A kind of high silicon ZSM-5 molecular sieve for adsorbing vocs and its preparation method and application

Abstract

The invention relates to a high-silicon ZSM-5 molecular sieve for adsorbing VOCs and its preparation method and application. The preparation method of the high-silicon ZSM-5 molecular sieve comprises the following steps: 1) Alkali source, template agent, aluminum source, pH buffer agent, silicon source and ZSM‑5 molecular sieve seed crystals were added to water and mixed uniformly to obtain a gel; 2) the gel in step 1) was placed in a hydrothermal kettle for high-temperature aging, and then hydrothermal crystallization was performed. After filtering, washing and drying, the high silicon ZSM‑5 molecular sieve is obtained. Compared with the prior art, the present invention can make silicon better enter the skeleton during the synthesis process, improve the utilization rate of silicon, and controllably adjust the silicon-aluminum ratio of the product through the feeding ratio, and the prepared high-silicon ZSM The content of cations (sodium ions, potassium ions or organic amine ions) in ‑5 molecular sieve is low, the ratio of silicon to aluminum is higher than 200, and the hydrophobicity is strong. It shows excellent performance in the adsorption and purification of VOCs waste gas with large air volume, low concentration and high humidity. .

Description

technical field [0001] The invention belongs to the technical field of high-silicon ZSM-5 molecular sieve synthesis, and relates to a high-silicon ZSM-5 molecular sieve for absorbing VOCs, a preparation method and application thereof. Background technique [0002] Volatile organic compounds (VOCs) refer to organic compounds with a saturated vapor pressure greater than 70Pa at room temperature, including hydrocarbons, aldehydes, ketones, alcohols, ethers, esters and other organic compounds, mainly from petrochemicals, coatings, spray paints, printing, rubber, Various chemical production processes such as pesticides. VOCs discharged into the atmosphere will destroy the ozone layer in the atmosphere even at a low concentration, stimulate the human respiratory system, etc., and induce human diseases in severe cases. At present, adsorption method is one of the commonly used VOCs purification methods, which has mature technology, simple operation, low operating cost and high puri...

AI Technical Summary

Problems solved by technology

[0005] US3941871A and US4061724A reported the use of organic amines as templates to prepare high-silicon ZSM-5 molecular sieves. Metal elements such as nickel and zinc need to be added to the system. Since aluminum exists in the silicon source in the form of impurities, the ratio of silicon to aluminum in the molecular sieve is difficult to achieve. Controllable preparation, high crystallization temperature, long crystallization time, high energy consumption and high cost

[0006] CN108862311A reported using alkyl ammoniums as templates to prepare by mixing silicon source, alkali source and ZSM-5 seed crystals. No additional aluminum source was added to the system, and the aluminum in the molecular sieve was introduced in the form of impurities. Compared with silicon and aluminum It is difficult to control, and after the molecular sieve is roasted, it is treated with acid leaching with hydrochloric acid, nitric acid, etc., and then exchanged with ammonium to prepare a high-silicon H-ZSM-5 molecular sieve for VOC degradation. The crystallization time is long and the yield is low. The preparation process complex and expensive

[0008] CN1057066C has reported that solid silica gel is used as a silicon source, ethylamine or n-butylamine etc. are used as templates, and after aging at a certain temperature, high-temperature crystallization obtains a ZSM-5 molecular sieve with a silicon-aluminum ratio of 100-600, but its crystallinity Low, and uncrystallized solid silicon source and product are difficult to separate

[0009] CN103011194B reported the use of liquid silicon source, organic amine template R1, acid or alkali, crystal seed, and aluminum source to crystallize at a certain temperature to obtain gel system A, and then use solid silicon source, organic amine template R2, acid Or alkali, seed crystal, and aluminum source are mixed and crystallized at a certain temperature to obtain gel system B, and then system A and B are mixed in a certain proportion and then crystallized to obtain a silicon-aluminum ratio of 100-400 and a particle size of less than 1.3 μm ZSM-5 molecular sieve, its preparation process is loaded down with trivial details, and needs to use two kinds of silicon source and template agent, and preparation cost is high

[0010] CN107285339A reported the use of solid silicon source, tetrapropylammonium bromide or tetrapropylammonium hydroxide as a template, and urea was added to the synthesis system to prepare a silicon-aluminum ratio of 300-600 and a particle size of about 3-6 μm , a high silicon ZSM-5 molecular sieve with an aspect ratio of about 5-10, adding urea to the system increases the preparation cost, its crystallinity is low, and it is difficult to separate the incompletely reacted solid silicon source from the product

[0011] CN110294483A has reported the use of mesoporous SiO 2 As silicon source, organic amine as template agent, adding glucose, polyethylene glycol or ethanol and other dispersants to the system, aging at a certain temperature and then crystallizing at high temperature, and pickling the crystallized sample to prepare silicon ZSM-5 molecular sieve with a high silicon-aluminum ratio of 200-1000, but mesoporous SiO 2 The preparation cost is relatively high, and at the same time, due to the addition of glucose and dispersant, and the prepared samples need to be pickled, the production process is increased and the cost is increased.

[0012] Therefore, the currently existing technology for preparing high-silicon ZSM-5 molecular sieves has cumbersome synthesis steps, low single-pot yield, and needs to add more organic additives, which increases the preparation cost and is not conducive to industrial production.

Images