ES2362891B1 - 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 as a catalyst an acidic carbon, described in Spanish patent ES2275415. Coals used as catalysts have the advantage of having a high specific surface area, with the appropriate acidity to give rise to this reaction, avoiding, as far as possible, the formation of by-products. # The use of catalysts in the acetal obtaining reaction decreases the reaction time, allows the process to be carried out under mild temperature conditions, reducing the production of unwanted 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 "Chemical and Chemical Industry" Technical Sector, understood as such in its broadest sense, since it also includes Pharmacy and its Industry (drug synthesis), Food and its Industry (food additive synthesis), Polymers and their industry (acetals are precursors of various plastics), Cosmetics and its Industry (synthesis mainly of fragrances and aromas) and Chemical Engineering or Process Engineering, the latter as the industrial application of Chemistry.

Technical Field of the Invention

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

where,

R1, R3 and R4 can be linear or branched hydrocarbon chains, containing aromatic or aliphatic groups, unsaturated or not, or both, containing or not heteroatoms such as N and / or O.

R1-R3 or R3-R4 can be hydrocarbon chains, linear or branched, containing aromatic or aliphatic groups, unsaturated or not, containing or not heteroatoms such as N and / or O.

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 acid catalysis is sufficiently known to appear in Organic Chemistry textbooks (PGM Wuts, TW 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 this could react instead of alcohol, giving rise to the corresponding hydrates of the carbonyl compound used, 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 obtain the hemiacetal (Figure 1), which generally reacts with another molecule of alcohol to give rise to the acetal (Figure 1).

For the reaction to be completed in a reasonable time and energy cost, the presence of an acid catalyst is necessary. Catalysts that need to dissolve in water cannot be used since this, as mentioned above, interferes with the reaction leading, again, to the formation of the starting products

or unwanted products, especially when it is in significant quantities. Therefore, the catalysts used in this process are, in general, soluble in organic solvents (for example, dry hydrochloric acid in absolute ethanol). Heterogeneous, solid catalysts can also be used (E. Pérez-Mayoral, R. M. Martín-Aranda, A. J. López-Peinado, P. Ballesteros, A. Zukal, J. ˇ

Cejka, Green Synthesis of Acetals / Ketals: Ef fi cient 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 MoO3 / SiO2 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, SO3 Functionalized silica for acetalization of carbonyl compounds with methanol and tetrahydropyranylation of alcohols, Tetrahedron Lett. 45 (2004) 5135-5138; S.-J. Ji, L. Wu, Acetalization of carbonyl compounds catalyzed by polymerbound 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 [OH2, OH-3] or [OH-4 , OH-6] diols, Top. Catal. 13 (2000) 335-338, among others) since they do not need to dissolve to act.

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

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

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greater robustness, supporting higher ranges of temperature and pressure.

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less corrosive capacity; This allows a longer duration of equipment in the industry.

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

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possibility of reusing the same catalyst, which means cost savings and in many cases of operating time.

The activity of a catalyst must be adequate for the reaction to be catalyzed. Low activity results in poor performance, which translates into low economic profitability or high production times. On the contrary, a very high activity results in the production of undesired reactions and thereby 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 process in equilibrium, the presence of water in the reaction medium can shift the equilibrium towards the formation of reagents, reaching a steady state that prevents better yields. If the equilibrium situation is not the desired one, it is possible to resort to various strategies to eliminate said compound (water). One of these strategies is the continuous distillation 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 reaction medium. These process modifications are different methodologies that do not affect the claims presented here.

In some process described, activated carbon has been used 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 adequately act as a catalyst in this reaction.

Detailed description of the invention

The present invention consists in the description of a synthetic process for the reaction between a compound containing a carbonyl group (aldehydes and / or ketones) and an 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 starting aldehydes and / or ketones and the corresponding alcohol or forming part of one 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, indicate this. 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 carbon prepared from a carbonaceous material (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 an amount that is at least 150% by weight of the sulfur content and varying amounts of hydrogen, nitrogen or other minor elements. This carbon 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 0 ° C and 300 ° C, depending on the reactivity of the compounds employed. The reaction can be carried out in the presence of a solvent other than the reagents used or carried out only with said reagents, methods can be used to remove water and other by-products formed, or not. The reaction is maintained under the conditions described until it is considered that it has reached equilibrium, the reaction has been completed, or the yield obtained is satisfactory.

The following figure (Figure 1) shows, in general, a scheme of the reaction used where R3 = R4. In the first stage of the reaction (first line of the fi gure), the hemiacetal is obtained. In the second stage of the reaction, said hemiacetal reacts with another molecule of alcohol to give rise to acetal. In both stages the above-mentioned catalyst is used.

Embodiments of the invention

Some examples of embodiment of the invention are described below.

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.

Example 2

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

Example 3

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

Example 4

To a mixture of 1 mol of benzaldehyde with 4 moles of ethanol and 3 moles of triethyl orthoformate, used both as a reagent and desiccant, 2% by mass of the said catalyst is added. The mixture is heated to 60 ° C and kept under stirring for 30 minutes. The yield obtained is greater than in the absence of triethyl orthoformate.

Industrial application

By using a solid catalyst, its mode of application is typical of heterogeneous catalysis. If the catalyzed reactions are carried out in the liquid phase, it is enough to mix the catalyst with the starting reagents. This can be done either discontinuously, filtering the catalyst at the end of the reaction to separate it and then reusing it, or continuously, by passing a stream of the reagents through an immobilized bed of the catalyst, renewing it when it is considered that He lost his activity. In the gas phase reactions 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 (4)

1. Procedure for obtaining acetals from aldehydes and / or ketones by reaction with alcohols, using as a catalyst an acidic carbon. Said catalyst, in whose preparation sulfuric acid has been used, has more than 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 content. of sulfur and varying amounts of hydrogen, nitrogen or other minor elements. The procedure for obtaining acetals claimed is characterized: a) Because it can be performed 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 includes until it is considered that it has reached equilibrium, the reaction has been completed, or the yield obtained is satisfactory. c) By the use of an acid catalyst of a carbonaceous nature, prepared from a carbonaceous material and sulfuric acid as described in the preamble of the present claim. 2. Method according to claim 1, comprises: a) The use of ketones, aldehydes and alcohols, as described in the invention, as well as their precursors. b) The use as catalyst of any carbonaceous material regardless of its shape, size or composition, the characteristics of which have been described in claim 1. SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 200902376 SPAIN Date of submission of the application: 22.12.2009 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: See Additional Sheet RELEVANT DOCUMENTS

Category

Documents cited Claims Affected

TO

MARTÍN-ARANDA, R. M. et al. "Acid activated Carbon for the acetalization of carbonylic compounds". Poster, 23nd Biennial Conference of Carbon, July 1997. American Carbon Society. Pennsylvania (USA). See Experimental. 1.2

TO

YANG, S. et al. "Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on carbon active carbon". Journal of Zhejiang University Science B, 2005, Vol. 5, N. 6, pages 373-377. See Summary and Experimental. 1.2

TO

EN 2275415 A1 (UNED & UNIVERSITY OF EXTREMADURA) 01.06.2007, claims 1-4. 1.2

TO

US 20040024260 A1 (DEGUSSA AG) 05.02.2004, page 2, paragraphs 14-19,26-29. 1.2

TO

US 5917059 A (BASF AKTIENGESELLSCHAFT) 29.06.1999, column 3, lines 33-36. 1.2

TO

RABINDRAN J. & PANDURANGAN, A. "Al-MCM-41 as an efficient heterogeneous catalyst in the acetalization of cyclohexanone with methanol, ethylene glycol and pentaerythiol". Journal of Molecular Catalysis A: Chemical, 2006, Vol. 256, pages 184-192. See summary. 1.2

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims • for claims no:

Date of realization of the report 18.02.2011

Examiner N. Martín Laso Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 200902376 CLASSIFICATION OBJECT OF THE APPLICATION C07B41 / 04 (01.01.2006) C01B31 / 08 (01.01.2006) B01J21 / 18 (01.01.2006) Minimum documentation sought (classification system followed by classification symbols) C07B, C01B, B01J Electronic databases consulted during the search (name of the database and, if possible, terms of search used) INVENES, EPODOC, WPI, NPL, XPESP, CAS. State of the Art Report Page 2/4  WRITTEN OPINION Application number: 200902376 Date of Completion of Written Opinion: 02.28.2011 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 1 and 2 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 1 and 2 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 200902376 1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

MARTÍN-ARANDA, R. M. et al. "Acid activated carbon for the acetalization of carbonylic compounds". Poster, 23nd Biennial Conference of Carbon, July 1997. American Carbon Society. Pennsylvania (USA). 1997

D02

YANG, S. et al. "Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on carbon active carbon". Journal of Zhejiang University Science B, 2005, Vol. 5, N. 6, pages 373-377. 04.10.2005

D03

ES 2275415 A1 (UNED & UNIVERSITY OF EXTREMADURA) 01.06.2007

D04

US 20040024260 A1 (DEGUSSA AG) 05.02.2004

D05

US 5917059 A (BASF AKTIENGESELLSCHAFT) 06/29/1999

D06

RABINDRAN J. & PANDURANGAN, A. "Al-MCM-41 as an efficient heterogeneous catalyst in the acetalization of cyclohexanone with methanol, ethylene glycol and pentaerythiol". Journal of Molecular Catalysis A: Chemical, 2006, Vol. 256, pages 184-192.

2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement The application refers to a process for obtaining acetals from aldehydes and / or ketones by reaction with alcohols, using as a catalyst an acidic carbon in whose preparation sulfuric acid has been used. Document D01 discloses a process for obtaining acetals from aldehydes by reaction with alcohols in which an activated carbon of an acidic character is used as catalyst in whose preparation nitric acid has been used. The acetal is prepared by mixing the aldehyde and the corresponding alcohol in the absence of solvent and heating the mixture at 75 ° C-110 ° C, then the carbon catalyst is added and allowed to react for 0.5-6 hours (Experimental). Document D02 discloses a process for obtaining acetals from aldehydes and / or ketones by reaction with alcohols in which an activated carbon impregnated with tungstosilic acid is used as catalyst. The acetal is prepared by mixing the alcohols with the ketone and the catalyst, heating to reflux and finally separating the acetal formed by distillation. Among the prepared acetals is the ethylenic acetal of cyclohexanone. (Summary, Experimental). Document D03 discloses a carbon catalyst in whose preparation sulfuric acid has been used and which has more than 40% by weight of carbon, between 0.5 and 15% by weight of sulfur, oxygen in an amount that it possesses at minus 150% by weight of sulfur content and varying amounts of hydrogen, nitrogen or other minor elements. Said catalyst has been used to carry out acylation reactions of alcohols (claims 1-4). Document D04 discloses a process for obtaining acetals from aldehydes and / or ketones by reaction with alcohols in which sulfonic acids, such as methanesulfonic acid or ptoluenesulfonic acid, can be used as catalysts. The acids can be used in soluble form or immobilized on a solid. It is considered that none of the above documents, taken alone or in combination, disclose or direct the person skilled in the art towards a procedure for obtaining acetals and / or ketones in which a coal is used as catalyst in whose preparation it has been used sulfuric acid, an acid that gives the carbon catalyst a certain acidity and specificity to carry out the acetal formation reaction. Therefore, the invention defined in claims 1 and 2 of the application is new and has inventive activity (Art. 6.1 and 8.1 LP 11/1986). State of the Art Report Page 4/4