Completed Research
Hydrodynamics, Mass Transfer and Modeling of the Liquid-Phase Toluene Oxidation Process
Romain Olivier Lemoine, PhD, 2005
(Thesis: University of Pittsburgh ETD or UMI Dissertation Publishing)
Liquid-phase toluene oxidation (LPTO) process is conventionally used in benzoic acid manufacture, the prime raw in the phenol production, caprolactam and glycol dibenzoates synthesis, and various food as well as pharmaceutical industries. Currently, the emphasis of LPTO process is shifted towards the production of high-value benzyl alcohols and benzaldehydes due to environmental problems and economic reasons linked to the phenol production and the toluene chlorination/hydrolysis process, traditionally used to produce the high-value alcohols and aldehydes. Typically, LPTO continuous process is carried out either in a modified cascade of agitated reactors or in a bubble column reactor, in which a mixture of toluene, homogeneous cobalt-based catalyst and air is fed to the reactor(s) under pressures of 1-20 bar and temperatures of 350-440 K. Successful designs and performances (selectivity, yield of the desirable products) of LPTO reactors require, among others, precise knowledge of the kinetics, hydrodynamics, and heat as well as mass transfer.
The first objective of this research project is to experimentally determine the hydrodynamic (critical mixing speed, induced gas flow rate, gas hold-up, bubble size and Sauter mean bubble diameter) and mass transfer (gas-liquid interfacial area, mass transfer coefficient and volumetric mass transfer coefficient) parameters for N2, O2 and air in pure toluene and typical reaction medium aimed at mimicking the actual yields of the continuous LPTO process under typical industrial conditions. The second objective of the project is to build algorithms to determine these parameters, based on correlations (empirical, neural network) developed using our experimental data along with literature values covering industrial ranges of operating conditions and reactor geometries. The ultimate goal of the project is to model, optimize, and predict the performance of LPTO process in lab-, pilot- and industrial-scale agitated reactors and bubble column reactors.