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

Abstract

The present invention provides a catalyst for selectively hydrogenating and removing alkynes from isoprene and a preparation method thereof. The preparation method comprises the following steps: (1) Prepare an aqueous solution containing a palladium compound, add potassium chloride thereto to obtain solution A, then add a diol to solution A and stir for a certain period of time at a certain temperature to obtain solution B; (2) Suspend SiO2 in solution B and stir for a certain period of time at a certain temperature to obtain suspension C; (3) Prepare an aqueous solution containing a nickel compound, add a certain amount of an anionic surfactant, and stir for a certain period of time at a certain temperature to obtain turbid liquid D; (4) Dropwise add turbid liquid D to suspension C, stir for a certain period of time at a certain temperature, then filter, wash, dry, and calcine to obtain an oxidized catalyst; (5) Reduce the oxidized catalyst to obtain a catalyst for selectively hydrogenating and removing alkynes from isoprene. The catalyst prepared by the present invention is suitable for removing a small amount of alkynes from isoprene, especially for selectively hydrogenating and removing a small amount of alkynes from the by-product isoprene in the ethylene production unit by naphtha cracking. The purified isoprene 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 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 a mixture of hydrocarbons containing alkanes, alkenes, cycloalkanes, cycloalkenes, dienes, alkynes, etc. with 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 producing 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 producing 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. Piperylene, as a raw material for producing petroleum resin, needs to be extracted from the C5 fraction. However, a small amount of alkynes (such as pentyne-1, pentyne-2, and isopropenylacetylene, 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 and making it difficult to polymerize). Therefore, it is necessary to remove impurities such as alkynes in piperylene before polymerizing to produce polymers such as petroleum resin.

[0003] At present, the main methods for removing a small amount of alkynes 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, generating safety hazards. In the absorption process, organic solvents are prone to volatilization, causing environmental pollution, which limits its application in industry. In comparison, selective hydrogenation can effectively remove alkynes 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 from olefins. The core of selective hydrogenation for removing alkynes is the preparation of selective hydrogenation catalysts. Compared with ordinary metals such as Ni, Co, and Fe, the noble metal Pd has excellent low-temperature catalytic activity and good selective hydrogenation activity. Commonly used selective hydrogenation catalysts for removing alkynes 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 the noble metal Pd on the support, its loading amount is relatively high, resulting in a high preparation cost. To address this problem, Zhang et al. (Zhou H, Yang X, Wang A, et al. Chinese Journal of Catalysis, 2016, 37(5): 692-699) prepared a Pd single-atom dispersed Pd / ZnO catalyst by reducing the Pd loading amount and reduction temperature. When Pd is dispersed as single atoms, the adsorption mode of ethylene on Pd will change from the relatively strong-binding σ bond to the relatively weak π bond, which is beneficial to the desorption of ethylene from the catalyst surface and thus inhibits the over-hydrogenation of ethylene. This catalyst can effectively remove acetylene in the acetylene selective hydrogenation system, but its selectivity for ethylene is poor. In order to overcome the defect of poor olefin selectivity in the alkyne removal process of the hydrogenation catalyst in the prior art. CN101081366A discloses a method for selective hydrogenation to remove diolefins. This catalyst uses palladium as the active component, nickel as the promoter, and zinc oxide as the carrier. The catalyst prepared by this method shows excellent catalytic activity and selectivity in the reaction of selective hydrogenation to remove diolefins. The conversion rate of butadiene is 93%, and the selectivity of butene is 72.5%. Although its butadiene conversion rate is relatively high, its selectivity is poor, and there is still residue of diolefins, which will still cause the inactivation of initiators in the subsequent polymerization process and affect the quality of polymerization products.

[0004] As can be seen from the above, there are many reports on selective hydrogenation catalysts for a small amount of diolefins or alkynes in C2-C4 monoolefin fractions at present. However, for the removal of a small amount of alkynes in isoprene, there is less research on the preparation of relevant selective hydrogenation catalysts.

[0005] In summary, there is an urgent need in the art to develop a selective hydrogenation catalyst for removing a small amount of alkynes from isoprene and its preparation method. 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 in isoprene and a preparation method thereof, and to make isoprene have a low loss rate.

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

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

[0009] (2) Suspend SiO2 in solution B and stir for a period of time at a certain temperature to obtain suspension C;

[0010] (3) Prepare an aqueous solution containing a nickel compound, add a certain amount of an anionic surfactant, and stir for a period of time at a certain temperature to obtain turbid solution D;

[0011] (4) Dropwise add turbid solution D to suspension C, stir for a period of time at a certain temperature, then filter, wash, dry and calcine to obtain an oxidized catalyst;

[0012] (5) Reduce the oxidized catalyst to obtain a catalyst for selectively hydrogenating and removing alkynes in isoprene.

[0013] 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 diol is methylene glycol, ethylene glycol or propylene glycol; more preferably, the volume ratio of the diol to deionized water is 1:(0.5 - 5).

[0016] 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.

[0017] In step (3) of the above preparation method, preferably, the nickel compound is nickel nitrate, nickel chloride or nickel acetate;

[0018] More preferably, the concentration of the nickel compound aqueous solution is 0.0001 mol / L - 0.0200 mol / L, and the molar ratio of palladium atoms to nickel atoms is 1:(0.1 - 20).

[0019] In step (3) of the above preparation method, preferably, the anionic surfactant is one or more of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123), polymer of propylene oxide and ethylene oxide (F127);

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

[0021] In step (3) of the above preparation method, preferably, the concentration of hydrochloric acid is 1 mol / L.

[0022] 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.

[0023] In step (4) 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;

[0024] More preferably, the calcination atmosphere is nitrogen, and the volume ratio of nitrogen to oxygen is 1:(0 - 0.15).

[0025] The present invention provides a catalyst for selective hydrogenation to remove alkynes from piperylene prepared by the above preparation method, and the conditions for its use in the selective hydrogenation reaction of piperylene to remove alkynes are a temperature of 25 - 70 °C, a liquid hourly space velocity of 10 - 50 h -1 , a pressure of 0.1 - 1 MPa, and a hydrogen-oil ratio of 10 - 50.

[0026] The beneficial effects of the present invention:

[0027] (1) Due to the dispersion effect of the anionic surfactant, the dispersion of Pd nanoparticles in the selective hydrogenation catalyst for removing alkynes provided by the present invention is improved. By introducing Ni for modification in a targeted manner, the number of corner-site atoms in the Pd nanoparticles is reduced, and the number of edge-site Pd atoms is increased, thereby improving the hydrogenation selectivity of the catalyst for piperylene, reducing the saturation rate of piperylene, and increasing the yield of piperylene.

[0028] (2) In the dispersed Pd nanoparticles of the present invention, a part of the long carbon chain of the anionic surfactant forms a protective layer after calcination, avoiding agglomeration during the calcination of the nickel-palladium bimetal, thereby increasing the number of active centers, which is beneficial to the adsorption and diffusion of hydrogen on the metal surface; another part of the long carbon chain forms a nickel-palladium-carbon alloy with nickel and palladium after calcination. The carbon alloy covers the low-active sites of Pd atoms and exposes the highly selective active sites, improving the activity of the catalyst for the reaction of alkynes. Detailed Embodiments

[0029] For a clearer understanding of the technical features, objectives, and beneficial effects 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. The experimental methods without specific conditions are conventional methods and conventional conditions well-known in the art, or conditions recommended by the instrument manufacturer.

[0030] Example 1

[0031] This example provides a method for preparing a catalyst for the selective hydrogenation of removing alkynes in isoprene, and the method includes the following steps:

[0032] 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 20 mL of ethylene glycol and stir at 40 °C for 4 h to obtain a solution containing Pd compounds.

[0033] Step 2: Weigh 2 g of silica (SiO2) support into the palladium compound solution to obtain a Pd-SiO2 suspension.

[0034] Step 3: Measure 10 mL of nickel chloride (NiCl2·6H2O) with a concentration of 0.008 mol / L and add it to the solution. Add 0.008 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) to the nickel solution and mix. Stir at 40 °C to obtain a solution containing Ni compounds.

[0035] Step 4: Dropwise add the solution containing Ni compounds into the above Pd-SiO2 suspension, and continue to stir for 3 h to obtain a NiPd-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, and finally calcine in a nitrogen atmosphere to obtain an oxidized-state selective hydrogenation catalyst.

[0036] Step 5: Reduce the obtained oxidized 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 the 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.

[0037] Example 2

[0038] 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 20 ml of ethylene glycol and stir at 40 °C for 4 h to obtain a solution containing Pd compounds.

[0039] Step 2: Weigh 2 g of silica (SiO2) support into the palladium compound solution to obtain a Pd-SiO2 suspension.

[0040] Step 3: Measure 10 mL of nickel chloride (NiCl2·6H2O) with a concentration of 0.008 mol / L and add it to the solution. Add 0.008 g of the polymer of propylene oxide and ethylene oxide (F127) to the nickel solution and mix. Stir at 40 °C to obtain a solution containing Ni compounds.

[0041] Step 4: Dropwise add the solution containing Ni compounds into the above Pd-SiO2 suspension and continue stirring for 3 h to obtain a NiPd-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 a nitrogen atmosphere to obtain the oxidized selective hydrogenation catalyst.

[0042] Step 5: Reduce the obtained oxidized 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 the 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.

[0043] Comparative Example

[0044] This comparative example provides a method for preparing a catalyst for selective hydrogenation to remove alkynes from isoprene, and the method includes the following steps:

[0045] 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, and stir the obtained sample at room temperature for 24 h, then dry it at 120 °C for 12 h. Then weigh 0.002 g of nickel chloride (NiCl2·6H2O) and dissolve it in deionized water. Impregnate it on the SiO2 impregnated with Pd in an equal volume, stir the obtained sample at room temperature for 24 h, and dry it at 120 °C for 12 h. Finally, calcine it in an air atmosphere at 450 °C for 4 h to obtain the reference catalyst. Reduce the obtained reference catalyst, with a reduction pressure of 1.5 MPa, a hydrogen flow rate of 20 mL / min, a temperature of 300 °C, and a reduction time of 4 h. Use the isoprene containing 2-pentyne as the raw material, and 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] Table 1 Selective hydrogenation reaction performance evaluation results of the catalysts prepared in the examples

[0047]

[0048] a (content of isoprene in raw material - content of isoprene in product) / content of isoprene in raw material

[0049] As can be seen from Table 1, the conversion rate of the impurity 2-pentyne in the two selective hydrogenation catalysts prepared by adding different anionic surfactants is 100%, indicating that the alkynes have been completely removed; among them, for the catalyst prepared using the anionic surfactant P123, the loss rate of isoprene is the least.

[0050] Table 2 Selective hydrogenation reaction performance evaluation results of the catalysts prepared in the comparative examples

[0051]

[0052] a (content of isoprene in raw material - content of isoprene in product) / content of isoprene in raw material

[0053] As can be seen from Table 2, for the catalyst prepared by the impregnation method, the loss rate of isoprene is relatively large, and the impurity 2-pentyne in it has not been completely removed.

[0054] 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 should be covered by the protection scope of the present invention.

Claims

1. Use of a catalyst for selectively hydrogenating and removing alkynes in isoprene in the selective hydrogenation and removal of alkynes in isoprene, characterized in that, The preparation method of the catalyst comprises the following steps: (1) Prepare an aqueous solution containing a palladium compound, add potassium chloride thereto to obtain solution A, then add ethylene glycol to solution A, and stir for a certain period of time at a certain temperature to obtain solution B; (2) Suspend SiO2 in solution B, and stir for a certain period of time at a certain temperature to obtain suspension C; (3) Prepare an aqueous solution containing a nickel compound, add a certain amount of an anionic surfactant, where the anionic surfactant is one or several of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and polymer of propylene oxide and ethylene oxide; and add a certain amount of hydrochloric acid to adjust the pH to acidic, and stir for a certain period of time at a certain temperature to obtain turbid liquid D; (4) Dropwise add turbid liquid D to suspension C, stir for a certain period of time at a certain temperature, then filter, wash, dry and calcine to obtain an oxidized catalyst; (5) Reduce the oxidized catalyst to obtain a catalyst for selectively hydrogenating and removing alkynes in pentadiene.

2. The application 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 application according to claim 1, characterized in that, In step (1), the volume ratio of ethylene glycol to deionized water is 1:(0.5 - 5).

4. The application according to claim 1, wherein In step (1), stir for a certain period of time at a certain temperature, the temperature is 40 - 70 °C, and the time is 4 - 8 h.

5. The application according to claim 1, characterized in that, In step (3), the nickel compound is nickel nitrate, nickel chloride or nickel acetate; the concentration of the aqueous solution of the nickel compound is 0.0001 mol / L - 0.0200 mol / L, and the molar ratio of palladium atoms to nickel atoms is 1:(0.1 - 20).

6. The application according to claim 1, characterized in that In step (3), the concentration of the anionic surfactant is 0.001 mol / L - 0.050 mol / L, and the molar ratio of nickel atoms to the anionic surfactant is 1:(1 - 20).

7. The application according to claim 1, characterized in that, In step (3), the concentration of the hydrochloric acid is 1 mol / L.

8. The application according to claim 1, wherein In step (3), stir for a certain period of time at a certain temperature, the temperature is 50 - 80 °C, and the time is 8 - 16 h.

9. The application according to claim 1, characterized in that, In step (4), 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 nitrogen.

10. The application according to claim 1, wherein The reaction conditions are as follows: temperature is 25 - 70 °C, liquid hourly space velocity is 10 - 50 h -1 , pressure is 0.1 - 1 MPa, and hydrogen-to-oil ratio is 10 - 50.

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