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采用微波加热离子交换方法改性天然沸石以增加其介孔容量,同时以传统回流加热离子交换方法制备的改性沸石作为对照,用非定域密度函数理论(NLDFT)和氮气在柱状、孔状硅介质上的吸附模型为依据,计算不同加热方法改性沸石的孔径分布曲线。结果表明,所选择模型和实际测得的样品等温线有很高的拟合程度。与传统BJH方法相比,NLDFT方法可以提供更多的孔径分布信息。相对于未改性沸石,微波加热改性天然沸石的介孔直径增加3~5 nm,而常规回流加热只增加直径在3 nm以下的介孔。这主要是由于沸石颗粒在回流加热过程中相互剧烈摩擦,导致沸石的结构受到破坏,沸石由层片状变为粉末状,而微波加热改性后的天然沸石仍保持原来的层片状。微波加热法提供了一个高效的天然沸石介孔容量增加途径。
The natural zeolite was modified by microwave-heated ion exchange to increase its mesopore capacity. At the same time, the modified zeolite prepared by the traditional reflux heating ion exchange method was used as a control. Using non-localized density function theory (NLDFT) and nitrogen in columnar, Based on the adsorption model of silica media, pore size distribution curves of zeolites modified by different heating methods were calculated. The results show that the selected model and the actual measured sample isotherms have a high degree of fit. Compared with the traditional BJH method, NLDFT method can provide more information about pore size distribution. Compared with the unmodified zeolite, the mesopore diameter of modified natural zeolite by microwave heating increased by 3 ~ 5 nm, while the conventional reflux heating only increased the mesopore diameter of 3 nm or less. This is mainly due to severe friction between the zeolite particles during the reflow heating, resulting in the destruction of the zeolite structure. The zeolite turns from lamellar to powdery, while the natural zeolite modified by microwave heating retains its original lamellar shape. Microwave heating provides an efficient way to increase the mesoporous capacity of natural zeolites.