Hydrogenation of Lactic Acid to 1,2‐Propanediol over Ru‐Based Catalysts

Abstract

The catalytic hydrogenation of lactic acid to 1,2‐propanediol with supported Ru catalysts in water was investigated. The influence of catalyst support (activated carbon, γ‐Al2O3, SiO2, TiO2, and CeO2) and promoters (Pd, Au, Mo, Re, Sn) on the catalytic performance was evaluated. Catalytic tests revealed that TiO2 yields the best Ru catalysts. With a monometallic Ru/TiO2 catalyst, a 1,2‐propanediol yield of 70 % at 79 % lactic acid conversion was achieved at 130 °C after 20 h reaction. Minor byproducts of the hydrogenation reaction were propionic acid, ethanol, 1‐propanol, and 2‐propanol. For the bimetallic catalysts, the addition of Pd and Au slightly enhanced the performance of Ru/TiO2, whereas the addition of common hydrogenation promoters such as Re, Mo, and Sn impaired the activity.

Selective Hydrogenation of Glycolic Acid to Renewable Ethylene Glycol over Supported Ruthenium Catalysts

“…In general, the trends observed match previous studies on LA hydrogenation [14,17,18] . High H 2 pressure is required to obtain high selectivity for the diol.…”

“…Up to 80 % of converted GA could not be identified, which is also the case for the investigation of different support materials below. In that way the results here are comparable to the study of Liu et al [17] . on LA hydrogenation who also could not close the carbon balance at elevated temperatures (>120 °C).…”

“…The lack of correlation between Ru dispersion and Ru content‐adjusted GA consumption for the catalysts prepared in this study (which show a comparable Ru dispersion below 5 %) prove that other catalyst properties also affect the catalytic behavior. While no ZrO 2 ‐supported Ru catalysts are reported for the analogous aqueous‐phase hydrogenation of LA, Ru/TiO 2 is reported to show exceptionally high activity, which was either explained by the redox behavior of the catalyst [17] or by direct interactions of the support material with the adsorbed acid, which might activate the C=O functionality [15] …”

“…This was explained by a combination of small Ru particle size of Ru on TiO 2 , which was further proven by a controlled variation of Ru particle size, and a direct role of the support, which is able to adsorb and activate the carboxylic group of LA. Ru/TiO 2 was also among the most active catalyst in a recent study by Liu et al., [17] who investigated Ru on several supports for the aqueous‐phase hydrogenation of LA. Based on temperature‐programmed reduction (TPR) profiles they suggest that the high activity of Ru/TiO 2 could also be attributed to the high reducibility of Ru on TiO 2 .…”

Cultivation and Biorefinery of Microalgae (Chlorella sp.) for Producing Biofuels and Other Byproducts: A Review

“…When microalgae are rich in carbohydrates, microalgal biomass can be used for the fermentative production of fine chemicals, such as succinic acid and lactic acid [161][162][163]. Because lactic acid has both carboxyl and hydroxyl groups, it can be converted into many useful chemicals, such as pyruvic acid, lactate esters, 1,2-propanediol, and acrylic acid [164]. The fermentative lactic acid yield of Lactobacillus plantarum 23 using the acid hydrolysis of Chlorella sp.…”