Catalytic combustion of chlorinated ethylenes over H‐zeolites

Abstract

Several H-zeolites (H-Y, H-ZSM-5 and H-MOR) were investigated for the catalytic combustion of chlorinated ethylenes, namely 1,1-dichloroethylene and trichloroethylene. Conversion was inversely related to the chlorine content of the feed molecule. H-ZSM-5 zeolite was the most active catalyst in 1,1-dichloroethylene combustion whereas H-MOR was the most effective zeolite for trichloroethylene destruction. Temperature-programmed desorption of ammonia and diffuse reflectance FT-IR measurements of adsorbed pyridine revealed that strong Brønsted acidity plays an important role in controlling the activity of H-zeolites. The main combustion products were CO, CO 2 , HCl, and Cl 2 . Additionally, small amounts of highly chlorinated by-products were also detected, namely trichloroethylene and tetrachloroethylene. H-zeolites showed a great selectivity to HCl formation.

Catalytic oxidation of butyl acetate over silver-loaded zeolites

“…These conversions were attributed to thermal oxidation and that catalyzed by sites other than silver. These sites were likely to be acid sites that have been widely reported in the literature [6,18]. It could be deduced from the result that the thermal combustion was also negligible below 350 • C and started to be significant at 400 • C. Any improvement in the conversion beyond that caused by thermal oxidation when the metal exchanged HZSM-5 was used could therefore be attributed to the positive effect of the metal.…”

“…This result indicated that active metal content alone could not result in a good catalyst. Other contributing factors are such as metal dispersion, available surface area, exchange site and other type of active site that could catalyze the reaction such as acid sites [6,8].…”

“…The competitive adsorption between the organic and water molecules on the catalyst's active sites always results in lower catalytic activity [12,14]. Recently, zeolites have gained much interest to be used as supports or even as catalysts for oxidation reactions [6,15]. The merit of zeolite-based catalyst is that the active metal components can be exchanged with the existing cations in the zeolite.…”

“…The selection between a metal oxide or a noble metal is generally influenced by several factors such as the nature of the gaseous stream to be treated and the presence of contaminants. However, it is generally accepted that noble metals are more active than metal oxides but the latter are more resistant to poisoning [6]. Pt and Pd are the most common noble metals used for total oxidation of VOCs [7] and usually, they are supported on an oxide such as Al 2 O 3 or SiO 2 .…”

Synthesis and Toluene Adsorption/Desorption Property of Beta Zeolite Coated on Cordierite Honeycomb by an In Situ Crystallization Method

“…Several investigations [28][29][30][31][32][33] pointed out that the HC adsorbed on zeolite can be protonated by acid sites and form the carbenium ions, which are in favor of cracking and oxidation. The higher acid strength would cause higher activity of cracking and oxidation for zeolite [34,35]. Due to greater acidity and higher strength of strong acid sites, the coated beta behaves with considerable activity for catalytic 36.0 a): the normalized amount with respect to the weight percent of coating.…”