Ultrafast and Continuous Flow Synthesis of Silicoaluminophosphates

Abstract

Silicoaluminophosphates are a class of crystalline microporous materials that have been widely used as catalysts and adsorbents. Two representative silicoaluminophosphates, SAPO-CHA (also called SAPO-34) and SAPO-AFI (also called SAPO-5), were synthesized in a tubular reactor within 10 and 5 min, respectively. The addition of a milled seed with small crystal size, the pretreatment of Al and Si sources by mechanical milling, and the employment of a high temperature condition were found to be the critical factors that contributed to the enhancement of crystallization rate of SAPO-CHA. The fast-synthesized SAPO-CHA possesses only isolated Si(OAl)4 species, indicating a great potential in catalytic applications. SAPO-CHA and SAPO-AFI usually appear as a pair of competing phases during the synthesis of SAPO-CHA/SAPO-AFI because of similarities in chemical compositions and formation conditions. Here, we show that, owing to the feature of rapid heating, the tubular reactor demonstrated itself as a facile and pre...