In‐situ IR Spectroscopy Study of Reactions of C3 Oxygenates on Heteroatom (Sn, Mo, and W) doped BEA Zeolites and the Effect of Co‐adsorbed Water

Abstract

The reactions of acetone and hydroxyacetone over heteroatom doped BEA zeolites (Sn, Mo, and W) in the presence and absence of H2O vapor are investigated using infrared spectroscopy. Acetone is converted to mesityl oxide over Sn‐BEA exclusively. At higher temperatures, larger oxygenates such as phorones, aromatics, and coke form. The presence of co‐adsorbed water in Sn‐BEA suppresses tautomerization. H2O vapor is also beneficial for minimizing coke formation at high temperatures. Hydroxyacetone is converted into 2‐hydroxypropanal over Sn‐BEA, exhibiting high affinity to Sn sites up to 400 °C. Sn‐BEA catalyzes conversion of hydroxyacetone into the enol in the absence of H2O, but exposure to H2O induces the formation of 2‐hydroxypropanal and subsequent conversion to acrolein. The Lewis acid descriptors are used to rationalize the reaction pathways. For the isomerization of hydroxyacetone into 2‐hydroxypropanal, the hardness of acid sites influences the reaction and correlates with the overall Lewis acidity of the catalysts, respectively. However, the size of the exchanged metal significantly affects aldol condensation, where keto and enol forms of acetone adsorb to active sites simultaneously.

Surface Chemistry of Ketones and Diketones on Lewis Acidic γ-Al2O3 Probed by Infrared Spectroscopy

“…It is well-known that strong Lewis acid sites, such as those on γ-Al 2 O 3 , facilitate the aldol condensation of acetone into diacetone alcohol. 46 This intermediate then undergoes dehydration to form mesityl oxide (Scheme 1). While a further extent of aldol condensation to form phorone, isophorone, and mesitylene products is possible, 47 no IR bands affiliated with these species were observed.…”

“…The adsorption of acetone (Figure b) presents a very similar set of spectra as that of mesityl oxide. It is well-known that strong Lewis acid sites, such as those on γ-Al 2 O 3 , facilitate the aldol condensation of acetone into diacetone alcohol . This intermediate then undergoes dehydration to form mesityl oxide (Scheme ).…”

Efficient one-pot tandem catalysis of glucose into 1,1,2-trimethoxyethane over W-Beta catalysts

“…5 The related pyridine peak of Sn-Beta increased to 1452.1 cm −1 (Fig. S9†), indicating that the Lewis acid intensity was stronger in Sn-Beta than that in W-Beta catalysts, 37 which is also demonstrated by the reaction results at different temperatures (Table S6 and Fig. S10†).…”

Surface Interactions of Erythrose on Assorted Metal Oxides: A Solid-State NMR Study

“…The olefinic carbon can also be formed by keto–enol tautomerization. Tautomerization is an important step for retro-aldol condensation which has been observed for similar systems using solid Lewis acid catalysts, and enols are known to be stabilized on Lewis acid surfaces. − …”