PEP Review 97-12
Acetic Acid by the Chiyoda/UOP Acetica™ Process
Published: September 1999
Acetic acid is produced commercially by low-pressure methanol carbonylation in the presence of a homogeneous rhodium (Rh) catalyst and a methyl iodide promoter. Chiyoda and UOP introduced the Acetica™ process, a novel technology based on a heterogeneous Rh catalyst in which the active Rh complex is chemically immobilized on a polyvinyl pyridine resin. Compared with existing homogeneous processes. immobilization increases catalyst concentration in the reaction mixture, which is directly proportional to the acetic acid production rate without the addition of either additional water or promoter. The heterogeneous system also results in reduced by-product formation as a consequence of lower water concentration and in reduced Rh losses as a result of catalyst immobilization.
The Acetica™ process uses a bubble-column reactor (chosen for its excellent three phase contacting) to minimize catalyst attrition and improve reactor flexibility. Because a moving impeller is not needed for mixing, a mechanical seal is unnecessary, which simplifies high-pressure operation and enables the use of low-purity CO.
With our process design, the estimated total fixed capital investment for an 800 million lb/yr (363,000 f/yr) low-pressure methanol carbonylation plant using the Acetica™ process is significantly lower than that required for the same plant using the homogenous Rh catalyst process. The corresponding estimated product value for using the supported Rh catalyst process is also lower.