Cellulose-Nanofiber-Mediated Sorption-Benefitting Holed Silicalite-1 Crystals.

Silicalite-1-type zeolites with unique intracrystal holes or cracks were successfully prepared using a cellulose nanofiber (CNF) as an additional mediating material, and their vapor phase adsorption properties toward methyl tert-butyl ether (MTBE) and n-nitrosodimethylamine (NDMA) were examined. It was found that the mixing protocol of CNF and structure-directing agents (SDAs), the addition amount of CNF, and the CNF/SDAs amount ratio play important roles in forming the holed silicalite-1. The synthesis route that preliminarily mixes CNF with SDAs in a series of controlled conditions is particularly beneficial for the formation of the holed silicalite-1 with mesoporosity and larger pores because the CNF-SDAs composite structure benefits the zeolite growth closely encompassing CNF inside the crystal structure. It also promotes the preferential formation of the orthorhombic phase vicinal to the CNF surface, namely, the surface of the formed internal holes or cracks, with the twin-type crystal size reduced as compared to the non-CNF-templated sample. On the contrary, the synthesis route that mixes CNF with SDAs-silicate composite ions tends to modify the twin-type crystal shape at the same time to form small but uniform well-crystallized particles with less holes or cracks and a dominative monoclinic phase. It was considered that both the inter-subunit structural defect and silanol defect whose content is increased with CNF addition influence the adsorptivity of MTBE and NDMA. Owing to the small twin-type crystal size, the smaller crystal subunits, and the favored short path from the surface of internal holes or cracks, the holed silicalite-1 derived from the CNF and SDA premixture assures the easiest access of adsorbate molecules to the most energetically favored sites and is most appropriate for the adsorption of both MTBE and NDMA among the examined zeolites.

Influence of Fe loadings on desulfurization performance of activated carbon treated by nitric acid.

A series of Fe supported on activated carbon treated by nitric acid are prepared by incipient wetness impregnation with ultrasonic assistance and characterized by N2 adsorption-desorption, X-ray diffraction, Fourier transform infrared spectrum and X-ray photoelectron spectroscopy. It has shown that Fe loadings significantly influence the desulfurization activity. Fe/NAC5 exhibits an excellent removal ability of SO2, corresponding to breakthrough sulfur capacity of 323 mg/g. With the increasing Fe loadings, the generated Fe3O4 and Fe2SiO4 increase, but Fe2(SO4)3 is observed after desulfurization. Fe/NAC1 has a Brunauer-Emmett-Teller (BET) surface area of 925 m2/g with micropore surface area of 843 m2/g and total pore volume of 0.562 cm3/g including a micropore volume of 0.300 cm3/g. With the increasing Fe loadings, BET surface area and micropore volume decrease, and those of Fe/NAC10 decrease to 706 m2/g and 0.249 cm3/g. The Fe loadings influence the pore-size distribution, and SO2 adsorption mainly reacts in micropores at about 0.70 nm. C=O and C-O are observed for all samples before SO2 removal. After desulfurization, the C-O stretching is still detected, but the C=O stretching vibration of carbonyl groups disappears. The stretching of S-O or S=O in sulfate is observed at 592 cm-1 for the used sample, proving that the existence of [Formula: see text].

[Adsorption performances for sulfur dioxide using imidazole ionic liquids].

To discover the SO2 adsorption laws of ionic liquids in simulating flue gas, the SO2 adsorbents 1-butyl-3-methylimidazolium chloride ([Bmim] Cl), 1-butyl-3-methylimidazolium nitrate ([Bmim] NO3), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim] BF4) and 1-amyl-3-methylimidazolium chloride [C5 mim] Cl ionic liquids were synthesized. The performances were studied under different conditions and the general rules of regeneration were explored. And the diversification of [Bmim] Cl chemical structures, which were pre-desulfated, post-desulfated and post-regenerated, were characterized by Fourier Transform Infrared Spectroscopy. The results illustrated that these ionic liquids all had the ability of SO2 adsorption, and the order of SO2 adsorption performances was [C5 mim] C1 > [Bmim] Cl > [Bmim] NO3 > [Bmim] BF4. The total SO2 adsorption amount of [C5 mim] Cl was 200. 8 mg/g, and the optimal adsorption temperature of [Bmim] Cl was 40 degrees C. The order of anions impacting adsorption performances of ionic liquids was Cl- > NO3- > BF4-. The sulfur capacity of ionic liquids decreased to 26.5 mg/g from 65.9 mg/g after desorption under the condition of heating (90 degrees C), vacuum (0.09 MPa) and 4.0 h. In addition, the chemical structures of ionic liquid had changed, and the forms of SO2 adsorbed by [Bmim] Cl were physico-chemical processes.