Microporous structure control of SiO2-ZrO2 composite membranes via Yttrium doping and an evaluation of thermal stability

Long-term thermal stability is one of the biggest challenges in the utilization of inorganic ceramic membranes in high-temperature separation and membrane reactor applications. This work demonstrated that yttrium doping into SiO2-ZrO2 enabled a membrane to maintain stable N-2 permeance in a long-term permeation test at 850 degrees C. Characterization techniques such as DLS, FTIR, XRD, and N-2 adsorption confirmed that doping with an yttrium/zirconium molar ratio of 1/9 was optimal. A comparison of the thermal stabilities of pristine SiO2-ZrO2 and Y-doped SiO2-ZrO2 samples calcined at 550-850 degrees C via XRD and N-2 adsorptions revealed that doping with yttria significantly minimized phase segregation and microstructural densification. Furthermore, a membrane prepared at 550 degrees C from pristine SiO2-ZrO2 showed an immediate decline in N-2 permeance from 6.0 x 10(-6) to 0.75 x 10(-6) mol m(-2) s(-1) Pa-1 during a 20-hour, long-term, thermal-stability test conducted at 850 degrees C. By contrast, after 24 h at 850 degrees C a Y-SiO2-ZrO2-derived membrane showed a reduction of only 5.5 x 10(-6) to 5.0 x 10 -6 mol m(-2) s(-1) Pa-1. Thus, the improved thermal stability of this SiO2-ZrO2 composite via yttrium doping heralds the opportunity for ceramic membranes that are more robust. [GRAPHICS] .

Automated summary

This study demonstrated that yttrium doping improved the thermal stability of SiO2-ZrO2 composite, enabling it to maintain stable permeance and minimizing phase segregation and microstructural densification at high temperatures. In comparison, the pristine SiO2-ZrO2 showed a rapid decline in permeance under high-temperature conditions.