Standard colorimetric method for measuring content of carbonyl compound in industrial methanol
阅读说明：本技术 工业甲醇中羰基化合物含量测定的标准比色法 (Standard colorimetric method for measuring content of carbonyl compound in industrial methanol ) 是由 张�杰 杜静 于 2020-07-03 设计创作，主要内容包括：工业甲醇中羰基化合物含量的标准比色法,属于工业甲醇领域。包括以下步骤：配制一系列羰基化合物含量各不相同的标准溶液,在一定条件下先后与2,4-二硝基苯肼、氢氧化钾反应后,观察发现随着羰基化合物含量的逐渐增加,颜色也会逐渐的由淡黄色递变到深红褐色。依据标液的颜色、羰基化合物含量的体积份质量数、甲醇等级等信息,制成标准比色卡片。将试样在同样的条件下反应完全后,与标准比色卡片进行比对,找出最接近的颜色,直接读出羰基化合物含量、甲醇样品等级等信息。可实现对羰基化合物含量的定量计算。该种测定方法具有直观快速,简便,对检测设备、仪器、场所、要求低等特点。(A standard colorimetric method for carbonyl compound content in industrial methanol belongs to the field of industrial methanol. The method comprises the following steps: a series of standard solutions with different carbonyl compound contents are prepared, and after the standard solutions are reacted with 2, 4-dinitrophenylhydrazine and potassium hydroxide in sequence under a certain condition, the observation shows that the color gradually changes from light yellow to dark reddish brown along with the gradual increase of the carbonyl compound content. And (4) preparing a standard colorimetric card according to the information of the color of the standard solution, the volume part mass number of the content of the carbonyl compound, the methanol grade and the like. And (3) after the reaction of the sample is completed under the same condition, comparing the reaction with a standard colorimetric card, finding out the closest color, and directly reading out the information such as the content of the carbonyl compound, the grade of the methanol sample and the like. The quantitative calculation of the content of the carbonyl compound can be realized. The measuring method has the characteristics of intuition, rapidness, simplicity, low requirements on detection equipment, instruments, places and the like.)
1. A standard colorimetric method for the carbonyl compound content in industrial methanol, characterized by comprising the following steps:
1) preparation of standard solution: respectively transferring standard solutions of carbonyl compounds (the specific transfer volume parts are shown in the column A of the table), diluting the standard solutions to 100 volume parts by using methanol without carbonyl, and shaking up;
A. transferring the volume part of the carbonyl compound standard solution; B. the volume part mass of the carbonyl compound contained in the colorimetric solution;
2) production of standard colorimetric cards: placing 40 colorimetric tubes at the same position of a white background; using the same digital camera to photograph each colorimetric tube, wherein the whole photographing time is controlled within 0.5 h; processing and developing the picture, and gradually changing the color from No. 1 to No. 40 from light yellow to red brown until the color is deepened to dark red brown; referring to the numbers in the table 1, the volume parts and mass numbers of carbonyl compounds contained in the solution, the methanol grade and other information, and preparing a standard colorimetric card;
3) calculating the result: the mass fraction ω of carbonyl compounds is calculated as carbonyl groups (CO), and the numerical value is expressed in% by the formula (1):
in the formula: m is the volume parts of the content of the carbonyl compound corresponding to the sample and a standard colorimetric card rho is the density of the industrial methanol, and the density value under the temperature condition of 20-25 ℃ is as follows: 0.792V-volume fraction of industrial methanol taken;
4) the distillation apparatus requires the use of a bayonet-type distillation head.
Technical Field
The invention relates to a standard colorimetric method capable of accurately and quickly measuring the content of carbonyl compounds in industrial methanol, in particular to a quick, direct and simple measuring method for the content of carbonyl compounds in industrial methanol in the production line.
Background
Industrial methanol is a very important basic raw material for chemical industry, and has huge production and sales volume. The content of carbonyl compounds is an important basis for judging the quality and grade of industrial methanol. Therefore, a great deal of research is carried out on the determination of the content of carbonyl compounds in industrial methanol, and the methods have wide application: (1) spectrophotometry: carbonyl compounds in a sample react with 2, 4-dinitrophenylhydrazine and potassium hydroxide under certain conditions, then a spectrophotometer is used for measuring absorbance, and finally the content of the carbonyl compounds is converted. (2) Volumetric method: reacting carbonyl compounds in the sample with hydroxylamine hydrochloride to generate acid, taking bromophenol blue as an indicator, titrating with sodium hydroxide solution, and calculating to obtain the content of the carbonyl compounds.
However, both of the above-mentioned methods require specialized equipment and equipment, and also impose high demands on the abilities and levels of the examiners. Moreover, it is also necessary to provide a dedicated inspection site, which greatly limits the versatility and flexibility of application of the two methods.
Disclosure of Invention
A standard colorimetric method for determining the content of carbonyl compounds in industrial methanol comprises the following steps:
1. preparation of solvent and test solution
1.1 preparation of a Carbonylfree methanol solution
Weighing 1000 parts by volume of methanol, adding 5 parts by volume of 2, 4-dinitrophenylhydrazine and 1 part by volume of hydrochloric acid (the mass fraction is 36.5%), controlling the water bath temperature at 95 ℃, refluxing for 4 hours, standing for 0.5 hour, changing a reflux device into a distillation device, discarding 30 parts by volume of distillate distilled initially and 50 parts by volume of yellow solution remained finally, and only collecting middle distillate. After the previous fraction is collected, a new receiving bottle is needed to collect the middle fraction. The temperature is controlled to be 86 ℃ in the distillation process, so that the distillate can be distilled at a constant speed. The distillate should be clear, transparent and colorless. The collected carbonyl-free methanol was stored in a brown reagent bottle.
1.2 potassium hydroxide-methanol solution: 100g/L
10 parts by volume of analytically pure potassium hydroxide were dissolved in 20 parts by volume of distilled water, and 80 parts by volume of carbonyl-free methanol were added.
32, 4-dinitrophenylhydrazine: 1g/L
Weighing 50 parts by volume of 2, 4-dinitrophenylhydrazine, weighing 50 parts by volume of carbonyl-free methanol, adding 10-30 parts by volume of carbonyl-free methanol, adding 0.5-1.0 part by volume of hydrochloric acid (mass fraction is 36.5%), and finally adding the rest of carbonyl-free methanol.
2. Standard colorimetric card production
2.1 carbonyl Compound Standard solution: 0.25mg/mL
Weighing 500 parts by volume of non-carbonyl methanol, taking 100 parts by volume of non-carbonyl methanol, weighing 0.322 parts by volume of 2-butanone into the 100 parts by volume of non-carbonyl methanol, and then adding the
2.2 Standard solution
The standard solutions of carbonyl compounds (the specific volume fractions are shown in Table A) were each pipetted, diluted to 100 volume fractions with methanol without carbonyl groups and shaken up.
A. Part by volume of the carbonyl Compound Standard solution in 2.1 B. part by volume and mass of the carbonyl Compound contained in the colorimetric solution
2.3 colorimetric solution
Transferring 2 parts by volume of standard solution (2.2) into 40 colorimetric tubes with the same specification respectively, adding 2 parts by volume of 2, 4-dinitrophenylhydrazine solution respectively, covering a stopper, reacting for (30 +/-2) min at the temperature of 20-25 ℃, adding 21 parts by volume of potassium hydroxide-carbonyl-free methanol solution, adding the stopper, shaking uniformly, and standing for (12 +/-1) min. The volume ratio of the standard colorimetric solution, the 2, 4-dinitrophenylhydrazine solution and the potassium hydroxide-carbonyl-free methanol solution is 1: 10.5. The parts by volume and the mass of the carbonyl compound contained in 25 parts by volume of the colorimetric solution are shown in column B of Table 1.
2.4 preparation of Standard colorimetric cards
Place 40 cuvettes on the same position on a white background. And (4) taking a picture of each colorimetric tube by using the same digital camera, wherein the whole photographing time is controlled within 0.5 h. The pictures were processed and printed, and the colors were gradually changed from light yellow to red brown from No. 1 to No. 40 to dark red brown. Referring to the numbers in Table 1, the volume parts and mass numbers of the carbonyl compounds contained in the solution, the methanol grade and other information, standard colorimetric cards were prepared.
3. Determination of samples
3.1 Standard colorimetry
Transferring 2 parts by volume of a sample containing a carbonyl compound into a colorimetric tube with the same specification, adding 2 parts by volume of 2, 4-dinitrophenylhydrazine solution, covering a stopper, reacting at the temperature of 20-25 ℃ for (30 +/-2) min, adding 21 parts by volume of potassium hydroxide-carbonyl-free methanol solution, and standing for (12 +/-1) min. The volume ratio of the sample solution, the 2, 4-dinitrophenylhydrazine solution and the potassium hydroxide-carbonyl-free methanol solution is 1: 10.5. And (3) placing the sample colorimetric tube under a white background, comparing the sample colorimetric tube with a standard colorimetric card, finding the closest color, and checking information such as a corresponding number, the content of the carbonyl compound, the grade of methanol and the like. The grade of the sample can be directly judged.
3.2 calculation of results
The mass fraction ω of carbonyl compounds is calculated as carbonyl groups (CO), and the numerical value is expressed in% by the formula (1):
in the formula:
m-mass portion of carbonyl compound content corresponding to sample and standard colorimetric card
Rho- - - -density of industrial methanol, density value at temperature conditions 20-25 ℃: 0.792
V- - - -the volume fraction of the industrial methanol taken the final reported result is three decimal places.
The standard colorimetric method for the content of the carbonyl compound in the industrial methanol preferably comprises the following operation steps: in the standard colorimetric method for the content of the carbonyl compound in the industrial methanol, a thorn-shaped distillation head is used in a distillation device in the step 1.1, and the collected front cut fraction and the residual amount of a distillation flask account for 3 percent and 5 percent of the volume fraction of the measured methanol respectively.
The volume ratio of the hydrochloric acid in the step 1.3 to the solution to be prepared in the standard colorimetric method for the content of the carbonyl compound in the industrial methanol is 1: 50-1: 100.
The invention has the advantages that:
1. the method is visual and rapid, and only relevant reactants need to be added into a sample to be detected, and the sample is compared with the labeled colorimetric card after half an hour, so that the corresponding color is directly found out. The content of carbonyl compounds is determined.
2. The method is simple and convenient, and special technicians are needed to complete the preparation of the solvent related to the
3. The test condition is simple, such as low requirements on detection equipment, instruments and places. Only one set of standard colorimetric card, one colorimetric tube, two medicines of 2, 4-dinitrophenylhydrazine solution and potassium hydroxide-carbonyl-free methanol solution are needed.
Drawings
FIG. 1 shows the standard colorimetric solution formulations and corresponding methanol grades
FIG. 2 shows the standard colorimetric solution formulations and corresponding methanol grades
FIG. 3 shows the standard colorimetric solution formulations and corresponding methanol grades
FIG. 4 shows the standard colorimetric solution formulations and corresponding methanol grades
FIG. 5 shows the standard colorimetric solution formulations and corresponding methanol grades
Detailed Description
The invention aims to overcome some defects of the measuring method and provide a method for quickly, directly and simply measuring the content of carbonyl compounds in any production flow and storage and transportation place of industrial methanol production, storage and transportation.
Referring to fig. 1-5, the technical solution adopted to solve the problems of the present invention is: the standard colorimetric method for measuring the content of the carbonyl compound in the industrial methanol is characterized by comprising the following steps of:
1. preparation of solvent and test solution
1.1 preparation of a Carbonylfree methanol solution
Weighing 1000 parts by volume of methanol, adding 5 parts by volume of 2, 4-dinitrophenylhydrazine and 1 part by volume of hydrochloric acid (the mass fraction is 36.5%), controlling the water bath temperature at 95 ℃, refluxing for 4 hours, standing for 0.5 hour, changing a reflux device into a distillation device, discarding 30 parts by volume of distillate distilled initially and 50 parts by volume of yellow solution remained finally, and only collecting middle distillate. After the previous fraction is collected, a new receiving bottle is needed to collect the middle fraction. The temperature is controlled to be 86 ℃ in the distillation process, so that the distillate can be distilled at a constant speed. The distillate should be clear, transparent and colorless. The collected carbonyl-free methanol was stored in a brown reagent bottle.
1.2 potassium hydroxide-methanol solution: 100g/L
10 parts by volume of analytically pure potassium hydroxide were dissolved in 20 parts by volume of distilled water, and 80 parts by volume of carbonyl-free methanol were added.
32, 4-dinitrophenylhydrazine: 1g/L
Weighing 50 parts by volume of 2, 4-dinitrophenylhydrazine, weighing 50 parts by volume of carbonyl-free methanol, adding 10-30 parts by volume of carbonyl-free methanol, adding 0.5-1.0 part by volume of hydrochloric acid (mass fraction is 36.5%), and finally adding the rest of carbonyl-free methanol.
2. Standard colorimetric card production
2.1 carbonyl Compound Standard solution: 0.25mg/mL
Weighing 500 parts by volume of non-carbonyl methanol, taking 100 parts by volume of non-carbonyl methanol, weighing 0.322 parts by volume of 2-butanone into the 100 parts by volume of non-carbonyl methanol, and then adding the
2.2 Standard solution
The standard solutions of carbonyl compounds (the specific volume fractions are shown in Table A) were each pipetted, diluted to 100 volume fractions with methanol without carbonyl groups and shaken up.
A. Part by volume of the carbonyl Compound Standard solution in 2.1 B. part by volume and mass of the carbonyl Compound contained in the colorimetric solution
2.3 colorimetric solution
Transferring 2 parts by volume of standard solution (2.2) into 40 colorimetric tubes with the same specification respectively, adding 2 parts by volume of 2, 4-dinitrophenylhydrazine solution respectively, covering a stopper, reacting for (30 +/-2) min at the temperature of 20-25 ℃, adding 21 parts by volume of potassium hydroxide-carbonyl-free methanol solution, adding the stopper, shaking uniformly, and standing for (12 +/-1) min. The volume ratio of the standard colorimetric solution, the 2, 4-dinitrophenylhydrazine solution and the potassium hydroxide-carbonyl-free methanol solution is 1: 10.5. The parts by volume and the mass of the carbonyl compound contained in 25 parts by volume of the colorimetric solution are shown in column B of Table 1.
2.4 preparation of Standard colorimetric cards
3. Determination of samples
3.1 Standard colorimetry
Transferring 2 parts by volume of a sample containing a carbonyl compound into a colorimetric tube with the same specification, adding 2 parts by volume of 2, 4-dinitrophenylhydrazine solution, covering a stopper, reacting at the temperature of 20-25 ℃ for (30 +/-2) min, adding 21 parts by volume of potassium hydroxide-carbonyl-free methanol solution, and standing for (12 +/-1) min. The volume ratio of the sample solution, the 2, 4-dinitrophenylhydrazine solution and the potassium hydroxide-carbonyl-free methanol solution is 1: 1: 10.5. and (3) placing the sample colorimetric tube under a white background, comparing the sample colorimetric tube with a standard colorimetric card, finding the closest color, and checking information such as a corresponding number, the content of the carbonyl compound, the grade of methanol and the like. The grade of the sample can be directly judged.
3.2 calculation of results
The mass fraction ω of carbonyl compounds is calculated as carbonyl groups (CO), and the numerical value is expressed in% by the formula (1):
in the formula:
m-mass portion of carbonyl compound content corresponding to sample and standard colorimetric card
Rho- - - -density of industrial methanol, density value at temperature conditions 20-25 ℃: 0.792
V- - - -the volume fraction of the industrial methanol taken the final reported result is three decimal places.
The standard colorimetric method for the content of the carbonyl compound in the industrial methanol preferably comprises the following operation steps: in the standard colorimetric method for the content of the carbonyl compound in the industrial methanol, a thorn-shaped distillation head is used in a distillation device in the step 1.1, and the collected front cut fraction and the residual amount of a distillation flask account for 3 percent and 5 percent of the volume fraction of the measured methanol respectively.
The volume ratio of the hydrochloric acid in the step 1.3 to the solution to be prepared in the standard colorimetric method for the content of the carbonyl compound in the industrial methanol is 1: 50-1: 100.
The invention has the advantages that:
1. the method is visual and rapid, and only relevant reactants need to be added into a sample to be detected, and the sample is compared with the labeled colorimetric card after half an hour, so that the corresponding color is directly found out. The content of carbonyl compounds is determined.
2. The method is simple and convenient, and special technicians are needed to complete the preparation of the solvent related to the
3. The test condition is simple, such as low requirements on detection equipment, instruments and places. Only one set of standard colorimetric card, one colorimetric tube, two medicines of 2, 4-dinitrophenylhydrazine solution and potassium hydroxide-carbonyl-free methanol solution are needed.