Published June 2018
This review presents a technoeconomic analysis of a methyl methacrylate (MMA) manufacturing process that was recently announced for commercialization by Evonik under the tradename LiMA®. This new MMA technology is based on ethylene, synthesis gas (syngas), and methanol.
MMA is a high-value monomer produced to make acrylic polymers, which are used for making plastics, surface coating resins, emulsion polymers, and extrusion compounds. The main end use of plastics include fabricated products such as building materials, lighting fixtures, signs, displays, sanitary items, glazing, lighting fixtures, lenses, appliances, etc. Demand for MMA is dependent on the economy, and specifically on economic cycle–sensitive applications in the construction and automotive industries. According to estimates received from some of the major players in the MMA production/marketing business, global MMA demand is expected to grow at an average annual growth rate (AAGR) of 3–4% in the next five years. Capacity over the same period is projected to grow at an AAGR of below 3%.
Evonik’s new MMA technology essentially has three process steps. In the first step, ethylene and syngas (of 1:1 molar ratio) are hydroformylated at 185–195°F (85–90°C) and 250–275 psia to produce propionaldehyde (PA). The reaction is catalytic, employing a rhodium-based catalyst in the form of a metal-organophosphorus ligand complex. Ethylene per-pass conversion is above 90%, and selectivity to propionaldehyde is around 95%. Ethane and CO2 are the main byproducts formed in the reaction. Separation of PA, byproducts, unreacted reactants, and catalyst is carried out in a straightforward manner through a sequence of steps, including cooling, condensation, liquid-gas separation, and distillation.
In the second step, PA reacts with formaldehyde (FA) used in the form of aqueous solution in the presence of a secondary amine and an acid to produce methacrolein (MAL). The reaction takes place in liquid phase in the temperature range of 248–410°F (120–210°C). Reactor pressure is 675–700 psia. FA and PA per-pass conversion are 100% and 99.4%, respectively. MAL selectivity is 98.7% based on PA. Product and byproducts separation is carried out by distillation.
In the final step of the process, MAL, methanol, and oxygen (air) are reacted in the presence of a proprietary catalyst comprising transition metals such as nickel or cobalt and gold nano-particles. The catalyst is supported on a silica-magnesia or silica-alumina-magnesia carrier. The reaction takes place at 194–203°F (90–95°C) and 85–110 psia. MAL per-pass conversion is about 70%, and selectivity to MMA is 95–97%. Product, byproducts, and unreacted reactants separation is carried out through a series of flashing, cooling, condensation, liquid-gas separation, and distillation steps carried out at different points in the process section.
This review, in the end, presents economic and environmental aspects of the process, including capital costs, production costs, utilities consumption, equipment sizes, carbon emissions, etc. Based on our analysis, we believe that LiMA® has a strong potential to produce MMA at lower costs and with lesser environmental impact than Lucite’s Alpha process.