Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Cracow, Poland.
Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Cracow, Poland.
Ultrason Sonochem. 2021 Jun;74:105581. doi: 10.1016/j.ultsonch.2021.105581. Epub 2021 May 3.
In this paper, the ultrasonic-assisted desilication technique was reported as an attractive and efficient way for the preparation of hierarchical zeolites with MFI structure type. The prepared materials were used as active catalysts for the dehydration of ethanol into diethyl ether and ethylene. For all catalysts, the selectivity to diethyl ether was ca 95% or higher up to 210 °C, with catalytic activity in the range of 40-68%. In case of desilicated zeolites, at 270-290 °C, the conversion of ethanol was full with selectivity to ethylene ca 80%. MFI-type commercial zeolite was treated with a sodium and/or tetrabutylammonium hydroxide aqueous solutions (NaOH or NaOH/TBAOH) for 30 min. In the case of the application of ultrasounds, a QSonica Q700 sonicator (60 W and 20 kHz) equipped with a "1" diameter horn was used. In all cases, desilication was performed in an ice bath in order to keep the procedure conditions at low temperature. It was indicated that the use of ultrasounds during desilication procedure caused higher extraction of silicon and aluminum, which was connected with an elevated mesoporosity in relation to the samples modified in the absence of ultrasounds. Ultrasonic-assisted treatment of MFI-type zeolite caused also an apparent formation of numerous holes inside zeolite grains, resembling the look of "swiss cheese". Furthermore, it was indicated that the samples prepared using ultrasonic irradiation exhibited enhanced catalytic properties in the dehydration of ethanol. For instance, MFI-type zeolite treated with NaOH/TBAOH alkaline mixture containing 10 mol% of TBAOH in the presence of ultrasounds (M-10 s) demonstrated higher both conversion of ethanol (59% vs. 47%) and selectivity to diethyl ether (95% vs. 93%) in comparison with zeolite modified conventionally (M-10c). The best catalyst was zeolite ultrasonically desilicated with NaOH/TBAOH solution of 70 mol% of TBAOH (M-70s). Generally, this catalyst indicated the highest conversion of ethanol, very high selectivity to diethyl ether (94-100%) at 150-210 °C and the highest selectivity to ethylene among investigated catalysts (21%, 66% and 84%) at 230 °C, 250 C and 270 °C.
本文报道了一种超声辅助脱硅技术，用于制备具有 MFI 结构类型的分级沸石。所制备的材料被用作乙醇脱水成乙醚和乙烯的活性催化剂。对于所有催化剂，在 210°C 下，乙醚的选择性高达 95%或更高，催化活性在 40-68%范围内。对于脱硅沸石，在 270-290°C 下，乙醇的转化率完全，乙烯的选择性约为 80%。MFI 型商业沸石用氢氧化钠和/或四丁基氢氧化铵水溶液（NaOH 或 NaOH/TBAOH）处理 30 分钟。在应用超声的情况下，使用 QSonica Q700 超声仪（60 W 和 20 kHz）配备一个“1”直径的变幅杆。在所有情况下，脱硅都是在冰浴中进行的，以保持低温下的程序条件。结果表明，在脱硅过程中使用超声会导致硅和铝的更高提取，这与在没有超声的情况下进行的样品的中孔率升高有关。超声辅助处理 MFI 型沸石还会导致沸石晶粒内部形成大量的孔，类似于“瑞士奶酪”的外观。此外，结果表明，使用超声辐射制备的样品在乙醇脱水反应中表现出增强的催化性能。例如，在存在超声的情况下，用含有 10 mol% TBAOH 的 NaOH/TBAOH 碱性混合物处理的 MFI 型沸石（M-10s）与传统方法改性的沸石（M-10c）相比，表现出更高的乙醇转化率（59%比 47%）和乙醚选择性（95%比 93%）。最佳催化剂是用 NaOH/TBAOH 溶液超声脱硅，其中 TBAOH 的摩尔分数为 70 mol%（M-70s）。通常，该催化剂在 150-210°C 下表现出最高的乙醇转化率、非常高的乙醚选择性（94-100%），以及在 230°C、250°C 和 270°C 下所有催化剂中最高的乙烯选择性（21%、66%和 84%）。
