Showing papers in "Journal of the Indian Institute of Science in 2010"

Environmental remediation by photocatalysis

Abstract: Photocatalysis refers to the oxidation and reduction reactions on semiconductor surfaces, mediated by the valence band holes and conduction band electrons, which are generated by the absorption of ultraviolet or visible light radiation. Photocatalysis is widely being practiced for the degradation and mineralization of hazardous organic compounds to CO2 and H2O, reduction of toxic metal ions to their non-toxic states, deactivation and destruction of water borne microorganisms, decomposition of air pollutants like volatile organic compounds, NOx, CO and NH3, degradation of waste plastics and green synthesis of industrially important chemicals. This review attempts to showcase the well established mechanism of photocatalysis, the use of photocatalysts for water and air pollution control, visible light responsive modified-TiO2 and non-TiO2 based materials for environmental and energy applications, and the importance of developing reaction kinetics for a comprehensive understanding and design of the processes.

Recent advances in auto exhaust catalysis

Abstract: In last 30 years innovative research in the area of auto exhaust catalysis is being developed and CeO2 has been found to play a major role in this area due to its unique redox properties. In this review, auto exhaust emission and its impact on earth’s environment, global concern and recent advances in science and technology in automotive exhaust catalysis have been documented. A new preparative method of dispersing metal ions by solution combustion technique over CeO2 and TiO2 resulting mainly Ce1−xMxO2−δ, Ti1−xMxO2−δ and Ce1−x−yTixMyO2−δ (M = Pd, Rh and Pt) catalysts, structure of these materials, their catalytic properties towards auto exhaust catalysis, structure–property relation and mechanism of catalytic reactions are accounted here. In these materials, metal ions are incorporated into substrate matrix to a certain limit in the solid solution form and we have established a new direction in heterogeneous catalysis by turning to the concept of dispersed metal ions as catalytically active sites from the conventionally nurtured idea of metal particles as active centers for catalysis.

Monitoring Himalayan cryosphere using remote sensing techniques

Abstract: In the Himalayas, large area is covered by glaciers, seasonal snow and changes in its extent can influence availability of water in the Himalayan Rivers. In this paper, changes in glacial extent, glacial mass balance and seasonal snow cover have been discussed. Field and satellite based investigations suggest, most of the Himalayan glaciers are retreating though the rate of retreat is varying from glacier to glacier, ranging from few meters to almost 50 meters per year, depending upon the numerous glacial, terrain and meteorological parameters. Retreat was estimated for 1868 glaciers in eleven basins distributed across the Indian Himalaya since 1962 to 2001/02. Estimates show an overall reduction in glacier area from 6332 to 5329 sq km, an overall deglaciation of 16 percent. Snow line at the end of ablation season on the Chhota Shigri glacier suggests a change in altitude from 4900 to 5200 m from late 1970’s to the present. Seasonal snow cover monitoring of the Himalaya has shown large amounts of snow cover depletion in early part of winter, i.e. from October to December. For many basins located in lower altitude and in south of Pir Panjal range, snow ablation was observed through out the winter season. In addition, average stream runoff of the Baspa basin during the month of December shows an increase by 75 per cent. This combination of glacial retreat, negative mass balance, early melting of seasonal snow cover and winter time increase in stream runoff suggest an influence of climate change on the Himalayan cryosphere.

Land use and land cover change in India:Aremote sensing & GIS prespective

Abstract: Land use and land cover change have been among the most important perceptible changes taking place around us. Although perceptible, the magnitude, variety and the spatial variability of the changes taking place has made the quantification and assessment of land use and land cover changes a challenge to scientists. Furthermore, since most of the land use and land cover changes are directly influenced by human activities, they rarely follow standard ecological theories. The Remote Sensing and Geographic Information System has proved to be very important in assessing and analyzing land use and land cover changes. Satellite-based Remote Sensing, by virtue of its ability to provide synoptic information of land use and land cover at a particular time and location, has revolutionized the study of land use and land cover change. The temporal information on land use and land cover helps identify the areas of change in a region. The use of Geoinformatics has enabled us to assign spatial connotations to land use land cover changes, namely, population pressure, climate, terrain, etc which drive these changes. This has helped scientists to quantify these tools and to predict various scenarios. This article gives a overview of the current trends in land use and land cover changes along with two case studies on the same subject, one case study on geospatial LULC change modeling and one on agent based land use and land cover change modeling.

Deep-sea ferromanganese deposits and their resource potential for India

Abstract: Due to rapidly depleting land-based mineral resources, oceanic mineral deposits gain greater significance. Ferromanganese deposits on the seabed (nodules) and seamounts (crusts) known for the enrichment of several transition metals were discovered during pioneering expeditions of H. M. S. Challenger during 1872–76. The metal contents in these deposits show large variations from basin to basin. For India, the Cu and Ni (1% each) in nodules and Co (0.7%) and Pt (0.5 ppm) in seamount crusts recovered from the Indian Ocean are important. The hydrogenous crusts are not only important as economically valuable deposits of Co and Pt, but also are potential paleoceanographic repositories. Ferromanganese nodule exploration by India began in 1981 and concluded with recognition by the International Seabed Authority as a Pioneer Investor in 1987. This exploration license provides India with exclusive exploration rights over an area of 150,000 km2 (Pioneer Area) in the Central Indian Ocean. Nearly 700 million tonnes of nodule resources are estimated in this mine site, which are expected to contain around 14 million tonnes of combined Cu and Ni metals valued approximately over Rs. 1000 billion at current average market rate. Quantitative resource evaluation for seamount ferromanganese crusts is not yet available due to limited exploratory work. However, a promising area of Co–Pt enriched ferromanganese crust occurrence has been discovered on the Afanasiy-Nikitin Seamounts in the Eastern Equatorial Indian Ocean by NIO scientists, which contains Co upto 0.9 % and Pt upto 1 ppm.

Mechanism design problems in carbon economics.

Abstract: Reduction of carbon emissions is of paramount importance in the context of global warming and climate change. Countries and global companies are now engaged in understanding systematic ways of solving carbon economics problems, aimed ultimately at achieving well defined emission targets. This paper proposes mechanism design as an approach to solving carbon economics problems. The paper first introduces carbon economics issues in the world today and next focuses on carbon economics problems facing global industries. The paper identifies four problems faced by global industries: carbon credit allocation (CCA), carbon credit buying (CCB), carbon credit selling (CCS), and carbon credit exchange (CCE). It is argued that these problems are best addressed as mechanism design problems. The discipline of mechanism design is founded on game theory and is concerned with settings where a social planner faces the problem of aggregating the announced preferences of multiple agents into a collective decision, when the actual preferences are not known publicly. The paper provides an overview of mechanism design and presents the challenges involved in designing mechanisms with desirable properties. To illustrate the application of mechanism design in carbon economics, the paper describes in detail one specific problem, the carbon credit allocation problem.

Alkylation of toluene by methanol over alkali exchanged zeolite-X: side chain versus ring alkylation

Abstract: The ring versus side-chain alkylation of toluene with methanol over alkali-exchanged zeolite-X of differing basicity has been investigated by in situ infrared spectroscopy and TPD measurements. Over the basic Cs-exchanged zeolite the product of alkylation is styrene/ethylbenzene while over the acidic Li-exchanged zeolite ring alkylation occurs to give mainly xylene as the product. FTIR and TPD investigations reveal that, the key difference in the two types of alkylation processes lies in the state of the adsorbed methanol present at higher temperatures in the zeolite. In basic zeolites, methanol decomposes to formaldehyde and formates. The former is the key ‘side-chain’ alkylating species that leads to the formation of styrene. In the acidic zeolites it is shown that methanol bound to the acid sites plays an active role in the ‘ring alkylation’ of toluene to xylene.

Hydrogen generation from ammonia borane using nanocatalysts

Abstract: The rapidly depleting petroleum feed stocks and increasing green house gas emissions around the world has necessitated a search for alternative renewable energy sources. Hydrogen with molecular weight of 2.016 g/mol and high chemical energy per mass equal to 142 MJ/kg has clearly emerged as an alternative to hydrocarbon fuels. Means for safe and cost effective storage are needed for widespread usage of hydrogen as a fuel. Chemical storage is the one of the safer ways to store hydrogen compared to compressed and liquefied hydrogen. It involves storing hydrogen in chemical bonds in molecules and materials where an on-board reaction is used to release hydrogen. Ammonia–borane, (AB, H3N·BH3) with a potential capacity of 19.6 wt% is considered a very promising solid state hydrogen storage material. It is thermally stable at ambient temperatures. There are two major routes for the generation of H2 from AB: catalytic hydrolysis/alcoholysis and catalytic thermal decomposition. There has been a flurry of research activity on the generation of H2 from AB recently. The present review deals with an overview of our efforts in developing cost-effective nanocatalysts for hydrogen generation from ammonia borane in protic solvents.

Computer-aided design of doped oxide catalysts

Abstract: An elementary overview of density functional theory and its application to computational catalyst design is presented. The central concepts like reactivity descriptor, Bronsted–Evans–Polanyi relationship, Sabatier principle and electronic structure factors that have enabled successful design of transition metal alloy surfaces as catalysts for relatively simple reaction systems are discussed. Extension of these concepts to the design of doped oxide catalysts is addressed. A viewpoint on the design of doped oxide catalysts as single site heterogeneous catalysts is provided. The case study presented in the design of doped oxide catalysts illustrates the synergism between experiments and computer aided catalysts design. Here, using doped oxide catalysts, mechanisms of non-and pseudo-Mars and Van Krevelen in heterogeneous catalytic oxidation were unraveled.

High powerACmotor drives: Status review and work at IISc

Abstract: A variety of solutions are available today from industry for high power variable speed AC motor drive applications, starting from a power rating of a few 100 kW to several 10’s of Megawatts. These drives can be classified on the basis of the electrical motor, the power converter and the control technique. The main drive types are reviewed.The salient features of each type of drive are pointed out along with their industrial applications.Following this, some research at IISc which has applications in high power drives is described briefly.