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

Air quality forecasting using a hybrid autoregressive and nonlinear model

The usual practices of air quality time-series forecasting are based on applying the models that deal with either the linear or nonlinear patterns. As the linear or nonlinear behavior of the time series is not known in advance, one applies the number of models and finally selects the one, which provides the most accurate results. The air pollutant concentration time series contain patterns that are not purely linear or nonlinear and applying either technique may give inadequate results. This study aims to develop a hybrid methodology that can deal with both the linear and nonlinear structure of the time series. The hybrid model is developed using the combination of autoregressive integrated moving average model,which deals with linear patterns and nonlinear dynamical model. To demonstrate the utility of the proposed technique,nitrogen dioxide concentration observed at a site in Delhi during 1999 to 2003 was utilized. The individual linear and nonlinear models were also applied in order to examine the performance of the hybrid model. The performance is compared for one-step and multi-step ahead forecasts using the error statistics such as mean absolute percentage error and relative error. It is observed that hybrid model outperforms the individual linear and nonlinear models. The exploitation of unique features of linear and nonlinear models makes it a powerful technique to predict the air pollutant concentrations

Nonlinear Analysis and Prediction of Coarse Particulate Matter Concentration in Ambient Air

This study attempts to characterize and predict coarse particulate matter(PM10) concentration in ambient air using the concepts of nonlinear dynamical theory.PM10 data, India, was used to study the applicability of the chaos theory. First, the autocorrelation function and fourier power spectrum were used to analyze the behavior of the time-series.The dynamics of the timr-series was additionally studied through correlation integral analysis and phase space reconstruction. The nonlibear predictions were then obtained using local polynominal approximation based on the reconstructed phase space. The results were then compared with the autoregressive model. The results of nonlinear analysis indicated the presence of chaotic character in the PM10 time-series. It was also obsered that the nonlinear local approximation outperforms the autoregressive model, because the observed relative error of prediction for the autoregessive model was greater then the local approximation model. The invariant measures of nonlinear dynamics computed for the predicted time-series using the two models also supported the same findings

Chemical hydrides: A solution to high capacity hydrogen storage and supply

Cycloalkanes are good candidate media for hydrogen storage (6.5 wt% and 60.62 kg H2/m3). A novel approach for the supply of hydrogen, through liquid organic hydrides (LOH) using catalytic reaction pair of dehydrogenation of cycloalkanes and hydrogenation of corresponding aromatics is a useful process for supply of hydrogen. Hydrogenation of aromatics is relatively well-established process. However, the efforts are needed to develop efficient catalyst for dehydrogenation of cycloalkanes. In this paper we review the dehydrogenation of cycloalkanes as useful reaction for storage of hydrogen in chemical hydrides. 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Life Cycle Testing of Hermetic Compressors With Alternatives to CFC-12

Life cycle tests of hermetic compressors were conducted using a specially designed test rig that employs a gas cycle. They were conducted at an ambient temperature of 50"C and suction and discharge pressures of 2.2 bar and 18.5 bar respectively. The oil temperature was maintained between 80- I 00"C. The duration of test was 2000h.After completion of the test, the oil samples were tested for total acid number and metal contents (Cu, Fe and Al). Any chemical degradation of refrigerant sample was assessed using NMR and F T-IR spectroscopes. The wear effects of compressor parts were measured using perthography.An assessment of conventional mineral oil with CF C-12 and various grades of hydrocarbon (HC-290 and HC-600a) blends including DIN grade, CARE-30, a blend of HC-290/HC-600a from Indian sources, destenched LPG, and commercial grade LPG has been done. HFC-134a and Polyol ester oil (POE) combination has also been studied. The comprehensive test results from the above assessment and comparative ratings are presente

Visible light active zeolite-based photocatalysts for hydrogen evolution from water

Hydrogen, considered as the fuel for future can be produced from non-conventional, renewable and plentiful source like water. Novel zeolite-based materials that show photocatalytic properties in the visible light have been synthesized by incorporating titanium dioxide (TiO2), heteropolyacid (HPA) and transition metals like cobalt (Co). These materials show high efficiency for water splitting under visible light irradiation. Hydrogen (H2) generation to the tune of 2730 mmol/h/g TiO2 has been obtained for the composite photocatalyst synthesized. Platinum (Pt) doping has also been attempted in this composite photocatalyst, however, no substantial enhancement in hydrogen generation was observed. The high efficiency of the composite photocatalyst suggests that the TiO2 which gets effectively dispersed and stabilized on the surface of zeolite works synergistically with transition metal like cobalt and heteropolyacid to make the material active in visible light for photoreduction of water to hydrogen. The aluminosilicate framework of zeolite also contributes towards delayed charge separation. This composite photocatalyst shows improvement in hydrogen evolution rate over other TiO2 based visibly active photocatalyst reported

Chemical hydrides: A solution to high capacity hydrogen storage and supply

Cycloalkanes are good candidate media for hydrogen storage (6.5 wt% and 60.62 kg H2/m3). A novel approach for the supply of hydrogen, through liquid organic hydrides (LOH) using catalytic reaction pair of dehydrogenation of cycloalkanes and hydrogenation of corresponding aromatics is a useful process for supply of hydrogen. Hydrogenation of aromatics is relatively well-established process. However, the efforts are needed to develop efficient catalyst for dehydrogenation of cycloalkanes. In this paper we review the dehydrogenation of cycloalkanes as useful reaction for storage of hydrogen in chemical hydrides. Keywords: Hydrogen storage; Liquid organic hydrides; Delivery to fuelling station; Cycloalkane

Surfactant-Modified Zeolite as a Slow Release Fertilizer for Phosphorus

The feasibility of using surfactant-modified zeolite(SMZ)as a carrier for fertilizer and for slow release of phosphorus (P)was investigated. Zeolite-A was modified by using hexadecytrimethylammonium bromide, a cationic surfactant, to modify its surface to increase its capacity to retainanion, namely, infrared, and scanning electron microscopy to study the effect of surfactant modification. Zeolite-A and SMZ were then subjected to P loading by treating them with fertilizer(KH2PO4). It was observed that the P loading on SMZ increased by a factor of 4.9 as compared to the unmodified Zeolite-A. A comparative study of the release of P from fertilizer-loaded unmodified zeolite-A and SMZ and from solid KH2PO4 was performed using the conatant flow percolation reactor. The result show that the P supply from fertilizer-loaded SMZ was available even after 1080 h of continuous percolation, whwreas P from KH2PO4 was exhausted within 264 h. The result indicate that SMZ is a good sorbent for PO4, and a slow release of P was achievable. These properties suggest that SMZ has a great potential as the fertilizer carrier for slow relese of P