FI58906B - FOERBAETTRAT FOERFARANDE FOER FRAMSTAELLNING AV VANILLIN - Google Patents

Description

EdSFn [ft] (11) Advertisement) publication 5 8906

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C (45) Patent granted 11 05 1931 Patent meddelat (51) Kv.ik.Vci.3 C 07 c 4-7 / 58 ENGLISH —EN N LAN D (21) P «« "ttl» »k * mu · - Patwittmeiciilng 783799 (22) H «k * ml * pllv« - AfM0kntnf * dag 11.12.78 * * (23) Alkupllva— · Glltlgh * t * d * f 11.12.78 (41) Tullut julkisukil —Bllvit affuntllg 22 06 80 Γ *** 1 ** 1- '. * | UNH ^. | IW) «. N.

FatmtOch regietarstyralaan AnsOkan utl ** d och uti. * Krift.n puMk ^ nd 30.01.81 (32) (33) (31) Fyjrrfetejr * Tuoik «u» - «« gird priori ** (71) Yhtyneet Paperitehtaat Oy, PL U0, 37601 Valkeakoski, Finland-Finland (Fl) (72) Heikki Ahonen, Valkeakoski, Finland-Finland (Fl) (7 ^) Oy Kolster Ab (54) Improved method for the production of vanillin - Förbättrat förfarande för framställning av vanillin

The invention relates to a process for the preparation of vanillin by oxidizing the ultrafiltered lignosulphate formed in the production of sulphite cellulose, extracting the vanillin thus obtained with alcohol and extracting vanillin from the alcohol as its Na salt and complexing the isolated vanillin bisulphite complex with SO 2 after.

The invention is characterized in that only a part of said lignosulphate product with a molecular weight of more than 50 to more than 5,000 is used for the preparation of vanillin, that an aqueous solution of vanillin removed from the alcohol extract as its Na salt is evaporated to 5-15 times its original concentration, preferably 10 wherein the concentrated vanillin is converted to its bisulfite complex using SO 2, that the concentrated aqueous solution of bisulfited vanillin is extracted free of non-aldehyde impurities with the same alcohol as the isolation of Na-vanillinate from the reaction mixture. to remove dissolved alcohol, and that the hisulfite complex is extracted during or immediately after decomposition as an organic solvent as free vanillin, that the organic solvent is u The free vanillin is washed in this Liu trap with slightly alkaline water, and that the organic solvent is evaporated off from the solution thus treated under a slight vacuum so that, in addition, the guaiacol is removed from the vanillin.

Vanillin is now produced mainly by oxidizing lignin from the decomposition of softwood sulphite cellulose under temporal conditions.

It is known from FI patent application l60 303 to enrich the lignin content of the waste liquor before oxidation by ultrafiltration. An advantage of the present invention over the known method is that the final purification of vanillin can be simplified by changing the properties of the raw material by ultrafiltration and using a raw material with a molecular weight of more than 50,000. In typical vanillin processes, this oxidized waste liquor is extracted, for example, with a partially water-soluble alcohol (Sandborn, FI Pat. No. 20,078 from 19 ^), whereby vanillin and all other low molecular weight Na-forming ingredients are dissolved in the alcohol phase in salt form. The dissolution is mainly due to the very high salt and alkali concentration of the oxidized aqueous phase, causing the so-called desalination effect. In another also known method, an oxidized broth is neutralized to release vanillin from its salts and extracted into an organic solvent under conditions below pH 7. The organic solvent used may be benzene, toluene, xylene or even an aliphatic solvent. This procedure is clear e.g. FI patent 17,966 from 1936.

In all known methods for the preparation of vanillin, after vanillin with its typical impurities has been transferred to a solvent, the aim is to separate this from these impurities.

U.S. Pat. No. k 021 1 * 93 discloses a process for separating phenolic impurities from vanillin by bisulphilizing a highly basic aqueous solution of Na vanillinate and adjusting the pH to 3.5 to ^ + 0, simultaneously extracting with alcohol to avoid precipitation of awkward tarry impurities from the solution, and decomposing hisulfiittikompleksi. The process according to the invention differs from the process known from U.S. Pat. No. 1,021,113 in that when concentrating an aqueous Na-vanillinate solution by evaporation to its multiple concentration before bisulphitation, it is not necessary to extract the solution with alcohol at the same time to precipitate tar-like impurities. adverse vanillin condensation and tar formation occur and thus facilitates subsequent distillation in the process.

3 58906

Most separation methods are of the type in which step by step vanillin is brought into an increasingly pure form as the main component. These separation operations mainly use physical separations and hisulfite complexation to separate aldehydes from other chemicals. Physical separation operations are often unsatisfactory for two reasons: They vaguely separate vanillin and impurity. They force the recirculation of large amounts of vanillin in the process, and thus, as the impurities continue to accumulate, there is an increasing need for separation. If, on the other hand, it is desired to avoid the recycling of impurities, large vanillin losses will inevitably occur.

The vanillin manufacturing process can be simplified if the amount of impurities can be reduced from the outset. It is obvious that starting from a raw material with a higher than usual lignosulfonate content also results in a higher than usual vanillin content in the oxidized broth. Oxidation methods are not addressed here, as they have been described in many patent and other publications.

It has now surprisingly been found that the largest impurity in vanillin, acetovanillin, is formed by oxidation mainly of low molecular weight lignins. Removal of low molecular weight lignins from the oxidizable broth prior to oxidation results in a 2/3 reduction in acetovanillin from normal. This advantage allows other improvements and simplifications in the vanillin manufacturing process described below.

In those vanillin production processes in which vanillin is extracted with alcohol, vanillin involves the addition of typical impurities, acetovanilone, parahydroxybenzaldehyde, guaiacol, vanillic acid, o-vanillin, in addition to a large amount of low molecular weight, partially desulfonated lignin.

The removal of vanillin from the alcohol can, of course, be carried out in a number of different ways, by evaporation or extraction in the form of the Na salt or by extraction as free vanillin. When vanillin is extracted from the alcohol as the Na salt, it is convenient to further treat it to form a sulfur dioxide bisulfite complex with the aid of sulfur dioxide. Non-aldehyde uncomplexed impurities can be easily extracted from this bisulfite complex, as can partially desulfonated lignins, which are referred to as "tars" at this stage. The relatively pure vanillin bisulfite complex thus obtained must be decomposed, and this decomposition is usually carried out using sulfuric acid, whereby sulfur dioxide is released. In such decomposition, however, a considerable portion of the vanillin is destroyed by polymerization, partly by itself, partly by its impurities.

It is also known to decompose the bisulfite complex of aldehydes using * 58906 bases, whereby the bisulfite is converted to sulfite. It is further known to extract aldehydes from such a complex solution directly as a solvent at an elevated temperature.

It has been found that the best method is to combine the two vanillin release methods described above. Decompose with alkali and extract as organic solvent at the same time. When soda is used for the decomposition, the end of the decomposition is reached at pH 7.9, which in extensive experiments has also proved to be the best pH for extraction.

Upon delivery at said pH, all tarry impurities remain in the alkaline aqueous phase and only the aldehydes are transferred to the organic solvent. The best organic solvents for use herein are aromatic solvents, especially toluene. From the resulting vanillin-toluene solution, it is now very advantageous to extract aldehydes which behave more acidically than vanillin, in particular p-hydroxybenzaldehyde. This is best done with mildly alkaline water.

The final purification is best carried out by evaporating the toluene, using a maximum temperature of 130 ° C and a pressure of about 5 kPa. Such evaporation can be performed in any apparatus, but is best accomplished with multiple thin film evaporators with different heating zones. Evaporation is carried out at constant pressure as the temperature rises towards the bottom of the apparatus from about 60 ° C to 130 ° C. Evaporation is then continued in another similar device at almost the same temperature, but now at a substantially lower pressure of 0.2 kPa. In this device, vanillin evaporates from its high molecular weight impurities and higher-boiling impurities. By proceeding as described, high purity crude vanillin with a purity of more than 99.5% is obtained.

The invention is illustrated in the accompanying figure and in the following example.

Example

Sulphite waste broth from Finnish spruce sulphite soup was purified by ultrafiltration until the lignosulphonate content of the solution, calculated on the dry matter, was about Ö0% and more than 60% of the lignosulphonate had a molecular weight (M ^) of more than 5,000, U8% of more than 10,000, 32% of more than 20,000 and 23% 1 * 525 kg of such a solution after oxidation, containing 1.53% by weight of vanillin and having a density of 1.22, was extracted continuously with butanol.

The butanol extraction took place at 53 ° C and the density of the water-saturated n-butanol used was 0.803. The raffinate resulting from the extraction contained 0.002% vanillin. The extract obtained contained 1.1 * 8% by weight of vanillin. In addition to the above, the extract contained 1.01% by weight of dissolved organic substances other than vanillin. The butanol extract was back-extracted with water containing 0.2% w / w. Na0H added. This was to prevent harmful emulsion formation in 5,590,906 extractions. The resulting aqueous raffinate now contained 2.88% by weight of vanillin, and the butanol extract contained 0.03% vanillin, respectively. The same butanol was used six times to extract vanillin from the oxidized feedstock. Butanol was not found to differ in any way after the first time and for the sixth time.

The resulting water containing vanillin Na salt, a total of 2,370 kg, was evaporated on a vacuum evaporator at 35 ° C to Π53 kg. The evaporated product contained about 150 g / kg of vanillin with a total dry matter of more than 300 g / kg.

A concentrated aqueous solution of Na-vanillate was treated in a stirred reactor with sulfur dioxide gas to form the Na-bisulfite complex of vanillin in a known manner. Sulfur dioxide gas was introduced into the reactor until the pH had dropped to h, 5 · The aqueous solution of the bisulfite complex became pale, and tar-like substances began to separate from it. Em. the solution was passed to an extraction column where it was treated countercurrently with n-butanol at 25 ° C. Non-aldehyde impurities were extracted from aqueous solution into butanol, as were tarry ingredients.

The bisulfite complex thus purified was clear and pale in color. The n-butanol used for the extraction contained e.g. 30 g / l guaiacol, 35 g / l acetovanillon and 5 g / l vanillin and about 100 g / l other, mainly tarry, desulphonated lignins.

The purified vanillin bisulfite complex was decomposed at 65 ° C using a vacuum to evaporate the solution and adding soda until the pH was 7.9. · The aqueous solution thus obtained was continuously extracted with toluene to give a clear yellowish toluene extract. This extract contained 8l g / l vanillin, the base product contained 2b g / l vanillin.

The resulting toluene extract was washed twice with a small amount of pure water to remove residues from the Na salts, as well as any heavy phase over-extracted. In the toluene solution thus obtained, the purity of vanillin is more than 98%. The toluene solution was evaporated, so that a small amount of guaiacol also evaporated with toluene.

Solid, brown-yellow crude vanillin with a melting point of 79.5 ° C was distilled in vacuo at a temperature of 10 ° C and a pressure of 1-2 mm Hg. During distillation, the entire distillate was recovered, leaving about 5% of the feed volume of the bottom product. The base product was completely dissolved in the live solution, and can be returned to the process. The color of the distillate was pale yellow and the melting point was 80 ° C. The resulting distillate was dissolved in water to a 5% solution, filtered through activated carbon to give a yellowish color, and crystallized from water in the usual manner by cooling to 5 ° C. The crystals were separated by filtration, and dried at 60 ° C and U-5 mm Hg for H hour. The melting point of the obtained crystals was 8.1 ° -82.2 ° C. In the gas chromatographic study, acetovanillon 0.05% and orthovanillin 0.05 # were detected as impurities in the gas chromatography. No trace of other impurities was detected.

Claims (2)

58906 6 A process for the preparation of vanillin by oxidizing sulphite cellulose and ultrafiltered lignosulphate, extracting the vanillin thus obtained with alcohol and extracting the vanillin from the alcohol as its Na salt and converting the isolated vanillin to a disulfite complex using a SO 2, purifying the bisulfite that only a part of said lignosulphate product with a molecular weight exceeding 50- $ 5,000 is used for the preparation of vanillin, that an aqueous solution of vanillin removed from the alcohol extract as its Na salt is evaporated to 5-15 times its original concentration, preferably 10 times the concentration, in which the concentration of vanillin is converted to its bisulphite complex using wars that the concentrated aqueous solution of bisulfited vanillin is extracted free of non-aldehyde impurities while alcohol as the isolation of Na-vanillinate from the reaction mixture took place, the purified bisulfite complex is decomposed alkali, preferably using soda, with decomposition at the boiling point of the mixture to remove dissolved alcohol, and the bisulfite complex is extracted during decomposition or immediately thereafter with organic solvent the vanillin is washed in this solvent with slightly alkaline water, and that the organic solvent is evaporated off from the solution thus treated under a slight vacuum so that the guaiacol is further removed from the vanillin. Process according to Claim 1, characterized in that the vanillin is extracted from the decomposed reaction mixtures at the decomposition temperature with an organic solvent, and in that said organic solvent is toluene.