Using biomass as a source of chemical building blocks instead of fossil resources is an important part of increasing the sustainability of the chemical industry. The pyrolysis of lignocellulose, for example, provides bio-oil. Removing some of the oxygen-containing groups in the resulting products can lead to value-added chemicals. For example, vanillin can be derived from bio-oil and then converted into 2-methoxy-4-methylphenol (MMP, pictured) via a catalytic hydrodeoxygenation (HDO) reaction. However, this reaction can be challenging to perform in a selective manner.

Jun Wu, Yong Li, Shaanxi University of Science & Technology, Xi’an, China, and colleagues have developed a catalyst for the conversion of vanillin to MMP via an HDO reaction that is based on highly dispersed Pd nanoparticles on nitrogen-doped hollow carbon spheres. The team first prepared SiO₂ nanosphere templates, which were then used in the polymerization of dopamine. The resulting precursor was carbonized at 600–1,000 °C. The thus obtained nitrogen-doped mesoporous hollow carbon spheres were reacted with potassium tetrachloropalladate to deposit Pd metal nanoparticles on their surface.

The team found that this process created a catalyst with highly dispersed Pd nanoparticles with small sizes and a narrow size distribution. This catalyst showed a high catalytic activity for the chemoselective HDO reaction of vanillin to MMP under mild reaction conditions. The system achieved 99 % conversion and 98 % MMP selectivity within 45 min at 50 °C under 1 atm of H₂. The team proposes that a metal-support interaction with the N-doped carbon carrier could enhance the adsorption and activation of H₂ and vanillin and, thus, lead to the observed high catalytic performance.

• Highly Dispersed Pd Nanoparticles Immobilized on N-Doped Hollow Carbon Spheres for Efficient Catalytic Hydrodeoxygenation of Biomass-Derived Vanillin under Atmospheric Conditions,
  Jun Wu, Liqian Liu, Xinyue Yan, Tingting Wang, Gang Pan, Jiahao Bai, Yong Li,
  ACS Sustainable Chem. Eng. 2024.
  https://doi.org/10.1021/acssuschemeng.4c07026