Published March 1990
Mitsubishi Gas Chemical (MGC) has developed a new methyl methacrylate (MMA) process based on acetone cyanohydrin. Unlike the conventional process based on acetone cyanohydrin, it does not produce ammonium sulfate by-product, which is costly to dispose of. Instead, it produces formamide by-product, which can be dehydrated to produce HCN for recycle, thus reducing HCN feed requirements. The MGC process also uses no sulfuric acid, thus reducing corrosivity.
In the MGC process, acetone cyanohydrin is converted to a-hydroxyisobutyramide (AHIBA), which is then esterified with methyl formate to produce methyl a-hydroxy isobutyrate (MAHIB) and formamide. The MAHIB is dehydrated to MMA, which is dried and purified by conventional means. The process is now in the pilot plant stage.
Preliminary estimates of investments, production costs, and product values have been made for the new MGC process for a 250 million Ib/yr (113,400 t/yr) MMA plant on the U.S. Gulf Coast. They are compared with costs for a conventional plant (acetone cyanohydrin route) and for plants that use processes starting with a C4 feed (t-butanol or isobutylene) , ethylene, or propylene.
Our preliminary estimate for the MGC process shows a capital requirement that is only about one-half that of the other processes. Raw material costs and total direct costs for the proposed MGC process are a little higher than for the ACH process, primarily because of the cost of methyl formate. At current olefin prices, other MMA processes offer lower raw material costs and total direct costs.
Because of its much lower estimated capital investment, the MGC process shows a lower product value than that for any of the other operating MMA processes. It is only slightly lower than the product value of MMA made from the C4 process, however. Only the propylene-based process, not yet commercial, shows a lower product value. Low-price methyl formate, perhaps by captive production, could reduce the costs of the MGC process significantly below that of any of the other processes.
We conclude that the MGC process could be an attractive choice for a new MMA plant, provided that the yields claimed by MGC can be verified, that methyl formate can be obtained at a low price, and that the capital investment is indeed so much lower than that of the competing processes.