Synthetic method of c-axis orientated type Zn-ZSM-5 molecular sieve under action of external magnetic field

Abstract

The invention provides a synthetic method of a c-axis orientated type Zn-ZSM-5 molecular sieve under the action of an external magnetic field, and belongs to synthetic methods of Zn-ZSM-5 molecular sieves. Through the specific action of the external magnetic field, the problem of orientated preferential growth of the morphology and structure in the crystal growth process of ZSM-5 is solved. The synthetic method comprises the following steps: adding prefabricated silicalite-1 seed crystals into a Zn<2+> doped mixed gel, conducting aging under the action of an external magnetic field with a specific strength, and then conducting crystallization, drying and roasting to obtain the c-axis orientated type Zn-ZSM-5. The technique has the characteristics that the external magnetic field with the specific strength has an obvious guiding action on the grain growth of the molecular sieve, the synthesized molecular sieve monomer when placed in the position of a horizontal magnetic induction line has a c-axis orientated structure, simultaneously a zinc type ZSM-5 molecular sieve new material with c-axis direction preferential growth can be successfully synthesized by doping once, the synthetic process is simple and has good repeatability, the specific area of the new material is larger, and the technique shows excellent methanol conversion, aromatic hydrocarbon yield, anti-carbon property and stability when applied to methanol aromatization reaction.

Description

technical field [0001] The invention relates to a synthesis method of Zn-ZSM-5 molecular sieve, in particular to a synthesis method of c-axis orientation type Zn-ZSM-5 molecular sieve under the action of an external magnetic field. Background technique [0002] ZSM-5 belongs to the MFI type molecular sieve. The channel structure consists of a straight cylindrical a-axis channel with an oval cross section (the channel size is 0.54nm×0.56nm) and a Z-shaped b-axis channel with an approximately circular cross section (the channel size is 0.52nm). ×0.58nm) intersections; the difference in the nanoscale pore structure of ZSM-5 molecular sieve with different axial orientations leads to huge differences in the mass transfer characteristics, adsorption characteristics and reaction characteristics of chemical molecules in the molecular sieve pores. Since the molecular sizes of benzene (B), toluene (T) and xylene (X) are similar to the pore diameter of ZSM-5 zeolite, the ZSM-5 zeolite ...

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Problems solved by technology

[0005] The purpose of the present invention is to provide a kind of synthetic method of the c-axis orientation type Zn-ZSM-5 molecular sieve under the action of an external magnetic field, to solve the excessive dosage of template agent existing in the hydrothermal synthesis method of synthesizing nanometer ZSM-5 molecular sieve , and the crystal phase growth and anti-coking of c-axis ZSM-5, and the problem of methanol conversion rate

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