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

Abstract

Liquid phase hydrogenolysis of ethyl lactate to 1,2-propanediol was performed over silica supporting cobalt catalysts prepared by two different methods: precipitation-gel (PG) technique and deposition-precipitation (DP) procedure. The cobalt species (Co 3 O 4 /cobalt phyllosilicate) present in the corresponding calcined PG and DP catalysts were different as a consequence of the preparation methods, and Co-OH-Co olation and Si-O-Co oxolation molecular mechanisms were employed to elucidate the chemical phenomena during the different preparation procedures. In addition, the texture (BET), reduction behavior (TPR and in-situ XRD), surface dispersion and state of cobalt species (XPS), and catalytic performance differ greatly between the samples. Because of small particle size, high dispersion of cobalt species and facile reducibility, the Co/SiO 2 catalyst prepared by precipitation-gel method presented a much higher activity than the catalyst prepared by deposition-precipitation method. Metallic cobalt is assumed to be the catalytically active site for the hydrogenolysis reaction according to the catalytic results of both cobalt samples reduced at different temperatures and the structure changes after reaction.

Effect of Metal Additives on Structure and Properties of a Co/SiO2 Hydrogenation Catalyst

“…This revealed that Zn, Fe, Cu, and Sn in Co-containing catalysts accelerated the formation of cobalt(II) silicate. On the basis of our results and previously reported results for similar cobalt-based catalysts [15,17,26], we propose that both Co 3 O 4 and cobalt phyllosilicate were present on the surface of the bimetallic catalysts. The absence of cobalt phyllosilicate diffraction peaks from the XRD patterns may have been due to the amorphous structure of this species.…”

“…(3) Table 2). Considering the Co 2p photoelectron spectra for the catalyst precursors, the Co 3 O 4 spinel structure has already been proved to present on the catalyst surface from the typical Co 2p spectrum [15,22]. The electronic properties of cobalt were changed by the incorporation of the additives: the Co 2p 3/2 peaks for all the bimetallic catalysts appeared at higher BE than the peaks for the monometallic catalyst (Fig.…”

“…The relative intensity of the shake-up satellite structures centered at around 787 and 804 eV was also observed for all the bimetallic catalysts. All these XPS features were derived from Co 2+ ions interacting with the support as cobalt(II) silicate [15,24,25] and were responsible for the H 2 -TPR profiles at high temperature, as will be described later. This revealed that Zn, Fe, Cu, and Sn in Co-containing catalysts accelerated the formation of cobalt(II) silicate.…”

“…Recently, vapor-phase hydrogenolysis of a lactate ester to 1,2-PDO over a Co/SiO 2 catalyst prepared by impregnation was systematically investigated [14], and a linear relationship between hydrogenolysis activity and the percentage of the bulk-like Co 3 O 4 in the catalyst was observed. In our previous work, we found that the method used to prepare the Co/SiO 2 catalyst signifi-cantly affects the liquid-phase hydrogenolysis of lactate to 1,2-PDO, owing to variations in the cobalt species formed [15]. The significant catalytic activities were in correlation with different cobalt species based on the inherent different chemical phenomena during contrary preparation procedures from the Co−OH−Co olation and Si−O−Co oxolation molecular mechanisms.…”

Bio-Based Chemicals from Renewable Biomass for Integrated Biorefineries

“…Therefore, to avoid this problem, carboxylic acids are usually converted into more readily reducible esters. Xue et al [263,264] investigated the use of a bi-functional Ru/TiO 2 catalyst for the conversion of lactic acid or lactates to propylene glycol in the liquid phase. The addition of some additives such as boron, tin, and iron to Ru-based catalysts has been reported in the literature [265].…”