关键词: 过氧化二叔丁基, 瞬时热解, 时间分辨质谱

Abstract: The mass distribution and time-of-flight(TOF)spectra for the pyrolytic fragments of di-tert-butyl peroxide (DTBP) seeded in He or Ar carrier gas have been achieved by using time-resolved mass spectrometric and high ternperature flash pyrolysis techniques,The dependence of DTBPconversion yield on the heated SiCtube temperature(T_s) shows that the precursor molecule in the carrier gas starts to decompose obviously at 900 K,and reaches complete decomposition at 1300 K. Two major fragments CH₃COCH₃ and CH₃·radical are observed.In a pulsed free jet expansion of 4% mole fraction of DTBP/Ar gas mixture,the TOFspectra of pyrolytic fragments measured at T_s=1000 K show that there are two peaks for CH₃COCHion(m/e=58)and its fragment ions,CH₃CO⁺ and CH (m/e=43 and 15).When He or N₂ is used as a carrier gas,however,only one peak is observed in its TOFspectra. This result implies that a fraction of jet-cooled CH₃COCH₃⁺(m/e=58) molecules combine with Ar and form the van der Waals molecules CH₃COCH₃.Ar_n. Formation of CH₃COCH₃·Ar_n is also suggested via the TOFexperiments in which acetone is used as a precursor seeded in Ar carrier gas. The proposed mechanism of DTBP flash pyrolysis mainly involves the initial split of the O-Obond of DTBP to generate(CH₃)₃CO·radical,followed by the decomposition of this radical into CH₃COCH₃ and CH₃·radical,and the recombination or secondary bi-molecular reactions of product radicals are suppressed in the flash pyrolysis of DTBP with a very shot contact time.

Key words: Di-tert-butyl peroxide, Hight-temperature flash pyrolysis, Time-resolved mass spectrometry