WO2022260560A1

WO2022260560A1 - Method for carrying out a chemical reaction with a catalyst susceptible to work-up and reaction system

Info

Publication number: WO2022260560A1
Application number: PCT/SA2022/050008
Authority: WO
Inventors: Mohammed Ansari; Khalil IBN SALAMAH; AbdulVasif SHAIKH
Original assignee: Global Company For Downstream Industries (Gdi)
Priority date: 2021-06-08
Filing date: 2022-06-07
Publication date: 2022-12-15

Abstract

The present invention relates to a method for carrying out a chemical reaction with a catalyst susceptible to a work-up, including in particular starvation of a reactant gas and quenching, using a reaction system comprising a reactor and a downstream buffer vessel connected to a discharge tube for discharging a worked-up product, wherein the reactor comprises at least one inlet, which is/are suitable for insertion of a reactant, the catalyst and the reactant gas, in particular hydrogen, and a connecting tube connected to the reactor and feeding the downstream buffer vessel for transferring a crude product from the reactor into the downstream buffer vessel with various steps and a reaction system for carrying out an air-sensitive, catalyzed reaction.

Description

Method for Carrying Out a Chemical Reaction with a Catalyst Susceptible to Work-Up and Reaction System

[01] The present invention relates to a method for carrying out a chemical reaction with a catalyst susceptible to a work-up, including in particular starvation of a reactant gas and quenching, and a reaction system.

[02] Many catalysts, for example hydrogenation catalysts like Raney nickel for preparing alcohols from corresponding carbonyl precursors in a hydrogenation reaction, are air sensitive and pyrophoric in nature and often pose handling problems. Such catalysts may, if not protected from air, catch fire and also undergo severe deactivation before the start of the hydrogenation process resulting in increased consumption of catalyst and poor quality of the desired product. Such catalysts can in principle be used for as many as 10 or more cycles conveniently with bare minimum top-up by adding a fresh aliquot after each cycle, provided deactivation is prevented. Catalyst deactivation occurs by ingress of air or catalyst poisons in the reactor system and when a hydrogen atmosphere is lost in the reactor and hydrogen starvation of the catalyst occurs.

[03] Thus, the deactivation, i.e. a loss of catalytic activity, leads to the requirement of high top-up amounts of catalyst before starting a subsequent batch/cycle and the catalyst lasts for fewer cycles than expected. Deactivation leads not only to increased consumption of catalyst but also to poor quality of the desired product or a higher proportion of by-product. Catalyst deactivation should be thus preferably prevented.

[04] Deactivation of the catalyst occurs particularly when the reaction product is worked up or when the heterogeneous catalyst is filtered off the product in order to be able to use it again in the next reaction. For this purpose, either a door of the reactor is opened and the product is extracted while the catalyst remains in the reactor, or the catalyst is completely filtered off and re-introduced in the reactor for subsequent batches. Gas exchange or air contact, i.e. oxygen ingress or hydrogen loss, occurs when the catalyst is filtered and the reactor door is opened to remove the product after each batch.

[05] When the catalyst is allowed retain in the bottom of the reactor as 'heel' after each batch, the required hydrogen density on the surface of the catalyst is maintained, i.e. starvation is avoided, yet ingress of air or oxygen laden impurities such as contaminated moisture, happen frequently despite taking best care particularly while processing hydroscopic reactants. The major drawback of this methodology is that it restricts the operations to batch mode only, thereby decreasing the throughput by not allowing to opt for semi continuous type of operation. The partial deactivation by entrained air has to be compensated by topping up with 2-10% of fresh catalyst, depending upon the extent of deactivation that has occurred during the preceding batches.

[06] When filtration or separation of the catalyst from the reaction mixture proceeds after each completed batch cycle; the separated catalyst often gets starved of hydrogen, i.e. extensive desorption, during the filtration process.

[07] US20160185902A1 discloses a continuous reaction device comprising multiple slurry bed stirred tank reactors connected in series or in combination of series connection and parallel connection, and also comprising an on-line solid-liquid separation device to perform separation of the reaction mixture from the catalyst.As no gaseous reactant is used, the complexity of maintaining particular gas density at the surface of catalyst does not exist. In addition, US20160185902A1 deals with ion exchange catalysts, which are neither air sensitive nor pyrophoric in nature, thus not requiring special handling to preserve catalytic activity during the course of the entire process.

[08] EP2781258A1 discloses a chemical reaction apparatus comprising a horizontal flow-type reactor inside of which has been partitioned into multiple chambers by multiple partition plates, and a liquid content horizontally flows with an unfilled space being provided thereabove; a microwave generator; and at least one waveguide that transmits the microwaves generated by the microwave generator to the unfilled space in the reactor. Due to the use of microwaves, the apparatus of EP2781258A1 can only be used for reactions under ambient pressure. In addition, EP2781258A1 is silent on using the apparatus for performing gas- liquid reactions such as hydrogenation, air oxidation or chlorination etc., as well as on handling any pyrophoric, air sensitive and/or hazardous catalysts (e.g. Raney Nickle or Raney Cobalt), which require adequate precautions like use of closed and pressurized tanks and cannot be handled under the influence of microwaves.

[09] The object of the invention is to provide a method of extending the lifespan of a catalyst that is sensitive to air or reactive gas starvation. It is also an object of the invention to minimize the retention time of a reaction mixture in a reactor.

[10] These objects are met by a method for carrying out a chemical reaction with a catalyst susceptible to a work-up, including in particular starvation of a reactant gas and quenching, using a reaction system comprising a reactor and a downstream buffer vessel connected to a discharged tube for discharging a worked-up product, wherein the reactor comprises at least one inlet, which is/are suitable for insertion of a reactant, the catalyst and the reactant gas, in particular hydrogen, and a connecting tube connected to the reactor and feeding the downstream buffer vessel for transferring a liquid or dissolved crude product from the reactor into the downstream buffer vessel with the following steps: i. performing the chemical reaction, which is catalyzed by the catalyst, between the reactant and the reactant gas under reaction conditions, in particular in a reactant gas atmosphere, in the reactor so that the crude product is obtained in the reactor, ii. transferring the crude product via the connecting tube into the downstream buffer vessel while the catalyst is retained in the reactor by an intermediate filter arranged in the connecting tube, and iii. working-up the crude product in the downstream buffer vessel and disconnecting a pressure connection established via the connecting tube between reactor and downstream buffer vessel using a disconnection device located in or at the connecting tube, so that different gas atmospheres can be created in the reactor and the downstream buffer vessel, and removing or replacing the reactant gas in the downstream buffer vessel while preserving the reactant gas atmosphere in the reactor and thereby retaining the catalyst under such protective atmosphere in the reactor, so that the catalyst is not fully degraded but usable in a further reaction and the worked-up product is obtained in the downstream buffer vessel.

[11] The method of the present invention thus allows to carry out a catalyzed chemical reaction without the deactivation of the catalyst by work-up or starvation of reactant gas. The service life of the catalyst is thereby increased. [12] The method furthermore allows to directly evacuate the crude product after the reaction and carry out the work-up of the crude product in a different vessel. A retention time of the product in the reactor is thus reduced. Also, for the work-up, a vessel, which would not necessarily withstand the conditions under which the reaction is carried out like high pressure or high temperature, can be utilized, i.e. the downstream buffer vessel. Thus, a higher throughput through the reactor especially equipped e.g. to withstand higher pressure of a hydrogenation reaction is achieved. A cheaper vessel can thereby be utilized for the work-up reaction.

[13] A key idea of the current invention is in particular that the method uses the reactor as a first container in which the reaction is occurring connected via the connection tube with the downstream buffer vessel as a second container in which a work up is occurring. Thus, a spatial separation of catalytic reaction and work-up is achieved which allows to avoid or minimize degradation of the catalyst.

[14] The arrangement of the intermediate filter in the connecting tube or in a position covering the connecting tube allows filtering of the crude product and retention of the catalyst in the reactor without the need of filtering the catalyst outside of the reactor. This further reduces the likelihood of potential degradation of the catalyst.

[15] The method may be used, for example, in the production of isopropyl alcohol from acetone. This method can, however, also be applied for hydrogenation reactions of several other unsaturated substrates like sulfolenes, alkenes, alkynes, or nitriles etc., to produce sulfolanes, alkanes, and amines in high yield and in high purity.

[16] An excess hydrogen present in the reaction mass may be removed from the downstream buffer vessel by depressurizing the downstream buffer vessel or by mild bubbling of dry nitrogen gas.

[17] In order to increase a throughput, many stirred tank reactors (hydrogenation reactors) can be deployed in series or in parallel in the upstream of the downstream buffer vessel, so that the entire process can be converted into semi-continuous mode. In this case, a filling volume of the downstream buffer vessel is considered at least three times higher than the filling volume of one stirred tank reactor. Therefore, out-flow of two or three hydrogenation reactors can be transported to one downstream buffer vessel one after another at pre-planned time intervals for ensuring an un-interrupted operation.

[18] The reaction mixture is transferred to the downstream buffer vessel via the connecting tube for example by virtue of the pressure of excess hydrogen available in the reactor.

[19] The downstream buffer vessel may be used to maintain the product streams, possibly from several batches of the hydrogenation reactor, for a certain period of time so that further downstream processes like stripping of excess hydrogen, separation of catalyst from liquid stream and recovering the final product in pure form, using a suitable product recovery system, becomes facile, quick and safe.

[20] The "reactant gas atmosphere" is obtained by the insertion of the reactant gas as the reactor and the downstream buffer vessel are forming together a gas tight system. The reaction system has optionally a gas outlet which allows a more efficient exchange of the gas atmosphere, as the gas atmosphere can be changed by introducing the reactant gas via the inlet and simultaneous removal of the existing gas atmosphere via the gas outlet. [21] The "reaction system" comprises thus the reactor connected via the connecting tube for transfer of the worked-up product to the downstream buffer vessel. The downstream buffer vessel has the discharge tube for discharging the product after work up. The intermediate filter is arranged in such position inside the connecting tube that it is able to retain the catalyst in the reactor. For example, the intermediate filter is positioned transversely in the connecting tube or covers an inlet of the connecting tube at the reactor so that all liquid flowing into the connecting tube is filtered.

[22] The "inlet" can be configured as quick release coupling. Each of the inlets is connected to a supply of reactant, the catalyst and/or the reactant gas. The reactor may have in particular one inlet connected to the reactant supply, the catalyst supply and the reactant gas supply or the reactor may have three inlets each connected to the reactant supply, the catalyst supply and the reactant gas supply, respectively.

[23] The "chemical reaction" is understood as the reaction of the reactant with the reactant gas with the help of the catalyst yielding the crude product. The reaction may in particular be the reaction of acetone and hydrogen catalysed by a Raney nickel catalyst yielding isopropanol.

[24] The "disconnecting device" is either a sealable valve or a flap which is able to keep different gas atmospheres in the reactor and the downstream buffer vessel separated to prevent a mixing of the two gas atmospheres and optionally also allows the creation of a different pressure in the reactor than the downstream buffer vessel.

[25] "Different gas atmospheres created in the rector and the downstream buffer vessel" is understood as one gas atmosphere in the reactor and a different gas atmosphere in the downstream buffer vessel. The "gas atmosphere" is understood as one type of gas or a mixture of different types of gas. This includes in particular a reactant gas in the reactor, such as hydrogen, and a protective gas, such as nitrogen, or air in the downstream buffer vessel. The creation of different gas atmospheres allows, for example, the removal of the reactant gas from the crude product located in the downstream vessel while keeping a reactant gas atmosphere in the reactant and thus preventing starvation and deactivation of the catalyst.

[26] The "discharge tube" is a tube that leads to a storage or bottling of the worked-up product.

[27] A "work-up" is understood as a method which is required to obtain a final product from a crude product for example by deactivation of a reactive but unreacted compound such as the catalyst, or the isolation and purification of one or several chemical compounds. The deactivation of unreacted compounds is also called "quenching".

[28] In a further embodiment, the crude product in step ii. is not completely transferred to the downstream buffer vessel and such amount of the crude product is retained in the reactor that the catalyst is fully covered by the retained crude product so that the retained crude product acts a protective cover.

[29] This method utilizes the fact that the retained crude product is at least partially saturated with the reactant gas and thereby prevents the starvation of the catalyst with reactant gas. Further, gas exchange is slowed down in the liquid phase of the retained crude product compared to a catalyst exposed to a gas atmosphere. Thus, any catalyst poison entering the reactor atmosphere is slowed in the process of reaching the catalyst as it has to cross the layer of crude product covering the catalyst. The retained crude product thereby helps in reducing catalyst deactivation, as reactant gas starvation of the catalyst and catalyst poisoning is reduced or essentially eliminated .

[30] A positive hydrogen pressure makes the reactant gas, e. g. hydrogen, act as a hydrogen blanket on the surface of catalyst located in the dead volume. This action keeps the catalyst in very healthy condition due to high reactant gas density prevailing around the dead volume. Hence, the catalyst could be used for the next cycle with no or minimum quantity of top-op aliquot of the catalyst.

[31] "Such amount of the crude product that the catalyst is fully covered by the retained crude product" is understood that most of the catalyst, for example 80 % or preferably 98 %, are located at the bottom of the reactor. The amount of crude product is then determined by draining the reactor until the minimum amount of crude product is retained in the reactor necessary to cover the catalyst located at the bottom of the reactor.

[32] To avoid the need of measuring the retained crude product level inside the reactor, the connecting tube of the reactor is arranged above a lowest interior point of the reactor, so that a volume between the lowest interior point of the reactor and the connecting tube is a dead volume which cannot be emptied via the connecting tube and which stores the retained product, wherein the connecting tube is attached in such position that the dead volume is more than 1%, preferably more than 3%, more preferably more than 5%, even more preferably more than 10%, even more preferably more than 15%, and most preferably more than 20% of the total volume of the reactor, wherein the connecting tube is attached in such position that the created dead volume is sufficient to receive at least 80% of the catalyst so that after transferring the crude product to the downstream buffer vessel via the connecting tube, the retained catalyst is stored in the dead volume and covered by the retained crude product.

[33] Measuring the level of retained crude product inside the reactor is prone to error and requires either a measuring unit or manual oversight. By arranging the connecting tube above a lowest interior point, the dead volume is automatically created and retained in the reactor, so that the crude product in the dead volume aids as a protective cover. A measuring unit or manual supervision becoming thereby dispensable.

[34] In a further embodiment, a product filter is arranged in or connected to the discharge tube in a filtering position with the further step of: iv. discharging the worked-up product from the downstream buffer vessel through the discharge tube and the product filter, so that the product filter separates solid particles, in particular residual catalyst particles, from the worked-up product.

[35] The product filter allows to filter the worked-up product to remove any particles that have been carried through the intermediate filter or that might have been formed during the work-up. Thus, a particle-free liquid or dissolved worked-up product is obtained after discharge via the discharge tube.

[36] In a further embodiment, the reactor further comprises a draining tube feeding the downstream buffer vessel, wherein the draining tube is equipped with a valve for intermittent operation, so that the intermediate filter of the connecting tube is bypassed by the draining tube, with the further steps of: v. repeating the steps i. to iii. one time or several times so that a larger quantity of the crude product than a single filling volume of the reactor is obtained in the downstream buffer vessel, wherein the repeated chemical reaction is carried out in each case with the retained catalyst until the catalyst is at least partially exhausted, vi. optionally discharging the worked-up product from the downstream buffer vessel, vii. transferring the at least partially exhausted catalyst from the reactor through the draining tube into the downstream buffer vessel, so that the at least partially exhausted catalyst is not retained in the reactor by the intermediate filter placed in the connecting tube, and viii. discharging of a content comprised in the downstream buffer vessel via the discharge tube of the downstream buffer vessel, so that the at least partially exhausted catalyst is retained and provided as a disposable filter cake by the product filter and an unloaded reaction system is obtained.

[37] After the complete exhaustion of the catalyst, the last cycled batch is transferred to the downstream buffer vessel along with the spent catalyst sludge. This spent catalyst sludge may be filtered off using a suitable solid-liquid separation device like sparkler filter or nutsche filter, plate filter or a candle filter.

[38] The "filling volume" is understood as the volume of liquid and dispensed particles present in the reactor while performing the chemical reaction. By repeating steps i. to iii. and filling the reactor various times with reactant, more volume of a liquid or dissolved crude product may be obtained in the downstream buffer vessel than it would fit by a single filling step in the reactor. [39] The "intermittent operation" allows the valve to be opened or closed so that the draining tube can be either blocked or unblocked for a flow of crude product and dispensed catalyst.

[40] A "partially exhausted catalyst" is understood as a catalyst which was used repeatedly in a chemical reaction until its catalytic activity is decreased or spent.

[41] The draining tube allows thus to transfer the crude product in the downstream buffer vessel without filtering it through the intermediate filter. The partially exhausted catalyst can thereby be flushed out of the reactor using the crude product as carrier into the downstream vessel.

[42] In one embodiment, the draining tube is attached to the lowest interior point of the reactor, so that the reactor can be completely drained using the draining tube. In another embodiment, additional rinsing of the reactor with a solvent is performed to remove adhering catalyst particles. In yet another embodiment, the discharging tube additionally has a valve to control a flow of crude product through the discharge tube. The crude product may thus be exclusively transferred via the draining tube.

[43] To remove reactant gas from the crude product and/or the worked-up product, the crude product and/or the worked-up product in the downstream buffer vessel is flushed with a protective gas using a protective gas sparger arranged in the downstream buffer vessel so that the reactant gas is washed out.

[44] "Flushing with a protective gas" is used for degassing, also called sparging, and means to bubble the protective gas through the liquid or dissolved crude or worked-up product to remove the reactant gas.

[45] The reactant gas may thus be fed back in the reactor in a further reaction. This prevents sudden outgassing of the reactant gas in later stages of the process and thus improves safety.

[46] In a further embodiment the reactor comprises a reactant gas sparger, in particular a hydrogen sparger, and/or a stirrer wherein the reactant gas sparger is at least partially connected to the inlet for hydrogen so that the hydrogen fed via the inlet for hydrogen and the reactant are actively mixed.

[47] In yet another embodiment the reactant is a compound such as acetone which can be hydrogenated e.g. via Raney nickel.

[48] The object of the present invention may further be solved by a reaction system comprising the reactor and the downstream buffer vessel connected to the discharge tube, wherein the reactor comprises the inlet for hydrogen, the reactant and the catalyst and the connecting tube feeding the downstream buffer vessel for transferring the crude product, wherein the intermediate filter is arranged in or connected to the connecting tube so that the crude product transferred through the connecting tube is filtered by means of the intermediate filter.

[49] In one embodiment, the connecting tube is arranged above the lowest interior point of the reactor, so that the volume between the lowest interior point of the reactor and the connecting tube is the dead volume which cannot be emptied via the connecting tube, wherein the connecting tube is attached in such position that the dead volume is less than 20%, preferably less than 15%, more preferably less than 10%, even more preferably less than 5%, even more preferably less than 3%, and most preferably less than 1% of the total volume of the reactor.

[50] In another embodiment, the product filter is arranged in or connected to the discharge tube so that solid particles, in particular residual catalyst, are separated from the worked-up product by means of the product filter.

[51] In yet another embodiment, the reactor further comprises the draining tube feeding the downstream buffer vessel, wherein the draining tube is equipped with the valve for intermittent operation, so that the intermediate filter of the connecting tube is bypassed by the draining tube.

[52] In another embodiment, the reactor comprises the reactant gas sparger, in particular the hydrogen sparger, and/or the stirrer, wherein the reactant gas sparger is connected to the inlet for hydrogen so that the hydrogen fed via the inlet for hydrogen and the reactant are actively mixed.

[53] In a further embodiment, the reactor or the downstream buffer vessel comprises the circulation means comprising the curved circulation tube arranged at the outside of the respective vessel and the circulation pump, wherein both ends of the circulation tube are connected to the interior space of the reactor or of the downstream buffer vessel and the circulation pump is associated with the circulation tube in such a way that the pumping action is obtained in the circulation tube so that the volume of the reactor or of the downstream buffer vessel can be circulated by means of the circulation tube.

[54] In yet another embodiment, the reactor or the downstream buffer vessel comprises two, three or more circulation means.

[55] In a particular embodiment, two tubes either each selected from the group consisting of the circulation tube, the connecting tube and the draining tube or each selected from the group consisting of the circulation tube and the discharge tube are configured in at least one section as a single tube and subsequently bifurcate so that the crude product or the worked- up product is conveyed into two different sections when introduced into the common section.

[56] Further aspects of the present invention will be apparent from Fig. 1 and from the description of particular embodiments, wherein

Fig. 1 shows a schematic set-up of different parts of a reaction system comprising a reactor and a downstream buffer vessel connected by a connecting tube for carrying out a catalyzed chemical reaction and for work-up.

[57] A hydrogenation reaction system 101 is used for repeated batch hydrogenations for the production of isopropanol in a catalytic process while preventing a deactivation of the hydrogenation catalyst. The hydrogenation reaction system 101 comprises a hydrogenation reactor 103 connected via a connecting tube 121 and a bypassing tube 125 with a downstream buffer vessel 105. The hydrogenation reaction system further comprises an isopropyl alcohol supply 107, a protective gas (e.g. nitrogen) supply 109, a hydrogen supply 111, a catalyst supply 113 and an acetone supply 115. Each of the protective gas supply 109 and the hydrogen supply 111 are connected with the hydrogenation reactor 103 and the downstream buffer vessel 105, respectively, to feed the gasses into the respective vessels. The catalyst supply 113 and the acetone supply 115 are only connected with the hydrogenation reactor 103 to provide the material for the hydrogenation reaction. Isopropyl alcohol is the reaction product of the hydrogenation reaction and is further used as a solvent. The isopropyl alcohol supply 107 is connected to the downstream buffer vessel 105 and to the catalyst supply 113 to flush the catalyst in the reactor. The hydrogenation reactor 103 is equipped with a hydrogen bubbler 117 connected to the hydrogen supply 111 to introduce hydrogen in a reaction mixture present in the hydrogenation reactor 103. The hydrogenation reactor 103 is further equipped with an agitator 119 to stir up solid catalyst particles and to keep or bring hydrogen bubbles in the reaction mixture.

[58] The connecting tube 121 which connects the hydrogenation reactor 103 and the downstream buffer vessel 105 is equipped with an intermediate filter 123 sealing the connecting tube 121 against transfer of the catalyst from the hydrogenation reactor 103 into the downstream buffer vessel 105. A crude product pump 131 is embedded in the bypassing tube 125 to drive the transfer of the catalyst and crude product from a lowest interior point of the hydrogenation reactor 103. The bypassing tube 125 is further equipped with a first switching valve 129 connected to a reactor recirculation tube 127 leading to a highest quarter section of the hydrogenation reactor 103. The first switching valve 129 is designed in such a way that the bypassing tube 125 can be blocked and a crude product fed in the bypassing tube 125 is directed in the reactor recirculation tube 127 back in the upper quarter section of the hydrogenation reactor 103. The hydrogenation reaction system 101 yet further comprises a candle filter 143 connected via a discharge tube 135 to the downstream buffer vessel 105. A worked-up product pump 133 is embedded in the discharge tube 135 to drive the transfer of a worked-up product from the downstream buffer vessel 105 ithrough a candle filter 143. The candle filter 143 is equipped with a product recovery tube 145 to discharge the worked-up product after filtering from the candle filter 143.

[59] The discharge tube 135 is equipped with a second switching valve 141 which is designed such that it is able to block the discharge tube and redirect the transfer of a worked-up product in the downstream of the worked-up product from the downstream buffer vessel 105 in an upper product recirculation tube 137 connected to the second switching valve and an upper section of the downstream buffer vessel 105 and a lower product recirculation tube 139 connected to the second switching valve 141 and a lower section of the downstream buffer vessel 105. The upper product recirculation tube 137 and the lower product recirculation tube 139 are used to redirect and thereby recirculate the worked-up product from the downstream buffer vessel 105. The protective gas supply 109 is further connected to the candle filter 143 to remove spent catalyst 147 from the candle filter 143.

[60] In the following, the usage of the hydrogenation reaction system 101 is described.

[61] For the production of a worked-up isopropyl alcohol using the hydrogenation system 101, first a crude isopropyl alcohol is prepared in the hydrogenation reactor 103 using steps i. to iii. In step i., the gas atmosphere in the hydrogenation reaction system 101 is replaced by a hydrogen atmosphere using the hydrogen supply 111. Further, catalyst and acetone are being fed in the hydrogenation reactor 103 from the catalyst supply 113 and the acetone supply 115. Hydrogen is bubbled in the reaction mixture using the hydrogen bubbler 117 and the reaction mixture stirred via the agitator 119. A hydrogenation reaction is occurring under these conditions yielding crude isopropyl alcohol. A pressure is building up in the reaction by the influx of hydrogen. Once the acetone conversion is sufficiently advanced, in step ii. a valve arranged at the hydrogenation reactor 103 and closing the connecting tube 121 is opened and the crude isopropyl alcohol is transferred by the hydrogen pressure through the connecting tube 121 into the downstream buffer vessel 105. The catalyst is held back by the intermediate filter 123 in the hydrogenation reactor 103.

[62] For work-up, in step iii. the crude isopropyl alcohol transferred into the downstream buffer vessel 105 is released of hydrogen gas by feeding nitrogen through the protective gas (e.g. nitrogen) sparger 142. While the hydrogen-nitrogen-mixture is fed back into the hydrogen supply, valves at the reactor are closed sealing the connecting tube 121 and the bypassing tube 125 so that a hydrogen atmosphere is kept in the hydrogenation reactor 103.

[63] The crude isopropyl alcohol is not fully discharged from the hydrogenation reactor 103, as the connecting tube 121 is arranged in such position above the lowest point of the hydrogenation reactor 103 that about 15% of the reactor volume are dead volume.

[64] The now worked-up isopropyl alcohol in the downstream buffer vessel 105 is pumped through the discharge tube using the worked-up product pump 133 guided by the second switching valve 141 through the upper product recirculation tube 137 and the lower product recirculation tube 139 back in the reactor to circulate the worked-up isopropyl alcohol and promote the release of residual dissolved hydrogen.

[65] The inner volume of the downstream buffer vessel 105 is e.g. four times as great as the inner volume of the hydrogenation reactor 103.

[66] Steps i. to iii. are repeated two times, i.e. two more batches of crude isopropyl alcohol are prepared in the hydrogenation reactor, transferred via the connecting tube 121 into the downstream buffer vessel 105 while retaining the catalyst in the hydrogenation reactor 103 and working-up the crude isopropyl alcohol in the downstream buffer vessel 105.

[67] In a final batch, steps i. to ii. are repeated, but the crude isopropyl alcohol is discharged via the bypassing tube 125 using the crude product pump 131 and fed into the downstream buffer vessel 105. Also the now depleted catalyst is transported by the crude isopropyl alcohol into the downstream buffer vessel 105. After final work-up the now worked-up isopropyl alcohol and the depleted catalyst are located in the downstream buffer vessel 105 and are transferred via the discharge tube 135 through the candle filter 143. The depleted catalyst is retained in the candle filter while the worked-up and filtered isopropyl alcohol is discharged via the product recovery tube 145. The depleted catalyst which is held back by the candle filter 143 is then discharged as spent catalyst cake 147 via nitrogen pressure applied from the nitrogen supply 109.

[68] The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description or the drawings.

Reference numerals

101 hydrogenation reaction system

103 hydrogenation reactor

105 downstream buffer vessel

107 isopropyl alcohol supply

109 protective gas supply

111 hydrogen supply

113 catalyst supply

115 acetone supply

117 hydrogen bubbler

119 agitator

121 connecting tube

123 intermediate filter

125 bypassing tube

127 reactor recirculation tube

129 first switching valve

131 crude product pump

133 worked-up product pump

135 discharge tube

137 upper product recirculation tube 139 lower product recirculation tube

141 second switching valve

142 protective gas sparger

143 candle filter

145 product recovery tube 147 spent catalyst

Claims

Claims:

1. Method for carrying out a chemical reaction with a catalyst susceptible to a work-up, including in particular starvation of a reactant gas and quenching, using a reaction system (101) comprising a reactor (103) and a downstream buffer vessel (105) connected to a discharge tube (135) for discharging a worked-up product, wherein the reactor (103) comprises at least one inlet, which is/are suitable for insertion of a reactant, the catalyst and the reactant gas, in particular hydrogen, and a connecting tube (121) connected to the reactor (103) and feeding the downstream buffer vessel (105) for transferring a liquid or dissolved crude product from the reactor (103) into the downstream buffer vessel (105) with the following steps: i. performing the chemical reaction, which is catalyzed by the catalyst, between the reactant and the reactant gas under reaction conditions, in particular in a reactant gas atmosphere, in the reactor (103) so that the crude product is obtained in the reactor (103), ii. transferring the crude product via the connecting tube (121) into the downstream buffer vessel (105), while the catalyst is retained in the reactor (103) by an intermediate filter (123) arranged in the connecting tube (121), and iii. working-up the crude product in the downstream buffer vessel (105) and disconnecting a pressure connection established via the connecting tube (121) between reactor (103) and downstream buffer vessel (105) using a disconnection device located in or at the connecting tube (121), so that different gas atmospheres can be created in the reactor (103) and the downstream buffer vessel (105), and removing or replacing the reactant gas in the downstream buffer vessel (105) while preserving the reactant gas atmosphere in the reactor (103) and thereby retaining the catalyst under such protective atmosphere in the reactor (103), so that the catalyst is not fully degraded but usable in a further reaction and the worked-up product is obtained in the downstream buffer vessel (105).

2. Method according to claim 1, wherein the crude product in step ii. is not completely transferred to the downstream buffer vessel (105) and such amount of the crude product is retained in the reactor (103) that the catalyst is fully covered by the retained crude product so that the retained crude product acts as a protective cover.

3. Method according to claim 2, wherein the connecting tube

(121) of the reactor (103) is arranged above a lowest interior point of the reactor (103), so that a volume between the lowest interior point of the reactor (103) and the connecting tube (121) is a dead volume which cannot be emptied via the connecting tube (121) and which stores the retained crude product, wherein the connecting tube (121) is attached in such position that the dead volume is less than 20%, preferably less than 15%, more preferably less than 10%, even more preferably less than 5%, even more preferably less than 3%, and most preferably less than 1% of the total volume of the reactor (103), wherein the connecting tube (121) is attached in such position that the created dead volume is sufficient to receive at least 80%, preferably 99%, of the catalyst so that after transferring the crude product to the downstream buffer vessel (105) via the connecting tube (121), the retained catalyst is stored in the dead volume and covered by the retained crude product.

4. Method according to any of the preceding claims, wherein a product filter is arranged in or connected to the discharge tube (135) in a filtering position with the further step of: iv. discharging the worked-up product from the downstream buffer vessel (105) through the discharge tube (135) and the product filter, so that the product filter separates solid particles, in particular residual catalyst particles, from the worked-up product.

5. Method according claim 4, wherein the reactor (103) further comprises a draining tube (125) feeding the downstream buffer vessel (105), wherein the draining tube (125) is equipped with a valve (129) for intermittent operation, so that the intermediate filter (123) of the connecting tube (121) is bypassed by the draining tube (125), with the further steps of: v. repeating the steps i. to iii. one time or several times so that a larger quantity of the crude product than a single filling volume of the reactor (103) is obtained in the downstream buffer vessel (105), wherein the repeated chemical reaction is carried out in each case with the retained catalyst until the catalyst is at least partially exhausted, vi . optionally discharging the worked-up product from the downstream buffer vessel (105), vii. transferring the at least partially exhausted catalyst from the reactor (103) through the draining tube (125) into the downstream buffer vessel (105), so that the at least partially exhausted catalyst is not retained in the reactor (103) by the intermediate filter (123) placed in the connecting tube (121), and viii. discharging of a content comprised in the downstream buffer vessel (105) via the discharge tube (135) of the downstream buffer vessel (105), so that the at least partially exhausted catalyst is retained and provided as a disposable filter cake by the product filter and an unloaded reaction system (101) is obtained.

6. Method according to any of the preceding claims, wherein the crude product and/or the worked-up product in the downstream buffer vessel (105) is flushed with a protective gas using a protective gas sparger (142) arranged in the downstream buffer vessel (105) so that the reactant gas is washed out.

7. Method according to any of the preceding claims, wherein the reactor (103) comprises a reactant gas sparger (117), in particular a hydrogen sparger, and/or a stirrer (119), wherein the reactant gas sparger (117) is connected to the inlet for hydrogen so that the hydrogen fed via the inlet for hydrogen and the reactant are actively mixed.

8. Method according to any of the preceding claims, wherein the reactant is a compound such as acetone which can be hydrogenated.

9. Reaction system (101) for carrying out an air-sensitive, catalyzed reaction and for subsequent work-up, wherein the reaction system (101) comprises a reactor (103) and a downstream buffer vessel (105) connected to a discharge tube (135) for a worked-up product, wherein the reactor (103) comprises an inlet for hydrogen, a reactant and a catalyst and a connecting tube (121) feeding the downstream buffer vessel (105) for transferring a crude product, wherein an intermediate filter (123) is arranged in or connected to the connecting tube (121) so that the crude product transferred through the connecting tube (121) is filtered by means of the intermediate filter (123).

10. Reaction system (101) according to claim 9, wherein the connecting tube (121) is arranged above a lowest interior point of the reactor (103), so that a volume between the lowest interior point of the reactor (103) and the connecting tube (121) is a dead volume which cannot be emptied via the connecting tube (121), wherein the connecting tube (121) is attached in such position that the dead volume is less than 20%, preferably less than 15%, more preferably less than 10%, even more preferably less than 5%, even more preferably less than 3%, and most preferably less than 1% of the total volume of the reactor (103).

11. Reaction system (101) according to claim 9 or 10, wherein a product filter (143) is arranged in or connected to the discharge tube (135) so that solid particles, in particular residual catalyst, are separated from the worked-up product by means of the product filter (143).

12. Reaction system (101) according to any of the claims 9 to

11, wherein the reactor (103) further comprises a draining tube (125) feeding the downstream buffer vessel (105), wherein the draining tube (125) is equipped with a valve (129) for intermittent operation, so that the intermediate filter (123) of the connecting tube (121) is bypassed by the draining tube (125).

13. Reaction system (101) according to any of the claims 9 to

12, wherein the reactor (103) comprises a reactant gas sparger (117), in particular a hydrogen sparger, and/or a stirrer (119), wherein the reactant gas sparger (117) is connected to the inlet for hydrogen so that the hydrogen fed via the inlet for hydrogen and the reactant are actively mixed.

14. Reaction system (101) according to any of the claims 9 to

13, wherein the reactor (103) or the downstream buffer vessel (105) comprises a circulation means comprising a curved or bend circulation tube (127, 137, 139) arranged at the outside of the respective vessel and a circulation pump (131, 133), wherein both ends of the circulation tube (127, 137, 139) are connected to an interior space of the reactor (103) or of the downstream buffer vessel (105) and the circulation pump (131, 133) is associated with the circulation tube (127, 137, 139) in such a way that a pumping action is obtained in the circulation tube so that a volume of the reactor (103) or of the downstream buffer vessel (105) can be circulated by means of the circulation tube (127, 137, 139).

15. Reaction system (101) according to claim 14, wherein the reactor (103) or the downstream buffer vessel (105) comprises two, three or more circulation means.