Acrolein production from renewable-resources: Glycerol and Ethanol routes

J-L. Dubois
Arkema,
France

Keywords: catalysis

Summary:

Acrolein is an important chemical intermediate for fine chemicals: it is the smallest functionalized aldehyde. It is also an intermediate in the methionine and acrylic acid production. Glycerol double intra-molecular dehydration leads to Acrolein over acidic catalysts [1-3]. Catalysts and a process have been developed and piloted by Arkema. Co-feeding oxygen at the dehydration stage, not only proved to be a solution to reduce the production of side products, but also to extend the time on stream of the catalyst [2]. One of the difficulties of this chemistry remains the slow but steady deactivation of the catalysts due to coke formation. Understanding the mechanism that leads to coke formation and the role of coke in the reaction selectivity has been carried out in fluid bed, for catalyst homogeneity [4]. As coke builds up on the catalyst, the reaction selectivity improves, while the catalyst active sites distribution is significantly affected [5,6]. Another challenge in this reaction is the content of propanaldehyde in the reaction product. Propanaldehyde will react as Acrolein in consecutive reactions like oxidations, acetalization… but will not polymerize (no double bond); leading to the same problem for its oxidation product: propionic acid versus acrylic acid. A solution, using oxidation catalysts, to selectively react propanaldehyde in the Acrolein rich stream has been investigated and patented. Acceptable low level of propanaldehyde have been obtained [7]. A second innovative route to Acrolein is the direct oxidation of a Methanol/Ethanol composition, called Alcohols Oxidative Coupling [8]. In that reaction mechanism, Methanol and Ethanol are oxidized to the respective aldehydes, followed by an aldolization reaction and a dehydration to Acrolein. Catalysts with the appropriate balance of redox and acid/base sites, such as those based on iron-molybdate type catalysts are able to produce Acrolein in a single-step reaction. Acknowledgements: the present research has received support from ADEME, EU FP7 and MITACS.