CN106824256B - Formaldehyde degradation catalyst and preparation method thereof - Google Patents
Formaldehyde degradation catalyst and preparation method thereof Download PDFInfo
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- CN106824256B CN106824256B CN201710190751.8A CN201710190751A CN106824256B CN 106824256 B CN106824256 B CN 106824256B CN 201710190751 A CN201710190751 A CN 201710190751A CN 106824256 B CN106824256 B CN 106824256B
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Abstract
The invention provides a formaldehyde degradation catalyst and a preparation method thereof. Firstly, providing a load with TiO2The ZSM-5 molecular sieve dispersion liquid is characterized in that the silica-alumina ratio of the ZSM-5 molecular sieve is (200-400): 1; then mixing the obtained dispersion liquid with a platinic acid solution, adjusting the pH value to 8-10 to obtain a pre-reduction treatment mixed liquid, and then mixing the pre-reduction treatment mixed liquid with NaBH4Mixing, and carrying out reduction reaction to obtain the formaldehyde degradation catalyst. The invention takes the molecular sieve with the limited silicon-aluminum ratio as a molecular channel and a load matrix, not only TiO2And Pt provides more sites for facilitating TiO2And the adsorption of Pt is beneficial to improving the catalytic degradation of formaldehyde and improving the catalytic activity; meanwhile, the molecular sieve with the silicon-aluminum ratio has lower water absorption, the phenomenon that the catalyst is deactivated due to the fact that moisture is condensed in a catalyst pore channel is avoided, silanization treatment is carried out after reduction reaction, and the stability and the water poisoning resistance of the catalyst are remarkably improved.
Description
Technical Field
The invention belongs to the technical field of indoor purification, and particularly relates to a formaldehyde degradation catalyst and a preparation method thereof.
Background
Along with the continuous improvement of the material culture level of people, the indoor decoration material volatilizes polluting gases, and formaldehyde is the most typical and most harmful gas organic matter in indoor air pollution. The formaldehyde is widely existed in building decoration materials and various indoor living goods, the release period is long, the formaldehyde can stimulate eyes, nose, throat organs and skin of people after being contacted for a long time, serious allergic symptoms such as rash and the like are caused, and the formaldehyde also has strong carcinogenic and cancer promotion effects, thereby causing great harm to the health of people. Therefore, the research on the indoor formaldehyde degradation and purification technology has very important practical significance in improving the living environment of people.
At present, the indoor formaldehyde degradation and purification technology mainly comprises an adsorption technology, a photocatalysis technology and a catalytic oxidation technology. The adsorption technology has limited adsorption capacity of the adsorbent, needs to be regenerated or replaced regularly, is easily affected by other atmospheres in the environment, and cannot eradicate formaldehyde pollution. The photocatalytic formaldehyde degrading technology mainly utilizes TiO2The principle of photocatalysis is to degrade and eliminate formaldehyde, and Chinese patent CN1208670 discloses a method for degrading and eliminating formaldehyde by using TiO2Powder ofThe photocatalyst is an active component, but the catalyst can perform degradation only under a specific external excitation light source, and the preparation method of the catalyst is complex. The catalytic oxidation technology utilizes oxygen in the air, and formaldehyde can be completely oxidized into pollution-free CO under the action of a catalyst2And H2O, is a clean and convenient method which can thoroughly eliminate formaldehyde pollution.
The existing formaldehyde catalytic oxidation catalyst is a noble metal catalyst, such as Pt/TiO2，Au/CeO2And Au/FeOx catalyst, but the noble metal catalyst has a problem of increasing the catalytic activity at the expense of increasing the noble metal content. For example, U.S. Pat. No. 5,5585083 discloses a Pt/SnO2The method for eliminating formaldehyde in air by using the catalyst needs to ensure that the catalyst has higher activity with the Pt content of 12%, but the Pt content in the catalyst is as high as 12%, so that the catalyst is expensive. In order to reduce the cost of the catalyst, metal oxide is taken as a carrier to load a noble metal component, so as to reduce the content of the noble metal, for example, Chinese patent CN101274281 discloses a Pt/Co-Ce-Sn catalyst, and specifically discloses that ceramic coated with Co-Ce-Sn composite oxide is taken as a carrier, Pt active component with the content not higher than 10% and metal oxide are taken as auxiliary agents, but the problem of reducing the content of the noble metal and simultaneously reducing the catalytic activity exists.
Disclosure of Invention
In view of the above, the invention provides a formaldehyde degradation catalyst and a preparation method thereof, and the formaldehyde degradation catalyst obtained by the preparation method provided by the invention has high catalytic activity and low preparation cost.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of an aldehyde degradation catalyst, which comprises the following steps:
(1) providing a supported TiO2The ZSM-5 molecular sieve has a silica-alumina ratio (calculated by the molar ratio of Si to Al in the molecular sieve) of (200-400): 1;
(2) mixing the aqueous dispersion obtained in the step (1) with a platinum-containing solution, and adjusting the pH value to 8 to E10, obtaining a pre-reduction treatment mixed solution; TiO is loaded in the dispersion liquid2The mass ratio of the ZSM-5 molecular sieve to platinum in the platinum-containing solution is (84-94.99): (0.01 to 1);
(3) mixing the pre-reduction treatment mixed solution obtained in the step (2) with NaBH4Mixing, and carrying out reduction reaction to obtain the formaldehyde degradation catalyst.
Preferably, the aqueous dispersion is loaded with TiO2The volume ratio of the mass of the ZSM-5 molecular sieve to the water is 1 g: (5-30) L.
Preferably, the load is TiO22In ZSM-5 molecular sieve of (1)2And the ZSM-5 molecular sieve in a mass ratio of 1: (9-29).
Preferably, NaBH is used in said step (3)4The volume ratio (0.05mol to 0.2mol) of the pre-reduction treatment mixed solution: 1L of the compound.
Preferably, the reduction reaction further comprises: carrying out silanization treatment on a product obtained by the reduction reaction; the silanization treatment comprises the following steps: and mixing the product obtained by the reduction reaction with tetraethyl orthosilicate, and roasting.
Preferably, the mass ratio of the tetraethyl orthosilicate to the product obtained by the reduction reaction is (3-10): (85-95).
Preferably, the roasting temperature is 400-500 ℃.
Preferably, the roasting time is 4-6 h.
The invention also provides a formaldehyde degradation catalyst prepared by the preparation method of the technical scheme, which comprises Pt particles and loaded TiO2The Pt particles are supported on TiO of the ZSM-5 molecular sieve2And/or a ZSM-5 molecular sieve surface.
Preferably, the formaldehyde degradation catalyst comprises SiO2And a base; the substrate comprises Pt particles and TiO loaded2The ZSM-5 molecular sieve of (1), wherein Pt particles in the matrix are loaded on TiO2And/or a ZSM-5 surface; the SiO2Supported on the surface and/or in the channels of the substrate.
The invention provides a formaldehyde removerThe preparation method of the catalyst comprises the steps of firstly providing a supported TiO2The ZSM-5 molecular sieve aqueous dispersion is characterized in that the silica-alumina ratio of the ZSM-5 molecular sieve is (200-400): 1; then mixing the obtained water dispersion with a platinum-containing solution, adjusting the pH value to 8-10 to obtain a pre-reduction treatment mixed solution, and then mixing the pre-reduction treatment mixed solution with NaBH4Mixing, carrying out reduction reaction to obtain formaldehyde degradation catalyst with limited TiO load2The mass ratio of the ZSM-5 molecular sieve to platinum is (84-94.99): (0.01-1). The invention takes the molar ratio of Si to Al as (200-400): 1 as molecular channel and load matrix, not only TiO2And Pt provides more sites for facilitating TiO2And the adsorption of Pt improves the utilization rate of noble metal on the premise of lower addition of Pt, thereby improving the catalytic degradation of formaldehyde and improving the catalytic activity; the invention takes ZSM-5 as a carrier and loads TiO2The catalyst is modified to improve the metal dispersion degree of Pt in the catalyst, increase the active sites of the catalyst and improve the catalytic activity; meanwhile, the cost of improving the activity of the catalyst by increasing a certain Pt loading amount can be reduced, and the problems that when the Pt metal loading amount is increased to a certain degree, Pt particles are gathered to grow so that active sites are reduced on the contrary and the catalytic activity is not increased and inversely reduced in the process of realizing the catalytic activity by simply increasing the Pt loading amount in the catalyst are solved.
Meanwhile, the adopted molecular sieve with the silicon-aluminum ratio has lower water absorption, and the deactivation of the catalyst due to the deactivation of the catalyst caused by the condensation of water in the pore channel of the catalyst is avoided. The results of the examples of the invention show that the conversion rate of the catalyst obtained by the invention to formaldehyde reaches 99.2%.
Furthermore, silanization treatment is needed after reduction reaction, so that the stability and the water poisoning resistance of the catalyst are obviously improved. In the invention, SiOCH is introduced through silanization treatment2CH3The group replaces active hydrogen on the surface of the carrier, the polarity is reduced after the active hydrogen is replaced, and the restriction of hydrogen bonds is reduced, so that the hydrophilicity of the surface of the catalyst is reduced, the hydrophobicity of the surface of the catalyst is improved, the water vapor in the formaldehyde gas is prevented from soaking into the catalyst substrate, the catalyst is unstable, and the moisture is further prevented from catalyzingThe agent is condensed in the pore channels to inactivate the catalyst and improve the water poisoning resistance of the catalyst. The results of the embodiment of the invention show that the inactivation parameter is not higher than 0.6 by combining the catalyst obtained in the subsequent silanization treatment step, and the catalyst has good water toxicity resistance and stability; and the catalyst activity is further improved.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a flow chart of the catalyst preparation of the present invention.
Detailed Description
The invention provides a preparation method of formaldehyde degradation catalyst, which firstly provides TiO loaded2The ZSM-5 molecular sieve aqueous dispersion is characterized in that the silica-alumina ratio of the ZSM-5 molecular sieve is (200-400): 1; then mixing the obtained dispersion liquid with a platinum-containing solution, and adjusting the pH value to 8-10, wherein TiO is loaded on the dispersion liquid2The mass ratio of the ZSM-5 molecular sieve to platinum in the platinum-containing solution is (84-94.99): (0.01-1) to obtain a pre-reduction treatment mixed solution, and then mixing the pre-reduction treatment mixed solution with NaBH4Mixing, and carrying out reduction reaction to obtain the formaldehyde degradation catalyst.
The invention takes the molar ratio of Si to Al as (200-400): 1 as molecular channel and load matrix, not only TiO2And Pt provides more sites for facilitating TiO2And the adsorption of Pt is beneficial to improving the catalytic degradation of formaldehyde and improving the catalytic activity; meanwhile, the adopted molecular sieve with the silicon-aluminum ratio has lower water absorption, and the deactivation of the catalyst due to the deactivation of the catalyst caused by the condensation of water in the pore channel of the catalyst is avoided.
The present invention provides a supported TiO2The aqueous dispersion of the ZSM-5 molecular sieve of (1). In the invention, the silica-alumina ratio of the ZSM-5 molecular sieve is (200-400) in terms of the molar ratio of Si to Al: 1, preferably (250-350): 1; in the embodiment of the present invention, the ratio of silicon to aluminum is specifically 225: 1. 275: 1. 325: 1. 375: 1. 380: 1. 385: 1. 390: 1 or 395: 1. in the present invention, the TiO-supporting material is a material having a high TiO content2In ZSM-5 molecular sieve of (1)2And the ZSM-5 molecular sieve in a mass ratio of 1: (9 to 29)) Preferably 1: (10-25), more preferably 1: (15-20).
In the present invention, the TiO-supporting material is a material having a high TiO content2The preparation method of the ZSM-5 molecular sieve preferably comprises the following steps: (a) with TiCl4Impregnating the ZSM-5 molecular sieve with the solution at the temperature of 20-25 ℃; (b) heating the impregnated molecular sieve to obtain the loaded TiO2The ZSM-5 molecular sieve of (1).
In the present invention, the TiCl4The amount of the solution is such that TiO is present in the amount of Ti content2The mass ratio of the ZSM-5 molecular sieve to the silicon-aluminum ratio in the scheme is within the range; the invention is to the TiCl4The concentration of the solution is not particularly critical. The impregnation method is not particularly required in the present invention, and the impregnation method known to those skilled in the art can be adopted. In the invention, the time for soaking is preferably 6-12 h, more preferably 8-10 h, and even more preferably 9 h. The impregnation process of the invention realizes the adsorption of Ti particles inside and outside the ZSM-5 molecular sieve pore channel.
In the present invention, the temperature of the heat treatment is preferably 400 to 450 ℃, and more preferably 425 to 430 ℃. In the present invention, the heat treatment is preferably performed by steam heating; in the present invention, the temperature of the water vapor is the temperature of the heat treatment. In the present invention, the time of the heat treatment is preferably 3 to 5 hours, more preferably 3.5 to 4.5 hours, and still more preferably 3 hours. The oxidation process of the Ti adsorbed in the heating treatment process of the invention obtains the loaded TiO2The ZSM-5 molecular sieve of (1).
Obtaining the loaded TiO2After the ZSM-5 molecular sieve is adopted, the invention preferably loads the TiO2Mixing the ZSM-5 molecular sieve with water to obtain the loaded TiO2The aqueous dispersion of the ZSM-5 molecular sieve of (1). In the present invention, the TiO-supporting material is a material having a high TiO content2The mass to water volume ratio of the ZSM-5 molecular sieve of (a) is preferably 1 g: (5-30) L, more preferably 1 g: (10-25) L, more preferably 1 g: (15-20) L. In the present invention, the mixing is preferably carried out by ultrasonic dispersion; in the invention, the time of ultrasonic dispersion is preferably 0.5-1 h,the power of the ultrasonic dispersion is preferably 250-300W.
After obtaining the aqueous dispersion, the obtained dispersion is mixed with a platinum-containing solution, and then the pH value is adjusted to 8-10, so that a pre-reduction treatment mixed solution is obtained. In the invention, the platinum-containing solution is preferably a chloroplatinic acid solution or a tetraammineplatinum nitrate solution and is used for improving the active component of the catalyst; in the present invention, the concentration of the platinum-containing solution is preferably 10 to 20g/L, and more preferably 12 to 15 g/L. In the present invention, TiO is supported in the dispersion liquid2The mass ratio of the ZSM-5 molecular sieve to the platinum in the platinum-containing solution is preferably (84-94.99): (0.01-1), more preferably (85-90): (0.05-0.5). The invention has no special requirement on the specific source of the platinic acid solution, and the platinum-containing solution which is well known to those skilled in the art can be adopted.
In the present invention, the mixing manner of the dispersion liquid and the platinum-containing solution is preferably ultrasonic dispersion; the time for ultrasonic dispersion is preferably 6-10 h, and further preferably 7-8 h; the temperature of ultrasonic dispersion is preferably 25-30 ℃; the frequency of the ultrasonic dispersion is preferably 20-30 kHz.
After a mixed solution of the dispersion liquid and the platinum-containing solution is obtained, the pH value of the mixed solution is adjusted to 8-10, preferably 8.5-9.5, and more preferably 9. In the invention, the pH value of the mixed solution is preferably adjusted by adopting an alkaline solution. In the present invention, the alkaline solution is preferably a sodium hydroxide solution, a potassium hydroxide solution, or ammonia water. In the present invention, the concentration of the alkaline solution is preferably 0.1 to 2mol/L, and more preferably 0.5 to 1.0 mol/L. The invention has no special requirement on the dosage of the alkaline solution so as to obtain the pH value.
The invention leads the obtained pre-reduction treatment mixed liquid and NaBH4Mixing, and carrying out reduction reaction to obtain the formaldehyde degradation catalyst. In the present invention, the NaBH4The volume ratio of the amount of the substance(s) to the pre-reduction treatment mixed liquid is preferably (0.05mol to 0.2 mol): 1L, more preferably (0.1mol to 0.1 mol): 1L, more preferably (0.5mol to 0.01 mol): 1L of the compound. In the invention, the pre-reduction treatment mixed solution and NaBH4OfThe combined mode is preferably ultrasonic dispersion; in the invention, the time of ultrasonic dispersion is preferably 2-3 h, and the frequency of ultrasonic dispersion is preferably 20-30 kHz. In the invention, NaBH is subjected to the ultrasonic dispersion process4The reduction effect on Pt ions is exerted, the preparation of the Pt noble metal catalyst can be realized under the room temperature condition, and the ultrasonic dispersion process improves the TiO2the/ZSM-5 and Pt are uniformly dispersed.
After the reduction reaction, the invention preferably carries out post-treatment on the reduction reaction product to obtain Pt-loaded TiO2The ZSM-5 molecular sieve catalyst. In the present invention, the post-treatment preferably includes suction filtration, washing and drying. The invention has no special requirements on the suction filtration mode, and the suction filtration mode which is well known by the technical personnel in the field can be adopted; in the invention, the washing is preferably carried out by deionized water, and the invention has no special requirement on the washing times so as to obtain a neutral suction filtration product; the suction filtration product is preferably dried by the method, and the method has no special requirement on the drying mode and can adopt the drying mode which is well known by the technical personnel in the field.
The invention also provides the formaldehyde degradation catalyst obtained by the preparation method of the technical scheme. In the present invention, the catalyst comprises Pt particles and TiO-supported particles2The Pt particles are supported on TiO of the ZSM-5 molecular sieve2And/or ZSM-5 molecular sieve surface, calculated as Pt/TiO2ZSM-5. In the present invention, the Pt particles and the TiO-supported particles2The mass ratio of the ZSM-5 molecular sieve is preferably (0.01-1): (84-94.99), more preferably (85-90): (0.05-0.5).
After the reduction reaction or the post-treatment, the present invention preferably subjects the obtained product to a silylation treatment. In the present invention, the silylation treatment preferably includes: and mixing the product obtained by the reduction reaction with tetraethyl orthosilicate, and roasting.
In the invention, the mass ratio of the tetraethyl orthosilicate to the product obtained by the reduction reaction is preferably (3-10): (85-95), more preferably (5-9): (86E ^ E90). In the invention, the product obtained by the reduction reaction is mixed with tetraethyl orthosilicate, and the tetraethyl orthosilicate is coated on the surface of the product obtained by the reduction reaction preferably in an impregnation mode; in the invention, the dipping temperature is preferably 20-25 ℃; in the invention, the soaking time is preferably 12-24 hours, and more preferably 15-20 hours. In the mixing process, tetraethyl orthosilicate is hydrolyzed to obtain a hydroxylated product, which is convenient to enter Pt particles and TiO loaded2In the pore channels of the ZSM-5 molecular sieve.
After the mixing, the mixture is preferably roasted to obtain the catalyst containing Pt particles and SiO2And supported with TiO2The ZSM-5 molecular sieve catalyst. In the invention, the roasting temperature is preferably 400-500 ℃, and more preferably 420-450 ℃; in the invention, the roasting time is preferably 4-6 hours, and more preferably 4.5-5 hours. The present invention has no special requirement on the roasting mode, and the roasting mode known to those skilled in the art can be adopted. In the roasting process, the carrier comprises Pt and supported TiO2The hydroxylation product of the ZSM-5 molecular sieve catalyst pore channel is decomposed to obtain SiO2The method improves the surface hydrophobicity of the catalyst, inhibits water vapor in formaldehyde gas from immersing into a catalyst substrate, makes the catalyst unstable, further avoids the water from condensing in a catalyst pore channel to inactivate the catalyst, and improves the water poisoning resistance of the catalyst.
The invention also provides a formaldehyde degradation catalyst obtained by the preparation method comprising the silanization treatment in the technical scheme, which comprises SiO2And a base; the substrate comprises Pt particles and TiO loaded2The ZSM-5 molecular sieve of (1), wherein Pt particles in the matrix are loaded on TiO2And/or ZSM-5 surface, the substrate being Pt/TiO2ZSM-5; the SiO2Supported on the surface and/or in the channels of the substrate, and is calculated as Pt/TiO as shown in figure 12/ZSM-5@SiO2. In the present invention, the Pt/TiO is2/ZSM-5@SiO2The mass percentage content of Pt in the alloy is preferably 0.01-1%, and more preferably 0.5%; the Pt/TiO2/ZSM-5@SiO2SiO 22The mass percentage of (b) is preferably 5-15%, more preferably 7.5-12.5%, and even more preferably 10%; the Pt/TiO2/ZSM-5@SiO2In which TiO is supported2The ZSM-5 molecular sieve has a mass percentage of preferably 84-94.99%, more preferably 87-92%, and even more preferably 89.5%.
The invention provides a preparation method of formaldehyde degradation catalyst, which firstly provides TiO loaded2The ZSM-5 molecular sieve aqueous dispersion is characterized in that the silica-alumina ratio of the ZSM-5 molecular sieve is (200-400): 1; then mixing the obtained water dispersion with a platinum acid solution, adjusting the pH value to 8-10 to obtain a pre-reduction treatment mixed solution, and then mixing the pre-reduction treatment mixed solution with NaBH4Mixing, carrying out reduction reaction to obtain formaldehyde degradation catalyst with limited TiO load2The mass ratio of the ZSM-5 molecular sieve to platinum is (84-94.99): (0.01-1). The invention takes the molar ratio of Si to Al as (200-400): 1 as molecular channel and load matrix, not only TiO2And Pt provides more sites for facilitating TiO2And adsorption of Pt with TiO2the/ZSM-5 is used as a carrier, which is beneficial to improving the dispersion degree of Pt, further realizing the increase of Pt active sites for formaldehyde degradation reaction, improving the catalytic degradation of formaldehyde and improving the catalytic activity on the premise of lower Pt addition; meanwhile, the adopted molecular sieve with the silicon-aluminum ratio has lower water absorption, and the deactivation of the catalyst due to the deactivation of the catalyst caused by the condensation of water in the pore channel of the catalyst is avoided.
Further, tetraethyl orthosilicate is hydrolyzed to obtain a hydroxyl compound, the hydroxyl compound enters a pore channel of the Pt/TiO2/ZSM-5 molecular sieve, and the hydrolysis-obtained hydroxyl compound is decomposed to obtain SiO in combination with the subsequent roasting process2Further, the catalyst is prevented from being deactivated by the condensation of water in the catalyst pore channel, and the water poisoning resistance of the catalyst is improved.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The catalyst prepared in the example is used for degrading formaldehyde by adopting a fixed bed reactor which is well known in the field, the reaction temperature is limited to 30 ℃, the formaldehyde concentration is 1000ppm, and the catalyst dosage is 0.3 g; wherein, the formaldehyde gas containing water is generated by a formaldehyde gas generator and is brought into a reaction system by air, the flow meter is 50ml/min, and products in different time periods are analyzed in real time by combining gas chromatography, so as to obtain the formaldehyde degradation rate of the catalyst.
Example 1
TiCl in a concentration of 30 wt%4Soaking ZSM-5 molecular sieve with the silica-alumina ratio of 200 in the solution at 25 ℃, and performing water vapor treatment at 400 ℃ to obtain the loaded TiO2ZSM-5 (TiO)2ZSM-5), in which TiO2And the ZSM-5 molecular sieve in a mass ratio of 1: 9;
according to TiO2The ratio of the mass of/ZSM-5 to the volume of deionized water is 1:5, and a certain amount of TiO is treated by ultrasonic treatment for 1h in a 250W ultrasonic instrument2the/ZSM-5 is dispersed in deionized water with corresponding proportion by ultrasound;
adding chloroplatinic acid solution with the concentration of 10g/L according to the load amount of Pt, and carrying out ultrasonic treatment for 6h at the temperature of 25 ℃. Then, adjusting the pH value of the system to 8 by using 0.1mol/L NaOH solution, continuing to perform ultrasonic treatment for 0.5h, and then adding NaBH according to the proportion of adding 0.2mol per unit volume4And continuing to perform ultrasonic reduction for 3 hours. Filtering the obtained product, washing to neutrality, and drying to obtain solid containing Pt and TiO2Catalyst for/ZSM-5 (Pt/TiO)2ZSM-5) in which Pt is mixed with TiO2The mass ratio of the/ZSM-5 is 1: 85.
The catalyst thus prepared was used for the degradation of formaldehyde, and the results are shown in ① and ② in Table 1, indicating that Pt/TiO thus prepared was used2the/ZSM-5 is used for degrading formaldehyde with water content of 0, and the degradation rate of the formaldehyde after different time is calculated, wherein the degradation rate of the formaldehyde after 10min is 99.2%, the degradation rate of the formaldehyde after 25h is 99%, and the degradation rate of the formaldehyde after 50h is 98.6%; the prepared Pt/TiO is mixed2ZSM-5 for water contentIs the degradation of 3000ppm of formaldehyde, and the degradation rate of formaldehyde after different time is calculated, wherein the degradation rate of formaldehyde after 10min is 78.4%, the degradation rate of formaldehyde after 25h is 68.3%, and the degradation rate of formaldehyde after 50h is 57.1%.
Example 2
TiCl in a concentration of 30 wt%4Soaking ZSM-5 molecular sieve with the silica-alumina ratio of 200 in the solution at 25 ℃, and performing water vapor treatment at 400 ℃ to obtain the loaded TiO2ZSM-5 (TiO)2ZSM-5), in which TiO2And the ZSM-5 molecular sieve in a mass ratio of 1: 9;
according to TiO2The ratio of the mass of/ZSM-5 to the volume of the deionized water is 1:5, ultrasonic treatment is carried out for 0.5h in a 250W ultrasonic instrument, and a certain amount of TiO is added2the/ZSM-5 is dispersed in deionized water with corresponding proportion by ultrasound;
adding chloroplatinic acid solution with the concentration of 10g/L according to the load amount of Pt, and carrying out ultrasonic treatment for 6h at the temperature of 25 ℃. Then, adjusting the pH value of the system to 9 by using 0.1mol/L NaOH solution, continuing to perform ultrasonic treatment for 0.5h, and then adding NaBH according to the proportion of adding 0.2mol per unit volume4And continuing ultrasonic reduction for 2 h. Filtering the obtained product, washing to neutrality, and drying to obtain solid containing Pt and TiO2Catalyst for/ZSM-5 (Pt/TiO)2ZSM-5) in which Pt is mixed with TiO2The mass ratio of ZSM-5 is 1: 85;
according to SiO2The loading capacity limits the dosage of tetraethyl orthosilicate, and the Pt/TiO prepared by soaking tetraethyl orthosilicate at 25 DEG C2ZSM-5, soaking for 12h, heating at 400 deg.C for 4h to complete silanization process to obtain Pt and SiO2And TiO2Catalyst for/ZSM-5 (Pt/TiO)2/ZSM-5@SiO2) Wherein Pt and SiO2With TiO2The mass ratio of the/ZSM-5 is 1: 14: 85.
the catalyst thus prepared was used for the degradation of formaldehyde, and the results are shown in ③ and ④ in Table 1, indicating that Pt/TiO thus prepared was used2/ZSM-5@SiO2The method is used for degrading formaldehyde with water content of 0, and formaldehyde degradation rates after different time periods are calculated, wherein the formaldehyde degradation rate after 10min is 99.8%, the formaldehyde degradation rate after 25h is 99.5%, and the formaldehyde degradation rate after 50h isThe degradation rate of formaldehyde is 99.3%; the prepared Pt/TiO is mixed2/ZSM-5@SiO2The method is used for degrading formaldehyde with water content of 3000ppm, and formaldehyde degradation rates after different time periods are calculated, wherein the formaldehyde degradation rate after 10min is 99.6%, the formaldehyde degradation rate after 25h is 99%, and the formaldehyde degradation rate after 50h is 99%.
Example 3
TiCl in a concentration of 30 wt%4Soaking ZSM-5 molecular sieve with the silica-alumina ratio of 400 in the solution at 25 ℃, and performing water vapor treatment at 400 ℃ to obtain the loaded TiO2ZSM-5 (TiO)2ZSM-5), in which TiO2And the ZSM-5 molecular sieve in a mass ratio of 1: 29;
according to TiO2The ratio of the mass of/ZSM-5 to the volume of the deionized water is 1:30, and a certain amount of TiO is treated by ultrasonic treatment for 1h in a 250W ultrasonic instrument2the/ZSM-5 is dispersed in deionized water with corresponding proportion by ultrasound;
adding chloroplatinic acid solution with the concentration of 10g/L according to the load amount of Pt, and carrying out ultrasonic treatment for 6h at the temperature of 25 ℃. Then, adjusting the pH value of the system to 10 by using 0.1mol/L NaOH solution, continuing to perform ultrasonic treatment for 0.5h, and then adding NaBH according to the proportion of adding 0.2mol per unit volume4And continuing to perform ultrasonic reduction for 3 hours. Filtering the obtained product, washing to neutrality, and drying to obtain solid containing Pt and TiO2Catalyst for/ZSM-5 (Pt/TiO)2ZSM-5) in which Pt is mixed with TiO2The mass ratio of the/ZSM-5 is 0.01: 94.99;
according to SiO2The loading capacity limits the dosage of tetraethyl orthosilicate, and the Pt/TiO prepared by soaking tetraethyl orthosilicate at 25 DEG C2ZSM-5, soaking for 24h, heating at 400 deg.C for 6h to complete silanization process to obtain Pt and SiO2And TiO2Catalyst of/ZSM-5, (Pt/TiO)2/ZSM-5@SiO2) Wherein Pt and SiO2With TiO2The mass ratio of ZSM-5 is 0.01: 5: 94.99.
comparative example 1
TiCl in a concentration of 30 wt%4Soaking ZSM-5 molecular sieve with the silica-alumina ratio of 50 in the solution at 25 ℃, and performing water vapor treatment at 400 ℃ to obtain the loaded TiO2ZSM-5 (TiO)2ZSM-5), in which TiO2And the ZSM-5 molecular sieve in a mass ratio of 1: 9;
according to TiO2The ratio of the mass of/ZSM-5 to the volume of the deionized water is 1:5, ultrasonic treatment is carried out for 0.5h in a 250W ultrasonic instrument, and a certain amount of TiO is added2the/ZSM-5 is dispersed in deionized water with corresponding proportion by ultrasound;
adding chloroplatinic acid solution with the concentration of 10g/L according to the load amount of Pt in the catalyst, and carrying out ultrasonic treatment for 6h at the temperature of 25 ℃. Then, adjusting the pH value of the system to 8.5 by using 0.1mol/L NaOH solution, continuing to perform ultrasonic treatment for 0.5h, and then adding NaBH according to the proportion of adding 0.2mol per unit volume4And continuing ultrasonic reduction for 2 h. Filtering the obtained product, washing to neutrality, and drying to obtain solid containing Pt and TiO2Catalyst for/ZSM-5 (Pt/TiO)2ZSM-5) in which Pt is mixed with TiO2The mass ratio of ZSM-5 is 1: 85;
according to SiO2The loading capacity limits the dosage of tetraethyl orthosilicate, and the Pt/TiO prepared by soaking tetraethyl orthosilicate at 25 DEG C2ZSM-5, soaking for 12h, heating at 400 deg.C for 4h to complete silanization process to obtain Pt and SiO2And TiO2Catalyst of/ZSM-5, (Pt/TiO)2/ZSM-5@SiO2) Wherein Pt and SiO2With TiO2The mass ratio of the/ZSM-5 is 1: 14: 85.
the catalyst thus prepared was used for the degradation of formaldehyde, and the results are shown in ⑤ in Table 1, which shows that Pt/TiO thus prepared2/ZSM-5@SiO2The method is used for degrading formaldehyde with water content of 3000ppm, and formaldehyde degradation rates after different time periods are calculated, wherein the formaldehyde degradation rate after 10min is 82.3%, the formaldehyde degradation rate after 25h is 76.7%, and the formaldehyde degradation rate after 50h is 71.5%.
TABLE 1 Formaldehyde degradation ratio of different catalysts
The deactivation parameter D ═ X in Table 1i-Xf)/Xi×100％，XiIs formaldehyde after reaction is stable for 10minThe degradation rate, i.e. the initial degradation rate of formaldehyde, and XfIs the formaldehyde degradation rate at 50h of reaction. Wherein the deactivation parameter is indicative of the stability or resistance of the catalyst to water poisoning. A small deactivation parameter indicates high catalyst stability or resistance to water poisoning, while a large deactivation parameter indicates poor catalyst stability or resistance to water poisoning.
From ① and ③ in Table 1, it is understood that in the treatment of formaldehyde gas containing no water vapor, Pt/TiO catalyst not subjected to silylation treatment in the present invention2The initial conversion of/ZSM-5 was 99.2%, and the conversion after 50h of reaction was 98.6%. Catalyst Pt/TiO treated by silanization in the invention2/ZSM-5@SiO2(Si/Al is 200), the initial conversion rate is 99.8%, and the conversion rate after 50h of reaction is still 99.3%, and the catalyst has high catalytic activity.
From ② and ④ in Table 1, it can be seen that the catalyst Pt/TiO of the present invention which has not been subjected to silylation treatment in treating HCHO gas containing water vapor2The initial conversion rate of/ZSM-5 was 78.4%, the conversion rate after 50h of reaction was reduced to 57.1%, and the catalyst deactivation parameter reached 27.2%. In the invention, the catalyst Pt/TiO is subjected to silanization treatment2/ZSM-5@SiO2(Si/Al is 200), the initial conversion rate reaches 99.6%, the conversion rate after 50h of reaction is still 99.1%, the reduction range of the formaldehyde conversion rate is small, and the catalyst deactivation parameter is only 0.5%. Therefore, the activity and the stability of the catalyst are greatly improved after the silanization treatment.
From ③ and ④ in Table 1, it can be seen that the silanized Pt/TiO catalyst2/ZSM-5@SiO2(Si/Al is 200), whether the formaldehyde gas containing no water vapor or the formaldehyde gas containing water vapor is treated, the formaldehyde degradation rate can reach more than 99 percent, the catalyst activity is high, and the stability and the water poisoning resistance are high (the inactivation parameter is only 0.5 percent).
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of a formaldehyde degradation catalyst comprises the following steps:
(1) providing a supported TiO2The ZSM-5 molecular sieve has a silica-alumina ratio (calculated by the molar ratio of Si to Al in the molecular sieve) of (200-400): 1;
(2) mixing the aqueous dispersion obtained in the step (1) with a platinum-containing solution, and adjusting the pH value to 8-10 to obtain a pre-reduction treatment mixed solution; TiO is loaded in the dispersion liquid2The mass ratio of the ZSM-5 molecular sieve to platinum in the platinum-containing solution is (84-94.99): (0.01 to 1);
(3) mixing the pre-reduction treatment mixed solution obtained in the step (2) with NaBH4Mixing, and carrying out reduction reaction to obtain the formaldehyde degradation catalyst.
2. The method according to claim 1, wherein the aqueous dispersion is loaded with TiO2The volume ratio of the mass of the ZSM-5 molecular sieve to the water is 1 g: (5-30) L.
3. The method according to claim 2, wherein the TiO-supporting material is supported on a support2In ZSM-5 molecular sieve of (1)2And the ZSM-5 molecular sieve in a mass ratio of 1: (9-29).
4. The method according to claim 1, wherein NaBH is added in step (3)4The volume ratio (0.05mol to 0.2mol) of the pre-reduction treatment mixed solution: 1L of the compound.
5. The method according to claim 1, further comprising, after the reduction reaction: carrying out silanization treatment on a product obtained by the reduction reaction; the silanization treatment comprises the following steps: and mixing the product obtained by the reduction reaction with tetraethyl orthosilicate, and roasting.
6. The preparation method according to claim 5, wherein the mass ratio of the tetraethyl orthosilicate to the product obtained by the reduction reaction is (3-10): (85-95).
7. The method according to claim 5, wherein the temperature of the calcination is 400 to 500 ℃.
8. The preparation method according to claim 5 or 7, wherein the roasting time is 4-6 h.
9. The formaldehyde degradation catalyst obtained by the preparation method of any one of claims 1 to 4, comprising Pt particles and TiO-loaded particles2The Pt particles are supported on TiO of the ZSM-5 molecular sieve2And/or a ZSM-5 surface.
10. The formaldehyde degradation catalyst obtained by the preparation method of any one of claims 5 to 8, which comprises SiO2And a base; the substrate comprises Pt particles and TiO loaded2The ZSM-5 molecular sieve of (1), wherein Pt particles in the matrix are loaded on TiO2And/or a ZSM-5 surface; the SiO2Supported on the surface and/or in the channels of the substrate.
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| CN113731479A (en) * | 2021-09-28 | 2021-12-03 | 无锡威孚环保催化剂有限公司 | HCHO catalyst capable of efficiently and rapidly degrading at room temperature and preparation method thereof |
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