442
Ind. Eng. Chem. Prod. Res. Dev. 1085, 24, 442-447
K. Figure 4 depicts the cryotip and shock mount. The slapper and booster used to initiate detonation are shown in Figure 5. We are proceeding to characterize the reactions and to verify the extent to which true detonation was achieved. E. Detonation-Velocity Measurements. We have measured the detonation velocity of liquid NO in graphite tubes at 115 K as a function of charge diameter (Davis, 1985). The failure diameter was found to be 8 mm, with the corresponding velocity near failure being 5160 m/s. The infinite-diameter velocity was found to be 5622 m/s. We are modifying our apparatus for measurements of detonation pressure and wave shape. Pressure will be determined by measuring the velocity of metal plates driven by the explosive and wave shape by streak-camera records of the deflection of a mirrored surface by the detonation front. F. Chemical Dynamics. We have studied the lowdensity (gas-phase) chemical dynamics of NO decomposition reactions. Our spectroscopic investigations (Blais, 1985) into a molecular chain mechanism for NO detonation proposed by Valentini et al. (1983) have confirmed our earlier notions that we cannot rely solely on experience and intuition gained from low-density gas-phase kinetics studies. Theoretical investigations into possible gas-phase reaction mechanisms have also been made by Stine and Noid (1983). Currently under study are the initiation and mechanism in the detonation of condensed-phase NO (Stine, 1984). We seek to gain insight into the influence of such effects as cage, many-body, and quantum effects on hypothetical mechanisms. A valence bond type of potential energy surface that allows a cluster of (NO), to dissociate into possible neutral subspecies is under development. Conclusions The Fundamental Research on Explosives Program seeks the fundamental knowledge of why and how chemical
changes take place in a detonating high explosive. We have demonstrated that a coordinated effort involving theory and experiment, reaching across scientific disciplines, is useful in attaining this knowledge. The advances achieved as a result of this program present avenues for innovation and further progress in the understanding of the fundamentals of high explosives utilization.
Acknowledgment This work is supported by Institutional Supporting Research and Development funds provided by the Los Alamos National Laboratory of the University of California under the auspices of the Department of Energy, Contract W-7405-ENG-36. Registry No. NO, 10102-43-9.
Literature Cited Agnew, S. F.; Swanson, 9.I.; Jones, L. H.; Mills, R . L.; Schiferl, D. J. fhys. Chem. 1983, 87, 5065. Agnew, S. F.; Swanson, B. I.; Jones, L. H.; Mills, R. L. J. Phys. Chem. 1985, 89, 1678. Blais, N. C. J. Phys. Chem., in press. Davis, W. C. Roc. Symp. Detonation 8th, in press. Greiner, N. R. Proc. Symp . Detonation Bth, in press. Hay, P. J.; Pack, R. T.; Martin, R. L. J. Chem. fhys. 1984, 8 1 , 1360. Johnson, J. D.; Shaw, M. S.; Holiin, B. L. J. Chem. Phys. 1984, 80, 1279. Moore. D. S.; Schmidt, S. C.; Shaner, J. W. fhys. Rev. Lett. 1983, 5 0 , 1819. Pack, R. T., Los Alamos National Laboratory, 1984, unpublished data. Schmidt, S. C.; Moore, D. S.; Schiferl, D.; Shaner. J. W. fhvs. Rev. Lett. 1983, 50, 661. Schott, G. L. in "Shock Waves in Condensed Matter-1983"; North-Holland: Amsterdam, 1984; p 49. Schott, G. L.; Shaw, M. S.; Johnson, J. D. J. Chem. Phys. 1985, 82, 4264. Shaw, M. S.; Johnson, J. D.; Holian, B. L. Phys. Rev. Lett. 1983, 50, 1141. Stine, J. R., Los Alamos National Laboratory, private communication, 1984. Stine, J. R., Noid, D. W. J. Phys. Chem. 1983, 8 7 , 3038. Stine, J. R., Noid, D. W. Chem. Phys. Lett. 1983, 100, 282. Stine, J. R., Noid, D. W. J. Chem. Phys. 1983, 78, 1876. Stine, J. R., Noid, D. W. J. Chem. fhys. 1983, 78, 3647. Vaientlni, J. J.; Nogar, N. S.; Breshears, W. D., Los Alamos National Laboratory, 1983, unpublished data.
Received for review January 22, 1985 Accepted May 10, 1985
Chemiluminescence in Autoxidation of Hydrocarbons. A Method for Fingerprinting and Evaluation of Oxidative Stability Ilgvarr J. Spilners' and John
F. Hedenburg
Gulf Research & Development Company, Pktsburgh, Pennsylvania 15230
Chemiluminescence (CL) was generated when mineral oils, lubricants, and synthetic hydrocarbons were autoxidized at elevated temperature. CL intensity measurements were useful as a rapid method for evaluation of relative oxidative stabilities, and CL spectra served to differentiate and fingerprint hydrocarbon materials. Mineral oils which had been more severely refined to achieve a hlgher oxidative stability gave lower CL intensity. CL spectra and spectral changes with tlme were useful to differentiate oils according to their crude sources. CL measurements required less tlme than the conventionaloxklatbn tests and a good agreement with A S N D943 oxidation test could be shown. CL was also useful in monitoring and assessing service life left in used lubricants.
Introduction Chemiluminescence (CL)is emitted in the first steps of autoxidation when peroxide radicals or radicals formed during the decomposition of hydroperoxides recombine
* Ilgvars J. Spiinen, 119 Alleyne Drive, Pittsburgh, PA
15215.
0198-4321/85/1224-0442$01.50/0
(Vasilev and Vichutinski, 1962a; Vasilev et al., 1959). By use of the basic autoxidation scheme (Reich and Stivala, 19691, the following interpretation of the reaction steps can be made for the conditions used. The hydrocarbon was heated first under nitrogen at 180 to 250 OC. Under these conditions, any residual peroxides which might have been present were decomposed and some 0 1985 American
Chemical Society
Ind. Eng. Chem. Prod. Res, Dev., Vol. 24,
+ LIGUT-TIGHT BLACK BOX
hydrocarbon radicals generated. RH R.
(1)
+
After this, oxidation was started with a relatively high flow of air or oxygen which would readily give peroxy radicals (Vasilev and Vichutinski, 1962a). R. 0 2 ROZ. (2)
+
No. 3, 1985 443
+
This reaction may be followed by formation of hydroperoxides and new hydrocarbon radicals. ROz. RH -* ROOH + R. (3) This chain reaction may be terminated by recombinations of two hydrocarbon radicals or a hydrocarbon radical with a peroxy radical. R- + R. RR (4) ROz. + R. R02R (5)
+
4
SUUTTER
+
4
CONTROLS
However, the most likely reaction step to take place is the recombination-disproportionation of peroxy radicals. ROp
+ R02.
K6
products
(6)
This requires practically no activation energy. In the presence of an excess of oxygen, hydrocarbon radicals should have been converted to peroxy radicals and reactions 4 and 5 are not significant (Vasilev and Vichutinski, 195213). Recombination-disproportionation of peroxy radicals (6) is a highly exothermic reaction which has sufficient energy (45-80 kcal/mol) to generate light in the visible region of spectrum (Vasilev et al., 1959; Goldenberg and Shmulovich, 1977),but reaction 3 would require some activation energy. Reaction step 6 is believed to proceed through an excited-state ketone which can relax to ground state by emitting a photon (Mendenhall, 1977). RO2. t RO2.
R'CR""
I1
0
-
RECORDERS PHOTOMULTIPLIER RCA 1P21
Figure 1. CL apparatus I. 7 HIGH
RECORDERS
VOLTAGE POWER SUPPLY
PHOTOMULTIPLIER HAMAMATSU R e 2 8 P WITH THERMOELECTRICALLY COOLED HOUSING
CONTROLS
E]
SHUTTER EXIT LENS SLIT
300-850 nm MONOCHROMATOR H - I O (INSRUMENTS S A . INC.) SCAN LINKEDCONTROLLER TO MICROPROCESSOR
1-
1
SLIT
ENTRANCE LENS
R'CR1In t ROH t 02
-
II
0 R'CR" t
I1
nY
AUTOMATED HYPODERMIC SVRINQE
HEATED STAINLESS STEEL REACTOR
1 OVERFLOW
Figure 2. CL apparatus 11.
0
Only one photon is emitted per lo8 to 1O'O terminations, most relaxations occurring by different paths (Kellogg, 1969). When CL is measured at the maximum intensity of the spectral peak, the initiation and termination rates for the reactions generating CL are equal and termination can be assumed to go only by reaction 6. The intensity of CL, measured in photons per unit time, is proportional to the rate of reaction, W,, and through the rate equation to the square of peroxy radical concentration, [RO,.] (Vasilev et al., 1959).
C1is a proportionality constant which is unknown and unmeasurable. It is essentially equal to the effective quantum efficiency for emission and will vary with the compmition of the oxidizable material. Hence, comparison of CL intensities has a greater validity if the compositions of the materials do not differ greatly by their hydrocarbon types. The few previous studies of chemiluminescence in hydrocarbon oxidation are included in a literature review (Clark et al., 1982). Instrumentation and Experimental Conditions For detection and measurement of CL, two types of apparatus, apparatus I (Figure 1))and apparatus I1 (Figure
2), were constructed (Spilners and Hedenburg, 1984). Various techniques were used for oxidation and measurements. The simpler CL apparatus I consists of a heated glass reactor, photomultiplier, detector, and recorders. The photomultiplier is located very close to the reactor and no monochromator is included. This arrangement avoided CL losses and allowed detection of high photon counts. Measurements were made at a set temperature to record induction time for CL to appear, to reach maximum intensity, and to observe changes in CL with time. Temperatures from 180 to 250 "C and the airflow set to a maximum of 330 cm3/min were used to oxidized a 5-mL liquid hydrocarbon sample in a glass tube. The photomultiplier (RCA/ 1P21) detected CL which was emitted through the bottom of the glass reactor tube. The more advanced CL apparatus I1 is a reactor-spectrometer. I t is equipped with a heated stainless steel reactor, liquid flow controls, a monochromator (ISA Inc., H-lo), a photomultiplier (Hamamatsu R928P), and recorders. Apparatus I1 could be operated with a liquid hydrocarbon material flowing through the reactor or in a stationary mode with 0.6 mL of sample oxidized as a thin layer spread inside the reactor. CL is emitted in the reactor, passes through an opening in the top of the reactor, and is focused on the entrance slit of the monochromator.
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 3, 1985
444
OIL A A OIL 8 0 OIL c OIL 0 75
r
T 191°C
a A
FINISHED LIGHT OIL B
A
0 0
t
z ,"
A
l
0 0
sok A .
.
* *
8
*
*
.
a
*
*
e
m
nm
650
TIME. MIN FROM BEGHNING OF OXIDATION
t
Figure 3. Chemiluminescence intensity changes with time for finished light oils. Maximum peak intensities for scans between 350 and 750 nm, 191 "C.
Thus only a relatively low photon stream was available for CL measurements at the narrow wavelength ranges selected by the monochromator. CL intensity measurements were made either over a period of time at a selected wavelength or CL spectra were obtained by scanning over the wavelength range of 350 to 800 nm. Temperatures between 170 and 220 "C were most suitable for generation of CL by oxidation of hydrocarbon materials. Oxygen flow was set at 130 cm3/min in most experiments. The CL values are relative to the system and reference samples would be required for comparison with other apparatus. Also time from the start of the test must be specified because of the time dependence of the intensity.
Results and Discussion The petroleum industry formulates lubricants using base oils finished to different degrees of severity and obtained from various crude oils. Identification of base stocks and detection of differences between oils by conventional analysis may sometimes be difficult. Furthermore, base oils are evaluated and compared by their oxidative stabilities and response to antioxidants. Standard oxidation tests are time-consuming, and repeatability of the test results and agreement between different tests is often questionable. The CL method of analyses which has been developed through this research allows observation of the oxidation of an oil or any liquid hydrocarbon material as it takes place. By measuring CL at different temperatures and times, differences are found which help to 'distinguish oils and their oxidative stabilities. CL measurements usually require only a very short time. Figure 3 plots CL intensity changes with time for four finished light oils when oxidized at 191 "C. The CL intensity rise for oils A and B is much higher than for oil D, while oil C showed an intermediate level. The differences in CL intensity for the four oils during this oxidation are sufficient to distinguish them from eaeh other. The CL values are the peak intensities reached during the scans, and the time scale gives minutes from the beginning of oxidation to the CL peak maximum. During an uninterrupted oxidation, scans were repeated in quick succession for about 80 to 100 min. Figure 4 shows the comparison of the CL spectra of two finished light oils, B and C , from different crudes and their changes with time. Oil B developed a secondary peak at about 630 nm after 10 to 16 min of oxidation. When two oils are blended, the blend may not represent additively the individual component CL spectra. New interactions are introduced which will also change the CL
650
450
n'
31'5
4
1
"
I6 14
'
FINISHED LIGHT OIL C
;
12
450
10
'
6
I
1
2
0
TIME, MIN. FROM THE BEGINNING OF OXIDATION
Figure 4. Comparison of CL spectra of two finished oils. COMPARISON OF CL P f A l INTENSlTlES AN0 SPECTRAL CHARACTERISTICS 100 96
W I I E H T DiSTlLLATf
50% W. LIQHT
DISTILLATE 50% F LIGHT
NEUTRAL
25%
w. LIQHT DISTILLATE
75% F.LIQHT NE"TR*L
10% w .
LIGHT
F.LIQHT NEUTRAL
DISTILLATE 90% F LIQHT NEUTRAL
Figure 5. CL spectra of light oils and their blends. Light distillate W and light neutral F.
spectrum of the blend. Figure 5 shows the spectrum of an unfinished oil, Light Distillate W, and a finished oil, Light Neutral F. The unfinished oil has a much higher CL intensity (a peak at 550 nm), corresponding to lower oxidative stability. The Light Neutral F has a much weaker CL peak at a lower wavelength (480 nm). When the two oils from different crudes are blended, CL of the blends give some spectral features of each of the oils. Chemiluminescence, as observed by apparatus I, provides a basis for comparison of the degrees of oxidative stability which have been achieved by refining at varying conditions. Table I lists light neutral base oils from different crude sources which have been solvent extracted with furfural at solvent/oil ratios of 0.5 to 3.5 and catalytically finished by hydrogenation at temperatures from 630 to 700 OF. Oils which were solvent extracted at the low ratios of 1.0 to 0.5 have the highest CL intensities,
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24,
Table I. Relationship of CL to Refining Severity.-' Light Neutral Base Oils from Different Crude Sources at 249 'Cb crude source of base oil 0 S
S 0 S G 0 S 0 S G S S 0 0 0 0
solv extrn furfural,
s/o 2.5 3.5 3.5 1.5 1.5 3.5 2.5 1.5 1.5 1.0 1.0 1.0 1.0 1.0 0.5 0.5 0.5
cat. finishing temp, O F , a t LHSV 3.0 700 700 630 700 700 700 630 660 660 630 660 660 700 660 630 700 660
CL intensity 26 30 32 35 36 44 47 54 64 66 67 72 78 87 120 126 177
-' Total CL measured with apparatus I. Low CL values indicate high oxidative stability. Oils refined using high solvent/oil (S/O) ratio give lower CL values. bBase oils are derived from three different crudes: 0, S, G; air flow: 330 cm3/min. cArbitrary units.
Table 111. Oxidative Stability of Base Oils" from Different Crude Sources. Comparison of CLbto D943, Rotary Bomb, and Cigre Tests medium neutrals S
0 S G S S 0 S 0 0 S 0 G 0
crude source of base oil
solv extrn furfural,
S 0 S G S S 0 0 S S 0 0 S 0 G 0
4.0 3.0 4.0 4.0 2.0 2.0 3.0 1.5 1.0 1.0 1.5 1.0 1.0 1.0 1.0 1.0
s/o
cat. finishing temp, O F , a t LHSV 3.0 700 700 630 700 700 660 630 700 630 700 660 700 660 630 660 660
CL intensity 28 34 34 45 60 62 63 72 90 99 102 111 117 144 159 171
CL intensit? 28 34 34 45 60 62 72 99 102 111 117 144 159 171
rotary bomb, min >300 152 237 180 160 125 135 115 152 117 123 122 118 133
D943, h 2463 1963 2060 2105 1568 1493 1451 1234 1366 1222 1216 907 1119 1013
Cigre 0.4 6.8 0.4 0.9 15.2 16.9 13.5 24.6 21.8 25.0 18.3 11.4 38.1 18.5
"CL testa made on uninhibited oils. All other tests on oils inhibited with 0.5% by w t of phenolic antioxidant. bCL intensity determined in apparatus I a t 249 "C and air flow of 330 cm3/min. High oxidative stability is indicated by low values in CL and Cigre tests and high values in D943 and rotary bomb tests. 'Arbitrary units. 110
Table 11. Relationship of CL to Refining Severity.-' Medium Neutral Base Oils from Different Crude Sources at 249 O C b
No. 3, 1985 445
l10 .o o
E .
* .
SO
.
.
.*
20
L
Figure 6. CL intensity vs. D943 (h). Oxidative stability of medium neutrals.
Total CL measured using apparatus I. Low CL values indicate high oxidative stability. High solvent/oil ratio gives lower CL values. Base oils are derived from three different crudes: 0, S, G air flow: 330 cm3/min. cArbitrary units.
consistent with oxidative instability. The same relationship of low S/O ratio and high CL is shown also in Table I1 for medium neutral oils. Higher finishing temperatures do not always reduce the CL intensity of the oil. The CL intensities (apparatus I) of medium neutrals from different crude sources in Table I1 are compared to ASTM D943, rotary bomb and Cigre oxidation test results in Table 111. Increasing CL intensity and decreasing the number of hours to the D943 oxidation termination point of total acid number, (TAN) = 2.0, shows the correlation of high CL intensity with decreasing oxidative stability for medium neutrals. The spread of data for oxygen absorption rate in rotary bomb test, D2272, is narrow and cannot be compared with CL. No comparison is possible of CL intensities with the widely irregular variations in the measurements of total oxidation products in the Cigre test. The relatively good correlation between CL intensity and D943 test data is illustrated in Figure 6, where any D943 values below 1400 to 1500 have corresponding CL values
INDUCTION T I M E ' ALLOWED
NONE
1 MIN
2 MIN
5 MIN.
10 MIN
MAXIMUM (PEAK)
27 3
28 5
30 3
32 4
33 8
CL INTENSITY
* TIME BETWEEN THE BEQlNNlNQ OF OXIDATION AND THE STAR? OF THE SCAN
Figure 7. Change in CL intensity with time for experimental transformer oil G at 202 OC;oxygen flow, 130 cm3/min.
of 80 or higher consistent with unsatisfactory oxidation stability. The CL intensity measurement at a constant temperature (249 "C) in apparatus I requires several minutes, the D943 test lasts from 1000 to 2500 h, the rotary bomb test takes less than 1h, while the Cigre test may require 5 days. CL intensities (apparatus 11) of oils may increase or decrease with time of oxidation. An example of this is shown in Figures 7 and 8 by two experimental transformer
446
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 3, 1985
Table IV. Comparison of CL Intensities"of New and Used Turbine Oils new turbine oil, T
induction time, minb none 5
WAVELENGTH m INDUCTION TIME' ALLOWED
,
550 450
NONE
MAXIMUM (PEAK1 CL INTENSITY
. TIME
,
29 7
4
I
,
,
550 4 5 0
550 4 5 0
550 450
1 MIN
2 MIN
5 MIN
10 MIN
26 7
27 3
24 9
23 1
2
5 5 0 450nm
BETWEEN THE BEGINNING OF OXIDATION AN0 THE START OF THE SCAN
Figure 8. Change in CL intensity for experimental transformer oil W at 202 "C; oxygen flow, 130 cm3/min.
5 10
,
I /
,
I
used turbine oil, T 2 d
used turbine oil, T3'
18.9 20.1 20.4 21.6 26.4
45.9 41.1 59.1 68.0 60.0
5.4 5.6 6.4 1.5 9.5
CL intensity in arbitrary units for the highest peak recorded. *Time in minutes allowed for oxidation a t 202 "C (oxygen flow 130 cm3/min, apparatus 11) before CL scan from 350 to 700 nm was started. Low CL values in the new oil, T, and the used oil recommended for further use, T1, indicate good oxidative stability. Higher CL values for the contaminated oil, T2, and used oil, T3, indicate oxidative instability. Recommended for further use. Contaminated e From a steam turbine, recommended for change. h
l504
I
4.1 5.1 4.9 6.8 8.2
1
,
I
used turbine oil, TIC
\ I
I
'
WAVELENGTH. nm
550 450
550 450
550 450
550 450
INDUCTION TIME. ALLOWED
NONE
1 MIN
2 MIN
5 MIN
MAXIMUM (PEAK) CL INTENSITY
15 3
18 0
20 4
21 3
I
550 450
10 MIN
*
IS2
Figure 9. Ghange in CL intensity for experimental transformer oil W1 a t 202 "C; oxygen flow, 130 cm3/min.
nm
WAVELENGTH
6 6 0 110 S I 0
04
460 060
77
610
460
02
h
I'
I
* TIME BETWEEN THE BEGINNING OF OXIDATION AND THE START OF THE SCAN
460
110
460
el0
28,
39,
e60
460
460
IOr
0
TIME IN MINUTES FROM THE BEQlNNlNG OF OXIDATION TO START O F THE SCAN 1350 TO BOOnm)
Figure 11. Synthetic hydrocarbon fluid. Change in CL spectrum with time of oxidation a t 202 "C, 130 cm3/min of O2flow.
1
WAVELENGTH
nm
INDUCTION T I M E ' ALLOWED MAXIMUM (PEAK1 C L INTENSITY
5 5 0 450
NONE
20 4
450
,
550 450
550 450
I MIN
2 MIN
5 MIN
21 8
24 3
18 6
+
TIME B E T W E E N THE BEGINNING OF OXIDATION AND THE START OF THE SCAN
I
20 1 +
! I
\I
6 0 7 6 0 110 760 31, 121,
I
! 660
80
