Performance of Pt/ZrO2-TiO2-Al2O3 and coke deposition during methylcyclohexane catalytic cracking

Three groups of ZrO2-TiO2-Al2O3 catalysts with and without Pt addition were prepared to comparatively investigate the coke performance during pyrolysis of supercritical methylcyclohexane at 650 °C and 4.0 MPa. From the data of gas chromatography-mass spectrometer, it was observed that the contents of alkenes in liquid products over Pt-loaded catalysts have higher values than those on pure supports. But for the aromatics, e.g., benzene and toluene, the yields over Pt-loaded samples are obviously less than those on pure supports. It revealed that the addition of Pt to the metal oxides supports prevented the formation of aromatics. With the characterization of XPS and TPO, the coke formed over pure supports was more ordered with a higher dehydrogenation extent than those produced on the Pt-loaded samples. According to our coke formation model, the results of product distribution could be owing to the Pt-loaded catalysts, which restrained the generation and polymerization of coke intermediates. PT3 obtained the best coke inhibition effect, which attributes to the reduced polymerization rate by Pt effect and pore diffusion effect. The acid and pore property have an influence on both the coke amount and the nature of coke, moreover, less amount of coke and easier-oxidized coke were obtained with Pt addition.