Specificity of Sites within Eight-Membered Ring Zeolite Channels for Carbonylation of Methyls to Acetyls

Abstract

The acid-catalyzed formation of carbon-carbon bonds from C1 precursors via CO insertion into chemisorbed methyl groups occurs selectively within eight-membered ring (8-MR) zeolite channels. This elementary step controls catalytic carbonylation rates of dimethyl ether (DME) to methyl acetate. The number of O-H groups within 8-MR channels was measured by rigorous deconvolution of the infrared bands for O-H groups in cation-exchanged and acid forms of mordenite (M,H-MOR) and ferrierite (H-FER) after adsorption of basic probe molecules of varying size. DME carbonylation rates are proportional to the number of O-H groups within 8-MR channels. Na+ cations selectively replaced protons within 8-MR channels and led to a disproportionate decrease in carbonylation turnover rates (per total H+). These conclusions are consistent with the low or undetectable rates of carbonylation on zeolites without 8-MR channels (H-BEA, H-FAU, H-MFI). Such specificity of methyl reactivity upon confinement within small channels appears to be unprecedented in catalysis by microporous solids, which typically select reactions by size exclusion of bulkier transition states.

First metal complexes of 6,6′-dihydroxy-2,2′-bipyridine: from molecular wires to applications in carbonylation catalysis

“…The conversion of methylacetate was determined by 1 H NMR spectroscopy (see ESI) and the only product observed was acetic acid As can be seen from run 3 in Table 1, complex [Rh(1)(CO) 2 ]SbF 6 catalysis the carbonylation 10 reaction with a turnover frequency (TOF) of 180 mol methyl acetate per mol catalyst per hour. Comparative experiments using an unfunctionalised 2,2'-bipyridine ligand gave similar results (run 2) and both ligand-substituted catalysts are slightly less active compared to the industrially used 15 Monsanto catalyst (run 1). So far, these initial experiments do not indicate any special effects due to the acid-functionalised 6,6'-dihydroxy-2,2'-bipyridine ligand 1 under the reaction conditions used.…”

“…Metal complexes with bipy ligands have been prepared, probably of all metals known, and numerous variations on the basic ligand 15 framework have been made. [1][2][3] However, one remarkably simple derivative that has been elusive so far is 6,6'-dihydroxy-2,2'-bipyridine (1).…”

Dimethyl Ether Carbonylation to Methyl Acetate over Nanosized Mordenites

“…After being crystallized at 433 K for 7 days under stirring, the solid product was filtrated, washed with water, dried at 383 K for 12 h, and finally calcined at 823 K for 8 h in air. The obtained Na-MOR was converted to NH 4 -MOR through four sequential ion exchanges with a 1.0 M NH 4 NO 3 aqueous solution at 353 K for 12 h. 4 The sample was dried at 383 K for 12 h and calcined at 773 K for 3 h in air, yielding HMOR. The Cu-HMOR catalyst was prepared by incipient impregnation, in which case 4.0 g of NH 4 -MOR was suspended in 8 mL of 0.35 M Cu(NO 3 ) 2 aqueous solution at room temperature.…”

“…The obtained Na-MOR was converted to NH 4 -MOR through four sequential ion exchanges with a 1.0 M NH 4 NO 3 aqueous solution at 353 K for 12 h. 4 The sample was dried at 383 K for 12 h and calcined at 773 K for 3 h in air, yielding HMOR. The Cu-HMOR catalyst was prepared by incipient impregnation, in which case 4.0 g of NH 4 -MOR was suspended in 8 mL of 0.35 M Cu(NO 3 ) 2 aqueous solution at room temperature. After being allowed to dry at 383 K for 12 h, the resulting solid was calcined at 773 K in air for 3 h. To remove the external copper species, the sample was washed with a 0.05 M HNO 3 aqueous solution.…”

A Link between Reactivity and Local Structure in Acid Catalysis on Zeolites

“…These strong effects of spatial constraints also led to low reactivity in catalysts containing only 10-MR, 12-MR, or mesoscopic channels ( Figure 2). 29 Such specificity of CH 3 *-CO reactions upon confinement appears to be unprecedented in catalysis by zeolites.…”