A porous catalyst and its preparation method and application

Abstract

The invention belongs to the field of catalysts and relates to a porous catalyst and its preparation method and application. Zirconium chloride, PET and heteropoly acid are dispersed in a solvent in a mass ratio of 1-20:1-20:1 to carry out a solvothermal reaction. The solvothermal reaction temperature is 100-200 DEG C and the reaction time is 8-24 hours. After the cooled solid is washed and dried, it is roasted at 80-450 DEG C for 1-6 hours to obtain a porous catalyst. The catalyst of the present invention can realize the liquid-phase dehydration reaction of 1-phenylethanol and efficiently convert it into styrene, not only significantly improving the conversion rate of the raw materials, but also the catalyst is easy to recycle, greatly reflecting its environmental friendliness, and providing a green and sustainable process route for synthesizing styrene.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts and relates to a porous catalyst and a preparation method and application thereof, in particular to a porous catalyst prepared by using PET as a precursor to coat a heteropolyacid and application thereof in the dehydration of 1-phenylethanol to prepare styrene. Background Art

[0002] As a crucial basic chemical raw material, styrene plays a crucial role in chemical production. It is one of the main raw materials for the production of styrene-butadiene rubber and styrene-butadiene latex, and is primarily used in the manufacture of various engineering plastics, including expandable polystyrene resin (EPS), PS, and ABS resin.

[0003] Currently, there are two main processes for producing styrene. One is the catalytic dehydrogenation of ethylbenzene: this method produces styrene through direct catalytic thermal dehydrogenation of ethylbenzene. This is the most traditional and mainstream process, accounting for 70% of global styrene production capacity. The other is the propylene oxide styrene co-production (PO / SM) process, developed by ARCO in the United States. Ethylbenzene reacts with oxygen to produce ethylbenzene hydroperoxide; ethylbenzene hydroperoxide is then epoxidized with propylene to produce propylene oxide, 1-phenylethanol, and acetophenone; 1-phenylethanol is dehydrated to produce styrene; the byproduct acetophenone is hydrogenated to produce 1-phenylethanol, which is then recycled back into the dehydration system to produce styrene. The PO / SM co-production process features low investment costs, good economics, large production scale, and strong risk tolerance, and its share of production capacity is continuously increasing.

[0004] Traditionally, 1-phenylethanol dehydration is performed in a gaseous state using titanium dioxide or aluminum oxide. Due to its high boiling point, the dehydration process consumes significant energy. Homogeneous catalysts such as H2SO4, oxalic acid, H3PO4, KHSO4, p-toluenesulfonic acid, and phosphorus ionic liquids have been used to reduce energy consumption. However, these catalysts are corrosive, making separation and recovery difficult. Summary of the Invention

[0005] The present invention aims to provide a porous catalyst, a preparation method and application thereof, in particular a preparation method for a porous catalyst coated with a heteropolyacid using PET (polyethylene terephthalate) as a precursor and its application in the dehydration of 1-phenylethanol to produce styrene. The catalyst exhibits high activity, high stability and easy separation in the dehydration reaction of 1-phenylethanol.

[0006] The technical solution for implementing the present invention is:

[0007] The first aspect of the present invention provides a method for preparing a porous catalyst, wherein zirconium chloride, PET and heteropoly acid are dispersed in a solvent in a mass ratio of 1-20:1-20:1 to carry out a solvothermal reaction. The solvothermal reaction temperature is 100-200°C and the reaction time is 8-24 hours. The cooled solid is washed and dried, and then calcined at 80-450°C for 1-6 hours to obtain a porous catalyst.

[0008] Furthermore, the heteropoly acid is one or more of phosphomolybdic acid, phosphotungstic acid, and vanadium oxyphosphomolybdic acid.

[0009] Furthermore, the solvent is a mixed solvent consisting of solvent A and solvent B, wherein solvent A is one or more of acetone, ethanol, and isopropanol; and solvent B is one or more of formic acid, acetic acid, propionic acid, and N,N-dimethylformamide.

[0010] Furthermore, the volume ratio of solvent A to solvent B is 1:0.5-5, preferably 1:1-3. Most preferably, solvent A is acetone, solvent B is formic acid, and the volume ratio of acetone to formic acid is 1:1.

[0011] Furthermore, the mass ratio of the zirconium chloride, PET and heteropoly acid is 1-5:1-5:1, more preferably 3-5:4-5:1, and most preferably 4.2:3:1.

[0012] Furthermore, the solvent thermal reaction temperature is 140-180° C., and the reaction time is 10-18 hours.

[0013] Furthermore, the calcination temperature is 80-350° C., and the calcination time is 1-3 hours.

[0014] Furthermore, the washing is performed using N,N-dimethylformamide (DMF) and ethanol.

[0015] The second aspect of the present invention provides a porous catalyst prepared by the above method, which is a heteropolyacid or heteropolyacid salt coated with UiO-66, wherein at least a portion of the heteropolyacid or heteropolyacid salt is distributed in the pores of the UiO-66, and the porous catalyst has a multi-level pore structure composed of micropores and mesopores.

[0016] A third aspect of the present invention provides an application of the above-mentioned porous catalyst in the dehydration reaction of 1-phenylethanol to prepare styrene, wherein the prepared porous catalyst, 1-phenylethanol and decalin solvent are placed in a three-necked flask with a condenser, and the reaction is carried out under continuous stirring at a reaction temperature of 100-200°C.

[0017] Advantages and beneficial effects of the present invention:

[0018] 1. The present invention greatly improves the performance and long-term operation stability of the porous catalyst in catalyzing the dehydration of 1-phenylethanol to prepare styrene by coating the heteropoly acid during the synthesis of the porous material.

[0019] 2. The porous catalyst synthesized by the present invention is easy to separate from the reaction solution after the reaction and is easy to recycle and regenerate. After the recycle and regeneration, the good catalytic effect can be restored. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are the XRD patterns of UiO-66, UiO-66 / HP, UiO-66 / HP-320℃, UiO-66@HP-80℃, UiO-66@HP-160℃, UiO-66@HP-240℃, UiO-66@HP-320℃, Al2O3 / HP, SiO2 / HP, HP, Simulated UiO-66.

[0021] Figure 2 This is the thermogravimetric analysis diagram of UiO-66.

[0022] Figure 3 These are the N2 adsorption-desorption curves of UiO-66, UiO-66 / HP, UiO-66@HP-80℃, UiO-66@HP-160℃, UiO-66@HP-240℃, and UiO-66@HP-320℃.

[0023] Figure 4 This is a graph showing the change in conversion rate of styrene to be prepared by dehydration of 1-phenylethanol using UiO-66, UiO-66 / HP, UiO-66 / HP-320℃, UiO-66@HP-80℃, UiO-66@HP-160℃, UiO-66@HP-240℃, UiO-66@HP-320℃, Al2O3 / HP, and SiO2 / HP over time.

[0024] Figure 5 This is a graph showing the change in selectivity of UiO-66, UiO-66 / HP, UiO-66 / HP-320℃, UiO-66@HP-80℃, UiO-66@HP-160℃, UiO-66@HP-240℃, UiO-66@HP-320℃, Al2O3 / HP, and SiO2 / HP for dehydration of 1-phenylethanol to produce styrene over time.

[0025] Figure 6 This is a graph showing the change in the stability of UiO-66@HP-3 for the dehydration of 1-phenylethanol to prepare styrene at 20℃.

[0026] Figure 7 This is the transmission electron microscopy (TEM) image of UiO-66@HP-320℃.

[0027] Figure 8 This is the HAADF-STEM dark field image of UiO-66@HP-320℃.

[0028] Figure 9 This is the energy dispersive X-ray spectroscopy (EDX) element overlay distribution diagram of UiO-66@HP-320℃.

[0029] Figure 10 This is the EDX carbon element distribution map of UiO-66@HP-320℃.

[0030] Figure 11 This is the EDX oxygen element distribution map of UiO-66@HP-320℃.

[0031] Figure 12 This is the EDX zirconium element distribution map of UiO-66@HP-320℃.

[0032] Figure 13 This is the EDX phosphorus element distribution map of UiO-66@HP-320℃.

[0033] Figure 14 This is the EDX molybdenum element distribution map of UiO-66@HP-320℃. DETAILED DESCRIPTION

[0034] In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the content described below is illustrative and not restrictive, and should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included within the scope of protection of the present invention.

[0035] Except for the self-made reagents in the following preparation examples, all other reagents used in the following examples were commercially available.

[0036] In the following examples, HP represents phosphomolybdic acid. Catalysts UiO-66, UiO-66 / HP, UiO-66 / HP-320°C, UiO-66@HP-80°C, UiO-66@HP-160°C, UiO-66@HP-240°C, UiO-66@HP-320°C, Al2O3 / HP, and SiO2 / HP were prepared by the following methods, respectively.

[0037] Example 1: UiO-66:

[0038] A method for preparing a porous catalyst comprises: weighing 840 mg of zirconium chloride and 600 mg of PET, dispersing the mixture in a mixed solution containing 10 ml of acetone and 10 ml of formic acid, transferring the mixture to a hydrothermal reactor, heating the mixture in a constant temperature oven at 160° C. for 12 hours, cooling the mixture, collecting the solid, washing the solid with N,N-dimethylformamide and ethanol, and drying the solid in an oven at 80° C. to obtain a white solid powder, which is recorded as UiO-66.

[0039] Example 2: UiO-66 / HP:

[0040] A method for preparing a porous catalyst comprises: dispersing the UiO-66 and phosphomolybdic acid obtained in Example 1 in ethanol, stirring and immersing the mixture for 6 hours, and then drying the mixture in an oven at 80° C. to obtain a light green solid powder, which is designated as UiO-66 / HP.

[0041] Example 3: UiO-66 / HP-320°C:

[0042] A method for preparing a porous catalyst comprises: calcining the UiO-66 / HP prepared in Example 2 in a muffle furnace at 320° C. for 2 hours to obtain a yellow-brown solid powder, which is recorded as UiO-66 / HP-320° C.

[0043] Example 4: UiO-66@HP-80°C:

[0044] A method for preparing a porous catalyst comprises: weighing 840 mg of zirconium chloride, 600 mg of PET, and 200 mg of phosphomolybdic acid, dispersing the mixture in a mixed solution containing 10 ml of acetone and 10 ml of formic acid, transferring the mixture to a hydrothermal reactor, heating the mixture in a constant temperature oven at 160°C for 12 hours, cooling the mixture, collecting the solid, washing the solid with N,N-dimethylformamide and ethanol, and drying the solid in an oven at 80°C to obtain a pink solid powder, which is labeled UiO-66@HP-80°C.

[0045] Example 5: UiO-66@HP-160°C:

[0046] A method for preparing a porous catalyst comprises: calcining the UiO-66@HP-80°C prepared in Example 4 in a muffle furnace at 160°C for 2 hours to obtain a pink solid powder, which is recorded as UiO-66@HP-160°C.

[0047] Example 6: UiO-66@HP-240°C:

[0048] A method for preparing a porous catalyst comprises: calcining the UiO-66@HP-80°C prepared in Example 4 in a muffle furnace at 240°C for 2 hours to obtain a light yellow solid powder, which is recorded as UiO-66@HP-240°C.

[0049] Example 7: UiO-66@HP-320°C:

[0050] A method for preparing a porous catalyst comprises: calcining the UiO-66@HP-80°C prepared in Example 4 in a muffle furnace at 320°C for 2 hours to obtain a yellow-brown solid powder, which is recorded as UiO-66@HP-320°C.

[0051] Example 8: Al2O3 / HP:

[0052] A method for preparing a porous catalyst comprises: calcining an unactivated γ-Al2O3 carrier at 500°C in a muffle furnace for 3 hours to obtain Al2O3; dispersing 836 mg of the obtained Al2O3 and 164 mg of phosphomolybdic acid in ethanol, stirring and impregnating the mixture for 6 hours; and drying the mixture in an oven at 80°C to obtain a white solid powder, which is designated as Al2O3 / HP.

[0053] Example 9: SiO2 / HP:

[0054] A method for preparing a porous catalyst comprises: calcining SiO2 in a muffle furnace at 500°C for 5 hours and using it as a carrier; dispersing 836 mg of the obtained SiO2 and 164 mg of phosphomolybdic acid in ethanol, stirring and immersing the mixture for 6 hours; and drying the mixture in an oven at 80°C to obtain a white solid powder, which is recorded as SiO2 / HP.

[0055] Figure 1 These are the X-ray diffraction patterns of phosphomolybdic acid (HP), UiO-66 simulated cards (Simulated UiO-66), UiO-66, UiO-66 / HP, UiO-66 / HP-320℃, UiO-66@HP-80℃, UiO-66@HP-160℃, UiO-66@HP-240℃, UiO-66@HP-320℃, Al2O3 / HP, and SiO2 / HP. The successful synthesis of the catalyst was confirmed through X-ray diffraction characterization and comparison with the simulated cards.

[0056] Figure 2 This is the thermogravimetric analysis of UiO-66, showing excellent thermal stability below 400°C. The weight loss observed between 30 and 150°C is attributed to the removal of water molecules adsorbed on the surface and in the pores of the material, while the weight loss between 150 and 400°C is associated with the removal of DMF molecules from the pores. Weight loss above 400°C indicates the gradual decomposition or loss of ligands from the framework. Therefore, UiO-66@HP was not calcined at 400°C to prevent the collapse of the UiO-66 framework.

[0057] Figure 3The N2 adsorption-desorption curves for UiO-66, UiO-66 / HP, UiO-66@HP-80°C, UiO-66@HP-160°C, UiO-66@HP-240°C, and UiO-66@HP-320°C show that the introduction of the heteropolyacid significantly reduces the surface area of ​​each material compared to UiO-66. This reduction in surface area is due to the presence of the heteropolyacid in the pores of the UiO-66 material, which is encapsulated in the UiO-66 during the synthesis process, resulting in a decrease in surface area after the introduction of the heteropolyacid. Another possible reason is that the presence of the heteropolyacid blocks or occupies the pores or surface of the material. After high-temperature treatment, the N,N-dimethylformamide solvent in the pores of UiO-66@HP-320°C evaporates completely, resulting in a larger specific surface area and exposing more active sites for contact with the feedstock, resulting in better conversion and selectivity.

[0058] Application Examples

[0059] 200 mg of the catalyst prepared in Examples 1 to 8, 1 mL of 1-phenylethanol, and 20 mL of decalin solvent were respectively placed in a three-necked flask with a condenser, and reacted under continuous stirring at a reaction temperature of 150° C.

[0060] Figure 4 and Figure 5 The conversion rate and selectivity of the catalysts prepared in 1 to 8 for the dehydration of 1-phenylethanol to prepare styrene over time are shown in Figure 1. Figure 4 and Figure 5 It can be seen that under the same reaction conditions, the conversion rate of UiO-66@HP-320℃ for the dehydration of 1-phenylethanol to styrene is significantly higher than that of other catalysts, and the selectivity is stable.

[0061] Figure 6 The stability of UiO-66@HP-320℃ for the dehydration of 1-phenylethanol to prepare styrene Figure 6 It can be seen that after 6 cycles of reaction, the conversion rate and selectivity of UiO-66@HP-320℃ for the dehydration of 1-phenylethanol to styrene did not change much, indicating that the catalyst had no obvious deactivation.

[0062] Figures 7 to 9 They are TEM image, HAADF-STEM dark field image, and energy dispersive X-ray spectroscopy (EDX) element superposition distribution map of UiO-66@HP-320℃. Figures 10 to 14 They are EDX carbon element surface distribution map, EDX oxygen element surface distribution map, EDX zirconium element surface distribution map, EDX phosphorus element surface distribution map and EDX molybdenum element surface distribution map. The element surface distribution maps show that C, O, Zr, P and Mo elements are evenly distributed in the catalyst.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. Application of a porous catalyst in the dehydration of 1-phenylethanol to prepare styrene, characterized in that: The preparation method comprises the following steps: dispersing zirconium chloride, PET and heteropoly acid in a solvent at a mass ratio of 1-20:1-20:1, performing a solvothermal reaction, wherein the solvothermal reaction temperature is 100-200°C, the reaction time is 8-24 hours, washing and drying the cooled solid, and then calcining at 80-350°C for 1-3 hours to obtain a porous catalyst; The heteropoly acid is one or both of phosphomolybdic acid and phosphotungstic acid; The solvent is a mixed solvent consisting of solvent A and solvent B, wherein solvent A is one or more of acetone, ethanol, and isopropanol; and solvent B is one or more of formic acid, acetic acid, propionic acid, and N,N-dimethylformamide. The volume ratio of the solvent A to the solvent B is 1:0.5-5.

2. The use according to claim 1, characterized in that The mass ratio of the zirconium chloride, PET and heteropoly acid is 1-5:1-5:

1.

3. The use according to claim 1, characterized in that The solvent thermal reaction temperature is 140-180° C., and the reaction time is 10-18 hours.

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