Producing high quality biofuels: Pt-based hydroisomerization catalysts evaluated using BtL-naphtha surrogates

• Low Pt loading zeolite-based catalysts tested in hydroisomerization of naphtha.
• Effect of zeolitic support (mordenite, ZSM-5 and BETA) on catalytic performance.
• Pt/ZSM-5 is efficient for hydroisomerization of light and heavy naphtha feeds.
• Highest activity of Pt/ZSM-5 relates with acidity and Pt morphology.

A series of low loading, platinum-containing catalysts was successfully synthesized impregnating three different acid zeolitic supports of similar SiO2/Al2O3 ratio (∼20) but various structure and acidic characteristics (mordenite, ZSM-5, BETA) with an aqueous H2PtCl6 solution. All catalysts were thoroughly characterized (ICP, XRD, N2 physisorption, FTIR-pyridine adsorption and HR-TEM) and studied as candidate hydroisomerization catalysts. In order to accomplish the above purpose, the Pt-loaded zeolites were tested using surrogate naphtha feeds focusing on the effect of the zeolite support, as well as the nature of the feed (additionally examining heavier feeds (>C6), such as BtL-naphtha) on the activity and selectivity of the catalysts. Both Pt/MOR and Pt/ZSM-5 materials contain large numbers of total and Brönsted acidity. However, Pt/ZSM-5 slightly prevails over Pt/MOR concerning acidity strength; thus exhibiting the highest catalytic activity (highest conversion). The same Pt/ZSM-5 catalyst was also able to successfully isomerize heavier hydrocarbons with limited cracking side reactions. Besides acidity, the efficiency of Pt/ZSM-5 is possibly attributed to the faster mobility of carbocation intermediates through its more interconnected structure and the formation of homogeneously dispersed, cubic-shaped and highly crystalline Pt particles along with highly dispersed Pt species on the zeolite surface.

Figure optionsDownload as PowerPoint slide