Amination of polylactic acid to alanine using a Ru–Co bimetallic catalyst

Abstract

The preparation of alanine from waste polylactic acid (PLA) is not only an effective way to recycle waste plastics, but also of great significance to develop a green, clean and efficient amino acid production process. In this work, we studied the synthesis of alanine by amination of PLA with ammonia solution over different types of supported bimetallic catalysts without external hydrogen. It was found that the bimetallic catalyst consisting of Ru and a non-precious metal Co supported on TiO₂ (Ru–Co/TiO₂) was efficient for the reaction. The selectivity of alanine and turnover frequency (TOF) were 65.2% and 1.5 h⁻¹, respectively. The synergistic effect existing between Ru and Co in the catalyst was crucial for the catalytic performance, and the content of precious metal Ru in the catalyst was lower. This was the first attempt to introduce a non-precious metal component into the catalyst for the amination of polylactic acid to alanine through thermocatalysis.