Nitrogen-carbon-modified catalyst for preparing butadiene from ethanol and acetaldehyde as well as preparation method and application of nitrogen-carbon-modified catalyst

Abstract

The invention discloses a nitrogen-carbon modified catalyst for preparing butadiene from ethanol and acetaldehyde as well as a preparation method and application of the catalyst, and belongs to the technical field of preparation of butadiene from ethanol and acetaldehyde. The active component of the catalyst is one or more than two of Zr, Hf, Ta, Y, Sn, Zn and Nb in an oxidation state, and the total loading amount of the active metal element M in the catalyst is greater than or equal to 0.1 wt%; the loading amount of the nitrogen element in the catalyst is greater than or equal to 0.1 wt%, the loading amount of the carbon element in the catalyst is greater than or equal to 0.1 wt%, the carrier is a silicon-based carrier, and the silicon-based carrier is obtained by dipping the silicon-based carrier with a soluble salt containing an active component M and a soluble nitrogen carbon source, drying and roasting in inert gas. According to the catalyst, the conversion rate of ethanol and acetaldehyde in the reaction for preparing butadiene through catalytic conversion of ethanol and acetaldehyde can reach 90% or above, the selectivity of butadiene reaches up to 80% or above, stable operation can be conducted for 300 hours or above, and good application prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing butadiene from ethanol and acetaldehyde, and specifically relates to a nitrogen-carbon modified ethanol-acetaldehyde-preparation-of-butadiene catalyst, a preparation method thereof, and application in the reaction of preparing butadiene by catalytic conversion of ethanol-acetaldehyde. Background Art

[0002] 1,3-Butadiene is one of the most important bulk chemicals, and its output is second only to ethylene and propylene. It is widely used in the preparation of synthetic rubber, synthetic resin and other products, and has a pivotal industrial use in the field of polymers. At present, the demand for butadiene has reached 16 million tons / year, and it is growing at a rate of 4% per year (Xu Churong. Research Progress of Butadiene Synthesis Technology in my country [J]. Fine and Specialty Chemicals, 2022, 30(08): 10-12.). Nowadays, more than 95% of butadiene is separated from by-products in the process of producing ethylene by steam cracking of naphtha, so the output of butadiene is greatly dependent on the output of ethylene. However, the increase in shale gas production has led to changes in the composition of cracking raw materials, and the output of butadiene has been greatly impacted. Therefore, finding a sustainable and green butadiene production path is now a top priority.

[0003] The technology of producing butadiene from ethanol has a long history, more than a hundred years ago, and was once the main process for industrial production of butadiene. As a green and sustainable biomass resource, ethanol has a wide range of sources and is inexpensive, which is comparable to non-renewable fossil resources as a raw material. Therefore, the preparation of butadiene using ethanol as a raw material has broad application prospects and important research significance.

[0004] There are two main production processes for ethanol-to-butadiene, namely the one-step process and the two-step process. The one-step process refers to using only ethanol as the raw material to produce butadiene in one step; while the two-step process refers to using ethanol and acetaldehyde as co-feed materials to produce butadiene. The two-step process has high stability because it does not contain a dehydrogenation center, but it will inevitably produce more dehydration and condensation by-products, resulting in a decrease in reaction selectivity. At present, the maximum stability of this reaction is only 168 hours, and there is still room for further improvement. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a nitrogen-carbon modified ethanol acetaldehyde to butadiene catalyst and its preparation method and application in the catalytic conversion of ethanol acetaldehyde to butadiene. The nitrogen-carbon modified catalyst prepared by the present invention has very high ethanol and acetaldehyde reaction activity, butadiene selectivity and stability, and the preparation method of the catalyst has significant advantages such as low cost, simplicity and ease of use and strong universality.

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

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

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

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

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

[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 white carbon black, silica sol, and mesoporous silica, and the specific surface area of ​​the porous silica is greater than 20m 2 / g.

[0012] In a second aspect, the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps: impregnating a solution containing a soluble salt of an active component M and a soluble nitrogen and carbon source on a silicon-based carrier, drying, and calcining in an inert gas at a calcination 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 nitrate, chloride, oxynitrate, oxychloride, and organic alcohol salt of M.

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

[0015] Based on the above technical scheme, further, the nitrogen and carbon sources are one or more of urea, cyanamide, dicyandiamide, melamine, thiourea, isobutyramide, diformyl hydrazide, and dopamine.

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

[0017] In a third aspect, the present invention provides the use of the above catalyst in the catalytic conversion of ethanol and acetaldehyde to prepare butadiene.

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

[0019] Preferably, the reaction temperature is 300-400°C, the molar ratio of acetaldehyde to ethanol is 1:1.2-1:3, and the reaction space velocity range is WHSV=0.25-6h -1 The inert gas is one or more of nitrogen, argon and helium, and the carrier gas space velocity is 3000-5000h -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 the present invention using the nitrogen-carbon modification strategy of urea-assisted pyrolysis to prepare a catalyst for ethanol to butadiene is universal and has an improvement effect on different commercial carriers without the need for lengthy molecular sieve synthesis steps; the catalyst reaction performance of different active components is also improved.

[0023] (2) The present invention only requires a simple impregnation method and a pyrolysis method to obtain the catalyst, and the preparation method is simple and efficient.

[0024] (3) The present invention improves the reaction conversion rate and selectivity by modifying the acid center of the catalyst through nitrogen-carbon modification, thereby improving the adsorption capacity of the active site for the reactant acetaldehyde, and obtaining a higher butadiene yield with good stability. The ethanol acetaldehyde conversion rate can reach more than 80%, and the butadiene selectivity is as high as more than 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The stability test results of the catalyst 8% Zr / SBA-15 are shown below;

[0026] Figure 2 These are the stability investigation results of the catalyst 8% Zr / NC@SBA-15. DETAILED DESCRIPTION

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

[0028] Example 1

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

[0030] Step A, zirconium oxynitrate (ZrO(NO 3 ) 2 ) was dissolved with 1.0 g urea in water and impregnated with an equal volume of commercial pure silicon SBA-15 carrier (purchased from Nankai Catalyst Factory). The Zr loading was selected as 2%, 4%, 8%, 12%, and 16%, respectively, and dried at 80°C for 8 h.

[0031] Step B, calcining the above samples at 550°C, 100 mL / min argon atmosphere for 4 h to obtain catalysts with different loading amounts of 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 of Example 1, except that urea is not added, and only zirconyl nitrate is added.

[0035] X% Zr / SBA-15 catalysts with different loadings were prepared by impregnation method. The preparation process is as follows:

[0036] Step A, dissolving zirconium oxynitrate in water, and impregnating it with commercial pure silicon SBA-15 carrier in equal volumes, with the loading amounts of Zr selected as 2%, 4%, 8%, 12%, and 16%, respectively, and drying at 80° C. for 8 h.

[0037] Step B, calcining the above samples at 550°C in air atmosphere for 4 hours to obtain catalysts with different loading amounts: 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 is similar to that of Example 1, with a Zr loading of 8%. The difference is that the carrier is replaced with deA1-beta, MFI, MWW, MCM-41 and gas phase SiO 2 Among them, the gas phase SiO 2 It was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., MFI and MCM-41 were purchased from Nankai Catalyst Factory, and the above carriers were used directly after purchase without further treatment.

[0041] The MWW synthesis method is as follows: deionized water, white carbon black, boric acid and piperidine (PI) are mixed and stirred evenly to form a 1SiO 2 :1.4PI:1.33H 3 BO 3 :19H 2 O was synthesized gel, and then placed in a rotary oven for crystallization at 130°C for 1 day, 150°C for 1 day, and 170°C for 5 days. The obtained sample was filtered, washed, dried at 80°C, and calcined at 550°C for 4h to obtain MWW-B sample. The above MWW-B sample was then mixed with 6mol / L nitric acid (solid-liquid ratio 1g / 20mL), refluxed at 100°C for 20h, then dried at 80°C, and calcined at 550°C for 4h, recorded as MWW.

[0042] The synthesis method of deAl-beta is as follows: a beta sample with a silicon-aluminum ratio of 12.5 was purchased from Nankai Catalyst Factory, and dealuminated. Beta was mixed with 16 mol / L nitric acid (solid-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 on different types of supports:

[0045] The preparation process is similar to that of Example 2, except that urea is not added and only zirconyl nitrate is added.

[0046] Example 3

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

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

[0049] Comparative Example 3

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

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

[0052] Example 4

[0053] Evaluation process of catalyst for preparing butadiene from ethanol and acetaldehyde: 0.25 g of the catalyst prepared in the above example was pelletized and loaded into a fixed bed reactor, and the raw materials were brought into the reactor by pump feeding and carrier gas (flow rate of 40 mL / min). The molar ratio of ethanol and acetaldehyde in the reaction material was 2:1, the feed rate was 0.005 ml / min, and the reaction space velocity was WHSV=0.96 h -1 , the reaction temperature is 350℃.

[0054] Calculation method of 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 the Zr / NC@SBA-15 catalyst with different loading amounts in Example 1 was evaluated. The reaction conditions were the same 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] It can be seen from the reaction results that when the Zr loading is 4-12%, the catalytic performance is relatively good, among which the loading of the active component Zr at 8% has a better catalytic performance, and the butadiene yield can reach more than 80%.

[0064] Example 6

[0065] The performance of the Zr / SBA-15 catalyst with different loading amounts in Comparative Example 1 was evaluated. The reaction conditions were the same as those in Example 4. The results are shown in Table 2.

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

[0067]

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

[0069] Example 7

[0070] The catalyst performance of Example 2 and Comparative Example 2 was evaluated by replacing different carriers at the same Zr loading. The reaction conditions were the same as those of Example 4. The results are shown in Table 3.

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

[0072]

[0073] From the data in the table, it can be seen that the reaction performance of Zr-based catalysts with different carriers modified by NC is improved, the butadiene selectivity is improved compared with that before modification, and the conversion rate is basically improved. Among them, the acetaldehyde conversion rate of all NC-modified catalysts is significantly improved, while the total conversion rate of deAl-beta and MCM-41 is reduced due to the reduced conversion rate of ethanol. This shows that this NC modification strategy is universal and suitable for Zr-based catalysts supported by various silicon-based carriers. Its effect on the reaction is that it greatly promotes the conversion of acetaldehyde, that is, it promotes the aldol condensation reaction, while slightly inhibiting the conversion of ethanol.

[0074] Example 8

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

[0076] Table 4 Catalytic performance of 8% Zr / NC@SBA-15 at different reaction temperatures

[0077]

[0078] It can be seen from the table that the 8% Zr / NC@SBA-15 catalyst provided by the present invention can react at an ultra-low temperature (250°C), and its optimal reaction temperature is 350°C. Above 325°C, it can ensure higher butadiene selectivity (>60%) and conversion rate (>50%).

[0079] Example 9

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

[0081] Table 5 Catalytic performance of 8% Zr / NC@SBA-15 under different space velocity conditions

[0082]

[0083] It can be seen from the data in the table that the catalyst provided by the present invention has good reaction performance at different reaction space velocities. -1 The best catalytic effect can be achieved.

[0084] Example 10

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

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

[0087]

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

[0089] Embodiment 11

[0090] The stability of 8% Zr / SBA-15 and 8% Zr / NC@SBA-15 was investigated. The reaction conditions were the same as those in Example 4. The results are shown in the attached Figure 1 and Figure 2 . As can be seen from the figure, the conversion rate of 8% Zr / SBA-15 dropped rapidly in the first 8 hours, from 71% to 60%. After 100 hours of operation, the total conversion rate dropped to about 52%. However, the conversion rate of the NC-modified 8% Zr / NC@SBA-15 catalyst did not change much within 300 hours, and the selectivity remained at a high level of about 73%. This shows that the NC-modified catalyst is not only much more active than the original 8% Zr / SBA-15, but also has greatly improved stability, reflecting the superiority of the NC modification strategy.

[0091] In summary, the present invention utilizes the nitrogen-carbon modification strategy of urea-assisted pyrolysis to prepare a catalyst for ethanol to butadiene, which can achieve high activity, high selectivity, and high stability in the preparation of butadiene. This method is universal and suitable for most metal-silicon-based carrier systems. It can also be mass-produced and easily applied industrially, and has broad application prospects.

Claims

1. A nitrogen-carbon modified ethanol acetaldehyde to butadiene catalyst, characterized in that: The catalyst is represented by M / NC@support, wherein M is an active component, which is one or more of Zr, Hf, Ta, Y, Sn, Zn, and Nb in an oxidized state, and the total loading of the active metal M element in the catalyst is ≥0.1wt%; NC represents nitrogen and carbon modification of the catalyst, the loading of the nitrogen element in the catalyst is ≥0.1wt%, and the loading of the C element in the catalyst is ≥0.1wt%; support is a silicon-based carrier.

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

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

4. The catalyst according to claim 1, characterized in that 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 white carbon black, silica sol, and mesoporous silica. The specific surface area of ​​the porous silica is greater than 20 m 2 / g.

5. The method for preparing the catalyst according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: impregnating a solution containing a soluble salt of an active component M and a soluble nitrogen and carbon source on a silicon-based carrier, drying the solution, and then calcining the solution in an inert gas at a temperature of 350-750° C. for a time of 1-24 hours to obtain the product.

6. The preparation method according to claim 5, characterized in that: The soluble salt of the active component M is one or more of nitrate, chloride, oxynitrate, oxychloride and organic alcohol salt of M; the nitrogen and carbon sources are one or more of urea, cyanamide, dicyandiamide, melamine, thiourea, isobutylamide, diformyl hydrazide and dopamine; and the inert gas is one or more of nitrogen, argon and helium.

7. The preparation method according to claim 5, characterized in that: The drying temperature is 60-200°C, the calcination temperature is 500-600°C, and the calcination time is 2-6 hours.

8. Use of the catalyst according to any one of claims 1 to 4 in the catalytic conversion of ethanol and acetaldehyde to prepare butadiene, characterized in that: The reaction is carried out in a fixed bed reactor at atmospheric pressure, the molar ratio of acetaldehyde to ethanol is 1:1-1:5, and the reaction space velocity range is WHSV=0.12-10h -1 , using inert gas as carrier gas, carrier gas space velocity GSHV = 500-10000h -1 , the reaction temperature is 200-500℃.

9. The use according to claim 8, characterized in that The reaction temperature is 300-400°C, the molar ratio of acetaldehyde to ethanol is 1:1.2-1:3, and the reaction space velocity range is WHSV=0.25-6h -1 The inert gas is one or more of nitrogen, argon and helium, and the carrier gas space velocity is 3000-5000h -1 .

10. The use according to claim 8, characterized in that During the reaction, 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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