Porous silica nano-flowers stabilized Pt-Pd bimetallic nanoparticles as heterogeneous catalyst for efficiently synthesizing guaiacol from 2-methoxycyclohexanol

Porous silica nano-flowers (KCC-1) immobilized Pt-Pd alloy NPs (Pt-Pd/KCC-1) with different mass ratios of Pd and Pt were successfully prepared by a facile in situ one-step reduction, using hydrazinium hydroxide as a reducing agent. The as-synthesized silica nanospheres possess radial fibers with a distance of 15nm, exhibiting a high specific surface area (443.56 m 2 ·g –1 ). Meanwhile, the obtained Pt-Pd alloy NPs are uniformly dispersed on the silica surface with a metallic particle size of 4–6 nm, which exist as metallic Pd and Pt on the surface of monodisperse KCC-1, showing the transfer of electrons from Pd to Pt. The as-synthesized 2.5%Pt-2.5%Pd/KCC-1 exhibited excellent catalytic activity and stability for the continuous dehydrogenation of 2-methoxycyclohexanol to prepare guaiacol. Compared with Pt or Pd single metal supported catalysts, the obtained 2.5%Pt-2.5%Pd/KCC-1 shows 97.2% conversion rate of 2-methoxycyclohexanol and 76.8% selectivity for guaiacol, which attributed to the significant synergistic effect of bimetallic Pt-Pd alloy NPs. Furthermore, turn over frequency value of the obtained 2.5%Pt-2.5%Pd/KCC-1 NPs achieved 4.36 s –1 , showing higher catalytic efficiency than other two monometallic catalysts. Reaction pathways of dehydro-aromatization of 2-methoxycyclohexanol over the obtained catalyst are proposed. Consequently, the obtained 2.5%Pt-2.5%Pd/KCC-1 NPs prove their potential in the dehydrogenation of 2-methoxycyclohexanol, while the kinetics and mechanistic study of the dehydrogenation reaction over the catalyst in a continuous fixed-bed reactor may provide valuable information for the development of green, outstanding and powerful synthetic pathway of guaiacol.