A method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires

Abstract

The present invention belongs to the technical field of resource recovery and utilization, and discloses a method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires. The steps are as follows: First, the USY molecular sieve is mixed with a Cu(NO3)2·3H2O solution by an impregnation method to prepare a Cu-USY molecular sieve; then the waste tires and the Cu-USY molecular sieve catalyst are loaded into a quartz tube reactor in layers for rapid catalytic pyrolysis to prepare waste tire pyrolysis oil. The present invention solves the problem that the selectivity of the USY catalyst for monocyclic aromatic hydrocarbons is not high during the pyrolysis of waste tires, resulting in a low yield of monocyclic aromatic hydrocarbons, especially the yield of p-cymene. At the same time, the USY molecular sieve is loaded with a cheap transition metal Cu, which saves costs and has high economic value. The pyrolysis oil rich in aromatic hydrocarbons prepared by this method has broad application prospects for the preparation of fuels or deep processing of chemicals.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recycling and utilization, and particularly relates to a method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires. Background Art

[0002] The progress of the economic society has brought about the rapid development of the automotive industry. With the increase in the number of motor vehicles, the quantity of waste tires has also been continuously increasing. Waste tires are extremely difficult to degrade naturally and have a service life of 80 - 100 years in landfills. Traditional stacking and landfilling waste a large amount of land resources and make it easy for mosquitoes and other pests to breed and spread diseases. Therefore, the treatment of waste tires has gradually attracted people's attention.

[0003] Among various treatment methods, the pyrolysis technology of waste tires can decompose tires into valuable chemical substances or fuels. Tire pyrolysis oil (TPO) is the main product in the pyrolysis process of waste tires, which contains abundant valuable chemical substances such as limonene, isoprene, ethylene, benzene, toluene, xylene, ethylbenzene, and p - cymene. These substances are important chemical raw materials and can be used as potential sources of light aromatic hydrocarbons. Notably, p - cymene (also known as p - isopropyltoluene) present in aromatic hydrocarbons is an important organic synthesis intermediate with high value and wide applications. It can be directly used as a food additive such as in candies and seasonings, and is used for synthesizing various polycyclic musk fragrances (umbellulone, tonalide, galaxolide), drugs, herbicides, fungicides, etc.

[0004] In the prior art, Shen Boxiong, in the article "Analysis of Catalytic Pyrolysis Oil from Waste Tires" [J]. Chemical Industry and Engineering Progress, 2007, (01): 82 - 85., used USY molecular sieve catalyst for catalytic pyrolysis of waste tires. On the one hand, the addition of the catalyst can reduce the pyrolysis temperature and energy consumption; on the other hand, compared with the microporous molecular sieve ZSM - 5 catalyst, the macromolecular hydrocarbons in the volatiles are more likely to enter the mesopores for reaction, resulting in a higher conversion rate of macromolecular hydrocarbons. However, the USY catalyst has fewer acid sites, and when used for the pyrolysis of waste tires, the selectivity for monocyclic aromatic hydrocarbons is not high, and the yield of monocyclic aromatic hydrocarbons is still low. To address the above problems, the USY molecular sieve is modified by metal loading. This method can adjust the acidic sites and physicochemical properties of the catalyst, improve the catalytic performance of the catalyst, and increase the relative content of monocyclic aromatic hydrocarbons, especially p - cymene, in the pyrolysis oil. Summary of the Invention

[0005] Aiming at the above - mentioned deficiencies of the prior art, the present invention provides a method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires. The method uses the impregnation method to load 1% - 5% of Cu metal on USY molecular sieve to prepare a modified Cu - USY molecular sieve, and uses this molecular sieve to rapidly catalytic pyrolyze waste tires to prepare pyrolysis oil with a higher content of monocyclic aromatic hydrocarbons.

[0006] Technical solution of the present invention:

[0007] A method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires, comprising the following steps:

[0008] (1) Prepare Cu-USY molecular sieve by impregnation method

[0009] First, slowly add USY powder to Cu(NO3)2·3H2O solution, then stir for 12 hours at ambient temperature, and vacuum distill the mixture at 40 °C to obtain a Cu-USY molecular sieve precursor; then, dry the Cu-USY molecular sieve precursor at 105 °C for 12 hours, and then calcine it in an air atmosphere at 550 °C for 5 hours to obtain a modified Cu-USY molecular sieve catalyst;

[0010] (2) Selectively prepare monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires

[0011] Load the waste tires and the Cu-USY molecular sieve catalyst into the reactor in layers, and carry out rapid catalytic pyrolysis to prepare waste tire pyrolysis oil. The total selectivity of monocyclic aromatic hydrocarbons in the waste tire pyrolysis oil is 55.26%-63.70%; wherein, rapid catalytic pyrolysis means heating the reactor to 350-550 °C at a heating rate of 20 °C / s in an N2 atmosphere and holding for 25 minutes to obtain pyrolysis oil rich in monocyclic aromatic hydrocarbons.

[0012] The USY molecular sieve has a silica-alumina ratio of 11.

[0013] The loading amount of Cu is 1%-5%.

[0014] The waste tires are dried at 110 °C for 12 hours, crushed to 70 mesh, and the mass ratio of the waste tires to the modified Cu-USY molecular sieve is 5:1.

[0015] Beneficial effects of the present invention:

[0016] 1. Using the Cu-USY molecular sieve catalyst can increase the proportion of monocyclic aromatic hydrocarbons in the pyrolysis oil. Compared with the unmodified parent USY molecular sieve catalyst, the relative content of monocyclic aromatic hydrocarbons has increased by up to 5%. Among them, the yields of specific aromatic hydrocarbons including toluene, ethylbenzene, xylene (p-xylene, o-xylene), 1,2,4-trimethylbenzene, p-cymene and naphthalene (1-methylnaphthalene, 2-methylnaphthalene) reach up to 42.92 mg / g, an increase of 57.58% compared with the parent USY catalyst; especially, the yield of p-cymene reaches up to 5.48 mg / g, an increase of 101.96% compared with the parent USY catalyst.

[0017] 2. The experimental method uses a transition metal Cu to load USY zeolite. The addition of Cu changes the acid site distribution of the USY catalyst, increases the Lewis acid sites of the catalyst, and reduces the acid sites. Moreover, metallic copper is inexpensive, cost-saving, and has high economic value. Meanwhile, the pyrolysis oil rich in aromatics prepared by this method has broad application prospects for the preparation of fuels or high-value chemicals. Description of the Drawings

[0018] Figure 1 It is a characterization result diagram of the catalyst; among them, (a) is the XRD spectrum; (b) is the scanning electron micrograph of the 1% Cu-loaded USY zeolite catalyst; (c) is the NH3-TPD spectrum; among them, 1 is the parent catalyst; 2-4 are the modified Cu-USY zeolites with loadings of 1%, 3%, and 5% respectively.

[0019] Figure 2 It is a schematic diagram showing the influence of different Cu-loaded USY zeolite catalysts on the content of specific aromatics.

[0020] Figure 3 It is a schematic diagram showing the influence of the 1% Cu-loaded USY zeolite catalyst on the content of specific aromatics at 350-550 °C. Detailed Embodiments

[0021] The present invention will be further described in detail below with reference to specific examples, but the present invention is not limited to the specific examples.

[0022] Example 1

[0023] First step, use USY zeolite with a silica-alumina ratio of 11, load waste tires and the USY zeolite catalyst into the reactor in layers according to a mass ratio of 5:1, and perform rapid catalytic pyrolysis.

[0024] Second step, under a N2 atmosphere, heat the reactor to 500 °C at a heating rate of 20 °C / s and hold for 25 minutes to prepare waste tire pyrolysis oil, where the total selectivity of monocyclic aromatics is 58.73%; the yield of specific aromatics is 27.23 mg / g; the yield of p-cymene is 2.71 mg / g.

[0025] Example 2

[0026] First step, use USY zeolite with a silica-alumina ratio of 11, mix 2 g of USY with 100 ml of a 3.15 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 1%; next, stir at ambient temperature for 12 hours, and subject the mixture to vacuum distillation at 40 °C; then, dry the modified catalyst in an oven at 105 °C for 12 hours. Finally, calcine in an air atmosphere at 550 °C for 5 hours.

[0027] In the second step, waste tires and 1% Cu-USY molecular sieve catalyst are loaded into the reactor in layers according to a mass ratio of 5:1, and rapid catalytic pyrolysis is carried out.

[0028] In the third step, under a N2 atmosphere, the reactor is heated to 500 °C at a heating rate of 20 °C / s and maintained for 25 minutes to prepare waste tire pyrolysis oil, in which the total selectivity of monocyclic aromatic hydrocarbons is 63.70%; the specific aromatic hydrocarbon yield reaches 42.92 mg / g, which is 57.58% higher than that of the parent USY catalyst; p-cymene reaches 5.48 mg / g, which is 101.96% higher than that of the parent USY catalyst.

[0029] Example 3

[0030] In the first step, USY molecular sieve with a silica-alumina ratio of 11 is used. 2 g of USY is mixed with 100 ml of 9.44 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 3%; next, it is stirred at ambient temperature for 12 hours, and the mixture is subjected to vacuum distillation at 40 °C; then, the modified catalyst is dried in an oven at 105 °C for 12 hours; finally, it is calcined in an air atmosphere at 550 °C for 5 hours.

[0031] In the second step, waste tires and 3% Cu-USY molecular sieve catalyst are loaded into the reactor in layers according to a mass ratio of 5:1, and rapid catalytic pyrolysis is carried out.

[0032] In the third step, under a N2 atmosphere, the reactor is heated to 500 °C at a heating rate of 20 °C / s and maintained for 25 minutes to prepare waste tire pyrolysis oil, in which the total selectivity of monocyclic aromatic hydrocarbons is 61.34%; the specific aromatic hydrocarbon yield reaches 38.09 mg / g, which is 39.88% higher than that of the parent USY catalyst; p-cymene reaches up to 4.25 mg / g, which is 56.83% higher than that of the parent USY catalyst.

[0033] Example 4

[0034] In the first step, USY molecular sieve with a silica-alumina ratio of 11 is used. 2 g of USY is mixed with 100 ml of 15.74 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 5%; next, it is stirred at ambient temperature for 12 hours, and the mixture is subjected to vacuum distillation at 40 °C; then, the modified catalyst is dried in an oven at 105 °C for 12 hours; finally, it is calcined in an air atmosphere at 550 °C for 5 hours.

[0035] In the second step, waste tires and 5% Cu-USY molecular sieve catalyst are loaded into the reactor in layers according to a mass ratio of 5:1, and rapid catalytic pyrolysis is carried out.

[0036] Step 3: Under an N2 atmosphere, heat the reactor to 500 °C at a heating rate of 20 °C / s and hold for 25 minutes to prepare pyrolysis oil from waste tires, where the total selectivity of monocyclic aromatic hydrocarbons is 59.41%; the specific aromatic hydrocarbon yield reaches 36.30 mg / g, an increase of 33.31% compared to the parent USY catalyst; the p-cymene reaches a maximum of 3.87 mg / g, an increase of 42.8% compared to the parent USY catalyst.

[0037] Example 5

[0038] Step 1: Use USY zeolite with a silica-alumina ratio of 11. Mix 2 g of USY with 100 ml of a 3.15 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 1%; next, stir for 12 hours at ambient temperature, and carry out vacuum distillation of the mixture at 40 °C; then, dry the modified catalyst in an oven at 105 °C for 12 hours; finally, calcine in an air atmosphere at 550 °C for 5 hours.

[0039] Step 2: Load waste tires and a 1% Cu-USY zeolite catalyst into the reactor in layers according to a mass ratio of 5:1 for rapid catalytic pyrolysis.

[0040] Step 3: Under an N2 atmosphere, heat the reactor to 350 °C at a heating rate of 20 °C / s and hold for 25 minutes to prepare pyrolysis oil from waste tires, where the total selectivity of monocyclic aromatic hydrocarbons is 49.95%; the specific aromatic hydrocarbon yield reaches 14.59 mg / g; the p-cymene reaches 4.56 mg / g.

[0041] Example 6

[0042] Step 1: Use USY zeolite with a silica-alumina ratio of 11. Mix 2 g of USY with 100 ml of a 3.15 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 1%; next, stir for 12 hours at ambient temperature, and carry out vacuum distillation of the mixture at 40 °C; then, dry the modified catalyst in an oven at 105 °C for 12 hours; finally, calcine in an air atmosphere at 550 °C for 5 hours.

[0043] Step 2: Load waste tires and a 1% Cu-USY zeolite catalyst into the reactor in layers according to a mass ratio of 5:1 for rapid catalytic pyrolysis.

[0044] Step 3: Under an N2 atmosphere, heat the reactor to 400 °C at a heating rate of 20 °C / s and hold for 25 minutes to prepare pyrolysis oil from waste tires, where the total selectivity of monocyclic aromatic hydrocarbons is 55.63%; the specific aromatic hydrocarbon yield reaches 24.73 mg / g; the p-cymene reaches 4.60 mg / g.

[0045] Example 7

[0046] First step: Use USY zeolite with a silica-alumina ratio of 11. Mix 2 g of USY with 100 ml of 3.15 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 1%. Next, stir for 12 hours at ambient temperature, and carry out vacuum distillation of the mixture at 40 °C. Then, dry the modified catalyst in an oven at 105 °C for 12 hours. Finally, calcine in an air atmosphere at 550 °C for 5 hours.

[0047] Second step: Load waste tires and 1% Cu-USY zeolite catalyst into the reactor in layers according to a mass ratio of 5:1, and carry out rapid catalytic pyrolysis.

[0048] Third step: Under a N2 atmosphere, heat the reactor to 450 °C at a heating rate of 20 °C / s and hold for 25 minutes to prepare waste tire pyrolysis oil, where the total selectivity of monocyclic aromatic hydrocarbons is 61.08%; the specific aromatic hydrocarbon yield reaches 34.27 mg / g; p-cymene reaches 4.96 mg / g.

[0049] Example 8

[0050] First step: Use USY zeolite with a silica-alumina ratio of 11. Mix 2 g of USY with 100 ml of 3.15 mmol / L Cu(NO3)2·3H2O solution, and the Cu loading is 1%. Next, stir for 12 hours at ambient temperature, and carry out vacuum distillation of the mixture at 40 °C. Then, dry the modified catalyst in an oven at 105 °C for 12 hours. Finally, calcine in an air atmosphere at 550 °C for 5 hours.

[0051] Second step: Load waste tires and 1% Cu-USY zeolite catalyst into the reactor in layers according to a mass ratio of 5:1, and carry out rapid catalytic pyrolysis.

[0052] Third step: Under a N2 atmosphere, heat the reactor to 550 °C at a heating rate of 20 °C / s and hold for 25 minutes to prepare waste tire pyrolysis oil, where the total selectivity of monocyclic aromatic hydrocarbons is 63.10%; the specific aromatic hydrocarbon yield reaches 42.28 mg / g; p-cymene reaches 4.81 mg / g.

[0053] As can be seen from the above embodiments, the copper-loaded USY catalysts all increase the selectivity of monocyclic aromatic hydrocarbons and the yield of specific aromatic hydrocarbons. Selectivities of monocyclic aromatic hydrocarbons of 63.70%, 61.34% and 59.41% are obtained on 1% Cu / USY, 3% Cu / USY and 5% Cu / USY respectively, among which the selectivity of monocyclic aromatic hydrocarbons obtained on 1% Cu / USY is the highest. The yield of specific aromatic hydrocarbons obtained on the 1% Cu / USY catalyst is the highest, being 42.92 mg / g. In addition, the yield of p-cymene obtained on the 1% Cu / USY catalyst is the highest, being 5.48 mg / g. Among them, the addition of Cu changes the physical and chemical properties of USY zeolite, improving the catalytic activity and product selectivity of the catalyst.

[0054] A relatively high catalytic pyrolysis temperature is beneficial to the formation of monocyclic aromatic hydrocarbons. As the temperature increases from 350 °C to 500 °C, the selectivity of monocyclic aromatic hydrocarbons increases from 49.95% to 63.10%. When the temperature rises from 500 °C to 550 °C, the selectivity of monocyclic aromatic hydrocarbons slightly decreases from 63.70% to 63.10%. In addition, the variation law of the yield of specific aromatic hydrocarbons with the reaction temperature is consistent with that of monocyclic aromatic hydrocarbons. 500 °C is the optimal catalytic pyrolysis temperature for the catalytic pyrolysis of waste tires to produce more monocyclic aromatic hydrocarbons and p-cymene while reducing the process energy consumption.

[0055] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should also be given the broadest interpretation so as to cover equivalent modifications, variations, and equivalent ratios and substances that are in line with the spirit of the present invention.

Claims

1. A method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires, characterized in that, The steps are as follows: (1)Prepare Cu-USY zeolite by the impregnation method First, slowly add USY powder to the Cu(NO3)2·3H2O solution. Next, stir for 12 hours at ambient temperature, and vacuum distill the mixture at 40 °C to obtain the Cu-USY zeolite precursor. Then, dry the Cu-USY zeolite precursor at 105 °C for 12 hours, and then calcine it in an air atmosphere at 550 °C for 5 hours to obtain the modified Cu-USY zeolite catalyst; (2)Selectively prepare monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires Load waste tires and the Cu-USY zeolite catalyst into the reactor in layers for rapid catalytic pyrolysis to prepare waste tire pyrolysis oil. The total selectivity of monocyclic aromatic hydrocarbons in the waste tire pyrolysis oil is 55.26%-63.70%. Among them, rapid catalytic pyrolysis means heating the reactor to 350-550 °C at a heating rate of 20 °C / s in an N2 atmosphere and holding for 25 minutes to obtain pyrolysis oil rich in monocyclic aromatic hydrocarbons; The loading amount of Cu is 1%-5%.

2. The method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires according to claim 1, characterized in that, The waste tires are dried at 110 °C for 12 hours and crushed to 70 mesh, and the mass ratio of waste tires to the modified Cu-USY zeolite is 5:

1.

3. The method for selectively preparing monocyclic aromatic hydrocarbons by catalytic pyrolysis of waste tires according to claim 1, characterized in that, The USY zeolite has a silica-alumina ratio of 11.

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