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    Home > Chemicals Industry > New Chemical Materials > Transition metal oxide molecular sieve achieves effective separation at higher temperature

    Transition metal oxide molecular sieve achieves effective separation at higher temperature

    • Last Update: 2021-06-28
    • Source: Internet
    • Author: User
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      High-purity C 2 H 4 and C 2 H 2 are the most commonly used basic raw materials for synthetic chemicals in industry
    .
    In the process of industrial production of ethylene, acetylene by-products will inevitably be produced.
    Even a small amount of acetylene can cause poisoning of the ethylene polymerization catalyst, and explosions in severe cases

    .
    At the same time, ethane is also an unavoidable by-product in the process of industrial ethylene production.
    The relative volatility and boiling point of the two are also very close, and the traditional low-temperature rectification energy consumption is large

    .
    Therefore, the separation of C 2 hydrocarbon gas mixtures such as C
    2 H 6 , C 2 H 4 and C 2 H 2 has always been a major challenge facing the chemical industry .
    Therefore, choosing an appropriate method to effectively separate the two is also a process worth exploring .


      

      Adsorption-based separation methods, such as adsorption separation and membrane separation, are effective methods to solve this problem because of their high efficiency and low cost
    .
    In recent years, many researchers have developed different types of microporous materials such as metal organic framework materials (MOFs), zeolites and activated carbons for the separation of C
    2 hydrocarbons, and have achieved good separation performance at low temperatures
    .
    However, the C
    2 H 4 production process requires high temperature, and the separation process at low temperature causes a lot of energy waste
    .
    So far, there have been few attempts to separate C
    2 hydrocarbons at high temperatures
    .
    And most of the separation temperature is not high enough

    .
    Therefore, the development of porous materials for high-temperature separation of C
    2 hydrocarbons is very important
    .

      Recently, the team of Professor Zhang Zhenxin and Li Yanshuo of Ningbo University reported that a kind of transition metal oxide molecular sieves (ZOMOs) based on ε-Keggin units, namely sodium cobalt molybdate (Na-CM), can be realized at higher temperatures.
    Effective separation of C
    2 hydrocarbons
    .

      

      Figure 1.
    POM structure model based on ε-Keggin unit

    .

      The material cavity (7.
    4 Å) is formed by connecting ten POM units, and the opening is only 3.
    4 Å, which
    is close to the size of C
    2 hydrocarbon gas
    .
    This material has different adsorption properties for C
    2 H 6 , C 2 H 4 and C 2 H 2 , and has strong interaction with C 2 H 4 and C 2 H 2 , and has a high ideal solution adsorption theory ( IAST) selectivity
    .

      

      Figure 2.
    Na-CM at 85℃, 100kPa, (a) C
    2 H 4 /C 2 H 6 , (b) C 2 H 2 /C 2 H 6 , (c) C 2 H 2 /C 2 H The breakthrough curve of 4 and (d) the corresponding gas breakthrough selectivity
    .

      The material shows good performance in terms of repeatability, stability and separation performance.
    Dynamic competitive adsorption experiments show that the material can effectively separate C
    2 binary mixtures and even ternary mixtures, and has high selectivity
    .
    When the temperature is increased to 85 ℃, the material can still maintain good separation performance

    .

      This result was recently published on Angewandte Chemie International Edition.
    The first author of the article is Wang Jie, a master's student at Ningbo University

    .

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