CN107764811B - Method for treating urea solution, method for determining concentration of urea solution and application of method - Google Patents

Method for treating urea solution, method for determining concentration of urea solution and application of method Download PDF

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CN107764811B
CN107764811B CN201610675725.XA CN201610675725A CN107764811B CN 107764811 B CN107764811 B CN 107764811B CN 201610675725 A CN201610675725 A CN 201610675725A CN 107764811 B CN107764811 B CN 107764811B
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urea solution
urea
concentration
solution
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CN107764811A (en
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孙裕苹
涂长志
陈世华
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China Petroleum and Chemical Corp
Sinopec Catalyst Co
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Sinopec Catalyst Co
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
    • G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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Abstract

The invention relates to the field of chemical tests, and discloses a treatment method of a urea solution, a method for determining the concentration of the urea solution and application of the method. The method for treating a urea solution of the present invention, which contains Ni2+、Zn2+The method is characterized by comprising a step of bringing the urea solution into contact with a complex breaker containing phosphate and/or sulfide ions. The method is directed to Ni-containing2+、Zn2+The urea solution of (2) can be used for quickly and accurately measuring the concentration of urea without complicated operations.

Description

Method for treating urea solution, method for determining concentration of urea solution and application of method
Technical Field
The invention relates to the field of chemical tests, in particular to a treatment method of a urea solution, a method for determining the concentration of the urea solution and application of the method.
Background
The urea solution used as the absorption liquid in the hypergravity reactor is used for treating ammonia nitrogen compounds in the exhaust gas of the device. The urea solution contains ammonia nitrogen, heavy metal ions of nickel and zinc and high-concentration urea, and is acidic.
In actual production, the concentration control of the urea solution has some problems, the pH value is taken as a basis to control the adding amount of fresh urea, so that the adding amount of the fresh urea has large deviation in the continuous production process, the pH value cannot accurately reflect the concentration of the urea in the supergravity absorption liquid, in order to ensure the treatment effect, the adding amount of the urea is often excessive, the excessive urea is crystallized and separated out from the solution, the circulation of the urea absorption liquid is influenced, and meanwhile, the supergravity reactor is also influenced to NOxThe effect of the treatment of (1).
At present, the method for detecting the concentration of urea at home and abroad usually adopts a volumetric method (titration method), a colorimetric method, instrument detection and the like. The volumetric method is a national standard specified method, but the method has the defects of complex operation, time consumption, difficulty in grasping a multi-titration end point, reagent injury to an operator and the like. And the existence of non-ferrous metal ion nickel in the supergravity absorption liquid greatly interferes with a titration method, a colorimetric method and the like depending on color identification, and normal detection cannot be realized. No solution to this technical problem has been reported at present.
Disclosure of Invention
The invention aims to provide a method for treating a urea solution, which aims at containing Ni2+、 Zn2+The urea solution of (2) can be used for quickly and accurately measuring the concentration of urea without complicated operations.
In order to achieve the above object, a first aspect of the present invention is to provide a method for treating a urea solution containing Ni2+、Zn2+The method comprises a step of contacting the urea solution with a complex breaker containing phosphate and/or sulfide ions.
In a second aspect of the present invention, there is provided a method for determining the concentration of a urea solution, which comprises determining the concentration of a urea solution obtained by treating a urea solution by the above-mentioned treatment method using a colorimetric method.
The invention also provides application of the method for determining the concentration of the urea solution in preparation of the absorption liquid in the hypergravity reactor.
The inventor of the invention has found through intensive research that a complex breaking agent containing phosphate radical and/or sulfide ions and Ni are adopted2+And Zn2+After the urea solution is contacted, the concentration of the urea can be directly and rapidly and accurately measured by a colorimetric method. Through the technical scheme, the urea solution is pretreated, the interference of nickel ions and dust particles is eliminated, and the Ni content is determined by adopting a colorimetric method with relatively simple and convenient steps, good stability and strong operability2+、Zn2+The urea content of (a).
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a method for treating a urea solution containing Ni2+、Zn2+The method comprises a step of contacting the urea solution with a complex breaker containing phosphate and/or sulfide ions.
According to the invention, Ni is contained in the urea solution2+And Zn2+The total molar amount of the complex breaking agent is 1 mol, and the usage amount of the complex breaking agent is 0.5-10 mol based on the total molar amount of phosphate radical and sulfide ion contained in the complex breaking agent. Specifically, when the complex breaking agent containing phosphate radical and/or sulfide ion only contains phosphate radical, the total molar amount of phosphate radical and sulfide ion contained in the complex breaking agent is the molar amount of phosphate radical; when the complex breaking agent containing phosphate radical and/or sulfur ion only contains sulfur ion, the total molar amount of phosphate radical and sulfur ion contained in the complex breaking agent is the molar amount of sulfur ion.
Preferably Ni with respect to the urea solution2+And Zn2+The total molar amount of the complex breaking agent is 1 mol, and the usage amount of the complex breaking agent is 4.5-7 mol based on the total molar amount of phosphate radical and sulfide ion contained in the complex breaking agent.
According to the present invention, the complex breaker containing phosphate may be one or more selected from the group consisting of phosphate, hydrogen phosphate and dihydrogen phosphate. Preferably, the complex breaker containing phosphate is an alkali metal salt; more preferably, the complex breaker containing phosphate is sodium salt and/or potassium salt; further preferably, the complex breaking agent containing phosphate radical is sodium dihydrogen phosphate.
According to the invention, the decomplexer containing sulfide ions is sulfide. Preferably, the decomplexer containing the sulfide ions is one or more of metal sulfides; more preferably, the sulfide ion-containing complex breaking agent is one or more of alkali metal sulfide and iron sulfide; more preferably, the sulfide ion-containing complex breaking agent is one or more of sodium sulfide, potassium sulfide and iron sulfide; particularly preferably, the complex breaking agent containing sulfide ions is sodium sulfide and/or potassium sulfide.
According to the invention, the conditions of said contact comprise: the temperature is-10-40 deg.C, and the time is 0-10 min; preferably, the conditions of the contacting include: the temperature is 10-30 deg.C, and the time is 3-8 min.
According to a preferred embodiment of the invention, after said contacting, the pH of said urea solution is adjusted to a value of 5-14, preferably 7-9. By adjusting the pH of the urea solution within the above range, the accuracy of urea concentration measurement can be improved. The pH of the urea solution can be adjusted by various methods conventional in the art, for example, by using various alkaline substances, preferably selected from NaOH, KOH and Ca (OH)2More preferably the pH of the urea solution is adjusted using NaOH.
According to the invention, Ni is contained in the urea solution2+Is 0.008 to 1 mol/L, and Zn is contained in the urea solution2+The concentration of (A) is 0.05-2 mol/L. Preferably, Ni contained in the urea solution2+Is 0.02 to 0.6 mol/L, more preferably 0.03 to 0.5 mol/L, Zn contained in the urea solution2+The concentration of (b) is 0.07 to 1.6 mol/L, more preferably 0.091 to 1.2 mol/L.
Furthermore, the urea solution according to the invention is used, for example, for treating NO in catalyst-containing exhaust gases with a urea solutionxObtained by a process other than containing Ni2+And Zn2+Besides, the material can also contain one or more selected from dust, nitrate radical, nitrite radical and ammonia nitrogen.
The invention also provides a method for measuring the concentration of the urea solution, which comprises the step of carrying out urea concentration measurement on the urea solution by a colorimetric method, wherein the urea solution is obtained by treating the urea solution by the treatment method.
Preferably, the colorimetric method is a dimethylaminobenzaldehyde colorimetric method.
The invention also provides application of the method for determining the concentration of the urea solution in preparation of the absorption liquid in the hypergravity reactor.
The present invention will be described in detail below by way of examples.
In the following examples, p-dimethylaminobenzaldehyde colorimetry was carried out in accordance with the following method.
1) Preparing a reagent:
color developing agent: accurately weighing 20.00g of p-dimethylaminobenzaldehyde, transferring the p-dimethylaminobenzaldehyde into a 1000mL volumetric flask, and adding absolute ethyl alcohol to a constant volume to obtain 20g/L of developer solution.
Sulfuric acid solution: according to the formula V (concentrated sulfuric acid): v (water) ═ 1: 8, preparing a 2 mol/L sulfuric acid solution.
Urea standard solution: a1000 mg/L standard solution of urea was prepared by weighing 1.000g (weighed to 0.0001g) of urea and dissolving in L000mL of deionized water.
2) Standard curve establishment
Taking 7 25mL colorimetric tubes, adding 0.00mL, 0.50 mL, 1.00mL, 2.00mL, 4.00mL, 6.00 mL and 8.00mL of urea standard solution, then adding 10.00mL, 9.50 mL, 9.00mL, 8.00mL, 6.00 mL, 4.00mL and 2.00mL of deionized water, then adding 10.00mL of color developing agent and 4.00mL of sulfuric acid solution into each colorimetric tube, shaking up, using deionized water to fix the volume to obtain the series of concentrations, and standing for 10 minutes. Scanning is carried out at different wave bands, and the wavelength lambda of the maximum absorption peak is determined to be 422 nm. The reaction solution (i.e., blank reagent) of the first cuvette was used as a reference solution, and the absorbance of the reaction solution of the 7 cuvettes was measured with a visible spectrophotometer at 422nm to prepare a standard curve.
3) And (5) determining the urea content in the sample solution.
Taking 2 25mL colorimetric tubes, respectively adding 1.00mL of sample solution, respectively adding 9.00mL of deionized water, 10.00mL of color developing agent and 4.00mL of sulfuric acid solution, mixing, shaking uniformly, metering the volume with deionized water, and standing for 10 minutes. The absorbance A of each solution was measured at 422nm using deionized water as a reference solution. The concentration of urea in this solution was determined using a calibration curve.
Test example
1) Taking 50mL of urea solution used as absorption liquid in a supergravity reactor, and measuring Ni in the urea solution by a spectrophotometric method (Shanghai cyanine scientific and technological instruments Co., Ltd., model 721 visible spectrophotometer)2+And Zn2+The concentration of (a) is 0.034 mol/L and 0.146 mol/L respectively;
2) adding sodium dihydrogen phosphate to urea solution, wherein the content of Ni in the urea solution is relatively low2+And Zn2+Adding 6 moles of sodium dihydrogen phosphate into the mixture, and uniformly mixing the mixture;
3) regulating the pH value of the urea solution to 8 by using NaOH;
4) the urea concentration in the urea solution was measured by dimethylaminobenzaldehyde colorimetry, and the measurement was repeated three times, with the measured urea concentrations being 14.4 mass%, and 14.5 mass%, respectively, and the time required for a single measurement being 20 min.
According to the test examples, the urea determination method provided by the application is simple to operate, short in time consumption and good in repeatability.
In the following examples and comparative examples, urea solutions prepared from urea, nickel nitrate, zinc nitrate and deionized water were used, wherein the urea concentration c in the urea solutions0The content of nickel nitrate was 15% by mass, the concentration of nickel nitrate was 0.034 mol/L, and the concentration of zinc nitrate was 0.146 mol/L. The concentration value of the urea is measured to be c, and the accuracy is (| c-c)0|/c0)×100％。
Example 1
1) Adding sodium dihydrogen phosphate to urea solution, wherein the content of Ni in the urea solution is relatively low2+And Zn2+Adding 6 moles of sodium dihydrogen phosphate into the mixture, and uniformly mixing the mixture;
2) regulating the pH value of the urea solution to 8 by using NaOH;
3) the urea concentration in the urea solution was determined to be 14.8 mass% by dimethylaminobenzaldehyde colorimetry with an accuracy of 98.7%.
Example 2
1) Adding sodium dihydrogen phosphate to urea solution, wherein the content of Ni in the urea solution is relatively low2+And Zn2+Adding 6 moles of sodium dihydrogen phosphate into the mixture, and uniformly mixing the mixture;
2) regulating the pH value of the urea solution to 7 by using NaOH;
3) the urea concentration in the urea solution was determined to be 15.2 mass% by dimethylaminobenzaldehyde colorimetry with an accuracy of 99%.
Example 3
1) Adding sodium dihydrogen phosphate to urea solution, wherein the content of Ni in the urea solution is relatively low2+And Zn2+Adding 6.5 moles of sodium dihydrogen phosphate into the mixture, and uniformly mixing the mixture;
2) regulating the pH value of the urea solution to 9 by using NaOH;
3) the urea concentration in the urea solution was determined to be 14.9 mass% by dimethylaminobenzaldehyde colorimetry with an accuracy of 99.3%.
Example 4
The urea concentration in the urea solution was determined as in example 1, except that Ni was contained in step 1) with respect to the urea solution2+And Zn2+To the reaction solution, 4.5 moles of sodium dihydrogenphosphate were added, based on the total molar amount of 1 mole. The urea concentration in the urea solution was measured to be 13.8 mass%, with an accuracy of 92%.
Example 5
The urea concentration in the urea solution was determined as in example 1, except that Ni was contained in step 1) with respect to the urea solution2+And Zn2+1 mole, and 7 moles of sodium dihydrogen phosphate was added. The urea concentration in the urea solution was measured to be 13.7 mass% with an accuracy of 91.3%.
Example 6
The urea concentration in the urea solution was determined according to the method of example 1In contrast, in step 1), Ni is contained in the urea solution2+And Zn2+1 mole, and 2 moles of sodium dihydrogen phosphate was added. The urea concentration in the urea solution was measured to be 12.3 mass% with an accuracy of 82%.
Example 7
The urea concentration in the urea solution was measured according to the method of example 1, except that in step 1), Ni was contained with respect to the urea solution2+And Zn2+1 mole, and 4 moles of sodium dihydrogen phosphate was added. The urea concentration in the urea solution was measured to be 13 mass% with an accuracy of 86.7%.
Example 8
The urea concentration in the urea solution was measured according to the method of example 1, except that the pH of the solution was adjusted to 5 in step 2). The urea concentration in the urea solution was measured to be 12% by mass with an accuracy of 80%.
Example 9
The urea concentration in the urea solution was determined according to the method of example 1, except that in step 1) sodium sulfide was added, in relation to the Ni content of the urea solution2+And Zn2+1 mole, and 6 moles of sodium sulfide was added. The urea concentration in the urea solution was measured to be 13.5 mass% with an accuracy of 90%.
Example 10
The urea concentration in the urea solution was determined according to the method of example 1, except that in step 1) sodium sulfide was added, in relation to the Ni content of the urea solution2+And Zn2+Total molar amount of 1 mole, 6.5 moles of sodium sulfide was added. The urea concentration in the urea solution was measured to be 14.2 mass% with an accuracy of 94.7%.
Comparative example 1
The urea solution obtained in example 1 was measured for urea concentration by the method of GB/T2441.5-2010, and the urea concentration in the urea solution was found to be 14.8 mass%, the accuracy was found to be 98.7%, and the time required for the measurement was 80 min.
Comparative example 2
Method according to example 1Determining the concentration of urea in the urea solution, except that FeCl is added in step 1)3Relative to Ni contained in the urea solution2+And Zn2+1 mole, 6 moles of FeCl were added3. The urea concentration in the urea solution was measured to be 10 mass% with an accuracy of 67%.
Comparative example 3
The urea solution obtained in example 1 was directly subjected to a dimethylaminobenzaldehyde colorimetric method to determine the urea concentration therein, and the urea concentration in the urea solution was 10.3% by mass with an accuracy of 69%.
It can be seen from the comparison between the above examples and comparative example 1 that, although the method of GB/T2441.5-2010 is highly accurate, the judgment of the titration end point thereof is influenced by the experience of the operator, the accuracy thereof is considered to be influenced by a large factor, and the operation takes a long time, which is not favorable for industrial production. The method can conveniently and quickly measure the concentration of the urea in the urea solution without complex operation.
Meanwhile, in the method of the present application, Ni contained in the urea solution is referred to2+And Zn2+The total molar weight of the urea is 1 mol, and when the usage amount of the complex breaking agent is 4.5-7 mol based on the total molar weight of phosphate radical and sulfide ion contained in the complex breaking agent, the measurement accuracy of the urea concentration is more than 90%, and the production requirement can be met.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (6)

1. Method for treating urea solution containing Ni2+、Zn2+The method is characterized by comprising a step of bringing the urea solution into contact with a complex breaker containing a phosphate group, and a step of adjusting the pH value of the urea solution to 7 to 9 after the contact;
wherein the complex breaking agent containing phosphate radical is sodium dihydrogen phosphate,
relative to Ni contained in the urea solution2+And Zn2+The total molar amount of the complex breaking agent is 1 mol, and the usage amount of the complex breaking agent is 6-6.5 mol based on the molar amount of phosphate radical contained in the complex breaking agent.
2. The method of claim 1, wherein the conditions of the contacting comprise: the temperature is-10-40 deg.C, and the time is 0-10 min.
3. Process according to claim 1 or 2, wherein the Ni contained in the urea solution2+Is 0.008 to 1 mol/L, and Zn is contained in the urea solution2+The concentration of (A) is 0.05-2 mol/L.
4. A method for determining the concentration of a urea solution, comprising colorimetrically determining the concentration of urea in the urea solution, characterized in that the urea solution is obtained by treatment according to the treatment method of any one of claims 1-3.
5. The method of claim 4, wherein the colorimetric method is a dimethylaminobenzaldehyde colorimetric method.
6. Use of a method for determining the concentration of a urea solution according to claim 4 or 5 in the preparation of an absorption liquid in a hypergravity reactor.
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