Acta Phys. -Chim. Sin. ›› 2002, Vol. 18 ›› Issue (03): 201-206.doi: 10.3866/PKU.WHXB20020303

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Study on the Formation of Mesopore during Hydrothermal Dealumination of Y Zeolite

Dong Song-Tao;Li Xuan-Wen;Li Da-Dong;Shi Ya-Hua;Nie Hong;Kang Xiao-Hong   

  1. Research Institute of Petroleum Processing,SinoPec,Beijing 100083;College of Chemistry and Molecular Engineering,Peking University,Beijing 100871
  • Received:2001-08-03 Revised:2001-11-08 Published:2002-03-15
  • Contact: Li Xuan-Wen

Abstract: Mesopore formation of Y zeolite in hydrothermal dealuminated process was studied over NH4NaY with different Na2O content.A “pseudosteady state" (PSS)was observed by merely raising temperature to 650 ℃,IR characteristic absorbency maintained and few dealumination occurred in this stage,therefore BET surface area,pore volume leveled down substantially.However,they could increase by introducing steam,even could be larger than that of the original NaY in 1 h,and could decrease by further treatment.It was pronounced that protons with high electron affinity formed in temperatureraising stage interacted strongly with frame oxygen,and brought about twist,relaxation and split of zeolite frame.However,sodalite cages with a certain amount of Na+ kept relatively stable.Then structure could be rearranged based on the stabilized sodalites under the high temperature,hydrothermal condition,but it couldn't heal over due to the existance of extraframe alumina and amorphous silica coming from framework dealumination,only sharp faujasite with damage (defects) in sodalite could be formed.This probably is the mechanism of mesopore formation.

Key words: Hydrothermal treatment, Mesopore, Mechanism, Pseudosteady state,  Diameter distribution