Use of base-treated molecular sieves in polycyclic aromatic hydrocarbon production processes

Abstract

This invention relates to the field of biomass catalytic conversion technology, and more specifically, to the application of an alkali-treated molecular sieve in the preparation of polycyclic aromatic hydrocarbons (PAHs). Using an alkali-treated molecular sieve as a catalyst, biomass ketones undergo aldol condensation / rearrangement / aromatization reactions in a fixed-bed reactor to synthesize PAHs in one step. The process route of this invention is simple and convenient to operate. Biomass ketones can be efficiently synthesized into renewable PAHs through a cascade of aldol condensation / rearrangement / aromatization reactions catalyzed by an alkali-treated molecular sieve. The reaction conditions of this invention are mild, the catalyst is inexpensive and readily available, and exhibits good catalytic performance. The conversion rate of biomass ketones is above 90%, the selectivity for PAHs is above 70%, and the catalyst exhibits good stability, showing no deactivation after 48 hours. This provides a novel approach for the sustainable synthesis of renewable PAHs from lignocellulose.

Description

Technical Field

[0001] This invention relates to the field of biomass catalytic conversion technology, and more particularly to the application of an alkali-treated molecular sieve in the preparation of 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), and has developed a series of routes for the efficient utilization of biomass and its platform compounds. Cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone, and methylcyclopentenone 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, resulting in a sharp decrease in both the cyclopentanone conversion rate and the yield of the target product. 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 an alkali-treated molecular sieve catalyst.

[0006] This invention uses alkali-treated molecular sieves as catalysts, and biomass ketones are used in a fixed-bed reactor to achieve continuous, efficient and green synthesis of polycyclic aromatic hydrocarbons through aldol condensation, rearrangement and subsequent dehydration aromatization reactions.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] An application of an alkali-treated molecular sieve in the preparation of polycyclic aromatic hydrocarbons (PAHs) involves using the alkali-treated molecular sieve as a catalyst to synthesize PAHs in one step via aldol condensation / rearrangement / aromatization reactions of biomass ketones in a fixed-bed reactor.

[0009] Based on the above scheme, preferably, the biomass ketones are one or more of cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone, and methylcyclopentenone.

[0010] The chemical structural formulas of the above-mentioned raw material biomass ketones and target product polycyclic aromatic hydrocarbons are shown in Table 1.

[0011] Table 1. Structural formulas of ketones from raw biomass and polycyclic aromatic hydrocarbons from target products.

[0012]

[0013]

[0014] Based on the above scheme, preferably, the molecular sieve 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.

[0015] Based on the above scheme, preferably, the molar silicon-to-aluminum ratio of the molecular sieve is 2-1000, more preferably 5-900, and even more preferably 5-800.

[0016] Based on the above scheme, preferably, the alkali used in the alkali treatment includes an inorganic alkali or an organic alkali; the inorganic alkali includes one of NaOH, KOH, Ca(OH)2, Na2CO3, K2CO3, NaHCO3, and KHCO3, and the organic alkali includes one of tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0017] Based on the above scheme, preferably, the concentration of the inorganic base is 0.01-5M, more preferably 0.1-4M, and even more preferably 0.2-3M; the concentration of the organic base is 0.01-5M, more preferably 0.1-4M, and even more preferably 0.2-3M.

[0018] Based on the above scheme, preferably, the treatment temperature using inorganic alkali is 30-150℃, more preferably 40-120℃, and even more preferably 50-100℃; the treatment temperature using organic alkali is 100-200℃, more preferably 120-190℃, and even more preferably 140-180℃.

[0019] Based on the above scheme, preferably, the treatment time using inorganic alkali is 0.5-6h, more preferably 0.5-4h, and even more preferably 0.5-2h; the treatment time using organic alkali is 12-96h, more preferably 18-84h, and even more preferably 24-72h.

[0020] Based on the above scheme, preferably, the reaction temperature in the fixed-bed reactor is 300-600℃, more preferably 350-500℃, and even more preferably 375-475℃.

[0021] Based on the above scheme, preferably, the reaction gas in the fixed-bed reactor is one of nitrogen, helium, and argon.

[0022] Based on the above scheme, preferably, the reaction pressure in the fixed-bed reactor is 0.0001-1 MPa, more preferably 0.0001-0.8 MPa, and even more preferably 0.0001-0.5 MPa.

[0023] Based on the above scheme, preferably, the molar ratio of reactant gas to biomass ketones in the fixed-bed reactor is 10-400:1, more preferably 20-300:1, and even more preferably 30-200:1.

[0024] Based on the above scheme, preferably, the space velocity of biomass ketones in the fixed-bed reactor is 0.01-10 h⁻¹. -1 Preferably 0.05-8h -1 More preferably 0.1-4h -1 .

[0025] This invention enables the 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.

[0026] The beneficial effects of this invention are:

[0027] 1. The process route of this invention is simple and easy to operate. Biomass ketones can be efficiently synthesized into renewable polycyclic aromatic hydrocarbons through cascade aldol condensation / rearrangement / aromatization reactions under the catalysis of alkaline-treated molecular sieves.

[0028] 2. The reaction conditions of this invention are mild, the catalyst is inexpensive and readily available, and the catalytic performance is good. The conversion rate of biomass ketones is over 90%, the selectivity of polycyclic aromatic hydrocarbons is over 70%, and the catalyst has good stability, with no deactivation observed after 48 hours. This invention provides a new approach for the sustainable synthesis of renewable polycyclic aromatic hydrocarbons from lignocellulose.

[0029] 3. 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

[0030] Figure 1 The above are gas chromatograms of the synthesis of polycyclic aromatic hydrocarbons from biomass ketones, where a is a sample of cyclopentanone and b is a sample of cyclohexanone.

[0031] Figure 2 The mass spectra of the target product, polycyclic aromatic hydrocarbon, are shown below: a is methylindene, b is tetrahydronaphthalene, and c is dimethyltetrahydronaphthalene. Detailed Implementation

[0032] 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.

[0033] 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. Alkali-treated 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.

[0034] Examples 1-10

[0035] Investigation of the reactivity of different biomass ketones in the synthesis of polycyclic aromatic hydrocarbons:

[0036] 0.6 g of alkali-treated molecular sieve catalyst 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 biomass ketone hourly 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.

[0037] Table 2. Reactivity of different biomass ketones in the synthesis of polycyclic aromatic hydrocarbons.

[0038]

[0039]

[0040] The data in Table 2 show that different biomass ketones can be efficiently synthesized into polycyclic aromatic hydrocarbons on alkaline-treated molecular sieve catalysts. Although the selectivity of the target products varied slightly, all biomass ketones were completely converted, and all the tested alkaline-treated molecular sieve catalysts exhibited good stability, with their activity remaining unchanged after 48 hours.

[0041] Examples 11-43

[0042] Using cyclopentanone as a raw material, the effects of different alkali treatments on the reaction activity of molecular sieve catalysts were investigated:

[0043] 0.6 g of alkali-treated molecular sieve catalyst 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 subjected to 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.

[0044] Table 3. Reactivity of molecular sieve catalysts with different alkali treatments for the synthesis of methylindene and tetrahydronaphthalene from cyclopentanone.

[0045]

[0046]

[0047]

[0048]

[0049] The data in Table 3 show that the different alkali-treated molecular sieve catalysts listed in the table all have good effects on the synthesis of methylindane and tetrahydronaphthalene from cyclopentanone. The initial silica-alumina ratio of the molecular sieve also has a certain influence on the conversion rate of cyclopentanone and the total selectivity of methylindane and tetrahydronaphthalene. Under the action of alkali-treated H-ZSM-5(160) molecular sieve (0.5M NaOH, 80℃, 1h) catalyst, complete conversion of cyclopentanone can be achieved, and the total selectivity of the target products methylindane and tetrahydronaphthalene reaches 89%. After 48h of reaction, the conversion rate of cyclopentanone remains at 100%, and the total selectivity of the target products methylindane and tetrahydronaphthalene remains unchanged.

[0050] Examples 42-80

[0051] Using cyclopentanone as a raw material, the effect of alkali treatment conditions on the catalytic activity of alkali-treated molecular sieve catalysts was investigated: 0.6 g of H-ZSM-5 (Si / Al ratio 160) molecular sieve catalysts treated under different alkali conditions were 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 subjected to 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.

[0052] Table 4. Effects of alkali treatment conditions on the catalytic activity of alkali-treated molecular sieve catalysts

[0053]

[0054]

[0055]

[0056]

[0057] The data in Table 4 show that the alkaline treatment conditions have a significant impact on the conversion rate of cyclopentanone and the total selectivity of methyl indenman and tetrahydronaphthalene. Using alkaline-treated H-ZSM-5(160) molecular sieve (0.5M NaOH, 80℃, 1h) as a catalyst, cyclopentanone can be completely converted, and the total selectivity of the target products methyl indenman and tetrahydronaphthalene is as high as 89%. The catalyst performance remains unchanged after 48h of reaction.

[0058] Examples 81-90

[0059] The effect of reaction temperature on the synthesis of methyl indane and tetrahydronaphthalene from cyclopentanone was investigated using an alkali-treated H-ZSM-5(160) molecular sieve catalyst: 0.6 g of the alkali-treated H-ZSM-5(160) molecular sieve catalyst (0.5 M NaOH, 80°C, 1 h) 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. 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 specified conditions, and the experimental results are shown in Table 5.

[0060] Table 5. Effect of temperature on the reaction activity of alkali-treated H-ZSM-5(160) molecular sieve catalyst.

[0061]

[0062] The data in Table 5 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 alkali-treated H-ZSM-5(160) molecular sieve (0.5M NaOH, 80, 1h) as a catalyst, cyclopentanone can be completely converted at 425℃, with a total selectivity of up to 90% for the target products methylindane and tetrahydronaphthalene. The catalyst performance remains unchanged after 48h of reaction.

[0063] Examples 91-98

[0064] The effect of gas pressure on the synthesis of methyl indane and tetrahydronaphthalene from alkali-treated H-ZSM-5(160) molecular sieve catalyst was investigated: 0.6 g of the alkali-treated H-ZSM-5(160) molecular sieve catalyst (0.5 M NaOH, 80, 1 h) 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 molar ratio of gas to cyclopentanone was controlled at 40:1, and the hourly space velocity of cyclopentanone was 0.4 h⁻¹. -1 The reaction was then carried out under different gas pressures, and the experimental results are shown in Table 6.

[0065] Table 6. Effect of gas pressure on the reaction activity of alkali-treated H-ZSM-5(160) molecular sieve catalyst.

[0066]

[0067] The data in Table 6 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.

[0068] Examples 99-110

[0069] The effect of the molar ratio of gas to cyclopentanone on the synthesis of methyl indenhydride and tetrahydronaphthalene from alkali-treated H-ZSM-5(160) molecular sieve catalyst was investigated: 0.6 g of the alkali-treated H-ZSM-5(160) molecular sieve catalyst (0.5 M NaOH, 80, 1 h) 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 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 7.

[0070] Table 7. Effect of the molar ratio of gas to cyclopentanone on the alkaline-treated H-ZSM-5(160) molecular sieve on the reactivity.

[0071]

[0072] As can be seen from the data in Table 7, under the same conditions, whether it is nitrogen or argon, the molar ratio of the gas to cyclopentanone has little effect on the reaction of cyclopentanone to methyl indenium and tetrahydronaphthalene.

[0073] Examples 111-121

[0074] The effect of cyclopentanone hourly space velocity on the synthesis of methyl indane and tetrahydronaphthalene from cyclopentanone was investigated using an alkali-treated H-ZSM-5(160) molecular sieve catalyst: A certain amount of the alkali-treated H-ZSM-5(160) molecular sieve catalyst (0.5M NaOH, 80, 1h) 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. The gas was set as nitrogen, 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 cyclopentanone hourly space velocities. The experimental results are shown in Table 8.

[0075] Table 8. Effect of space velocity of cyclopentanone on the reaction activity of alkali-treated H-ZSM-5(160) molecular sieve catalyst.

[0076]

[0077] The data in Table 8 show that, under the same conditions, the space velocity (WHV) of cyclopentanone has a significant impact on the conversion of cyclopentanone to methylindenhydride and tetrahydronaphthalene. Increasing the WHV of cyclopentanone will improve the overall selectivity of methylindenhydride and tetrahydronaphthalene to some extent, but excessively high WHV of cyclopentanone will reduce the reactivity, and both the conversion rate of cyclopentanone and the overall selectivity of methylindenhydride and tetrahydronaphthalene will decrease significantly.

[0078] Example 122

[0079] Cyclohexanone was used instead of cyclopentanone as a raw material, and the reaction was carried out under the same conditions as in Example 114. Cyclohexanone was completely converted, and the selectivity of the target product dimethyltetrahydronaphthalene reached 89%.

[0080] Example 123

[0081] 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 86%.

[0082] Example 124

[0083] Using methylcyclopentanone instead of cyclopentanone as a 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 85%.

[0084] Example 125

[0085] Using methylcyclopentenone instead of cyclopentanone as a 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 84%.

[0086] Comparative Example 1

[0087] Using cyclopentanone as the raw material and untreated H-ZSM-5(160) molecular sieve as the catalyst, with the remaining conditions the same as in Example 114, after 6 hours of reaction, the conversion rate of cyclopentanone decreased to 65%, and the total selectivity of the target products methylindane and tetrahydronaphthalene also decreased to 70%.

[0088] Comparative Example 2

[0089] Cyclohexanone was used instead of cyclopentanone as the raw material, and H-ZSM-5(160) molecular sieve without alkali treatment was used as the catalyst. The other conditions were the same as in Example 114. After 6 hours of reaction, the conversion rate of cyclohexanone decreased to 60%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 68%.

[0090] Comparative Example 3

[0091] Using 2,5-hexanedione instead of cyclopentanone as the raw material, and H-ZSM-5(160) molecular sieve without alkali treatment as the catalyst, with the other conditions the same as in Example 79, after 6 hours of reaction, the conversion rate of 2,5-hexanedione decreased to 58%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 65%.

[0092] Comparative Example 4

[0093] Using methylcyclopentanone instead of cyclopentanone as the raw material, and H-ZSM-5(160) molecular sieve without alkali treatment as the catalyst, the remaining conditions were the same as in Example 79. After 6 hours of reaction, the conversion rate of methylcyclopentanone decreased to 50%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 60%.

[0094] Comparative Example 5

[0095] Using methylcyclopentenone instead of cyclopentanone as the raw material, and untreated H-ZSM-5(160) molecular sieve as the catalyst, with the other conditions the same as in Example 79, after 6 hours of reaction, the conversion rate of methylcyclopentenone decreased to 52%, and the selectivity of the target product dimethyltetrahydronaphthalene also decreased to 62%.

[0096] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. Use of an alkali-treated molecular sieve in a process for the preparation of methylindane, tetrahydronaphthalene, dimethyltetrahydronaphthalene, characterized in that The biomass ketones are one or more of cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone and methylcyclopentenone. The biomass ketones are one or more of cyclopentanone, cyclohexanone, 2,5-hexanedione, methylcyclopentanone and methylcyclopentenone. The molecular sieve includes one or more of 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 base used in the base treatment includes an inorganic base or an organic base, the inorganic base includes one of NaOH, KOH, Ca(OH)2, Na2CO3, K2CO3, NaHCO3 and KHCO3, and the organic base includes one of tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. The reaction temperature in the fixed bed reactor is 300-600℃, and the space velocity of the biomass ketone is 0.01-10h -1 .

2. Use according to claim 1, characterized in that: The molar silicon-to-aluminum ratio of the molecular sieve is 2-1000.

3. Use according to claim 1, characterized in that: The concentration of the inorganic base is 0.01-5M, and the concentration of the organic base is 0.01-5M.

4. Use according to claim 1, characterized in that: The treatment temperature using the inorganic base is 30-150℃, and the treatment time is 0.5-6h; the treatment temperature using the organic base is 100-200℃, and the treatment time is 12-96h.

5. Use according to claim 1, characterized in that: The reaction pressure in the fixed bed reactor is 0.0001-1MPa.

6. Use according to claim 5, characterized in that: The reaction gas in the fixed bed reactor is one of nitrogen, helium or argon, and the molar ratio of the reaction gas to the biomass ketones in the fixed bed reactor is 10-400:1.

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