Mohan K. Dongare

Catalytic dehydration of lactic acid to acrylic acid using calcium hydroxyapatite catalysts

A series of calcium hydroxyapatite (HAP) catalysts were synthesised with a Ca/P ratio ranging from 1.3 to 1.89 by a co-precipitation method that involved changing the pH of the calcium and phosphorous precursors. The physicochemical characterization by XRD, SEM, BET surface area and CO2 and NH3-TPD techniques confirmed the hydroxyapatite formation. These HAP catalysts were used for the vapour phase dehydration of lactic acid to acrylic acid. The HAP catalyst with a Ca/P ratio of 1.3 was found to be the most efficient catalyst among the synthesised series, which gave 100% conversion of lactic acid and 60% selectivity towards acrylic acid at 375 °C when a 50% (w/w) aqueous solution of lactic acid was used. The higher selectivity towards acrylic acid has been correlated to the increased acidity and reduced basicity of the HAP catalyst with a Ca/P ratio of 1.3 compared to the other HAP catalysts. The catalyst was found to be very stable and no deactivation was observed even after 300 h of reaction time. In situ FTIR studies were performed for understanding the mechanistic aspects and showed the formation of calcium lactate as an intermediate species during the dehydration of lactic acid to acrylic acid.

Regioselective nitration of phenol over solid acid catalysts

Abstract Phenol is selectively nitrated in liquid phase to ortho-nitrophenol in high yield using dilute nitric acid over solid acid catalysts. Zeolite H-beta was found to be a very active catalyst for nitration of phenol to ortho-nitrophenol at room temperature in carbon tetrachloride as a solvent. Compared to the conventional process, phenol nitration over solid acid catalyst is a clean and environment friendly process with a simpler workup procedure for quantitative isolation of the products.

Synthesis and characterization of copper-stabilized zirconia as an anode material for SOFC

Solid oxide fuel cells (SOFC) are now being seriously considered for alternate energy source because of the environmental hazards associated with the use of fossil fuels and their limited availability. As a part of the development of these fuel cells, we have synthesized a series of CuO–ZrO2 samples with varying concentration of CuO. In this paper, we present the study of copper-stabilized zirconia as an anode material in SOFC. The role of copper oxide in stabilizing zirconia and the possible reasons for the increase in catalytic activity of the relevant composition have been discussed using the experimental data.

Regioselective nitration of o-xylene to 4-nitro-o-xylene using nitric acid over solid acid catalysts

Abstract The regioselective nitration of o -xylene to 4-nitro- o -xylene (4-NOX) has been studied in the liquid and vapor phase over zeolites H-beta, H-ZSM-5 and silica supported molybdenum oxide (MoO 3 /SiO 2 ) catalysts. Zeolite H-beta showed the maximum conversion of 28% and 63% selectivity for 4-NOX in liquid phase nitration at 70 °C with 70% HNO 3 . The conversion increased to 65% when the reaction was carried out in vapor phase at 150 °C using dilute 30% HNO 3 . The formation of α-methylphenyl nitromethane by alkyl nitration in liquid phase was decreased in vapor phase reaction. The formation of oxidation products was also decreased in vapor phase reaction with minor amounts of dinitro and ipso-products. The influence of experimental parameters such as temperature, nitric acid concentration and WHSV on conversion and selectivity has been investigated. The use of dilute nitric acid and the selective formation of 4-NOX using dilute HNO 3 makes this process environmental friendly with a potential for commercialization.

Benzoylation of anisole over borate zirconia solid acid catalyst

B2O3/ZrO2 solid catalyst containing 30 mol% boron oxide prepared by wet impregnation method and calcined at 500 °C showed efficient catalytic activity in liquid phase benzoylation of anisole with benzoyl chloride (BOC) in nitrobenzene solvent at 150 °C. B2O3/ZrO2 catalyst under study has shown comparable performance with conventional homogeneous AlCl3 catalyst as well as heterogeneous catalysts such as zeolite H-beta and sulphated zirconia with maximum conversion and selectivity to the corresponding 4-methoxy benzophenone (4-MBP). The effect of various experimental parameters such as temperature, nature of solvent, reaction time and the effect of various benzoylating agents has been discussed. The conversion of anisole to 4-MBP increases significantly with increasing reaction time and temperature. The maximum conversion of about 91% with yield of acylated product >96% and selectivity for 4-MBP >94% was observed after 22 h. 2-MBP was found to be <4%. The phenyl benzoate (3%) formed by the O-benzoylation of anisole was found to be a major side product. The catalyst was recycled three times without any appreciable decrease in the anisole conversion showing its stability.

Vapor phase nitration of benzene using mesoporous MoO3/SiO2 solid acid catalyst

Nitration of benzene has been carried out in the vapor phase, using dilute nitric acid as the nitrating agent, over mesoporous MoO3/SiO2 solid acid catalyst with more than 90% benzene conversion and 99.9% selectivity for mononitrobenzene. A series of MoO3/SiO2 catalysts with varying MoO3 loadings (1–30 mol%) were prepared using a sol–gel technique and characterized using X-ray diffraction analysis (XRD), BET specific surface area analysis, temperature-programmed desorption (TPD) of ammonia, and FTIR spectroscopic analysis of adsorbed pyridine. XRD analysis revealed the amorphous nature of the catalyst for 1 and 10 mol% MoO3 loading, and the formation of a crystalline α-MoO3 phase on the amorphous silica support at higher MoO3 loading. The BET surface area for pure silica support was 606 m2 g−1 and the pore size distribution in the range 40–80 A, showing the mesoporous nature of amorphous silica. The BET surface area decreased to 583 m2 g−1 with incorporation of 1% MoO3 and further decreased to 180 m2 g−1 with increasing MoO3 loading up to 20%. Above 10% MoO3 loading, formation of crystalline MoO3 clusters on amorphous silica was observed. Ammonia-TPD showed a drastic increase in acid strength after addition of 1% MoO3 compared to pure silica support and the acid strength increased with increasing MoO3 content. Among the series of catalysts prepared, MoO3/SiO2 containing 20 mol% MoO3 was found to be the most active catalyst for benzene nitration, without showing any deactivation after more than 1000 h, showing a very high potential for commercialization.

Nonstoichiometric calcium pyrophosphate: a highly efficient and selective catalyst for dehydration of lactic acid to acrylic acid

Calcium phosphate catalysts were prepared by co-precipitation method using calcium nitrate and mixtures of ammonium and different sodium phosphates as calcium and phosphate precursors, respectively. Depending on the phosphate precursor, the pH of the synthesis mixture changed during the catalyst precipitation. The catalyst characterisation by XRD and ICP revealed the formation of a calcium pyrophosphate structure with varying Ca/P ratio from 1.02 to 0.76 which could be correlated to the different pH of the synthesis solutions. Vapour phase dehydration of lactic acid to acrylic acid was carried out using these calcium pyrophosphate catalysts. Non-stoichiometric calcium pyrophosphate catalyst with Ca/P ratio 0.76 was found to be the most efficient catalyst among the synthesized series with 100% lactic acid conversion and 78% acrylic acid selectivity at 375 °C. The higher selectivity for acrylic acid has been correlated to the increased acidity and reduced basicity of non-stoichiometric calcium pyrophosphate compared to other stoichiometric pyrophosphates. In situ FTIR studies showed the formation of a higher amount of calcium lactate on non-stoichiometric compared to stoichiometric pyrophosphate leading to higher selectivity for acrylic acid.

One-Pot Synthesis of 2,4,5-Trisubstituted Imidazoles Using MoO3/SiO2, an Efficient and Recyclable Catalyst

Abstract A simple one-pot synthesis has been developed for the synthesis of 2,4,5-trisubstituted imidazoles using an efficient and recyclable MoO3/SiO2 solid acid catalyst by condensation of benzil or benzoin, benzaldehyde, and ammonium acetate in acetonitrile as a solvent. Using this solid catalyst, the reactions could be carried out under mild reaction conditions with very good yield of imidazoles, up to 95%. This catalyst could be recycled very easily, which makes this methodology environmentally benign.

Synthesis of Carbamates Using Yttria-Zirconia Based Lewis Acid Catalyst

Abstract A variety of amines react with chloroformates in the presence of catalytic amount of yttria-zirconia based catalyst to afford the corresponding carbamates in excellent yields.

Transesterification of Diethyl Oxalate with Phenol over Sol–Gel MoO3/TiO2 Catalysts

The transesterification of diethyl oxalate (DEO) with phenol to form diphenyl oxalate (DPO) has been carried out in the liquid phase over very efficient MoO(3)/TiO(2) solid-acid sol-gel catalysts. A selectivity of 100 % with a remarkable maximum yield of 88 % were obtained, which opens the route to downstream phosgene-free processes for the synthesis of polycarbonates. Interpretation of the results of various acidity measurements (NH(3) and pyridine desorption, methanol oxidation as a probe reaction) allowed us to identify the catalytic sites as Lewis acid sites.