Selective Oxidation of 1,2-Propanediol to Lactic Acid Over Synergistic AuCu/TiO 2 Catalysts
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Selective Oxidation of 1,2-Propanediol to Lactic Acid Over Synergistic AuCu/TiO2 Catalysts Feng Du1 · Hongmei Wang1 · Xin Jin1 · Wenan Deng1 · Chuan Li1 · Zhixiang Ren1 · Hao Yan1 · Bin Yin1 Received: 2 October 2018 / Accepted: 10 January 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract This paper reported synergistic bimetallic AuCu/TiO2 catalysts for selective oxidation of 1,2-propanediol to lactic acid under very mild conditions (T 92%). Surface characterization reveals that while AuCu forms alloy structure with larger particle size based on TEM images, strong interaction between Au and Cu species is critical for performance enhancement. According to experimental studies on the influence of 1,2-propanediol and NaOH concentration on reaction rates, it is highly possible that 1,2-propanediol is reacted following single-site Langmuir–Hinshelwood mechanism while NaOH acts as a promoter and may block surface sites under relatively higher concentration. Graphical Abstract
Keywords Bimetallic catalyst · Oxidation · 1,2-Propanediol · Lactic acid
1 Introduction Replacing fossil-based feedstocks with renewable ones has been one of the most popular topics in energy industry. In the past decade, increasing research efforts have been focused on the development of environmentally friendly conversion processes that transform renewable biomass into value-added Feng Du and Hongmei Wang have contributed equally to this work. * Xin Jin [email protected] 1
State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Qingdao 266580, Shandong, China
chemicals [1–4]. In this context, carboxylic acids are very desirable intermediates in the cosmetic, textile, leather, pharmaceutical and food industries. Lactic acid (LA), which is conventionally produced from biocatalytic process from carbohydrates, is known as the most promising building block chemicals for the production of functional polymers and degradable plastics. LA-derived products have gained extensive interests from industry due to their high biocompatibility [5–7]. However, several disadvantages fermentation of carbohydrates, including slow reaction rates, large water consumption, high cost and biological sludge restrain further application of LA-derived downstream chemicals [8]. Therefore, there demand more efficient catalytic conversion technologies for facile synthesis of LA under mild conditions.
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Biomass-derived polyols, such as glycerol (GLY) and 1,2-propanediol (PDO) are known as important platform chemicals [1]. Catalytic conversion of these polyols to LA via supported metal catalysts is considered as promising alternate way to biocatalytic routes. It has been reported that the synthesis of LA by alkaline hydrothermal conversion of glycerol at a elevated temperature and pressure. The yield of LA can reach 80% or more [9–11]. In addition, some recent studies also show that oxidation of PDO can selectively form LA as major product. However, these p
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