Dissolution and Absorption: A Molecular Mechanism of Mesopore Formation in Alkaline Treatment of Zeolite

Abstract

With the aim to optimize alkaline treatment of zeolites to obtain hierarchical zeolites, dissolution and absorption mechanisms relevant to mesopore formation were investigated at an atomistic scale by density functional calculations. In the dissolution processes, dealumination is energetically more favorable than desilication, though both processes can occur. The dissolved Al species prefer to be absorbed back onto zeolite surfaces whereas the dissolved Si species tend to aggregate in solution. The dissolution process promotes but the absorption process hampers the mesopore formation, laying foundation for understanding the mesoporosity influenced by the variations of zeolite framework and solution