Direct Synthesis of Methyl Propionate from n -Propyl Alcohol and Methanol Using Gold Catalysts
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Direct Synthesis of Methyl Propionate from n-Propyl Alcohol and Methanol Using Gold Catalysts Guangliang Liu Æ Gang Li Æ Haiyan Song
Received: 1 October 2008 / Accepted: 12 November 2008 / Published online: 26 November 2008 Ó Springer Science+Business Media, LLC 2008
Abstract Gold nanoparticles supported on TiO2 were prepared using deposition–precipitation (DP) method and the catalysts were characterized by ICP, XRD, TEM, H2-TPR, UV–Vis, NH3-TPD and pyridine adsorbed FT-IR. The Au/TiO2 was used to catalyze the aerobic oxidation of n-propyl alcohol dissolved in methanol and methyl propionate was synthesized. The results showed that 5% Au/TiO2 calcined at 673 K exhibited excellent catalytic performance in direct synthesis of methyl propionate. The selectivity of methyl propionate could reach 99% and the maximum n-propyl alcohol conversion was 63%. Au/TiO2 was stable and it could be reused for 6 cycles without significant deactivation when a base additive was added. The base dramatically improved the activity of gold catalysts and decelerated the deactivation of Au/TiO2. Keywords Gold catalyst Oxidative esterification Methyl propionate Aerobic oxidation
1 Introduction In recent years, heterogeneous gold catalysts have attracted extensive attentions and they have been applied to a variety of reactions, such as the oxidation of CO [1, 2], the oxidation of alcohol [3–5] and aldehyde [6, 7], water–gas shift reaction [8, 9], direct synthesis of hydrogen peroxide from H2 and O2 [10–13] and so on. Very recently, selective oxidation of 1, 4-butanediol [14] and catalytic transfer
G. Liu G. Li (&) H. Song State Key Laboratory of Fine Chemicals, Department of Catalytical Chemistry and Engineering, Dalian University of Technology, 116012 Dalian, China e-mail: [email protected]
hydrogenation reaction [15] have been investigated. Some reactions will be industrialized. Meanwhile, the investigations of new reactions over gold catalysts are in progress. A great many potential applications of gold catalysts are probably to be carried out due to their high activity and less pollution to the environment. Methyl esters have been used in organic synthesis as intermediate. The addition of methyl ester ethoxylates also gives detergent manufacturers another choice from the ethoxylate menu [16]. They are considered to be promising and prospective alternative diesel fuels to fossil diesel fuels and their roles as specific additives can be substantially more important [17, 18]. However, the conventional route of producing methyl esters in which a two-step synthetic procedure first involving the synthesis of carboxylic acids is required. What’s more, the catalysts are mainly superacid, heteropoly acids and concentrated sulfuric acid which are of high toxicity and erosion. Although oxidative esterification of alcohols over Pd catalyst was already reported, the Pd catalyst has a problem of catalyst deactivation [19]. So a kind of stable and environmental friendly catalyst and a new reaction route are required for the synthesis of me
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