CN110586050A

CN110586050A - Hydrophobic Y molecular sieve for VOCs adsorption and preparation method thereof

Info

Publication number: CN110586050A
Application number: CN201910883157.6A
Authority: CN
Inventors: 刘庆岭; 史佳琦; 郑燕飞; 赵倩; 宋春风; 纪娜
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2019-09-18
Filing date: 2019-09-18
Publication date: 2019-12-20

Abstract

The invention belongs to the field of VOCs treatment, and particularly relates to a hydrophobic Y molecular sieve for VOCs adsorption and a preparation method thereof. The whole preparation method is simple in process, mild to the environment and free of using precision instruments, and the hydrophobically modified molecular sieve keeps the inherent good adsorption performance of the molecular sieve on VOCs, so that the method has a wide application prospect in industrial production for adsorbing water-containing VOCs.

Description

Hydrophobic Y molecular sieve for VOCs adsorption and preparation method thereof

Technical Field

The invention belongs to the field of VOCs treatment, and particularly relates to a hydrophobic Y molecular sieve for VOCs adsorption and a preparation method thereof.

Background

Volatile Organic Compounds (VOCs) are a general term for organic compounds having a melting point lower than room temperature and a boiling point of 50 to 260 ℃. With the development of industrialization, the emission of VOCs is increasing, and as an important precursor of photochemical smog and Secondary Organic Aerosol (SOA), VOCs pose a serious threat to the environment. In addition, most VOCs have high toxicity and can cause neurological dysfunction and cellular carcinogenesis, which can have serious effects on human health. Thus, efficient removal of VOCs has become one of the most urgent research areas.

Several techniques for the treatment of VOCs have been developed, including catalytic oxidation, condensation, absorption, and adsorption. However, in practical applications, the oxidation technique requires excessive operating costs for removing VOCs, high reaction temperatures, and long residence times. In terms of biological treatment, the removal efficiency of VOCs is low and the duration is long. Furthermore, the secondary treatment of the scrubbing liquid and the absorbent also increases the operating costs of the condensation and absorption technology. Compared to these techniques, adsorption processes are widely used to remove low concentrations of VOCs due to their simplicity of operation, high efficiency, and relatively low operating costs, where the type and nature of the adsorbent is critical to the adsorption technology. The efficient adsorbent needs to have the characteristics of large specific surface area, high adsorption capacity, hydrophobicity, easiness in regeneration and the like, and the traditional activated carbon material is inflammable, difficult to regenerate, short in service life, poor in adsorption performance in a waste gas environment with high humidity and difficult to apply to actual industrial production. Therefore, there is an urgent need to develop an environmentally friendly, highly efficient and hydrophobic adsorbent for VOCs.

Disclosure of Invention

The invention aims to provide a hydrophobic Y molecular sieve for absorbing VOCs and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a hydrophobic Y molecular sieve for VOCs adsorption comprises the steps of paving an activated Y-shaped molecular sieve on the surface of a porcelain gray dish by adopting a vapor deposition method, placing polydimethylsiloxane around the Y-shaped molecular sieve, placing the Y-shaped molecular sieve in a muffle furnace, treating for 2-6 hours at 200-235 ℃, and cooling to room temperature to obtain the hydrophobic Y molecular sieve coated with the polydimethylsiloxane.

The activation process of the Y-type molecular sieve comprises the steps of placing the Y-type molecular sieve in a muffle furnace for roasting and activating, wherein the roasting temperature is 450-650 ℃, and the roasting time is 1-3 hours.

The preparation method of the polydimethylsiloxane comprises the following steps: mixing the polydimethylsiloxane prepolymer and the curing agent according to the mass ratio of 13-10: 1, stirring at room temperature for 20-30 min, standing to remove bubbles, and heating in an oven at 80-100 ℃ for 3-5 h to obtain the polydimethylsiloxane prepolymer.

The mass ratio of the activated Y molecular sieve to the polydimethylsiloxane is 2-1: 1.

The application also comprises the hydrophobic Y molecular sieve for absorbing the VOCs, which is obtained by the preparation method.

Compared with the prior art, the invention has the beneficial effects that:

the molecular sieve has the unique properties of simple synthesis, high adsorption capacity, good thermal stability and the like, and is a good candidate material as a VOCs adsorbent. Polydimethylsiloxane (PDMS) is low cost, safe, non-toxic, and exhibits excellent hydrophobicity after curing. The polydimethylsiloxane is coated on the surface of the molecular sieve by a vapor deposition method to endow the molecular sieve with hydrophobicity. The whole preparation method is simple in process, mild to environment and free of using precision instruments, and the hydrophobically modified molecular sieve keeps the inherent good adsorption performance of the molecular sieve on VOCs, so that the method has wide application prospects in adsorbing water-containing VOCs in industrial production.

Drawings

FIG. 1 is an XRD spectrum of PDMS @ Y-1 and the original Y molecular sieve of the sample in example 1;

FIG. 2 is the acetone adsorption breakthrough curves for sample PDMS @ Y-1 and the original Y molecular sieve in example 1;

FIG. 3 is a graph showing the effect of wettability of the sample PDMS @ Y-1 and the original Y molecular sieve in example 1;

FIG. 4 is a graph of the static water absorption of the sample PDMS @ Y-1 and the original Y molecular sieve of example 1.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments.

Example 1: 1g of a commercially available CBV-712 type Y molecular sieve was weighed and placed in a muffle furnace to be calcined at 550 ℃ for 1.5h for use. Weighing 2g of commercially available Dow Corning SYLGARD 184 polydimethylsiloxane prepolymer and 0.2g of curing agent in a beaker, stirring at room temperature for 30min to mix uniformly, standing to remove bubbles, and heating in an oven at 80 ℃ for 3h to cure. Weighing 0.6g of activated Y molecular sieve, paving the Y molecular sieve on the surface of a porcelain grey dish as far as possible to form a uniform thin layer, placing 0.3g of solidified polydimethylsiloxane fragments around the Y molecular sieve, sealing the porcelain grey dish by using an aluminum foil, placing the porcelain grey dish into a muffle furnace, treating the porcelain grey dish at 235 ℃ for 4 hours, and cooling the porcelain grey dish to room temperature to obtain the polydimethylsiloxane-coated hydrophobic Y molecular sieve, wherein the label is PDMS @ Y-1.

The XRD spectrums of PDMS @ Y-1 and the original Y molecular sieve are shown in figure 1, and it can be seen that the crystal structure of the molecular sieve is not changed by coating PDMS on the surface of the Y molecular sieve by a vapor deposition method.

FIG. 2 is a penetration curve of PDMS @ Y-1 and an original Y molecular sieve for adsorbing acetone, and dynamic adsorption amounts of PDMS @ Y-1 and the original Y molecular sieve for acetone are calculated by the curve to be 77.11mg/g and 75.53mg/g respectively, which shows that the hydrophobic modification method can retain inherent porosity of the Y molecular sieve and does not affect the adsorption performance of the Y molecular sieve for VOCs.

FIG. 3 is a graph showing the wettability effect of PDMS @ Y-1 and an original Y molecular sieve, and it can be seen that water drops rapidly spread on the surface of the original Y molecular sieve and completely wet solid powder, and the droplets on the surface of the modified Y molecular sieve are in a globular shape and can stably stay without wetting the solid powder, thereby visually and clearly showing that the material coated with PDMS by a vapor deposition method has excellent hydrophobicity.

FIG. 4 shows the static water absorption of PDMS @ Y-1 and the original Y molecular sieve, the water absorption of the unmodified Y molecular sieve is 15.45% under the same conditions, the water absorption of the material coated with PDMS is 8.75%, and the water absorption is significantly reduced, which confirms that the modified Y molecular sieve has good hydrophobicity.

Example 2

The vapor deposition temperature was changed to 200 ℃ and the remaining steps were the same as in example 1. The dynamic adsorption capacity of PDMS @ Y-2 to acetone obtained in the sample is 75.57mg/g, which is not reduced compared with the original molecular sieve (75.53mg/g), and shows that the porosity of the Y molecular sieve is completely retained after modification, but the hydrophobicity is slightly lower than that of the sample in example 1, and the static water absorption capacity is 9.13%.

Example 3

The vapor deposition time was shortened to 2 hours and the remaining steps were the same as in example 1. The dynamic adsorption capacity of the obtained sample PDMS @ Y-3 to acetone is 76.64mg/g, which shows that the porosity and adsorption performance of the original Y molecular sieve are completely retained, but the sample has poor hydrophobicity and the static water absorption capacity is 9.42%.

Example 4

The mass ratio of the Y molecular sieve to the polydimethylsiloxane was changed from 2:1 to 1:1, and the rest of the procedure was the same as in example 1. The dynamic adsorption capacity of the obtained sample PDMS @ Y-4 to acetone is 73.83mg/g, the porous structure of the Y molecular sieve is basically reserved, the hydrophobicity of the sample PDMS @ Y-4 is superior to that of PDMS @ Y-1, and the static water absorption capacity of the sample PDMS @ Y-4 is 8.38%.

Example 5

The vapor deposition time was extended to 6 hours and the rest of the procedure was the same as in example 1. The dynamic adsorption capacity of the obtained sample PDMS @ Y-5 to acetone is 70.64mg/g, which is reduced compared with the original Y molecular sieve, and shows that the deposition time is too long, so that partial pores of the Y molecular sieve are blocked, and the adsorption performance is reduced, but the sample shows the best hydrophobicity, and the static water absorption capacity is 7.66%.

According to the embodiments 1 to 5, the polydimethylsiloxane vapor deposition method can improve the hydrophobicity of the Y molecular sieve, and can well retain the inherent porosity and adsorption performance of the Y molecular sieve, so that the method is suitable for adsorbing VOCs in actual industrial production. In addition, the longer deposition time and the increased dosage of polydimethylsiloxane are both beneficial to enhancing the hydrophobicity of the material, but the longer deposition time or the excessive dosage of polydimethylsiloxane can block partial pores of the Y molecular sieve, so that the adsorption performance is reduced. Therefore, when the deposition time is 4 hours and the mass ratio of the molecular sieve to the polydimethylsiloxane is 2:1, the modified material has the best comprehensive performance.

The above description is only a preferred embodiment of the present invention, and for those skilled in the art, the present invention should not be limited by the description of the present invention, which should be interpreted as a limitation.

Claims

1. A preparation method of a hydrophobic Y molecular sieve for VOCs adsorption is characterized in that a vapor deposition method is adopted, the activated Y-shaped molecular sieve is paved on the surface of a porcelain gray dish, polydimethylsiloxane is placed around the Y-shaped molecular sieve, the Y-shaped molecular sieve is placed in a muffle furnace to be treated for 2-6 hours at the temperature of 200-235 ℃, and the Y-shaped molecular sieve is cooled to room temperature to obtain the hydrophobic Y molecular sieve coated with the polydimethylsiloxane.

2. The preparation method of the hydrophobic Y molecular sieve for VOCs adsorption of claim 1, wherein the activation process of the Y molecular sieve is to roast and activate the Y molecular sieve in a muffle furnace at 450-650 ℃ for 1-3 h.

3. The method of claim 1, wherein the polydimethylsiloxane is prepared by the following steps: mixing the polydimethylsiloxane prepolymer and the curing agent according to the mass ratio of 13-10: 1, stirring at room temperature for 20-30 min, standing to remove bubbles, and heating in an oven at 80-100 ℃ for 3-5 h to obtain the polydimethylsiloxane prepolymer.

4. The method for preparing the hydrophobic Y molecular sieve for absorbing VOCs according to claim 1, wherein the mass ratio of the activated Y molecular sieve to the polydimethylsiloxane is 2-1: 1.

5. A hydrophobic Y molecular sieve for VOCs adsorption obtained by the preparation method of any one of claims 1-4.