerides hydroconversion pathways were dependent on temperature and the triglycerides could be hydrocracked to lower range hydrocarbons (C5-C14) by increasing the reaction temperatures.

Synthesis of hierarchical mesoporous vanadium silicate-1 zeolite catalysts for styrene epoxidation with organic hydroperoxide

Hierarchical mesoporous vanadium silicate-1 zeolites were successfully synthesized via a hydrothermal route using amphiphilic organosilanes as pore-directing templates. Also, to investigate the effect of the amount of vanadium metal on the physicochemical properties and catalytic activity, different hierarchical mesoporous vanadium silicate-1 zeolites have been successfully synthesized with varying vanadium contents. The physicochemical properties of these materials were characterized by various techniques, e.g. nitrogen sorption (for surface area, pore volume and pore size distribution), FTIR, TEM, SEM and UV-visible spectroscopy. UV-visible and X-ray photoelectron spectroscopy analysis showed that the vanadium atom was effectively incorporated into the framework of vanadosilicate. The samples have high BET and external surface areas. The catalytic performance of the hierarchical mesoporous vanadium silicate-1 zeolites was investigated in the oxidation of styrene with tert-butyl hydroperoxide as the oxidant. The amount of vanadium content plays a very important role not only in the physicochemical properties of the samples but also in the catalytic conversion of styrene and the selectivity of the products. The sample with the lowest vanadium content shows a 49% styrene conversion, the highest (54%) styrene oxide selectivity and the highest (189) turn-over frequency. Meanwhile, the sample with the highest vanadium content shows the highest (85%) styrene conversion and the highest (49.5%) benzaldehyde selectivity with respect to the other products.

Hierarchical mesoporous Fe/ZSM-5 with tunable porosity for selective hydroxylation of benzene to phenol

Hierarchical mesoporous Fe–ZSM-5 zeolite with catalytically active surface Fe species is prepared by introduction of Fe3+ in the synthesis gel of mesoporous ZSM-5 and the material synthesised with the optimum Fe content and optimum porosity is highly active and selective for the hydroxylation of benzene to phenol with nitrous oxide. The porosity of the material is controlled by the synthesis gel composition (organosilane template concentration). Samples prepared at high template/Si ratio (0.11) show lower zeolitic crystallinity and lower micropore volume but higher strong acidity than the samples prepared with low template/Si ratio (0.036). Samples with very high surface area, high strong acidity, low zeolitic wall crystallinity and 0.93 wt% Fe content show 1.3 times higher phenol formation rate than a steamed H-ZSM-5 sample. Silylation of the mesoporous catalyst resulted in 2-fold increase in initial phenol formation rate compared to steamed microporous H-ZSM-5 which is attributed to improved hydrophobicity and reduced Lewis acid sites, resulting in better desorption of the phenol product from catalyst.

Single-step catalytic liquid-phase hydroconversion of DCPD into high energy density fuel exo-THDCPD

Hydroconversion of dicyclopentadiene (DCPD) into high energy density jet propellant JP-10 has been successfully achieved with a greener single-step route over supported gold catalyst. The physicochemical properties of the catalysts were studied with XRD, SEM, TEM, N2-adsorption, NH3-TPD. The influence of reaction conditions like temperature, pressure, time etc. were studied in detail. The studies reveal that pressure and temperature play crucial roles in the reaction. Moderate acid sites in the catalysts are chiefly involved in isomerization and gold catalyzes hydrogenation of the intermediates. Analysis of the product stream at different intervals indicates a dissociation–recombination mechanism for the reaction. Reusability of the catalyst was tested by conducting five runs with the same catalyst. Even after the fifth run, the catalyst retains relatively high conversion and selectivity to exo-tetrahydrodicyclopentadiene (exo-THDCPD).

Development of Hydroprocessing Route to Transportation Fuels from Non-Edible Plant-Oils

Catalysts with tunable porosity, crystallinity and acidity can selectively produce aviation fuels and road transportation fuels via hydroprocessing of non-edible oils. Here we discuss several catalyst supports—mesoporous alumina, silica–alumina and hierarchical mesoporous zeolites, developed and used as support for hydroprocessing catalysts (Ni–Mo, Co–Mo, Ni–W), for the selective production of transportation fuels. These developed catalysts were used for the hydroconversion of waste cooking-oil, jatropha-oil, algal-oil and their mixtures with petroleum refinery oils. The physicochemical properties of the catalyst were tuned for optimal performance on the basis of evaluation results on high pressure fixed bed microreactors and pilot scale reactors. These studies targeted the production of transportation fuels (gasoline, kerosene and diesel) by hydroprocessing (hydrotreating or hydrocracking) renewable feed stocks or co-processing with fossil based oils. Modelling and process optimization studies for prediction of kinetic rate parameters and to know the reaction pathways for the conversion of these feed stocks to various range of hydrocarbon fuels, were also carried out. These studies provided the vital information that the reaction pathways were temperature dependent.

Depolymerization of cellulosic feedstocks using magnetically separable functionalized graphene oxide

Hydrolysis of cellulose into saccharides using a magnetically separable functionalized graphene is reported for potential applications in the environmentally benign saccharification of cellulose. Crystalline pure cellulose is hydrolyzed by graphene bearing –SO3H, –COOH and –OH functional groups in combination with iron nanoparticles. We observed nearly complete hydrolysis of cellulose into glucose and small (4–5 unit size) oligomers using low (1:1) catalyst to cellulose ratio. The apparent activation energy for the hydrolysis of cellulose into glucose using these catalysts is estimated to be 12 kJ mol−1, several times smaller than that for sulfuric acid under optimal conditions (170 kJ mol−1). The catalyst can be readily magnetically separated from the saccharide solution after the reaction for reuse in the reaction without loss of activity. Nearly complete hydrolysis of sugarcane bagasse into water soluble saccharides with repeated recycling was also possible. The catalytic performance of the graphene-based catalyst is attributed to the ability of the water soluble nanostructured material with a large concentration of polar groups (–OH, –COOH) which readily adsorb cellulose, while providing a large concentration of acidic functionality to hydrolyze the cellulose.

Mesoporous TUD-1 supported indium oxide nanoparticles for epoxidation of styrene using molecular O2

Activation of molecular O2 by metal or metal oxide nanoparticles is an area of recent research interest. In this work, for the first time, we report that indium oxide nanoparticles of <3 nm size dispersed on mesoporous silica (TUD-1) can activate molecular O2 and produce styrene epoxide with a selectivity of 60% and styrene conversion around 25% under mild conditions. It is found that neither indium oxide nor TUD-1 themselves respond to the styrene epoxidation reaction. The computational studies provide evidence that an oxygen molecule is highly polarized when it is located near the interface of both surfaces. The kinetic study shows that the reaction is of pseudo-first order and that the activation energy for styrene conversion is 12.138 kJ mol−1. The catalysts are recyclable for up to four regeneration steps, with the styrene conversion and styrene epoxide selectivity almost unchanged.