Heide-Lore Zubowa

Synthesis and properties of the silicoaluminophosphate molecular sieve SAPO-31

The silicoaluminophosphate molecular sieve SAPO-31 has been synthesized and characterized by XRD, 27Al, 29Si, and 31P MASNMR, IR spectroscopy, electron microscopy, DTA-TGA, chemical analysis, and the catalytic conversion of methanol to light olefins. The results from XRD and NMR investigations show that hydration causes structural changes of the framework.

On the confinement of liquid crystals in molecular sieves: dielectric measurements

Abstract The molecular dynamics of 4-octyl-4′-cyanobiphenyl and 4-pentyl-4′-cyanobiphenyl, confined to the mesopores with diameters less than 25 A of the molecular sieve AlMCM-41, was investigated over a wide temperature range using broadband dielectric spectroscopy. As expected, the phase transitions of the bulk liquid crystals cannot be detected for the confined molecules. A new, slow relaxational process occurs over the whole temperature range due to the motions of the molecules confined in the pores; the temperature dependence of the characteristic frequency obeys a Vogel–Fulcher–Tamman (VFT) law associated with a glassy state. The orientational order within these small pores is mostly dominated by the local environment.

Improvement of catalytic properties of SAPO-31 molecular sieves by using an activated form of Si02

Abstract SAPO-31 molecular sieves the synthesis of which is based on different types of SiO2 were physicochemically characterized by X-ray diffraction, IR, temperature-programmed desorption of ammonia,29Si magic angle spinning nuclear magnetic resonance and catalytically investigated in the conversion of methanol to lower alkenes and in the isomerization of n-heptane. The use of ultradispersed SiO2 generated in a capacitively coupled high frequency plasma (CCP) allowed us to synthesize SAPO-31 molecular sieves of Bronsted acidities which are higher than with samples based on traditional silicon sources. Results of the conversion of methanol and of the isomerization of n-heptane show that the use of plasma-chemically generated silica in the synthesis of SAPO type molecular sieves can be a way to improve their catalytic properties.

Catalytic properties of the gallophosphate cloverite 1 Gas-phase formation of methyl tert.-butyl ether

Abstract A viable catalytic application of the gallophosphate cloverite is reported for the gas phase etherification of isobutene to methyl-tert.-butyl ether under atmospheric flow conditions at temperatures from 363 to 383 K following appropriate decomposition of the quinuclidine template.