Highly efficient and greener synthesis of TS-1 in a flow system by recycling the mother liquid

In this work, a highly efficient synthetic route for TS-1 zeolites has been developed in a flow system, a greener preparation method is further proposed by recycling the mother liquid. The prepared TS-1 by recycling the mother liquid contained no extraframework Ti species with uniform size and high crystallization as well as excellent catalytic performance for cyclohexanone ammoximation in the flow system containing a tubular reactor and an autoclave. As the fast heating rate of flow chemical process, the crystallization time was shortened to 20 min at 175 °C. Due to the short crystallization, hardly TPAOH participated in the Hofmann elimination reaction except for the structure-directing usage. The full recycle of remained TPAOH in the mother liquid was reused after being concentrated via vacuum distillation, and this novel recycling technology could have 98.5% TPAOH utilization as well as 98.3% TS-1 yield. These results indicate that the flow chemical process plays a key role in the new greener approach for the TS-1 synthesis.