CN103962174A - AgCo bimetallic catalyst with adsorption-catalysis double functions for use in removal of formaldehyde and preparation method thereof - Google Patents

Abstract

The invention discloses an AgCo bimetallic catalyst with dual functions of adsorption and catalysis for eliminating formaldehyde and a preparation method thereof. The bimetallic catalyst uses a mesoporous silicon material modified with 3-aminopropyltriethoxysilane as the bimetallic catalyst The carrier, the active components are transition metals cobalt and silver. Compared with the noble metals Pt and Au, the price of Ag nano-metals is relatively low, which reduces the practical application cost; using Co as one of the active components on the bimetal, compared with the above-mentioned noble metal/oxide catalysts, the oxides are formed from the support Become the active component and reduce the content of the oxide component; use APTES modified mesoporous silicon material as the catalyst carrier, compared with the oxide carrier, the large increase in specific surface area is conducive to the dispersion of the active component and the normal temperature resistance to formaldehyde adsorption. The method has simple steps and a short period, and strong Ag and Co metal interactions are generated during the synthesis process, which is helpful for the low-temperature catalytic oxidation elimination of formaldehyde.

Description

A kind of AgCo bimetallic catalyst with adsorption-catalysis double function to eliminate formaldehyde and preparation method thereof

technical field

The invention relates to the technical field of indoor air formaldehyde purification, and relates to an AgCo bimetallic catalyst with dual functions of adsorption and catalysis for eliminating formaldehyde and a preparation method thereof.

Background technique

Formaldehyde, also known as formaldehyde, has high toxicity and has been identified as a carcinogenic and teratogenic substance by the World Health Organization. It is an important VOC (Volatile Organic Compounds) pollutant. Formaldehyde has a wide range of sources, and building decoration and decoration materials, as well as a variety of indoor daily necessities, can slowly release formaldehyde. With the improvement of people's living standards, the quality requirements of indoor air are becoming more and more stringent, so the elimination and degradation of indoor formaldehyde has very important practical significance.

Formaldehyde treatment technology includes activated carbon adsorption technology, non-thermal plasma purification technology, photocatalytic technology and catalytic oxidation technology. At present, the most commonly used method is the adsorption method, but the removal and purification cycle of the adsorption method is long, and the adsorbent needs to be replaced regularly. The water vapor in the air has a great impact on its adsorption performance, and it cannot fundamentally eliminate formaldehyde pollution. Recently, there have been many researches on photocatalytic oxidation technology. For example, Chinese patent 00129180.7 has announced a photocatalyst for purifying air. It uses titanium oxide powder as the main catalyst, but it must have light. When the concentration is low, an external light source such as an ultraviolet lamp is required. Cause inconvenience and cost increase. Thermal catalytic decomposition of formaldehyde has become a research hotspot due to its advantages of low energy consumption, low operation and good selectivity, but its low-temperature catalytic performance is still not ideal. Although the internationally renowned chemical journal AppliedCatalysis B: Environmental (2013,132–133(0):245-255)(2014,154–155(0):73-81), Angewandte Chemie International Edition(2012, 51(38): 9628-9632) have reported several catalyst materials for complete catalytic oxidation to eliminate formaldehyde at room temperature: Pt/TiO ₂ , Au/CeO ₂ and Au/FeO _x catalysts, but they are expensive and generally use metal oxide carrier materials loaded precious metal components. Moreover, conditions such as solution pH and temperature need to be strictly controlled during the preparation process. For example, the Chinese patent (CN1714930A) pointed out in the formaldehyde catalyst material that the noble metal is supported on the metal oxide carrier: a certain amount of oxygen species O ^2- , O ⁻ , O ^2- , And when it is mainly O ^- , the activity of the noble metal component can be improved. If the acidity of the solution is not properly controlled during the preparation of metal oxides, the formaldehyde conversion rate of the catalyst will decrease. Therefore, further development of new low-cost, low-temperature and high-efficiency formaldehyde catalytic oxidation catalysts, reducing the actual application cost, and simplifying the catalyst preparation process are the current research directions for formaldehyde catalytic oxidation elimination.

Mesoporous MCM-41 and SBA-15 silicon materials with high specific surface area and regular pore diameter (2.0-10.0nm) are better materials for pollutant adsorption and catalytically active component load dispersion. The present invention utilizes the characteristics such as the stable structure and unique pore structure of the catalyst prepared by the selected AgCo bimetal supported on the mesoporous silicon material, and can be used as an effective formaldehyde adsorption material at room temperature to achieve formaldehyde protection at room temperature. At the same time, formaldehyde is completely converted into harmless carbon dioxide and water by catalytic combustion at a suitable low temperature (30-100 ° C) by using silver and cobalt bimetallic active components.

Contents of the invention

The invention provides an AgCo bimetallic catalyst with dual functions of adsorption and catalysis to eliminate formaldehyde and a preparation method thereof. Formaldehyde can be decomposed into non-toxic and harmless compounds at relatively low temperatures by using transition metals cobalt (Co) and silver (Ag). Carbon dioxide and water, and their prices are relatively cheap compared with precious metals such as Pt, Au, etc., which reduces the cost of their practical application.

The technical scheme that the present invention adopts is as follows:

An AgCo bimetallic catalyst with dual functions of adsorption and catalysis to eliminate formaldehyde, using 3-aminopropyltriethoxysilane (APTES) modified mesoporous silicon material as the carrier of the bimetallic catalyst, and the active component is a transition metal Cobalt (Co) and Silver (Ag). The mesoporous silicon material may be at least one of mesoporous silicon materials such as MCM-41, SBA-15, and SiO ₂ . Compared with the noble metals Pt and Au, the price of Ag nano-metals is relatively low, which reduces the practical application cost; using Co as one of the active components on the bimetal, compared with the above-mentioned noble metal/oxide catalysts, the oxides are formed from the support become active components and reduce the content of oxide components; APTES-modified mesoporous silicon molecular sieve materials are used as catalyst supports. Compared with oxide supports, the specific surface area is greatly improved, and the dispersion of active components and the The adsorption capacity of formaldehyde will eventually improve the formaldehyde elimination capacity of the catalyst.

The AgCo bimetallic catalyst provided by the invention adopts two-step method preparation, specifically as follows:

(1) The mesoporous silicon material and APTES are condensed and refluxed at 80-100°C for 12-24h under anhydrous conditions or absolute ethanol conditions, then centrifuged and washed, dried at 80-100°C for 12-24h, and 500-800°C Calcination for 6-8 hours; the resulting APTES-modified mesoporous silicon material was prepared into a solution, then added silver nitrate (AgNO ₃ ), stirred at room temperature for 15-30 minutes, continued to add NaBH ₄ solution for chemical reduction, continued to stir at room temperature for 15-30 minutes, and then centrifuged , Wash, and prepare the sample.

(2) Add cobalt nitrate (Co(NO ₃ ) ₂ 6H ₂ O) to the sample obtained in step (1), stir at room temperature for 15-30 minutes, continue to add NaBH ₄ solution for chemical reduction, and continue stirring at room temperature for 15-30 minutes before proceeding After centrifuging and washing, the resultant is dried at 80-100°C for 12-24 hours, and calcined at 500-800°C for 6-8 hours.

The activity evaluation of the catalyst was carried out in a straight-tube fixed-bed continuous-flow differential reactor. The reactor was a straight quartz reaction tube with an inner diameter of 8 mm. The catalyst loading was 200-500 mg, and the formaldehyde gas was generated by a formaldehyde gas generator. Gas volume composition: oxygen: 10-20%, argon: 80-90%, formaldehyde control concentration is 100-500ppm, reaction space velocity is 9000-36000mL/g h. For the gas whose formaldehyde concentration is 500 times higher than GB/T18883-2002, the catalyst can completely adsorb within 2 hours, and has a strong adsorption capacity. After reacting for 60 minutes, the product gas was analyzed online by GC-7890II gas chromatograph equipped with FID detector. The conversion rate of formaldehyde is about 90% or more below 100°C. The concentration after purification meets the national standard.

In the invention, the raw material of the catalyst is cheap and easy to obtain, the preparation method is simple, and the volatile organic pollutant-formaldehyde in the air can be effectively removed. This adsorption-low-temperature catalytic dual-functional AgCo bimetallic catalyst can effectively adsorb formaldehyde at room temperature, which is an ideal adsorption material; and convert pollutant formaldehyde into harmless CO ₂ and H through low-temperature catalytic oxidation technology ₂ O, no other by-products, no secondary pollution. The use temperature of the catalyst is 30-100°C, which is an energy-saving catalyst. At the same time, the catalytic activity of the catalyst is higher than that of manganese, cobalt oxide or rare earth composite oxide catalysts. Compared with platinum, rhodium, palladium, gold and other precious metal catalysts, it has low price and relatively abundant resources, and the production method of the catalyst is simple and low in cost, so it has potential application value.

Description of drawings

Figure 1 is the formaldehyde catalytic oxidation reaction activity curve of AgCo/APTESMCM-41 prepared by two-step method with different Ag/Co mass ratios.

Fig. 2 is the H ₂ -TPR curves of different Ag/Co mass ratios of AgCo/APTESMCM-41 prepared by two-step method.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with technical solutions and accompanying drawings.

Example 1

Condensate and reflux 2.0g MCM-41 and 10.0g APTES in 200mL of absolute ethanol at 80-100°C for 24h, centrifuge, wash, dry at 80°C for 24h, and calcinate at 500°C for 6h to obtain APTESMCM-41 sample; weigh 1.0 g APTESMCM-41 in 40mL deionized water to obtain APTESMCM-41 aqueous solution, stirred at room temperature for 15 minutes, added 0.0945g AgNO ₃ , stirred at room temperature for 15 minutes, quickly added 10mL of 2M NaBH ₄ solution for chemical reduction, continued to stir at room temperature for 30 minutes, then centrifuged and washed , to obtain a 6% Ag/APTESMCM-41 sample; dissolve the washed Ag/APTESMCM-41 sample in 40mL deionized water and stir at room temperature for 15min, then add 0.099gCo(NO ₃ ) ₂ ·6H ₂ O, stir at room temperature for 15min, continue to rapidly Add 10mL of 2M _NaBH4 solution for chemical reduction, continue to stir at room temperature for 30min, then centrifuge and wash; finally, dry the centrifuged and washed sample at 80°C for 24h, and calcinate at 500°C for 6h to obtain 6Ag2Co/APTESMCM-41 sample (Ag The mass fraction is 6%, the mass fraction of Co is 2%, and the mass ratio of Ag/Co is 3/1).

Example 2

According to the preparation method of Example 1, 0.126g AgNO ₃ was added to the APTESMCM-41 sample, Co(NO ₃ ) ₂ 6H ₂ O was not added, and the remaining steps remained the same to obtain the 8Ag0Co/APTESMCM-41 sample (the mass of Ag The fraction is 8%, the mass fraction of Co is 0%, and the mass ratio of Ag/Co is 1/0).

Example 3

According to the preparation method of Example 1, 0.396g Co(NO ₃ ) ₂ 6H ₂ O was added to the APTESMCM-41 sample without adding AgNO ₃ , and the rest of the steps remained the same to obtain 0Ag8Co/APTESMCM-41 sample (the mass of Ag The fraction is 0%, the mass fraction of Co is 8%, and the mass ratio of Ag/Co is 0/1).

Example 4

According to the preparation method of Example 1, 0.063g AgNO ₃ , 0.198g Co(NO ₃ ) ₂ ·6H ₂ O were added to the APTESMCM-41 sample, and the rest of the steps remained the same to obtain the 4Ag4Co/APTESMCM-41 sample (Ag The mass fraction is 4%, the mass fraction of Co is 4%, and the mass ratio of Ag/Co is 1/1).

Example 5

According to the preparation method of Example 1, 0.0315g AgNO ₃ and 0.297g Co(NO ₃ ) ₂ ·6H ₂ O were added to the APTESMCM-41 sample respectively, and the rest of the steps remained the same to obtain the 2Ag6Co/APTESMCM-41 sample (Ag The mass fraction is 2%, the mass fraction of Co is 6%, and the mass ratio of Ag/Co is 1/3).

Claims (3)

1. one kind has the AgCo bimetallic catalyst of the difunctional elimination formaldehyde of absorption-catalysis, it is characterized in that, two kinds of active components of this AgCo bimetallic catalyst are respectively cobalt and silver, inhale, and the mesoporous silica molecular sieve after 3-aminopropyl triethoxysilane is modified is as the carrier of bimetallic catalyst.

2. AgCo bimetallic catalyst according to claim 1, is characterized in that, described mesoporous silica molecular sieve is MCM-41, SBA-15, SiO ₂in at least one.

3. the preparation method of the AgCo bimetallic catalyst described in claim 1 or 2, is characterized in that following steps:

(1) mesoporous silicon material and APTES are carried out under anhydrous condition or absolute ethyl alcohol condition to centrifugal, washing at 80～100 DEG C after condensing reflux 12～24h, dry 12～24h at 80～100 DEG C, 500～800 DEG C of calcining 6～8h; After being prepared into solution, mesoporous silicon material after gained APTES modifies adds silver nitrate (AgNO ₃), stirring at normal temperature 15～30min, continues to add NaBH ₄solution carries out electronation, continues to carry out centrifugal, washing after stirring at normal temperature 15～30min, makes sample;

(2) gained sample in step (1) is added to cobalt nitrate (Co (NO ₃) ₂6H ₂o), stirring at normal temperature 15～30min, continues to add NaBH ₄solution carries out electronation, continues to carry out centrifugal, washing after stirring at normal temperature 15～30min dry 12～24h at 80～100 DEG C of gains, 500～800 DEG C of calcining 6～8h.