Dehydration of tert-butyl alcohol in a reactive distillation column

• Main Author: Abella, Leonila C.
• Format: text
• Language: English
• Published: Animo Repository 1999
• Subjects: Alcohol; Distillation; Separation (Technology); Kinetic theory of liquids; Chemical processes; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/828
• Institution: De La Salle University

The continuing rise in energy prices has highlighted the need for energy recovery. Considering that large amount of energy are released to the environment in the form of low-temperature waste heat, these can be utilized effectively if they will be upgraded to high temperature heat sources. Chemical heat pump is one of the industrial heat recovery systems which makes use of a reversible inorganic/organic reaction. However, few studies have been done on the chemical heat pumps that upgrade heat sources below 373 K because there are few effective reversible reactions (Kato et al 1996). One of these reactions is the dehydration of tert-butyl alcohol (TBA) to isobutene (IB) and water (H2O).The dehydration of tert-butyl alcohol (TBA) in the liquid phase was studied by using an ion exchange resin, Amberlyst 15 (A15) in the H+ form. A preliminary experiment was done using dry and wet resins in a semi-batch reactor at 338 K. The results with the dry resin in the semi-batch reactor were different from those with the wet resin due to the swelling of resin in the presence of water. Thus, for the kinetic study, experiments were carried out in a semi-batch reactor using 14g of wet resins at reaction temperatures of 333, 338, 343 and 349 K. This study focuses on the application of reactive distillation to the liquid phase dehydration of tert-butyl alcohol to produce isobutene and water at reduced pressures. The dehydration was carried out in a reactive distillation column with a catalyst-bed filled with 50g of Amberlyst 15, ion exchange resins, at various reduced pressures ranging from 50 to 101 kPa and at different feed flowrates of 1.81x10-4 to 5.58x10-4 mol/s. The resins are cylindrical pellets with an average diameter and height of 7.8 mm. The conditions for the complete conversion are determined by changing the feed flowrate and pressure in order to support the applicability of this reaction system to a chemical heat pump. Experimental results are compared with the results simulated by using ASPEN PLUS Process Simulator (Release 9.2 and Version 10). In the kinetic study, a rate equation which considered the inhibition of water using the Langmuir-Hinshelwood kinetic model was formulated. The experimental results agreed well with the calculated ones. The use of reactive distillation could facilitate the complete dehydration of tert-butyl alcohol by avoiding the strong inhibition of water in this reaction. The dehydration of tert-butyl alcohol to isobutene and water can be used as an endothermic reaction for a chemical heat pump to upgrade heat sources below 373 K. Simulated results in a reactive distillation agreed well with the experimental results.The endothermic liquid-phase dehydration of tert-butyl alcohol in a reactive distillation column at reduced pressures could be utilized as a reaction for a chemical heat pump.