Method for enhancing degradation of ester VOCs with cerium oxide supported palladium single atom catalyst under low-temperature microwave

Abstract

A method for enhancing degradation of ester volatile organic compounds with a cerium oxide supported palladium single atom catalyst under low-temperature microwave comprises the steps of firstly preparing a single atom catalyst Pd/CeO.sub.2, adding the catalyst Pd/CeO.sub.2 into a reaction cavity, initiating microwave radiation to enhance the catalysis reaction, and quickly introducing an ester compound with a concentration of 50˜5000 mg/m.sup.3 and a space velocity of 2000˜100000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to react when the reaction temperature is 10˜80° C. A catalyst packed column is provided in the reaction cavity, the vapor phase sampling port is defined at the bottom of the reaction cavity, and an exhaust port is defined at the top of the cavity. The microwave method can enhance and activate active sites, prevent the aging of active sites, and enable the chemical reaction rate to be increased by more than 17.9%.

Claims

1. A method for enhancing degradation of ester volatile organic compounds (VOCs) with a cerium oxide loaded palladium single atom catalyst under low-temperature microwave, comprising the following steps: (a) preparation of a catalyst: (1) dissolving a cerium-containing compound into deionized water to form a solution; adding NaOH in the solution, until pH=8-10, stirring, and then reacting in a water bath pot to obtain cerium oxide-containing solution; (2) adding a palladium-containing compound and sodium borohydride together into the cerium oxide-containing solution to react; (3) after the reaction is ended, centrifuging the solution on a centrifuge, and then removing the solution in a centrifuge tube to obtain a precipitation product; and (4) washing the precipitation product with deionized water, drying overnight, and calcining in a muffle furnace at N.sub.2 atmosphere containing 3-7% of H.sub.2 to obtain a single atom catalyst Pd/CeO.sub.2; (b) microwave-assisted enhancement of degradation: adding the catalyst Pd/CeO.sub.2 into a reaction cavity, opening a stirrer, initiating microwave radiation to enhance a catalysis reaction, and quickly introducing an ester compound with a concentration of 50-5000 mg/m.sup.3 and a space velocity of 2000-100000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to degrade the ester VOCs when a reaction temperature is 10-80° C.

2. The method according to claim 1, wherein, the cerium-containing compound is one or two of cerium nitrate and cerium chloride; a concentration of the cerium-containing compound dissolved into deionized water is 0.3-0.6 mol/L.

3. The method according to claim 1, wherein, the water bath pot is at a constant temperature of 70-100° C.; and the cerium oxide-containing solution is obtained by reacting for 3-5 h.

4. The method according to claim 1, wherein, the palladium-containing compound is one or two of palladium chloride and potassium tetrachloropalladate.

5. The method according to claim 1, wherein, a mass ratio of the palladium-containing compound to sodium borohydride to the cerium oxide-containing solution is 1:(1-1.5):(10-100).

6. The method according to claim 1, wherein, a speed, of the centrifuge is 6000-10000 rpm, and centrifugation is carried out for 5-15 min.

7. The method according to claim 1, wherein, the precipitation product is dried overnight at 70-110° C.

8. The method according to claim 1, wherein, calcination is carried out for 1.5-2.5 h in the muffle furnace at the N.sub.2 atmosphere containing 6-10% of H.sub.2 and having a temperature of 250-350° C.

9. The method according to claim 1, wherein, a microwave power of a microwave reactor is 200 W-700 W.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram of a reaction device for enhancing degradation of ester VOCs with a cerium oxide supported palladium single atom catalyst under low-temperature microwave according to the disclosure;

(2) In the FIGURE, 1—microwave generation source and display panel; 2—annular water load; 3—E surface bent waveguide; 4—catalyst packed column; 5—microwave reaction cavity; 6—infrared thermometer; 7—vapor phase sampling port; 8—exhaust port.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(3) The technical solutions in embodiments of the disclosure will be clearly and completely described in combination with embodiments of the disclosure in the following. Obviously, the described embodiments are only a part of embodiments of the disclosure but not all of the embodiments. Based on embodiments of the disclosure, other embodiments obtained by one of ordinary skill in the art without creative efforts are all included in the protection scope of the disclosure.

(4) Provided is a method for enhancing degradation of ester VOCs with a cerium oxide supported palladium single atom catalyst under low-temperature microwave, comprising the following steps:

(5) (a) preparation of a catalyst:

(6) (1) dissolving a cerium-containing compound into deionized water so that its concentration is 0.3˜0.6 mol/L;

(7) (2) adding NaOH in the solution until pH=8˜10, and completely reacting for 3˜5 h in a constant-temperature water bath pot of 70˜100° C. after stirring to obtain cerium oxide-containing solution;

(8) (3) adding a palladium-containing compound and sodium borohydride together into the cerium oxide-containing solution, and stirring for 1˜3 h, wherein, a mass ratio of the palladium-containing compound added in the solution to sodium borohydride added in the solution to the cerium oxide-containing solution is 1:(1˜1.5):(10˜100);

(9) (4) after the reaction is ended, centrifuging the solution on a centrifuge at 6000˜10000 rpm for 5˜15 min, and then removing the solution in a centrifuge tube to obtain a precipitation product; and

(10) (5) washing the precipitation product with deionized water, then drying the precipitation product overnight at 70˜110° C., and calcining in a muffle furnace at the N.sub.2 atmosphere containing 6˜40% of H.sub.2 and having a temperature of 250˜350° C. for 1.5˜2.5 h to obtain a single atom catalyst Pd/CeO.sub.2.

(11) (b) microwave-assisted enhancement of degradation:

(12) adding the catalyst Pd/CeO.sub.2 into a reaction cavity, opening a stirrer, initiating microwave radiation to enhance the catalysis reaction, and quickly introducing an ester compound with a concentration of 50˜5000 mg/m.sup.3 and a space velocity of 2000˜100000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to react when a reaction temperature is 10˜80° C.

(13) The cerium-containing compound in the step (a) is one or two of cerium nitrate and cerium chloride.

(14) The palladium-containing compound in the step (a) is one or two of palladium chloride and potassium tetrachloropalladate.

(15) The microwave power of the microwave reactor in the step (b) is 200 W˜700 W.

(16) The catalyst of the disclosure can be used for purifying various low-concentration organic waste gases and other combustible component waste gases, such as industrial exhaust gases and automobile exhausts.

Example 1

(17) (a) preparation of a catalyst:

(18) (1) dissolving cerium nitrate into deionized water to form a solution in which the concentration of the cerium nitrate is 0.6 mol/L;

(19) (2) adding NaOH in the solution until pH=10, and completely reacting for 5 h in a constant-temperature water bath pot of 100° C. after stirring to obtain cerium oxide-containing solution;

(20) (3) adding palladium chloride and sodium borohydride together into the cerium oxide-containing solution, and stirring for 3 h, wherein, a mass ratio of palladium chloride added in the solution to sodium borohydride added in the solution to the cerium oxide-containing solution is 1:1.5:10;

(21) (4) after the reaction is ended, centrifuging the solution on a centrifuge at 10000 rpm for 15 min, and then removing the solution in a centrifuge tube to obtain a precipitation product; and

(22) (5) washing the precipitation product with deionized water, then drying the precipitation product overnight at 110° C., and calcining in a muffle furnace at the N.sub.2 atmosphere containing 10% of H.sub.2 and having a temperature of 350° C. for 2.5 h to obtain a single, atom catalyst. Pd/CeO.sub.2.

(23) (b) microwave-assisted enhancement of degradation:

(24) adding the catalyst Pd/CeO.sub.2 into a reaction cavity, opening a stirrer, regulating the microwave power to 500 W, initiating microwave radiation to enhance the catalysis reaction, and quickly introducing an ester compound with a concentration of 2000 mg/m.sup.3 and a space velocity of 100000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to react when a reaction temperature is 60° C.

(25) Test of catalytic property is carried out in a plasma reactor with a voltage of 25 kV. The content of a methylbenzene gas is detected by a chromatographic instrument. The removal rate of methyl formate 1 # is seen in Table 1. Catalytic reaction is carried out under the microwave-free condition, and other detection conditions are unchanged. The removal rate of methyl formate 1 # is seen in Table 2.

Example 2

(26) (a) preparation of a catalyst:

(27) (1) dissolving cerium chloride into deionized water so that its concentration is 0.5 mol/L;

(28) (2) adding NaOH in the solution until pH=9, and completely reacting for 4.5 h in a constant-temperature water bath pot of 90° C. after stirring to obtain cerium oxide-containing solution;

(29) (3) adding potassium tetrachloropalladate and sodium borohydride together into the cerium oxide-containing solution, and stirring for 2.5 h, wherein, a mass ratio of potassium tetrachloropalladate added in the solution to sodium borohydride added in the solution to the cerium oxide-containing solution is 1:1.5:40;

(30) (4) after the reaction is ended, centrifuging the solution on a centrifuge at 8000 rpm for 12 min, and then removing the solution in a centrifuge tube to obtain a precipitation product; and

(31) (5) washing the precipitation product with deionized water, then drying the precipitation product overnight at 100° C., and calcining in a muffle furnace at the N.sub.2 atmosphere containing 8% of H.sub.2 and having a temperature of 300° C. for 2 h to obtain a single atom catalyst Pd/CeO.sub.2.

(32) (b) microwave-assisted enhancement of degradation:

(33) adding the catalyst Pd/CeO.sub.2 into a reaction cavity, opening a stirrer, regulating the microwave power to 400 W, initiating microwave radiation to enhance the catalysis reaction, and, quickly introducing an ester compound, with a concentration of 5000 mg/m.sup.3 and a space velocity of 50000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to react when a reaction temperature is 80° C.

(34) Test of catalytic property is carried out in a plasma reactor with a voltage of 25 kV. The content of a methylbenzene gas is detected by a chromatographic instrument. The removal rate of ethyl acetate 2 # is seen in Table 1. Catalytic reaction is carried out under the microwave-free condition, and other detection conditions are unchanged. The removal rate of ethyl acetate 2 # is seen in Table 2.

Example 3

(35) (a) preparation of a catalyst:

(36) (1) dissolving cerium nitrate into deionized water to form a solution in which the concentration of the cerium nitrate is 0.4 mol/L;

(37) (2) adding NaOH in the solution until pH=8.5, and completely reacting for 4 h in a constant-temperature water bath pot of 80° C. after stirring to obtain cerium oxide-containing solution;

(38) (3) adding palladium chloride, potassium tetrachloropalladate and sodium borohydride together into the cerium oxide-containing solution, and stirring for 2 h, wherein, a mass ratio of palladium chloride added in the solution to potassium tetrachloropalladate added in the solution to sodium borohydride added in the solution to the cerium oxide-containing solution is 1:1:2.4:70;

(39) (4) after the reaction is ended, centrifuging the solution on a centrifuge at 7000 rpm for 5 min, and then removing the solution in a centrifuge tube to obtain a precipitation product; and

(40) (5) washing the precipitation product with deionized water, then drying the precipitation product overnight at 90° C., and calcining in a muffle furnace at the N.sub.2 atmosphere containing 7% of H.sub.2 and having a temperature of 300° C. for 2 h to obtain a single atom catalyst Pd/CeO.sub.2.

(41) (b) microwave-assisted enhancement of degradation:

(42) adding the catalyst Pd/CeO.sub.2 into a reaction cavity, opening a stirrer, regulating the microwave power to 700 W, initiating microwave radiation to enhance the catalysis reaction, and quickly introducing an ester compound with a concentration of 500 mg/m.sup.3 and a space velocity of 20000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to react when a reaction temperature is 10° C.

(43) Test of catalytic property is carried out in a plasma reactor with a voltage of 25 KV. The content of a methylbenzene gas is detected by a chromatographic instrument. The removal rate of isobutyl acetate 3 # is seen in Table 1. Catalytic reaction is carried out under the microwave-free condition, and other detection conditions are unchanged. The removal rate of isobutyl acetate 3 # is seen in Table 2.

Example 4

(44) (a) preparation of a catalyst:

(45) (1) dissolving cerium nitrate into deionized water to form a solution in which the concentration of the cerium nitrate is 0.3 mol/L;

(46) (2) adding NaOH in the solution until pH=8, and completely reacting for 3 h in a constant-temperature water bath pot of 70° C. after stirring to obtain cerium oxide-containing solution;

(47) (3) adding potassium tetrachloropalladate and sodium borohydride together into the cerium oxide-containing solution, and stirring for 1 h, wherein, a mass ratio of potassium tetrachloropalladate added in the solution to sodium borohydride added in the solution to the cerium oxide-containing solution is 1:1.5:100;

(48) (4) after the reaction is ended, centrifuging the solution on a centrifuge at 6000 rpm for 8 min, and then removing the solution in a centrifuge tube to obtain a precipitation product; and

(49) (5) washing the precipitation product with deionized water, then drying the precipitation product overnight at 70° C., and calcining in a muffle furnace at the N.sub.2 atmosphere containing 6% of H.sub.2 and having a temperature of 250° C. for 1.5 h to obtain a single atom catalyst Pd/CeO.sub.2.

(50) (b) microwave-assisted enhancement of degradation:

(51) adding the catalyst Pd/CeO.sub.2 into a reaction cavity, opening a stirrer, regulating the microwave power to 200 W, initiating microwave radiation to enhance the catalysis reaction, and quickly introducing an ester compound with a concentration of 50 mg/m.sup.3 and a space velocity of 2000 h.sup.−1 into the reaction cavity from a vapor phase sampling port to react when a reaction temperature is 35° C.

(52) Test of catalytic property is carried out in a plasma reactor with a voltage of 25 KV. The content of a methylbenzene gas is detected by a chromatographic instrument. The removal rate of methyl acrylate 4 # is seen in Table 1. Catalytic reaction is carried out under the microwave-free condition, and other detection conditions are unchanged. The removal rate of methyl acrylate 4 # is seen in Table 2.

(53) TABLE-US-00001 TABLE 1 Catalytic Purification Reaction Property of Ester Compounds on Catalyst under Microwave Condition Catalyst Reaction condition 1# 2# 3# 4# Space velocity (h.sup.−1) 100000 50000 20000 2000 Voltage (kV) 25 25 25 25 Pre-treatment (mg/m.sup.3) 2000 5000 500 50 Post-treatment (g/m.sup.3) 78 205 24.5 2.6 Reaction time (min) 35.3 16.8 33.9 30.4 Removal rate (%) 96.1 95.9 95.1 94.8

(54) TABLE-US-00002 TABLE 2 Catalytic Purification Reaction Property of Ester Compounds on Catalyst under Microwave-free Condition Catalyst Reaction condition 1# 2# 3# 4# Space velocity (h.sup.−1) 100000 50000 20000 2000 Voltage (kV) 25 25 25 25 Pre-treatment (mg/m.sup.3) 2000 5000 500 50 Post-treatment (g/m.sup.3) 139 370 39.5 4.2 Reaction time (min) 44.1 21.3 40.1 38.5 Removal rate (%) 93.1 92.6 92.1 91.6