The term naphthenic acid, as commonly used in the petroleum industry, refers

collectively to all of the carboxylic acids present in crude oil. Commercial naphthenic

acids contain varying amounts of sulfur compounds and water. Due to the presence of

a wide range of molecules and carboxylic fragments in the QMS data, it is impossible

to determine the exact ions collected for some of the molecular weights that could

correspond to different compounds or compounds of different chemical structure that

share the same chemical formula and hence the same molecular mass.

Most of the detected species are matched with chemical compounds that are

expected to be present in naphthenic acids. However, fragments from broken bonds

upon heating the naphthenic acids are also expected to be seen in the QMS data. The

suggested fragments are summarized in the table below and the postulated sulfur-

containing molecules are highlighted in red.

Fragment ion mass (amu) Fragment Name

2 H2 Hydrogen

3 H3 Triatomic hydrogen

12 C Carbon

13 CH  

14 CH2 Methylene

15 CH3 Methyl group

16CH4 Methane

O Oxygen

17 OH Hydroxide

18 H2O Water

19 H3O Hydronium

20 CH2H6  

21 CH3H6  

26 C2H2 Acetylene

27 C2H3 Vinyl

28CO Carbon monoxide

C2H4 Ethylene

29 C2H5 Ethyl functional group

30C2H6 Ethane

CH2OEstradiol benzoate /

Formaldehyde

31 CH3O Methoxy

32

O2 Oxygen

CH4O Methanol

C2H8  

36 H4O2  

37 CH9O  

38 CH10O  

39 C2H15  

40 C2H16  

41C2OH  

C3H5 c-propyl

42 C3H6 Propene / Cyclopropane

43 C3H7 Propyl

44

CO2 Carbon Dioxide

C3H8 Propane

C2H4O Acetaldehyde / Ethenol

45 CO2H  

46

CH2S Thioformaldehyde

C2H6O Ethanol

CH3OCH3 Dimethyl ether

C3H10 Isobutane

CH2O2 Formic acid

50CH6O2  

C2H10O  

51 CH7O2  

52 CH8O2  

53 CH9O2  

54 C2H14O  

55 C2H15O  

56 C2O2 Ethylene dione

57C2HO2  

C4H9 Butyl

58

C2H2O2 Acetolactone / Glyoxal

C2H2S Thiirene

C3H5OH Glycerol

C4H10 Butane

C3H6O Acetone

64

S2 Diatomic sulfur

SO2 sulfur dioxide

CH4O3 Orthoformic acid

65 HSO2  

66H2SO2 Hyposulfurous acid

C2H10O2  

67H3SO2  

C5H7 Pentadienyl

68 C4H4O Furan

69 C4H5O  

70C5H10 Cyclopentane

C4H6O Crotonaldehyde / Dihydrofuran

71 C4H7O  

72

C3H4O2 Acrylic acid

C4H8O Tetrahydrofuran / Butanone

C2OS  

C5H12 Isopentane / Neopentane

77C6H5 Phenyl ring

CHSO2  

78

CH2S2 Dithioformic acid

C2H6SO Dimethylsulfoxide

C6H6 Benzene

79 CH7SO  

80SO3 Sulfur trioxide

C6H8 1,3-Cyclohexadiene

81HSO3 Bisulfite

C6H9  

82 H2SO3 Sulfurous acid

83 C4H3O2  

84

C4H4S Thiophene

C4H4O2Cycloprop-2-ene carboxylic acid

/ Diketene

C6H12Cyclohexane /

Methylcyclopentane

85 C4H5O2  

86

C4H6O2 Mthacrylic acid / Vinyl acetate

C6H14 Hexane

C5H10O Cyclopentanol / Isoprenol

91C2H3S2  

C6H5CH2 Benzyl

92 C2H4S2 Dithietane

93 C2H5S2  

96

S3 Sulfur clusters

CH4O3S Methanesulfonic acid

C5H4O2 Furfural / Pyrones

97 C5H5O2 Furan-2-carboxylic acid