Many researchers have investigated the optimization of the above-mentioned
processes. Luyben (2010) studied the gas-phase process on the SPA catalyst and economically
optimized the process with a simple model. Total annualized cost (TAC),
which accounts for initial investment with a three-year payback time, operating costs,
and raw material costs, was the objective function to be minimized in that study.
Pathak et al. (2011) studied the vapor-phase and reactive distillation (RD) process
of CDTech for cumene. They also used TAC as the objective function and concluded
that the reactive distillation process is 47% cheaper than the conventional gas-phase
process. Lei et al. (2009) considered a zeolite-based process that uses two fixed-bed
reactors. They started with side stream draw from a distillation column to reduce
energy consumption. They further modified the alkylation reactor and replaced it
with a reactive distillation column and concluded that the energy consumption and
total investment can be reduced in this way. However, they did not include any economic
evaluation in the optimization procedure. Norouzi and Fatemi (2012) studied
gas-phase production of cumene on SPA catalyst and developed an economic model
that comprised initial investment, operating costs, labor costs, raw material costs,
revenue, plant life, and inflation, among other factors. The net present value
(NPV) was chosen as the objective function, and a statistical procedure, response
surface method, was chosen to adjust operational conditions and to find the global
optimum of the process to maximize the NPV.