2012 Spring Symposium
David W. Johnson
Lucite International UK Ltd
Abstract — A brief outline of Lucite International’s new “Alpha” methyl methacrylate technology is described including process scale up and the first exploitation in Singapore in late 2008. The technology was developed from 0.5g/h lab scale to 500g/h pilot and thence directly to 12te/h commercial scale. The plant was commissioned from first introduction of chemicals to 100% rate within 3 weeks and currently operates at over 16te/h with exceptional reliability.
Two catalytic steps are key to the technology. In the first, carbon monoxide, ethylene and methanol are reacted in solution with a novel palladium phosphine catalyst which gives methyl propionate in 99.9+% selectivity in a continuous process at ppm level palladium concentrations at 100C and 10bar total pressure. The catalyst activity and life is very sensitive to operating conditions. After extensive process development, activities of 15,000 moles/mole Pd/h and life of >1x107moles methyl propionate/mole Pd are routinely achieved on the commercial plant.
The second stage catalyst, composed of caesium/zirconia/silica reacts methyl propionate with formaldehyde at 330C and 1–2barg to form methyl methacrylate (MMA) and water. The selectivity is about 93% to MMA based on methyl propionate and over 80% on formaldehyde fed. The presentation describes some of the steps in development of the catalyst including comparisons with catalysts for similar process disclosed by competitors. A discussion of the mechanism of formation of MMA and byproducts is made in terms of surface reactions between reactants and products. A 2-site model is proposed involving both strongly basic and hydroxylic, weakly acidic sites. Reactions catalysed in byproduct formation include decarboxylations, combined condensation-decarboxylations, hydride transfers and acid catalysis. Lucite has found that competitive catalysts have the wrong balance of acidity and basicity and result generally in high levels of hydride transfer and acid catalysis products.
Speaker’s Biography: The author has a BA (Natural Sciences, Chemistry) from Oxford University a PhD in radiation chemistry and carried out postdoctoral research in LEED/XPS/UPS before joining ICI Ltd in 1977. Within ICI he worked initially on nitrate promoted silver ethylene oxide catalysts followed by 4 years in ICI’s New Science Group studying the structure of novel zeolites synthesised by ICI co-workers. Since 1990 he has worked in the area of MMA process design and led the exploratory research team which defined the Alpha process and currently leads Lucite’s (formerly ICI Acrylics) chemistry team. His current interests are process improvement for the Alpha technology and introduction of biotechnology into MMA manufacture.