Understanding reaction processes for n-heptane over 10Mo2C/SZ catalyst

- In-situ carburisation of molybdena/sulfated zirconia produces stable hydroisomerisation catalysts.
- Quantitative relationship between number of hydrogenation/dehydrogenation and acid sites determined.
- Catalytic data provides evidence for multiple reaction pathways.

Supported carbided molybdena catalysts was prepared by treating MoO3/sulfated zirconia in methane/hydrogen (1:4 volumetric ratio) at 923 K. Characterisation shows the oxide to be different from the carbide phase. Carburisation did not induce phase change of the support with the tetragonal phase remaining dominant but did results in some changes to the textural properties. Lewis acid site density was constant in transforming from oxide to carbide forms while Brønsted acidity site densities was diminished by ca 10% to give a Brønsted/Lewis density ratio 2.46 in the carbide form. The ratio of hydrogenation sites to (Brønsted) acid sites on the carbidic form of the catalyst was 0.12. Increasing temperature and decreasing WHSV augmented heptane conversion but leads to multiple cracking. Analysis of the product distribution as a function of conversion or as a function of temperature implied that the reaction did not simply proceed via a single consecutive reaction pathway Conversion increased the research octane number (RON) due to of the increased fraction of pentane isomers.

nC7 conversion over Mo2C/SZ followed multiple reaction routes leading to enhanced RON.65