Mechanistic Study of Selective Oxidation of Dimethyl Ether to Formaldehyde over Alumina-supported Molybdenum Oxide Catalyst

Abstract

XPS and IR spectroscopies were used to investigate the surface intermediates of dimethyl ether (DME) oxidation to formaldehyde over MoOx/Al 2 O 3 catalyst. The reaction performances were tested by employing three typical reaction conditions, depending on the O 2 /DME ratio and the reaction temperature. When there was sufficient oxygen present in the reaction media, a terminal or bridged CH 3 O* species formed by DME dissociation was highly active and rapidly reacted with lattice oxygen to produce formaldehyde, leading to higher selectivity of HCHO. When oxygen was consumed completely or only DME was present in the reaction media, CH 3 O species bonded to more than two Mo atoms ðl-OCH 3 Þ and CH x (x=1-3) species attached to the Mo atoms were observed and the relative ratio of ðl-OCH 3 Þ/Mo-CH x was significantly dependent on the reduction degree of MoO x domains. The ðl-CH 3 OÞ species was related to the formation of CH 3 OH or CO x , and the Mo-CH x species led to the formation of CH 4 .

Continuous Hydrothermal Decarboxylation of Fatty Acids and Their Derivatives into Liquid Hydrocarbons Using Mo/Al2O3 Catalyst

“…Thus, large increase in C on the spent catalyst indicates the deposition from the decarboxylation reaction. This C potentially may be bound with multiple Mo ions, which is hard to remove by simple hexane washing or vacuum drying . The existence of different states of Mo was also confirmed in the spent 10 wt % Mo–Al 2 O 3 catalyst using high-resolution XPS spectra (Figure b and Table S7).…”

“…This C potentially may be bound with multiple Mo ions, which is hard to remove by simple hexane washing or vacuum drying. 82 The existence of different states of Mo was also confirmed in the spent 10 wt % Mo−Al 2 O 3 catalyst using high-resolution XPS spectra (Figure 3b and Table S7). A higher percentage of Mo(IV) (77%) was found in spent sample compared to the fresh one (40%), whereas the Mo(VI) component was decreased from 51 to 11% and the Mo(V) amount remained relatively constant at 9−12%, respectively.…”

Efficient V2O5/TiO2 composite catalysts for dimethoxymethane synthesis from methanol selective oxidation

“…The pore volume of VTiAl increased slightly to 0.25 cm 3 g À1 compared with that of VTi sample (0.15 cm 3 g À1 ) while the number increased sharply to 0.55 cm 3 g À1 for VTiSi sample, which may favor the subsequent reaction. [37][38][39][40] Sample VTiSi had much more active oxygen than others. Table 2 showed the results of binding energies and peak tting results.…”

“…The binding energy around 530.8 eV was the characteristic of lattice oxygen species of TiO 2 and V 2 O 5 , and the binding energy at 532.3 eV could be attributed to active surface oxygen species, including surface oxygen of adsorbed oxygen species, weakly bonded oxygen and hydroxyl-like groups. [37][38][39][40] Sample VTiSi had much more active oxygen than others. The reference V2p 3/2 peak positions for V 2 O 5 and V 2 O 4 were around 517.4 and 516.3 eV, respectively.…”

Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethyl Ether Direct Oxidation over Carbon‐Based Catalysts

“…Recent advances in the synthesis of DME from syngasd erived from coal, biomass,a nd natural gas lead us to consider DME as ac heaper and less toxic raw materialf or the synthesis of high-value-addedc hemicals currently produced from methanol, such as DMMx, methyl formate (MF), dimethoxyethane (DMET),etc. [5][6][7][8][9][10][11][12] For the direct oxidation reaction of DMEt oD MMx, the challenge is not only to breakt he CÀOb ond of DME molecule,b ut also to maintain the stability of the CÀOb ondo fD MMx molecules. The whole reactionp rocess is quite complicated.…”