Furfural is a target structure obtained from hemicellulose-rich biomass. According to the U.S. Department of Energy, furfural stands out as one of the top 15 added-value chemicals. The main inclusion criterion was the ability of furfural to serve an analogous role in the bio-refinery as a primary building block, which makes it of high importance in many industries, such as plastic, pharmaceuticals, and agrochemicals. Particularly in the biofuel industry, where furfural is a precursor to so-called P-series fuel.
Nowadays, China, the Dominican Republic, and South Africa produce large quantities of furfural through the dehydration of pentoses, using mineral acids as a homogeneous catalyst and high-pressure steam to provide heat energy. Current industrial production operates at less than 33 percent of the theoretical yield, and it still has technical and environmental drawbacks, such as poor waste management and poor selectivity. Therefore, the use and development of a sustainable heterogeneous catalytic process for the biomass conversion to furfural is the rate-determining step toward conversion viability. Moreover, in the last decade, the production of materials in the nanoscale regime has attracted more attention. Nano-scale catalysts exhibit improved textural properties and optimal acidity, resulting in better selectivity adjustment.
In this study, copper and zinc-based catalysts were synthesized using two different approaches. The first approach uses high-intensity ultrasound to obtain a nano-scale catalyst (Zn-doped CuO NPs) with enhanced catalytic activity. The second approach uses a sol-gel route followed by supercritical drying to obtain copper-zinc based aerogel catalysts with minimal silica support. The morphology of the catalysts was examined using scanning electron microscopy (SEM). The crystal structures weredetermined by X-ray diffraction (XRD). The pore size distribution and the specific surface area were examined using BET. The catalytic activity of the Zn-doped CuO nanoparticles (NPs) was examined as a model during the dehydration reaction of xylose. In addition to that, we have compared the catalytic activity of the Zn-doped CuO NP with that of the Cu/silica aerogel, the Cu-Zn/silica aerogel, etc. The dehydration reaction into furfural was studied using a stainless steel mini reactor (Parr reactor) in a monophasic aqueous medium at 150 °C within 12h. The responses evaluated were xylose conversion (Xc) and reaction yield (Y), and they were conducted using RP-HPLC. The aerogel-based catalysts have a large surface area of around 550 m2/g, high termal stability, which enhances their catalytic activity and enables them to considerably convert the xylose to furfural, as confirmed by HPLC.