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Four groups of catalysts have been tested for hydrodeoxygenation (HDO) of phenol as a model compound of bio-oil, including oxide catalysts, methanol synthesis catalysts, reduced noble metal catalysts, and reduced non-noble metal catalysts. In total, 23 different catalysts were tested at 100 bar H2 and 275 °C in a batch reactor. The experiments showed that none of the tested oxides or methanol synthesis catalysts had any significant activity for phenol HDO under the given conditions, which were linked to their inability to hydrogenate the aromatic ring of phenol. HDO of phenol over reduced metal catalysts could effectively be described by a kinetic model involving a two-step reaction in which phenol initially was hydrogenated to cyclohexanol and then subsequently deoxygenated to cyclohexane. Among reduced noble metal catalysts, ruthenium, palladium, and platinum were all found to be active, with activity decreasing in that order. Nickel was the only active non-noble metal catalyst. For nickel, the effect of support was also investigated and ZrO2 was found to perform best. Pt/C, Ni/CeO2, and Ni/CeO2-ZrO2 were the most active catalysts for the initial hydrogenation of phenol to cyclohexanol but were not very active for the subsequent deoxygenation step. Overall, the order of activity of the best performing HDO catalysts was as follows: Ni/ZrO2 > Ni-V2O5/ZrO2 > Ni-V2O5/SiO2 > Ru/C > Ni/Al2O3 > Ni/SiO2 ≫ Pd/C > Pt/C. The choice of support influenced the activity significantly. Nickel was found to be practically inactive for HDO of phenol on a carbon support but more active than the carbon-supported noble metal catalysts when supported on ZrO2. This observation indicates that the nickel-based catalysts require a metal oxide as a carrier on which the activation of the phenol for the hydrogenation can take place through heterolytic dissociation of the O–H bond to facilitate the reaction.

Electrification of conventionally fired chemical reactors has the potential to reduce CO2 emissions and provide flexible and compact heat generation. Here, we describe a disruptive approach to a fundamental process by integrating an electrically heated catalytic structure directly into a steam-methane–reforming (SMR) reactor for hydrogen production. Intimate contact between the electric heat source and the reaction site drives the reaction close to thermal equilibrium, increases catalyst utilization, and limits unwanted byproduct formation. The integrated design with small characteristic length scales allows compact reactor designs, potentially 100 times smaller than current reformer platforms. Electrification of SMR offers a strong platform for new reactor design, scale, and implementation opportunities. Implemented on a global scale, this could correspond to a reduction of nearly 1% of all CO2 emissions.

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