Sensitivity Analysis and Parameter Optimization for the Fractionative Catalytic Conversion of Lignocellulosic Biomass in the Polyoxometalate–Ionosolv Concept

Abstract

The recently developed polyoxometalate (POM)− ionosolv concept offers an interesting strategy to generate two valuable product streams from lignocellulosic biomass, a solid cellulose-rich pulp and short-chain carboxylic acids like formic acid and acetic acid in a simple and cost-efficient manner. This study aimed to find optimum parameters for the two steps of the transformation by performing a sensitivity analysis on the initial ionosolv fractionation step as well as kinetic investigations of the following POM-catalyzed oxidation step. The results were transferred to the POM−ionosolv concept to find the overall process optimum. Beech wood was used as an industrially relevant substrate for ionosolv fractionation with the low-cost ionic liquid triethylammonium sulfate, [TEA][HSO 4 ], and the HPA-5 [H 8 PV 5 Mo 7 O 40 ] POM catalyst for the oxidation of the dissolved components in an oxygen atmosphere. As the most seminal finding, we defined optimum conditions of 125 °C, 1200 rpm, 30 bar oxygen, and 24 h reaction time in ionic liquid containing 70% water, achieving 72% xylose extraction from beech wood, which resulted in a 39% formic acid yield. We suggest that the fractionation and catalytic conversion are carried out at different water contents for maximum conversion efficiency for each step.

H8[PV5Mo7O40] – A Unique Polyoxometalate for Acid and RedOx Catalysis: Synthesis, Characterization, and Modern Applications in Green Chemical Processes

“…Higher water content in the reaction solution also leads to higher FA yields. In addition, also a higher FA selectivity was observed [123] . Furthermore, the authors showed that the HPA‐5 catalyzed system is also applicable for the conversion of softwood (pine) and grass with cellulose recoveries of 33 % for pine and 38 % for grass (60 % and 71 % cellulose content in the pulp).…”

“…The cellulose remains in the solid‐state, whereas the lignin is dissolved and can later be precipitated by adding precipitating agents (Figure 15). [123] …”

“…In the second study from Bukowski et al [123] . on the advanced POM‐IonosolvConcept, the focus was on the improvement of the applied process parameters.…”

“…In this kinetic study, the reaction order for xylose oxidation was determined to 1.13. The rate constant was calculated to 2.00 mol L −1 h −1 and the activation energy to 67.37 kJ mol −1 [123] …”

“…[122] The cellulose remains in the solid-state, whereas the lignin is dissolved and can later be precipitated by adding precipitating agents (Figure 15). [123] With this new concept in hand, the authors were able to highlight that HPA-5 as catalyst is also soluble, stable and catalytically active in ionic liquids. Initially, beech wood (hard-Figure 14.…”