Chandrashekar Pendem

Preparation of the CuCr2O4 spinel nanoparticles catalyst for selective oxidation of toluene to benzaldehyde

CuCr2O4 spinel nano.particles with size between 30 and 60 nm were prepared by a hydrothermal synthesis method in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). It was found that the catalyst is highly active in the selective oxidation of toluene with H2O2 at 75° C. The catalyst was characterized by XRD, ICP-AES, XPS, BET-surface area, SEM, TEM and EXAFS. Factors effecting reaction parameters, such as the substrate to oxidant molar ratio, weight of the catalyst, reaction time, etc., were investigated in detail. The investigation revealed that the size of the catalyst as well as the spinel phase plays a crucial role in the activity by favoring the oxidation of toluene. The reusability of the catalyst was examined by conducting repeat experiments with the same catalyst; it was observed that the catalyst displayed no significant changes in its activity even after 5 reuses. A toluene conversion of 57.5% with 84.4% selectivity towards benzaldehyde was observed after 10 hours over the CuCr2O4 spinel nanoparticles catalyst.

Room temperature selective oxidation of cyclohexane over Cu-nanoclusters supported on nanocrystalline Cr2O3

Cu-nanoclustures supported on nanocrystalline Cr2O3 were prepared by a hydrothermal synthesis method in the presence of surfactant, cetyltrimethylammonium bromide (CTAB). It was found that the catalyst is highly active for the selective oxidation of cyclohexane with H2O2 at room temperature. The catalyst was characterized by XRD, ICP-AES, XPS, TPR, BET-surface area, SEM, TEM and EXAFS. The effect of Cu loading and the influence of reaction parameters, such as the substrate to oxidant molar ratio and reaction time, were investigated in detail. The investigation revealed that the size of copper plays a crucial role towards the activity by favoring the oxidation of cyclohexane. The reusability of the catalyst was tested by conducting repeat experiments with the same catalyst, where it was found that the catalyst displays no changes in its activity and selectivity even after 4 reuses. The cyclohexane conversion of 86% with a cyclohexanone selectivity of 85%, and an overall C6 selectivity (cyclohexanol and cyclohexanone) of 100% was achieved after 3 h of reaction at room temperature, over 4.3 wt% Cu loaded on nanocrystalline Cr2O3.

Aqueous phase reforming of glycerol to 1,2-propanediol over Pt-nanoparticles supported on hydrotalcite in the absence of hydrogen

Pt-nanoparticles, in the range of 2–5 nm, supported on hydrotalcite (HT), were used as a catalyst for the selective hydrogenolysis of glycerol to produce 1,2-propanediol by aqueous phase reforming in the absence of any added hydrogen. The catalyst was characterized by XRD, N2-sorption, pulse chemisorption, TPR, XPS, SEM, TEM, EXAFS. The influence of reaction parameters like reaction time, pressure, etc., were studied in detail. The study reveals that the Pt-nanoparticles are the active sites for the selective conversion of glycerol to 1,2-propanediol. The role of the support also plays an important role in the hydrogenolysis. The hydrogen required for the hydrogenolysis is derived from the reforming of H2O over the Pt-HT catalyst. The mechanism of the hydrogenolysis reaction is also proposed. A glycerol conversion of 98% with a 1,2-propanediol selectivity of 74% was achieved over 3 wt% Pt supported on HT. The reusability of the catalyst was tested by conducting four runs with the same catalyst and it was found that after four reuses, the conversion and selectivity was almost same.

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).

Partial oxidation of methane to synthesis gas over Pt nanoparticles supported on nanocrystalline CeO2 catalyst

Pt-nanoparticles supported on CeO2 have been prepared by a post synthesis method (Pt–CeO2PS). In the post synthesis method, CeO2 nanoparticles were prepared by a hydrothermal method, followed by the deposition of Pt nanoparticles over the CeO2. The prepared catalyst was characterized by XRD, BET-surface area, TPR, SEM, TEM, XPS and XAFS. It was observed that the catalyst prepared by the post synthesis method contained Pt nanoparticles with sizes between 2–5 nm supported on CeO2 nanoparticles with sizes between 20–60 nm. The catalytic performance of the Pt–CeO2PS catalyst was evaluated in the partial oxidation of methane for synthesis gas production. The Pt–CeO2PS catalyst could activate methane at 350 °C. We believe that the nanosized Pt particles and the synergy between the Pt particles, the CeO2 nanoparticles and the presence of a strong metal–support interaction play key roles in the activation of methane at such a low temperature. Different reaction parameters, like Pt-loading, reaction temperature, space velocity, and time on stream, were studied in detail. The Pt–CeO2PS catalyst does not deactivate till 100 h with a constant H2/CO mole ratio of 1.9 at 800 °C.

Pt nanoparticle supported on nanocrystalline CeO2: highly selective catalyst for upgradation of phenolic derivatives present in bio-oil

Pt nanoparticle supported on nanocrystalline CeO2 was prepared, and it was found that the catalyst can selectively hydrogenate phenolic derivatives present in bio-oil. The catalyst was characterized by XRD, XPS, ICP-AES, EXAFS, SEM and TEM. TEM micrograms confirm the presence of very small Pt nanoparticles supported on nanocrystalline CeO2. The catalyst was found to be very effective in liquid phase hydrogenation of phenol and phenolic compounds present in bio-oil in the presence of molecular H2. The synergy between the surface and very small Pt particles on the nanocrystalline CeO2 plays the most vital role towards the extremely high catalytic activity of the catalyst. The reusability of the catalyst was tested, and it was found that the catalyst does not exhibit any significant change in its catalytic activity even after five reuses. The catalyst showed ∼100% conversion with very high selectivity after 3 h in phenol conversions of 100% with >98% cyclohexanol selectivity achieved after 3 h of reaction at 100 °C in aqueous medium.

Preparation of CeO2 nanoparticles supported on 1-D silica nanostructures for room temperature selective oxidation of styrene

CeO2 nanoparticles of 2–5 nm size supported on 1-D silica nanostructure with diameter of ∼25–40 nm and a length of ∼1–4 μm were synthesized hydrothermally and it was found that the catalyst is very active for selective oxidation of styrene to styrene oxide at room temperature.

Single-step synthesis of hierarchical BxCN: a metal-free catalyst for low-temperature oxidative dehydrogenation of propane

A boron- and nitrogen-co-doped mesoporous carbon (BxCN) material with a hierarchical pore structure has been synthesized from a new boron precursor via a nanocasting approach. The newly synthesized material was thoroughly characterized by different characterization techniques. It was observed that the BxCN material has an excellent specific surface area, versatile pore diameter and large pore volume. Moreover, the pore diameter can be tuned by varying the amount of the boron source. By using solid-state MAS NMR and XPS, we demonstrated the N–B–C-type structure of the material. The material presented here has excellent stability under an oxygen atmosphere and we also confirmed the catalytic proficiency of this newly developed material in C–H bond activation reactions. The mesoporous BxCN material displays promising catalytic activity for the oxidative dehydrogenation of propane (6.7%) with excellent selectivity for propylene (84.6%) without the presence of any metal.

Highly selective transfer hydrogenation of α,β-unsaturated carbonyl compounds using Cu-based nanocatalysts

Simultaneous dehydrogenation of cyclohexanol to cyclohexanone and hydrogenation of α,β-unsaturated carbonyl compounds to corresponding α,β-unsaturated alcohols was carried out in a single pot reaction without addition of any external hydrogen donor. Cu nanoclusters supported on nanocrystalline MgO were found to be the active catalyst for the chemoselective transfer hydrogenation of unsaturated carbonyl compounds to produce the corresponding alcohols with very high yields. Transfer hydrogenation of cyclohexanol and cinnamaldehyde produced cyclohexanone and cinnamyl alcohol with 100% selectivity. This Cu/MgO catalyst can be easily recovered and recycled up to more than five times without any significant loss of activity, which confirmed the true heterogeneous nature of this catalyst. Several α,β-unsaturated compounds were also tested for this reaction and it was found that for all the cases the yield is >95%. The ease of handling without requiring high pressure H2 or a hazardous hydrogen source makes this transfer hydrogenation more practical and useful.

Hydrogenation of 5-hydroxymethylfurfural to 2,5 dimethylfuran over nickel supported tungsten oxide nanostructured catalyst

2,5 Dimethylfuran (DMF) can be considered as a promising new generation alternative fuel, which has the potential to solve the fossil fuel shortage and also the ongoing global warming issues. Although there are several reports in the literature on the production of DMF from 5-hydroxymethylfurfural, in most of the cases, the operating pressure is very high and expensive metals, such as Pd, Pt, and Rh, have been used in the presence of organic solvents. Herein, we report the preparation of nickel oxide nanoparticles supported on nanostructured tungsten oxide and the use of this catalyst as a heterogeneous catalyst for the selective hydrogenation of the biomass-derived platform molecule 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF), a liquid fuel, at 10 bar H2 pressure and 180 °C temperature in an aqueous medium. The catalyst was characterized using XRD, TEM, SEM, XPS, Raman and FTIR spectroscopies, TGA, and ICP-AES techniques. The catalyst showed >99% conversion of HMF with 95% selectivity of DMF without the use of any additives under optimized reaction conditions. The effect of reaction parameters, such as temperature, pressure of H2, and the loadings of Ni, was investigated and has been discussed in detail. The reusability of the catalyst was tested by conducting repeat experiments with the spent catalyst, where it was found that the catalyst displayed no changes in its activity and selectivity even after 5 successive runs. Based on the experimental results, a possible reaction pathway has been proposed.