Reaction and Spectroscopic Studies of Sodium Salt Catalysts for Lactic Acid Conversion

Abstract

Catalytic conversion of lactic acid to 2,3-pentanedione over sodium salts and base on low surface area silica support has been studied. Yield and selectivity toward 2,3-pentanedione are optimal at around 300 °C, 3−4 s residence time, and 0.5 MPa total pressure. Anions of initial salt catalysts used do not participate in lactic acid condensation to 2,3-pentanedione once steady-state conditions have been achieved; instead, sodium lactate has been identified by postreaction FTIR spectroscopy as the primary, stable species on the support during reaction. Sodium lactate is believed to be an intermediate in 2,3-pentanedione formation. Conversion of a sodium salt to sodium lactate is greatest when the salt used has a low melting point and a volatile conjugate acid; the extent of conversion depends weakly on reaction time and temperature within experimental conditions. At high temperature (∼350 °C), sodium lactate decomposes to sodium propanoate and sodium acetate, which may explain reduced 2,3-pentanedione yields at higher temperatures.

Selectivity Control in the Catalytic Dehydration of Methyl Lactate: The Effect of Pyridine

“…Lewis acid sites are known to be able to catalyze dehydration reactions. [20][21][22][23][24][25][26][27][28]41 Moreover, Na + in NaY has been shown 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 25 to be active in the dehyration of IPA, which is a useful surrogate molecule for ML because both have a secondary hydroxyl group and IPA cannot generate Brønsted acid sites on NaY via ionexchange. 41 To further explore the hypothesis that Lewis acid sites are the active sites for ML dehydration, IPA dehydration is used as a model reaction.…”

Deactivation behavior of alkali-metal zeolites in the dehydration of lactic acid to acrylic acid

“…2,3-pentanedione is mainly produced over basic catalysts ( Fig. 1, path D) and at elevated pressures [17]. The esterification to PLA (Fig.…”

“…In this way, bulk and supported nitrates [17,19], phosphates [13,19,20], alkali-metal salts [17,21], and hydroxyapatites [22] have been employed as catalysts. While selectivities to AA with values up to 60% were achieved on the latter [22], selectivities to AA up to 77% were found on a barium sulfate catalyst [23].…”

Liquid Phase Hydrogenolysis of Biomass‐derived Lactate to 1,2‐Propanediol over Silica Supported Cobalt Nanocatalyst

“…19 A great deal of effort has been put towards the transformation of lactate into high-valued raw chemicals. [19][20][21][22][23][24][25][26][27] And the most attractive utilization is to produce 1,2-propanediols by an alternative route involving selective hydrogenolysis of lactic acid/lactate ester, which is considered as a promising and environmentally friendly route for 1,2-propanediol production [20][21][22][23][24][25] from renewable resources instead of from non-renewable petroleum. Luo et al 22,23 have done the pioneer work on liquid-phase hydrogenolysis of ethyl lactate over Ru-B/Al 2 O 3 amorphous catalyst, and 91% selectivity of 1,2-propanediol was achieved with 90.7% lactate conversion over the optimal tin doped Ru-B amorphous catalyst.…”