ELSEVIER 6 June 1997 Chemical Physics Letters 271 (1997) 73-78 CHEMICAL PHYSICS LETTERS Facile production of higher hydrocarbons from ethane in a catalytic supersonic nozzle Lina Shebaro l, Benjamin Abbott, Theodore Hong, Alkwin Slenczka 2, Bretislav Friedrich, Dudley Herschbach Department of Chemistry and Chemical Biology, Harvard Universi~, 12 Oxford St., Cambridge, MA 02138, USA Received 17 March 1997 Abstract Flowing ethane, typically at 80 Torr, 1000°C, and 10 ms contact time, through a supersonic nozzle made of nickel or molybdenum converts roughly 40% to higher hydrocarbons. In the mass spectra of the products, CnHm, the most prominent peaks contain even numbers of carbon atoms (n = 4 ..... 12), but there are also substantial peaks with odd carbon atom numbers (n = 3 ..... 11). The largest peaks have m = n hydrogen atoms, but many others also appear. For n = 6 the mass spectrum indicates benzene is probably the sole product, with yield up to 15%. Under the same conditions methane does not form higher hydrocarbons. 1. Introduction Molecular beams generated by expansion of gases through a supersonic nozzle have long offered a versatile tool for both collision and spectroscopic experiments [1]. Many applications exploit the markedly nonequilibrium character of the gas flow. This produces drastic cooling of molecular motion and also enables generating beams of chemical species that are not feasible to study in an equilib- rium gas. These include a host of van der Waals adducts [2] and atomic and molecular clusters [3]. t Also at Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02167, USA. 2 Present address: Institut ftir Physikalische und Theoretische Chemie, Universit~it Regensburg, D-93053 Regensburg, Germany. Several special nozzle designs have been developed to handle refractory [4], delicate [5], or reactive species, particularly organic free radicals [6]. An especially fruitful technique has been vaporization by laser ablation of solids into the gas flow [7]; this led to the discovery in carbon clusters of fullerene molecules. Here we report a remarkably facile syn- thesis of hydrocarbons, including numerous free rad- icals and benzene, by an extremely simple means. This employs a nozzle fashioned from a catalytic metal to form precursor radicals, which presumably are swept from the metal surface into the flowing gas and induce chain reactions. On simply flowing ethane gas through such a nozzle, at typically 80 Torr, 1000°C, and 10 ms contact time, we find that roughly 40% is converted to higher hydrocarbons, CnH m. These hydrocarbons contain from n = 3 to 12 carbon atoms and a range 0009-2614/97/$17.00 Copyright © 1997 Elsevier Science B.V. All rights reserved. PII S0009-2614(97)00437-5