Komandur V. R. Chary

Kinetics of esterification of aromatic carboxylic acids over zeolites Hβ and HZSM5 using dimethyl carbonate

Abstract Esterification of benzoic acid and substituted benzoic acids has been carried out efficiently over zeolite Hβ and HZSM5 in an autoclave using dimethyl carbonate (DMC) as the methylating agent. The wide applicability of this esterification method to esterify a wide range of aromatic carboxylic acids has been demonstrated. This method is a viable and safe alternative to other esterification processes, involving harmful alkylating agents and chemicals. Strong acid sites are responsible for the reaction. The reaction proceeds inside as well as outside the pores of the zeolites. The pore architecture of the zeolites and mass transfer limitations come into play only when the molecular diameter of the reactant molecules is greater than the pore size of the zeolites. Kinetic study shows that the reaction is first-order with respect to acid concentration.

Vapour phase dehydration of glycerol over VPO catalyst supported on zirconium phosphate

A series of VPO catalysts supported on porous zirconium phosphate with varying VPO loadings ranging from 5–30 wt% were prepared by solid–solid wetting method. The calcined catalysts are well characterized by BJH for pore size distribution, X-ray diffraction (XRD), FTIR, scanning electron microscopy (SEM), temperature programmed reduction (TPR) and UV diffuse reflectance spectroscopy. The acidic properties of the catalysts were investigated by ex-situ FTIR analysis of adsorbed pyridine and temperature programmed desorption (TPD) of NH3. The catalytic properties were evaluated for the gas phase dehydration of glycerol to acrolein. The results of pore size distribution by the BJH method suggest that the VPO loadings considerably affect the textural properties. XRD and FTIR analysis suggest that the formation of vanadyl pyrophosphate phase on the zirconium phosphate support. SEM image of unsupported VPO catalyst clearly exhibits the formation of a rosette like structure. UV-DRS study reveals the formation of vanadyl pyrophosphate phase along with some extent of vanadium orthophosphate phase. TPR analysis suggests that the reducibility of the active VPO phase depends on the VPO loading and also the active phase strongly interacts with the support. The results of vapour phase glycerol dehydration reaction are well correlated with the acidity of the catalysts measured by the ex-situ adsorbed pyridine by FTIR and TPD of ammonia. The findings derived from several characterization techniques clearly suggest that VPO species is highly dispersed on the ZrP support.

Hydrodesulfurization on MoS2/MgO

A series of Mo/MgO catalysts with loadings ranging from 2–12 wt% Mo were studied by oxygen chemisorption, X-ray diffraction and activity for thiophene hydrodesulfurization (HDS) reaction. The results obtained from the above measurements are compared with those on Mo/-γ-Al2O3. These results indicated that molybdenum is better dispersed on MgO. Hydrodesulfurization activity per g. Mo is found to be higher in the case of Mo/MgO. The higher activities are attributed to the increase in dispersion of Mo on MgO. A linear correlation is obtained between oxygen chemisorption and HDS activity. The parallelism between HDS and oxygen chemisorption is explained.

Alkylation of phenol with methanol over molybdenum oxide supported on NaY zeolite

A series of MoO3/NaY catalysts were prepared with Mo loadings ranging from 2 to 16 wt% and characterized by X-ray diffraction (XRD), BET specific surface area and temperature-programmed desorption (TPD) of ammonia. XRD results revealed that the crystallinity of NaY zeolite was found to decrease with increase in Mo loading in the catalysts. The total acidity measured by ammonia TPD of the catalysts was found to decrease with increase in Mo loading. The catalytic properties were evaluated for the vapor phase alkylation of phenol with methanol and the results were correlated with results obtained from different characterization techniques. The conversion of phenol decreases as Mo loading increases in the catalyst. With increase in Mo loading on NaY zeolite the selectivity for the formation of C-alkylated compounds was decreased. However, the selectivity towards the formation of O-alkylated products was increased.

Vapor phase selective hydrogenation of acetone to methyl isobutyl ketone (MIBK) over Ni/CeO2 catalysts

Ceria supported nickel oxide catalysts with varying nickel loadings from 1.0 to 20.0 wt% were prepared by the impregnation method. The catalysts were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (UV-DRS), temperature programmed reduction (TPR), temperature programmed desorption (TPD) of CO2, and surface area measurements. The dispersion of nickel and metal area were determined by the hydrogen chemisorption method. The X-ray diffraction patterns suggest the presence of crystalline NiO phase beyond 2.5 wt% of Ni on ceria. The UV-visible diffuse reflectance spectra reveal the presence of two types of nickel species on the CeO2 support. TPR patterns reveal the presence of highly dispersed surface free nickel oxide species at lower temperatures and bulk NiO at higher temperatures. The basicity of the catalysts measured by the CO2 TPD method was found to increase with an increase in nickel loading up to 2.5 wt% and decrease with further increase in nickel loading. The vapor phase condensation and selective hydrogenation of acetone to methyl isobutyl ketone (MIBK) were carried out on Ni/CeO2 catalysts and the catalytic properties are correlated with the results of CO2 TPD measurements and also with the dispersion of the nickel species supported on ceria.

Catalytic performance of Pt/AlPO4 catalysts for selective hydrogenolysis of glycerol to 1,3-propanediol in the vapour phase

Hydrogenolysis of glycerol to 1,3-propanediol was investigated in the vapour phase over a series of Pt/AlPO4 catalysts with platinum loadings ranging from 0.5 to 3 wt%. The catalysts were prepared by a wet impregnation method and characterized by various techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), BET surface area, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and CO-chemisorption methods. Ex situ pyridine adsorbed FTIR analysis and temperature programmed desorption (TPD) of NH3 were employed to investigate the acidic properties of the catalysts. Further, the effect of reaction temperature, hydrogen flow rate, glycerol concentration and various contents of platinum (0.5 to 3 wt%) have been investigated to find the optimum reaction conditions. Superior performance with almost 100% conversion of glycerol and above 35% selectivity to 1,3-propanediol was obtained over 2 wt% Pt/AlPO4 at 260 °C and atmospheric pressure. The influence of acidity of the catalyst and its correlation to the catalytic performance (selectivity and conversion) has been studied. The high strength of weak acidic sites and Bronsted acidity of the catalyst measured by NH3-TPD and Pyr-FTIR were concluded to play a key role in selective formation of 1,3-propanediol. XRD, TEM and CO-chemisorption studies revealed that platinum was well dispersed on AlPO4 which further contributed to higher catalytic activity for glycerol hydrogenolysis.

Vapour phase methylation of pyridine with methanol over the Zn1 − xMnxFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1) ferrite system

Alkylation of pyridine by methanol to methylpyridines has been studied in the vapour phase in a fixed bed reactor, in the temperature range 473–723 K over the Zn1−xMnxFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1) ferrospinel system. 2-Picoline and 3-picoline were found to be major products. It was observed that, systems possessing high x values are highly selective for 2-picoline. Reaction parameters were optimized over MnFe2O4. A maximum yield of 67.6% of 2-methylpyridine, with a selectivity of 79.5%, and 17.5% of 3-methylpyridine with a selectivity of 20.5%, was obtained over MnFe2O4 at a temperature of 673 K, using a methanol to pyridine molar ratio of 5 and weight hour space velocity of 0.2 h−1. Catalyst characterization has been made by XRD, infrared spectroscopy and ammonia desorption methods. A tentative mechanism for production of 2-picoline and 3-picoline, involving dihydropyridine as the intermediate has been proposed.

Vapour phase ammoxidation of toluene over vanadium oxide supported on Nb2O5-TiO2

Vanadium oxide catalysts with V2O5 loadings ranging 1 to 9% (w/w) supported on 1∶1 wt% Nb2O5–TiO2 mixed oxide have been prepared by the wet impregnation method. The calcined samples were characterized by X-ray diffraction (XRD), pulse oxygen chemisorption and temperature programmed desorption (TPD) of NH3. Dispersion of vanadia was determined by oxygen chemisorption at 643 K in a dynamic method. At low V2O5 loadings, vanadia is found to be present in a highly dispersed state. X-Ray diffraction results also suggest that vanadium oxide exists in a highly dispersed state at lower loadings and in a crystalline V2O5 phase at higher vanadia loadings (5 wt% and above). The dispersion of vanadia was found to decrease with V2O5 loading due to the formation of V2O5 crystallites. The catalytic properties were evaluated for the vapor phase ammoxidation of toluene to benzonitrile and correlated with characterization results.

Characterization and catalytic properties of MoO3–V2O5/Nb2O5 catalysts

Abstract The influence of molybdenum oxide on the dispersion of vanadium oxide supported on niobia was investigated. A series of MoO3–V2O5/Nb2O5 catalysts with varying MoO3 content ranging from 1% to 5% (w/w) with fixed V2O5 content were prepared by impregnation of previously prepared 5 wt% V2O5/Nb2O5 with requisite amounts of ammonium molybdate solution. X-ray diffraction patterns indicate the presence of β-(Nb,V)2O5 phase with the addition of MoO3 up to a loading of 3 wt%. Temperature-programmed reduction (TPR) results suggest that the reducibility is decreasing with MoO3 loading. The results of temperature programmed desorption (TPD) of ammonia suggest that the acidity of the catalysts increased with the addition of MoO3. The catalytic properties of the catalysts in the ammoxidation of 3-picoline were correlated with the characterization data.

Dispersion and reactivity of molybdenum oxide catalysts supported on titania

Abstract A series of MoO 3 catalysts with Mo loadings ranging from 2 to 10 w/w% supported on TiO 2 were prepared and investigated by X-ray diffraction (XRD), temperature programmed reduction (TPR) and oxygen chemisorption measurements. Dispersion of molybdena was determined by the oxygen chemisorption at 623 K and by static method on the samples prereduced at the same temperature. At low Mo loadings, i.e. below 6% Mo, molybdenum oxide was found to present in a highly dispersed amorphous state. TPR profiles of MoO 3 /TiO 2 samples suggest that the reduction of MoO 3 to Mo proceeds in two stages and the reducibility of MoO 3 increases with Mo loading in the catalysts. The catalytic properties were evaluated for the vapor-phase ammoxidation of toluene to benzonitrile and are related to the oxygen chemisorption sites.