Nanoparticles of vanadia–zirconia catalysts synthesized by polyol-mediated route: Enhanced selectivity for the oxidative dehydrogenation of propane to propene

A polyol-mediated route was employed to obtain nanoparticles of vanadia–zirconia (10 nm) and Ti⁴⁺-modified zirconia catalyst for the selective oxidative dehydrogenation reaction of propane to propene. The catalytic activity and selectivity of samples thus prepared were compared with the values for the sample synthesized by the conventional impregnation method. More dispersed amorphous vanadia species on zirconia support could be obtained by polyol method compared to those obtained by conventional impregnation route, as discerned from transmission electron microscopy (TEM) and Raman studies. Raman spectra of samples prepared by polyol method indicated the presence of monovanadate and polyvanadate species on the zirconia support surface, whereas the impregnated sample showed the existence of aggregated vanadia besides mono and polyvanadate species though the vanadia loading was the same on all samples. XPS studies revealed that vanadia existed as both V⁵⁺ and V⁴⁺ in the samples prepared by the polyol method, whereas only V⁵⁺ state was seen in the impregnated sample. The catalysts prepared by polyol method exhibited enhanced selectivity for propene formation compared to the sample prepared by impregnation method. The enhanced selectivity is attributed to the presence of dispersed vanadia species with lower valence state of vanadium. The present results demonstrate that the polyol-mediated synthesis is an efficient method for the preparation of supported vanadia catalysts containing such active species.     

Controlled aggregation of gold nanoparticle networks induced by alkali metal ions

Gold nanoparticle networks were obtained by linking them with cysteine modified triethyleneglycols. The oligo-ether linker molecule initially having a linear structure probably adopts a crown ether type structure upon complexation with alkali metal ions that leads to a controlled aggregation of the network. The extent of aggregation depends on the degree of conformational change in the molecule upon complexation with the metal ion, which in turn is governed by the metal ion radius leading to a dependence of red shift of the surface plasmon resonance on the metal ion radius. Since this network is present in the organic solvent they also act as phase transferring agent for the alkali metal ions from aqueous to organic media.     

Thermodynamics,kinetics and microstructural evolution of Ti0.43Zr0.07Cr0.25V0.25 alloy upon hydrogenation

Zr substituted Ti₂CrV alloy with Ti_0.43Zr_0.07Cr_0.25V_0.25 composition was synthesized by arc melting method and its crystal structure, microstructure and hydrogen storage performance were investigated. XRD and microstructural analyses confirmed that the alloy forms Laves phase related BCC solid solution. The enthalpy of hydride formation as derived from pressure composition absorption isotherms is ?56.33 kJ/mol H₂. The desorption temperature of the hydride is significantly lower (by ～50 K) than that of Ti₂CrV hydride indicating lower thermal stability of the hydride compared to its unsubstituted analogue. The alloy shows better cyclic stability over the unsubstituted one. This work also offers mechanistic insight into hydrogen absorption reaction of Ti_0.43Zr_0.07Cr_0.25V_0.25 alloy by analyzing the hydriding kinetics data with standard kinetic models. The rate-determining steps of hydrogen absorption reaction were identified as random nucleation and growth of hydride followed by 1D and 3D diffusion of hydrogen atoms through the hydride layer. The present study is expected to provide valuable information for the better development of Ti–Cr–V based hydrogen storage alloys.     

Barium borosilicate glass as a matrix for the uptake of dyes

Barium borosilicate (BBS) and sodium borosilicate (SBS) glass samples, prepared by the conventional melt-quench method, were used for the uptake of Rhodamine 6G dye from aqueous solution. The experimental conditions were optimized to get maximum uptake and was found to be 0.4 mg of dye per gram of BBS glass sample. For the same network former to modifier ratio, barium borosilicate glasses are found to have improved extent of uptake for the dye molecules from aqueous solutions compared to sodium borosilicate glasses. Based on ²⁹Si MAS NMR studies on these glasses, it is inferred that significantly higher number of non-bridging oxygen atoms present in barium borosilicate glasses compared to sodium borosilicate glasses is responsible for its improved uptake of Rhodamine 6G dye. ¹¹B MAS NMR studies have confirmed the simultaneous existence of boron in BO₃ and BO₄ configurations in both barium borosilicate and sodium borosilicate glasses. The luminescence studies have established that the dye molecule is incorporated into the glass matrix through ion exchange mechanism by replacing the exchangeable ions like Na⁺/Ba²⁺ attached with the non-bridging oxygen atoms present in the glass.     

Highly dispersed phase of SnO2 on TiO2 nanoparticles synthesized by polyol-mediated route: Photocatalytic activity for hydrogen generation

TiO₂–SnO₂ mixed oxides (Ti:Sn = 98:2 (TS2), 95:5 (TS5) and 90:10 (TS10) by atomic weight) of large surface area and small particle size, in which SnO₂ is in a dispersed phase on TiO₂, have been synthesized by a polyol-mediated route. Characterization by various techniques has shown that a highly dispersed phase of SnO₂ on anatase TiO₂ is formed in TS2 sample. No separate discernible phases corresponding to cassiterite SnO₂ or rutile TiO₂ is seen in TS2 sample, whereas rutile TiO₂ and SnO₂ are observed besides the anatase phase of TiO₂ in TS5 and TS10 samples. The average particle size of the mixed oxide samples is ～20 nm. All samples absorb visible light and the onset of absorption was ～425 nm. These mixed oxides show emission from defect levels arising due to the anion vacancies present in TiO₂. The visible light absorption of these samples is attributed to the presence of defect levels in the bandgap of TiO₂. Photocatalytic activity of these samples for hydrogen generation from water using methanol as sacrificial reagent was studied under sunlight type radiation. The results indicate that mixed oxides have better activity compared to pure TiO₂ synthesized by the same method and the activity decreases with increasing SnO₂ concentration in TiO₂. The enhanced activity of TS2 sample is ascribed to the efficient charge separation from TiO₂ to SnO₂ owing to the high dispersion of SnO₂ in TiO₂. The decreased photocatalytic activity with increased SnO₂ concentration is due to the aggregation of SnO₂ on TiO₂, which results in relatively poor dispersion of SnO₂ and decreased charge transfer efficiency, but still maintains better photocatalytic activity compared to TiO₂. In addition loading Pd co-catalyst produces a pronounced increase in the hydrogen yield due to the accumulation of electrons in the metal from the TiO₂ and SnO₂ semiconductors and the increased reductive power of the Pd loaded mixed oxide nanoparticles.     

Experimental evaluation of kaolin stabilised with class F fly ash

Bulletin of Engineering Geology and the Environment - This study aims to investigate the effectiveness of fly ash (FA) in stabilising a kaolin soil through laboratory tests. Kaolin is an example of...     

Faceted classification of manufacturing processes for sustainability performance evaluation

Sustainability characterization of manufacturing processes is key to the inventory data development for life cycle analysis of products and processes in manufacturing industries. The ability of an organization to compare and contrast this sustainability performance in a variety of manufacturing process categories is crucial for purposes of evaluating and improving the process performance or doing tradeoff analysis for dealing with suboptimal performance. In such a situation, it is necessary to abstract this information into broader, aggregated, and consistent viewpoints such that similarities and contrasts in sustainability performance are visually deliberated. For developing such a visual system, the abstracted viewpoint should be transformed to a process classification scheme. A faceted approach to manufacturing process classifications has been proposed in this work for this purpose. We developed a visual interface to navigate the process classification scheme. We also provide a means by which dynamic hierarchical taxonomies can be generated by ranking the abstracted viewpoints called facets and classifiers.     

Light‐weight thermal insulating fly ash cenosphere ceramics

Light weight fly ash cenosphere (FAC) ceramic composites were developed by simple slip casting method. Thermal properties, Bulk density, Microstructure, flexural strength, and phase analysis of the FAC ceramic composites were measured. The results proved that the FAC have ability to lower bulk density and thermal conductivity effectively. The lowest thermal conductivity achieved for FAC ceramic composites (0.27 W/m.K) was further reduced 0.21 W/m.K by adding combustible additives ie activated charcoal and corn starch. The flexural strength, bulk density and thermal conductivity of FAC ceramic composites reduced consistently with an increase in FAC content. The maximum flexural strength of 13.45 MPa was achieved with 50% FAC and the minimum flexural strength of 4.07 MPa was obtained with 80% FAC. The open porosity increased from 35.51% to 43.76% and 38.19% with an addition of 15% activated charcoal and corn starch, respectively, when compared to no additives. The bulk density of 699, 619, and 675 kg/m³ was achieved with 80% FAC, 80% FAC with the addition of 15% activated charcoal and corn starch, respectively. The 80% FAC ceramic composite shows low thermal expansion coefficient 6.54 × 10^?6/°C at the temperature of 50°C then it varies between 3.7 and 5 × 10^?6/°C in the temperature range above 100°C. These results prove that the developed light weight FAC ceramic are excellent low‐cost thermal insulating materials.     

Size-dependent adsorption and conformational changes induced in bovine serum albumin (BSA) on exposure to titanium dioxide (TiO2) nanoparticles

In this study, TiO₂ nanoparticles (NPs) of different sizes were synthesized using sol gel method and calcined at different temperatures ranging from 200 to 700°C. The specific surface area of TiO₂ was found to decrease with the increase in calcination temperature. It was observed that adsorption of bovine serum albumin (BSA) on TiO₂ NPs obeyed the Freundlich adsorption isotherm, and the isotherm parameters were calculated from equilibrium adsorption batch experiments. The kinetics of adsorption was best fitted by pseudo-first-order kinetic model. The effect of particle dosage on BSA adsorption was also studied and it was observed that the adsorption increased with the increase in particle dosage and decrease in particle size. The conformational changes of BSA on exposure to TiO₂ NPs of various sizes were investigated using circular dichroism spectropolarimetry. The results suggested that BSA underwent a distortion in the secondary structure which was quantified by the percent α-helicity. A size-dependent distortion was observed. The α-helix content changed from 32.3% for pure BSA to 21.9% when exposed to NPs calcined at 200°C (350 mg/L) and to 28.4% for NPs calcined at 700°C at the same concentration.     

Fermentation Dynamics During Production of Bhaati Jaanr,a Traditional Fermented Rice Beverage of the Eastern Himalayas

Bhaati jaanr is an inexpensive high calorie mild-alcoholic beverage prepared from steamed glutinous rice, consumed as a staple food beverage in the Eastern Himalayan regions of Nepal, India and Bhutan. In this paper, fermentation dynamics including growth kinetics and physico-chemical changes during fermentation of bhaati jaanr were studied. The population of filamentous moulds declined significantly (P < 0.05) each day and finally disappeared after the 5^th day. The load of yeasts increased significantly (P < 0.05) from 10⁵ cfu/g to 10⁸ cfu g^?1 within two days. Lactic acid bacteria (LAB) increased significantly (P < 0.05) from 10⁶ cfu g^?1 to 10⁷ cfu g^?1 in the first day and decreased significantly (P < 0.05) to 10⁵ cfu/g at the end of the fermentation. The pH decreased and acidity increased during fermentation. The alcohol content increased significantly (P < 0.05) up to 10% on the tenth day. The reducing sugar content increased significantly (P < 0.05) until the third day and then decreased, followed by a decrease in total sugar content. Maximum activities of saccharification and liquefaction of rice were observed on the third day of fermentation. It was revealed that Saccharomycopsis fibuligera and Rhizopus spp. play important roles in the saccharification process of rice in bhaati jaanr fermentation. The mean pH, acidity, moisture and alcohol content of the product were 3.5%, 0.24%, 83.4% and 5.9%, respectively.