ARTICLE DOWNLOAD

Microwave-Assisted Catalyst-Free Oxidative Conversion of a Lignin Model Compound to Value-Added Products Using TEMPO

10$
ARTICLE DOWNLOAD

Microwave-Assisted Catalyst-Free Oxidative Conversion of a Lignin Model Compound to Value-Added Products Using TEMPO

10$

Jia-Yin Lin, Jechan Lee & Kun-Yi Andrew Lin 

Abstract

As oxidative conversion of vanillyl alcohol (VAL) to vanillin (VN) represents an important process for valorization of lignin compounds, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) is employed for the first time as an oxidant to oxidize VAL in the absence of catalysts using microwave irradiation (MWI). In comparison with H2O2, persulfate and peroxymonosulfate, TEMPO leads to the significantly higher selectivity of vanillin (SVN) and yield of VN. In addition, MWI is also more effective than conventional hydrothermal process for converting VAL to VN with a much higher SVN. A longer reaction time is highly favorable for VAL conversion to VN by TEMPO using MWI with a much higher SVN and yield of VN. Besides, the SVN and yield of VN from VAL oxidation by TEMPO using MWI could be also significantly improved at the elevated temperature with a higher TEMPO dosage. The optimal condition for VAL conversion to VN by TEMPO using MWI is the usage of 1.5 g of TEMPO for 7.5 min of MWI at 160 °C and the highest yield of VN is 17% with SVN of 99%, which is higher than many reported values of catalyst-involved processes. TEMPO can be also re-used to oxidize VAL to generate VN with quite stable yield of VN and SVN. These results indicate that TEMPO, even without catalysts, can successfully and effectively convert VAL to the value-added phenolic products, such as VN. The findings of this study can be useful for further investigating TEMPO-mediated oxidation of lignin compounds.

Only units of this product remain
Year 2020
Language English
Format PDF
DOI 10.1007/s12649-019-00646-5