Patent Description:
The catalyzed reactions of a gas with liquid reactant have typically been performed in stirred batch or continuously stirred reactors maintaining an overpressure of the reactant gas and continuous injection of the gas reactant into the liquid. Batch reactors tend to efficiently use the catalyst (i.e., have a high turnover number "TON" of the catalyst), but suffer from high capital costs for given throughput and down time between batches. In some instances, the stirring of the batch reaction may be accomplished by bubbling the gas reactant through the liquid reactant (i.e., bubble reactor).

Continuously stirred reactors may continuously produce product, but suffer from inefficient use of the catalyst and require continuous separation, recycling and replenishment of the catalyst. Such operations may involve complex methods and techniques such as separation membranes that may foul and result in inconsistent operation or product.

Plug flow reactors have not generally been used for these reactions because typically they involve long coils of tubes to realize sufficient residence time and sufficient heat transfer area. Because these reactions typically require an over feed of the gas reactant, beyond the solubility limit in the liquid/solvent, there often is accumulation of the gas reactant in the high points of the piping resulting in variable liquid hold up/residence time in the reactor as well as inconsistent reaction conditions through the reactor.

Accordingly, it would be desirable to provide a method of reacting a gas and liquid reactant that avoids one or more of the problems of the prior art such as one of those mentioned above. <CIT> discloses a bubble reactor for catalysed gas-liquid reactions.

Applicant has discovered that a hybrid vertical bubble plug flow reactor ("reactor") herein may be used to react and gas reactant and liquid reactant allowing for well controlled reaction conditions, effective and efficient use of the catalyst (e.g., high TON), while avoiding problems associated with batch bubble reactors, continuous stirred tank reactors and typical plug flow reactors.

The first aspect of the invention is a method of reacting a gas reactant and liquid reactant according to claim <NUM>. Vertical herein means that the tubular member's length is essentially parallel with the gravitational field vector of the earth (i.e., would be essentially parallel with the plumb line of a plumb bob when determining vertical).

A second aspect which is not part of the claimed subject-matter is a reactor comprised of a bottom inlet and a top outlet having vertical tubular member disposed there between, wherein the bottom inlet has separate gas reactant inlet and separate liquid reactant inlet whereby the gas reactant is mixed with the liquid reactant and the outlet has an extraction port, the extraction port extending sufficiently to withdraw the liquid product from the reactor and maintain a gaseous head space within the tubular member of the reactor.

The method is particularly suited for reacting a liquid reactant and gas reactant that do not react quickly and typically require a catalyst such as the carbonylation of an epoxide by carbon monoxide. Other reactions may include, for example, hydrogenation reactions (e.g., H<NUM> reacted with unsaturated hydrocarbons and hydrocarbon oxidation (e.g., oxygen "air" with cyclohexane).

<FIG> is an illustration of the hybrid vertical tube reactor of this invention.

The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. The specific embodiments of the present disclosure as set forth are not intended to be exhaustive or limit the scope of the disclosure.

The method employs a hybrid vertical bubble plug flow reactor (reactor) <NUM> illustrated in <FIG>, but not limited thereto. The reactor <NUM> has a bottom inlet <NUM> and top outlet <NUM> connected by tubular member <NUM>. The bottom inlet is comprised of separate gas reactant inlet <NUM> and liquid reactant inlet <NUM>. The bottom inlet may be further comprised of a drain <NUM> or other inlet for introduction of other components. In the bottom inlet <NUM> the gas reactant is mixed with the liquid reactant which may be mixed with a solvent in mixing area <NUM>. The gas reactant inlet <NUM> may also be comprised of a sparger (not shown) to cause the formation of desired gas reactant bubble size within the liquid reactant and to facilitate the saturation of the liquid reactant and, if used, solvent. The inlet may further be comprised of a screen mesh or the like <NUM> or the like to retain optional packing <NUM> in the vertical tubular member <NUM> or to further disperse or reduce the gas reactant bubbles. The mesh may be any to be used to encourage the rupture of bubbles into smaller bubbles and retain packing such as the product offered from Sealing Devices Inc. , a pipe flange gasket with inlaid 316SS #<NUM> mesh. It is understood that the bottom inlet may be configured in any manner that allows for the injection and mixture of the reactants at the bottom of the tubular member <NUM> such as radial inlets at the bottom of the tubular member <NUM> or vertical tubes traversing within the tubular member from the top and exiting at the bottom of tubular member <NUM>.

The outlet <NUM> is fitted with any suitable gas liquid separation method such as those known in the art. In one embodiment, the outlet <NUM> is comprised of extraction tube <NUM> that extends sufficiently into the liquid product, solvent and residual liquid reactant (reactor liquid <NUM>) to allow for the extraction of said reactor liquid <NUM> and to allow head space <NUM> to be maintained providing an overpressure of the gas reactant. In an alternative, the extraction tube may be replaced by any other outlet such as a radial extraction port that also allows the headspace to be maintained. The extraction tube, port or other outlet for the liquid product and residual solvent and unreacted liquid reactants, may be accompanied by a separate gas outlet. The outlet <NUM> has effluent outlet <NUM> for transporting the reactor liquid <NUM> for further processing such as separation, further reaction, recovery of solvent and/or catalyst and gaseous outlet <NUM> for maintaining the overpressure of gases within the reactor utilizing suitable flow controllers, tanks, valves and apparatus such as those known in the art (not pictured), which may be integrated or integral with the reactor.

It has been discovered that the reactor surprisingly may be used to react a gas and liquid reactant. In particular, the method allows for the catalyst to be more effectively and efficiently used realizing high TONs. Turnover Number (TON) is used as commonly understood in the art, wherein for continuous reactions the amount of catalyst and product produced in a given time results in the TON for continuous reactions and is given by (moles product/time)/(moles catalyst/time). TONs indicate the efficacy of the catalyst for continuous reactions where the output of the product is similar. In performing the method of the invention, a liquid reactant is injected into the mixing area <NUM> through the liquid reactant inlet <NUM> and the gas reactant is injected into the mixing area <NUM> through the gas reactant inlet <NUM> where bubbles of the gas reactant are formed in the liquid reactant. The reactants may be cooled or heated when injected depending on the type of reaction being performed. For example, it may be desirable to inject cooled reactants for exothermic reactions such as carbonylation described herein.

The tubular member <NUM> is vertically oriented with it being understood some deviation from vertical may be acceptable, but, in essence, the reaction zone is straight without any bends or other obstructions that can entrap the gas reactant. The tubular member <NUM> may have any cross-sectional shape such a square, rectangle, quadrilateral, hexagon, pentagon oval or circle with a circle being preferred. The materials of construction may be any that is compatible with the reactants and conditions used to react the reactants and is readily determinable by one of ordinary skill in the art. For example, when the reactants are an epoxide and carbon monoxide, stainless steel (e.g., <NUM> or <NUM> stainless steel), inorganic glasses, organic plastics (e.g. engineering polymers) and ceramics may be used.

The length of the reactor <NUM> and tubular member <NUM> may be any length and diameter useful to realize the desired reaction conditions such as residence time. Typically, the diameter of the tubular member may be from <NUM>, <NUM>, <NUM> or <NUM> to <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. It is understood that the diameter of a non-cylindrical tubular member is taken as the largest dimension of the cross-section of such tubular member. Generally, the aspect ratio (length/diameter) is at least about <NUM>, <NUM> or <NUM> to any commercially practicable ratio such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>.

In an embodiment, the reactor <NUM> may be comprised of multiple tubular members <NUM> in parallel with separate or shared flanging for injection of the reactants and removal of the products. Such parallel configurations of tubular members <NUM> may be contained in a common vessel, for example, that may have a heating element or heat transfer fluid to heat or cool such tubular members <NUM> commonly. In another embodiment, the reactors <NUM> may be configured in series, for example, to inject further or different reactants or catalysts or react the products from one reactor in a subsequent reactor to form a different product. Likewise, a combination of parallel and series reactors may be configured to allow for the continuous formation of differing products and adjust the mix of such product.

In another embodiment, the tubular member <NUM> may be further comprised of one or more radial inlets along its length for injecting further reactants or other components (e.g., solvent, stabilizers, surfactants or the like). It is understood that such other components, just like the solvent may also be injected in the bottom inlet. For example, a radial inlet may be used to inject the same gas reactant or liquid reactant inserted in the bottom inlet <NUM> along the length of the tubular member <NUM>. If a gas reactant is injected through a radial inlet it may incorporate a sparger as described herein. In another embodiment, differing reactants may be inserted through the radial inlet or inlets to form differing desired final products. As previously described, the reactants or any further components may be heated or cooled depending on the desired reaction or reaction conditions.

The rate of injection of the gas reactant/liquid reactant is such that it results in a molar excess of the stoichiometric amount for the desired reaction of the gas reactant. Illustratively, the molar ratio (or equivalent ratio) of the gas reactant/liquid reactant is greater than <NUM>, <NUM>. <NUM>, <NUM> or <NUM> to about <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. It is believed, without being limiting in any way, that the excess of gas reactant allows for maintaining of the saturation of the liquid reactant with the gas reactant throughout the resident time within the reactor so as to avoid starvation of the gas reactant in the reactor. Likewise, excess amounts of gas reactant, is believed, without being limiting may cause evaporation of the liquid reactant, product or solvent into the bubbles formed within the liquid reactant and thus inhibiting the catalyzed reaction.

Desirably, the bubbles that are formed in the liquid reactant are of a size that enhances the saturation within the liquid reactant and even distribution throughout the reactor. In an embodiment a sparger may be used when injecting the gas reactant. The sparger may be any commonly used in the chemical or biochemical industries. For example, the sparger may be a porous sintered ceramic frit or porous metal frit such as those available from Mott Corp. Farmington, CT. The pore size of the porous sintered frit sparger may be any useful such as those having a pore size of <NUM> micrometer, <NUM> micrometer, <NUM> micrometers to <NUM> micrometer, <NUM> micrometers, <NUM> micrometers or <NUM> micrometers. Examples of other gas spargers that may be suitable include perforated plate, needle, spider, or combination thereof of varying sized openings depending on the desired gas bubble size.

In another embodiment, the bubble size desired or distribution of the reactants may be facilitated by using packing <NUM> within the reactor. The packing <NUM> may be any useful for causing disruption of larger bubble formation and to break up larger bubbles such as those known in the art or distributing of the reactants. For example, the packing <NUM> may be a porous packing such as commonly used in plug flow reactors to ensure good radial mixing and facilitate plug flow through the reactor. Packing <NUM> may be beads of any useful shape, a monolithic or segmented inline static mixing structure or screw structure, distribution plates or sieves.

In a further embodiment, the bubble size desired may be facilitated by the use of a surface active agent including but not limited to ionic (cationic, anionic, and amphoteric surfactants) or nonionic surfactants that are separately added. The surface active agent may be entrained in the liquid reactant when inserted or be separately inserted into the inlet <NUM>. In an embodiment, the surface active agent may be insitu produced as a by-product. For example, a glycolic oligomer may be produced when carbonylating an epoxide or lactone with carbon monoxide.

When the packing <NUM> is a bead, the bead may be any useful shape, such as sphere, spheroid, cone, cylinder, flat perforated sheet having any cross-sectional shape, tube, cube or fibrous. In an embodiment, the beads may be monosized (same volume or equivalent spherical diameter, if not spheres) or of varying sizes including bimodal, trimodal or of a continuous size distribution. Generally, the bead size is <NUM> to about <NUM>.

The size of the beads may be any useful size, that facilitates the plug flow and disruption of the bubble as described above. The packing <NUM> generally creates a void fraction of about <NUM>% to <NUM>% within the tubular member <NUM>. Typically, the void fraction is <NUM>% or <NUM>% to <NUM>%, <NUM>% or <NUM>%.

The packing <NUM> may be made of any suitable material useful to handle the reactants and reaction conditions employed. Suitable bead materials may include, for example, ceramics (e.g., crystalline oxides, nitrides, carbides, and amorphous silicates, aluminates, borates and combinations thereof), plastics (e.g., polyolefins, fluoropolymers, polycarbonates, polyesters and combinations thereof), metals (e.g., transition metals and alloys thereof) or combinations of any of the aforementioned. Particular examples include porous, borosilicate glass, silica glass, soda-lime glass, alumina, stainless steel, nickel alloy or combinations thereof. In a particular embodiment, the packing <NUM> is a perforated <NUM> stainless steel tabs available under the tradename PROPAK (Cannon Instrument Co. In an embodiment, the method employs both a sparger and packing. In further embodiments, the packing <NUM> may be catalytic as described below.

In the method, it is desirable for the gas bubbles to flow through the reactor <NUM> at a velocity (speed) that is the same or faster than the liquid reactant. Without being limiting in any way, this is believed to facilitate the saturation of the gas reactant into the liquid reactant as well as create agitation throughout the reactor improving the reaction efficiency and effectiveness (e.g., higher TONs and selectivity). Typically, the bubbles have a velocity that is at least about <NUM> or <NUM> to <NUM>, <NUM> or <NUM> times faster through the reactor <NUM> than the liquid reactant and any solvent if used. In other words, the bubbles have a residence time that is less than the liquid reactants by a similar proportion as given for the speed (e.g., <NUM> or <NUM> to <NUM>, <NUM> or <NUM> the residence time).

In an embodiment, a head space <NUM> of gas is maintained within tubular member <NUM>, for example, to facilitate the saturation of the gas reactant in the liquid reactant and solvent if used. The head space <NUM> may be maintained, as previously described, at any pressure useful for reaction conditions used to react particular reactants. As an illustration, when the liquid reactant is an epoxide (e.g., ethylene oxide and/or propylene oxide) or beta lactone (beta butyrolactone and/or beta propiolactone) and gas reactant is carbon monoxide, the pressure may range from greater than <NUM>, <NUM>, <NUM>, <NUM> or <NUM> bar to about <NUM>, <NUM>, <NUM> or <NUM> bar. In an embodiment, the head space <NUM> may also be used to facilitate the maintenance of the liquid reactant in the liquid state. For example, if the reactant is normally a gas at ambient conditions (ambient conditions in essence <NUM> to <NUM> and ~ <NUM> atm), the liquid reactant may be maintained in part by having a sufficient overpressure such as described above.

The method may be carried out at any useful temperature for the particular reactants and desired product. Illustratively, for the carbonylation of an epoxide or lactone, the temperature may be from about <NUM>, <NUM>, <NUM> to <NUM>, <NUM>, <NUM>, or <NUM>. The heating or cooling of the reactor may be carried out by any suitable method or apparatus such as those known in the art. For example, the reactor <NUM> may include a temperature controlling jacket, not pictured. Typically, this may involve heat exchanging conduits such as channels in the wall of the tubular member <NUM>, that allows for cooling or heating liquid to pass through and transfer heat into or out of the reactor or it may be any known heating or cooling methods such as heating tape or tube or tubes wrapped around the tubular member <NUM> , channels within the walls of the tubular member <NUM>, or tubes within the tubular member <NUM> (i.e., the reactants contact the tube walls within the reactor) or any combination thereof to control the temperature of the reaction or immersed heating/cooling tubes within tubular member <NUM>.

The method may use any rate of introduction of the reactants to realize a suitable residence time within the reactor <NUM>. Typically, the residence time within the reactor <NUM> may be from <NUM>, <NUM> or <NUM> minutes to <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> or <NUM> hour depending on the reactants such as epoxides, lactones or combination thereof with carbon monoxide. In an embodiment, surprisingly, the reactor <NUM> may be used to carbonylate an epoxide to a lactone, which then further reacts to form an anhydride. It is surprising, because there is a continuous feed of epoxide into the reactor and the catalyst is highly selective in forming the lactone in the presence of the epoxide. The method may also recycle the effluent, for example, to realize a desired product mix and in particular recycled CO, when performing the carbonylation reaction described here may be particularly desirable.

In the method the reaction is carried out in the presence of a catalyst. The catalyst may be a homogeneous catalyst, heterogeneous catalyst or combination thereof. In an embodiment, the catalyst is present in the liquid reactant when injected into the reactor <NUM> via liquid reactant inlet <NUM>. For example, the catalyst is a homogeneous catalyst dissolved in the liquid reactant or heterogeneous catalyst present as a particle in the liquid reactant (slurry) prior to insertion into the reactor <NUM>. In another embodiment the catalyst is comprised of a heterogenous catalyst that is anchored to a support, which may be use as the packing <NUM> in part or wholly. As an illustration, the heterogeneous catalyst may be supported catalyst useful in the carbonylation of epoxides or lactones such as described in copending application <CIT>. The The support may be a porous ceramic such as a packing bead described above and, in an embodiment, may be a zeolite such as described in paragraph <NUM> of said copending application incorporated herein by reference, silica, titania, silver (e.g., silver in clay binder). Other exemplary catalysts for carbonylation of epoxides or lactones are described in <CIT> and <CIT> and <CIT> and <CIT>.

The amount of catalyst may be any useful amount and may depend on the particular reactants and desired product. Typically, the amount of catalyst present in the reactor is about <NUM>% to <NUM>% by weight of the amount of reactants present in the reactor <NUM>. Illustratively, if the catalyst is a homogeneous catalyst dissolved or entrained in the liquid reactant, the amount of the catalyst is about <NUM>%, <NUM>%, <NUM>% to about <NUM>%, <NUM>% or <NUM>% by weight of the liquid reactant and catalyst. As a further illustration, the amount of homogeneous catalyst when carbonylating an epoxide or lactone with carbon monoxide is fed into the reactor along with the epoxide or lactone at molar ratio of liquid reactant/catalyst of <NUM>, <NUM> to <NUM>,<NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>,<NUM> or <NUM>,<NUM>.

The liquid reactant may be present, mixed with or entrained in a solvent. Any useful solvent may be used. The solvent may be used to enhance, for example, the presence of the gas reactant in the liquid reactant. As an illustration, when the liquid reactant is an epoxide, the solvent may be an organic solvent such as an aliphatic hydrocarbon, aromatic hydrocarbon, halogenated solvent, ether, ester, ketone, nitrile, amide, carbonate, alcohol, amine, sulfone, mixture thereof or combination thereof. Exemplary solvents may include diethyl ether, methy-t-butyl ether, tetrahydrofuran, <NUM>,<NUM>-dioxane, glyme, diglyme, triglyme, higher glymes, or mixtures thereof. The amount of solvent may be any useful amount for performing the method and may vary over a wide range. For example, the amount of solvent to liquid reactant by weight (solvent/liquid reactant) may vary from <NUM>, <NUM> or <NUM> to <NUM>, <NUM>, or <NUM>.

The gas reactant may also be present, mixed with or entrained in another gas. The gas reactant for example may be mixed with another gas such as an inert gas or nitrogen. In a particular embodiment, the reactant gas is carbon monoxide that is mixed with hydrogen such as in a commercial syngas, which may be used in the carbonylation of an epoxide, lactone or combination thereof as described in <CIT>.

In a particular embodiment of the method, the liquid reactant is an epoxide or lactone and carbon monoxide to form their corresponding carbonylation lactone, anhydride products. refers to a substituted or unsubstituted oxirane. Substituted oxiranes include monosubstituted oxiranes, disubstituted oxiranes, trisubstituted oxiranes, and tetrasubstituted oxiranes. Such epoxides may be further optionally substituted. In some embodiments, epoxides comprise a single oxirane moiety. In some embodiments, epoxides comprise two or more oxirane moieties. Lactone may be any lactone such as those produced when carbonylating the aforementioned epoxides. Examples of such epoxides and lactones include ethylene oxide, propylene oxide and their corresponding lactone carbonylation products beta propiolactone and beta butyrolactone. Examples of such lactones include beta propiolactone and beta butyrolactone and their corresponding carbonylation products succinic anhydride and methylsuccinic anhydride. Further examples of epoxides and lactones are in Table A (between paragraphs <NUM> and <NUM>) of <CIT>.

The following examples are provided to illustrate the method and reactor without limiting the scope of the invention. All parts and percentages are by weight unless otherwise noted. Table <NUM> shows the ingredients used in the Examples and Comparative Examples.

A lab scale hybrid bubble plug flow reactor <NUM> made of <NUM> stainless steel and tubular member <NUM> fabricated using a <NUM> inch diameter pipe that is <NUM> feet long having flanges at the top outlet <NUM> and bottom outlet <NUM> in a similar manner as depicted in <FIG>, except that the gas reactant inlet and liquid reactant inlet and drain were made using a two radial port bleed flange and a bottom drain valve <NUM>. The tubular member <NUM> is packed with PROPAK packing leaving about <NUM> inch head space <NUM>. The reactor has a <NUM> stainless strainer <NUM> (a pipe flange gasket with inlaid 316SS #<NUM> mesh available from Sealing Devices Inc) at the top of the bottom bleeder flange. A ¼" <NUM> stainless steel dip tube <NUM> is used to extract the effluent as described herein.

The reactor is preheated and maintained at the temperature shown in Table <NUM>. Ethylene oxide in tetrahydrofuran (THF) is injected into the reactor and CO is separately injected into the reactor as shown in Table <NUM> for each Example. Each Example is run over a period of hours ensuring that the reaction occurs over multiple residence times. The catalyst used is the same for each example. The catalyst is essentially the same as described in <CIT>. The effluent composition and concentrations are shown in Table <NUM>. The performance metrics of the reactor are shown in Table <NUM>. All concentrations are by mass unless indicated otherwise. No gas bubble accumulation is observed in any of the Examples.

Example <NUM> shows that an anhydride may be made in the reactor in one reactor. The other Examples display the wide variety of run conditions that may be used when reacting a liquid and gas reactant.

Example <NUM> is made using the same reactor as Examples <NUM>-<NUM> and run under the conditions shown in Table <NUM>. Comparative example <NUM> is made in a continuously stirred reactor under conditions having a substantially comparable residence time and reactor outlet beta propiolactone (bPL) concentration as Example <NUM>, which is also shown in Table <NUM>. From this, it is readily apparent that the reactor of the present invention has a much higher TON for a given residence time and bPL output than a continuously stirred reactor operating under similar conditions and product output. Surprisingly, the bPl output is equivalent using substantially less catalyst per mole of product produce and essentially the same residence time, which is reflected in the substantial increase in the TON on a unit time basis.

Claim 1:
A method of reacting a gas reactant and liquid reactant comprising:
(i) introducing the gas reactant and liquid reactant into a hybrid vertical bubble plug flow reactor, having a bottom inlet and a top outlet connected by a tubular member, separately at the bottom inlet, wherein the gas reactant and liquid reactant are mixed and introduced at a rate resulting in a molar ratio of gas reactant/liquid reactant that is in excess of a stoichiometric amount and the gas reactant forms bubbles within the liquid reactant, optionally:
wherein the liquid reactant is a gas at ambient conditions and the reactor is maintained at a pressure and temperature for the liquid reactant to be maintained as a liquid,
wherein the bubbles traverse the reactor at a speed, and wherein the liquid reactant traverse the reactor at a speed and the speed of the bubbles is the same or greater than the speed of the liquid reactant,
(ii) allowing the gas and liquid reactants to react and form a reaction product as they flow upwards through the hybrid vertical bubble plug flow reactor in the presence of a catalyst, and
(iii) removing the reaction product at the top outlet.