Steam catalytic cracking was performed over metal modified BEA zeolite. Nickel and cobalt were introduced to the desilicated BEA zeolite by substitution treatment. The method of metal incorporation used here allowed incorporation of the metal(s) into the framework matrix of BEA in tetrahedral form together with the external surface. The successful incorporation of nickel/cobalt into the BEA framework in tetrahedral form was confirmed from FTIR spectra and UV–vis. The quantity of metals attached to BEA zeolite was calculated by EDX. The changes and defects of the BEA structure were studied from XRD patterns and SEM micrographs. The metal incorporation significantly increased the total acidity, as confirmed by NH3-TPD and pyridine FTIR analysis. The attachment of metals considerably increased the conversion of n-dodecane as compared to the parent sample. The stability of BEA zeolite was also enhanced significantly. However, the addition of Co to Ni incorporated BEA zeolite had a negative effect on both n-dodecane conversion and BEA stability.

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The hydrothermal stability of 1-D medium pore zeolites ZSM-22 with different nominal Si/Al ratios (30, 46, 80, and 100) was investigated in hot liquid water environments at different temperatures (100, 150, 200, and 250 °C) and different exposure times (6, 12, 36, 72, and 144 h). The changes in the zeolite structure, phase transformation, and textural properties were characterized by X-ray diffraction, scanning electron microscopy, 27Al and 29Si magic-angle spinning nuclear magnetic resonance, temperature-programmed desorption of ammonia, IR spectra, and X-ray fluorescence. After the treatment in a hot water environment, TON framework suffered from desilication (silicon extraction), phase transformation, and crystallinity change. The degree of desilication via siloxane hydrolysis is dependent on the treatment time and temperature. At high temperature (250 °C), severe desilication, textural properties degradation, and formation of extra-framework Al species (EFAL) were observed. This formed EFAL worked as a covering layer protecting the venerable Si bonds and mitigated further leaching of Si species from TON framework with time progress. On the contrary, selective removal of Si species at temperatures lower than 250 °C was observed without the appearance of EFAL.

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This study emphasizes tuning the synthesis conditions of MFI zeolites to achieve better catalytic properties by optimizing the mesoporosity, the balance between Brønsted and Lewis sites, and the zeolite particle sizes. The MFI zeolites were hydrothermally synthesized at various temperatures employing different silica sources. The synthesis temperature was varied between 110 to 180 °C at constant synthesis time (15 h). Different silicon sources led to variations in structure, morphology, and size of the MFI zeolite along with tuned Lewis and Brønsted acid sites in parallel correlation with shape selectivity of the reaction. The catalytic activities of synthesized zeolites were investigated in the catalytic cracking of n -dodecane to produce value-added chemicals. The zeolite synthesized at 180 °C using fumed silica presented the highest catalytic conversion (96.6%), while maximum light olefin gaseous products (73.1%) were obtained for the sample synthesized at 140 °C using tetraethyl orthosilicate as the silica source. The MFI zeolite synthesized at 180 °C employing tetraethyl orthosilicate as a silica source facilitated the formation of both naphthenes and aromatics (71.3%) as major liquid products.