CN112108147A

CN112108147A - Platinum-manganese-based bimetallic catalyst for catalyzing ethylene oxide at low temperature

Info

Publication number: CN112108147A
Application number: CN202010958654.0A
Authority: CN
Inventors: 戴洪兴; 陈美琦; 刘雨溪; 邓积光; 敬林; 侯志全
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2020-09-13
Filing date: 2020-09-13
Publication date: 2020-12-22

Abstract

A platinum-manganese based bimetallic catalyst for low-temperature catalytic oxidation of ethylene belongs to the field of catalytic chemistry and environmental chemistry. Mixing Pt₂Mn bimetallic nanoparticle to TiO₂On a carrier, and then burning to form Pt-MnO_x/TiO₂A catalyst wherein the loading of metallic platinum was 1.6 wt% (mass fraction). The preparation method comprises the following steps: in oilIn an amine system, an oil phase reduction method is adopted to simultaneously reduce platinum acetylacetonate and manganese decacarbonyl to form Pt with uniform size₂Mn bimetallic particles, and loading the metal particles to TiO by dipping method₂On the support, the Pt loading was 1.6 wt% (mass fraction). Will load Pt₂The Mn catalyst is burned at 300 ℃ to form Pt-MnO_x/TiO₂And (3) a nano catalyst. Pt-MnO obtained by the invention_x/TiO₂The nano catalyst has uniform nano particle size and good application prospect in the field of catalysis.

Description

Platinum-manganese-based bimetallic catalyst for catalyzing ethylene oxide at low temperature

Technical Field

The invention relates to Pt-MnO_x/TiO₂A nano catalyst and a preparation method thereof, in particular to a method for preparing Pt with uniform size by adopting an oil phase reduction method₂Mn alloy particles supported on TiO by dipping₂Surface, subsequent burning to form Pt-MnO_x/TiO₂And (5) structure. Pt-MnO with high catalytic activity for ethylene oxidation_x/TiO₂A nano catalyst belongs to the field of catalytic chemistry and environmental chemistry.

Background

Ethylene is a small-molecular volatile organic compound, is one of the largest chemical products in the world, and is also the core of the petrochemical industry. Ethylene products play an important role in national economy. The yield of the petroleum has been taken as one of important marks for measuring the development level of the petrochemical industry in one country in the world. In industry, ethylene is a basic chemical raw material for synthetic fibers, synthetic rubbers, synthetic plastics (polyethylene and polyvinyl chloride), synthetic ethanol (alcohol), and is also used for the production of vinyl chloride, styrene, ethylene oxide, acetic acid, acetaldehyde, ethanol, explosives, and the like, and is also used as a ripener for fruits and vegetables. However, ethylene has a strong anesthetic effect, and a person loses consciousness immediately if inhaling a large amount of ethylene. And the ethylene causes pollution to water, soil and atmosphere, so that the elimination of the ethylene in the environment is necessary. And the fruits and vegetables can release ethylene in greenhouses and fruit and vegetable storage places, so that the fruits and vegetables are rotten. Thus, the elimination of ethylene at these locations is also of great commercial value.

With the development of catalytic technology and catalyst materials, a great deal of research work has been carried out on the complete oxidation of ethylene. Michaele et al (Z. Michaele, et al, [ J. ]]A.Marca, environ.Sci.Technol.,2000,34:5206), Keller et al (N.Keller,et al.,[J]Chem.rev,2013,133:5029) and Thomas et al (a.w.thomas, et al, [ J]J.phys.chem.c,2011,115:16537) photocatalytic oxidation of ethylene on titania-based materials was carried out in a continuous reactor. However, these reactions require complex working conditions and are less efficient at eliminating ethylene at or below room temperature. Further, in the above report, ozone was used as a strong oxidizing agent. However, excess of O₃Which causes secondary pollution and must be removed efficiently, this additional chemical process adds to the cost of industrial application.

Ahn et al (H.G.ahn, et al, [ J ]]Nanotechnol.2006,6:3599) preparation of Au/Co by deposition₃O₄Ethylene can be completely catalytically oxidized at 165 ℃. Li, etc. (W.C.Li, et al, [ J ]]Chem.eng.j.2016,293:243) supported Co oxide on mesoporous C spheres, completely catalyzing the oxidation of ethylene at 185 ℃. However, these reports show that the temperature of the complete ethylene oxide is too high to be commercially used. Kumar et al (D.Kumara, et al, [ J.)]Top.Catal.2007,46:169) Pd/SiO was determined using the kinetic equation₂Can completely catalyze and oxidize ethylene at 150-200 ℃.

Hao et al (Z.P.Hao, et al, [ J.)]J.Am.chem.Soc.2010,132:2608) loading Au on Co₃O₄Thereby realizing the complete catalytic oxidation of ethylene under low temperature. Fukuoka et al (a. Fukuoka, et al, [ J ]]Angew. chem. int. ed.2013,52:6265) reported that Pt nanoparticles supported on MCM-41 could completely catalyze the oxidation of ethylene at 0 ℃, but the stability was poor due to the tendency of carbon deposition on the catalyst surface.

To our knowledge, no literature reports on Pt₂Preparation of Pt-MnO from Mn nanocrystal_x/TiO₂The method of the catalyst and the research on the catalytic oxidation of ethylene.

Disclosure of Invention

The invention aims to provide Pt-MnO for catalyzing ethylene oxidation at high efficiency and low temperature_x/TiO₂A nano catalyst and a preparation method thereof, in particular to a method for preparing Pt by adopting an oil phase reduction method₂Mn nanocrystals prepared by impregnating Pt₂Mn nanocrystal loading to commercial TiO₂On a carrier, followed by burningFiring to form Pt-MnO_x/TiO₂。

The PtMn bimetal nanocrystal is characterized in that the prepared nanocrystal is uniform in size and uniform in dispersion, and the preparation method mainly comprises the following steps:

(1) feeding materials according to the molar ratio of metal platinum to manganese of 1: 2: weighing acetylacetone platinum, adding the acetylacetone platinum into a mixed solution consisting of benzyl ether, oleylamine and oleic acid, stirring for 5min, heating to 265 ℃ in a nitrogen protective atmosphere, stirring for 10min, and marking as a solution A, wherein each 0.10mmol of acetylacetone platinum corresponds to 5mL of benzyl ether, 3.68mL of oleylamine and 0.63mL of oleic acid; weighing decacarbonyl dimanganese, adding the decacarbonyl dimanganese into oleylamine, stirring until the decacarbonyl dimanganese is completely dissolved, and marking as a solution B, wherein each 0.10mmol of decacarbonyl dimanganese corresponds to 6mL of oleylamine; keeping the temperature of the solution A at 265 ℃ for 10min in a nitrogen atmosphere, dripping the solution B into the solution A, reacting for 1h at 265 ℃, cooling to room temperature, performing centrifugal separation, and washing twice with cyclohexane to obtain Pt with uniform size₂And (3) Mn bimetal nanocrystalline. And finally dispersing the nano particles obtained by centrifugation into cyclohexane for storage.

(2) The obtained Pt₂The Mn bimetal nanocrystalline is loaded on a carrier by adopting an isovolumetric impregnation method, and then the Pt-MnO is obtained through a burning process_x/TiO₂And (3) a nano catalyst. The method comprises the following specific steps:

calculating the required Pt content according to a certain load₂Amount of Mn bimetallic solution, adding certain amount of TiO₂The carrier is added to the measured cyclohexane solution containing the bimetallic nanocrystals. Stirring, dipping for 8h, and centrifuging to obtain the supported catalyst. Loading the obtained catalyst into a porcelain boat, placing the porcelain boat in a muffle furnace, raising the temperature from room temperature to 280-320 ℃, preferably 300 ℃ at the speed of 5 ℃/min, keeping the temperature for 6h, and reducing the temperature to room temperature to obtain Pt-MnO_x/TiO₂A catalyst.

Pt₂Mn nanocrystal loading to commercial TiO₂On a support, wherein Pt₂Mn nanocrystalline in TiO₂The loading on the carrier is 1.4 wt% to 1.8 wt%.

The catalyst obtained by the invention is used for C₂H₄Has excellent catalytic activity and stability。

At C₂H₄The catalyst has a T of 100ppm, an oxygen content of 20% and a space velocity of 20000mL/(g h)_90％(the reaction temperature required for 90% conversion of ethylene) was 45 ℃. And the conversion rate of 90% can be kept for more than 20 h.

The invention has the characteristics of uniform particle size of the nano particles, controllable size, simple preparation process and the like.

Pt-MnO prepared by the invention_x/TiO₂The catalyst has the characteristics of uniform bimetal particle size and good crystallinity, is in a high dispersion state on the surface of a carrier, and has good application prospect in the field of catalysis.

The crystal structure, particle morphology and catalytic oxidation activity of the obtained catalyst on ethylene were measured by using instruments such as a D8 ADVANCE type X-ray diffractometer (XRD), a JEOL-2010 type Transmission Electron Microscope (TEM) and shimadzu GC-2010 Gas Chromatography (GC). The results show that each catalyst prepared by the method of the invention has better crystallinity, Pt-MnO_xThe nano particles are in a high dispersion state on the surface of the carrier, and the catalytic oxidation activity and stability of the bimetallic supported catalyst to ethylene are obviously improved compared with those of a pure platinum catalyst.

Drawings

FIG. 1 shows Pt-MnO prepared_x/TiO₂And Pt/TiO₂XRD spectrum of the catalyst, wherein curves (a) and (b) are Pt and Pt, respectively₂XRD spectrogram of Mn nano particle, wherein (c) and (d) are Pt/TiO respectively₂And Pt-MnO_x/TiO₂XRD spectrum of (1);

FIG. 2 shows Pt-MnO prepared_x/TiO₂And Pt/TiO₂TEM photograph of the catalyst, in which FIGS. (A), (B), (C) and (D) are Pt, respectively₂Mn particles, Pt-MnO_x/TiO₂And Pt/TiO₂A TEM photograph of;

FIG. 3 shows Pt-MnO prepared_x/TiO₂And Pt/TiO₂Catalytic activity profile of the catalyst for ethylene oxidation.

FIG. 4 shows Pt-MnO prepared_x/TiO₂And Pt/TiO₂Catalytic stability profile of the catalyst for ethylene oxidation.

Detailed Description

The following examples are given for the purpose of illustration. To further explain the present invention, the present invention will be described with reference to the accompanying drawings to obtain Pt-MnO with excellent catalytic activity for ethylene oxidation_x/TiO₂A catalyst.

Example 1

(1) Feeding materials according to the molar ratio of metal platinum to manganese of 1: 2: 0.10mmol of platinum acetylacetonate is weighed and added to a mixed solution of 5mL of benzyl ether, 3.68mL of oleylamine and 0.63mL of oleic acid, stirred for 5min, heated to 265 ℃ under a nitrogen atmosphere and stirred for 10min, and the solution A is marked. 0.10mmol of manganous decacarbonyl was weighed into 6mL of oleylamine and stirred until completely dissolved, and was noted as solution B. Keeping the temperature of the solution A at 265 ℃ for 10min in a nitrogen atmosphere, dripping the solution B into the solution A, reacting for 1h at 265 ℃, cooling to room temperature, performing centrifugal separation, and washing twice with cyclohexane to obtain Pt with uniform size₂And (3) Mn bimetal nanocrystalline. And finally dispersing the nano particles obtained by centrifugation into cyclohexane for storage.

Or (1) preparing Pt nanoparticles by an oil phase reduction method: 0.10mmol of platinum acetylacetonate is weighed and added to a mixed solution of 5mL of benzyl ether, 3.68mL of oleylamine and 0.63mL of oleic acid, stirred for 5min, heated to 260 ℃ under a nitrogen atmosphere, and stirred for 10min, and the solution A is marked. 1.95mmol of borane tert-butylamine complex was weighed into 6mL of oleylamine and stirred until complete dissolution, denoted as solution B. And (3) keeping the temperature of the solution A at 260 ℃ for 10min in a nitrogen atmosphere, dripping the solution B into the solution A, reacting for 1h at 260 ℃, cooling to room temperature, performing centrifugal separation, and washing twice by using cyclohexane to obtain the Pt metal nano-crystal with uniform size. Finally dispersing the nano particles obtained by centrifugation into cyclohexane for storage

(2) The obtained Pt₂The Mn bimetal nanocrystal is loaded on a carrier by adopting an impregnation method, and then is subjected to a burning process to obtain Pt-MnO_x/TiO₂And (3) a nano catalyst. The method comprises the following specific steps:

calculating the required P content according to a certain loadt₂The amount of the Mn bimetallic solution and the Pt monometal solution is equal to that of TiO₂The carrier is added to the measured cyclohexane solution containing the metal nanocrystals. Stirring, dipping for 8h, and centrifuging to obtain the supported catalyst. Loading the obtained catalyst into a porcelain boat, placing in a muffle furnace, heating from room temperature to 300 deg.C at a rate of 5 deg.C/min, maintaining at the temperature for 6 hr, and cooling to room temperature to obtain Pt-MnO_x/TiO₂And Pt/TiO₂A catalyst. Pt₂Mn nanocrystalline in TiO₂The loading on the support was 1.6 wt%.

(3) At C₂H₄Pt-MnO under the reaction conditions of concentration of 100ppm, oxygen content of 20% and space velocity of 20000mL/(g h)_x/TiO₂T of catalyst_90％(the reaction temperature required for 90% conversion of ethylene) was 45 ℃. And can keep the conversion rate of 90 percent for more than 20 hours. Pt/TiO 2₂Catalyst T_90％(the reaction temperature required for 90% conversion of ethylene) was 55 ℃. And the conversion rate of 90% can be kept as long as 5 h.

Claims

1. Pt-MnO for catalyzing ethylene oxidation at high efficiency and low temperature_x/TiO₂The nano catalyst is characterized in that the Pt is prepared by adopting an oil phase reduction method₂Mn nanocrystals prepared by impregnating Pt₂Mn nanocrystal loading to commercial TiO₂On a carrier, and then burning to form Pt-MnO_x/TiO₂。

2. The Pt-MnO of claim 1 for high efficiency low temperature catalysis of ethylene oxidation_x/TiO₂Nano-catalyst, characterized in that Pt₂Mn nanocrystal loading to commercial TiO₂On a support, wherein Pt₂Mn nanocrystalline in TiO₂The loading on the carrier is 1.4 wt% to 1.8 wt%.

3. The Pt-MnO of claim 1 or 2 for high efficiency low temperature catalysis of ethylene oxidation_x/TiO₂The preparation method of the nano catalyst is characterized by comprising the following steps of:

(1) feeding materials according to the molar ratio of metal platinum to manganese of 1: 2: weighing acetylacetone platinum, adding the acetylacetone platinum into a mixed solution consisting of benzyl ether, oleylamine and oleic acid, stirring for 5min, heating to 265 ℃ in a nitrogen protective atmosphere, stirring for 10min, and marking as a solution A, wherein each 0.10mmol of acetylacetone platinum corresponds to 5mL of benzyl ether, 3.68mL of oleylamine and 0.63mL of oleic acid; weighing decacarbonyl dimanganese, adding the decacarbonyl dimanganese into oleylamine, stirring until the decacarbonyl dimanganese is completely dissolved, and marking as a solution B, wherein each 0.10mmol of decacarbonyl dimanganese corresponds to 6mL of oleylamine; keeping the temperature of the solution A at 265 ℃ for 10min in a nitrogen atmosphere, dripping the solution B into the solution A, reacting for 1h at 265 ℃, cooling to room temperature, performing centrifugal separation, and washing twice with cyclohexane to obtain Pt with uniform size₂Mn bimetallic nanocrystalline; finally dispersing the nano particles obtained by centrifugation into cyclohexane for storage;

(2) the obtained Pt₂The Mn bimetal nanocrystalline is loaded on a carrier by adopting an isovolumetric impregnation method, and then the Pt-MnO is obtained through a burning process_x/TiO₂A nano-catalyst; the method comprises the following specific steps:

4. The Pt-MnO of claim 1 or 2 for high efficiency low temperature catalysis of ethylene oxidation_x/TiO₂Use of nanocatalysts for C₂H₄Catalytic oxidation of (2).

5. Use according to claim 4 at C₂H₄The catalyst has a T of 100ppm, an oxygen content of 20% and a space velocity of 20000mL/(g h)_90％(reaction temperature required for 90% conversion of ethylene) was 45DEG C; and the conversion rate of 90% can be kept for more than 20 h.