Heterogeneous catalysts for glycerol and glycol valorization via amination pathways

The processing of glycerol, as a by-product of biodiesel production, into valuable chemicals is a promising area from both economic and environmental perspectives. One of the approaches to glycerol valorization is the amination of glycerol and its derivatives (for example, propylene glycol), leading to the production of various amines with high added value. Ammonia, as well as primary and secondary amines can act as aminating agents. This review is devoted to the amination processes of various glycols and glycerol using heterogeneous catalysts.

Two main approaches to the catalytic amination process are considered: reductive amination in the presence of hydrogen and direct amination without the introduction of additional hydrogen. These approaches differ not only in the amination process mechanism but also in the nature of the catalyst and the process conditions. The traditional reductive amination catalysts are non-noble transition metals (Ni, Cu, and Co), noble metals (Ru, Pd, Pt, Rh, and Ir), or their combinations deposited on porous supports. Typical examples of direct amination catalysts are zeolites (e.g., Y, ZSM-5, and MOR) and porous acid oxides. For all cases, the general features of the processes of reductive and direct amination are considered, and specific examples are systematized. The key problems in this area are summarized, and the tasks necessary for the successful implementation of the valorization process of glycerol via the catalytic amination process are formulated.