Thin and well-defined MFI type molecular sieve films were grown on a range of ATR crystals by employing a seeding method. The type of ATR crystal does not influence film morphology. FTIR spectroscopy was used to evaluate the coated ATR crystals as sensor probes. These novel sensor probes could be used to detect low concentrations of organic molecules in a gas flow.
Thin and continuous silicalite-1 films with controllable thickness between 200 and 800 nm were synthesized on steel supports by a method employing seeding. A variety of steel types ranging from ordinary carbon steel to highly corrosion resistant steel were used. Continuous transparent silicalite-1 films were formed on all steel types after zeolite synthesis. The type of steel did not affect the film morphology, the thickness or the preferred orientation of the crystals. The (5 0 1) reflection dominates in the XRD pattern for thin films whereas the (1 0 1) and (3 0 3) reflections dominate for thicker films. The silicalite-1 films on various stainless steel supports were stable during calcination, whereas a relatively thick magnetite/hematite film formed on carbon steel upon calcination and the silicalite-1 film detached.
Hydroprocessing catalysts were prepared using fibrillar aluminas as carrier materials and sulphides of nickel and molybdenum as active substances. The fibrillar aluminas were obtained from fibrillar boehmite samples prepared at three different synthesis conditions resulting in different fibril sizes. After extrudation and deposition of metals, catalysts combining large surface areas with large average pore diameters were obtained. The catalysts were tested for hydrodemetallisation of an atmospheric residue and the results were compared with those obtained for a commercial reference catalyst with a similar loading of nickel and molybdenum. Two of the catalysts prepared using fibrillar alumina as carrier material were more active than the commercial catalyst. The third catalyst containing the largest alumina fibrils was inferior to the other catalysts in all respects. Catalyst deactivation was investigated in a long-term hydroprocessing experiment using a heavy vacuum residue containing large amounts of metals as a feed oil. The catalyst prepared using fibrillar alumina used in this test showed a constant level of hydrodemetallisation even after 500 h on stream whereas the reference catalyst was completely deactivated after 350 h.
Hydroprocessing catalysts were prepared using fibrillar alumina and attapulgite as carrier materials and nickel and molybdenum as active substances. With fibrillar alumina as primary particles, a carrier material was obtained which combined a large surface area (138 m2/g) with a large average pore diameter (252 Å). Due to side-by-side association of the fibers, attapulgite did not yield a catalyst carrier with as large pores as was expected. The catalysts were tested for hydroprocessing of an atmospheric petroleum resid, and the results were compared with those obtained for a commercial catalyst with similar loading of nickel and molybdenum. The catalyst prepared using fibrillar alumina as carrier material was more active than the commercial catalyst for hydrodemetalization, equally active for hydrodesulfurization, and less active for hydrodenitrogenation. The catalyst prepared using attapulgite as carrier material was inferior to the other two catalysts in all respects. © 1995 American Chemical Society.
Stable colloidal suspensions of discrete crystals of titanium silicalite-1 with an average ultimate crystal size of less than 100 nm are prepared in the presence of ethanol at 100°C with crystallization times of less than 48 hours.
Stable colloidal suspensions containing discrete TS-1 crystals with average crystal sizes less than 100 nm and with a narrow particle size distribution have been synthesized from clear homogeneous solutions. The products were characterized with respect to crystallinity, crystal size and size distribution, Ti incorporation, specific surface areas, the nature of the Ti species in the products, and the colloidal crystals surface electric charge. The influence of several parameters including synthesis mixture composition and crystallization temperature on crystal size and Ti incorporation were investigated. The synthesis of colloidal crystals with an average size less than 100 nm is favored by low crystallization temperatures (100°C), a highly basic environment, concentrated mixtures, and low Ti contents in the synthesis solutions. The maximum incorporation of tetrahedrally coordinated Ti was 0.84 mol %. High crystallization temperatures (>100°C) favor products with a low Si/Ti molar ratio, but larger crystals are formed, >100 nm, and octahedrally coordinated Ti and extra-framework Ti are detected. A preliminary investigation of the clear hydrolyzed precursor solution and its freeze-dried amorphous equivalent showed that small particles with an average size of 4.8 nm exist in the solution and a certain degree of ordering resembling the MFI structure was present in the precursor particles
Alumina beads were coated with ZSM-5 films ranging from 150 nm to 2300 nm ill thickness. The ZSM-5 boated alumina beads were Subsequently hydrothermally treated in a silicalite-1 synthesis solution ill two steps Whereupon a dense silicalite-1 film was formed oil top of the ZSM-5 film. The materials were tested with two probe reactions and the reactivity was compared before and after coating with silicalite-1. As expected, the para-xylene (pX) isomerization reactivity showed no change for samples with and without the top layer of silicalite-1 for equal amounts Of zeolite. Surprisingly, the triisopropylbenzene (TIPB) conversion did not decrease after the silicalite-1 film was introduced. As measured by XPS, the aluminum concentration at the Surface of the uncalcined silicalite-1 film surface was lower compared to that at the Surface of the calcined ZSM-5 film. However, after calcination the concentration of aluminum was higher at the silicalite-1 film surface than at the ZSM-5 film Surface. These results Suggest that aluminum migrates from the ZSM-5 film into the silicalite-1 film during calcination and testing which results in all active top layer.
Well-defined ZSM-5 films were prepared on cordierite monoliths using the seed film method. The monoliths were seeded with silicalite-1 seeds and hydrothermally treated either at 75 or at 150 °C in a single or several steps. By adding sodium hydroxide to the solution, the aluminum concentration in the zeolite increased. Consequently, films with different Si/Al ratios were prepared. The film thickness could be controlled from 110 nm to 9 μm. Multi-step synthesis was used to prevent bulk crystallization and ultrasound treatment was found to be beneficial (in order) to remove sedimented crystals on the top of the coatings. The zeolite-coated monoliths were active for p-xylene isomerization, and the test results indicated that the films became less deactivated than the films prepared on alumina beads.