A nitrogen-carbon modified ethanol acetaldehyde to butadiene catalyst, a preparation method and application thereof

Abstract

The application discloses a nitrogen-carbon modified ethanol acetaldehyde butadiene catalyst and a preparation method and application thereof, and belongs to the technical field of butadiene prepared from ethanol and acetaldehyde. An active component of the catalyst is one or two or more of Zr, Hf, Ta, Y, Sn, Zn and Nb in an oxidized state, the total loading of an active metal M element in the catalyst is greater than or equal to 0.1 wt%, the loading of nitrogen in the catalyst is greater than or equal to 0.1 wt%, the loading of carbon in the catalyst is greater than or equal to 0.1 wt%, and a carrier is a silicon-based carrier. The catalyst is obtained by impregnating a solution containing a soluble salt of the active component M and a soluble nitrogen-carbon source on the silicon-based carrier, drying and calcining in an inert gas. In the reaction of preparing butadiene from ethanol acetaldehyde by catalytic conversion, the ethanol acetaldehyde conversion rate of the catalyst can reach more than 90%, the butadiene selectivity is as high as more than 80%, the catalyst can be stably operated for more than 300 hours, and the catalyst has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of ethanol and acetaldehyde to butadiene production, specifically relating to a nitrogen-carbon modified ethanol-acetaldehyde to butadiene catalyst, its preparation method, and its application in the catalytic conversion of ethanol and acetaldehyde to butadiene. Background Technology

[0002] 1,3-Butadiene, as one of the most important bulk chemicals, ranks second only to ethylene and propylene in terms of production. It is widely used in the preparation of synthetic rubber, synthetic resins, and other products, playing a crucial industrial role in the polymer field. Currently, the demand for butadiene has reached 16 million tons per year and is growing at a rate of 4% annually (Xu Churong. Research progress on butadiene synthesis technology in my country [J]. Fine and Specialty Chemicals, 2022, 30(08): 10-12). Currently, over 95% of butadiene is obtained as a byproduct of naphtha steam cracking to produce ethylene, thus butadiene production is highly dependent on ethylene production. However, the growth in shale gas production has led to changes in the composition of cracking feedstocks, significantly impacting butadiene production. Therefore, finding a sustainable and green butadiene production route is an urgent priority.

[0003] The technology for producing butadiene from ethanol has a long history, dating back over a century, and was once the main process for industrial butadiene production. Ethanol, as a green and sustainable biomass resource, is widely available and inexpensive, making it a valuable alternative to non-renewable fossil resources. Therefore, using ethanol as a raw material to produce butadiene has broad application prospects and significant research value.

[0004] There are two main processes for producing butadiene from ethanol: the one-step process and the two-step process. The one-step process uses only ethanol as a raw material to produce butadiene in one step. The two-step process uses ethanol and acetaldehyde as feedstocks to produce butadiene. The two-step process has higher stability because it does not involve dehydrogenation centers, but it inevitably produces more dehydration and condensation byproducts, leading to a decrease in reaction selectivity. Furthermore, the current highest stability of this reaction is only 168 hours, indicating room for further improvement. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a nitrogen-carbon modified ethanol-acetaldehyde catalyst for butadiene production, its preparation method, and its application in the catalytic conversion of ethanol-acetaldehyde to butadiene. The nitrogen-carbon modified catalyst prepared by this invention has very high ethanol and acetaldehyde reactivity, butadiene selectivity, and stability. Moreover, the catalyst preparation method has significant advantages such as low cost, simplicity, ease of implementation, and broad applicability.

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

[0007] In a first aspect, the present invention provides a nitrogen- and carbon-modified catalyst for the production of butadiene from ethanol and acetaldehyde. The catalyst is represented by M / NC@support, wherein M is the active component, which is one or more of Zr, Hf, Ta, Y, Sn, Zn, and Nb in oxidized state, and the total loading of the active metal M element in the catalyst is ≥0.1wt%; NC represents the nitrogen and carbon modification of the catalyst, wherein the loading of nitrogen element in the catalyst is ≥0.1wt%, and the loading of C element in the catalyst is ≥0.1wt%; support is a silicon-based support.

[0008] Based on the above technical solution, the loading of element M in the catalyst is further 1-50 wt%; the loading of element nitrogen in the catalyst is 1-15 wt%; and the loading of element C in the catalyst is 0.5-25 wt%.

[0009] Preferably, the loading of element M in the catalyst is 1.5-30 wt%; the loading of element nitrogen in the catalyst is 1.5-10 wt%; and the loading of element C in the catalyst is 1.5-20 wt%.

[0010] More preferably, the loading of element M in the catalyst is 4-20 wt%; the loading of element nitrogen in the catalyst is 2-8 wt%; and the loading of element C in the catalyst is 2-15 wt%.

[0011] Based on the above technical solution, further, the silicon-based carrier is a silicon-based molecular sieve or porous silica. The silicon-based molecular sieve includes one or more of SBA-15, SBA-16, silicate-1, deAl-beta, MCM-41, and MWW; the porous silica includes one or more of silica, silica sol, and mesoporous silica, and the specific surface area of ​​the porous silica is >20 m². 2 / g.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps: impregnating a solution containing a soluble salt of active component M and a soluble nitrogen and carbon source onto a silicon-based support, drying it, and then calcining it in an inert gas at a temperature of 350-750°C for 1-24 hours to obtain the catalyst.

[0013] Based on the above technical solution, further, the soluble salt of the active component M is one or more of the following: nitrate, chloride, oxynitrate, oxychloride, and organic alkoxide.

[0014] Based on the above technical solution, the nitrogen and carbon source is one or more of urea, cyanamide, dicyandiamide, melamine, and thiourea.

[0015] Based on the above technical solution, the nitrogen and carbon source is one or more of urea, cyanamide, dicyandiamide, melamine, thiourea, isobutyramide, diformylhydrazine, and dopamine.

[0016] Based on the above technical solution, the drying temperature is further 60-200℃, the calcination temperature is 500-600℃, and the calcination time is 2-6 hours.

[0017] Thirdly, the present invention provides the application of the above-mentioned catalyst in the catalytic conversion of ethanol and acetaldehyde to prepare butadiene.

[0018] Based on the above technical solution, the reaction is further carried out in a fixed-bed reactor at atmospheric pressure, with a molar ratio of acetaldehyde to ethanol of 1:1 to 1:5, and a reaction space velocity (WHSV) range of 0.12-10 h⁻¹. -1 Using inert gas as the carrier gas, the carrier gas space velocity (GSHV) is 500-10000 h⁻¹. -1 The reaction temperature is 200-500℃.

[0019] Preferably, the reaction temperature is 300-400℃, the molar ratio of acetaldehyde to ethanol is 1:1.2-1:3, and the reaction space velocity (WHSV) is 0.25-6 h⁻¹. -1 The inert gas is one or more of nitrogen, argon, and helium, and the carrier gas space velocity is 3000-5000 h⁻¹. -1 .

[0020] Based on the above technical solution, further, in the reaction process, the total conversion rate of ethanol and acetaldehyde is 40-95%, and the selectivity of 1,3-butadiene product is 50-80%.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The method of preparing catalyst for ethanol-to-butadiene production using nitrogen-carbon modification strategy of urea-assisted pyrolysis is universal and has an improvement effect on different commercial supports. It does not require a lengthy molecular sieve synthesis step and also improves the catalyst reaction performance for different active components.

[0023] (2) The present invention can obtain the catalyst by simply using impregnation and pyrolysis, and the preparation method is simple and efficient.

[0024] (3) This invention modifies the acid center of the catalyst by nitrogen and carbon modification, thereby improving the adsorption capacity of the active site for the reactant acetaldehyde, thus improving the reaction conversion rate and selectivity, and obtaining a high butadiene yield with good stability. The conversion rate of ethanol and acetaldehyde can reach more than 80%, and the butadiene selectivity is as high as 75%. On the preferred Zr / NC@SBA-15 catalyst, the reaction can run stably for more than 300 hours, which is better than all known catalysts reported so far and has a good application prospect. Attached Figure Description

[0025] Figure 1 The results are from the stability study of the 8% Zr / SBA-15 catalyst.

[0026] Figure 2 The results are from the stability study of the catalyst 8% Zr / NC@SBA-15. Detailed Implementation

[0027] The following detailed description is provided through specific embodiments.

[0028] Example 1

[0029] Using Zr as the active component, X% Zr / NC@SBA-15 catalysts with different loadings of NC were prepared by impregnation method:

[0030] Step A: Dissolve zirconium oxynitrate (ZrO(NO3)2) and 1.0g of urea in water, and impregnate it with a commercial pure silicon SBA-15 support (purchased from Nankai Catalyst Factory) in equal volume. The loading of Zr is selected as 2%, 4%, 8%, 12%, 16%, and dried at 80℃ for 8h.

[0031] Step B: The above samples were calcined at 550℃ and 100 mL / min in an argon atmosphere for 4 h to obtain catalysts with different loadings: 2% Zr / NC@SBA-15, 4% Zr / NC@SBA-15, 8% Zr / NC@SBA-15, 12% Zr / NC@SBA-15, and 16% Zr / NC@SBA-15.

[0032] Comparative Example 1

[0033] Preparation of non-NC modified X% Zr / SBA-15 catalyst:

[0034] The preparation process is similar to that in Example 1, except that urea is not added, only zirconium oxynitrate is added.

[0035] The impregnation method was used to prepare X% Zr / SBA-15 catalysts with different loadings. The preparation process is as follows:

[0036] Step A: Dissolve zirconium oxynitrate in water and impregnate it with a commercially available pure silicon SBA-15 carrier in equal volume. The Zr loading is selected as 2%, 4%, 8%, 12%, 16%, and dried at 80℃ for 8 hours.

[0037] Step B: The above samples were calcined in air at 550°C for 4 hours to obtain catalysts with different loadings: 2% Zr / SBA-15, 4% Zr / SBA-15, 8% Zr / SBA-15, 12% Zr / SBA-15, and 16% Zr / SBA-15.

[0038] Example 2

[0039] Preparation of NC-modified Zr-based catalysts with different types of supports:

[0040] The preparation process was similar to that in Example 1, with a Zr loading of 8%. The difference was that the support was replaced with deAl-beta, MFI, MWW, MCM-41, and gaseous SiO2. The gaseous SiO2 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and MFI and MCM-41 were purchased from Nankai Catalyst Factory. All the supports were used directly after purchase without further processing.

[0041] The synthesis method of MWW is as follows: Deionized water, silica, boric acid, and piperidine (PI) are mixed and stirred evenly to form a synthetic gel with the composition 1SiO2:1.4PI:1.33H3BO3:19H2O. This gel is then crystallized in a rotary oven at 130℃ for 1 day, 150℃ for 1 day, and 170℃ for 5 days. The resulting sample is filtered, washed, dried at 80℃, and calcined at 550℃ for 4 hours to obtain the MWW-B sample. The MWW-B sample is then mixed with 6mol / L nitric acid (solid-liquid ratio 1g / 20mL), refluxed at 100℃ for 20 hours, dried at 80℃, and calcined at 550℃ for 4 hours, denoted as MWW.

[0042] The deAl-beta synthesis method is as follows: A beta sample with a silicon-to-aluminum ratio of 12.5 was purchased from Nankai Catalyst Factory and subjected to dealuminization treatment. The beta was mixed with 16 mol / L nitric acid (solid-to-liquid ratio 1 g / 20 mL), refluxed at 80 °C for 24 h, dried at 80 °C, and calcined at 550 °C for 4 h to obtain deAl-beta.

[0043] Comparative Example 2

[0044] Preparation of non-NC-modified Zr-based catalysts with different types of supports:

[0045] The preparation process is similar to that in Example 2, except that urea is not added, only zirconium oxynitrate is added.

[0046] Example 3

[0047] Preparation of NC-modified catalysts with different active components on the same support:

[0048] The preparation process is similar to that in Example 1, except that zirconium oxynitrate is not added to the water, but hafnium chloride (hafnium loading of 8%), yttrium chloride (yttrium loading of 8%), tantalum chloride (tantalum loading of 8%), and zinc chloride (zinc loading of 8%) are added respectively.

[0049] Comparative Example 3

[0050] Preparation of non-NC-modified catalysts with different active components on the same support:

[0051] The preparation process is similar to that in Example 3, except that urea is not added.

[0052] Example 4

[0053] Evaluation process of the catalyst for the production of butadiene from ethanol and acetaldehyde: 0.25 g of the catalyst prepared in the above examples was granulated and packed into a fixed-bed reactor. The feedstock was introduced into the reactor by pump feeding and carrier gas (flow rate of 40 mL / min). The molar ratio of ethanol to acetaldehyde in the reactants was 2:1, the feed rate was 0.005 mL / min, and the reaction space velocity (WHSV) was 0.96 h⁻¹. -1 The reaction temperature is 350℃.

[0054] Methods for calculating reaction conversion rate and selectivity:

[0055] Ethanol conversion rate (%) = (n 反应前的乙醇 -n 反应后剩余乙醇 ) / n 反应前的乙醇 *100%

[0056] Acetaldehyde conversion rate (%) = (n 反应前的乙醛 -n 反应后剩余乙醛 ) / n 反应前的乙醛 *100%

[0057] Total conversion rate (%) = (n 反应前的乙醇和乙醛 -n 反应后剩余乙醇和乙醛 ) / n 反应前的乙醇和乙醛 *100%

[0058] Butadiene selectivity (%) = 2n 产物中丁二烯 / (n 反应前的乙醇和乙醛 -n 反应后剩余乙醇和乙醛 )*100%

[0059] Example 5

[0060] The performance of Zr / NC@SBA-15 catalysts with different loadings in Example 1 was evaluated under the same reaction conditions as in Example 4. The results are shown in Table 1.

[0061] Table 1 Catalytic performance of Zr / NC@SBA-15 catalysts with different loadings in Example 1

[0062]

[0063] The reaction results show that the catalytic performance is relatively good when the Zr loading is 4-12%, and the catalytic performance is better when the loading of the active component Zr is 8%, with the butadiene yield reaching more than 80%.

[0064] Example 6

[0065] The performance of Zr / SBA-15 catalysts with different loadings in Comparative Example 1 was evaluated under the same reaction conditions as in Example 4. The results are shown in Table 2.

[0066] Table 2 shows the catalytic performance of Zr / SBA-15 catalysts with different loadings in Comparative Example 1.

[0067]

[0068] As can be seen from the data in Table 1-2, under the same Zr loading, the Zr / NC@SBA-15 of the present invention has higher conversion rate and butadiene selectivity than the catalyst without nitrogen and carbon modification, and the conversion rate of acetaldehyde is significantly improved, which shows the uniqueness and superiority of the present invention.

[0069] Example 7

[0070] The catalyst performance evaluation in Example 2 and Comparative Example 2 was conducted with the same Zr loading but different supports. The reaction conditions were the same as in Example 4, and the results are shown in Table 3.

[0071] Table 3 Catalytic performance of catalysts in Example 2 and Comparative Example 2

[0072]

[0073] The data in the table show that the reaction performance of Zr-based catalysts on different supports after NC modification was improved. Butadiene selectivity was increased compared to unmodified catalysts, and conversion rates were generally improved. Specifically, the acetaldehyde conversion rate was significantly improved in all NC-modified catalysts, while the decrease in overall conversion rates of deAl-beta and MCM-41 was due to a reduction in ethanol conversion. This indicates that the NC modification strategy is universal and applicable to various silicon-based supported Zr-based catalysts. Its effect on improving the reaction lies in greatly promoting the conversion of acetaldehyde, i.e., promoting the aldol condensation reaction, while slightly inhibiting the conversion of ethanol.

[0074] Example 8

[0075] The catalytic performance of 8% Zr / NC@SBA-15 was investigated at different reaction temperatures. Other reaction conditions were the same as in Example 4. The results are shown in Table 4.

[0076] Table 48% Zr / NC@SBA-15 Catalytic performance at different reaction temperatures

[0077]

[0078] As can be seen from the table, the 8% Zr / NC@SBA-15 catalyst provided by this invention can react at ultra-low temperatures (250℃), with the optimal reaction temperature being 350℃. High butadiene selectivity (>60%) and conversion rate (>50%) can be guaranteed above 325℃.

[0079] Example 9

[0080] The catalytic performance of 8% Zr / NC@SBA-15 was investigated under different space velocities. Other reaction conditions were the same as in Example 4. The results are shown in Table 5.

[0081] Table 58% Zr / NC@SBA-15 Catalytic performance under different space velocity conditions

[0082]

[0083] The data in the table show that the catalyst provided by this invention exhibits good reaction performance at different reaction space velocities (WHSVs), with the best performance at a WHSV of 0.96 h⁻¹. -1 When the time is right, the optimal catalytic effect can be achieved.

[0084] Example 10

[0085] The reaction performance of NC-modified catalysts and non-NC-modified catalysts with different active components on the same support in Example 3 and Comparative Example 3 was evaluated. The reaction conditions were the same as in Example 4, and the results are shown in Table 6.

[0086] Table 6. Catalytic performance of NC-modified and non-NC-modified catalysts in Example 3 and Comparative Example 3.

[0087]

[0088] As can be seen from the data in the table, the NC-modified catalyst preparation method provided by this invention has an improving effect on different active components. It is mainly reflected in the significant improvement of acetaldehyde conversion rate and the high level of butadiene selectivity, demonstrating the superiority and universality of this preparation method.

[0089] Example 11

[0090] The stability of 8% Zr / SBA-15 and 8% Zr / NC@SBA-15 was investigated under the same reaction conditions as in Example 4. The results are shown in Appendix. Figure 1 and Figure 2 As shown in the figure, the conversion rate of 8% Zr / SBA-15 decreased rapidly in the first 8 hours, from 71% to 60%, and after 100 hours of operation, the total conversion rate dropped to around 52%. In contrast, the NC-modified 8% Zr / NC@SBA-15 catalyst showed little change in conversion rate over 300 hours, maintaining a high selectivity of around 73%. This indicates that the NC-modified catalyst not only exhibits significantly higher activity than the original 8% Zr / SBA-15 but also demonstrates a substantial improvement in stability, showcasing the superiority of the NC modification strategy.

[0091] In summary, this invention utilizes a nitrogen-carbon modification strategy based on urea-assisted pyrolysis to prepare a catalyst for the production of butadiene from ethanol. This method achieves high activity, high selectivity, and high stability in the production of butadiene. Furthermore, it is universally applicable to most metal-silicon-based support systems and can be mass-produced, making it easy for industrial applications and demonstrating broad application prospects.

Claims

1. The application of a nitrogen-carbon modified catalyst for the catalytic conversion of ethanol-acetaldehyde to butadiene in the reaction of ethanol-acetaldehyde to butadiene, characterized in that, The reaction was carried out in a fixed-bed reactor at atmospheric pressure, with a molar ratio of acetaldehyde to ethanol of 1:1 to 1:5, and a reaction space velocity (WHSV) ranging from 0.12 to 10 h⁻¹. -1 Using inert gas as the carrier gas, the carrier gas space velocity (GSHV) is 500-10000 h⁻¹. -1 The reaction temperature is 200-500°C. o C; The catalyst is represented by M / NC@support, where M is the active component, which is one or more of the oxidized forms of Zr, Hf, Ta, Y, and Zn, and the total loading of the active metal M element in the catalyst is ≥0.1 wt%; NC represents the nitrogen and carbon modification of the catalyst, with the loading of nitrogen element in the catalyst being ≥0.1 wt% and the loading of C element in the catalyst being ≥0.1 wt%; support is a silicon-based support. The catalyst preparation method includes the following steps: impregnating a solution containing a soluble salt of active component M and a soluble nitrogen and carbon source onto a silicon-based support, drying it, and then calcining it in an inert gas at a calcination temperature of 350-750°C. o C, roasting time is 1-24 hours, then it is obtained.

2. The application according to claim 1, characterized in that, The loading of M in the catalyst is 1-50 wt%; the loading of nitrogen in the catalyst is 1-15 wt%; and the loading of C in the catalyst is 0.5-25 wt%.

3. The application according to claim 2, characterized in that, The loading of M in the catalyst is 4-20 wt%; the loading of nitrogen in the catalyst is 2-8 wt%; and the loading of C in the catalyst is 2-15 wt%.

4. The application according to claim 1, characterized in that, The silicon-based support is a silicon-based molecular sieve or porous silica. The silicon-based molecular sieve includes one or more of SBA-15, SBA-16, silicate-1, deAl-beta, MCM-41, and MWW. The porous silica includes one or more of silica, silica sol, and mesoporous silica, and the specific surface area of ​​the porous silica is >20 m². 2 / g.

5. The application according to claim 1, characterized in that, The soluble salt of the active component M is one or more of the following: nitrate, chloride, oxynitrate, oxychloride, and organic alkoxide of M; the nitrogen and carbon source is one or more of the following: urea, cyanamide, dicyandiamide, melamine, thiourea, isobutyramide, dicarboxyhydrazide, and dopamine.

6. The application according to claim 1, characterized in that, Drying temperature is 60-200°C o C, Firing temperature is 500-600 o C, roasting time is 2-6 hours.

7. The application according to claim 1, characterized in that, The reaction temperature is 300-400°C. o C, the molar ratio of acetaldehyde to ethanol is 1:1.2-1:3, and the reaction space velocity range is WHSV = 0.25-6 h. -1 The inert gas is one or more of nitrogen, argon, and helium, and the carrier gas space velocity is 3000-5000 h⁻¹. -1 .

8. The application according to claim 7, characterized in that, In the reaction process, the total conversion rate of ethanol and acetaldehyde is 40-95%, and the selectivity of 1,3-butadiene product is 50-80%.

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