Zeolite membranes with reduced thickness
and high continuity are
of paramount importance for accelerating selective gas separation
for resemblant molecules, and the synthesis of such membranes remains
a grand challenge. Herein, we developed an interzeolite conversion
synthesis approach to grow NaA zeolite membranes on NaX. The conversion
of NaX into NaA proceeded via mild hydrothermal treatment of a dilute
synthesis solution, preferentially forming a continuous polycrystalline
NaA layer on the surface of NaX, which was precrystallized on a porous
alumina support. The thickness of the NaA zeolite membrane was successfully
controlled to the submicron scale (500 nm). The synthesized NaA membrane
functioned as a selective separator for C2H2 and C2H4 gases. Taking the traditionally in
situ grown membrane as a reference, the interzeolite-derived membrane
exhibited a 3.5-fold separation factor and ∼4.0 times C2H2 permeance. This approach provides an alternative
synthesis option for zeolite membranes with advanced properties, and
high efficiency in terms of superior gas selectivity and permeability
is promising in precise gas separation.
igh-silica SSZ-13 zeolite membranes are promising in industrial separations of light gases and continuous membranes are highly demanded for better separation performances. Herein, pure-phase, continuous and thin SSZ-13 zeolite membranes were synthesized using dual templates of N,N,Ntrimethtyl-1-adamantammonium hydroxide(TMAdaOH) and tetraethylammonium hydroxide(TEAOH). Systematical investigations of TMAdaOH/TEAOH ratios and their concentrations show that TMAdaOH acts as the main structure-directing agent in the formation of the SSZ-13 zeolite. TMAdaOH cooperatively plays with TEAOH in promoting the SSZ-13 crystal intergrowth to form a continuous polycrystalline membrane. Additionally, appropriate introduction of TEAOH is able to adjust the membrane thickness to the crystal-comparable size of ca. 2.0 μm. The SSZ-13 membranes are further applied for N2/NO2 separation, which is firstly reported on zeolite membranes. The gas permeation results show that the SSZ-13 membrane synthesized by the dual-template approach exhibits selective separation of N 2 over NO 2 with N 2 /NO 2 separation factor of 7.6 and N 2 permeance of 1.66×10 -8 mol•m -2 •s -1 •Pa -1 .
Materials as stationary phase are crucial for chromatographic analysis of hydrogen gas isotopes. Herein, the Cu-Fe/ZSM-5 zeolite with ion-exchanged Fe3+-Cu2+ is prepared for H2/D2 chromatographic analysis. High-resolution H2/D2 separation is...
Highly permeable zeolite membranes are desirable for fast gas separation in the industry. Reducing the membrane's thickness is deemed to be an optimal solution for permeability improvement. Herein, we report the synthesis route of thin SSZ-13 zeolite membranes via the conversion of template-contained surface gels. The synthesis gel is fully crystallized into crack-free SSZ-13 membranes assisted with dual templates of N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) and tetraethylammonium hydroxide (TEAOH). The specific functions of TMAdaOH for structure directing and TEAOH for crystallization regulating are well discussed. Thin surface gel layer is impregnated onto porous alumina with subsequent crystallization into a 500 nm thick membrane. This submicron-thick membrane exhibits high H 2 permeance with 50 × 10 −8 mol s −1 m −2 Pa −1 during hydrogen separation. Meanwhile, the separation factors are retained around 23.0 and 31.5 for H 2 /C 2 H 6 and H 2 /C 3 H 8 , respectively. This approach offers a possibility for obtaining high-quality zeolite membranes for efficient hydrogen separation.
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