Process for preparing a levulinic-acid ester and gamma-valerolactone

Abstract

The invention relates to a process for preparing a levulinic-acid ester or alkyl levulinate, in particular ethyl levulinate, comprising the following steps: - preparing a solution containing furfuryl alcohol, an alcohol as solvent, and hydrochloric acid as catalyst acid, - esterifying this solution at a temperature in the range of 60-100°C to form alkyl levulinate, - neutralizing the catalyst acid in the mixture thus obtained, and - separating the alkyl levulinate from the humins formed as by-products. The invention also relates to a process for preparing gamma-valerolactone (GVL) by hydrogenating the alkyl levulinate obtained or obtainable by the process.

Description

[0001] Process for the preparation of a levulinic acid ester and gamma-valerolactone

[0002] DESCRIPTION

[0003] The invention relates to a process for producing a levulinic acid ester or alkyl levulinate, in particular ethyl levulinate, according to claim 1, and in a further aspect to a process for producing gamma-valerolactone (GVL), as well as the process products obtainable or obtained therefrom.

[0004] TECHNICAL BACKGROUND

[0005] Gamma-valerolactone (GVL) is a solvent with properties similar to acetone, but due to its human and environmental compatibility, as well as its significantly higher boiling point, it is suitable for more advanced applications. The production of GVL is known, for example, based on renewable raw materials, such as hexoses or fructoses. However, the yield is low, and byproducts, also known as humic acids, are produced that are more or less difficult to remove. For example, to produce one kilogram of GVL from fructose, three kilograms of fructose are required, resulting in two kilograms of humic acids and formic acid.

[0006] Levulinic acid esters are used industrially, for example, as plasticizers or solvents, and in the production of free levulinic acid by hydrolysis of the ester. Levulinic acid and its esters are suitable as starting materials and intermediates in the production of a variety of chemicals for industrial and pharmaceutical purposes. For example, levulinic acid esters are suitable as starting materials for the production of gamma-valerolactone (GVL).

[0007] Various processes for the production of ethyl levulinate and gamma-valerolactone (GVL) are known from the state of the art. However, the commercial use of levulinic acid esters is problematic in practice, as the known production processes are not very practical from a commercial perspective, as the yields are rather low and the costs are relatively high. Fundamentally, a key problem in GVL or ethyl levulinate production is to minimize humin formation, prevent the formed humins from sticking to the container wall, and ensure that the formed ethyl levulinate is separated from the humins as efficiently as possible. US 3,752,849 describes an acidic hydrolysis of furfuryl alcohol using hydrochloric acid as the catalyst and aliphatic ketone as the solvent.

[0008] US 2023 / 0322655 describes a process in which furfuryl alcohol is reacted with alcohols at temperatures of 125–180 °C using sulfonic acid as a catalyst to form levulinic acid ester. A yield of only 60–90% is achieved.

[0009] WO 2023 / 094511 also describes a process for the production of levulinic acid ester from furfuryl alcohol and aliphatic alcohols, especially butanol, at 105–160 °C using inorganic acids, preferably sulfuric acid, as catalyst. This process does not describe any measures to reduce the formation of sticky contaminants in the technical equipment, including those caused by humic acids. Furthermore, the choice of a nickel catalyst for the esterification explicitly discourages the use of hydrochloric acid as the catalyst acid, as this damages the nickel catalyst.

[0010] US 4,236,021 describes a process for producing alkyl levulinates from furfuryl alcohol by esterification with an aliphatic alcohol. The esterification is carried out with butanol in the presence of HCl. The butyl levulinate precipitate is then dissolved with an additional solvent. However, the humic acids cannot be satisfactorily separated, and a recovery of butyl levulinate as a pure product of only <60% can be achieved, which is prohibitive given the high product price of several thousand euros / t. A further disadvantage of using butanol for the esterification is the formation of traces of butyric acid, which has a negative odor in the product.

[0011] WO 2014 / 037560 describes a process for producing levulinic acid from a biomass hydrolysate by esterification with an aliphatic alcohol and subsequent possible hydrogenation to gamma-valerolactone. This involves dissolving the biomass hydrolysate in an alcohol, adding acid to the solution, heating the mixture to 150 to 250 °C, and hydrolyzing it in a reactor to form levulinic acid. However, introducing water into the system requires a high energy input, and nanofiltration is not suitable for humic substances of the type in question.

[0012] CN 115055195 describes a process for the production of gamma-valerolactone from alkyl levulinates by hydrogenation, in which the alkyl levulinate is hydrogenated with hydrogen and a nickel-based catalyst at >5 bar hydrogen partial pressure and temperatures of 80 to 250 °C. In the known processes for the production of alkyl levulinates, sticky byproducts, particularly humins, are regularly formed during hydrolysis. These often form extremely sticky deposits in the technically required equipment. These deposits are difficult to remove and reduce the yield. The higher the reaction temperature, the faster degradation products and byproducts of the reaction form. These humins, which in their sticky state are often laden with sulfur components, are difficult to treat or incinerate.

[0013] The invention is therefore based on the object of reducing or eliminating the disadvantages mentioned above and of creating a process in which the formation of sticky by-products, in particular humins, is minimal, the yield is high, and the humins formed do not lead to sticky deposits. Furthermore, it is an advantageous object to provide a process in which the by-products and residues are easy to remove and, in particular, the most complete possible separation of the levulinic acid ester formed from the by-products or humins is possible.

[0014] This object is achieved by a method according to claim 1.

[0015] SUMMARY OF THE INVENTION

[0016] According to the invention, a process for producing a levulinic acid ester or alkyl levulinate, in particular ethyl levulinate, is provided, comprising the following steps:

[0017] - Preparation of a solution containing furfuryl alcohol, an alcohol as solvent, and hydrochloric acid as catalyst acid,

[0018] - Esterification of this solution at a temperature in the range of 60 - 100 °C to form alkyl levulinate,

[0019] - neutralization of the catalyst acid in the mixture thus obtained,

[0020] - Separation of the alkyl levulinate formed from the impurities formed as by-products, particularly sticky ones, in particular humins.

[0021] The underlying reaction in the formation of ethyl levulinate is as follows:

[0022] It was initially surprising that when using HCl as the catalyst acid and relatively low temperatures between 60 and 100 °C, the reaction rate for the complete conversion of furfuryl alcohol in an ethanol solution is between 4 and 6 hours and the humins formed are not sticky, compared to the deposits that form when using sulfuric acid and sulfonic acids or at temperatures above 100 °C.

[0023] In order to avoid the formation of by-products and degradation products, it has proven particularly advantageous to neutralize the hydrochloric acid in the reaction mixture after the reactor.

[0024] In this way, the formation of sticky by-products, especially humins, can be significantly reduced and the resulting humins do not lead to sticky deposits and are easily removed. Furthermore, the resulting levulinic acid ester can be easily and almost completely separated from the by-products or humins, resulting in high yields and high purity of the final products.

[0025] Further advantageous embodiments of the method are described below:

[0026] It is advantageous for the alcohol to be an alkyl alcohol, especially ethanol. With regard to the distillative processing of the reactor stream, consisting of levulinic acid ester, alcohol, water, HCl, and humic acids, it is advantageous to use ethanol as the reactant and solvent because ethyl levulinate has a relatively high vapor pressure compared to, for example, butyl levulinate, and also because ethanol can be condensed even under moderate vacuum.

[0027] Furthermore, it is advantageous if the solution contains 10 to 30 wt.% furfuryl alcohol.

[0028] To increase the yield, it has proven advantageous if the water content in the solution is < 5 wt.%, especially < 1 wt.%, preferably < 0.25 wt.%, especially approximately 0.2 wt.%. Surprisingly, it has been found that the amount of humins formed, and thus also the yield, depends strongly on the water content of the reactants used. For example, at a water content of 6 wt.%, the yield of ethyl levulinate drops to only 75%, whereas at a water content of 0.2 wt.%, the yield increases to over 92%.

[0029] Furthermore, it is advantageous if the solution contains 0.1 to 2 wt.% hydrochloric acid.

[0030] In this context, it is advantageous if the hydrochloric acid is supplied to the solution as a gas, in particular pre-dried, preferably anhydrous.

[0031] An advantageous process procedure provides that the esterification takes place at a temperature in the range of 70 - 90 °C.

[0032] Furthermore, the esterification can take place in a reactor, in particular in a continuously operated tubular reactor.

[0033] An advantageous process procedure provides that the supply of furfuryl alcohol and the other components into the reactor takes place continuously over the entire course of the reaction, wherein it is provided in particular that furfuryl alcohol is supplied at several superimposed height positions of the reactor.

[0034] Since the humin formation from parallel reactions and subsequent reactions takes place simultaneously with the main reaction, it has proven particularly advantageous to start the furfuryl alcohol content of the reaction mixture with approximately 50 g / l and to continue the further supply of raw material until the optimal supply of between 150 and 280 g / l furfuryl alcohol in the reaction mixture is reached.

[0035] Another advantageous step is the neutralization of the catalyst acid with ammonia. Since the humic acids are to be incinerated after the separation of ethyl levulinate, neutralization with ammonia is advantageous. It is also advantageous at this point to keep the water content low and to supply ammonia as a gas, especially pre-dried, preferably anhydrous.

[0036] Advantageously, an ethanol stream, in particular with > 99.8%, an HCl stream, in particular in the form of HCl gas, in particular with > 98%, and a furfuryl alcohol stream, in particular with > 99%, are continuously mixed and an alcoholic solution, in particular with 10 to 30 wt.% furfuryl alcohol and 0.1 to 2 wt.% hydrochloric acid and a water content of < 5 wt.%, in particular < 1 wt.%, preferably < 0.25 wt.%, is prepared as a continuous material stream, which is then esterified to the alkyl levulinate at a temperature in the range of 60 - 100 °C, preferably 70 - 90 °C, in particular in a continuously operated reactor.

[0037] The excess alcohol is advantageously separated from the reaction mixture with the added water.

[0038] A particularly advantageous embodiment provides that the separation of the alkyl levulinate from the humins, and in particular also from other by-products, takes place by spray drying and / or in a spray dryer.

[0039] The separation of humins or other sticky byproducts often proves extremely difficult. Humins, in particular, deposit on the heating surface in an evaporator at temperatures as low as 100 °C, blocking it before ethyl levulinate can evaporate. In US Pat. No. 4,236,021, for example, approximately 10% triacetin or phthalates are added to the ethyl levulinate / humin mixture, yet evaporation yields of only <60% are achieved. It was therefore surprising that ethyl levulinate can be obtained with a 99% yield by fine atomization in a spray dryer at around 200-250 °C, especially when the residence time is short enough, specifically 1-5 seconds.

[0040] This produces a fine-grained powder that can easily be mixed into liquid fuel or blown directly into a combustion chamber, while ethyl levulinate is evaporated from the humins. The amount of HCl bound in the humins is released during combustion and washed out as dilute acid, which can then be reused in the process. It is therefore advantageous to first distill the neutralized mixture to separate the alkyl levulinate from the humins, and especially from other by-products. A mixture of alkyl levulinate and humins is then withdrawn from the bottom product, and this mixture is then spray-dried or spray-dried in a spray dryer, whereby the alkyl levulinate is evaporated and removed.

[0041] In this context, it is advantageous if the supplied mixture, in particular in a spray dryer, is atomized via an atomizing nozzle in an inert gas stream at a temperature of > 200 °C, whereby the alkyl levulinate is evaporated and removed and the humins are removed in the lower region of the spray dryer.

[0042] The invention also relates to the alkyl levulinate which is obtainable or obtained by the process according to the invention.

[0043] The distillate from the spray dryer is then fed to the subsequent hydrogenation.

[0044] According to a further advantageous aspect of the invention, a process for producing gamma-valerolactone (GVL) by hydrogenating the alkyl levulinate obtained or obtainable from the process according to the invention is provided.

[0045] The reaction proceeds as follows:

[0046] The hydrogenation of ethyl levulinate is particularly advantageous in a batch reactor at 10–30 bar hydrogen pressure and a reaction temperature of <200 °C, preferably at 150 °C, with 10–80 g / l of Raney nickel or molybdenum doping. A conversion of 99–100% and a yield of >95 wt.% are achieved. However, it should be noted that at reaction temperatures >150 °C, the released ethanol reacts to form methane, which hinders the hydrogenation, so the reactor gas must be vented during the reaction.

[0047] Surprisingly, it has been shown that at temperatures of 150 °C, methane formation is almost completely avoided, but the conversion to gamma-valerolactone is not complete and a residue of 10 - 50 % remains only up to 4-hydroxypentanoic acid ethyl ester (4HPE), depending on the catalyst.

[0048] Surprisingly, it has been shown that the cleavage of the ester occurs very advantageously in a reactive distillation at temperatures >190 °C, if the released ethanol is distilled off at the same time and thus the ring closure to the gamma-valerolactone can take place.

[0049] In this context, it is therefore advantageous for conversion and yield if the hydrogenation of the alkyl levulinate with hydrogen takes place at a temperature of 100 - 200 °C, in particular at 140 - 160 °C.

[0050] An advantageous process procedure provides that the alkyl levulinate is hydrogenated with hydrogen and a nickel-based catalyst at > 5 bar hydrogen partial pressure and at a temperature of 100 to 200 °C and the formed gamma-valerolactone (GVL) is separated by distillation from the released alcohol, water and by-products.

[0051] It may be particularly advantageous if, after the hydrogenation of the alkyl levulinate, the mixture containing gamma-valerolactone (GVL) and 4-hydroxypentanoic acid ethyl ester (4HPE) is subjected to a reactive distillation at a temperature of 150 - 210 °C, in particular at 170 - 200 °C, in particular at >190 °C, in order to convert the 4HPE to GVL as completely as possible.

[0052] Also according to the invention is gamma-valerolactone (GVL), which is obtainable or obtained by the process according to the invention.

[0053] Furthermore, it is advantageous if, in the processes according to the invention for producing alkyl levulinate and / or gamma-valerolactone (GVL), the alcohol recovered in the respective process steps is dried, in particular freed from the water introduced, and reused as a solvent and reactant for the esterification, wherein the drying is preferably carried out by adsorption on zeolites or by entraining agent distillation. The invention also relates in particular to a process for producing gamma-valerolactone (GVL), in which furfuryl alcohol reacts in acidic, alcoholic solution to form levulinic acid and, by simultaneous esterification, is converted to alkyl levulinate, which is converted to gamma-valerolactone in a hydrogenation reaction, while the alcohol is again recovered and recycled.

[0054] An advantageous process for the preparation of gamma-valerolactone (GVL) from furfuryl alcohol by esterification with an aliphatic alcohol and subsequent hydrogenation of the resulting alkyl levulinate is characterized in that 10 to 30 wt.% of furfuryl alcohol are dissolved in an alcohol and 0.1 to 2 wt.% HCl is added to the solution, this mixture is heated to 60 - 100 °C and hydrolyzed to alkyl levulinate in one or more reactors, the catalyst acid is neutralized and the excess alcohol is separated from the reaction mixture with the introduced water, and the formed alkyl levulinate is separated from the formed salts and by-products (humins), alkyl levulinate is hydrogenated with hydrogen and a nickel-based catalyst at >5 bar hydrogen partial pressure and 100 to 200 °C and the formed gamma-valerolactone (GVL) is separated by distillation from the released alcohol, water and by-products, while the recovered alcohol is freed from the introduced water and is used again as a solvent and reactant for the esterification.

[0055] BRIEF DESCRIPTION OF THE FIGURES AND LISTS

[0056] The process according to the invention is described below using an exemplary and non-limiting embodiment and a schematic representation of an exemplary plant (Fig. 1). In this context, reference is also made to the following lists of reference symbols for the devices or apparatus (some with functional descriptions) as well as the material or product flows. DESCRIPTION OF THE FIGURES AND EMBODIMENT

[0057] The overall process essentially comprises three relevant sub-steps:

[0058] • Production of ethyl levulinate

[0059] • Hydrogenation of ethyl levulinate

[0060] • Recovery of dehydrated ethanol

[0061] Production of ethyl levulinate (Fig. 1 , bottom left area):

[0062] In a mixer 4, an ethanol stream 2 (> 99.8%, ethanol 100 kg / h, water 0.2 kg / h) is mixed with an HCl stream 3 in the form of HCl gas (> 98%, HCl 1.3 kg / h) and a furfuryl alcohol stream 1 (> 99%, 5 or 5 x 5 kg / h furfuryl alcohol) to form a solution of these three components. A low water content of 0.2 wt.% in this case is advantageous for the yield.

[0063] This solution is heated to 80 °C in a preheater or heat exchanger 5 and fed into a reactor 6, where esterification to ethyl levulinate takes place. Reactor 6 used here is a continuously operated tubular reactor with a diameter of 350 mm and a height of 5000 mm. It is made of glass fiber reinforced plastic (GRP) and features a perfluoroalkoxy PFA liner.

[0064] An additional 5 kg / h of furfuryl alcohol is continuously added at each quarter of the height of reactor 6. At the top outlet of reactor 6, the conversion is 99.9%, and product stream 7 contains 33.8 kg / h of ethyl levulinate and 1.5 kg / h of humic acids (ethanol 90 kg / h, EL 33.8 kg / h, HCl 1.3 kg / h, humic acids 1.5 kg / h, water 0.7 kg / h).

[0065] To neutralize the product stream 7 or the catalyst acid, 1.4 kg / h of ammonia gas 8 is fed into the mixer 9.

[0066] The neutralized product stream 7 is then fed to a distillation column 10 in which a product stream 19 of ethanol and water (EtOH 90 kg / h, water 0.7 kg / h) is distilled off at the top, while in the bottom a product stream 23 containing ethyl levulinate and humins, namely a mixture of 33.8 kg / h ethyl levulinate and 1.5 kg / h humins, is withdrawn and fed to a spray dryer 24 to separate the humins. In the spray dryer 24, the supplied product stream 23 (EL 33.8 kg / h, NH4CI 2.7 kg / h, humic acid 1.5 kg / h) is atomized via a Laval two-component atomizer nozzle 18 by nitrogen pressurized gas into a nitrogen stream 33 (360 kg / h), 33b (40 kg / h 2.5 bar abs) at >220 °C to a droplet size of <100 micrometers, whereby the contained ethyl levulinate evaporates within 3 seconds.The humic acids with the ammonium chloride remain as dust and are withdrawn at the lower discharge cone of the spray dryer 24 in stream 26 (humic acids 1.5 kg / h, NH4CI 2.7 kg / h, EL 0.3 kg / h) and removed from the system.

[0067] The evaporated ethyl levulinate is passed through a dust filter 25 for humic separation in a nitrogen stream 27 (nitrogen 400 kg / h, EL 33.7 kg / h).

[0068] Hydrogenation of ethyl levulinate (Fig. 1 , bottom right area):

[0069] The hydrogenation of the resulting ethyl levulinate stream 29 (33.5 kg / h EL) to GVL and 4-hydroxypentanoic acid ester (4HPE) takes place in alternating hydrogenation reactors 38 and 39 at 150 °C after feeding a catalyst 40 (Evonik MC811) with a hydrogen stream 37 at 20 bar hydrogen pressure (0.5 kg / h, 20 bar abs). The reaction time is 2.5 hours, and the batch time is 3 hours. 5.4 kg of catalyst is added per batch, and the reactor capacity is 100 kg.

[0070] The conversion is 100%, with 80% of the ethyl levulinate being converted to GVL, and 20% of the reactor contents being present as 4HPE. The reactor contents from the hydrogenation reactors 38 and 39 are then blown off into a flash tank 41.

[0071] The degassed product stream 46 containing GVL and 4HPE (GVL 20 kg / h, 4HPE 5.5 kg / h, EtOH 8.3 kg / h, water 0.1 kg / h, high boilers 0.3 kg / h) is freed from catalyst in filter 36. The separated catalyst is fed back to the hydrogenation reactors 38, 39 in stream 40 (1.8 kg / h).

[0072] The liquid phase 47 after separation of the catalyst (GVL 20 kg / h, 4HPE 5.5 kg / h, EtOH 8.3 kg / h, water 0.1 kg / h, high boilers 0.3 kg / h) is then fed to a reactive distillation 48. In this reactive distillation 48, the remaining 4HPE is converted to GVL in tunnel trays with a residence time of 50 minutes at a temperature range of 190 to 206 °C, while the released ethanol is condensed. Ethanol and water, as well as volatile impurities, are distilled off overhead or are withdrawn in stream 52 (EtOH 10 kg / h, water 0.1 kg / h) and fed to the recovery process.

[0073] From the bottom product of reactive distillation 48, the GVL formed in stream 54 (GVL 23 kg / h, high boilers 0.3 kg / h) is separated from the high-boiling impurities overhead in another distillation column or high boiler column 55. In the bottom product, the high boilers are separated in stream 63 (high boilers 0.3 kg / h).

[0074] The purity of the gamma-valerolactone obtained in stream 61 (GVL 23 kg / h) is > 99.8 wt.%.

[0075] Recovery of dehydrated ethanol (Fig. 1 , top left area):

[0076] The three ethanol streams 19 (EtOH 90 kg / h, water 0.7 kg / h), 52 (EtOH 10 kg / h, water 0.1 kg / h) and 72 (EtOH 10 kg / h, water 0.6 kg / h) are dried to 0.2 wt.% water content by passing the collected or combined ethanol stream over a zeolite adsorber 64 (3 Angstrom zeolite Köstrolith 3AK).

[0077] Regeneration of adsorber 64 occurs in nitrogen stream 65, from which the desorbed water is condensed in condenser 68, and the dried nitrogen stream 65 is heated to 195 °C in heater 67. The condensate from 68 is freed of ethanol in wastewater stripper 69 and discharged. The ethanol obtained here is also recycled in stream 72 (EtOH 10 kg / h, water 0.6 kg / h).

[0078] The dried ethanol is added to product stream 21 to compensate for losses and forms ethanol stream 2 used for esterification to ethyl levulinate in reactor 6.

[0079] In the above descriptions, some reference symbols from Fig. 1 or the following lists were not explicitly mentioned. These are mostly standard components or processes that are less relevant to the method according to the invention and do not require separate mention. Their function is clear from Fig. 1 and the lists without a separate description. List - Designations of the device parts or equipment in Fig. 1 (some with functional description):

[0080] 4 mixers or static mixers

[0081] 5 Preheater Esterification

[0082] 6 Reactor Esterification

[0083] 9 Mixer Neutralization

[0084] 10 Distillation Ethanol Separation

[0085] 11 Circulation pump

[0086] 12 sump evaporators

[0087] 13 Ethanol condenser

[0088] 18 Nitrogen atomizing nozzle

[0089] 24 spray dryers

[0090] 25 dust filter humic separation

[0091] 28 Capacitor ethyl levulinate

[0092] 31 Blower nitrogen circuit

[0093] 32 heaters

[0094] 32a Nitrogen Compressor

[0095] 34 hydrogenation storage tanks

[0096] 35 Feed pump hydrogenation

[0097] 36 Catalytic converter filter

[0098] 38 Hydrogenation Reactor 1

[0099] 39 Hydrogenation reactor 2

[0100] 41 expansion tanks

[0101] 42 Ethanol Condenser

[0102] 44 Hydrogenation product pump

[0103] 48 Reactive distillation

[0104] 49 Circulation pump

[0105] 50 sump evaporators

[0106] 51 Ethanol condenser

[0107] 55 High-boiling column

[0108] 56 Circulation pump

[0109] 57 sump evaporator

[0110] 58 GVL capacitor

[0111] 64 adsorbers

[0112] 66 nitrogen blowers

[0113] 67 Nitrogen heater 68 Water / ethanol condenser

[0114] 69 Wastewater Stripper

[0115] 70 Ethanol condenser

[0116] 74 sump evaporators

[0117] List - Material flow table for Fig. 1 (all % values ​​in wt%):

[0118] Abbreviations:

[0119] EtOH ... Ethanol

[0120] HCl ... hydrochloric acid

[0121] EL ... Ethyl levulinate

[0122] GVL ... Gamma-Valerolactone

[0123] 4HPE ... 4-Hydroxypentanoic acid ethyl ester

[0124] 1 furfuryl alcohol, > 99%, 25 kg / h

[0125] 2 Ethanol, > 99.8%, 100 kg / h, water 0.2 kg / h

[0126] 3 HCI gas, > 98%, 1.3 kg / h

[0127] 7 Ethanol 90 kg / h, EL 33.8 kg / h, HCl 1.3 kg / h, humine 1.5 kg / h, water 0.7 kg / h

[0128] 8 NH31.4 kg / h

[0129] 19 EtOH 90 kg / h, water 0.7 kg / h

[0130] 20 Vacuum 0.3 bar abs

[0131] 21 EtOH make up (flows into 2)

[0132] 23 tbsp 33.8 kg / h, NH4CI 2.7 kg / h, humine 1.5 kg / h

[0133] 26 humins 1.5 kg / h, NH4CI 2.7 kg / h, EL 0.3 kg / h

[0134] 27 Nitrogen 400 kg / h, EL 33.7 kg / h

[0135] 29 tablespoons 33.5 kg / h

[0136] 33 Nitrogen 360 kg / h

[0137] 33b Nitrogen 40 kg / h 2.5 bar abs

[0138] 37 Hydrogen 0.5 kg / h 20 bar abs

[0139] 40 Catalyst 1.8 kg / h

[0140] 43 Hydrogen 0.05 kg / h

[0141] 46 GVL 20 kg / h, 4HPE 5.5 kg / h, EtOH 8.3 kg / h, water 0.1 kg / h, high boiler 0.3 kg / h

[0142] 47 Liquid phase after catalyst separation (GVL 20 kg / h, 4HPE 5.5 kg / h, EtOH 8.3 kg / h, water 0.1 kg / h, high boilers 0.3 kg / h)

[0143] 52 EtOH 10 kg / h, water 0.1 kg / h

[0144] 54 GVL 23 kg / h, high boilers 0.3 kg / h Vacuum 0.3 bar abs GVL 23 kg / h high boilers 0.3 kg / h Nitrogen make up EtOH 10 kg / h, water 0.6 kg / h Water 1.4 kg / h

Claims

PATENT CLAIMS 1. A process for the preparation of a levulinic acid ester or alkyl levulinate, in particular ethyl levulinate, comprising the following steps: - Preparation of a solution containing furfuryl alcohol, an alcohol as solvent, and hydrochloric acid as catalyst acid, - Esterification of this solution at a temperature in the range of 60 - 100 °C to form alkyl levulinate, - neutralization of the catalyst acid in the mixture thus obtained, - Separation of the alkyl levulinate from the humins formed as by-products.

2. Process according to claim 1, characterized in that the alcohol is an alkyl alcohol, in particular ethanol.

3. Process according to one of the preceding claims, characterized in that the solution contains 10 to 30 wt.% furfuryl alcohol.

4. Process according to one of the preceding claims, characterized in that the solution contains 0.1 to 2 wt.% hydrochloric acid.

5. Process according to one of the preceding claims, characterized in that the hydrochloric acid is supplied to the solution as a gas, in particular pre-dried, preferably anhydrous.

6. Process according to one of the preceding claims, characterized in that the water content in the solution is < 5 wt.%, in particular < 1 wt.%, preferably < 0.25 wt.%.

7. Process according to one of the preceding claims, characterized in that the esterification takes place at a temperature in the range of 70 - 90 °C.

8. Process according to one of the preceding claims, characterized in that the esterification takes place in a reactor (6), in particular in a continuously operated tubular reactor.

9. Process according to one of the preceding claims, characterized in that the supply of furfuryl alcohol and the further components, in particular into the reactor (6), takes place continuously over the entire course of the reaction, wherein it is provided in particular that furfuryl alcohol is supplied at several superimposed height positions of the reactor (6).

10. Process according to one of the preceding claims, characterized in that the neutralization of the catalyst acid is carried out by ammonia, wherein it is provided in particular that ammonia is supplied as a gas, in particular pre-dried, preferably anhydrous.

11. Process according to one of the preceding claims, characterized in that an ethanol stream (2), in particular with > 99.8%, an HCl stream (3), in particular in the form of HCl gas, in particular with > 98%, and a furfuryl alcohol stream (1), in particular with > 99%, are continuously mixed and an alcoholic solution, in particular with 10 to 30 wt.% furfuryl alcohol and 0.1 to 2 wt.% hydrochloric acid and a water content of < 5 wt.%, in particular < 1 wt.%, preferably < 0.25 wt.%, is prepared as a continuous material stream, which is then esterified to the alkyl levulinate at a temperature in the range of 60 - 100 °C, preferably 70 - 90 °C, in particular in a continuously operated reactor (6).

12. Process according to one of the preceding claims, characterized in that the separation of the alkyl levulinate from the humins, and in particular also from other by-products, takes place by spray drying and / or in a spray dryer (24).

13. Process according to one of the preceding claims, characterized in that in order to separate the alkyl levulinate from the humins, and in particular also from other by-products, the neutralized mixture is first distilled, a mixture of alkyl levulinate and humins is withdrawn in the sump, and this mixture is then spray-dried or subjected to spray-drying in a spray dryer (24), wherein the alkyl levulinate is evaporated and withdrawn.

14. Method according to one of the preceding claims, characterized in that the supplied mixture is atomized in the spray dryer (24), in particular via an atomizing nozzle (18), in an inert gas stream at a temperature of > 200 °C, wherein the alkyl levulinate evaporated and removed and the humins are removed in the lower part of the spray dryer (24).

15. Alkyl levulinate obtainable by the process according to any one of claims 1 to 14.

16. A process for the preparation of gamma-valerolactone (GVL) by hydrogenating the alkyl levulinate obtained from the process according to any one of claims 1 to 14, or by hydrogenating alkyl levulinate obtainable according to claim 15.

17. A process for the preparation of gamma-valerolactone (GVL) according to claim 16, wherein the hydrogenation, in particular nickel-catalyzed, of the alkyl levulinate with hydrogen takes place at a temperature of 100 to 200 °C, in particular at 140 to 160 °C.

18. A process for the preparation of gamma-valerolactone (GVL) according to any one of claims 16 to 17, wherein the alkyl levulinate is hydrogenated with hydrogen and a nickel-based catalyst at > 5 bar hydrogen partial pressure and at a temperature of 100 to 200 °C and the gamma-valerolactone (GVL) formed is separated by distillation from the released alcohol, water and by-products.

19. A process for the preparation of gamma-valerolactone (GVL) according to any one of claims 16 to 18, wherein after the hydrogenation of the alkyl levulinate, the mixture containing gamma-valerolactone (GVL) and 4-hydroxypentanoic acid ethyl ester (4HPE) is subjected to a reactive distillation at a temperature of 150 to 210 °C, in particular at 170 to 200 °C, for the most complete possible conversion of the 4HPE to GVL.

20. A process for the preparation of gamma-valerolactone (GVL) according to any one of claims 16 to 19, wherein the reactive distillation is carried out at temperatures of >190 °C and the released ethanol is distilled off simultaneously.

21. Gamma-valerolactone (GVL) obtainable by a process according to any one of claims 16 to 20.

22. A process for the preparation of alkyl levulinate and / or gamma-valerolactone (GVL) according to any one of the preceding claims, wherein the alcohol recovered in the respective process steps is dried, in particular freed from the water introduced, and is reused as solvent and reactant for the esterification, wherein the drying is preferably carried out by adsorption on zeolites.

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