The carbonylation of methanol to form methyl acetate and acetic acid was investigated using phosphine modified nickel iodide as the metal catalyst precursor. The course of the reaction was monitored using a high pressure, high temperature in Ε½ . situ Cylindrical Internal Reflectance FTIR reactor CIR-REACTOR to acquire data under autogenous conditions. The Ε½ . capabilities of the reactor permit reaction monitoring at temperatures of 1908C and pressures of 13.6 kPa 1500 psig . In this study the reaction kinetics and in situ observations were made at temperatures between ambient and 1608C with an operating Ε½ . pressure of 8.16 kPa 900 psig for most reactions. This study used methyl acetate as a solvent, and both methyl acetate and acetic acid were products of the catalytic reaction. Conditions were optimized at 1608C using organo-phosphine modified Ε½ . yy NiI as the catalyst precursor. Under the applied reaction conditions, no anionic carbonyl species such as Ni CO I were 2
x y
detected at high carbonylation rates, in contrast to the anionic carbonyls reported in the rhodium catalyzed acetic acid Ε½ . process. In the rapid kinetic regime, only trace amounts of Ni CO were formed in the reactor at steady state. The 4 Ε½ . experimental results suggest a new mechanism involving Ni PPh as one of the active metal complex intermediates 3 2
reacting in a slow step with methyl iodide. The in situ reaction monitoring experiments readily enabled the determination of the concentrations of organonickel species as well as the concentration of carbonylation products under fast reaction conditions.