Surfactant recovery from mesoporous metal-modified materials (Sn-, Y-, Ce-, Si-MCM-41), by ultrasound assisted ion-exchange extraction and its re-use for a microwave in situ cheap and eco-friendly MCM-41 synthesis
Different metal substituted (Y, Sn and Ce) MCM-41 materials were synthesized and detemplated by a low temperature surfactant removal methodology. All metal substituted materials showed an increase in the d_(100) lattice parameter compared to the parent MCM-41 matrices. The increase depends on both the metal type and amount that is successfully incorporated by direct conventional hydrothermal synthesis. The metal modified MCM-41 materials were detemplated by an ultrasound assisted (US) ion-exchange process using methanol as the solvent (NhUNCVUS/MeOH). The effect of the ultrasound amplitude, extraction time and salt concentration were explored, and optimal values were determined for Y-MCM-41 detemplation (40 mM of NH4NO3, 60% of US amplitude and 15 min of adiabatic treatment). The removal percentage achieved with these values was in the following order: Y (97.7%) > Ce (94.4%) > Sn (92.1%) > Si (90.3%). Several techniques (SAXS, FT1R, TGA, ~1H MAS, ~(29)Si HPDEC MAS NMR and N2 physisorption) demonstrated that the mesoporous materials keep their hexagonal structure and high surface area after the NH4NO3/US/MeOH surfactant extraction. Moreover, the thermal shrinkage of the structure was reduced in the following order: Si (0.6%) < Sn (4%) < Ce (5%) < Y (9%) < calcined samples (from 9 to 15%). The surfactant recovered was successfully recycled in a consecutive microwave assisted hydrothermal synthesis cycle (MW-HT). The synergy of different strategies (MW-HT synthesis, NH4NO3/ US/MeOH surfactant removal and surfactant recovery) produces considerable time, energy and cost abatement, environmental impact reduction and promising scale up projections in the eco-friendly synthesis of MCM-41 materials.
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机译:合成了不同的金属取代(Y,Sn和Ce)MCM-41材料,并通过低温表面活性剂去除方法对其进行了描绘。与母体MCM-41矩阵相比,所有金属取代的材料均显示d_(100)晶格参数增加。这种增加取决于直接常规水热合成成功引入的金属类型和数量。通过使用甲醇作为溶剂(NhUNCVUS / MeOH)的超声辅助(US)离子交换工艺对金属改性的MCM-41材料进行了设计。探讨了超声振幅,提取时间和盐浓度的影响,并确定了Y-MCM-41脱模板(40 mM NH4NO3、60%US振幅和15分钟绝热处理)的最佳值。用这些值实现的去除百分比按以下顺序:Y(97.7%)> Ce(94.4%)> Sn(92.1%)> Si(90.3%)。几种技术(SAXS,FT1R,TGA,〜1H MAS,〜(29)Si HPDEC MAS NMR和N2物理吸附)证明,在NH4NO3 / US / MeOH表面活性剂萃取后,介孔材料保持六边形结构和高表面积。此外,结构的热收缩率按以下顺序减小:Si(0.6%)展开▼