Tuning of textural properties of germanosilicate zeolites ITH and IWW by acidic leaching

摘要

The possibility to adjust textural properties of ITH and IWW zeolites by the variation of conditions(e.g.temperature, p H, duration) of acidic leaching was shown. While the growth of the temperature of acid treatment caused the increasing amount of leached Ge atoms and enhancing volumes of both micro and mesopores at 80 ℃, the mesopore volume in ITH(Si/Ge = 3.4 and 5.8) and IWW(Si/Ge = 3.3) zeolites changed with the duration of the treatment(p H = 2; T = 80 ℃) as follows: 96 h < 1 h < 24 h. Independently on the chemical composition and zeolite topology, the treatment of germanosilicate zeolites at p H = 2–7 resulted in development of both micro and mesoporosity accompanied by the extraction of substantial amount of Ge atoms, while the increasing acidity up to p H = 0 resulted in some reduction of Ge extraction and in the development of mesopores at maintained value of micropore volume when compared with initial germanosilicates. The higher activity(i.e. number of reactant molecules converted per active site) of germanosilicate with modified micro-mesoporous channel system in comparison with parent IWW zeolite in esterification of levulinic acid was attributed to enhanced accessibility of active sites.