High catalytic activity of Pt–Pd containing USY zeolite catalyst for low temperature CO oxidation from industrial off gases

AbstractSmall amounts (0.15wt%) of platinum and palladium were incorporated in porous, high surface area, ultra–stable H–USY–Zeolite by ion exchange method, and their catalytic activity was studied for carbon monoxide (CO) oxidation reaction, under various conditions of industrial importance. The catalyst was characterized by p–XRD, chemical analysis, SEM, TEM, evaluated for catalytic activity using a steady state, fixed bed catalytic reactor. The catalysts show high CO oxidation activity and it was possible to convert 0.044 mmols of CO per gram of catalyst at 120 °C, at a space velocity of 60 000 h−1 and with 100 ppm CO concentration in feed gas. The high catalytic activity of this noble metal catalyst also appears to be a factor of porous structure of zeolite facilitating mass transfer; high surface area as well as highly dispersed catalyst sites of palladium and platinum on zeolite structure. Introduction of acidic sites in zeolites probably makes them more resistant towards SO2, while their surface area and pore characteristics make this catalyst efficient even under high space velocity conditions, thus suggesting the potential of larger pore size zeolites over conventional porous materials for industrial applications

Ordered intermetallic Pt–Cu nanoparticles for the catalytic CO oxidation reaction

Platinum-based intermetallic nanoparticles (NPs), using the abundantly available element copper, with an average particle size of 4–5 nm on a g-Al2O3 support were prepared successfully to reduce the consumption of Pt for the removal of CO through the catalytic oxidation reaction from flue gases. Intermetallic Pt–Cu NPs (Pt3Cu, PtCu, and PtCu3) with a Pt loading weight of 5 wt% were prepared on the g-Al2O3 support by a simple wet impregnation method followed by calcination at various temperatures (500–800 �C) in a H2 environment and they were characterized by powder X-ray diffraction analysis (pXRD), high resolution transmission electron microscopy (HR-TEM), selective area electron diffraction (SAED) method, etc. Despite the higher synthesis temperature of these intermetallic NPs, they were not agglomerated and formed a highly ordered intermetallic structure. The surface of the intermetallic Pt–Cu NPs with cubic-type structure (Pt3Cu and PtCu3) is enclosed of {200} facets, regardless of the significant difference in their compositions. Whereas the surface of rhombohedral-type intermetallic PtCu NPs is enclosed of {104} facets. Although the Pt-loading weight of these intermetallic NPs was the same, Pt3Cu NPs showed a stable and enhanced catalytic activity compared to the other intermetallic PtCu and PtCu3 NPs. Pt3Cu NPs showed an onset and maximum conversion temperature of 50 and 125 �C, respectively. The intermetallic phase between Pt and Cu of Pt3Cu NPs did not decompose; however, the intermetallic phase did decompose for PtCu and PtCu3 NPs after catalytic CO oxidation. Unlike PtCu and PtCu3 NPs, the Pt3Cu NPs were not agglomerated and they were finely dispersed even after catalytic CO oxidation

Nanosized materials for environmental and energy related applications

Efforts are being made to develop nanomaterials for addressing issues related to energy, environment and resource conservation. In this connection, research is being conducted at Environmental Materials Unit in the area of development of nanosized structural analogues related to molecular sieves and zeolites, surface functionalised zeolites, pervoskite based catalytic materials, multifunctional metals/metal oxide materials, carbon and photocatalytically active materials. Several environmental and energy technologies have emerged with substantial benefits from nanotechnology, which include reduction in waste and improved energy efficiency, environmentally benign composite structures, waste remediation and energy conversion. Some of the key research areas include carbon capture, water-splitting reaction for hydrogen generation, biomimetic sequestration of CO2, and Diesel Particulate Filter (DPF) regeneration

New improved syntheses of LaRuO3 perovskites and their applications in environmental catalysis

Unsupported and supported LaRuO3 type lanthanum ruthenate perovskites have been synthesized using co-precipitation and other improved techniques, which results in synthesis of LaRuO3 with better physical properties. ‘Freeze-drying’, ‘in situ’ synthesis, co-precipitation and ‘deposition precipitation’ techniques have been used mostly for the first time to synthesize LaRuO3 perovskite with ruthenium in 3+ oxidation state. These innovative synthesis methods have resulted in formation of LaRuO3 with improved, physical and catalytic properties. Alumina supported LaRuO3 has also been prepared which shows remarkable improvement in surface area and catalytic activity for certain reactions of environmental importance. These methods offer non-tedious, easy synthesis of Ru(III) perovskite at relatively lower temperature. LaRuO3 shows reasonably high thermal stability and can be a potential candidate for many catalytic reactions even at elevated temperatures

User perception study for performance evaluation of domestic defluoridation techniques for its application in rural areas

Fluoride concentrations in ground water have been monitored in rural areas of Dhar and Jhabua districts in Madhya Pradesh, India. A correlation of fluoride concentration with pH, TDS and conductivity has been estimated to identify surrogate monitoring parameter. Further, fluoride removal from drinking water has been achieved by using adsorbents specially developed for domestic applications. These adsorbents have been evaluated using three different methods namely; loose adsorbent, pre-packed sachet and packed bamboo column. Comparative evaluation of these methods has been demonstrated in the laboratory and field. The stringent limit of 1 mg/L for fluoride concentration in drinking water has been achieved by use of specially designed adsorbents. A feedback from end-users in Tarapur and Ukala villages of Dhar districts Madhya Pradesh regarding the adsorbents and its acceptability has been collected. User’s perception regarding these household treatments reveals encouraging response for defluoridation methods. According to user’s perception loose adsorbent approach emerged out as most simple, clean and safe household defluoridation method

Single enzyme nanoparticle for biomimetic CO2 sequestration

Nanoparticle technology is being increasingly used in environmental sciences. We prepared single enzyme nanoparticle (SEN) by modifying the surface of carbonic anhydrase (CA) with a thin layer of organic/inorganic hybrid polymer. SEN-CA appears to be improving the stability of free enzyme. CA, as ubiquitously found enzyme, is involved in gaseous CO2 sequestration and is being looked as a promising candidate for combating global warming. We report here physical characterization of SEN-CA using transmission electron microscope (TEM), Fouriertransform infrared analysis (FTIR), X-ray diffraction analysis (XRD), and energy dispersive X-ray (EDX). Average size of SEN-CA particles appears to be in the range of 70–80 nm. We also report the effect of SEN formation on the kinetic parameters of free CA such as Michaelis–Menten constant (Km), maximum reaction velocity (Vmax), and storage stability of free CA and SEN-CA. The Vmax of SEN-CA (0.02857 mmol/min/ mg) and free enzyme (0.02029 mmol/min/mg) is almost similar. Km has decreased from 6.143 mM for SEN-CAto 1.252 mMfor free CA. The stabilization of CA by SEN formation results in improved the half-life period (up to 100 days). The formation of carbonate was substantiated by using gas chromatography (GC). The conversion of CO2 to carbonate was 61 mg of CaCO3/mg of CA and 20.8 mg of CaCO3/mg of CA using SEN-CA and free CA, respectively

Thermally stable ruthenium-based catalyst for methane combustion

Ruthenium shows high thermal stability when incorporated in perovskite type structure. Perovskite type lanthanum ruthenate materials can be synthesized using various improved methods and can be used even for high temperature applications like methane combustion. La3.5Ru4.0O13 material in supported and un-supported forms has been synthesized using various techniques, mostly used for the first time to synthesize this material. This improved synthesis of La3.5Ru4.0O13 resulted in improved physical and catalytic properties. This paper reports synthesis of supported and un-supported La3.5Ru4.0O13 materials and laboratory evaluations of their catalytic activity towards methane combustion reaction. La3.5Ru4.0O13 shows high thermal stability, which could be due to stable 4+ oxidation state of ruthenium and its incorporation in perovskite type structure. Ruthenium based materials show good activity for methane oxidation probably due to intrinsic activity of their ruthenium component

Functionalized Fly Ash Based Alumino-Silicates for Capture of Carbon Dioxide

Fly ash contains mainly alumina and silica as its main constituents. A novel method for the extraction of highly stable alumino-silicates from fly ash has been developed. The as-extracted alumino-silicate has been further functionalized with APTES ((3-aminopropyl)triethoxysilane), TRIS buffer (tris(hydroxymethyl)aminomethane), and AMP (3-amino-2-methyl-1-propanol) to impart basicity for carbon dioxide adsorption. A dynamic adsorption capacity of 6.62 mg/g has been observed for FAS (fly ash based alumino-silicate) and has improved by a factor of 4.0, with an adsorption capacity of 26.5 mg/g for AMP-functionalized FAS at 55 �C with 15% CO2 inN2. The positive influence of water was observed with an improvement of adsorption capacity to 34.82 mg/g at 55 �C with 15% CO2, 82% N2, and 3% water vapor. The adsorbent is studied for adsorption capacity at varying temperatures, and the best performing adsorbent is characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermal analysis, and elemental analysis to study the morphological properties of the present adsorbent support. The excellent thermal stability of synthesized material suggested the formation of promising aluminosilicate for CO2 adsorption

Biomimetic carbon dioxide sequestration using immobilized bio-composite materials

Mesoporous alumina has been synthesized using egg shell membrane (ESM) as template. Aluminum ion has been loaded on ESM by simple adsorption technique and then calcined to obtain the mesoporous alumina. The characterizations of alumina loaded ESM (ESMAl) have been done by various techniques like XRD, TEM, EDX and surface area. From immobilization studies the optimum pH and temperature for free and immobilized CA were determined to be 7.5 and 25 ◦C, respectively. The Km and Vmax of immobilized CA was found to be 5.3 mM and 1.753 �moles/ml/min by p-NPA assay. The storage stabilities for free and immobilized CA were performed at 25 ◦C and it was found that the half life period for immobilized CA has been improved by a factor 1.25 as compared to free CA. From leaching study the immobilized CA could be reused up to 7th cycles. The carbonation capacity of immobilized CA was found to be 24.84 mg of CaCO3/mg of enzyme as compared to 33.05 mg of CaCO3/mg of enzyme for free CA

Catalytic Converter Modeling: Artificial Neural Networks for Perovskite Based Catalyst

Two-stroke vehicles including two and three wheelers constitute about 62% of vehicles in India, and about 45-50% in other developing countries in the region. These are the major contributors to vehicular pollution. Catalytic converters based on perovskite have been developed for 2- stroke vehicles. Detailed characterization was carried out during development of alumina washcoat and synthesis of perovskite catalyst to establish the thermal stability of alumina washcoat and phase formation of catalysts. A number of prototypes based on alumina-supported perovskite have been prepared and tested for mass conversion efficiency with respect to CO, HC and NOx using the Indian Driving Cycle (IDC). A catalytic converter model has been developed using the MATLAB artificial neural network toolbox for performance prediction. Experimental data generated during the detailed characterization of catalytic converters and its evaluation on engine dynamometer has been used as training data. The model was used for prediction of conversion efficiencies and mid-bed temperature. Keep-one-out method was used for comparison of predicted and experimental values. The algorithm developed predicts the performance very well and will be able to give prior information on the performance in view of future emission standards