Voc adsorbing molecular sieve, its preparation method and application

Abstract

The application relates to the field of VOCs treatment, and discloses a VOCs adsorption molecular sieve, a preparation method and application thereof. The method comprises the following steps: 1) sequentially performing first ion exchange, calcination and second ion exchange on NaY molecular sieve to obtain NH4NaY molecular sieve; 2) performing hot-pressing treatment on the NH4NaY molecular sieve and water under the condition that the pressure is 0.1-0.7 MPa to obtain hot-pressing treated molecular sieve; and 3) performing acid treatment on the hot-pressing treated molecular sieve and acid. In step 1), the first ion exchange and the second ion exchange are performed under the condition that the pressure is 0.2-1.5 MPa. The method only needs to perform two ammonium ion exchanges and once calcination under the pressurized condition to prepare the NH4NaY molecular sieve with extremely high exchange degree, and further prepare the VOCs adsorption molecular sieve with excellent adsorption performance without long-time and multiple water vapor treatment at high temperature.

Description

Technical Field

[0001] This invention relates to the field of VOCs treatment, specifically to a VOCs adsorption molecular sieve, its preparation method, and its application. Background Technology

[0002] VOCs are short for volatile organic compounds, generally referring to organic compounds with a saturated vapor pressure higher than 70 Pa at room temperature and a boiling point lower than 260℃ under normal pressure. These include aromatic hydrocarbons, esters, alcohols, aldehydes, and ethers. VOCs are ubiquitous in the atmosphere, soil, and aquatic ecosystems, possessing significant irritant and toxic properties. They can damage the human respiratory and immune systems, and in severe cases, may even cause cancer, birth defects, or mutations, posing serious threats to human health and the environment.

[0003] Currently, VOCs treatment technologies mainly include condensation recovery, adsorption recovery, direct oxidation, catalytic oxidation, photocatalysis, and biodegradation. Among them, adsorption is widely recognized as one of the most effective treatment technologies for low-concentration VOCs due to its advantages such as simple system, low cost, and low energy consumption.

[0004] Numerous studies have shown that Y molecular sieves possess high specific surface area and pore structure, and after modification, exhibit high hydrothermal stability and hydrophobic properties. They can be repeatedly regenerated and reused, making them an excellent VOCs adsorbent for complex working conditions. However, the current preparation process for hydrophobic Y molecular sieves is quite cumbersome. It requires first preparing NH4NaY molecular sieves by repeatedly exchanging NaY molecular sieves with ammonium and calcining, and then further subjecting NH4NaY molecular sieves to prolonged and repeated high-temperature heat treatment before obtaining the VOCs adsorption molecular sieve.

[0005] In the process of preparing NH4NaY molecular sieves from NaY molecular sieves, current methods either require at least two calcination treatments, or repeated calcination 4-5 times followed by one calcination, and then another 4-5 calcinations. This process is not only extremely complex but also time-consuming and energy-intensive. Furthermore, when further preparing NH4NaY molecular sieves into VOCs adsorption molecular sieves, it generally requires multiple harsh steam treatments, and the adsorption performance of the resulting molecular sieves remains insufficient.

[0006] Therefore, there is an urgent need to provide a simple and efficient method for preparing VOCs adsorption molecular sieves from NaY molecular sieves. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of complex preparation processes and insufficient adsorption performance of existing VOCs adsorption molecular sieves, and to provide a VOCs adsorption molecular sieve, its preparation method, and its applications. The method provided by this invention can prepare VOCs adsorption molecular sieves starting from NaY molecular sieves. It only requires two ammonium ion exchanges and one calcination under pressure to prepare NH4NaY molecular sieves with extremely high exchange rates, and further eliminates the need for prolonged and repeated steam treatment at high temperatures to obtain VOCs adsorption molecular sieves with excellent adsorption performance.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing VOCs adsorption molecular sieves, the method comprising the following steps:

[0009] 1) NaY molecular sieve was subjected to first ion exchange, calcination and second ion exchange in sequence to obtain NH4NaY molecular sieve;

[0010] 2) The NH4NaY molecular sieve was hot-pressed with water under a pressure of 0.1-0.7 MPa to obtain the hot-pressed molecular sieve.

[0011] 3) The hot-pressed molecular sieve is then subjected to acid treatment.

[0012] In step 1), the first ion exchange and the second ion exchange are carried out under a pressure of 0.2-1.5 MPa.

[0013] Preferably, the method of the first ion exchange includes: performing a first ion exchange between NaY molecular sieve and a first exchange solution containing ammonium ions.

[0014] Preferably, the concentration of ammonium ions in the first exchange solution is 0.1-2 mol / L, more preferably 0.6-2 mol / L.

[0015] Preferably, the weight ratio of the NaY molecular sieve to the first exchange liquid is 1-50:1, more preferably 5-30:1.

[0016] Preferably, the first ion exchange is carried out under a pressure of 0.5-1 MPa.

[0017] Preferably, the conditions for the first ion exchange further include: a temperature of 30-180°C and a time of 5-100 min; more preferably, the conditions for the first ion exchange further include: a temperature of 130-150°C and a time of 40-60 min.

[0018] Preferably, the calcination conditions include a temperature of 300-800℃ and a time of 0.5-5h; more preferably, the calcination conditions include a temperature of 400-600℃ and a time of 1.5-4h.

[0019] Preferably, the second ion exchange method includes: subjecting the roasted product to a second ion exchange treatment with a second exchange solution containing ammonium ions.

[0020] Preferably, the concentration of ammonium ions in the second exchange solution is 0.1-2 mol / L, more preferably 0.6-2 mol / L.

[0021] Preferably, the weight ratio of the calcination product to the second exchange liquid is 1-50:1, more preferably 5-30:1.

[0022] Preferably, the second ion exchange is carried out under a pressure of 0.5-1 MPa.

[0023] Preferably, the conditions for the second ion exchange further include: a temperature of 30-180°C and a time of 5-100 min; more preferably, the conditions for the second ion exchange further include: a temperature of 140-150°C and a time of 30-50 min.

[0024] Preferably, in step 1), the silicon-to-aluminum ratio of the NaY molecular sieve is 2-10:1, more preferably 5-6:1.

[0025] Preferably, the Na2O content in the NH4NaY molecular sieve obtained in step 1) is less than 0.5% by weight; more preferably, it is 0.1-0.2% by weight.

[0026] Preferably, in step 2), the hot pressing treatment is carried out under the condition that water is continuously introduced.

[0027] Preferably, the amount of water used is 0.2-5 g / h relative to 1 g of the NH4NaY molecular sieve, more preferably 0.5-2 g / h.

[0028] Preferably, in step 2), the hot pressing treatment is carried out under a pressure of 0.2-0.5 MPa, more preferably under a pressure of 0.3-0.4 MPa.

[0029] Preferably, the hot pressing conditions further include: a temperature of 300-700℃ and a time of 5-300 min; more preferably, the hot pressing conditions further include: a temperature of 500-650℃ and a time of 20-60 min.

[0030] Preferably, in step 2), the acid is an inorganic acid and / or an organic acid.

[0031] Preferably, the inorganic acid is one or more of nitric acid, sulfuric acid, and hydrochloric acid.

[0032] Preferably, the organic acid is one or more selected from oxalic acid, oxalic acid, citric acid, and tartaric acid.

[0033] Preferably, the acid is used in the form of an aqueous solution of the acid; more preferably, the concentration of the acid in the aqueous solution of the acid is 0.3-1.5 mol / L.

[0034] Preferably, the weight ratio of the hot-pressed molecular sieve to the aqueous solution of the acid is 1:5-30, more preferably 1:10-20.

[0035] Preferably, the acid treatment conditions include a temperature of 30-90°C and a time of 10-100 min; more preferably, the acid treatment conditions include a temperature of 40-80°C and a time of 15-60 min.

[0036] The second aspect of the present invention provides a VOCs adsorption molecular sieve prepared by the method described in the first aspect of the present invention.

[0037] Preferably, the VOCs adsorption molecular sieve has a crystallinity retention rate of over 70%, a silica-alumina ratio of 50-200:1, and a specific surface area of ​​900 m². 2 / g or more, pore volume is 0.55cm³ 3 / g or more, with a mesoporous pore volume of 0.25-0.3cm³. 3 / g.

[0038] The third aspect of this invention provides the application of the VOCs adsorption molecular sieve described in the second aspect of this invention in VOCs treatment.

[0039] The method described in this invention organically combines pressurized ion exchange, high-temperature calcination, hot pressing, and acid treatment to provide a method for preparing VOCs adsorption molecular sieves with excellent hydrophobic and adsorption properties.

[0040] The above technical solution eliminates the need for repeated ammonium ion exchange or calcination. It only requires two ammonium ion exchanges and one calcination within a specific pressure range to obtain NH4NaY molecular sieves with a high degree of exchange.

[0041] Furthermore, by performing a simple hot-pressing process under limited pressure conditions, combined with a subsequent acid treatment process, the silica-alumina ratio of NH4NaY molecular sieve can be significantly increased, while maximizing the preservation of the crystallinity of NH4NaY molecular sieve, thereby preparing a VOCs adsorption molecular sieve with excellent adsorption and hydrophobic properties. Detailed Implementation

[0042] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0043] Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.

[0044] In this invention, the mesopore refers to a pore with a diameter of 2-50 nm.

[0045] The first aspect of this invention provides a method for preparing VOCs adsorption molecular sieves, the method comprising the following steps:

[0046] 1) NaY molecular sieve was subjected to first ion exchange, calcination and second ion exchange in sequence to obtain NH4NaY molecular sieve;

[0047] 2) The NH4NaY molecular sieve was hot-pressed with water under a pressure of 0.1-0.7 MPa to obtain the hot-pressed molecular sieve.

[0048] 3) The hot-pressed molecular sieve is then subjected to acid treatment.

[0049] In step 1), the first ion exchange and the second ion exchange are carried out under a pressure of 0.2-1.5 MPa.

[0050] The inventors of this invention unexpectedly discovered during their research that, in the process of preparing VOCs adsorption molecular sieves from NaY molecular sieves, by sequentially performing a first ion exchange, calcination, and a second ion exchange under specific pressure during the ammonium exchange process of the NaY molecular sieve, a highly exchangeable NH4NaY molecular sieve can be obtained. Furthermore, using the NH4NaY molecular sieve obtained in this way, VOCs adsorption molecular sieves can be prepared very simply and efficiently by hot-pressing with water under specific pressure and then acid-treated with acid. Compared to traditional methods that require multiple ammonium exchanges, multiple steam treatments, and multiple acid-base solution washing treatments, this method has a simpler process flow, lower energy consumption, and the VOCs adsorption molecular sieves prepared in this way exhibit excellent hydrophobic and adsorption properties, thus completing this invention.

[0051] The preparation method of the VOCs adsorption molecular sieve described in the first aspect of the present invention will be described in detail below.

[0052] In step 1), the NaY molecular sieve is subjected to a first ion exchange, calcination, and a second ion exchange in sequence to obtain NH4NaY molecular sieve. The first ion exchange and the second ion exchange are carried out under a pressure of 0.2-1.5 MPa.

[0053] By sequentially performing one ion exchange, calcination, and a second ion exchange under the above conditions, the Na2O content in the NH4NaY molecular sieve obtained after the exchange can be reduced to less than 0.5% by weight, which meets the requirements for subsequent preparation of VOCs adsorption molecular sieves.

[0054] In this invention, there are no special requirements for the NaY molecular sieve used as a raw material. Conventional NaY molecular sieves in the art can be used. For example, the silicon-to-aluminum ratio of the NaY molecular sieve can be 2-10:1, preferably 5-6:1.

[0055] Furthermore, unless otherwise specified, in this invention, the silicon-to-aluminum ratio refers to the molar ratio of SiO2 to Al2O3 in NH4NaY molecular sieves or hydrophobic VOCs adsorption molecular sieves.

[0056] According to the present invention, firstly, the NaY molecular sieve is subjected to a first ion exchange with a first exchange solution containing ammonium ions. The source of the ammonium ions in the first exchange solution is not particularly limited, and can be any raw material commonly used in ammonium exchange that can provide ammonium ions. For example, the ammonium ions can be derived from one or more of ammonium sulfate, ammonium nitrate, and ammonium chloride, preferably ammonium sulfate.

[0057] Furthermore, the concentration of ammonium ions in the first exchange solution containing ammonium ions is not particularly limited, as long as the first ion exchange can be carried out. For example, the concentration of ammonium ions in the first exchange solution can be 0.1-2 mol / L, preferably 0.6-2 mol / L, and more preferably 1-2 mol / L, thereby further increasing the rate of the first ion exchange and improving the degree of exchange.

[0058] Furthermore, the weight ratio of the NaY molecular sieve to the first exchange solution is not particularly limited and can be within a conventional range in the art. For example, the weight ratio of the NaY molecular sieve to the first exchange solution can be 1-50:1, preferably 5-30:1, and more preferably 10-20:1. By performing the first ion exchange within the above range, the exchange rate can be further promoted and the degree of exchange can be improved.

[0059] Furthermore, as described above, the first ion exchange is carried out under a pressure of 0.1-1.5 MPa, preferably under a pressure of 0.3-1 MPa, and more preferably under a pressure of 0.5-1 MPa. By carrying out the first ion exchange within this pressure range, the degree of exchange of the first ion exchange can be greatly improved, and the Na2O content after the first ion exchange can be significantly reduced.

[0060] In addition to the pressure conditions mentioned above, the conditions for the first ion exchange may also include: a temperature of 30-180°C and a time of 5-100 min; preferably, the conditions for the first ion exchange may further include: a temperature of 40-150°C and a time of 10-50 min. By conducting the first ion exchange under the above temperature and time conditions, the effect of the first ion exchange can be further improved, which helps to facilitate the smooth progress of subsequent steps.

[0061] After the first ion exchange is completed, the product obtained after the first ion exchange can be washed and subjected to solid-liquid separation to obtain the molecular sieve after the first ion exchange. Here, the washing and solid-liquid separation can be performed using washing and solid-liquid separation methods commonly used in the art, which will not be described in detail here.

[0062] Next, the product after the first ion exchange is calcined.

[0063] There are no particular limitations on the roasting method and conditions. Conventional roasting methods in the art can be used. For example, the roasting conditions may include a temperature of 300-800℃ and a time of 0.5-5h. Preferably, the roasting conditions include a temperature of 400-600℃ and a time of 1.5-4h.

[0064] Subsequently, the roasted product was subjected to a second ion exchange treatment with a second exchange solution containing ammonium ions.

[0065] In the second exchange solution containing ammonium ions, the source of the ammonium ions is not particularly limited, and can be any raw material commonly used in ammonium exchange that can provide ammonium ions. For example, the ammonium ions can be derived from one or more of ammonium sulfate, ammonium nitrate, and ammonium chloride, preferably ammonium sulfate.

[0066] Furthermore, the concentration of ammonium ions in the second exchange solution containing ammonium ions is not particularly limited, as long as the second ion exchange can be carried out. For example, the concentration of ammonium ions in the second exchange solution can be 0.1-2 mol / L, preferably 0.6-2 mol / L, and more preferably 1-2 mol / L, thereby further increasing the rate of the second ion exchange and improving the degree of exchange.

[0067] Furthermore, the weight ratio of the calcined product to the second exchange solution is not particularly limited and can be within the conventional range in the art. For example, the weight ratio of the calcined product to the second exchange solution can be 1-50:1, preferably 5-30:1, and more preferably 10-20:1. By performing the second ion exchange within the above range, the exchange rate can be further promoted and the degree of exchange can be improved.

[0068] Furthermore, as described above, the second ion exchange is carried out under a pressure of 0.1-1.5 MPa, preferably under a pressure of 0.5-1 MPa, and more preferably under a pressure of 0.6-1 MPa. By carrying out the second ion exchange within this pressure range, the degree of exchange can be greatly improved, and the Na2O content after the second ion exchange can be significantly reduced, thus meeting the requirements for subsequent preparation and obtaining a high-performance VOCs adsorption molecular sieve.

[0069] In addition to the pressure conditions mentioned above, the conditions for the second ion exchange may also include: a temperature of 30-180℃ and a time of 5-100 min; preferably, the conditions for the second ion exchange may further include: a temperature of 40-150℃ and a time of 10-50 min. By conducting the second ion exchange under the above temperature and time conditions, the effect of the second ion exchange can be further improved, which facilitates the smooth progress of subsequent steps and further enhances the performance of the prepared VOCs adsorption molecular sieve.

[0070] The above steps can be used to prepare NH4NaY molecular sieves, and the Na2O content in the obtained NH4NaY molecular sieves is less than 0.5% by weight; preferably, the Na2O content in the obtained NH4NaY molecular sieves is 0.1-0.2% by weight.

[0071] Next, in step 2), the NH4NaY molecular sieve is subjected to hot pressing with water to obtain a hot-pressed molecular sieve. The hot pressing is carried out under a pressure of 0.1-0.7 MPa.

[0072] In step 2), when the NH4NaY molecular sieve is subjected to hot pressing with water, the amount of water used can be selected according to the amount of NH4NaY molecular sieve used. In addition, the water can be added all at once or continuously at a certain rate.

[0073] During the research process, it was discovered that by performing the hot-pressing treatment under the condition of continuous water flow, not only can the processing time be significantly shortened and the amount of water introduced be reduced, but also the damage to the crystallinity and pore structure of the molecular sieve caused by a large amount of water introduced at one time can be prevented. This can further significantly improve the adsorption performance of the prepared hydrophobic VOCs adsorption molecular sieve.

[0074] Therefore, in this invention, preferably, when the NH4NaY molecular sieve is hot-pressed with water, all the NH4NaY molecular sieve is placed in the reaction vessel, and then water is continuously added to the reactor according to the amount of NH4NaY molecular sieve. For example, relative to 1g of NH4NaY molecular sieve, the amount of water added can be 0.1-20g / h, preferably 0.2-5g / h, and more preferably 0.5-2g / h. By continuously adding water and controlling the amount of NH4NaY molecular sieve and water within the above ranges, the hot-pressing reaction effect can be further guaranteed, and the hydrophobic and adsorption properties of the prepared hydrophobic VOCs adsorption molecular sieve can be further improved.

[0075] In this invention, the conditions of the hot-pressing treatment are crucial. If the pressure, temperature, and / or time of the hot-pressing treatment are too high, the morphology and crystallinity of the molecular sieve may be damaged, thereby affecting the hydrophobic and adsorption properties of the prepared hydrophobic VOCs adsorption molecular sieve. Conversely, if the pressure, temperature, and / or time of the hot-pressing treatment are too low, the desired effect of the hot-pressing treatment cannot be achieved. On the one hand, the improvement in the silicon-to-aluminum ratio is limited, and even after acid treatment, sufficient hydrophobic effect cannot be achieved. On the other hand, the specific surface area and pore volume of the finally prepared VOCs adsorption molecular sieve are insufficient, resulting in insufficient adsorption capacity and affecting the performance of the VOCs adsorption molecular sieve.

[0076] Therefore, in this invention, preferably, the hot-pressing treatment is carried out under a pressure of 0.2-0.5 MPa, more preferably under a pressure of 0.3-0.4 MPa. This can further significantly improve the adsorption performance of the prepared VOCs adsorption molecular sieve.

[0077] In addition to pressure, the hot-pressing conditions may also include: a temperature of 300-700℃ and a time of 5-300 min; more preferably, the hot-pressing conditions may further include: a temperature of 500-650℃ and a time of 20-60 min. By performing hot-pressing under the above conditions, the hydrophobic and adsorption properties of the prepared hydrophobic VOCs adsorption molecular sieve can be significantly improved.

[0078] Next, in step 3), the hot-pressed molecular sieve is subjected to acid treatment.

[0079] In this invention, there is no particular limitation on the type of acid. For example, the acid can be an organic acid and / or an inorganic acid.

[0080] Examples of such organic acids include oxalic acid, citric acid, tartaric acid, and acetic acid.

[0081] Examples of such inorganic acids include nitric acid, sulfuric acid, and hydrochloric acid.

[0082] In this invention, the acid is preferably an inorganic acid, and more preferably nitric acid.

[0083] Furthermore, in this invention, the acid is preferably used in the form of an aqueous solution. In this case, the concentration of the acid in the aqueous solution can be, for example, 0.3-1.5 mol / L, preferably 0.5-1 mol / L.

[0084] At this point, according to the present invention, in step 2), there is no particular limitation on the amount of the hot-pressed molecular sieve and the aqueous solution of the acid. For example, the weight ratio of the hot-pressed molecular sieve to the aqueous solution of the acid can be 1:5-30, preferably 1:10-20. This allows for a further increase in the silicon-to-aluminum ratio and further improves the adsorption performance of the hydrophobic VOCs adsorption molecular sieve obtained after acid treatment.

[0085] In step 2) of this invention, the conditions for acid treatment are not particularly limited. For example, the conditions for acid treatment may include: a temperature of 30-90°C and a time of 10-100 min; preferably, the conditions for acid treatment include: a temperature of 40-80°C and a time of 15-60 min. By performing acid treatment under these conditions, the silicon-to-aluminum ratio can be further increased, thereby improving the hydrophobic properties of the obtained adsorption molecular sieve. Simultaneously, its specific surface area and pore volume can be further increased, further enhancing the adsorption performance of the prepared hydrophobic VOCs adsorption molecular sieve.

[0086] Furthermore, in this invention, after the acid treatment, the acid-treated product can be washed, dried, or otherwise processed. The washing and drying processes can all be performed using conventional methods in the art, which will not be elaborated here.

[0087] By employing the method described in the first aspect of this invention, through ammonium exchange under specific pressure conditions, followed by hot pressing and acid treatment under specific pressure, the crystallinity of the Y molecular sieve can be maximized, and the silicon-to-aluminum ratio can be significantly increased. For example, the silicon-to-aluminum ratio can be increased from 20-10:1 to 50-200:1, and the prepared VOCs adsorption molecular sieve has a crystallinity higher than 900 μm. 2 Specific surface area per g, 0.55 cm² 3 Pore ​​volume above / g and 0.25-0.3cm 3 / g mesoporous pore volume. It has excellent hydrophobic and adsorption properties.

[0088] According to a particularly preferred embodiment of the present invention, firstly, the NaY molecular sieve is subjected to a first ion exchange with a first exchange solution containing ammonium ions, wherein the content of ammonium ions in the first exchange solution is 1-2 mol / L, and the conditions for the first ion exchange include: a pressure of 0.5-1 MPa, a temperature of 130-150°C, and a time of 40-60 min. Next, the first exchange product is washed and filtered, and then calcined, wherein the calcination conditions include: a temperature of 400-600°C, and a time of 1.5-4 h. Then, the calcined product is subjected to a second ion exchange with a second exchange solution containing ammonium ions, wherein the content of ammonium ions in the second exchange solution is 1-2 mol / L, and the conditions for the second ion exchange include: a pressure of 0.5-1 MPa, a temperature of 140-150°C, and a time of 30-50 min, to obtain NH4NaY molecular sieve.

[0089] Subsequently, the NH4NaY molecular sieve was subjected to hot-pressing treatment with water. The amount of water used was 0.5-2 g / h relative to 1 g of the NH4NaY molecular sieve. The hot-pressing treatment conditions included: pressure of 0.3-0.4 MPa, temperature of 500-650℃, and time of 20-60 min, to obtain the hot-pressed molecular sieve.

[0090] Next, the obtained hot-pressed molecular sieve is subjected to acid treatment with an aqueous solution of acid, wherein the concentration of the acid in the aqueous solution is 0.8-1.2 mol / L, and the acid treatment conditions include a temperature of 40-60℃ and a time of 30-60 min. Thus, not only can hydrophobic VOCs adsorption molecular sieves with excellent hydrophobicity and adsorption capacity be prepared, but the preparation process is also very simple and the preparation time is greatly shortened, making it very suitable for large-scale industrial production.

[0091] A second aspect of the present invention provides a VOCs adsorption molecular sieve prepared by the method described in the first aspect of the present invention.

[0092] According to a second aspect of the present invention, the crystallinity retention rate of the VOCs adsorption molecular sieve is 70% or more, preferably 75% or more.

[0093] On the other hand, the silicon-to-aluminum ratio of the VOCs adsorption molecular sieve is 50-200:1, preferably 100-150:1.

[0094] Furthermore, the specific surface area of ​​the VOCs adsorption molecular sieve can reach up to 900 m². 2 / g or more, preferably 950m 2 / g or more, preferably 960-980m 2 / g.

[0095] Furthermore, the pore volume of the VOCs adsorption molecular sieve is 0.55 cm³. 3 / g or more, preferably 0.55-6cm 3 / g.

[0096] In addition, the mesopore volume of the VOCs adsorption molecular sieve is 0.25-0.3 cm³. 3 / g, preferably 0.26-0.28cm 3 / g.

[0097] Furthermore, the water adsorption capacity of the VOCs adsorption molecular sieve can be as high as 0.016 g / g, preferably 0.016-0.02 g / g.

[0098] Based on the above characteristics, the VOCs adsorption molecular sieve described in the second aspect of the present invention has excellent hydrophobicity and adsorption properties, and is very suitable for the adsorption treatment of VOCs.

[0099] The third aspect of this invention provides the application of the VOCs adsorption molecular sieve described in the second aspect of this invention in VOCs treatment.

[0100] The present invention will be described in detail below through embodiments.

[0101] Crystallinity was determined by X-ray diffraction (XRD).

[0102] Crystallinity retention rate refers to the ratio of the crystallinity of the hydrophobic VOCs adsorption molecular sieve to the crystallinity of the NaY molecular sieve.

[0103] The silicon-to-aluminum ratio was determined by X-ray fluorescence spectroscopy.

[0104] Specific surface area, pore volume, and mesopore volume were measured by nitrogen physical adsorption method;

[0105] In the following examples and comparative examples, the NaY molecular sieve raw materials used were prepared according to conventional methods, and their relevant parameters are shown in the table below.

[0106]

[0107] Example 1

[0108] 1) Place 50g of NaY molecular sieve in a reaction vessel, add an ammonium sulfate aqueous solution with an ammonium ion concentration of 1mol / L, and carry out the first ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution is 20:1, the exchange temperature is 140℃, the time is 45min, and the pressure is 0.75MPa to obtain the first ion exchange product.

[0109] 2) The first ion exchange product was washed and filtered, and then calcined at 500℃ for 3 hours to obtain the calcined product.

[0110] 3) The calcined product was mixed with an ammonium sulfate aqueous solution with an ammonium ion concentration of 1.5 mol / L for a second ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution was 20:1. The exchange temperature was 150℃, the time was 40 min, and the pressure was 1 MPa to obtain NH4NaY molecular sieve with a Na2O content of 0.15% by weight.

[0111] 4) Place 20g of the NH4NaY molecular sieve obtained in step 3) into a container, heat it to 600℃, and then use a high-pressure pump to pass water into the container at a rate of 12g / h for hot pressing treatment. The pressure of the hot pressing treatment is 0.4Mpa and the time is 55min, to obtain the sample after hot pressing treatment.

[0112] 5) The hot-pressed sample was mixed with a 1 mol / L nitric acid aqueous solution at a weight ratio of 1:15 and then subjected to acid treatment at a temperature of 40°C for 50 min.

[0113] 6) The acid-treated sample obtained in step 5) is washed and dried to obtain VOCs adsorption molecular sieve A1.

[0114] Example 2

[0115] 1) Place 50g of NaY molecular sieve in a reaction vessel, add an ammonium sulfate aqueous solution with an ammonium ion concentration of 1.5mol / L, and carry out the first ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution is 15:1, the exchange temperature is 150℃, the time is 50min, and the pressure is 1MPa to obtain the first ion exchange product.

[0116] 2) After washing and filtering the first ion exchange product, it is calcined at 550℃ for 2 hours to obtain the calcined product.

[0117] 3) The calcined product was mixed with an ammonium sulfate aqueous solution with an ammonium ion concentration of 1.5 mol / L for a second ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution was 18:1. The exchange temperature was 140℃, the time was 40 min, and the pressure was 0.75 MPa to obtain NH4NaY molecular sieve with a Na2O content of 0.19% by weight.

[0118] 4) Place 20g of the NH4NaY molecular sieve obtained in step 3) into a container, heat it to 600℃, and then use a high-pressure pump to pass water into the container at a rate of 15g / h for hot pressing treatment. The pressure of the hot pressing treatment is 0.35Mpa and the time is 45min, to obtain the sample after hot pressing treatment.

[0119] 5) The hot-pressed sample was mixed with a 0.8 mol / L nitric acid aqueous solution at a weight ratio of 1:20 and then subjected to acid treatment at a temperature of 50°C for 50 min.

[0120] 6) Wash and dry the acid-treated sample obtained in step 5) to obtain VOCs adsorption molecular sieve A2.

[0121] Example 3

[0122] 1) Place 50g of NaY molecular sieve in a reaction vessel, add an ammonium sulfate aqueous solution with an ammonium ion concentration of 1.2mol / L, and carry out the first ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution is 20:1, the exchange temperature is 135℃, the time is 50min, and the pressure is 0.55MPa to obtain the first ion exchange product.

[0123] 2) After washing and filtering the first ion exchange product, it is calcined at 530℃ for 2.5h to obtain the calcined product.

[0124] 3) The calcined product was mixed with an ammonium sulfate aqueous solution with an ammonium ion concentration of 1.3 mol / L for a second ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution was 18:1. The exchange temperature was 145℃, the time was 45 min, and the pressure was 0.75 MPa to obtain NH4NaY molecular sieve with a Na2O content of 0.13% by weight.

[0125] 4) Place 20g of the NH4NaY molecular sieve obtained in step 3) into a container, heat it to 600℃, and then use a high-pressure pump to pass water into the container at a rate of 18g / h for hot pressing treatment. The pressure of the hot pressing treatment is 0.32Mpa and the time is 50min to obtain the sample after hot pressing treatment.

[0126] 5) The hot-pressed sample was mixed with a 0.9 mol / L nitric acid aqueous solution at a weight ratio of 1:18 and then subjected to acid treatment at a temperature of 50°C for 40 min.

[0127] 6) Wash and dry the acid-treated sample obtained in step 5) to obtain VOCs adsorption molecular sieve A3.

[0128] Example 4

[0129] 1) Place 50g of NaY molecular sieve in a reaction vessel, add an ammonium sulfate aqueous solution with an ammonium ion concentration of 2mol / L, and carry out the first ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution is 15:1, the exchange temperature is 145℃, the time is 45min, and the pressure is 0.75MPa to obtain the first ion exchange product.

[0130] 2) After washing and filtering the first ion exchange product, it is calcined at 520℃ for 3 hours to obtain the calcined product.

[0131] 3) The calcined product was mixed with an ammonium sulfate aqueous solution with an ammonium ion concentration of 2 mol / L for a second ion exchange. The weight ratio of NaY molecular sieve to the ammonium sulfate aqueous solution was 20:1, the exchange temperature was 140℃, the time was 50 min, and the pressure was 0.6 MPa to obtain NH4NaY molecular sieve with a Na2O content of 0.11% by weight.

[0132] 4) Place 20g of the NH4NaY molecular sieve obtained in step 3) into a container, heat it to 640℃, and then use a high-pressure pump to pass water into the container at a rate of 10g / h for hot pressing treatment. The pressure of the hot pressing treatment is 0.33Mpa and the time is 50min, to obtain the sample after hot pressing treatment.

[0133] 5) The hot-pressed sample was mixed with a 1.1 mol / L nitric acid aqueous solution at a weight ratio of 1:13 and then subjected to acid treatment at a temperature of 50°C for 50 min.

[0134] 6) Wash and dry the acid-treated sample obtained in step 5) to obtain VOCs adsorption molecular sieve A4.

[0135] Example 5

[0136] The procedure is carried out according to the method described in Example 1, except that...

[0137] In step 4), the pressure of the hot pressing treatment is 0.2 MPa, and VOCs adsorption molecular sieve A5 is obtained.

[0138] Example 6

[0139] The procedure is carried out according to the method described in Example 1, except that...

[0140] In step 4), the pressure of the hot pressing treatment is 0.1 MPa, and VOCs adsorption molecular sieve A6 is obtained.

[0141] Example 7

[0142] The procedure is carried out according to the method of Example 1, except that...

[0143] In step 4), 20g of NH4NaY molecular sieve is placed in a container, heated to 600℃, and then 11g of water is added at once using a high-pressure pump for hot pressing to obtain VOCs adsorption molecular sieve A7.

[0144] Comparative Example 1

[0145] The procedure is carried out according to the method described in Example 1, except that...

[0146] In step 1), the first ion exchange is carried out under non-pressurized conditions.

[0147] In step 3), the second ion exchange is carried out under non-pressurized conditions, resulting in a Na2O content of 2.5% by weight in the NH4NaY molecular sieve.

[0148] Finally, VOCs adsorption molecular sieve D1 was obtained.

[0149] Comparative Example 2

[0150] The procedure is carried out according to the method described in Example 1, except that...

[0151] Step 4) is carried out under non-pressurized conditions to obtain VOCs adsorption molecular sieve D2.

[0152] Test case

[0153] The dynamic water and toluene adsorption capacity of the hydrophobic VOCs adsorption molecular sieve was tested using the following method:

[0154] The hydrophobic VOCs adsorption molecular sieves prepared in the above examples and comparative examples were subjected to tableting and granulation. A 20-40 mesh hydrophobic VOCs adsorption molecular sieve sample was obtained and placed in an adsorption tube. Then, a gas to be treated, containing a concentration of 1700 mg / m³, was introduced into the adsorption tube under normal pressure. 3 Toluene was used in an adsorption tube with a relative humidity of 50%, a temperature of 30°C, and a volume hourly space velocity of 1000 mL / (min / g). The concentration of toluene at the outlet of the adsorption tube was detected by gas chromatography, and the relative humidity at the outlet of the adsorption tube was detected by a hygrometer.

[0155] The water adsorption capacity and toluene adsorption capacity of the hydrophobic VOCs adsorption molecular sieve sample were calculated according to the following formulas:

[0156]

[0157]

[0158] Where F is the volumetric flow rate (mL / min), W is the weight of the hydrophobic VOCs adsorption molecular sieve sample, w0 is the relative humidity (%) of the gas to be treated, and wi C0 represents the relative humidity (%) at the outlet of the adsorption tube, and C0 represents the toluene concentration (mg / m³) of the gas to be treated. 3 ), C i Toluene concentration at the adsorption tube outlet (mg / m³) 3 ), t s The saturation adsorption time (min) is the time required for adsorption.

[0159] The test results are shown in Table 1.

[0160] Table 1

[0161]

[0162] As can be seen from the results in Table 1, if no pressurized exchange is carried out during the exchange of NaY molecular sieve with ammonium ions, and only the first and second ion exchanges are carried out under normal pressure, the sodium oxide content in the resulting NH4NaY molecular sieve will be too high. Furthermore, when it is further prepared into a VOCs adsorption molecular sieve, the crystallinity of the product will be greatly reduced, the silicon-aluminum ratio will be only slightly improved, the pore structure will be damaged, and the adsorption performance of the prepared VOCs adsorption molecular sieve will be poor.

[0163] Furthermore, when molecular sieves are treated with water, if the treatment is carried out at atmospheric pressure without applying pressure, not only will the crystallinity retention rate of the molecular sieve be reduced, but the silicon-to-aluminum ratio of the molecular sieve will not be significantly improved. The specific surface area, pore volume, and mesopore volume of the resulting hydrophobic VOCs adsorption molecular sieve will all be at a low level, and its water adsorption capacity and toluene adsorption capacity will be insufficient.

[0164] On the other hand, a comparison between Example 1 and Example 7 shows that by continuously introducing water during the hot pressing process, the crystallinity and pore structure of the molecular sieve can be avoided. Compared with the preparation method of adding water once, the water adsorption capacity and toluene adsorption capacity of the hydrophobic VOCs adsorption molecular sieve obtained in this way are significantly improved.

[0165] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a VOCs adsorption molecular sieve, characterized in that, The method includes the following steps: 1) NaY molecular sieve was subjected to first ion exchange, calcination and second ion exchange in sequence to obtain NH4NaY molecular sieve; 2) The NH4NaY molecular sieve was hot-pressed with water under a pressure of 0.3-0.4 MPa to obtain the hot-pressed molecular sieve. 3) The hot-pressed molecular sieve is then subjected to acid treatment. In step 1), the first ion exchange and the second ion exchange are carried out under a pressure of 0.2-1.5 MPa. The calcination conditions include: a temperature of 300-800℃ and a time of 0.5-5 hours. In step 1), the silica-to-alumina ratio of the NaY molecular sieve is 2-10:

1. In step 2), the hot pressing treatment is carried out under the condition of continuous water flow. The conditions for the hot pressing treatment also include: a temperature of 300-700℃ and a time of 5-300 minutes. The VOCs adsorption molecular sieve has a crystallinity retention rate of over 70%, and its silica-to-alumina ratio is 50-200:

1. The silicon-to-aluminum ratio of the NaY molecular sieve and the silicon-to-aluminum ratio of the VOCs adsorption molecular sieve are the molar ratios of SiO2 and Al2O3 in the molecular sieve.

2. The method according to claim 1, wherein, The first ion exchange method includes: performing a first ion exchange between NaY molecular sieve and a first exchange solution containing ammonium ions.

3. The method according to claim 2, wherein, The concentration of ammonium ions in the first exchange solution is 0.1-2 mol / L; The weight ratio of the NaY molecular sieve to the first exchange liquid is 1-50:

1.

4. The method according to claim 1, wherein, The first ion exchange was carried out under a pressure of 0.5-1 MPa.

5. The method according to claim 1, wherein, The conditions for the first ion exchange also include: a temperature of 30-180℃ and a time of 5-100min.

6. The method according to claim 1, wherein, The roasting conditions include a temperature of 400-600℃ and a time of 1.5-4h.

7. The method according to any one of claims 1-6, wherein, The second ion exchange method includes: subjecting the roasted product to a second ion exchange treatment with a second exchange solution containing ammonium ions.

8. The method according to claim 7, wherein, The concentration of ammonium ions in the second exchange solution is 0.1-2 mol / L; The weight ratio of the calcination product to the second exchange liquid is 1-50:

1.

9. The method according to claim 1, wherein, The second ion exchange was carried out under a pressure of 0.5-1 MPa.

10. The method according to claim 1, wherein, The conditions for the second ion exchange also include: a temperature of 30-180℃ and a time of 5-100 min.

11. The method according to any one of claims 1-6, wherein, In step 1), the silicon-to-aluminum ratio of the NaY molecular sieve is 5-6:

1.

12. The method according to any one of claims 1-6, wherein, In step 1), the Na2O content in the obtained NH4NaY molecular sieve is less than 0.5% by weight.

13. The method according to any one of claims 1-6, wherein, In step 2), the amount of water used is 0.2-5 g / h relative to 1 g of the NH4NaY molecular sieve.

14. The method according to any one of claims 1-6, wherein, The hot pressing conditions also include: a temperature of 500-650℃ and a time of 20-60 minutes.

15. The method according to any one of claims 1-6, wherein, In step 3), the acid is an inorganic acid and / or an organic acid.

16. The method according to claim 15, wherein, The inorganic acid is one or more of nitric acid, sulfuric acid, and hydrochloric acid; The organic acid is one or more of oxalic acid, oxalic acid, citric acid and tartaric acid; The acid is used in the form of an aqueous solution of the acid.

17. The method according to claim 16, wherein, The concentration of the acid in the aqueous solution is 0.3-1.5 mol / L.

18. The method according to claim 16, wherein, The weight ratio of the hot-pressed molecular sieve to the aqueous solution of the acid is 1:5-30.

19. The method according to any one of claims 1-6, wherein, The acid treatment conditions include: a temperature of 30-90℃ and a time of 10-100 min.

20. The VOCs adsorption molecular sieve prepared by the method according to any one of claims 1-19.

21. The VOCs adsorption molecular sieve according to claim 20, wherein the specific surface area of ​​the VOCs adsorption molecular sieve is 900 m². 2 / g or more; The pore volume of the VOCs adsorption molecular sieve is 0.55 cm³. 3 / g or more; The mesopore volume of the VOCs adsorption molecular sieve is 0.25-0.3 cm³. 3 / g.

22. The application of the VOCs adsorption molecular sieve according to claim 20 or 21 in VOCs treatment.

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