Atmospheric hydrodeoxygenation of phenol as pyrolytic‐oil model compound for hydrocarbon production using Ag/TiO₂ catalyst

Abstract

Hydrodeoxygenation (HDO) kinetics of phenol over Ag/TiO 2 catalyst was investigated at 415-600 K and 1 atm. The use of oxophilic TiO 2 support has improved phenol conversion due to its preferential activation of C-O bond.Product analysis confirmed the occurrence of direct deoxygenation (DDO) and hydrogenation-dehydration (HYD) pathways to produce benzene and cyclohexane, respectively. Both phenol hydrogenolysis and hydrogenation steps are the respective rate-limiting steps for DDO and HYD pathways of phenol HDO over Ag/TiO 2 . Based on the transition state theory, negative entropy changes of activation during HDO indicated that the HDO reactants formed activated complexes that had more orderly bonding configurations prior to the hydrogenolysis, hydrogenation, and dehydration steps. Under the present conditions, the catalyst was stable after 4 hr of HDO runs and able to be regenerated via H 2 -activation and calcination in air at 553 K with at least 98.9% removal efficiency to remove coke deposits and reform Ag metal species after HDO.

Temperature‐programmed reduction of silver(I) oxide using a titania‐supported silver catalyst under a H2 atmosphere

“…A similar hydrogen consumption rate was observed when hydrogen flow velocity was increased, indicating that reduction was not limited by external mass transfer. For internal mass transfer, the values of Thiele modulus, internal effectiveness factor, and Weisz–Prater criterion were computed based on the first order of reduction for Ag/TiO 2 where ϕ 1 is the Thiele modulus, η is the internal effectiveness factor, C W − P is the Weisz–Prater criterion, R cat is the particle radius (56.57 nm for Ag/TiO 2 ‐10 sample), k is the reduction rate constant, D e is the effective diffusivity, is the Knudsen diffusivity of H 2 , ϕ p is the porosity (0.4), σ c is the constriction factor (0.8), is the tortuosity (3), d is the pore diameter (9.53 nm), R is the ideal gas constant, T is the reduction temperature, M A is the molecular mass of H 2 .…”

“…For internal mass transfer, the values of Thiele modulus, internal effectiveness factor, and Weisz-Prater criterion were computed based on the first order of reduction for Ag/TiO 2 . [52] where ϕ 1 is the Thiele modulus, η is the internal effectiveness factor, C W − P is the Weisz-Prater criterion, R cat is the particle radius (56.57 nm for Ag/TiO 2 -10 sample), k is the reduction rate constant, D e is the effective diffusivity, D K ð Þ H 2 is the Knudsen diffusivity of H 2 , ϕ p is the porosity (0.4), σ c is the constriction factor (0.8), e τ is the tortuosity (3), d is the pore diameter (9.53 nm), R is the ideal gas constant, T is the reduction temperature, M A is the molecular mass of H 2 . Based on these data, the values for ϕ 1 , η, and C W − P are 1.01 × 10 −5 , 0.9999 and 1.02 × 10 −10 for the first peak and 8.2 × 10 −6 , 1.00 and 6.72 × 10 −11 for the second peak at their respective reduction peak temperatures (389.3 and 490 K).…”

Sustainable biomass hydrodeoxygenation in biphasic systems

“…A wide range of phenolic model compounds (such as phenol, guaiacol, cresol and anisole) have been applied in biomass HDO reactions. [159][160][161][162] And, in HDO reactions, the type of reaction product and the differences in reaction pathways strongly depend on the catalyst. Recently, Teles et al 163 investigated the effect of metal type on the selective HDO reaction of phenol over silica-loaded catalysts.…”

“…89 (b) CO consumption TOF in different solvents. 159 Fig. 13 The effect of the type of metal in the catalyst on the kinds of phenol selective HDO product.…”

TiO2-Based Water-Tolerant Acid Catalysis for Biomass-Based Fuels and Chemicals

“…This observation obviously indicates the beneficial role of TiO 2 and its Lewis acidity for efficient HDO of lignin-derived oxygenates. Oxophilicity character of TiO 2 support, which is directly related to its Lewis acidic strength, was found to play a crucial role in phenol conversion due to its preferential activation of C–O bond . Depending on the reaction conditions, both direct deoxygenation and hydrogenation–dehydration pathways are possible over Ag/TiO 2 catalyst, giving benzene and cyclohexane, respectively, from the HDO of phenol.…”