The effect of palladium dispersion and promoters on lactose oxidation kinetics

Päivi Mäki-Arvela, Elena V. Murzina, Betiana Campo, Teemu Heikkilä, Anne Riikka Leino, Krisztian Kordas, Dorit Wolf, Anton V. Tokarev, Dmitry Yu Murzin

Research output: Contribution to journalArticleScientificpeer-review

11 Citations (Scopus)

Abstract

Lactose oxidation was investigated at 70 °C and at pH 8 using oxygen as an oxidant over a comprehensive set of commercially available mono- and multi-metallic as well as promoted Pd catalysts with active carbon, alumina and calcium carbonate as catalyst supports. An optimum cluster size of 6-10 nm resulted in the highest initial turnover frequencies. High conversion levels above 90% were achieved on Pd/C catalyst, as well as over Pd/Al 2O3 and (Pd-Pb)/CaCO3, whereas (Pd-V)/C catalyst gave only 30% conversion after 200 min. The latter catalyst was relatively inactive due to its high support acidity and profound deactivation during oxidation. Besides the main oxidation product, lactobionic acid, also, lactulose was generated as a result of lactose isomerisation under alkaline conditions. The electrochemical potentials of the catalysts were measured during lactose oxidation. The main result of these measurements was that, when the electrochemical potential of the catalyst increased very quickly, its oxidation activity was low due to metal over-oxidation. The selectivities to the desired product, lactobionic acid, were relatively high, above 80% for most of the catalysts, except for (Pd-V)/C. Furthermore, the selectivity to the lactobionic acid decreased with increasing metal dispersion, thus, indicating that the optimum metal particle sizes for producing high amounts of lactobionic acid is above 3 nm.

Original languageEnglish
Pages (from-to)423-442
Number of pages20
JournalResearch on Chemical Intermediates
Volume36
Issue number4
DOIs
Publication statusPublished - Jun 2010
MoE publication typeA1 Journal article-refereed

Keywords

  • Active carbon
  • Catalyst potential
  • Dispersion
  • Lactose oxidation
  • Palladium

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