Synthesis, characterization and adsorptive denitrogenation performance of bimodal mesoporous Ti-HMS/KIL-2 composite: A comparative study on synthetic methodology

Novel titanosilicate composites with bimodal mesopores using molecular sieves Ti-HMS and Ti-KIL-2 as structural components were successfully synthesized by two-step and dual-template methods in a comparative study. The as-synthesized Ti-HMS/KIL-2 samples were characterized by a series of techniques including X-ray diffraction, UV–vis, N 2 sorption and scanning electronic microscopy, and their performance was tested in adsorptive denitrogenation for model fuel containing pyridine or quinoline. Although Ti-HMS/KIL-2 composites were constructed following the different pathway of self-assembly, most of them obtained coexisting properties and structures of Ti-HMS and Ti-KIL-2, as well as the intact framework Ti in tetrahedral coordination. A key finding is that the mesopores size of Ti-KIL-2 component in the composite can be regulated via the introduction of Ti-HMS precursor or organic template dodecylamine. Especially, the composites of dual-template method presented hierarchical mesopores with obvious bimodal distribution. In addition to constructing the hierarchical structure, introduction of Ti-HMS into Ti-KIL-2 matrix improved the adsorptive denitrogenation performance, which was influenced by the synthetic strategy of Ti-HMS/KIL-2. The target adsorbates achieved the best match with the adjustable pores of Ti-HMS/KIL-2. Therefore, (0.6 D )Ti-HMS/KIL-2 and (0.5 T )Ti-HMS/KIL-2 as the optimized adsorbents obtained remarkable adsorption efficiency respectively for pyridine and quinoline. Essence of the adsorptive denitrogenation process was revealed via the adsorption isotherms and the adsorption thermodynamics. Finally, Ti-HMS/KIL-2 composites achieved the improvement in hydrothermal stability and recyclability during adsorption of pyridine and quinoline, and exhibited the potential of industrial application.