WO2008080358A1

WO2008080358A1 - High throughput catalytic process development method and apparatus

Info

Publication number: WO2008080358A1
Application number: PCT/CN2007/071386
Authority: WO
Inventors: Richard F. Bauman; Rocco A. Fiato
Original assignee: Accelergy Shanghai R & D Center Co., Ltd.
Priority date: 2006-12-29
Filing date: 2007-12-29
Publication date: 2008-07-10
Also published as: CN101274252A

Abstract

A catalytic process development apparatus comprises a laboratory scale plug flow reactor. A second laboratory scale plug flow reactor has a conversion no greater than 25% of the conversion of said first reactor when operating under the same conditions of temperature and pressure as said first reactor. A temperature control device, said first and second reactors being disposed in said temperature control device for providing a common controlled temperature environment for said reactors.

Description

HIGH THROUGHPUT CATALYTIC PROCESS DEVELOPMENT METHOD AND APPARATUS

FIELD OF INVENTION

This invention relates to methods and apparatus for the low cost, accelerated development of catalysts and plug flow catalytic processes from discovery to commercial readiness, and more particularly to laboratory scale plug flow reactor apparatus and methods useful for the accelerated scale-up of catalytic processes.

BACKGROUND OF THE INVENTION hi order to scale-up a plug flow catalytic process, it is necessary to define the impact of time on stream, residence time, catalyst particle size, shape and other characteristics, and temperature profile on reaction rate and selectivity. The first step in a traditional scale-up program generally involves the selection, and definition of the intrinsic properties of, the catalyst. This step is typically performed isothermally with a diluted, crushed or powdered catalyst to minimize mass transfer limitations. A process variable study is performed to determine the impact of space velocity, pressure, and residence time on reaction rate and selectivity. Activity and selectivity maintenance are then determined over a six to twelve month operating period. At the end of the operation, a second process variable study is performed to determine whether these properties have changed during time on stream.

Next, a commercial form of the catalyst is tested in an isothermal reactor. The commercial catalyst is of a larger particle size than the crushed catalyst and may have a special shape to minimize pressure drop during operation. The larger particle size generally results in a lower reaction rate and a selectivity loss due to limitations on mass transfer of reactants or products in and out of the catalyst pores. Operations generally consist of performing process variable studies at the beginning and end of an activity and selectivity maintenance run. This operation can be run in a laboratory scale reactor and typically lasts approximately one year.

The final step in the scale-up process is to test the commercial catalyst under adiabatic conditions, normally in a demonstration scale reactor containing one or more reactor tubes. The tubes in the demonstration scale reactor would have internal diameter of approximately 1 inch, and in some cases up to 4 inches in diameter. In some cases, to further explore heat transfer effects, a configuration containing up to about 6-8 tubes arranged at commercial spacing could be used. In an exothermic reaction, the temperature profile depends upon the degree to which heat is continuously removed, as in a tubular reactor, or the reactor is simply a plug flow reactor without a specific heat removal capability. The temperature profile can have a significant impact on selectivity, reaction rate, and activity maintenance. The test run also provides a measure of the tendency for the catalyst to produce hot spots or temperature runaways. Here again, the operating period can exceed one year.

This sequential approach typically takes in excess of three years to complete and may not provide all of desired data for scale-up. For many catalysts, the reaction rate and selectivity may be a function of residence time as well as time on stream. This can be the result of changes in the catalyst state or form, due to exposure for extended periods of time, or it may be due to the changing gas and liquid composition from the reactor inlet to the outlet. Examples would include oxidation from water formed during conversion, formation of a support over layer, poisoning, e.g., by reaction with hydrogen sulfide and ammonia, etc. hi addition, surface catalytic reactions and buildup of feed and products in the pores can result in reductions in mass transfer rate to the catalyst.

More recently, High Throughput Experimentation (HTE) techniques have been proposed as a source of data for new catalysts and processes. These HTE experiments are normally performed under conditions that minimize heat and mass transfer effects. Small volumes (less than 2 ml) of catalyst and high heat transfer rates are utilized. This approach is useful for comparing the intrinsic properties of an array of candidate catalysts but does not provide the data required for scale-up. See, for example, U.S. Patent numbers 6,149,882 and 6.869,799.

SUMMARY OF THE INVENTION hi accordance with the invention, there is provided a low cost method and apparatus for developing catalytic processes from discovery to commercial readiness. The catalytic process development apparatus allows for simultaneous testing of one or more catalysts in one or more forms. According to a first embodiment of the invention, a first laboratory scale plug flow reactor receiving a fresh reactant feed and operating at a relatively high conversion (typically, 60 to 80%), has all or a portion of its effluent connected to the inlet of second laboratory scale plug flow reactor having a substantially lower conversion (typically, 5 to 20%) and, typically, a relatively shallow catalyst bed. The inlet of the second plug flow reactor also receives a controlled amount of such fresh reactant feed. Depending upon the ratio of effluent to fresh feed, the shallow bed of the second plug flow reactor simulates the performance of a selected cross-sectional slice of a commercial scale plug flow reactor. hi accordance with a second embodiment of the invention, additional low conversion laboratory scale plug flow reactors, which can have shallower beds than the first high conversion reactor, can be connected in parallel with such second plug flow reactor to receive controlled amounts of effluent from the first high conversion plug flow reactor and fresh reactant feed. If the low conversion plug flow reactors all contain the same catalyst, and the ratio of effluent from the first plug flow reactor to fresh reactant feed fed to the low conversion plug flow reactors is varied, the performance of different cross-sectional slices of a commercial scale plug flow reactor can be simulated simultaneously. It is also possible to add controlled amounts of other components to the feed to some or all of the low conversion reactors in order to investigate the impact of reaction products, byproducts or contaminants on the performance of different slices of a commercial scale plug flow reactor. The ratios of effluent to fresh reactant feed or the additions of reaction products, byproducts or contaminants may be varied in time in order to investigate the transient response of different slices of a commercial scale plug flow reactor both during the period after the changed feed condition is introduced as a catalyst bed slice adjusts to the changed feed, and during the period after the changed feed condition is removed as a catalyst bed slice recovers from the changed feed condition. The term "plug flow reactor", as used herein refers to fixed bed reactors, packed bed reactors, trickle bed reactors and monolithic reactors operating either in a once through or a recycle mode. The term "laboratory scale plug flow reactor" as used herein, refers to a plug flow reactor in which each reactor stage has an internal diameter of less than 4 inches, preferably less than 2 inches, and more preferably less than 1 inch; a length of less than 8 feet, preferably less than 4 feet, more preferably less than 1 foot; and a catalyst charge of less than 800 grams, preferably less than 400 grams, more preferably less than 25 grams (excluding inert diluent particles charged to the reactor).

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of a plug flow reactor arrangement in accordance with the invention;

Figure 2 is a schematic representation of a multistage, composite series-connected, isothermal plug flow reactor in accordance with the invention;

Figure 3 illustrates an assembled, schematic diagram of reactors and a separator in accordance with one embodiment of the present invention;

Figure 4 illustrates an assembled, schematic diagram of the reactors and the separator in accordance with another embodiment of the present invention; and

Figure 5 illustrates an assembled, schematic diagram of the reactor and the separator in accordance with yet another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figure 1 of the drawings, there is illustrated an embodiment of the apparatus of the invention which can be used for investigating the longitudinally dependent mass transfer, kinetics and heat transfer characteristics of a commercial scale plug flow reactor, in this case a fixed bed reactor. The laboratory scale fixed bed reactor 11 contains a bed 13 of commercial sized catalyst particles. Reactor 11 is supplied with fresh reactant feed from the source 15. Effluent from the reactor 11 is supplied to laboratory scale fixed bed reactor stages 17-1 through 17-n through control valves 19-1 through 19-n for feeding controlled amounts of effluent from reactor 11 to such reactors. A valve 14 can be disposed behind the reactor 11 for sampling the effluents of the reactor 11. Each of the reactors 17-1 through 17-n contains a low conversion catalyst bed 21-1 through 21-n of catalyst particles mixed with enough inert diluent particles so that the catalyst beds operate in a substantially isothermal mode. The low conversion catalyst beds 21-1 through 21 -and are typically much shallower in depth than the bed 13 in the first plug flow reactor 11 and operate at a conversion of 25% or less, preferably between 5 and 20% conversion. The source 15 also supplies controlled amounts of fresh reactant feed to the inlets of the reactor stages 17-1 through 17-n through control valves and 23-1 through 23-n.

For exothermic reactions, the fresh reactant feed being supplied to the reactor stages 17-1 through 17-n can be preheated by the heater 18. The effluents from the reactor or stages 17-1 through 17-n can be sampled by means of sampling valves 25-1 through 25-n. Controlled amounts of other feed components can be fed to the inlets of some or all of the reactor stages 17-1 through 17-n from source 29 through one or more control valves 31. The source 29 is shown connected through control valves 31 only to reactor stage 17-n, but can also be connected to one or more additional reactor stages either through control valve 31 or through separate individual control valves (not shown). Such other feed components may, for instance, consist of reaction products, byproducts or feed contaminants.

The reactor 11 is normally operated at a relatively high conversion, typically between about 60 to 80%. If the reactor 11 is operated at a given conversion level, e.g. 80%, the input to the individual reactor stages 17-1 through 17-n can represent any degree of conversion from zero to 80% by using the control valves 19-1 through 19-n and 23-1 through 23-n to adjust the ratio of reactor 11 effluent to fresh reactant feed being supplied to the individual reactor stages 17-1 through 17-n. Thus, if the valves 19-1 and 23-1 are adjusted such that reactor stage 17-1 receives only effluent from the reactor 11, and the thickness of the catalyst bed 21-1 is such that it performs an additional 5% conversion on such effluent, the catalyst bed 21-1 is equivalent to a cross-sectional slice of a plug flow reactor in which the conversion between 80 and 85% takes place. Similarly, if the valves 19-2 and 23-2 are adjusted such that the input to reactor stage 17- 2 is equivalent to the effluent of a reactor operating at 40% conversion, and the thickness of the catalyst bed 21-2 is such that it performs an additional 5% conversion on such effluent, the catalyst bed simulates a cross-sectional slice of a catalyst bed in which the conversion between 40 and 45% takes place. Thus, the catalyst beds 17-1 through 17-n can simulate the performance of a cross-sectional slice of a plug flow reactor positioned at any longitudinal position along the catalyst bed. The catalyst beds 21-1 through 21-n in reactors 17-1 through 17-n can therefore replicate successive longitudinal portions of the catalyst bed of a composite plug flow reactor, and permits the measurement and analysis of the characteristics and performance of successive longitudinal portions of a large catalyst bed, thereby allowing determination of longitudinal gradients in reactor characteristics and performance that heretofore have been inaccessible.

It is also possible to use the source 29 to vary the concentrations of the trace components present in the fresh feed in a selected reactor stage 17-1 through 17-n, for instance by adding selected concentrations of such trace components, in order to quantify the effect of such trace components on various parts of the composite catalyst bed under a full range of operating conditions. By doing this it would be possible to map the critical longitudinal portions of a commercial scale catalyst bed in a commercial system in which the catalyst is most vulnerable to poisoning or other inhibitory reactions caused by poisons or other natural byproducts of the reaction being practiced.

The catalyst beds 21-1 through 21-n need not all have the same composition. For instance, the beds 21-1 and 21-2 could contain crushed and commercial-size catalyst particles, respectively, in each case mixed with an amount of inert diluent particles such that the beds operate in isothermal mode. In this case the mass transfer, heat transfer and kinetics characteristics of a cross-sectional slice of a catalyst bed located at any longitudinal position in the catalyst bed can be investigated, hi a different application, the catalyst beds 21-1 through 21-n could contain catalyst particles of different chemical or physical compositions, in which case the performance of the different catalysts at different longitudinal slices of a composite plug flow reactor can be investigated. In order to prevent heat loss or gain in the effluent from the reactor 11 being fed to the reactor stages 17-1 through 17-n, the connecting tubing and valves are preferably surrounded by insulating material and the entire system comprising the reactor 11 and the reactor stages 17-1 through 17-n can be surrounded by temperature control devices 33 and 35, respectively, or alternatively, the reactor 11 and reactor stages 17-1 through 17-n can be immersed in the same temperature control device, depending on the needs of the application. Additionally, particularly for exothermic reactions, the reactant feed from the source 15 being supplied to the reactor stages 17-1 through 17-n can be heated by the heater 18 before it is supplied to such reactor stages. The heater 18 can take the form of any of well-known indirect heating arrangements, such as a heating coil in a fluidized sand bath, or an infrared furnace in order to have the appropriate temperature conditions in the catalyst bed inlet portions of such reactor stages.

The temperature control devices 33 and 35, for an exothermic reaction such as the Fischer-Tropsch reaction, can contain a material, such as circulating boiling water, for extracting heat from the reactors 11 and 17-1 through 17-n in order to maintain such reactors at a substantially constant temperature. For an endothermic process, such as paraffin dehydrogenation or catalytic reforming, the temperature control devices 33 and 35 could contain apparatus, such as an electrical heater, to supply heat to the reactors 11 and 17-1 through 17-n in order to maintain the substantially constant desired temperature. Alternatively, for both exothermic and endothermic catalytic processes, the temperature control devices 33 and 35 can consist, e.g., of a cooled or heated fluidized sand bath in which the reactors are immersed. hi an alternative arrangement that reactor 11 and the reactor stages 17-1 through 17- n can be arranged in parallel with one another in a temperature control device such as a fluidized sand bath for a more compact and convenient configuration. This arrangement has the advantage that the fluidized sand bath need not be so deep as it would be if the reactors were arranged vertically, and in that the sampling valves 25-1 through 25-n in the sampling about 27 can be situated outside the fluidized sand bath and so are accessible for maintenance or adjustment during operation of the reactors. If the effluents from the reactor 11 and the reactor stages 17-1 through 17-n contain multiple phases, the transfer lines connecting the outlet of reactor 11 to the inlets of the reactor stages 17-1 through 17-n need to be configured in such a way as to avoid a slug flow in the lines. This can be accomplished using lines having high Reynolds numbers or with the use of static mixers. The sampling valves 25-1 through 25-n and 27 implemented as iso-kinetic sampling valves, although other arrangements such as described elsewhere in this specification can also be used.

The apparatus and method of the invention can also be used to investigate various operating parameters of a plug flow reactor for scale-up or other purposes in accordance with the method of the invention. For example, the longitudinally dependent activity maintenance of a catalyst bed can be investigated as a function of time on stream under different conditions of temperature, pressure and catalyst shape and size. Other longitudinally dependent process parameters that can be investigated using the apparatus and method of the invention include the effects of different space velocities, reaction products and by-products, different operating temperatures and pressures, time on stream, and different catalyst sizes and shapes, on matters such as e.g., conversion, productivity, kinetics and selectivity, and on changes in catalyst physical and chemical properties such as active site crystal size, oxidation, and growth of an over-layer of support on the surface of the catalyst active sites.

Depending on the reaction being studied and the data needed, the analysis of the feed and the effluents from the reactor stages 17-1 through 17-n can include, e.g., conventional GC/MS or UV or IR characterization of the reactant and product stream(s), and/or analysis of the catalyst system by XRD, diffuse reflectance IR or other spectroscopic techniques that are well known in the art. These studies would allow the performance attributes of the system to be quantified as a function of the longitudinal position in the catalyst bed. Such knowledge would allow the system to be optimized with direct knowledge of the catalytic reaction kinetics and performance attributes of each point and permit the design of catalyst systems in which, e.g., the catalyst particles may have different chemical or physical characteristics in different portions of the catalyst bed so as to operate at peak productivity or selectivity as a function of the local environment.

The catalyst beds in the reactor stages 17-1 through 17-n may be a crushed or powdered catalyst or a commercial-size catalyst. Most measurements made in gathering data for the scale up of a catalytic reactor need to be made with the reactor operating in a substantially isothermal regime. In order for the reactor stages 17-1 through 17-n to operate in a substantially isothermal regime, the catalyst particles in the beds 21-1 through 21-n are diluted with an inert particulate matter, typically in a ratio of up to about 8-10 to 1. If measurements need to be made with the reactor operating in a substantially adiabatic regime, the catalyst in the beds of the reactors 17-1 through 17-n is less diluted, and depends on the heat of reaction of the process under study and reactor diameter. The ratio of catalyst particles to diluent particles in a catalyst bed depends upon a number of factors, including the amount of heat generated by the reaction and the activity of the catalyst particles in the bed. The appropriate ratio for a given reaction, catalyst, reactor diameter and catalyst particle size can easily be determined by one of ordinary skill in the art by a simple experiment.

A commercial-size catalyst in a plug flow reactor typically has particle size of about 1 to 5mm. The crushed or powdered catalyst, which is typically formed by crushing a commercial-size catalyst, typically has a particle size of about 0.10 - 0.20 mm. the crushed or powdered catalyst particles are normally preferably as small as can be obtained while still retaining a performance qualities of the catalyst. The interior diameter of a reactor should be about 10 times the diameter of the smaller of the diluent or catalyst particles and the minimum would typically be in the range of about 10 to 50 mm (0.4 to 2 inches) for a bed containing commercial-size catalyst particles and diluent. Crushed or powdered catalyst particles are typically more active than the commercial- size catalyst particles because of lower mass transfer resistance. Therefore, particularly for exothermic reactions, in order for a reactor containing a bed of crushed or powdered catalyst to operate at the same temperature as a similar reactor containing commercial- size catalyst, the ratio of inert diluent particles to catalyst particles in the bed of crushed or powdered catalyst particles normally needs to be higher than that of the bed containing commercial-size catalyst particles in order that the heat release per unit volume of the to catalyst beds is the same. The interior diameter of a reactor containing crushed catalyst, can, if desired, be smaller, in the range of about 5 to 12mm, than that of a reactor containing the commercial size catalyst. For reasons of flexibility in the use of the multistage reactor 11 in different applications, however, it may be preferable that the crushed catalyst bed have the same interior diameter as that required for a bed containing commercial-size catalyst particles. Alternatively, the interior diameter of a reactor being used with a bed of crushed or powdered catalyst particles may be reduced by the use of a thermally conductive sleeve within the reactor.

The preferred minimum height of a reactor stage is determined either by mixing or heat release considerations. For isothermal operation, if mixing is the limiting factor, the height should be selected so as to be sufficient to avoid bypassing. Typically, this would be at least about 50 times the average diameter of the particles, or about 50 to 250 mm (2 to 10 inches) for a reactor stage containing a bed of commercial-size catalyst particles.

The reactors 17-1 through 17-n can also be used to investigate the transient response of a reactor to temporary changes in the composition of the feed to various points in a composite catalyst bed by using the source 29 for temporarily adding the materials of interest to a selected reactor stage 17-1 through 17-n and monitoring the time dependent response of that stage to such added materials both during and after the time that such materials are added.

The reactant and other material feeds, and reaction products and byproducts in reactor effluents supplied or generated in the embodiments of the invention described herein may be either gaseous, liquid or mixed phase (such as e.g., gas/liquid or two or more immiscible liquids). Feeds and effluents consisting of gases can be handled using well known conventional back pressure regulators and gas flow control systems with mass flow controllers. Controlled amounts of liquids can be pumped in high-pressure environments using known pumps such as a Ruska pump or a Syringe pump. If the effluent from the reactor 11, the fresh reactant feed or the constituents added by the source 29 contain multiple phases, particularly of such phases are immiscible, such as water and hydrocarbons or liquid and gas, it is important to avoid slug flow. In such case, sampling valves may consist of e.g., iso-kinetic sampling valves such as available from Proserv AS, or splitters such as described in U.S. Patent No. 4,035,168. Alternatively, the stream may be sampled immediately after a static mixer such as available from Proserv AS, which homogenizes the multiphase stream. In combining immiscible feeds or feeds and effluent to a reactor stage, or in conducting the multiphase effluent from the outlet of reactor 11 to the inlet of the reactor stage 17-1 through 17-n, it is typically the practice to manifold of the streams into a line having a high Reynolds number similar in concept to a fuel injection system in an automobile engine. Alternatively, static mixers such as available from Proserv AS or from Admix, Inc., Manchester, NH, can also be used. In this case, some simple initial testing may be desirable to confirm that the operating conditions are leading to the homogeneity of the stream passing through the device. If the gas and liquid are well mixed in a transfer line, it is possible, for instance, to take a combined liquid and gas sample in a sample bomb connected to the reactor line via double block valves. The bomb would be at atmospheric pressure or slightly above. The block valves would be opened and liquid and gas would be allowed to flow into the bomb. The two block valves would then be closed, the sample bomb removed from the reactor and the contents analyzed. The presence of a small concentration of an inert gas such as Argon in the stream can be used to allow closure of the material balance. Alternatively, if the phases are not well mixed, one could employ gas/liquid separators and analyze the gas and liquid phases separately with an internal standard such as He or Ar and overall carbon balance analysis to link the two. This could be accomplished e.g., by using a gas sample bomb attached to the top of the line and a liquid sample bomb attached to the bottom of the line.

A major area of concern in understanding and controlling the characteristics and performance of a plug flow reactor is the adsorption or reaction of a feed component, product or byproduct with the catalyst surface. For instance, in the cobalt catalyzed Fischer-Tropsch and hydrocracking processes, materials such as ammonia, carbon monoxide, hydrogen sulfide, can tie up active catalyst sites, reduce reaction rate and adversely impact product selectivity. The reactions caused by these materials can take time to equilibrate and can also take time to be released after removal of the material from the feed stream to the reactor.

Ammonia is known to react with cobalt Fischer-Tropsch and hydrocracking catalysts, causing activity to decline and line out. Upon removal of the ammonia from the feed, hydrogen can be used to remove the ammonia from the catalyst surface. In investigating the effects of ammonia on different portions of the composite catalyst bed, ammonia can be added to the inlet of any of the stages of probe reactor, thereby replicating the effect of the presence of ammonia in the feed to a selected longitudinal slice of the composite catalyst bed. By controlling the conversion level in a given catalyst slice, e.g., by adjusting temperature and/or flow rate and/or reactant partial pressures in a probe reactor stage, it is possible to define the effect of the ammonia under various operating conditions. By varying the hydrogen concentration in the feed to one or more probe reactor stages, it is possible, for example, to investigate the effect of increased hydrogen on the ammonia-contaminated catalyst in different portions of the composite catalyst bed, e.g., the bed with the greatest activity decline.

Carbon monoxide is tightly held on a cobalt Fischer-Tropsch catalyst, which can reduce available surface for hydrogen, thereby making hydrogen the rate limiting step. By varying the concentrations of carbon monoxide and hydrogen in the feed to selected stages of the reactor stages 17-1 through 17-n, it is possible to determine the impact of carbon monoxide and hydrogen concentration on reaction rate and selectivity.

The addition of water to a plug flow reactor in Fischer-Tropsch and heavy oil upgrading and conversion processes is believed to have a positive impact on reaction rate. Adding controlled amounts of water to selected stages of the reactor stages 17-1 through 17-n would permit the study of the impact of the added water on reaction rate and selectivity in selected longitudinal slices of the composite catalyst bed.

The amount of Conradson carbon is usually utilized in correlations for hydrotreater performance. Wax has a similar impact on Fischer-Tropsch catalysts, hi general, carbon and heavy wax deposits on a catalyst inhibit the diffusion of reactants to the catalyst surface and the removal of reaction products from the catalyst surface. This tends to lead to activity reduction via unwanted side reactions with deposits on the catalyst surface or with the diffusion limited reactants or both, hi the case of beds containing commercial- size catalyst particles where the diffusion path is the longest, this sort of diffusion limitation can limit overall catalyst life and require costly steps to maintain system performance. Adding different molecular weight fractions of these materials to ones of the reactor stages 17-1 through 17-n would allow the determination of what portion of the composite catalyst bed is impacted the most. The effects of various regeneration techniques such as by the addition of hydrogen, water, or a light solvent can also be determined my controlling the feeds to the relevant stages of the reactor stages 17-1 through 17-n, thereby to define the preferred rejuvenation technique. These issues will be particularly important in processing of heavy feeds from tar sands, shale, heavy oil deposits, and coal. These feeds are known to carry many contaminants that can lead to catalyst poisoning, and in situ regeneration, in order to avoid the cost of frequent replacement with fresh unused catalyst, is frequently the only means to make the overall process economically viable.

Polynuclear aromatics are also known to inhibit a catalyst by forming carbonaceous overlayers on catalyst sites that reduce selectivity and activity of hydroprocessing catalysts. The effect of the presence of polynuclear aromatics in the feed at various longitudinal portions of a composite catalyst bed of a plug flow reactor can be determined by adding the polynuclear aromatics to selected stages of the reactor stages 17-1 through 17-n. This can be used to help define in what portion of the composite catalyst bed the polynuclear aromatics have their greatest impact, and what can be done to improve the process design and catalyst performance. hi a further embodiment of the invention, one or more of the reactor stages 17-1 through 17-n can consist of a substantially fully back-mixed reactor instead of a plug flow reactor stage. The distribution a catalyst, feed and products in the back-mixed reactor stage is substantially uniform so that the back-mixed reactor stage corresponds to a single, narrow, horizontal slice of a commercial scale plug flow reactor catalyst bed. By controlling the relative concentrations of fixed bed reactor 11 effluent and fresh reactant feed, it is possible for the back-mixed reactor stage to replicate any selected horizontal slice of the catalyst bed of a composite plug flow reactor. The back-mixed reactor stage can, for instance, be a two-phase fluidized bed reactor, a three-phase slurry reactor, or a three phase ebulated bed reactor.

Other experiments to be performed that aid in the scaling up of a catalytic process include, for example, investigating the characteristics of a plurality of different catalysts simultaneously. Alternatively, a crushed catalyst in one reactor stage can be compared with a plurality of different shapes or sizes of commercial-size versions of the catalyst in other reactor stages. Using such an arrangement, one can design a layered composite catalyst bed in which the intrinsic behavior of each catalyst layer is matched to the local kinetic and mass transfer environment, so that the overall response of the system is varied longitudinally so as to obtain behavior characteristics in each longitudinal portion of the composite reactor that are optimum for process performance.

If the catalyst beds of reactor stages 17-1 through 17-n contain crushed or powdered catalyst particles, and the reactor is operated isothermally, measurements of the crushed or powdered catalyst results can be considered to represent the Intrinsic Reaction Rate (free of mass transfer and heat transfer limitations) and selectivity of the catalyst at Start of Run. Thereafter, during time on stream, the crushed or powdered catalyst results can be considered to represent a running Intrinsic Reaction Rate for the catalyst in the catalyst bed of that stage that includes the effects of catalyst aging. This is equivalent to an Effectiveness Factor of 1.0, where the Effectiveness Factor is equal to the Observed Reaction Rate divided by the Intrinsic Reaction Rate, hi addition, selectivity data provides a direct measure of the Intrinsic Selectivity versus conversion for both fresh and aged catalysts. These data are very useful in developing a model for the scaling-up of a composite plug flow reactor to commercial scale.

If the catalyst beds of some of the reactor stages 17-1 through 17-n contain commercial-size catalyst particles and are operated isothermally in parallel with reactor stages containing crushed or powdered catalyst in the same temperature control device, a comparison of the performance of the two sets of reactor stages can yield data that permits the determination of the longitudinally dependent Effectiveness Factor and other information that is extremely useful in the scaling up of the catalytic process to a commercial-size.

Analysis of the effluent from the reactor stages containing the commercial-size catalyst provides data concerning the Observed Reaction Rate versus residence time. Since the Intrinsic Reaction Rate is known, the Effectiveness Factor versus conversion can be obtained directly from the conversion versus residence time plots for the crushed and commercial size catalysts. Knowing the Effectiveness Factor, the Intrinsic Reaction Rate (K), and the diameter (related to L) of the full size catalyst particles, it is also possible to determine the Effective Diffusivity versus conversion for the full size particle from the Thiele Modulus.

This data provides critical insight into the mechanism of mass transfer limitations. For instance, a low Effective Diffusivity at the inlet of a reactor suggests mass transfer resistance in the pores or on the catalyst surface due to feed components, initial products of the reaction, or lower than expected concentration of a component of the feed at the active catalyst sites when considering actual partial pressures of the components of the effluent stream. A low Effective Diffusivity at the outlet of a reactor could suggest product buildup or reaction of the effluent stream with the catalyst. In reactions involving multiple reactants having substantially different diffusivities, the Observed Reaction Rate and selectivity are generally related to the Effectiveness Factor since this represents the change in composition between the gas phase and the catalyst surface.

With the data acquired from the two sets of reactor stages and limited data on the Intrinsic Activation Energy, it is possible to develop a model to predict the performance of a multi-stage adiabatic reactor. Data obtained in an adiabatic reactor provides a test of the reactor model. In addition, the behavior of an adiabatic reactor provides an indication of the likelihood and location of "hot spots" or temperature runaways in an exothermal catalytic process, and hence the need for greater heat removal. hi an adiabatic reactor, it is possible to produce hot spots in the reactor, which may cause the adiabatic reactor to run away. Also, in an adiabatic reactor, because reaction parameters, such as temperature, kinetics parameters, etc., can change continuously, it is difficult to measure the reaction parameters by direct measurement. Dividing an adiabatic reactor into multistage series-connected reactor stages can help determine reaction parameters at different locations along a flow direction of the reactor, but it is difficult to keep continuities of the reaction parameters, especially temperature, between adjacent reactor stages.

Therefore, it is difficult to directly measure reaction parameters in an adiabatic reactor, and to exactly and securely determine reaction characteristics in the adiabatic reactor, such as kinetics, mass transfer, heat transfer etc.

Fig. 2 illustrates a schematic diagram of a composite multistage laboratory scale plug flow reactor 607. The reactor 607 includes first, second and third series-connected reactor stages 61, 63 and 65, each having a catalyst bed 62, 64 and 66. The reactor 607 further includes a fresh reactant conduit 70 which connects an inlet of the first reactor stage 61 to a source 60, so that the source 60 can provide feeds, which are normally fresh reactants, to the first reactor stage 61. The reactor 607 further includes connecting conduits 71 and 72 to connect the first and second reactor stages 61 and 63, and the second and the third reactor stages 63 and 65, respectively. A first sampling valve 67 is disposed between the first and second reactor stages 61 and 63, and has an output 601 to facilitate sampling effluents from the first reactor stage 61. Here in this document, a device is said to be disposed between two stages of the reactor does not necessarily mean that the device is physically disposed between the two stages of the rector but that the device is between the two stages of the reactor along a flow of reactants. A second sampling valve 68 is disposed on the conduit 72 and has an output 602 for sampling effluents from the second reactor stage 63. A third sampling valve 69 is disposed between an outlet of the third reactor stage 65 and a device, such as a fourth reactor stage or a product accumulator (not shown) and has an output 603 for sampling effluents from the third reactor stage 65. A sampling valve connected to the fresh reactant conduit 70 may also be provided in order to permit analysis of the feeds.

In one embodiment, the reactor stages 61, 63 and 65 are isothermal reactor stages, which are used together to simulate an adiabatic reactor. Thus, temperature control devices 604, 605 and 606 are provided to control the temperature of the reactor stages 61, 63 and 65 respectively. A preheater (not shown) may be disposed between the source 60 and the first reactor stage 61 to preheat the feeds from the source 60 so that when the feeds flow into the first reactor stage 61, the feeds have already reached a desired temperature for the feeds. Alternatively, the preheater can also be disposed in the first reactor stage 61.

In one embodiment, when using the isothermal reactor stages 61, 63 and 65 to simulate the characteristics of an adiabatic reactor, the temperature setting for each of the temperature control devices 604, 605 and 606 should be determined first. Generally, for a given catalytic process, based on data derived from operating the adiabatic reactor in practice, the temperature setting for the first temperature control device 604 and temperature variation in the first reactor stage 61 can be determined. Then, based on information from the first reactor stage 61, the temperature setting of the second temperature control device 605 can also be determined, and so on. Thus, after the temperature settings of each of the temperature control devices 604, 605 and 606 is determined, the reactor stages 61, 63 and 65 can be used to simulate the characteristics of the adiabatic reactor. In this embodiment, the temperature of the temperature control devices 604, 605 and 606 are defined as Tl, T2 and T3, which are different from each other. Different catalytic processes may have different Tl, T2 and T3 settings. Alternatively, a common temperature control device (not shown) can be provided to control the temperatures of reactor stages 61, 63 and 65 together.

Thus, the isothermal reactor stages 61, 63 and 65 can respectively simulate successive catalyst bed slices of a catalyst bed of a larger adiabatic reactor. Thus, the characteristics of the catalyst bed, which is simulated by the catalyst beds 62, 64 and 66, are determined. Because it is relatively easy to operate the isothermal reactor stages, characteristics associated with the larger adiabatic reactor can be determined by simulating the adiabatic reactor using the isothermal reactor stages, hi this embodiment, the first, second and third reactor stages 61, 63 and 65 can be arranged upright.

For a particular catalytic process between at least two successive reactors, for example a particular catalytic process in a multistage series-connected reactor stages, if an effluent fluid from one reactor stage is homogeneous, such as in a gas phase, transferring effluent fluid can be quite straightforward by using a properly sized and shaped tube connecting an outlet of one reactor stage to an inlet of a following reactor stage. In many catalytic processes, however, the effluent from a reactor stage may be in a multiphase state, meaning that it includes one or more gaseous fluids, which are fluids in gas phase (such as gases, vapors or mixtures of gases and vapors), and one or more liquid fluids, which are fluids in one or more liquid phases (such as water phase, oil phase, other immiscible phases and partial emulsion phases, etc.)

The multiphase fluid is often a multi-component fluid, each component being in its own state, which can be a single-phase state or multiphase state. If the multi-component fluid is in thermodynamic equilibrium, the fluid can be transferred directly by a tube connecting two successive reactor stages.

However, in certain catalytic processes, such as hydrodesulphurization etc., the multi-component fluid may not be in thermodynamic equilibrium. So, when the multi- component fluid is transferred directly through the tube connecting the outlet of one reactor stage to the inlet of the following reactor stage, the states of the components may vary during the transfer such that continuity or consistency of the fluid between adjacent two reactor stages may be broken. Thus, it is difficult to use the multistage series- connected reactor stages to model a plug reactor and to measure and optimize the corresponding catalytic processes.

Fig. 3 illustrates a schematic diagram in accordance with one embodiment of the present invention, hi this embodiment, a catalytic process development apparatus includes a composite multistage laboratory scale plug flow reactor 707 which includes first and second series-connected reactor stages 71 and 73. The reactor stages 71 and 73 include catalyst beds 72 and 74, respectively. The catalytic process development apparatus further includes temperature control devices 701 and 702 disposed on the reactor stages 71 and 73 respectively, and a fresh reactant conduit 77. The fresh reactant conduit 77 is connected an inlet of the first reactor stage 71 to a source 70 so that the source 70 can provide feeds which are normally fresh reactants to the first reactor stage 71. hi this embodiment, the catalytic process development apparatus further includes a separator 703, first and second effluent conduits 78, a gas conduit 75 and a liquid conduit 76. The first conduit 78 is connected an outlet of the first reactor stage 71 to an inlet of the separator 703. The gas conduit 75 and the liquid conduit 76 connect the separator 703 to an inlet of the second reactor stage 73. The second effluent conduit 78 connect an outlet of the second reactor to a following device (not shown), such as another separator. The reactants from the source 70 are fed into the first reactor stage 71. A multiphase effluent fluid from the first reactor stage 71 is sent into the separator 703, wherein gaseous fluid(s) in the multiphase fluid are separated from liquid fluid(s), and both are introduced into the second reactor stage 73 through the gas conduit 75 and the liquid conduit 76 respectively.

Referring to Fig. 3, the catalytic process development apparatus further includes a flow restrictor 705 disposed on the gas conduit 75 to control flow resistance in the gas conduit 75, resulting in a gas pressure difference (pressure drop) ΔP between two sides of the flow restrictor 705. Assuming a gas pressure in the first reactor 71 and the separator 703 is Pl, a gas pressure in the second reactor 73 is P2. Thus, Pl> P2 due to the flow restrictor 705, and AP=P 1-P2. . hi one embodiment, AP is large enough so that it can drive the liquid fluid in the separator 703 to enter into the liquid conduit 76 and to flow into the second reactor stage 73 but is also small enough so that it can not affect reactions in the second reactor stage 73. The flow restrictor 705 can be a restricting valve, an orifice, or other restricting means etc. When properly sized and shaped, the gas conduit 75 can function as the flow restrictor 705. The flow resistance of the gaseous fluid can be adjusted by many ways, such as electrical, electromagnetic, pneumatic, mechanical or thermal ways etc., which are familiar to those ordinary skills in the art. The electromagnetic ways are preferred.

Additionally, the catalytic process development apparatus further includes a differential pressure sensor (not shown) disposed across the flow restrictor 705 or two ends of the gas conduit 75 to measure the AP. Combined AP and physical properties of the gaseous fluid, information about a mass flow rate of the gaseous fluid can be determined. hi one embodiment, if AP is too small, the liquid fluid can not flow but accumulate in the separator 703. If AP is too large, the liquid fluid may keep flowing until all the liquid fluid in the separator 703 is transported to the second reactor stage 73. When the liquid fluid in the separator 703 is drawn out, the gaseous fluid may flow through the liquid conduit 76. Thus, AP is reduced due to an extra pathway for the gaseous fluid. Then, the liquid fluid begins to accumulate in the separator 703 and blocks the liquid conduit 76. Subsequently, the AP restores to a desired value little by little, and the liquid fluid starts to flow again. Thus, the flow rates of the gaseous and liquid fluids may fluctuate with respect to time because of fluctuation of the AP, which is disadvantageous to the second reactor stage. hi a preferred embodiment, the catalytic process development apparatus includes a liquid level sensor 706 disposed in the separator 703. The liquid lever sensor 706 monitors variation of a liquid level 704 in the separator 703. Liquid sensor signals from the liquid level sensor 706 are used to control the flow restrictor 705 to generate a suitable AP to drive the liquid fluid in such a manner that the liquid level 704 is maintained at a desired substantially constant level. Thus, the fluctuation of the fluids in the separator 703 can be eliminated. When the liquid fluid is transferred stably through the liquid conduit 76, the liquid mass flow rate information can also be obtained by using the measured ΔP in combination with physical properties of the liquid fluid. hi one embodiment, in certain low pressure reactions including low pressure FT synthesis etc., a small pressure drop ΔP may still be too big to tolerate, especially when the reactor stage is long or there are many reactor stages. Additionally, in the process of adjusting ΔP to maintain the liquid level 704 by the liquid level sensor 706 and the flow restrictor 705, the fluctuation of ΔP may also affect liquid flow in the first reactor stage 71.

Fig. 4 illustrates a similar schematic diagram as the diagram of Fig. 3. In this embodiment, the flow restrictor 705 is removed from the gas conduit 75, so, there is no pressure drop ΔP on the gaseous fluid. Meanwhile, a liquid pump 707 is disposed on the liquid conduit 76. The liquid level signals are used to control the liquid pump 707 to maintain the liquid level 704 at the desired constant level. Additionally, because an output pressure of the liquid pump 707 is approximately equal to its input pressure, it does not create a pressure drop between the first and the second reactor stages 71 and 73. hi this embodiment, the liquid pump 707 includes a positive displacement pump or a centrifuge pump etc. Additionally, the liquid pump 707 can have metering capability, which can be used to obtain the liquid flow rate information directly. In order to cause the liquid fluid to be distributed uniformly in the second reactor stage 73, a sprayer or similar spraying devices (not shown) can be adopted inside the reactor stage 73. Alternatively, a check valve (not shown) may be disposed on the liquid conduit 76 and located behind the liquid pump 707 to prevent the liquid fluid in the liquid conduit 76 from reflux. hi the embodiments of the present invention, the gaseous fluid and the liquid fluid in the effluent of the first reactor stage 71 are separated in the separator 703, and then transported to the second reactor stage 73. Thus, possible interactions between the gaseous fluid and the liquid fluid in the effluent during transport can be minimized, and the potential of altering the states of the components in the effluent by fluid distribution and recombination processes can be reduced. The continuity or consistency of the components of the fluid can be maintained between the first and second reactor stages 71 and 73. Additionally, separation of the gaseous fluid and the liquid fluid also makes it easy for sampling the fluids for species analysis, whether continuously or intermittently, on-line or off-line.

As mentioned above, in certain catalytic processes, there are different types of liquid phases for the multiphase effluent fluid, hi one example of the FT synthesis, its effluent may contain water phase liquid(s) and oil phase liquid(s). In order to transport such multiphase fluid uniformly, an agitation device (not shown) can be provided to cause homogenization of the multiphase fluid. The agitation device may include a mechanical stirring device, a magnetic stirring device or an ultrasonic stirring device etc. In one embodiment, the ultrasonic stirring device is provided, which can be installed near a bottom of the separator 703. The ultrasonic stirring device can provide sufficient homogenization of the liquid fluid, while having minimum interference to the performance of the liquid level sensor 706 and also without significantly increasing liquid temperature.

Referring to Figs. 3-4, if the separator 703 is operated in a temperature which is higher than that of the first reactor stage 71, portions of volatile species in the liquid phase in the separator 703 may be evaporated and enter into the gas phase so as to alter the states of the species. If the separator 703 is operated in the temperature which is lower than that of the first reactor stage 71, portions of vapors in the gas phase in the separator 703 may be condensed and enter into the liquid phase so as to also alter the states of the species. As a result, variations in the effluent from the first reactor stage 71 can be produced during its transfer to the second reactor stage 73. Therefore, for certain catalytic processes, it is preferred that the temperature of the separator 703 is the same as that of the effluent from the first reactor stage 71. Thus, the states of the species of the effluent are preserved.

Referring to Fig. 5, for example, in order to keep the temperature of the separator 703 being the same as that of the effluent of the first reactor stage 71, the separator 703 is integrated into the first reactor stage 71. The integrated first reactor stage 71 and the separator 703 can enjoy operation simplicity and also minimize the potential of altering the states of the components.

The composite multistage reactor 707 can include three or more series-connected reactor stages. The outlet of each of the reactor stages can connect to a separator. The separator and the reactor stage can be separate from or integrated with each other. All the reactor stages can also be arranged upright along a vertical line.

Claims

1) Catalytic process development apparatus for developing a commercial scale plug flow catalytic process, comprising: a) a laboratory scale plug flow reactor having an inlet and an outlet and containing a catalyst bed; b) a second laboratory scale plug flow reactor having an inlet and outlet and containing a catalyst bed, said second plug flow reactor, when operating under the same conditions of temperature and pressure as said first reactor, having a conversion no greater than 25% of the conversion of said first reactor; c) a source of fresh reactant feed connected to the inlet of said first reactor; d) a first control valve, said source of fresh reactant feed being connected through said control valve to the inlet of said second plug flow reactor; e) a second control valve, the effluent of said first reactor being connected through said second control valve to the inlet of said second plug flow reactor; f) sampling valves connected to the outlets of said first and second reactors for sampling the effluents of said first and second plug flow reactors, respectively; and g) a temperature control device, said first and second reactors being disposed in said temperature control device for providing a common controlled temperature environment for said reactors.

2) The apparatus of Claim 1 further including instrumentation connected to said sampling valves for sensing characteristics of the effluent of each said reactors

3) The apparatus of Claim 1 further including a) one or more additional laboratory scale plug flow reactors, each of said additional reactors having an inlet and an outlet and containing a catalyst bed, said additional reactors, when operating under the same conditions of temperature, pressure and flow rate as said first reactor, having a conversion no greater than 25% of the conversion of said first reactor; b) one or more control valves connected one each between said source of fresh reactant feed the inlets of the said one or more additional plug flow reactors for supplying controlled amounts of fresh reactant feed to said additional plug flow reactors, said additional plug flow reactors being disposed in said temperature control device for providing a common controlled temperature environment for said additional plug flow reactors; c) one or more control valves connected one each between the outlet of said first reactor and the inputs of said additional plug flow reactors for supplying controlled amounts of effluent from said first reactor to said additional plug flow reactors; d) sampling valves connected to the outlets of said additional plug flow reactors for sampling the effluents of said additional plug flow reactors.

4) The apparatus of Claim 1 further including a source for feeding controlled amounts of an additional feed to the inlet of said second reactor.

5) The apparatus of Claim 4 wherein said additional feed includes a product or by product of the reaction occurring in said first and second reactors.

6) The apparatus of Claim 4 wherein said additional feed includes a contaminant of said fresh reactant feed.

7) The apparatus of Claim 1 further including a heater for heating the fresh reactant feed being supplied to said second reactor from said source of fresh reactant feed.

8) The apparatus of Claim 1 wherein the conversion in said second plug flow reactor, when operated at the same conditions of temperature and pressure as the first plug flow reactor is between five and 20%.

9) A method for developing a plug flow catalytic process comprising the steps of: a) feeding fresh reactant feed to the inlet of a first laboratory scale plug flow catalytic reactor having an inlet and in outlet and a bed containing catalyst particles; b) feeding selected amounts of effluent from said first plug flow reactor and fresh reactant feed to the inlet of a second laboratory scale plug flow catalytic reactor having an inlet and outlet and a bed containing catalyst particles, said second reactor having a conversion of not more than 25% of the conversion of the first reactor when operating at the same conditions of temperature and pressure and mass velocity as said first reactor; and c) measuring characteristics of the effluents from the outlets of said reactors for deducing information concerning longitudinal gradients across a plug flow catalytic reactor.

10) The method of Claim 9 wherein said catalyst beds of said first and second plug flow reactors include catalyst particles and inert diluent particles, and wherein the amounts of diluent particles in the catalyst beds are selected so as to achieve substantially isothermal operation.

11) The method of Claim 10 further including the step of feeding selected amounts of a material to the inlets of one or more of said second and said one or more additional reactors for determining the response of a selected portion of the catalyst bed of a plug flow catalytic reactor to the presence of said material.

12) The method of claim 12 wherein said material is a product or a byproduct of the reaction taking place in the first reactor.

13) The method of Claim 9 wherein said material is a contaminant found in the fresh reactant feed.

14) The method of Claim 9 further including the step of sampling the effluents of said first and second reactors. 15) The method of Claim 9 further including the steps of feeding selected amounts of effluent from said first reactor and fresh reactant feed to one or more additional reactors, each of said additional reactors having a conversion not more than 25% of the conversion of the first reactor when operating under the same conditions of pressure, temperature and mass flow rate, and measuring characteristics of the effluents of said one or more additional reactors for deducing additional information concerning the performance of plug flow reactor systems.