Reaction Kinetics of Vanillin Hydrogenation in Aqueous Solutions Using a Ru/C Catalyst

Abstract

Aqueous phase processing (APP) of bio-oil represents a candidate technique for the production of renewable hydrogen (H 2 ) in a fast pyrolysis-based biorefinery. Low temperature hydrogenation of the water-soluble portion of bio-oil is a useful intermediate step of APP. In this work, the reaction kinetics of mild aqueous-phase hydrogenation of vanillin (VL), a model compound of the bio-oil aqueous fraction, was studied using Ru/C catalyst. The investigated aromatic aldehyde was converted to vanillyl alcohol (VA) and creosol (CR). Catalytic runs were performed in a slurry reactor in the 318−338 K range using different catalyst loadings (0.2−0.8 kg/m 3 ), initial VL concentrations (32.9 to 65.7 mM) and H 2 partial pressures (0.69− 2.07 MPa). The initial rates varied linearly with respect to both initial VL concentration and H 2 partial pressure. Four Langmuir− Hinshelwood−Hougen−Watson (LHHW) type kinetic models were proposed assuming that surface reaction was ratedetermining. These models were simplified to a second order reaction model based on bulk concentration of the reacting species. From the temperature dependence of the second order reaction rate constant, the activation energy was found to be 41.2 kJ/mol.

Kinetics of Catalytic Hydrogenation of 5-Hydroxymethylfurfural to 2,5-bis-Hydroxymethylfuran in Aqueous Solution over Ru/C

“…The experimental setup was earlier discussed in previous works [24][25][26][27]. In this work, we investigated kinetics in the 313-343 K range at different H 2 partial pressures (0.69-2.07 MPa) and catalyst concentrations (0.3-0.7 kg/m 3 ).…”

Cobalt Nanoparticles Supported on Nitrogen‐Doped Carbon: An Effective Non‐Noble Metal Catalyst for the Upgrade of Biofuels

“…At 40 bar H 2 pressure, the H 2 concentrationi ni sopropanol can be considered to be constant, thus the reaction can be presumed to be pseudo-first order.F igure 3a shows the plot of ln(C t /C 0 ) versust ime at 60, 70, and 80 8Cf or the hydrogenation of vanillin into vanillyla lcohol, and the reactionr ate constants k were determined to be 0.00125, 0.00227, and 0.00334 min À1 at 60, 70, and8 08C, respectively.S imilarly,t he values of k for the hydrogenolysis of vanillyl alcohol into MMP were calculated to be 0.00297, 0.00415, and 0.00705 min À1 at 120, 130, and 140 8C, respectively (Figure 3b). [31] Study of the possible reaction pathway Transformation of the carbonylgroup into am ethyl group proceeds by the following three pathways (Scheme 1): hydrogenation/dehydration (path A), hydrogenation/hydrogenolysis (path B), and direct hydrogenolysis of the C=Ob ond (path C). There were few reports on the kinetic studies of the transfer hydrogenation of vanillin into MMP.T he activation energy of the deoxygenation of vanillin over Co/N-C-600 was a little highert han that over the noblem etal catalystR u/C (41.2 kJ mol À1 ).…”

“…There were few reports on the kinetic studies of the transfer hydrogenation of vanillin into MMP.T he activation energy of the deoxygenation of vanillin over Co/N-C-600 was a little highert han that over the noblem etal catalystR u/C (41.2 kJ mol À1 ). [31] Study of the possible reaction pathway Transformation of the carbonylgroup into am ethyl group proceeds by the following three pathways (Scheme 1): hydrogenation/dehydration (path A), hydrogenation/hydrogenolysis (path B), and direct hydrogenolysis of the C=Ob ond (path C). In the case of the transformation of vanillin into MMP,i t should not undergo the hydrogenation/dehydration pathway (path A), as no hydrogen atom is adjacent to the hydroxyl group in vanillyl alcohol.…”

Nickel on nitrogen-doped carbon pellets for continuous-flow hydrogenation of biomass-derived compounds in water

“…38,[50][51][52][53][54][55] Most of these studies reported a high conversion yield of Xyl and Xyt in a batch system, temperature range from 120°C-190°C, H 2 pressure of 2.0 MPa-8.0 MPa at longer reaction times of 2-6 h. [50][51][52][53][54][55] From the lignin fraction, vanillin (V), for instance, is used in food, beverages, pharmaceuticals, and fragrances but also fuel additives. 56,57 The vanillin hydrogenation product, 2-methoxy-4-methylphenol (MMP), is used as a fuel additive or food flavour and also as a sustainable source of bisphenolic compounds. 58 Typically, the hydrogenation of V to vanillyl alcohol (VA) or MMP is conducted using supported precious metal (Pd, Pt, Ru, and Rh) catalysts in batch systems and high pressure of H 2 (0.5 MPa-10 MPa).…”