Handling of petrochemical waste oil (PWO) is costly, tedious, and risky to human health and environment. Hence, upcycling of PWO for biomass conversion to platform chemicals would be very advantageous. Herein, a highly porous sheet-like structure of sulfonated graphene oxide (sGO) catalyst was synthesized from PWO. The synthesized sGO possessed high surface area (246.2 m2 g1) due to its mesoporosity and high content of sulfonic groups (2.4 mmol g−۱) grafted onto its surface. As its application, the synthesized sGO was employed to convert fructose to levulinic acid (LA) within deionized water. The high yield (61.2 mol %) of LA was obtained under a condition of 160 °C, 1 h, and 6 g g−۱ fructose to sGO weight ratio. It can be reused several times (5 runs) with no severe degradation of catalytic activity. Therefore, the sGO derived from petrochemical waste oil would be considered as an environmentally benign catalyst for producing platform chemicals, i.e. LA from fructose and other biomass derivatives.
Heavy reliance on depleting fossil resources to produce platform chemicals and fuels contributes to the economic dilemma and rising emission of greenhouse gases [1-3]. Hence, alternative ways including utilization of biomass in integrated biorefineries have been explored to compete with fossil-based refineries . Biomass is a renewable resource that can be exploited to produce many high value-added products, i.e. alcohol, 5- hydroxymethylfurfural (5-HMF), furfural, formic acid (FA) and levulinic acid (LA) [5, 6]. LA is considered as top ten platform chemicals, which could be further utilized to produce succinic acid, resins, polymers, herbicides, pharmaceuticals, flavoring agents, solvents, plasticizers, anti-freeze agents and biofuels/oxygenated fuel additives [3, 7]. Generally, conversion of biomass into LA involves multiple steps, which are (1) hydrolysis of cellulose to glucose, (2) isomerization of glucose to fructose, (3) dehydration of fructose to HMF, and (4) further hydrolysis to form equimolar LA and FA [2, 8]. These processes are often realized through chemical or enzymatic routes. Nevertheless, the chemical route has been recognized as high potential for commercially viable LA production [9, 10].
n the past, homogeneous acid catalysts (e.g. H2SO4, HCl, H3PO4) were used to ensure a high conversion of reactants because of lower mass transfer resistance . However, those acidic catalysts are corrosive, detrimental to the environment, and non-recyclable [8, 10, 12]. Hence, heterogeneous solid acid catalysts, such as ion-exchange resins, sulfated metal oxides, modified mesoporous silica, zeolites, and natural clays have been developed to overcome the disadvantages of those homogeneous acid catalysts [13, 14]. Recently, several of these types of catalysts have been used for conversion of fructose to LA from actual biomass [15-17].