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Determination of Low Content Naphthalene in Coke Oven Gas by Gas Chromatography

Abstract: In this paper, the split-free analysis method was used to determine naphthalene in gas. The gas sample was directly taken with a syringe, and anhydrous ethanol was used as an absorbent. The retention time was qualitative and quantified by external standard method.

1 Introduction The determination of naphthalene content in coal gas in China has long been based on the bitter acid method. Although the accuracy is higher, the lower limit of quantification is high, and the absorption treatment operation is cumbersome and time-consuming (3 to 4 hours); the corresponding national standard gas chromatography also exists. The operation is cumbersome (1 to 2 hours), the lower limit of quantitation is high, and the xylene absorption liquid is toxic and pollutes the environment, so its application and promotion are limited. The cold rolling production line of the company has high requirements on the technical indicators of gas quality. The naphthalene in the purified gas can reach below 10mg/m3, and the requirements for the inspection cycle are further improved. Therefore, it is urgent to improve the sensitivity and accuracy of the analytical method and shorten the analysis cycle. .

2 Experimental part 2. 1 Instrument and reagent chromatograph: Shandong Jinpu GC-2010 capillary column: 30m × 0.25mm × 0. 5μmSE-54 detector: FID data processing: N2000 workstation sampler: 10μl micro syringe sampler: 100ml glass syringe, No. 9 injection needle absorption bottle: 5ml naphthalene: chromatographically pure anhydrous ethanol: analytical purity 2. 2 analysis principle The so-called splitless analysis method is to set the initial temperature of the column to a lower temperature (50-60 ° C), Close the split port before injecting the sample. After the sample is vaporized, after the sample is mostly guided into the column (1~2min), open the split port, raise the column temperature, and wash the ingredients at the front end of the column at low temperature. The method of de-separation, separation and detection is generally applicable to the analysis of low-concentration samples with higher boiling points. However, this method tends to thermally decompose the compound and is therefore not suitable for the analysis of readily decomposable compounds.

2.3 Chromatographic conditions Column temperature: 60 ° C (2 min) 200 ° C (5 min)

Vaporization temperature: 2OO °C Detector: 200 ° C column population pressure: 140 kPa air pressure: 50 kPa hydrogen pressure: 60 kPa split flow: 40.8 ml / min septum purge: 12.2 ml / min tail blow: 32 ml / min sampling time: 1.5 min Sampler: 1 μl 2. 4 qualitative method Under the selected conditions, sequentially inject 10 μl of ethanol and 5% naphthyl ethanol solution with a syringe of l0, the retention time was 2.98 min, 7.04 min, respectively, and determined at these two retention times. The peaks in this order correspond to ethanol and naphthalene.

2. 5 standard curve drawing Using a micro-syringe to extract standard samples (2, 5, 10, 20, 50mg / m ') lμl injection column, measuring the peak area of ??naphthalene, each standard analysis of two measurements of naphthalene peak The area is averaged and the standard curve is drawn according to the external standard method. The result is shown in Fig. 1. The regression coefficient is r=0.999562, and the linear relationship is good.

5 Conclusion a. The method has good reproducibility for determining the content of naphthalene in coke oven gas, and the accuracy and precision of the results are high.

b. The experimental method is simple and convenient, and the analysis period is shortened from 3 to 4 hours of the national standard to 20 to 30 minutes, which can meet the needs of cold rolling monitoring and analysis.

c. The method has low quantitative limit and high sensitivity, and can accurately determine 2rag/m in gas. Naphthalene can meet the requirements of cold rolling gas technical specifications.

(Source: China Chemical Instrument Network)

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