The thermal decomposition of furan was studied behind reflected shocks in a single shock tube, over the temperature range 1050-1460 K, at total gas densities of approximately 3 X mol/cm3. Methylacetylene and carbon monoxide are the major reaction products and are formed by the reaction furan -CH3C*H + CO (l), with a rate constant kl = 1015.25*0.5 exp(-(77.5 f 2.5) X 103/Rq s-l. A second initiation reaction produces acetylene and ketene according to the reaction furan -CH*H + CH2=€0 (2), with a rate constant k2 = 1014.7M.5 exp(-(77.5 * 2.5) X 103/Rq 8. The rate constant obtained for the overall decomposition of furan in the temperature range 106C-1260 K is = 10'5.43M.45 exp(-(78.3 i 2.0) X 103/Rg s-'. The overall pyrolysis rate measured in this investigation is about 8 times lower than the rate extrapolated from an estimated value suggested for the low-pressure pyrolysis. Additional reaction products which appear in the pyrolysis are CH,=C=CH,, C4H6, C2H4, CH4, C4H4, C4H2, and C&6. They appear in noticable quantities at high temperatures and are probably secondary products. IntroductionWe have recently published an investigation describing the thermal decomposition of tetrahydrofuran behind reflected shocks, in a single-pulse shock tube.' A wide spectrum of products was analyzed in this pyrolysis and a mechanism for their formation was suggested.In an effort to elucidate the pyrolysis pattern of other fivemember ring ethers, we have carried out a detailed investigation of the pyrolysis of furan behind reflected shocks.As in the case of tetrahydrofuran, very little effort has been devoted in the past to the study of the thermal reactions of furan. The only investigation that we are aware of is a recent study by Grela, Amorebieta, and Colussiz who studied the very low pressure pyrolysis (VLPP) of furan, 2-methylfuran, and 2,5-dimethylfuran over the temperature range 1050-1270 K. The reactant molecules were heated in a steady flow reactor and the product analysis was done by an on-line mass spectrometry. The overall pyrolysis was determined by the decay of the parent ion intensity at m l z 68 (F), 82 (MF), and 96 (DMF).

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The thermal decomposition of acetonitrile was studied behind reflected shocks in a single pulse shock tube over the temperature range 1350-1950 K at overall densities of approximately 3 x mol/cc. Methane and hydrogen cyanide are the major reaction products. They are formed by an attack of H and CH, radicals on acetonitrile. The initiation step of the pyrolysis is the self dissociation of acetonitrile:(1) CHsCN -CHZCN + H for which the following rate constant was obtained: k 1 = 6.17 x 101'exp(-96.6 x 103/RT)sec-'. Where R is given in units of cal/K mol. Additional reaction products which appear in the pyrolysis are: C,H,, CzH4, CH2-CHCN, CH=CCN, C2HSCN, C2N2, and C 3 , . Acetylene is formed from methane pyrolysis and becomes a major reaction product at high temperatures. Acrilonitrile and cyanoacetylene are secondary products originating from the C&CN radical. Fhte parameters €or the formation of the reaction products are given.

The pyrolysis of 2,s-dihydrofuran was studied behind reflected shocks in a single-pulse shock tube over the temperature range 880-1080 K. The main channel of the pyrolysis is the dehydrogenation reaction to form hydrogen and furan. The rate constants for this reaction obtained at high temperatures scatter along the Arrhenius line extrapolated from the low temperatures. Over the temperature range 615-1030 K (low-and high-temperature data), the rate constant kuni = 5.3 X 1Ol2 exp(-48.5 X 103/RT) s-' is valid over more than 6 orders of magnitude in its value. Several reaction products accompany the dehydrogenation although at a much lower rate. The product distribution shows that propylene is the main pyrolitic product, followed by acetylene and methane. U CH2OCH2 -CH3 + HCO HCO -CO t H H + 0 -H2 t 0, C3H6 -C3H4 (schematic presentation) C3H6 f CH3 -C4He f H C4He -C4Hs (schematic presentation)

129ChemInform Abstract (over the temp. range 880-1080 K; furan, propylene, and CO as main products, dehydrogenation being the main channel of pyrolysis).