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 precise platform to control over the phase selection between SAPO-CHA and SAPO-AFI by tuning the crystallization kinetics, which could not be realized in the conventional autoclaves. A continuous flow process was also established to synthesize these two silicoaluminophosphates with high efficiency and flexibility. These results demonstrate a comprehensive strategy to achieve the minute-order synthesis of two important silicoaluminophosphates and could be very useful to direct the ultrafast synthesis of other crystalline materials.

Recent Progress in Methanol‐to‐Olefins (MTO) Catalysts

“…The remarkably reduced synthesis time was attributed to the fast heat transfer of the stainless‐steel tubular reactor in oil bath and rapid nucleation induced by the addition of SAPO‐34 seeds. In addition, Okubo and co‐workers reported the fast flow synthesis of SAPO‐34 under the assistance of seeds . With the development of new synthetic methods and the deepening mechanistic understanding of the crystallization process and MTO reaction, the synthesis efficiency of SAPO‐34 with high catalytic performance is expected be continuously improved.…”

Ultrafast synthesis of AFX-Type zeolite with enhanced activity in the selective catalytic reduction of NOx and hydrothermal stability

“…[30][31][32][33][34] Recently, the ultrafast synthesis techniques that involves tubular reactor with the assistance of seed that reduces the synthesis time of zeo-type and zeolites viz., AFI, CHA, MFI, ERI, and MOR down to several minutes were reported by us. 30,[35][36][37][38][39][40][41][42] Table S1 † compares the experimental conditions of these zeolites with the current study. Tubular reactor has proven effective to overcome the thermal lag faced in conventional autoclave (Fig.…”

Synthesis of ATN‐Type FeAPO‐39 Molecular Sieves without Solvent using the Additional Structure‐Directing Effect of the Iron Source

“…Traditionally, the syntheses of aluminophophate‐based zeolites usually required the presence of solvents such as water and alcohols. The use of solvent not only caused high autogenous pressure, but also brought about the dissolution of inorganic‐sources in the solvent, which gave rise to waste production and low synthesis efficiency. In order to solve these problems, great efforts have been devoted to developing new synthesis strategy.…”

“…More importantly, this synthesis route can reduce waste generation and increase zeolite yield. [6c], However, up to now only several aluminophosphate molecular sieves including AFI, AEL, CHA, SOD and GIS were created by this method. [6c], [7c], Thus, from both the fundamental and technological points of view, extending this method to other topology structures is highly desirable.…”