Envlron. Scl. Technol. 1986, 2 0 , 393-397
England, C.; Corcoran, W. H. Znd. Eng. Chem. Fundam. 1974, 13, 373-384. Sakamaki, F.; Hatakeyama, S.; Akimoto, H. Int. J. Chem. Kinet. 1983, 15, 1013-1029. Carter, W. P. L.; Atkinson, R.; Winer, A. M.; Pitts, J. N., Jr.; Znt. J. Chem. Kinet. 1981,13, 735-740. Carter, W. P. L.; Atkinson, R.; Winer, A. M.; Pitts, J. N., Jr.; Znt. J . Chem. Kinet. 1982, 14, 1071-1103. Pitts, J. N., Jr.; Sanhueza, E.; Atkinson, R.; Carter, W. P. L.; Winer, A. M.; Harris, G. W.; Plum, C. N. Znt. J. Chem. Kinet. 1984, 16, 919-939. Akimoto, H.; Hoshino, M.; Inoue, G.; Sakamaki, F.; Washida, N.; Okuda, M. Environ. Sci. Technol. 1979, 13, 471-475. Schwartz, S. E.; White, W. H. Adv. Environ. Sci. Technol. 1983,12, 1-46. Schwartz, S.E. In “SO2, NO and NOz Oxidation Mechanisms: Atmospheric Considerations”, Calvert, J. G., Ed.; Butterworth: Boston, MA, 1984; p p 173-208. Fateley, W. G.; Bent, H. A.; Crawford, B., Jr. J. Chem. Phys. 1959, 31, 204-217. Bolduan, F.; Jodl, H. J.; Loewenschuss, A. J. Chem. Phys. 1984,80, 1739-1743. Bandow, H.; Akimoto, H.; Akiyama, S.; Tezuka, T. Chem. Phys. Lett. 1984, 111, 496-500. Anbar, M.; Taube, H. J. Am. Chem. SOC.1955, 77, 2993-2994.
(18) White, E. H.; Feldman, W. R. J . Am. Chem. SOC. 1957, 79, 5832-5833. (19) Cooney, R. P.; Tsai, P. J. Raman Spectrosc. 1980,9,33-38. (20) Wada, Y.; Otsuka, K.; Morikawa, A. J . Catal. 1981, 71, 136-143. (21) Jonsson, A.; Persson, K. -A.; Bertilsson, B. M. “Organic Nitrites in the Exhaust Emissions from Alcohol Fueled Vehicles”, Proceedings of the Fifth International Alcohol Fuel Technology Symposium, Auckland, New Zealand, 1982; p p 3-179-3-186. (22) Ito, K.; Yano, T.; Takahashi, F. “Methyl Nitrite Formation in Exhaust Gases Emitted from a Methanol Fueled S.I. Engine”, Proceedings of the Fifth International Alcohol Fuel Technology Symposium, Auckland, New Zealand, 1982; pp 3-171-3-178. (23) Okada, J.; Koda, S.; Akita, K. Fuel 1985, 64, 553-557. (24) Whitten, G. Z.; Pullman, J. B. “Methanol Fuel Substitution Can Reduce Urban Ozone Pollution”, Proceedings of the Sixth International Alcohol Fuel Technology Symposium, Ottawa, Canada, 1984; pp 2-61-2-65. (25) Wilson, K. W.; McCormack, M. C. “Methanol As an Ozone Control Strategy in the Los Angeles Area”, Proceedings of the Sixth International Alcohol Fuel Technology Symposium, Ottawa, Canada, 1984; pp 2-68-2-74. Received for review April 29,1985. Accepted November 5,1985.
Formation of Methyl Nitrite in the Surface Reaction of Nitrogen Dioxide and Methanol. 2. Photoenhancement Hajime Aklmoto” and Hiroo Takagl Division of Atmospheric Environment, The National Institute for Environmental Studies, P.O. Tsukuba-gakuen, Ibaraki 305, Japan
The surface reaction of NO2 and methanol described in the preceding paper was studied in the evacuable smog chamber under the irradiation of UV-visible light (2290 nm). Kinetic analysis of the gaseous reactant and products with the aid of computer modeling revealed that the surface reaction to yield CH30N0 and HN03 is enhanced by the irradiation. The apparent second-order rate constant of the surface reaction increases linearly with light intensity, and the photoenhancement factor ranged from 1.8 to 5.9 for the kl value (primary NO2 photolysis rate) of 0.16-0.38 min-l and for the NO2 and methanol initial concentrations of 5 and 30 ppm, respectively.
Introduction In the preceding paper (I) (referred to as paper l ) , a thermal surface reaction of NO2 and methanol
+
(1) CH30H 2 NO2 ?!!+ CH30N0 + HN03 has been characterized in dark in the smog chamber. In the present study, the kinetics of the surface reaction of NO2 and methanol have been studied under UV-visible irradiation. The observed evidence that the apparent rate of reaction 1 is enhanced under the irradiation will be reported in the present paper. This result may be of interest being relevant to the analogous reaction of NO2 and water,
wall
HzO + 2N02 HONO + HNOB (2) which has been discussed ( 2 , 3 )in relation to the unknown radical source issue for the smog chamber studies raised by Carter et al. (4, 5 ) . 0013-936X/86/0920-0393$01.50/0
Experimental Section Several runs of CH30H (5-20 ppm)-NO2 (37-60 ppm)-dry air (1atm) were carried out at 30 “C using the evacuable and bakable smog chamber at the National Institute for Environmental Studies (NIES). Full accounts of the chamber system have been reported previously (6), and a brief description has been given in paper 1. In each run, the chamber was first filled with purified dry air, and then methanol was injected using air as the carrier gas. After a reference spectrum had been recorded, NO2 was next introduced with the carrier gas, and the IR measurement was made approximately every 10-20 min. The formation of CH30N0 in the dark was monitored for the first ca. 2 h after the injection of NO2, and then the irradiation by a solar simulator (6) was commenced and continued for another ca. 2 h. The reaction mixture in the chamber was mixed with the two fans during runs. The light intensity was measured by primary NO2 photolysis rate (6) and was varied in the range of 0.16-0.38 min-l. Concentrations of the reactants and the products were measured by means of a long-path (221.5-m) FTIR set in the chamber. Spectral resolution of 1 cm-l was employed, and 128 scans were accumulated to obtain a spectrum. Absorption peaks and absorption coefficients (base 10, torr-l m-l) used for the quantitative measurement are as follows: CH,OH (2847 cm-l; 0.0711, Q-branch), CH30N0 (1445 cm-l; 0.0408, peak only), HCHO (1745 cm-l, 0.690, &-branch), and CH30N02 (1292 cm-l; 0.476, Q-branch peak to P-branch valley). Computer Simulation and Reaction Model. Computer simulation for the reaction system studied was carried out by using the reaction model given in Table I.
0 1986 American Chemical Society
Environ. Sci. Technol., Vol. 20, No. 4, 1986
393
Table I. Photochemical Reaction Model for CH30H-NO,-Air System no. 1
2 3 4 5
6 7 8 9 10 11
reaction
- + + - + + - o2+ + + + + - + + - + + +
NO^ + hu
NO
+
-+
+
+
+
- + o2 + + + + -+ + + - + + - + - + + - + + - + + + + + - + + + + + - + -- ++ + - + + + - + + o2Y o3 + NO^
NO O(3P) NO2 E. NO3 o ( 3 ~ ) NO Y NO^ o ( ~ P ) O3 202 o('D) Y o ( 3 ~ ) O('D) HzO 20H O('D) O3 -+ O2 O2 O('D) O3 O2 20(3P) O3 NO NO2 O2 O3 + NOp NO3 O2 O3 OH HOB O2 O3 HOz OH 2 0 2 2NO 02 -+ 2N02 NO NO3 2N02 NO OH Y HONO NO HOz OH NO2 NO2 NO3 Nz05 NO2 OH % HNO, NO2 HOz HOzNOz HOpNOz HOz + NO2 HONO OH NO2 H 2 0 Np05 NO2 NO3 2H02 Hp02 02 2H02 H2O H2Oz 02 H20 Hz02 OH HzO HOz co + OH 4 H O +~ coZ
38 39 40
NO2 + HzO HONO N205+ H 2 0 2HN03 CH3OH + NO2 CH3ONO
o(3~)
7.1 x 3.0 2.4 X 2.5 x 4.2 x 1.6 X
13 14 14 15, 16 15,16 15
10-4 10'' 10-3 10-3 lo-'
10-14 10-12 lo-''
10-12 10-15 10" 10-10 10-'0 10-10 10-14 10-17 10-14 10-15 10-38 10-11 lo-''
10-l' 10-2 lo-''
10-2
lo-''
10-30
lo-"
10-13
17 17 17 17 17 17 17 17 17 17 17 17 17 19 17 17 17 20 17 17 18
21 17 17 23 17 17
Surface Reactions 7.0 x 10-24 2.0 x 2.2 x 10-20
+
-
Organic Reactions CH30H + 2 N 0 2 CH30N0 + HNO, CH30H + O(3P)% HCHO + HOz + OH HCHO + o ( 3 ~4 ) H O + ~ co + OH CH30H + OH 4 HCHO + H 0 2 + H 2 0 CHBONO + OH % OOCHzONO + H 2 0 HCHO + OH % H 0 2 + CO + H20 OOCHZONO + NO -.+ HCHO + 2N02 CH30 + Oz HCHO + H 0 2 CH30 + NO Y CH30N0 CH30 + NO 4 HCHO H02 + NO CH30 + NO2 CH30N02 CH30 + NO2 HCHO + HONO
52
10,11 12
1.4 X 9.3 x 6.6 X 9.5 x 2.5 X 6.0 x 1.7 X 2.4 x
-+
-
1.8 X lo-'
1.2 x 10-12 1.1 x 10-11
-+
50 51
9, 11 10, 11
1.4 x 9.3 x 1.5 X 2.1 x 8.9 x 7.0 X 2.2 x 1.2 x 1.2 x 1.9 x 3.7 x 7.2 x 2.1 x 1.9 x 2.0 x 4.8 X 8.2 X
o(3~)
-
1.0 7.6 x 10-3 5.1 X lo-'
Inorganic Reactions
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
41 42 43 44 45 46 47 48 49
ref
Photochemical Reactions
o(3~)
h~ 02 O(lD) O3 h~ 0(3~) HONO hv OH NO Hi02 h~ 20H NO3 hv NO O2 NO3 hu NOz O(3P) HCHO hu 4 2H02 CO HCHO + hu Hz + CO CH30N0 + hu CH30 NO 03
rate constant,n molecule-' cm3 s-I
+
4 23 1
1.2 x 10-36
1
1.5 x 10-14 1.7 x 10-13 1.1 x 10-12
24 17 25 26 17 17 17 27, 28 27, 28 28 28
1.8 x
1043
1.0 x 7.6 X 1.4 x 1.7 X 3.0 X 1.6 X 1.0 x
10-11
lo-''
10-15 lo-" lo-''
10-l' 10-12
Relative rate for photochemical reactions.
Calculations were performed on a Hitac 180 computer using a CHEMK program for the integration of coupled kinetic equations originally written by Whitten and Hog0 (7). The subroutines employ the Gear algorithm (8)for the variable step-size integration. Accounts on the reaction model are given below. (i)Relative Photolysis Rates. All the photolysis rates were calculated by using the typical spectral distribution of our solar simulator given before (6). The summation CJxax&was taken at 5-nm intervals at
