Alkaline earth metal (Mg,Ca,Sr and Ba)-doped Mo-V-Sb-O x catalysts,prepared by a dry-up method,have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions.The...Alkaline earth metal (Mg,Ca,Sr and Ba)-doped Mo-V-Sb-O x catalysts,prepared by a dry-up method,have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions.The catalysts have been characterized by N2 adsorption-desorption,temperature-programmed desorption (TPD) of NH3,SEM and XRD.Influence of water vapor on the catalytic performance,particularly on the selectivities to acetic acid and acrylic acid,has also been studied.The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-O x catalysts.The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals,which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid.The catalytic activity and product selectivities were found to be influenced by the reaction temperature,C3H8/O2 ratio and space velocity.A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.展开更多
The oxidative coupling of methane to C2 hydrocarbons has been studied over a series of La-promoted CaO (La/Ca = 0.05) catalysts, prepared using different precursor salts for CaO and La2O3 (viz. acetates, carbonates, n...The oxidative coupling of methane to C2 hydrocarbons has been studied over a series of La-promoted CaO (La/Ca = 0.05) catalysts, prepared using different precursor salts for CaO and La2O3 (viz. acetates, carbonates, nitrates and hydroxides) and catalyst preparation methods (viz. physical mixing of precursors, co-precipitation using ammonium carbonate/sodium carbonate as a precipitating agent), under different reaction conditions (temperature: 700-850℃, CH4/O2 ratio: 4.0 and 8.0, and GHSV: 51360 cm3 g-1 h-1). The surface area and surface basicity/base strength distribution of the catalysts have also been investigated. The surface properties and catalytic activity/selectivity of the La-promoted CaO catalysts vary from catalyst to catalyst depending on the catalyst precursors used and catalyst preparation method. The basicity/base strength distribution is strongly influenced by the precursors (for CaO and La2O3) and catalyst preparation method. Basicity (total and strong basic sites measured in terms of CO2 chemisorbed at 50℃ and 500℃, respectively) observed for the catalyst prepared by co-precipitation method is higher than that of the catalysts prepared by physical mixing method. The catalysts prepared by the nitrates of La-and Ca-and coprecipitated by the solution of sodium carbonate and ammonium carbonate exhibit different catalytic performance in OCM. The finding that no direct relationship between the surface basicity and catalytic activity/selectivity in OCM exists indicates that basicity is not solely responsible for obtaining high selectivity to C2 hydrocarbons.展开更多
A cheap and recyclable ZnO-beta zeolite was used as catalyst for the synthesis of benzothiazole derivatives.This method provides several advantages such as environmental friendliness,short reaction times,high yields,s...A cheap and recyclable ZnO-beta zeolite was used as catalyst for the synthesis of benzothiazole derivatives.This method provides several advantages such as environmental friendliness,short reaction times,high yields,simple work-up procedure and catalyst was successfully reused for four cycles without significant loss of activity.展开更多
A new robust heterogeneous, versatile, an environmentally benign, eco-friendly, recyclable CuFAP catalyst has been developed for the direct synthesis of nitriles and amides from aldehydes at 100°C for 6 h and 4 h...A new robust heterogeneous, versatile, an environmentally benign, eco-friendly, recyclable CuFAP catalyst has been developed for the direct synthesis of nitriles and amides from aldehydes at 100°C for 6 h and 4 h, respectively, under neat reaction condition using hydroxylamine hydrochloride in the presence and the absence of tosyl chloride, respectively. Also the recyclability of catalyst as well as influence of solvents, additives on catalysts performance was investigated. The protocol can be considered as an alternative to conventional method for the synthesis of nitriles and amides in good to excellent yields. A highlight of our protocol is the easy separation of catalyst from reaction mixture, hence the catalyst is reused several times without significant loss of its catalytic activity.展开更多
Solvent free, highly efficient method has been developed using ecofriendly, heterogeneous reusable cobalt chloride catalyst at ambient reaction conditions for the O-acylation of various alcohols and phenols with acety...Solvent free, highly efficient method has been developed using ecofriendly, heterogeneous reusable cobalt chloride catalyst at ambient reaction conditions for the O-acylation of various alcohols and phenols with acetyl chloride in excellent yield in a short reaction time. The catalyst is recycled several times without loss of catalytic activity.展开更多
In the coal-based combustion and gasification processes, the mineral matter contained in the coal (predominantly oxides), is left as an incombustible residue, termed ash. Commonly, ash deposits are formed on the heat ...In the coal-based combustion and gasification processes, the mineral matter contained in the coal (predominantly oxides), is left as an incombustible residue, termed ash. Commonly, ash deposits are formed on the heat absorbing surfaces of the exposed equipment of the combustion/gasification processes. These deposits lead to the occurrence of slagging or fouling and. consequently, reduced process efficiency. The ash fusion temperatures (AFTs) signify the temperature range over which the ash deposits are formed on the heat absorbing surfaces of the process equipment. Thus, for designing and operating the coal-based processes, it is important to have mathematical models predicting accurately the four types of AFTs namely initial deformation temperature, softening temperature, hemispherical temperature, and flow temperature. Several linear/nonlinear models with varying prediction accuracies and complexities are available for the AFT prediction. Their principal drawback is their applicability to the coals originating from a limited number of geographical regions. Accordingly, this study presents computational intelligenee (CI) based nonlinear models to predict the four AFTs using the oxide composition of the coal ash as the model input. The CI methods used in the modeling are genetic programming (GP), artificial neural networks, and support vector regression. The no table features of this study are that the models with a better AFT prediction and generalization performanee, a wider application potential, and reduced complexity, have been developed. Among the Ci-based models, GP and MLP based models have yielded overall improved performanee in predicting all four AFTs.展开更多
Adsorption properties of layered anionic clay-composites for the removal of anionic dyes from water were studied. The dye adsorption capacities of the composites were higher than the pristine clay. The clay-alginate c...Adsorption properties of layered anionic clay-composites for the removal of anionic dyes from water were studied. The dye adsorption capacities of the composites were higher than the pristine clay. The clay-alginate composite with 5.9% alginate showed highest adsorption for both the dyes. The maximum adsorption capacity of the composite was enhanced by 51% for Acid Green 25 and 160% for Acid Green 27, compared to the pristine layered clay sample. The adsorption isotherm data were fitted to the Langmuir, Freundlich and Temkin isotherm models. The isotherm data could be explained well using the Freundlich isotherm model. Adsorption kinetics was analyzed using normal first order and Lagergren first order kinetic models.展开更多
The capture of CO_(2) by transition metal(Mn,Ni,Co and Zn)aluminates,calcium aluminate,calcium zirconate,calcium silicate and lithium zirconate was carried out at pre-and post-combustion temperatures.The prepared meta...The capture of CO_(2) by transition metal(Mn,Ni,Co and Zn)aluminates,calcium aluminate,calcium zirconate,calcium silicate and lithium zirconate was carried out at pre-and post-combustion temperatures.The prepared metal adsorbents were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),surface area analysis and acidity/alkalinity mea-surements.The different experimental variables affecting the adsorbents ability to capture CO_(2),such as the mol ratio of metal ions,the pressure of CO_(2),the exposure time and the temperature of the adsorbent were also investigated.Calcium zirconate captured 13.85 wt-%CO_(2) at 650℃ and 2.5 atm and calcium silicate captured 14.31 wt-%at 650℃.Molecular sieves(13X)and carbon can only capture a negligible amount of CO_(2) at high temperatures(300℃–650℃).However,the mixed metal oxides captured reasonable amount of CO_(2) at these higher temperatures.In addition,calcium aluminate,calcium zirconate,calcium silicate and lithium zirconate adsorbents captured CO_(2) at both pre and post-combustion temperatures.The trend for the amount of captured carbon dioxide over the adsorbents was calcium aluminate<lithium zirconate<calcium zir-conate<calcium silicate.展开更多
文摘Alkaline earth metal (Mg,Ca,Sr and Ba)-doped Mo-V-Sb-O x catalysts,prepared by a dry-up method,have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions.The catalysts have been characterized by N2 adsorption-desorption,temperature-programmed desorption (TPD) of NH3,SEM and XRD.Influence of water vapor on the catalytic performance,particularly on the selectivities to acetic acid and acrylic acid,has also been studied.The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-O x catalysts.The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals,which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid.The catalytic activity and product selectivities were found to be influenced by the reaction temperature,C3H8/O2 ratio and space velocity.A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.
文摘The oxidative coupling of methane to C2 hydrocarbons has been studied over a series of La-promoted CaO (La/Ca = 0.05) catalysts, prepared using different precursor salts for CaO and La2O3 (viz. acetates, carbonates, nitrates and hydroxides) and catalyst preparation methods (viz. physical mixing of precursors, co-precipitation using ammonium carbonate/sodium carbonate as a precipitating agent), under different reaction conditions (temperature: 700-850℃, CH4/O2 ratio: 4.0 and 8.0, and GHSV: 51360 cm3 g-1 h-1). The surface area and surface basicity/base strength distribution of the catalysts have also been investigated. The surface properties and catalytic activity/selectivity of the La-promoted CaO catalysts vary from catalyst to catalyst depending on the catalyst precursors used and catalyst preparation method. The basicity/base strength distribution is strongly influenced by the precursors (for CaO and La2O3) and catalyst preparation method. Basicity (total and strong basic sites measured in terms of CO2 chemisorbed at 50℃ and 500℃, respectively) observed for the catalyst prepared by co-precipitation method is higher than that of the catalysts prepared by physical mixing method. The catalysts prepared by the nitrates of La-and Ca-and coprecipitated by the solution of sodium carbonate and ammonium carbonate exhibit different catalytic performance in OCM. The finding that no direct relationship between the surface basicity and catalytic activity/selectivity in OCM exists indicates that basicity is not solely responsible for obtaining high selectivity to C2 hydrocarbons.
文摘A cheap and recyclable ZnO-beta zeolite was used as catalyst for the synthesis of benzothiazole derivatives.This method provides several advantages such as environmental friendliness,short reaction times,high yields,simple work-up procedure and catalyst was successfully reused for four cycles without significant loss of activity.
文摘A new robust heterogeneous, versatile, an environmentally benign, eco-friendly, recyclable CuFAP catalyst has been developed for the direct synthesis of nitriles and amides from aldehydes at 100°C for 6 h and 4 h, respectively, under neat reaction condition using hydroxylamine hydrochloride in the presence and the absence of tosyl chloride, respectively. Also the recyclability of catalyst as well as influence of solvents, additives on catalysts performance was investigated. The protocol can be considered as an alternative to conventional method for the synthesis of nitriles and amides in good to excellent yields. A highlight of our protocol is the easy separation of catalyst from reaction mixture, hence the catalyst is reused several times without significant loss of its catalytic activity.
文摘Solvent free, highly efficient method has been developed using ecofriendly, heterogeneous reusable cobalt chloride catalyst at ambient reaction conditions for the O-acylation of various alcohols and phenols with acetyl chloride in excellent yield in a short reaction time. The catalyst is recycled several times without loss of catalytic activity.
文摘In the coal-based combustion and gasification processes, the mineral matter contained in the coal (predominantly oxides), is left as an incombustible residue, termed ash. Commonly, ash deposits are formed on the heat absorbing surfaces of the exposed equipment of the combustion/gasification processes. These deposits lead to the occurrence of slagging or fouling and. consequently, reduced process efficiency. The ash fusion temperatures (AFTs) signify the temperature range over which the ash deposits are formed on the heat absorbing surfaces of the process equipment. Thus, for designing and operating the coal-based processes, it is important to have mathematical models predicting accurately the four types of AFTs namely initial deformation temperature, softening temperature, hemispherical temperature, and flow temperature. Several linear/nonlinear models with varying prediction accuracies and complexities are available for the AFT prediction. Their principal drawback is their applicability to the coals originating from a limited number of geographical regions. Accordingly, this study presents computational intelligenee (CI) based nonlinear models to predict the four AFTs using the oxide composition of the coal ash as the model input. The CI methods used in the modeling are genetic programming (GP), artificial neural networks, and support vector regression. The no table features of this study are that the models with a better AFT prediction and generalization performanee, a wider application potential, and reduced complexity, have been developed. Among the Ci-based models, GP and MLP based models have yielded overall improved performanee in predicting all four AFTs.
文摘Adsorption properties of layered anionic clay-composites for the removal of anionic dyes from water were studied. The dye adsorption capacities of the composites were higher than the pristine clay. The clay-alginate composite with 5.9% alginate showed highest adsorption for both the dyes. The maximum adsorption capacity of the composite was enhanced by 51% for Acid Green 25 and 160% for Acid Green 27, compared to the pristine layered clay sample. The adsorption isotherm data were fitted to the Langmuir, Freundlich and Temkin isotherm models. The isotherm data could be explained well using the Freundlich isotherm model. Adsorption kinetics was analyzed using normal first order and Lagergren first order kinetic models.
文摘The capture of CO_(2) by transition metal(Mn,Ni,Co and Zn)aluminates,calcium aluminate,calcium zirconate,calcium silicate and lithium zirconate was carried out at pre-and post-combustion temperatures.The prepared metal adsorbents were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),surface area analysis and acidity/alkalinity mea-surements.The different experimental variables affecting the adsorbents ability to capture CO_(2),such as the mol ratio of metal ions,the pressure of CO_(2),the exposure time and the temperature of the adsorbent were also investigated.Calcium zirconate captured 13.85 wt-%CO_(2) at 650℃ and 2.5 atm and calcium silicate captured 14.31 wt-%at 650℃.Molecular sieves(13X)and carbon can only capture a negligible amount of CO_(2) at high temperatures(300℃–650℃).However,the mixed metal oxides captured reasonable amount of CO_(2) at these higher temperatures.In addition,calcium aluminate,calcium zirconate,calcium silicate and lithium zirconate adsorbents captured CO_(2) at both pre and post-combustion temperatures.The trend for the amount of captured carbon dioxide over the adsorbents was calcium aluminate<lithium zirconate<calcium zir-conate<calcium silicate.
