N. Lingaiah

Microwave heating during catalyst preparation : influence on the hydrodechlorination activity of alumina-supported palladium-iron bimetallic catalysts

Abstract Alumina-supported Pd–Fe mono- and bimetallic catalysts have been prepared by microwave irradiation and by conventional calcination methods. The catalysts were characterised by powder X-ray diffraction (XRD), temperature-programmed reduction (TPR) and nitrogen adsorption measurements. Hydrogen chemisorption measurements were performed after low- and high-temperature reduction (LTR and HTR) of the catalyst. Hydrodechlorination of chlorobenzene was carried out on the reduced catalysts. Microwave heating changed the crystallite size and the susceptibility of the catalysts to alloy formation, with a resultant increase in the activity of the reduced catalysts for the hydrodechlorination of chlorobenzene.

NiO/Ce1−xNixO2−δ as an alternative to noble metal catalysts for CO oxidation

A series of NiO/CeO2 catalysts were prepared by using the combustion method and characterized by using XRD, N2-physisorption, TEM, UV-visible, Raman, XPS, ICP-OES and H2-TPR. Typical results indicated the NiO/CeO2 had a better performance than CeO2 for CO oxidation and 15 wt% NiO/CeO2 is active and stable, whereas catalysts with a higher NiO content of 20 and 30 wt% deactivated at 130 °C onwards. The high activity and excellent stability of 15% NiO/CeO2 catalysts can be ascribed to their high oxygen vacancy, high dispersion of NiO and strong metal–support interaction that leads to synergy between NiO and CeO2.

Catalytic hydrogenolysis of biodiesel derived glycerol to 1,2-propanediol over Cu–MgO catalysts

Selective hydrogenolysis of glycerol to 1,2-propanediol over Cu–MgO catalysts is reported. A series of Cu–MgO catalysts with varying Cu content were prepared by a co-precipitation method. The physico-chemical properties of the catalysts were derived from BET surface area, X-ray diffraction, temperature programmed reduction of hydrogen, temperature programmed desorption of carbon dioxide, X-ray photoelectron spectroscopy, transmission electron microscopy and dissociative N2O adsorption techniques. The activity results showed that Cu content on MgO has a significant role in glycerol conversion as well as formation of 1,2-propanediol. Well dispersed Cu species and accessible basic sites of MgO are the essential requirements for high glycerol hydrogenolysis activity. 20 wt% of Cu content on MgO is identified as an optimum Cu content. The catalyst is equally active even with crude glycerol and glycerol containing alkali salts as impurity. Different reaction parameters were evaluated and optimized reaction conditions were established.

Solvent-free hydration of alkynes over a heterogeneous silver exchanged silicotungstic acid catalyst

Silver exchanged silicotungstic acid (AgSTA) catalysts were prepared and characterized by X-ray diffraction, FT-IR spectroscopy, laser Raman, temperature programmed desorption of ammonia, FT-IR pyridine adsorption and X-ray photo electron spectroscopy. The activity of the catalysts was evaluated for the hydration of non-activated alkynes to corresponding carbonyl compounds without addition of any acid co-catalyst under solvent-free conditions. The highest catalytic activity was obtained for the catalyst with partially silver exchanged STA. This catalytic system provides one of the most straight forward syntheses of carbonyl compounds from terminal alkynes with Markovnikov-type regioselectivity. The catalyst can be recovered by simple filtration and is reusable without loss of activity and selectivity. A plausible reaction mechanism for the AgSTA catalyzed hydration of alkynes is proposed.

Samarium-exchanged Heteropoly Tungstate: An Efficient Solid Acid Catalyst for the Synthesis of Glycerol Carbonate from Glycerol and Benzylation of Anisole

Samarium‐exchanged heteropoly tungstate (SmxTPA) is an efficient catalyst for the synthesis of glycerol carbonate from glycerol and urea. The catalysts with varying Sm content were prepared and characterized by FT‐IR spectroscopy, XRD, laser Raman spectroscopy, temperature‐programmed desorption of ammonia, and X‐ray photo electron spectroscopy. The activity of the catalysts is related to the Lewis and Brønsted acidity, which depends on the Sm content in the catalysts. Partially exchanged SmxTPA catalyst showed high activity, owing to a higher number of Lewis acidic sites. The catalyst exhibited consistent activity and selectivity during recycling. A plausible reaction mechanism is presented. The catalyst also exhibited high activity in the acid‐catalyzed benzylation of anisole.

An efficient reusable silver-exchanged tungstophosphoric acid heterogeneous catalyst for solvent-free intermolecular hydroamination of alkynes

Hydroamination of alkynes with both aromatic and aliphatic amines proceeds efficiently in the presence of silver-exchanged tungstophosphoric acid (AgTPA) catalyst under solvent-free conditions to afford ketimines in excellent yields.

Studies on magnesia supported mono- and bimetallic Pd-Fe catalysts prepared by microwave irradiation method

Magnesia supported mono- and bimetallic Pd-Fe catalysts were prepared by conventional and microwave irradiation method. The prepared catalysts were characterised by N2 adsorption, temperature programmed reduction, selective hydrogen chemisorption and X-ray diffraction (XRD). The conventionally prepared catalysts after high temperature reduction (HTR) showed the formation of Pd-Fe alloy. In the case of microwave irradiated catalysts the formation of Pd-Fe alloy is limited during HTR reduction. These catalysts activity was tested in hydrodechlorination (HDC) of chlorobenzene. The catalysts prepared by microwave irradiation method are more active compared to conventionally prepared ones. The microwave irradiation leads to different morphology of the bimetallic catalysts. The HDC activity results are discussed in terms of structural differences between the catalysts prepared by conventional and microwave irradiation.

Transesterification of glycerol with dimethyl carbonate for the synthesis of glycerol carbonate over Mg/Zr/Sr mixed oxide base catalysts

A series of Mg/Zr/Sr based mixed oxide catalysts with varying molar ratios were prepared by a co-precipitation method. The X-ray diffraction and temperature programmed desorption of CO2 were used to derive the characteristics of the catalysts. These catalysts were evaluated for the synthesis of glycerol carbonate by the transesterification of glycerol with dimethyl carbonate. The transesterification activity depended on the molar ratio of the Mg/Zr/Sr and the pre-treatment temperature of the catalysts. The catalysts basicity was influenced by the molar ratio of the mixed oxides and calcinations temperature. The catalyst with a Mg/Zr/Sr molar ratio of 3 : 1 : 1, calcined at 650 °C, showed the highest glycerol conversion and selectivity to glycerol carbonate. During this reaction, the formation of glycidol by the decarbonylation of glycerol carbonate was observed over the catalysts with a high basic strength. The reaction parameters also influence the glycerol conversion and selectivity to glycerol carbonate.

Structure and activity of microwave irradiated silica supported Pd-Fe bimetallic catalysts in the hydrodechlorination of chlorobenzene

A series of silica supported Pd–Fe bimetallic catalysts were prepared by conventional as well as microwave heating methods. The catalysts were characterised by nitrogen adsorption (for BET surface area), X-ray diffraction (XRD), temperature-programmed reduction (TPR) and hydrogen chemisorption for their physico-chemical properties and were evaluated for chlorobenzene (CB) hydrodechlorination (HDC) activity. The catalysts prepared with microwave irradiation resulted into higher hydrodechlorination activity compared to their conventionally prepared analogues. These results are explained in terms of differences in the Pd morphology observed during the microwave irradiation.

Biodiesel production from used cooking oil by two-step heterogeneous catalyzed process.

The present study demonstrates the production of biodiesel from used cooking oil containing high free fatty acid by a two-step heterogeneously catalyzed process. The free fatty acids were first esterified with methanol using a 25 wt.% TPA/Nb(2)O(5) catalyst followed by transesterification of the oil with methanol over ZnO/Na-Y zeolite catalyst. The catalysts were characterized by XRD, FT-IR, BET surface area and CO(2)-TPD. In the case of transesterification the effect of reaction parameters, such as catalyst concentration, methanol to oil molar ratio and reaction temperature, on the yield of ester were investigated. The catalyst with 20 wt.% ZnO loading on Na-Y exhibited the highest activity among the others. Both the solid acid and base catalysts were found to be reusable for several times indicating their efficacy in the two-step process.