Platinum–M (M = Ni, Cr, Mn, Fe) Bimetallic Modified Carbon Fibers Enable Self-Supported Catalytic Methylcyclohexane Dehydrogenation

In this study, carbon fiber raw materials were modified via a gas–liquid phase mixed oxidation method (CF-GL), and a series of bimetallic Pt–M/CF-GL (M = Ni, Cr, Mn, or Fe) catalysts were constructed. The fibrous Pt–M/CF-GL served as self-supporting catalysts that exhibited excellent air permeability and mass transfer efficiency. When stacked into carbon fiber paper with a basis weight of 60 g/m2, the air permeability reached 100 mL/m2·Pa·s and the porosity was up to 80%. Catalysts were prepared using 0.5 wt % Ni, Cr, Mn, or Fe and a Pt loading of 0.5 wt %. The catalytic effect of the Pt–Fe/CF-GL material was the best among the tested catalysts. The methylcyclohexane (MCH) conversion and the toluene (TOL) selectivity reached 34.6% and 97.2%, respectively, and the hydrogen release rate was 136.06 mmol/g(Pt)/min. These results were likely due to the strong interaction between Fe and Pt, which influenced the electronic structure of Pt. Modulating the loading ratio of Pt and Fe revealed optimal catalytic performance when Pt:Fe = 1:2 (MCH conversion = 79.3%, TOL selectivity = 98.5%, and hydrogen release rate = 310.93 mmol/g(Pt)/min). The MCH conversion and hydrogen release rate of Pt–Fe/CF-GL (with Pt:Fe = 1:2) both increased more than 3-fold compared with Pt/CF-GL (with the same Pt loading). Thus, the catalytic performance of the precious metal Pt was enhanced by the nonprecious metal Fe. Moreover, Pt–M/CF-GL does not need to be mixed with quartz sand, which enhances the mass transfer efficiency of the gas–solid two-phase reaction and facilitates catalyst recovery and reuse.