A zeolite membrane complex includes a porous support and a zeolite membrane provided on the support and composed of RHO-type zeolite. In a case where a surface of the zeolite membrane is measured by an X-ray diffraction method, a peak intensity derived from a (310) plane of RHO-type zeolite is not higher than 0.4 times a peak intensity derived from a (110) plane thereof and a peak intensity derived from a (211) plane thereof is not higher than 0.3 times the peak intensity derived from the (110) plane.

A method of producing a silicalite membrane, which includes heating an aqueous solution that includes a dopant precursor and structure-directing template agents to form silicalite seeds incorporated with a dopant, depositing a buffer layer on a ceramic substrate prior to depositing the silicalite seeds on the buffer layer, contacting the ceramic substrate with a solution including the silicalite seeds to form a silicalite layer from the silicalite seeds on the ceramic substrate, and removing the structure-directing template agents to form the silicalite membrane, where the silicalite layer includes silicalite crystals incorporated with a dopant and each of the silicalite crystals has a hollow structure which forms the pores of the silicalite layer. The silicalite membrane includes a ceramic substrate having a buffer layer formed thereon, and a silicalite layer formed on the buffer layer, where the silicalite layer includes silicalite crystals incorporated with a dopant.

The present invention discloses a new method for synthesizing a high-quality inorganic film by microwave heating, which relates to the field of preparation of inorganic materials. The method for synthesizing a high-quality inorganic film by microwave heating in the present invention allows a fine design and control of the temperature increase process during microwave heating, wherein the matrix and the synthesis solution is put into the microwave reactor at first, the temperature interval between the initial temperature and the target temperature of the synthesis solution is then divided into multiple sections, each of which sets a temperature increase rate, and then when the temperature reaches the target temperature after the designed temperature increase process, the synthesis solution reacts for a period of time at the target temperature, finally the high-quality inorganic film can be obtained after the treatment of washing and drying. The inorganic film prepared by the method of the present invention is dense and thin.

Provided is a zeolite membrane composite used for separation of a mixture, which has a high separation factor and is easily produced while maintaining a practically usable permeation flow rate. The zeolite membrane composite includes: a porous support; and an aluminosilicate zeolite membrane formed on a surface of the porous support and having a framework density of 10 or more and 17 or less. A Si/Al molar ratio of a surface of the zeolite membrane is 5 or more, and a ratio (A.sub.e/A.sub.0) of a developed membrane area A.sub.e in consideration of unevenness on the surface of the zeolite membrane to an apparent membrane area A.sub.0 not in consideration of the unevenness on the surface of the zeolite membrane is 2 or more and 20 or less.

Provided is a method for separating ammonia gas using zeolite membrane having excellent separation stability at a high temperature capable of separating ammonia gas from a mixed gas composed of multiple components including ammonia gas, hydrogen gas, and nitrogen gas to the permeation side with high selectivity and high permeability. Also provided is a method for separating ammonia by selectively permeating ammonia gas from a mixed gas containing at least ammonia gas, hydrogen gas, and nitrogen gas using a zeolite membrane, wherein the ammonia gas concentration in the mixed gas is 1.0% by volume or more.

Disclosed are a CHA zeolite membrane and a method of preparing the same, and more particularly, a CHA zeolite membrane having high capacity to separate CO.sub.2/N.sub.2 and CO.sub.2/CH.sub.4 even under wet conditions using a membrane produced using a synthetic precursor having a controlled ratio of Si and Al, a method of preparing the same, and a method of capturing and removing carbon dioxide using the membrane.

A support is a porous ceramic support for supporting a zeolite membrane. The hydraulic conductivity of the support is less than or equal to 1.1×10.sup.−3 m/s. In the support, the total content of alkali metal and alkaline earth metal in a surface part within 30 μm from a surface in a depth direction perpendicular to the surface is less than or equal to 1% by weight.

A zeolite membrane composite including a porous support and a zeolite membrane formed on a surface of the porous support. The zeolite membrane has an LTA-type crystal structure. The first atomic ratio: Si/Al of silicon element (Si) to aluminum element (Al) in the zeolite membrane is 1.29 or greater and 1.60 or less.

In production of a zeolite membrane complex, a starting material solution containing at least a structure-directing agent and FAU-type zeolite particles having an average particle diameter of 50 to 500 nm is prepared. Then, a support is immersed in the starting material solution to form a zeolite membrane on the support by hydrothermal synthesis, the zeolite membrane being composed of AFX-type zeolite. After that, the structure-directing agent in the zeolite membrane is removed.

Provided is a method for preparing a defect-free DDR molecular sieve membrane. Sigma-1 molecular sieve is used as an inducing seed crystal to prepare and obtain a continuous and compact DDR molecular sieve membrane on the surface of a porous ceramic support. An ozone atmosphere or an external field assisted technology is used to remove a template in the pores of the molecular sieve membrane at a low temperature. The invention avoids the formation of intercrystal defects and cracks, an activated DDR molecular sieve membrane has a good selectivity for separating CO2, and the membrane preparation time is significantly reduced.