Esterification kinetics of acetic acid with methanol was studied with solid acid catalyst in an isothermal batch reactor at 333À353 K. Different types of ion exchange catalyst (Indion 130, Indion 190, and Amberlyst 15 wet) were used for the esterification of acetic acid. It was found that Indion 130 was an effective catalyst for acetic acid esterification. The effects of stirrer speed, reaction temperature, initial reactant concentration, and catalyst loading on reaction rate were investigated and optimized. Temperature dependence of the reaction rates and activation energies was determined by an Arrhenius plot. A complete kinetic equation for describing the reaction catalyzed by Indion 130 was developed. This equation can be used in the simulation and design of the catalytic distillation column for the synthesis of methyl acetate.

The complex nature of diclofenac limits its biological degradation, posing a serious threat to aquatic organisms. Our present work aims to eliminate diclofenac from wastewater through photocatalytic degradation using TiO-SnO mixed-oxide catalysts under various operating conditions such as catalyst loading, initial diclofenac concentration and initial pH. Different molar ratios of Ti-Sn (1:1, 5:1, 10:1, 20:1 and 30:1) were prepared by the hydrothermal method and were characterized. The results indicated that addition of Sn in small quantity enhances the catalytic activity of TiO. Energy Band gap of the TiO-SnO catalysts was found to increase with an increase in Tin content. TiO-SnO catalyst with a molar ratio of 20:1 was found to be the most effective when compared to other catalysts. The results suggested that initial drug concentration of 20 mg/L, catalyst loading of 0.8 g/L and pH 5 were the optimum operating conditions for complete degradation of diclofenac. Also, the TiO-SnO catalyst was effective in complete mineralization of diclofenac with a maximum total organic carbon removal of 90% achieved under ultraviolet irradiation. The repeatability and stability results showed that the TiO-SnO catalyst exhibited an excellent repeatability and better stability over the repeated reaction cycles. The photocatalytic degradation of diclofenac resulted in several photoproducts, which were identified through LC-MS.

Methanol selective oxidation to formaldehyde over a modified FeÀMo catalyst with two different stoichiometric (Mo/Fe atomic ratio = 1.5 and 3.0) was studied experimentally in a fixed bed reactor over a wide range of reaction conditions. The physicochemical characterization of the prepared catalysts provides evidence that Fe 2 (MoO 4 ) 3 is in fact the active phase of the catalyst. The experimental results of conversion of methanol and selectivity towards formaldehyde for various residence times were studied. The results showed that as the residence time increases the yield of formaldehyde decreases. Selectivity of formaldehyde decreases with increase in residence time. This result is attributable to subsequent oxidation of formaldehyde to carbon monoxide due to longer residence time.

T he spouted bed systems are efficient fluid-solid contacting devices, and find applications in particle drying and coating operations. In order to predict the performance of continuous spouted beds, a detailed knowledge of particle residence times in the bed becomes essential. Information concerning the gross mixing behaviour of solids can be obtained from either stimulus-response experiments or theoreticaI/semi-empirical models. A considerable amount of literature is available to understand the particle residence time distributions and solids mixing in single spouted beds (Mathur and Epstein, 1974). Based on the available information it may be concluded that the solids mixing in a single spout bed could be approximated to near perfect mixing.In the case of multiple spouted beds, Foong et al. (1975) conducted some solids mixing experiments in a flat bottom column having seven spouts arranged such that one spout at the centre was completely surrounded by six, and having a triangular pitch of 150 mm. Wheat and millet were used as bed materials with air as the spouting fluid. The bed was operated close to minimum spouting condition. Based on their data, they concluded that the total bed volume comprised of 85.5% mixed flow region, 1.7% plug flow region and 12.8% dead water region.The multispout systems reported by Murthy and Singh (1994) consisted of square spout cells arranged in a rectangular column having 2 or 3 cells in line, or 4 cells arranged in square pitch. The transitions found in the operation of these multiple spouted beds were represented by phase diagrams (Murthy and Singh, 1996) and the following were identified in these diagrams: static bed (region 1); partially spouted bed (region 2); stable spouting (region 3); spout oscillations and interference (region 4); and chaotic bed (region 5). When the bed was operated close to minimum spouting condition (region 3), the bed was stable with steady spouting; here, each spout cell could be treated as a single spout unit. However, as the fluid velocity was increased, the spout oscillations and interference of spout fountains increased (region 4), which in turn increased the solids transfer between the cells through the fountains in the upper regions of the cells; but, the solids recirculation in the lower portions of the bed remained unchanged.It appears, therefore, that the solids mixing behaviour in the multiple spouted beds having geometry used by Murthy and Singh (1 994) should depend on whether the bed was operated in region 3 or 4. The present study aims at understanding such a behaviour. ExperimentalThe experiments were conducted in four rectangular columns having two and three spout cells; each spout cell was of square cross-section, and was provided with an inverted pyramid (apex angle 60") at the bottom. The spout cell configurations are shown in Figure 1. The broader sides of the column were made of transparent perspex sheets for visual observations. The fluid inlet to each cell was a 12 mm diameter orifice. A polymer material (pink colour, dp = 1....