Preparation method and application of a composite metal oxide catalyst for efficiently catalyzing methanol and isobutene to produce isoprene

Abstract

The application discloses a preparation method and application of a composite metal oxide for efficiently preparing isoprene from methanol and isobutene under low-temperature conditions. The route can reduce a reaction flow, reduce process operation complexity, and avoid the serious problems of difficult large-scale transportation of formaldehyde raw materials and production pipe network blockage caused by polymerization of the formaldehyde into a solid. The methanol conversion rate of the composite metal oxide catalyst Mo-Fe-La-O is about 89%, and the isoprene selectivity is as high as 92%, and the catalyst has stable reaction performance in continuous operation for 55 hours. The catalyst preparation method is simple, and a lower reaction temperature is favorable for reducing energy consumption; in addition, the reaction raw materials methanol and isobutene can be obtained from fossil resources such as coal and natural gas, and can also be obtained from biomass. Therefore, the synthesized isoprene is renewable, which is favorable for relieving the dependence on fossil resources, is of great significance to the sustainable development of human society, and has a very good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalyst for catalyzing the reaction of methanol and isobutene to prepare isoprene, and a preparation method and application thereof, and belongs to the field of petrochemical industry or biomass platform compound conversion. Specifically, a catalyst for catalyzing the reaction of methanol and isobutene to prepare isoprene at a relatively low temperature, with high methanol conversion rate, high isoprene selectivity and good stability, and a preparation method and application thereof are provided. BACKGROUND

[0002] As a very important chemical raw material, isoprene has a wide application in rubber, latex, pharmaceutical and pesticide intermediates, and fine chemical synthesis. At present, the main method for preparing isoprene in industry is to separate the by-product C5 fraction produced in the process of steam cracking of naphtha to produce ethylene, but this method is based on fossil resources, and the process flow is complex and the energy consumption is high. At present, fossil resources are rapidly consumed and face depletion, which is not conducive to the sustainable development of human society. High-purity isoprene can be produced by Prins condensation reaction of formaldehyde and isobutene. Formaldehyde can be prepared by methanol oxidation reaction, and biomass conversion can produce methanol; the other reactant isobutene can be obtained from biomass-based isobutanol, or directly from biomass. Therefore, the Prins condensation reaction to produce isoprene is a sustainable route.

[0003] There are one-step and two-step methods for preparing isoprene by Prins reaction. Among them, the two-step method refers to that formaldehyde and isobutene first undergo Prins condensation on an acidic catalyst to generate 4,4-dimethyl-1,3-dioxane (DMD), and then DMD is decomposed on another acid catalyst to generate isoprene. This route has high complexity and high energy consumption, and it is difficult to realize industrial scale production. The one-step method is that formaldehyde and isobutene directly generate isoprene in a fixed bed reactor. At present, solid acid catalysts such as molecular sieves, oxides, phosphates and heteropoly acids are mainly used for preparing isoprene by one-step method. However, the solid acid catalysts are easy to form carbon deposition, which leads to the reduction of reaction activity and stability. In addition, the main problem of one-step method is the source of formaldehyde. At present, the main sources of formaldehyde are paraformaldehyde and formaldehyde aqueous solution. Paraformaldehyde needs to be dissolved in an organic solvent and is relatively expensive. Formaldehyde aqueous solution has high requirements for catalyst water resistance. In addition, formaldehyde has a low boiling point (-19.5℃), is not environmentally friendly and is toxic, which leads to high transportation cost. High-concentration formaldehyde is easy to self-aggregate into a solid, which seriously affects the process and causes huge economic losses. Therefore, considering all the above-mentioned adverse factors, it is urgent to find an alternative source of formaldehyde.

[0004] In view of this, the present application proposes to use CH3OH / O2 as a substitute for formaldehyde to react with isobutene to produce isoprene in a one-step method on a composite metal oxide catalyst in a fixed bed reactor. SUMMARY

[0005] In order to solve the problems of inconvenient operation, easy carbon deposition and low stability of catalysts in the reaction of formaldehyde with isobutene, the present application provides a catalyst for efficiently catalyzing the reaction of methanol with isobutene to produce isoprene with high selectivity under low temperature conditions. The catalyst has the advantages of simple preparation method, high methanol conversion rate and isoprene selectivity, low reaction temperature and stable catalyst performance. When the catalyst is applied to the reaction of methanol with isobutene to produce isoprene, high activity and high selectivity of isoprene can be achieved under low temperature conditions. Under the optimal reaction conditions, the methanol conversion rate of the Mo-Fe-La-O composite metal oxide catalyst is about 89%, the isoprene selectivity is as high as 92%, and the catalyst has certain stability and stable reaction performance for 55 h of continuous operation.

[0006] A catalyst for efficiently catalyzing the one-step reaction of methanol with isobutene to produce isoprene with high selectivity under low temperature conditions, wherein the catalyst is a composite metal oxide catalyst; the active component of the composite metal oxide catalyst includes molybdenum iron oxide and an added metal M.

[0007] According to the above technical solution, as a preferred embodiment, the added metal M is one or more than two of yttrium, lanthanum, cerium, samarium, ytterbium, vanadium, tungsten, copper and aluminum.

[0008] According to the above technical solution, as a preferred embodiment, the molar ratio of molybdenum, iron and metal M in the catalyst is Mo:Fe:M=2:0.5-10:0.005-0.5, preferably 2:0.5-2:0.005-0.3.

[0009] According to the above technical solution, as a preferred embodiment, the molybdenum iron oxide catalyst can be prepared by co-precipitation, impregnation or sol-gel method.

[0010] According to the above technical solution, as a preferred embodiment, the composite metal oxide catalyst can be prepared by co-precipitation, impregnation or sol-gel method.

[0011] According to the above technical solution, as a preferred embodiment, the preparation method of the composite metal oxide catalyst includes the following steps: under stirring conditions, HNO3 is added dropwise to a molybdenum salt solution until the pH is 1-3, then a mixed solution of iron salt and metal salt is slowly added dropwise to the above-mentioned molybdenum salt solution, the obtained mixed solution is stirred at 25-150℃ for 2-24h, then it is subjected to suction filtration, washing, drying at 80-110℃ for 20-24h and calcination at 350-500℃ for 5-8h to obtain the composite metal oxide catalyst.

[0012] According to the technical scheme, as a preferred, the molybdenum salt precursor in the catalyst is ammonium molybdate or molybdenum pentachloride, and the metal iron salt precursor is ferric nitrate, ferric sulfate, ferric acetate or ferric chloride; when the metal M is one or more than two of yttrium, lanthanum, cerium, samarium, ytterbium, copper and aluminum, the metal M salt precursor is the corresponding nitrate, sulfate or acetate of yttrium, lanthanum, cerium, samarium, ytterbium, copper and aluminum; when the metal M is vanadium, the vanadium salt precursor is ammonium metavanadate or vanadium chloride; and when the metal M is tungsten, the tungsten salt precursor is ammonium metatungstate or tungsten chloride.

[0013] According to the technical scheme, as a preferred, the concentration of the molybdenum salt solution in the catalyst is 0.05-0.5M, the concentration of the iron salt solution is 0.02-0.3M, and the concentration of the metal M salt solution is 0.001-0.03M.

[0014] The application also relates to the use of the composite metal oxide catalyst in the reaction of preparing isoprene from methanol and isobutene.

[0015] According to the technical scheme, as a preferred, the composite metal oxide catalyst needs a pretreatment process, and the pretreated catalyst is used to catalyze the reaction of preparing isoprene from methanol and isobutene.

[0016] According to the technical scheme, as a preferred, the loading amount of the composite metal oxide catalyst is 0.1-1g, preferably 0.1-0.6g.

[0017] According to the technical scheme, as a preferred, in the pretreatment process of the composite metal oxide catalyst, the pretreatment atmosphere is a mixture of nitrogen and oxygen, the proportion of oxygen is 5%-30%, the flow rate of the pretreatment mixed gas is 20-50mL / min, the pretreatment temperature is 300-500℃, the pretreatment time is 0.5-3h, and the heating rate is 1-10℃ / min.

[0018] According to the technical scheme, as a preferred, in the use of the composite metal oxide catalyst in the reaction of preparing isoprene from methanol and isobutene, methanol and isobutene enter the fixed bed reactor at the same time, the molar ratio of methanol to isobutene is 1:(1-10), the reaction temperature is 180-300℃, the reaction pressure is 0.1-5MPa, the loading amount of the composite metal oxide catalyst is 0.1-1g, the reaction atmosphere is a mixture of nitrogen and oxygen, the proportion of oxygen is 5%-30%, the flow rate of the mixed gas is 10mL / min-50mL / min, the methanol mass space velocity is 0.5-5g CH3OH / h cat. .

[0019] The present application applies different composite metal oxide catalysts in the reaction of preparing isoprene from methanol and isobutene.

[0020] The advantages of the present application are as follows:

[0021] From the aspect of catalyst preparation: the raw materials such as metal salts are cheap and easy to obtain, the catalyst composition is simple, the preparation method is easy to operate, and the prepared catalyst has multiple active sites such as redox and acid-base.

[0022] From the aspect of isoprene production: the composite metal oxide catalyst can catalytically convert methanol and isobutene into isoprene in a fixed bed reactor in one step, and high methanol conversion rate, high isoprene selectivity and good stability can be maintained at a relatively low temperature. This route has many advantages, such as reducing the reaction process, reducing the complexity of process operation, and more importantly, avoiding the serious pipe blocking problem caused by the self-polymerization of formaldehyde raw materials. It is a brand new isoprene production route.

[0023] From the aspect of sustainable development: the reactants methanol and isobutene can be obtained from fossil resources such as coal and natural gas, and can also be obtained from biomass. Therefore, the isoprene synthesized by this route is renewable, which reduces the dependence on fossil resources and is of great significance to the sustainable development of human society, and has very good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Figure is the reaction performance diagram of different composite metal oxides in the reaction of preparing isoprene from methanol and isobutene at a reaction temperature of 200℃.

[0025] Figure 2 Figure is the reaction performance diagram of Mo-Fe-La-O composite metal oxides with different La contents in the reaction of preparing isoprene from methanol and isobutene at a reaction temperature of 210℃.

[0026] Figure 3 Figure is the stability evaluation diagram of Mo-Fe-La-O composite metal oxide catalysts in the reaction of preparing isoprene from methanol and isobutene.

[0027] Figure 4 (a) is the XRD spectrum of different composite metal oxides, and (b) is the XRD spectrum of composite metal oxides with different La contents. DETAILED DESCRIPTION

[0028] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but in no way limit the present application.

[0029] EXAMPLE

[0030] The present application will be described in detail by the following examples, but the scope of the claims of the present application is not limited by these examples. Also, the examples are given only to achieve the purpose, but do not mean that these conditions must be met to achieve the purpose.

[0031] 1. Preparation of different composite metal oxides

[0032] Example 1

[0033] Weigh 3g of ammonium heptamolybdate, dissolve in 50mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added dropwise to the molybdate solution until the pH is 2. Weigh 3.4g of iron nitrate and 276mg of lanthanum nitrate, dissolve in 50mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, dry at 110°C for 12h, calcine at 420°C for 5h, to obtain powder-like composite metal oxide, tablet, sieve, take 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1La-O, wherein the molar ratio of Mo:Fe:La is 2:1:0.1.

[0034] Comparative Example 1

[0035] Weigh 3g of ammonium heptamolybdate, dissolve in 50mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added dropwise to the molybdate solution until the pH is 2. Weigh 3.4g of iron nitrate, dissolve in 50mL of deionized water, then slowly drop the iron salt solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, dry at 110°C for 12h, calcine at 420°C for 5h, to obtain powder-like molybdenum iron oxide, tablet, sieve, take 20-40 mesh catalyst particles, recorded as 2Mo-Fe-O, wherein the molar ratio of Mo:Fe is 2:1.

[0036] Example 2

[0037] Weigh 3g of ammonium heptamolybdate, dissolve in 50mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added dropwise to the molybdate solution until the pH is 2. Weigh 3.4g of iron nitrate and 325mg of yttrium nitrate, dissolve in 50mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, dry at 110°C for 12h, calcine at 420°C for 5h, to obtain powder-like composite metal oxide, tablet, sieve, take 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1Y-O, wherein the molar ratio of Mo:Fe:Y is 2:1:0.1.

[0038] Example 3

[0039] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 369 mg of cerium nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1Ce-O, wherein the molar ratio of Mo:Fe:Ce is 2:1:0.1.

[0040] Example 4

[0041] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 378 mg of samarium nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1Sm-O, wherein the molar ratio of Mo:Fe:Sm is 2:1:0.1.

[0042] Example 5

[0043] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 382 mg of ytterbium nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1Yb-O, wherein the molar ratio of Mo:Fe:Yb is 2:1:0.1.

[0044] Example 6

[0045] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain an ammonium molybdate solution, under stirring conditions, HNO3 is added dropwise to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 99.4 mg of ammonium metavanadate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1V-O, wherein the molar ratio of Mo:Fe:V is 2:1:0.1.

[0046] Example 7

[0047] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain an ammonium molybdate solution, under stirring conditions, HNO3 is added dropwise to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 209.3 mg of ammonium metatungstate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1W-O, wherein the molar ratio of Mo:Fe:W is 2:1:0.1.

[0048] Example 8

[0049] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain an ammonium molybdate solution, under stirring conditions, HNO3 is added dropwise to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 205.3 mg of copper nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1Cu-O, wherein the molar ratio of Mo:Fe:Cu is 2:1:0.1.

[0050] Example 9

[0051] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 318.7 mg of aluminum nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.1Al-O, wherein the molar ratio of Mo:Fe:Al is 2:1:0.1.

[0052] Example 10

[0053] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 27.6 mg of lanthanum nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.01La-O, wherein the molar ratio of Mo:Fe:La is 2:1:0.01.

[0054] Example 11

[0055] Take 3 g of ammonium heptamolybdate, dissolved in 50 mL of deionized water to obtain ammonium molybdate solution, under stirring conditions, HNO3 is added to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 138 mg of lanthanum nitrate, dissolved in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h, to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.05La-O, wherein the molar ratio of Mo:Fe:La is 2:1:0.05.

[0056] Example 12

[0057] Take 3 g of ammonium heptamolybdate, dissolve in 50 mL of deionized water to obtain an ammonium molybdate solution, under stirring conditions, add HNO3 dropwise to the molybdate solution until the pH is 2. Take 3.4 g of iron nitrate and 552 mg of lanthanum nitrate, dissolve in 50 mL of deionized water, then slowly drop the mixed solution into the above molybdate solution, stir at 80°C for 5h, then perform suction filtration, washing, drying at 110°C for 12h, calcining at 420°C for 5h to obtain a powder-like composite metal oxide, tabletting, sieving, taking 20-40 mesh catalyst particles, recorded as 2Mo-Fe-0.2La-O, wherein the molar ratio of Mo:Fe:La is 2:1:0.2.

[0058] 2. Application of different catalysts in the reaction of methanol and isobutene to prepare isoprene

[0059] All reactions were carried out in a continuous flow fixed bed reactor equipped with a gas mass flow meter and an online product analysis chromatograph. The online product analysis used a Shimadzu GC-2014C gas chromatograph with FID / TCD dual detectors. FID detected isobutene, methanol, isoprene, isopentenol, methyl acetal, dimethyl ether, methyl formate, and TCD detected CO2, CO, etc. The catalytic performance of the catalyst was evaluated by measuring the change trend of methanol conversion and isoprene selectivity during the reaction process.

[0060] Example 13

[0061] The performance evaluation experiment of 2Mo-Fe-0.1La-O obtained in Example 1 in the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pretreated by heating to 400°C at 10°C / min under 30 mL / min of 15% O2 / N2 mixed gas before the reaction, and the pretreatment was carried out for 1h. After pretreatment, the catalyst was used to catalyze the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200°C, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 30 mL / min of 15% O2 / N2 mixed gas, the methanol mass space velocity was 2.4 g CH3OH / h cat. , and the isobutene mass space velocity was 12 g / h. The reaction results are shown in Figure 1 .

[0062] Comparative Example 2

[0063] The performance evaluation experiment of the 2Mo-Fe-O catalyst obtained in Comparative Example 1 for the preparation of isoprene from methanol and isobutylene was conducted in a continuous flow fixed-bed experimental setup. The specific reaction conditions were as follows: the catalyst dosage was 0.5 g; before the reaction, the catalyst was pretreated by heating to 400 °C at 10 °C / min under a 15% O₂ / N₂ mixed gas at a flow rate of 30 mL / min and purging for 1 h. After pretreatment, the catalyst was used to catalyze the reaction of methanol and isobutylene to prepare isoprene at a reaction temperature of 200 °C, a reaction pressure of 2 MPa, a methanol to isobutylene molar ratio of 1:5, a 15% O₂ / N₂ mixed gas at a flow rate of 30 mL / min, and a methanol mass hourly space velocity (MHSV) of 2.4 g. CH3OH / g cat. h. The reaction results are as follows Figure 1 As shown.

[0064] Example 14

[0065] The performance evaluation experiment of the 2Mo-Fe-0.1YO catalyst obtained in Example 2 for the preparation of isoprene from methanol and isobutylene was conducted in a continuous flow fixed-bed experimental setup. The specific reaction conditions were as follows: the catalyst dosage was 0.5 g; before the reaction, the catalyst was pretreated by heating to 400 °C at 10 °C / min under a 15% O2 / N2 mixed gas at a flow rate of 30 mL / min and purging for 1 h. After pretreatment, the catalyst was used to catalyze the reaction of methanol and isobutylene to prepare isoprene at a reaction temperature of 200 °C, a reaction pressure of 2 MPa, a methanol to isobutylene molar ratio of 1:5, a 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and a methanol mass hourly space velocity (MHSV) of 2.4 g. CH3OH / g cat. h. The reaction results are as follows Figure 1 As shown.

[0066] Example 15

[0067] The performance evaluation experiment of the 2Mo-Fe-0.1Ce-O catalyst obtained in Example 3 for the preparation of isoprene from methanol and isobutylene was conducted in a continuous flow fixed-bed experimental apparatus. The specific reaction conditions were as follows: the catalyst dosage was 0.5 g; before the reaction, the catalyst was pretreated by heating to 400 °C at 10 °C / min under a 15% O2 / N2 mixed gas at a flow rate of 30 mL / min and purging for 1 h. After pretreatment, the catalyst was used to catalyze the reaction of methanol and isobutylene to prepare isoprene. The reaction temperature was 200 °C, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutylene was 1:5, the reaction atmosphere was a 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass hourly space velocity was 2.4 g. CH3OH / g cat. h. The reaction results are as follows Figure 1 As shown.

[0068] Example 16

[0069] The performance evaluation experiment of the 2Mo-Fe-0.1Sm-O obtained in Example 4 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experiment device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pretreatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / h cat. . The reaction results are shown in Table 16. Figure 1

[0070] Example 17

[0071] The performance evaluation experiment of the 2Mo-Fe-0.1Yb-O obtained in Example 5 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experiment device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pretreatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / h cat. . The reaction results are shown in Table 17. Figure 1

[0072] Example 18

[0073] The performance evaluation experiment of the 2Mo-Fe-0.1V-O obtained in Example 6 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experiment device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pretreatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / h cat. . The reaction results are shown in Table 18.​​Figure 1 The results are shown in Table 1.

[0074] Example 19

[0075] The performance evaluation experiment of the 2Mo-Fe-0.1W-O obtained in Example 7 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 30 mL / min of 15% O2 / N2mixed gas at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pretreatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 30 mL / min of 15% O2 / N2mixed gas, the mass space velocity of methanol was 2.4 g CH3OH / h cat. , and the reaction results are shown in Table 1. Figure 1

[0076] Example 20

[0077] The performance evaluation experiment of the 2Mo-Fe-0.1Cu-O obtained in Example 8 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 30 mL / min of 15% O2 / N2mixed gas at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pretreatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 30 mL / min of 15% O2 / N2mixed gas, the mass space velocity of methanol was 2.4 g CH3OH / h cat. , and the reaction results are shown in Table 1. Figure 1

[0078] Example 21

[0079] The performance evaluation experiment of the 2Mo-Fe-0.1Al-O obtained in Example 9 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 30 mL / min of 15% O2 / N2mixed gas at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pretreatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 200 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 30 mL / min of 15% O2 / N2mixed gas, the mass space velocity of methanol was 2.4 g​​CH3OH / g cat. h. The reaction results are shown in Table 1. Figure 1

[0080] Comparative Example 3

[0081] The performance evaluation experiment of the 2Mo-Fe-O obtained in Comparative Example 1 for catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pre-treatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 210 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / g cat. h. The reaction results are shown in Table 1. Figure 2

[0082] Example 22

[0083] The performance evaluation experiment of the 2Mo-Fe-0.01La-O obtained in Example 10 for catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pre-treatment was completed, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 210 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / g cat. h. The reaction results are shown in Table 1. Figure 2

[0084] Example 23

[0085] ​​​The performance evaluation experiment of the 2Mo-Fe-0.05La-O obtained in Example 11 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pre-treatment, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 210 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / g cat. h. The reaction results are shown in Table 2. Figure 2

[0086] Example 24

[0087] The performance evaluation experiment of the 2Mo-Fe-0.2La-O obtained in Example 12 in catalyzing the reaction of methanol and isobutene to prepare isoprene was carried out in a continuous flow fixed bed experimental device, and the specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pre-treated by purging under 15% O2 / N2 mixed gas at a flow rate of 30 mL / min at a temperature increasing rate of 10 ℃ / min to 400 ℃ for 1 h before the reaction. After the pre-treatment, the catalyst was used in the reaction of methanol and isobutene to prepare isoprene, the reaction temperature was 210 ℃, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 15% O2 / N2 mixed gas at a flow rate of 30 mL / min, and the methanol mass space velocity was 2.4 g CH3OH / g cat. h. The reaction results are shown in Table 2. Figure 2

[0088] Figure 1 For the reaction performance comparison of different composite metal oxides at a reaction temperature of 200 ℃, it can be seen that the methanol conversion rate on the 2Mo-Fe-O is low, and there is more CO x in the product, resulting in a low isoprene selectivity. The methanol conversion rate and the isoprene selectivity of the composite metal oxides after adding metals are different, and the isoprene selectivity is obviously improved. Among them, after adding La, the isoprene selectivity of the 2Mo-Fe-0.1La-O is increased to about 90%, and the methanol conversion rate is increased from about 60% to about 80%. In addition, the methanol conversion rates of the 2Mo-Fe-0.1Ce-O, 2Mo-Fe-0.1V-O and 2Mo-Fe-0.1W-O catalysts are obviously improved, while the addition of other metals is not very obvious in improving the methanol conversion rate, and the conversion rate is increased to about 67% after adding Y, Sm, Yb, Co and Al.

[0089] ​​The optimum addition of metal La is determined, Figure 2 The reaction performance of 2Mo-Fe-La-O catalysts with different La contents at a reaction temperature of 210°C was compared. As shown in the figure, a small amount of La has a great influence on the reaction activity. When the La content increases from 0.01 to 0.1, the methanol conversion rate increases from ~80% to ~89%, and the isoprene selectivity increases from ~74% to 92%, indicating that the addition of La is beneficial to the conversion of methanol and promotes the Prins reaction of formaldehyde and isobutene. When the La content continues to increase, the methanol conversion rate does not change significantly, and the CO x selectivity increases, resulting in a decrease in isoprene selectivity.

[0090] 3. Stability evaluation of composite metal oxide 2Mo-Fe-0.1La-O catalyst

[0091] Example 25

[0092] The stability evaluation experiment of the 2Mo-Fe-0.1La-O catalyst obtained in Example 1 for preparing isoprene from methanol and isobutene was carried out in a continuous flow fixed bed experimental device. The specific reaction conditions were as follows: the catalyst dosage was 0.5 g, the catalyst was pretreated by heating to 400°C at 10°C / min under 30 mL / min of 15% O2 / N2 mixed gas for 1 h before the reaction. After the pretreatment was completed, the catalyst was used for the reaction of preparing isoprene from methanol and isobutene, the reaction temperature was 200°C, the reaction pressure was 2 MPa, the molar ratio of methanol to isobutene was 1:5, the reaction atmosphere was 30 mL / min of 15% O2 / N2 mixed gas, the methanol mass space velocity was 2.4 g CH3OH / h cat. . The reaction results are shown in Table 1. Figure 3

[0093] Figure 3 The stability evaluation of the composite metal oxide 2Mo-Fe-0.1La-O catalyst was carried out. After 55 h of continuous reaction, the methanol conversion rate slowly decreased to ~85%, and the isoprene selectivity slowly decreased to ~88%, indicating that the catalyst has certain stability.

[0094] 4. XRD analysis of different catalysts

[0095] Example 26

[0096] The catalyst 0.5 g in Comparative Example 1 was subjected to XRD test, and the specific conditions were as follows: the tube voltage was 40 kV, the tube current was 100 mA, the ray source was Cu Kα, the scanning speed was 10° / min, and the scanning range was 2θ=10-60°. It is recorded as 2Mo-Fe-O. The test results are shown in Table 2. Figure 4

[0097] ​​Example 27

[0098] XRD tests were carried out on 0.5 g of each catalyst in Examples 1-12, under the following conditions: tube voltage 40 kV, tube current 100 mA, ray source Cu Ka, scanning speed 10° / min, scanning range 2θ = 10-60°. Respectively, 2Mo-Fe-xM-O. The test results are shown in Table 1. Figure 4

[0099] Figure 4 are XRD patterns of different catalysts. Mo-Fe-O oxides are composed of two phases of MoO3 and Fe2(MoO4)3, and exist as their respective phases. As can be seen from the XRD, after adding metals, the composition and proportion of the two phases have changed, especially after adding La, V, Ce, W, the intensity of MoO3 and Fe2(MoO4)3 two phases has been significantly enhanced, especially in 2Mo-Fe-0.1La-O, the intensity of MoO3 and Fe2(MoO4)3 two phases has been significantly increased, which indicates that the increase of MoO3 and Fe2(MoO4)3 phases, the active sites for methanol oxidation to formaldehyde, may improve the methanol conversion rate, so that the catalyst has higher catalytic activity at lower temperature.​

Claims

1. The application of a catalyst in the low-temperature, high-efficiency, high-selectivity one-step catalytic reaction of methanol and isobutylene to produce isoprene, characterized in that: The catalyst is a composite metal oxide catalyst; the active component of the catalyst includes molybdenum iron oxide and added lanthanum metal. The molar ratio of molybdenum, iron, and metallic lanthanum in the catalyst, Mo:Fe:La, is 2:0.5~10:0.05~0.

2. The preparation method of the composite metal oxide catalyst includes the following steps: under stirring conditions, HNO3 is added dropwise to a molybdenum salt solution until the pH is 1-3, and then a mixed solution of iron salt and lanthanum salt is slowly added dropwise to the above molybdenum salt solution to obtain a mixed solution. The solution is stirred at 25-150 °C for 2-24 h, then filtered and washed, dried at 80-110 °C for 20-24 h, and calcined at 350-500 °C for 5-8 h to obtain the composite metal oxide catalyst. The composite metal oxide catalyst was pretreated with an O2 / N2 mixed gas and then used to catalyze the reaction of methanol and isobutylene at a reaction temperature of 180~210 °C.

2. The application as described in claim 1, characterized in that: The molybdenum salt is ammonium molybdate or molybdenum pentachloride; the iron salt is ferric nitrate, ferric sulfate, ferric acetate, or ferric chloride; and the lanthanum salt is its corresponding nitrate, sulfate, or acetate. The concentration of the molybdenum salt solution is 0.05~0.5 M.

3. The application as described in claim 1, characterized in that: The composite metal oxide catalyst is loaded with 0.1~1g; the oxygen volume ratio in the pretreated mixed gas is 5%~30%, the mixed gas flow rate is 20~50mL / min, the pretreatment temperature is 300~500°C, the pretreatment time is 0.5~3h, and the heating rate is 1~10°C / min.

4. The application as described in claim 1, characterized in that: Methanol and isobutylene are simultaneously introduced into a fixed-bed reactor, with a methanol to isobutylene molar ratio of 1:(1~10). The reaction pressure is 0.1~5 MPa, and the reaction atmosphere is a mixture of nitrogen and oxygen, with oxygen accounting for 5%~30% by volume. The flow rate of the mixed gas is 20~50 mL / min, and the methanol mass hourly space velocity is 0.5~5 g. CH3OH / ( g cat·h) .

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