Synthesis of size-controlled boehmite sols: application in high-performance hydrogen-selective ceramic membranes. Issue 24 (13th June 2022)

• Record Type: Journal Article
• Authors: Wang, Hongsheng; Lundin, Sean-Thomas B.; Takanabe, Kazuhiro; Oyama, S. Ted
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 24(2022)
• Page Start: 12869
• Page End: 12881
• Publication Date: 2022-06-13
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2ta03148e
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Microporous Si–Ta membrane fabrication via CVD is studied with emphasis on the formation of graded and defectless γ-Al2 O3 intermediate layers using size-controlled boehmite sols. The membrane shows excellent H2 selectivity and hydrothermal stability. Abstract : A hydrogen-selective silica–tantala composite membrane was prepared by chemical vapor deposition (CVD) of tetraethyl orthosilicate (TEOS) and tantalum ethoxide (TaEO) at 650 °C. The membrane composite consisted of a thin ( ca. 15 nm) silica–tantala toplayer, a graded γ-alumina interlayer, and a porous zirconia tubular support. The graded γ-alumina interlayer was deposited via a sol–gel process using progressively smaller mono-dispersed boehmite (AlOOH) sols, with the boehmite sol nanoparticle size optimized by adjusting the solution pH and aging time. The resultant ceramic membrane exhibited high H2 selectivities over CH4, N2, and O2 of 16 000, 5000, and 640, respectively, with an H2 permeance of 1.4 × 10 −7 mol m −2 s −1 Pa −1 at 650 °C. Exposure to 16 mol% steam at 650 °C for 200 h caused an H2 permeance decline of 25%, and simultaneous H2 selectivity increase over CH4, N2 and O2 to 71 900, 42 600 and 2460, respectively. The hydrothermal stability and the final H2 selectivities are the highest ever reported for silica-based membranes. The high performance is attributed to the defect-free deposition of the silica–tantala layer due to the optimization of the graded γ-alumina interlayer. Optimization of boehmite sol particle size and stability is crucial for state-of-the-art membranes, with these results also applicable in different fields.