Estudo de efeitos de transporte na síntese de éter etil terc-butílico em fase líquida.

Abstract

Tertiary Ethers may be used as octane booster in gasoline in substitution of lead compounds. Methyl Tertiary Butyl Ether (MTBE), produced from isobutene and methanol has been used as octane booster for years in some countries. But the Ethyl Tertiary Butyl Ether (ETBE) has been considered a promising additive for gasoline due to important characteristics in comparison to MTBE: lower vapor pressure and toxicity. In addition, E T B E is produced from ethanol, a renewable raw material, in a liquid phase heterogeneous catalytic process. In this work an evaluation of mass transfer in the particle of the catalyst used was carried out. The effects of ethanol concentration on the reaction rate were studied using a Langmuir-Hinshelwood-Hougen-Watson kinetic model. The ethanol/isobutene molar ratio was kept below the unity to reproduce industrial operation conditions. Experiments were carried in a batch stirred PARR reactor of one liter, designed for MTBE synthesis. To maintain the system in liquid phase, temperature was kept at 60 °C and pressure at 25 kgf/cm2. A C4 industrial stream containing isobutene and other inert compounds like butanes and butenes, was used with pure ethanol to produce ETBE. Catalyst used was the sulphonic resin Amberlyst 15-C from Rohm & Haas. All the experiments were conducted far from equilibrium and sufficiently agitated to avoid mass film transport effects around catalyst particles. Results showed that the reduction of ethanol concentration leads to an increase of the initial reaction rate of E T B E production. This behavior coincide with the formation of undesired diisobutene and a non reactive nucleus to the production of ETBE. Intraparticle mass transport was quantified using theoretical calculation of the effectiveness factor. This was done using the ratio between the effective rate and the intrinsic rate without transport effects. The effective rate was obtained from the integration of the rate of reaction profile in the particle of catalyst.