Life Cycle Inventory of Methyl Methacrylate Yong Li, Evan Griffing, Celia Ponder, Michael Overcash Department of Chemical & Biomolecular Engineering North Carolina State University, Raleigh, NC 27695. Summary of LCI information.
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Yong Li, Evan Griffing, Celia Ponder, Michael Overcash
Department of Chemical & Biomolecular Engineering
North Carolina State University, Raleigh, NC 27695
Summary of LCI information
"A hundred years after we are gone and forgotten, those who never heard of us will be living with the results of our actions."--Oliver Wendell Homes
Among many methacrylic monomers, methyl methacrylate (MMA) is the most important. Application of MMA is mainly in construction/remodeling activity, automotive applications and original equipment manufacture. World consumption of methyl methacrylate was about 2.5 million metric tons in 2005, The methacrylamide sulfate route has dominated the commercial production of MMA since 1934. In this study, design-based approach methodology is used to obtain life cycle inventory data of MMA manufacturing process.
In this study, we use design-based approach methodology to obtain most of the life cycle inventory data, in which the life cycle information of MMA production is obtained using chemical engineering design techniques. The functional unit is defined as 1000 kg MMA product.In an effort to be more transparent and reflect the main process variables, the energy values and chemical losses are for the actual manufacturing processes. Energy to generate the utilities and emissions after waste management are not included.
97.6% sulfuric acid is further purified to 99% before pumped to the reactor 1. The acetone cyanohydrin and sulfuric acid in reactor 1 have a mole ratio of 1:1.86, and the reactor is operated at 90oC, and 1 atm1. The sulfuric acid serves both as a specific reactant and as a solvent for the reaction, which appears to involve an α-sulfatoamide intermediate. After the initial reaction, the mixture is subjected to brief thermal cracking at 140 oC to convert most of the α-hydroxyisobutyramide byproduct to methacrylamide sulfate. In general, for this stage, the acetone cyanohydrin conversion is typically 100% with selectivity about 90-95% to methacrylamide sulfate2.
In the next stage, sulfuric acid serves as catalyst in a combined hydrolysis/esterification of the methacrylamide sulfate to a mixture of methyl methacrylic acid and methyl methacrylate. Ammonium bisulfate is formed as a coproduct at equimolar amounts to the amount of methacrylate formed. The esterification is carried out at 140 oC and 7 atm2.Some of the by-products from this stage include dimethyl ether, methyl α-hydroxy-isobutyrate etc. The reactor effluent is separated using a decanter. The lower layer is steam stripped to recover methacrylic acid for recycling to the hydrolysis-esterification stage. The waste ammonium acid-sulfate from the steam stripping step is treated with ammonia to produce fertilizer ammonium sulfate. The upper layer passes through a flash to remove low boiling components such as dimethyl ether and acetone, and a dehydration column to remove water. The product is then purified through a distillation column.
.Methacrylic acid and derivatives, Ullmann's Encyclopedia of Industrial Chemistry, 2005 online version, Wiley-VCH Verlag GmbH&Co.KGaA.
2. Methacrylic acid and derivatives, Kirk-Othmer Encyclopedia of Chemical Technology, Vol 16, pp227-270, John Wiley & Sons.
1. About 3 tons of ammonium sulfate will be generated for every ton of MMA production. Therefore, allocation will be need to use this LCI data.
2. Major energy source consumed in this process is steam energy. Evaporator and reactor 3 consume the most energy in the process.
Process Flow Diagram of The Methacrylamide Sulfate Route