The use of niobium compounds as catalyst in the production of biofuels: a review

Abstract

The need to replace fossil fuels with biofuels is not a fresh topic in the academic community. Researchers have been studying and developing alternative fuels for decades and, as a result, fuels such as biodiesel and first-generation ethanol have been consolidated on the market. However, these first-generation biofuels compete with the food industry, which affects their supply and price. On the other hand, second-generation fuels are produced from lignocellulosic biomass and organic waste from urban and agro-industrial activities, not competing with the food industry. Nevertheless, most of these processes are still economically unfeasible. Two of the main contributions to this unfeasibility are the low performance of the processes (low conversion of raw material and low selectivity of products of interest) and the high cost of catalysts, which are often made of noble metals of little availability. Niobium is a metal with several applications, but still little explored industrially as a catalyst, despite having interesting properties for this purpose. This review article compiles works involving the use of niobium and its compounds as a catalyst in various biofuel production processes, such as esterification, pyrolysis, liquefaction, Fischer-Tropsch synthesis, deoxygenation, among others. In addition to the literature review, this paper presents a critical analysis regarding the applications of each process and technology as well as the research developed by the authors.