Hydroisomerization, hydrocracking and dehydrocyclization of n-pentane and n-hexane using mono- and bimetallic catalysts promoted with fluorine

Abstract

The hydroconversion activities and selectivities of 0.35 wt.% Pt/Al2O3 promoted by addition of a second metal such as Ir, Rh, Re or U to form adducts (1:1) have been studied for the conversion of n-pentane and n-hexane at different temperatures of 300–500°C, except for Rh catalysts (from 150 to 500°C) in the presence of H2 atmosphere, 0.049 mol/h. Incorporation of 3.0 wt.% F in the mono- and bimetallic catalysts was also examined. The reaction carried out in a microreactor chromatographic pulse method. The total pressure was 108.5 kPa. The study revealed that three reactions are in competition: hydroisomerization produced isoalkanes, hydrocracking produced methane, ethane and propane and dehydrocyclization produced methylcyclopentane and benzene. The reaction temperature influenced the acidity and selectivities. Over most of the samples hydroisomerization and hydrocracking selectivities changed at ∼400°C. Incorporation of second metal and fluorination improved the activity of Pt/Al2O3. The fluorinated PtU/Al2O3 showed a significant activity and selectivity. The orders of selectivities of fluorinated bimetallic catalysts are: PtU>PtRe>PtIr>PtRh for hydroisomerization, PtRh>PtU>PtIr>PtRe for hydrocracking and PtRe>PtIr>PtU>PtRh for dehydrocyclization. Rh-containing catalysts are highly selective for hydrogenolysis.