Characterization of shape selective properties of zeolites via hydroisomerization of n-hexane

In this work we use the hydroisomerization of n-hexane as a catalytic test reaction to investigate the shape selective properties of a series of zeolites (mordenite, Y, ZSM-5, ZSM-12, TNU-9, SSZ-25, SSZ-26, SSZ-32, SSZ-33, SSZ-56, SSZ-57 and SSZ-75). The yield ratio of mono-branched isomers (2- and 3-methylpentane) to di-branched isomers (2,2- and 2,3-dimethylbutane) and the yield ratio of 2,3- to 2,2-dimethylbutane provide a useful tool for characterizing the effective pore sizes of zeolites. The high octane isomer 2,3-dimethylbutane (RON 101.0) can be selectively produced over 2,2-dimethylbutane (RON 91.8) by choosing zeolites (e.g., TNU-9 and SSZ-75) which have the appropriate pore sizes, demonstrating some new examples of the shape selectivities of zeolite catalysis. This catalytic test reaction is complementary to the vapor phase hydrocarbon adsorption for the investigation of the shape selective properties and effective pore sizes of zeolites.

Graphical abstractHydroisomerization of n-hexane over Pd/TNU-9.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► n-Hexane hydroisomerization is systematically studied as a catalytic test reaction. ► A series of new examples of shape selectivities of zeolite catalysis are reported. ► 2,3-DMBu is selectively produced vs. 2,2-DMBu in zeolites such as TNU-9 and SSZ-75. ► This test reaction is complementary to hydrocarbon adsorption for zeolite research.