화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.118, No.44, 10201-10209, 2014
Reaction Rate Constant of CH2O + H = HCO + H-2 Revisited: A Combined Study of Direct Shock Tube Measurement and Transition State Theory Calculation
The rate constant of the H-abstraction reaction of formaldehyde (CH2O) by hydrogen atoms (H), CH2O + H = H-2 + HCO, has been studied behind reflected shock waves with use of a sensitive mid-IR laser absorption diagnostic for CO, over temperatures of 1304-2006 K and at pressures near 1 atm. C2H5I was used as an H atom precursor and 1,3,5-trioxane as the CH2O precursor, to generate a well-controlled CH2O/H reacting system. By designing the experiments to maintain relatively constant H atom concentrations, the current study significantly boosted the measurement sensitivity of the target reaction and suppressed the influence of interfering reactions. The measured CH2O + H rate constant can be expressed in modified Arrhenius from as k(CH2)O+H(1304-2006 K, 1 atm) = 1.97 X 10(11)(T/K)(1.06) exp(-3818 K/T) cm(3) mol(-1)s(-1), with uncertainty limits estimated to be +18%/-26%. A transition-state-theory (TST) calculation, using the CCSD(T)-F12/VTZ-F12 level of theory, is in good agreement with the shock tube measurement and extended the temperature range of the current study to 200-3000 K, over which a modified Arrhenius fit of the rate constant can be expressed as k(CH2)O+H(200-3000 K) = 5.86 X 10(3)(T/K)(3.13) exp(-762 K/T) cm(3) mol(-1)s(-1).