The role of silver species on the hydrothermal stability of zeolite catalysts

Permanent deactivation of acidic zeolite catalysts due to dealumination of the zeolite framework occurs during the regeneration under steaming at high temperature. The stability of zeolite catalysts modified with silver species is investigated. It is found that the stability of the zeolite framework can be improved during steaming by Ag ion-exchange. Silver species can prevent their correlated Al sites in zeolite catalysts from dealuminizing because of the replacement of protonic cations with Ag cations under steaming in air, and the effects of silver species decrease when the steaming treatment is carried out in nitrogen or 100% steam. Moreover, unlike phosphorus or rare earth cations, Ag modified zeolite catalysts can provide the same acid strength as protonic zeolite catalysts during the reaction after the reduction of Ag cations with hydrogen or hydrocarbons. This alternative stabilization method is expected to have serious implications for making stable zeolite catalysts in many applications.

Silver species can prevent their correlated Al sites in zeolite catalysts from dealumination because of the replacement of H+ with Ag+ under steaming in air, and their effects decrease when the steaming treatment is carried out in nitrogen or 100% steam.Figure optionsDownload as PowerPoint slideResearch highlights
► The stability of zeolite can be improved during steaming by introducing Ag+ into it.
► Ag species can prevent zeolite from dealuminizing under steaming in air.
► Their effects decrease during steaming in nitrogen or 100% steam.
► Ag–zeolite catalysts can provide the same acid sites as H-form one after reduction.