Long-chain linear terminal alkene aromatisation catalysed by ruthenium supported on solids

Abstract

The present invention discloses a method for the synthesis of alkylated benzenes, such as xylene and ethylbenzene, with yields greater than 50%, by means of the isomerisation, cyclisation and dehydrogenation of the corresponding long-chain linear terminal alkenes on ruthenium catalytic species supported on solids. The method comprises at least the following steps: - A first step in which the long-chain linear terminal alkene is put into contact with a supported ruthenium catalyst. - A second step of heating the obtained mixture. - A third step of recovering the product and the catalyst using washing and filtration.

Description

[0001] AROMATIZATION OF TERMINAL AND LINEAR LONG-CHAIN ​​ALKENES CATALYZED BY SOLID-SUPPORTED RUTHENIUM

[0002] DESCRIPTION

[0003] FIELD OF INVENTION

[0004] The present invention describes a process for the synthesis of alkylated benzenes, such as xylenes and ethylbenzene, with yields greater than 50%, by means of the isomerization, delamination and dehydrogenation of the corresponding long-chain linear terminal alkenes over ruthenium catalytic species supported on solids.

[0005] BACKGROUND

[0006] Methylated and ethylated benzene derivatives are essential industrial products for the welfare state, as they are needed in a variety of processes from fuels to precursors in detergents, polymerization, pharmaceuticals, and many other industrial uses. Currently, methylated and ethylated benzene derivatives are synthesized by petrochemical catalytic cracking from fossil sources, so modern industry demands alternative processes to obtain these types of compounds. One possibility is the use of long-chain linear compounds, such as C8 octane, which can be dehydrogenated and cyclized by a catalyst to obtain the corresponding aromatic C8 compounds, which include the three isomers of xylene and ethylbenzene (Chemistry Letters (1985), (10), 1483-6; Nature Chemistry (2011), 3(2), 167-171 ;

[0007] Catalysis Science & Technology (2014), 4(12), 4378-4385; Applied Catalysis, A: General (2013), 456, 105-117; Applied Catalysis, A: General (2012), 447-448, 135-143; Journal of Catalysis 218 (2003) 12-23; Catal. Sci. Technol. 2023, 13, 1677-1685). However, this process is plagued with a large number of side reactions arising from the use of acidic / basic solids as catalysts and the high temperature required to produce the reaction, of more than 500 0 C (WG2001047841 A1 (2001); Journal of Molecular Catalysis A: Chemical (2014), 395, 398-408; Journal of Catalysis (2016), 340, 66-75; Applied Catalysis, A: General (2012), 421-422, 58-69), which makes the process extremely inefficient.

[0008] The reaction mechanisms for octane described to date appear to demonstrate that one of the most important intermediates in the reaction is the corresponding terminal alkene (1-octene), which dehydrogenates and cyclizes to the corresponding desired aromatic compounds more readily than octane (Journal of Molecular Catalysis A: Chemical (2004), 210(1-2), 211-216). Interestingly, 1-octene is currently a cheaper and more widely available compound than octane itself, since the telomerization reaction of butadiene, recently implemented industrially in multitonnes per year (Org. Process Res. Dev. 2019, 23, 1654-1658; EP 3080136 (2020)), allows the direct production of 1-octene without the need to go through octane (Angew. Chem. Int. Ed. 2009, 48, 3598-3614; ChemCatChem 2019, 11, 1153-1166). In fact, the latter is obtained by catalytic hydrogenation of the former.Therefore, it seems convenient to use 1-octene as a starting material instead of octane, which however has hardly been studied in the literature. This lack of studies on the aromatization of 1-octene, and also of other related long-chain terminal alkenes, is largely due to the ease with which the defined functional group undergoes undesired reactions at the high reaction temperatures currently required with strong Lewis acid / base based catalysts, such that the linear alkene chain is broken to form mostly cracking products, which then react with each other to form a wide variety of undesired products (Journal of Catalysis (1976), 42(2), 247-56; Microporous and Mesoporous Materials 119 (2009) 18-2; Catal. Sci. Technol., 2019, 9, 7034-7044).In fact, the few publications that we can find in the literature about the aromatization of 1-octene show that the best yield to xylenes and ethylbenzene obtained to date does not exceed 30%, after complete conversion of the alkene (Fuel 87 (2008) 3660-3663). ISOMERIZATION. u sopor ao

[0009] (catalytic)

[0010] Scheme 1: Catalytic route presented here for the synthesis of xylenes and ethylbenzene by aromatization of 1-octene with supported ruthenium catalysts.

[0011] Supported ruthenium species have recently been described to catalyze the isomerization of terminal alkenes to internal alkenes without the need for ligands or solvents (Nature Communications (2022) 13:2831). Thus, a catalyst with solid-supported ruthenium would be expected to be able to transform 1-octene (or other long-chain terminal alkenes) in the gas phase to the corresponding internal alkene, which could then undergo dehydrogenations to cyclize and form the final aromatic, all of these processes also catalyzed by the supported ruthenium.This new synthetic and catalytic strategy would allow the aromatization reaction of long-chain terminal alkenes to be carried out at moderate temperatures, around 300 °C, in the absence of strong acidic or basic species, thus avoiding the vast majority of undesired reactions associated with high reaction temperatures and aggressive catalytic species, which lead to cracking reactions, over-hydrogenations, or over-alkylation of the aromatic ring with the alkene itself (Friedel-Crafts). Figure 1 shows the synthetic scheme of our methodology presented here. Note that only the recent discovery of the facile isomerization of terminal alkenes with neutral ruthenium-supported species allows us to venture the success of the aromatization of long-chain linear alkenes (ES2929364 (2021)).However, this approach does not consider dehydrogenation and aromatization among the possible reactions following isomerization. The third step is epoxidation, bromination, and diacetoxylation, three examples proposed if the second reaction yields the cis and trans isomers of methyl isoeugenol. The aromatization of alkenes has also been addressed in other processes using catalysts such as H-ZSM-5 or GaH-ZSM-5 zeolites, which oligomerize the define and then cyclize it to obtain the corresponding aromatic compound naphthene (W02009079213A2). Alternatively, metal oxides with molecular oxygen can be used, which dimerizes the define to the diene and then cyclizes it to the corresponding aromatic compound. However, these approaches are completely different from the one proposed here because they involve intermolecular reactions of the alkene.Alternatively, once the 3 to 6 carbon atom define has been obtained, dehydrogenation is carried out to obtain a di or polyolefin (US2011172475A1), as in the isomerization process of isobutene into linear butenes, but in different steps and not in a single step. Selectivities for obtaining p-xylene of 90% are included if isooctane is used as raw material, not the alkene, also considering as an alternative dehydration and cycling under reducing conditions using hydrogenation catalysts to obtain hydrogen as a co-product. Other compound catalysts have been used for the aromatization of 3 to 8 carbon atom defines, and they can be regenerated in situ with hydrogen and water vapor (US2011257452A1). Reaction conditions include a temperature of 350-650°C, a pressure of 30-300 psi, and a weight hourly space velocity of 0.3 to 10 hours.A second aromatization step, the interconversion of defins, is detailed, including isomerization, oligomerization, and defination cleavage to form naphthene. In a third step, cycloalkanes are dehydrogenated by delamination and hydrogen transfer to form the corresponding aromatic compounds. These synthetic strategies are fundamentally different from the single-step catalytic approach from 1-octene.

[0012] The synthetic strategy shown in Figure 1 , based on non-aggressive catalytic species (neither acidic nor basic), also allows the use of amorphous supports without restrictions to molecular trafficking, which are very common in the current processes described for 1-octane (Applied Catalysis, A: General (2010), 386(1-2), 201-210; Russian Journal of Inorganic Chemistry (2011), 56(2), 168-172). These catalytic solids based on acids / bases and micropores facilitate the cracking processes, while Ru on amorphous solids will present even higher activity on long-chain alkenes than on short-chain alkenes, something unusual for acid catalysts and that will allow the selective aromatization of long-chain terminal alkenes without side reactions.

[0013] DESCRIPTION OF THE INVENTION

[0014] The present invention describes a process for the synthesis of alkylated benzenes, such as xylenes and ethylbenzene, with yields greater than 50%, by means of the isomerization, delamination and dehydrogenation of the corresponding long-chain linear terminal alkenes on solid-supported ruthenium catalytic species, comprising at least the following steps:

[0015] - A first aromatization stage in which the long-chain linear terminal alkene is contacted with a supported ruthenium catalyst and heated.

[0016] - A second stage of recovery of the product and the catalyst by washing and filtration, using any method such as with an apolar organic solvent (such as acetone, hexane) and gravity or vacuum filtration on paper or filter glass.

[0017] In the first step of the process, the long-chain linear terminal alkene is aromatized. Three reactions take place in this aromatization step: isomerization, delamination, and dehydrogenation of the long-chain linear terminal alkene, which are selectively transformed into the desired aromatics. This avoids the vast majority of undesired reactions associated with high reaction temperatures and aggressive catalytic species, which lead to cracking, over-hydrogenation, or over-alkylation of the aromatic ring with the alkene itself. In other words, in addition to the fact that the process described here is different from other known processes, it also presents clear practical advantages. For example, the recovery of the aromatic product and the catalyst is more efficient, clean, and simpler, and no intermolecular reactions of the alkene are required. All of this results in a process yield greater than 50%.

[0018] According to a particular embodiment of the present invention, the amount of long-chain linear terminal alkene that the mixture may contain is in amounts between 1%-100% by weight, preferably between 80%-100%.

[0019] According to another particular embodiment of the present invention, the linear terminal alkene chain is comprised between 7 and 16 carbon atoms, preferably between 8 and 12 carbon atoms, and particularly with 8 carbon atoms (1-octene). Finally, 1-octene can come from different sources and compositions selected from Ce-Cie mixtures, bioalkenes and combinations thereof.

[0020] According to another particular embodiment, the proportion of inert gas (nitrogen or argon) will be between 0% and 99%, preferably between 0% and 20%.

[0021] As previously mentioned, the process of the present invention requires a supported ruthenium catalyst, preferably ruthenium on carbon. Furthermore, the ruthenium may be supported or intimately mixed with compatible solids. A compatible solid is defined as one that supports and / or activates the ruthenium for the reaction. Examples of such solids include inorganic oxides and activated carbon as supports. The amount of supported ruthenium in the present invention can range from 0.01% to 10% by weight of ruthenium relative to the support.

[0022] According to a particular embodiment of the present invention, the reaction temperature may be between 200 and 350 °C, preferably between 280 and 320 °C.

[0023] According to a particular embodiment of the present invention, the reaction can be carried out under pressures between 1 and 20 bars, preferably 2 to 5 bars.

[0024] According to another particular embodiment of the present invention, the reaction can be carried out in a flow reactor, loaded with the catalyst and passing the reagent in the gas phase, at temperatures between 200 and 300 °C and with a contact time between 0.1 and 48 h.

[0025] The present invention also relates to the product obtained according to the process described above for 1-octene as the starting alkene.

[0026] Thus, the product is a mixture of xylenes (ortho-, meta- and para) and ethylbenzene in molar proportions of 1:9 to 9:1, preferably 5:5.

[0027] Throughout the description and claims, the word "comprise" and its variants are not intended to exclude other technical features, additives, components, or steps. For those skilled in the art, other objects, advantages, and features of the invention will be apparent partly from the description and partly from the practice of the invention.

[0028] BRIEF DESCRIPTION OF THE FIGURES

[0029] Figure 1: Catalytic conversion results for the reaction of different terminal alkenes with Ru / C as catalyst in a tubular reactor at 200 °C.

[0030] Figure 2: Catalytic results for the reaction of 1-octene with Ru / C as catalyst in a tubular reactor at 200 °C.

[0031] Figure 3: Catalytic results for the reaction of 1-decene with Ru / C as catalyst in a tubular reactor at 200 °C.

[0032] Figure 4: Catalytic results for the reaction of 1-octene with Ru / C as catalyst in a tubular reactor at 300 °C.

[0033] Figure 5: Catalytic results for the reaction of 1-decene with Ru / C as catalyst in a tubular reactor at 300 °C.

[0034] EXAMPLES Non-limiting examples of the present invention are detailed below:

[0035] Example 1: Reaction procedure in a tubular reactor with ruthenium-on-carbon catalyst for different linear alkenes at 200 °C.

[0036] Gas-phase isomerization was studied for terminal definites C4, C6, C8, and C10. The reactions were carried out in a packed-bed reactor with 100 mg Ru / C (5 wt%) at a total flow rate of 5 mL / min, using N2 as an inert vehicle. The C4 and C6 isomerization reactions were followed by on-line GC, and the C8 and C10 isomerization reactions were followed by NMR, collecting the products in a cold trap at the reactor outlet. The molar flow rates of the reactants were maintained at 0.033 mmol / min for 1-butene and 1-hexene, and reduced to 0.014 mmol / min for 1-octene and 1-decene due to the limitations of the saturation temperatures in the bubbler. 1-Butene was fed to the reactor by mixing a pure stream of the define from a pressurized cylinder with pure N2. 1-Hexene, 1-Octene, and 1-Decene were fed to the reactor by saturation of the N2 carrier in a bubbler, at 15 °C, 65 °C, and 95 °C, respectively.The reactor was purged for 30 min with 20 ml / min of N2 after loading the catalyst and then heated to 200 °C. The catalyst was placed in the center of the reactor tube, packed between some glass wool.

[0037] The conversion results obtained are shown in Figure 1. As can be seen, short-chain terminal alkenes (1-butene and 1-hexene) rapidly poison the Ru / C catalyst after rapid conversion, while long-chain terminal alkenes (1-octene and 1-decene) maintain a relatively stable conversion over time.

[0038] Figure 2 shows the selectivity results for 1-octene at the reaction conditions described above. It can be seen that the only reaction products found are the corresponding isomerized internal alkenes, demonstrating that the Ru / C-catalyzed reaction in the tubular reactor follows the pathway proposed in Scheme 1. Figure 3 shows the selectivity results for 1-decene at the reaction conditions described above. It can be seen that the only reaction products found are the corresponding isomerized internal alkenes, demonstrating also for 1-decene that the Ru / C-catalyzed reaction in the tubular reactor follows the pathway proposed in Scheme 1.

[0039] Example 2: Reaction procedure in a tubular reactor with ruthenium-on-carbon catalyst for 1-octene at 300 °C.

[0040] The gas-phase isomerization of 1-octene (C8) was studied. The reaction was carried out in a packed bed reactor containing 100 mg Ru / C (5% by weight) at a total flow rate of 5 ml / min, using N2 as an inert carrier, and the reaction was monitored by NMR, with products collected in a cold trap at the reactor outlet. The molar flow rate of the reactant was maintained at 0.014 mmol / min by saturating the N2 carrier in a bubbler at 65 °C. The reactor was purged for 30 min with 20 ml / min of N2 after loading the catalyst and then heated to 300 °C. The catalyst was placed in the center of the reactor tube, packed between glass wool.

[0041] Figure 4 shows the selectivity results for 1-octene under the reaction conditions described above (300 °C). It can be seen that the aromatic products xylenes + ethylbenzene are the majority after only 50 minutes of reaction, with a yield of 60%. This is more than double the yield currently reported in the literature (Fuel 87 (2008) 3660-3663).

[0042] Example 3: Reaction procedure in a tubular reactor with ruthenium-on-carbon catalyst for 1-decene at 300 °C.

[0043] The gas-phase isomerization of 1-decene (C10) was studied. The reaction was carried out in a packed bed reactor containing 100 mg Ru / C (5% by weight) at a total flow rate of 5 ml / min, using N2 as an inert carrier, and the reaction was monitored by NMR, with products collected in a cold trap at the reactor outlet. The molar flow rate of the reactant was maintained at 0.014 mmol / min by saturating the N2 carrier in a bubbler at 95 °C. The reactor was purged for 30 min with 20 ml / min of N2 after loading the catalyst and then heated to 300 °C. The catalyst was placed in the center of the reactor tube, packed between some glass wool. Figure 5 shows the selectivity results for 1-decene at the reaction conditions described above (300 °C). It can be observed that C10 aromatic products, including naphthalenes and indenes, are the majority throughout the reaction, with a yield of 56% after 50 min of reaction.Here, some minor cleavage products are already observed, always below 15%, and decane as the main unwanted product, originating from the hydrogenation reaction of decenes with the hydrogen released in the dehydrogenation processes.

Claims

CLAIMS 1. Procedure for the synthesis of alkylated benzenes from the corresponding alkenes, characterized in that it comprises at least the following steps: - A first aromatization step in which a long-chain linear terminal alkene is contacted with a supported ruthenium catalyst and heated, - A second stage of recovery of the product and the catalyst by washing and filtration.

2. Process for the synthesis of alkylated benzenes, according to claim 1, characterized in that in the first aromatization stage the 3 reactions of isomerization, delamination and dehydrogenation of the long-chain linear terminal alkene occur selectively to the desired aromatics.

3. Process for the synthesis of alkylated benzenes, according to claims 1 and 2, with yields greater than 50%, by means of the isomerization, delamination and dehydrogenation in one step of the corresponding long-chain linear terminal alkenes on catalytic ruthenium species supported on solids.

4. Method for the synthesis of alkylated benzenes, according to any of claims 1 to 3, characterized in that the amount of long-chain linear terminal alkene that the mixture may contain is in quantities between 1%-100% by weight, preferably between 80%-100%.

5. Method for the synthesis of alkylated benzenes, according to any of claims 1 to 4, characterized in that the linear terminal alkene chain comprises between 7 and 16 carbon atoms.

6. Method for the synthesis of alkylated benzenes, according to claim 5, characterized in that the linear terminal alkene chain comprises between 8 and 12 carbon atoms.

7. Method for the synthesis of alkylated benzenes, according to any of claims 5 to 6, characterized in that the linear terminal alkene chain is formed in particular by 8 carbon atoms (1-octene).

8. Process for the synthesis of alkylated benzenes, according to claim 7, characterized in that the 1-octene comes from different sources and compositions selected from Ce-Cie mixtures, bioalkenes and combinations thereof.

9. Method for the synthesis of alkylated benzenes, according to any of the preceding claims, characterized in that the proportion of inert gas (nitrogen or argon) will be between 0% and 99%, preferably between 0% and 20%.

10. Process for the synthesis of alkylated benzenes, according to any of the preceding claims, characterized in that a ruthenium catalyst supported on compatible solids selected from inorganic oxide or activated carbon, as well as combinations thereof, is used.

11. Process for the synthesis of alkylated benzenes, according to claim 10, characterized in that the amount of supported ruthenium ranges from 0.01% to 10% by weight of ruthenium with respect to the support.

12. Process for the synthesis of alkylated benzenes, according to the preceding claims, characterized in that the reaction temperature is between 200 and 380 °C.

13. Process for the synthesis of alkylated benzenes, according to claim 12, characterized in that the reaction temperature is between 280 and 320 °C.

14. Method for the synthesis of alkylated benzenes, according to any of the preceding claims, characterized in that the reaction is carried out under pressures between 1 and 20 bars.

15. Method for the synthesis of alkylated benzenes according to any of the preceding claims, characterized in that it is carried out in a continuous tubular reactor.

16. Method for the synthesis of alkylated benzenes according to claim 15, characterized in that it is carried out in a reactor loaded with the catalyst, the reagent and inert gas with a contact time between 0.1 and 48 h.

17. Process for the synthesis of alkylated benzenes, according to any of the preceding claims, characterized in that the long-chain linear terminal alkene is 1-octene and the product recovered in step 3 is a mixture of xylenes (ortho-, meta- and para) and ethylbenzene in molar proportions of 1:9 to 9:

1.

18. Process for the synthesis of alkylated benzenes, according to claim 17, characterized in that the molar proportions of the mixture of xylenes (ortho-, meta- and para) and ethylbenzene is 5:5.

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