A platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction and its preparation method and application

Abstract

The present invention relates to the technical field of catalyst preparation, and in particular to a platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction, and a preparation method and application thereof. The present invention provides a catalyst using asphalt-based spherical activated carbon as a carrier, H 2 PtCl 6 6H 2 O is a metal precursor and triphenylmethylphosphine chloride is a platinum-ionic liquid complex catalyst. 6 ] 2‑ The strong interaction between the precursor and the ligand effectively regulates the electronic properties of the active metal, promotes the anchoring and dispersion of platinum active species on the carrier surface, and enhances the catalyst's adsorption and activation ability for hydrogen chloride and acetylene, thereby significantly improving the activity and stability of the catalyst. The preparation method is simple and efficient, and has great value for industrial application and promotion.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction, and a preparation method and application thereof. Background Art

[0002] Polyvinyl chloride (PVC) is the world's second largest engineering resin material after polyethylene resin, and is widely used in construction, industry, agriculture, daily necessities, etc. As an important intermediate in the production of PVC, the main production methods of vinyl chloride (VCM) are ethylene method, ethane method and acetylene method. Based on the energy structure characteristics of my country's "rich in coal, poor in oil, and little gas", the acetylene method occupies a dominant position in the production of vinyl chloride in my country. At present, the mercury (HgCl2) catalyst used in the acetylene method to produce vinyl chloride has good catalytic activity and selectivity, but its volatility and high toxicity have caused serious harm to human health and the ecological environment. At the same time, according to the requirements of the Minamata Convention, it is imperative to research and develop environmentally friendly non-mercury catalysts.

[0003] Decades of research have shown that precious metal catalysts such as Au, Ru, and Pt exhibit good catalytic activity in the acetylene hydrochlorination reaction. Carbon deposition and agglomeration or valence change of active species are the main causes of catalyst deactivation. In view of these reasons, researchers have improved the activity and stability of catalysts by modifying carriers, adding ligands or other metal additives, etc. Since platinum is expensive and the stability of Pt / C catalysts is poor, constructing catalysts with rich and highly dispersed platinum active species has become a key and difficult task.

[0004] The orbital characteristics of platinum determine its flexible coordination chemistry. On the one hand, the similar peripheral s, p, and d equivalent orbitals of platinum are easier to form hybrid orbitals with strong bonding ability to accept lone pairs of electrons provided by heteroatoms, and have strong electrostatic effects on heteroatoms. The effective nuclear charge of the ion is large and the polarization ability to heteroatoms is also strong. On the other hand, the unsaturated d orbital is conducive to its covalent bonding with heteroatoms to form highly dispersed or even single-atom catalysts. Whether it is possible to prepare active components of metal complexes through unsaturated coordination between ligands and platinum ions to improve the catalytic activity and stability of platinum-based catalysts has not yet been published. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction. The provided catalyst uses asphalt-based spherical activated carbon as a carrier, H2PtCl6·6H2O as a metal precursor, and triphenylmethylphosphine chloride as a ligand; it can effectively improve the catalytic activity and stability of the platinum-based catalyst.

[0006] In order to achieve the purpose of the invention, the technical solution of the present invention is as follows:

[0007] The invention provides a platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction. The catalyst uses asphalt-based spherical activated carbon as a carrier, H2PtCl6·6H2O as a metal precursor, and triphenylmethylphosphine chloride as a ligand; the molar ratio of the metal precursor to the ligand is 1:0.5-2.

[0008] Further preferably, the molar ratio of the metal precursor to the ligand is 1:1.

[0009] Furthermore, based on the total weight of the platinum-ionic liquid complex catalyst, the loading amount of platinum atoms is 0.5-2 wt.%, preferably 1 wt.%.

[0010] In a specific embodiment, the present invention also provides a method for preparing the platinum-ionic liquid complex catalyst as described above, the preparation method comprising:

[0011] The triphenylmethylphosphine chloride ligand is dissolved in deionized water, and a metal platinum precursor and asphalt-based spherical activated carbon are added; after stirring the reaction at room temperature, the mixture is transferred into a water bath for immersion heat activation reaction, and after the reaction is completed, the mixture is dried at a constant temperature to obtain a platinum-ionic liquid complex catalyst.

[0012] The molar ratio of the metal platinum precursor to the triphenylmethylphosphine chloride ligand is 1:0.5-2.

[0013] Preferably, the stirring reaction time is 2 to 4 hours; the immersion heat activation reaction temperature is 60 to 80° C. and the time is 10 to 12 hours.

[0014] The constant temperature drying is performed at a temperature of 120 to 140° C. and a time of 10 to 14 hours.

[0015] The loading amount of platinum atoms in the platinum-ionic liquid complex catalyst is 0.5-2 wt.%, preferably 1 wt.%.

[0016] In a specific embodiment, the present invention also provides a method for preparing vinyl chloride by acetylene hydrochlorination, the method comprising mixing acetylene with hydrogen chloride to obtain vinyl chloride, the reaction being carried out under the catalysis of the platinum-ionic liquid complex catalyst as described above. The acetylene hydrochlorination reaction is a gas phase reaction.

[0017] The main reactions involved in the acetylene hydrochlorination process include:

[0018] Main reaction: C2H2+HCl→CH2=CHCl

[0019] Non-polymerization side reactions:

[0020] CH2=CHCl+HCl→CH3CHCl2

[0021] CH2=CHCl+HCl→CH2ClCH2Cl

[0022] Polymerization side reactions:

[0023] 2CH2=CHCl→CH2ClCH=CCl-CH3

[0024] 2C2H2→CH2=CH-C≡CH

[0025] Existing thermodynamic studies have shown that the above main reaction is greatly affected by the polymerization side reaction, and the non-polymerization side reaction has little effect on the main reaction. The above main and side reactions are exothermic reactions, but the thermal effect of the polymerization side reaction is greater than that of the main reaction. Higher temperatures are more conducive to inhibiting the polymerization side reaction (polymerization products may be deposited on the catalyst surface to form carbon deposits), improving the selectivity of the main reaction and reducing carbon deposits, but metal catalysts have the problem of valence deactivation at high temperatures. After comprehensively considering the effects of temperature on polymerization side reactions and catalyst reduction deactivation, the acetylene hydrochlorination reaction temperature is controlled at 200°C.

[0026] The volume ratio of acetylene to hydrogen chloride adopts the commonly used volume ratio of 1:1 to 2 in the art. Preferably, the volume ratio of acetylene to hydrogen chloride in the present invention is 1:1.15.

[0027] The gas phase reaction is carried out in a fixed bed reactor, and the platinum-ionic liquid complex catalyst is loaded in the fixed bed reactor. The acetylene space velocity control range adopts the commonly used control range in this field, specifically 90~720h -1 Preferably, the acetylene space velocity in the present invention is controlled at 180h -1 .

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention provides a platinum-ionic liquid complex catalyst with asphalt-based spherical activated carbon as a carrier, H2PtCl6·6H2O as a metal precursor, and triphenylmethylphosphine chloride as a ligand. 2-The strong interaction between the precursor and the ionic liquid promotes the anchoring and dispersion of the platinum active component on the carrier surface. In addition, the electron transfer between the heteroatoms in the ligand and the platinum precursor stabilizes more Pt(II) active species and enhances the catalyst's adsorption and activation ability for hydrogen chloride and acetylene reactants. This significantly improves the activity and stability of the catalyst. The prepared catalyst is applied to the acetylene hydrochlorination reaction and has the characteristics of high activity and good stability. The initial activity can reach 99.69%, and the activity remains above 94% after 24 hours of reaction. It has good industrial application value. Compared with the existing metal catalysts for acetylene hydrochlorination reaction, the active components in the metal complex catalyst of the present invention are highly dispersed, not easy to lose and agglomerate, and simultaneously activate acetylene and hydrogen chloride reactants, greatly improving the catalytic activity and stability of existing metal catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 TEM comparison of catalyst 1Pt-1IL / SAC and comparative example Pt / SAC before and after reaction; in the figure, (a) is before Pt / SAC reaction; (b) is after Pt / SAC reaction; (c) is before 1Pt-1IL / SAC reaction; (d) is after 1Pt-1IL / SAC reaction;

[0032] Figure 2 The TPD curves of catalyst 1Pt-1IL / SAC and comparative examples Pt / SAC and IL / SAC for reactants hydrogen chloride and acetylene; in the figure, (a) is hydrogen chloride as the reactant, and (b) is acetylene as the reactant. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In the present invention, "wt.%" means weight percentage.

[0034] The invention provides a platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction. The catalyst uses asphalt-based spherical activated carbon as a carrier, H2PtCl6·6H2O as a metal precursor, and triphenylmethylphosphine chloride as a ligand; the molar ratio of the metal precursor to the ligand is 1:0.5-2.

[0035] Further preferably, the molar ratio of the metal precursor to the ligand is 1:1.

[0036] Furthermore, based on the total weight of the platinum-ionic liquid complex catalyst, the loading amount of platinum atoms is 0.5-2 wt.%, preferably 1 wt.%.

[0037] The total weight of the catalyst is calculated as follows: m 总 =m 载体 +m 稳定态金属前驱体 +m 配体 .

[0038] Because the metal precursor contains crystal water, but the crystal water will be removed during the thermal activation of the catalyst. In addition to the crystal water leaving the chloroplatinic acid, a molecule of HCl will also be released, and the stable state precursor becomes PtCl4. Therefore, the above-mentioned stable state precursor refers to the part of the metal precursor that finally exists in the catalyst.

[0039] For example, in Example 2, the load is calculated as follows: m Pt / (m 载体 +m 稳定态金属前驱体 +m 配体 )=0.02077g / (2g+0.04364g+0.03330g)=1.0wt%.

[0040] The preparation method of the platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination reaction of the present invention is as follows:

[0041] The triphenylmethylphosphine chloride ligand is completely dissolved in deionized water, and then a metal platinum precursor and asphalt-based spherical activated carbon are added in sequence, stirred at room temperature for 2 to 4 hours, then moved into a 60 to 80° C. water bath and maintained for 10 to 12 hours, and finally dried at a constant temperature of 120 to 140° C. for 10 to 14 hours to obtain a platinum-ionic liquid complex catalyst.

[0042] The present invention utilizes the above-mentioned platinum-ionic liquid complex to carry out acetylene hydrochlorination reaction. The acetylene hydrochlorination reaction process is as follows: the prepared platinum-ionic liquid complex catalyst is loaded into a fixed bed reactor, acetylene and hydrogen chloride reaction gas are introduced, and the reaction temperature is 200°C and the acetylene space velocity (GHSV) is 180h -1 , the volume ratio of acetylene to hydrogen chloride is 1:1.15, and the reaction is carried out for 24 hours.

[0043] Example 1

[0044] 0.01651 g of triphenylmethylphosphonium chloride was completely dissolved in 20 mL of deionized water, followed by the addition of 5.468 mL of H2PtCl6·6H2O aqueous solution (Pt concentration was 0.0193 mol·L -1) and 2 g of pitch-based spherical activated carbon (SAC), stirred at room temperature for 2 h, then moved into a 70 °C water bath and kept for 12 h, and finally dried at a constant temperature of 120 °C for 12 h to obtain 1Pt-0.5IL / SAC.

[0045] Example 2

[0046] 0.03330 g of triphenylmethylphosphonium chloride was completely dissolved in 20 mL of deionized water, followed by the addition of 5.514 mL of H2PtCl6·6H2O aqueous solution (Pt concentration was 0.0193 mol·L -1 ) and 2 g SAC, stirred at room temperature for 2 h, then moved into a 70 °C water bath and kept for 12 h, and finally dried at 120 °C for 12 h to obtain 1Pt-1IL / SAC.

[0047] Example 3

[0048] 0.05037 g of triphenylmethylphosphonium chloride was completely dissolved in 20 mL of deionized water, followed by the addition of 5.560 mL of H2PtCl6·6H2O aqueous solution (Pt concentration was 0.0193·mol L -1 ) and 2 g SAC, stirred at room temperature for 2 h, then moved into a 70 °C water bath and kept for 12 h, and finally dried at 120 °C for 12 h to obtain 1Pt-1.5IL / SAC.

[0049] Example 4

[0050] 0.06773 g of triphenylmethylphosphonium chloride was completely dissolved in 20 mL of deionized water, followed by the addition of 5.607 mL of H2PtCl6·6H2O aqueous solution (Pt concentration was 0.0193 mol·L -1 ) and 2 g SAC, stirred at room temperature for 2 h, then moved into a 70 °C water bath and kept for 12 h, and finally dried at 120 °C for 12 h to obtain 1Pt-2IL / SAC.

[0051] Comparative Example 1 (without ligand)

[0052] 5.424 mL of H2PtCl6·6H2O aqueous solution (Pt concentration 0.0193 mol·L -1 ) was added into 20 mL of deionized water, followed by 2 g of SAC, stirred at room temperature for 2 h, then moved into a 70 °C water bath and kept for 12 h, and finally dried at 120 °C for 12 h to obtain Pt / SAC.

[0053] Comparative Example 2 (without adding metal precursor)

[0054] 0.03330 g of triphenylmethylphosphonium chloride was completely dissolved in 20 mL of deionized water, followed by the addition of 2 g of SAC, and the mixture was stirred at room temperature for 2 h, then moved into a 70 °C water bath and kept for 12 h, and finally dried at a constant temperature of 120 °C for 12 h to obtain IL / SAC.

[0055] Example 5

[0056] The gas mixture entering the gas chromatograph is mainly acetylene and vinyl chloride, and sometimes a very small amount of 1,1-dichloroethane impurity gas is produced. The peak area normalization method is used for calculation. Since the hydrogen chloride after the reaction is completely absorbed, the reaction volume in the system can be considered as a constant value. The acetylene conversion rate (X A ) and vinyl chloride selectivity (S VC ) is calculated as follows:

[0057] Acetylene conversion calculation method: X A =(Ψ A0 -Ψ A ) / Ψ A0 *100%, the average value is taken as the value of 3 measurements.

[0058] VCM selectivity calculation method: S VC =Ψ VC / (I-Ψ A )*100%, taking the average value of 3 measurements.

[0059] Among them, A0 , A and VC The test results of acetylene hydrochlorination catalyzed by each catalyst are shown in Table 1.

[0060] Table 1. Performance of different catalysts for acetylene hydrochlorination

[0061]

[0062] It can be seen from Table 1 that when the molar ratio of the platinum precursor to triphenylmethylphosphine chloride is 1:0.5-2, the maximum conversion rate of acetylene is significantly improved compared with the comparative example. Especially when the molar ratio of the two is 1:1, the catalytic activity of the platinum-based catalyst 1Pt-1IL / SAC is significantly better than that of other catalysts, and the conversion rate decreases the least during the 24h reaction. This is because [PtCl6] 2-The interaction between the precursor and the ligand provides a guarantee for the anchoring and dispersion of the platinum active species on the activated carbon support, and effectively inhibits the rapid deactivation caused by the aggregation and loss of the platinum active species during the reaction. In addition, triphenylmethylphosphine chloride has a strong electron-donating ability, and the electron transfer between the heteroatom functional group and the metal precursor stabilizes the Pt(II) active species and improves the catalyst's adsorption capacity for the reactants hydrogen chloride and acetylene, thereby significantly improving the activity and stability of the catalyst.

[0063] Figure 1 The TEM comparison of the catalyst 1Pt-1IL / SAC and the comparative example Pt / SAC before and after the reaction; in the figure, (a) is before the reaction of Pt / SAC; (b) is after the reaction of Pt / SAC; (c) is before the reaction of 1Pt-1IL / SAC; (d) is after the reaction of 1Pt-1IL / SAC. Figure 1 It can be seen that the formation of platinum-ionic liquid complex significantly improves the anchoring and dispersion of platinum active species on the carrier.

[0064] Figure 2 The TPD curves of the catalyst 1Pt-1IL / SAC and the comparative examples Pt / SAC and IL / SAC for the reactants hydrogen chloride and acetylene are shown in Figure 1. (a) is hydrogen chloride as the reactant, and (b) is acetylene as the reactant. Figure 2 It can be seen that compared with Pt / SAC and IL / SAC, 1Pt-1IL / SAC catalyst has stronger TCD signals for hydrogen chloride and acetylene. It can be seen that the regulation of the electronic properties of platinum species by the structure of triphenylmethylphosphine chloride itself makes the adsorption capacity of platinum-ionic liquid complex catalyst for reaction gases hydrogen chloride and acetylene stronger.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A platinum-ionic liquid complex catalyst for catalyzing acetylene hydrochlorination, characterized in that: The catalyst uses asphalt-based spherical activated carbon as a carrier, H2PtCl6·6H2O as a metal precursor, triphenylmethylphosphine chloride as a ligand, and the molar ratio of the metal precursor to the ligand is 1:0.5-2; based on the total weight of the platinum-ionic liquid complex catalyst, the loading amount of Pt atoms in the catalyst is 0.5-2 wt.%.

2. The platinum-ionic liquid complex catalyst according to claim 1, characterized in that The molar ratio of the metal precursor to the ligand is 1:

1.

3. A method for preparing a platinum-ionic liquid complex catalyst, characterized in that: The preparation method comprises: dissolving triphenylmethylphosphine chloride ligand in deionized water, adding metal platinum precursor and asphalt-based spherical activated carbon; stirring the reaction at room temperature, transferring the carbon into a water bath for immersion heat activation reaction, and drying at a constant temperature after the reaction is completed to obtain a platinum-ionic liquid complex catalyst; the molar ratio of the metal platinum precursor to the triphenylmethylphosphine chloride ligand is 1:0.5-2, and the loading amount of platinum atoms in the platinum-ionic liquid complex catalyst is 0.5-2 wt.%.

4. The preparation method according to claim 3, characterized in that: The stirring reaction time is 2-4 h; the immersion heat activation reaction temperature is 60-80°C and the time is 10-12 h.

5. The preparation method according to claim 3, characterized in that: The constant temperature drying is performed at a temperature of 120-140°C and a time of 10-14 hours.

6. Use of the platinum-ionic liquid complex catalyst according to any one of claims 1 to 2 in acetylene hydrochlorination reaction.

7. The use according to claim 6, characterized in that: The reaction conditions of the acetylene hydrochlorination reaction are: reaction temperature 200 °C, acetylene space velocity GHSV 180 h -1 , the volume ratio of acetylene to hydrogen chloride is 1:1.15.

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