FI57742C - PROCEDURE FOR FRAMSTATION OF 3-METHOXY-4-HYDROXIBENTSALDEHYD - Google Patents

Description

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Patent · oeh regleterrtyralaan Ainekin uttagd oeh uti.ikdftm publicerad 30.06.80 (32) (33) (31) Pyritty «tuolkuut — Begird prlerlt * 10.02.75

Norway-Norway (NO) 750420 (71) Borregaard Industries Limited, 1701 Sarpsborg, Norway-Norway (NO) (72) Hans Evju, Sarpsborg, Norway-Norway (NO) (74) Berggren Oy Ab (5 * 0 Method of production 3 -methoxy-U-hydroxybenzaldehyde - Preparation of 3-methoxy-U-hydroxybenzaldehyde

The present invention relates to a process for the preparation of 3-methoxy-4-hydroxybenzaldehyde, better known as vanillin, hereinafter referred to as.

Vanillin is currently produced industrially by oxidizing the waste solution obtained from the sulphite process of cellulose production. This waste solution contains e.g. a significant part of the lignin content of cooked wood in the form of its various derivatives. When oxidizing the waste solution, more specifically when oxidizing the lignin component of the waste solution, e.g. vaniliinia. Calculated on a dry basis, such a waste solution contains about 45% lignin, about 30% sugar and about 25% inorganic constituents. During alcoholic fermentation, 60-65% of the sugar in the waste solution can be removed so that the fermented waste solution contains, on a dry basis, about 55% lignin, about 1% sugar and about 30% inorganic constituents.

As a raw material for the production of vanillin, a fermentation or unused waste solution can be used, which is oxidized as described in Norwegian Patent Publication No. 8 * 1422. According to this patent, the oxidation is carried out by heating the waste solution in a strongly alkaline state and contacting it with molecular oxygen, keeping the reaction mixture in the range of 100-185 ° C for most of the reaction time, and preferably at a temperature not exceeding 170 ° C, and introducing oxygen into the fine mixture. in a form containing air diluted with an inert gas, the partial pressure of oxygen being kept below 0.46 kg / cm in the gas mixture. When using such an oxidation method, it is preferable to use an oxidation catalyst, e.g. a copper salt such as copper sulfate. It is also disclosed in this patent publication that it is preferable to use 0.7 to 1.2 parts by weight of sodium hydroxide per 1 part by weight of solids in the waste solution.

When vanillin is prepared according to a known method using e.g. the method according to the above-mentioned Norwegian patent publication 84422, a relatively high specific consumption of sodium hydroxide per amount of vanillin produced takes place. In addition, a coating consisting mainly of inorganic compounds settles in the autoclave and its associated piping system, leading to the necessary extraction equipment for the vanillin formed. This is especially the case when using calcium sulphite waste solution, whether or not this has been used in advance. This means that the manufacturing equipment must be cleaned regularly, either by washing or, if necessary, by manual cleaning.

Cleaning production equipment becomes expensive both in terms of direct labor costs and production losses, and washing and cleaning equipment also causes production process-technically unfavorable interruptions.

The object of the present method is therefore to completely or partially eliminate said formation of deposits in the manufacturing plant.

It has now surprisingly been shown that if the waste solution is ultrafiltered as disclosed in Norwegian Patent Publication No. 127,545, there are no difficulties with respect to said settlements forming in the production plant. It has also been found that when using the production equipment used for the production of vanillin according to the prior art, i.e. in the case of production equipment in which deposits have formed, these deposits are lost when ultrafiltered waste solution is used in the same equipment.

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As is apparent from Norwegian Patent Publication 127.5 ^ 5, relatively pure lignin fractions can be obtained by fractionation of a sulphite waste solution by the method described therein, since the waste solution can be fractionated on the basis of the molecular weight of its constituents.

Using the method according to the invention, i. first the ultrafiltered waste solution and then the oxidation of the relatively pure lignin concentrate thus obtained, a further advantage is obtained that the production of vaniline per autoclave unit is higher, the specific consumption of sodium hydroxide is lower and, as previously mentioned, the autoclave and production equipment remain substantially hardware cleaning can be eliminated in whole or in part. Experiments have shown that a higher vanillin yield can be obtained by using a fraction containing lower molecular weight lignin compounds, but in industrial production it is hardly advantageous to prepare vanillin from an ultrafiltered sulphite waste solution from a specific lignin fraction, because for practical reasons which is substantially free of low molecular weight ingredients such as sugar and inorganic compounds.

Ultrafiltration of the waste solution can be accomplished in accordance with Norwegian Patent Publication 127 5 ^ 5 using membranes adjusted to retain a more specified average molecular weight fraction. By carrying out the filtration in two or more steps and using suitable membranes, it is possible to separate the molecular weight fraction of lignin which gives the highest yield of vanillin, calculated from lignin, namely the smaller molecular weight fraction.

The following examples illustrate the process of the invention using as a starting material a calcium sulfite waste solution obtained from the production of cellulose from spruce, and this waste solution is hereinafter referred to as a stock solution.

Comparative Examples A and B show the preparation of vanillin from this stock solution when used without prior ultrafiltration.

The autoclave used in the production of vanillin was of the type described in Norwegian Patent Publication 8aa22 Figure 1.

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Example A

The autoclave was filled with about 40 to 55 volumes of a liquid containing 7 parts by weight of water, 0.8 parts by weight of sodium hydroxide and 0.0167 parts by weight of copper sulfate pentahydrate for each part of solids of the above-mentioned stock solution. The autoclave was then sealed and the oxidation was performed as described in Example 2 of Norwegian Patent 84422.

The yield of vanillin obtained was 6.1% based on the solids in the waste solution, which corresponds to 13.5% based on lignin.

Example B

In this experiment, a stock solution previously used in the preparation of alcohol was used, and the autoclave was filled to about 40% by volume with a liquid containing 7 parts by weight of water, 0.8 parts by weight of sodium hydroxide and 0 parts by weight of solids from the stock solution of alcohol production. .0167 parts by weight of copper sulfate pentahydrate. The liquid was oxidized as described in Example A to give vaniline 7.5 in yield of 16 based on the solids in the spent waste solution, corresponding to 13.6% based on lignin.

Example 1

The above stock solution was ultrafiltered using a membrane with a molecular weight cut-off of about 6,000, whereby the smaller molecular substances in the waste solution were removed. A concentrate with a solids content of 49.5% of the solids content of the stock solution was obtained, and the solids content of the concentrate comprised 74% lignin.

The resulting lignin-enriched concentrate was used in the preparation of vanillin.

About 40 to 55 volumes of the autoclave were filled with a liquid containing 7 parts by weight of water, 0.8 parts by weight of sodium hydroxide and 0.0167 parts by weight of copper sulfate pentahydrate per part by weight of solids obtained, and the liquid was oxidized as described in Example A.

The yield of vanillin was 9.8% based on the solids in said concentrate, which is about 31% higher than that obtained using the alcoholic acid solution, and the yield of 5,57742 was 13.3% based on lignin.

Example 2

The above base liquor was ultrafiltered so that solids having a molecular weight of less than 65,000 were removed as a filtrate. A concentrate having a solids content of 23% of the solids in the neural solution was obtained, and the solids in the obtained concentrate had a lignin content of 75.5% and a lignin molecular weight greater than about 65,000. , the solids ratios of water, sodium hydroxide and catalysts were the same as in the above examples. The yield of vanillin was 9% based on the solids in said concentrate, which corresponds to 11.9% based on lignin.

Example 3

The stock solution was ultrafiltered in two steps, using membranes with a molecular weight cut-off of about 65,000 in the first step. The filtrate from the first step containing solids with a molecular weight of less than about 65,000 was used in the second step ultrafiltration using filtration membranes having the molecular weight cut-off was about 6,000. The concentrate from the second step thus contained solids with a molecular weight in the range of 6,000-65,000.

The solids in the latter concentrate accounted for 25.5% of the solids content of the stock solution and the lignin content of the solids was 72%. The concentrate was used to prepare vanillin using the preparation method of the previous examples, with the ratio of solids, water, sodium hydroxide and catalysts in the reaction liquid being the same as described above. The yield of vanillin, calculated from the amount of solids in said concentrate, was 10.7 l, which is 9.2% higher than the yield obtained in Example 1 and ^ 3% higher than that obtained by oxidizing the fermentation effluent solution according to Example B.

Calculated from lignin, the yield of vanillin was 14.9% ·

As can be seen from the above examples, the process of the invention provides a significantly higher yield based on the amount of solids in the reaction liquid subjected to oxidation by air 6 57742, which has several important advantages, namely a significantly higher yield per autoclave volume and a significantly higher yield of sodium hydroxide used. which is of great importance because about 75% of the chemical costs of using the prior art are caused by sodium hydroxide. As can be seen from the comparison of Example B and Example 3, the increase in yield based on the solids content of the reaction liquid used was more than 40%, and using the same amount of sodium hydroxide in both examples, greater than 40% increase in yield based on sodium hydroxide used is achieved using the process of the invention.

As mentioned above, the present method provides the additional advantage that the difficulty of settling in autoclaves and subsequently fitted equipment is eliminated in whole or in part, which is of great importance in the industrial production of vanillin, as it completely or partially eliminates equipment cleaning costs. interruption and guarantee the continuity of production. It is assumed that the effective operating time can be increased by 5-10% when using the method according to the invention.