Novel insights into the recovery and recyclability of homogeneous polyoxometalate catalysts applying an efficient nanofiltration process for the selective catalytic oxidation of humins
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引用次数: 0
Abstract
Selective catalytic oxidation (SCO) of humins is a promising strategy to valorize undesired side streams of biomass conversion processes. Keggin-type polyoxometalates are efficient catalysts for the SCO of humins giving platform chemicals like formic acid, acetic acid or their respective esters up to combined yields of 51 %. Moreover, one of the main challenges for establishing continuous processes is the efficient catalyst recycling and product separation. Herein, we combined an optimization study for the process parameters in SCO with an integrated product separation carried out by using nanofiltration membranes. For this purpose, an enhanced reaction system consisting of 5 vol% methanol addition for CO2 suppression in combination with 1.5 mmol pTSA as solubility promotor was applied using H5[PV2Mo10O40] (HPA-2) as a catalyst achieving a maximum humin conversion of 90 % resulting in 57 % carboxylic ester selectivity. In subsequent studies, an appropriate XN 45 nanofiltration membrane was identified allowing for >99 % catalyst and >90 % additive retention efficiently separating the acidic reaction products in the permeate. Furthermore, long-time stability of the membrane and thus of the separation process could be confirmed up to 168 h time on stream. Based on these results, the developed process represents an important milestone in the valorization of humins combined with efficient separation of the molecular polyoxometalate catalyst and could therefore be the basis for future developments.
期刊介绍:
ChERD aims to be the principal international journal for publication of high quality, original papers in chemical engineering.
Papers showing how research results can be used in chemical engineering design, and accounts of experimental or theoretical research work bringing new perspectives to established principles, highlighting unsolved problems or indicating directions for future research, are particularly welcome. Contributions that deal with new developments in plant or processes and that can be given quantitative expression are encouraged. The journal is especially interested in papers that extend the boundaries of traditional chemical engineering.