Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation
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DOI：
10.5194/acp-13-5715-2013
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发表时间：
2013-01-01
影响因子：
6.3
通讯作者：
Martin, S. T.
中科院分区：
文献类型：
--
作者：
Liu, Y. J.;Herdlinger-Blatt, I.;Martin, S. T.
异戊二烯（ISOP; C5 H8）的光氧化化学在连续流动室中的条件下，异戊二烯衍生的过氧自由基（RO 2）的反应是由氢过氧（HO 2）途径为主的研究。使用具有可切换H3 O+和NO+试剂离子的质子转移反应飞行时间质谱仪（PTR-TOF-MS）进行产物分析。产物甲基乙烯基酮（MVK; C4 H6 O）和甲基丙烯醛（MACR; C4 H6 O）区分使用NO+试剂离子。在+25 ° C和< 2%相对湿度下，通过HO 2途径的MVK和MACR产率分别为（3.8 +/- 1.3）%和（2.5 +/- 0.9）%。通过NO途径的产率分别为（41.4 ± 5.5）%和（29.6 ± 4.2）%。通过HO 2途径产生MVK和MACR意味着同时产生羟基（（6.3 +/- 2.1）%）和氢过氧基（（6.3 +/- 2.1）%），这意味着HO 2既是反应物又是产物，HOx再循环为（12.6 +/- 4.2）%。其他异戊二烯氧化产物，被认为主要是有机氢过氧化物，也有助于在相同的质量-电荷（m/z）比的离子强度作为MVK和MACR产品离子HO 2占主导地位的条件。通过放置冷阱，这些产物被选择性地从气相中除去当纳入区域和全球化学传输模型时，本研究中报告的MVK和MACR的产率以及伴随的HOx再循环可以提高异戊二烯的HO 2反应途径模拟的准确性，这被认为是全球范围内大气产生的异戊二烯衍生的过氧自由基的大约一半的命运。
The photo-oxidation chemistry of isoprene (ISOP; C5H8) was studied in a continuous-flow chamber under conditions such that the reactions of the isoprene-derived peroxyl radicals (RO2) were dominated by the hydroperoxyl (HO2) pathway. A proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) with switchable H3O+ and NO+ reagent ions was used for product analysis. The products methyl vinyl ketone (MVK; C4H6O) and methacrolein (MACR; C4H6O) were differentiated using NO+ reagent ions. The MVK and MACR yields via the HO2 pathway were (3.8 +/- 1.3)% and (2.5 +/- 0.9) %, respectively, at +25 degrees C and < 2% relative humidity. The respective yields were (41.4 +/- 5.5)% and (29.6 +/- 4.2)% via the NO pathway. Production of MVK and MACR via the HO2 pathway implies concomitant production of hydroxyl ((6.3 +/- 2.1) %) and hydroperoxyl ((6.3 +/- 2.1) %) radicals, meaning a HOx recycling of (12.6 +/- 4.2)% given that HO2 was both a reactant and product. Other isoprene oxidation products, believed to be mostly organic hydroperoxides, also contributed to the ion intensity at the same mass-to-charge (m/z) ratios as the MVK and MACR product ions for HO2-dominant conditions. These products were selectively removed from the gas phase by placement of a cold trap (-40 degrees C) inline prior to the PTR-TOF-MS. When incorporated into regional and global chemical transport models, the yields of MVK and MACR and the concomitant HOx recycling reported in this study can improve the accuracy of the simulation of the HO2 reaction pathway of isoprene, which is believed to be the fate of approximately half of atmospherically produced isoprene-derived peroxy radicals on a global scale.