A catalyst for preparing alpha olefin by dehydrating primary alcohol, its preparation method and application

Abstract

This invention discloses a catalyst, preparation method, and application for the dehydration of primary alcohols to prepare α-olefins. The catalyst comprises the following components by mass percentage: a first metal oxide at 55-89 wt.%, a second metal oxide at 10-40 wt.%, and a ThO2 promoter at 1-5 wt.%; the first metal oxide is Al2O3, TiO2, SnO2, or ZrO2; and the second metal oxide is Nb2O5 or Ga2O3. This invention, by introducing a second metal oxide for doping and synergistically controlling its content ratio with the first metal oxide and ThO2, utilizes the oxygen coordination difference between the two metal ions to induce structural mismatch, significantly increasing the number of acid sites and enhancing their strength to a suitable range, thereby avoiding olefin isomerization caused by excessive acidity. Using this catalyst for the dehydration of primary alcohols to prepare α-olefins can significantly improve the conversion rate of primary alcohols and the selectivity of α-olefins.

Description

Technical Field

[0001] This invention belongs to the field of alcohol dehydration to olefin preparation technology, specifically relating to a catalyst for primary alcohol dehydration to α-olefin preparation, its preparation method, and its application. Background Technology

[0002] Alpha-olefins are a class of hydrocarbons with carbon-carbon double bonds at the ends of their molecules, possessing the general molecular formula CH2=CH-R (where R is an alkyl group). They are important petrochemical raw materials and intermediates, widely used as comonomers, in the production of lubricants, emulsifiers, surfactants, and oil additives. Methods for preparing alpha-olefins include paraffin cracking, ethylene oligomerization, Fischer-Tropsch synthesis, and alcohol dehydration. Among these, paraffin cracking, with its harsh reaction conditions, complex operation, low product purity, and high energy consumption, has been gradually phased out. Ethylene oligomerization is a mature process and currently the main method for producing alpha-olefins. Fischer-Tropsch synthesis uses syngas as a raw material, producing products with similar carbon numbers, making separation difficult and costly. Alcohol dehydration offers mild reaction conditions, a simple process, safe operation, and produces products with concentrated carbon numbers, making separation easy and promising for industrial applications.

[0003] Catalysts for alcohol dehydration reactions are typically composite oxide catalysts. For example, patent application CN118217961A discloses a highly stable catalyst for the dehydration of high-carbon primary alcohols to α-olefins, its preparation method, and its application, prepared from at least the following raw materials: an aluminum source and a tetravalent metal ion additive M. 4+ (M=Ti4) + Zr4 + Sn 4+ Ce 4+ The molar ratio of the aluminum source and the tetravalent metal ion additive is according to M. 4+ / Al 3+ The value is calculated to be 0.05~0.5. Although the catalyst used in this method has relatively good stability, its activation ability for alcohols is low, the initial activity of the reaction is low, and the reaction induction period is long.

[0004] Patent application CN116099523A discloses a composite metal oxide catalyst for the synthesis of α-olefins, its preparation method, and its application. The catalyst comprises a first metal oxide, a second metal oxide, and an auxiliary agent. The first metal oxide includes one or more of Al₂O₃, TiO₂, or CeO₂; the second metal oxide includes MgO; and the auxiliary agent includes Y₂O₃. The preparation method involves: ball milling the first and second metal oxides until homogeneous, calcining them, mixing them with an alkaline solution, reacting them under high temperature and pressure, and drying to obtain an intermediate; immersing the intermediate in an organic solution of the auxiliary agent, drying, and calcining to obtain the final product. This catalyst possesses a hydrophobic surface and acid-base active sites, inhibiting the formation of aliphatic ethers. However, the introduction of alkaline earth metal oxides into the catalyst leads to a high number of double bond isomers as byproducts.

[0005] Patent application CN116037096A discloses a catalyst for the dehydration of 2-ols, a method for preparing the same, and a method for preparing α-olefins from the dehydration of 2-ols. The catalyst comprises a main component, an alkaline earth metal oxide, and a rare earth metal oxide. The main component is selected from at least one of zirconium oxide, silicon oxide, titanium oxide, and aluminum oxide. The content of the alkaline earth metal oxide is 0.05-10 parts by weight relative to 100 parts by weight of the main component; the content of the rare earth metal oxide is 0.01-12 parts by weight. This catalyst has synergistic acid-base sites, which can effectively suppress carbon deposition of double bonds, but its selectivity for terminal olefins is low.

[0006] In summary, existing catalysts still suffer from problems such as insufficient reactivity and numerous isomers that urgently need to be addressed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the first aspect of this invention provides a catalyst for the dehydration of primary alcohols to prepare α-olefins, which combines excellent primary alcohol dehydration activity with terminal olefin selectivity.

[0008] The present invention provides a catalyst for the dehydration of primary alcohols to prepare α-olefins, comprising the following components in weight percentage: a first metal oxide content of 55-89 wt.%, a second metal oxide content of 10-40 wt.%, and an auxiliary agent ThO2 content of 1-5 wt.%. The first metal oxide is Al2O3, TiO2, SnO2 or ZrO2; The second metal oxide is Nb2O5 or Ga2O3.

[0009] While the first metal oxide can provide the acidic sites required for the dehydration reaction of primary alcohols, the number of inherently acidic sites is limited and the acidity is relatively weak, resulting in insufficient catalytic activity. Therefore, this invention introduces a second metal oxide for doping and controls the content ratio of the first metal oxide, the second metal oxide, and the promoter ThO2 to synergistically regulate the surface acidity of the catalyst.

[0010] Within the controlled ratio range of the first and second metal oxides in this invention, structural mismatch occurs during the formation of the composite oxide due to the different oxygen coordination structures of the two metal ions. This not only significantly increases the number of acidic sites on the catalyst surface but also significantly enhances the proportion of weak and moderately strong acids, thus adapting to the dehydration reaction of primary alcohols. It effectively avoids the problem of excessive acidity caused by an excess of the second metal oxide. While excessive acidity helps improve the conversion rate of primary alcohols, it can trigger severe olefin isomerization side reactions, thereby reducing the selectivity of α-olefins.

[0011] Furthermore, by controlling the concentration ratio of hydrogen peroxide and alkaline precipitant in the preparation method, the first metal oxide and the second metal oxide can be uniformly co-precipitated, resulting in a composite oxide with uniform composition. This ensures that acidic sites are uniformly distributed on the catalyst surface, thereby comprehensively improving the catalyst's reaction activity.

[0012] In addition, the appropriate addition of the auxiliary agent ThO2 can promote the rapid desorption of α-olefin products generated by the dehydration reaction of primary alcohols from the acidic surface, effectively suppress the double bond isomerization side reaction, and improve the selectivity of α-olefins.

[0013] Preferably, the concentration of acidic sites in the catalyst for the dehydration of primary alcohols to α-olefins is 0.38~0.67 mmol·g. -1 The proportion of weak acids and moderately strong acids is 72-86%.

[0014] The suitable acid site concentration and acid strength of the catalyst for the dehydration of primary alcohols to prepare α-olefins provided by this invention can ensure that the primary alcohol molecules are effectively activated to drive the reaction to proceed efficiently, thereby obtaining a high conversion rate, while minimizing the occurrence of α-olefin isomerization side reactions caused by excessive acidity or excessively dense sites, thus ensuring high selectivity.

[0015] Preferably, the catalyst for the dehydration of primary alcohols to prepare α-olefins has a specific surface area of ​​50-400 m². 2 / g, with an average pore size of 3~20 nm and an average pore volume of 0.1~0.9 cm³. 3 / g.

[0016] On the other hand, the present invention also provides a method for preparing the catalyst for the dehydration of primary alcohols to α-olefins: S1. Dissolve the first metal source and the second metal source in ethanol-water, add a mixed solution of hydrogen peroxide and alkaline precipitant, wherein the molar ratio of hydrogen peroxide to alkaline precipitant is 0.05:1~0.2:1, adjust the pH of the system to 8~11, then age it, and then calcine it to obtain the composite oxide. S2. Roast the Th salt to obtain ThO2; S3. The composite oxide is mixed with ThO2, ball-milled, and then calcined to obtain the catalyst for the dehydration of primary alcohol to prepare α-olefin.

[0017] This invention, by controlling the molar ratio of hydrogen peroxide and an alkaline precipitant, not only ensures that the pH of the system is adjusted to a suitable range, allowing complete precipitation of both the first and second metal sources, but also, because the first metal (such as Al)... 3+ ) and second metals (such as Nb) 5+The hydrolysis and precipitation rates of the first metal and the second metal differ, making simultaneous precipitation difficult and leading to phase separation. To address this, this invention uses hydrogen peroxide to assist co-precipitation. By increasing the precipitation rate of the second metal to match that of the first metal, a homogeneous composite oxide is obtained, ensuring uniform distribution of acidic sites on the catalyst surface and comprehensively enhancing the catalyst's reactivity. Simultaneously, it avoids an excessively high molar ratio of hydrogen peroxide to alkaline precipitant, which would result in a phase-separated structure of a second metal oxide core and a first metal oxide shell, and an excessively low molar ratio, which would also result in a phase-separated structure of a first metal oxide core and a second metal oxide shell.

[0018] Preferably, both the first metal source and the second metal source are selected from nitrates, chlorides, sulfates, or metal alkoxides of the first metal oxide and the second metal oxide.

[0019] Preferably, the aging temperature is 60~120 ℃ and the aging time is 1~12 h.

[0020] This invention, by controlling the aging time, ensures the precipitation and nucleation growth of the first and second metal sources, resulting in a larger number of composite oxides with greater specific surface area and larger pore size. This increases the number of acidic sites and better catalyzes the dehydration reaction of primary alcohols. It also avoids problems such as excessively high aging temperatures and excessively rapid growth, which could lead to catalyst particle aggregation and a decrease in specific surface area.

[0021] Preferably, in S1, the calcination conditions are as follows: the temperature is increased from room temperature to 300°C at a heating rate of 1~10°C / min, and the holding time is 1~5 h, followed by increasing the temperature to 400~900°C at the same heating rate, and the holding time is 1~10 h.

[0022] This invention, by controlling the calcination conditions of the composite oxide, enables pre-crosslinking at a low temperature with a relatively low heating rate, followed by promotion of complete dehydration of hydroxyl groups to transform into composite oxides at a higher temperature. This results in a composite oxide with a homogeneous phase and a large pore size, forming channels that facilitate the diffusion and contact of reactant and product molecules, thereby improving the catalyst's reactivity. Simultaneously, it minimizes the risk of abnormal grain growth and over-sintering caused by excessively rapid heating or excessively high temperatures, which could lead to a sharp decrease in the specific surface area of ​​the composite oxide or collapse of the pore structure.

[0023] Preferably, the Th salt is selected from nitrates or chlorides.

[0024] Preferably, in S2, the calcination conditions are: increasing the temperature from room temperature to 600-900 °C at a rate of 2-5 °C / min and maintaining the temperature for 0.5-12 h.

[0025] This invention promotes the full thermal decomposition of Th salts by controlling the calcination conditions, forming well-crystallized ThO2, which helps to exert the inhibitory effect of this additive on the double bond isomerization side reaction. A moderate heating rate ensures a stable and controllable decomposition process, minimizing the risk of violent decomposition, grain aggregation, and abnormal growth caused by excessively rapid heating.

[0026] Preferably, in S3, the calcination conditions are: heating from room temperature to 350-400 ℃ at a heating rate of 0.5-3 ℃ / min, and holding for 0.5-5 h.

[0027] On the other hand, the present invention also provides an application of the catalyst for the dehydration of primary alcohols to prepare α-olefins in the catalytic dehydration of primary alcohols to prepare α-olefins, using a fixed-bed reactor with nitrogen as the carrier gas, so that the primary alcohol undergoes a dehydration reaction to generate α-olefins under the action of the catalyst.

[0028] The catalyst for the dehydration of primary alcohols to α-olefins described in this invention exhibits a high concentration of acidic sites and suitable acid strength, with a uniform distribution of acidic sites, demonstrating excellent catalytic activity. Simultaneously, the promoter introduced into the catalyst can selectively adsorb and isolate the generated α-olefins, effectively inhibiting their isomerization and thus significantly improving product selectivity. Therefore, when this catalyst is used for the dehydration reaction of primary alcohols, it can maintain stable performance over long-term operation, improving the conversion rate of primary alcohols and the selectivity of α-olefins.

[0029] Preferably, the primary alcohol is C3~C6. 18 Primary alcohols, with a mass concentration of 10-70%.

[0030] Preferably, the solvent for the primary alcohol is a short-chain saturated alkane, which is a C6-C8 straight-chain alkane, cycloalkanes, or monobranched alkane.

[0031] Preferably, the reaction conditions for the dehydration reaction are: liquid hourly space velocity (LHSV) of 0.5–2 h⁻¹. -1 Pressure 5~30 bar, reaction temperature 180~290 ℃.

[0032] Preferably, the conversion rate of the primary alcohol is ≥99%, and the selectivity of the α-olefin is ≥98%.

[0033] The reaction conditions provided by this invention are highly compatible with the characteristics of the catalyst prepared by this invention, which can ensure that primary alcohols are fully converted under suitable space velocity, temperature and pressure, while effectively suppressing side reactions, thereby ensuring high efficiency and high selectivity of the reaction.

[0034] Compared with the prior art, the present invention has the following beneficial effects: The limited number and weak intensity of inherent acidic sites in the first metal oxide lead to insufficient catalytic activity. Therefore, this invention introduces a second metal oxide for doping and synergistically controls its content ratio with the first metal oxide and ThO2. Under this ratio, the oxygen coordination difference between the two metal ions induces structural mismatch, significantly increasing the number of acidic sites and enhancing their intensity to a suitable range, thereby avoiding olefin isomerization caused by excessive acidity. Furthermore, by controlling the precipitation conditions to achieve uniform co-precipitation, a composite oxide with uniform composition is obtained, ensuring a uniform distribution of acidic sites and comprehensively improving reaction activity and selectivity. Attached Figure Description

[0035] Figure 1 This is a morphology diagram of the catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1 654.9 g of Al(NO3)3・9H2O and 23.11 g of NbCl5 were added to a 1 L beaker, followed by 200 mL of a 1:1 ethanol-water solution. The mixture was stirred for 30 min until completely dissolved. A mixture of 0.1 mol / L H2O2 and 2 mol / L ammonia (volume ratio 0.05:1) was prepared and added dropwise to the salt solution at a rate of 2 mL / min. The pH was adjusted to 8, and the mixture was stirred for 1 h after the addition was complete. The mixture was then transferred to a polytetrafluoroethylene reactor and aged in a 60 °C water bath for 12 h, stirring for 10 min every 2 h. After aging, the mixture was filtered and washed until the pH of the filtrate reached 7. The filtrate was then dried at 105 °C for 12 h. The sample was placed in a muffle furnace and heated to 300 °C at a rate of 1 °C / min and held for 5 h. Then, the temperature was increased to 400 °C at a rate of 1 °C / min and held for 10 h, yielding 99 g of composite oxide.

[0038] 1.818 g of Th(NO3)4·4H2O was placed in a muffle furnace and heated to 600 °C at 2 °C / min and held for 12 h to obtain 1 g of ThO2. 99 g of the composite oxide was ball-milled with 1 g of ThO2 at 300 r / min for 2 h. Subsequently, it was placed in a muffle furnace and heated to 350 °C at 0.5 °C / min and held for 5 h to obtain 100 g of catalyst. Figure 1 As shown.

[0039] The catalyst prepared in Example 1 of this invention has a specific surface area of ​​325 m². 2 / g, with an average pore size of 16 nm and an average pore volume of 0.6 cm³. 3 / g.

[0040] The concentration of acidic sites in the catalyst prepared in Example 1 of this invention is 0.59 mmol·g. -1 The proportion of weak acids and moderately strong acids is 79%.

[0041] Example 2 Add 158.6 g Zr(SO4)2·4H2O and 170.8 g Ga(NO3)3·9H2O to a 1 L beaker, then add 400 mL of an ethanol-water solution (3:1 volume ratio) and stir for 40 min until completely dissolved. Prepare a mixture of 0.4 mol / L H2O2 and 2 mol / L NaOH (0.2:1 volume ratio) and add it dropwise to the salt solution at 5 mL / min, adjusting the pH to 11. After the addition is complete, stir for 2 h. Transfer to a 500 mL polytetrafluoroethylene reactor and age in a 120 ℃ oven for 1 h. Filter and wash until the filtrate is free of SO4. 2- The sample was dried at 110 °C for 8 h. The dried sample was placed in a muffle furnace and heated to 300 °C at 10 °C / min and held for 1 h. Then the temperature was increased to 900 °C at 10 °C / min and held for 1 h to obtain 95 g of composite oxide.

[0042] 7.08 g of ThCl4 was placed in a muffle furnace and heated to 900 °C at 5 °C / min and held for 0.5 h to obtain 5 g of ThO2. 95 g of the composite oxide and 5 g of ThO2 were added to 80 mL of ethanol, ball-milled at 400 r / min for 3 h, and dried at 100 °C. The temperature was then increased to 400 °C at 3 °C / min and held for 0.5 h to obtain 100 g of catalyst.

[0043] The catalyst prepared in Example 2 of this invention has a specific surface area of ​​207 m². 2 / g, with an average pore size of 13 nm and an average pore volume of 0.4 cm³. 3 / g.

[0044] The concentration of acidic sites in the catalyst prepared in Example 2 of this invention is 0.48 mmol·g. -1 The proportion of weak acids and moderately strong acids is 76%.

[0045] Example 3 306.9 g of Ti(OC4H9)4 was slowly added dropwise to 200 mL of a 2:1 ethanol-water solution, and stirred for 30 min until a clear solution was formed. Then, 83.2 g of Nb(NO3)5 was added (in a 1 L beaker), and stirring was continued for 20 min until completely dissolved. A mixture of 0.24 mol / L H2O2 and 2 mol / L Na2CO3 (volume ratio 0.12:1) was prepared and added dropwise to the salt solution at a rate of 3 mL / min, adjusting the pH to 9.5. After the addition was complete, the mixture was stirred for 1.5 h. The mixture was then transferred to a polytetrafluoroethylene reactor and aged at 90 °C for 6 h. After aging, the mixture was filtered and washed until the pH of the filtrate reached 7, and then dried at 105 °C for 10 h. The sample was placed in a muffle furnace and heated to 300 °C at 5 °C / min and held for 3 h, followed by heating to 650 °C at 5 °C / min and holding for 5 h, yielding 97 g of composite oxide.

[0046] 5.46 g of Th(NO3)4・4H2O was placed in a muffle furnace and heated to 750 °C at 3.5 °C / min and held for 6 h to obtain 3 g of ThO2. 97 g of the composite oxide and 3 g of ThO2 were ball-milled at 350 r / min for 2.5 h. The mixture was then placed in a muffle furnace and heated to 375 °C at 1.5 °C / min and held for 2.5 h to obtain 100 g of catalyst.

[0047] The catalyst prepared in Example 3 of this invention has a specific surface area of ​​187 m². 2 / g, average pore size is 6 nm, average pore volume is 0.8 cm³. 3 / g.

[0048] The concentration of acidic sites in the catalyst prepared in Example 3 of this invention is 0.42 mmol·g. -1 The proportion of weak acids and moderately strong acids is 72%.

[0049] Example 4 112.3 g of SnCl2·2H2O and 37.6 g of GaCl3 were added to a 1 L beaker, followed by 300 mL of a 1:2 ethanol-water solution. The mixture was stirred for 35 min until completely dissolved. A mixture of 0.15 mol / L H2O2 and 2 mol / L K2CO3 (volume ratio 0.075:1) was prepared and added dropwise to the salt solution at a rate of 4 mL / min. The pH was adjusted to 10, and the mixture was stirred for 1.5 h after the addition was complete. The mixture was then transferred to a polytetrafluoroethylene reactor and aged in a 100 ℃ water bath for 8 h. After aging, the mixture was filtered and washed until the pH of the filtrate reached 7. The filtrate was then dried at 105 ℃ for 11 h. The sample was placed in a muffle furnace and heated to 300 ℃ at 7 ℃ / min and held for 2 h. Then, the temperature was increased to 750 ℃ ​​at 7 ℃ / min and held for 6 h to obtain 95 g of composite oxide.

[0050] 9.1 g of Th(NO3)4・4H2O was placed in a muffle furnace and heated to 800 °C at 4 °C / min and held for 4 h to obtain 5 g of ThO2. 95 g of the composite oxide and 5 g of ThO2 were ball-milled at 320 r / min for 2.5 h. The mixture was then placed in a muffle furnace and heated to 360 °C at 1 °C / min and held for 4 h to obtain 100 g of catalyst.

[0051] The catalyst prepared in Example 4 of this invention has a specific surface area of ​​375 m². 2 / g, with an average pore size of 17 nm and an average pore volume of 0.9 cm³. 3 / g.

[0052] The concentration of acidic sites in the catalyst prepared in Example 4 of this invention is 0.67 mmol·g. -1 The proportion of weak acids and moderately strong acids is 82%.

[0053] Example 5 169.9 g of ZrOCl2・8H2O and 143.1 g of Ga(NO3)3・9H2O were added to a 1 L beaker, followed by 350 mL of a 2:3 ethanol-water solution. The mixture was stirred for 40 min until completely dissolved. A 0.2 mol / L H2O2 and 2 mol / L Li2CO3 mixture (0.1:1 volume ratio) was prepared and added dropwise to the salt solution at a rate of 3.5 mL / min. The pH was adjusted to 9, and the mixture was stirred for 2 h after the addition was complete. The mixture was then transferred to a polytetrafluoroethylene reactor and aged at 80 °C for 10 h. After aging, the mixture was filtered and washed until no Cl- was found in the filtrate. - (No white precipitate was formed upon addition of AgNO3 solution), and the sample was dried at 110 °C for 9 h. The sample was then placed in a muffle furnace and heated to 300 °C at 6 °C / min and held for 3 h, followed by heating to 800 °C at 6 °C / min and holding for 4 h to obtain 95 g of composite oxide.

[0054] 7.08 g of ThCl4 was placed in a muffle furnace and heated to 850 °C at 3 °C / min and held for 3 h to obtain 5 g of ThO2. 95 g of the composite oxide and 5 g of ThO2 were ball-milled at 380 r / min for 3 h. Subsequently, the mixture was placed in a muffle furnace and heated to 380 °C at 2 °C / min and held for 2 h to obtain 100 g of catalyst.

[0055] The catalyst prepared in Example 5 of this invention has a specific surface area of ​​94 m². 2 / g, average pore size is 8 nm, average pore volume is 0.3 cm³. 3 / g.

[0056] The concentration of acidic sites in the catalyst prepared in Example 5 of this invention is 0.38 mmol·g. -1 The proportion of weak and moderately strong acids is 80%.

[0057] Example 6 Add 523.0 g of Al2(SO4)3·18H2O and 41.6 g of NbCl5 to a 1 L beaker, add 400 mL of a 1:3 ethanol-water solution, and stir for 45 min until completely dissolved. Precipitation: Prepare a mixture of 0.12 mol / L H2O2 and 2 mol / L triethylamine (concentration ratio 0.06:1), and add it dropwise to the salt solution at 2.5 mL / min, adjusting the pH to 8.5. After the addition is complete, stir for 1.5 h. Transfer to a 500 mL polytetrafluoroethylene reactor and age in a 70 ℃ water bath for 11 h. Filter and wash until the filtrate is free of SO4. 2- (No white precipitate was formed upon addition of BaCl2 solution), dried at 105℃ for 12 h; heated to 300℃ at 4℃ / min and held for 4 h in a muffle furnace, then heated to 600℃ at 4℃ / min and held for 8 h to obtain 98 g of composite oxide.

[0058] 3.64 g of Th(NO3)4·4H2O was placed in a porcelain boat and heated in a muffle furnace at 2.5 ℃ / min to 700 ℃ and held for 10 h to obtain 2 g of ThO2. 98 g of the composite oxide and 2 g of ThO2 were added to 55 mL of ethanol, ball-milled at 340 r / min for 2 h, and dried at 80 ℃. The temperature was increased to 350 ℃ at 0.8 ℃ / min and held for 3 h to obtain 100 g of catalyst.

[0059] The catalyst prepared in Example 6 of this invention has a specific surface area of ​​400 m². 2 / g, average pore size is 7 nm, average pore volume is 0.1 cm³. 3 / g.

[0060] The concentration of acidic sites in the catalyst prepared in Example 6 of this invention is 0.53 mmol·g. -1 The proportion of weak acids and moderately strong acids is 86%.

[0061] Example 7 Add 201.9 g TiCl4 dropwise to 200 mL of a 1:1 ethanol aqueous solution containing 5 mL concentrated hydrochloric acid, stir for 30 min until a clear solution is formed, then add 39.9 g Nb(NO3)5, and continue stirring for 25 min until completely dissolved. Prepare a mixture of 0.18 mol / L H2O2 and 2 mol / L ammonia (concentration ratio 0.09:1), and add it dropwise to the salt solution at 3 mL / min, adjusting the pH to 8.8. After the addition is complete, stir for 2 h. Transfer to a 500 mL polytetrafluoroethylene reactor and age at 95 ℃ for 7 h. Filter and wash until the filtrate is free of Cl. - (No white precipitate was formed upon addition of AgNO3 solution), dried at 110 ℃ for 10 h; heated to 300 ℃ at 8 ℃ / min and held for 2.5 h in a muffle furnace, then heated to 500 ℃ at 8 ℃ / min and held for 9 h to obtain 97 g of composite oxide.

[0062] 4.25 g of ThCl4 was placed in a porcelain boat and heated in a muffle furnace at 3.8 ℃ / min to 780 ℃ and held for 5 h to obtain 3 g of ThO2. 97 g of the composite oxide and 3 g of ThO2 were added to 60 mL of ethanol, ball-milled at 360 r / min for 2.5 h, and dried at 90 ℃. The temperature was increased to 1.2 ℃ / min and held for 3.5 h to obtain 100 g of catalyst.

[0063] The catalyst prepared in Example 7 of this invention has a specific surface area of ​​50 m². 2 / g, average pore size is 4 nm, average pore volume is 0.9 cm³. 3 / g.

[0064] The concentration of acidic sites in the catalyst prepared in Example 7 of this invention is 0.62 mmol·g. -1 The proportion of weak acids and moderately strong acids is 83%.

[0065] Example 8 209.1 g of Zr(NO3)4·5H2O and 80.9 g of NbCl5 were added to a 1 L beaker, followed by 380 mL of a 3:2 ethanol-water solution. The mixture was stirred for 50 min until completely dissolved. A mixture of 0.16 mol / L H2O2 and 2 mol / L Na2CO3 (concentration ratio 0.08:1) was prepared and added dropwise to the salt solution at a rate of 4 mL / min to adjust the pH to 10.5. After the addition was complete, the mixture was stirred for 2.5 h. The solution was transferred to a 500 mL polytetrafluoroethylene reactor and aged in a 110 ℃ oven for 5 h. The solution was filtered and washed until the pH of the filtrate reached 7, then dried at 105 ℃ for 11 h. The solution was then heated in a muffle furnace at a rate of 9 ℃ / min to 300 ℃ and held for 2 h, followed by a further heating at a rate of 9 ℃ / min to 850 ℃ and held for 5 h to obtain 95 g of the composite oxide.

[0066] 9.1 g of Th(NO3)4·4H2O was placed in a porcelain boat and heated in a muffle furnace at 4.5 ℃ / min to 820 ℃ and held for 4.5 h to obtain 5 g of ThO2. 95 g of the composite oxide and 5 g of ThO2 were added to 75 mL of ethanol, ball-milled at 400 r / min for 3 h, and dried at 100 ℃. The temperature was then increased to 390 ℃ at 2.5 ℃ / min and held for 1.5 h to obtain 100 g of catalyst.

[0067] The catalyst prepared in Example 8 of this invention has a specific surface area of ​​264 m². 2 / g, average pore size is 3 nm, average pore volume is 0.7 cm³. 3 / g.

[0068] The concentration of acidic sites in the catalyst prepared in Example 8 of this invention is 0.59 mmol·g. -1 The proportion of weak acids and moderately strong acids is 79%.

[0069] Example 9 124.8 g of Sn(NO3)2・3H2O and 124.0 g of Ga(NO3)3・9H2O were added to a 1 L beaker, followed by 320 mL of a 2:1 ethanol-water solution. The mixture was stirred for 40 min until completely dissolved. A mixture of 0.14 mol / L H2O2 and 2 mol / L KOH (concentration ratio 0.07:1) was prepared and added dropwise to the salt solution at a rate of 3.2 mL / min to adjust the pH to 9.2. After the addition was complete, the mixture was stirred for 2 h. The solution was transferred to a 500 mL polytetrafluoroethylene reactor and aged in a water bath at 85 ℃ for 9 h. The solution was filtered and washed until the pH of the filtrate reached 7, then dried at 110 ℃ for 9 h. The solution was then heated in a muffle furnace at a rate of 5 ℃ / min to 300 ℃ and held for 3.5 h, followed by a further heating at a rate of 5 ℃ / min to 700 ℃ and held for 7 h to obtain 96 g of the composite oxide.

[0070] 5.67 g of ThCl4 was placed in a porcelain boat and heated in a muffle furnace at 3.2 ℃ / min to 760 ℃ and held for 6 h to obtain 4 g of ThO2. 96 g of the composite oxide and 4 g of ThO2 were added to 65 mL of ethanol, ball-milled at 330 r / min for 2.5 h, and dried at 88 ℃. The temperature was increased to 1.8 ℃ / min and held for 3 h to obtain 100 g of catalyst.

[0071] The catalyst prepared in Example 9 of this invention has a specific surface area of ​​328 m². 2 / g, average pore size is 18 nm, average pore volume is 0.5 cm³. 3 / g.

[0072] The concentration of acidic sites in the catalyst prepared in Example 9 of this invention is 0.46 mmol·g. -1The proportion of weak acids and moderately strong acids is 76%.

[0073] Comparative Example 1 654.9 g of Al(NO3)3・9H2O and 15.26 g of NbCl5 were added to a 1 L beaker, followed by 200 mL of a 1:1 ethanol-water solution. The mixture was stirred for 30 min until completely dissolved. A mixture of 0.1 mol / L H2O2 and 2 mol / L ammonia (volume ratio 0.05:1) was prepared and added dropwise to the salt solution at a rate of 2 mL / min. The pH was adjusted to 8, and the mixture was stirred for 1 h after the addition was complete. The mixture was then transferred to a polytetrafluoroethylene reactor and aged in a 60 °C water bath for 12 h, stirring for 10 min every 2 h. After aging, the mixture was filtered and washed until the pH of the filtrate reached 7. The filtrate was then dried at 105 °C for 12 h. The sample was placed in a muffle furnace and heated to 300 °C at a rate of 1 °C / min and held for 5 h. Then, the temperature was increased to 400 °C at a rate of 1 °C / min and held for 10 h to obtain 95 g of composite oxide.

[0074] 1.818 g of Th(NO3)4・4H2O was placed in a muffle furnace and heated to 600 °C at 2 °C / min and held for 12 h to obtain 1 g of ThO2. 99 g of the composite oxide was ball-milled with 1 g of ThO2 at 300 r / min for 2 h. Subsequently, it was placed in a muffle furnace and heated to 350 °C at 0.5 °C / min and held for 5 h to obtain 100 g of catalyst.

[0075] The catalyst prepared in Example 1 of this invention has a specific surface area of ​​240 m². 2 / g, average pore size is 3 nm, average pore volume is 1.3 cm³. 3 / g.

[0076] The concentration of acidic sites in the catalyst prepared in Example 1 of this invention is 0.28 mmol·g. -1 The proportion of weak acids and moderately strong acids is 41%.

[0077] Comparative Example 2 Add 158.6 g of Zr(SO4)2·4H2O and 200.7 g of Ga(NO3)3·9H2O to a 1 L beaker, then add 400 mL of an ethanol-water solution (3:1 volume ratio) and stir for 40 min until completely dissolved. Prepare a mixture of 0.4 mol / L H2O2 and 2 mol / L NaOH (0.2:1 volume ratio) and add it dropwise to the salt solution at 5 mL / min, adjusting the pH to 11. After the addition is complete, stir for 2 h. Transfer to a 500 mL polytetrafluoroethylene reactor and age in a 120 ℃ oven for 1 h. Filter and wash until the filtrate is free of SO4. 2-The sample was dried at 110 °C for 8 h. The dried sample was placed in a muffle furnace and heated to 300 °C at 10 °C / min and held for 1 h. Then the temperature was increased to 900 °C at 10 °C / min and held for 1 h to obtain 95 g of composite oxide.

[0078] 7.08 g of ThCl4 was placed in a muffle furnace and heated to 900 °C at 5 °C / min and held for 0.5 h to obtain 5 g of ThO2. 95 g of the composite oxide and 5 g of ThO2 were added to 80 mL of ethanol, ball-milled at 400 r / min for 3 h, and dried at 100 °C. The temperature was then increased to 400 °C at 3 °C / min and held for 0.5 h to obtain 100 g of catalyst.

[0079] The catalyst prepared in Example 2 of this invention has a specific surface area of ​​46 m². 2 / g, average pore size is 8 nm, average pore volume is 0.6 cm³. 3 / g.

[0080] The concentration of acidic sites in the catalyst prepared in Example 2 of this invention is 0.23 mmol·g. -1 The proportion of weak and moderately strong acids is 38%.

[0081] Application Example 1 20 g of the catalyst prepared in Example 1 was packed into a fixed bed, and a 10% (w / w) 1-propanol-n-hexane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 5 bar, 180 °C, and a liquid hourly space velocity of 0.5 h⁻¹. -1 .

[0082] Application Example 2 35 g of the catalyst prepared in Example 2 was packed into a fixed bed, and a 70% (w / w) 1-octadecyl-2-methylheptane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 30 bar and at 290 °C, with a liquid hourly space velocity of 2 h⁻¹. -1 .

[0083] Application Example 3 25 g of the catalyst prepared in Example 3 was packed into a fixed bed, and a 40% (w / w) 1-decyl alcohol-cyclohexane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 17 bar and at 235 °C, with a liquid hourly space velocity of 1.2 h⁻¹. -1 .

[0084] Application Example 4 22 g of the catalyst prepared in Example 4 was packed into a fixed bed, and a 20% (w / w) 1-pentanol-n-heptane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 10 bar and at 200 °C, with a liquid hourly space velocity of 0.5 h⁻¹. -1 .

[0085] Application Example 5 28 g of the catalyst prepared in Example 5 was packed into a fixed bed, and a 50% (w / w) 1-octanol-cycloheptane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 20 bar and at 250 °C, with a liquid hourly space velocity of 1.5 h⁻¹. -1 .

[0086] Application Example 6 30 g of the catalyst prepared in Example 6 was packed into a fixed bed, and a 60% (w / w) 1-dodecyl-n-octane solution was used as the feed liquid. The reaction was carried out at 270 °C under nitrogen pressure of 25 bar and a liquid hourly space velocity of 2 h⁻¹. -1 .

[0087] Application Example 7 31 g of the catalyst prepared in Example 7 was packed into a fixed bed, and a 30% (w / w) 1-butanol-cyclohexane solution was used as the feed liquid. The reaction was carried out at a nitrogen pressure of 5 bar and a temperature of 220 °C, with a liquid hourly space velocity of 1 h⁻¹. -1 .

[0088] Application Example 8 29 g of the catalyst prepared in Example 8 was packed into a fixed bed, and a 55% (w / w) 1-hexadecyl-2-methylhexane solution was used as the feed liquid. The reaction was carried out at a nitrogen pressure of 30 bar and a temperature of 280 °C, with a liquid hourly space velocity of 1.8 h⁻¹. -1 .

[0089] Application Example 9 34 g of the catalyst prepared in Example 9 was packed into a fixed bed, and a 45% (w / w) 1-nonanol-n-hexane solution was used as the feed liquid. The reaction was carried out at a nitrogen pressure of 18 bar and a temperature of 240 °C, with a liquid hourly space velocity of 1.3 h⁻¹. -1 .

[0090] Application Comparative Example 1 20 g of the catalyst prepared in Comparative Example 1 was packed into a fixed bed, and a 10% (w / w) 1-propanol-n-hexane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 5 bar, 180 °C, and a liquid hourly space velocity of 0.5 h⁻¹. -1 .

[0091] Application Comparative Example 2 20 g of the catalyst prepared in Comparative Example 2 was packed into a fixed bed, and a 10% (w / w) 1-propanol-n-hexane solution was used as the feed liquid. The reaction was carried out under nitrogen pressure of 5 bar, 180 °C, and a liquid hourly space velocity of 0.5 h⁻¹. -1 .

[0092] Performance Analysis The activity test results of the dehydration of primary alcohols to α-olefins in Examples 1-9 and Comparative Examples 1 and 2 of this invention are shown in Table 1.

[0093] Table 1. Activity test results of the dehydration reaction of primary alcohols to α-olefins in Application Examples 1-9 and Comparative Examples 1 and 2 of this invention. As can be seen from the table above, the prepared catalyst has good dehydration activity of primary alcohols, with a conversion rate of over 99% and an α-olefin yield of over 98%, showing good prospects for industrial application.

[0094] As shown in Table 1, the catalyst prepared in this invention exhibits excellent comprehensive performance in the dehydration reaction of primary alcohols: the conversion rate of primary alcohols is higher than 99%, and the yield of α-olefins is higher than 98%. This indicates that by synergistically constructing suitable acidity and uniformly distributed active sites through a specific ratio of the first and second metal oxides, and by using ThO2 promoters to promote product desorption and inhibit isomerization, a balance between high conversion rate and high selectivity can be achieved. The catalyst has good prospects for industrial application.

[0095] As shown in Comparative Example 1, when the content of the second metal oxide is too high, the catalyst surface becomes too acidic. Although this can improve the conversion rate of primary alcohols, it leads to significant side reactions such as double bond isomerization of the generated α-olefins, resulting in a significant decrease in selectivity. As can be seen from Comparative Example 2, when the content of the second metal oxide is too low, its regulatory effect on acidic sites is insufficient, the improvement of acidity and strength on the catalyst surface is limited, resulting in the primary alcohol conversion rate not being able to stably reach more than 99%, and the reaction activity being insufficient, which cannot meet the requirements of high-efficiency production.

Claims

1. A catalyst for the dehydration of primary alcohols to prepare α-olefins, characterized in that, The product comprises the following components by mass percentage: 55-89 wt.% of the first metal oxide, 10-40 wt.% of the second metal oxide, and 1-5 wt.% of the ThO2 additive. The first metal oxide is Al2O3, TiO2, SnO2 or ZrO2; The second metal oxide is Nb2O5 or Ga2O3.

2. The catalyst for the dehydration of primary alcohols to prepare α-olefins according to claim 1, characterized in that, The concentration of acidic sites in the catalyst for the dehydration of primary alcohols to α-olefins is 0.38–0.67 mmol·g. -1 The proportion of weak acids and moderately strong acids is 72-86%.

3. The catalyst for the dehydration of primary alcohols to prepare α-olefins according to claim 1, characterized in that, The catalyst for the dehydration of primary alcohols to prepare α-olefins has a specific surface area of ​​50-400 m². 2 / g, with an average pore size of 3~20 nm and an average pore volume of 0.1~0.9 cm³. 3 / g.

4. A method for preparing a catalyst for the dehydration of primary alcohols to α-olefins according to any one of claims 1-3, characterized in that, include: S1. Dissolve the first metal source and the second metal source in ethanol-water, add a mixed solution of hydrogen peroxide and alkaline precipitant, wherein the molar ratio of hydrogen peroxide to alkaline precipitant is 0.05:1~0.2:1, adjust the pH of the system to 8~11, then age it, and then calcine it to obtain the composite oxide. S2. Roast the Th salt to obtain ThO2; S3. The composite oxide is mixed with ThO2, ball-milled, and then calcined to obtain the catalyst for the dehydration of primary alcohol to prepare α-olefin.

5. The method for preparing the catalyst for the dehydration of primary alcohols to α-olefins according to claim 4, characterized in that, The first metal source and the second metal source are both selected from the nitrate, chloride, sulfate or metal alkoxide of the first metal oxide and the second metal oxide.

6. The method for preparing the catalyst for the dehydration of primary alcohols to α-olefins according to claim 4, characterized in that, The aging temperature is 60~120 ℃, and the aging time is 1~12 h.

7. The method for preparing the catalyst for the dehydration of primary alcohols to α-olefins according to claim 4, characterized in that, In S1, the calcination conditions are as follows: the temperature is increased from room temperature to 300 ℃ at a heating rate of 1~10 ℃ / min, and the holding time is 1~5 h, and then the temperature is increased to 400~900 ℃ at the same heating rate, and the holding time is 1~10 h.

8. The application of the catalyst for the dehydration of primary alcohols to α-olefins according to any one of claims 1-3 in the catalytic dehydration of primary alcohols to α-olefins, wherein a fixed-bed reactor is used and nitrogen is used as the carrier gas, so that the primary alcohol undergoes a dehydration reaction to generate α-olefins under the action of the catalyst.

9. The application of the catalyst for the dehydration of primary alcohols to α-olefins according to claim 8 in the catalytic dehydration of primary alcohols to α-olefins, characterized in that, The reaction conditions for the dehydration reaction are: liquid hourly space velocity (LHSV) 0.5–2 h⁻¹. -1 Pressure 5~30 bar, reaction temperature 180~290 ℃.

10. The application of the catalyst for the dehydration of primary alcohols to α-olefins according to claim 9 in the catalytic dehydration of primary alcohols to α-olefins, characterized in that, The conversion rate of the primary alcohol is ≥99%, and the selectivity of the α-olefin is ≥98%.

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