Conversion of cellulose to levulinic acid using metal-doped silica catalysts

Today, for many reasons (the decrease in the reserve capacity of fossil fuels used in many areas such as coal, oil, and natural gas, environmental pollution caused by the use of these fuels, the harmful effects of greenhouse gases such as CO2 in the atmosphere and many other reasons), technology strategies have been developed to discover, test and create different types of fuels that can be used as alternatives to fossil fuels and to conduct R&D studies to use products that have been used. In addition, the development of hybrid systems and their use after the trial phase has increased considerably in recent years. In addition, chemical products that are used in many areas have also been developed and have led to the creation of new technologies. The number of technological developments in this direction is numerous and it is observed that the investments made in this direction are increasing as they become increasingly popular. Levulinic acid, a versatile flexible platform chemical produced from biomass, is an important chemical with various transformation forms that can be directed to fuels and chemicals. Levulinic acid is a flexible platform chemical that can be synthesized from biomass and offers a sustainable and renewable alternative to petroleum-based raw materials. It has great potential due to its wide range of applications in various industries including pharmaceuticals, polymers, solvents, and food additives. Levulinic acid can be produced by the conversion of biomass such as cellulose, hemicellulose and lignocellulosic materials. The conversion process usually involves the release of sugars by hydrolysis of biomass, followed by dehydration of these sugars and their acid-catalyzed conversion to levulinic acid. Many methods have been developed to increase the efficiency and product yield of levulinic acid from biomass sources. These methods include acid hydrolysis, enzymatic hydrolysis, and thermochemical processes such as pyrolysis and hydrothermal treatment. In this study, levulinic acid was produced from cellulose in a single step using SiO2 and metal-doped (Al, W, Sr, Ni, and Cu) catalysts. In experiments using water as a solvent, the conversion of cellulose to valuable chemicals was tested in an autoclave at 200°C for 6 hours. The crystal structures, surface properties, surface acidity, and metal amounts of all synthesized catalysts were characterized by XRD, N2 adsorption/desorption analysis, pyridine-FTIR analysis, and ICP analysis. As a result of the studies, it was determined that aluminum accumulation played an important role in the conversion of cellulose. While the cellulose conversion rate of SiO2 was 37.76%, it was observed that the cellulose conversion rate increased to 100% depending on the aluminum amount. On the other hand, it was determined that cellulose was converted into valuable chemicals such as levulinic acid, formic acid, acetic acid, and furfural in addition to 5-HMF during the conversion process. The conversion of cellulose to levulinic acid, formic acid, and acetic acid with high efficiency in a single step was provided by the Si-4Al-W catalyst.