Method for synthesis of mesoporous molecular sieve and byproduct cryolite by use of fluosilicic acid

Abstract

The present invention discloses a method for synthesis of mesoporous molecular sieve and byproduct cryolite by use of fluosilicic acid. The aminated fluosilicic acid amide is added into a surfactant solution, heated, stirred, and uniformly dispersed; solution pH is adjusted to 3-7 with queous ammonia, and the solution is stirred and refluxed; the solution is filtered by suction and separated; the resulting filter cake is washed and dried to obtain a surfactant-containing mesoporous molecular sieve precursor, and mesoporous molecular sieve Si-MMS is obtained by pickling or roasting; if the fluorosilicic acid is mixed with an aluminum source or a titanium source, corresponding Si / Al-MMS or Si / Ti-MMS molecular sieve can be obtained; the resulting filtrate is treated with aqueous ammonia to adjust the pH to 4-7, the aluminum source is added, the pH is adjusted to 2 with an acid, the filtrate is heated to 50-100 DEG C and is thermally insulated for 10-50min; sodium sulfate solution is added, and the filtrate is thermally insulated for 0.5-1.5 h at 50-90 DEG C; and the filtrate is filtered, and the filter cake is washed, and dried to obtain the cryolite. According to the method, silicon as a silicon mesoporous material precursor is recycled, silicon recovery rate reaches 100%; fluorine in the filtrate is directly prepared into the cryolite, and the fluoride recovery rate reaches 98%.

Description

technical field [0001] The invention belongs to the field of comprehensive utilization of resources, and in particular relates to a method for synthesizing mesoporous molecular sieves by using fluosilicic acid and producing cryolite by-product. Background technique [0002] Fluorosilicic acid, a by-product of phosphate fertilizer, is produced by absorbing silicon fluoride gas produced during the production of phosphoric acid from phosphate rock by water. Phosphate fertilizer by-product fluosilicic acid only a small part is fully utilized, most of them are wasted. In China, only a few companies have the ability to use fluosilicic acid to produce cryolite and other high value-added products. Most phosphate fertilizer factories have a large amount of industrial fluosilicic acid prepared into sodium fluosilicate and other fluosilicate backlogs, even Some phosphate fertilizer plants directly discharge silicon fluoride gas into the atmosphere or directly discharge fluosilicic aci...

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Problems solved by technology

Chinese patent CN201410308680.3 discloses a method for preparing potassium fluoride to co-produce silica by using fluosilicic acid. Potassium fluoride and silica are prepared by reacting potassium carbonate, calcium hydroxide and fluosilicic acid, but the process flow Too complex and low added value

The latest progress is to use the fluorine in fluosilicic acid to produce hydrogen fluoride, such as the Russian patent USSR174610, which uses electrodialysis to purify the fluosilicic acid solution, and then adds concentrated sulfuric acid to decompose hydrogen fluoride. Industrialized production of the Buss process, etc., but these methods have certain disadvantages, such as high energy consumption, and do not make good use of silicon resources

Chinese patent 200310104114.2 discloses a preparation method of ammonium bifluoride, which uses fluorine-containing waste gas and fluorosilicic acid as raw materials, ammonium, filtration, and washing to obtain ammonium fluoride solution, then concentrates, decomposes, and dries to obtain ammonium bifluoride product. In this patent, the high energy consumption in the process of concentration and decomposition leads to the energy consumption of the entire production process, and the concentration of dilute ammonia water produced in the process of concentration and decomposition of ammonium fluoride solution is low. It is a big problem to scale up to industrial production for recycling or treatment.

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