@article { ISI:000274954400005, title = {Gas-phase oxidant-free oxidation of cyclohexanol over V2O5-MoO3-M2O (M = Na, K, Cs) catalysts}, journal = {Indian Journal of Chemical Technology}, volume = {17}, number = {1}, year = {2010}, month = {JAN}, pages = {43-49}, publisher = {NATL INST SCIENCE COMMUNICATION-NISCAIR}, address = {DR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIA}, abstract = {

Oxidant-free oxidation (dehydrogenation) of cyclohexanol is carried out in a down-flow integral laboratory scale reactor using different alkali doped catalysts. The effect of reaction temperature, contact time (W/F) and doping of alkali metals is studied to check its effect on nature of prominent products of the reaction (cyclohexanone and cyclohexene). At lower temperature the cyclohexanone prevails whereas at higher temperature cyclohexene is observed in prominence. Acid-modified catalysts (with boron and phosphorous) facilitated cyclohexene selectivity whereas alkali modified catalysts facilitated cyclohexanone selectivity. Calcination of sodium modified catalyst at different temperatures under static condition affect characteristic phase intensity and cyclohexanone selectivity. XRD investigation showed formation of different inorganic phases as the characteristic of dopant. Cesium modified catalyst showed better dehydrogenation activity.

}, keywords = {Cyclohexanol, dehydration, Dehydrogenation, Electronegativity, V2O5-MoO3}, issn = {0971-457X}, author = {Vyawahare, Y. K. and Chumbhale, Vilas R. and Pardhy, S. A. and Samuel, V. and Aswar, A. S.} } @article {44596, title = {Cyclohexylation of resorcinol with cyclohexanol catalyzed by tungstophosphoric acid supported zirconia catalysts}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {18}, year = {2018}, month = {APR}, pages = {2986-2992}, abstract = {

We demonstrate a highly active and reusable heterogeneous catalyst system, tungstophosphoric acid (TPA) supported on zirconia (ZrO2), for the cyclohexylation of resorcinol by cyclohexanol to produce value added chemicals such as 2-cyclohexyl resorcinol, 4-cyclohexyl resorcinol and 3-Hydroxy cyclohexyl phenyl ether under liquid phase reaction condition. TPA/ZrO2 catalysts prepared with different TPA loadings (5-30 wt.\%) by wet impregnation method and calcined in the temperature range of 650-850 degrees C were characterized by Nitrogen sorption analysis, XRD, FTIR, DTG and DTA, and P-31 MAS NMR spectroscopy. Among the catalysts studied, 15 wt.\% TPA/ZrO2 catalyst calcined at 750 degrees C gave the highest conversion of resorcinol (51.2\%) with the selectivities for 3-Hydroxy cyclohexyl phenyl ether (53.9\%) and 2-cyclohexyl resorcinol and 4-cyclohexyl resorcinol together (46.1\%) under optimum reaction conditions. However, the selectivity of the products were controlled by varying the reaction conditions. At higher conversion of resorcinol (78.9\%), only C-alkylated products were formed at 200 degrees C with 15 wt.\% TPA/ZrO2 catalyst calcined at 750 degrees C. The combination of TPA and ZrO2 coupled with calcination temperature offered an excellent platform for the conversion of resorcinol into O- or C-alkylated products.

}, keywords = {15\% TPA/ZrO2, Cyclohexanol, Cyclohexylation, Keggin TPA, Resorcinol}, issn = {1533-4880}, doi = {10.1166/jnn.2018.14342}, author = {Balasubramanian, V. V. and Devassay, B. M. and Halligudi, S. B. and Deepika, R. and Umbarakar, S. B. and Vinu, A.} } @article {46320, title = {Mechanistic insights into the pathways of phenol hydrogenation on Pd nanostructures}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {7}, year = {2019}, month = {OCT}, pages = {17126-17136}, type = {Article}, abstract = {

Product selectivity in aqueous phase phenol hydrogenation on well-defined supported Pd nanostructures (spheres, cubes, and octahedra) was studied using defined experiments and density functional theory (DFT) simulations. On Pd spheres and octahedra, the reaction initially showed high selectivity (in the first 3 h, at 363 K and 5 bar H-2 pressure) toward the partially hydrogenated product cyclohexanone. On prolonged operation (\>20 h of reaction time), a shift in the product selectivity (up to 100\%) toward the completely hydrogenated product cyclohexanol was observed on Pd spheres and octahedra. In contrast, the reaction on Pd cubes, which only had {100} facets, showed a high selectivity (similar to 90\%) toward the product cyclohexanone even after 40 h, at the same reaction conditions. Since the {111} facets are expected to be the majority sites on a spherical particle, we attribute the selectivity trend observed on spherical Pd particles to be primarily controlled by the selectivity trend on the Pd{111} facets. This observation was further confirmed on performing the hydrogenation reaction on a mixture of Pd cube and Pd octahedron particles in a ratio of 25:75 (representing the site ratio of a spherical particle). DFT simulations provided a mechanistic insight into the reactivity of the two different facets ({100} and {111}) toward phenol hydrogenation. The calculations revealed that the selectivity significantly depended on the activation barriers involved in cyclohexanone hydrogenation on the Pd{111} facets (77 and 57 kJ/mol) as compared to those on the Pd{100} facets (97 and 101 kJ/mol).

}, keywords = {Cyclohexanol, cyclohexanone, facet-dependent reactivity, phenol hydrogenation}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.9b03392}, author = {Porwa, Govind and Gupta, Shelaka and Sreedhala, S. and Elizabeth, Joes and Ithan, Tuhin Suvra and Haider, M. Ali and Vinod, C. P.} } @article {46306, title = {Understanding the influence of alumina supported ruthenium catalysts synthesis and reaction parameters on the hydrodeoxygenation of lignin derived monomers}, journal = {Molecular Catalysis}, volume = {480}, year = {2020}, month = {JAN}, pages = {UNSP 110525}, type = {Article}, abstract = {

Up-gradation of lignin derived monomers to value-added and fuel grade products is important to make overall bio-refinery process economical. Although, few studies are devoted on this work yet, systematic study on commercially viable (low loading of metal, recyclable catalyst, mild conditions, high selectivities etc.) is scarce and typically done under harsh conditions. Herein, we report, the methodical effect of support (SiO2, Al2O3 (acidic, basic and neutral), SiO2-Al2O3) on the hydrodeoxygenation (HDO) of lignin derived various monomers, guaiacol, veretrol, eugenol, phenol using very low loading (0.5 wt\%) Ru catalyst. Very high yield (82\%) of cyclohexanol from guaiacol could be achieved in presence of cyclohexane as a solvent and Ru/Al2O3-Acidic catalyst at 225 degrees C and under 1 MPa H-2 pressure. The detailed study on the effect of solvent, stability and adsorption of reactant \& products etc. is done and it was observed that products are more prone to adsorb and undergo further reactions. The complete characterization of fresh and spent catalysts revealed that lower catalyst reduction temperature and presence of Ru in partially higher oxidation state proved by XPS, helps in enhancing the cyclohexanol formation. Subsequently, role of Ru particle size and support on the activity was also investigated.

}, keywords = {Cyclohexanol, Hydrodeoxygenation, lignin, reaction pathway, supported metal catalyst}, issn = {2468-8231}, doi = {10.1016/j.mcat.2019.110525}, author = {Singh, Dheerendra and Dhepe, Paresh L.} } @article {47109, title = {Efficient catalytic transfer hydrogenation-hydrodeoxygenation of lignin derived monomers: investigating catalyst properties-activity correlation}, journal = {Catalysis Communications}, volume = {149}, year = {2021}, month = {JAN }, pages = {106220}, type = {Article}, abstract = {

Reduction of O/C ratio of lignin derived monomers via hydrodeoxygenation (HDO) pathway is conventionally furnished using molecular hydrogen under severe conditions. Nonetheless, due to a prerequisite to accomplish HDO through commercially attractive methodology we report, HDO reactions of various phenolic compounds via catalytic transfer hydrogenation (CTH) pathway using very low loading of Ru (0.5 wt\%) on neutral and acidic Al2O3 under nitrogen atmosphere. With guaiacol as a substrate, 74\% cyclohexanol yield at 225 degrees C in the presence of IPA is realized. Bi-functionality of metal state, acidity of support and nature of alcohol are perceived to be responsible for the variation in activity.

}, keywords = {Catalytic transfer hydrogenation (CTH), Cyclohexanol, Hydrodeoxygenation, lignin, Supported metal catalysts}, issn = {1566-7367}, doi = {10.1016/j.catcom.2020.106220}, author = {Singh, Dheerendra and Dhepe, Paresh L.} } @article {47627, title = {Mechanistic investigations on the catalytic transfer hydrogenation of lignin-derived monomers over Ru catalysts: theoretical and kinetic studies}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {9}, year = {2021}, month = {OCT}, pages = {14040-14050}, type = {Article}, abstract = {The hydrodeoxygenation (HDO) reaction of oxygenated compounds such as lignin-derived phenolics is well studied using molecular H-2 as a hydrogen source, yet the use of high pressures discourages its use on an industrial scale. As an alternative, the catalytic transfer hydrogenation (CTH) pathway provides in situ hydrogenation species, which reduces the need for the high-pressure infrastructure required when molecular hydrogen is used. Nevertheless, this strategy is scantly studied, and in lieu with this, herein we report the kinetic and mechanistic investigations of the CTH strategy for the HDO of guaiacol, phenol, anisole veratrole, and eugenol to their respective products. For potential commercialization purposes, low loading of metal, milder reaction conditions, and high selectivity toward desired products with a high H/C ratio were considered while designing catalysts (0.5 wt \% Ru on SiO2-Al2O3, SiO2, Al2O3-acidic, Al2O3-basic, and Al2O3-neutral) for these reactions. As high as 74\% cyclohexanol yield from guaiacol was achieved at 225 degrees C in the presence of isopropyl alcohol (IPA) as the hydrogen source and over the Ru/Al2O3-acidic catalyst reduced at 150 degrees C. A detailed kinetic study is carried out to understand the interaction of the substrate and intermediates with the catalyst and the influence of reaction parameters on the product formation. It was observed that the cisisomer of 2-methoxycyclohexanol rapidly undergoes further conversion than the trans-isomer. The experimental observations are substantiated through density functional theory (DFT) studies on Ru(0001) and guaiacol molecule complexes. DFT studies indicate that the adsorption of the cis-isomer is more exothermic as compared to that of the trans counterpart, and the underlying electronic factors are elucidated using charge density difference and density of states plots.}, keywords = {catalytic transfer hydrogenation, Cyclohexanol, DFT, Hydrodeoxygenation, kinetics, lignin monomers, Supported metal catalysts}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c02942}, author = {Khan, Tufeil Sartaj and Singh, Dheerendra and Samal, Pragnya Paramita and Krishnamurty, Sailaja and Dhepe, Paresh Laxmikant} } @article {48950, title = {Phenol hydrogenation to cyclohexanol catalysed by palladium supported on CuO/CeO2}, journal = {Chemistry-an asian jounrnal}, volume = {18}, year = {2023}, month = {JUN }, type = {Journal Article}, abstract = {

Hydrogenation of phenol to cyclohexanone/cyclohexanol is an important reaction in production of nylon-6, nylon-66 and in petroleum industry. Liquid phase phenol hydrogenation over Pd-CuO/CeO2 was carried out under mild conditions. Palladium impregnated over CuO/CeO2 synthesized by co-precipitation method showed excellent catalytic activity for phenol hydrogenation (99\% conversion with 80\% cyclohexanol yield) at 90 degrees C and 10 bar H-2 pressure in water. Commercial 10\%Pd/C showed only 8\% phenol conversion under identical conditions. The detailed characterization revealed significant improvement in surface area of ceria after addition of CuO and decrease in crystallite size with creation of defects in CeO2 lattice. XPS analysis showed Pd loading on CuO/CeO2 to cause hydrogen spillover on the surface leading to increase in the oxygen vacancies. The interaction of phenol with catalyst surface studied by detailed FTIR analysis, revealed activation of phenol on oxygen vacancy of ceria as phenoxide ion with perpendicular orientation of aromatic ring on catalyst surface.

}, keywords = {Cyclohexanol, Hydrogen spillover, oxygen vacancies, Pd-CuO/CeO2, phenol hydrogenation}, issn = {1861-4728}, doi = {10.1002/asia.202300119}, author = {Kasabe, Mirabai M. and Kotkar, Vaibhav R. and Dongare, Mohan K. and Umbarkar, Shubhangi B.} }