The Design And Development Of Nanomaterials And Their Applications In Heterogeneous Catalysis

In this thesis,we developed highly efficient,low-cost and durable nanomaterials for Photocatalytic color switching,hydrogenation reactions and conversion of Biomass into alkanes and valuable chemicals.The study includes three parts;in the first part,efficient Photocatalytic intelligent ink has been synthsisized.Oxygen sensitive photoreversible intelligent ink capable of assessment with human eye is the on-going demand of modern era.In food industry,redox dye based oxygen indicator films have been proposed but the leaching of dyes from the film which contaminates the food is one un-solved issue.On the other hand,it is also highly desirable to develop rewritable paper which significantly reduces the pressure on modern society for the production and consumption of paper.Herein,we have developed oxygen deficient TiO2-x/methylene blue(MB)sol without relying on external sacrificial electron donors(SEDs)for photoreversible color switching.Oxygen vacancies in TiO2-x can work as electron donor to favors the adsorption of substrate and improve the charge separation which is required for redox-based color switching system.The problems of rewriteable paper and food packaging are addressed as two sides of a single coin in this paper.We have used hydroxyethyl cellulose(HEC)for rewritable paper which can significantly delay the oxidation of leuco-MB(LMB)through hydrogen bonding and retain the printed information for a long time.The dye leaching from oxygen indicator films is also significantly reduced(only 1.54%)by using furcelleran as the coating polymer which is extracted from edible red seaweed.In the second part,highly reduced TiO support was synthesized and noble metal nanoparticles were loaded,which provides synergistic effect on boosting catalytic hydrogenation activity.The low-temperature polymorph of titanium monoxide is used as support and promoter,which contains vacancies in both the Ti and O sublattices with ordered distribution.The lattice vacancies increase the donor density and enhance the adsorption of substrate and hydrogen,and subsequently lower the activation energy required for the hydrogen dissociation.Moreover,the existence of strong metal-support interactions in Pd/TiO ascertained from HRTEM and XPS analysis is responsible both for the strong binding of Pd nanoparticles and improved electronic conductivity,resulting in enhanced catalytic performance.The as synthesized Pd/TiO catalyst has been evaluated for the hydrogenation of styrene and 4-nitrophenol(4-NP)and shows excellent performance.The rate constant for 4-NP reduction over Pd/TiO is 0.05 s-1,which is higher than the previously reported data,moreover,the catalyst shows good stability up to 10 successive cycles.Hydrogenation of styrene is conducted at ambient conditions using Pd/TiO as catalyst,which exhibits remarkably high turnover frequency(TOF)of 4838 h-1.The catalyst can be recovered and recycled several times without a marked loss of activity.The results show that our Pd/TiO catalyst is one of the highest activity amongst reported heterogeneous hydrogenation catalysts.The obtained Pd/TiO catalyst may hold great potential in catalysis for organic transformations and other reactions.In the last and third part,we developed noble-metal free vanadium-substituted potassium salt of Phosphotungstic acid as heterogeneous catalyst for HDO of pine sawdust into alkanes and valuable chemicals with high yield(73.5%)and excellent conversion efficiency(86.2%).The higher Brensted acidity of Phosphotungstic acid greatly favors deoxygenation reactions of lignocellulosic components.Moreover,the synergism between keggin-anion,potassium and vanadium entities supports fast multi-electron redox transformations and greatly improves thermal stability.The cellulosic components were selectively converted into pentanes,hexanes and hydrocarbons.The lignin fraction of biomass was also converted into Phenolic compounds.It is worth mentioning that raw biomass was used as obtained without pretreatment,separation and hydrolysis process in comparison with the existing approaches,thus saving tremendous amount of energy and reducing the cost for large scale production.