ES2362891A1 - PROCEDURE FOR OBTAINING ACETALS THROUGH ACID CATALYSIS USING CARBON MATERIALS. - Google Patents

Abstract

Procedure for obtaining acetals from alcohols and aldehydes by reaction with ketones, using an acid carbon as catalyst, described in Spanish patent ES2275415. The carbons used as catalysts have the advantage of having a high specific surface area, with adequate acidity to give rise to this reaction, avoiding, as far as possible, the formation of by-products. The use of catalysts in the reaction to obtain acetals reduces the time reaction, allows the process to be carried out under mild temperature conditions, reducing the production of undesired compounds and, therefore, the overall cost of the process. The main novelty of this procedure is the use of a novel catalyst, as described in the application.

Description

Procedure for obtaining acetals by acid catalysis using carbonaceous materials.

Technical sector

This invention belongs to the Technical Sector "Chemistry and Chemical Industry", understood as such in its sense broader, as it also includes Pharmacy and its Industry (drug synthesis), Food and its Industry (synthesis of food additives), Polymers and their industry (acetals are precursors of various plastics), Cosmetics and its Industry (synthesis mainly of fragrances and aromas) and Engineering Chemistry or Process Engineering, the latter as the application Chemical industry.

Technical Field of the Invention

In the present invention a process for the preparation of the compounds of Formula General A indicated below:

one

in where,

R 1, R 3 and R 4 can be chains linear or branched hydrocarbons, containing groups aromatic or aliphatic, unsaturated or not, or both, containing or not heteroatoms such as N and / or O.

R 1 -R 3 or R 3 -R 4 may be hydrocarbon chains, linear or branched, containing aromatic or aliphatic groups, unsaturated or not, containing or not heteroatoms such as N I or.

R2 may have the same meaning as R1 (in the case of ketones), or be a hydrogen atom (in the case of aldehydes.

State of the art

Obtaining acetals by catalysis acid is known enough to appear in books of Text of Organic Chemistry (P. G. M. Wuts, T. W. Greene (2007) In: Greene's protective groups in organic synthesis, 4th ed. Wiley, New Jersey, Ch. 4, p 431 and others). The reaction is carried out in the absence of water, since it could react instead of alcohol, giving place to corresponding carbohydrate compound hydrates employee, in some cases considered as unwanted products. The process involves the reaction between a molecule of a carbonyl compound, aldehyde or ketone, with a molecule of alcohol to get the hemiacetal (figure 1), which usually reacts with another molecule of alcohol to give rise to acetal (Figure 1).

For the reaction to complete in a while and at a reasonable energy cost, the presence of a acid catalyst Catalysts that need to be used cannot be used dissolve in water since it is, as mentioned above, interferes with the reaction leading, again, to the formation of Starting products or unwanted products, especially when This is found in significant quantities. Therefore, the catalysts that are used in this process are, in general, soluble in organic solvents (for example, hydrochloric acid dry in absolute ethanol). Catalysts can also be used heterogeneous, solid, (E. Pérez-Mayoral, R. M. Martín-Aranda, A. J. López-Peinado, P. Ballesteros, A. Zukal, J. \ check {C} ejka, Green Synthesis of Acetals / Ketals: Efficient Solvent-Free Process for the Carbonyl / Hydroxyl Group Protection Catalyzed by SBA-15 Materials, Top. Catal. 52 (2009) 148-152; S. B. Umbarkar, T. V. Kotbagi, A. V. Biradar, R. Pasricha, J. Chanale, M. K. Dongare, A.-S. Mamede, C. Lancelot, E. Payen, Acetalization of glycerol using mesoporous MoO 3 / SiO 2 solid acid catalyst, J. Mol. Catal. A: Chem. 310 (2009) 150-158; M. W. C. Robinson, A. E. Graham, Mesoporous aluminosilicate promoted protection and deprotection of carbonyl compounds, Tetrahedron Lett. 48 (2007) 4727-4731; W. Otani, K. Kinbara, Q. Zhang, K. Ariga, T. Aida, Catalysis of a Peptidic Micellar Assembly Covalently Immobilized within Mesoporous Silica Channels: Importance of Amphiphilic Spatial Design, Chem. Eur. J. 13 (2007) 1731-1736; B. Thomas, S. Prathapan, S. Sugunan, Synthesis of dimethyl acetal of ketones: design of solid acid catalysts for one-pot acetalization reaction, Micropor. Mesopor. Mater. 80 (2005) 65-72; K.-i. Shimizu, E. Hayashi, T. Hatamachi, T. Kodama, Y. Kitayama, SO_ {3} H-functionalized silica for acetalization of carbonyl compounds with methanol and tetrahydropyranylation of Alcoholics, Tetrahedron Lett. 45 (2004) 5135-5138; S.-J. Ji, L. Wu, Acetalization of carbonyl compounds catalyzed by polymer-bound metal complexes, Journal of Molecular Catalysis A: Chemical 202 (2003) 41-46; T. Kawabata, T. Mizugaki, K. Ebitani, K. Kaneda, Highly efficient heterogeneous acetalization of carbonyl compounds catalyzed by a titanium cation-exchanged montmorillonite, Tetrahedron Lett. 42 (2001) 8329-8332; S. Porwanski, P. Salanski, N. Panaud, G. Descotes, A. Bouchu, Y. Queneau, Regioselectivity in acid- or base-catalysed acetalation of sucrose: selection of [OH-2, OH-3] or [OH-4, OH-6] diols, Top. Catal. 13 (2000) 335-338, among others) since these do not They need to dissolve to act.

Heterogeneous catalysts have several advantages over homogeneous (dissolved) catalysts, so They are the most used in industrial processes:

- ease of reagent separation and products; the catalyst is in solid phase so it can easily be separated by a simple filtration stage (solid phase catalyst, different from the liquid or gas phase more common in the final products).

- greater robustness, supporting higher ranges of temperature and pressure.

- lower corrosive capacity; this allows a Longer duration of equipment in the industry.

- lower toxicity, since most of they are harmless in contact with the skin and not volatile, which allows to easily comply with the current safety regulations of use.

- possibility of reusing it catalyst, which means cost savings and in many cases operation time.

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The activity of a catalyst must be the suitable for the reaction to catalyze. A low activity results in poor performance, which translates into low profitability Economic or high production times. On the contrary, a very high activity results in the production of reactions not desired and thereby to contamination of the desired compound with reaction byproducts. This is especially important in this reaction, since acetals and hemiacetals are sensitive to acidic media For this reason, the degree of acidity of the Catalyst must be carefully controlled.

Another aspect to consider is the production of water as a reaction byproduct (figure 1). Being a equilibrium process, the presence of water in the reaction medium can shift the balance towards reagent formation, reaching a steady state that prevents getting better yields If the equilibrium situation is not the desired one, it is possible to resort to various strategies to eliminate such compound (water). One of these strategies is distillation continues by formation of an azeotrope. Another, the use of compounds that can act as reagents and at the same time as desiccants, such as trialkyl orthoformate, in the case of acyclic acetals, which remove water from the medium of reaction. These process modifications are different. methodologies that do not affect the claims here raised.

In some procedure described it has been used activated carbon in the acetal obtaining reaction, but never used as a catalyst but as an adsorbent of water and by-products. An activated carbon that has not been prepared to have acidic properties will not act properly as a catalyst in this reaction.

Detailed description of the invention

The present invention consists in the description of a synthetic procedure for the reaction between a compound containing a carbonyl group (aldehydes and / or ketones) and a alcohol. The molar ratio between both compounds can be 1: 1 (recommended for obtaining mixed acetals, that is, those acetals formed by intramolecular reaction with a hydroxyl group present in aldehydes and / or starting ketones and the corresponding alcohol or that are part of a cycle), 1: 2 (suitable for obtaining symmetric acetals) or higher than the latter if technical reasons, depending on the reagents used and the conditions used, as indicated. In addition to these compounds an acid catalyst is added in amounts that can vary from 0.1 to 20% of the reagent mass. This catalyst, in our case is a coal prepared from a material carbonaceous (mineral coal, charcoal, activated carbon or others) by treatment with sulfuric acid, which has more than 40% by weight of carbon, between 0.5 and 15% by weight of sulfur, oxygen in a amount that is at least 150% by weight of the sulfur content and varying amounts of hydrogen, nitrogen or other elements minority This coal can be in the form of monoliths, dust, granules, fibers, fabrics or others. The use of this catalyst in this Reaction is the main novelty of this invention.

The reaction is generally carried out in a temperature range between 0ºC and 300ºC, depending on the reactivity of the compounds used. The reaction can take carried out in the presence of a solvent other than reagents used or performed only with said reagents being able to employ methods to remove water and other formed by-products, or not. The reaction is maintained under the conditions described. until it is considered that it has reached equilibrium, it has completed the reaction, or the yield obtained is satisfactory.

In the following figure (figure 1), in general, a scheme of the reaction used where R 3 = R 4. In the first stage of the reaction (first line of the figure) the obtaining of the hemiacetal is represented. In the second stage of the reaction, said hemiacetal reacts with another Alcohol molecule to give rise to acetal. In both stages it employs the catalyst mentioned above.

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Embodiments of the invention

Some examples of embodiment of the invention.

Example 1

To a mixture of 1 mol of cyclohexanone and 2 moles of methanol is added 2% by mass of the catalyst mentioned. The mixture is heated to 60 ° C and kept under stirring for 30 minutes

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Example 2

To a mixture of 1 mol of cyclohexanone with and 4 1 mol% of butanol is added by mass of the catalyst mentioned. The mixture is heated until the azeotrope begins to distill water / butanol, and stays that way for 4 hours. The performance that is obtained is greater than in the absence of distillation.

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Example 3

To a mixture of 1 mol of benzaldehyde with 4 moles of ethanol are added 2% by mass of the catalyst mentioned. The mixture is heated to 60 ° C and kept under stirring for 30 minutes

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Example 4

To a mixture of 1 mol of benzaldehyde with 4 moles of ethanol and 3 moles of triethyl orthoformate, used both as reagent and desiccant, 2% by mass of the cited catalyst. The mixture is heated to 60 ° C and maintained in Stirring for 30 minutes. The yield you get is higher that in the absence of triethyl orthoformate.

Industrial application

When using a solid catalyst, its mode of Application is typical of heterogeneous catalysis. In case of perform the reactions catalyzed in liquid phase, just Mix the catalyst with the starting reagents. This can perform well discontinuously, filtering the catalyst at terminate the reaction to separate it and then reuse it, or well continuously, by passing a stream of reagents for an immobilized bed of the catalyst, renewing it when it is considered that you have lost your activity. In the reactions In the gas phase it is advisable to carry out the reaction by passing a gaseous stream of the reagents through an immobilized bed of the catalyst.

Other documents

1. Spanish patent ES2275415 (application no. 200501605).

Claims (2)

1. Procedure for obtaining acetals a starting from aldehydes and / or ketones by reaction with alcohols, using as a catalyst an acidic carbon. Said catalyst, in whose preparation has been used sulfuric acid, has more than one 40% by weight of carbon, between 0.5 and 15% by weight of sulfur, oxygen in an amount that is at least 150% by weight of the sulfur content and varying amounts of hydrogen, nitrogen or Other minority elements. The procedure for obtaining acetals claimed is characterized : a) Because it can be done at temperatures from 0 to 300 ° C, with stirring or in its absence, in continuous or discontinuous and at pressures from 0.1 to 1000 atm. b) Because the duration of the procedure understand until it is considered that it has reached equilibrium, it has completed the reaction, or the yield obtained is satisfactory. c) By the use of an acid catalyst of carbonaceous nature, prepared from a carbonaceous material and sulfuric acid as described in the preamble herein claim.

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2. Method according to claim 1, understands: a) The use of ketones, aldehydes and alcohols, as described in the invention, as well as its precursors. b) The use as catalyst of any material carbonaceous regardless of its shape, size or composition, whose characteristics have been described in claim 1.