CN111215075A

CN111215075A - Catalyst for eliminating ethylene coupling nitrous oxide produced by oxidative dehydrogenation of ethane and preparation and application thereof

Info

Publication number: CN111215075A
Application number: CN201811411803.0A
Authority: CN
Inventors: 林坚; 周岩良; 王晓东
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2018-11-25
Filing date: 2018-11-25
Publication date: 2020-06-02
Anticipated expiration: 2038-11-25
Also published as: CN111215075B

Abstract

The invention relates to a catalyst for eliminating ethylene coupled nitrous oxide produced by oxidative dehydrogenation of ethane, and preparation and application thereof. Specifically, the NiX composite metal oxide (NiX-MO) is prepared by taking ultrathin NiX hydrotalcite (NiX-HT, X ═ Al, Ga and In) as a precursor, the active component is NiO, and the ratio of Ni to X can be regulated and controlled to be 2-5. Wherein the ultra-thin NiX-HT is prepared by coprecipitation and microemulsion method, and NiX-MO is obtained by roasting the hydrotalcite at 400-700 deg.C. The catalyst can be at 400-650 deg.C₂H₆And N₂O volume ratio of 0.5-5, He or N₂Under equilibrium conditions, ethane is converted into ethylene with high selectivity, and N can be eliminated₂O, and does not deposit carbon, and does not deactivate after running for 240h continuously. The nickel-based catalyst improved based on the ultrathin hydrotalcite has the selectivity reaching 100 percent under a certain conversion rate. The important significance of ultrahigh ethylene selectivity lies in atom economy, so that ethane carbon atoms are nearly 100% utilized, and meanwhile, products are ethylene and water, so that the product separation cost is reduced, and the method has a good industrial application prospect.

Description

Catalyst for eliminating ethylene coupling nitrous oxide produced by oxidative dehydrogenation of ethane and preparation and application thereof

Technical Field

The invention relates to a catalyst for eliminating ethylene coupling nitrous oxide produced by oxidative dehydrogenation of ethane, a preparation method and application thereof

Technical Field

Ethylene is an important organic chemical raw material and one of the important marks of the national petrochemical development level. The global ethylene demand reaches 1.53 million tons in 2016, and will also keep the demand increasing at 520 million tons per year. At present, the raw materials for producing ethylene still mainly comprise naphtha and ethane. However, with the development of shale gas exploration and exploitation technology, the production rate of shale gas per year will reach 104% in 2012-2040 years (aust.j.agr.resource.eco.59 (2015) 571). The ethane is used as associated gas, the yield is increased greatly, and the cheap and sufficient raw materials enable the ethane to produce the ethylene with greater economic benefit. Taking the total cost of producing each ton of ethylene from different feedstocks in 2012 as an example (petrochemical technology and economics 1(2015)1), ethane is $ 521, imported ethane is $ 690, and naphtha is $ 1086. Since the production cost of ethane as a raw material is the lowest as compared with other raw materials, the proportion of ethane in the ethylene production raw material has been increasing in recent years.

The conventional mode of ethylene generation is dominated by steam cracking. But the steam cracking is limited by thermodynamics, the reaction temperature is about 1000 ℃, and the energy consumption is high; the number of byproducts is large, and the separation cost is high; the equipment is seriously coked and needs to be stopped and cleaned regularly. The ethylene preparation by oxidative dehydrogenation of ethane is an exothermic reaction, and thermodynamic limitation does not exist; the reaction temperature is lower (300-650 ℃), and the requirement on equipment is low; and the catalyst has no carbon deposition and equipment coking phenomena, and is a very promising ethylene production mode.

At present, the catalyst for preparing ethylene by oxidative dehydrogenation of ethane mainly comprises Pt-based, Ni-based, Mo-based composite oxides, alkali metal halides, carbon and boron nitride non-oxide catalysts. PtSn/Al is reported in literature (Science 285(1999)712)₂O₃Adding a large amount of hydrogen (C) into the reaction₂H₆:O₂:H₂2:1:2), ethane conversion of 73% at 950 ℃, ethylene selectivity of 83%. However, the reaction temperature is high, and the oxidation system is added with a large amount of hydrogen, so that the explosion risk is caused, and meanwhile, the cost of the noble metal is high, and the large-scale application is difficult. United carbon patents (US Patent 4250346 and CN 85103650 a) reported that the movnbsbco catalyst had an ethane conversion of 73% and an ethylene selectivity of 71% at 400 ℃ and performed a pilot plant. However, the catalyst and the preparation conditions are relatively complex, so that the catalyst repeatability is to be improved, and the industrialization is not realized at present. LiKCl/MgO + Dy reported in the literature (J.Am.chem.Soc.136(2014)12691)₂O₃The catalyst has ethane conversion rate up to 80% and ethylene selectivity up to 90% at 625 deg.c, but after some reaction period, the catalyst is deactivated obviously owing to Cl loss. The NiMO (M is Sn, Ti, W) catalyst reported in the literature (ACS Catal.6(2016)2852) has ethane conversion rate of 30% and ethylene selectivity of 80% under the condition of 350 ℃, and the NiO-based catalyst has better reaction activity but is easy to be over-oxidized so as to reduce the selectivity. The ethylene selectivity of the catalyst is best about 90 percent at present, and the catalyst shows the reaction performance close to 100 percent selectivity.

In the system of ethane oxidative dehydrogenation coupled with nitrous oxide elimination, the common catalyst comprises a supported Fe-based, V-based and Mo-based catalyst. The Fe-ZSM5 catalyst reported in the literature (appl. Catal. B-environ.64(2006)201) has the ethane conversion rate of 22% and the ethylene selectivity of 70% under the condition of 400 ℃, but aromatic organic matters are easily generated on the Fe-based catalyst to cause the catalyst to be deactivated. The Mo/Si-Ti catalyst reported in the literature (J.Phy.chem.C 113(2009)10112) has ethane conversion of 4.3% and ethylene selectivity of 85% at 600 ℃. Although these catalysts show superior selectivity under nitrous oxide conditions compared to oxygen systems, overall ethylene selectivity is not high. Therefore, it is of great significance to develop a catalyst which can eliminate nitrous oxide and generate ethylene with high selectivity.

Disclosure of Invention

The invention provides a catalyst for eliminating ethylene coupled nitrous oxide produced by oxidative dehydrogenation of ethane, and a preparation method and application thereof. Elimination as referred to herein means facilitating dissociation of nitrogen-oxygen bonds, promoting N₂And (4) decomposing the O.

In order to achieve the purpose, the technical scheme of the invention is as follows: the catalyst for eliminating ethylene coupled nitrous oxide produced by oxidative dehydrogenation of ethane is a composite oxide consisting of Ni and an auxiliary agent X, and is expressed as NiX-MO, and the molar ratio of Ni to X is 2-5.

Taking the NiAl-MO catalyst as an example, the preparation method comprises the following steps: mixing Ni (NO)₃)₂·6H₂O and Al (NO)₃)₃·9H₂Dissolving O in water according to the required molar ratio to obtain the metal salt solution. And dissolving NaOH and alkali metal salt together in water to obtain an alkali metal salt solution. Putting the alkali metal salt solution in a water bath at 20-90 ℃, dropping the metal solution into the alkali solution at 1-3mL/min, continuously stirring, adding Sodium Dodecyl Sulfate (SDS), adjusting the pH to 9.0-12.0 by using 1-4M NaOH, continuously stirring for 12-24h, filtering, washing, drying, and calcining in a muffle furnace at 400-700 ℃ for more than 1h to obtain the NiAl-MO catalyst.

The reaction condition for eliminating the ethylene coupling nitrous oxide prepared by the oxidative dehydrogenation of ethane is continuous fixed bed reaction, and raw material gas forms C₂H₆Pressure 2-50kPa, C₂H₆And N₂O volume ratio of 0.5-5, He or N₂Under the condition of equilibrium and normal pressure, the space velocity is 6000 to 72000mL/g_cat/h。

Compared with the prior art, the invention has the substantial characteristics that:

1. according to the invention, the thickness of the hydrotalcite can be regulated and controlled by using the amount of SDS (sodium dodecyl sulfate) as a surfactant by using a coprecipitation combined microemulsion method, so that an ultrathin hydrotalcite precursor is obtained, and the NiX-MO catalyst is obtained after roasting, has a stable structure and does not deactivate after continuously running for 240 hours.

2. The invention can convert ethane into ethylene with high selectivity, and when the conversion rate of ethane is 10%, the selectivity of ethylene is close to 100%. At 27% conversion, ethylene selectivity was greater than 90%, which is the best result in nickel oxide based catalysts.

3. The invention can utilize N at the same time₂O is an oxidant and can be used for greenhouse gas N₂The conversion of O is eliminated.

Drawings

Fig. 1 is an XRD pattern of hydrotalcite precursor obtained by adding different contents of surfactant.

FIG. 2 is a TEM image of hydrotalcite precursors obtained by adding different amounts of surfactant, wherein (a) SDS is 0g, (b) SDS is 0.9g, (c) SDS is 3.6g, (d) SDS is 14.4 g.

FIG. 3 shows Ni₃Catalytic performance of Al-MO at different temperatures.

FIG. 4 shows Ni₃The catalytic performance of the Al-MO at different space velocities is compared with the results of the prior literature.

FIG. 5 shows the formula of Ni₃Evaluation of stabilizer for Al-MO.

Detailed Description

The following examples will help to understand the present invention, but the scope of the present invention is not limited to these examples.

The present invention will be described in detail with reference to examples.

Example 1: ni₂Al-MO catalyst preparation

9.70g of Ni (NO)₃)₂·6H₂O and 6.25g of Al (NO)₃)₃·9H₂O was dissolved together in 50mL of ultrapure water, and 2.40g of NaOH and 4.24g of Na were added₂CO₃The solutions were dissolved together in 50mL of ultrapure water. Adding aqueous alkali into water bath at 65 deg.C, dropping metal solution into aqueous alkali at 2mL/min, stirring, adding 14.4g sodium dodecyl sulfate surfactant, adjusting pH to 10.0 with NaOH, stirring in water bathStirring for 18h, filtering, washing and drying to obtain ultrathin Ni₂Al-HT hydrotalcite precursor (the number of layers of hydrotalcite is 1-10, the total thickness is 1-10nm), and then calcining in a 600 ℃ muffle furnace for 3h to obtain Ni₂Al-MO catalyst.

Example 2: ni₃Al-MO catalyst preparation

10.89g of Ni (NO)₃)₂·6H₂O and 4.68g of Al (NO)₃)₃·9H₂O was dissolved together in 50mL of ultrapure water, and 2.40g of NaOH and 4.24g of Na were added₂CO₃The solutions were dissolved together in 50mL of ultrapure water. Putting the alkali solution into a water bath at 65 ℃, dropping the metal solution into the alkali solution at 2mL/min, continuously stirring, adding 14.4g of sodium dodecyl sulfate surfactant, adjusting the pH to 10.0 by NaOH, stirring in the water bath for 18h, filtering, washing and drying to obtain the ultrathin Ni₃Al-HT precursor (the number of layers of hydrotalcite is 1-10, the total thickness is 1-10nm), and then calcining in a muffle furnace at 600 ℃ for 3h to obtain Ni₃Al-MO catalyst.

Example 3: ni₄Al-MO catalyst preparation

11.63g of Ni (NO)₃)₂·6H₂O and 3.75g of Al (NO)₃)₃·9H₂O was dissolved together in 50mL of ultrapure water, and 2.40g of NaOH and 4.24g of Na were added₂CO₃The solutions were dissolved together in 50mL of ultrapure water. Putting the alkali solution into a water bath at 65 ℃, dropping the metal solution into the alkali solution at 2mL/min, continuously stirring, adding 14.4g of sodium dodecyl sulfate surfactant, adjusting the pH to 10.0 by NaOH, stirring in the water bath for 18h, filtering, washing and drying to obtain the ultrathin Ni₄Al-HT precursor (the number of layers of hydrotalcite is 1-10, the total thickness is 1-10nm), and then calcining in a muffle furnace at 600 ℃ for 3h to obtain Ni₄Al-MO catalyst.

Example 4: ni₃Ga-MO catalyst preparation

10.89g of Ni (NO)₃)₂·6H₂O and 5.22g of Ga (NO)₃)₃·9H₂O was dissolved together in 50mL of ultrapure water, and 2.40g of NaOH and 4.24g of Na were added₂CO₃The solutions were dissolved together in 50mL of ultrapure water. Putting the alkali solution into a water bath at 65 ℃, dropping the metal solution into the alkali solution at 2mL/min, continuously stirring, adding 14.4g of sodium dodecyl sulfate surfactant, adjusting the pH to 10.0 by NaOH, stirring in the water bath for 18h, filtering, washing and drying to obtain the ultrathin Ni₃Al-HT precursor (the number of layers of hydrotalcite is 1-10, the total thickness is 1-10nm), and then calcining in a muffle furnace at 600 ℃ for 3h to obtain Ni₃Ga-MO catalyst.

Example 5: ni₃In-MO catalyst preparation

10.89g of Ni (NO)₃)₂·6H₂O and 3.76g of In (NO)₃)₃·xH₂O was dissolved together in 50mL of ultrapure water, and 2.40g of NaOH and 4.24g of Na were added₂CO₃The solutions were dissolved together in 50mL of ultrapure water. Putting the alkali solution into a water bath at 65 ℃, dropping the metal solution into the alkali solution at 2mL/min, continuously stirring, adding 14.4g of sodium dodecyl sulfate surfactant, adjusting the pH to 10.0 by NaOH, stirring in the water bath for 18h, filtering, washing and drying to obtain the ultrathin Ni₃In-HT precursor (the number of layers of hydrotalcite is 1-10, the total thickness is 1-10nm), and then calcining In a muffle furnace at 600 ℃ for 3h to obtain Ni₃An In-MO catalyst.

Example 6: preparation of Ni by adjusting different amounts of SDS₃Al-MO

10.89g of Ni (NO)₃)₂·6H₂O and 4.68g of Al (NO)₃)₃·9H₂O was dissolved together in 50mL of ultrapure water, and 2.40g of NaOH and 4.24g of Na were added₂CO₃The solutions were dissolved together in 50mL of ultrapure water. Putting the alkali solution into a water bath at 65 ℃, dropping the metal solution into the alkali solution at 2mL/min, continuously stirring, adding 14.4g, 3.6g,0.9g and 0g of sodium dodecyl sulfate surfactant respectively, adjusting the pH to 10.0 by NaOH, stirring in the water bath for 18h, filtering, washing and drying to obtain the ultrathin Ni₃Al-HT precursor (the number of layers of hydrotalcite is 1-10, the total thickness is 1-10nm), and then calcining in a muffle furnace at 600 ℃ for 3h to obtain Ni₃Al-MO catalyst.

Comparative example 1: preparation of NiO by impregnation method/Al₂O₃Catalyst and process for preparing same

3.15g of Ni (NO) were weighed₃)₂·6H₂Dissolving O in proper amount of ultrapure water, adding 1g of gamma-Al₂O3, stirring uniformly, and soaking for 24h at room temperature. Then putting the mixture into an oven at 80 ℃ for overnight drying, uniformly grinding the mixture, and roasting the mixture in a muffle furnace at 600 ℃ for 3 hours to obtain NiO/Al₂O₃A catalyst.

Comparative example 2: preparation of cp-Ni by coprecipitation method₃Al-MO catalyst

The specific preparation process is shown in example 6, when 0g of surfactant is added, the catalyst is prepared by coprecipitation method, and the obtained catalyst is named cp-Ni₃Al-MO。

Results

All ethane conversion and ethylene selectivity calculations in this patent are as follows:

C₂H₆conversion＝(C₂H₆(in)-C₂H₆(out))/C₂H₆(in)

C₂H₄selectivity＝C₂H₄(out)/(C₂H₆(in)-C₂H₆(out))

wherein C is₂H₆(in) represents the amount of ethane in the reaction gas; c₂H₆(out) represents the amount of ethane in the product; c₂H₄(out) represents the amount of ethylene in the product.

1. Different NiAl ratios and reaction properties of NiX catalysts

As shown in Table 1, it can be seen from examples 1,2 and 3 that adjusting the ratio of Ni to Al yields Ni_xThe Al-MO catalyst shows excellent ethane oxidative dehydrogenation performance, and the selectivity of ethylene is more than 90%. Wherein Ni₃The Al-MO has the highest catalytic activity, and the conversion rate of ethane is 27% and the selectivity reaches 90% under the condition of 600 ℃. As can be seen from examples 4 and 5, Ni was produced₃Ga-MO and Ni₃The In-MO catalyst also shows better ethylene selectivity, which is more than 90% at a certain conversion rate.

2. Reactivity of catalysts prepared by different preparation methods

Ni prepared by combining co-precipitation with microemulsion method in example 2₃Al-MO catalyst-NiO Al obtained by impregnation method in comparative example 1₂O₃Catalyst and cp-Ni co-precipitated in comparative example 2₃Al-MO catalyst at different temperatures and normal pressure, C₂H₆:N₂He is 1:1:48 (molar ratio), and the space velocity is 6000mL/g_catThe evaluation was carried out under the conditions of/h, and the detailed results are shown in Table 2. NiO/Al obtained by impregnation₂O₃The catalyst has the lowest reaction temperature but the worst selectivity, and when the ethane conversion rate is close to 10 percent, the ethylene selectivity is only 55 percent; Cp-Ni prepared by coprecipitation method₃Al-MO, ethylene selectivity is improved to 73%; ni obtained by using ultra-thin hydrotalcite prepared by micro-emulsion method as precursor₃Al-MO with selectivity higher than 98%.

3. Different amounts of SDS to Ni₃Influence of Al-MO

Example 6 catalyst precursor Ni₃The XRD results of Al-HT are shown in FIG. 1, and as the content of the surfactant increases, the intensity of the XRD peak decreases and the peak profile widens, indicating that the precursor becomes smaller. As a result of electron microscopy, as shown in fig. 2, it can be seen that the thickness of hydrotalcite gradually decreased. The detailed catalytic properties are shown in table 3. It can be seen that the selectivity of ethylene is improved from 61% to over 90% after the surfactant is added, which indicates that the addition of the surfactant can greatly improve the selectivity of ethylene. After the surfactant is added, the thickness of the hydrotalcite is gradually reduced, and the reaction activity of the catalyst is continuously improved correspondingly. Ni prepared from ultrathin hydrotalcite precursor at 600 DEG C₃The Al-MO catalyst has ethane conversion rate of 27% and selectivity of 90%. 4.Ni₃Catalytic performance of Al-MO under different oxidants

The catalyst obtained in example 2 was tested under the conditions of oxygen and nitrous oxide as oxidants, respectively. The results are shown in Table 1, example 2, at a reaction temperature of 600 ℃ and under normal pressure, C₂H₆:N₂He ═ 1:1:48 (molar ratio) or C₂H₆:O₂He is 2:1:97 (molar ratio), and the space velocity is 6000mL/g_catUnder the condition of the reaction time of the catalyst,with N₂O is an oxidant, the conversion rate of ethane is 27%, and the selectivity reaches 90%; with O₂The conversion of ethane was 50% and the selectivity reached 78% as oxidant. Description of O₂Exhibits higher reactivity with N₂O is the oxidant, and the selectivity is better.

5.Ni₃Catalytic performance of Al-MO at different temperatures

The catalyst obtained in example 2 was subjected to 460 to 600 ℃ under normal pressure, respectively, to obtain C₂H₆:N₂The space velocity of O and He is 1:1:48 (mol ratio) is 6000mL/g_catThe results of the test under the/h condition are shown in FIG. 3. It can be seen that at low conversions the ethylene maintains 100% selectivity, at 560 ℃ the ethane conversion is 10% and the ethylene selectivity is greater than 98.3%, which is one of the best results reported so far.

6.Ni₃Catalytic performance of Al-MO at different space velocities

The catalyst obtained in the example 2 is used at an airspeed of 6000-72000mL/g_catAt 600 ℃ under normal pressure, C₂H₆: N₂Test was performed under the conditions of O: He ═ 1:1:48 (molar ratio). While comparing the results with the recent nickel-based catalysts under oxygen conditions. As shown in fig. 4, as the space velocity increases, the ethane conversion decreases and the ethylene selectivity increases. Ni prepared by thin-layer hydrotalcite in all nickel-based catalysts₃The Al-MO catalyst has optimal ethylene selectivity.

7.Ni₃Stability Properties of Al-MO

The catalyst obtained in example 2 was subjected to a reaction at 560 ℃ under normal pressure, C₂H₆:N₂The space velocity of O and He is 1:1:48 (mol ratio) is 6000mL/g_catThe stability test was carried out for 240h under the/h conditions, and the results are shown in FIG. 5. It can be seen that the activity of the catalyst is improved to a certain extent, the ethylene selectivity is reduced to a certain extent, but the ethylene selectivity is maintained to be more than 90%, and obvious inactivation does not occur after 240 hours of reaction.

TABLE 1 reactivity of different catalysts

TABLE 2 reactivity of catalysts prepared by different preparation methods

TABLE 3. different surfactant amounts give Ni₃Catalytic properties of Al-MO

Claims

1. A catalyst for eliminating ethylene coupled nitrous oxide produced by oxidative dehydrogenation of ethane is characterized in that: the catalyst is a composite oxide consisting of Ni and an auxiliary agent X, and is expressed as NiX-MO;

the active component is NiO, and the auxiliary agent X is any one or more than two oxides of Al, Ga and In; the atomic ratio of Ni and X can be controlled between 2-5.

2. A method of preparing the catalyst of claim 1, wherein: the preparation method adopts a coprecipitation method combined with a microemulsion method, and comprises the following specific processes:

1) mixing Ni (NO)₃)₂·6H₂O and Al (NO)₃)₃·9H₂Dissolving O in water according to the required molar ratio to obtain a metal solution;

2) dissolving NaOH and an alkali metal salt solution in water to obtain an alkali solution;

3) putting the alkali solution in an environment of 20-90 ℃, dripping the metal solution into the alkali solution under the condition of stirring, adding Sodium Dodecyl Sulfate (SDS), adjusting the pH to 9.0-12.0 by using 1-4M NaOH, then stirring for 12-24h, filtering, washing and drying to obtain a hydrotalcite precursor NiAl-HT, and then calcining for more than 1h in a 400-700 ℃ muffle furnace to obtain the NiAl-MO catalyst.

3. The method for preparing the catalyst according to claim 2, wherein: ni (N) in metal salt solutionO₃)₂The molar concentration of (A) is 0.25-1.5M.

The molar concentration of NaOH in the alkali solution is 0.1-3M, and the molar concentration of alkali metal salt is 0.1-3M;

Ni(NO₃)₂the molar ratio of the sodium hydroxide to NaOH in the alkali solution is 0.2-2;

the final molar concentration of the sodium dodecyl sulfate in the system is 0.01-1M.

4. The method for preparing the catalyst according to claim 2, wherein: the alkali metal salt is one or more of sodium chloride, sodium carbonate, sodium sulfate, potassium chloride, potassium carbonate and potassium sulfate, preferably one or two of sodium carbonate and potassium carbonate.

5. The method for preparing the catalyst according to claim 2, wherein: the precursor before the catalyst is calcined is ultrathin hydrotalcite, the number of layers of the hydrotalcite is 1-10, and the total thickness is 1-10 nm.

6. Use of the catalyst according to claim 1 for the oxidative dehydrogenation of ethane to ethylene.

7. Use of a catalyst according to claim 6, characterized in that: reacting in a fixed bed reactor filled with a catalyst, wherein the reaction is a continuous fixed bed reaction, and feeding a raw material gas C₂H₆Pressure 2-50kPa, in N₂O and O₂One or two of the raw materials are oxidant and raw material gas C₂H₆And oxidant in a volume ratio of 0.5-5, as He or N₂One or two of the gases are balance gases, the total pressure of the gases introduced into the fixed bed reactor is normal pressure, and the total airspeed of the gases is 6000 to 72000ml g_cat ^-1h^-1Through a fixed bed reactor containing a catalyst.

8. Use of a catalyst according to claim 6, characterized in that: when an oxidizing agent containing N is used₂O is, N is in the oxidant₂Molar content of O1-100%, and the catalyst can be coupled with nitrous oxide to improve the conversion rate of the reaction.