Preparation, characterization, and catalytic activity of H5PMo10V2O40 immobilized on nitrogen-containing mesoporous carbon (PMo10V2/N-MC) for selective conversion of methanol to dimethoxymethane

Abstract

Nitrogen-containing mesoporous carbon (N-MC) was synthesized by a templating method using SBA-15 and polypyrrole as a templating agent and a carbon precursor, respectively. The N-MC was then modified to have a positive charge, and thus, to provide a site for the immobilization of [PMo 10 V 2 O 40 ] 5− . By taking advantage of the overall negative charge of [PMo 10 V 2 O 40 ] 5− , H 5 PMo 10 V 2 O 40 (PMo 10 V 2 ) catalyst was chemically immobilized on the N-MC support as a charge-matching component. Characterization results showed that nitrogen in the N-MC played an important role in forming a nitrogen-derived functional group (amine group), and PMo 10 V 2 catalyst was finely and chemically immobilized on the nitrogen-derived functional group of N-MC support. In the vapor-phase selective conversion of methanol, the PMo 10 V 2 /N-MC catalyst showed a higher conversion of methanol than the bulk PMo 10 V 2 catalyst. Furthermore, the PMo 10 V 2 /N-MC catalyst showed a higher selectivity for dimethoxymethane (a product formed by bifunctional oxidation-acid-acid catalysis) and a higher selectivity for methylformate (a product formed by bifunctional oxidation-acid-oxidation catalysis) than the PMo 10 V 2 catalyst. Reaction pathway for selective conversion of methanol to dimethoxymethane over PMo 10 V 2 /N-MC catalyst could be controlled by changing the methanol feed rate.

Use of Nitrogen-Containing Carbon Supports To Control the Acidity of Supported Heteropolyacid Model Catalysts

“…% nitrogen in N–C-1000 is not effective in reducing the acid activity, contrary to common belief that a small amount of nitrogen doped in carbon would significantly affect the support–HPA interaction. This has not been noted in previous literature, because most researchers have used unsupported HPAs as a benchmark to compare their catalysts. ,− Supports with higher nitrogen content (N–C-600 and mpgC 3 N 4 ), which have not been studied as supports for POMs before, produced much lower DME formation rate, regardless of coverage levels. mpgC 3 N 4 suppressed almost all of the acid activity to 2–3 orders of magnitude below that of C and N–C-1000.…”

“…Although some oxide supports have been reported to decompose HPAs, because of their basicity, there are successful cases in which intact HPAs are preserved on, for example, nitrogen-containing carbon supports. Amine-decorated carbon (N content = 1.7 wt % and 1.1 wt %), and carbon embedded with other N-containing species (e.g., pyridinic, graphitic nitrogen) (N content = 2 wt %, , 3.6 wt %, and 10.6 wt %) and nitrogen-containing polymers such as polyaniline (N content = 15 wt %) have been used as supports for HPAs. They have proven useful in isopropanol oxidation, ,,, methacrolein oxidation, methanol oxidation, and isopropanol decomposition, displaying, in all cases, a decrease in acid catalytic activity and enhanced oxidation activity, compared to unsupported HPAs.…”

“…Amine-decorated carbon (N content = 1.7 wt % and 1.1 wt %), and carbon embedded with other N-containing species (e.g., pyridinic, graphitic nitrogen) (N content = 2 wt %, , 3.6 wt %, and 10.6 wt %) and nitrogen-containing polymers such as polyaniline (N content = 15 wt %) have been used as supports for HPAs. They have proven useful in isopropanol oxidation, ,,, methacrolein oxidation, methanol oxidation, and isopropanol decomposition, displaying, in all cases, a decrease in acid catalytic activity and enhanced oxidation activity, compared to unsupported HPAs. While nitrogen appears to play an important role by neutralization of some acidity, thus promoting selective oxidation pathways, the nature of the HPA–support interaction is unclear.…”

Dimethoxymethane as a Cleaner Synthetic Fuel: Synthetic Methods, Catalysts, and Reaction Mechanism

“…Guo et al reported the same effect for SBA-15-supported H 3 PMo 12 O 40 . Kim et al explored N-doped mesoporous carbon as support to immobilize H 5 PMo 10 V 2 O 40 . DMM selectivity remained at medium level (50%) probably due to nonoptimized acidic and redox properties.…”

Processes for the production of oxymethylene ethers: promising synthetic diesel additives

“…While most studies for the direct synthesis of OME 1 were carried by means of the commonly available supports such as TiO 2 , N-doped mesoporous carbon was tested as a support. [44] However, the conclusion was not convinced due to the lack of comparable studies using carbon supports.…”