Issue 17, 2016

Glycerol oxidehydration to pyruvaldehyde over silver-based catalysts for improved lactic acid production

Abstract

Sustainable technologies for the valorisation of the burgeoning amounts of glycerol (GLY) obtained as waste in the production of biodiesel are increasingly sought after. Its conversion into lactic acid (LA) is appealing due to the versatility of this platform chemical and its high added value. Here, we introduce Ag-based catalysts for the oxidehydration of GLY to pyruvaldehyde (PAl) and demonstrate the superiority of this compound in comparison to dihydroxyacetone (DHA) as the intermediate of an alternative two-step GLY-to-LA process. Evaluation of various metals and carriers identified Ag/Al2O3 as the best performer for PAl production. This was rationalised based on the optimal redox potential of the metal and the high concentration of Lewis-acid sites and the limited Brønsted acidity of the support. At 623 K and O2/GLY = 0.5, a PAl yield of 80% was attained, which remained stable for 24 h. Characterisation of the used catalyst indicated that the surface of the silver nanoparticles was partially oxidised upon reaction. Density functional theory (DFT) modelling revealed that the oxidation of acetol obtained from GLY after the initial dehydration step is kinetically and thermodynamically favoured on a partially oxidised silver surface (AgOx/Ag) compared to metallic (Ag) or fully oxidic (Ag2O) ones. Finally, we show that PAl can be isomerised into LA and methyl lactate over Sn-containing zeolites with the same rates as DHA but at a 40 K lower temperature (343 vs. 383 K). This not only allows for energy savings but also for a remarkably increased catalyst stability.

Graphical abstract: Glycerol oxidehydration to pyruvaldehyde over silver-based catalysts for improved lactic acid production

Supplementary files

Article information

Article type
Paper
Submitted
30 Mar 2016
Accepted
23 May 2016
First published
23 May 2016

Green Chem., 2016,18, 4682-4692

Glycerol oxidehydration to pyruvaldehyde over silver-based catalysts for improved lactic acid production

G. M. Lari, R. García-Muelas, C. Mondelli, N. López and J. Pérez-Ramírez, Green Chem., 2016, 18, 4682 DOI: 10.1039/C6GC00894A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements