Liquid phase process for the preparation of isophorone

Abstract

The invention relates to a liquid phase process for the preparation of isophorone, wherein acetone is continuously reacted catalytically under the addition of isopropylidene acetone, wherein at least 50 wt% of the isopropylidene acetone added is added after passing at least 50% of the reactor volume.

Description

Technical Field

[0001] This invention relates to a liquid-phase method for preparing isophorone. Background Technology

[0002] Isophorone is an important industrial chemical, particularly important as a feedstock for the synthesis of isophorone nitrile, which is further used to synthesize isophorone diamine, an epoxy curing agent, and isophorone diisocyanate, which can be prepared from isophorone diamine. The latter is of great importance in the field of polyurethane chemistry. Therefore, the preparation methods of isophorone have attracted considerable attention.

[0003] JP H09-157207 A and JP H09-157208 A disclose methods for preparing isophorone from acetone in the gas phase. The reaction is carried out in the presence of isopropylidene acetone. A disadvantage of the above methods is that the gas-phase reaction requires high temperatures. Furthermore, the heterogeneous catalyst (zeolite) used must be replaced and regenerated periodically.

[0004] The aforementioned drawbacks can be overcome by synthesizing isophorone from acetone via a base-catalyzed liquid-phase method: DE 1 205525 B discloses a method for preparing isophorone in the liquid phase, wherein acetone undergoes a condensation reaction to generate isophorone. To remove the considerable amounts of isopropyl acetone (Mesityloxid) and the excessive condensate (Überkondensate) generated, these byproducts can be treated with an alkaline aqueous solution at a higher temperature. This document discloses that isopropyl acetone completely decomposes at this temperature.

[0005] DE 26 45 281 A1 discloses a liquid-phase method for preparing isophorone, wherein acetone, water, and a base catalyst react. The isophorone is then separated by distillation.

[0006] US 5,849,957 A discloses a method for preparing isophorone from acetone in the presence of a magnesium oxide catalyst. The generated byproducts include isopropylacetone, and these byproducts can be recycled.

[0007] US 2,419,051 A discloses a method for preparing isophorone and acetone, wherein the self-condensation product of acetone (with a boiling point higher than that of isophorone) reacts with an alkali metal hydroxide to generate isophorone and acetone.

[0008] GB 733,650 A discloses that acetone can be converted into isophorone and the intermediate isopropylacetone and higher condensation products under alkaline catalysis. In a preferred embodiment, the higher condensation products are returned to the reaction mixture.

[0009] CN 103435461 A discloses a method for preparing isophorone from acetone, wherein unreacted acetone can be recycled back into the reaction.

[0010] DE 25 20 681 A1 discloses a method for preparing isophorone, wherein acetone is reacted in the presence of potassium hydroxide to generate isophorone. The generated byproducts can be converted back to acetone during hydrolysis and then fed back into the reaction.

[0011] CN 102367223 A discloses a method for preparing isophorone, wherein acetone undergoes a condensation reaction in the presence of a catalyst. Unreacted acetone is separated and recycled back to the reaction. High-boiling-point substances containing 12 or more carbon atoms are then fed into a hydrolysis process.

[0012] US 2,344,226 A discloses a method for preparing isophorone, wherein acetone is heated in the presence of an alkali metal hydroxide. The isopropylidene acetone generated as an intermediate product can be reintroduced into the reaction mixture along with similarly generated components such as diacetone alcohol, phorone, and higher condensation products.

[0013] US 4,086,188 A discloses a method for preparing isopropylacetone and isophorone. The document states that it is ideal for the ratio of the formed isopropylacetone to the formed isophorone to be less than 1, because otherwise excess isopropylacetone must be recycled.

[0014] DE 10 2010 062 587 A1 discloses a liquid-phase method for preparing isophorone from acetone, wherein an alkaline aqueous solution can be used as a catalyst. The generated low-boiling products (including isopropylidene acetone and diacetone alcohol) can be recycled back to the reactor along with unreacted acetone.

[0015] WO 2012 / 076317 A1 discloses a liquid-phase method for preparing isophorone from acetone, wherein an alkaline aqueous solution can be used as a catalyst. The low-boiling products generated herein (including isopropylacetone and diacetone alcohol) can also be recycled back into the reaction.

[0016] It has been found that adding isopropylacetone (especially by recycling the isopropylacetone generated during the aldol condensation of acetone to isophorone) can reduce the amount of acetone required. However, in existing methods known to date, the conversion rates based on acetone, isopropylacetone, and diacetone alcohol are reduced, which is disadvantageous. Summary of the Invention

[0017] Therefore, the object of the present invention is to provide a liquid-phase method for preparing isophorone from acetone in the presence of isopropylacetone, by which a higher conversion rate can be achieved. It has been unexpectedly discovered that the above-mentioned object of the present invention can be achieved when at least 50% by weight of the added isopropylacetone is added after passing through at least 50% of the reactor volume.

[0018] Therefore, the present invention relates to a liquid-phase method for preparing isophorone, wherein acetone is reacted continuously in the presence of a catalyst under the condition of addition of isopropylacetone, wherein at least 50% by weight of the added isopropylacetone is added after passing through at least 50% of the reactor volume.

[0019] The method described in this invention is a liquid-phase method. In corresponding methods, the reaction is carried out in the liquid phase. Therefore, the method according to this invention is not carried out in the gas phase or in supercritical acetone.

[0020] The reaction is preferably carried out at a temperature of 100-250°C, more preferably 120-250°C, and particularly preferably 180-250°C, and a pressure of 5-50 bar, more preferably 10-50 bar, and particularly preferably 20-50 bar, wherein the above values ​​can be combined with each other in any way.

[0021] The reaction is carried out in the presence of a catalyst. The catalyst used can be a homogeneous catalyst or a heterogeneous catalyst. A homogeneous catalyst is preferred.

[0022] The condensation of acetone to isophorone is preferably carried out via alkaline catalysis. The alkaline solution used is preferably used. More preferably, the alkaline catalyst is selected from NaOH and KOH.

[0023] The content of the alkali, especially an alkaline solution, more preferably NaOH or KOH, is preferably less than or equal to 5% by weight, more preferably less than or equal to 1% by weight, and particularly preferably less than or equal to 0.5% by weight, based on the total mass of the reaction composition. Most particularly preferably, 0.005-0.5% by weight of NaOH is used as a catalyst.

[0024] Especially when using an alkaline aqueous solution as a catalyst, the reaction proceeds in the presence of water. Furthermore, water is also generated during the condensation reaction. The water content of the reaction mixture (based on the amount of water introduced into the reactor, using the amounts of acetone, water, and isopropyl acetone introduced) is preferably less than or equal to 40% by weight, more preferably less than or equal to 30% by weight.

[0025] The acetone content in the mixture (based on the amount of acetone introduced into the reactor, using the amounts of acetone, water and isopropyl acetone introduced as a reference) is preferably greater than or equal to 25% by weight, more preferably greater than or equal to 50% by weight, and even more preferably greater than or equal to 65% by weight.

[0026] The formation of isophorone by aldol condensation of acetone is carried out under the condition of adding isopropylacetone. The content of isopropylacetone is preferably 0.1-50% by weight, more preferably 0.5-25% by weight, and even more preferably 0.8-10% by weight, based on the amount of acetone, water and isopropylacetone introduced.

[0027] The reaction proceeds continuously in the reactor. In this paper, a continuous reaction process refers to the continuous feeding of feed and catalyst into the reactor, while the continuous discharge of products, unreacted feed, and intermediates.

[0028] Reactors suitable for continuous reaction processes can preferably be groups consisting of free tubular reactors, stirred tank cascades, fixed bed reactors, trickle bed reactors, slurry reactors, pressurized distillation reactors, reactive distillation reactors, microstructured reactors, membrane reactors, chamber reactors, static mixers, and bubble columns.

[0029] The reactor is preferably a flow reactor.

[0030] According to the invention, at least 50% by weight of the added isopropylacetone is added after passing through at least 50% of the reactor volume. Here, the reactor volume refers to the volume in which acetone, in the presence of a catalyst, reacts with itself and any intermediates (including isopropylacetone) to form isophorone. More preferably, the reactor volume refers to the reactor volume in which acetone, in the presence of a catalyst, contacts itself and any intermediates (including isopropylacetone) at a pressure and temperature selected from the preferred pressure and temperature ranges described above. Especially when using a flow reactor or a tubular reactor (with a constant diameter cross-section / pipeline), the position after x% of the reactor volume corresponds to x% of the reactor length.

[0031] The addition of isopropyl acetone can be carried out continuously, but it is not necessary. To achieve positive performance, a semi-continuous or discontinuous method of adding isopropyl acetone may also be considered. However, continuous addition of isopropyl acetone is preferred.

[0032] A particularly high conversion rate can be achieved when at least 60% by weight, more preferably at least 70% by weight, and even more preferably at least 75% by weight of isopropyl acetone is added after passing through at least 50% of the reactor volume.

[0033] According to the invention, at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, and even more preferably at least 75% by weight, of isopropylidene acetone is added after at least 50% of the reactor volume has been filled, which can be implemented through two or more feed ports all located at the position after at least 50% of the reactor volume has been filled. Preferably, at least 50% by weight, more preferably at least 60% by weight, even more preferably at least 70% by weight, and very particularly preferably at least 75% by weight, of isopropylidene acetone is added after at least 50% of the reactor volume has been filled, through two or more, more preferably three or more, and most particularly preferably four or more feed ports all located at the position after at least 50% of the reactor volume has been filled. The preferred upper limit for the number of these feed ports is preferably 20, more preferably 15, and even more preferably 10.

[0034] The remaining percentage fraction of the added isopropylidene acetone relative to 100% by weight (for at least 50% by weight of the added isopropylidene acetone, the remainder is less than or equal to 50% by weight after 50% reactor volume; for at least 60% by weight of the added isopropylidene acetone, the remainder is less than or equal to 40% by weight after 50% reactor volume; for at least 70% by weight of the added isopropylidene acetone, the remainder is less than or equal to 30% by weight after 50% reactor volume; for at least 75% by weight of the added isopropylidene acetone, the remainder is less than or equal to 25% by weight after 50% reactor volume) is added before at least 50% reactor volume has been reached. This addition can also be made through one or more, preferably two or more, more preferably three or more feed ports. The preferred upper limit for the number of feed ports is 15, more preferably 10, and even more preferably 5.

[0035] It is preferable not to add isopropyl acetone before passing through at least 25% of the reactor volume, as this achieves particularly good conversion.

[0036] It is preferable not to add isopropyl acetone before passing through at least 50% of the reactor volume, as this achieves particularly good conversion along with particularly good selectivity.

[0037] The added isopropylidene acetone is preferably derived from the post-treatment of a reaction mixture containing valuable materials used in a liquid-phase method for preparing isophorone.

[0038] The reaction mixture containing valuable material after the entire reactor volume has passed can be post-treated and separated into individual components. In this case, in addition to isophorone, acetone, low-boiling substances (i.e., substances with boiling points lower than isophorone, especially diacetone alcohol and isopropylidene acetone), higher condensation products of acetone (over-condensation products, i.e., substances with boiling points higher than isophorone, especially xylitone and isoxylitone), water, and catalyst are obtained.

[0039] The separation of the components can be carried out using any separation method, especially distillation, flash evaporation, crystallization, extraction, adsorption, permeation, phase separation, or a combination of the above methods, continuously or intermittently, in single or multiple stages. Distillation is preferred, performed in one or more devices.

[0040] More preferably, the fractions are separated by reactive distillation downstream of the reactor (preferably in a reactive distillation column).

[0041] Particularly preferably, the separation and isophorone synthesis (reaction) are carried out spatially separately in a reaction distillation column with a side stream.

[0042] Preferably, separation is performed to obtain the following three fractions: i) Fractions containing unreacted acetone, water, and low-boiling substances (especially diacetone alcohol and isopropylidene acetone); ii) The fractions containing coloring substances are particularly concentrated therein; and iii) The fraction containing, in particular, isophorone, higher condensation products, water, and catalyst (i.e., the valuable stream). This fraction subsequently undergoes hydrolysis.

[0043] The fraction i) is preferably condensed and subsequently recycled back to the reactor for further reaction. In another preferred embodiment, it is discharged as a vapor stream mainly comprising acetone, water, and low-boiling substances (mainly diacetone alcohol and isopropylidene acetone), condensed, and added back to the reactor with the feed acetone, water, and optional catalyst.

[0044] In a preferred embodiment of the invention, isopropyl acetone is added by adding a fraction containing acetone, water, and a low-boiling-point substance, which can be obtained by distillation of the reaction mixture containing valuable materials after the entire reactor volume has passed. In principle, isopropyl acetone can be added together with other low-boiling-point substances (especially diacetone alcohol), water, and acetone. When calculating the percentage content of isopropyl acetone, any low-boiling-point substances that may be present and different from isopropyl acetone are not considered; that is, the percentage value is always based on the amount of acetone, water, and isopropyl acetone added. More preferably, this fraction corresponds to the fraction i) described above.

[0045] The fraction preferably has the following composition: 60-85% by weight acetone, 10-25% by weight water, 0.5-10% by weight diacetone alcohol, and 0.5-10% by weight isopropylidene acetone.

[0046] Further preferred: - From the fraction containing acetone, water, and low-boiling substances, preferably fraction i), • Separate acetone and water from low-boiling substances, preferably by distillation, and • Add acetone and water to the feed end of the reactor.

[0047] In this equally preferred embodiment, isopropylidene acetone is added by adding a low-boiling-point substance, which preferably consists mainly of a mixture of isopropylidene acetone and diacetone alcohol, and is obtained by the following method: - The reaction mixture containing valuable materials, after passing through the entire reactor volume, is distilled to obtain a fraction containing acetone, water, and low-boiling substances; and - Acetone and water are then separated from the fraction, preferably by distillation.

[0048] In a preferred embodiment, fraction ii) is collected as a side stream from a distillation column, preferably a reactive distillation column, and optionally neutralized and further post-processed. This fraction can be further purified, and the valuable materials contained therein can be recycled back into the method. During the post-processing, all conventional separation methods can be employed, such as distillation, flash evaporation, crystallization, extraction, adsorption, permeation, phase separation, or combinations thereof. Purification can be carried out continuously or intermittently, in single or multiple stages. Purification is preferably achieved by distillation. Particularly preferred is purification by a combination of neutralization or extraction and subsequent distillation, preferably carried out in a reactive distillation column. The post-processed phase containing the valuable product, including isophorone, high-boiling point, and optionally a catalyst, is preferably fed into hydrolysis. Another valuable product phase, mainly comprising acetone, diacetone alcohol, and isopropylidene acetone, is preferably recycled back into the reaction. However, this operation is preferably not carried out due to the high equipment cost. Any residues that may result can be thermally utilized.

[0049] Fraction iii) is preferably obtained at the bottom of the distillation column and can be withdrawn from there to obtain a valuable stream.

[0050] The valuable stream from the aldol condensation reaction is then preferably subjected to hydrolysis (b). The purpose of hydrolysis is to convert some or all of the byproducts contained in the valuable stream into isophorone, acetone, or other usable valuable products. Hydrolysis can be carried out in any conventional reactor, distillation column, or combination thereof. Hydrolysis is preferably carried out by reactive distillation, in which the low-boiling product formed, mainly composed of diacetone alcohol and isopropylidene acetone, is directly separated from the hydrolysis zone and recycled back to the reaction, thus no longer participating in the side reactions during hydrolysis.

[0051] Very particularly preferably, the hydrolysis of fraction iii) can be carried out in a single apparatus by reactive distillation, preferably in a reactive distillation column, wherein the reaction mixture is simultaneously separated into fractions i) to iii), such that the products formed are separated accordingly, and fraction iii) is hydrolyzed.

[0052] Hydrolysis can be carried out in any mixing ratio of organic components and water, with or without a catalyst. The water concentration in hydrolysis is 30.1–99.9% by weight based on the total mass of the components present. In the case of homogeneous catalysis, the same catalyst used in the aldol condensation reaction is preferably used in the hydrolysis. Based on the total mass of the composition, a catalyst concentration of 0.001–10% by weight, particularly preferably 0.05–1% by weight, is preferred. The pressure in the hydrolysis reactor is 1–200 bar, preferably 20–60 bar. Particularly preferably, the hydrolysis is carried out at least at the same pressure as in the isophorone synthesis step (reaction). The hydrolysis temperature is 100–300°C, preferably 210–260°C. Particularly preferably, when using a reactive distillation column, a temperature or temperature distribution corresponding to the boiling point temperatures of the bottom and each separation stage or reaction stage is formed.

[0053] Hydrolysis can be carried out in one or more devices, in a single stage or in multiple stages.

[0054] The resulting hydrolysis product then preferably undergoes phase separation (c) after being discharged from the hydrolysis reactor of the reactive distillation column and cooled.

[0055] Phase separation yields a substantially organic fraction i) and a substantially aqueous fraction ii). In the case of homogeneous catalysis in the aldol condensation reaction, the aqueous fraction ii) also contains a catalyst. Conventional phase separation vessels, with or without internal components, can be used for phase separation. Phase separation is carried out at temperatures of 0–200°C, preferably 0–100°C, particularly preferably 20–70°C, and at pressures of 1–150 bar, preferably 20–60 bar, particularly preferably the same as those used in hydrolysis.

[0056] The essentially organic phase i) containing the target product isophorone can be optionally neutralized and purified by conventional methods to obtain isophorone with the desired purity and color stability. All conventional separation methods can be used, particularly distillation, flash evaporation, crystallization, extraction, adsorption, permeation, phase separation, and combinations thereof. Purification can be continuous or intermittent, single-stage or multi-stage, under pressure or reduced pressure. Purification is preferably achieved by distillation. Particularly preferred is purification by a combination of neutralization or extraction followed by distillation.

[0057] The essentially aqueous fraction (ii) can be fed into wastewater purification. Here, the reaction water, which is the main component, along with any possible catalyst, is separated from any remaining organic components (e.g., isophorone, acetone, and higher condensation products). Wastewater purification is preferably carried out in one or more distillation columns.

[0058] Isophorones prepared by the method according to the invention are suitable for a variety of applications. They are particularly suitable for the production of isophorone nitrs. Isophorone nitrs can also be advantageously used to synthesize isophorone diamines, especially by amination and hydrogenation. Isophorone diamines can then be converted to isophorone diisocyanates.

[0059] Therefore, this invention relates not only to isophorones that can be prepared by the method of this invention, but also to the application of such isophorones in the preparation of isophorone nitriles, isophorone diamines and / or isophorone diisocyanates.

[0060] Unless otherwise stated, all percentages (%) given are mass percentages. Attached Figure Description

[0061] Figure 1 The diagram schematically illustrates a laboratory apparatus used to conduct experiments of the present invention. Detailed Implementation

[0062] The invention is described by way of example in the following embodiments, but the invention should not be limited to the embodiments described in the embodiments. The scope of the invention is derived from the entire specification and claims. Example

[0063] The experiment was conducted in a continuously operating laboratory setup (see...). Figure 1 The apparatus comprises: containers for acetone, aqueous sodium hydroxide solution, and isopropylacetone; a feed metering pump; a tubular reactor heated by a heat transfer oil; a back pressure regulating valve; and online GC and sampling ports for offline detection. Feed metering is performed via an HPLC pump at a volumetric flow rate ranging from 0.4 to 5.4 mL / min. The tubular reactor has a volume of 235 mL and consists of 16 separate coil units, totaling 256 coils. Efficient mixing is achieved by reversing the flow direction every 6.25% of the reactor volume. Isopropylacetone is metered into the reactor through T-connectors located at 0%, 25%, 50%, 75%, and 100% of the reactor volume. For precise control of the volumetric flow rate, the addition is performed using appropriate flow-limiting elements. The reaction process is analyzed using an online gas chromatograph with a pressure-stable plunger injector. Verification of the online measurements is achieved by collecting sample material after the reaction and analyzing it using an offline gas chromatograph.

[0064] 1. Isophorone is prepared from acetone via an alkaline-catalyzed reaction, wherein isopropylidene acetone is added at 0% of the reactor volume. Acetone (5.39 mL / min) and an aqueous sodium hydroxide solution (0.169 wt% in water, 1.42 mL / min) were combined before the reactor. Isopropylacetone (0.42 mL / min, 6 wt% of the total feed) was metered at 0%. The reaction was carried out in a tubular reactor at 200 °C, 35 bar, and an average residence time of 35 min. The conversion based on acetone, isopropylacetone, and diacetone alcohol was 8.0%, and the selectivity for isophorone was 89.6%.

[0065] 2. Isophorone is prepared from acetone via an alkaline-catalyzed reaction, wherein isopropylidene acetone is added at 50% of the reactor volume. Acetone (5.39 mL / min) and an aqueous sodium hydroxide solution (0.169 wt% in water, 1.42 mL / min) were combined before the reactor. Isopropylacetone (0.42 mL / min, 6 wt% of the total feed) was metered in after 50% of the reactor volume. The reaction was carried out in a tubular reactor at 200 °C, 35 bar, and an average residence time of 35 min. The conversion based on acetone, isopropylacetone, and diacetone alcohol was 8.4%, and the selectivity for isophorone was 89.5%.

[0066] 3. Isophorone is prepared from acetone via an alkaline-catalyzed reaction, wherein isopropylidene acetone is added at reactor volumes of 25%, 50%, 75%, and 100%. Acetone (5.39 mL / min) was combined with an aqueous sodium hydroxide solution (0.169 wt% in water, 1.42 mL / min) before the reactor. Isopropylacetone (total: 0.42 mL / min, 6 wt% of total feed) was metered stepwise after reactor volumes of 25%, 50%, 75%, and 100% (0.11 mL / min in each case, 1.5 wt% of total feed). The reaction was carried out in a tubular reactor at 200 °C, 35 bar, and an average residence time of 35 min. The conversion based on acetone, isopropylacetone, and diacetone alcohol was 8.6%, and the selectivity for isophorone was 86.4%.

Claims

1. A liquid-phase method for preparing isophorone, wherein, Acetone reacts continuously in the presence of a catalyst and with the addition of isopropylacetone. Its features are, At least 50% by weight of isopropyl acetone is added after passing through at least 50% of the reactor volume.

2. The method according to claim 1, Its features are, The reaction is carried out at a temperature of 100-250°C and a pressure of 5-50 bar.

3. The method according to claim 1 or 2, Its features are, The catalyst is selected from NaOH and KOH.

4. The method according to any one of the preceding claims, Its features are, The reactor is selected from a reactor group consisting of tubular reactors, stirred tank cascades, fixed bed reactors, trickle bed reactors, slurry reactors, pressurized distillation reactors, reactive distillation reactors, microstructure reactors, membrane reactors, chamber reactors, static mixers, and bubble columns.

5. The method according to any one of the preceding claims, Its features are, The reactor is a flow reactor.

6. The method according to any one of the preceding claims, Its features are, At least 60% by weight of the added isopropyl acetone is added after passing through at least 50% of the reactor volume.

7. The method according to any one of the preceding claims, Its features are, At least 50% by weight of isopropyl acetone is added through two or more feed ports located at least 50% of the reactor volume after passing through at least 50% of the reactor volume.

8. The method according to any one of the preceding claims, Its features are, Isopropylacetone is not added until at least 25% of the reactor volume has passed.

9. The method according to claim 8, Its features are, Isopropylacetone is not added until at least 50% of the reactor volume has been filled.

10. The method according to any one of the preceding claims, Its features are, The added isopropyl acetone is derived from the post-treatment of the reaction mixture containing valuable materials in the liquid phase method.

11. The method according to claim 10, Its features are, Isopropyl acetone is added by adding a fraction containing acetone, water, and low-boiling substances, which can be obtained by distillation of the reaction mixture containing valuable materials after the entire reactor volume has passed.

12. The method according to claim 10, Its features are, The addition of isopropylacetone is achieved by adding a low-boiling-point substance, which is obtained through the following method: - The reaction mixture containing valuable materials, after passing through the entire reactor volume, is distilled to obtain a fraction containing acetone, water, and low-boiling substances; and - Then acetone and water are separated from the fraction.

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