Glycerol valorization to lactic acid catalyzed by hydroxyapatite‐supported palladium particles

Abstract

BACKGROUND Catalytic formation of lactic acid from biomass glycerol is a sustainable alternative to the conventional fermentation process starting from carbohydrate and the chemical route using HCN and acetaldehyde. Highly concentrated glycerol can be effectively converted to lactic acid using hydroxyapatite‐supported palladium particles in the presence of NaOH. RESULTS The 3% hydroxyapatite‐supported palladium catalyst (Pd3/HAP) demonstrates excellent activity (TOF = 1274 h−1 for a batch time of 90 min) with a high selectivity (95%) towards lactic acid at 99% glycerol conversion (230 °C, NaOH:glycerol molar ratio = 1.1, and glycerol/total Pd intake = 1926). Under the same reaction conditions, the selectivities of lactic acid were 82% and 90% on Pd0.75/HAP and Pd1.5/HAP catalysts, respectively. The Pd3/HAP catalyst was recycled five times in a batch set‐up without a significant drop in activity and lactic acid selectivity, which is indicative of good catalyst stability. CONCLUSIONS Pd‐based catalysts on available hydroxyapatite supports are efficient catalysts for glycerol selective oxidation. The catalysts possess active PdO and Pd0 species well dispersed on the functionalized hydroxyapatite support. Pd0 nanoparticles and NaOH synergistically catalyze the reaction process. © 2018 Society of Chemical Industry

Cu catalysts supported on CaO/MgO for glycerol conversion to lactic acid in alkaline medium employing a continuous flow reaction system

“…14 In addition, the fermentation route may not be able to meet the growing demand for LA of the chemical industry. 15 Research of new alternatives for chemical routes to produce LA has been of great interest in the last decades. 16 One of the alternative production routes is the hydrothermal conversion of glycerol to LA in alkaline medium which was rst described by Kishida et al 17 In this study Kishida used an autoclave reactor and NaOH or KOH as catalyst and aer 90 min at 300 C an aqueous solution of glycerol was converted into sodium lactate with yield higher than 90 mol% with 100% of glycerol conversion, employing NaOH or KOH/glycerol molar ratio equal to 3.78.…”

Functional characterization of bimetallic CuPdxnanoparticles in hydrothermal conversion of glycerol to lactic acid

“…As the glycerol concentrations were increased from 1.5 to 3.0 mol L −1 , the glycerol conversions over CuPd 0.5 , CuPd 1 , CuPd 2 , CuPd 3 , CuPd 4 , and CuPd 5 catalysts decreased from 96.0% to 89.2%, 97.3% to 90.5%, 98.4% to 92.3%, 98.5% to 94.7%, 99.5% to 97.1%, and 100% to 96.9%, respectively, showing a decrease trend for the glycerol conversions. bimetallic CuPd x catalysts can provided abundant reactive sites for the glycerol molecules, leading to efficient conversion process in low glycerol concentration (Shen et al, ).…”

“…The presence of NaOH has a positive effect on glycerol deprotonation, thus the conversion increases with the molar ratio of NaOH/glycerol. However, studies on glycerol alkaline hydrothermal conversion to lactic acid indicated that low concentration of NaOH are more effective for obtaining high glycerol conversion and lactic acid yields due to the relative solubility in water (Shen et al, ).…”

“…The growing market demand for pure lactic acid has been estimated to 260,000 ton in 2008. With a growing demand rate, the overall production of lactic acid and poly(lactic acid) are forecast over 1 million by 2020 (Shen et al, ). Although the carbohydrate fermentation route has potential uses in lactic acid industrial production, this time‐consuming and low productivity process may not be suitable for meeting the lactic acid demand in commercial applications.…”

“…Glycerol, a major byproduct of biodiesel production, can be catalytically transformed into lactic acid by chemical catalysis (Shen et al, , ; Shen, Yin, Wang, Lu, & Zhang, ) or biological fermentation (Hong et al, ; Song, Sun, Wei, & Xiu, ) as one of the cheapest sources. The global market size for glycerol was 2.47 million tons in 2014 and has been estimated to grow annually at 6.5% from 2015 to 2022 (Dai et al, ).…”