Zeolites carbon-containing residues

HRMAS 13c-NMR is a promising method to investigate the nature of carbon-containing residues trapped in zeolitic structures when running hydrocarbons and oxygenates conversion reactions (10). 

The first Y-zeolite hydrocracking catalysts contained residual sodium ions in the sodalite cages that were mobile during operation and they entered the supercage. This led to a loss of cracking activity. Treatment of the zeolite with an anunonium salt solution removed the mobile sodium ions and restored acidity. The redistribution of palladium with ammonia solution could be combined with an exchange of sodium ions to rejuvenate the catalyst in one step. This was done before reactivation by burning off the carbon deposits. 

Figure 6.11 shows the product yields for each catalyst. The products are classified into four lumps, i.e. gas (carbon number 1-4), gasoline (5-11), heavy oil (above 12), and a carbonaceous residue referred to as coke. In the figure, PE oil represents the feed oil and contains a 34% gasoline fraction. The feed oil was effectively cracked by solid acid catalysts. The gasoline yield was highest with REY zeolite. HZSM-5(65) yielded the... 

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