Adsorption and Thermal Decomposition of 2-Iodoethanolon Ni(100)-Intermediates of Oxidation of Hydrocarbons: Hydroxyalkyls and Oxametallacycles

Abstract

Based on the study of the adsorption and thermal reactions of 2-iodoethanol on clean Ni(100) surface, further research and discussion were conducted on the results of experimental data, and the mechanism of chemical reaction was analyzed in detail. Two potential intermediates (2-hydroxyethyl and oxametallacycle surface species) in catalytic oxidation hydrocarbons were studied. 2-iodoethanol adsorbed molecularly on Ni(100) at 100 K starts chemical reaction around 140 K and produces small amounts of ethylene and water, due to the concerted decomposition or disproportionation of the adsorbed molecular species. Around 150 K with an initial C-I bond scission, 80% of 2-iodoethanol decompose to form-0(H) CH2CH2-, while 20% of 2-iodoethanol transform to 2-hydroxyethyl intermediates. The subsequent reaction of the 2-hydroxyethyl species around 160 K concerns two competing reactions: a reductive elimination with surface hydrogen to yield ethanol, and a β-H elimination to from surface vinyl alcohol. At the same temperature, the-O(H)CH2CH2-intermediate dehydrogenates to a -OCH,CH2-oxametallacycle species. Both 2-hydroxyethyl and oxametallacycle species tautomerize to acetaldehyde, around 210 K and above 250 K, respectively. Some of that acetaldehyde desorbs while the rest decomposes to hydrogen and carbon monoxide. The implications of this chemical process to catalysis are discussed.