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46 OCTOBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 10 CHEMICAL TREATMENT the samples. In the presence of standards for the listed compounds 1 to 10, these were searched based on their retention times and their mass spectra at exact mass (±50 ppm accuracy). As none of these refer- ence compounds were detected in the naphtha sample, 12 additional organochlo- ride compounds (Items 11 to 22 in Table 1) commonly used for refining operations were also investigated by extracting the total ion chromatogram on exact masses of fragments. As illustrated in Figure 3, the presence of TCE in the studied sample could be confirmed by the mass spectra, the exact masses, and the isotope ratios. Similarly, PCE could be evidenced in the studied naphtha sample. The presence of TCE and PCE was further confirmed by comparing the mass spectra in a high-reso- lution mode (Figure 3) with NIST mass spectral librar y and molecular formula generation. The concentration of TCE and PCE in the naphtha sample was determined by TABLE 1. REFERENCE ORGANIC CHLORINATED COMPOUNDS Sample tR (min) Reference Compound Formula MW Exact Mass Fragment 1 10.156 2-chloro-2-methylpropane C 4 H 9 Cl 92 77.021 C 3 H 6 Cl 2 16.836 1-chloro-2-methylbutane C 5 H 11 Cl 106 63.008 C 2 H 4 Cl 3 18.070 2-chloro-pentane C 5 H 11 Cl 106 63.008 C 2 H 4 Cl 4 19.899 1-chloropentane C 5 H 11 Cl 106 63.008 C 2 H 4 Cl 5 26.938 chlorobenzene C 6 H 5 Cl 112 112.005 C 6 H 5 Cl 6 27.894 1-chlorohexane C 6 H 13 Cl 120 91.029 C 4 H 8 Cl 7 36.537 1-chloroheptane C 7 H 15 Cl 134 91.029 C 4 H 8 Cl 8 40.258 Benzyl chloride C 7 H 7 Cl 126 126.018 C 7 H 7 Cl 9 45.052 1-chlorooctane C 8 H 17 Cl 148 91.029 C 4 H 8 Cl 10 53.152 1-chlorononane C 9 H 19 Cl 162 91.029 C 4 H 8 Cl 11 N/A Vinyl chloride C 2 H 3 Cl 62.498 61.9923 C 2 H 3 Cl 12 N/A trichlorotrifluoroethane (Freon 113) C 2 Cl 3 F 3 187.376 150.9329 C 2 Cl 2 F 3 13 N/A chlorobutadiene (chloroprene) C 4 H 5 Cl 88.536 88.0079 C 4 H 5 Cl 14 N/A dichloromethane CH 2 Cl 2 84.933 83.9533 CH 2 Cl 2 15 N/A 1,2-dichloropropane (propylene dichloride) C 3 H 6 Cl 2 112.986 109.9690 C 3 H 4 Cl 2 16 N/A tetrachloromethane CCl 4 153.823 116.9066 CCl 3 17 N/A 1,2-dichloropropane C 3 H 6 Cl 2 112.986 63.0001 C 2 H 4 Cl 18 N/A TCE C 2 HCl 3 131.388 129.9139 C 2 HCl 3 19 N/A chloroform CHCl 3 119.378 82.9455 CHCl 2 20 N/A PCE C 2 Cl 4 165.833 165.8719 C 2 Cl 4 21 N/A 1,1,1,2-tetrachloroethane C 2 H 2 Cl 4 167.849 130.9222 C 2 H 2 Cl 3 22 N/A 1,1,2,2-tetrachloroethane C 2 H 2 Cl 4 167.849 167.8876 C 2 H 4 Cl 4 e x t e r n a l c a l i b r a t i o n u s i n g b o t h t h e GC-µECD and GC-HR-TOF-MS data. The results are presented in Table 2. The total contribution to organochloride content is thus ~9.0 ppm for TCE and P CE com- pounds. These results also indicate that the chloride present in the sample was mainly organic. Conclusions The root cause of the corrosion inci- dent that occurred at the NHT unit was attributed to the high organic chloride in the naphtha feed. Two high-chloride excur- sion events were recorded in the naphtha feeds after the corrosion incident. A naph- tha feed sample was taken during the last high-chloride excursion event as the refer- ence sample. The UOP991 result of the ref- erence sample showed that the total chlo- ride was 9.6 ppm. Successful identification of the potential sources of organochlorides confirmed that two organochloride com- pounds were detected in the analyzed sample; namely, tetrachloroethylene and TCE. Acknowledgment The authors would like to thank Dr. David Frank from the Research Institute for Chromatography on the work conducted using high-resolution mass spectrometry (GC-HR-TOF-MS) on the collected naphtha sample. References 1 NACE International Task Group 274, "Effect of Nonextractable Chlorides on Refiner y Corrosion and Fouling," Technical Commit- tee Report (2005), NACE International Publi- cation 34105. 2 J. Gutzeit, "Effect of Organic Chloride Con- tamination of Crude Oil on Refinery Corro- sion ," C O RRO SIO N 2000, pap er no. 694 (Houston, TX: NACE, 2000). 3 K. Brooks, "Organic Chloride Contamination Rears Its Ugly Head Again," Oil & Gas J. 60, 48 (1962): pp. 74-75.