Conclusions
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1.
As the Na2O content of ultrahigh-silica zeolites increases, the yield of liquid catalysate and aromatic hydrocarbons from isobutylene at 500°C decreases.
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2.
As the temperature of preliminary calcination increases from 500 to 1000°C, the water-sorption capacity of ultrahigh-silica zeolites gradually decreases. Calcination at 800–1000°C hardly affects the total zeolite activity but decreases its activity in the dehydrocyclization and hydrogen redistribution reactions. After zeolite calcination at 1000°C, an increase in selectivity for p-xylene formation is observed.
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3.
The change in the catalytic properties of ultrahigh-silica zeolites after calcination at 800–1000°C is related to the removal of a small number of OH groups which enter into the composition of the active centers. The selectivity increase for p-xylene formation can be attributed to some changes in the pore structure at high temperature which make the diffusion of m- and o-xylene difficult.
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Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1310–1315, June, 1981.
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Minachev, K.M., Kondrat'ev, D.A., Nefedov, B.K. et al. Effect of composition and calcination temperature on the catalytic properties of ultrahigh-silica zeolite in isobutylene conversions. Russ Chem Bull 30, 1042–1047 (1981). https://doi.org/10.1007/BF00950290
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DOI: https://doi.org/10.1007/BF00950290