Kinetics, gas-liquid mass transfer, and modeling of the soybean oil hydrogenation process

The kinetics for soybean oil hydrogenation using a commercial Ni/Al2O3 catalyst were investigated in a 2 X 10(-3) m(3) agitated reaction calorimeter operating under a wide range of temperatures (383-443 K), pressures (0.12-0.68 MPa), and catalyst loadings (0.02-0.16 Ni wt %). A simple model (model 1) and a novel comprehensive model (model 2) were developed to describe the hydrogenation process based on Langmuir-Hinshelwood kinetic expressions. The catalyst activity and mass-transfer coefficients were incorporated in both models. Under isothermal conditions, modeling results showed that increasing k(L)a values and pressure and decreasing temperature and catalyst loading decrease the trans fatty acid (TFA) content in the partially hydrogenated soybean oil. Using model 2, a nonisothermal batch reactor was simulated and the results indicated that good heat-transfer control is required to minimize the amount of TFA produced. Also, k(L)a appeared to be the rate-limiting step in the overall process, and accordingly proper gas-liquid mixing is crucial in commercial hydrogenation reactors.