a b s t r a c tIn this study, heterogeneous Fenton-like degradation of reactive azo dye Rhodamine 6G in water was investigated over a CuFeZSM-5 zeolite catalyst prepared by hydrothermal synthesis. At initial pH of 3.4, a color removal of 100% was achieved after a reaction time of 45 min. TOC elimination was measured to be 51.8% after 2 h of oxidation. Initial decolorization rate was described by an equation of −r A0 = 4.56 × 10 2 e −24.83/RT C R6G,0 C 0.35 H 2 O 2 ,0 where R is in kJ/mol. The leaching of iron and copper cations from zeolite structure into the solution during oxidation was dependent on pH strongly. The regulation of pH from 6.5 (dye solution pH) to 3.4, increased leaching for iron from 0.7 to 0.8 mg/dm 3 and for copper from 1.4 to 2.1 mg/dm 3 . The copper was totally leached from the catalyst during the process at pH 3.4.

No abstract

The catalytic isomerization reaction of α-pinene to camphene over a clinoptilolite catalyst was investigated in a batch reactor open to the atmosphere between 130 and 155°C. The catalyst was selective to the isomerization of α-pinene to camphene. The effects of several variables, such as reaction temperature, amount of catalyst, stirring speed and catalyst particle size, on the conversion of α-pinene and selectivity to camphene were determined. The reaction fits a first-order parallel reaction with rate constants of k 1 = 3.020·10 −2 e −33381.6/RT for the production of camphene and of k 2 = 1.576·10 −2 e −31096.53/RT for the production of limonene. JAOCS 74, 1145JAOCS 74, -1151JAOCS 74, (1997. KEY WORDS:Camphene, isomerization, kinetics of isomerization of α-pinene, selective catalyst.The purpose of this study was to investigate the effects of several variables, such as reaction temperature, amount of catalyst, stirring speed and catalyst particle size, on the conversion of α-pinene to camphene (X c ), and on the overall selectivity for camphene over an activated clinoptilolite zeolite catalyst, which was found as the most selective after a selectivity screening test. We also wanted to develop a suitable rate equation for the isomerization of α-pinene to camphene.Camphene is an important industrial chemical from which many products of commerce, such as toxaphene, isobornyl acetate, isoborneol, and camphor are made. Comparatively small amounts are used to produce fragrance chemicals by reaction with phenols.Camphene is produced commercially by treatment of α-pinene over acidic catalysts in the absence of water (Scheme 1). It can be produced similarly from β-pinene and from pinene-containing materials, such as gum turpentine, wood turpentine and sulfate turpentine, which are obtained in the manufacture of paper from delignification of wood. Isomerization of α-pinene is generally carried out at reflux temperature in the presence of titania, minerals that contain a specific group of silicates (halloysite, zeolites), or activated clays. Preparation of the catalyst has a great influence on product yields and composition. The chief by-products of the isomerization are tricyclene, which is always obtained with camphene as an equilibrium product, and p-menthadienes.Many one-step methods with catalysts have been suggested in the literature (1) for the preparation of camphene. Various types of catalysts, both organic and inorganic, as well as mineral, have been reported to promote the isomerization of pinene directly to camphene. The catalysts must be treated with an acid to activate the surface. The time for complete conversion of the terpene being isomerized varies with the nature and amount of the catalyst used and the temperature employed. Carson (2) used chlorites, and Kirkpatrick (3) tried halloysite as catalyst for the isomerization of pinene to camphene and obtained a yield of 60% by weight. Korotov et al.(4) prepared camphene by isomerization of pinene in the presence of TiO 2 . Afanas'eva and coworkers (5,6) st...

This paper describes the ultrasonic degradation of oxalic acid. The effects of ultrasonic power, H(2)O(2), NaCl, external gases on the degradation of oxalic acid were investigated. Reactor flask containing oxalic acid was immersed in the ultrasonic bath with water as the coupling fluid. Representative samples withdrawn were analysed by volumetric titration. Degradation degree of oxalic acid increased with increasing ultrasonic power. It was observed that H(2)O(2) has negative contribution on the degradation of oxalic acid and there was an optimum concentration of NaCl for enhancing the degradation degree of oxalic acid. Although bubbling nitrogen gave higher degradation than that for bubbling air, both gases (for 20 min before sonication and during sonication together) could not help to enhance the degradation of oxalic acid when compared with the degradation without gas passage.

Catalysts prepared by ion exchange of clinoptilolite-based natural zeolite tuffs with NH 4 + , Ba 2+ and Pb 2+ were investigated in the isomerization reaction of ␣-pinene at atmospheric pressure under nitrogen flow. Activity and selectivity to mono-, bi-and tricyclic products were correlated with acidity strength.