CS218738B1 - Method of making the 2-furaldehyde by pressureless continuous process - Google Patents

Abstract

The invention relates to a process for the preparation of 2-furaldehyde non-pressurized plant-based continual process materials containing pentosanes, where pentose prehydrolysates prepared in the first step using dilute sulfuric acid at the concentration 0.5 to 2.5%, respectively. dilute acid of hydrochloric acid at a concentration of 0.2 to 1% w / w in the second stage undergo dehydration of the pentoses to 2-furaldehyde, using as catalyst hydrochloric acid at a concentration of 5 to 15% wherein the dehydration products formed are separated so that the hydrochloric acid is free of 2-furaldehyde is fed into the reaction space and 2-furaldehyde is removed from the reaction medium distillation with water. The resulting product of the production method according to overtaking The invention is used in the manufacture of rhodium derivatives (furfuryl alcohol, tetrahydrofuran); refining oils, for preparing herbicides, for preparation resins as well as for the preparation of various nitrofurane derivatives that are used in pharmaceuticals industry.

Description

The invention relates to a process for the production of 2 -uraldehyde by a pressureless continuous process from various pentose and oligopentose containing solutions, such as e.g. pre-hydrolysates of different pentosanes containing plant raw materials, aqueous beech chip prehydrolysates resulting from a two-stage pulp production process, sulphite leaches from deciduous wood processing, pulp refining solutions of hemicelluloses, as well as waste from dialysis hemicelluloses;

The processes used to date for the preparation of 2-furaldehyde are largely one-stage, in which the pentosane hydrolysis and pentose dehydration are carried out in pressure equipment at a pressure of 0.7 to 1.2 MPa, with or without catalyst addition, while in the second In this case, acetic acid and formic acid, which are formed during the process, act as catalysts. There are facilities that operate both continuously and continuously. More recently, a non-pressurized one-step continuous process for the production of 2-furaldehyde and acetic acid was utilized using fluid technology according to U.S. Pat. U.S. Patent No. 5,768,549; 120 136, which can only be used to process free-flowing, granular pentosanes containing feedstocks that meet the fluidization conditions. Practically only sawdust of deciduous trees and the pulp of corn cobbles are considered. In this way, it is not possible to process fibrous agricultural waste materials and chips.

| All prior art processes for the production of 2-furaldehyde, which are mostly single-stage, have a number of disadvantages. In the case of pressure one-stage processes, these are in particular:

- 2-furaldehyde yields hardly reach 50% of the theoretical yield, - pressure equipment is capital intensive and requires a special solution to feed the feedstock to the reactor and empty lignocellulose, - in one-stage pressure equipment it is not possible to process small plant waste and sawdust, they are large, high steam consumption, - the concentration of 2-furaldehyde in the condensates is low and an additional amount of energy is required to isolate the 2-furaldehyde from the solution, - lignocellulosic waste is considerably moist and incinerated, or otherwise used.

The non-pressurized continuous process using fluid technology, although it has a number of advantages over pressure processes, also has some drawbacks. Only loose grained plant material such as e.g. sawdust and crushed corn cob. Fine fractions of unsorted raw material The drift, together with the formed 2-furaldehyde condensates, clog sequential bottlenecks of the device, limiting the continualization of the manufacturing process. When the granular material is fed to the reactor via a turnstile, airborne oxygen enters the reactor, which is known to decompose 2-furaldehyde, which reduces its yield. The condensation of the 2-furaldehyde vapors produced in the inert gas stream is more difficult, some of the non-condensed 2-furaldehyde vapors in the system are recirculated and thereby lost at the expense of recovery.

The above-mentioned drawbacks are solved by the invention, which consists in that in the first step pentose pre-hydrolysates are prepared using dilute sulfuric acid at a concentration of 0.5 to 2.5%, respectively. of dilute hydrochloric acid at a concentration of 0.2 to 1% are subjected to a dehydration of pentoses to 2-furaldehyde in a second step, using 5 to 15% hydrochloric acid as catalyst, whereby the dehydration products formed are separated such that -furaldehyde is led to the reaction space and 2-furaldehyde is removed from the reaction medium by distillation with water vapor. The dilute mineral acids used in the preparation of the prehydrolysates by partial hydrolysis are also further used for the dehydration of pentoses to 2-furaldehyde. In case dilute sulfuric acid is used, sodium chloride is added to the reaction mixture. According to the present invention, industrial solutions of pentoses and pentosanes, in particular beech chip prehydrolysate from pulp production, mother syrups after crystallization of D-xylose, pulp refining hemicelluloses and alkali cellulose preparations, can be used as the starting material dehydrated with hydrochloric acid.

The resulting degradation humic products are used either as a filler or as a humus-forming substance in the preparation of compost. The degraded lignocellulosic waste produced after treatment is used for briquetting and incineration or for the preparation of activated carbon, possibly as a humus-forming organic substance for composting. By appropriate delignification, pulp can be recovered from the lignocellulose.

The process according to the invention has a number of advantages over the known, in particular pressure-producing processes. It allows processing of any plant raw materials containing pentosanes. Only 2-furaldehyde is used only for Tahohydrolyzable pentosans, while it is used for 2-furaldehyde. wherein the lignocellulose residue may be used after treatment for various purposes such as e.g. for the preparation of pulp, for the preparation of agglomerated materials, for feeding, for the preparation of briquettes for combustion, resp. for the preparation of charcoal or activated charcoal etc. The yield of 2-furaldehyde to pentosanes is substantially higher. The device is not pressureless and therefore it is possible to use an acid-resistant enamelled reaction vessel and to use it. control that resists dilute HCl. The concentration of 2-furaldehyde in the solutions is high. The steam consumption is substantially lower than that of the currently used methods, since a suitable solution is simply to utilize the physically heat of the leaving residues after the reaction to preheat the incoming prehydrolysates. The non-pressurized system operates continuously, allowing good regulation and addressing environmental issues. »

For the dehydration of pentoses, the conditions for the formation of 2-furaldehyde are optimally selected and the decomposition conditions are limited as much as possible. As is known, the rate of dehydration of pentoses and the yield of 2-furaldehyde depend on the type of catalyst, its concentration, the reaction temperature, the time of the reaction, and the concentration of pentoses in solution. In the analytical determination of pentosans, 10 to 13% hydrochloric acid is often used as catalyst, often in the presence of NaCl. However, the spread of hydrochloric acid as a very effective dehydration catalyst at higher temperatures, however, in the plant; During long-term operation, its high and aggressiveness prevents it. The present invention is progressing to solve this problem by means of a new technological process and the use of suitable equipment materials, thereby achieving a higher effect.

i Example 1

Diluted mother syrup was used to prepare 2-furaldehyde after separation of D-xylose crystals. obtained by prehydrolysis of beech sawdust with dilute sulfuric acid. The content of pentoses - D-xylose and L-arabinose was 76%, calculated on dry weight. To ; 25 liters of 13% by weight were added to the reaction vessel hydrochloric acid and after heating to the temperature [boiling point], the investigated | solution obtained by diluting the syrup to a concentration of 30% solids. 5% hydrochloric acid was used for dilution. A 16.6 liter solution containing 5.18 kg of dry matter was used for the experiment. The resulting 2-furaldehyde was stripped in the next step. From this amount, 1.968 kg of crude 2-furaldehyde was obtained, which was neutral. The yield of 2-furaldehyde was 37.9%, calculated on dry weight. She left after the experiment! in a cauldron, hydrochloric acid and a precipitate of carbohydrate decomposition humic substances which were easy to filter out and the hydrochloric acid filtrate after treatment was used for the next experiment.

J Example 2

Concentrated beech chip prehydrolysate (ex works Bukóza, n. P., Vranov) was used for dehydration. The pentose content of the prehydrolysate was 45%, calculated on dry weight. This solution was adjusted to a dry matter concentration of 25% with 5% hydrochloric acid. 19.2 liters of solution were used for the experiment. j. 4.8 kg of dry matter. The experiment was carried out as in Example 1. The reaction solution used was the filtrate from the reaction solution of Experiment One. 1.05 kg of crude 2-furaldehyde was obtained, m.p. j. yield 22%, calculated on dry weight of the prehydrolysate.

Example 3

Neutralized concentrated thickened wheat straw prehydrolysate was used for dehydration and was obtained by partial hydrolysis with 1% sulfuric acid at 125 ° C for 2 hours. The pre-hydrolyzate was adjusted to a dry matter content of 25% with 5% HCl. The pentose content was 52% on dry weight basis. Experimental procedure as in Example 1. 17 liters of solution were used in the experiment. j. 4.24 kg of dry matter and 1.06 kg of crude 2-furaldehyde were obtained, m.p. j. 25% yield on dry matter and prehydrolysate.

Example 4

For the dehydration, a corn corn seed hydrolyzate was obtained, which was obtained by hydrolyzing corn corn pulp with 1.5% sulfuric acid at 128 ° C for a hydrolysis time of 120 min, calculated from the hydrolysis temperature. The hydrolyzate was concentrated by evaporation in vacuo to a dry matter content of 28% without prior neutr; of sulfuric acid. The pentose content of the prehydrolysate was 85%, calculated on the dry weight of the prehydrolysate. 20 liters of solution were used for the experiment. j. 5.6 kg of prehydrolysate dry matter. 25 L of 12% hydrochloric acid and 4.5 kg of sodium chloride were added to the reaction vessel. After heating the solution to boiling point, the test solution started to be added from the separatory funnel and, at the same time, through the lower outlet of the reaction vessel, water was introduced into the reaction medium, which accelerated the distillation of the 2-furaldehyde formed. 2.38 kg of crude 2-furaldehyde was obtained as a yield

42.5% calculated on the dry matter of the prehydrolysate.

Example 5

Bagassa partial hydrolyzate (supplied by ICIDCA-Habana from Cuba) was used for dehydration. Partial hydrolysis of the bagasse was carried out with 2% sulfuric acid at the boiling point of the mixture for 2 h, calculated from the boiling point. The hydrolyzate without neutralization was concentrated to 26% organic solids by evaporation under reduced pressure. The pentose content of the prehydrolysate was 73%. 15 liters of solution were used for the experiment. j. 3.9 kg of dry matter. The experimental conditions were the same as in Example 4. 1.43 kg of crude 2-furaldehyde were obtained, which represents a 36.6% yield calculated on the dry weight of the prehydrolysate.

For a more advantageous utilization of the reactor volume as well as for energy, the hydrolyzate obtained in the first stage must be concentrated to dryness up to 50% in a multipurpose evaporator.

T

Example 6

A partial hydrolyzate of beech chips was used for dehydration. Parallel hydrolysis of beech chips was carried out with 2% sulfuric acid at boiling point for 2 h, in that the prehydrolysate obtained from the first batch of beech chips was used after adjusting the sulfuric acid concentration to hydrolyze the second batch of beech chips and this prehydrolysate was by adjusting the sulfuric acid concentration used to hydrolyze a third batch of beech chips. The prehydrolysate thus obtained was concentrated by evaporation under reduced pressure to a dry matter content of 20% without first neutralizing the sulfuric acid. 100 liters of test solution containing 20 kg of organic substance were used for the experiment. The pentose content was 67%, calculated as the dry matter of organic substances. To the reaction vessel were added 100 liters of 12% hydrochloric acid and 18 kg of sodium chloride. After the solution was heated to boiling point, a sample was added to the reactor. Water vapor was fed through the bottom of the reactor to accelerate the perimeter of 2-furaldehyde formed from the reaction medium. 7.6 kg of crude 2-furaldehyde were obtained, which represents a yield of 38%, calculated on the dry weight of the organic slaughter.

Example 7

Unsorted was used to prepare 2-furaldehyde

Claims (4)

5 dry matter content 20% without previous sulfuric acid neutralization. A 100 liter test solution containing 20 kg of organic material was used for the experiment. Pentose content 67%, dry matter count of organic matter. 100 L of 12% hydrochloric acid and 18 kg of sodium chloride were added to the reaction vessel. After heating the solution at the boiling point, a doreaktor sample was added. Water vapor was fed through the lower reactor outlet to accelerate the 2-furaldehyde formed from the reaction medium. 7.6 kg of crude 2-furaldehyde was obtained, representing a yield of 38%, calculated on the dry matter of organic yarns. Example 7 Unsorted PR.EDMET was used to prepare 2-furaldehyde CLAIMS 1. A process for the production of 2-furaldehyde by a stepwise batch process of pentosan-free plant materials, characterized in that the first stage of the pentose prehydrolyte, using dilute sulfuric acid at a cone-centering concentration of 0.5 to 2.5%, respectively. dilute hydrochloric acid having a concentration of 0.2 to 1% and subjecting the second stage to dehydration of pentoses to 2-furaldehyde, with a hydrochloric acid of 5 to 15% being used as the catalyst, whereby the dehydration products formed separate from the 2-furaldehyde-free hydrochloric acid it leads to the reaction space and 2-fluoraldehyde is removed from the reaction medium by steam distillation. 2. Process according to claim 1, characterized in that 218738 maize chips are ground. The same apparatus was used for dehydration as in Example 6. The reaction mixture was used from the experiment of Example 6 - after decomposition of the decomposition humic substances. 10 kg of 85% corn maize shreds, i.e. 8.5 kg absolute dry grit, were charged to the reactor. After the reaction mixture was heated to room temperature, water was fed to the reaction vessel to maintain the volume of the cooking mixture at the same level. 1.87 kg of crude 2-furaldehyde was obtained, yielding 22% of 2-furaldehyde, calculated on dry weight basis. The residue after the reaction was black in color, with no filtration difficulties. The solids post-filtering solution was dark brown in color and can be used for further dehydration of lipids. the diluted mineral acids used in the preparation of the prehydrolysates by partial hydrolysis are also used to dehydrate pentoses to 2-fural-dehyd. 3. A method according to claim 2, wherein dilute sulfuric acid is added to the reaction mixture with the addition of sodium chloride. 4. Process according to claim 1, characterized in that industrial solutions of pentoses and pentozanes, in particular prehydrolysate decomposition pulps, mother liquors after crystallization of D-xylose, solutions of hemicellulose from pulp refining and preparation are used as hydrochloric acid dehydrated starting material. alkali cellulose.