1、Designation: E3146 18Standard Test Method forDetermination of Carbonyls in Pyrolysis Bio-Oils byPotentiometric Titration1This standard is issued under the fixed designation E3146; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the carbo-nyl content of bio-oils derived from thermochemical de
3、com-position of lignocellulosic biomass and their deoxygenatedproducts. This method is used for determination of carbonylsbetween 0.5 and 8 mol/kg.1.2 Review the current and appropriate Safety Data Sheets(SDS) for detailed information concerning toxicity, first aidprocedures, and safety precautions
4、and proper personal protec-tive equipment.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
5、he user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization establish
6、ed in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:D664 Test Method for Acid Number of Petroleum Productsby Potentiomet
7、ric TitrationD1193 Specification for Reagent WaterD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3. Terminology3.1 Definitions:3.1.1 Bio-Oil, nThe crude liquid product of convertingsolid biomass into a liqu
8、id via fast pyrolysis or other thermo-chemical conversion process.3.1.2 Carbonyl, nThe chemical functional group consist-ing of a carbon-oxygen double bond, C=O. For this method,this includes all aldehydes and ketones; carboxylic acids,esters, and lactone groups are not measured by this method.3.1.3
9、 fast pyrolysis, nPyrolysis conducted with rapid heat-ing and short reaction time; within approximately 2 seconds.3.1.4 pyrolysis, nChemical decomposition of organic ma-terials by heating in the absence of oxygen.4. Summary of Test Method4.1 A bio-oil sample is dissolved in dimethylsulfoxide(DMSO) a
10、nd solutions are added containing hydroxylaminehydrochloride (NH2OHHCl) and triethanolamine (TEA). Themixture is sealed, stirred, and heated to 80 C for 2 hours.Carbonyl compounds (aldehydes and ketones) react withNH2OHHCl forming the corresponding oxime and liberatingHCl. Liberated HCl is consumed
11、by TEA, which drives thereaction forward. After the reaction, unconsumed TEA istitrated with a standardized HCl titrant to determine the molarconcentration of carbonyls in the sample.5. Significance and Use5.1 While pyrolysis bio-oils are comprised of a large varietyof compounds and chemical functio
12、nal groups, quantificationof carbonyl groups is especially important. Carbonyls areknown to be responsible for the instability of bio-oil duringboth storage and processing. This method can be used toquantify the total carbonyl content of bio-oils.6. Interferences6.1 The selectivity of the method was
13、 tested by using1-butanol, 1-pentanol, tertiary-butanol, 2-propanol, ethylacetate, acetic acid, xylose and glucose as model compounds,representing alcohol, ester, carboxylic acid and carbohydratesin the bio-oil. No interferences were seen for ethyl acetate oracetic acid. Monosaccharides are measured
14、 using this method.Addition of alcohols causes interferences, but it is dependenton chain length. The reason is as yet undetermined but may berelated to solvent properties of the alcohol rather than reaction1This test method is under the jurisdiction of ASTM Committee E48 onBioenergy and Industrial
15、Chemicals from Biomass and is the direct responsibility ofSubcommittee E48.05 on Biomass Conversion.Current edition approved Jan. 1, 2018. Published January 2018. DOI: 10.1520/E314618.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThi
16、s international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (T
17、BT) Committee.1with NH2OHHCl or TEA. Tests with primary, secondary andtertiary butanol have shown the same effect.7. Apparatus7.1 Analytical balance, accurate to 0.0001 g.7.2 Micro Reaction Vial, borosilicate glass, cone shapedinside with at least 5 mL capacity and PTFE lined caps. SeeFig. 1.7.3 Tri
18、angular Magnetic Stirring Bar, PTFE lined andsuitable size for use with micro reaction vessels.7.4 Dry Block Heater with Magnetic Stirrer, capable ofmaintaining a temperature of 80 C, for use with micro reactionvials. See Fig. 2.7.4.1 A hot water bath with flat circular magnetic stirrer isalso accep
19、table.7.5 Potentiometric TitratorAutomatic titration systemscapable of adding fixed increments of titrant at fixed timeintervals (monotonic) or variable titrant increments with elec-trode stability between increment additions (dynamic) withendpoint seeking capabilities as prescribed in the method. A
20、tthe very least, the automatic titration system shall meet theperformance and specification requirements as warranted bythe manufacturer.7.5.1 Amonotonic or dynamic mode of titrant addition shallbe used. During the titration, the speed and volume of theaddition may vary depending on the rate of chan
21、ge of thesystem. The recommended minimum volume increment is0.05 mL, and the recommended maximum volume incrementis 0.1 mL. A signal drift of 10 mV/min and endpoint recogni-tion set to last is recommended to ensure endpoint detection.When using a monotonic titrant addition, the waiting timebetween i
22、ncrement additions shall be sufficient to allow formixing and a stable electrode response. Wait at least 10 sbetween additions.7.6 Buret, capable of delivering titrant in 0.02 mL or largerincrements. The buret tip shall deliver titrant directly into thetitration vessel (immersed about 25 mm in liqui
23、d) withoutexposure to the surrounding air.7.7 Titration Stand, suitable for supporting the electrode,stirrer and buret.7.8 Sensing Electrode, standard pH, suitable for non-aqueous titrations.7.9 Reference ElectrodeSilver/Silver Chloride (Ag/AgCl)Reference Electrode, filled with 1M-3M LiCl in ethanol
24、.7.10 Combination pH ElectrodesSensing electrodes mayhave the Ag/AgCl reference electrode built into the sameelectrode body, which offers the convenience of working withand maintaining only one electrode. A combination pH elec-trode designed for non-aqueous titrations of organic solvents isneeded fo
25、r titration of ethanol and ethanol blends. The combi-nation pH electrode shall have a sleeve junction on thereference compartment and shall use an inert ethanolelectrolyte, 1 to 3 mol/L (M) LiCl in ethanol. Combination pHelectrodes shall have the same or better response than a dualelectrode system.
26、They shall have a movable sleeve for easyrinsing and addition of electrolyte.7.11 Titration Beaker, borosilicate glass or plastic beaker ofsuitable size for the titration.7.12 Variable-Speed Mechanical Stirrer, a suitable type,equipped with either magnetic stirrer and stirring bars orpropeller-type
27、stirring paddle. The rate of stirring shall besufficient to produce vigorous agitation without spattering andwithout stirring air into the solution.7.12.1 If an electrical stirring apparatus is used, it shall beelectrically correct and grounded so that connecting or discon-necting the power to the m
28、otor will not produce a permanentchange in the instrument reading during the course of thetitration.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the
29、 commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.2Other grades may beused provided it is first ascertained that the reagent is of2Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For sugg
30、estions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia andNational Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.FIG. 1 Micro Reaction Vial w
31、ith PTFE Lined Cap and TriangularMagnetic Stirring BarFIG. 2 Dry Block HeaterE3146 182sufficiently high purity to permit its use without lessening theaccuracy of the determination.8.1.1 Commercially available solutions may be used inplace of laboratory preparations provided the solutions havebeen ce
32、rtified as being equivalent.8.1.2 Alternate volumes of the solutions may be prepared,provided the final solution concentration is equivalent.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water that meetsthe requirements of either Type I, II, or
33、III of SpecificationD1193.8.3 Ethanol, reagent grade (WarningFlammable andtoxic).NOTE 1Do not use ethanol containing 2-butanone or other ketonedenaturant as this will interfere with this method.8.4 Lithium Chloride, LiCl.8.5 Lithium Chloride ElectrolytePrepare a 1M3M solu-tion of lithium chloride (L
34、iCl) in ethanol.8.6 Commercial Aqueous pH 4 and pH 7 Buffer SolutionsThese solutions shall be replaced at regular intervals consistentwith their stability or when contamination is suspected. Infor-mation relating to their stability is provided by the manufac-turer.8.7 Hydroxylamine hydrochloride (NH
35、2OHHCl), 99%purity.8.8 Hydroxylamine hydrochloride solution (Solution A)Add 7.7 g of hydroxylamine hydrochloride and 50 mL of waterto a 250 mL volumetric flask. Swirl until all solids aredissolved, then dilute up to the mark with ethanol.8.9 Sodium Carbonate (primary standard, Na2CO3), 99%purity.8.1
36、0 Triethanolamine (TEA), 99% purity.8.11 Triethanolamine solution (Solution B)Add 17.4 mLof triethanolamine to a 250 mL volumetric flask, then dilute upto the mark with ethanol.8.12 Hydrochloric acid (HCl), concentrated (WarningToxic and corrosive).8.13 Hydrochloric acid solutionPrepare 0.1N solutio
37、n byadding 10 ml concentrated HCl and 1 L water.8.14 4-(Benzyloxy)benzaldehyde (4-BBA), 99% purity.9. Sampling, Test Specimens, and Test Units9.1 Make sure the oil sample is at room temperature prior towithdrawing an aliquot for analysis. Bio-oil should be thor-oughly homogenized to obtain a represe
38、ntative sample. Mix byshaking vigorously for at least 1 minute, and visually inspectthe sample to ensure it is homogenous. Some bio-oils mayrequire longer shaking times.9.2 Exposure to oxygen and heat should be minimized toprevent sample degradation prior to analysis.10. Preparation of Apparatus10.1
39、 Prepare the titrator in accordance with the manufactur-ers instructions. Any visible air bubbles in the buret tip shallbe eliminated prior to titration since this can lead to errors.10.2 Preparation of ElectrodesWhen the combination pHelectrode contains Ag/AgCl reference with an electrolyte,which i
40、s not 1 to 3 mol/L (M) LiCl in ethanol, the electrolyteshall be replaced. Drain the electrolyte from the electrode(vacuum suction), wash away all the salt (if present) with waterand then rinse with ethanol. Rinse several times with LiClelectrolyte solution. Finally, replace the sleeve and fill theel
41、ectrode with the LiCl electrolyte to the filling hole. Whenrefitting the sleeve, ensure that there will be a free flow ofelectrolyte into the system.10.3 Maintenance and Storage of Electrodes:10.3.1 Follow the manufacturers instructions for storageand use of the electrode.10.3.2 Prior to each titrat
42、ion, soak the prepared electrode inwater for at least 2 min. Rinse the electrode with waterimmediately prior to use. The glass membrane needs to berehydrated after titration of non-aqueous solutions.10.3.3 When not in use, immerse the lower half of thecombination electrode in LiCl electrolyte. Do no
43、t allow elec-trodes to remain immersed in a titrated sample solution for anylonger than it is necessary. While the electrodes are notextremely fragile, handle them carefully at all times.11. Calibration and Standardization11.1 Calibration of Electrode:11.1.1 Verify that the electrode is filled with
44、1 to 3 mol/L(M) LiCl in ethanol solution (see 10.2).11.1.2 Prepare the two buffer solutions, pH 7.0 and pH 4.0by placing approximately 50 mL of each solution in individualbeakers.11.1.3 Calibrate the electrode using the two buffer solutionsaccording to the manufacturers instructions. Immerse theelec
45、trode in each buffer solution, adjust the stirring speed sothat adequate mixing occurs without forming a vortex and waitfor the instrument reading. When the reading is complete, rinsethe electrode in high purity water, wipe gently and repeat themeasurements with the other buffer solution. Record the
46、 pHvalue with an accuracy of 0.01 and the temperature with anaccuracy of 0.1 C. The measured pH values should be within60.05 pH units of the buffers certified value.11.1.3.1 Verify that the calibration slope is between 0.95and 1.02. An ideal pH glass electrode has a slope of 1.00(100 % of the Nernst
47、 slope) and an electrode zero point of0 mV for pH 7 at 25 C. In practice, the electrode zero pointpotential shall be within 615 mV (corresponding to pH 6.75 to7.25) and the slope shall be 0.95 (56.2 mV per pH at 25 C).The electrode zero point and the electrode slope may change asa result of the agin
48、g of the glass membrane or contamination ofthe diaphragm. If the electrode slope falls below 0.95, followthe electrode manufacturers instructions for electrode mainte-nance or replace the electrode. The pH electrode shall becalibrated at regular intervals using fresh buffer solutions.11.1.3.2 The sl
49、ope is automatically stored in the titrator.11.1.3.3 The slope is not used for sample analysis, butrather, it provides information on the responsiveness of theelectrode. An electrode not meeting the stated criteria is notsuitable to perform this method.11.2 Standardization of HCl titrant:E3146 18311.2.1 Weigh 0.10 to 0.15 g of sodium carbonate intotitration beaker and record weight.11.2.2 Add magnetic stir bar and 25 mL of water.11.2.3 Titrate with HCl titrant using automatic titrator andrecord endpoint.11.2.4 Prepare two additional sodium car
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