Preparation, Characterization and Surface Free Energy of Nickel-Doped Silica Organic–Inorganic Hybrid Membrane for H2/CO2 Separation

Abstract

Nickel-doped silica organic–inorganic hybrid (Ni/SiO2) membranes based on tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) were prepared via a sol–gel process for H2/CO2 separation. The influence of calcination temperature and Ni-doping amount on the microstructure and surface free energy of Ni/SiO2 materials was investigated. The permeance of H2 and CO2 and vapor stability of the membranes were tested. For the Ni/SiO2 membrane, the optimal calcination temperature should be 350 °C and Ni/TEOS molar ratio is 0.1. After calcination at 350 °C, nickel element exists in form of Ni–O–Si structure and crystalline NiO with small grain size. At this temperature, the water contact angle of Ni/SiO2 film achieved a maximum of (96.1±0.4)° and the surface free energy reached the minimum. The H2 and CO2 permeance of freshly-prepared the Ni/SiO2 membrane was 7.86×10−6 and 1.50×10−6 mol m−2 Pa−1 s−1, respectively, at 25 °C and a pressure difference of 0.4 MPa. Compared with the pure SiO2 membrane, the H2 permeance and H2/CO2 selectivity of Ni/SiO2 membrane increased by 20.9% and 15.9%, respectively. After aging in the moist condition for 7 d, the H2 permeance of Ni/SiO2 membrane was reduced by 6.9% and the H2/CO2 selectivity increased by 4.7%. The Ni/SiO2 membrane showed higher H2 permeance, H2/CO2 selectivity and vapor stability than pure SiO2 membrane.