Hydrogen forms of natural mordenite and clinoptilolite were used as catalysts for styrene oligomerization and as matrices to hold the resultant oligomers in order to prepare intense and light-resistant pigments. In contrast to synthetic zeolites of similar pore sizes (mainly H-ZSM-5, H-mordenite), the natural zeolites did not form products with an intense (pink) colouration. H-mordenite samples treated with styrene developed some colour due to styrene oligomers (the chromophore) whereas, in treated clinoptilolites, colour formation was negligible due to the lack of access of styrene molecules into the elliptical channels. The results of catalytic tests for cracking of cumene (cumene and styrene have similar molecular sizes) were consistent with the styrene oligomerization results. They indicate a noticeable catalytic activity with natural H-mordenite and a lack of activity with clinoptilolite. On the other hand, catalytic tests for propan-2-ol decomposition indicate a high activity with both natural zeolites, which confirms the presence of acid sites and their accessibility to small alcohol molecules.

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