A. Aranzabal

Enhanced activity of zeolites by chemical dealumination for chlorinated VOC abatement

Abstract The objective of this work is to evaluate the dealumination via ammonium hexafluorosilicate treatment as an effective method for enhancing the catalytic performance of H-Y zeolite in chlorinated VOC oxidative destruction. A series of Y zeolites with various Si/Al ratios was prepared from a commercial sample and then tested for the catalytic decomposition of 1,2-dichloroethane as a model reaction. In general, these modified Y zeolites exhibited a higher activity than that of the parent material, the zeolite subjected to 50% dealumination resulting the most active catalyst. This increase in activity was associated with the development of strong acidity due to dealumination. Likewise, 50% dealuminated sample showed an improved catalytic behaviour for the destruction of other typical chlorinated pollutants, namely, dichloromethane (DCM) and trichloroethylene (TCE). The ease of destruction was found to follow this trend: 1,2-dichloroethane > dichloromethane > trichloroethylene.

Synthesis of cordierite monolithic honeycomb by solid state reaction of precursor oxides

The synthesis of cordierite monolithic honeycombs by solid state reaction at high temperature of alumina, kaolin, talc and silica has been studied. The synthesized honeycombs have been characterized by DTA and XRD. The crystal composition of the samples have been observed to be very dependent on temperature and time of reaction. Thermal treatment of the monolithic precursors at 1400°C for 30 minutes allows formation of high purity cordierite with high crystallinity, maintaining the desired monolithic structure of the honeycombs.

State of the art in catalytic oxidation of chlorinated volatile organic compounds

Chlorine-containing organic compounds (Cl-VOC) require special attention due to their distinct toxicity, high stability and persistence in the environment. Removal of Cl-VOC by catalytic oxidation over a wide variety of catalysts has been presented in literature. This paper reviews the state of the art in this subject, including different model compounds, nature of catalysts, and oxidation activity. Catalyst selectivity (CO2 vs. CO and HCl vs. Cl2), by-products formation and the causes of deactivation are also analyzed as the most important factors in the catalyst selection for practical applications.

Screening of Fe–Cu-Zeolites Prepared by Different Methodology for Application in NSR–SCR Combined DeNOx Systems

The NOx NH3-SCR performance of several Cu and Fe catalysts supported on BETA and ZSM-5 zeolites has been studied in single SCR and double NSR–SCR configuration, and the activity related to the nature and reducibility of metal species on the catalyst surface. Intermediate ammonia formed in NSR improved greatly NOx conversion at the exit of the double NSR–SCR configuration, which was practically totally converted to N2.

Deep catalytic oxidation of chlorinated VOC mixtures from groundwater stripping emissions

The total oxidation chlorinated VOCs mixtures, with composition similar to those expected from groundwater air strippers, over Pd/Al2O3 and Pt/A2O3 catalyst at temperatures from 200 to 550°C was investigated. 1,2-Dichloroethane showed greater oxidability, followed by dichloromethane and 1,1- dichioroethylene and trichloroethylene. The addition of hydrocarbons to a chlorinated feed produced changes in the reactivity order of the chlorinated VOCs, indicating the existence of a complex reaction system due to the energetically non-uniform catalytic surface.

Catalytic behaviour of H-type zeolites in the decomposition of chlorinated VOCs

Abstract Several H-type zeolites were investigated for their activity and selectivity during TCE oxidative decomposition in dry and humid conditions. These catalysts showed high activity resulting H-MOR to be the most active. The catalytic behaviour appeared to be determined by strong Bronsted acidity. The main oxidation products were CO, CO 2 , HCl and Cl 2 . Water enhanced the catalytic activity at lower temperatures and also promoted the selectivity to deep oxidation products generation (CO 2 and HCl).

30-P-18-Analysis of the deep catalytic oxidation of binary CVOCs mixtures over H-ZSM-5 zeolite

Publisher Summary This chapter discusses the oxidative decomposition of the binary mixtures of chlorinated volatile organic compounds (CVOCs) [1,2-dichloroethane (DCE), dichloromethane(DCM), and trichloroethylene(TCE)] over H-ZSM-5 zeolite. The ease of destruction decreased in the order: DCE>DCM>TCE. The main oxidation products are carbon monoxide (CO), carbon dioxide (CO2), hydrochloric acid (HCl), and chlorine (Cl2). Some other chlorinated byproducts are detected as well, such as vinyl chloride, methyl chloride, and tetrachloroethylene. The destruction of chlorinated mixtures induced an inhibition of the oxidation of each CVOC. An important decrease in the formation of intermediates is noticed, and HCl selectivity is largely improved.