PYROLYSIS OF ETHYL ESTERS IN A MICROREACTOR Paper

PYROLYSIS OF ETHYL ESTERS IN A MICRO-REACTOR Paper 3978 CORY ROGERS, Department of Mechanical Engineering, University of Colorado Boulder, CO JESSIE P PORTERFIELD, Radio and Geoastronomy Division, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, JOHN W DAILY, Department of Mechanical Engineering, University of Colorado Boulder, CO BARNEY ELLISON, Department of Chemistry, University of Colorado, Boulder, CO NICOLE LABBE, Department of Mechanical Engineering, University of Colorado, Boulder, CO

Combustion: Fuel (+ M) “radicals” TOF detection Use Micro-Reactor to understand 1 st steps dilute fuel entrained in 1 atm carrier gas behind pulsed valve 1 mm ID x 3 cm long Si. C tube @ 300 – 1700 K 20 K Cs. I window Detection: a) universal b) multiplexed c) sensitive VUV photoionization Matrix IR

Pyrolysis of Esters if methanol replaced by ethanol, ethyl esters will be formed Use Fatty Acid Esters as biofuels

Classical Organic Chemistry of Ester Pyrolysis well studied. De. Puy and King, “Pyrolytic cis Eliminations” Chem. Revs. 1960, 431 -457. Esters with b-H atoms decompose synchronously: Hurd and Blunck, “The Pyrolysis of Esters” J. Am. Chem. Soc. 1938, 60, 2419 -2425. Typical pyrolysis in solution about 400 ºC k. I (CH 3 COOCH 2 CH 3) = 5 x 1012 exp(-48. 0/RT)

Synchronous Decomposition? Curtin and Kellom, “Elimination and Replacement Reactions of dl- erythro- and dl -threo-2 -Deutero-1, 2 -diphenylethanol and Derivatives” J. Am. Chem. Soc. 1953, 75, 6011 -6018. Gas Phase Beadle, Golden, Benson, “Very Low-Pressure Pyrolysis: VI. The Decomposition of Ethyl Acetate. ” Int. J. Chem. Kinetics 1972, 4, 265 -271. k. I (CH 3 COOCH 2 CH 3) = 4 x 1012 exp(-48. 0/RT)

In the Micro-Reactor, we anticipate: 6 – centered 4– centered ? keto ⇋ enol

In the Micro-Reactor, we anticipate: CH 3 CH 2 COOCH 2 CH 3 (+ M) → CH 3 CH 2 COOH + CH 2=CH 2 m/z 74 Ethyl Ester Pyrolysis CH 3 CH 2 COOCH 2 CH 3 (+ M) → CH 3 CH=C=O + CH 3 CH 2 OH m/z 56 m/z 46 CH 3 CH 2 COOCH 2 CH 3 (+ M) ⇋ CH 3 CH=C(OH)OCH 2 CH 3 → CH 3 CH=C=O + CH 3 CH 2 OH m/z 102 enol CH 3 CH 2 COOH (+ M) → CH 3 CH=C=O + H 2 O m/z 74 m/z 56 Carboxylic Acid Pyrolysis CH 3 CH 2 COOH (+ M) ⇋ CH 3 CH=C(OH)2 → CH 3 CH=C=O + H 2 O enol m/z 56 CH 3 CH=C=O (+ M) → H + CH 2 CH=C=O → H + CH 2=C=C=O → CO + CH 2=C: → HC≡CH m/z 55 m/z 54 CH 3 CH=C=O (+ M) → CO + CH 3 CH: → CH 2=CH 2 m/z 28 m/z 26

CH 3 CH=C=O CH 2=CH 2 CH 3 CH 2 COOH

expected 4 -centered enol

CH 3 CH 2 COOH → CH 3 CH=C=O + H 2 O m/z 56 CH 3 -CH 2 COOH → CH 3 + [CH 2 CO-OH] → CH 2=C=O + OH m/z 15 m/z 42

Conclusion: Ethyl Ester Pyrolysis CH 3 CH 2 COOCH 2 CH 3 (+ M) → CH 3 CH 2 COOH + CH 2=CH 2 m/z 74 CH 3 CH 2 COOCH 2 CH 3 (+ M) → CH 3 CH=C=O + CH 3 CH 2 OH m/z 56 6 center m/z 46 4 center CH 3 CH 2 COOH (+ M) → CH 3 CH=C=O + H 2 O m/z 56 Carboxylic Acid Pyrolysis CH 3 CH 2 COOH (+ M) ⇋ CH 3 CH=C(OH)2 → CH 3 CH=C=O + H 2 O 4 center m/z 56 CH 3 CH=C=O (+ M) → H + CH 2 CH=C=O → H + CH 2=C=C=O → CO + CH 2=C: → HC≡CH m/z 55 m/z 54 CH 3 -CH 2 COOH → CH 3 + [CH 2 CO-OH] → CH 2=C=O + OH m/z 15 m/z 42 m/z 26

Thermal decomposition of methyl esters is a mess. CH 3 COOCH 3 → products CH 3 CH 2 COOCH 3 → products Porterfield, Bross, Ruscic, Thorpe, Nguyen, Baraban, Stanton, Daily, Ellison, “Thermal Decomposition of Potential Ester Biofuels Part I: Methyl Acetate and Methyl Butanoate. ” J. Phys. Chem. A 2017, 121, 4658 -4677.