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We report the design and synthesis of cesium‐doped hydroxyapatite for direct and high‐yield conversion of biobased lactic acid to 2,3‐pentanedione (72.3 %). Cs species derived from CsNO3 at high temperature of calcination is introduced into the hydroxyapatite structure to regulate its acid–base properties. It is found that a balance of acid–base chemistry favors the condensation of lactic acid to 2,3‐pentanedione. As a result, the undesired reactions such as lactic acid dehydration, decarbonylation, and coking are suppressed. Instead, a concerted catalysis between surface basic site and acidic site for lactic acid condensation to 2,3‐pentanedione dominates on the cesium‐doped hydroxyapatite catalyst, leading to a highly selective process for direct conversion of bio‐lactic acid to 2,3‐pentanedione.

The production of 2,3-pentanedione from lactic acid over SiO2-supported alkali metal nitrates under various conditions was investigated. Using nitrate (NO3-) as the anion, the effect of alkali metal cations on Claisen condensation of lactic acid into 2,3-pentanedione was focused on. Among precursors such as LiNO3, NaNO3, KNO3, and CsNO3, CsNO3 displayed the best catalytic performance. Characterization of the fresh and used catalysts by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy revealed that all MNO3 (M = Li, Na, K, Cs) salts were transformed into alkali metal lactates during the reaction. Alkali metal lactates were identified as active species for catalytic Claisen condensation of lactic acid into 2,3-pentanedione. CO2 temperature-programmed desorption (TPD) results of the used catalysts showed that the CsNO3/SiO2 catalyst was the most alkaline. For that reason, the CsNO3/SiO2 catalyst displayed the highest catalytic performance of those examined. The effects of reaction temperature and loading amount of CsNO3 on reaction performance

The gas-phase hydrodeoxygenation of LA to propionic acid over Fe and its oxides was firstly investigated under various conditions. The catalysts were characterized by nitrogen adsorption-desorption, XRD, FT-IR, H 2 -TPR and SEM. Fe 3 O 4 as active species was confirmed. Due to that reason, Fe 2 O 3 can be efficiently transformed in situ to Fe 3 O 4 under an atmosphere containing hydrogen derived from decarboxylation/or decarbonylation reaction of lactic acid, which offers the most excellent catalytic performance. The catalyst is sensitive to reaction temperature. LA conversion and its consumption rate increased with an increase of reaction temperature. Similarly, propionic acid selectivity also increased with reaction temperature in the range of 360-390 C. But with further enhancement of reaction temperature from 390 to 400 C, it drastically decreased since the formation rate of propionic acid reduced at 400 C. The catalyst displayed an excellent adaptability in a wide range of LA LHSV except for 1.3 h À1 . More importantly, at high LA LHSV of 26.3 h À1 , the catalyst offered a satisfactory stability within 100 h on stream. Under the optimal reaction conditions, 96.7% of LA conversion and 46.7% of propionic acid selectivity were achieved.Scheme 2 The possible reaction paths for propionic acid synthesis from LA.Scheme 3 The possible paths for hydrogen formation.This journal is

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