Non-noble metal catalysts for transfer hydrogenation of levulinic acid: The role of surface morphology and acid-base pairs

Abstract

Hydrogen energy is obtained by consuming a large amount of fossil-based feedstocks in industry. The harsh operating conditions, release of toxic by-products and high energy consumption will hinder the development of hydrogen energy. Therefore, finding greener and more sustainable hydrogenation technologies is very important. Transfer hydrogenation processes, use hydrogen source from bio-alcohols, acids and water, is a promising technology and results in safer reaction environment, better atomic economy and lower capital investment. It is essential for the development and utilization of hydrogen energy. In this review, we take the conversion of levulinic acid as a representative example to illustrate the design principles of dual-functionalized catalysts and mechanistic aspects for transfer hydrogenation. Alcohol and formic acid are most frequently used as H-donors in transfer hydrogenation of levulinic acid. Therefore, the efficiency for H-donating and related mechanisms have been discussed in details. We have been focusing on non-noble metal materials due to the higher abundance and milder reaction conditions needed compared to noble metal. Morphology and structure of various catalysts, acid-base pairs on catalytic activation of C–H and C=O bonds for transfer hydrogenation of levulinic acid and plausible mechanism will be systematically discussed.