UOP 382-1981 WATER IN REGENERATOR BOTTOMS FROM HYDROGEN FLUORIDE ALKYLATION.pdf
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1、 COPYRIGHT 1978, 1981 UOP LLCALL RIGHTS RESERVEDUOP Methods are available through ASTM International, 100 Barr Harbor Drive, PO Box C700, 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
2、.org, 610.832.9555 FAX, or 610.832.9585 PHONE.WATER IN REGENERATOR BOTTOMSFROM HYDROGEN FLUORIDE ALKYLATIONUOP Method 382-81SCOPERegenerator bottoms from hydrogen fluoride (HF) alkylation are often 2-phase systems. The lower phaseis relatively rich in HF, containing about 30-40%; and the upper phase
3、 is essentially hydrocarbon containingsmall concentrations (about 0-5%) of HF. The water content of the HF-rich lower phase is usually less than10%, and that of the upper phase is usually less than 5%. This method is satisfactory for the determinationof water in both types of samples. The unsaturate
4、s present in the oil do not interfere in the titration forwater.OUTLINE OF METHODThe sample is weighed into a dried polypropylene bottle and the excess HF vaporized in the presence ofpentane or isooctane. Pyridine in excess is added to the oily residue. The resulting solution is titrated withdilute
5、Karl Fischer reagent, using a dead-stop indicator to detect the endpoint. The titration is based onreactions represented as follows:22 2 3H O+I +SO 2HI+SOKarl Fischer reagent is a mixture of iodine, pyridine, and sulfur dioxide. Iodine does not oxidize sulfurdioxide except in the presence of water.
6、As can be seen from the equation above, the consumption of iodineand sulfur dioxide is stoichiometrically related to the amount of water present.On reaction with water, the dark brown reagent (the brown color is caused by the presence of free iodine)becomes light yellow as the “free” iodine becomes
7、chemically combined. A small excess of the reagent willchange the color back to brown because “free” iodine again exists. This phenomenon is commonly taken asthe endpoint of the reaction when the visual endpoint technique is used.The dead-stop electrometric method for detection of the endpoint is a
8、special case of a two platinumelectrode system with a small dc voltage applied. Karl Fischer reagent is added to the titration cell. In thepresence of an excess of the Fischer reagent, the cathode is depolarized and current flows between theelectrodes. Water in excess of that required to react with
9、the Fischer reagent is added. The electrodesbecome polarized and current no longer flows between them. The excess water is then titrated with theIT IS THE USERS RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TODETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. E
10、FFECTIVE 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 MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED INTHIS PROCEDUR
11、E SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTIONEQUIPMENT (PPE).2 of 8382-81dilute Fischer reagent. At the endpoint, when a slight excess of the dilute Fischer reagent is present, thecathode is again depolarized and current again flows between the electrodes. This current ch
12、ange isdetected by a galvanometer.APPARATUSBeaker, polypropylene, 500-mLBottles, polypropylene, narrow mouth, screw cap, 60-, 480-, and 960-mLKarl Fischer moisture determinator. See Fig. 1 for diagram and assembly of the various componentsrequired. If desired, a simpler apparatus or a commercial uni
13、t may be substituted, provided that resultsare comparable to those obtained by the described assembly.1. Titration cell. See Fig. 2 for details of fabrication. The cell is designed with 4 openings. The Ts 29/42male joint accommodates a Ts 29/42 female joint, through which the platinum electrodes are
14、 fused. ATs 19 stopper fits into another opening through which the sample is introduced into the cell. The thirdopening accommodates a buret tip to which is attached a spherical 12/5 female joint. Fit an exhausttube into the cell through a stopcock and a spherical 12/5 male joint to remove the spent
15、 liquid afterthe completion of an analysis.2. Platinum electrodes. Fuse 2 platinum electrodes, available from Leeds and Northrup, Cat. No. 117421complete with glass insulators, into a cylindrical head equipped with a Ts 29/42 female joint whichfits into the male joint of the titration cell. Equip th
16、e head with a glass tube fitted with a spherical 12/5female joint as a vent when the cell is drained of spent liquid.3. Dead-stop indicator. Construct according to Fig. 3 or use a commercial equivalent employing amicroammeter of 0-20 a range. Switch No. 1 must be in the “On” position during operatio
17、n.Switch No. 2 is used to set the instrument for maximum sensitivity prior to titrating. This setting ismade by adjusting the needle of the meter to full-scale deflection with the variable rheostat whenSwitch No. 2 is in the “Off” position. Switch No. 2 must be moved to the “On” position duringtitra
18、tion. The meter is connected to the platinum electrodes with alligator clips. A more permanentconnection may be made if desired.4. Buret, 2-way, 50-mL modified. Modify the delivery tip of the buret with a spherical 12/5 female jointand connect to the titration cell by means of a connecting tube equi
19、pped with spherical 12/5 joints.The refill tube is also equipped with a spherical 12/5 female joint.5. Karl Fischer reagent reservoir. A 2-liter brown bottle fitted with a Ts 29/42 male joint. The cap is aTs 29/42 female joint with a glass tube fused to it and extending down to within 1 mm of the bo
20、ttomof the bottle. A glass tube with a spherical 12/5 female joint is fused at a 90 angle into the headwhich serves as a pressuring system for refilling the buret. The reservoir is connected to the refill sideof the buret by a glass tube fitted with spherical 12/5 joints.6. Waste trap. A 500-mL filt
21、er flask equipped with a 1-hole rubber stopper and a glass tube. Connect theside arm of the flask to the exhaust tube of the titration cell. With the stopcock open and a fingerclosing off the vent on the constant N2pressure control scrubber, the waste will be pressured out fromthe cell into the trap
22、. Drying tubes filled with Drierite or equivalent are used to protect reagents andthe titration cell from the inclusion of atmospheric moisture. Closing of the vent from the constant N23 of 8382-81Figure 1Diagram of Karl Fischer Moisture Determinator4 of 8382-81Figure 2Karl Fischer Titration Cell5 o
23、f 8382-81Figure 3Dead-Stop Indicator For Determination Of Watercontrol scrubber is also used to apply pressure to the Karl Fischer reagent reservoir when refilling theburet. Fig. 1 is a schematic sketch of the equipment and is not drawn to scale. In making theseconnections, use discretion to make th
24、e whole assembly compact. However, be sure there is enoughspace around the stopcock of the buret so that it may be manipulated without hindrance from theelectrode system.7. Constant N2pressure control scrubber. A 250-mL gas washing bottle fitted with a bell bottomdispersion tip. Sufficient glycol is
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