Seed-directed fluorine-free synthetic method of AlPO4-34

Abstract

A seed-directed fluorine-free synthetic method of AlPO4-34 is characterized in that relative molecular sieve crystal that is ground is used as seed crystal, the seed crystal is added into a mixture ofan aluminum source, a phosphorus source, an organic templating agent and water in the molar ratio of Al2O3:P2O5:R:H2O being 1.0:(0.8-1.0):(7.0-9.0):50; synthetic gel is made by uniform mixing and istransferred into a stainless steel kettle; hydrothermal crystallization is performed under 170-200 DEG C and self-generated pressure for 1-20 days; the crystalized material is cooled naturally to roomtemperature before conventional molecular sieve aftertreatment; cooling is performed before washing and drying to obtain the finished product.

Description

technical field [0001] The invention relates to an aluminum phosphate molecular sieve AlPO 4 The synthesis of -34, specifically, is to use suitable molecular sieves as seed crystals instead of hydrofluoric acid, and prepare high-crystallinity AlPO under the action of suitable organic templates. 4 -34 molecular sieves. Background technique [0002] AlPO 4 -34 is composed of aluminum phosphate, its structure is similar to chabazite, it has open channels of eight-membered rings, and double six-membered rings are interlaced to form a cage structure skeleton, in which 1 / 3 of Al adopts six coordination, and adjacent Al passes through F Or OH bridging, 2 / 3 of Al adopts four coordination to form AlO 4 tetrahedron, with PO 4 The tetrahedrons are connected alternately. Its unique structure and weak acidity make it stable when used as a catalyst for the conversion of methanol to olefins (MTO), the short reaction life of the catalyst can be improved, and it has broad application pr...

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Problems solved by technology

[0004] CN 106672990 A discloses a small grain AlPO 4 The synthetic method of -34 aluminum phosphate molecular sieve, but this method has used the highly corrosive hydrofluoric acid and the expensive tetraethylammonium hydroxide templating agent in the synthesis, and this not only has increased cost, also can be produced after the product is carried out Environmental pollution during the processing

CN 102092738 B discloses a hydrothermal fluorine-free synthesis of AlPO 4 -34 method, however, it was found that due to the fluorine-free composition of AlPO 4 The crystallization of -34 is very sensitive to the presence of water, and the interference of water in its structure formation cannot be controlled only under hydrothermal conditions, resulting in the formation of molecular sieves with other structures, and the purity of the product is not high

CN 104445244 B discloses a kind of aluminum phosphate molecular sieve AlPO 4 -34 and its fluorine-free preparation method, but this method needs to firstly mix the aluminum source, water and phosphorus source to obtain a semi-dried gel after evaporation and concentration of the gel, and then add an organic template to make a synthetic colloid. This method Not only makes the operation process complicated, but also the reaction system is difficult to stir evenly, especially in the case of large-scale synthesis

CN 102424396 A discloses a fluorine-free synthesis of AlPO by a mixed solvothermal method 4 -34 method, which is characterized in the synthesis of AlPO with isopropanol or ethylene glycol and water mixed solvent 4 -34, but the synthesis disclosed by this method requires the use of a large amount of organic solvents, which not only increases the cost, but also easily causes environmental pollution during the processing of the late synthesis products

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