A full-spectrum response photo-thermal catalyst for low-temperature methane dry reforming and a preparation method thereof

Abstract

This invention belongs to the field of photocatalytic methane conversion technology, specifically relating to a full-spectrum responsive supported catalyst, its preparation method, and its application in photothermal methane dry reforming. An Rh / TiN catalyst is prepared by supporting a co-catalyst Rh on the surface of a full-spectrum responsive metal-like titanium nitride (TiN) using an impregnation-reduction strategy. Under simulated sunlight irradiation, this catalyst effectively lowers the energy barrier of the methane dry reforming reaction, promotes the activation of methane and carbon dioxide molecules, and achieves high efficiency in photothermal catalytic methane dry reforming. The photocatalyst has a simple preparation process, considerable yield, and exhibits excellent stability, showing broad application prospects in low-temperature methane dry reforming and other fields.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic methane conversion technology, specifically involving a full-spectrum responsive supported catalyst, its preparation method, and its application in the field of photothermal methane dry reforming conversion. Background Technology

[0002] The dry reforming of methane (CO2 + CH4 → 2CO + 2H2) catalytically converts greenhouse gases CO2 and CH4 into syngas (CO and H2), offering dual advantages in mitigating the greenhouse effect and providing high-value chemical feedstocks. However, both CO2 and CH4 are thermodynamically extremely stable molecules; their high bond energies and chemical inertness make them difficult to activate. Traditional dry reforming of methane typically requires 700... o Only at temperatures above 30°C can the reaction proceed effectively; harsh reaction conditions can easily lead to catalyst coking, sintering, and deactivation.

[0003] In recent years, photothermal synergistic catalysis, as a technology based on the coupling of photocatalysis and thermocatalysis, has been widely applied in energy conversion, environmental remediation, and other fields. It is well known that thermocatalysis is energy-intensive, involves numerous side reactions, and suffers from poor product selectivity. The initial energy provided by photocatalysis sometimes fails to effectively activate the target reaction. Addressing the shortcomings of both traditional thermocatalysis and photocatalysis, photothermal synergistic catalysis holds promise for activating target reactions within a low-temperature range, achieving better results than either thermocatalysis or photocatalysis alone, thus realizing low-energy, high-efficiency catalytic conversion. Photothermal catalysis of methane dry reforming shows promise for achieving low-energy, high-efficiency catalytic conversion and is an effective alternative to traditional thermocatalysis. However, developing a methane dry reforming catalyst that can operate efficiently and with good stability under mild reaction conditions remains a significant challenge.

[0004] Currently, traditional inorganic semiconductor photocatalytic materials (TiO2, ZnO, ZrO2, etc.) suffer from poor light absorption and low carrier separation efficiency, which severely limits catalytic conversion efficiency. Metal nitrides, due to their full-spectrum light absorption, unique electronic properties, and special band structure, are considered a promising class of photocatalysts. However, single-component metal nitride photocatalysts lack corresponding active sites for activating CO2 and CH4 molecules. To address these issues, this invention modifies the surface of titanium nitride (TiN) with a full-spectrum response using a co-catalyst Rh to prepare an Rh / TiN catalyst, which is then applied to the photothermal catalytic dry reforming of methane. The co-catalyst Rh effectively promotes the activation of CO2 and CH4 molecules, improves the separation efficiency of photogenerated carriers, and enhances the kinetics of the redox reaction at the surface, thereby improving catalytic efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a full-spectrum responsive photothermal catalyst, its preparation method, and its application in the field of methane dry reforming. The Rh / TiN catalyst provided by this invention effectively lowers the reaction barrier of methane dry reforming under photothermal synergy, promotes the activation of CO2 and CH4 molecules, and can operate efficiently and with good stability under mild reaction conditions. The catalyst has a simple preparation process, considerable yield, and promising prospects for industrial application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A full-spectrum responsive photothermal catalyst for low-temperature dry reforming of methane is prepared by supporting a co-catalyst Rh on titanium nitride (TiN) with full-spectrum responsiveness, wherein the loading amount of Rh is 0.1~3 wt%.

[0008] The catalyst is prepared by subjecting commercial titanium dioxide powder to high-temperature nitriding to obtain titanium nitride powder, and then using an impregnation-reduction method to support the co-catalyst Rh on the surface of the titanium nitride to obtain an Rh / TiN catalyst; the preparation method includes the following steps:

[0009] (1) Commercial titanium dioxide powder was calcined in an ammonia atmosphere to obtain black gold titanium nitride (TiN) powder;

[0010] (2) Disperse titanium nitride (TiN) powder in deionized water, add rhodium chloride aqueous solution and stir evenly, then add NaOH solution containing sodium borohydride to prepare Rh / TiN catalyst.

[0011] Furthermore, the flow rate of ammonia in step (1) is 100-200 mL·min. -1 .

[0012] Furthermore, the calcination temperature in step (1) is 750-850 °C and the time is 6-10 h.

[0013] Furthermore, in step (2), the mass ratio of sodium borohydride to metal Rh is between 1:2 and 1:20.

[0014] Furthermore, the concentration of the NaOH solution mentioned in step (2) is 5 ~ 20 g·L. -1 between.

[0015] The catalyst can be used in the dry reforming reaction of methane.

[0016] The significant advantages of this invention are:

[0017] (1) This invention utilizes high-temperature nitriding of commercial titanium dioxide to prepare titanium nitride (TiN) powder with full-spectrum response, and then uses Rh co-catalyst supported on the surface to prepare Rh / TiN catalyst. It can effectively reduce the barrier of methane dry reforming reaction under photothermal synergy, promote the activation of CO2 and CH4 molecules, and can operate efficiently and have good stability under mild reaction conditions.

[0018] (2) The catalyst involved in this invention has a simple preparation process and a considerable yield, and has good prospects for industrial application. Attached Figure Description

[0019] Figure 1 The XRD patterns are of TiN and 1.0%Rh / TiN prepared in Examples 1 and 2.

[0020] Figure 2 The DRS spectra of TiN and 1.0%Rh / TiN prepared in Examples 1 and 2 are shown.

[0021] Figure 3 SEM images of TiN (a) and 1.0%Rh / TiN (b) prepared in Examples 1 and 2.

[0022] Figure 4 The graph shows a comparison of the performance of TiN and 1.0%Rh / TiN prepared in Examples 1 and 2 under photothermal conditions.

[0023] Figure 5 This is a long-term performance graph of the 1.0% Rh / TiN prepared in Example 2. Detailed Implementation

[0024] A full-spectrum responsive photothermal catalyst for low-temperature dry reforming of methane, the preparation method of which includes the following steps:

[0025] (1) Place 300-500 mg of commercial titanium dioxide powder in a ceramic boat, and then transfer it into a high-temperature tube furnace. First, introduce a flow rate of 100-200 mL·min. -1 Ammonia gas was introduced into the tube for 30 minutes to purge the air inside; then, the temperature was raised to 750~850 ℃ and calcined for 6~10 h. After calcination was completed, the temperature was lowered to room temperature, the sample was taken out, TiN powder was obtained, and it was stored for a period of time for later use.

[0026] (2) Disperse the obtained TiN powder in 16 mL of deionized water, and add rhodium chloride aqueous solution (concentration of 10 g·L⁻¹). -1 After stirring evenly, add 4 mL of NaOH solution containing 10-100 mg of sodium borohydride (NaBH4) (concentration 5-20 g·L⁻¹). -1After the reaction is complete, Rh / TiN is obtained by centrifugation and drying.

[0027] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0028] Example 1: Preparation of TiN

[0029] Weigh 300 mg of commercial titanium dioxide powder and place it in a ceramic boat. Then, transfer it into a high-temperature tube furnace and purge the air in the tube with ammonia gas at a flow rate of 100-200 mL / min for 30 min. Subsequently, raise the temperature to 760 °C and calcine for 7.5 h. After calcine is completed, lower the temperature to room temperature, remove the TiN powder, and store it for a period of time before use.

[0030] Example 2 Preparation of 1.0% Rh / TiN

[0031] 450 mg of TiN powder prepared in Example 1 was dispersed in 16 mL of deionized water, and 0.45 mL of rhodium chloride solution (concentration 10 g·L⁻¹) was added. -1 After stirring evenly, add 4 mL of NaOH solution containing 45 mg of sodium borohydride (concentration 10 g·L⁻¹). -1 After the reaction is complete, centrifuge and dry.

[0032] Figure 1 The XRD patterns of the prepared TiN and 1.0% Rh / TiN are shown below. Figure 1 As shown, all diffraction peaks in the XRD pattern of the TiN sample match the standard XRD pattern of TiN (JCPDS: 38-1420), and no other impurity peaks were detected, indicating that a highly crystalline, pure-phase TiN sample was obtained. In contrast, the XRD pattern of the 1.0%Rh / TiN sample showed no characteristic peaks of Rh species other than the diffraction peaks of TiN, indicating a high degree of dispersion of Rh species.

[0033] Figure 2 The DRS diagrams for the prepared TiN and 1.0%Rh / TiN are shown. As shown, both TiN and 1.0%Rh / TiN exhibit UV-Vis-NIR light absorption. Compared to the TiN sample, the light absorption of the 1.0%Rh / TiN sample shows a slight blue shift.

[0034] Figure 3 SEM images of (a) TiN and (b) 1.0%Rh / TiN are shown. As shown, both TiN and 1.0%Rh / TiN exhibit coral-like morphology, indicating that the modification process of the co-catalyst did not alter the morphology of the TiN samples.

[0035] Example 3: 1.0% Rh / TiN photothermal methane dry reforming

[0036] A quartz reactor filled with 125 mg of TiN prepared in Examples 1 and 2 and 1.0% Rh / TiN catalyst was placed in a fixed-bed reactor, and a continuous flow rate of 60 mL / min was introduced. -1 The CO2 / CH4 / He ratio is 47 / 47 / 6 for the feed gas. The photothermal reaction is carried out directly using xenon lamp radiation on the catalyst without the need for an external heating source.

[0037] Figure 4 The figure shows a performance comparison between TiN and 1.0%Rh / TiN under photothermal conditions. As shown, the co-catalyst Rh can effectively improve the efficiency of the methane dry reforming reaction. Furthermore, at the same temperature, the photothermal catalysis efficiency of 1.0%Rh / TiN is higher than that of thermal catalysis.

[0038] Figure 5 This is a long-term performance graph of the 1.0% Rh / TiN prepared in Example 2. As shown in the figure, the catalyst can maintain its activity for 50 hours.

[0039] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. The application of Rh / TiN catalyst in photothermal catalytic dry reforming of methane, characterized by: Without using an external heating source, a xenon lamp is used to directly irradiate the catalyst to carry out a dry reforming reaction of methane; the reaction system temperature is 350~650 ℃ and the light intensity is 1000~4000 mW·cm. -1 The Rh / TiN catalyst is prepared by loading the co-catalyst Rh onto titanium nitride TiN using an impregnation-reduction method. The titanium nitride TiN is obtained by nitriding commercial titanium dioxide powder at high temperature. The loading amount of co-catalyst Rh on TiN is 0.1~3 wt%.

2. The application according to claim 1, characterized in that: The specific preparation method of the Rh / TiN catalyst includes the following steps: (1) Commercial titanium dioxide powder was calcined in an ammonia atmosphere to obtain black gold TiN powder; (2) Disperse TiN powder in deionized water, add rhodium chloride aqueous solution and stir evenly, then add NaOH solution containing sodium borohydride to prepare Rh / TiN catalyst.

3. The application according to claim 2, characterized in that: The ammonia flow rate in step (1) is 100-200 mL·min. -1 .

4. The application according to claim 2, characterized in that: The calcination temperature in step (1) is 750 ~ 850 ℃ and the time is 6 ~ 12 h.

5. The application according to claim 2, characterized in that: The mass ratio of sodium borohydride to metal Rh used in step (2) is between 1:2 and 1:

20.

6. The application according to claim 2, characterized in that: The concentration of the NaOH solution mentioned in step (2) is 5 ~ 20 g·L. -1 between.

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