UCRLJC-119269 PREPRINT
Compounds Produced by Motor Burnouts of Refrigeration Systems
Carolyn Koester Ruth Hawley-Fedder
Linda Foiles
This paper was prepared fox submittal to the 43rd ASMS Conference on Mass Spectrometry &
Allied Topics, Atlanta, Georgia May 21-26,1995
DISCLAIMER
This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.
DISCLAIMER
Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
Compounds Produced by Motor Burnouts of Refrigeration Systems
Carolyn J. Koester*, Ruth A. Hawley-Fedder, and Linda Foiles Lawrence Livermore National Laboratory, Livermore, CA 94568
Introduction: The phase-out of chlorofluorocarbons has necessitated the introduction of alternate refrigerants. R22 (CF2CIH), R134a (CF3C H 2F), and R507 (50/50 CHF~CFS/CF~CH~) are newer fluids which are used in cooling systems. Recently, concern over the possible formation of toxic compounds during electrical arcing through these fluids has prompted us to identify their electrical breakdown products by electron ionization GC/MS. For example, it is known that perfluoroisobutylene (PFIB), which has an threshold limit value of 10 ppb (set by the American Conference of Government Industrial Hygienists), is produced from the thermal and electrical breakdown of some refrigerants. We have used specially designed test cells, equipped with electrodes, to simulate the electrical breakdown of R22, R134a, and R507 in refrigeration systems.
Experimental: R22, R134a, or R507 were introduced into a test cell as gases. The test cell used for experiments at 15 PSI was made of epoxy, had a 93 mL volume, and had brass electrodes having a surface area of 0.8 in2. The cell used for experiments at high pressure and temperature was made of vespel, had a volume of 77 mL, and had brass electrodes with a surface area of 0.3 in2. The test cell had been previously filled with 1% by weight of the appropriate oil--Calgon C4 was used with R22 and EM Karate RL-327 was used with R134a and R507. Oil was added to the cells to simulate conditions expected in motors--oils are used to lubricate pistons in compressors and it is known that some contamination of the refrigerant by this oil will occur. The cell was then evacuated to 20 mtorr before being filled with the selected refrigerant. The refrigerant, as a gas, was subjected to up to 200,000 electrical pulses (30 psec, 20 kV pulsed-breakdown at 100 Hz) and the resulting gas mixture was sampled and analyzed by GC/MS with a Hewlett-Packard 5989. The GC column (Restek RTX-1, 105 m, 250 pm i.d., 1 pm film thickness) was temperature programmed as follows: -30°C for 13 min, ramped at 5"C/min to 150"C, held for 10 min, ramped at 10°C to 300"C, and held for 10 min. The MS was operated in the electron ionization mode and scanned from 30u to 650u in 1.1 sec.
Results: The formation of many new compounds was observed; Table 1 shows the major compounds produced when R22 was subjected to electrical breakdown at 15 PSI and 20°C. Compounds were tentatively identified by using mass spectral data bases. Many of the compounds that were produced at 15 PSI and 20°C were also produced at 200°C and at higher pressures; however, the distribution of products changed slightly. The total amount of breakdown products increased with increasing arc exposure for experiments performed at 15 PSI and for experiments performed at higher pressures.
Conclusions: Many different compounds are formed at parts-per-thousand concentrations as electrical arcs are passed through refrigerants. PFIB was not present in sufficient quantities to be detected by GC/MS; thus, we plan to use the more sensitive GC/ECD to
look for its presence. The variety of compounds produced suggest that interesting chemistry is occurring, including the formation and recombination of radicals to produce species which are larger than their parents. The electrical burnout of actual refrigeration motors will be performed to determine how well our test cells simulate processes that can occur in refrigeration systems.
Table 1. Major compounds present after 100,000 arcs passed through R22 at 15 PSI and 20°C. Each number represents the average of duplicate measurements.
Tentative Identification "gig R22
te traf luoroe thene 300
dichlorotetrafluoroethane 50 hexafluoropropene 40
dichlorodifluoroethene 10
dichlorodifluoromethane (R12) 200
dichlorohexaf luoropropane 10
trichloropentafluoropropane 9
chlorotrifluoropropyne 8 chloropentafluoropropene 8
dichlorodif luoroethene 8 trichloropropene 8 dichlorodifluoroethene 7 Jchlorine & fluorine containing hydrocarbon 1 trichlorofluoromethane 61 dichloroethyne 6 trichlorofluoroethylene 6 chlorodifluoromethane 5 dichloro tetrafluorocyclobutene 5
Acknowledgments: We thank Dave Goerz, Gary Mease, Ken Leighton, and John Sze for support in the construction and operation of the test cells. We also thank the Air Conditioning and Refrigeration Technology Institute for funding.
Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract W-7405-ENG-48.
