Small-scale reactor having improved mixing

a reactor for conducting laboratory reactions comprises includes reaction vessel, a catalyst holder in the reaction vessel, and a drive system configured to drive reciprocating linear movement of the catalyst basket. The catalyst holder can be configured to hold a plurality of catalyst particles so the catalyst particles remain spaced apart from one another. A reactor for conducting laboratory reactions can also include a reaction vessel, an impeller in the reaction vessel, and a drive system configured to drive reciprocating linear movement of the impeller.

FIELD OF THE INVENTION

The present invention relates generally to small-scale (e.g., laboratory and/or bench top) reactor systems used to research chemical reactions, and more particularly to methods and apparatus for mixing reaction materials in small-scale reactor systems.

BACKGROUND

Small-scale laboratory reactors are commonly used to explore and conduct research into topics of interest associated with chemical reactions. Many different types of experiments can be performed to study reaction materials, reaction variables, processes associated with chemical reactions, and other aspects of chemical reactions. Reaction materials include chemical reagents, catalysts, catalyst promoters, catalysts inhibitors, catalyst supports, and reaction products. For example research may be conducted into factors that may affect the desirability and/or economic viability of using particular reaction materials, process variables, and/or manufacturing techniques to carry out commercially significant chemical reactions.

Many chemical reactions require or can be facilitated by presence of a catalyst in a reaction vessel. As is generally known, a catalyst is a substance that can facilitate a chemical reaction without itself being consumed in the reaction. Typically, a catalyst must come into contact with one or more of the chemical reagents to catalyze the reaction. Heterogeneous catalysts are in a different phase than the chemical reagents. Most heterogeneous catalysts are solid phase and act on liquid and/or gaseous reagents. One common technique for conducting reactions involving a heterogeneous catalyst is to place a porous catalyst basket inside a reaction vessel containing liquid and/or gaseous reagents. The catalyst is placed in the catalyst basket before the reaction is started.

The catalyst is typically dispersed on the surface of a catalyst support, such as pellets made of a zeolite or other suitable porous material. The catalyst support pellets form a catalyst bed in the catalyst basket. The basket is at least partially porous so the fluid reagents can pass through the basket and contact the catalyst in the basket. But the pores or openings in the basket are small enough to retain the catalyst support pellets in the basket. Thus, the catalyst is generally confined to the catalyst basket.

During the reaction, a mixing system may be used to mix the reagents and produce flow of the reagents through the catalyst bed. One type of mixing system includes a rotating stirrer (e.g., impeller) that stirs liquid phase reaction materials. The catalyst basket can remain stationary as the stirrer causes fluid reagents to flow radially outward through the catalyst bed. One example of this is in U.S. Pub. Application No. 20040042942. Another type of mixing system rotates the catalyst basket in the reaction vessel. The rotating basket performs the function of an impeller and stirs the fluid reagents while generating flow of fluid reagents through the catalyst bed in the basket.

Currently used reactors having catalysts baskets are often unable to obtain good gas-liquid mass transfer, particularly in relatively smaller-sized reactors (e.g., reactors having an internal volume less than about 2500 mL. In smaller-sized reactors the impellers need to be designed to allow for the physical presence of the catalyst baskets. The catalyst baskets also must be designed to hold a sufficient volume of catalyst. Consequently, because of the limited amount of space inside smaller-sized reactors, the effective blade diameter of the impellers is much less than ideal for generating good KLa values.

In order to obtain decent KLa values in smaller-sized reactors, high rotational rates for the baskets/impellers are required. However, shear forces increase as the speed of rotation is increased. In conventional reactors having catalyst baskets, the increased shear forces can degrade larger catalyst particles, generating fines. Fines are undesirable because they make results difficult to interpret during characterization of the system because the experiments are designed to study the intrinsic activity of the catalyst on large catalyst particles. When high speed rotary agitation is introduced to increase mass transfer, fine particles are generated and the reaction is a combination of slurry and large particle catalyst. The inability to achieve good KLa values in smaller-sized reactors sometimes leads scientists to conduct tests in larger reactors that more closely resemble a pilot reactor or production reactor. However, larger reactors require more materials and longer setup times. This is more expensive and increases the time required to bring new products to market.

Also, when there are both gas and liquid phase reagents it can be difficult to achieve good mixing of the gas and liquid phase materials in a reactor having a catalyst basket. The catalyst basket is typically at least partially immersed in the liquid phase. The conventional mixing systems direct liquid flow radially outward through the catalyst bed. Flow of the liquid phase in a radial direction does little to mix the gaseous phase into the liquid. In some cases the conventional catalyst basket can impede mixing of gas and liquid phase reagents, particularly to the portion of the liquid phase below the basket.

The inventor has developed improved systems and methods for mixing reaction materials in a laboratory reactor system, which will be described in detail below.

SUMMARY

In one aspect, a reactor for conducting laboratory reactions comprises a reaction vessel, a catalyst basket in the reaction vessel, and a drive system configured to drive reciprocating linear movement of the catalyst basket.

In another aspect, a reactor for conducting laboratory reactions comprises a reaction vessel and a catalyst holder in the reactor. The catalyst holder is configured to hold a plurality of catalyst particles so the catalyst particles remain spaced apart from one another.

In another aspect, a reactor for conducting laboratory reactions comprises a reaction vessel, an impeller in the reaction vessel, a drive system configured to drive reciprocating linear movement of the impeller. Other aspects and features will also be apparent hereinafter.

Corresponding features are given corresponding reference numbers throughout the drawings.

DETAILED DESCRIPTION

Referring now to the drawings, first toFIG. 1, one embodiment of a reactor is generally indicated at reference numeral10. The reactor10includes a reaction vessel12, a catalyst basket14(broadly a catalyst holder), and a mixing system16(broadly, a drive system) connected to the catalyst basket for driving motion of the catalyst basket.

The reaction vessel12can be any container suitable for containing the reaction materials involved in a reaction of interest. The reaction vessel12may be a vial, pressure vessel, well, or other structure capable of containing liquids, slurries, or other non-gaseous materials. The reaction vessel12may be sealed (e.g., include a head) to contain gaseous reaction mixtures. Moreover, the reaction vessel12can include one or more inlets (e.g., to provide gaseous and/or liquid feedstock) and/or outlets (e.g., to regulate pressure and/or evacuate reaction products or byproducts during a reaction). The reaction vessel12can be a stand-alone system or it can be one of an array of reaction vessels. Although the volume of the reaction vessel12may vary within the scope of the invention, the reaction vessel is suitably a relatively small-scale reaction vessel to facilitate running multiple different experiments using a relatively small amount of reaction materials. For example, the internal volume of the reaction vessel12is suitably in the range of about 1 mL to about 50 L, more suitably in the range of about 10 mL to about 5 L, and still more suitably in the range of about 20 mL to about 500 mL.

The catalyst basket14can be any structure suitable for containing a catalyst. As illustrated inFIG. 2, for example, the catalyst basket14is configured to enclose a space for holding catalyst particles within a cylindrical sidewall and circular top and bottom walls. At least some parts of the basket14are permeable to liquid and/or gas. As illustrated inFIG. 2, the top and bottom walls are made of a material that is permeable to liquid and gaseous reaction materials. For example, the top and bottom walls are suitably made of a metal mesh or porous metal material having pores or openings large enough to accommodate flow of liquid and gas therethrough, but small enough to contain catalyst particles within the enclosed space. The volume of the space enclosed by the catalyst basket14can vary within the broad scope of the invention. However, it can be desirable for the catalyst basket14to be relatively small to facilitate experiments using small amounts of catalyst and other reaction materials. For instance, the catalyst basket14is suitably designed to contain between about 0.1 mL to about 5 L, more suitably between about 0.5 mL to about 300 mL, and still more suitably between about 1 mL and about 30 mL.

The catalyst basket14is drivingly connected to a drive system configured to move the catalyst basket within the reaction vessel12. InFIGS. 1 and 2, the drive system16includes a spindle18connected to the basket14. The drive system16is suitably configured to drive the catalyst basket14to rotate in a direction R and also to reciprocate along a linear path P, as illustrated schematically inFIG. 1. For example, the drive system16can suitably drive the catalyst basket14to rotate on the axis of the spindle18and simultaneously reciprocate along a linear path P (e.g., a substantially vertical path) parallel to the spindle. The result of rotation and simultaneous linear movement is a helical path H, as shown inFIG. 2. Accordingly, the drive system16is suitably configured to drive the catalyst basket14along a helical path H, meaning points on the catalyst basket that are not on the axis of rotation move in a helical path as the drive system simultaneously drives rotation and linear movement of the catalyst basket, as illustrated inFIG. 2.

The drive system16is suitably configured to drive the rotation of the catalyst basket14at a relative slow speed. For example, the drive system16is suitably configured to rotate the catalyst basket14at a speed in the range of 0 rpm to about 600 rpm. As noted by the low end of the range, in some cases it may be desirable to rotate the catalyst basket14at a very low speed or not at all. In contrast, some conventional reactors that use pure rotary motion have to drive rotating catalyst baskets at speeds as high as 2,000 rpm to achieve adequate mass transfer rates. The reactor10is also configured to achieve desired high mass transfer rates while maintaining relatively low shear conditions in the catalyst bed. During high speed rotation of a catalyst basket in conventional reactors shear forces (which increase as the speed of rotation is increased) degrade larger catalyst particles, generating so-called fines. Fines are undesirable because the can make results difficult to interpret. When high speed rotary agitation is introduced to obtain good gas-liquid mass transfer, fine particles are generated and the reaction is a combination of slurry and large particle catalyst. However, it is often desirable to study the intrinsic activity of the catalyst on large catalyst particles in which case the production of fines introduces an unwanted variable. The reactor10described herein advantageously allows relatively high mass transfer rates in the range of about 0.1 to about 1.2 S−1while at the same time limiting shear forces acting on the catalyst particles and thereby reducing the number of fines produced. In some cases production of fines can be substantially eliminated.

The drive system16is suitably operable to adjust the pitch of the helical path H by changing the ratio of the angular velocity relative to the linear velocity. For example, the drive system16is suitably operable to drive the catalyst basket14at an angular velocity in the range of about 0 rpm to about 600 rpm and to simultaneously drive the catalyst basket14to move at a maximum linear velocity in the range of 0 to 1.0 m/s. It is understood that the linear velocity may vary depending on the linear position of the basket14on its reciprocating path P. In some cases it may be desirable to drive linear movement of the catalyst basket14according to a harmonic oscillation, such as by using a Scotch Yoke to convert rotary movement to sinusoidal reciprocating movement. The frequency of the linear oscillatory component of the motion is suitably in the range of about 1 Hz to about 10 Hz.

The reactor10is suitably configured to drive flow of fluid reaction materials through the catalyst basket14in a direction that includes a non-radial direction. The reactor10is also configured to drive fluid reaction materials through all parts of a catalyst bed that occupies substantially all of the cross sectional area of the reactor vessel12at the position of the catalyst basket14. This is in contrast to conventional reactors that use simple rotary motion (of a catalyst basket or stirrer) to produce flow of reaction materials through a catalyst bed. In the case of simple rotary motion, fluids are driven radially outward through the catalyst bed until they reach a point at which they either exit the catalyst bed (in the case of a gap between the catalyst bed and the reactor sidewall) or are forced in a vertical direction by the reactor sidewall or another barrier to infinite flow in the radial direction. This radial flow tends to result in stagnation of fluid flow at various locations in the catalyst bed.

The reactor10is suitably configured so the catalyst basket14divides the internal space of the reactor into different zones. As illustrated inFIG. 2, for example, the catalyst basket14is sealed against the internal sidewall of the reactor vessel12(e.g., by an O-ring20) to limit flow of reaction materials between a zone below the catalyst basket and a zone above the catalyst basket. The seal between the catalyst basket14and the reactor sidewall limits the amount of material that can flow between the upper and lower zones without flowing through the porous catalyst basket. This can enhance flow of reaction materials through the bed of particles in the catalyst basket14. Referring toFIG. 2, which illustrates the catalyst basket14in the midst of a downstroke for example, the reactor10is configured so the linear reciprocating motion of the catalyst basket changes the volumes of the upper and lower zones defined by the catalyst basket. There will commonly be substantially incompressible liquid reaction materials in the lower zone of the reactor10, in which case the downward movement of the catalyst basket14forces liquid reaction materials to flow through the bed of particles in the catalyst basket. Even if there are compressible gaseous reaction materials in the upper and lower zones of the reactor10, the reciprocating linear movement of the catalyst basket14combined with the seal between the catalyst basket and the reactor sidewall will produce alternating pressure differentials across the catalyst basket that will drive reaction materials (gaseous and/or liquid) through the porous catalyst basket.

The reactor10is configured to allow users to select multiple different operating modes by adjusting the level of liquid reaction materials in the reactor10relative to the catalyst basket14. In particular, the way the bed of catalyst materials in the catalyst basket14interacts with the reaction materials depends on the level of the liquid reaction materials relative to the upper and lower extremes of the reciprocating linear motion of the catalyst basket. For example, if the liquid level is high enough that the catalyst basket14is completely submerged throughout the reciprocating linear cycle, the reactor10operates as a submerged bed reactor10. On the other hand, if the liquid level is lower than the catalyst basket14throughout the reciprocating linear cycle, the reactor10operates as a trickle bed reactor. Moreover, if the liquid level is between the upper and lower extremes of the linear reciprocating movement of the catalyst basket14, the reactor10operates as a hybrid between a submerged bed reactor and a trickle bed reactor as the catalyst basket is repeatedly submerged in and then withdrawn from the liquid reaction materials. Accordingly, the mode in which the reactor10operates can be selected by adjusting the volume of liquid reaction materials in the vessel12and/or by adjusting the position of the catalyst basket14relative to the rest of the reactor.

FIG. 3illustrates one embodiment of a magnetic coupling22that can be used to drive linear oscillatory and rotary motion of the spindle12, and thereby drive the corresponding motions of the catalyst basket14. The coupling22includes a pressurizable casing24configured to receive the upper end of the spindle12and to allow linear oscillatory movement of the upper end of the spindle within the casing. The casing24has closed end and an open end opposite the closed end. A flange25extends radially outward at the open end. A groove in the flange receives an O-ring26for forming a seal with the upper portion of the reactor vessel12. The casing24suitably has a substantially cylindrical sidewall having a circular cross sectional shape. The sidewall suitably has a substantially uniform thickness and substantially cylindrical inner and outer surfaces. A bearing28is mounted at the open end of the casing24. The bearing28suitably allows linear movement of the spindle18relative to the bearing while also allowing rotary movement of the spindle relative to the bearing. The spindle18extends through the bearing into the casing24.

A magnetic follower30is secured to the spindle inside the casing. A magnetic driver32is secured to a carriage34outside the casing24. Together, the magnetic follower30and the magnetic driver32form the magnetic coupling22. In general, any structural arrangement having the capability of producing a linear oscillatory and rotational movement of the magnetic follower30using magnetic attraction and/or magnetic repulsion forces associated with movement of the magnetic driver32can be used within the broad scope of the invention.

InFIG. 3for instance, one or more magnets36are suitably secured to the upper end of the spindle18in the casing24so linear and rotational movements of the magnets relative to the spindle are limited to constitute the magnetic follower. As illustrated inFIG. 3, the one or more magnets36are secured on the end of the spindle18between a pair of retainers37extending outward from the spindle that limit linear movement of the magnet(s) relative to the spindle. The retainers37can suitably be annular flanges extending radially outward from the spindle18, but other structures can be used instead. Adhesive or other suitable fasteners can be used to limit rotational movement of the magnet(s) relative to the spindle. One or more splines (not shown) can also be included on the magnets and/or on the spindle to engage one or more grooves in the other of the magnets and the spindle to limit rotation of the magnets relative to the spindle. The magnets36, bearing28, and spindle18are arranged so the bearing maintains spatial separation between the magnets of the magnetic follower30and the inner surface of the sidewall of the casing24.

The magnetic driver32in the embodiment illustrated inFIG. 3includes one or more magnets38secured to the carriage34(e.g., by adhesive or any suitable fasteners). A bearing40is secured to an inner surface of the carriage34. The casing24extends through the bearing40so the bearing is positioned between the outer surface of the casing and the carriage34. The bearing40connecting the casing24to the carriage34is suitably substantially similar to the bearing28connecting the spindle18to the casing in that it allows both rotational and linear motion of the carriage relative to the casing. The magnets38, carriage24, and bearing40are arranged so the bearing maintains spatial separation between the magnets of the magnetic driver32and the outer surface of the sidewall of the casing24. The carriage34can have variety of configurations within the broad scope of the invention. For example, the carriage34is suitably a substantially cylindrical sleeve having radially inwardly extending retainers41at its opposite open ends. The retainers41can be radially inwardly extending annular flanges, for instance. The carriage34suitably also includes one or more retainers42extending between the bearing40and the magnets38of the magnetic driver32, as illustrated. This retainer42is also suitably a radially inwardly extending annular flange, although other configurations are also possible.

The carriage40is connected to a drive mechanism (not shown inFIG. 3) configured to drive rotational movement of the carriage about an axis coincident with the longitudinal axis of the spindle while at the same time driving reciprocating linear movement along the same axis. Various drive mechanisms are suitable. For example, those skilled in the art will recognize various combinations of Scotch Yoke mechanisms (e.g., the Scotch Yoke mechanism16′ illustrated inFIG. 11), cams, and gears can be used to produce simultaneous rotary and reciprocating linear movement of the carriage using one or more motors. The drive mechanism is optionally configured to allow adjustment to the angular frequency and/or the frequency of the linear reciprocating motion and/or the maximum linear velocity. For example, the drive mechanism can be configured so a first motor is used to drive rotation and a different motor is used to drive the reciprocating linear motion. Moreover, one or both of the motors can be a variable speed motor to provide the ability to adjust the angular velocity of the rotary movement relative to the maximum speed and/or frequency of the reciprocating linear motion. Further, the drive mechanism is optionally configured to allow adjustment to the amplitude of the linear reciprocating motion. For example, the drive mechanism suitably includes an adjustable length crank arm used in combination with a Scotch Yoke mechanism, as illustrated inFIG. 11.

FIG. 12illustrates another embodiment of a drive mechanism50that is suitable and which includes a pneumatic cylinder52configured to drive reciprocating movement of the carriage34. For example, a double action cylinder52or single action, spring return cylinder can be used. In either case, the direction the cylinder52moves, and thus the direction the catalyst basket14moves, can be reversed whenever desired (e.g., using a controller to operate a valve that controls operation of the cylinder).

FIGS. 13 and 14illustrate additional embodiments of suitable drive mechanisms60,70that can produce reciprocating linear motion and rotary motion at the same time. In the embodiment illustrated inFIG. 13, a rotary motor61is attached to the output shaft of a reciprocating driver62(e.g., linear motor, pneumatic cylinder, or Scotch Yoke mechanism). The rotary motor61is secured to the carriage34(e.g., by a rotary bearing63) so the motor and carriage move with one another as the motor is driven back and forth by the linear driver62. A timing belt64or other suitable drive component drivingly connects the rotating output shaft65of the motor61to the carriage34so the rotary motor rotates the carriage. The magnets38on the carriage exert forces on the follower that cause the movement of the follower30to follow the carriage34. The drive mechanism70inFIG. 14is substantially the same as the drive system60inFIG. 13except that the rotary motor61is replaced with a hollow rotary motor71. An inner rotor72of the motor71is hollow and the carriage34is secured to the rotor within the central opening of the hollow rotor. Other types of drive systems can also be used without departing from the scope of the invention.

To use the reactor10one or more liquid reaction materials are placed in the reactor. One or more gaseous reaction materials are also added to the reactor10. The level of liquid reaction materials is selected to determine which mode the reactor10will operate in: submerged bed, trickle bed, or hybrid. Again, this can be done by adjusting the volume of reaction materials in any particular reactor or by selecting a reactor having a different geometry and/or catalyst basket position. During the reaction, the catalyst basket14is driven to rotate while simultaneously being driven to reciprocate along the linear path P (e.g., move up and down along a substantially vertical path). This action drives fluid reaction materials through the catalyst bed in a non-radial direction. For example, liquid reaction materials are suitably driven upwardly through the catalyst bed on the downstroke and is driven downwardly through the catalyst bed on the upstroke. There can also be a radial component to fluid flow through the catalyst bed due to the rotary motion of the catalyst basket14, however, the action of the catalyst basket substantially prevents formation of stagnation points within the catalyst bed.

The combination of rotary motion and reciprocating linear motion produces substantially higher gas-liquid mass transfer coefficients (KLa) than could be achieved without the combined motion. For example, Table 1 below indicates the gas-liquid mass transfer coefficient achieved using only linear motion of a catalyst basket in a 15.3 mL reactor. In other words, rotary motion for this experiment was 0 rpm.

Those skilled in the art will recognize the gas-liquid mass transfer coefficients achieved with the reciprocating linear motion (shown in Table 1) are very high compared to those that would be achieved by conventional mixing techniques. For example, as shown in table 2, corresponding data showing the mass transfer coefficients achieved using the same reactor and chemistry but without linear motion and with rotary motion (with two different impellers) shows the pure rotary motion is unable to achieve the relatively high mass transfer coefficients achieved with the reciprocating linear motion.

It is understood that adding rotational movement to the catalyst basket in combination with the reciprocating linear movement will also produce significantly higher mass transfer coefficients than conventional techniques. The ability to achieve high gas-liquid mass transfer coefficients at relatively low RPMs (e.g., from 0 rpm up to about 600 rpm) protects the catalyst materials in the catalyst basket from degradation due to excessive shear forces.FIG. 14shows a comparison of the mass transfer coefficients for reactions performed in a conventional impeller reactor, a pitched blade reactor, and the reactor10at various rotational speeds. The impeller reactor and pitched blade reactor were operated at rotational speeds in excess of 900 RPM, while the reactor10was operated at rotational speeds of about 300 RPM or less. As can be seen, the reactor10had a significantly higher liquid mass transfer coefficient at lower rotational speeds.

FIG. 4illustrates another embodiment of a reactor110of the present invention. The reactor110illustrated inFIG. 4is constructed and can be operated in substantially the same way as the reactor10inFIGS. 1-3, except as noted. Features of the reactor110that correspond with features of the reactor10are given the same reference number, plus 100. The reactor110includes a liquid barrier119and a positioned above the catalyst basket114. The liquid barrier119has an opening through which the spindle118holding the catalyst basket extends and an O-ring121forming a seal between the spindle and the liquid barrier. Another O-ring123forms a seal between the liquid barrier119and the reactor vessel112. A gas permeable/liquid impermeable structure125is included in the liquid barrier119to allow gas to flow through the liquid barrier but limit flow of liquid through the liquid barrier. During operation, this reactor110forces liquid upward through the catalyst basket on the downstroke by creating a high pressure zone in a space that is too small to contain all the liquid reaction materials. On the upstroke, the catalyst basket114lifts liquid reaction materials until the upper surface of the liquid contacts the liquid barrier. The liquid barrier forces liquid downward through the catalyst bed on the latter part of the upstroke.

Another embodiment of a reactor210of the present invention is illustrated inFIG. 5. This embodiment is substantially identical to the embodiment illustrated inFIG. 4, except that the liquid barrier219includes a one-way valve227instead of a gas permeable structure125.

FIG. 6illustrates still another embodiment of a reactor310of the present invention. This embodiment is substantially identical to the embodiment illustrated inFIG. 4, except as noted. Features of the reactor310that correspond with features of the reactor110are given the same reference number, plus 200. The spindle318in this embodiment supports a gas trapping plate331above the catalyst basket314. The gas trapping plate331has one or more recessed areas333in its underside. The gas trapping plate331moves up and down with the up and down reciprocating movement of the catalyst basket314. There is no seal, however, between the gas trapping plate331and the reactor vessel312. Thus, fluid reaction materials can flow around the gas trapping plate331. The gas trapping plate331is suitably positioned at an elevation on the spindle318that will result in repeated submersion of the gas trapping plate in the liquid reaction materials on the downstroke followed by withdrawal of the gas trapping plate on the upstroke. Gas bubbles G are trapped by the receptacles in the gas trapping plate as the plate is submerged into the liquid reaction materials on the downstroke. This can enhance mixing gaseous reaction materials into the liquid reaction materials.

FIG. 7illustrates yet another embodiment of a reactor410of the present invention. This embodiment is substantially identical to the embodiment illustrated inFIG. 4, except as noted. Features of the reactor410that correspond with features of the reactor110are given the same reference number, plus 300. In this embodiment, a dip tube441extends through the liquid barrier419and the catalyst basket414. The liquid barrier419and dip tube441are held at a fixed elevation in the reactor and do not move with the reciprocating linear motion of the catalyst basket414. The drive system416is suitably configured to produce linear reciprocating motion of the catalyst basket414without any rotation (i.e., rotation is suitably 0 rpm). The dip tube441includes a gas permeable liquid seal (not shown; e.g., a porous membrane) that allows gas to flow through the dip tube but blocks flow of liquid through the dip tube. This reactor is configured to mix gas into a pool of liquid reaction materials at the bottom of the reaction vessel412. In particular, the low pressure zone created under the catalyst basket414on its upstroke draws gas from above the liquid barrier down through the dip tube into the liquid at the bottom of the reactor410.

FIG. 8illustrates still another embodiment of a reactor510of the present invention. This embodiment is substantially similar to the embodiment illustrated inFIG. 4, except as noted. Features of the reactor510that correspond with features of the reactor110are given the same reference number, plus 400. One difference between the reactor110illustrated inFIG. 4and the reactor510illustrated inFIG. 8is that the reactor inFIG. 8has an adjustable volume catalyst basket514. In particular, the elevation of a porous sheet551forming the top of the catalyst basket514is adjustable. There are various different ways to allow for height adjustments. For example, the reactor system suitably includes a set of spacers having multiple different sizes that can be positioned to block upward movement of the catalyst basket. Thus, the volume of the catalyst basket can be decreased by using a larger spacer and/or increased by using a smaller spacer. The ability to adjust the volume of the catalyst basket514allows the catalyst particles to be clamped in place by the top551of the catalyst basket to reduce grinding of particles against one another. In turn, the ability to reduce particle grinding can reduce the undesirable generation of fine catalyst particles. If desired, the volume of the catalyst basket514can be decreased so that it can hold only a single layer of catalyst particles, as illustrated in the right side ofFIG. 8.

Moreover, the right side ofFIG. 8illustrates the reactor being used with a catalyst holder514that is configured to hold a plurality of catalyst particles so the catalyst particles remain spaced apart from one another. In particular, a compliant porous particle locking sheet553is inserted in the catalyst basket514above the single layer of catalyst particles. A plurality of pockets are formed in the bottom of the locking sheet553. The pockets are suitably sized so no more than a single catalyst particle can fit into each pocket. As illustrated inFIG. 9, a pair of particle locking sheets553A,553B can be arranged so at least some of the pockets of the respective sheets are in registration with one another so they collectively hold the particles spaced apart from one another. If desired, multiple particle locking sheets can be stacked on top of one another to hold multiple layers of catalyst particles so that substantially every catalyst particle in the catalyst basket is spaced from substantially every other catalyst particle. One example, of a suitable particle locking sheet can be formed by embossing dimples in a thin, compliant, highly-porous stainless steel mesh disk. The size of the dimples/pockets can be varied to suit the size of the catalyst particles.

FIG. 10illustrates another embodiment of a reactor610of the present invention. This embodiment is substantially similar to the embodiment illustrated inFIG. 4, except as noted. Features of the reactor610that correspond with features of the reactor110are given the same reference number, plus 500. One difference is that the catalyst basket is replaced with an impeller561. The drive system516described above is connected to the impeller561in a manner similar to the catalyst basket114so the drive system drives linear motion of the impeller. The drive system516optionally also drives rotation of the impeller561. The impeller561has three lobes563spaced equi-angularly about central portion which is connected to the drive system by a shaft518. There are optionally a plurality of openings565in the impeller. As illustrated inFIG. 10, for example, a series of small openings565is located within each lobe563of the impeller. The openings565allow fluid (e.g., gas and liquid) to pass through the impeller lobes, which may be desirable to create additional eddies and/or break up larger gas bubbles into smaller gas bubbles to facilitate mass transfer between gas and liquid phase(s). The reactor510illustrated inFIG. 10is suitable for conducting reactions in which catalyst particles are suspended in the liquid reaction materials. In particular, the drive system516can move the impeller repeatedly up and down through the liquid reaction materials to maintain the catalyst particles in a suspended condition.

When introducing elements of the apparatus and methods described and illustrated herein, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” and variations thereof are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “forward” and “rearward” and variations of these terms, or the use of other directional and orientation terms, is made for convenience, but does not require any particular orientation of the components.