Cross-aldol condensation of aldehydes using supported amines and organic acid promoters

Abstract

Processes for cross-aldol condensation of alkyl aldehydes that include providing a reactant mixture including a first alkyl aldehyde, a second alkyl aldehyde, and an acid promoter, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde, and the feed stock having a molar ratio of 1:1 or more of the first alkyl aldehyde to the second alkyl aldehyde; and contacting the reactant mixture with a solid-supported basic catalyst in a reactor; operating the reactor to generate a product mixture containing a cross-aldol product of the first alkyl aldehyde and the second alkyl aldehyde.

Description

[0001] CROSS-ALDOL CONDENSATION OF ALDEHYDES USING SUPPORTED AMINES AND ORGANIC ACID PROMOTERS FIELD Embodiments relate to processes for the generating branched aldehyde products by cross-aldol condensation using solid-supported basic catalysts and an organic acid promoter. BACKGROUND Cross-aldol condensation is a type of organic reaction that involves the formation of a carbon- carbon bond between two carbonyl compounds (aldehydes or ketones). In cross-aldol condensation, carbonyl compounds combine to form a β-hydroxy carbonyl compound product under acidic or basic conditions. For example, a basic catalyst, such as hydroxide (OH) , may be used to deprotonate an α- carbon of one carbonyl compound, producing an enolate capable of subsequent nucleophilic attack. The enolate species can then combine with another carbonyl compound to generate a condensation product. Cross-aldol condensations proceed readily under standard catalytic conditions, but traditional catalysts offer little control over selectivity for the cross-aldol product. Standard reaction conditions utilizing hydroxide catalysts also involve combination of the carbonyl reactants with an aqueous phase, which must be removed from the resulting product mixture. In addition to the target cross- aldol product, product mixtures often contain significant amounts of self-aldol condensation byproducts, which lead to increased costs in terms of starting materials and time and processes to remove undesired products, catalysts, and caustic aqueous waste. Previous approaches to cross-aldol condensation include few ways to increase cross-aldol selectivity, and have focused predominantly on the use of activated substrate molecules having different rates of catalyst activation for aldol condensation. For example, selectivity may be introduced through the use of aldehydes having higher rates of reactivity in the presence of ketones, or the use of steric controls such as cross-aldol reactions between branched or functionalized aldehyde and linear aldehydes. SUMMARY Embodiments disclosed herein include processes for cross-aldol condensation of alkyl aldehydes, including providing a reactant mixture including a first alkyl aldehyde, a second alkyl aldehyde, and an acid promoter, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde, and the feed stock having a molar ratio of 1:1 or more of the first alkyl aldehyde to the second alkyl aldehyde; and contacting the reactant mixture with a solid-supported basic catalyst in a reactor; operating the reactor to generate a product mixture containing a cross-aldol product of the first alkyl aldehyde and the second alkyl aldehyde. In another aspect, embodiments disclosed herein include systems for cross-aldol condensation of aldehydes including: a reactor including a solid-supported basic catalyst; a reactor input for providing a reactant mixture that includes a first alkyl aldehyde, a second alkyl aldehyde, and one or more acid promoters, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde; and a reactor output for obtaining a product mixture containing 20 wt% or more of the cross-aldol product of the first alkyl aldehyde and the second alkyl aldehyde. DETAILED DESCRIPTION Embodiments disclosed herein relate to processes for cross-aldol condensation using a catalyst system that include a solid-supported basic catalyst used in combination with a feed containing one or more acid promoters to generate branched aldehyde products from various alkyl aldehydes with improved reactant conversion and product yield. Methods may include batch or continuous processes that include reacting a first alkyl aldehyde and a second alkyl aldehyde having a higher carbon number in the presence of a solid-supported basic catalyst and acid promoter. Cross-aldol condensations disclosed herein include a catalyst system containing supported (or heterogenous) solid-supported basic catalysts and acid promoters that enables high reactant conversion and product yield, particularly when compared to alternative methods utilizing unsupported basic catalysts (i.e., aqueous hydroxide). Solid-supported basic catalysts may include modified resins and substrates capable of catalyzing cross-aldol condensation between unmodified alkyl aldehydes without the requirement for aldehyde activation or functionalization to direct the reaction or increase reactivity. Moreover, the use of a heterogeneous catalyst reduces the need for introducing aqueous streams associated with unsupported basic catalysts, and minimizes or omits the need for post-reactor separation of the catalyst from the product stream. Methods disclosed herein include reacting the at least two alkyl aldehydes in the presence of a solid-supported basic catalyst under cross-aldol condensation conditions to yield a product mixture containing a fraction of longer-chain, branched aldehydes. Cross-aldol reactions proceed by an addition reaction shown in Eq. 1 that is followed by a condensation reaction shown in Eq.2. In both equations, R₁ and R₂ represent unique alkyl substituents attached to the carbonyl groups. 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) Eqs. 1 and 2 are shown as reactions between two aldehydes, however, one or both of the species may be ketones without departing from the scope of the disclosure. The catalyst is a solid-supported basic catalyst containing basic functional groups capable of donating electrons with compounds in the surrounding medium. Solid-supported basic catalysts may be made from an inert matrix (e.g., polymer, silica) that is functionalized with varying levels of basic functional groups (e.g., primary or secondary amines). An exemplary reaction is shown in Eq. 3, depicting the reaction of butyraldehyde with nonanal to generate a mixture of cross-aldol C13 isomers and self-aldol products. the be in continuous methods (e.g., flow reactor), the solid-supported basic catalyst may be regenerated (continuously or intermittently) to allow for repeated catalyst use. Cross-aldol condensations may be performed between two or more alkyl aldehydes. As used herein, alkyl aldehydes are differentiated as “first” and “second,” where the first alkyl aldehyde as a lower carbon number than the second alkyl aldehyde. The alkyl aldehydes may have the general formula of RCH2C(H)=O, where R is an alkyl group that may be linear and / or non-functionalized (i.e., include aldehydes having non-branching alkyl substituents). In some cases, the first alkyl aldehyde has a carbon number in the range of 2 to 6 and the second alkyl aldehyde has a carbon number in the range of 7 to 20. Suitable reactant aldehydes include acetaldehyde, propanal, n-butanal, n-pentanal, hexanal, heptanal, octanal, longer chain aldehydes, and the like. In one example, cross- aldol condensations are used to generate branched C13 aldehydes or alcohols from linear C4 and C9 aldehydes as shown in Scheme II. Cross-aldol condensations may proceed from a reactant mixture (i.e., for a batch process) or feed (i.e., for a continuous process) containing a molar ratio of first alkyl aldehyde:second alkyl aldehyde in a range of 4:1 to 1:4, 3:1 to 1:3, or 2:1 to 1:2. Alkyl aldehydes may be provided as is suitable for the particular reaction (i.e., batch or continuous). In batch methods, aldehydes may be added at the same time or in sequence, and at the total concentration or added, respectively, into a batch reactor in one or more fractions. In batch methods, the combined aldehyde concentration in the reactant mixture as a percent by weight (wt%) ranging from 5 wt% to 99.9 wt%, 25 wt% to 95 wt%, or 40 wt% to 80 wt%. The resulting product mixture of a batch reaction may contain the cross-aldol product at a percent by weight (wt%) of 20 wt% or more, 30 wt% or more, or 40 wt% or more, or ranging from 5 wt% to 99.9 wt%, 25 wt% to 95 wt%, or 40 wt % to 80 wt%. In flow or continuous methods, the combined aldehyde concentration in the reactant mixture as a percent by weight (wt%) ranging from 5 wt% to 99.9 wt%, 25 wt% to 95 wt%, or 40 wt% to 80 wt%. The resulting product mixture of a flow reaction may be provided as an exit stream containing the cross-aldol product at a percent by weight (wt%) of 5 wt% or more, 10 wt% or more, or 20 wt% or more. Cross-aldol condensations disclosed herein may be catalyzed by one or more solid-supported basic catalysts, including basic ion exchange resins. While not limited by a particular theory, solid- supported basic catalysts may include catalysts containing nucleophilic primary and / or secondary amines that reversibly react with carbonyl-containing species that activate carbonyl-containing species and promote enolate formation. Ion exchange catalysts may include a heterogeneous catalyst support that contains or is functionalized with one or more basic moieties, including primary or secondary, amines, which are capable of reacting with carbonyl species and promoting enolate formation. Amine moieties may be anchored to the support by any suitable linker and / or anchoring chemistry, and may include amines and polyamines (monoamine, diamine, triamine, etc.), and may include linear, branched, substituted, and / or heterocyclic (e.g., piperazine) amines. Catalyst supports include any solid substance that is inert under the reaction conditions and can be modified with the selected basic functional group. The support material can be inert materials including various polymers (e.g., crosslinked and non-crosslinked) including vinylaromatics such as styrene divinylbenzene, and the like, or oxides such as silica, alumina, and titania. The catalyst support can be in the form of powder, granules, pellets, or the like that are dimensioned for operation in the selected reactor. Examples of solid-supported basic catalysts may include catalyst supports (e.g., resins, inorganics) functionalized with amines such as monoalkyl amines, dialkyl amines, polyamines, cyclic dialkylamines, and the like. Solid-supported basic catalysts may be stable for any suitable operation temperature, including temperatures up to 100oC or up to 150oC, including at temperatures of 40oC or more, or in the range of 40oC to 150oC, 50oC to 150oC, or 60oC to 100oC. Solid-supported basic catalysts disclosed herein may have an active site concentration in the range of 0.01 eq / mL to 10 eq / mL. Solid-supported basic catalysts may be added at a molar percent of moles of base content of the catalyst to total moles aldehydes (mol%) of at least 1 mol%, at least 5 mol%, or at least 10 mol%, or in a range of 1 mol% to 20 mol%, or 1 mol% to 10 mol%. Solid-supported basic catalysts may be stored and / or placed into a reactor with a compatible solvent that is not water and unreactive in the reaction conditions. Solvents may include one or more hydrocarbons, including alkanes and alkenes having 4 to 15 carbon atoms. Solvents may be present in the reaction mixture and / or the product mixture at a percent by weight (wt%) of 10 wt% or more, or in a range of 10 wt% to 80 wt%. Cross-aldol condensations disclosed herein may utilize one or more acid promoters that stabilize and / or enhance catalytic activity. Acid promotors may include C1 to C12 alkyl acids and polyacids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, and the like, aromatic acids such as benzoic acid, salicylic acids, acetyl salicylic acid, and the like. Cross-aldol condensations may include one or more acid promoters at a percent by weight (wt%) of the total aldehyde content of 2.5 wt% or more, 3 wt% or more; 40 wt% or less, 30 wt% or less, or 25 wt% or less, such as in a range between 2.5 wt% to 40 wt%, 2.5 wt% to 30 wt%, or 2.5 wt% to 40 wt%. Cross-aldol condensations may include one or more acid promoters at a mole percent (mol%) relative to the combined moles of the first alkyl aldehyde and the second alkyl aldehyde of at least 1 mol%, at least 5 mol%, or at least 10 mol%, or in a range of 1 mol% to 20 mol%, or 1 mol% to 10 mol%. In some cases, solid-supported basic catalysts may undergo some level of deactivation during the reaction. Without being limited by theory, this may be due to the association with water or other polar species with the active sites of the catalyst that function to block active site access. In order to regenerate the catalyst, a regenerating solvent may be contacted with the catalyst and used to wash away aqueous and polar deactivating contaminants. Regenerating solvents may include glycol ethers such as anisole (methyl phenyl 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 (diglyme), diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, 1,2-dimethoxyethane (monoglyme), ethylene glycol monobutyl ether, triethylene glycol dimethyl ether (triglyme), 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. Methods may include batch and continuous processes that contain the general steps of providing a reactant mixture containing a first alkyl aldehyde and a second alkyl aldehyde, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde, and the feed stock having a molar ratio of 1:1 or more of the first alkyl aldehyde to the second alkyl aldehyde; and contacting the reactant mixture with a solid-supported basic catalyst in a reactor; operating the reactor to generate a product mixture containing a cross-aldol product of the aldehydes. The cross-aldol condensations described herein may be carried out in any reactor of suitable design, including batch, semi-batch reactors, and continuous flow reactors, without limitation as to design, size, geometry, flow rates, etc. (e.g., plug-flow reactors, continuous stirred-tank reactors, and the like). Example reaction parameters are given below and in the examples. Generally, reaction pressures run from atmospheric to about 100 atm, with temperatures ranging roughly from 0° C to 300° C. Cross-aldol condensations may be performed at suitable temperatures. For example, a reaction mixture or stream may be maintained at 60 °C or more during the condensation reaction. Aqueous fluids may deactivate the solid-supported basic catalyst by associating with active sites. Prior to cross-aldol condensation, solid-supported basic catalysts may be activated by drying at 90°C to 100 °C (or higher depending on the catalyst) to remove adsorbed water. Moreover, the solid- supported basic catalysts may be regenerated in batch or continuous settings by contacting the catalyst (in situ or removed from the reactor) with a regenerating solvent. The selected catalysts are then loaded into the desired reactor and the reactant mixture is added or fed into the reaction zone at the specified temperature for the specified time. The cross-aldol product may be separated from a reaction mixture by any suitable method, such as solvent extraction, crystallization, distillation, vaporization, wiped film evaporation, falling film evaporation, phase separation, and filtration. For example, in a continuous process the liquid reaction mixture (containing aldehyde product, etc.), i.e., reaction fluid, removed from the reaction zone can be passed to a separation step, e.g., distillation column, wherein the desired aldehyde product can be separated via distillation, in one or more stages, under normal, reduced or elevated pressure, from the liquid reaction fluid, and further purified. The portion of the liquid reaction mixture that is not removed in the product stream from the separation step, containing aldehyde products, aldehyde feed, solvent, water, reaction byproducts, feedstock impurities, and the like, may then be recycled back to the reactor either in total or in part. Systems for forming cross-aldol condensates may include a reactor (batch or continuous) containing a solid-supported basic catalyst; a reactor input for providing a reactant mixture containing a first alkyl aldehyde and a second alkyl aldehyde, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde; and a reactor output for obtaining a product mixture comprising 20 wt% or more of the cross-aldol product of the first alkyl aldehyde and the second alkyl aldehyde. The numerical ranges disclosed herein include all values from, and including, the lower and upper value and all values in between. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight and all test methods are current as of the filing date of this disclosure. EXAMPLES The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 1 provides the materials used in the following examples.

[0002] Table 1: Materials used in the examples Component Description Supplier y Table 2: Solid-s pp y p Catalyst Product Description Specification Supplier a h a h a h leleleleus) methods as described below. In these examples, conversion of a selected analyte (A) is defined as: ^^^^^^^^^^^^^ ^^^^^^^^^^ =^^^^^,^^^^^^^^^^^^^^^^^^^^^,^(4) Yield of C13 is $^%^& ^"# '^^()^^( ^^^^^! ^^ ^"#= $^%^& ^! *^( (5) Selectivity of product I from reactant A is: 0∗$^%^& +^^^,-^^^-. =^,^^^ / ^^ ^$^%^&^,^^^$^%^&^,^^^(6) where x is the stoichiometric ratio required to convert A to i. In the examples, “Cross-aldol selectivity” is denoted as a ratio of the cross-aldol product selectivity and the self-aldol product selectivity determined according to Eq. 6, respectively. Unless otherwise specified in the examples, samples were tested under the following batch or continuous process conditions. Batch Method Batch reactions were performed on a Radleys Carousel 12 Plus Reaction Station with external overtemperature control with the provided reactor vials and lids. Cooling for reflux was provided by flowing water. In a standard run, catalyst was loaded in the reactor vial in an open lab. The premade aldehyde feed mixture of butanal, nonanal, decane, and 1-octene (37 / 37 / 3 / 23 wt%, respectively, “2:1 C4:C9”) was then added to the vial in a purge box. Where applicable, the acid promoter was added as part of the feed mixture or separately. 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 with 500 rpm mixing and for the desired time. Following, the vials were removed from the carousel, uncapped, and the reaction mixture was filtered via syringe through a 0.2 μm filter and diluted in an approximately 2:1 isopropanol:reaction mixture ratio for GC analysis. Gas chromatography was performed on an Agilent 7890B GC equipped with a flame ionization detector using an Agilent J&W DB-17 column (Part Number 123-1732). The GC method involves a 5 min hold at 50°C followed by a 10°C / min ramp to 280°C and a 2 min hold for a total run time of 30 min. Calibration of butanal, nonanal, 2-ethylhexanal, and 2-methylpentanal were completed by dilution of the pure materials in isopropanol to obtain standards of 40, 25 and 1 wt%. 2-ethylhexenal (89% purity) and octadecenal (83% purity) were calibrated at the same levels following synthesis of these materials by the self-aldol condensation of butanal and nonanal, respectively, using published methods described in Ostrowski, K. A.; Lichte, D.; Stuck, M.; Vorholt, A. J., Tetrahedron, 2016, 72 (5), 592. A response factor for the tridecenal (C13product of the cross-aldol condensation of butanal and nonanal) was estimated based on linear interpolation from plotting response factors of the available aldehydes versus number of carbons. Decane was used as an internal standard for all components at 2 wt% decane and isopropanol was used as the diluent. Flow Reactor Method Flow reactions were performed in a custom-built flow reactor. Briefly, the reactor is a ½” OD stainless steel reactor connected up and downstream with 1 / 16” stainless steel tubing. There is PTFE tubing from selection valve 1 to the Gilson HPLC 305 pump equipped with a 5SC pump head. The reactor is placed vertically within a continuously N2 purged oven and solution flow is upwards. A catalyst bed is packed within the reactor by loading catalyst diluted with quartz beads to achieve an approximate 6” bed height. Above and below the catalyst bed, quartz wool was added to the reactor. A Type K thermocouple was placed in the reactor coaxial to the catalyst bed within the bed or at the top of the bed and the temperature was recorded continuously. Samples were collected periodically during a run for product analysis by GC. Gas chromatography of flow reactor samples was performed on an Agilent 7890A GC equipped with a flame ionization detector using an Agilent J&W DB-17 column (Part Number 123- 1732LTM). The GC method involves a 5 min hold at 50°C followed by a 10°C / min ramp to 280°C and a 2 min hold for a total run time of 30 min. Calibration of butanal, nonanal, octenal, and octadecenal were completed by dilution of 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 levels. A response factor for the tridecenal (product of the cross-aldol condensation of butanal and nonanal) was estimated based on linear interpolation from plotting response factors of the available aldehydes versus number of carbons. Decane was used as an internal standard for all components at 2 wt% decane and toluene was used as the diluent. Example 1: Batch reaction using a solid-supported basic catalyst and acid promoter In this example, different silica-supported basic catalysts were analyzed for conversion and C13 yield performance during batch reaction. For each sample, the catalyst was dried overnight in a 90°C static oven prior to use. Reaction components were reacted at various temperatures for 1 hour reaction time under 500 rpm mixing in the Radleys Carousel 12 Plus Reaction Station. The reaction formulation include a 2:1 weight ratio of C4:C9, 5 mol% amine for the selected catalyst based on total aldehyde concentration, and 10 mol% acetic acid as acidic promoter. Results are shown in Table 3. Table 3: Batch cross-aldol condensation results Supported basic resinTemperatureC4 Conversion (%) C9 Conversion (%)C13 Yield esu ts n cate t at s ca-supporte cata ysts w t an ac c promoter ex t goo overall reactant conversion for linear aldehydes and C13 yield that increases with increasing temperatures. Example 2: Batch reaction using polystyrene-supported basic catalyst and acid promoter In this example, different polystyrene-supported basic catalysts were analyzed for conversion and C13 yield performance during batch reaction. Testing conditions were conducted under substantially the same conditions of Example 1. Results are shown in Table 4. Table 4: Batch cross-aldol condensation results basic TemperatureConversion° Tab le 4 demonstrates that amines supported on polystyrene with an acetic acid co-catalyst are also active for aldol condensation of linear aldehydes, demonstrating multiple supports can be used in conjunction with acetic acid and still generate activity, and that increasing temperature gives improved conversion and C13 yield. Example 3: Flow reaction using polystyrene-supported basic catalyst and acid promoter In this example, the C4 and C9 conversion and C13 yield was studied for a flow reactor process including solid-supported basic catalyst PS-Triamine. The flow reactor column was loaded to a 6” bed height with 1.5 g PS-Triamine in quartz beads that was dried at 90°C. The reactor column was operated in flow at 0.15 mL / min (1 hour residence time), with a feedstock containing 37 wt% C4, 36.6 wt% C9, 2.0 wt% decane (as internal standard), 4.6 wt% acetic acid, with a balance of octene. Results are shown in Table 5. Table 5: Cross-aldol flow reaction results with PS-Triamine and acidic promoter Time (min) C4 Conversion C9 Conversion C13 Yield % % % % % % % % % % % % % % % % % % % % % % % % % % Table 5 demonstrates that a catalyst system containing PS-triamine and acidic promoter acetic acid can be used to perform cross-aldol condensation of linear alkanes. The catalyst system shows stable activity for 20 bed turnovers based on C4 and C9 conversion and C13 yield. Example 4: Flow reaction using polystyrene-supported basic catalyst and acid promoter In this example, the C4 and C9 conversion and C13 yield was studied for a flow reactor process including solid-supported basic catalyst PS-Piperazine. The flow reactor column was loaded to a 6” bed height with 1.5 g PS-Piperazine in quartz beads that was dried at 90°C. The reactor column was operated in flow at 0.15 mL / min (1 hour residence time), with a feedstock containing 37 wt% C4, 36.6 wt% C9, 2.0 wt% decane (as internal standard), 4.6 wt% acetic acid, with a balance of octene. Results are shown in Table 5. Table 6: Cross-aldol flow reaction results with PS- Piperazine and acidic promoter % % % % % % % % % % % Table 6 dem ons ra e a a ca a ys sys em con a n ng - peraz ne and acidic promoter acetic acid can be used to perform cross-aldol condensation of linear alkanes. The catalyst system shows stable activity for 20 bed turnovers based on C4 and C9 conversion and C13 yield. Example 5: Flow reaction using polystyrene-supported basic catalyst and acid promoter In this example, the C4 and C9 conversion and C13 yield was studied for a flow reactor process including solid-supported basic catalyst PS-Triamine. The flow reactor column was loaded to a 6” bed height with 1.5 g PS-Triamine in quartz beads that was dried at 90°C. The reactor column was operated in flow at 0.15 mL / min (1 hour residence time), with a feedstock containing 37 wt% C4, 36.6 wt% C9, 2.0 wt% decane (as internal standard), 4.6 wt% acetic acid, with a balance of octene. Results are shown in Table 5. Table 7: Cross-aldol flow reaction results Temperature ResidenceConversionC9 t C13 Yi ldTabl d C9 conversion and C13 yield using a supported amine catalyst with acetic acid in the feed solution in a flow reactor. Aldehyde conversion and product yield can be obtained across a variety of conditions with maximum yield and conversion obtained at high temperatures and long residence times. Comparative Example 1: Comparison of flow reaction with and without acidic promoter In this example, the C4 and C9 conversion and C13 yield was studied for a flow reactor process including solid-supported basic catalyst PS-Triamine with and without acidic promoter. The flow reactor column was loaded to a 6” bed height with 1.5 g PS-Triamine in quartz beads that was dried at 90°C. The reactor column was operated in flow at 0.15 mL / min (1 hour residence time), with a feedstock containing 37 wt% C4, 36.6 wt% C9, 2.0 wt% decane (as internal standard), 4.6 wt% acetic acid, with a balance of octene. Results are shown in Table 8. Table 8: Cross-aldol flow reaction results Table 8 dem onstrates the benefit of a catalyst system containing acetic acid and a supported amine catalyst in a flow reactor. In the absence of acetic acid, C4 and C9 conversion are depressed and there is minimal product yield. With the introduction of acetic acid in the feed solution, C4 and C9 conversion and product yield are all significantly improved at otherwise comparable conditions. A supported amine catalyst on its own without acetic acid does not otherwise generate appreciable activity. Comparative Example 2: Comparison of batch reaction with and without acidic promoter In this example, different polystyrene-supported basic catalysts were analyzed for conversion and C13 yieldperformance during batch reaction. Testing conditions were conducted under substantially the same conditions of Example 1 at 60oC, with 5 mol% amine for the catalyst, and 5 mol% acetic acid based on total aldehyde concentration. Results are shown in Table 9. Table 9: Cross-aldol batch reaction results C4 ConversionC9 Conversion C13 Yield ) Ta nd supported amine do not generate the same activity as that of a supported amine with acetic acid as a co-catalyst. The best relative C4 and C9 conversions and product yields are obtained when using acetic acid as a co-catalyst and conversion and yield are depressed when using a supported carboxylic acid in place of acetic acid. Comparative Example 3: Comparison of batch reaction with and without acidic promoter In this example, cross-aldol condensations performed with PS-triamine were followed by acetic acid in series of batch reactions. Testing conditions were conducted under substantially the same conditions of Example 1, with 121.4 mg PS-triamine, 2 g of feedstock (37 wt% C4, 36.6 wt% C9, 2.0 wt% decane (as internal standard), and a balance of octene). The catalyst was then filtered out and 4.8 wt% acetic acid was added and reacted for an additional 1 h at 70°C. Results are shown in Table 10. Table 10: Cross-aldol flow reaction results C13 Yield C4 ConversionC9 Conversion ate catalysts does not result in significant C13 yield. Limited aldehyde conversion was observed with PS- triamine and low C13 yield. Upon filtering the catalyst and then adding acetic acid, additional C4 and C9 conversion was observed, but C13 yield remains nearly unchanged. These results demonstrate that the supported amine and acetic acid are both required for appreciable C13 yield. Comparative Example 4: Batch reaction without basic catalyst In this example, different polystyrene-supported basic catalysts were analyzed for conversion and selectivity performance during batch reaction. Testing conditions were conducted under substantially the same conditions of Example 1 at 70oC and 4.8 wt% acetic acid based on total aldehyde concentration. Results are shown in Table 9. Table 11: Cross-aldol flow reaction results C13 Yield from Table 11 demonstrates using only acetic acid as a catalyst in the absence of a supported amine results in minimal aldehyde conversion with no observed C13. Both acetic acid and a supported amine are required for significant aldehyde conversion and product yield. While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims 1. A process for cross-aldol condensation of alkyl aldehydes, comprising: providing a reactant mixture comprising a first alkyl aldehyde, a second alkyl aldehyde, and an acid promoter, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde, and the feed stock having a molar ratio of 1:1 or more of the first alkyl aldehyde to the second alkyl aldehyde; and contacting the reactant mixture with a solid-supported basic catalyst in a reactor; operating the reactor to generate a product mixture comprising a cross-aldol product of the first alkyl aldehyde and the second alkyl aldehyde.

2. The process of claim 1, wherein the solid-supported basic catalyst comprises a catalyst support functionalized with one or more of monoalkyl amines, dialkyl amines, polyamines, cyclic dialkylamines.

3. The process of claim 1, wherein the first alkyl aldehyde has a carbon number in the range of 2 to 6 and the second alkyl aldehyde has a carbon number in the range of 7 to 20.

4. The process of claim 1, wherein the acid promoter comprises a C1 to C12 alkyl acid or polyacid.

5. The process of claim 1, wherein the acid promoter is present at a mole percent (mol%) relative to the combined moles of the first alkyl aldehyde and the second alkyl aldehyde of at least 1 mol%.

6. The process of claim 1, wherein operating the reactor comprises maintaining the solid- supported basic catalyst to at least 1 mol% base content relative to the combined moles of the first alkyl aldehyde and the second alkyl aldehyde.

7. The process of claim 1, wherein the reactor is operated at a temperature of 50 °C or more.

8. The process of claim 1, further comprising regenerating the solid-supported basic catalyst with a glycol ether.

9. A system for cross-aldol condensation of aldehydes comprising: a reactor comprising a solid-supported basic catalyst; a reactor input for providing a reactant mixture comprising a first alkyl aldehyde, a second alkyl aldehyde, and one or more acid promoters, the first alkyl aldehyde having a lower carbon number than the second alkyl aldehyde; and a reactor output for obtaining a product mixture comprising 20 wt% or more of the cross- aldol product of the first alkyl aldehyde and the second alkyl aldehyde.

10. The system of claim 9, wherein the reactor is a batch reactor.

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