Catalysis of Organic..

Liu, Cant and Smith 13116. The Conversion of Aminoalcoholsto Aminocarboxylic Acid Salts overChromia-Promoted Skeletal Copper CatalystsAbstractDongsheng S. Liu, Noel W. Cant and Andrew J. SmithSchool of Chemical Engineering and Industrial Chemistry,The University of New South Wales, Sydney NSW 2052. Australiaandrew.smith@unsw.edu.auThe rates of oxidative dehydrogenation of a range of monoalcohols and diols, withand without amino groups, has been studied over skeletal copper catalysts in anautoclave that allows the reactants to be preheated to reaction temperature prior tomixing. Chromia, introduced by deposition during leaching, improves activity andstability. Some aspects of the reactivity order are consistent with the inductive effectof NH 2 and OH groups in weakening CH bonds but steric effects on adsorption viathe nitrogen atom appear necessary to explain the low rates observed for alkylsubstitution at this position. NMR spectra of samples taken at different conversionsshow that the two OH groups in diethanolamine react in sequence forming2-hydroxyethylglycine as an intermediate. Much of the progress of the reaction canbe modeled assuming first order kinetics but the final stages proceed faster thanpredicted.IntroductionThe trail-blazing patent of Goto et al. (1) for the oxidative dehydrogenation ofaminoalcohols to the corresponding aminocarboxylic acid salts over Raney® coppercatalysts in strongly alkaline solutions was cast in terms of the general reactionR 1 R 2 NCH 2 CH 2 OH + OH - → R 1 R 2 NCH 2 COO - + 2 H 2 [1]Published work since then has largely concentrated on two specific reactions, theconversion of ethanolamine to glycinate e.g. (2, 3)H 2 NCH 2 CH 2 OH + OH - → H 2 NCH 2 COO - + 2 H 2 [2]and that of diethanolamine to iminodiacetate for use in the production of theherbicide, glyphosate, e.g. (4, 5)HN(CH 2 CH 2 OH) 2 + 2 OH - → HN(CH 2 COO - ) 2 + 4 H 2 [3]Patents describing improved catalysts for this class of reactions often claimsuitability for a wide range of substrates (6-9). However there is no data comparing