A catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in piperylene and a preparation method thereof

Abstract

The present invention provides a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in piperylene and a preparation method thereof. The preparation method includes the following steps: (1) Prepare an aqueous solution containing a palladium compound, add potassium chloride thereto to obtain solution A, then add ethanol and a nonionic surfactant to solution A, and stir for a period of time at a certain temperature to obtain solution B; (2) Suspend SiO2 in water, add a certain amount of an amphoteric surfactant to obtain suspension C; (3) Dropwise add solution B to suspension C, and stir for a period of time at a certain temperature to obtain suspension D; (4) Prepare an aqueous solution containing a copper compound, add a certain amount of a precipitant, and stir for a period of time at a certain temperature to obtain turbid solution E; (5) Dropwise add turbid solution E to suspension D, stir for a period of time at a certain temperature, then filter, wash, dry, and calcine to obtain an oxidized catalyst; (6) Reduce the oxidized catalyst to obtain a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in piperylene. The catalyst prepared by the present invention is applicable to the removal of a small amount of alkynes and cyclopentadiene in piperylene, and is particularly applicable to the selective hydrogenation and removal of a small amount of alkynes and cyclopentadiene in piperylene by-produced in the ethylene production unit by naphtha cracking. The purified piperylene can be directly used for polymerizing to produce resins and rubbers.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and relates to a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in piperylene and a preparation method thereof. Background Art

[0002] In recent years, with the continuous expansion of the ethylene production scale in China and the continuous growth of the production capacity of ethylene from liquid hydrocarbons as raw materials, the production of C5 fraction has become increasingly abundant. The composition of the C5 fraction is very complex, mainly composed of mixed hydrocarbons such as alkanes, alkenes, cycloalkanes, cycloalkenes, dienes and alkynes containing 4-6 carbon atoms. Among them, the components with higher content and utilization value are isoprene (ISP, mass fraction of 15%-20%), piperylene (PD, mass fraction of 10%-19%), and cyclopentadiene (CPD, mass fraction of 14%-19%). These dienes are important raw materials for the production of petrochemical and fine chemical products such as isoprene rubber, butyl rubber, ethylene-propylene rubber, petroleum resin, thermoplastic elastomer and unsaturated polyester. Among them, piperylene is the main raw material for the production of aliphatic petroleum resin. The molecular chain segments of this petroleum resin are mainly aliphatic hydrocarbon structures, with low acid value, good adhesion performance, water and ethanol resistance, chemical corrosion resistance, and good compatibility. It has been gradually applied to fields such as pressure-sensitive adhesives, light-colored hot-melt adhesives, powder coatings, light-colored hot-melt marking paints, paints and printing ink additives. As a raw material for the production of petroleum resin, piperylene needs to be extracted from the C5 fraction. However, a small amount of alkynes (such as pentyne-1, pentyne-2 and isopropenyl acetylene, etc.) and cyclopentene contained in the C5 fraction, with a total content of about 0.1-2 wt.%, due to their active chemical properties, have a serious impact on the polymerization process of piperylene (inactivating the initiator, resulting in difficult polymerization). Therefore, before polymerizing to produce polymers such as petroleum resin with piperylene as the raw material, impurities such as alkynes and cyclopentadiene need to be removed.

[0003] At present, the main methods for removing a small amount of alkynes and cyclopentadiene from olefins are extractive distillation and selective hydrogenation. Among them, extractive distillation increases the relative volatility between the components to be separated, enabling the separation of components with similar boiling points in the C5 fraction. However, this method has disadvantages such as complex process flow and high energy consumption. And during the separation process, alkynes will be concentrated in some equipment, posing safety hazards. In the absorption process, organic solvents are prone to volatilization, causing environmental pollution, which limits its industrial application. In comparison, selective hydrogenation can effectively remove alkynes and cyclopentadiene from olefins, improve the yield of olefins, and has a simple process flow, low energy consumption, and environmental friendliness. It is currently the most widely used technology for removing alkynes and cyclopentadiene from olefins. The core of selective hydrogenation for removing alkynes and cyclopentadiene is the preparation of selective hydrogenation catalysts. Compared with ordinary metals such as Ni, Co, and Fe, noble metal Pd has excellent low-temperature catalytic activity and good selective hydrogenation activity. Commonly used selective hydrogenation catalysts for removing alkynes and cyclopentadiene from olefins use Pd as the active metal and load it on inert supports such as γ-Al2O3 or SiO2. However, due to the poor dispersion of noble metal Pd on the support, its loading amount is relatively high, resulting in a high preparation cost. To address this issue, Wei Guobin et al. (Wei Guobin, Yang Siyuan, Zhang Jingchang, et al. Petrochemical Technology, 2012, 41(11): 1239-1244.) prepared Pd nanoparticles by the microemulsion method and loaded them on γ-Al2O3 to prepare a highly dispersed Pd catalyst. This catalyst can effectively remove acetylene in the acetylene selective hydrogenation system, but its selectivity for ethylene is poor. To overcome the defect of poor olefin selectivity in the existing hydrogenation catalyst dealkylation process. CN111097445A discloses a method for selective hydrogenation of isoprene to remove alkynes. This catalyst uses palladium as the active component, copper as the promoter, and alumina as the support. The catalyst prepared by this method shows excellent catalytic activity and selectivity in the selective hydrogenation of isoprene to remove alkynes. The total remaining alkyne content is 10 μg / g, and the loss rate of isoprene is 1.0%. Although its isoprene loss rate is relatively low, the alkynes are not completely removed, which will still cause the inactivation of the initiator in the subsequent polymerization process and affect the quality of the polymerization product; moreover, its reaction uses a two-stage reactor, increasing the equipment investment.

[0004] As can be seen from the above, currently, more reports are focused on the development of selective hydrogenation catalysts for a small amount of dienes or alkynes in C2-C4 monoolefin fractions and selective hydrogenation dealkylation catalysts for a small amount of isoprene in the C5 fraction. However, for the removal of a small amount of alkynes and cyclopentadiene in piperylene, the preparation of relevant selective hydrogenation catalysts has not been reported.

[0005] In summary, there is an urgent need in the art to develop a selective hydrogenation catalyst and its preparation method for removing a small amount of alkynes and cyclopentadiene from piperylene. Summary of the Invention

[0006] To solve the above technical problems, the object of the present invention is to provide a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene and a preparation method thereof. The catalyst has excellent hydrogenation selectivity, can effectively remove alkynes and cyclopentadiene in isoprene, and has a low loss rate of isoprene.

[0007] To achieve the above object, the present invention provides a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene and a preparation method thereof. The method includes the following steps:

[0008] (1) Prepare an aqueous solution containing a palladium compound, add potassium chloride to obtain solution A, then add a monohydric alcohol and a nonionic surfactant to solution A, and stir for a period of time at a certain temperature to obtain solution B;

[0009] (2) Use SiO2 as a carrier and suspend it in water, add a certain amount of amphoteric surfactant to obtain suspension C;

[0010] (3) Dropwise add solution B to suspension C, and stir for a period of time at a certain temperature to obtain suspension D;

[0011] (4) Prepare an aqueous solution containing a copper compound, add a certain amount of precipitant to obtain turbid solution E;

[0012] (5) Dropwise add turbid solution E to suspension D, stir for a period of time at a certain temperature, then filter, wash, dry and calcine to obtain an oxidized catalyst;

[0013] (6) Reduce the oxidized catalyst to obtain a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene. In step (1) of the above preparation method, preferably, the palladium compound is palladium acetate, palladium chloride or palladium nitrate;

[0014] More preferably, the concentration of the aqueous solution of the palladium compound is 0.001 mol / L - 0.010 mol / L; the molar ratio of palladium atoms to chlorine atoms is 1:(1 - 5).

[0015] In step (1) of the above preparation method, preferably, the monohydric alcohol is methanol, ethanol, n-propanol or isopropanol; preferably, the volume ratio of the monohydric alcohol to deionized water is 1:(0.5 - 5).

[0016] In step (1) of the above preparation method, preferably, the nonionic surfactant is polyethyleneimine, polyacrylic acid or polyvinylpyrrolidone;

[0017] More preferably, the concentration of the non-ionic surfactant is 0.010 mol / L - 0.200 mol / L, and the molar ratio of palladium atoms to the non-ionic surfactant is 1:(10 - 30).

[0018] In step (1) of the above preparation method, preferably, the reaction temperature of the reaction is 40 - 70 °C, and the reaction time is 4 - 8 h.

[0019] In step (2) of the above preparation method, preferably, the amphoteric surfactant is one or more of sulfonates of fatty acid methyl ester ethoxylates, dodecyl dimethyl betaine, coconut oil amide propyl hydroxysulfobetaine, lauroyl amide propyl betaine, and glutathione;

[0020] More preferably, the concentration of the amphoteric surfactant is 0.001 mol / L - 0.050 mol / L, and the molar ratio of copper atoms to the amphoteric surfactant is 1:(1 - 20).

[0021] In step (3) of the above preparation method, preferably, the reaction temperature of the reaction is 50 - 80 °C, and the reaction time is 8 - 16 h.

[0022] In step (4) of the above preparation method, preferably, the copper compound is copper acetate, copper chloride, or copper nitrate;

[0023] More preferably, the concentration of the aqueous solution of the copper compound is 0.0001 mol / L - 0.0200 mol / L, and the molar ratio of palladium atoms to copper atoms is 1:(0.1 - 20).

[0024] In step (4) of the above preparation method, preferably, the precipitating agent is one or more of sodium carbonate, sodium hydroxide, or urea;

[0025] More preferably, the concentration of the aqueous solution of the precipitating agent is 0.001 mol / L - 0.100 mol / L, and the molar ratio of copper atoms to the precipitating agent is 1:(10 - 30).

[0026] In step (5) of the above preparation method, preferably, the drying temperature is 100 °C - 150 °C, and the drying time is 12 - 24 h; the calcination temperature is 400 °C - 600 °C, and the time is 4 h - 12 h;

[0027] More preferably, the calcination atmosphere is a mixed gas of nitrogen and oxygen, and the volume ratio of nitrogen to oxygen is 5 - 1:1.

[0028] The present invention provides a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene prepared by the above preparation method. The conditions for the reaction of selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene are as follows: the temperature is 25 - 70 °C, the liquid hourly space velocity is 10 - 50 h -1 , the pressure is 0.1 - 1 MPa, and the hydrogen-oil ratio is 10 - 50.

[0029] Advantages of the present invention:

[0030] (1) Through the dispersion of the amphoteric surfactant, the dispersion of PVP-coated Pd nanoparticles in the catalyst provided by the present invention for selectively hydrogenating and removing alkynes and cyclopentadiene is improved, and agglomeration during calcination is avoided, thereby increasing the number of active centers, facilitating the adsorption and diffusion of hydrogen on the metal surface, and enhancing the activity of the catalyst for the reaction of alkynes and cyclopentadiene.

[0031] (2) In the Pd nanoparticles dispersed by the amphoteric surfactant in the present invention, Cu is introduced directionally through different precipitants for modification, reducing the number of corner atoms in the Pd nanoparticles and increasing the number of edge-site Pd atoms, thereby improving the hydrogenation selectivity of the catalyst for isoprene, reducing the saturation rate of isoprene, and increasing the yield of isoprene. Detailed implementation manners

[0032] For a clearer understanding of the technical features, objectives, and advantages of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention. In the examples, all original reagent materials are commercially available, and the experimental methods without specific conditions are conventional methods and conventional conditions well-known in the art, or conditions recommended by the instrument manufacturer.

[0033] Example 1

[0034] This example provides a preparation method of a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene, and the method includes the following steps:

[0035] Step 1: Measure 10 mL of palladium chloride (PdCl2) with a concentration of 0.004 mol / L and 10 mL of potassium chloride (KCl) with a concentration of 0.008 mol / L respectively. After mixing, add 0.09 g of the non-ionic surfactant polyvinylpyrrolidone (PVP), and stir at 40 °C for 4 h to obtain a solution containing Pd compounds.

[0036] Step 2: Weigh 0.0158 g of sulfonate of amphoteric surfactant fatty acid methyl ester ethoxylate (FMES) and dissolve it in 20 mL of deionized water. After stirring evenly, add 2 g of carrier SiO2 and stir for 4 h to obtain a SiO2 suspension. Add it to an aqueous solution containing Pd compound and stir at 40 °C for 12 h to obtain a Pd-SiO2 suspension.

[0037] Step 3: Weigh 0.347 g of precipitant anhydrous sodium carbonate (Na2CO3) and dissolve it in 10 mL of deionized water. Stir. After it is completely dissolved, measure 10 mL of copper nitrate (Cu(NO3)2∙3H2O) with a concentration of 0.008 mol / L and add it to this solution. Stir at 40 °C to obtain a solution containing Cu compound.

[0038] Step 4: Dropwise add the solution containing Cu compound into the above Pd-SiO2 suspension, and continue stirring for 3 h to obtain a CuPd-SiO2 suspension. After the reaction is completed, filter and wash, then place the sample in an oven and dry at 120 °C for 12 h. Finally, calcine in an air atmosphere to obtain an oxidized state selective hydrogenation catalyst.

[0039] Step 5: Reduce the obtained oxidized state catalyst. The reduction pressure is 1.5 MPa, the hydrogen flow rate is 20 mL / min, the temperature is 300 °C, and the reduction time is 4 h to obtain an activated hydrogenation catalyst. For the activated catalyst, the reaction performance evaluation conditions are a temperature of 30 °C, a liquid hourly space velocity of 15 h -1 , a pressure of 0.1 MPa, and a hydrogen-oil ratio of 10.

[0040] Example 2

[0041] Step 1: Measure 10 mL of palladium chloride (PdCl2) with a concentration of 0.004 mol / L and 10 mL of potassium chloride (KCl) with a concentration of 0.008 mol / L respectively. After mixing, add 0.09 g of non-ionic surfactant polyvinylpyrrolidone (PVP) and heat and stir at 40 °C for 4 h to obtain a solution containing Pd compound.

[0042] Step 2: Weigh 0.008 g of amphoteric surfactant glutathione and dissolve it in 20 mL of deionized water. After stirring evenly, add 2 g of carrier SiO2 and stir for 4 h to obtain a SiO2 suspension. Add it to an aqueous solution containing Pd compound and stir at 40 °C for 12 h to obtain a Pd-SiO2 suspension.

[0043] Step 3: Weigh 0.347 g of precipitant anhydrous sodium carbonate (Na2CO3), dissolve it in 10 mL of deionized water, stir. After it is completely dissolved, measure 10 mL of copper nitrate (Cu(NO3)2∙3H2O) with a concentration of 0.008 mol / L and add it to this solution. Stir at 40 °C to obtain a solution containing Cu compound.

[0044] Step 4: Dropwise add the solution containing Cu compound into the above Pd-SiO2 suspension, continue to stir for 3 h to obtain a CuPd-SiO2 suspension. After the reaction is completed, filter and wash, then place the sample in an oven and dry at 120 °C for 12 h. Finally, calcine it in an air atmosphere to obtain an oxidized state selective hydrogenation catalyst.

[0045] Step 5: Reduce the obtained oxidized state catalyst. The reduction pressure is 1.5 MPa, the hydrogen flow rate is 20 mL / min, the temperature is 300 °C, and the reduction time is 4 h to obtain an activated hydrogenation catalyst. For the activated catalyst, the reaction performance evaluation conditions are a temperature of 30 °C, a liquid hourly space velocity of 15 h -1 , a pressure of 0.1 MPa, and a hydrogen-oil ratio of 10.

[0046] Example 3

[0047] Step 1: Measure 10 mL of palladium chloride (PdCl2) with a concentration of 0.004 mol / L and 10 mL of potassium chloride (KCl) with a concentration of 0.008 mol / L respectively. After mixing, add 0.09 g of non-ionic surfactant polyvinylpyrrolidone (PVP), and stir at 40 °C for 4 h to obtain a solution containing Pd compound.

[0048] Step 2: Weigh 0.0079 g of amphoteric surfactant dodecyl dimethyl betaine (BS-12), dissolve it in 20 mL of deionized water, stir evenly, add 2 g of carrier SiO2, and stir for 4 h to obtain a SiO2 suspension. Add it to the aqueous solution containing Pd compound and stir at 40 °C for 12 h to obtain a Pd-SiO2 suspension.

[0049] Step 3: Weigh 0.347 g of precipitant anhydrous sodium carbonate (Na2CO3), dissolve it in 10 mL of deionized water, stir. After it is completely dissolved, measure 10 mL of copper nitrate (Cu(NO3)2∙3H2O) with a concentration of 0.008 mol / L and add it to this solution. Stir at 40 °C to obtain a solution containing Cu compound.

[0050] Step 4: Slowly add the solution containing Cu compound drop by drop into the above Pd-SiO2 suspension, and continue stirring for 3 h to obtain a CuPd-SiO2 suspension. After the reaction is completed, filter and wash the sample, then place the sample in an oven and dry it at 120 °C for 12 h. Finally, calcine it in an air atmosphere to obtain an oxidized state selective hydrogenation catalyst.

[0051] Step 5: Reduce the obtained oxidized state catalyst. The reduction pressure is 1.5 MPa, the hydrogen flow rate is 20 mL / min, the temperature is 300 °C, and the reduction time is 4 h to obtain an activated hydrogenation catalyst. For the activated catalyst, the reaction performance evaluation conditions are a temperature of 30 °C, a liquid hourly space velocity of 15 h -1 , a pressure of 0.1 MPa, and a hydrogen-oil ratio of 10.

[0052] Comparative Example

[0053] This comparative example provides a method for preparing a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene, and the method includes the following steps:

[0054] Weigh 0.0074 g of palladium chloride (PdCl2) and dissolve it in hydrochloric acid (HCl) solution. Impregnate it on 2 g of silica (SiO2) powder in an equal volume manner, and stir the obtained sample at room temperature for 24 h, then dry it at 120 °C for 12 h; then weigh 0.0399 g of copper nitrate (Cu(NO3)2∙3H2O) and dissolve it in deionized water, and impregnate it on the SiO2 impregnated with Pd in an equal volume manner. Stir the obtained sample at room temperature for 24 h, dry it at 120 °C for 12 h, and finally, calcine it in an air atmosphere at 450 °C for 4 h to obtain a reference catalyst. Reduce the obtained reference catalyst. The reduction pressure is 1.5 MPa, the hydrogen flow rate is 20 mL / min, the temperature is 300 °C, and the reduction time is 4 h. Using isoprene containing 2-pentyne and cyclopentadiene as the raw material, the reaction performance evaluation conditions are a temperature of 30 °C, a liquid hourly space velocity of 15 h -1 , a pressure of 0.1 MPa, and a hydrogen-oil ratio of 10.

[0055] Table 1 Selective hydrogenation reaction performance evaluation results of the catalysts prepared in the examples

[0056]

[0057] a (Content of isoprene in the raw material - Content of isoprene in the product) / Content of isoprene in the raw material

[0058] As can be seen from Table 1, the conversion rates of impurities 2-pentyne and cyclopentadiene in the three selective hydrogenation catalysts prepared by adding different surfactants are 100%, indicating that alkynes and cyclopentadiene have been completely removed; among them, the catalyst prepared using surfactant FMES has the lowest loss rate of pentadiene.

[0059] Table 2 Evaluation results of the selective hydrogenation reaction performance of the catalysts prepared in the comparative examples

[0060]

[0061] a (Content of pentadiene in the raw material - Content of pentadiene in the product) / Content of pentadiene in the raw material

[0062] As can be seen from Table 2, for the catalyst prepared by the impregnation method, the loss rate of pentadiene is relatively large, and impurities 2-pentyne and cyclopentadiene are not completely removed.

[0063] Finally, it should be noted that the above examples are only used to illustrate the implementation process and characteristics of the present invention, rather than limiting the technical methods of the present invention. Although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A preparation method of a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in piperylene, characterized in that, It includes the following steps: (1) Prepare an aqueous solution containing a palladium compound, add potassium chloride thereto to obtain solution A, then add a monohydric alcohol and a nonionic surfactant to solution A, and stir and react at a certain temperature for a period of time to obtain solution B; (2) Use SiO2 as a carrier and suspend it in water, add a certain amount of amphoteric surfactant to obtain suspension C; the amphoteric surfactant is one or more of sulfonate of fatty acid methyl ester ethoxylate, dodecyl dimethyl betaine, coconut oil amide propyl hydroxysulfobetaine, lauryl amide propyl betaine, glutathione; (3) Dropwise add solution B to suspension C, stir and react at a certain temperature for a period of time to obtain suspension D; (4) Prepare an aqueous solution containing a copper compound, add a certain amount of precipitant to obtain turbid solution E; (5) Dropwise add turbid solution E to suspension D, stir for a period of time at a certain temperature, then filter, wash, dry and calcine to obtain an oxidized catalyst; (6) Reduce the oxidized catalyst to obtain a catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene.

2. The preparation method according to claim 1, characterized in that, In step (1), the palladium compound is palladium acetate, palladium chloride or palladium nitrate; the concentration of the aqueous solution of the palladium compound is 0.001 mol / L - 0.010 mol / L; the molar ratio of palladium atoms to chlorine atoms is 1:(1 - 5).

3. The preparation method according to claim 1, characterized in that, In step (1), the monohydric alcohol is methanol, ethanol, n-propanol or isopropanol; the volume ratio of the monohydric alcohol to deionized water is 1:(0.5 - 5).

4. The preparation method according to claim 1, characterized in that, In step (1), the nonionic surfactant is polyethyleneimine, polyacrylic acid or polyvinylpyrrolidone; the concentration of the nonionic surfactant is 0.010 mol / L - 0.200 mol / L, and the molar ratio of palladium atoms to the nonionic surfactant is 1:(10 - 30).

5. The preparation method according to claim 1, characterized in that, In step (1), the reaction temperature is 40 - 70 °C, and the reaction time is 4 - 8 h.

6. The preparation method according to claim 1, characterized in that, In step (2), the concentration of the amphoteric surfactant is 0.001 mol / L - 0.050 mol / L, and the molar ratio of copper atoms to the amphoteric surfactant is 1:(1 - 20).

7. The preparation method according to claim 1, wherein In step (3), the reaction temperature is 50 - 80 °C, and the reaction time is 8 - 16 h.

8. The preparation method according to claim 1, characterized in that, In step (4), the copper compound is copper acetate, copper chloride or copper nitrate; the concentration of the aqueous solution of the copper compound is 0.0001 mol / L - 0.0200 mol / L, and the molar ratio of palladium atoms to copper atoms is 1:(0.1 - 20).

9. The preparation method according to claim 1, characterized in that, In step (4), the precipitant is one or more of sodium carbonate, sodium hydroxide, urea; the concentration of the aqueous solution of the precipitant is 0.001 mol / L - 0.100 mol / L, and the molar ratio of copper atoms to the precipitant is 1:(10 - 30).

10. The preparation method according to claim 1, characterized in that, In step (5), the drying temperature is 100 °C - 150 °C, and the drying time is 12 - 24 h; the calcination temperature is 400 °C - 600 °C, and the time is 4 h - 12 h; the calcination atmosphere is a mixed gas of nitrogen and oxygen, and the volume ratio of nitrogen to oxygen is (1 - 5):

1.

11. A catalyst for selectively hydrogenating and removing alkynes and cyclopentadiene in isoprene, characterized in that, The catalyst is prepared by the method according to any one of claims 1-10.

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