Application of m-in2o3 bifunctional catalyst in selective hydrogenation of 4,6-dinitroresorcinol

Abstract

The application provides application of a high-dispersion metal-oxide M-In2O3 bifunctional catalyst in a reaction of selective hydrogenation of 4,6-dinitroresorcinol into 4,6-diaminoresorcinol, and the catalyst is prepared by the following method: (1) preparing an indium precursor solution, then obtaining an indium hydroxide mixed solution by a precipitation method, and preparing a carrier In2O3 through filtration, washing, drying, calcination and reduction; (2) dispersing the carrier In2O3 in anhydrous ethanol, then depositing metal atoms M on the carrier In2O3 by using an atomic layer deposition technology (ALD), and obtaining the M-In2O3 bifunctional catalyst. The high-dispersion metal-oxide M-In2O3 bifunctional catalyst has higher 4,6-diaminoresorcinol selectivity, higher atomic utilization rate and higher catalytic activity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and in particular relates to application of a high-dispersion metal-oxide M-In2O3 bifunctional catalyst in a 4,6-dinitroresorcinol (DNR) selective hydrogenation reaction to 4,6-diaminoresorcinol (DAR). BACKGROUND

[0002] High-performance synthetic fiber poly-p-phenylene benzobisoxazole fiber (PBO) has a wide application prospect in the fields of new vehicles, aerospace, etc. due to its high mechanical strength, good flame resistance and other advantages. 4,6-diaminoresorcinol (DAR) is one of the important monomers for synthesizing PBO fiber, and selective hydrogenation of 4,6-dinitroresorcinol (DNR) is an important method for synthesizing DAR.

[0003] The DNR hydrogenation synthesis reaction is crucial for the large-scale production of PBO fiber, and therefore controllable preparation and performance regulation of the catalyst in the DNR hydrogenation synthesis DAR reaction are of great significance. The current DNR hydrogenation catalysts are mostly supported noble metal catalysts. Although the supported noble metal catalysts (such as commercial Pd / C catalyst) have high catalyst activity and can achieve high selectivity, the Pd-based catalysts have the disadvantage of easy deactivation. In addition, the noble metal catalysts are expensive, and reducing the usage amount of noble metal under the condition of achieving the same catalytic hydrogenation performance is also an important problem. Therefore, it is still a great challenge to prepare a DNR selective hydrogenation catalyst with high conversion rate, high selectivity, high stability and better economy.

[0004] The active site of a single-atom catalyst is isolated, stable and easy to separate, and has the advantages of homogeneous catalysis and heterogeneous catalysis. The single-atom catalyst anchors metal atoms through the interaction between the metal and the support, and can achieve higher metal atom exposure probability under the condition of the same metal usage amount compared to the supported catalyst, greatly improving the utilization rate of metal atoms. Therefore, the present application will start with the In2O3 support and use atomic layer deposition technology to deposit noble metals on the modified In2O3 support, aiming to achieve higher catalyst activity and higher DAR selectivity under the premise of lower noble metal usage amount. SUMMARY

[0005] The first object of the present application is to provide a preparation method of a high-dispersion metal-oxide M-In2O3 bifunctional catalyst. The prepared high-dispersion metal-oxide M-In2O3 bifunctional catalyst has the characteristics of high catalyst activity, high DNR conversion rate, high DAR selectivity and not easy to deactivate.

[0006] To achieve the above-mentioned objects, the technical solutions adopted by the present application are as follows:

[0007] A preparation method of a high-dispersion metal-oxide M-In2O3 bifunctional catalyst, comprising the following steps:

[0008] (1) preparing an indium precursor solution, then obtaining an indium hydroxide mixed solution by a precipitation method, and preparing a carrier In2O3 through filtration, washing, drying, calcination and reduction;

[0009] (2) dispersing the carrier In2O3 in anhydrous ethanol, and then depositing metal atoms M on the carrier In2O3 by using an atomic layer deposition technology (ALD) to obtain an M-In2O3 bifunctional catalyst;

[0010] In the step (1), the indium precursor is indium nitrate hydrate or indium chloride, the reaction temperature of the precipitation method is controlled to be 50-90℃, the drying temperature is controlled to be 60-100℃, and the drying time is 10-18h; the calcination temperature is controlled to be 400-700℃, and the calcination time is 2.5-4.5h; the reduction temperature is controlled to be 200-500℃, and the reduction time is 2-5h; in the step (2), the metal atoms M are one or both of Pt and Pd.

[0011] In the step (1), the preparation of the indium precursor solution is specifically the preparation of an indium precursor aqueous ethanol solution, which aims to dissolve the indium precursor. The applicant found that if the indium precursor is completely dissolved in anhydrous ethanol, part of the indium precursor will not be dissolved, but when an appropriate amount of water is added, the indium precursor can be well dissolved. Preferably, the mass-volume ratio of the indium precursor, ethanol and water is 1g:(1-5)mL:(5-15)mL.

[0012] In the step (1), the precipitation method is specifically adding an appropriate amount of an ammonia water and ethanol mixed solution to the indium precursor solution under stirring, and continuing to heat and stir until the reaction is complete to obtain a mixed solution containing indium hydroxide. In the present application, the mixed solution of ammonia water and ethanol is added, which has two advantages: first, the mixture can reduce the irritancy of ammonia water; second, it can ensure that the indium precursor is completely converted into indium hydroxide under the action of ammonia water to form a mixed solution containing indium hydroxide. Preferably, the mass-volume ratio of the indium precursor, 25wt% ammonia water and anhydrous ethanol is 1g:(1-10)mL:(5-20)mL.

[0013] In summary, the mass-volume ratio of ethanol, water contained in the reaction system of the indium precursor and the preparation of In2O3 carrier is 1g:(6-25)mL:(5-15)mL. The addition amount of ammonia water can be flexibly selected according to the concentration of ammonia water and the need to completely precipitate the indium. Good dissolution effect of the indium precursor is one of the prerequisites to ensure that the carrier In2O3 has a loose and porous and uniform indium oxide surface.

[0014] It should be noted that in the preparation process of the carrier In2O3 in step (1), the drying temperature must be controlled at 60-100℃, and the drying time is 10-18h, so as to ensure that the carrier In2O3 has good structure and ensure that the carrier In2O3 maintains good structural stability in the subsequent calcination process; at the same time, the calcination temperature must be controlled at 400-700℃, which can effectively ensure that the finally obtained carrier In2O3 has a loose and porous and uniform indium oxide surface, and has a large specific surface area, which provides a good basis for the anchoring of the metal M, and is one of the prerequisites for the subsequent high dispersion of the metal atom M on the carrier In2O3 by using atomic layer deposition technology (ALD).

[0015] The application further provides that in step (1), the reaction temperature of the precipitation method is controlled under water bath conditions, and the temperature of the water bath can be controlled at 50-90℃.

[0016] The application further provides that in step (1), the addition rate of the ammonia water and ethanol mixed solution is controlled at 1.0-6.0mL / min, the stirring rate is controlled at 150-300rpm / min, and the heat preservation and stirring time is 20-60min.

[0017] Preferably, in step (1), the reaction temperature of the precipitation method is controlled at 80℃, the addition rate of the ammonia water and ethanol mixed solution is controlled at 1.5mL / min, the stirring rate is controlled at 180rpm / min, and the heat preservation and stirring reaction time is 40min.

[0018] The application further provides that in step (1), the washing step is first washed with deionized water, and then washed with anhydrous ethanol; it should be noted that the washing step is first washed with deionized water, which can wash away the water-soluble impurities and ions contained in the indium hydroxide, and then washed with anhydrous ethanol, which can wash away the water and part of the residual impurities contained in the indium hydroxide. And because the boiling point of anhydrous ethanol is lower than that of water, it can ensure that the subsequent indium hydroxide can be dried at low temperature in a short time.

[0019] The application further provides that in step (1), in the calcination step, the heating rate of calcination is 5-10℃ / min; and the reduction condition is reduction in H2 atmosphere at 200-500℃ for 2-5h.

[0020] Preferably, in the step (1), the drying temperature is controlled at 80℃, and the drying time is 12h; the calcination temperature is controlled at 400℃, and the calcination time is 3h, and the heating rate of calcination is 5℃ / min; the reduction temperature is controlled at 300℃, and the reduction time is 2.5h.

[0021] Under the above conditions, the uniformity of the prepared In2O3 carrier can be effectively ensured, so as to ensure that the finally obtained In2O3 carrier has a loose and porous and uniform indium oxide surface.

[0022] The application further provides that, in the step (2), the specific step of dispersing the carrier In2O3 in anhydrous ethanol is to ultrasonically treat the carrier In2O3 in an appropriate amount of anhydrous ethanol to make it uniformly dispersed. Specifically, the ultrasonic treatment time is 25-60min, and the ultrasonic power is 25-100Hz. Preferably, in the step (2), ultrasonic dispersion is used, the ultrasonic treatment time is 30min, and the ultrasonic power is 53Hz.

[0023] The application further provides that, in the step (2), the M precursor for providing the metal atom M is respectively palladium hexafluoroacetylacetonate [Pd(hfac)2] and trimethyl(methylcyclopentadienyl)-platinum(IV) [MeCpPtMe3].

[0024] IV represents the valence state.

[0025] The application further provides that, in the step (2), the atomic layer deposition technology (ALD) used in the application is a prior art, which is based on surface self-saturation reaction to deposit Pt or Pd on the In2O3 carrier. First, the M precursor is heated to 65-75℃ to obtain sufficient vapor pressure, the substrate temperature is set to 200-300℃, and the inlet pipeline is kept above 110℃ to avoid condensation of the precursor. The ALD deposition process includes four steps, namely, M precursor pulse, nitrogen purging, ozone pulse and nitrogen purging. After the M precursor is exposed to ozone, other groups are oxidized and removed, and only the required M metal atom is loaded on the In2O3 carrier.

[0026] The application further provides that, in the step (2), Pt and Pd can be considered as supported metals, and those skilled in the art can select the deposition cycles, pulses and exposure time of ALD to obtain the required loading amount. Generally speaking, the more the deposition cycles, the higher the loading amount. Preferably, the deposition cycles are 1-10 cycles.

[0027] The application further provides that the loading amount of the metal atom M in the high-dispersion metal-oxide M-In2O3 bifunctional catalyst is 0.1wt%-7.0wt%, and the high-dispersion bifunctional M-In2O3 catalyst prepared under the above loading amount conditions has excellent catalytic activity.

[0028] Preferably, when the loading amount of the metal atom M is 1.0wt%-5.0wt%, excellent catalytic activity can be ensured, the loading amount of the metal atom M is small, the economic cost of the catalyst is reduced, and better economic benefits are obtained.

[0029] The second object of the application is to provide a high-dispersion metal-oxide M-In2O3 bifunctional catalyst prepared by the above preparation method of the high-dispersion metal-oxide M-In2O3 bifunctional catalyst, which has a large specific surface area and a loose and uniform In2O3 carrier, and Pt or Pd metal is deposited on the In2O3 carrier by using atomic layer deposition technology, so as to prepare a high-dispersion monatomic metal-oxide bifunctional catalyst M-In2O3.

[0030] The third object of the application is to provide the application of the above high-dispersion metal-oxide M-In2O3 bifunctional catalyst in the reaction of DNR selective hydrogenation to prepare DAR.

[0031] Preferably, the reaction conditions of the DNR selective hydrogenation to prepare DAR are as follows: methanol is used as the solvent, the reaction concentration is 0.1-0.8mg (DNR) / mL (methanol), the reaction temperature is 0-100℃, the reaction pressure is 0.2-1.0MPa H2, the stirring speed is 400-800rpm, and the reaction time is 2-12h.

[0032] Preferably, the reaction temperature of the DNR selective hydrogenation to prepare DAR is 5-80℃, and more preferably 30-50℃.

[0033] Compared with the prior art, the application has the following beneficial effects:

[0034] (1) The preparation method of the high-dispersion metal-oxide M-In2O3 bifunctional catalyst uses In2O3 which has certain selective hydrogenation catalytic activity as a carrier, DNR and H2 can be synergistically adsorbed and reacted on the carrier, and Pt and Pd atoms are stably anchored on the prepared carrier In2O3 by using the relatively mature atomic layer deposition technology. The preparation process is simple, the loading amount of the noble metals Pt and Pd is low, the cost is low, the metal dispersion is high, the atomic utilization rate is high, the atomic layer deposition technology has strong repeatability, and the performance of the catalyst product is more stable.

[0035] (2) Compared with the traditional supported catalyst, the metal is deposited on the oxide In2O3 by the ALD method, avoiding the metal particle agglomeration phenomenon caused by high-temperature calcination and high-temperature reduction in the traditional impregnation method. The metal dispersion of Pt and Pd in the high-dispersion bifunctional M-In2O3 catalyst is high, which can be uniformly dispersed on the surface of the catalyst in the form of single atom or small cluster, greatly improving the exposure area of noble metal atoms, reducing the amount of noble metal, and the catalyst is not easy to deactivate. At the same time, in addition to the high-dispersion metal atoms Pt and Pd can realize the activation of hydrogen and the subsequent hydrogenation reaction, the carrier In2O3 can also cooperatively perform selective hydrogenation to cooperatively realize higher selectivity. In the reaction of DNR selective hydrogenation to prepare DAR, the high-dispersion metal-oxide M-In2O3 bifunctional catalyst has higher DAR selectivity, higher atomic utilization rate and higher catalytic activity.

[0036] Therefore, the active metal atoms M are anchored on the metal oxide carrier In2O3 by using the atomic layer deposition technology, which on the one hand makes the metal atoms highly dispersed on the surface of the carrier In2O3, realizes the high dispersion effect, and improves the atomic utilization rate; on the other hand, the oxygen vacancies on the In2O3 and the special In2O3 active sites cooperatively realize the purpose of higher catalyst activity and higher DAR selectivity at a lower temperature, achieving the effect of the bifunctional catalyst. At the same time, the use amount of metal is reduced, the cost of the catalyst is reduced, and higher economic benefits are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The XRD comparison chart of the carrier In2O3A and the commercial In2O3 prepared in Example 1 is shown in the following figure.

[0038] Figure 2 The N2 physical adsorption chart of the carrier In2O3A and the commercial In2O3 prepared in Example 1 is shown in the following figure.

[0039] Figure 3 The XRD chart of Pt-In2O3 with different turns obtained in Examples 7, 11-13 is shown in the following figure. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be described in detail below with specific examples. It should be understood that the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples of the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of the present application. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as familiar to those skilled in the art.

[0041] Atomic layer deposition technology principle: atomic layer deposition (ALD) is a kind of chemical vapor thin film deposition technology based on order, surface self-saturation reaction, which is a method of forming thin film by alternately pulsing gaseous precursors into the reaction chamber and generating gas-solid phase chemical adsorption reaction on the surface of the deposition substrate.

[0042] The atomic layer deposition process is carried out by two half-reactions A and B in four basic steps: 1) precursor A exposure, pulse adsorption reaction; 2) inert gas purging of excess reactants and by-products; 3) precursor B exposure; 4) inert gas purging of excess reactants and by-products, then sequentially circulating to realize the layer-by-layer growth of thin film on the surface of the substrate (i.e. deposition substrate).

[0043] In the present application, the atomic layer deposition equipment model is D1004882 of Notus Technology Co., Ltd., and the atomic layer deposition is carried out according to its operation instruction. The main operation steps are:

[0044] (a) Start the reactor circulating water, open the N2 inert gas cylinder, confirm the raw material heating temperature and pipeline temperature in the reactor, and prevent condensation during the raw material transportation;

[0045] (b) The substrate dispersed in anhydrous ethanol by ultrasonic dispersion is coated on a glass plate, and after the ethanol is naturally volatilized, the glass plate is placed in the reactor for deposition;

[0046] (c) After M precursor exposure, pulse adsorption reaction, inert gas purging, one cycle of raw material deposition is completed, and then ozone exposure, inert gas purging. In this step, the reaction deposition cycle or pulse time and other parameter values can be adjusted according to the required film amount;

[0047] (d) After the reaction is completed, the glass sheet is taken out and cooled to room temperature, and the substrate on the glass sheet is collected with a scraper to obtain the required powder catalyst.

[0048] The operation parameters in the following examples are as follows: reactor temperature: 250℃, feed pipeline temperature: 150℃, tail gas pipe temperature: 80℃, and the rest of the operation parameters such as pulse time and deposition cycle number are determined by different catalysts.

[0049] In the following examples, the metal dispersion is measured by dynamic chemical adsorption method and hydrogen-oxygen titration.

[0050] Example 1, preparation of carrier In2O3A

[0051] The preparation of the carrier In2O3A of the present embodiment includes the following steps:

[0052] (a) 6 g of indium precursor, hydrated indium nitrate, was dissolved in 25 mL of anhydrous ethanol (purity > 99.8%) and 90 mL of deionized water, dissolved uniformly to obtain an indium precursor ethanol aqueous solution, which was stored in a reactor; 25 mL of 25 wt% ammonia water was mixed with 40 mL of anhydrous ethanol (purity > 99.8%) to obtain an ammonia water ethanol mixture; the reactor was placed in a water bath, the temperature of the water bath was controlled at 80°C, and then the ammonia water ethanol mixture was added to the indium precursor ethanol aqueous solution at a speed of 1.5 mL / min by means of a laminar flow pump under stirring at a speed of 180 rpm / min, and after the addition was completed, the reaction was continued for 40 min to ensure the reaction was complete, and an indium hydroxide-containing mixture was obtained.

[0053] (b) The indium hydroxide-containing mixture of step (a) was cooled to room temperature and filtered, and the obtained indium hydroxide was washed with deionized water for 3 times and then washed with an ethanol solution for 3 times, dried at 80°C for 12 h, and then calcined in a muffle furnace at 400°C for 3 h, with a calcination temperature rising rate of 5°C / min; the sample after calcination was reduced in a H2 atmosphere at 300°C for 2.5 h to obtain a light yellow indium oxide powder, which was named as carrier In2O3A.

[0054] The XRD comparison chart of the carrier In2O3A prepared in this example and commercial In2O3 is shown in Figure 1 , and the N2 physical adsorption and desorption curve of In2O3A and commercial In2O3 is shown in Figure 2 . As can be seen from Figure 1 , the XRD chart of the carrier In2O3A shows that the main diffraction peak positions appear at 2θ = 21.6°, 30.7°, 35.5°, 51.1°, 60.8°, which correspond to the diffraction peaks of (211), (222), (123), (440) and (622) crystal planes (JCPDS PDF #97-001-4387 / 97-064-0179) respectively. As can be seen from Figure 2 , the adsorption isotherm of the carrier In2O3A corresponds to the IV isotherm in the IUPAC standard, and it can be found that there is a clear hysteresis loop between the adsorption isotherm and the desorption isotherm, which is the result of capillary condensation, and usually occurs in mesoporous materials. The specific surface area of the carrier In2O3A is 66.0 m 2 / g, the pore volume is 0.50 cm 3 / g, and the average pore size is 30.2 nm. The specific surface area, pore volume and average pore size of the In2O3A synthesized in Example 1 are all greater than those of the commercial In2O3, thereby more effectively ensuring that the prepared carrier has a loose and porous indium oxide surface, which provides a good basis for anchoring metal atoms.

[0055] Example 2, preparation of carrier In2O3B

[0056] The preparation steps of the carrier In2O3B of this example are basically the same as those of Example 1, except that the calcination temperature in step (b) is 550°C, and the carrier In2O3B is obtained.

[0057] The adsorption-desorption curve of the carrier In2O3B prepared in this example is similar to that of In2O3A. The specific surface area of the carrier In2O3B is 55.40 m 2 / g, which is also greater than the specific surface area of the commercial In2O3.

[0058] Example 3, Preparation of carrier In2O3C

[0059] The preparation steps of the carrier In2O3C of this example are basically the same as those of Example 1, except that the calcination temperature in step (b) is 700°C, and the carrier In2O3C is obtained.

[0060] The adsorption-desorption curve of the carrier In2O3C prepared in this example is similar to that of In2O3A. The specific surface area of the carrier In2O3C is 50.20 m 2 / g, which is also greater than the specific surface area of the commercial In2O3.

[0061] Example 4, Preparation of carrier In2O3D

[0062] The preparation steps of the carrier In2O3D of this example are basically the same as those of Example 1, except that the drying temperature in step (b) is 60°C, and the carrier In2O3D is obtained.

[0063] The adsorption-desorption curve of the carrier In2O3D prepared in this example is similar to that of In2O3A. The specific surface area of the carrier In2O3D is 56.70 m 2 / g, which is also greater than the specific surface area of the commercial In2O3.

[0064] Example 5, Preparation of carrier In2O3E

[0065] The preparation steps of the carrier In2O3E of this example are basically the same as those of Example 1, except that the drying temperature in step (b) is 90°C, and the carrier In2O3E is obtained.

[0066] The adsorption-desorption curve of the carrier In2O3E prepared in this example is similar to that of In2O3A. The specific surface area of the carrier In2O3E is 52.10 m 2 / g, which is also greater than the specific surface area of the commercial In2O3.

[0067] Example 6, Preparation of carrier In2O3F

[0068] The preparation steps of the carrier In2O3F of this example are basically the same as those of Example 1, except that the drying temperature in step (b) is 100°C, and the carrier In2O3F is obtained.

[0069] The adsorption-desorption curve of the carrier In2O3F prepared in this example is similar to that of In2O3A. The specific surface area of the carrier In2O3F is 47.60 m 2 / g, which is also greater than that of the commercial In2O3.

[0070] In summary, when the drying temperature is 60-100°C and the calcination temperature is in the range of 400-700°C, the specific surface area of the carrier In2O3 prepared in Examples 1-6 is 47.60-66.00 m 2 / g.

[0071] Example 7, Preparation of Pt-In2O3 Catalyst

[0072] The preparation of the Pt-In2O3 catalyst of this example includes the following steps:

[0073] (A) 100 mg of the carrier In2O3A was added to 20 mL of anhydrous ethanol, and then ultrasonic treatment was carried out at room temperature for 30 min, with an ultrasonic power of 53 Hz, to obtain a uniformly dispersed dispersion liquid.

[0074] (B) The dispersion liquid obtained in step (A) was poured onto a quartz plate with a size of 80 mm x 80 mm x 2 mm, and after the liquid on the quartz plate was completely volatilized, atomic deposition of Pt was carried out using ALD technology. The precursor of metal Pt and the reducing agent used in the ALD technology were trimethyl(methylcyclopentadienyl)-platinum(IV) [MeCpPtMe3] and ozone, and ultra-high purity nitrogen was used as the carrier gas, with a flow rate of 50 mL / min. It was heated to 70°C to obtain sufficient vapor pressure, the substrate temperature was set to 250°C, and the inlet pipeline was kept at 150°C to avoid condensation of the precursor. After four steps of MeCpPtMe3 exposure, nitrogen blowing, ozone pulse and nitrogen blowing, the deposition cycle number was set to 1c, and the pulse time was set to 0.6 s, to obtain 0.6 s-Pt 1c -In2O3A catalyst.

[0075] The XRD spectrum of 0.6 s-Pt 1c -In2O3A is shown in FIG. 1. The XRD spectrum of 0.6 s-Pt Figure 3 1c -In2O3 is shown in FIG. 2. The XRD spectrum of 0.6 s-Pt 1c ​- The characteristic peaks of In2O3A can be attributed to the (211), (222), (440), (123) and (622) planes of In2O3 material, respectively. By comparing with the XRD standard card of Pt (JCPDS PDF#97-004-1525), it can be found that no diffraction peaks belonging to Pt nanoparticles are detected, indicating that the metal Pt has a high dispersion state on In2O3. The ICP detection shows that the Pt loading is 0.30%. The Pt dispersion is 55.10%.

[0076] Example 8, Preparation of Pt-In2O3 catalyst

[0077] The preparation steps of this example are basically the same as those of Example 7, except that in the atomic layer deposition step of step (B), the pulse time is 1.0 s, and 1.0 s-Pt is obtained. 1c - In2O3A catalyst. The ICP detection shows that the Pt loading is 0.52%. The Pt dispersion is 57.40%.

[0078] Example 9, Preparation of Pt-In2O3 catalyst

[0079] The preparation steps of this example are basically the same as those of Example 7, except that in the atomic layer deposition step of step (B), the pulse time is 2.0 s, and 2.0 s-Pt is obtained. 1c - In2O3A catalyst. The ICP detection shows that the Pt loading is 0.96%. The Pt dispersion is 66.30%.

[0080] Example 10, Preparation of Pt-In2O3 catalyst

[0081] The preparation steps of this example are basically the same as those of Example 7, except that in the atomic layer deposition step of step (B), the pulse time is 3.0 s, and 3.0 s-Pt is obtained. 1c - In2O3A catalyst. The ICP detection shows that the Pt loading is 1.18%. The Pt dispersion is 53.70%.

[0082] Example 11, Preparation of Pt-In2O3 catalyst

[0083] The preparation steps of this example are basically the same as those of Example 9, except that in the atomic layer deposition step of step (B), the deposition cycle number is set to 2c, and 2.0 s-Pt is obtained. 2c - In2O3A catalyst, whose XRD spectrum is shown in Figure 3 Pt 2c - In2O3. The ICP detection shows that the Pt loading is 1.5%, and the Pt dispersion is 50.70%.

[0084] Example 12, Preparation of Pt-In2O3 catalyst

[0085] The preparation steps of this example are basically the same as those of Example 9, except that in the atomic layer deposition step of step (B), the deposition cycle number is set to 5c, and 2.0s-Pt is obtained 5c The XRD spectrum of the In2O3A catalyst is shown in FIG. 2A. Figure 3 The Pt content in the In2O3A catalyst is shown in FIG. 2B. 5c The Pt loading is 3.62% and the Pt metal dispersion is 33.60% as detected by ICP.

[0086] Example 13, Preparation of Pt-In2O3 catalyst

[0087] The preparation steps of this example are basically the same as those of Example 9, except that in the atomic layer deposition step of step (B), the deposition cycle number is set to 10c, and 2.0s-Pt is obtained 10c The XRD spectrum of the In2O3A catalyst is shown in FIG. 2A. Figure 3 The Pt content in the In2O3A catalyst is shown in FIG. 2B. 10c The Pt loading is 3.62% and the Pt metal dispersion is 33.60% as detected by ICP.

[0088] Examples 14-18, Preparation of Pt-In2O3 catalyst

[0089] The preparation steps of Examples 14-18 are basically the same as those of Example 9, except that:

[0090] In Example 14, the carrier In2O3B is used in step (B) to obtain 2s-Pt 1c In2O3B catalyst;

[0091] In Example 15, the carrier In2O3C is used in step (B) to obtain 2s-Pt 1c In2O3C catalyst;

[0092] In Example 16, the carrier In2O3D is used in step (B) to obtain 2s-Pt 1c In2O3D catalyst;

[0093] In Example 17, the carrier In2O3E is used in step (B) to obtain 2s-Pt 1c In2O3E catalyst;

[0094] In Example 18, the carrier In2O3F is used in step (B) to obtain 2s-Pt 1c In2O3F catalyst.

[0095] Example 19, Preparation of Pd-In2O3 catalyst

[0096] The preparation steps of this example are basically the same as those of Example 9, except that in the atomic layer deposition step of step (B), palladium hexafluoroacetylacetonate [Pd(hfac)2] is used as the Pd precursor, heated to 70°C to obtain sufficient vapor pressure, and one ALD cycle is completed through the four steps of Pd(hfac)2 precursor exposure, nitrogen purging, ozone pulse, and nitrogen purging, the deposition cycle is set to 1c, the pulse time is 2s, and 2s-Pd is obtained. 1c The Pd loadings are 0.90% and the Pd metal dispersions are 65.20% for In2O3A catalysts.

[0097] Examples 20-24, Preparation of Pd-In2O3 catalyst

[0098] The preparation steps of Examples 20-24 are basically the same as those of Example 19, except that:

[0099] In2O3B is used as the carrier in step (B) of Example 20 to obtain 2s-Pd 1c In2O3B catalyst;

[0100] In2O3C is used as the carrier in step (B) of Example 21 to obtain 2s-Pd 1c In2O3C catalyst;

[0101] In2O3D is used as the carrier in step (B) of Example 22 to obtain 2s-Pd 1c In2O3D catalyst;

[0102] In2O3E is used as the carrier in step (B) of Example 23 to obtain 2s-Pd 1c In2O3E catalyst;

[0103] In2O3F is used as the carrier in step (B) of Example 24 to obtain 2s-Pd 1c In2O3F catalyst.

[0104] Example 25, Preparation of Pd-In2O3 catalyst

[0105] The preparation steps of this example are basically the same as those of Example 19, except that in the atomic layer deposition step of step (B), the deposition cycle is changed from 1c to 2c to obtain 2.0s-Pd 2c The Pd loadings are 1.64% and the Pd metal dispersion is 53.2% for In2O3A catalysts.

[0106] Example 26, Preparation of Pd-In2O3 catalyst

[0107] The preparation steps of this example are basically the same as those of Example 19, except that in the atomic layer deposition step of step (B), the deposition cycle is changed from 1c to 5c, to obtain 2.0s-Pd 5c The Pd loading is 3.38% and the Pd metal dispersion is 38.4% for the In2O3A catalyst, as determined by ICP.

[0108] Example 27, Preparation of Pd-In2O3 catalyst

[0109] The preparation steps of this example are basically the same as those of Example 19, except that in the atomic layer deposition step of step (B), the deposition cycle is changed from 1c to 10c, to obtain 2.0s-Pd 10c The Pd loading is 6.95% and the Pd metal dispersion is 25.4% for the In2O3A catalyst, as determined by ICP.

[0110] Comparative Example 1, Preparation of Pt-In2O3 catalyst by equal volume impregnation method

[0111] An equal volume impregnation method was used to load 0.96wt% of metal Pt on the In2O3A support. The specific steps are as follows:

[0112] (1) 3.944g of the support In2O3A was weighed and dried at 120°C for 2 hours before use;

[0113] (2) 0.08g of chloroplatinic acid solution was weighed and dissolved in 4mL of deionized water, and then added dropwise to the support In2O3A while stirring, to obtain a toothpaste-like impregnation mixture.

[0114] (3) The impregnation mixture was aged at room temperature for 12 hours, and then transferred to a 120°C oven for drying for 12 hours to remove water. The dried powder sample was calcined in a 300°C muffle furnace for 2 hours and then the temperature was increased to 400°C for calcination for 2 hours. After calcination was completed, the sample was cooled to room temperature, ground and sieved (200 mesh) to obtain the Pt-In2O3 catalyst prepared by the impregnation method.

[0115] Comparative Example 2, Preparation of Pt-CNT catalyst

[0116] The preparation steps of this example are basically the same as those of Example 9, except that the support carbon nanotube CNT is used instead of the support In2O3A.

[0117] Comparative Example 3, Preparation of Pd-CNT catalyst

[0118] The preparation steps of this example are basically the same as those of Example 18, except that the carrier carbon nanotube CNT is used instead of the carrier In2O3A.

[0119] Example 28, evaluation of catalytic performance

[0120] The high-dispersion metal-oxide M-In2O3 bifunctional catalysts prepared in Examples 7-27 are used to evaluate the catalytic hydrogenation activity of DNR; the DNR hydrogenation reaction performance evaluation is carried out in a hydrogenation reaction kettle of a rock instrument, the reaction is carried out with methanol as the solvent, the reaction concentration is 0.1-0.8 mg (DNR) / mL (methanol), the reaction temperature is 0-100°C, the reaction pressure is 0.2-1.0 MPa H2, the stirring speed is 400-800 rpm, and the reaction time is 2-12 h.

[0121] The specific steps are as follows: 60 mL of DNR solution is added to the inner container of a 100 mL reaction kettle, the gas tightness of the equipment is tested by repeatedly introducing argon before the reaction starts, then the temperature is raised to the required reaction temperature in an inert gas atmosphere, and after the temperature is stable, the inert gas is replaced with 0.2-1.0 MPa of hydrogen, and the stirring speed is set. At this moment, the reaction starts, the temperature and pressure are maintained constant, and about 1 mL is taken out at 0, 10, 20, 30, 60, 90, 120, 150, 180, 210 and 240 min. The components in the reactants and products are analyzed by Waters UPLC ultra-high performance liquid chromatography.

[0122] The DNR conversion rate C of the high-dispersion bifunctional M-In2O3 catalysts prepared in Examples 7-27 is tested DNR , the intermediate ANR selectivity S ANR , and the product DAR selectivity S DAR The catalytic performance of the catalysts of the present application for the selective hydrogenation of DNR to prepare DAR is evaluated by testing the DNR conversion rate C

[0123]

[0124]

[0125]

[0126] Table 1, evaluation results of high-dispersion bifunctional Pt-In2O3 catalysts for the selective hydrogenation of DNR to prepare DAR

[0127]

[0128]

[0129] As can be seen from the data in Table 1, the In2O3 prepared in the application has certain catalytic activity under the conditions of calcination temperature of 400-700℃ and drying temperature of 60-100℃, but the catalytic activity is poor. The conversion rate of DNR is all below 80%, most of the raw materials converted are at the intermediate ANR stage, the second nitro group is difficult to continue hydrogenation, and therefore the selectivity of the target product DAR still maintains at a low level, all less than 20%. Therefore, in order to solve the difficulty in DAR production, the In2O3 carrier needs to be modified to find a catalyst with high catalytic activity and high selectivity.

[0130] As can be seen from the comparison of Examples 7-10, when the deposition circle number is one, the high dispersion bifunctional Pt-In2O3 catalyst prepared by adjusting the pulse time in the range of 0.6-3s can achieve 100% DNR conversion rate under the reaction condition of 30℃, and the DAR selectivity is in the range of 86.8%-90.75%. It can be seen that the selectivity of the target product is greatly improved after the indium oxide carrier is modified with Pt. It is found by comparison that when the pulse time is 2s, the DAR selectivity is the highest, which can reach 90.75%, which may be related to the higher metal dispersion of the synthesized high dispersion Pt-In2O3 bifunctional catalyst.

[0131] As can be seen from the comparison of Examples 9, 11-13, when the pulse time is kept at 2s, the high dispersion bifunctional Pt-In2O3 catalyst prepared by changing the deposition circle number to 1c, 2c, 5c and 10c can achieve 100% DNR conversion rate, and at the same time has a higher DAR selectivity in the range of 85.73%-90.82%. And with the increase of the deposition circle number, the DAR selectivity is gradually decreased, which may be due to the change of the Pt species from single atom to cluster with the increase of the deposition circle number, thereby causing the change of the geometric structure and electronic structure of the catalyst, and further affecting the reaction performance of the catalyst. It can be found that the metal dispersion is the best when the deposition circle number is 1c, which is 66.30%.

[0132] As can be seen from Examples 9, 14-18, when the pulse time is 2s and the deposition circle number of Pt is 1c, by changing the carrier to In2O3A, In2O3B, In2O3C, In2O3D, In2O3E and In2O3F (the drying temperature and calcination temperature during the preparation of In2O3 are different), the DAR selectivity is very high, which is 88.40%-90.75%, and the DNR conversion rate is 100%. When the carrier is In2O3A, the metal dispersion of the high dispersion bifunctional Pt-In2O3 catalyst is the best, which is 66.30%, and the DAR selectivity is the highest, which is 90.75%.

[0133] Compared with Comparative Example 1, the catalyst with 0.96wt% Pt supported on In2O3A using equal volume impregnation method and chloroplatinic acid as Pt precursor, the Pt-In2O3 catalyst prepared by atomic layer deposition technology has higher metal dispersion, and when used in the reaction of DNR selective hydrogenation to prepare DAR, the high dispersion bifunctional Pt-In2O3 catalyst prepared by atomic layer deposition in the application has higher catalytic activity and DAR selectivity.

[0134] Compared with Comparative Example 2, the Pt-CNT catalyst is prepared by using loose and porous carbon nanotubes CNT as the carrier for atomic layer deposition, and the Pt-In2O3 catalyst prepared by atomic layer deposition technology in the application has higher metal dispersion, and when used in the reaction of DNR selective hydrogenation to prepare DAR, the high dispersion bifunctional Pt-In2O3 catalyst prepared by atomic layer deposition in the application has higher catalytic activity and DAR selectivity.

[0135] Table 2, evaluation results of high dispersion bifunctional Pd-In2O3 catalyst for DNR selective hydrogenation to prepare DAR

[0136]

[0137]

[0138] From the data of Examples 19-24 in Table 2, it can be seen that the metal dispersion of the Pd-In2O3 catalyst in the application is high, when the deposition cycle is set to 1c and the pulse time is 2s, the carrier is changed to In2O3A, In2O3B, In2O3C, In2O3D, In2O3E and In2O3F, and when the loading amount is 0.88%-0.95%, the metal dispersion is in the range of 59.61%-65.20%, the conversion rate of DNR can reach 100%, and the DAR selectivity is 86.29%-88.63%.

[0139] The Pd-In2O3 catalyst of Example 19 has a conversion rate of 100% at 15℃, but due to the low reaction temperature, the selectivity of DAR is only 57.63% after 240min of reaction, and a large amount of substances remain in the ANR stage. At 50℃, the conversion rate of DNR can reach 100%, and the selectivity of DAR is 85.23%. The above results show that in the range of 30-50℃, the high dispersion bifunctional Pd-In2O3 catalyst prepared in the application has good catalytic activity and DAR selectivity.

[0140] From the data of examples 19, 25-27, it can be seen that when the pulse time is kept constant at 2s, the DNR conversion rate of the high dispersion bifunctional Pd-In2O3 catalyst prepared by changing the deposition cycle to 1c, 2c, 5c and 10c can all reach 100%, and at the same time has a high DAR selectivity in the range of 84.92%-87.98%. And with the increase of the deposition cycle, the selectivity of DAR is gradually decreasing, it is speculated that due to the increase of the deposition cycle, the form of Pd species changes from single atom to cluster, thereby causing the change of the geometric structure and electronic structure of the catalyst, thereby further affecting the reaction performance of the catalyst. It can be found that the metal dispersion of 1c is the best, which is 65.20%, and the DAR selectivity of this group of catalysts is also the best, which is 87.98%.

[0141] Compared with comparative example 3, carbon nanotubes CNT are used as atomic layer deposition carriers to prepare Pd-CNT catalysts, and the metal dispersion of the Pd-In2O3 catalyst prepared by the atomic layer deposition technology in the application is higher. When it is used in the DNR selective hydrogenation reaction to prepare DAR, the high dispersion bifunctional Pd-In2O3 catalyst prepared by the atomic layer deposition in the application has higher catalytic activity and DAR selectivity.

[0142] Compared with the carrier In2O3, the Pd-In2O3 catalyst prepared by loading metal Pd atoms on the carrier In2O3 by the atomic layer deposition technology in the application has the characteristics of high dispersion bifunctionality. When it is used in the DNR hydrogenation reaction, the selectivity of DAR is 84.92%-88.63% in the range of 30-50℃, and at the same time has a 100% DNR conversion rate, and has high catalytic activity.

[0143] As can be easily understood by those skilled in the art, under the same other catalytic conditions, the high dispersion metal-oxide M-In2O3 bifunctional catalyst prepared in the application has higher DAR selectivity compared with the conventional Pt-based catalyst or Pd-based catalyst, because a small amount of metal atoms M is introduced into the oxide by the atomic layer deposition method, avoiding the metal particle agglomeration phenomenon caused by the conventional method.

[0144] In summary, the high dispersion metal-oxide M-In2O3 bifunctional catalyst of the application has very excellent catalytic activity and high DAR selectivity, the cost of preparing the high dispersion metal-oxide M-In2O3 bifunctional catalyst of the application is significantly reduced, which is more conducive to the industrial application of M-based catalysts, and at the same time provides a way for the model study of the bifunctional metal-oxide M-In2O3 catalyst.

[0145] Example 29, stability evaluation of the catalyst

[0146] In order to verify the accuracy of the embodiments of the present application and evaluate the stability of the high-dispersion metal-oxide M-In2O3 bifunctional catalyst of the present application, the DNR selective hydrogenation to prepare DAR was evaluated by using the Pt-In2O3 catalyst with a loading of 7.08% in Example 13 and the Pd-In2O3 catalyst with a loading of 6.95% in Example 27. In this example, the reaction temperature was set to 30℃, the reaction time was 240 min, and the catalyst and product at the end of the reaction were separated by centrifugal washing and then were continuously put into the next batch of reaction under the same conditions for five cycles. The data results are shown in Tables 3 and 4:

[0147] Table 3: Stability evaluation of high-dispersion bifunctional Pt-In2O3 catalyst

[0148] Cycle number DNR conversion / % DAR selectivity / % 1 100 85.73 2 100 85.20 3 100 83.43 4 100 82.20 5 100 81.19

[0149] Table 4: Stability evaluation of high-dispersion bifunctional Pd-In2O3 catalyst

[0150]

[0151]

[0152] The DNR selective hydrogenation to prepare DAR was evaluated by using the Pt-In2O3 catalyst with a loading of 7.08% in Example 13 and the Pd-In2O3 catalyst with a loading of 6.95% in Example 27. After 240 min of reaction, the conversion rate of DNR was 100%, and the selectivity was 85.73% and 84.92%, respectively. After the catalyst and reactants at the end of the reaction were centrifugally washed and then were put into a new reaction, the selectivity of DAR was 81.19% and 80.83%, respectively, after 5 cycles, indicating that the catalyst had good catalyst stability.

[0153] The above results show that the high-dispersion metal-oxide M-In2O3 bifunctional catalyst of the present application has good stability.

[0154] The present application is described in detail, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application, and any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. Use of a highly dispersed metal-oxide M-In2O3 bifunctional catalyst in the reaction of selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, The high-dispersed metal-oxide M-In2O3 bifunctional catalyst is prepared by a preparation method comprising the following steps: (1) preparing an indium precursor solution, then obtaining an indium hydroxide mixed solution by a precipitation method, and preparing a carrier In2O3 by filtration, washing, drying, calcination and reduction; (2) dispersing the carrier In2O3 in anhydrous ethanol, and then depositing metal atoms M on the carrier In2O3 by an atomic layer deposition technology (ALD) to obtain a M-In2O3 bifunctional catalyst; In the step (1), the indium precursor is indium nitrate hydrate or indium chloride, the drying temperature is controlled to be 60-100 ℃, and the drying time is 10-18 h; the calcination temperature is controlled to be 400-700 ℃, and the calcination time is 2.5-4.5 h; the reduction condition is reduction in H2 atmosphere at 200-500 ℃ for 2-5 h; in the step (2), the metal atom M is one or both of Pt and Pd. The reaction conditions for selectively hydrogenating 4,6-dinitroresorcinol to 4,6-diaminoresorcinol are as follows: methanol is used as the solvent, the concentration of 4,6-dinitroresorcinol is 0.1-0.8 mg / mL, the reaction temperature is 0-100 ℃, the reaction pressure is 0.2-1.0 MPa H2, the stirring speed is 400-800 rpm, and the reaction time is 2-12 h.

2. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 1 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the step (1), the preparation of the indium precursor solution is the preparation of an indium precursor aqueous ethanol solution; and the precipitation method is adding an ammonia water-ethanol mixed solution to the indium precursor solution under stirring, and continuing to heat and stir until the reaction is complete to obtain a mixed solution containing indium hydroxide.

3. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 2 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the step (1), the reaction temperature of the precipitation method is controlled to be 50-90 ℃, the addition rate of the ammonia water-ethanol mixed solution is controlled to be 1.0-6.0 mL / min, the stirring speed is controlled to be 150-300 rpm / min, and the heat and stirring time is controlled to be 20-60 min.

4. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 2 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the step (1), the reaction temperature of the precipitation method is controlled to be 80 ℃, the addition rate of the ammonia water-ethanol mixed solution is controlled to be 1.5 mL / min, the stirring speed is controlled to be 180 rpm / min, and the heat and stirring time is controlled to be 40 min.

5. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 1 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the step (1), the washing step is first washing with deionized water and then washing with anhydrous ethanol; and in the calcination step, the heating rate of calcination is 5-10 ℃ / min.

6. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 5 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the step (1), the drying temperature is controlled to be 80 ℃, the drying time is 12 h; the calcination temperature is controlled to be 400 ℃, the calcination time is 3 h, and the heating rate of calcination is 5 ℃ / min; and the reduction temperature is controlled to be 300 ℃, and the reduction time is 2.5 h.

7. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 1 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the step (2), the carrier In2O3 is ultrasonically dispersed in anhydrous ethanol, the ultrasonic dispersion time is 25-60 min, and the ultrasonic power is 25-100 Hz.

8. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 1 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In step (2), the carrier In2O3 is ultrasonically dispersed in anhydrous ethanol for 30 min at a power of 53 Hz.

9. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 1 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In step (2), the M precursor for providing the metal atom M is respectively palladium hexafluoroacetylacetonate [Pd(hfac)2] and trimethyl(methylcyclopentadienyl)-platinum (IV) [MeCpPtMe3]. IV represents the valence state.

10. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 1 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the high-dispersity metal-oxide M-In2O3 bifunctional catalyst, the loading of the metal atom M is 0.1 wt%-7.0 wt%.

11. Use of the highly dispersed metal-oxide M-In203 bifunctional catalyst according to claim 8 in the reaction of the selective hydrogenation of 4,6-dinitroresorcinol to 4,6-diaminoresorcinol, characterized in that, In the high-dispersity metal-oxide M-In2O3 bifunctional catalyst, the loading of the metal atom M is 1.0 wt%-5.0 wt%. In step (2), the carrier In2O3 is ultrasonically dispersed in anhydrous ethanol for 30 min at a power of 53 Hz. In step (2), the M precursor for providing the metal atom M is respectively palladium hexafluoroacetylacetonate [Pd(hfac)2] and trimethyl(methylcyclopentadienyl)-platinum (IV) [MeCpPtMe3]. IV represents the valence state. In the high-dispersity metal-oxide M-In2O3 bifunctional catalyst, the loading of the metal atom M is 0.1 wt%-7.0 wt%. In the high-dispersity metal-oxide M-In2O3 bifunctional catalyst, the loading of the metal atom M is 1.0 wt%-5.0 wt%.

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