Valorization of secondary feedstocks from the agroindustry by selective catalytic oxidation to formic and acetic acid using the OxFA process

Abstract

The selective oxidative conversion of seven representative fully characterized biomasses recovered as secondary feedstocks from the agroindustry is reported. The reaction system, known as the “OxFA process,” involves a homogeneous polyoxometalate catalyst (H8PV5Mo7O40), gaseous oxygen, p-toluene sulfonic acid, and water as solvent. It took place at 20 bar and 90 °C and transformed agro-industrial wastes, such as coffee husks, cocoa husks, palm rachis, fiber and nuts, sugarcane bagasse, and rice husks into biogenic formic acid, acetic acid, and CO2 as sole products. Even though all samples were transformed; remarkably, the reaction obtains up to 64, and 55% combined yield of formic and acetic acid for coffee and cocoa husks as raw material within 24 h, respectively. In addition to the role of the catalysts and additive for promoting the reaction, the influence of biomass components (hemicellulose, cellulose and lignin) into biogenic formic acid formation has been also demonstrated. Thus, these results are of major interest for the application of novel oxidation techniques under real recovered biomass for producing value-added products. Graphical abstract

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

“…The main reaction conditions were adjusted based on the previous optimization of the first step to allow a future combination of both steps in one single unit operation (p = 30 bar, T = 125 °C, n = 1200 rpm). Moreover, the water content was approximated as a compromise between optimum fractionation (40 wt % in step 1) and optimum oxidation (100 wt % in pure oxidation 8 to the average value of 70 wt %).…”

“…A promising approach is the fractionative oxidation of lignocellulosic biomass for biorefining . Hereby, cellulose acts as a source of sustainable glucose after enzymatic saccharification, while carboxylic acids such as formic and acetic acids are derived from the hemicellulose and lignin. − The recently demonstrated polyoxometalate (POM)–ionosolv concept enables fractionation of lignocellulosic biomass into a solid cellulose-rich pulp that is suitable for enzymatic saccharification and a dissolved hemicellulose and lignin fraction which are converted into formic and acetic acids . It is known that a protic ionic liquid (IL) water mixture consisting of the ionosolv IL triethylammonium hydrogen sulfate, [TEA]­[HSO 4 ], mixed with 20–40 wt % water, can be used for extracting hemicellulose and lignin from a lignocellulosic feedstock, while a soluble polyoxometalate (POM) catalyst has the ability to catalytically convert soluble components to short-chain carboxylic acids like formic and acetic acids in the presence of molecular oxygen as the oxidant .…”

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

“…In detail, different lignocellulosic and algae feedstock could be converted to FA in high yields up to 55 % for pomace as a substrate. Furthermore, Ponce et al [113] . could show that even secondary feedstocks from the agroindustry like coffee husks, palm rachis or sugarcane bagasse could be effectively oxidized to FA by HPA‐5 in yields up to 55 %.…”

“…In detail, different lignocellulosic and algae feedstock could be converted to FA in high yields up to 55 % for pomace as a substrate. Furthermore, Ponce et al [113] could show that even secondary feedstocks from the agroindustry like coffee husks, palm rachis or sugarcane bagasse could be effectively oxidized to FA by HPA-5 in yields up to 55 %. This study, and the fact that pTSA acts as a promoter to bring insoluble biomass into solution, highlights the potential of this concept to catalytically convert even more complex biomass into FA.…”

“…This study, and the fact that pTSA acts as a promoter to bring insoluble biomass into solution, highlights the potential of this concept to catalytically convert even more complex biomass into FA. [113] In 2017, Albert [114] reported a study with the aim of expanding the OxFA technology to realize a fractionated conversion of the main components of lignocellulosic biomass in order to produce biogenic FA and high-grade cellulose in one reaction vessel. [114] In the first experiments, several HPA-x catalysts, were screened for the stepwise oxidation of model substrates of lignocellulosic biomass.…”