CN112858569A - Method for determining moisture content in oil product - Google Patents
Method for determining moisture content in oil product Download PDFInfo
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- CN112858569A CN112858569A CN202110042687.5A CN202110042687A CN112858569A CN 112858569 A CN112858569 A CN 112858569A CN 202110042687 A CN202110042687 A CN 202110042687A CN 112858569 A CN112858569 A CN 112858569A
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- 238000000034 method Methods 0.000 title claims abstract description 78
- 239000003921 oil Substances 0.000 claims abstract description 53
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 51
- 239000000295 fuel oil Substances 0.000 claims abstract description 8
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 84
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 53
- XNWFRZJHXBZDAG-UHFFFAOYSA-N 2-METHOXYETHANOL Chemical compound COCCO XNWFRZJHXBZDAG-UHFFFAOYSA-N 0.000 claims description 28
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 20
- 239000002798 polar solvent Substances 0.000 claims description 19
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 10
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 10
- 239000000084 colloidal system Substances 0.000 claims description 9
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 claims description 8
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 6
- 238000003869 coulometry Methods 0.000 claims description 5
- QSJXEFYPDANLFS-UHFFFAOYSA-N Diacetyl Chemical compound CC(=O)C(C)=O QSJXEFYPDANLFS-UHFFFAOYSA-N 0.000 claims description 4
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 4
- QARVLSVVCXYDNA-UHFFFAOYSA-N bromobenzene Chemical compound BrC1=CC=CC=C1 QARVLSVVCXYDNA-UHFFFAOYSA-N 0.000 claims description 4
- 239000003153 chemical reaction reagent Substances 0.000 claims description 4
- LQNUZADURLCDLV-UHFFFAOYSA-N nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1 LQNUZADURLCDLV-UHFFFAOYSA-N 0.000 claims description 4
- AVQQQNCBBIEMEU-UHFFFAOYSA-N 1,1,3,3-tetramethylurea Chemical compound CN(C)C(=O)N(C)C AVQQQNCBBIEMEU-UHFFFAOYSA-N 0.000 claims description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 2
- 150000001408 amides Chemical class 0.000 claims description 2
- 150000001555 benzenes Chemical class 0.000 claims description 2
- 235000013877 carbamide Nutrition 0.000 claims description 2
- 150000002148 esters Chemical class 0.000 claims description 2
- GNOIPBMMFNIUFM-UHFFFAOYSA-N hexamethylphosphoric triamide Chemical compound CN(C)P(=O)(N(C)C)N(C)C GNOIPBMMFNIUFM-UHFFFAOYSA-N 0.000 claims description 2
- 150000002576 ketones Chemical class 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 150000002825 nitriles Chemical class 0.000 claims description 2
- LYGJENNIWJXYER-UHFFFAOYSA-N nitromethane Chemical compound C[N+]([O-])=O LYGJENNIWJXYER-UHFFFAOYSA-N 0.000 claims description 2
- HXJUTPCZVOIRIF-UHFFFAOYSA-N sulfolane Chemical compound O=S1(=O)CCCC1 HXJUTPCZVOIRIF-UHFFFAOYSA-N 0.000 claims description 2
- 150000003457 sulfones Chemical class 0.000 claims description 2
- 150000003462 sulfoxides Chemical class 0.000 claims description 2
- 150000003672 ureas Chemical class 0.000 claims description 2
- 238000001514 detection method Methods 0.000 abstract description 8
- 238000004458 analytical method Methods 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 15
- 238000005259 measurement Methods 0.000 description 14
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 8
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 8
- 238000004821 distillation Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 238000004448 titration Methods 0.000 description 7
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- RAXXELZNTBOGNW-UHFFFAOYSA-N imidazole Natural products C1=CNC=N1 RAXXELZNTBOGNW-UHFFFAOYSA-N 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 4
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 4
- OISVCGZHLKNMSJ-UHFFFAOYSA-N 2,6-dimethylpyridine Chemical compound CC1=CC=CC(C)=N1 OISVCGZHLKNMSJ-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000003209 petroleum derivative Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- BSKHPKMHTQYZBB-UHFFFAOYSA-N 2-methylpyridine Chemical compound CC1=CC=CC=N1 BSKHPKMHTQYZBB-UHFFFAOYSA-N 0.000 description 2
- FKNQCJSGGFJEIZ-UHFFFAOYSA-N 4-methylpyridine Chemical compound CC1=CC=NC=C1 FKNQCJSGGFJEIZ-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- -1 alcohol ether compound Chemical class 0.000 description 2
- 238000003556 assay Methods 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 238000004939 coking Methods 0.000 description 2
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 2
- GBMDVOWEEQVZKZ-UHFFFAOYSA-N methanol;hydrate Chemical compound O.OC GBMDVOWEEQVZKZ-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000012086 standard solution Substances 0.000 description 2
- 235000010269 sulphur dioxide Nutrition 0.000 description 2
- ZUHZGEOKBKGPSW-UHFFFAOYSA-N tetraglyme Chemical compound COCCOCCOCCOCCOC ZUHZGEOKBKGPSW-UHFFFAOYSA-N 0.000 description 2
- LEEANUDEDHYDTG-UHFFFAOYSA-N 1,2-dimethoxypropane Chemical compound COCC(C)OC LEEANUDEDHYDTG-UHFFFAOYSA-N 0.000 description 1
- GZHQUHIMIVEQFV-UHFFFAOYSA-N 1,6-dimethoxyhexane Chemical compound COCCCCCCOC GZHQUHIMIVEQFV-UHFFFAOYSA-N 0.000 description 1
- IWDFHWZHHOSSGR-UHFFFAOYSA-N 1-ethylimidazole Chemical compound CCN1C=CN=C1 IWDFHWZHHOSSGR-UHFFFAOYSA-N 0.000 description 1
- VMCIKMLQXFLKAX-UHFFFAOYSA-N 1-methoxy-2-[2-[2-[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]ethoxy]ethoxy]ethane Chemical compound COCCOCCOCCOCCOCCOCCOC VMCIKMLQXFLKAX-UHFFFAOYSA-N 0.000 description 1
- MCTWTZJPVLRJOU-UHFFFAOYSA-N 1-methyl-1H-imidazole Chemical compound CN1C=CN=C1 MCTWTZJPVLRJOU-UHFFFAOYSA-N 0.000 description 1
- NRGGMCIBEHEAIL-UHFFFAOYSA-N 2-ethylpyridine Chemical compound CCC1=CC=CC=N1 NRGGMCIBEHEAIL-UHFFFAOYSA-N 0.000 description 1
- HZEOUPCNUWSUFL-UHFFFAOYSA-N 4,5,5-trimethyl-4-pentan-3-yl-1H-imidazole Chemical compound C(C)C(C1(N=CNC1(C)C)C)CC HZEOUPCNUWSUFL-UHFFFAOYSA-N 0.000 description 1
- YSWBFLWKAIRHEI-UHFFFAOYSA-N 4,5-dimethyl-1h-imidazole Chemical compound CC=1N=CNC=1C YSWBFLWKAIRHEI-UHFFFAOYSA-N 0.000 description 1
- CPHGOBGXZQKCKI-UHFFFAOYSA-N 4,5-diphenyl-1h-imidazole Chemical compound N1C=NC(C=2C=CC=CC=2)=C1C1=CC=CC=C1 CPHGOBGXZQKCKI-UHFFFAOYSA-N 0.000 description 1
- VJXRKZJMGVSXPX-UHFFFAOYSA-N 4-ethylpyridine Chemical compound CCC1=CC=NC=C1 VJXRKZJMGVSXPX-UHFFFAOYSA-N 0.000 description 1
- XVMSFILGAMDHEY-UHFFFAOYSA-N 6-(4-aminophenyl)sulfonylpyridin-3-amine Chemical compound C1=CC(N)=CC=C1S(=O)(=O)C1=CC=C(N)C=N1 XVMSFILGAMDHEY-UHFFFAOYSA-N 0.000 description 1
- VYXKTNXWRUPDGG-UHFFFAOYSA-N 6-ethylpyridine Chemical compound CCC1=C=CC=C[N]1 VYXKTNXWRUPDGG-UHFFFAOYSA-N 0.000 description 1
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 1
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 239000011280 coal tar Substances 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 150000002460 imidazoles Chemical class 0.000 description 1
- 229940079865 intestinal antiinfectives imidazole derivative Drugs 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- HWEFNRWYNIBQFD-UHFFFAOYSA-N methanol;sulfur dioxide Chemical compound OC.O=S=O HWEFNRWYNIBQFD-UHFFFAOYSA-N 0.000 description 1
- 239000001814 pectin Substances 0.000 description 1
- 235000010987 pectin Nutrition 0.000 description 1
- 229920001277 pectin Polymers 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 150000003222 pyridines Chemical class 0.000 description 1
- 229930195734 saturated hydrocarbon Natural products 0.000 description 1
- 239000010117 shenhua Substances 0.000 description 1
- HELHAJAZNSDZJO-OLXYHTOASA-L sodium L-tartrate Chemical compound [Na+].[Na+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O HELHAJAZNSDZJO-OLXYHTOASA-L 0.000 description 1
- 229960002167 sodium tartrate Drugs 0.000 description 1
- 239000001433 sodium tartrate Substances 0.000 description 1
- 235000011004 sodium tartrates Nutrition 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000004291 sulphur dioxide Substances 0.000 description 1
- YFNKIDBQEZZDLK-UHFFFAOYSA-N triglyme Chemical compound COCCOCCOCCOC YFNKIDBQEZZDLK-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
- G01N31/168—Determining water content by using Karl Fischer reagent
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Molecular Biology (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
The invention relates to the field of analysis and detection, and discloses a method for determining the water content in an oil product. The method can quickly and accurately determine the moisture content in the oil product sample containing the heavy oil, and enlarges the detection range of the Karl Fischer method.
Description
Technical Field
The invention relates to the field of analysis and detection, in particular to a method for determining the moisture content in an oil product.
Background
Currently, national standard methods for determining the moisture of petroleum products and coking products comprise GB/T2288-2008 coking product moisture determination, GB/T260-2016 petroleum product moisture determination, GB/T6283-2008 chemical product moisture content determination-Karl Fischer method (general method), and GB/T6284-2006 chemical product moisture determination general method-drying reduction method. The above methods are broadly divided into three categories: the first method is a distillation method, and the determination principle is that a sample is mixed with an anhydrous solvent, and the water content is determined by distillation; secondly, a gravimetric method, heating at the temperature of 105-110 ℃ to lose the moisture of the sample seeds, and calculating the moisture content according to the mass difference; and thirdly, performing a chemical reaction between water in the sample and a Karl Fischer reagent, determining a titration end point through electrode detection potential, and calculating the water content of the sample according to the amount of the Karl Fischer reagent consumed by titration.
Although the existing analysis methods can detect the content of water, the distillation method generally needs about 40 minutes of distillation due to the requirement on the distillation speed, takes longer time and has great influence on the detection and unloading efficiency when entering a factory; on one hand, if the oil contains light components, the light components volatilize when the oil is heated at 105-110 ℃ to cause the loss of sample mass and influence the accuracy of the measurement result of water, and on the other hand, the precision of the gravimetric method is limited, and the repeatability of the measurement of the water content with lower content is poor; the Karl Fischer method has great advantages in the aspects of analysis time and precision, and the problem exists at present that oil products containing heavy components are poor in solubility, particularly oil products with high colloid and asphaltene contents can directly wrap double platinum needles of an electrode, so that the electrode cannot correctly indicate potential change in reaction and cannot normally measure the moisture content.
Disclosure of Invention
The invention aims to solve the problems that the distillation method is long in determination time and the Karl Fischer method cannot detect the moisture content in heavy-component oil products in the prior art, and provides a method for detecting the moisture content in the oil products.
In order to achieve the above object, the present invention provides a method for determining the water content in an oil product, which comprises reacting water in an oil product sample with a karl fischer reagent in the presence of methanol and an aprotic polar solvent, and determining the water content in the oil product sample.
The method can quickly and accurately determine the moisture content in the oil product sample containing the heavy oil, and enlarges the detection range of the Karl Fischer method.
The method of the invention greatly improves the efficiency of analyzing the water content of the oil product containing heavy oil, reduces the analysis time from 40-50min of the original distillation method to 10-15min, improves the detection efficiency of entering a factory, and saves the waiting time for unloading.
Detailed Description
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 measuring the water content in an oil product, which comprises the steps of reacting water in an oil product sample with a Karl Fischer reagent in the presence of methanol and an aprotic polar solvent, and measuring the water content in the oil product sample.
In the present invention, the oil may be an oil existing in the art, such as petroleum, coal tar, and the like. The method of the invention is suitable for any oil product in the field, and is more suitable for oil products containing heavy oil.
In the present invention, heavy oil means crude oil having an API gravity of 22.3 or less.
In the present invention, preferably, the heavy oil comprises pectin and asphaltene.
Among them, the gum is a substance which is soluble in n-hexane and toluene, but insoluble in ethyl acetate.
Among them, asphaltenes are those which are insoluble in low molecular weight saturated hydrocarbons (e.g., n-hexane) and soluble in aromatic hydrocarbons (e.g., toluene).
Preferably, the total content of colloids and asphaltenes in the oil sample is 20% by weight or less.
In the present invention, it is preferable that the ratio of the total weight of methanol and the aprotic polar solvent to the weight of the oil sample is 10 to 20:1, for example, can be 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, and any range between any two values.
In the present invention, the volume ratio of methanol to the aprotic polar solvent is preferably 0.4 to 3:1, and may be, for example, 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.8:1, 3:1, and any range consisting of any two values, more preferably 1.5 to 3:1, more preferably 2 to 2.5: 1. Within the above preferable range, the accuracy of the measured moisture content can be further improved.
In the present invention, the aprotic polar solvent may be an existing aprotic polar solvent, and may include, but is not limited to, tetrahydrofuran, amides, ketones, esters, ureas, nitrohydrocarbons, nitriles, sulfoxides, benzenes, and sulfones.
Although the aprotic polar solvent can be used for measuring the water content in the oil product, the use of acetone is not recommended in practical operation because the use of acetone for about 2 to 3 times can cause the adhesion of electrodes. Preferably, the aprotic polar solvent is selected from at least one of tetrahydrofuran, N-dimethylformamide, hexamethylphosphoric triamide, chlorobenzene, bromobenzene, acetone, butanedione, N-methylpyrrolidone, 1,3, 3-tetramethylurea, nitrobenzene, nitromethane, acetonitrile, sulfolane and dimethyl sulfoxide.
More preferably, the aprotic polar solvent is tetrahydrofuran and/or dimethylformamide. Within the above preferable range, the accuracy of the measured moisture content can be further improved.
In the present invention, preferably, the method of the reaction comprises: mixing an oil sample, methanol and an aprotic polar solvent, and dropwise adding a Karl Fischer reagent into the obtained mixture to react.
The method of the dropwise addition may be referred to an operation generally used in a titration method which is conventional in the art.
In the present invention, the method for determining the moisture content may be based on or modified on the karl fischer method, which is the determination of the moisture content in the chemical products of GB/T6283-.
More preferably, the method of determination is direct coulometry. The accuracy of the determined moisture content can be further improved using the preferred method.
It should be understood that, in order to further improve the accuracy of detection, methanol and the aprotic polar solvent may be titrated by using the karl fischer reagent before the karl fischer reagent titrates the oil sample, so that the moisture contained in the methanol and the aprotic polar solvent reacts with the karl fischer reagent to avoid interference.
In the present invention, the karl fischer reagent may be a karl fischer reagent existing in the art as long as the determination of the water content can be achieved.
In a preferred embodiment of the invention, the karl fischer reagent comprises iodine, sulphur dioxide, methanol or a substitute thereof and pyridine or a substitute thereof.
Wherein, the substitute of methanol can be alcohol ether compound without hydroxyl, including but not limited to at least one of glycol dimethyl ether, propylene glycol dimethyl ether, hexylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and hexaethylene glycol dimethyl ether.
Among these, alternatives to pyridine include, but are not limited to, pyridine derivatives, imidazole and imidazole derivatives, preferably at least one of 2-methylpyridine, 4-methylpyridine, 2, 6-dimethylpyridine, 2-ethylpyridine, 4-ethylpyridine, 2-methyl, 6-ethylpyridine, dimethylimidazole, diethyltetramethylimidazole, N-methylimidazole, N-ethylimidazole and diphenylimidazole.
The karl fischer reagent preferably further comprises water.
In the present invention, preferably, the ratio of iodine, sulfur dioxide methanol or a substitute thereof, pyridine or a substitute thereof, and water in the karl fischer reagent is 1: 0.9-1.1: 2.7-3.3: 0.9-1.1: 0.9-1.1.
In the present invention, before the water content is measured, the karl fischer reagent may be titrated to measure the titer T (in mg/mL) of the karl fischer reagent.
In the present invention, the method of titrating the titer of the karl fischer reagent may include: sodium tartrate calibration method, water calibration method and water-methanol standard solution calibration method (see GB/T6283-2008 part 8.2.1).
The titer T of karl fischer reagent can be calculated according to the following formula:
wherein, m represents the standard sample mass, g;
a- -coefficient, 1000 mg/g;
VKF--the volume of karl fischer reagent, ml, was consumed.
In the present invention, preferably, the water content in the oil sample is calculated according to the following formula:
wherein, m represents the standard sample mass, g;
b- -coefficient, 0.1;
VKF--the volume of karl fischer reagent consumed, ml;
V0-blank value, ml;
c- -divisor, 1.0;
t- -titer, mg/mL.
In the present invention, when the calibration is performed by the water calibration method, the standard sample is water; preferably, the experimental water meets the three-stage water specification of GB/T6682.
When calibrated using standard substance calibration methods, the standards refer to water-methanol standard solutions.
The present invention will be described in detail below by way of examples.
In the present invention, the reagents and drugs used are commercially available unless otherwise specified.
Oil samples 1-3 were purchased raw oil from Ordos coal oil-processing company, Inc., Shenhua coal oil-processing chemical Co., Ltd.
Wherein, the content of colloid and asphaltene in sample 1 is 7.23 wt% of colloid content and 2.22 wt% of asphaltene content respectively;
the contents of colloid and asphaltene in sample 2 were 13.87 wt% for colloid and 4.02 wt% for asphaltene, respectively;
the content of colloid and asphaltene in sample 3 was 9.43 wt% for colloid and 2.53 wt% for asphaltene, respectively.
Karl Fischer's reagent was purchased from Tianjin Si you Fine Chemicals Co., Ltd; on a molar basis, iodine: sulfur dioxide: methanol: pyridine: water-1: 1:3:1: 1.
The assay was repeated 5 times for each experiment and the data obtained was analyzed using Excel software.
Test example 1
This test example is intended to illustrate a titration method of Karl Fischer's reagent
The titer T is determined by using water as a standard substance, the specific method is shown in GB/T6283-20088.2.1, and the titer T of the Karl Fischer reagent is determined and calculated according to the following formula:
wherein, m represents the standard sample mass, g;
a- -coefficient, 1000 mg/g;
VKF--the volume of karl fischer reagent, ml, was consumed.
The titer T of Karl Fischer reagent was determined to be 5.2540 mg/mL.
Reference ratio
This reference example is used to illustrate the water content of a reference oil
The water content of oil samples 1-3 was determined according to the GB/T260-2016 Petroleum products moisture assay, with the results shown in Table 1.
Example 1
This example illustrates the method of determining water content in oil products according to the invention
Methanol and Dimethylformamide (DMF) are used as solvents for determining the water content in the oil samples 1-3. Wherein the volume ratio of methanol to DMF is 7.5:2.5, 7:3, 6:4, 4:7 and 3:7, and the total volume of methanol and DMF is 25 mL.
Specifically, the water content of the oil samples 1-3 is sequentially measured according to the direct coulometry method in GB/T6283-2008. Wherein, 2g of oil sample is weighed and added into a titration flask, the sample weighing standard is up to 0.0001g, the end point is titrated by a Karl Fischer reagent, and the milliliter number of the consumed Karl Fischer reagent is recorded. And setting a blank test, wherein no sample is added during the test, and the time for opening the titration bottle cap is consistent with the time for opening the bottle cap by the measured sample.
The water content in the oil sample is calculated according to the following formula:
wherein, m represents the standard sample mass, g;
b- -coefficient, 0.1;
VKF--the volume of karl fischer reagent consumed, ml;
V0-blank value, ml;
c- -divisor, 1.0;
t- -titer, mg/mL.
The method of the embodiment can be used for continuous and multiple times of measurement, and the continuous and accurate measurement times can reach more than 8 times.
The results of calculating the water content are shown in table 1.
TABLE 1
When the volume ratio of methanol to DMF is 1:4, the method can also be used for measuring the moisture content in an oil product sample, but the condition that the electrode is adhered appears after 4-5 times of tests, the test precision and the test accuracy are reduced, and therefore, the method is not suitable for use because of needing to be cleaned for many times in actual measurement.
Example 2
This example illustrates the method of determining water content in oil products according to the invention
The procedure is as described in example 1, except that tetrahydrofuran is used instead of dimethylformamide, the volume ratio of methanol to tetrahydrofuran being 7: 3.
The method of the embodiment can be used for continuous and multiple times of measurement, and the continuous and accurate measurement times can reach more than 8 times. The results of calculating the water content are shown in table 2.
Example 3
This example illustrates the method of determining water content in oil products according to the invention
The procedure is as described in example 1, except that chlorobenzene is used instead of dimethylformamide, the volume ratio of methanol to chlorobenzene being 7: 3.
The method of this example was used to determine the presence of an electrode stuck after 2-3 consecutive measurements. The results of calculating the water content are shown in table 2.
Example 4
This example illustrates the method of determining water content in oil products according to the invention
The procedure was followed as described in example 1 (methanol to dimethylformamide in a 7:3 volume ratio) except that pyridine in the Karl Fischer reagent was replaced by imidazole and the titer T of the Karl Fischer reagent was determined to be 5.3245 mg/mL.
The method of the embodiment can be used for continuous and multiple times of measurement, and the continuous and accurate measurement times can reach more than 8 times.
The results of calculating the water content are shown in table 2.
Comparative example 1
Comparative example for illustrating the method for determining the Water content in a comparative oil product
The procedure is as described in example 1, except that instead of methanol, ethanol is used in a volume ratio of 7:3 to DMF.
The electrode was easily bonded after 4 times or more of measurement by the method of this comparative example.
The results of calculating the water content are shown in table 1.
Comparative example 2
Comparative example for illustrating the method for determining the Water content in a comparative oil product
The procedure was carried out as described in example 1, except that n-hexane was used instead of dimethylformamide, and the volume ratio of methanol to n-hexane was 7: 3.
The electrode was easily bonded after 3 times or more of measurement by the method of this comparative example.
The results of calculating the water content are shown in table 1.
Comparative example 3
Comparative example for illustrating the method for determining the Water content in a comparative oil product
The procedure was followed as described in example 1, except that methanol was used instead of dimethylformamide, i.e. methanol alone was used. During the measurement, a large amount of undissolved sample was found at the bottom of the titration cell.
The results of calculating the water content are shown in table 1.
Comparative example 4
Comparative example for illustrating the method for determining the Water content in a comparative oil product
The procedure was followed as described in example 1, except that dimethylformamide was used instead of methanol, i.e. dimethylformamide alone was used.
The electrode was easily bonded after 3 times or more of measurement by the method of this comparative example.
The results of calculating the water content are shown in table 2.
TABLE 2
As can be seen from the results in tables 1 and 2, the method of the present invention has the effects of significantly better accuracy and precision when the dimethylformamide and/or tetrahydrofuran are added into the solvent methanol respectively, and the water content in the oil sample is measured under the condition of the optimized volume ratio of methanol and dimethylformamide/tetrahydrofuran.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (10)
1. A method for determining the water content in an oil product, characterized in that the method comprises reacting water in an oil product sample with a Karl Fischer's reagent in the presence of methanol and an aprotic polar solvent, and determining the water content in the oil product sample.
2. The method of claim 1, wherein the ratio of the total weight of methanol and aprotic polar solvent to the weight of the oil sample is 10-20: 1; and/or
The volume ratio of methanol to aprotic polar solvent is 0.4 to 3:1, preferably 1.5 to 3:1, more preferably 2-2.5: 1.
3. The method according to claim 1 or 2, wherein the aprotic polar solvent is selected from at least one of tetrahydrofuran, amides, ketones, esters, ureas, nitrohydrocarbons, nitriles, sulfoxides, benzenes and sulfones.
4. The process according to any one of claims 1 to 3, wherein the aprotic polar solvent is selected from at least one of tetrahydrofuran, N-dimethylformamide, hexamethylphosphoric triamide, chlorobenzene, bromobenzene, acetone, butanedione, N-methylpyrrolidone, 1,3, 3-tetramethylurea, nitrobenzene, nitromethane, acetonitrile, sulfolane and dimethyl sulfoxide.
5. The process according to any one of claims 1 to 4, wherein the aprotic polar solvent is tetrahydrofuran and/or dimethylformamide.
6. The method of any of claims 1-5, wherein the oil sample comprises heavy oil.
7. The process according to any of claims 6, wherein the heavy oil comprises gums and asphaltenes.
8. The method of claim 7, wherein the total content of colloids and asphaltenes in the oil sample is 20% or less by weight.
9. The method of any one of claims 1-8, wherein the method of reacting comprises: mixing an oil sample, methanol and an aprotic polar solvent, and dropwise adding a Karl Fischer reagent into the obtained mixture to react.
10. The method of claim 9, wherein the method of assaying comprises direct coulometry and back-coulometry;
preferably, the method of determination is direct coulometry.
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