KR100979106B1 - mesoporous MFI zeolite supporting metal oxides - Google Patents

Abstract

The present invention relates to a mesoporous zeolite having an MFI crystal structure in which a metal oxide is supported, and provides a zeolite having an MFI crystal structure in which a metal oxide is supported through the nanocarbon template and has metal mesopores.

In the present invention, a mesoporous MFI crystal structure zeolite carrying a metal oxide is synthesized by a direct synthesis method. In particular, since it is synthesized in the microwave irradiation environment, the process is simple and the metal oxide is uniformly distributed in the mesopores produced by using the nanocarbon as a template and shows more active points.

Mesopores generated in the zeolite crystals allow for rapid diffusion and delivery of materials, thus increasing the reaction rate in catalyst reactions, reducing side reactions, increasing selectivity, and extending catalyst life. Synthesis using nanocarbon under microwave can be applied to supporting other metal oxides and can be used as an industrial catalyst.

In the present invention, a nano-carbon was used to obtain a zeolite carrying a metal oxide with a single calcination, and a low cost metal salt was used to prepare a framework that can be economically prepared by reducing the synthesis time by microwave synthesis.

Metal Oxide, Mesoporous Zeolite, Directly Supported, Nanocarbon, Dehydrogenation, Microwave, Branched Alkylation

Description

Mesoporous zeolite with MFC crystal structure supported by metal oxides {mesoporous MFI zeolite supporting metal oxides}

The present invention relates to the direct synthesis of metal oxide-supported mesoporous zeolite catalysts, and more particularly, to mesoporous zeolites in which metal oxide nanoparticles are supported in mesopores in zeolite crystals. More particularly, the present invention relates to mesoporous zeolites having a MFI crystal structure in which metal oxides having catalytic activity in mesopores produced using nanocarbon particles as a template are directly supported in the process of zeolite synthesis.

Metal oxides are widely used in petrochemical, fine chemistry and biochemistry as important catalysts. In particular, nanoparticles of metal oxides are one of the important ways to increase the activity of the catalyst. In catalytic applications, metal oxide nanoparticles are used on substrates with high specific surface area to avoid aggregation problems.

Silica mesoporous materials (MCM-41, SBS-15), which have recently been studied a lot, have pore structures arranged in uniform pore sizes, which are widely used as supports for metal oxide nanoparticles, but have high thermal stability due to their low thermal stability. Supports for catalysts applied to gas phase reactions have disadvantages (F.-S. Xiao, Y. Han, Y. Yu, X. Meng, M. Yang, and S. Wu, J. am. Chem. Soc 124 (2002) 888).

Thermally stable zeolites have a micropore size of 3 to 12 microns, which results in a slow diffusion rate for the reactants and only allows small molecules to pass through.

In order to solve the disadvantages of the silica mesoporous body and the zeolite, many studies have been made to synthesize zeolite crystals having mesoporous. A typical example is the use of solid materials as templates.

Claus J.H. Jacobsen et al. (Claus J.H. Jacobsen et al. U.S. Pat.No. 6565826 (2003)) synthesized mesoporous zeolite crystals using practical and industrially feasible carbon nanoparticles as templates. Tao (Tao et al. PCT 03/104148 (2003)) et al. Synthesized zeolites with uniform mesopores using carbon aerosols. Claus J.H. Jacobsen calcined the nanocarbon to support the metal ligand compound in the mesoporous produced. They conclude that the mesopore of zeolite produced by using nanocarbon as a template can support a metal compound uniformly and stably. The supporting process is obtained by depositing a metal compound in mesoporous produced by calcination after synthesis and then calcining again.

Recently we have described 5% MgO (Sang-Eon Park et al Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, United States, April 6-10, 2008, PETR-113) and 14% TiO2-ZrO2 ( Mesoporous zeolite loaded with Sang-Eon Park, Catalysis today accepted) was synthesized by microwave using direct method and applied to catalysis. In addition, the synthesis by microwave reduces the reaction time, enables uniform heating, uniform nucleation, rapid condensation and selectivity of the structure, and makes it easy to control the size and shape of the particles (US Pat. No. 20010054549 (2001) .

The present invention is to provide a mesoporous zeolite in which a metal oxide is well dispersed and stably supported.

The present invention also provides a mesoporous zeolite on which a metal oxide is supported by a direct synthesis method using microwaves.

According to the present invention, there is provided a zeolite having an MFI crystal structure in which mesopores having a nanocarbon template and a metal oxide supported on the nanocarbon template are provided. In the present invention, the mesopore forms a nanocarbon, which is a solid material, as a template instead of a commonly used surfactant. In the present invention, the metal oxide is supported on the zeolite of the MFI crystal structure through the nanocarbon template. Preferably, when the nanocarbon is immersed in an aqueous metal ion solution and the pH is increased, the metal hydroxide is deposited on the nanocarbon using the nanocarbon as a seed. To start. Synthesizing zeolite by mixing zeolite precursor with nanocarbon deposited as metal hydroxide as a template and removing nanocarbon by calcination yields zeolite of MFI crystal structure in which metal oxide is evenly dispersed and supported. As shown in the above example, the term "metal oxide is supported through a nanocarbon template" means that a metal material is loaded on a nanocarbon used as a template to synthesize a zeolite, thereby introducing the metal into the zeolite structure and burning the template to remove the metal. It means that the material remains as an oxide in the mesoporous structure of the zeolite. The nanocarbon on which the zeolite precursor and the metal hydroxide are deposited is preferably subjected to the synthesis process in a microwave irradiation environment. The supported metal hydroxide is preferably Ti hydroxide, Zr hydroxide, Mg hydroxide or mixtures thereof. The amount of metal supported on the calcined final zeolite is preferably 0.1 to 25% by weight of the silica weight. If this range is not exceeded, catalytic activity falls and it is difficult to carry a metal oxide beyond this range.

The technique of the present invention is applicable to all zeolites that can be synthesized by microwave.

According to the present invention, a zeolite having an MFI crystal structure in which TiO 2 -ZrO 2 double oxide is supported is used as a catalyst having excellent performance in dehydrogenation of ethylbenzene.

In addition, according to the present invention, MgO-supported MFI crystal zeolite is used as a catalyst having excellent performance in branched alkylation.

The carbon used in the present invention is carbon in the form of nanoparticles, preferably the particle size is in the range of 5-20 nm, the specific surface area is in the range of 1000-2000 m ² / g and most preferably the particle size is 10-20 nm. And the BET surface area is around 1500 m ² / g. The weight ratio of the supported metal oxide to carbon is preferably in the range of 0.6-0.9. The weight ratio of metal to zeolite in the metal oxide in the final mesoporous zeolite is preferably 0.01-0.25.

In the method of obtaining a zeolite having an MFI crystal structure in which the metal oxide of the present invention is supported, first, nanocarbon is mixed with a metal ion solution and alkali is added to increase the pH, and then the metal hydroxide begins to be deposited using the nanocarbon as a nucleus. The nano-carbon on which the metal hydroxide is deposited is collected and heated with a zeolite precursor to obtain a zeolite in which the nano-carbon is dispersed and calcined at a high temperature to obtain a zeolite having an MFI crystal structure in which the metal oxide is evenly supported.

More specifically, the nano-carbon deposited with metal hydroxide is obtained by mixing the nanocarbon in a metal ion solution such as nitrate and chloride, and adjusting the pH with 5% ammonia water to deposit the hydroxide on the carbon surface. Preferably the metal ion concentration of the aqueous solution is 0.01-0.5 molar concentration and the pH range of the deposition finish is 9-14. The carbon-metal mixture of nanocarbons on which metal hydroxides are deposited is mixed with a zeolite synthetic solution and crystallized by heating for 30 to 120 minutes in a range of 130 to 170 degrees with microwave. The black crystalline mixture is preferably calcined once in the range of 400 to 600 ° C. to obtain mesoporous zeolite crystals carrying metal oxide nanoparticles. The size of the supported metal oxide nanoparticles is 5-50 nm.

The zeolite of the present invention is capable of rapid diffusion and transfer of materials due to mesopores in crystals, and is widely applied in the field of catalysts by metal oxides of nanoparticles which are uniformly distributed and supported. In particular, it is possible to extend the activity and service life of the catalyst in high temperature gas phase reaction.

The present invention will be described in detail by way of examples.

In the present invention, a mesoporous MFI crystal structure zeolite carrying a metal oxide is synthesized by direct synthesis. In particular, since it is directly synthesized in a microwave irradiation environment, the process is simple and the metal oxide is uniformly distributed in the mesopores produced by using the nanocarbon as a template and shows more active points.

The zeolite of the present invention supported with TiO 2 -ZrO 2 double oxide showed stable reactivity in the reaction process of 30 hours in the dehydrogenation reaction of ethylbenzene and the coke deposited on the catalyst was also significantly reduced. Zeolites of the present invention, supported with MgO, can also be used as catalysts for branched alkylation with optimal basicity.

Mesopores produced in zeolite crystals can be used for rapid diffusion and delivery of materials, resulting in faster reaction rates, lower side reactions, higher selectivity, and longer catalyst life. Direct synthesis using nanocarbon under microwave can be applied to supporting other metal oxides and can be used as an industrial catalyst.

In the present invention, the nano-carbon was used to support the metal oxide with one time of calcination to synthesize zeolite, and the economical efficiency was achieved by using a cheap metal salt and reducing the synthesis time by microwave synthesis.

The present invention is illustrated by the following examples. Synthesis methods, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, gas adsorption and desorption, and dehydrogenation of ethylbenzene to synthesize styrene monomer are described in detail.

Example 1

Metal hydroxide deposited Nanocarbon  Produce

In a 500 ml beaker, 6 g of 12 nm particle size and 200 ml of 1500 m ² / g specific surface carbon (BP-2000, Carbot Corp., USA) and 200 ml of ZrOCl2 and TiCl4 1.5 mM solution are stirred mechanically. Neutralize the pH of the solution to 10 with 5% aqueous ammonia. The deposited material is washed with distilled water to neutral. Dry in a 120 degree oven for 24 hours.

Mezzo  On zeolite TiO2 - ZrO2  Support of Double Metal Oxide Nanoparticles

30 g of 20% tetrapropylaluminum hydroxide ("TPAOH") solution is mixed with 30 g of distilled water and 15 g of TEOS and stirred at room temperature for 4 hours to obtain a clear solution. After the deposited nanocarbon was added and stirred for 1 hour, the microwave was kept at 165 degrees for 1 hour and the power was 300W. The crystallized product is filtered off, washed with distilled water and dried at 120 degrees. The template material is removed by calcining at 550 ° C for 6 hours.

Synthesized zeolite crystals (TZ / CS-1) were analyzed by X-ray diffractometer. Crystals of a typical MFI structure were synthesized (FIG. 1), and the crystal structure of the metal oxide was supported in the form of nanoparticles in the mesopores in the crystal, showing no diffraction reflection. The transmission electron microscope showed mesopores in the zeolite crystals and the TiO 2 and ZrO 2 supported therein were confirmed by EDX analysis (FIG. 2). Raman spectra show that the double oxide forms a new crystal structure (Figure 3). Temperature programmed desorption (TPD) analysis of NH3 and CO2 confirmed that more acid and base points of the supported nanoparticles appeared than before (FIG. 4 and FIG. 5).

Example 2

MgO  Nanoparticles Supported Mezzo  Preparation of Zeolite

Zeolite was synthesized using magnesium hydroxide-supported nanocarbon as a template according to Example 1, except that 200 ml of a magnesium nitrate solution of 0.5 mM was used instead of 200 ml of a 1.5 mM solution of ZrOCl2 and TiCl4.

The synthesized crystals can be seen as X-ray diffractometer and the MFI structure, and the MgO crystals do not show diffraction reflection because nanoparticles are supported in mesopores. Mesopores and supported MgO were confirmed by transmission electron microscopy. Temperature programmed desorption (TPD) analysis of CO 2 confirmed that the base point of the supported nanoparticles was more present than before (FIG. 6).

Example 3

In dehydrogenation of ethylbenzene To mezzo Supported TiO2 - ZrO2 Catalytic Reactivity Test of

0.5 g of the dehydrogenation catalyst prepared in Example 1 was charged into a fixed bed catalyst reactor made of 1-30 cm stainless steel with a size of 18-30 mesh, and then pretreated with nitrogen at 600 ° C. for 1 hour before reaction. Phosphorus alkylbenzene was reacted by passing the catalyst bed through a liquid injection pump under a stream of carbon dioxide. Alkylbenzene is injected using a metering pump, and carbon dioxide gas (20 ml / min) passing through the flow control unit is mixed with alkyl benzene (at a rate of 0.4 g / min), preheated to 200 ° C. in a preheater, and then 0.4 Inject at a rate of g / min. After the reaction, the reactants and products in the liquid phase were analyzed by a gas chromatograph (DS6200 dormant device) directly connected to the apparatus, and the results are shown in FIG. Ethylbenzene conversion and styrene yield were defined as follows.

% Ethylenebenzene conversion (%) = 100X {concentration of ethylbenzene injected-concentration of ethylbenzene remaining after reaction) / concentration of ethylbenzene injected}

Styrene yield (%) = 100X (concentration of styrene produced by reaction / concentration of ethylbenzene injected)

Example 4

0.5 g of the catalyst prepared in Example 2 was packed into a fixed bed catalyst reactor made of 1 cm stainless steel with an internal diameter of 18-30 mesh and then pretreated with nitrogen at 550 ° C. for 3 hours before reaction. At 500 degrees, reactants toluene and methanol were reacted by passing the catalyst bed through a liquid injection pump under a nitrogen stream at a molar ratio of 10: 1. The nitrogen gas passing through was mixed with the reactant, preheated to 150 ° C. in a preheater, and injected into the reactor at a rate of 0.4 g / min. After the reaction, the reactants and products in the liquid phase were analyzed by a gas chromatograph (DS6200 dormer) directly connected to the apparatus. The yield of C8 (ethylbenzene and styrene) was 8% at 2 hours of reaction (Figure 8). The C8 (ethylbenzene and styrene) yield is calculated as follows.

C8 yield (%) = 100X {(concentration of styrene produced by reaction + ethylbenzene concentration) / (concentration of methanol injected-concentration of methanol remaining after reaction)}

1 shows XRD patterns of (a) TiO ₂ , (b) ZrO ₂ , (c) TiO ₂ -ZrO ₂ , (d) CS-1 and (e) TZ / CS-1

Figure 2 shows (a) SEM image, (b) TEM image, (c) EDXS spectrum of white region in TEM image and (D) EDXZS spectrum of black region in TEM image of TZ / CS-1, respectively.

3 shows Raman spectra of (a) TiO ₂ , (b) ZrO ₂ , (c) TiO ₂ -ZrO ₂ , and (d) TZ / CS-1, respectively.

4 shows (a) TiO ₂ -ZrO _2, respectively. Bioxide and (b) NH ₃ of TZ / CS-1 TPD Profile

Figure 5 is respectively (a) TiO ₂ -ZrO ₂ of the double oxide and (b) TZ / CS-1 CO 2 TPD profile

Figure 6 shows CO ₂ TPD of a) MgO, b) CS-1, c) 1% MgO / CS-1 and d) 5% MgO / CS-1, respectively.

7 is a graph of conversion rate of dehydrogenation of ethylbenzene

8 is a graph of the yield and selectivity of toluene branched alkylation reaction on MgO catalyst

Claims (8)

Zeolite of MFI crystal structure having mesoporous as the template of carbon nanoparticles in the range of particle size 5-20 nm and metal oxide supported through the carbon nanoparticle template The zeolite having an MFI crystal structure according to claim 1, wherein a metal oxide is supported by using the carbon nanoparticles on which the metal hydroxide is deposited as a template. The zeolite of claim 2, wherein a Ti hydroxide, a Zr hydroxide, a hydroxide of Mg, or a mixture thereof is deposited on the surface of the carbon nanoparticles. 3. The zeolite of MFI crystal structure according to claim 2, wherein the amount of metal of the metal oxide supported on the final zeolite is 1-25% by weight of the silica weight. The MFI of claim 2, wherein the metal oxide obtained by synthesizing zeolite using carbon nanoparticles immersed in aqueous metal ion solution and raising pH to deposit the metal hydroxide as a template, and removing the carbon nanoparticles by calcination is supported. Zeolite with crystal structure The zeolite having an MFI crystal structure according to claim 5, wherein the carbon nanoparticles on which the metal hydroxide is deposited and the zeolite precursor are synthesized by applying a microwave and then calcined to carry a metal oxide. 4. The zeolite of MFI crystal structure according to claim 3, wherein the supported metal oxide is TiO2-ZrO2 double oxide and is used as a dehydrogenation catalyst of ethylbenzene. 4. The zeolite of MFI crystal structure according to claim 3, wherein the supported metal oxide is MgO and is used as a catalyst for branched alkylation.

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