Copper-based catalyst as well as preparation and application thereof

Abstract

The invention discloses a copper-based catalyst and preparation and application thereof, the copper-based catalyst comprises a CeO2 modified activated carbon carrier and active components loaded on the CeO2 modified activated carbon carrier, and the active components comprise CuCl2, SnCl4 and CsCl; according to the copper-based catalyst, the cerium oxide modified activated carbon is adopted as the carrier, SnCl4 and CsCl are introduced into the active components to cooperate with CuCl2, the activity and stability of the catalyst are effectively improved, and on the premise that the catalytic performance is guaranteed, the loading amount of copper is remarkably reduced, use of heavy metal is reduced, and the environmental risk is reduced.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a copper-based catalyst and its preparation and application. Background Technology

[0002] Vinyl chloride monomer is the main raw material for the production of polyvinyl chloride (PVC), and its production processes mainly include the ethylene process and the acetylene process. In the industrial application of the acetylene process for synthesizing vinyl chloride, the traditionally used mercuric chloride catalyst has been restricted and phased out due to its high toxicity and environmental hazards. Therefore, the development of efficient and environmentally friendly mercury-free catalysts has become a key research focus. Copper-based catalysts, due to their good catalytic activity and relatively low environmental toxicity, are considered a feasible alternative to mercuric chloride catalysts.

[0003] However, current copper-based catalysts generally suffer from high copper loading, with some catalysts reaching over 20 wt% copper. Although copper is less toxic than mercury, it still poses certain environmental risks as a heavy metal. Furthermore, during the reaction, copper species are prone to valence state changes, such as being reduced to a metallic state or converted into less active basic copper chloride, leading to catalyst deactivation. Simultaneously, activated carbon supports are prone to carbon deposition during long-term reactions, further affecting the catalyst's stability and lifespan.

[0004] Therefore, how to maintain or even improve catalytic performance while reducing copper loading has become a key issue that urgently needs to be addressed for the industrial application of copper-based catalysts. Summary of the Invention

[0005] In view of this, this application provides a copper-based catalyst and its preparation and application, which addresses the problem of how to improve catalytic performance while reducing copper loading.

[0006] To achieve the above technical objectives, this application adopts the following technical solution: In a first aspect, this application provides a copper-based catalyst, comprising a CeO2-modified activated carbon support and an active component supported on the CeO2-modified activated carbon support, wherein the active component is CuCl2, SnCl4 and CsCl.

[0007] Secondly, this application provides a method for preparing a copper-based catalyst, comprising the following steps: Obtain a dried CeO2-modified activated carbon carrier; CuCl2, SnCl4, and CsCl were dissolved in acid to obtain an impregnation solution. CeO2-modified activated carbon support was added to the impregnation solution for column impregnation, followed by rotary evaporation and segmented drying to obtain a copper-based catalyst.

[0008] Preferably, based on the mass of the CeO2 modified activated carbon carrier, the amount of CuCl2 added is 10-12%; the amount of SnCl4 added is 1-5%; and the amount of CsCl added is 1-2%.

[0009] Preferably, the preparation method of CeO2 modified activated carbon carrier is as follows: Activated carbon is immersed in Ce(NO3)3 solution, centrifuged and dried, and then heat-treated under an inert atmosphere to obtain CeO2 modified activated carbon carrier.

[0010] Preferably, the final temperature of the heat treatment is 300-700℃, the time is 2-3h, and the heating rate of the heat treatment is 5-8℃ / min.

[0011] Preferably, the activated carbon is also subjected to acid washing pretreatment.

[0012] Preferably, the segmented drying procedure is as follows: drying at 80-90℃ for 10 hours, drying at 100-110℃ for 4 hours, and drying at 130-140℃ for 12 hours.

[0013] Preferably, the impregnation temperature is 65-70℃; the rotary evaporation temperature is 65-70℃; and the rotary evaporation time is 10-12h.

[0014] Preferably, the acid is hydrochloric acid with a concentration of 1-2 mol / L.

[0015] Thirdly, this application provides an application of a copper-based catalyst in the preparation of vinyl chloride.

[0016] The beneficial effects of this application are as follows: The copper-based catalyst of this application effectively improves the activity and stability of the catalyst by using cerium oxide-modified activated carbon as a support and introducing SnCl4 and CsCl into the active components. Among them, the introduction of cerium oxide not only regulates the pore structure of activated carbon and reduces carbon deposition during the reaction, but also its abundant oxygen vacancies help stabilize the valence state of copper species, inhibiting the reduction or conversion of copper into low-activity products during the reaction, thereby extending the service life of the catalyst. The synergistic effect of tin and cesium further optimizes the dispersion state of copper and enhances the selectivity and catalytic efficiency of the catalyst for the acetylene hydrochlorination reaction. In addition, while ensuring catalytic performance, the copper loading is significantly reduced, the use of heavy metals is reduced, and environmental risks are reduced. Attached Figure Description

[0017] Figure 1 The results show the changes in catalyst performance at different calcination temperatures. Figure 2 The test results show the effect of different Sn addition amounts on the catalytic performance of the catalyst; Figure 3 The results show the test effects of different catalyst promoters on the catalytic performance of the catalyst. Figure 4 The results show the catalytic performance test results of the catalyst obtained in Example 1. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] This application provides a copper-based catalyst, comprising a CeO2-modified activated carbon support and active components supported on the CeO2-modified activated carbon support, wherein the active components are CuCl2, SnCl4 and CsCl.

[0020] The inventors discovered that the deactivation problem of copper-based catalysts in the acetylene-to-vinyl chloride synthesis process is due to: 1. Cu 2+ The surrounding electronic environment of Cu has changed, for example, Cu 2+ Reduced to Cu 0 1. The coordination structure of CuCl2 has changed to form more stable basic copper chloride, etc., or the support has carbon deposition behavior, resulting in a rapid decrease in activity; 2. Activated carbon as a support has a certain proportion of micropores, mesopores and macropores. The more micropores, the greater the activated carbon loading, but the easier it is to form carbon. The fewer micropores, the lower the catalyst activity and product selectivity, and it is impossible to maintain the catalyst activity under the premise of a large loading.

[0021] The support in this application is CeO2-modified activated carbon. The oxygen vacancies in the transition metal oxide CeO2 are used to protect the valence state of Cu, thereby solving the problem of Cu being easily reduced and improving the activity of the catalyst. At the same time, using CeO2 as a support for activated carbon can reduce the number of micropores in the activated carbon, reduce carbon deposition, and not affect the catalyst activity. The active components include CuCl2, SnCl4, and CsCl. CsCl, as a catalyst promoter, can form a stable active center structure with the chlorides of copper and tin elements, preventing the active sites from being covered, improving the acetylene conversion rate, and reducing the amount of heavy metals used. SnCl4, as one of the active components of the two-component catalyst, works synergistically with CuCl2 to improve the acetylene conversion rate and enhance the stability of the catalyst.

[0022] In some embodiments, based on the mass of the CeO2 modified activated carbon carrier, the amount of CuCl2 added is 10-12%; the amount of SnCl4 added is 1-5%; and the amount of CsCl added is 1-2%.

[0023] In this embodiment, the addition of Sn not only affects the valence state of Cu species, but also affects dispersion and coke deposition. However, excessive additives can occupy or cover the active sites on the catalyst, leading to a decrease in catalytic activity. In addition, since the saturated vapor pressure of Sn chloride is much lower than that of Cu, the temperature inside the reactor is high after the reaction is exothermic, and Sn is lost quickly. Therefore, excessive addition does not improve the stability of Cu catalyst.

[0024] This application provides a method for preparing a copper-based catalyst, comprising the following steps: S1. Obtain a dried CeO2-modified activated carbon carrier; S2. Dissolve CuCl2, SnCl4, and CsCl in acid to obtain an impregnation solution. Add CeO2-modified activated carbon support to the impregnation solution for column impregnation, followed by rotary evaporation and segmented drying to obtain a copper-based catalyst.

[0025] This application uses a column impregnation + rotary evaporation method to ensure that the active components are uniformly loaded onto the CeO2 modified activated carbon carrier, while segmented drying helps to prevent component decomposition.

[0026] In some embodiments, the preparation method of CeO2 modified activated carbon carrier is as follows: Activated carbon is immersed in Ce(NO3)3 solution, centrifuged and dried, and then heat-treated under an inert atmosphere to obtain CeO2 modified activated carbon carrier.

[0027] In some embodiments, the final temperature of the heat treatment is 300-700°C, the time is 2-3 hours, and the heating rate of the heat treatment is 5-8°C / min.

[0028] Preferably, the final temperature of the heat treatment is 700°C.

[0029] In some embodiments, the activated carbon is further subjected to acid washing pretreatment.

[0030] In some embodiments, the specific steps of the acid washing pretreatment are as follows: treating activated carbon with 5wt% nitric acid solution at 80°C for 2 hours.

[0031] In some embodiments, the segmented drying process is as follows: drying at 80-90℃ for 10 h, drying at 100-110℃ for 4 h, and drying at 130-140℃ for 12 h.

[0032] In some embodiments, the impregnation temperature is 65-70°C; the rotary evaporation temperature is 65-70°C; and the rotary evaporation time is 10-12 hours.

[0033] In some embodiments, the acid is 1-2 mol / L hydrochloric acid.

[0034] This application provides an application of a copper-based catalyst in the preparation of vinyl chloride.

[0035] The following specific embodiments further illustrate this solution.

[0036] Example 1 A copper-based catalyst includes a CeO2-modified activated carbon support and an active component supported on the CeO2-modified activated carbon support, wherein the active component is a CuCl2 / SnCl4 / CsCl composite.

[0037] A method for preparing copper-based catalysts includes the following steps: S1. Add 50g of acid-washed activated carbon to 120 mL of Ce(NO3)3 solution and impregnate at 25℃ for 3 h. Then centrifuge and dry the impregnated activated carbon at 110℃ to constant weight. Then place it in a tube furnace (N2 atmosphere) and heat treat at 700℃ for 2 h with a heating rate of 5℃ / min. Take 50g of CeO2-AC and put it into an electric heating drying oven and dry at 110℃ to constant weight for later use to obtain the dried CeO2 modified activated carbon carrier (CeO2-AC). S2. Under stirring conditions, CuCl2, SnCl4, and CsCl were completely dissolved in hydrochloric acid solution (1 mol / L) to prepare an impregnation solution. The amount of CuCl2 added was 12%, SnCl4 was 4%, and CsCl was 1% based on the mass of the CeO2-modified activated carbon support. The dried and cooled CeO2-AC was added to a jacketed chromatography column. At T=65℃, 120 mL of the impregnation solution was slowly passed through the column, repeated several times until the test solution Cu... 2+ Once the concentration remains constant, the impregnation is complete. The activated carbon is then removed from the chromatography column and placed in a round-bottom flask. It is then evaporated using a rotary evaporator at T=65℃ for 10 hours. After centrifugation, it is placed in an oven and dried at 80℃ for 10 hours, 100℃ for 4 hours, and 130℃ for 12 hours to obtain the copper-based catalyst, denoted as 12%Cu-4%Sn-1%Cs / CeO2-AC.

[0038] Example 2 A copper-based catalyst, otherwise identical to Example 1, except that the amount of SnCl4 added is 3%, and the product is denoted as 12%Cu-3%Sn-1%Cs / CeO2-AC. Comparative Examples 1-4 A method for preparing a copper-based catalyst is the same as in Example 1, except that SnCl4 and CsCl are not added, and in step S1, the heat treatment temperatures are 300℃, 500℃, 700℃, and 900℃ respectively, and the products are successively labeled as 12%Cu / CeO2-AC-300℃, 12%Cu / CeO2-AC-500℃, 12%Cu / CeO2-AC-700℃, and 12%Cu / CeO2-AC-900℃.

[0039] Comparative Examples 5-10 A method for preparing a copper-based catalyst is the same as in Example 1, except that it does not include the addition of CsCl, and in step S2, the amount of SnCl4 added is 0%, 1%, 2%, 3%, 4%, and 5% respectively, and the products are successively named 12%Cu / CeO2-AC, 12%Cu-1%Sn / CeO2-AC, 12%Cu-2%Sn / CeO2-AC, 12%Cu-3%Sn / CeO2-AC, 12%Cu-4%Sn / CeO2-AC, and 12%Cu-5%Sn / CeO2-AC.

[0040] Comparative Examples 11-13 A method for preparing a copper-based catalyst is the same as in Example 1, except that CsCl is replaced with KCl, NaCl, and Na2SO4 respectively, and the products are respectively denoted as 12%Cu-4%Sn-1%KCl / CeO2-AC, 12%Cu-4%Sn-1%NaCl / CeO2-AC, and 12%Cu-4%Sn-1%Na2SO4 / CeO2-AC.

[0041] Comparative Example 14 A method for preparing a copper-based catalyst is the same as in Example 1, except that it does not include the addition of CsCl, and the product is denoted as 12%Cu-4%SnCeO2-AC.

[0042] Comparative Example 15 A method for preparing a copper-based catalyst is the same as in Example 1, except that CsCl is replaced with Na2SO4 and the amount of SnCl4 added is 2%. The product is denoted as 12%Cu-2%Sn-1%NaCl / CeO2-AC.

[0043] Testing and Evaluation The copper-based catalysts obtained in each embodiment and comparative example were evaluated, and the specific steps were as follows: The catalyst performance was tested in a fixed-bed reactor. First, a certain amount of quartz sand was added to the reactor, followed by the prepared catalyst. During loading, a wooden mallet or stick was used to compact the catalyst. After loading, the reactor was heated to 100°C, then dried with nitrogen. Dew point analysis was performed; if the moisture content was below 600 ppm, the fixed-bed temperature was set to 130°C. Nitrogen was used to purge the pipeline and remove impurities from the pipeline and reactor. Hydrogen chloride gas was then introduced to activate the catalyst. After 4 hours of continuous operation, the hydrogen chloride content at the reactor inlet and outlet was analyzed every 2 hours, with the difference not exceeding 2%. Hydrogen chloride and acetylene were purified and dried before entering a premixing device. The feed ratio of the reaction gases was controlled by adjusting the flow meter to achieve the set space velocity. The reactor outlet exhaust gas passed through a buffer bottle, an HCl absorption bottle, and a silica gel drying tube before entering a gas chromatograph for analysis.

[0044] The evaluation was performed using a GC-9790 gas chromatograph with a GDX-301 packed column and an FID detector. The column temperature was 150℃ and the detector temperature was 120℃. The analytes were acetylene, vinyl chloride, and dichloroethane. The mole fraction of each component was determined using the external standard method.

[0045] After oxide modification, the crystal phase structure of the support may change with the calcination temperature, thus affecting the catalyst activity. At 120 °C, nitrogen was purged for 60 min, followed by hydrogen chloride activation for 120 min, with the feed ratio V(HCl) / V(C₂H₂) controlled at 1.05 and the space velocity at 180 h⁻¹. -1 Under the conditions, the performance of the 12% Cu / CeO2-AC catalyst was investigated with different calcination temperatures. The results are as follows: Figure 1 As shown, where Figure 1 (a) shows the effect of different calcination temperatures on the acetylene conversion rate of the Cu catalyst. Figure 1(b) shows the effect of vinyl chloride selectivity; the results indicate that the initial acetylene conversion rates at 12% Cu / CeO2-AC-300℃, 12% Cu / CeO2-AC-500℃, 12% Cu / CeO2-AC-700℃, and 12% Cu / CeO2-AC-900℃ are 72.1%, 74.5%, and 74.5%, respectively. The initial acetylene conversion rates were 78.2% and 70.1%, respectively. The 12% Cu / CeO2-AC catalyst at 700℃ exhibited the highest initial acetylene conversion rate and selectivity. As the reaction progressed, the acetylene conversion rate increased after calcination, but remained highest at 700℃. This indicates that from 300℃ to 700℃, the acetylene conversion rate increases with increasing temperature. Higher temperatures result in more active centers being formed, and the exposed crystal faces of the calcined cerium oxide vary at higher temperatures, leading to different catalyst activities. Furthermore, the activation of some carbon in the catalyst at higher temperatures also increases its activity. However, the acetylene conversion rate decreases at 900℃. Excessively high temperatures damage the active components, and some heat-sensitive active components are lost, resulting in lower catalyst activity. Therefore, above 700℃, the catalyst activity decreases with increasing calcination temperature. Excessively high calcination temperatures are detrimental to improving the acetylene conversion rate, while 700℃ is the optimal calcination temperature for the catalyst.

[0046] At 120 °C, nitrogen gas was purged for 60 min, followed by activation with hydrogen chloride for 120 min. The feed ratio V(HCl) / V(C2H2) was controlled at 1.05, and the space velocity was 180 h⁻¹. -1 Under the conditions, the catalytic performance of catalysts with different Sn addition amounts was investigated, and the results are as follows: Figure 2 As shown, where Figure 2 (a) shows the effect of different Sn addition amounts on the acetylene conversion rate of Cu catalyst. Figure 2 (b) shows the effect of different Sn addition amounts on the catalyst hot spot temperature; Figure 2In the study, 12% Cu / CeO2-AC was prepared at 700℃. The results showed that without Sn addition, the initial conversion rate was lower compared to other catalysts, and the hot spot temperature inside the reactor was also lower, leading to premature contact of the catalyst with high-concentration materials and rapid deactivation. Therefore, the acetylene conversion rate was lowest after stabilization at 20 h. With increasing Sn addition, the acetylene conversion rate first increased and then decreased. When the Sn addition was 4%, the acetylene conversion rate reached a stable value of 93% after 20 h. Simultaneously, after stabilization at 20 h, the selectivity of all these catalysts for VCM was higher than 90%. Sn addition not only affects the valence state of Cu but also affects dispersion and coke deposition. Conversely, excessive additives may occupy or cover active sites on the catalyst, leading to reduced catalytic activity. Furthermore, since the saturated vapor pressure of Sn chloride is much lower than that of Cu, the reactor temperature is high after the reaction is exothermic, resulting in rapid Sn loss. Therefore, excessive addition did not improve the stability of the Cu catalyst; the catalyst stability exhibited a non-linear dependence on Sn content. In addition, the two-component catalyst did not show obvious deactivation within 12 hours, indicating that the synergistic effect between the metals was obvious. However, the catalyst selectivity gradually improved with the increase of Sn addition. The higher the temperature, the better the selectivity for vinyl chloride monomer. At the same time, the hot spot trend inside the reactor can also be seen to show that temperature and selectivity are also correlated.

[0047] In this application, CsCl is used as a catalyst promoter to assist the active component in catalysis and reduce the amount of heavy metals used. To rapidly screen for promoters that promote copper-based catalysts, the catalyst testing conditions were adjusted: nitrogen was purged at 120°C for 60 min, followed by activation with hydrogen chloride for 120 min. The feed ratio V(HCl) / V(C₂H₂) was controlled at 1.05, and the space velocity was 500 h⁻¹. -1 The multi-component copper catalyst was evaluated, and suitable composite catalyst promoters were screened and optimized by examining catalytic performance. The results are as follows: Figure 3 As shown; where Figure 3 (a) shows the effect of different additive amounts on the acetylene conversion rate of Cu catalyst. Figure 3 (b) shows the effect of different additive amounts on the vinyl chloride selectivity of Cu catalyst.

[0048] Mercury-free catalysts prepared with different additives exhibit varying catalytic activities. Adding appropriate additives can enhance catalytic activity. For example, adding CsCl to a copper-tin mercury-free catalyst increased the initial acetylene conversion by approximately 0.47%, but the conversion did not significantly decrease after 12 hours of reaction. This may be because the initial reaction rate was too high, resulting in excessive heat release and catalytic activation. Adding Na3PO4 to the same catalyst did not significantly increase the initial acetylene conversion, but the conversion decreased significantly after 12 hours, indicating that Na3PO4 did not promote the catalyst's activity. Adding other metal chlorides such as NaCl, KCl, or Na2SO4 to the same catalyst resulted in a decrease in acetylene conversion selectivity, suggesting that NaCl, KCl, or Na2SO4 have a certain inhibitory effect on the mercury-free catalyst and cannot form stable active center structures with copper-tin chlorides. They may even cover the surface of the active centers, interfering with the normal reaction and increasing the conversion rate of byproducts.

[0049] The copper-based catalyst obtained in Example 1 was tested using a single-tube test platform. During the test, the catalyst testing conditions were adjusted based on the acetylene content, vinyl chloride content, and hot spot temperature at the reactor outlet. The catalyst operation was divided into three stages: induction, maturation, and decline. During the induction stage, the temperature was controlled by adjusting the space velocity of the acetylene-hydrogen chloride mixture. When the temperature was ≤140℃, the space velocity was gradually increased to 30-40 h⁻¹. -1 During the maturation period, control the gas-air mixture space velocity to 30-40 h⁻¹. -1 The reaction temperature was controlled at 150-170℃; during the decay period, the temperature was gradually increased according to the acetylene gas content at the outlet. The life test experiment involved a catalyst loading of 7000g, and the test results were as follows: Figure 4 As shown. Long-term testing of the prepared Cu-based catalyst revealed that the Cu-based catalyst in Example 1 achieved a single-tube acetylene conversion rate greater than 75% within 500 hours. The conversion rate decreased in the later stages of the reaction. During the test, blockage of the mixed gas caused a 6-hour gas supply stoppage, resulting in a sharp drop in catalyst performance. The reaction was subsequently restored by heating and restarting the gas supply. Overall, the catalyst performed well during the test, with a relatively stable acetylene conversion rate. The hot spot temperature initially rose rapidly, but stabilized later as control became more refined. However, industrial-scale heating was not performed during the test; heating was initiated after 500 hours, which effectively extended the catalyst lifetime.

[0050] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A copper-based catalyst, characterized in that, It includes a CeO2-modified activated carbon carrier and active components supported on the CeO2-modified activated carbon carrier, wherein the active components are CuCl2, SnCl4 and CsCl.

2. A method for preparing a copper-based catalyst as described in claim 1, characterized in that, Includes the following steps: Obtain a dried CeO2-modified activated carbon carrier; CuCl2, SnCl4, and CsCl are dissolved in acid to obtain an impregnation solution. The CeO2-modified activated carbon support is added to the impregnation solution for column impregnation, followed by rotary evaporation and segmented drying to obtain the copper-based catalyst.

3. The method for preparing the copper-based catalyst according to claim 2, characterized in that, Based on the mass of the CeO2 modified activated carbon carrier, the amount of CuCl2 added is 10-12%; the amount of SnCl4 added is 1-5%; and the amount of CsCl added is 1-2%.

4. The method for preparing the copper-based catalyst according to claim 2, characterized in that, The preparation method of the CeO2 modified activated carbon carrier is as follows: Activated carbon is immersed in Ce(NO3)3 solution, centrifuged and dried, and then heat-treated under an inert atmosphere to obtain the CeO2 modified activated carbon carrier.

5. The method for preparing the copper-based catalyst according to claim 2, characterized in that, The final temperature of the heat treatment is 300-700℃, the time is 2-3 hours, and the heating rate of the heat treatment is 5-8℃ / min.

6. The method for preparing the copper-based catalyst according to claim 2, characterized in that, It also includes acid washing pretreatment of the activated carbon.

7. The method for preparing the copper-based catalyst according to claim 2, characterized in that, The segmented drying procedure is as follows: drying at 80-90℃ for 10 hours, drying at 100-110℃ for 4 hours, and drying at 130-140℃ for 12 hours.

8. The method for preparing the copper-based catalyst according to claim 2, characterized in that, The impregnation temperature is 65-70℃; the rotary evaporation temperature is 65-70℃, and the rotary evaporation time is 10-12h.

9. The method for preparing the copper-based catalyst according to claim 2, characterized in that, The acid is 1-2 mol / L hydrochloric acid.

10. The application of a copper-based catalyst as described in claim 1 in the preparation of vinyl chloride.

Images