Abstract
The adsorption capacities of two synthesized zeolites (crystalline ZSM-5 and semi-crystalline faujasite Y) for a mixture of indole, quinoline and carbazole were studied. The different samples obtained show different crystalline degree, mesoporosity and Si/Al ratios. The synthesis procedure is based on the simultaneous depolymerization of a mixture of high surface area silica, such as rice hull ashes (RHA), and a crystalline zeolite, such as clinoptilolite or faujasite. The depolymerization step is followed by a partial reorganization induced by a structure-directing agent. A model mixture of nitrogenous compounds was prepared, then it was mixed with the zeolite samples and the amount adsorbed of nitrogenous compounds was determined by gas chromatography. Analysis of the adsorbed molecules reveals selectivity in favor of quinoline, followed by indole and then carbazole. The best adsorbent properties correspond to the solid with highest porous volume. The samples obtained were characterized by X-ray diffraction, 29Si and 27Al magic-angle spinning nuclear magnetic resonance, X-ray fluorescence and Fourier transform infrared spectroscopy. The Barrett-Joyner-Halenda (BJH) pore size distribution and the Brunauer-Emmet-Teller (BET) surface area values were obtained from N2 adsorption/desorption isotherms.
Highlights
The production of ultralow sulfur diesel (ULSD) is imperative worldwide due to current air pollution
Nitrogenous compounds present in straight run gas oil (SRGO), coker gas oil (CGO) and light cycle oil (LCO), which are used as feedstocks for diesel fuel production, have been identified as strong inhibitors of HDS reactions due to catalyst poisoning
The following results were obtained by increasing the amount of clinoptilolite mixed with rice hull ash (RHA) in the starting material mixture and hydrolyzing with Tetrapropylammonium hydroxide (TPA)
Summary
The production of ultralow sulfur diesel (ULSD) is imperative worldwide due to current air pollution. A novel technique for the preparation of mesoporous adsorbents using gels obtained from depolymerized silicates has been reported by our group.[41,42,43,44,45,46] This technique first involves the simultaneous depolymerization of a mixture of high-surface-area silica, such as rice hull ash (RHA), and of a crystalline zeolite, such as clinoptilolite or faujasite. For FTIR study of nitrogen compound interactions, the indole was adsorbed at room temperature and progressively desorbed at different temperatures under vacuum.
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