CN101695651B - Copper and iron-loaded modified activated carbon absorbent and method for preparing same - Google Patents

Abstract

A copper-iron modified activated carbon adsorbent and a preparation method thereof, characterized in that conventional coal-based activated carbon is used as the carrier of the adsorbent, and oxides of two transition metals, copper and iron, are loaded on the carrier as active components. The molar ratio of copper and iron in said oxide is 5～20:1. The modified activated carbon adsorbent of the present invention has simple preparation method, strong operability, high purification efficiency and low purification cost; dephosphorization of waste gas can be realized after adsorption is saturated, and waste resources can be realized; the reaction condition is mild and easy to realize. The invention also applies for the preparation method of the modified activated carbon adsorbent.

Description

A kind of copper iron modified activated carbon adsorbent and preparation method thereof

technical field

The invention relates to a preparation technology of an adsorbent, in particular to a preparation method of a loaded adsorbent for purifying low-concentration phosphine, and belongs to the technical field of adsorption and separation.

Background technique

Phosphine (PH ₃ ) is a colorless, foul-smelling gas at room temperature, highly toxic, also known as phosphine or phosphine, and was included in the "Highly Toxic Substances Catalog" issued by the Ministry of Health of the People's Republic of China "middle. PH ₃ is mainly produced in the processes of yellow phosphorus production, magnesium powder preparation, acetylene production, sodium hypophosphite production, and grain storage fumigation and insecticide. Its discharge will cause air pollution, endanger the environment and human health, and affect the reuse of yellow phosphorus tail gas containing PH ₃ and calcium carbide furnace tail gas. The purification of yellow phosphorus tail gas to produce high-purity CO technology is the main topic of my country's "Tenth Five-Year Plan" chemical environmental protection research, but the existence of phosphine gas in yellow phosphorus tail gas will poison the one-carbon chemical catalyst, which seriously restricts the resource utilization of waste. In order to use the carbon monoxide in the tail gas to produce products with high added value, it is necessary to remove the phosphine impurity in the yellow phosphorus tail gas. At present, there are many purification technologies for low-concentration PH ₃ at home and abroad, mainly including combustion method, chemical oxidation absorption method, catalytic oxidation method and adsorption method.

The combustion method is a traditional purification method. The process flow of this method is simple, and the purification efficiency of PH ₃ can reach 100%.

The chemical oxidation absorption method uses the reducing property of phosphine to react with phosphine in a solution containing oxidants (such as sodium hypochlorite, potassium permanganate, sulfuric acid, hydrogen peroxide, phosphoric acid, etc.) to realize the purification of phosphine . The method needs to consume oxidant, and the dephosphorization efficiency is closely related to the concentration of oxidant, while the concentration of oxidant decreases rapidly during the absorption reaction, so there are high operating costs, easy fluctuations in dephosphorization efficiency, and poor operability of the device.

The catalytic oxidation method uses activated carbon as an oxidation catalyst, mixes 1% oxygen into the gas containing PH ₃ , and preheats it to about 110°C to pass through the activated carbon bed, and PH ₃ is oxidized to P ₂ O ₅ under the catalytic oxidation of activated carbon and P ₂ O ₃ , since the adsorption capacity of activated carbon on P ₂ O ₅ and P ₂ O ₃ is much larger than that of PH ₃ , so that the gas can be further purified. Each kilogram of catalyst can purify 700-1000m ^{3 of} tail gas, which is equivalent to consuming 2.5-4kg of catalyst (without considering regeneration) to purify 1 ton of yellow phosphorus tail gas. The advantage of the catalytic oxidation method is that the dephosphorization effect is good and the purification degree is high. The disadvantage is that the regeneration of activated carbon is difficult, the failure is also faster, and the catalyst needs to be consumed at the same time.

The adsorption method is a purification method that uses an adsorbent to remove pH ₃ through physical adsorption or chemical adsorption. Physical adsorption utilizes the van der Waals force between the adsorbate molecule and the adsorbent. Usually, the physical adsorption performance of phosphine on the adsorbent is weak, so there are not many related studies. At present, chemical adsorption is widely used. Typical adsorption methods include activated carbon adsorption, metal oxides and temperature swing adsorption. U.S. Patent No. US 5182088 discloses a chemical adsorbent prepared by co-precipitation method with commonly used copper and zinc oxides as active components, adding AgO, HgO and other accelerators. The chemical adsorbent has a significantly improved adsorption capacity, but due to the need for Adding accelerators such as noble metals (AgO) or highly polluting heavy metals (HgO, CdO) will inevitably increase the production cost and the cost of waste disposal in the future.

The activated carbon adsorption method utilizes the reducibility of PH ₃ to react with the active components on the activated carbon to generate P ₂ O ₅ and P ₂ O ₃ to realize the deep purification of yellow phosphorus tail gas. Activated carbon has a large specific surface area and various active groups. It can be used alone as an adsorbent or modified carrier to adsorb and treat various pollutants in exhaust gas. It is one of the first choice materials for adsorption and purification. The adsorption capacity of activated carbon is mainly determined by the activated carbon Pore structure, in order to improve its adsorption efficiency, adsorption selectivity and catalytic performance, it is often necessary to adjust the pore structure of activated carbon and change its surface chemical properties. But the adsorption capacity of fresh activated carbon for pH ₃ is not high. Impregnating certain metal compounds in activated carbon as modifiers can significantly enhance the catalytic activity of activated carbon, which can not only reduce the reaction temperature, but also greatly increase the adsorption capacity.

The above methods all have defects such as low dephosphorization accuracy, high energy consumption, low efficiency, complicated process, large investment or secondary pollution, especially the adsorption capacity for PH ₃ is not high. The yellow phosphorus tail gas purified by the above method fails to meet the requirements of one-carbon chemical industry. The yellow phosphorus tail gas is a gas source rich in carbon monoxide, but the comprehensive utilization of the yellow phosphorus tail gas is limited due to the impurity of phosphine contained in it. Therefore, it is an urgent task to develop a series of adsorbents with high adsorption capacity to remove phosphine impurities from yellow phosphorus tail gas and achieve better purification effect.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a kind of adsorbent with high adsorption capacity for adsorbing and removing phosphine gas from yellow phosphorus tail gas and its preparation method, the adsorbent provided by the present invention does not need to add Accelerators such as noble metals (AgO) or highly polluting heavy metals (HgO, CdO).

The copper-iron modified activated carbon adsorbent provided by the present invention uses conventional commercially available coal-based activated carbon as the carrier of the adsorbent, and is characterized in that the oxides of two transition metals, copper and iron, are loaded on the carrier as active components, The composition of said modified activated carbon adsorbent is calculated in % by weight: copper oxide is 1.30～1.51% in terms of copper element, iron oxide is 0.057～0.23% in terms of iron element, and the balance is activated carbon; The molar ratio of copper and iron in the oxide is 5-20:1.

The copper-iron modified activated carbon adsorbent provided by the invention is prepared through the following methods:

A. Wash conventional coal-based activated carbon with distilled water, then use ultrasonic cleaning for 40 minutes, and dry at a constant temperature of 80-120°C for 12-24 hours;

B. Immerse the activated carbon treated in step A into a nitrate aqueous solution containing copper and iron in a certain ratio. The concentration of the nitrate aqueous solution is 55.11～67.93g/L, and the molar ratio of copper and iron is 5～20:1 , the solid/liquid ratio of the immersed activated carbon and nitrate aqueous solution is 1041.67g/L, fully stirred, and ultrasonically impregnated at 30°C for 40-60 minutes, and the impregnated activated carbon was taken out and dried at 80-100°C for 12 ~24 hours;

C. Calcining the activated carbon after step B at a temperature of 200-600°C for 2-8 hours, taking it out and cooling it to room temperature in a drying dish to obtain a copper-iron modified activated carbon adsorbent for adsorbing low-concentration phosphine gas.

Compared with the prior art, the present invention has the following advantages or positive effects:

1. The method is simple and operable, which improves the purification efficiency and reduces the purification cost;

2. When the adsorption is saturated, dephosphorization of waste gas can be realized, and waste resources can be realized;

3. The reaction conditions are mild and easy to realize.

Description of drawings

Figure 1 is a comparison of the phosphine adsorption capacity of activated carbon loaded with different active components in the example.

Experimental conditions: 4.17g adsorbent, PH ₃ concentration at the inlet of the adsorption column is 1000ppm, nitrogen is the carrier gas, oxygen content is 1%, the adsorption condition is constant temperature 70°C, under normal pressure, the space velocity is 3000/h, and the total flow rate is 450ml/min .

Detailed ways

The present invention will be further described below with embodiment.

Example 1

Wash the conventional commercially available coal-based activated carbon with distilled water, and then perform conventional ultrasonic cleaning for 40 minutes, place it in an oven to dry, and dry it at 100°C for 18 hours and take it out for use; weigh 1.2202g Cu(NO ₃ ) ₂ ·3H ₂ O Mix with 0.4102g Fe(NO ₃ ) ₃ 9H ₂ O to make Cu/Fe=5:1 (molar ratio), dissolve with 24ml distilled water to obtain the impregnation solution; weigh 25g of the above-mentioned dried activated carbon and immerse in the impregnation solution , fully stirred, impregnated with conventional ultrasound at 30°C for 60 minutes, then placed in an oven, dried at 100°C for 12 hours; finally placed in a muffle furnace, baked at 350°C for 6 hours, and taken out Place in a desiccator and cool to room temperature to obtain an activated carbon adsorbent for adsorbing low-concentration phosphine gas. The purification effect is shown in Table 1.

Table 1 Purification effect:

time/minute 40 80 120 180 240 300 360 420 Purification efficiency (%) 100 99 98 96 95 92 90 87

Example 2

The coal-based activated carbon was washed with distilled water, cleaned by conventional ultrasonic cleaning, and then dried in an oven, dried at 80°C for 24 hours and taken out for use; weighed 1.2202g Cu(NO ₃ ) ₂ ·3H ₂ O and 0.2051gFe(NO ₃ ) ₃ 9H ₂ O mixed to make Cu/Fe = 10:1 (molar ratio), dissolved in 24ml of distilled water to obtain the impregnating solution; weigh 25g of the above-mentioned dried activated carbon and immerse in the impregnating solution, fully stir, Under the condition of ℃, use conventional ultrasonic impregnation for 50 minutes, put it in an oven and dry it at 80℃ for 24 hours; finally put it in a muffle furnace and bake it at 200℃ for 8 hours, take it out and put it in a drying dish and cool it to room temperature, you can get The activated carbon adsorbent that adsorbs low-concentration phosphine gas, the purification effect is shown in Table 2.

Table 2 Purification effect:

time/min 150 160 360 420 480 540 600 660 Purification efficiency (%) 100 99 98 96 95 94 92 88

Example 3

The coal-based activated carbon was washed with distilled water, cleaned by conventional ultrasonic cleaning, and then dried in an oven, dried at 120°C for 12 hours and taken out for use; weighed 1.2202g Cu(NO ₃ ) ₂ ·3H ₂ O and 0.1025gFe(NO ₃ ) ₃ 9H ₂ O mixed to make Cu/Fe = 20:1 (molar ratio), dissolved in 24ml of distilled water to obtain the impregnating solution; weigh 25g of the above-mentioned dried activated carbon and immerse in the impregnating solution, fully stir, Under the condition of ℃, use conventional ultrasonic impregnation for 40 minutes, put it in an oven and dry it at 90 ℃ for 18 hours; finally put it in a muffle furnace and bake it at 600 ℃ for 2 hours, take it out and put it in a drying dish to cool to room temperature, you can get The activated carbon adsorbent that adsorbs low-concentration phosphine gas, the purification effect is shown in Table 3.

Table 3 Purification effect:

time/min 150 160 360 420 480 540 600 660 Purification efficiency (%) 100 99 98 96 95 94 92 88

comparative example

Put the coal-based activated carbon in an oven, wash it with distilled water, and then wash it with conventional ultrasonic waves, then put it in an oven to dry, and dry it at 100°C for 12 to 24 hours and take it out for use; weigh 1.2202g Cu(NO ₃ ) ₂ ·3H ₂ O Dissolve 24ml of distilled water to obtain the impregnating solution; weigh 25g of the above-mentioned dried activated carbon and immerse in the impregnating solution, stir thoroughly, impregnate with conventional ultrasound at 30°C for 40 minutes, and dry at 100°C for 12 to 24 hours; Finally, place it in a muffle furnace and bake it at 350°C for 6-8 hours, take it out, put it in a drying dish and cool it to room temperature, and then you can get an activated carbon adsorbent that adsorbs low-concentration phosphine gas. The purification effect is shown in Table 4.

Table 4 Purification effect:

time/min 65 105 120 180 240 300 360 420 Purification efficiency (%) 100 99 98 97 95 93 91 89

As can be seen from the four tables in the example, the purification efficiency at the initial stage of adsorption can reach 100%, and as the adsorption process continues, the purification efficiency gradually declines, but the adsorbent prepared by loading activated carbon with Cu: Fe (20: 1) has no effect on phosphorus The purification effect of hydrogen hydride is obviously better than that of the other two adsorbents, and the purification efficiency is still above 90% when the reaction lasts for about 600 minutes. It can be seen from Figure 1 that the adsorption capacity of two-component copper and iron modified coal-based activated carbon for phosphine is higher than that of single-component copper, in which iron plays an auxiliary role, so that copper can be better loaded on the surface of activated carbon , but it does not mean that the greater the proportion of iron in the impregnation solution, the better the adsorption effect on phosphine, and the ratio of the two must be within a certain range. In addition, the ratio of the active component to the carrier component of the adsorbent of the present invention needs to be within a certain range. When the active component is too low, a competitive adsorption capacity cannot be achieved; when the active component is too high, the specific surface area will be reduced. , and correspondingly reduces the adsorption capacity.

Claims (2)

1. copper iron-loaded modified activated carbon absorbent; With the carrier of conventional coal mass active carbon as adsorbent; It is characterized in that the oxide of copper loaded, two kinds of transition metal of iron is as active component on this carrier, the composition of said modified activated carbon absorbent is counted with weight %: Cu oxide counts 1.30～1.51% with copper; Ferriferous oxide counts 0.057～0.23% with ferro element, and surplus is an active carbon; The mol ratio of copper and iron is 5～20: 1 in the said oxide.

2. the preparation method of a copper iron-loaded modified activated carbon absorbent as claimed in claim 1 is characterized in that having following preparation section:

A, conventional coal mass active carbon is clean with distilled water used ultrasonic waves for cleaning 40 minutes again, and freeze-day with constant temperature is 12～24 hours under 80～120 ℃ of temperature conditions;

B, operation A active carbon processed is immersed in the nitrate aqueous solution of the certain proportioning contain copper, iron; The concentration of nitrate aqueous solution is 55.11～67.93g/L, and wherein the mol ratio of copper and iron is 5～20: 1, and the active carbon of immersion and the solid-liquid of nitrate aqueous solution are than being 1041.67g/L; Fully stir; Under 30 ℃ of conditions, with ultrasonic immersing 40～60 minutes, take out the active carbon after flooding, drying is 12～24 hours under 80～100 ℃ of temperature;

C, will pass through process B active carbon 200～600 ℃ of roasting temperatures 2～8 hours, take out and place drying basin to be cooled to room temperature, can obtain the copper iron-loaded modified activated carbon absorbent of adsorption of Low Concentration phosphine gas.

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