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BACKGROUND: The production of value‐added chemicals from pyrolysis oil or its fractions is of great significance for the valorization of biomass. Diols, including ethylene glycol (EG) and 1,2‐propylene glycol (1,2‐PG), are important bulk chemicals with widespread industrial applications. Here we investigated the production of diols from pyrolysis oil water‐soluble fraction (WS) using a hybrid catalyst (Ni + H2WO4). RESULTS: Firstly, levoglucosan, glycolaldehyde and acetol, three main components in WS, were respectively selected as the single model compound, and their respective conversions into diols were investigated at different temperatures for different reaction times. The result showed the optimum reaction temperature and time were 180 °C and 2 h respectively, under which a EG yield of 53.8% and 1,2‐PG yield of 5.2% were obtained from levoglucosan conversion, a EG yield of 98.6% was obtained from glycolaldehyde conversion, and a 1,2‐PG yield of 98.5% was obtained from acetol conversion. The reaction pathway of levoglucosan conversion was analyzed. Secondly, the model mixture of levoglucosan, glycolaldehyde and acetol was used to simulate the real WS, and their conversion was investigated at different ratios of H2WO4 to Ni. The result showed the optimum catalyst composition was 0.15 g H2WO4 and 0.3 g Ni, under which a EG yield of 76.4% and 1,2‐PG yield of 38.4% were obtained. Thirdly, the real original WS was converted under the optimum reaction conditions and the result only gave a EG yield of 19.1% and 1,2‐PG yield of 25.8% (based on the carbon moles of main substrates), which were much less than the two yields of model mixture. That was related to the presences of other types of chemicals in original WS. After the original WS being adsorbed by activated carbon, the yields of EG and 1,2‐PG could be increased to 39.2% and 37.9%, respectively. CONCLUSION: The presences of certain other types of chemicals (such as acids, furans, phenolics and cyclopentanones) in original WS inhibited the production of diols. The activated carbon adsorption could efficiently remove most of furans, phenolics and cyclopentanones in original WS and increased significantly the diols yields. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Glycerol hydrogenolysis to 1,2‐propylene glycol in a continuous down‐flow fixed‐bed reactor with 60 %Cu/Al2O3 catalyst was investigated. The routes of main, intermediate and by‐products formation were proposed. It is shown that an increase in the catalyst particle size from 0.1–0.16 to 1.6–2.5 mm transfers the process from the kinetic mode to an intermediate mode between the kinetic and internal diffusion controlled reaction rate. In this case, the observed activation energy decreased by 30 %. The optimal conditions for the process have been determined. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: The conversion of fructose to 1,2‐propylene glycol (PG) is an important process from cellulosic biomass to high‐value added chemicals. Herein, Ru‐WOx/hydroxyapatite (HAP) catalyst was employed for this reaction and reached up to 91.3% yield of PG at 180 °C, 1 MPa initial hydrogen for 8 h in water. On this catalyst, Ru and WOx were highly dispersed on HAP support and they interacted with each other to form a special catalytic center. The lack of isolated Ru or RuW alloy site led to a moderate activity for hydrogenolysis and hindered the further conversion of PG to propanol. The weak basic HAP support efficiently prevented the humin formation. This precisely controlled catalyst has potential in green PG production. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: The conversion of fructose to 1,2‐propylene glycol (PG) is an important process from cellulosic biomass to high‐value added chemicals. Herein, Ru‐WOx/hydroxyapatite (HAP) catalyst was employed for this reaction and reached up to 91.3% yield of PG at 180 °C, 1 MPa initial hydrogen for 8 h in water. On this catalyst, Ru and WOx were highly dispersed on HAP support and they interacted with each other to form a special catalytic center. The lack of isolated Ru or RuW alloy site led to a moderate activity for hydrogenolysis and hindered the further conversion of PG to propanol. The weak basic HAP support efficiently prevented the humin formation. This precisely controlled catalyst has potential in green PG production. [ABSTRACT FROM AUTHOR]

In the several publications reviewed in this article, propylene glycol (PG; 1,2-propylene glycol) is described as a very weak contact sensitizer, if at all. However, particular exposures to PG-containing products might be associated with an elevated risk of sensitization. To identify such exposures, we analysed patch test data of 45 138 patients who have been tested with 20% PG in water between 1992 and 2002. Out of these, 1044 patients (2.3%) tested positively, 1083 showed a doubtful, follicular or erythematous reaction (2.4%) and 271 explicit irritant reactions (0.6%). This profile of patch test reactions is indicative of a slightly irritant preparation, and thus, many of the ‘weak positive’ reactions must probably be interpreted as false positive. No private or occupational exposures associated with an increased risk of PG sensitization were identified, except for lower leg dermatitis. Therefore, according to our patch test data, PG seems to exhibit very low sensitization potential, and the risk for sensitization to PG on uncompromised skin seems to be very low. [ABSTRACT FROM AUTHOR]