Molybdenum Dioxide in Carbon Nanoreactors as a Catalytic Nanosponge for the Efficient Desulfurization of Liquid Fuels

Abstract

The principle of a "catalytic nanosponge" that combines the catalysis of organosulfur oxidation and sequestration of the products from reaction mixtures is demonstrated. Group VI metal oxide nanoparticles (CrO x , MoO x , WO x ) are embedded within hollow graphitized carbon nanofibers (GNFs), which act as nanoscale reaction vessels for oxidation reactions used in the decontamination of fuel. When immersed in a model liquid alkane fuel contaminated with organosulfur compounds (benzothiophene, dibenzothiophene, dimethyldibenzothiophene), it is found that MoO 2 @GNF nanoreactors, comprising 30 nm molybdenum dioxide nanoparticles grown within the channel of GNFs, show superior abilities toward oxidative desulfurization (ODS), affording over 98% sulfur removal at only 5.9 mol% catalyst loading. The role of the carbon nanoreactor in MoO 2 @GNF is to enhance the activity and stability of catalytic centers over at least 5 cycles. Surprisingly, the nanotube cavity can selectively absorb and remove the ODS products (sulfoxides and sulfones) from several model fuel systems. This effect is related to an adsorptive desulfurization (ADS) mechanism, which in combination with ODS within the same material, yields a "catalytic nanosponge" MoO 2 @GNF. This innovative ODS and ADS synergistic functionality negates the need for a solvent extraction step in fuel desulfurization and produces ultralow sulfur fuel.

Confined Heteropoly Blues in Defected Zr‐MOF (Bottle Around Ship) for High‐Efficiency Oxidative Desulfurization

“…POMs, in particular Keggin‐type POMs, have been reported to show remarkable ODS activity after incorporating with MOFs. [ 33–35 ] The Keggin‐type phosphomolybdate acid (PMA, H 3 PMo 12 O 40 , P/Mo = 1/12) itself shows certain ODS activity. PMA possesses four kinds of oxygen atoms (Figure 1b): the tetrahedral oxygen (O a ) coordinated with heteroatom P, the bridging oxygen (O b ) connected with different trimetallic clusters (Mo 3 O 10 ), the bridging oxygen (O c ) in the same trimetallic cluster (Mo 3 O 10 ), and the terminal oxygen (O d ).…”

Stereochemistry of Simple Molecules inside Nanotubes and Fullerenes: Unusual Behavior of Usual Systems

“…On the other hand, the calculated energy barrier for Cl − exchange in the S N 2 reaction within nanotubes was higher by 6.6 kcal/mol in comparison with the gas phase [69]. Later, it was shown that SWCNTs may be used as effective nanoreactors for preparative syntheses of inorganic [70] and organic [71][72][73][74][75] products with high yields; it is also possible to achieve enantiomeric excess of the products by using a racemic mixture of P and M enantiomers of (n,m) chiral nanotubes [76].…”

Preparation of WO3/CNT catalysts in presence of ionic liquid [C16mim]Cl and catalytic efficiency in oxidative desulfurization

“…Based on the advantages of ODS, various types of catalyst such as polyoxometalates, ionic liquids and metal oxides have been developed. Tungsten trioxide (WO 3 ) has been applied in various fields because of its acidic and thermal stability and good crystallinity .…”

“…During the process of ODS, organic sulfur compounds can be oxidized under mild conditions to sulfones or sulfoxides, which can be easily removed by polar extractants. 7,8 Based on the advantages of ODS, various types of catalyst such as polyoxometalates, 9,10 ionic liquids 11 and metal oxides 12,13 have been developed. Tungsten trioxide (WO 3 ) has been applied in various fields because of its acidic and thermal stability and good crystallinity.…”

“…[14][15][16][17] However, the activity of WO 3 in ODS applications is limited by its low specific surface area. Therefore numerous porous materials such as ZrO 2 , 18,19 TiO 2 , 13 SBA-15, 20 g-C 3 N 4 21 and Al 2 O 3 22 have been investigated to increase the catalytic activity of WO 3 in ODS. Although combining WO 3 with carbon nanotubes (CNT) has been reported, 23,24 most of these reports applied mainly to the field of electrochemistry, using WO 3 as an auxiliary agent to change the interaction between metals and carriers to increase the 3404 www.soci.org C Wang et al catalytic activity effectively.…”