Cross-aldol condensation of alkylaldehydes using solid-supported Brønsted acid catalysts

Abstract

A process for cross-aldol condensation of alkylaldehydes comprises providing a reaction mixture containing a first alkylaldehyde and a second alkylaldehyde, wherein the first alkylaldehyde has fewer carbon atoms than the second alkylaldehyde, and the feedstock has a molar ratio of 1:1 or greater between the first alkylaldehyde and the second alkylaldehyde; contacting the reaction mixture with a solid-supported Brønsted acid catalyst in a reactor; and operating the reactor to produce a product mixture containing a cross-aldol product of the first alkylaldehyde and the second alkylaldehyde.

Description

Technical Field

[0001] Embodiments relate to a process for producing branched aldehyde products by cross-aldol condensation using a solid-supported Bronsted acid catalyst.

Background Art

[0002] Cross-aldol condensation is a type of organic reaction involving the formation of a carbon-carbon bond between two carbonyl compounds (aldehydes or ketones). In cross-aldol condensation, the carbonyl compounds combine under acidic or basic conditions to form a β-hydroxycarbonyl compound product. For example, a basic catalyst such as hydroxide (OH) or an amine can be used to deprotonate the α-carbon of one carbonyl compound, generating an enolate that can then undergo a nucleophilic attack. The enolate species can then combine with another carbonyl compound to form a condensation product.

[0003] Cross-aldol condensation proceeds readily under standard catalytic conditions, but conventional catalysts have little control over the selectivity of the cross-aldol product. Standard reaction conditions using hydroxide catalysts also involve a combination of carbonyl reactants and an aqueous phase, which must be removed from the resulting product mixture. In addition to the desired cross-aldol, the product mixture often contains significant amounts of self-aldol condensation by-products, which result in increased costs in terms of time and process for removing starting materials, as well as unwanted products, catalysts, and caustic aqueous waste. Previous approaches to cross-aldol condensation have included little in the way of increasing cross-aldol selectivity and have mainly focused on using activated substrate molecules with different rates of catalytic activation for aldol condensation. For example, selectivity can be introduced through the use of stereocontrol such as the use of an aldehyde with a higher reaction rate in the presence of a ketone, or a cross-aldol reaction between a branched or functionalized aldehyde and a linear aldehyde.

Summary of the Invention

[0004] Embodiments disclosed herein include a process for cross-aldol condensation of alkylaldehydes, comprising: providing a reaction mixture containing a first alkylaldehyde and a second alkylaldehyde, wherein the first alkylaldehyde has fewer carbon atoms than the second alkylaldehyde, and the feedstock has a molar ratio of 1:1 or greater of the first alkylaldehyde to the second alkylaldehyde; contacting the reaction mixture with a solid-supported Brønsted acid catalyst in a reactor; and operating the reactor to produce a product mixture containing a cross-aldol product of the first alkylaldehyde and the second alkylaldehyde.

[0005] In another embodiment, the embodiment includes a system for cross-aldol condensation of aldehydes, comprising: a reactor containing a solid-supported Brønsted acid catalyst; a reactor input section providing a reaction mixture containing a first alkylaldehyde and a second alkylaldehyde, wherein the first alkylaldehyde has fewer carbon atoms than the second alkylaldehyde; and a reactor outlet section for obtaining a product mixture containing 20% ​​by weight or more of a cross-aldol product of the first alkylaldehyde and the second alkylaldehyde. [Modes for carrying out the invention]

[0006] Embodiments disclosed herein relate to a process for cross-aldol condensation using a solid-supported Brønsted acid catalyst to produce branched aldehyde products from various alkylaldehydes with improved selectivity and conversion rates. The method may include a batch process or a continuous process comprising reacting a first alkylaldehyde with a second alkylaldehyde having a greater number of carbon atoms in the presence of a solid-supported Brønsted acid catalyst. In some cases, the process may produce cross-aldol condensation products having selectivity for two or more cross-aldol products with respect to the concentration of competing auto-aldol products.

[0007] The cross-aldol condensation disclosed herein involves a supported (or heterogeneous) solid-supported Brønsted acid catalyst having improved selectivity and conversion rates compared to alternative methods utilizing unsupported basic catalysts (i.e., aqueous hydroxides). The solid-supported Brønsted acid catalyst may include a resin capable of catalyzing cross-aldol condensation between unmodified alkylaldehydes without requiring activation or functionalization of the aldehyde to drive the reaction or enhance its reactivity. Furthermore, the use of a heterogeneous catalyst reduces the need to introduce an aqueous stream, which is associated with unsupported basic catalysts, while minimizing or eliminating the need for post-reactoral separation of the catalyst from the product stream.

[0008] A method disclosed herein involves reacting at least two alkylaldehydes under cross-aldol condensation conditions in the presence of a solid-supported Brønsted acid catalyst to obtain a product mixture containing a fraction of long-chain branched aldehydes. The cross-aldol reaction proceeds by an addition reaction shown in Formula 1, followed by a condensation reaction shown in Formula 2. In both formulas, R1 and R2 represent unique alkyl substituents bonded to the carbonyl group. R1CH2C(H)=O+R2HC(H)=O+catalyst→R2CH(OH)CH(R1)C(H)=O(1) R2CH(OH)CH(R1)C(H)=O→R2CH=C(R1)C(H)=O+H2O(2)

[0009] Although Formulas 1 and 2 are shown as reactions between two aldehydes, one or both species may be ketones without departing from the scope of this disclosure.

[0010] This catalyst is a solid-supported Brønsted acid catalyst containing acidic functional groups that can exchange positively charged hydrogen cations with cations from the surrounding medium. The solid-supported Brønsted acid catalyst may be prepared from an inert matrix (e.g., polymer, silica) functionalized with varying levels of acidic functional groups (e.g., sulfonates, carboxylates, phosphonates). An exemplary reaction is shown in Equation 3, demonstrating that the reaction of butyraldehyde with nonanal produces a mixture of crossed aldol C13 isomers and autoaldol products.

[0011] [ka]

[0012] The method can be applied to batch and flow reactor setups, including methods for regenerating the catalyst for repeated use. For example, following a batch reaction, the catalyst may be regenerated using a suitable solvent and then reused in one or more sequential reactions. Similarly, in a sequential method (e.g., a flow reactor), a solid-supported Brønsted acid catalyst may be regenerated (continuously or intermittently) to enable repeated use of the catalyst.

[0013] Cross-aldol condensation may be carried out between two or more alkylaldehydes. As used herein, alkylaldehydes are distinguished as "first" and "second," with the first alkylaldehyde having fewer carbon atoms than the second alkylaldehyde. Alkylaldehydes may have the general formula RCH2C(H)=O, where R is an alkyl group that can be linear and / or non-functionalized (i.e., including aldehydes having unbranched alkyl substituents). In some cases, the first alkylaldehyde has a carbon number in the range of 2 to 6, and the second alkylaldehyde has a carbon number in the range of 7 to 20. Suitable reactant aldehydes include acetaldehyde, propanal, n-butanal, n-pentanal, hexanal, heptanal, octanal, and long-chain aldehydes. In one embodiment, as shown in Scheme II, cross aldol condensation is used to produce branched C13 aldehydes or alcohols from linear C4 and C9 aldehydes.

[0014] Cross-aldol condensation can proceed from a reaction mixture (i.e., in a batch process) or feed (i.e., in a continuous process) where the molar ratio of the first alkylaldehyde to the second alkylaldehyde is in the range of 4:1 to 1:4, 3:1 to 1:3, or 2:1 to 1:2. The alkylaldehydes can be supplied in a manner suitable for a particular reaction (i.e., batch or continuous). In the batch process, the aldehydes may be added simultaneously or sequentially, in their total concentration, or each in one or more fractions, to the batch reactor.

[0015] In the batch method, the combined aldehyde concentration in the reaction mixture is in the range of 5% to 99.9% by weight, 25% to 95% by weight, or 40% to 80% by weight, as weight percent (W%). The product mixture obtained from the batch reaction may contain cross-aldol products in weight percent (W%) of 20% or more, 30% or more, or 40% or more, or in the range of 5% to 99.9% by weight, 25% to 95% by weight, or 40% to 80% by weight. In the flow or continuous method, the combined aldehyde concentration in the reaction mixture is in the range of 5% to 99.9% by weight, 25% to 95% by weight, or 40% to 80% by weight, as weight percent (W%). The product mixture obtained from the flow reaction may be provided as an outlet stream containing cross-aldol products in weight percent (W%) of 5% or more, 10% or more, or 20% or more.

[0016] The cross-aldol condensation disclosed herein can be catalyzed by one or more solid-supported Brønsted acid catalysts comprising an acidic ion exchange resin. The ion exchange catalyst may comprise one or more acidic moieties, such as sulfonic acids, carboxylic acids, and phosphonic acids, or a heterogeneous catalyst support functionalized with them.

[0017] The catalyst support comprises any solid material that is inert under reaction conditions and can be modified with selected acidic functional groups. The support material may be a variety of polymers containing vinyl aromatics such as styrenedivinylbenzene (e.g., crosslinked and uncrosslinked), or an inert material containing oxides such as silica, alumina, and titania. The catalyst support may be in the form of a powder, granules, pellets, etc., sized for operation in a selected reactor. Examples of solid-supported Brønsted acid catalysts include sulfonated resins, sulfonic acid derivatives, carboxylic acid resins, phosphonic acid resins, sulfonimide resins, phenolic resins, and derivatives.

[0018] The solid-supported Brønsted acid catalyst may be stable to any preferred operating temperature range, including temperatures above 60°C, or up to 200°C, including temperatures in the ranges of 40°C to 200°C, 50°C to 150°C, or 60°C to 100°C, or up to 300°C.

[0019] The solid-supported Brønsted acid catalysts disclosed herein may have acid moiety concentrations ranging from 0.0001 equivalents / mL to 10 equivalents / mL.

[0020] The solid-supported Brønsted acid catalyst may be added in a molar percentage (mol%) of the number of moles of the acid content of the catalyst relative to the total number of moles of aldehyde, in the range of 5 mol%, 10 mol%, or 20 mol%, or 1 mol% to 20 mol%, or 1 mol% to 10 mol%.

[0021] The solid-supported Brønsted acid catalyst may be stored and / or placed in the reactor with a suitable solvent that is unreactive under the reaction conditions, rather than water. The solvent may contain one or more hydrocarbons, including alkanes and alkenes having 4 to 15 carbon atoms. The solvent may be present in the reaction mixture and / or product mixture in an amount of 10% by weight or more, or in the range of 10% to 80% by weight.

[0022] In some cases, solid-supported Brønsted acid catalysts may undergo some degree of deactivation during the reaction. Without being limited to theory, this may be due to the association of the catalyst's active site with water or other polar species, which function to block access to the active site. To regenerate the catalyst, a regeneration solvent can be brought into contact with the catalyst and used to wash away aqueous and polar deactivating contaminants. Examples of regenerating solvents include glycol ethers such as anisole (methylphenyl ether), tert-butyl methyl ether, dibenzyl ether, diethyl ether, dioxane, diphenyl ether, methyl vinyl ether, tetrahydrofuran, triisopropyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether (diglym), diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, 1,2-dimethoxyethane (monoglym), ethylene glycol monobutyl ether, triethylene glycol dimethyl ether (triglym), triethylene glycol monomethyl ether, acetone, diisobutyl ketone, methyl n-propyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, and combinations thereof.

[0023] The method may include batch and continuous processes, comprising the overall steps of: providing a reaction mixture containing a first alkylaldehyde and a second alkylaldehyde, wherein the first alkylaldehyde has fewer carbon atoms than the second alkylaldehyde, and the feedstock has a molar ratio of 1:1 or more between the first alkylaldehyde and the second alkylaldehyde; contacting the reaction mixture with a solid-supported Brønsted acid catalyst in a reactor; and operating the reactor to produce a product mixture containing cross-aldol products of the aldehydes.

[0024] The crossed aldol condensations described herein can be carried out in any reactor of suitable design (e.g., plug flow reactor, continuous stirred tank reactor, etc.) including batch reactors, semi-batch reactors, and continuous flow reactors, which are not limited with respect to design, size, shape, flow rate, etc. Examples of reaction parameters are provided below and in the examples. Generally, the reaction pressure is from atmospheric pressure to about 100 atmospheres, and the temperature ranges from approximately 0 °C to 300 °C. The crossed aldol condensation can be carried out at a suitable temperature. For example, the reaction mixture or reaction stream can be maintained at 60 °C or higher during the condensation reaction.

[0025] An aqueous fluid can deactivate the solid-supported Bronsted acid catalyst by associating with the active acid sites. Prior to the crossed aldol condensation, the solid-supported Bronsted acid catalyst can be activated by drying at 90 °C to 100 °C (or a higher temperature depending on the catalyst) to remove adsorbed water. Further, the solid-supported Bronsted acid catalyst can be regenerated in batch or continuous mode by contacting the catalyst (in situ or removed from the reactor) with a regeneration solvent. The selected catalyst is then loaded into the desired reactor, and the reaction mixture is added or fed to the reaction zone at a specified temperature for a specified time.

[0026] The crossed aldol product can be separated from the reaction mixture by any suitable method such as solvent extraction, crystallization, distillation, evaporation, wiped film evaporation, falling film evaporation, phase separation, and filtration. For example, in a continuous process, the liquid reaction mixture removed from the reaction zone (containing the aldehyde product, etc.), i.e., the reaction fluid, can be sent to a separation step, e.g., a distillation column, where the desired aldehyde product is separated from the liquid reaction fluid by distillation in one or more stages under atmospheric pressure, reduced pressure, or high pressure and can be further purified. The portion of the liquid reaction mixture that is not removed in the product stream from the separation step contains the aldehyde product, aldehyde feed, solvent, water, reaction by-products, feedstock impurities, etc., and can then be recycled to the reactor either in whole or in part.

[0027] A system for forming a crossed aldol condensate may include a reactor (batch or continuous) containing a solid-supported Bronsted acid catalyst, a reactor inlet for providing a reaction mixture containing a first alkyl aldehyde and a second alkyl aldehyde, wherein the first alkyl aldehyde has fewer carbon atoms than the second alkyl aldehyde, and a reactor outlet for obtaining a product mixture containing 20 wt% or more of the crossed aldol product of the first alkyl aldehyde and the second alkyl aldehyde.

[0028] The methods disclosed herein can be carried out under batch or continuous conditions where the crossed aldol selectivity, defined as the concentration of the crossed aldol product in the product mixture (or product mixture stream) relative to the concentration of the self-aldol product of the second alkyl aldehyde in the product mixture, is 2.3 or greater, 2.5 or greater, or 3.0 or greater, or in the range of 2.3 - 4.0, or 2.3 - 3.5.

[0029] The numerical ranges disclosed herein include all values including the lower and upper limits, and all values between them. Unless stated to the contrary, not implied by the context, or not customary in the art, all parts and percentages are by weight, and all test methods are the latest as of the filing date of this disclosure.

Examples

[0030] The following examples are provided to illustrate embodiments of the invention but are not intended to limit its scope. The materials used in the following examples are shown in Table 1. The solid-supported Bronsted acid catalysts are shown in Table 2, where all catalysts contained sulfonic acid functional groups.

[0031] <X

Table 1

[0032]

Table 2

[0033] The cross-aldol condensation products were produced using batch or flow reactor (continuous) methods, as described below. In these examples, the conversion rate of the selected analyte (A) is defined as follows:

[0034]

number

[0035] The selectivity of product I from reactant A is,

[0036]

number

[0037] In the examples, "cross-aldol selectivity" is expressed as the ratio of cross-aldol product selectivity to self-aldol product selectivity, which are determined according to Equation 5.

[0038] Unless otherwise specified in the examples, the samples were tested under the following batch or continuous process conditions.

[0039] Batch method The batch reaction was carried out on a Radleys Carousel 12 Plus Reaction Station with external overtemperature control, equipped with the provided reactor vials and lids. Cooling for reflux was performed by circulating water. In a standard experiment, the catalyst was loaded into the reactor vials in an open laboratory. A pre-prepared aldehyde feed mixture of butanal, nonanal, decane, and 1-octene (37 / 37 / 3 / 23 wt%, "C4:C9 in a 2:1 ratio," respectively) was then added to the vials in a purge box. The vials were then capped and sealed, removed from the purge box, and heated on the carousel reactor in a fume hood at the specified temperature for the desired time while mixing at 500 rpm. Subsequently, the vials were removed from the carousel, the lids were removed, and the reaction mixture was filtered through a 0.2 μm filter using a syringe and diluted to approximately 2:1 isopropanol:reaction mixture ratio for GC analysis.

[0040] Gas chromatography was performed using an Agilent J&W DB-17 column (part number 123-1732) on an Agilent 7890B GC with a flame ionization detector. The GC method involved holding at 50°C for 5 minutes, followed by heating to 280°C at 10°C / min and holding for 2 minutes, for a total run time of 30 minutes.

[0041] Calibration of butanal, nonanal, 2-ethylhexanal, and 2-methylpentanal was completed by diluting the pure materials in isopropanol to obtain standards of 40, 25, and 1% by weight. 2-ethylhexenal (89% purity) and octadecenal (83% purity) were calibrated to the same level after synthesizing these materials by self-aldol condensation of butanal and nonanal, respectively, using the published method described in Ostrowski, KA, Lichte, D., Stuck, M., Vorholt, AJ, Tetrahedron, 2016, 72(5), 592. Tridecenal (C) of cross-aldol condensation of butanal and nonanal 13The response coefficients of the products were estimated based on linear interpolation from plots of response coefficients versus carbon number of available aldehydes. Decane was used as an internal standard for all components at 2 wt% decane, and isopropanol was used as a diluent.

[0042] Flow reactor method The flow reaction was carried out in a custom-made flow reactor. Briefly, the reactor is a 1 / 2-inch OD stainless steel reactor connected upstream and downstream with 1 / 16-inch stainless steel tubing. There is PTFE tubing from selector valve 1 to a Gilson HPLC 305 pump with a 5SC pump head. The reactor is placed vertically in a continuously N2-purged oven, with the solution flowing upwards. The catalyst bed is filled into the reactor by loading catalyst diluted with quartz beads to achieve a bed height of approximately 6 inches. Quartz wool was added to the reactor above and below the catalyst bed. A K-type thermocouple was placed coaxially with the catalyst bed in the reactor or on top of the bed to continuously record the temperature. Samples were collected periodically during the experiment for product analysis by GC.

[0043] Gas chromatography of flow reactor samples was performed using an Agilent 7890A GC with a flame ionization detector, employing an Agilent J&W DB-17 column (part number 123-1732LTM). The GC method involved holding at 50°C for 5 minutes, followed by heating to 280°C at 10°C / min and holding for 2 minutes, for a total run time of 30 minutes.

[0044] Calibration of butanal, nonanal, octenal, and octadecenal was completed by diluting the pure materials in toluene to obtain standards of 40, 30, 15, 5, and 1 wt%. Octenal (92% purity) and octadecenal (88% purity) were calibrated at the same level. The response coefficient of tridecenal (product of the cross-aldol condensation of butanal and nonanal) was estimated based on linear interpolation from plots of response coefficients versus carbon number of available aldehydes. Decane was used as an internal standard of 2 wt% decane for all components, with toluene used as a diluent.

[0045] Example 1: Batch reaction using a solid-supported Brønsted acid catalyst In this example, different solid-supported Brønsted acid catalysts were analyzed for their conversion rate and selectivity during batch reactions. Each sample was dried overnight in a static oven at 90°C before use. The reaction components were reacted at 60°C for 1 hour while being mixed at 500 rpm in a Radleys Carousel 12 Plus Reaction Station. The reaction formulations were a 2:1 C4:C9 weight ratio and a catalyst load of 150 mg (5 mol% of the acid content of Amberlite FPX62 relative to the total aldehyde), or 6.7 g solution / g catalyst. The results are shown in Table 3.

[0046] [Table 3]

[0047] The results indicate that cross-aldol condensation of C4 and C9 alkylaldehydes proceeds on an acidic ion exchange catalyst compared to a NaOH catalyst solution (homogeneous, comparative). Importantly, compared to the NaOH catalyst system, the solid-supported Brønsted acid catalyst tends to favor the cross-aldol condensation of C9 with C4 to form C13, rather than the self-aldol condensation of C9 to form C18. The ratio of selectivity for cross-aldol condensation to selectivity for self-aldol condensation is improved compared to the NaOH catalyst system. This is also in contrast to the prior art, which has demonstrated cross-aldol condensation of an aldehyde with a second reagent (ketone or further activated) of a different functional group to obtain a non-statistical product mixture.

[0048] Example 2: Temperature effect on batch reactions using solid-supported Brønsted acid catalysts In this example, the effect of temperature on the conversion rate of C9 to C13 aldehydes using the solid-supported Brønsted acid catalyst Amberlite FPX62 was analyzed during a batch reaction. The reaction components were reacted for 1 hour (unless otherwise specified) at a temperature in the range of 60°C to 100°C while being mixed at 500 rpm in a Radleys Carousel 12 Plus Reaction Station. The reaction formulation consisted of a C4:C9 weight ratio of 2:1 and a catalyst load of 150 mg (5 mol% of the acid content of Amberlite FPX62 relative to the total aldehyde). Before combining with the aldehyde, Amberlite FPX62 was dehydrated overnight in an oven at 90°C. The results are shown in Table 4.

[0049] [Table 4]

[0050] The results demonstrated that varying the temperature and time provided some degree of control over the conversion rates of C4 and C9, as well as the cross-aldol selectivity, respectively. Here, higher cross-aldol selectivity was obtained at relatively low temperatures (particularly 60°C). Example 3: Flow reaction using a solid-supported Brønsted acid catalyst

[0051] In this example, the conversion rates of C4 and C9 and the cross-aldol selectivity of C13 were studied for a flow reactor process containing the solid-supported Brønsted acid catalyst Amberlite FPX62. Amberlite FPX62, dried at 90°C, was loaded into a flow reactor column to a floor height of 6 inches. The reactor column was operated at a flow rate of 0.15 mL / min (residence time of 1 hour), a C4:C9 weight ratio of 2:1, 4.27 g of catalyst, and a temperature of 98°C.

[0052] [Table 5]

[0053] The results indicate that Amberlite FPX62 can be used in a flow reactor, but it deactivates during flow, as observed by a decrease in C4 and C9 conversion rates.

[0054] Example 4: Regeneration of solid-supported Brønsted acid catalyst activity under flow conditions In this example, the conversion rates of C4 and C9 and the cross-aldol selectivity of C13 were studied in a flow reactor process using Amberlite FPX62 in a flow reactor, and the results were compared with those after catalyst regeneration using diglim. Amberlite FPX62, dried at 90°C, was loaded into the flow reactor column to a floor height of 6 inches. The reactor column was operated at a flow rate of 0.67 mL / min (residence time of 15 minutes), a C4:C9 weight ratio of 2:1, 4.27 g of catalyst, and a temperature of 82.8°C. Following experiments with fresh catalyst, diglim regeneration was performed at 34°C and a flow rate of 0.33 mL / min for 2 hours.

[0055] [Table 6]

[0056] [Table 7]

[0057] The results shown in Tables 6 and 7 demonstrate that the solid-supported Brønsted acid catalyst can be regenerated between multiple experiments, and its conversion activity can be restored to that of a fresh catalyst.

[0058] Example 5: Flow reaction using a solid-supported Brønsted acid catalyst In this example, the conversion rates of C4 and C9 and the C13 cross-aldol selectivity were studied in a flow reactor process including the ion exchange resin Amberlyst 46. Amberlyst 46, dried at 90°C, was loaded into the flow reactor column to a floor height of 6 inches. The reactor column was operated at a flow rate of 0.15 mL / min (residence time of 1 hour), a C4:C9 weight ratio of 2:1, 4.27 g of catalyst, and a temperature of 82.8°C.

[0059] [Table 8]

[0060] Table 8 shows the transition of the second solid-supported Brønsted acid catalyst, Amberlist 46, from batch reaction to flow reaction for selective cross-aldol condensation.

[0061] The above describes exemplary embodiments, but other and further embodiments may be devised without departing from their basic scope, the scope of which is determined by the following claims.

Claims

1. A process for the cross-aldol condensation of alkylaldehydes, To provide a reaction mixture comprising a first alkylaldehyde and a second alkylaldehyde, wherein the first alkylaldehyde has fewer carbon atoms than the second alkylaldehyde, and the supply material has a molar ratio of 1:1 or higher between the first alkylaldehyde and the second alkylaldehyde. In the reactor, the reaction mixture is brought into contact with a solid-supported Brønsted acid catalyst, A process comprising operating the reactor to produce a product mixture containing a cross-aldol product of the first alkylaldehyde and the second alkylaldehyde.

2. The process according to claim 1, wherein the solid-supported Brønsted acid catalyst comprises one or more of the following: a sulfonated resin, a sulfonic acid derivative, a carboxylic acid resin, a phosphonic acid resin, a sulfonimide resin, and a phenolic resin.

3. The process according to claim 1, wherein the product mixture has a cross-aldol selectivity of 2.3 or more, defined as the concentration of the cross-aldol product in the product mixture relative to the concentration of the auto-aldol product of the second alkylaldehyde in the product mixture.

4. The process according to claim 1, wherein the first alkylaldehyde has a number of carbon atoms in the range of 2 to 6, and the second alkylaldehyde has a number of carbon atoms in the range of 7 to 20.

5. The process according to claim 1, wherein the solid-supported Brønsted acid catalyst comprises a sulfonated resin.

6. The process according to claim 1, wherein operating the reactor includes maintaining the solid-supported Brønsted acid catalyst at an acid content of at least 5 mol% with respect to the total number of moles of the first alkylaldehyde and the second alkylaldehyde.

7. The process according to claim 1, wherein the reactor is operated at a temperature of 60°C or higher.

8. The process according to claim 1, further comprising regenerating the solid-supported Brønsted acid catalyst with a glycol ether.

9. The process according to claim 1, wherein the product mixture contains 50% by weight or more of the cross-aldol product.

10. A system for cross-aldol condensation of aldehydes, A reactor containing a solid-supported Brønsted acid catalyst, A reactor input unit for providing a reaction mixture comprising a first alkylaldehyde and a second alkylaldehyde, wherein the first alkylaldehyde has fewer carbon atoms than the second alkylaldehyde, A system comprising a reactor outlet for obtaining a product mixture containing 20% ​​by weight or more of a cross-aldol product of the first alkylaldehyde and the second alkylaldehyde.

11. The system according to claim 10, wherein the reactor is a batch reactor.

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