1、TITRIMETRIC DETERMINATIONOF CO2IN ETHANOLAMINESUOP Method 829-82SCOPEThis method is for the titrimetric determination of carbon dioxide in ethanolamine solutions used forscrubbing gas streams such as those found in hydrogen plants that contain only carbon dioxide as the acidiccontaminant. The presen
2、ce of hydrogen sulfide or sulfur dioxide will produce high results, since thesecomponents will be included in the titration.OUTLINE OF METHODThe amine sample is dissolved in anhydrous methanol. The amine/methanol solution is titrated with astandard methanolic sodium hydroxide solution using thymolph
3、thalein as the indicator, and the CO2contentcalculated.APPARATUSBalance, torsion or top-loading type, 500 g capacity, capable of weighing to 0.01 gBeaker, 250-mLBottle, dropping, 30-mL capacityBuret, 50-mL, with Teflon, stopcock, 0.1-mL subdivisions (2 required)Cylinder, graduated, 100-mL, glass, 1.
4、0-mL subdivisionsFlask, Erlenmeyer, 500-mLFlask, volumetric, 100-mL and one-literPipet, volumetric transfer, 10-mLStirrer, magnetic, with Teflon-coated stirring bar, Sargent-Welch Scientific Co., Cat. No. S-76490, orequivalentIT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRAC
5、TICES AND TODETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH ANDSAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THISPROCEDURE IN THE MANNER PRESCRIBED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS(MSDS) OR EXPERIMENTAL
6、MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED INTHIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTIONEQUIPMENT (PPE). COPYRIGHT 1982 UOP LLCALL RIGHTS RESERVEDUOP Methods are available through ASTM International, 100 Barr Harbor Drive, PO Box C700
7、, West Conshohocken PA 19428-2959,United States. The Methods may be obtained through the ASTM website, www.astm.org, or by contacting Customer Service atserviceastm.org, 610.832.9555 FAX, or 610.832.9585 PHONE.2 of 3829-82REAGENTSAll reagents shall conform to the specifications established by the Co
8、mmittee on Analytical Reagents ofthe American Chemical Society, when such specifications are available, unless otherwise specified.References to water mean deionized or distilled water.Bromothymol blue indicator. Dissolve 0.1 g of bromothymol blue in 100 mL of 20% methanol in water.Methanol, absolut
9、e, 99.8% minimum puritySodium hydroxide solution, methanolic, 0.5-M. Dissolve 21g of sodium hydroxide in 100 mL of water.Quantitatively transfer to a one-liter volumetric flask, cool and dilute to volume with absolutemethanol. Standardize the methanolic sodium hydroxide with 0.5-M standard sulfuric
10、acid in 100 mLof absolute methanol containing 5 drops of thymolphthalein indicator. Before adding the 0.5-M sulfuricacid to the methanol, titrate the methanol with methanolic sodium hydroxide to a light blue color.Sulfuric acid solution, aqueous, 0.5-M. Standardize with tris(hydroxymethyl)aminometha
11、ne and usebromothymol blue for the indicator. Titrate to a yellow color.Thymolphthalein indicator. Dissolve 10 g of thymolphthalein in absolute methanol, transfer to a 100-mLvolumetric flask and dilute to volume with absolute methanol.Tris(hydroxymethyl)aminomethane, ultrapure, acidimetric standard,
12、 Sargent-Welch Scientific Co., Cat.No., SC15540-025 GM, or equivalentPROCEDURETo a 500-mL Erlenmeyer flask containing a magnetic stirring bar add 100 mL of absolute methanol and 5drops of thymolphthalein indicator. Place the flask on the magnetic stirrer and start the stirrer. Titrate themethanol wi
13、th 0.5-M methanolic sodium hydroxide to a light blue color. Read the volume added to thenearest 0.1mL. This titration represents the methanol blank. Pipet 10 mL of amine sample (see NOTE) intothe 500-mL Erlenmeyer flask containing the above solution. Titrate the amine and methanol solution with0.5-M
14、 methanolic sodium hydroxide to a light blue color. Read the total volume of titrant used to the nearest0.1 mL.CALCULATIONSCalculate the volume of carbon dioxide in the sample solution at standard conditions (15.6 C and 101.3kPa) as follows:3.2(A B)Cubic feet of carbon dioxide/gal of amine solutionM
15、V=where:A = total volume of standard methanolic sodium hydroxide added, mLB = volume of standard methanolic sodium hydroxide for blank, mLM = molarity of methanolic sodium hydroxide solutionV = sample volume, mL3 of 3829-82NOTEAnalysis of samples containing alkaline carbonates or acidic compounds re
16、sulting from aminedecomposition will be incorrect since these components will effect the titration. To compensate for theseeffects, the sample can be heated overnight under reflux conditions to remove the majority of the CO2.Titration of the refluxed sample can then be used along with the titration
17、of the original sample to obtain anapproximate CO2content.PRECISIONAn estimated standard deviation is not reported since insufficient data are available at present to permitthis calculation with at least 4 degrees of freedom.TIME FOR ANALYSISThe elapsed time for one analysis is 1.0 hour. The labor requirement is 0.5 hour.REFERENCEMethod SM-100, The Girdler Corp., Louisville, KYSUGGESTED SUPPLIERSargent-Welch Scientific Co., 7300 N. Linder Ave., Skokie, IL 60077
