Dimethyl ether standard HG/T3934-2007

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Dimethyl ether standard HG/T3934-2007: Date: 2009-7-11 11:43:28; Clicks: 94. Key point: The standard for dimethyl ether (Chemical Industry Standard of the People’s Republic of China, HG/T3934-2007)… Chemical Industry Standard of the People’s Republic of China HG/T3934-2007 – Dimethyl ether; Published on 2007-04-13, implemented on 2007-10-01; Issued by the **Development and Reform Commission of the People’s Republic of China. Preface: Appendix A of this standard is of informational nature. This standard was proposed by the China Petroleum and Chemical Industry Association. This standard is under the jurisdiction of the Organic Subcommittee of the National Chemical Standardization Technical Committee (SAC/TC63/SC2). The organizations responsible for drafting this standard are Shandong Jiutai Chemical Technology Co., Ltd., SNOW GROUP CO., LTD., and Sichuan Lutianhua Lvyuan Alcohol Industry Co., Ltd. Companies involved in the drafting of this standard: Zhongshan Kaida Fine Chemicals Co., Ltd. and Henan Anyang Zhenyuan Group Co., Ltd. Main drafters of this standard: Li Qi, Wang Tianshou, Zhang Xiaolong, Du Jing, Li Quanfa, Wang Tiehong, Zhou Qiuxiang, Li Jinlai. HG/T 3934-2007 Dimethyl ether 1 Scope This standard specifies the requirements, test methods, inspection rules, as well as marking, packaging, transportation, storage, and safety aspects for dimethyl ether. This standard applies to the production, testing, and sales of dimethyl ether produced by dehydration via the gas-phase or liquid-phase method using methanol, or dimethyl ether synthesized directly from syngas, as well as dimethyl ether recovered from other production processes. Type I of this product is primarily used as an industrial raw material for propellants in aerosols, foaming agents, refrigerants, and chemical intermediates, while Type II is mainly used as a raw material for domestic fuels, vehicle fuels, and industrial fuels. Structural formula: CH3OCH3 Relative molecular mass: 46.07 (based on the international relative atomic masses of 2005) 2 Normative references The provisions in the following documents become part of this standard through reference to the General Principles for Sampling Chemical Products. For any referenced documents dated, all subsequent amendment sheets (excluding corrections) or revised versions shall not be applicable to this standard; however, parties who reach an agreement based on this standard are encouraged to consider whether the latest versions of such documents can be used. For reference documents without a date, the latest version applies to this standard. GB 190－1990 Marking for packaging of dangerous goods; GB/T 1250 Methods for expressing and determining limit values; GB 5842－1986 Liquefied petroleum gas cylinders; GB/T 6678－2003; GB/T 6680－2003 General rules for sampling liquid chemical products; GB/T 6682－1992 Specifications and test methods for water used in analytical laboratories (eqv ISO 3696:1987); GB/T 7373－1987 Industrial dichlorodifluoromethane (F22); GB/T 9722－2006; GB 14193－1993; GB/T 7376－1987 Determination of trace moisture in industrial fluoromethanes – Karl Fischer method; General rules for gas chromatography of chemical reagents; Regulations for filling liquefied gas cylinders; GB 15380－2001 Small-volume liquefied petroleum gas cylinders; SH/T 0232－1992 Copper sheet corrosion test for liquefied petroleum gas; SH 0233－1992 Sampling method for liquefied petroleum gas. 3 Properties: A colorless gas or compressed liquefied gas with a volatile ether-like odor. The liquid density ranges from 0.660 g/cm3 to 0.680 g/cm3. 4 It is required that the quality of dimethyl ether as specified in HG/T 3934-2007 shall meet the technical requirements shown in Table 1. Table 1 Technical Requirements Item Type I Type II Mass fraction of dimethyl ether /% ≥ 99.9 99.0 Mass fraction of methanol /% ≤ 0.05 0.5 Mass fraction of water /% ≤ 0.03 0.3 Copper sheet corrosion test ≤ — Grade 1 Acidity (as H2SO4) /% ≤ 0.0003 — Note: Acidity is tested for Type I products when used as refrigerants. 5 Test Methods 5.1 Warnings Some of the test procedures specified in the test methods may lead to dangerous situations. Operators should take appropriate safety and health measures. 5.2 General provisions Unless otherwise specified, only reagents confirmed to be of analytical grade and grade 3 water as specified in GB/T 6682 shall be used in the analysis. 5.3 Determination of dimethyl ether content 5.3.1 Method summary: Using gas chromatography, under selected chromatographic operating conditions, the sample is vaporized and passed through a chromatographic column, allowing the various components to be separated; detection is carried out using a thermal conductivity detector ； Alternatively, components such as carbon monoxide and carbon dioxide in the sample are converted into hydrocarbons through a methane converter, and detected using a flame ionization detector. The content of dimethyl ether is calculated using the area normalization method. 5.3.2 Reagents 5.3.2.1 Hydrogen, volume fraction ≥99.8 %. 5.3.2.2 Nitrogen, volume fraction ≥99.8 %. 5.3.2.3 Air, purified by activated carbon and molecular sieves. 5.3.2.4 Instruments 5.3.3.1 Standard samples for calibration: available commercially; the background sample is dimethyl ether, containing corresponding impurity components (carbon monoxide, carbon dioxide, methane, ethylene, ethane, acetylene, propylene, propane, methanol, etc.), with the concentrations of these components being similar to those in actual samples. 5.3.3 Gas chromatograph: One equipped with a thermal conductivity detector (TCD) for operation with capillary columns, or one equipped with a flame ionization detector (FID) and a methanation converter (for converting carbon monoxide and carbon dioxide); the overall sensitivity and stability of such gas chromatographs shall meet the requirements specified in GB/T 9722–2006. 5.3.3.2 Recorder: Chromatography workstation or chromatography data processor. 5.3.3.3 Injector: 1 mL glass syringe (such as a BCG injection syringe with good sealing properties), or an automatic six-way valve equipped with a heating device and a 1 mL dosing ring. 5.3.3.4 Sampler: Made of stainless steel, it is a dual-valve type liquefied petroleum gas sampler that complies with SH 0233－1992 standards; its operating pressure, as specified in HG/T 3934-2007, is greater than 3.1 MPa. 5.3.3.5 Constant temperature water bath. 5.3.4 Chromatographic analysis conditions The recommended chromatography column and operating conditions are shown in Table 2. Typical chromatograms and retention times are provided in Appendix A. Other chromatography columns and operating conditions that can achieve the same level of separation can also be used. Table 2 Recommended Chromatography Columns and Operating Conditions
Item | Capillary Column Method | Packing Column Method
Chromatography Column Fixed Phase | Polystyrene-divinylbenzene (PLOT-Q column) | Copolymer of divinylbenzene and styrene, particle size 0.18 mm–0.25 mm
Column Material | Fused quartz | Stainless steel or glass tube
Column Length/m | 30 | 3
Column Inner Diameter/mm | 0.53 | 0.53
Membrane Thickness/μm | 40.0 | —
Detector | Thermal conductivity detector | Flame ionization detector
Column Oven Temperature: Initial temperature 50°C, held for 2 min; then heated at a rate of 10°C/min to 150°C
Initial temperature 50°C, held for 6 min; then heated at a rate of 10°C/min to 80°C, held for 9 min; then heated at a rate of 10°C/min to 150°C, held for 15 min
Vaporization Chamber Temperature/°C | 250 | 150
Detector Temperature/°C | 250 | 360
Six-way Valve Oven Temperature/°C | 100 | 100
Methanation Converter Temperature/°C | 360
Carrier Gas Flow Rate/(mL/min) | — | 30 (N2)
Average Linear Velocity of Carrier Gas/(cm/s) | 64 (H2 or He) | —
Fuel Gas Flow Rate/(mL/min) | — | 30 (H2)
Auxiliary Gas Flow Rate/(mL/min) | — | 300 (Air)
Split Ratio | 5:1 | —
Injection Volume/mL (Gas) | 0.1 | 1

5.3.5 Analysis Procedure
5.3.5.1 Determination of Calibration Factors
5.3.5.1.1 Adjust the instrument according to the chromatography operating conditions in Table 2. Open the valve of the calibration standard sample cylinder, adjust the flow rate to an appropriate level, and use the calibration standard sample to continuously purge the automatic six-way valve and empty it; then take a sample of the calibration standard sample for analysis ； Alternatively, a standard sample can be drawn using a glass syringe from the standard sample cylinder for calibration and then injected. The measurement is repeated three times, and the average of the peak areas from these three trials is taken as the result. 5.3.5.1.2 Result calculation. Using dimethyl ether, the background sample of the calibration standard sample, as reference R, the relative mass correction factor for impurity component i is calculated according to formula (1): HG/T 3934-2007 = ..................(1) Where: the mass fraction of the impurity component in the calibration standard sample, expressed as a percentage (%); the peak area of the impurity component ； The mass fraction of reference R, expressed as a percentage (%). The peak area of reference R. 5.3.5.2 Determination of the sample 5.3.5.2.1 Sampling. Seal the dry and clean sampler to the sample cylinder using a metal connector; ensure that the sampler’s vent valve is oriented upward. Open the shut-off valve of the sample cylinder, then sequentially open the sampler’s inlet valve and vent valve to allow the sample to fully fill the sampler. After that, close the sampler’s vent valve so that the liquid sample can enter the sampler. When the volume of the sample occupies 80% of the sampler’s capacity, sequentially close the sampler’s inlet valve and the shut-off valve of the sample cylinder, and then remove the sampler. 5.3.5.2.2 Measurement. Start the gas chromatograph, adjust the instrument according to the chromatography operating conditions listed in Table 2, and once it is stable, prepare for sample injection and analysis. Invert the sampler and connect it as shown in Figure 1, controlling the temperature of the constant-temperature water bath between 40 ℃ and 60 ℃. Open valves A and C, and slowly open flow control valve B to allow the liquid sample to flow out while controlling the vaporization rate and replacing the air in the pipeline. The gas discharged from the flushing pipeline is led outside. After complete flushing and replacement, close valve C, immediately rotate the six-way valve to the sampling position, and introduce the collected gas sample into the chromatography column for analysis. Quantification is performed using the area-normalization method. Figure 1: Connection diagram of the vaporization sample system. 5.3.6 Result calculation: The mass fraction ω of dimethyl ether, expressed as a percentage, is calculated using formula (2): ω = Σ ×(100 / ω) (2) Where: A is the area of the multiple peaks corresponding to dimethyl ether ； Relative mass correction factor for component i ； Peak area of component i in Group A (component i does not include water) ； ω 4.6 is the value of moisture measured as a mass fraction. The arithmetic mean of the results of two parallel measurements is taken as the final measurement value, with the absolute difference between the two parallel results not exceeding 0.1 %. 5.3.7 Arbitration 4 HG/T 3934-2007 adopts the capillary column method as the arbitration method. 5.4 Determination of methanol content 5.4.1 Analytical procedure Follow the procedures specified in 4.4. 5.4.2 Calculation of results The mass fraction ω of methanol, expressed as a percentage, is calculated using formula (3): ω = Σ ×100 ...............(3) Where: A is the peak area of methanol ； Relative mass correction factor for methanol ； Peak area of component i in Group A (component i does not include water) ； Relative mass correction factor for component i. The arithmetic mean of the two parallel measurement results is taken as the measurement value, and the absolute difference between the two parallel measurement results shall not exceed 5% of the arithmetic mean of these two values. 5.4.3 Arbitration Capillary column chromatography is used as the arbitration method. 5.5 Determination of moisture 5.5.1 Karl Fischer coulometric method (Method 1) 5.5.1.1 Method overview The moisture in the sample reacts quantitatively with iodine and sulfur dioxide in the electrolyte as follows: H2O + I2 + SO2 → SO3 + 2HI; I2 + 2e-. The number of iodine molecules that participate in the reaction is equal to the number of water molecules. The iodine generated through electrolysis is proportional to the amount of electric charge consumed. According to Faraday’s law, the amount of water can be determined by measuring the amount of electric charge used. 5.5.1.2 Instruments 5.5.1.2.1 Coulometric moisture analyzer: detection sensitivity of 0.1μg H2O. Other microwater detectors that can meet the analysis requirements can also be used. 5.5.1.2.2 Dual-valve liquefied petroleum gas sampler – the requirements are the same as those in 5.3.3.4. 5.5.1.2.3 Borel liquefied petroleum gas sampler, with a pressure resistance of over 1.0 MPa, a volume of 10 mL, and equipped with an attached stainless steel tube that is 150 mm to 300 mm in length and 0.5 mm in inner diameter. 5.5.1.2.4 Stainless steel thin tube of 5 mm. 5.5.1.2.5 5.5.1.2.6 Injector: Liquid hydrocarbon flash vaporization sampling injector (LG-5) ； Alternatively, a sampling tube with a length of 150 mm to 300 mm and an inner diameter of 0.5 mm can be used: a thin stainless steel tube with an inner diameter of 0.5 mm. Electronic balance: maximum weighing capacity of not less than 2,000 g, with a resolution of 0.01 g. 5.5.1.3 Reagents: Electrolyte used in conjunction with the Coulombic moisture analyzer (commercially available reagents). 5.5.1.4 Analysis steps: Add the electrolyte, turn on the instrument, adjust the coulometric moisture analyzer, and prepare for sample analysis. 5.5.1.4.1 Direct injection. Connect the glass liquefied petroleum gas sampler (5.5.1.2.3) to the two-valve liquefied petroleum gas sampler filled with dimethyl ether (5.5.1.2.2) using a sampling tube. Open the valves of each sampler, use the sample to rinse the glass liquefied petroleum gas sampler, and gradually close its valve; once liquid has entered, close the valve completely. After an appropriate amount of sample has entered, close the valve of the two-valve liquefied petroleum gas sampler, remove the sampling tube inserted into the glass liquefied petroleum gas sampler, and weigh it to an accuracy of 0.01 g. Insert the dry stainless steel tube of the sampler at the bottom of the electrolytic cell of the coulometric moisture analyzer; the other end of this tube is connected to the glass LPG sampler. The sampling rate should be such that no dew forms on the outer wall of the sampler, and the amount of sample taken should be adjusted according to the moisture content of the sample. After sampling is complete, weigh the glass LPG sampler again, with an accuracy of 0.01 g. Immediately after sample injection, potentiometric titration is carried out, and the mass of water or the mass fraction of water displayed by the coulometric moisture analyzer is read. 5.5.1.4.2 Flash injection. Connect the dual-valve liquefied petroleum gas sampler filled with dimethyl ether to the liquid hydrocarbon flash vaporization sampling injector; set the sampling volume to 2 L. After thorough displacement, press the “automatic sampling” button. Once the sampling volume reaches 2 L, the instrument will automatically stop sampling for analysis, and the mass of water or the mass fraction of water displayed by the coulombic moisture meter will be read. 5.5.1.5 Calculation of results The mass fraction of water, ω, expressed as a percentage, is calculated using formula (4): ω = ×100 ................（4） Where: The value of the mass of water in the sample, in grams (g) ； The values of the mass of the sampler and the sample before sampling, in grams (g) ； The values of the mass of the sampler and the sample after sampling, in grams (g). The arithmetic mean of the two parallel measurement results is taken as the measurement value, and the absolute difference between the two parallel measurement results shall not exceed 10% of the arithmetic mean of these two values. 5.5.2 Karl Fischer titration method (Method 2): Performed according to the method for ω specified in GB/T 7376. 5.5.3 The flash injection method of the Karl Fischer coulometric titration is used as the reference method for arbitration. 5.6 Copper sheet corrosion test: Conducted in accordance with the method specified in SH/T 0232. 5.7 Determination of acidity 5.7.1 Analytical procedure Follow the provisions in 2.3 of GB/T 7373－1987. 5.7.2 Calculation of the mass fraction ω of the acid (expressed as H2SO4), with values given in %, is carried out using formula (5): ω = ×100 ...............(5) Where: V is the exact value of the volume of the sodium hydroxide standard titrant consumed by the sample, expressed in liters (mL) ； V0 is the exact value of the volume of sodium hydroxide standard titrant consumed in the blank test, expressed in liters (mL) ； The exact value of the concentration of the sodium hydroxide standard titration solution, in units of moles per liter (mol/L) ； The value of the sample’s mass, in grams (g) ； M is the molar mass of sulfuric acid, expressed in grams per mole (g/mol) (M=98.07). 6 Inspection Rules 6.1 This standard adopts type inspection and factory inspection. 6.1.1 All items in Table 1 of the technical requirements of this standard are type inspection items. Under normal circumstances, a type inspection should be carried out at least once every three months. Type testing shall also be carried out in any of the following situations. a) Update key production processes. b) The main raw materials have changed. c) Suspension of production and resumption of production. d) There are significant differences between the factory inspection results and those of the previous type inspection. 6 HG/T 3934-2007 e) As stipulated in the contract. 6.1.2 All items for Type I products listed in Table 1 of the technical requirements of this standard are inspection items at the time of departure from the factory; for Type II products, the dimethyl ether content, water content, and methanol content are inspection items at the time of departure from the factory. Factory inspection is carried out once per batch. 6.2 Dimethyl ether is considered as one batch when it consists of products of uniform quality in equal mass, or when it corresponds to the amount of product in one storage tank or one truck. 6.3 The number of sampling units for dimethyl ether cylinder packaging shall be determined in accordance with the provisions of GB/T 6678－2003. 6.4 The sampling method for dimethyl ether shall be carried out in accordance with the provisions of GB/T 6680–2003 and SH 0233–1992. The total sampling volume should meet the requirements of the testing. 6.5 Dimethyl ether shall have its product quality inspected by the quality control department of the manufacturer in accordance with the provisions of this standard. The manufacturer shall ensure that each batch of products leaving the factory meets the requirements of this standard. Each batch of products leaving the factory shall be accompanied by a quality certificate, which shall include: the product name, product model, name of the manufacturer, address of the manufacturer, production date or batch number, and the standard number. 6.6 The determination of test results is carried out using the rounding value comparison method specified in GB/T 1250. If any one of the test results does not meet the requirements of these standards, products in steel cylinders shall be sampled again from twice as many packaging units for testing, while products stored in tanks or transported in tank cars shall also be sampled again for testing. If even just one parameter from the re-inspection does not meet the requirements of these standards, the entire batch of products is considered unqualified. 7 Packaging, Transportation, and Storage 7.1 The packaging containers for dimethyl ether shall bear firm and clear markings, including: product name, trademark, manufacturer’s name, address, net content, batch number, product grade, standard number, and the “Flammable Liquid” label as specified in GB 190–1990. 7.2 Dimethyl ether in small quantities is transported in cylinders; the quality of these cylinders shall comply with the requirements of GB 5842 and GB 15380, and the filling process shall conform to the provisions of GB 14193. Large quantities of products are transported using liquid tank trucks. 7.3 Dimethyl ether should be stored in liquefied gas storage tanks, which must be placed in a cool and dry location, away from sources of fire and heat. Exposure to direct sunlight is strictly prohibited, and cooling devices should be installed on the tanks during summer. 7.4 Steel cylinders and liquefied gas tank trucks containing dimethyl ether are pressure vessels; open flames, impacts, drops, and exposure to sunlight are strictly prohibited during transportation and handling. Maintain a positive pressure inside the packaging and storage containers to prevent air from entering. 8 Safety 8.1 Dimethyl ether is a flammable substance; when mixed with air, it forms an explosive mixture. It can catch fire and explode in the presence of open flames or high temperatures. Its explosion limit ranges from 3.5% to 26%. 8.2 Dimethyl ether is a chemically substance with low toxicity. At normal temperature and pressure, it is a highly flammable gas that is non-corrosive, with only mild irritation to the respiratory tract. 8.3 When the concentration of dimethyl ether in the environment is high, on-site personnel should take necessary protective measures and wear protective equipment. 8.4 Dimethyl ether has a certain swelling effect on some rubbers. HG/T 3934-2007 Appendix A (Informative Appendix) Typical chromatograms and retention times for the determination of dimethyl ether content. A.1 The typical chromatogram obtained using capillary column gas chromatography is shown in Figure A.1. 1 Air + Carbon monoxide ； 8 Propylene ； 2 Methane ； 9 Propane ； 3 Carbon dioxide ； 10 Dimethyl ether ； 4 Ethylene ； 11 Methanol ； 5 Acetylene ； 12 6 Ethane ； 13 7 Water ； Figure A.1 Typical chromatogram of gas chromatography using a capillary column (PLOT-Q) for the determination of dimethyl ether content. A.2 The retention times for gas chromatography with capillary columns are shown in Table A.1. Retention time of 1-butene by capillary column (PLOT-Q) gas chromatography ； Unknown substance. Table A.1 Component Name, Retention Time/min: 1 Air + Carbon Monoxide: 1.381; 2 Methane: 1.474; 3 Carbon Dioxide: 1.778; 4 Ethylene: 2.247; 5 Acetylene: 2.361; 6 Ethane: 2.635; 7 Water: 5.241; 8 Propylene: 6.078; 9 Propane: 6.449; 10 Dimethyl Ether: 6.668; 11 Methanol: 9.333; 12 1-Butene: 10.968; 13 Unknown substance: 11.357. Figure A.2 shows a typical chromatogram obtained using gas chromatography with a packed column. 1 Carbon monoxide ； 6 Propylene ； 2 Methane ； 7 Dimethyl ether ； 3 Carbon dioxide ； Typical chromatogram for the determination of dimethyl ether content by packed column gas chromatography; retention time by packed column gas chromatography: 8, methanol ； 4 Ethylene ； 9 1-Butene ； 5 Acetylene ； 10 Unknown substances. Figure A.2 A.4 The retention times for packed column gas chromatography are shown in Table A.2. Table A.2 Sequence Number Component Name Retention Time/min 1 Carbon monoxide 1.684 2 Methane 2.080 3 Carbon dioxide 3.641 4 Ethylene 5.317 5 Acetylene 6.195 6 Propylene 14.729 7 Dimethyl ether 16.389 8 Methanol 24.208 9 1-Butene 27.348 10 Unknown substance 29.517