Zeolite Preparation Coupled with Alkali Recovery from Catalytic Gasification Ash by One-Step Hydrothermal Treatment

Catalytic gasification ash (CGA) imposes potential hazards to the environment and additional costs for gasification. To recover the alkali catalysts and to reutilize CGA, the deactivation of Na2CO3, zeolite preparation by hydrothermal processing of CGA (HPGA), and the Cu2+ adsorption behaviors of the prepared zeolite and its kinetics were studied. The results show that the catalytic reactivity of Na2CO3 is very high, but Na2CO3 is easy to generate deactivated sodium aluminum silicate (NaAlSiO4). These reactions are responsible for the deactivation of Na2CO3, but fortunately, the process of Na2CO3 deactivation during gasification also can accomplish the activation of Al and Si matters in coal. As a result, CGA can directly transform into zeolite by HPGA without further alkali addition and sintering treatment. Simultaneously, 41% of Na can be recovered during HPGA, and the prepared zeolite has a much higher Cu2+ adsorption capacity compared with CGA. The novel process of catalyst recovery coupled with zeolite preparation provides a feasible and environmentally friendly way for utilization of CGA without alkali addition and sintering treatment.