Patent Application
20100056360
Mesoporous materials have been used as catalytic support in chemical reactions. These materials are typically dispersed in liquid medium using slight agitation. However, after use, separation of the mesoporous materials after a chemical reaction and subsequent purification of products can be cumbersome.
Magnetic mesoporous materials as chemical catalyst and methods of making magnetic mesoporous materials as catalyst are provided. In one embodiment, a magnetic mesoporous material catalyst comprises a mesoporous material comprising mesopores, a chemical catalyst embedded in the mesopores, and magnetic nanoparticles trapped within walls of the mesoporous material.
The Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the components of the present disclosure, as generally described herein, and illustrated in the Figures, may be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.
In one embodiment, a method of making a magnetic mesoporous material catalyst is provided. A mesoporous material that includes mesopores can be employed in this method. The mesoporous material or mesoporous substrate can be a material containing mesopores having diameters from about 1 nm (nanometers) and 50 nm. In one embodiment, the mesopores can have diameters from about 2 nm and to about 10 nm. In some embodiments, the mesopores can have a variety of shapes including circles, hexagons, and etc. The mesopores of the mesoporous material can be generally uniform in size, but need not be substantially uniform. Moreover, the mesoporous material contains pores or gaps in addition to pores in the mesopore size range.
The magnetic nanoparticles can undergo a calcination process 5a to reduce surfactant coating on the surface. The calcination process 5a can include heating the magnetic nanoparticles at temperatures below the melting temperature of the magnetic nanopartcles. In one embodiment, the temperature during the calcination process 50 can be from about 200° C. to about 1500° C., such as about 300° C. to about 1000° C. or about 400° C. to about 900° C. The calcination process 5a can improve adhesion of the magnetic nanoparticles to walls of the mesoporous material by removing a surfactant coating on the surface of the magnetic nanoparticles. However, the magnetic nanoparticles can lose their magnetic property after the calcination process 5a. In some embodiments, the magnetic nanoparticles can be oxidized to metal oxides of the magnetic nanoparticles, such as from Fe3O4 to Fe2O3, during the calcination process 5a. The magnetic nanoparticles can regain their magnetic property after a latter heat-treatment process.
After the calcination process 5a, the magnetic nanoparticles can undergo a mixing process 5b with one or more precursors of the mesoporous material. The precursors can include a surfactant template (or a structure directing agent) and silica source. In some embodiments, the surfactant template includes an array of rods, sheets, spheres, or etc. The surfactant in the template can include quaternary alkyltrimethylammonium salts, poly tri-block copolymer, etc. In some embodiments, the silica source can include Tetraethyl orthosilicate (TEOS), sodium silicate, amorphous silica, and/or Kanemite. The mixing process 5b can comprise a variety of agitations with the magnetic nanoparticles and the precursors of the mesoporous material. In some embodiments, the mixing process 5b can be performed under hydrothermal conditions. In some embodiments, mixing can include sonication, shaking, swirling, etc. The precursors resulting mixture of precursors and magnetic nanoparticles can be reacted to form a mesoporous material in which the magnetic nanoparticles are trapped within the walls of the mesoporous material to form a magnetic mesoporous material.
After the magnetic nanoparticles are trapped within the walls of the mesoporous material, the magnetic nanoparticles can undergo a heat-treatment process 5c if necessary to regain their magnetic property that can be lost after the calcination process 5a. The heat-treatment process 5c can comprise heating and subsequently heat-treating the magnetic mesoporous material. In some embodiments, the heat-treatment process 5c comprises heating in air at temperature of from about 200° C. to about 1000° C., such as about 400° C. to about 600° C., and subsequently heating at temperature of from about 200° C. to about 2000° C., such as about 500° C. to about 900° C., under reducing atmosphere, such as atmosphere with H2 in a gas mixture with an inert gas, such as N2 or Ar. The percentage of H2 in the gas mixture in some embodiments is from about 1% to about 30% of the gas mixture, such as from about 10% to about 20% of the gas mixture. In some embodiments, heating the magnetic mesoporous material in air can remove surfactants in channels of the mesopores. In some embodiments, the heat-treatment process 5c can reduce the metal oxides of the previous magnetic nanoparticles to initial magnetic nanoparticles. In one embodiment, metal oxide Fe2O3 can be reduced to initial magnetic nanoparticle Fe3O4 during the heat-treatment process 5c.
A chemical catalyst addition process 5d of the magnetic mesoporous material can provide the magnetic mesoporous material catalyst. In some embodiments, the chemical addition process 5d can include depositing and trapping the chemical catalysts in the mesopores of the magnetic mesoporous material.
The magnetic mesoporous material catalyst can be added to one or more chemical reactants to perform a chemical reaction 5e. In one embodiment, the chemical reaction 5e can include providing reactants for the chemical reaction 5e, adding the magnetic mesoporous material catalyst, and conducting the chemical reaction 5e. The mesoporous material catalyst can perform catalysis during the chemical reaction 5e. In some embodiments, the chemical reaction can include organic reactions, hydrogenation, synthesis, analysis, substitution, metathesis, redox reactions, etc.
After the chemical reaction 5e, the magnetic mesoporous material catalyst can be removed to purify a chemical product. A separation process 5f can help isolation of the magnetic mesoporous material catalyst. The magnetic mesoporous material catalyst containing the magnetic nanoparticles can be separated by applying a magnetic field to the liquid medium containing the magnetic mesoporous material catalyst and the chemical product. In one embodiment, the applying of the magnetic field attracts the magnetic mesoporous material catalyst. In another embodiment the applying of the magnetic field repels the magnetic mesoporous material catalyst.
From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
