Highly dispersed Cu supported on mesoporous Al‐KIT‐6 for oxidative carbonylation of methanol to dimethyl carbonate

Abstract

Microporous NaY zeolite is a common support of Cu catalysts for oxidative carbonylation of methanol, but the dispersion of Cu species on NaY is usually subjected to its micropore size. Here, ordered mesoporous KIT‐6 was employed as the support for Cu catalyst and Al was incorporated into its framework to increase the surface acidity, which eventually improves the surface exchange capacity and Cu dispersion. The evolution of the state of Cu species on KIT‐6 was analyzed combined with control of Cu loading. The physicochemical properties of the supports and corresponding catalysts were characterized by N2 adsorption–desorption, X‐ray diffraction, ammonia temperature programmed desorption, Fourier transform infrared spectra, transmission electron microscopy, hydrogen temperature programmed reduction, and X‐ray photoelectron spectroscopy. It was found that mesoporous KIT‐6 showed better Cu dispersion than microporous NaY zeolite. Agglomerated CuO, dispersed CuO, and Cu2+ are the major Cu species observed on the catalyst surface. The increased surface acidic sites of KIT‐6 by Al incorporation promoted the formation of Cu2+ and dispersion of CuO. With the increase in Cu loading, the Cu2+ content in the catalyst was decreased gradually along with increase in the bulk CuO. It was speculated that some exchanged Cu2+ could be transformed into highly dispersed CuO and even bulk CuO after calcination at a high Cu loading. Combined with the catalyst evaluation results, it was deduced that highly dispersed Cu2+ and CuO particles play significant roles in catalytic activity. The catalyst Cu/Al‐K‐10 achieved the highest space time yield of dimethyl carbonate of 135.4 mg/(g·h), which is 2.7 times the Cu/K‐10 owing to its more dispersed Cu species. This laid the basis for preparing highly dispersed Cu species on mesoporous silica supports.

Amorphous CeO2–Cu Heterostructure Enhances CO2 Electroreduction to Multicarbon Alcohols

“…The peaks centered at 936.4 and 955.7 eV, and the characteristic satellite peak, suggest the presence of Cu 2+ in the form of CuO. 28,29 The deconvoluted O 1s spectrum (Figure S5 in the Supporting Information) indicates that the spent CeO 2 −Cu sample surface contains different oxygen species. Specifically, the peaks located at 535.8 and 533.9 eV can be attributed to the oxygen groups in a Nafion binder 30 residual.…”

Unusual Copper Oxide Dispersion Achieved by Combining the Confinement Effect and Guest–Host Interaction Modulation

“…Because Al is introduced by direct synthesis, some Al should exist in the framework. The presence of framework bridging Si-OH-Al groups has been demonstrated by Yan et al using IR and NH 3 -TPD, which increases the number of acid sites in SBA-15. The introduction of Cu may break the −OH bonds and locate on the network oxygen with the formation of [Si-O-Cu-O-Al] groups .…”

“…A previous study indicates that the Al-doped SBA-15 with the Si/Al ratio of 22 is effective for Cu dispersion . By comparing the mesoporous silica doped with different amounts of Al (Si/Al = 5, 40, and 80), it was also reported that the sample with the Si/Al ratio of 40 is a good support for Cu dispersion . On the basis of these previous investigations, the material with the Si/Al ratio of 30 was thus selected.…”

“…25 By comparing the mesoporous silica doped with different amounts of Al (Si/Al = 5, 40, and 80), it was also reported that the sample with the Si/Al ratio of 40 is a good support for Cu dispersion. 26 On the basis of these previous investigations, the material with the Si/Al ratio of 30 was thus selected. The obtained product containing template before calcination was denoted as Al-AS.…”

Role of metal co‐cations in improving CuY zeolite performance for DMC synthesis: A theoretical study

“…[1][2][3][4][5] Recently, development of effective catalysts to produce DMC through oxidative carbonylation of methanol, which is thermodynamically favorable has received greater attention. [6][7][8][9][10][11][12][13][14][15][16][17][18] Being, chloride-free, CuY zeolite has shown greate potential to obtain high activity and excellent selectivity for oxidative carbonylation reaction. [16][17][18][19][20][21][22][23] Generally, Cu exchanged zeolite Y, CuY was prepared by ion-exchange of NaY zeolite with the ammonia solution of copper nitrate, followed by calcination at high temperatures in an inert atmosphere.…”