Method for representing active phase of hydrodesulfurization catalyst through double-beam in-situ infrared low-temperature probe adsorption
Through the dual-beam in-situ infrared low-temperature probe adsorption characterization method, the interference problem of traditional infrared spectroscopy technology in the recognition of active phase of hydrodesulfurization catalysts is solved, and the high-sensitivity catalyst active phase characterization is achieved, which simplifies operation and accurately recognizes the true active phase of the catalyst.
Patent Information
- Application Number
- CN202510424792.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art is difficult to accurately identify the active phase of the hydrodesulfurization catalyst under in situ conditions. Traditional infrared spectroscopy technology is affected by the background atmosphere of the probe molecules and oxidation, so it is impossible to accurately characterize the true active phase of the catalyst.
The adsorption characterization method of dual-beam in situ infrared low-temperature probes is adopted. By using a dual-beam infrared cell under in situ vulcanization conditions, combined with a liquid nitrogen low-temperature environment, the background atmosphere interference is eliminated and the probe molecules are avoided, and infrared spectrograms of the catalyst surface are collected in real time.
It realizes high sensitivity of catalyst active phase characterization under in situ conditions, simplifies the operating process, and can accurately identify the true active phase points and quantity of the catalyst, which is suitable for dynamic surface process research under real reaction conditions.
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Figure CN120253741A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalyst characterization. Specifically, it relates to a method for characterizing the active phase of a hydrodesulfurization catalyst by dual-beam in-situ infrared low-temperature probe adsorption. Background Art
[0002] The rapid development of social economy has led to an increasing demand for energy, and also brought serious environmental pollution problems. The use of diesel with high sulfur content in automobiles is the root cause of inhalable lung pm2.5 pollution, and substances such as sulfur oxides generated after its combustion are likely to cause acid rain and environmental pollution. With the improvement of people's environmental awareness, the standards for fuel oil in the refining field are getting higher and higher. Developing environmentally friendly fuels is extremely urgent. Nowadays, the most effective method internationally is to carry out hydrodesulfurization technology (HDS). Its basic process is to catalytically convert organic sulfur compounds in diesel into hydrocarbons under the hydrogenation conditions of high temperature and high pressure, and at the same time remove sulfur in the form of hydrogen sulfide. Hydrogenation catalysts play a core role in the hydrogenation process. Molybdenum sulfide-based catalysts are commonly used catalysts in the hydrodesulfurization process and have been applied to industrial hydrogenation reactions since the 1940s and are still common catalysts in many hydrogenation reactions so far.
[0003] So far, even the latest generation of hydrodesulfurization catalysts is still based on the classic composition, that is, Co(Ni)Mo(W) sulfides supported on alumina, but their performance and stability have been significantly improved. The main reason is that people's understanding of the structure of the hydrodesulfurization active phase and the level of the catalyst action mechanism has been continuously improved, enabling scientists to continuously try to develop catalysts with higher desulfurization activity. Deeply understanding the "structure-activity relationship" between the structure of the hydrodesulfurization catalyst active phase and its catalytic performance is the key to developing catalysts. Therefore, the development of a method for characterizing the active phase structure of hydrodesulfurization catalysts is of great significance.
[0004] Infrared spectroscopy technology is an important tool for studying the structural properties of catalysts and can directly obtain information on surface species of catalysts. For catalyst research, information such as the surface structure information, changes in active sites, adsorption modes of reactants, and reaction intermediates under its working state is of great significance. In-situ infrared technology can simulate the environment when the catalyst is working and study its reaction mechanism through the infrared spectrum of the catalyst under the working state, providing theoretical support for the development of new hydrodesulfurization catalysts. By the method of adsorbing probe molecules with infrared spectroscopy, specific adsorption signals can be generated for the active sites in the hydrodesulfurization catalyst, so as to observe specific infrared characteristics, provide information on the adsorption mode, and indirectly understand the nature of the sites.
[0005] However, due to various characteristics of sulfide-based catalysts, such as the sulfidation step, the high sensitivity of sulfide catalysts to air contact, the variable forms of elements in the catalyst, and the interference of the probe molecule gas background, etc., the characterization of the catalytic system is challenging. Probe molecules such as CO and NO are not only adsorbed on the active sites of the catalyst but also present in the background atmosphere. Using traditional single-beam infrared cannot subtract the probe molecules in the background atmosphere, which affects the identification of the active phase sites. In addition, NO gas molecules are easily oxidized to NO2 by the traditional normal-temperature adsorption method, causing a change in the adsorption sites of the active phase and making it impossible to accurately identify the active phase sites. Summary of the Invention
[0006] Aiming at the deficiencies of the prior art, the present invention provides a method for characterizing the active phase of a hydrodesulfurization catalyst by dual-beam in-situ infrared low-temperature probe adsorption, which is simple to operate, highly sensitive, can subtract the background atmosphere under in-situ sulfidation conditions and avoid the influence of probe molecule oxidation under low-temperature conditions, so as to obtain the infrared characterization of the true active phase information of the catalyst, and can realize the dual-beam infrared characterization of low-temperature probe adsorption under in-situ sulfidation conditions of the hydrodesulfurization catalyst.
[0007] To solve the above problems, the technical solutions adopted by the present invention are as follows:
[0008] A method for characterizing the active phase of a hydrodesulfurization catalyst by dual-beam in-situ infrared low-temperature probe adsorption, comprising the following steps:
[0009] (1) Sample preparation: Take the oxidized catalyst powder and press it into a self-supporting wafer, and place it on the catalyst sample support ring of the dual-beam infrared cell.
[0010] (2) Catalyst pretreatment: The oxidized catalyst needs to undergo an in-situ sulfidation step to form a sulfided active phase. The specific operation is as follows: Connect the inlet and outlet of the dual-beam infrared cell to the sulfiding gas and the tail gas absorption device respectively for in-situ sulfidation of the oxidized catalyst to obtain a sulfided catalyst. After sulfidation, evacuate and seal the system, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation.
[0011] (3) Infrared spectrum test: Place the dual-beam infrared cell on the infrared spectrometer, connect the vacuum device and continue the evacuation process. After that, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce the required adsorbed probe molecules into the dual-beam infrared cell, continuously and real-time collect the sample spectrum and the reference spectrum, and perform subtraction to obtain the final dual-beam infrared spectrum of the probe molecules adsorbed on the catalyst surface.
[0012] The dual-beam infrared cell adopts the dual-beam in-situ transmission infrared cell disclosed in Patent CN116337769 A.
[0013] Preferably, the diameter of the self-supporting wafer is 10 mm to 15 mm.
[0014] Preferably, the oxidized catalyst includes CoMo / Al2O3, NiMo / Al2O3 or NiW / Al2O3.
[0015] Preferably, it further includes characteristic peak identification: adsorbing probe molecules by infrared spectroscopy, which can generate specific signals for unpromoted and promoted active phase points. After adsorption, specific infrared characteristics are observed, providing information on the adsorption mode and indirect position properties; the number of different adsorption sites is evaluated by absorbance.
[0016] Preferably, evacuating and sealing the system includes closing the inlet valve and the outlet valve, removing the sulfide gas and tail gas absorption device, opening the inlet valve to connect to the vacuum device, evacuating the double-beam infrared cell, and then closing the inlet valve.
[0017] Preferably, the sulfide gas is a 1% - 20% H2S / H2 mixed gas, and the gas flow rate is controlled at 10 ml / min to 30 ml / min by a rotameter to ensure sufficient contact between H2S and the catalyst sample at the sulfidation temperature.
[0018] Preferably, the sulfidation temperature is 340 - 360 °C.
[0019] Preferably, the probe molecule gas includes CO, NO or a CO, NO mixed gas.
[0020] The beneficial effects of the present invention are as follows:
[0021] (1) The operation is simple, without a complex sample preparation process; it has high sensitivity and can detect low-content active phases.
[0022] (2) It can realize in-situ sulfidation pretreatment of oxidized catalyst samples, ensure the stability of the active phase of sulfided catalyst samples, and prevent the oxidation of sulfided catalyst samples from resulting in the inability to obtain true active phase information.
[0023] (3) By using a double-beam infrared cell, reference spectra and sample spectra can be collected simultaneously, which is suitable for real-time research on the dynamic surface process of gas-solid multiphase catalytic processes under real reaction conditions and can eliminate the influence of gas-phase molecular vibration and thermal radiation.
[0024] (4) Adsorption of probe molecules is carried out at liquid nitrogen temperature (-196 °C) to avoid the influence of probe molecule oxidation on the change of active phase adsorption sites. Description of the Drawings
[0025] Figure 1 It is a characterization diagram of the low-temperature CO infrared adsorption active phase of the in-situ sulfided catalyst for Examples 1 - 4.
[0026] Figure 2 In-situ sulfurization catalyst low-temperature NO infrared adsorption active phase characterization diagram for Examples 5-8. Detailed implementation manners
[0027] The following describes in detail the specific embodiments of the present invention.
[0028] In Example, the double-beam infrared cell uses the double-beam in-situ transmission infrared cell disclosed in Patent CN116337769 A.
[0029] Example 1
[0030] Weigh 20 mg of Mo / Al2O3 hydrodesulfurization oxidized catalyst powder A1 with a mass fraction of 14% MoO3, press it into a self-supporting wafer with a diameter of 14 mm, and place the self-supporting wafer on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and the tail gas absorption device. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, heat it to 340 °C at a rate of 10 °C / min, and keep it at 340 °C for 1 h. The sulfided catalyst sample is black. After sulfidation, close the inlet valve and the outlet valve and remove the sulfiding gas and the tail gas absorption device. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, evacuate the residual gas in the sample cell, and ensure that the catalyst active phase is not affected by air oxidation; after evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample wafer to the beam position, connect the vacuum device again to evacuate the system, and after completion, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce CO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and the reference spectrum, and perform subtraction to obtain the final double-beam infrared spectrum of CO adsorbed on the catalyst surface, which can judge the different sites of the sulfided catalyst active phase and perform quantitative calculation according to its peak area. The characterization result is C1.
[0031] Example 2
[0032] Weigh 20 mg of the oxidized Mo / Al2O3 hydrodesulfurization catalyst powder A2 containing 1.9% CoO and 14% MoO3 by mass fraction, press it into a self-supporting disc with a diameter of 14 mm, and place the self-supporting disc on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and the tail gas absorption device. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, heat it to 340 °C at a rate of 10 °C / min, and keep it at 340 °C for 1 h. The sulfided catalyst sample is black. After sulfiding, close the inlet valve and the outlet valve and remove the sulfiding gas and the tail gas absorption device. Open the inlet valve and connect it to the vacuum device, evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation; after evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample wafer to the beam position, connect the vacuum device again to evacuate the system, and after completion, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce CO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and the reference spectrum, perform subtraction, and obtain the final double-beam infrared spectrum of CO adsorbed on the catalyst surface, which can judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. The characterization result is C2.
[0033] Example 3
[0034] Weigh 20 mg of the CoMo / Al2O3 hydrodesulfurization oxidized catalyst powder A3 containing 3.1% CoO and 14% MoO3 by mass fraction, press it into a self-supporting wafer with a diameter of 14 mm, and place the self-supporting wafer on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and tail gas absorption devices. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, heat it to 340 °C at a rate of 10 °C / min, and keep it at 340 °C for 1 h. The sulfided catalyst sample is black. After sulfiding, close the inlet valve and outlet valve and remove the sulfiding gas and tail gas absorption devices. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation; after evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample wafer to the beam position, connect the vacuum device again to evacuate the system, and after completion, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce CO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and reference spectrum, perform subtraction, and obtain the final double-beam infrared spectrum of CO adsorbed on the catalyst surface, which can judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. The characterization result is C3.
[0035] Example 4
[0036] Weigh 20 mg of the CoMo / Al2O3 hydrodesulfurization oxidized catalyst powder A4 containing 7.3% CoO and 14% MoO3 by mass fraction, press it into a self-supporting disc with a diameter of 14 mm, and place the self-supporting disc on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and tail gas absorption devices. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, and raise the temperature to 340 °C at a rate of 10 °C / min. Keep it at 340 °C for 1 h under the sulfiding temperature condition. The sulfided catalyst sample is black. After sulfiding, close the inlet valve and outlet valve and remove the sulfiding gas and tail gas absorption devices. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation; after evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample piece to the beam position, connect the vacuum device again to evacuate the system. After that, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce CO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and the reference spectrum, and perform subtraction to obtain the final double-beam infrared spectrum of CO adsorbed on the catalyst surface, which can judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. The characterization result is C4.
[0037] Example 5
[0038] Weigh 20 mg of the Mo / Al2O3 hydrodesulfurization oxidized catalyst powder A1 containing 14% MoO3 by mass fraction, press it into a self-supporting wafer with a diameter of 14 mm, and place the self-supporting wafer on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and the tail gas absorption device. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, and raise the temperature to 340 °C at a rate of 10 °C / min. Keep it at 340 °C for 1 h. The sulfided catalyst sample is black. After sulfiding, close the inlet valve and the outlet valve and remove the sulfiding gas and the tail gas absorption device. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation. After evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample wafer to the beam position, connect the vacuum device again to evacuate the system. After that, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce NO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and the reference spectrum, and perform subtraction to obtain the final double-beam infrared spectrum of NO adsorbed on the catalyst surface, which can judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. Record the characterization result as N1.
[0039] Example 6
[0040] Weigh 20 mg of the CoMo / Al2O3 hydrodesulfurization oxidized catalyst powder A2 containing 1.9% CoO and 14% MoO3 by mass fraction, press it into a self-supporting disc with a diameter of 14 mm, and place the self-supporting disc on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and tail gas absorption devices. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, heat it to 340 °C at a rate of 10 °C / min, and keep it at 340 °C for 1 h. The sulfided catalyst sample is black. Close the inlet valve and outlet valve and remove the sulfiding gas and tail gas absorption devices. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation; after evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample piece to the beam position, connect the vacuum device again to evacuate the system, and after completion, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce NO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and reference spectrum, perform subtraction, and obtain the final double-beam infrared spectrum of NO adsorbed on the catalyst surface, which can judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. Record the characterization result as N2.
[0041] Example 7
[0042] Weigh 20 mg of the CoMo / Al2O3 hydrodesulfurization oxidized catalyst powder A3 with a mass fraction of 3.1% CoO and 14% MoO3, press it into a self-supporting disc with a diameter of 14 mm, and place the self-supporting disc on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and the tail gas absorption device. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, heat it up to 340 °C at a rate of 10 °C / min, and keep it at 340 °C for 1 h. The sulfided catalyst sample is black. After sulfiding, close the inlet valve and the outlet valve and remove the sulfiding gas and the tail gas absorption device. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation. After evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample slice to the beam position, connect the vacuum device again to evacuate the system. After that, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce NO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and the reference spectrum, and perform subtraction to obtain the final double-beam infrared spectrum of NO adsorbed on the catalyst surface, which can be used to judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. Record the characterization result as N3.
[0043] Example 8
[0044] Weigh 20 mg of the CoMo / Al2O3 hydrodesulfurization oxidized catalyst powder A4 containing 7.3% CoO and 14% MoO3 by mass fraction, press it into a self-supporting wafer with a diameter of 14 mm, and place the self-supporting wafer on the catalyst sample support ring of the double-beam infrared cell. The spectral background reference ring is left empty. The inlet and outlet are respectively connected to the sulfiding gas and tail gas absorption devices. The sulfiding gas uses a 10% H2S / H2 mixed gas. Adjust the sulfiding gas flow rate to 20 ml / min, heat it to 340 °C at a rate of 10 °C / min, and keep it at 340 °C for 1 h. The sulfided catalyst sample is black. After sulfiding, close the inlet valve and outlet valve and remove the sulfiding gas and tail gas absorption devices. Open the inlet valve and connect the vacuum device to evacuate the double-beam infrared cell, pump out the residual gas in the sample cell, and ensure that the active phase of the catalyst is not affected by air oxidation; after evacuation, close the inlet valve, transfer the double-beam infrared cell to the infrared spectrometer, fix the double-beam infrared cell with an iron stand, adjust the sample wafer to the beam position, connect the vacuum device again to evacuate the system, and after completion, inject liquid nitrogen (-196 °C) into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton. Open the outlet valve, introduce NO into the double-beam infrared cell, continuously and real-time collect the catalyst sample spectrum and reference spectrum, perform subtraction, and obtain the final double-beam infrared spectrum of NO adsorbed on the catalyst surface, which can judge the different sites of the active phase of the sulfided catalyst and perform quantitative calculation according to its peak area. Record the characterization result as N4.
[0045] Evaluate the hydrodesulfurization reaction performance of the samples in the examples: The raw material is a n-decane solution containing 0.45 wt% 4,6-DMDBT. The reaction conditions are: the catalyst dosage is 1.5 g, mixed and loaded with 1.0 g of quartz sand, the pressure is 3 MPa, the temperature is 320 °C, and the space velocity is 14 h -1 , and the hydrogen-oil ratio is 500. The catalyst is sulfided before evaluation. In a hydrogen gas stream of 100 ml / min, the reactor is heated from room temperature to 340 °C at a rate of 10 °C / min and kept for 4 h. During this period, it is sulfided with a cyclohexane solution containing 5 wt% CS2 for 4 h. The evaluation results are shown in Table 1. The results show that the addition amount of Co promoter significantly affects the reaction performance of the catalyst, and overall shows a "volcano-shaped" curve relationship where the reaction performance first increases and then decreases with the increase of the CoO addition amount. When the CoO addition amount is 3.1%, the reaction performance reaches the highest value, and when the promoter content is further increased, the reaction performance decreases.
[0046] The results of Examples 1-4 are as Figure 1 shown. IR / CO produced two main bands, corresponding to the unpromoted Mo sites (~2110 cm -1 ) and the CoMoS sites (~2070 cm -1)。By measuring the molar extinction coefficients in these IR / CO bands, the number of sites can be calculated, and thus the dispersion and promotion degree of the sulfide plate can be calculated. The CoMoS sites (~2070 cm -1 ) show a peak envelope, and 2072 - 2074 and 2082 - 2085 cm -1 can be respectively assigned to partially and fully promoted M-edge sites, and 2054 - 2057 cm -1 is assigned to partially promoted S-edge sites. When Co is added in excess, the peak position shifts significantly towards lower wavenumbers, and the Co9S8 phase at 2092 cm -1 and 2065 cm -1 appears. It can be seen that with the increase of cobalt content, the promoting effect of the promoter Co increases, resulting in a gradual decrease in the concentration of the MoS2 phase, and the content of the CoMoS phase first increases and then decreases. When the addition amount of CoO is 3.1 wt%, the content of the CoMoS active phase reaches the maximum value. By fitting the adsorption peaks of CO with the sulfide phase and attributing the peak positions, the proportion of different sites can be obtained. When the addition amount of CoO is higher than 3.1 wt%, the excessive addition of cobalt leads to an increase in Co9S8 and does not form an effective CoMoS active phase structure.
[0047] The CO-IR spectra of each catalyst are further decomposed by a mixed Gaussian-Lorentz function, and the concentrations of the fine structures of the MoS2 and CoMoS phases are calculated as shown in Table 2. The content of fully promoted M-edge sites gradually decreases, the content of partially promoted M-edge sites first decreases and then slightly increases, and the content of partially promoted S-edge sites first increases and then decreases. By calculating its S- / M- ratio, it is found that when the molar ratio of CoO / CoO + MoO3 is 0.3, the catalyst has the highest S- / M- ratio. The results show that the CoMoS structure with a high S- / M- is more conducive to the hydrodesulfurization reaction.
[0048] The low-temperature NO adsorption double-beam infrared characterization of the catalysts in Examples 4 - 8 can effectively characterize the Co9S8 phase information in the hydrodesulfurization catalyst. As Figure 2 shown, three main characteristic spectral peaks appear, namely the MoS2 sites (~1703 cm -1 ), the species jointly acting on Co and Mo (~1790 cm -1 ), and the Co9S8 sites (~1855 cm -1 ). After adding the Co promoter, a characteristic peak of the Co9S8 phase appears at 1860 cm -1 , and with the increase of the Co loading amount, the intensity of this characteristic peak gradually increases. At the same time, 1703 cm -1The intensity of the non-promoting phase gradually decreases, indicating that the addition of excessive Co does not form an effective CoMoS active phase structure, but forms an inactive Co9S8 phase, resulting in a decrease in reaction performance.
[0049] Table 1 Hydrodesulfurization reaction performance of catalysts and metal loadings
[0050]
[0051] Table 2 Comparison of data on the content of each active phase of the catalysts
[0052]
Claims
1. A method for in-situ infrared low-temperature probe adsorption characterization of the active phase of a hydrodesulfurization catalyst with dual-beam, characterized in that: It includes the following steps: (1) Sample preparation: Take the oxidized catalyst powder and press it into a self-supporting wafer, and place it on the catalyst sample support ring of the double-beam infrared cell; (2) Catalyst pretreatment: Connect the inlet and outlet of the double-beam infrared cell to the sulfide gas and tail gas absorption device respectively to carry out in-situ sulfidation of the oxidized catalyst to obtain the sulfided catalyst. After sulfidation, evacuate and seal the system; (3) Infrared spectroscopy test: Place the double-beam infrared cell on the infrared spectrometer, connect the vacuum device and continue to evacuate. After that, inject liquid nitrogen into the double-layer cold source cup until the temperature of the catalyst sample is stable, and collect the infrared spectrum of the catalyst sample skeleton; Open the outlet valve, introduce the required adsorbed probe molecule into the double-beam infrared cell, continuously and real-time collect the sample spectrum and reference spectrum, and perform subtraction to obtain the final double-beam infrared spectrum of the probe molecule adsorbed on the catalyst surface.
2. The method for in-situ infrared low-temperature probe adsorption characterization of the active phase of a hydrodesulfurization catalyst according to claim 1, characterized in that: The oxidized catalyst includes CoMo / Al2O3, NiMo / Al2O3 or NiW / Al2O3.
3. The method for in-situ infrared low-temperature probe adsorption characterization of the active phase of a hydrodesulfurization catalyst according to claim 1, characterized in that: It also includes characteristic peak identification: Adsorbing probe molecules by infrared spectroscopy can generate specific signals for unpromoted and promoted active phase sites. After adsorption, specific infrared characteristics are observed, providing information on the adsorption mode and indirect positional properties; Evaluate the number of different adsorption sites by absorbance.
4. The method for characterizing the active phase of a hydrodesulfurization catalyst by dual-beam in-situ infrared low-temperature probe adsorption according to claim 1, wherein: Evacuating and sealing the system includes closing the inlet valve and outlet valve and removing the sulfide gas and tail gas absorption device, opening the inlet valve and connecting the vacuum device, evacuating the double-beam infrared cell and then closing the inlet valve.
5. The method for characterizing the active phase of a hydrodesulfurization catalyst by dual-beam in-situ infrared low-temperature probe adsorption according to claim 1, characterized in that: The sulfide gas uses a 1% - 20% H2S / H2 mixed gas, and the gas flow rate is controlled by a rotameter to be 10 ml / min - 30 ml / min.
6. The method for in-situ infrared low-temperature probe adsorption characterization of the active phase of a hydrodesulfurization catalyst according to claim 1, characterized in that: The sulfidation temperature is 340 - 360 °C.
7. The method for characterizing the active phase of a hydrodesulfurization catalyst by in-situ infrared low-temperature probe adsorption using a dual-beam as claimed in claim 1, wherein: The probe molecule gas includes CO, NO or a CO, NO mixed gas.