Application of nanomolecular sieves in the preparation of polycyclic aromatic hydrocarbons

Abstract

This invention discloses the application of nano-molecular sieves in the preparation of polycyclic aromatic hydrocarbons (PAHs). The nano-molecular sieves are one or more of the following nanostructures: H-ZSM-5, H-USY, H-Y, H-β, H-MOR, H-ZSM-35, H-MCM-22, H-ZSM-22, and H-ZSM-11. The catalyst used in this invention is inexpensive and readily available, and the preparation process is simple. It exhibits high catalytic activity and selectivity for the aldol condensation, rearrangement, and subsequent dehydration aromatization of biomass ketones. This invention provides a process for the sustained and efficient conversion of lignocellulose-based platform compounds into PAHs using nano-molecular sieve catalysts.

Description

Technical Field

[0001] This invention relates to the application of a nano-molecular sieve in the process of preparing polycyclic aromatic hydrocarbons. Background Technology

[0002] To meet the needs of sustainable development and environmental protection, the catalytic conversion of renewable, abundant, and carbon-neutral biomass into high-quality fuels and high-value-added chemicals has attracted widespread attention.

[0003] Methylindene, tetrahydronaphthalene, and alkylated tetrahydronaphthalene are important chemicals widely used in the chemical, pharmaceutical, and rubber industries. They are also important additives for improving the thermal stability and shock resistance of aviation fuels. Currently, industrially, tetrahydronaphthalene is mainly prepared by catalytic hydrogenation of naphthalene, the most abundant aromatic compound in coal tar. CN108059581A provides a method for preparing tetrahydronaphthalene by hydrogenation of naphthalene, in which a mixture of naphthalene and benzene is hydrogenated at 240–320°C, and the product is hydrogenated again. Then, the secondary hydrogenation product is sequentially cooled, flash-evaporated, and separated to obtain the tetrahydronaphthalene product. CN108325517A discloses a method for producing tetrahydronaphthalene from industrial naphthalene containing many impurities, using sulfided Ni... x Al y Si z Mo 10 Using composite metals as catalysts, the conversion rate of naphthalene exceeds 95% under optimal conditions, and the selectivity of tetrahydronaphthalene approaches 100%. Furthermore, CN109092315A found that oxidized NiMo / Al2O3 catalysts also have significant effects on the selective hydrogenation of naphthalene to tetrahydronaphthalene. Alkylated tetrahydronaphthalene is usually obtained by alkylation of tetrahydronaphthalene, while methyl indane is usually obtained by further isomerization of tetrahydronaphthalene; a large amount of methyl indane is present in the reaction products of tetrahydronaphthalene catalytic cracking. Although the above methods are commonly used, the raw materials are non-renewable, and the yields of tetrahydronaphthalene, alkylated tetrahydronaphthalene, and methyl indane obtained from fossil fuels are low. They also involve cumbersome distillation and separation processes or catalyst preparation, complex equipment, and high energy consumption. Therefore, in the long run, it is necessary to develop green and renewable technologies for the production of tetrahydronaphthalene, alkylated tetrahydronaphthalene, and methyl indane, among other polycyclic aromatic hydrocarbons.

[0004] Our research group has long been engaged in the catalytic conversion of biomass into oils and chemicals (CN113968776A, CN107814676A and CN 108117474A). We have developed a series of routes for the efficient utilization of biomass and its platform compounds. Cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone, methylcyclopentenone, and methylcyclohexanone are important biomass platform compounds. The synthesis of methyl indenhydride and tetrahydronaphthalene from renewable biomass ketone cyclopentanone has also been reported in our previous work. However, using traditional molecular sieves as catalysts, the catalyst gradually deactivates after 6 hours of reaction, and the conversion rate of cyclopentanone and the yield of the target product decrease sharply. Summary of the Invention

[0005] The purpose of this invention is to provide a new process for the sustainable preparation of polycyclic aromatic hydrocarbons (PAHs) from lignocellulose-derived platform compounds under the action of nano-molecular sieve catalysts.

[0006] This invention is achieved through the following technical solution: using nano-molecular sieves as catalysts, biomass ketones are synthesized in a fixed-bed continuous reactor through aldol condensation, rearrangement, and subsequent dehydration aromatization reactions to achieve continuous, efficient, and green synthesis of polycyclic aromatic hydrocarbons.

[0007] The chemical structural formulas of the above-mentioned raw material biomass ketones and target product polycyclic aromatic hydrocarbons are shown in Table 1.

[0008] Table 1. Structural formulas of ketones from raw biomass and polycyclic aromatic hydrocarbons from target products.

[0009]

[0010] Based on the above scheme, preferably, the biomass ketones are one or more of cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone, methylcyclopentenone, and methylcyclohexanone.

[0011] Based on the above scheme, preferably, the nano-molecular sieve catalyst includes one or more of H-ZSM-5, H-USY, HY, H-β, H-MOR, H-ZSM-35, H-MCM-22, H-ZSM-22, and H-ZSM-11 with nanostructures. The size of the nano-molecular sieve catalyst is in the range of 10-100 nm; the smaller size of the nano-molecular sieve is beneficial for mass transfer and inhibiting coke formation (good resistance to carbon deposition and carbon buildup).

[0012] Based on the above scheme, preferably, the molar silicon-to-aluminum ratio of the nano-molecular sieve is 2-500, more preferably between 5-400, and even more preferably between 5-300.

[0013] Based on the above scheme, preferably, the reaction temperature in the fixed-bed reactor is 300-600℃, more preferably between 350-500℃, and even more preferably between 375-475℃.

[0014] Based on the above scheme, preferably, the reaction gas in the fixed bed reactor is one of nitrogen, helium or argon, and the pressure is 0.0001-1 MPa, more preferably between 0.0001-0.8 MPa, and even more preferably between 0.0001-0.5 MPa.

[0015] Based on the above scheme, preferably, the molar ratio of gas to biomass ketones in the fixed-bed reactor is 10-400:1, more preferably, the molar ratio of gas to biomass ketones is between 20-300:1, and more preferably, the molar ratio of gas to biomass ketones is between 30-200:1.

[0016] Based on the above scheme, preferably, the space velocity of biomass ketones in the fixed-bed reactor is 0.01-10 h⁻¹. -1 The preferred biomass ketones have a space velocity of 0.05-8 h⁻¹. -1 More preferably, biomass ketones have a space velocity of 0.1-4 h⁻¹. -1 between.

[0017] The method described in this invention can achieve efficient and sustainable one-step conversion of lignocellulose-derived biomass ketones into high-value-added polycyclic aromatic hydrocarbons such as methyl indane, tetrahydronaphthalene, and alkylated tetrahydronaphthalene.

[0018] The beneficial effects of this invention are as follows: The process route is simple and easy to operate. Biomass ketones can be completely converted under the catalysis of nano-molecular sieves, and then efficiently synthesized into renewable polycyclic aromatic hydrocarbons (PAHs) through a cascade of aldol condensation / rearrangement / aromatization reactions. The reaction conditions are mild, the catalyst is inexpensive and readily available, and has good catalytic performance. The conversion rate of biomass ketones is over 90%, the selectivity of PAHs is over 70%, and the catalyst has good stability, showing no deactivation after 48 hours. This provides a novel approach for the sustainable synthesis of renewable PAHs from lignocellulose. This invention is highly operable, has low energy consumption, and is environmentally friendly. It is a green and efficient new catalytic route that can be used in actual industrial production. Attached Figure Description

[0019] Figure 1 The images show gas chromatograms of the synthesis of polycyclic aromatic hydrocarbons from biomass ketones, with a using cyclopentanone as the raw material (Example 1) and b using cyclohexanone as the raw material (Example 2).

[0020] Figure 2The following are mass spectra of the target polycyclic aromatic hydrocarbons (PAHs) when cyclopentanone and cyclohexanone are used as raw materials. a is methyl indane (Example 1), b is tetrahydronaphthalene (Example 1), and c is dimethyltetrahydronaphthalene (Example 2). Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0022] In the experiment to prepare polycyclic aromatic hydrocarbons from biomass ketones, the reactor was a fixed bed, and a pure biomass ketone solution was pumped in at a certain rate using a liquid chromatography pump. Nanoscale molecular sieves were used as catalysts, and the reaction was carried out under set temperature, gas pressure, gas-to-biomass ketone molar ratio, and biomass ketone space velocity.

[0023] The catalysts used in the examples were purchased from Tianjin Nanhua Catalyst Co., Ltd.; the catalyst size was 10-100 nm; among them, the nano H-ZSM-5 (Si / Al ratio 160) had a size of 50 nm.

[0024] Examples 1-12

[0025] Investigation of the reactivity of different biomass ketones in the synthesis of polycyclic aromatic hydrocarbons: 0.6 g of one or more of the following catalysts was uniformly mixed with 2 g of quartz sand (40-70 mesh) and packed into a fixed-bed continuous reactor. The temperature was increased to 450 °C at a rate of 10 °C / min. Then, the reactor was subjected to nitrogen pressure of 0.01 MPa, a nitrogen-to-biomass ketone molar ratio of 40:1, and a cyclopentanone time space velocity of 0.4 h⁻¹. -1 The reaction was carried out under the following conditions, and the experimental results are shown in Table 2.

[0026] Table 2. Reactivity of different biomass ketones in the synthesis of polycyclic aromatic hydrocarbons.

[0027]

[0028]

[0029] The data in Table 2 show that different biomass ketones can be efficiently synthesized into polycyclic aromatic hydrocarbons (PAHs) on nano-molecular sieve catalysts. All biomass ketones achieved complete conversion, but the selectivity of the target products varied slightly. Under the action of the nano-H-ZSM-5 (Si / Al ratio 2:1) molecular sieve catalyst, cyclopentanone conversion was 100%, and the total selectivity of the target products methyl indenmannite and tetrahydronaphthalene reached 82%. Even after 48 hours of reaction, cyclopentanone was still completely converted, and the total selectivity of the target products methyl indenmannite and tetrahydronaphthalene remained as high as 81%.

[0030] Examples 13-45

[0031] The activity of different nano-molecular sieve catalysts in the synthesis of methylindene and tetrahydronaphthalene from cyclopentanone was investigated: 0.6 g of one or more of the following catalysts was uniformly mixed with 2 g of quartz sand (40-70 mesh) and packed into a fixed-bed continuous reactor. The temperature was increased to 450 °C at a rate of 10 °C / min, and then the reaction was carried out under nitrogen pressure of 0.01 MPa, a nitrogen-to-cyclopentanone molar ratio of 40:1, and a cyclopentanone time space velocity of 0.4 h⁻¹. -1 The reaction was carried out under the following conditions, and the experimental results are shown in Table 3.

[0032] Table 3. Reactivity of different nano-molecular sieve catalysts in the synthesis of methylindene and tetrahydronaphthalene from cyclopentanone.

[0033]

[0034]

[0035]

[0036] The data in Table 3 show that the nano-molecular sieve catalysts listed in the table all have good effects on the synthesis of methylindane and tetrahydronaphthalene from cyclopentanone. The silicon-to-aluminum ratio of different nano-molecular sieves also has a certain influence on the conversion rate of cyclopentanone and the total selectivity of methylindane and tetrahydronaphthalene. Under the action of the nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst, complete conversion of cyclopentanone can be achieved, with a total selectivity of 87% for the target products methylindane and tetrahydronaphthalene. After 48 hours of reaction, the conversion rate of cyclopentanone remains at 100%, and the total selectivity of the target products methylindane and tetrahydronaphthalene is still as high as 87%.

[0037] Examples 46-55

[0038] The effect of reaction temperature on the synthesis of methylindene and tetrahydronaphthalene from cyclopentanone was investigated using a nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst. 0.6 g of the nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst used in Example 16 was uniformly mixed with 2 g of quartz sand (40-70 mesh) and packed into a fixed-bed continuous reactor. The temperature was increased to the investigated temperature at a rate of 10 °C / min. The reaction was then carried out under nitrogen pressure of 0.01 MPa, a nitrogen to cyclopentanone molar ratio of 40:1, and a cyclopentanone time space velocity of 0.4 h⁻¹. -1 The reaction was carried out under the specified conditions, and the experimental results are shown in Table 4.

[0039] Table 4. Effect of temperature on the reaction activity of nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst.

[0040]

[0041]

[0042] The data in Table 4 show that, under the same conditions, the reaction temperature has a significant impact on the conversion rate of cyclopentanone and the total selectivity of methylindane and tetrahydronaphthalene. Increasing the reaction temperature will improve the reaction activity to some extent, but excessively high temperatures will decrease the total selectivity of methylindane and tetrahydronaphthalene. Using nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve as a catalyst, cyclopentanone can be completely converted at 425℃, with a total selectivity of up to 88% for the target products methylindane and tetrahydronaphthalene. The catalyst performance remains unchanged after 48 hours of reaction.

[0043] Examples 56-63

[0044] The effect of gas pressure on the synthesis of methylindane and tetrahydronaphthalene from cyclopentanone was investigated using a nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst. 0.6 g of the nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst used in the above examples was uniformly mixed with 2 g of quartz sand (40-70 mesh) and packed into a fixed-bed continuous reactor. The temperature was increased to 425 °C at a rate of 10 °C / min, with the gas-to-cyclopentanone molar ratio controlled at 40:1 and the cyclopentanone hourly space velocity (HSV) at 0.4 h⁻¹. -1 The reaction was then carried out under different gas pressures, and the experimental results are shown in Table 5.

[0045] Table 5. Effect of gas pressure on the reaction activity of nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst.

[0046]

[0047]

[0048] The data in Table 5 show that, under the same conditions, the type of gas has almost no effect on the conversion of cyclopentanone to methylindane and tetrahydronaphthalene, and the catalyst performance and stability remain unchanged. Furthermore, gas pressure has no effect on the conversion rate of cyclopentanone, but it does have some influence on the overall selectivity of methylindane and tetrahydronaphthalene. As the gas pressure gradually decreases, the overall selectivity of the target product gradually increases and then remains constant. Using nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve as a catalyst, cyclopentanone can be completely converted under a nitrogen pressure of 0.001 MPa, with an overall selectivity of up to 88% for the target products methylindane and tetrahydronaphthalene. After 48 hours of reaction, the conversion rate of cyclopentanone remains at 100%, and the overall selectivity of the target product is also as high as 89%.

[0049] Examples 64-75

[0050] The effect of the molar ratio of gas to cyclopentanone on the reactivity of cyclopentanone in the synthesis of methyl indenhydride and tetrahydronaphthalene was investigated using nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst: 0.6 g of the nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst used in the above examples was uniformly mixed with 2 g of quartz sand (40-70 mesh) and packed into a fixed-bed continuous reactor. The temperature was increased to 425 °C at a rate of 10 °C / min, the gas pressure was controlled at 0.001, and the hourly space velocity (HSV) of cyclopentanone was 0.4 h⁻¹. -1 The reaction was then carried out under different molar ratios of gas to cyclopentanone, and the experimental results are shown in Table 6.

[0051] Table 6. Effect of the molar ratio of gas to cyclopentanone on the reaction activity of nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst.

[0052]

[0053]

[0054] The data in Table 6 show that, under the same conditions, the molar ratio of gas to cyclopentanone, whether nitrogen or argon, has little effect on the conversion of cyclopentanone to methylindenhydride and tetrahydronaphthalene. Using nano-H-ZSM-5 molecular sieve (Si / Al ratio 160) as a catalyst, cyclopentanone can be completely converted at a nitrogen-to-cyclopentanone molar ratio of 100:1, with a total selectivity of 89% for the target product. The conversion rate of cyclopentanone and the total product selectivity remain unchanged after 48 hours of reaction.

[0055] Examples 76-86

[0056] The effect of space velocity (WHV) on the synthesis of methyl indane and tetrahydronaphthalene from cyclopentanone on the catalyst of nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve: A certain amount of nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst used in the above examples was uniformly mixed with 2g of quartz sand (40-70 mesh) and packed into a fixed-bed continuous reactor. The temperature was increased to 425℃ at a rate of 10℃ / min. Nitrogen gas was used as the gas, and the nitrogen pressure was controlled at 0.001. The molar ratio of nitrogen to cyclopentanone was 50:1. The reaction was then carried out at different WHVs of cyclopentanone. The experimental results are shown in Table 7.

[0057] Table 7. Effect of space velocity on the reaction activity of cyclopentanone on nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve catalyst.

[0058]

[0059]

[0060] The data in Table 7 show that, under the same conditions, the space velocity (H₂W₀) of cyclopentanone has a significant impact on the conversion of cyclopentanone to methylindane and tetrahydronaphthalene. Increasing the H₂W₀ of cyclopentanone improves the overall selectivity for methylindane and tetrahydronaphthalene to some extent; however, excessively high H₂W₀ reduces the reactivity, significantly decreasing both the conversion rate of cyclopentanone and the overall selectivity for methylindane and tetrahydronaphthalene. Using nano-H-ZSM-5 (Si / Al ratio 160) molecular sieve as a catalyst, a cyclopentanone H₂W₀ of 0.5 h₂W₀ was achieved. -1 The reactants can be completely converted, and the total selectivity of the target products methylindane and tetrahydronaphthalene reaches a maximum of 90%. The catalyst performance remains unchanged after 48 hours of reaction.

[0061] Example 87

[0062] Cyclohexanone was used instead of cyclopentanone as a raw material, and the reaction was carried out under the same conditions as in Example 79. Cyclohexanone was completely converted, and the selectivity of the target product dimethyltetrahydronaphthalene reached 87%. After 48 hours of reaction, the conversion rate of cyclohexanone was still 100%, and the selectivity of the target product was as high as 88%.

[0063] Example 88

[0064] Using 2,5-hexanedione instead of cyclopentanone as the starting material, the reaction was carried out under the same conditions as in Example 79. 2,5-hexanedione was completely converted, and the selectivity of the target product dimethyltetrahydronaphthalene reached 85%. After 48 hours of reaction, the conversion rate of 2,5-hexanedione remained at 100%, and the selectivity of the target product was still 85%.

[0065] Example 89

[0066] Using methylcyclopentanone instead of cyclopentanone as the raw material, the reaction was carried out under the same conditions as in Example 79. Methylcyclopentanone was completely converted, and the selectivity of the target product dimethyltetrahydronaphthalene reached 82%. After 48 hours of reaction, methylcyclopentanone was still completely converted, and the selectivity of the target product was 81%.

[0067] Example 90

[0068] Using methylcyclopentenone instead of cyclopentanone as the raw material, the reaction was carried out under the same conditions as in Example 79. Methylcyclopentenone was completely converted, and the selectivity of the target product dimethyltetrahydronaphthalene reached 80%. After 48 hours of reaction, the conversion rate of methylcyclopentenone and the selectivity of the target product remained consistent, at 100% and 80%, respectively.

[0069] Example 91

[0070] Using methylcyclohexanone instead of cyclopentanone as a raw material, the reaction was carried out under the same conditions as in Example 79. Methylcyclohexanone was completely converted, and the selectivity of the target product tetramethyltetrahydronaphthalene reached 86%. After 48 hours of reaction, the conversion rate of methylcyclohexanone was maintained at 100%, and the selectivity of the target product reached 87%.

[0071] Comparative Example 1

[0072] Using cyclopentanone as the raw material and 1.0 μm H-ZSM-5 (Si / Al ratio of 160) molecular sieve as the catalyst, with the other conditions the same as in Example 79, after 6 h of reaction, the conversion rate of cyclopentanone decreased to 65%, and the total selectivity of the target products methyl indenman and tetrahydronaphthalene also decreased to 70%.

[0073] Comparative Example 2

[0074] Cyclohexanone was used instead of cyclopentanone as the raw material, and 1.0 μm H-ZSM-5 molecular sieve (Si / Al ratio of 160) was used as the catalyst. The other conditions were the same as in Example 79. After 6 h of reaction, the conversion rate of cyclohexanone decreased to 60%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 68%.

[0075] Comparative Example 3

[0076] Using 2,5-hexanedione instead of cyclopentanone as the raw material, and 1.0 μm H-ZSM-5 molecular sieve (Si / Al ratio of 160) as the catalyst, with the other conditions the same as in Example 79, after 6 h of reaction, the conversion rate of 2,5-hexanedione decreased to 57%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 64%.

[0077] Comparative Example 4

[0078] Using methylcyclopentanone instead of cyclopentanone as the raw material, and 1.0 μm H-ZSM-5 (Si / Al ratio of 160) molecular sieve as the catalyst, with the other conditions the same as in Example 79, after 6 h of reaction, the conversion rate of methylcyclopentanone decreased to 51%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 59%.

[0079] Comparative Example 5

[0080] Using methylcyclopentenone instead of cyclopentanone as the raw material, and 1.0 μm H-ZSM-5 (Si / Al ratio of 160) molecular sieve as the catalyst, with the other conditions the same as in Example 79, after 6 h of reaction, the conversion rate of methylcyclopentenone decreased to 52%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 61%.

[0081] Comparative Example 6

[0082] Using methylcyclohexanone instead of cyclopentanone as the raw material, and 1.0 μm H-ZSM-5 molecular sieve (Si / Al ratio of 160) as the catalyst, with the other conditions being the same as in Example 79, after 6 h of reaction, the conversion rate of cyclohexanone decreased to 65%, and the selectivity of the target product tetramethyltetrahydronaphthalene also decreased to 62%.

Claims

1. The application of nano-molecular sieves in the preparation of tetrahydronaphthalene, methylindenhydride, dimethyltetrahydronaphthalene, or tetramethyltetrahydronaphthalene, characterized in that, The process is as follows: using nano-molecular sieves as catalysts, biomass ketones undergo aldol condensation / rearrangement / aromatization reactions in a fixed-bed continuous reactor to achieve the renewable and continuous synthesis of polycyclic aromatic hydrocarbons. The nano-molecular sieve catalyst is one or more of the following nano-sized molecules: H-ZSM-5, H-USY, HY, H-β, H-MOR, H-ZSM-35, H-MCM-22, H-ZSM-22, and H-ZSM-11. The biomass ketones are one or more of cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone, methylcyclopentenone and methylcyclohexanone; The reaction temperature in the fixed-bed reactor is 300-600℃; The reaction gas in the fixed-bed reactor is one of nitrogen, helium or argon, and the pressure is 0.0001-1 MPa.

2. The application according to claim 1, characterized in that: The molar silicon-to-aluminum ratio of the nanomolecular sieve is 2-500.

3. The application according to claim 1, characterized in that: The size of the nanomolecular sieve catalyst is 10-100 nm.

4. The application according to claim 1, characterized in that: The molar ratio of gas to biomass ketones in the fixed-bed reactor is 10-400:

1.

5. The application according to claim 1, characterized in that: The space velocity (WHSV) of biomass ketones in a fixed-bed reactor is 0.01–10 h⁻¹. -1 .

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