Microstructure reactor for heterogeneous catalytic exothermic reaction by using efficient evaporative cooling

Abstract

The invention relates to a microreactor for carrying out at least one catalytic reaction between two or more reactants in each case, comprising the following stacked sequence: a reaction surface (1) for carrying out at least one exothermic reaction; and a cooling region (6) which is at least divided into separate fields (6) with feed and discharge means for the coolant.

Description

[0001] The invention relates to a microstructure reactor for performing catalytic reactions.

[0002] Microstructured reactors have been implemented in various embodiments and have been commercialized for microprocess technology in certain applications. Their design specifically takes into account the boundary conditions of microtechnology. Microstructured reactors include at least, but are not limited to, a reaction zone with at least one inflow and at least one outflow. A controlled reaction occurs in the reaction zone, whereby a catalyst is used in at least one reaction zone. One embodiment may also be catalyst-free. As a basic principle, the reaction zone can be designed as a mixing well or continuous flow well that allows fluids to merge and / or branch.

[0003] A distinction is usually made between simple cross-flow and countercurrent or parallel flow processes. In many cases, there is a cross-flow-like sharing. If a coolant is used that has not undergone a phase change, the result is an uneven cooling capacity for different reaction channels within the plate of the entire system. The number of reaction channels passed by each cooling channel is different. The temperature increase leads to higher temperatures in the cooling channels below. Since the reaction rate of the chemical reaction rises exponentially with respect to the temperature in a specific reaction channel, this leads to an additional conflict between the cooling capacity of the coolant and the exothermic capacity of the reaction. In addition, the viscosity of the fluid changes, which in turn leads to an uneven distribution of the medium on the individual channels and on the cooling plates and reaction plates, which is also undesirable. In this regard, the uneven distribution of the reaction medium is a problem, because this naturally means different residence times.

[0004] In the case of evaporative cooling, it is even more complicated. When using a coolant, if a single phase is maintained, the heat to be removed changes along the reaction channel. With respect to the cross-flow arrangement that exists at least in part, this means different degrees of evaporation. This is not ideal for using the generated steam for other subsystems in the whole process to improve the efficiency of the entire process chain. For the achievable overall steam level of the coolant, this uniform distribution has an additional negative impact. Therefore, the steam is first released in the area where the reaction proceeds faster. The increase in the coolant velocity that occurs here leads to a reduction in the throughput of a specific cooling channel by involving pressure exchanges in the entire system, and thus enhances the influence of different degrees of evaporation of the coolant between the channels of the plate. In addition, the temperature control of the reaction is more difficult. The reaction channel through which pure steam passes can no longer be fully cooled because the mass flow rate and specific heat capacity of the steam are much smaller.

[0005] In addition, in order to carry away the heat of the reaction, the generally conventional area and volume requirements of the catalytic reaction (>90% in all cases) are much larger than the required channel surface. This means that the plane with the cooling channel is usually seriously oversized. In other words, from one point of view, the possible heat transfer coefficient is higher than the required heat transfer coefficient. In addition, the calculable heat flow of each pair of plates consisting of reaction and cooling is greater than the reaction enthalpy to be transferred. This fact may additionally increase the impact of local non-uniform evaporation laterally relative to the reaction channel. This is because the evaporation of the coolant may occur earlier and be completed in advance. In extreme cases, the evaporation process may be carried out before the actual cooling channel and the distribution of the coolant in the longitudinal direction of the reaction channel become more difficult. Due to the usual vertical orientation of the reaction channel, this means that the distribution of the cooling channel also occurs vertically and is affected by gravity. Therefore, by forming bubbles in front of the cooling channel, it is ultimately possible to prevent access to certain areas.

[0006] There are several solutions to the outstanding problems in the prior art. Flow control with phase change in microchannels is described in WO 002004017008. WO 002004037418 describes a cross-flow configuration with a catalyst packing, wherein the catalyst is graded to control the heat generated. The possibility of influencing the distribution in the channel structure by pressure is mentioned in WO 002005044442. In WO 002005075606, a Fischer-Tropsch synthesis process using a promoter in a microreactor (>25% cobalt loading) is proposed. The document also relates to the possibility of using different numbers of channels along the reaction zone to cool the reaction. Subsequently, the possibility of temperature gradients with different coolants is known from WO 002005082519. The content of WO002005065387 is in principle the possibility of using the reaction zone for evaporation. WO 002011075746 discloses the necessary measures to prevent excessive deformation of the grooved design of the microchannel by strengthening the sidewalls. WO 002012054455 and WO2011134630 generally show the distribution of reactant gases in the coolant with part cross flow arrangement, part addition of reactants and heat exchange. Finally, US 6994829 describes the use of (tortuous) small channels for evaporation, and then superheating in straight larger channels. The connection of two known reactions is disclosed by US 7014835 and DE 10044526. DE102005022958 discloses the use of columnar structures to carry out multiphase reactions with reactant feeds. The continuous implementation of catalytic reactions with intermediate cooling is proposed in DE 10201210344.

[0007] In none of these documents are described the necessary measures for efficient distribution of the coolant in a cross-flow configuration with complete evaporation but not necessarily superheating. Partial addition is used for the reaction and graded catalyst beds / cooling zones are proposed for better cooling.

[0008] The object of the present invention is therefore to solve the problems described. More specifically, the difficulty of achieving a uniform temperature throughout the reactor by means of a parallel distribution structure remains.

[0009] This object is achieved by a microstructured reactor for carrying out an exothermic reaction between two or more reactants, which are passed in fluid form over one or more catalysts, the microstructured reactor comprising at least one stacking sequence as follows:

[0010] a) at least one layer having one or more catalysts for carrying out at least one exothermic reaction;

[0011] b) at least one layer divided into two or more cooling fields;

[0012] c) at least one layer having a distributor structure:

[0013] - having lines for coolant distribution,

[0014] - have connections for conveying coolant to the distributor structure lines and for connecting to the cooling field,

[0015] - a connection for discharging the heated coolant from the cooling station, and

[0016] - Lines and connections for discharge of heated coolant from the stacking sequence.

[0017] According to the invention, there is therefore at least one stacking sequence. Thus, the microstructured reactor can have any desired number of stacking sequences. The stacking sequences are preferably arranged as mirror images of each other. In this regard, the individual layers can be constructed in the form of plates or in the form of films.

[0018] The thickness of the individual layers is preferably within the following ranges:

[0019] Layer a) 0.5 mm to 10 mm, preferably 1 mm to 3 mm

[0020] Layer b) 0.1 mm to 5 mm, preferably 0.3 mm to 0.6 mm

[0021] Layer c) 1 mm to 10 mm, preferably 1 mm to 3 mm.

[0022] According to the invention, one or more layers may have structures on their surface. The structures provided in layer a) are used to accommodate the catalyst. Thus, these structures may be reaction channels or also referred to as reaction tanks, which are filled with particles of catalyst material or coated with catalyst. The height of the reaction channels may be from 0.4 mm to 8 mm, preferably from 0.8 mm to 1.5 mm.

[0023] According to the present invention, preferably cobalt, iron, nickel, rhodium or ruthenium should be considered as catalyst. Compounds containing these elements can also be used. Equivalent combinations of one or more of the elements are feasible. Likewise, the catalyst can be used together with other suitable catalysts mentioned known to those skilled in the art.

[0024] According to the present invention, catalyst is used for reaction. According to the present invention, these are exothermic reactions. For this, preferably make the fluid containing reactant or being composed of it pass on the surface containing catalyst. These can be gaseous fluid or liquid fluid containing relevant reactant or being composed of it. By using them, the reaction zone that fluid is converted is formed on catalyst. About the fluid used according to the present invention, for example, synthesis gas, hydrogen / oxygen and hydrocarbon (for example methane, olefin etc.) can be used. Two or more described fluids can be combined arbitrarily.

[0025] An example of an application is the Fischer-Tropsch reaction. Here, a variety of liquids consisting mainly of alkanes of different chain lengths are formed from synthesis gas (a mixture of carbon monoxide and hydrogen), which are converted into synthetic fuels containing diesel or kerosene by appropriate refining steps. In the process of conversion, olefins and isomers may also be formed. Alkanes can exist in liquid or gaseous form. The relevant reactions are highly exothermic and can be carried out in the present microstructured reactor.

[0026] The stacking sequence according to the invention comprises a cooling field as layer b). This means that one or more cooling fields are provided in this layer. The heat generated by the reaction surface is absorbed by these cooling fields. The individual fields have the same cooling properties or have the same cooling capacity as each other. Thus, uniform cooling of the entire reaction zone is achieved. According to the invention, each field along a specific supply channel and / or distributor structure provides almost the same amount of coolant at almost the same temperature.

[0027] The cooling field can have various structures. It is important that the channel of the coolant that has been heated or turned into vapor form is curved, i.e. has at least one bend. In this way, the influence of weight on the flow is small and any ejection of droplets is avoided. In the cooling field, the coolant runs in a ring and / or wave form (layer (2)) and then is discharged through the distributor structure (layer (3)).

[0028] The coolant used according to the invention is preferably a liquid. In the simplest case, this is water. Apart from this, other coolants can also be used. Examples are ammonia, butane, ethylene glycol, fluorochlorocarbons and propane. All other coolants known to the person skilled in the art can also be used. It is also possible to use two or more of the coolants mentioned in combination of compounds.

[0029] According to the invention, a distributor structure for coolant feeding is provided. The coolant is supplied to the individual fields through the structure. The coolant is evenly distributed to the respective fields by the pressure loss on each cooling field being significantly greater than the pressure loss in the channels of the distributor structure.

[0030] According to the invention, the individual cooling zones are provided with lines for the coolant inflow and outflow. In each individual cooling zone, there is an inflow and outflow of cooling liquid.

[0031] According to the invention, the supply line for the coolant is arranged so that the hydraulic diameter gradually decreases in the flow direction of the coolant. In contrast, the discharge channel is arranged so that the hydraulic diameter gradually increases in the flow direction of the coolant. Preferably, the discharge channel is 2 to 20 times larger than the feed channel. In the absence of pressure, diameters up to 100 times higher can be considered. The hydraulic diameter of the feed channel is preferably 500 μm to 5 mm, most preferably 700 μm to 2 mm. As a basic principle, the hydraulic diameter depends on the total length and the amount of coolant distribution. The hydraulic diameter grows with the amount of distribution.

[0032] Thus, the feed and discharge of the coolant are located within one layer, in other words, on the same plane. The coolant (optionally, the evaporation of the coolant) takes place in another layer (plane). Thus, the heat flow between the reaction layer (layer 1) and the cooling field is independent of the entry temperature of the coolant in a single layer (2).

[0033] When carrying out exothermic reaction according to the present invention, cooling is realized by cooling field.The independent feed of supplying coolant to separate cooling field along reaction section causes generally uniform cooling, is distributed on the whole length of reaction.The heated coolant is discharged from each cooling field again respectively.Within the scope of the present invention, the evaporation of coolant can be preferred, and it is discharged again by discharge line.This means that according to the present invention, the uniform distribution of fresh coolant is realized on the whole reaction section, and the steam discharge heated by exothermic reaction is discharged.In this regard, the pipeline for discharging the steam of cooling field is arranged to make it have the position of maximum clearance at a distance from the distributor structure carrying coolant, that is, between the supply and discharge of coolant, that is to say, the position between the supply line carrying cooler coolant to cooling field and the discharge line discharging heated coolant, optionally from the steam of stacking sequence / reactor.Therefore, any heat conduction between these sections is prevented.

[0034] The heat flow between the reaction layer (layer 1) and the cooling field in layer 2, independent of the inlet temperature of the coolant, ensures an even-out of the temperature in the reaction zone, despite the fact that the coolant entering the well is below boiling temperature over the surface of each layer, which may reach several square meters in size. The use of a combination of two layers (one for cooling by the cooling field and the other for the distributor structure of the coolant) prevents overheating of the reactor and ensures a uniform temperature distribution, essentially in an isothermal state.

[0035] The distributor structure has a plurality of preferably symmetrically arranged pipelines for the feed and discharge of the coolant arranged side by side (arranged in parallel). This results in a flow control that periodically alternates between countercurrent and parallel flow between the feed and discharge - but cross-flow associated with the flow of the reactants - without taking into account the flow in the cooling field layer. Likewise, in this way, the maximum gap between the feed and discharge of the coolant as described above is achieved.

[0036] I. Reference numerals

[0037] 1.Layer a)

[0038] 2. Layer b)

[0039] 3. Layer c)

[0040] 4. Water

[0041] 5. Steam

[0042] 6. Cooling Field

[0043] 7. Coolant feeding

[0044] 8. Unstructured Layers

[0045] 9. Steam discharge

[0046] 10. Supply to each cooling area

[0047] 11. Longitudinal route of reaction medium

[0048] 12. Transverse direction of coolant

[0049] 13. Reaction medium

[0050] 14. Independent discharge of coolant

[0051] II. Overview of the Figures

[0052] Figure 1 The arrangement of the layers is shown in detail.

[0053] Figure 2 The cooling field with feed and discharge lines is shown.

[0054] Figure 3The supply and discharge of coolant is shown in a three-dimensional diagram.

[0055] Figure 4 Shows the paths of the reaction medium and coolant.

[0056] From the figure, it can be seen that the individual layers include: an unstructured layer 8 (i.e., layer a) marked with number 1, a layer b) marked with number 2, and a layer c) marked with number 3. Layer 2 is arranged below layer 1, and a distributor structure 3 is arranged below it. In other words, between layer 1 and distributor structure 3, there is a layer 2 with a cooling field 6. Above and below this stacking sequence, there are other stacking sequences, which are arranged as mirror images of the stacking sequence described. Here, the coolant is transported to the cooling field 6 via pipeline 7 through pipeline 10. Due to the exothermic reaction occurring under the influence of the catalyst in layer 1, the coolant is heated. The heated coolant (e.g., water 4), which is usually present as steam, is discharged through pipeline 5. The steam generated periodically is finally discharged through pipeline 9. In this way, the occurrence of temperature gradients is avoided, which is usually the result of exothermic reactions, wherein the cold zone agent is guided along the reaction section. Using these configurations according to the prior art, the coolant gradually heats up and may reach the reaction temperature in extreme cases.

[0057] The coolant, for example water 4, can be fed separately into the feed line 7 via a feed point 14. From here, the coolant is fed to each cooling zone 6 via line 10. In this regard, the coolant in line 7 is directed in a transverse direction 12 to the direction of the volume flow of the reaction medium 13. This means that the reaction medium 13 is directed in a longitudinal direction 11 relative to the coolant, for example water 4.

Claims

1. A microstructured reactor for an exothermic reaction between two or more reactants, the reactants passing in fluid form over one or more catalysts, the microstructured reactor comprising at least one stacking sequence as follows: a) at least one layer (1) having one or more catalysts for carrying out at least one exothermic reaction; b) at least one layer (2) divided into two or more separate cooling zones (6), in which the channels of the coolant which has been heated or changed into vapor form are bent, in which the coolant runs in a loop and / or in a wave shape; c) at least one layer (3) having a distributor structure through which the cooling liquid is supplied to the individual fields, - having lines for coolant distribution, - have connections for feeding coolant to the distributor structure lines and for connection to the cooling field, - a connection for discharging the heated coolant from the cooling station, and - lines and connections for discharging the heated coolant from the stacking sequence, in, The supply pipeline for the coolant is arranged so that the hydraulic diameter gradually decreases in the flow direction of the coolant, and the discharge channel is arranged so that the hydraulic diameter gradually increases in the flow direction of the coolant, the microstructured reactor has a plurality of stacking sequences, and the stacking sequences are arranged in the form of mirror images of each other, And it is characterized in that, in the distributor structure, the pipeline for conveying the coolant feed is arranged so as to have a maximum gap between it and the pipeline for discharging the coolant from the cooling field.

2. The microstructured reactor according to claim 1, characterized in that: The individual layers are designed in the form of plates or in the form of films.

3. The microstructured reactor according to claim 2, characterized in that: The individual layers have the following thicknesses: Layer a) 0.5mm to 10mm, Layer b) 0.1mm to 5mm, Layer c) 1 mm to 10 mm.

4. A microstructured reactor according to any one of the preceding claims, characterized in that One or more layers have structures on their surface.

5. The microstructured reactor according to claim 4, characterized in that: The catalyst is filled into the structure.

6. The microstructure reactor according to claim 5, characterized in that: The structure is a reaction channel or reaction tank filled with particles.

7. The microstructured reactor according to claim 6, characterized in that: The height of the reaction channel or reaction groove is 0.4 mm to 8 mm.

8. A microstructured reactor according to any one of the preceding claims, characterized in that Each cooling zone has a single feed and discharge of coolant in a distributor structure.

9. A microstructured reactor as claimed in any one of the preceding claims, characterized in that The catalyst is a cobalt, iron, nickel, rhodium or ruthenium catalyst, or contains these elements.

10. A microstructured reactor according to any one of the preceding claims, characterized in that In a distributor configuration, the coolant feed and discharge are arranged in cross-flow relative to the flow of the reactants.

Images