Bipul Sarkar

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.

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.

Acid–Base Cooperative Catalysis over Mesoporous Nitrogen‐Rich Carbon

WOx nanoclusters (2–3 nm) embedded on a mesoporous nitrogen‐rich carbon material were synthesized by using novel methodology. This material was very effectively capitalized as a new carbon‐based acid–base cooperative catalyst for sequential acetal hydrolysis and Knoevenagel condensation reactions. The protocol was also explored for the nitroaldol condensation reaction.

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.

Synthesis of AgWCN x Nanocomposites for the One-Step Conversion of Cyclohexene to Adipic Acid and Its Mechanistic Studies

A novel catalyst composed of silver nanoparticles grafted on WCNx has been prepared by using a facile pH-adjusted method. The material reported in this study presents a non-mineral acid route for the synthesis of the industrially significant monomer adipic acid through the selective oxidation of cyclohexene. Ag has been stabilized in the hydrophobic matrix during the formation of the mesoporous silica material by using aniline as stabilizing agent. A cyclohexene conversion of 92.2 % with 96.2 % selectivity for adipic acid was observed with the AgWCNx -2 catalyst, therefore, the AgWCNx catalyst was found to be efficient for the direct conversion to adipic acid with respect to their monometallic counterparts. The energy profile diagrams for each reaction path by using the AgWCNx catalyst were studied along with their monometallic counterparts by using the Gaussian 09 package. The reported material can avoid the use of harmful phase-transfer catalysts (PTC) and/or chlorinated additives, which are two among other benefits of the reported work.