Methane Carbonylation with CO on Sulfated Zirconia:  Evidence from Solid-State NMR for the Selective Formation of Acetic Acid

Abstract

Using 13C and 1H solid-state NMR it has been shown, that methane can be carbonylated with carbon monoxide to give acetic acid on solid acid catalyst, sulfated zirconia. The carbonylation occurs at 473−573 K with high selectivity and essential conversion. The reaction proceeds both in the absence and in the presence of molecular oxygen. In the presence of oxygen, the catalyst can be used for the carbonylation of further portion of methane without reactivation in air. The mechanism of the reaction is discussed. The reaction observed opens up new possibilities of using sulfated zirconia-based solid catalysts for the synthesis of acetic acid from methane and carbon monoxide.

n-Butane conversion on sulfated zirconia: in situ 13C MAS NMR monitoring of the kinetics of the 13C-label scrambling and isomerization

“…On the contrary, for Pt-SZ catalysts and in the presence of H 2 , a monomolecular mechanism was proposed [3,7,9]. By means of in situ NMR monitoring of the isomerization of 13 C-labeled n-butane ([1) 13 C]-n-butane) on sulfated zirconia we observed a 13 C-label scrambling in the initial n-butane [8] in agreement with Adeeva et al [6] who applied GC-MS. This label scrambling shows the alkane activation on solid acids.…”

“…Two different mechanisms have been suggested for the isomerization of alkanes on SZ, one monomolecular [3,4] and the other bimolecular [4][5][6]. Recently published investigations of the 13 C-label distribution in the reaction product isobutane [7,8] confirmed earlier suggestions [4][5][6] that a bimolecular reaction mechanism is realized for the conversion of n-butane on pure sulfated zirconia. On the contrary, for Pt-SZ catalysts and in the presence of H 2 , a monomolecular mechanism was proposed [3,7,9].…”

“…The spectra were recorded as a function of time at temperatures of 291-323 K. The conversion of [1) 13 C]-n-butane on SZ can be described by the pathways shown in scheme 1. Here, A and B denote [1) 13 C]-n-butane and [2) 13 C]-n-butane, respectively, and C denotes a double 13 C-labeled isobutane [8].…”

“…The necessity to form a highenergetic primary isobutyl cation as intermediate or transition state during the isomerization of n-to isobutane via a monomolecular mechanism provides a possible explanation for the low rate constant in comparison with the 13 C-label scrambling in the initial n-butane [13]. However, it was unequivocally demonstrated in several studies that n-butane isomerizes on SZ via a bimolecular mechanism [6][7][8]. This implies that on SZ the monomolecular label scrambling in n-butane is faster than the bimolecular isomerization of n-to isobutane.…”

Understanding Methane Aromatization on a Zn‐Modified High‐Silica Zeolite

“…The latter species interacts with Zn-CH 3 to produce acetaldehyde (d = 31 ppm for CH 3 and d = 226 ppm for the carbonyl group, [7] Figure 3 a). At higher reaction temperatures, acetic acid (d = 22 ppm for CH 3 and d = 186 ppm for COOH [11] ) is formed as the result of the further oxidation of acetaldehyde (Figure 3 b). Finally, at 823 K, which is used for the co-conversion of propane and methane, the only 13 C-labeled product observed is carbon dioxide (d = 127 ppm, Figure 3 c) which is formed by decarboxylation of acetic acid.…”