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Abstract: The aim of this work is the investigation of the solubility of three disperse dyes in a mixture of CO2 and ethanol. Experimental solubilities of disperse blue 79, disperse orange 3 and solvent brown 1 in a mixture containing 5.5mol% of ethanol in carbon dioxide have been measured using a dynamic apparatus and compared with those in pure carbon dioxide [A. Ferri, M. Banchero, L. Manna, S. Sicardi, J. Supercrit. Fluids 30 (2004) 41–49]. The effect of the co-solvent is so pronounced that solubilities similar to those measured in pure carbon dioxide have been achieved in the mixture at pressures 100bar lower. The experimental results have been correlated with three different approaches: the Peng–Robinson equation of state [D.Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–63], the semi-empirical Chrastil equation modified for ternary systems [J.C. Gonzales, M.R. Vieytes, A.M. Botana, J.M. Vieites, L.M. Botana, J. Chromatogr. A 910 (2001) 119–125] and, finally, a correlation recently proposed by our research group for binary systems [A. Ferri, M. Banchero, L. Manna, S. Sicardi, J. Supercrit. Fluids 32 (2004) 27–35] here applied for the first time to ternary systems. The results have pointed out that the third semi-empirical equation gives the best agreement between the experimental and calculated solubilities. [Copyright &y& Elsevier]

Abstract: Mass transfer limitation is often the controlling mechanism of the conversion rate in trickle bed reactors, where catalysts with a huge activity are employed. Modelling and interpretation of reactor performance would then require the knowledge of the proper mass transfer coefficients. Anyway, mass transfer coefficients that can be found in the literature are widespread and are obtained mostly for non-foaming and non-reacting systems. In this paper, we examined the catalytic hydrogenation of -methyl styrene to cumene (foaming and reacting system) in an isothermal laboratory reactor and in a pilot scale adiabatic one. The first aim of the work is to propose a scale-up criterion, as a useful tool to estimate performances of a pilot scale plant from those of a laboratory scale. Moreover, a model that considers the reaction as instantaneous is proposed; the aim of the model is to demonstrate how the systems where organic liquids are involved are improperly described with the mass transfer coefficients which can be found in the literature. [Copyright &y& Elsevier]

Unsteady-state operation of trickle-bed reactors (TBRs) is a promising technique to improve reactor performances especially when mass transfer phenomena are rate controlling. Among the different techniques, fast-mode modulation of the liquid flow rate seems to be one of the most successful. In fact cycling the liquid flow rate at very low frequencies can induce the reactor to work at the high-interaction regime where mass and heat transfer phenomena are strongly enhanced. Fast-mode periodic operation, then, can be considered an extension of the natural high-interaction regime at a mean range of gas and liquid flow rate normally associated with trickling regime in steady-state conditions.Experimental tests have been performed in a TBR employing -methyl styrene hydrogenation on Pd/C catalyst in unsteady-state conditions by “on–off” fast-mode liquid modulation. Results have been compared with the steady-state experiments at the corresponding average liquid flow rate, revealing a conversion rate improvement up to 60%. All experiments have been performed in isothermal conditions, so conversion improvement can be ascribed only to mass transfer increase and not to thermal effects. The variation of gas and liquid flow rates and liquid cycle parameters presented several important implications about the optimal working conditions. [Copyright &y& Elsevier]