Micro and Nanobubble Based Strategy for Gas–Liquid–Solid Multiphase Reactions: Palladium-Catalysed Hydrogenation of Carbon–Carbon Unsaturated Bonds

Abstract

An autoclave-free, gas–liquid–solid multiphase hydrogenation of carbon–carbon unsaturated bonds using hydrogen micro and nanobubbles (MNBs) is developed. The process allows the liquid phase of the reaction mixture to maintain a high concentration of hydrogen gas.

Key words

gas–liquid–solid multiphase reactions - hydrogenation - micro and nanobubbles - heterogeneous catalysis - homogeneous catalysis

• References

• 1a The Handbook of Homogeneous Hydrogenation . de Vries JG, Elsevier CJ. Wiley-VCH; Weinheim: 2007
• 1b Klabunovskii E, Smith GV, Zsigmond A. Heterogeneous Enantioselective Hydrogenation: Theory and Practice . Springer; Dordrecht: 2006
• 2a Yoshida J.-I. Chem. Rec. 2010; 10: 332
• 2b Irfan M, Glasnov TN, Kappe CO. ChemSusChem 2011; 4: 300
• 2c Jones RV, Godorhazy L, Varga N, Szalay D, Urge L, Darvas F. J. Comb. Chem. 2006; 8: 110
• 2d Kobayashi J, Mori Y, Okamoto K, Akiyama R, Ueno M, Kitamori T, Kobayashi S. Science 2004; 304: 1305
• 3a Mase N, Mizumori T, Tatemoto Y. Chem. Commun. 2011; 47: 2086
• 3b Mase N, Mizumori T. Piping Engineering 2011; 53: 48
• 3c The preliminary results were discussed at the summer Symposium of the Japanese Society for Process Chemistry, Tokyo, Japan, 2010, 1P-32.
• 4 Wilhelm E, Battino R, Wilcock RJ. Chem. Rev. 1977; 77: 219
• 5 Typical procedure for the hydrogenation of unsaturated carbon–carbon bonds using the H₂-MNB strategy. The hydrogenation was carried out in a 100 mL vial equipped with an MNB generator without additional stirring. Alkene or alkyne 1 (20 mmol) was dissolved in MeOH (80 mL) and the soln warmed to 30 °C. Using the MNB generator (MA3-FS), H₂-MNBs were introduced into the reactor in the presence of palladium on alumina spheres (Pd/Al₂O₃) (0.5% Pd, 2–4 mm, 0.1 mmol, 0.5 mol%) at a H₂ flow rate of 5 mL/min. Aliquots were taken from the mixture periodically to monitor the reaction progress using GC analysis. After the completion of the hydrogenation reaction, the MeOH was evaporated in vacuo to afford the desired alkane 1 in excellent purity. We further examined the hydrogenation of styrene (1a) in the presence of the following heterogeneous catalysts: 5% Pd/C, 5% Pd/C E type, 5% Pd/C NX type, 5% Pd/C K type and 2.7 wt% Pd/C spheres, however, increasing back pressure then clogging of the flow system occurred during operation.
• 6a Crabtree R. Acc. Chem. Res. 1979; 12: 331
• 6b Crabtree RH, Davis MW. J. Org. Chem. 1986; 51: 2655
• 7 The preliminary results were discussed at the 42^nd Annual Meeting of the Union of Chemistry-Related Societies in Chubu Area, Nagano, Japan, 2011, 1P-08.
• 8 Preliminary experimental determinations of the average size (158 nm) and concentration (0.27 × 10⁸ particles/mL) of H₂ nanobubbles using the MA3-FS generator were performed using a NanoSight LM10-HS. On the other hand, no formation of H₂ nanobubbles was observed under standard bubbling or balloon conditions.