US3461042A - Determination of nitrogen - Google Patents
Determination of nitrogen Download PDFInfo
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- US3461042A US3461042A US528732A US3461042DA US3461042A US 3461042 A US3461042 A US 3461042A US 528732 A US528732 A US 528732A US 3461042D A US3461042D A US 3461042DA US 3461042 A US3461042 A US 3461042A
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title description 57
- 229910052757 nitrogen Inorganic materials 0.000 title description 29
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 62
- 229910021529 ammonia Inorganic materials 0.000 description 31
- 239000001257 hydrogen Substances 0.000 description 23
- 229910052739 hydrogen Inorganic materials 0.000 description 23
- 238000000034 method Methods 0.000 description 23
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 20
- 239000003054 catalyst Substances 0.000 description 15
- 230000008569 process Effects 0.000 description 15
- -1 hydrogen ions Chemical class 0.000 description 11
- 238000004458 analytical method Methods 0.000 description 10
- 238000004448 titration Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 229910017464 nitrogen compound Inorganic materials 0.000 description 9
- 150000002830 nitrogen compounds Chemical class 0.000 description 9
- 239000003792 electrolyte Substances 0.000 description 7
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000000571 coke Substances 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 5
- 238000009835 boiling Methods 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 239000003921 oil Substances 0.000 description 4
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000000395 magnesium oxide Substances 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- 239000003208 petroleum Substances 0.000 description 3
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 238000007696 Kjeldahl method Methods 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 238000005513 bias potential Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- DOBUSJIVSSJEDA-UHFFFAOYSA-L 1,3-dioxa-2$l^{6}-thia-4-mercuracyclobutane 2,2-dioxide Chemical compound [Hg+2].[O-]S([O-])(=O)=O DOBUSJIVSSJEDA-UHFFFAOYSA-L 0.000 description 1
- VEPOHXYIFQMVHW-XOZOLZJESA-N 2,3-dihydroxybutanedioic acid (2S,3S)-3,4-dimethyl-2-phenylmorpholine Chemical compound OC(C(O)C(O)=O)C(O)=O.C[C@H]1[C@@H](OCCN1C)c1ccccc1 VEPOHXYIFQMVHW-XOZOLZJESA-N 0.000 description 1
- 229920001342 Bakelite® Polymers 0.000 description 1
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 239000005751 Copper oxide Substances 0.000 description 1
- 241000698776 Duma Species 0.000 description 1
- PCNDJXKNXGMECE-UHFFFAOYSA-N Phenazine Natural products C1=CC=CC2=NC3=CC=CC=C3N=C21 PCNDJXKNXGMECE-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000000184 acid digestion Methods 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000004637 bakelite Substances 0.000 description 1
- 150000007514 bases Chemical class 0.000 description 1
- 229940075397 calomel Drugs 0.000 description 1
- 238000013375 chromatographic separation Methods 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000005443 coulometric titration Methods 0.000 description 1
- 238000003869 coulometry Methods 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical compound Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000003350 kerosene Substances 0.000 description 1
- PIJPYDMVFNTHIP-UHFFFAOYSA-L lead sulfate Chemical compound [PbH4+2].[O-]S([O-])(=O)=O PIJPYDMVFNTHIP-UHFFFAOYSA-L 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910000474 mercury oxide Inorganic materials 0.000 description 1
- 229910000370 mercury sulfate Inorganic materials 0.000 description 1
- UKWHYYKOEPRTIC-UHFFFAOYSA-N mercury(ii) oxide Chemical class [Hg]=O UKWHYYKOEPRTIC-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005497 microtitration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 1
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 description 1
- 150000002897 organic nitrogen compounds Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- YPNVIBVEFVRZPJ-UHFFFAOYSA-L silver sulfate Chemical compound [Ag+].[Ag+].[O-]S([O-])(=O)=O YPNVIBVEFVRZPJ-UHFFFAOYSA-L 0.000 description 1
- 229910000367 silver sulfate Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000001256 steam distillation Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
Images
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
- G01N31/002—Determining nitrogen by transformation into ammonia, e.g. KJELDAHL method
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/42—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
- G01N27/44—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte using electrolysis to generate a reagent, e.g. for titration
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/11—Automated chemical analysis
- Y10T436/115831—Condition or time responsive
- Y10T436/116664—Condition or time responsive with automated titrator
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/17—Nitrogen containing
- Y10T436/176152—Total nitrogen determined
Definitions
- This invention relates to a method and apparatus for automatic quantitative analysis. More specifically to a process and apparatus for the detection of the nitrogen content of nitrogen-containing materials. Analyses for nitrogen are required in many research and process laboratories. In the petroleum industry, for example, the several deleterious efiects of nitrogen compounds make it necessary to determine nitrogen in concentrations down to about 1 p.p.m. in a variety of feeds and products.
- Kjeldahl which employ a sulfuric acid digestion and steam distillation of ammonia
- Dumas methods which use an oxidation of nitrogen compounds to elemental nitrogen over hot copper oxide, require less time but are less sensi' tive.
- the third method, the ter Meulen method has heretofore not been extensively used nor has it been employed along with an automatic tritrating system. This method employs the catalytic production of ammonia.
- this process and apparatus can be used to determine nitrogen in quantities smaller than 1 p.p.m. in less than minutes.
- this process and apparatus can be used with a gas chromatography system for the selective detection of nitrogen compounds.
- the figure is a schematic illustration of the nitrogen analysis apparatus.
- the process comprises converting nitrogen contained in the material to be analyzed to ammonia, said nitrogen being catalytically convertible to ammonia, and automatically titrating the ammonia electrochemically. More specifically, the nitrogen compounds are passed over a catalyst, nickel-on-magnesium oxide for example, in a stream of nitrogen, thereby converting the nitrogen contained in the compounds to ammonia. The ammonia is then titrated automatically in a micro titration cell. This titration may be carried out coulometrically with any known ammonia titratable reactant. For example, as disclosed in a copending application, Serial No. 529,134, filed even date with the instant application, coulometrically generated hydrogen ions provide excellent results. Ammonia entering the titration cell is titrated automatically 3,461,042 Patented Aug. 12, 1969 with hydrogen ions generated coulometrically within the cell. The titration reaction can be written as:
- the nickel-on-magnesium catalyst is prepared by adding a nickel nitrate hexahydrate solution slowly to a magnesium oxide slurry with vigorous stirring. The precipitate is then decanted, washed, compacted, and dried. The nickel oxide is then reduced to nickel metal by heating in the presence of hydrogen.
- a catalyst tube containing a catalyst bed is heated preferably to a temperature of about 440 or l0 C. The catalyst tube is then filled with a 3" section of catalyst and purged with hydrogen for thirty seconds. The catalyst tube is then connected to a titration cell, provided with an automatic stirrer and containing a suitable electrolyte.
- Hydrogen flow rate through the catalyst tube is not particularly critical. Quantitative ammonia production has been obtained at rates from 10 to 1,000 ml. per minute. The rate chosen for usual operationabout 500 ml. per minute-is fast enough to keep peak Widths relatively narrow and yet not so fast as to cause significant noise in the titration cell.
- the apparatus of this invention comprises a titrating zone containing an electrolyte; means communicating with the titrating zone for catalytically converting the nitrogen to ammonia; means electrically in communication with the titrating zone for determining a potential difference in the electrolyte caused by introducing the ammonia into the titrating zone; means electrically in communication with the titrating zone for continuously r generating titrant to eliminate the potential difference; and
- the apparatus contains a titration cell 4 containing an electrolyte wherein the titration reaction is carried out.
- a sensing electrode pair consisting of reference electrode 12 and sensor electrode 14 and a generating electrode pair consisting of anode 8 and cathode 10.
- Electrodes 8, 12 and 14 are positioned in a titrating zone of the cell with electrode 10 being positioned in that part of the cell which is outside the titrating zone. Mixing or difussion of electrolyte between the titrating zone and the part containing electrode 10 is prevented by glass frit 6.
- Electrodes 8 and 10 are interchangeable so that for a particular titration cathode 10 may be positioned within the titration zone and anode 8 outside of that zone. In addition it may be desirable for a particular reference electrode to place electrode 12 outside the titrating zone with appropriate electrolytic connection.
- the material to be analyzed is placed over a catalyst bed contained within catalyst tube 2.
- the nitrogen compounds are converted to ammonia in catalyst tube 2 in the presence of humidified hydrogen.
- the gaseous ammonia is introduced into the titrating zone of cell 4.
- Titrant concentration is sensed by electrode pair 12 and 14.
- Reference electrode 12 may be any standard half cell, such as silver sulfate, lead sulfate, calomel, mercury sulfate or oxide, silver chloride, hydrogen, glass, etc.
- the original concentration of titrant within the cell is fixed by a reference potential established within the electronic system.
- This reference potential is called a bias potential.
- the bias potential is applied by the control electronics to one input of the coulometer differential amplifier and is equal and opposite to the potential of the reference/sensor electrode pair, 12 and 14 which is applied to the other input.
- the amplifier receives a zero signal and titrating ions are not generated; however, when ammonia enters, a potential difference in the electrolyte is established and the voltage shift of the sensor electrode is applied to the amplifier, and a flow of current is produced in the generator circuit to form titrating ions at the anode.
- the cell operates efficiently (i.e., the titrant generation peaks are the most narrow without significant overshoot) when the Original concentration of hydrogen ion titrant is kept between about and 10* moles per liter; the preferred range is 10 to 10*.
- the bias setting is chosen to give hydrogen ion concentrations in the range indicated above.
- the bias voltage which is equal and opposite to the refe'rence/ sensor voltage (neglecting overvoltage), can be computed approximately by:
- (H+) is the desired hydrogen ion concentration and E is the standard potential of the reference electrode, E is the standard potential of the hydrogen electrode. If generation of titrant is too fast or too slow, the bias can be adjusted a few millivolts either way until it becomes optimum.
- the process of this invention may also be used with a gas chromatographic column.
- the column selected should give efiicient separations and not react with or strongly adsorb petroleum nitrogen compounds and be able to be taken to relatively high temperatures without causing detector response or catalyst deactivation.
- a column satisfying these requirements was a foot by A; inch I.D. stainless steel section packed with 9% by weight of 12,000 nolecular weight polyethylene (Bakelite DYLT) on Chromosorb-W previously coated with 3% potassium cardonate. This column gave good separating efiiciencies, was unreactive, and was usable to 330 C., which was mfiicient to elute samples as high boiling as gas oils.
- EXAMPLE I Using the procedure as outlined above, the response of the detection system was first tested by measuring the number of coulombs used in titrant generation for injection of 1.00 ,ul. of .00610 N ammonium hydroxide, which was added to the coulometric titration cell by calibrated syringe. The coulombs used were found to be .000584. Assuming 96,500 coulombs would produce 1 equivalent of H+, which would titrate 1 equivalent of NH OH or 35.0 grams, .000584 coulomb would titrate .212 g. NH OH. Actual ,ug. NH OH in 1 ,ul. of .00610 N NH OH is .214 ,ug. NH4OH.
- Typical total nitrogen results are shown in Table I for 8 single compound synthetics and 5 petroleum fractions analyzed previously by a Kjeldahl method.
- the three pyridine analyses show that a wide range of concentrations can be analyzed without difficulty.
- the agreement for the several different types of nitrogen compounds suggests that essentially all types of organic nitrogen compounds can be analyzed accurately.
- Heavy virgin gas 0 605 600 Catalytic naphtha. 2 0.5 0.8
- a process for continuously and rapidly determining the nitrogen content of a nitrogen-containing material, said nitrogen being catalytically convertible to ammonia comprising the steps of converting said nitrogen, contained in said material, to ammonia, and automatically titrating said ammonia electrochemically, in the presence of hydrogen gas, with hydrogen ions as the titrant, said hydrogen ions obtained from said hydrogen gas.
- a process for the determination of the nitrogen content of a nitrogen-containing material, said nitrogen being catalytically convertible to ammonia said process comprising the steps of catalytically converting, in the presence of hydrogen, said nitrogen contained in said material to ammonia and automatically titrating said ammonia, in the presence of hydrogen gas, with coulometrically generated hydrogen ions as the titrant, said hydrogen ions obtained from said hydrogen gas according to the reaction: /2H +H++e-.
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- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Molecular Biology (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Description
Aug. 12, 1 969 R. L. MARTIN ET AL 3,4
DETERMINATION OF NITROGEN Filed Feb. 21, 1966 Heating Gail Ronald L. Martin Nitrogen Compound Humid/fled Hydrogen INVENTORS.
Robert J. Fla/mar United States Patent DETERMINATION OF NITROGEN Ronald L. Martin, 'Glenwood, and Robert J. Flannery,
Olympia Fields, 111., assignors to Standard Oil Company, Chicago, 11]., a corporation of Indiana Filed Feb. 21, 1966, Ser. No. 528,732 Int. Cl. B01k N00 US. Cl. 204-1 4 Claims ABSTRACT OF THE DISCLOSURE An apparatus and process for determining the nitrogen content of a nitrogen-containing material by catalytically converting the nitrogen to ammonia and by automatically titrating the ammonia electrochemically, in the presence of hydrogen gas, with hydrogen ions which are generated according to the equation:
This invention relates to a method and apparatus for automatic quantitative analysis. More specifically to a process and apparatus for the detection of the nitrogen content of nitrogen-containing materials. Analyses for nitrogen are required in many research and process laboratories. In the petroleum industry, for example, the several deleterious efiects of nitrogen compounds make it necessary to determine nitrogen in concentrations down to about 1 p.p.m. in a variety of feeds and products.
Essentially all of the methods for determining total nitrogen use one of three basic approaches, Kjeldahl, Dumas, or ter Meulen. Modifications and improvements of the basic methods are many, yet none have both high sensitivity and short analysis times. Kjeldahl methods, which employ a sulfuric acid digestion and steam distillation of ammonia, are the most popular and are relatively sensitive, but require a careful and experienced analysis and take at least an hour. Dumas methods, which use an oxidation of nitrogen compounds to elemental nitrogen over hot copper oxide, require less time but are less sensi' tive. The third method, the ter Meulen method, has heretofore not been extensively used nor has it been employed along with an automatic tritrating system. This method employs the catalytic production of ammonia. A process has now been discovered which offers the advantages of high sensitivity and greatly reduced analysis time. For example, this process and apparatus can be used to determine nitrogen in quantities smaller than 1 p.p.m. in less than minutes. In addition, this process and apparatus can be used with a gas chromatography system for the selective detection of nitrogen compounds.
The accompanying drawing illustrates a particular embodiment of this invention.
The figure is a schematic illustration of the nitrogen analysis apparatus.
Briefly stated, the process comprises converting nitrogen contained in the material to be analyzed to ammonia, said nitrogen being catalytically convertible to ammonia, and automatically titrating the ammonia electrochemically. More specifically, the nitrogen compounds are passed over a catalyst, nickel-on-magnesium oxide for example, in a stream of nitrogen, thereby converting the nitrogen contained in the compounds to ammonia. The ammonia is then titrated automatically in a micro titration cell. This titration may be carried out coulometrically with any known ammonia titratable reactant. For example, as disclosed in a copending application, Serial No. 529,134, filed even date with the instant application, coulometrically generated hydrogen ions provide excellent results. Ammonia entering the titration cell is titrated automatically 3,461,042 Patented Aug. 12, 1969 with hydrogen ions generated coulometrically within the cell. The titration reaction can be written as:
NH OH+H+- NH ++H O The reaction for coulometric generation of titrant is:
Current used in the generation is amplified and recorded against time to give a direct measure of the amount of ammonia titrated.
A specific embodiment of the invention is as follows:
The nickel-on-magnesium catalyst is prepared by adding a nickel nitrate hexahydrate solution slowly to a magnesium oxide slurry with vigorous stirring. The precipitate is then decanted, washed, compacted, and dried. The nickel oxide is then reduced to nickel metal by heating in the presence of hydrogen. A catalyst tube containing a catalyst bed is heated preferably to a temperature of about 440 or l0 C. The catalyst tube is then filled with a 3" section of catalyst and purged with hydrogen for thirty seconds. The catalyst tube is then connected to a titration cell, provided with an automatic stirrer and containing a suitable electrolyte.
The combination of higher temperature and humidified hydrogen permits analysis of higher boiling samples than were previously possible by catalytic means. At the lower temperatures, many or most nitrogen compounds boiling above the kerosene range failed to yield ammonia quantitatively. The major difficulty associated with the higher boiling samples is coke formation on the catalyst. This difiiculty is lessened in two ways with humidified hydrogen, the rate of coke formation is decreased, and more significantly, ammonia adsorption on the coke is decreased. Without humidified hydrogen, ammonia adsorption increased as coke accumulates and the peaks soon become too tailing to be measured accurately. A temperature of 440 C. is about optimum; higher temperatures give less adsorption of ammonia, but also lead to a more rapid accumulation of coke.
Hydrogen flow rate through the catalyst tube is not particularly critical. Quantitative ammonia production has been obtained at rates from 10 to 1,000 ml. per minute. The rate chosen for usual operationabout 500 ml. per minute-is fast enough to keep peak Widths relatively narrow and yet not so fast as to cause significant noise in the titration cell.
Briefly, the apparatus of this invention comprises a titrating zone containing an electrolyte; means communicating with the titrating zone for catalytically converting the nitrogen to ammonia; means electrically in communication with the titrating zone for determining a potential difference in the electrolyte caused by introducing the ammonia into the titrating zone; means electrically in communication with the titrating zone for continuously r generating titrant to eliminate the potential difference; and
means for measuring the amount of titrant generated, this amount being a measure of the nitrogen content.
More particularly, with reference to the figure, the apparatus contains a titration cell 4 containing an electrolyte wherein the titration reaction is carried out. In electrolytical contact with the electrolyte is a sensing electrode pair consisting of reference electrode 12 and sensor electrode 14 and a generating electrode pair consisting of anode 8 and cathode 10. Electrodes 8, 12 and 14 are positioned in a titrating zone of the cell with electrode 10 being positioned in that part of the cell which is outside the titrating zone. Mixing or difussion of electrolyte between the titrating zone and the part containing electrode 10 is prevented by glass frit 6. Electrodes 8 and 10 are interchangeable so that for a particular titration cathode 10 may be positioned within the titration zone and anode 8 outside of that zone. In addition it may be desirable for a particular reference electrode to place electrode 12 outside the titrating zone with appropriate electrolytic connection.
The material to be analyzed is placed over a catalyst bed contained within catalyst tube 2. The nitrogen compounds are converted to ammonia in catalyst tube 2 in the presence of humidified hydrogen. The gaseous ammonia is introduced into the titrating zone of cell 4. Titrant concentration is sensed by electrode pair 12 and 14. Reference electrode 12 may be any standard half cell, such as silver sulfate, lead sulfate, calomel, mercury sulfate or oxide, silver chloride, hydrogen, glass, etc.
The original concentration of titrant within the cell is fixed by a reference potential established within the electronic system. This reference potential is called a bias potential. The bias potential is applied by the control electronics to one input of the coulometer differential amplifier and is equal and opposite to the potential of the reference/sensor electrode pair, 12 and 14 which is applied to the other input. When the two voltages are equal, the amplifier receives a zero signal and titrating ions are not generated; however, when ammonia enters, a potential difference in the electrolyte is established and the voltage shift of the sensor electrode is applied to the amplifier, and a flow of current is produced in the generator circuit to form titrating ions at the anode. This generation continues until the original titrating ion concentration is restored and the reference/ sensor voltage again equals the bias voltage. The amount of titrant generated is measured and recorded by the readout, such amount being a measure of the nitrogen content in the sample. If hydrogen ions generated by the generator electrode are the titrant, which is disclosed in the copending application referred to above, the cell operates efficiently (i.e., the titrant generation peaks are the most narrow without significant overshoot) when the Original concentration of hydrogen ion titrant is kept between about and 10* moles per liter; the preferred range is 10 to 10*.
The bias setting is chosen to give hydrogen ion concentrations in the range indicated above. For example, the bias voltage, which is equal and opposite to the refe'rence/ sensor voltage (neglecting overvoltage), can be computed approximately by:
where (H+) is the desired hydrogen ion concentration and E is the standard potential of the reference electrode, E is the standard potential of the hydrogen electrode. If generation of titrant is too fast or too slow, the bias can be adjusted a few millivolts either way until it becomes optimum.
The process of this invention may also be used with a gas chromatographic column. The column selected should give efiicient separations and not react with or strongly adsorb petroleum nitrogen compounds and be able to be taken to relatively high temperatures without causing detector response or catalyst deactivation. A column satisfying these requirements was a foot by A; inch I.D. stainless steel section packed with 9% by weight of 12,000 nolecular weight polyethylene (Bakelite DYLT) on Chromosorb-W previously coated with 3% potassium cardonate. This column gave good separating efiiciencies, was unreactive, and was usable to 330 C., which was mfiicient to elute samples as high boiling as gas oils.
It is a significant feature of the titrating means of this nvention that hydrogen gas, which is used as the eluting gas if gas chromatographic separation is carried out, and vhich is necessary in the step of converting nitrogen-conaining compounds to ammonia, is also necessary in the itration step. The hydrogen gas bubbles through the reacion zone at all times and acts as a carrier for the am nonia sample. As hydrogen gas bubbles past the generator lectrode, some of the hydrogen is adsorbed thereon. It s well known that hydrogen bubbled into aqueous solution containing a platinized platinum electrode will adsorb on the electrode surface and fix its potential at a value dependent on the pH. The presence of hydrogen gas on the electrode fixes the electrode potential at a value such that hydrogen ions can be generated from hydrogen gas according to the reaction:
The following examples are given by way of illustration:
EXAMPLE I Using the procedure as outlined above, the response of the detection system was first tested by measuring the number of coulombs used in titrant generation for injection of 1.00 ,ul. of .00610 N ammonium hydroxide, which was added to the coulometric titration cell by calibrated syringe. The coulombs used were found to be .000584. Assuming 96,500 coulombs would produce 1 equivalent of H+, which would titrate 1 equivalent of NH OH or 35.0 grams, .000584 coulomb would titrate .212 g. NH OH. Actual ,ug. NH OH in 1 ,ul. of .00610 N NH OH is .214 ,ug. NH4OH.
It may, therefore, be seen that the process of this invention may be used to obtain results which are within 1% of the actual values.
EXAMPLE II Similar measurements were then made for pyridine, and the coulombs used in titrant generation were again found to be quantitative within experimental error.
Typical total nitrogen results are shown in Table I for 8 single compound synthetics and 5 petroleum fractions analyzed previously by a Kjeldahl method. The three pyridine analyses show that a wide range of concentrations can be analyzed without difficulty. The agreement for the several different types of nitrogen compounds suggests that essentially all types of organic nitrogen compounds can be analyzed accurately.
The last two analyses in Table I show that samples in the vicinity of 1 p.p.m. can be analyzed accurately without a prior concentration step.
TABLE I.ANALYSES FOR TOTAL NITROGEN Nitro en .m. Single-compound synthetics 1 g p p Known Found Pyridine 4. 2 4. 4
Phenazine 154 158 Other samples:
Light catalytic cycle oil 241 233 Shale naphtha 1, 900 1, 920
Heavy virgin gas 0 605 600 Catalytic naphtha. 2 0.5 0.8
Percolated heavy cycle oil 2 2 1. 7
1 Prepared in nitrogen-tree reformatos. 2 K eldahl analysis after a prior concentration step; estimated uncertainty is about i50 0 relative.
interferences to the nitrogen detection system are extremely few. Basic compounds other than ammonia could interfere, but few, if any such compounds, would be present or would be formed during passage through the catalyst.
Having described the invention, what is claimed is:
1. A process for continuously and rapidly determining the nitrogen content of a nitrogen-containing material, said nitrogen being catalytically convertible to ammonia, said process comprising the steps of converting said nitrogen, contained in said material, to ammonia, and automatically titrating said ammonia electrochemically, in the presence of hydrogen gas, with hydrogen ions as the titrant, said hydrogen ions obtained from said hydrogen gas.
2. The process of claim 1 wherein said nitrogen is catalytically converted to ammonia by passing said nitrogen-containing material over a nickel-on-magnesium oxide catalyst in the presence of hydrogen.
3. The process of claim 1 wherein said automatic titration is performed coulometrically.
4. A process for the determination of the nitrogen content of a nitrogen-containing material, said nitrogen being catalytically convertible to ammonia, said process comprising the steps of catalytically converting, in the presence of hydrogen, said nitrogen contained in said material to ammonia and automatically titrating said ammonia, in the presence of hydrogen gas, with coulometrically generated hydrogen ions as the titrant, said hydrogen ions obtained from said hydrogen gas according to the reaction: /2H +H++e-.
References Cited UNITED STATES PATENTS 2,758,079 8/1956 Eckfeldt 204-195 6 2,832,734 4/ 1958 Eckfeldt 204-495 2,954,336 9/1960 Grutsch 204195 OTHER REFERENCES Holowchak, Analytical Chem., vol. 24, #11, Novem 5 her 1952, pp. 17544757.
T. TUNG, Assistant Examiner US. Cl. X.R.
53 33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, |-6LD +2 Dated August 3.2, 1969 Inventor(e) Ronald L. Martin et :11.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 1, line 0+, the first appearance of the word "nitrogen" should read --hyd.rogen--@ Column line 20, the word "coulomb" should be --coulombs--.
SIGNED AN'D SEALED APR 1 4.1970
(SEAL) Attest:
Edward M. Fletcher, 11'. WILLIAM E. 'SQHUYLER, JR- Gommissioner of Patents Attesting Officer
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US52873266A | 1966-02-21 | 1966-02-21 |
Publications (1)
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US3461042A true US3461042A (en) | 1969-08-12 |
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ID=24106931
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US528732A Expired - Lifetime US3461042A (en) | 1966-02-21 | 1966-02-21 | Determination of nitrogen |
Country Status (3)
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US (1) | US3461042A (en) |
FR (1) | FR1516307A (en) |
GB (1) | GB1149832A (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3929587A (en) * | 1974-09-23 | 1975-12-30 | Delta F Corp | Apparatus and method for maintaining a stable electrolyte in oxygen analysis |
US3964869A (en) * | 1973-03-01 | 1976-06-22 | N.K. Verwaltungs Ag | Analytical apparatus for serial determination of nitrogen in samples by the Kjeldahl method |
US4036704A (en) * | 1972-12-11 | 1977-07-19 | Hitachi, Ltd. | Liquid chromatographical method |
US4081345A (en) * | 1975-08-04 | 1978-03-28 | Max-Planck-Gesellschaft Zur Foerderung Der Wissenschaften E.V. | Apparatus for determining small amounts of nitrogen |
US4348359A (en) * | 1980-07-16 | 1982-09-07 | Mitsubishi Chemical Industries, Limited | Device for determining various types of trace nitrogen |
US4409080A (en) * | 1981-06-18 | 1983-10-11 | Texaco Inc. | System for monitoring a cathodically protected structure |
US4929314A (en) * | 1989-07-07 | 1990-05-29 | The Dow Chemical Company | Coulometric titrator apparatus and method |
WO1995000842A1 (en) * | 1993-06-22 | 1995-01-05 | The University Of Newcastle | Electrochemical sensor |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2758079A (en) * | 1950-03-29 | 1956-08-07 | Leeds & Northrup Co | Electrolytic determination of the concentration of a constituent in a fluid |
US2832734A (en) * | 1952-02-14 | 1958-04-29 | Leeds & Northrup Co | Coulometric systems |
US2954336A (en) * | 1957-07-30 | 1960-09-27 | Standard Oil Co | Universal titrating agent generator |
-
1966
- 1966-02-21 US US528732A patent/US3461042A/en not_active Expired - Lifetime
-
1967
- 1967-02-21 FR FR95857A patent/FR1516307A/en not_active Expired
- 1967-02-21 GB GB8087/67A patent/GB1149832A/en not_active Expired
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2758079A (en) * | 1950-03-29 | 1956-08-07 | Leeds & Northrup Co | Electrolytic determination of the concentration of a constituent in a fluid |
US2832734A (en) * | 1952-02-14 | 1958-04-29 | Leeds & Northrup Co | Coulometric systems |
US2954336A (en) * | 1957-07-30 | 1960-09-27 | Standard Oil Co | Universal titrating agent generator |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4036704A (en) * | 1972-12-11 | 1977-07-19 | Hitachi, Ltd. | Liquid chromatographical method |
US3964869A (en) * | 1973-03-01 | 1976-06-22 | N.K. Verwaltungs Ag | Analytical apparatus for serial determination of nitrogen in samples by the Kjeldahl method |
US3929587A (en) * | 1974-09-23 | 1975-12-30 | Delta F Corp | Apparatus and method for maintaining a stable electrolyte in oxygen analysis |
US4081345A (en) * | 1975-08-04 | 1978-03-28 | Max-Planck-Gesellschaft Zur Foerderung Der Wissenschaften E.V. | Apparatus for determining small amounts of nitrogen |
US4348359A (en) * | 1980-07-16 | 1982-09-07 | Mitsubishi Chemical Industries, Limited | Device for determining various types of trace nitrogen |
US4409080A (en) * | 1981-06-18 | 1983-10-11 | Texaco Inc. | System for monitoring a cathodically protected structure |
US4929314A (en) * | 1989-07-07 | 1990-05-29 | The Dow Chemical Company | Coulometric titrator apparatus and method |
WO1995000842A1 (en) * | 1993-06-22 | 1995-01-05 | The University Of Newcastle | Electrochemical sensor |
Also Published As
Publication number | Publication date |
---|---|
GB1149832A (en) | 1969-04-23 |
FR1516307A (en) | 1968-03-08 |
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