ISOMERIZATION OF ALKENYL BRIDGED RING COMPOUNDS TO ALKYLIDENE BRIDGED RING COMPOUNDS

Abstract: A process and catalyst for isomerizing olefins are disclosed. The process and catalyst are particularly useful for isomerizing alkenyl bridged ring compounds to the corresponding alkyladiene bridged ring compounds. The isomerization catalyst comprises an oxygen treated mixture of an alkali metal on a calcined support having a surface area of 125 to 195 m<2>/g. The catalyst is particularly useful for isomerizing 5-vinyl-2-norbornene to 5-ethylidiene-2-norbornene. The catalyst is very active and highly selective and resistant to catalyst poisons. The process contacts the catalyst with an alkenyl bridged ring compound and yields the corresponding alkyladiene bridged ring compound.

Description: ISOMERIZATION OF ALKENYL BRIDGED RING COMPOUNDS TO ALKYLIDENE BRIDGED RING COMPOUNDS BACKGROUND OF THE INVENTION 1. Field of the Invention This application is a continuation-in-part of application Seri No. 07/700,016 filed 5/14/91. The present invention relates to a process f isomerizing olefins, and particularly for isomerizing alkenyl bridged ri compounds to the corresponding alkylidene bridged ring compound by use of highly active and highly selective isomerization catalyst. The process of t invention may be used to isomerize 5-vinyl-2-norbornene (hereinafter "VNB") 5-ethylidene-2-norbornene (hereinafter "ENB"), which is used commercially in t production of elastomeric polymers and synthetic rubber. The process of t invention may also be used to isomerize a terminal olefin to an internal olef which may be used as a reactant in the synthesis of chemicals or as an alkylati feedstock to yield octane enhancing gasoline additives. The highly acti isomerization catalyst is prepared by adding an alkali metal to alumina and th activating the mixture by careful oxidation of the alkali metal. The present invention also relates to an isomerization catal wherein the alumina has a surface area ranging from 125 to 195 m 2 /g, and to catalyst which has been activated at a temperature above 55°C. 2. Description of the Prior Art — The isomerization of olefins is well-known. Olefins are oft isomerized to produce the type of olefin necessary for a chemical synthesis or a process for making fuels or fuel additives. For instance, the use of ENB a monomer in the production of rubbery polymers is well known. ENB may produced by reacting 1,3-butadiene and cyclopentadiene in an addition reacti commonly known as a Diels-Alder reaction, yielding VNB which is the catalytically isomerized to ENB. Known isomerization catalysts include liquid bases, such as mixtures of alkali metal hydroxides and aprotic organic solvents, mixtures of alkali metal amides and amines, and mixtures of organic alkali metal compounds and aliphatic amines. Unfortunately, the catalytic activity of the liquid bases is relatively low, and therefore a large amount of these expensive catalysts must be used. Also, recovery of the catalyst from the reaction mixture is very difficult, requires complicated separation and recovery steps and consumes a large amount of energy. Solid isomerization catalysts are also known, for example, alkali metals carried on large surface area anhydrous suppoπs such as activated carbon, silica gel, alumina and the like. These solid catalysts are difficult to handle because they may ignite and lose activity on contact with oxygen. Also, the - isomerization performance of these solid catalysts is poor, because conversion and selectivity are low. U.S. Patent 3,897,509 discloses that heating an alkali metal, an alkali metal hydroxide and alumina yields an alkali catalyst composition which is described to be stable on exposure to air and water and active in various chemical reactions. Particularly the catalyst is said to be useful in the isomerization of alkenyl bridged ring compounds to the corresponding alkylidene bridged ring compounds. Thus, it is useful for the production of alkylidene bridged ring compounds such as ENB which, as mentioned above, is valuable in the production of synthetic rubber. The preferred method of forming the catalyst of U.S. 3,897,509 is by heating and mixing an alkali metal, an alkali metal hydroxide and alumina at a temperature higher than the melting point of the alkali metal; however, the catalyst may also be prepared without the use of an alkali metal hydroxide if the starting alumina contains water. U.S. Patent 3,405,196 discloses a process in which a terminal olefin is converted to an internal olefin in the presence of a supported alkali-metal catalyst that has been pretreated with an oxygen containing gas such as nitrous oxide. The catalyst used contains an alkali metal dispersed on a high-surface area, substantially inert support. The alkali metal may be selected from sodium, potassium, rubidium and cesium. The desired catalyst support material is a high surface area, large pore, and slightly acidic alumina. The catalyst is primarily used to convert 1-pentene to 2-pentene and 1-butene to 2-butene and is not used to isomerize an alkenyl bridged ring compound to an alkylidene bridged ring compound. The prior art catalysts are either explosive or lack desirably high activities. These and other disadvantages of the prior art are overcome by the present invention, which provides a new selective and efficient catalyst for isomerization of olefins. SUMMARY OF THE INVENTION The present invention relates to a process and catalyst for isomerizing olefins, and particularly to isomerizing alkenyl bridged ring compounds to the corresponding alkylidene bridged ring compounds by use of a highly active and highly selective isomerization catalyst. In a preferred embodiment, the process of the invention is used for isomerizing 5-vinyl-2«norbornene an alkenyl bridged ring compound, to 5-ethylidene-2-norbornene, an alkylidene bridged ring compound, which is used commercially as the diene monomer in ethylene- propylene-diene monomer rubber (EPDM). The highly active isomerization catalyst is prepared by adding an alkali metal to a properly prepared calcined support material followed by careful oxidation of the alkali metal. Preferably, the calcined support material has a surface area of from 125 to 195 m 2 /g. The inventive process for isomerizing an alkenyl bridged rin compound to the corresponding alkylidene bridged ring compound comprise contacting the alkenyl bridged ring compound with an isomerization catalys comprising an alkali metal dispersed on a calcined support wherein th isomerization catalyst is treated with an oxygen containing gas before contact with the alkenyl bridged ring compound. One particular embodiment of the process for catalyticaUy isomerizing a chemical plant stream comprises contacting the stream comprising an alkenyl bridged ring compound with an activated catalyst- The activated catalyst is prepared by heating a support material to form a calcined support material, contacting the calcined support material with an alkali metal to form a catalyst precursor mixture of alkali metal and calcined support material, and contacting the catalyst precursor mixture with an activating gas. Another embodiment of the invention provides a catalyst which has been activated at a higher temperature than is known in the art. The activated catalyst is prepared by: (a) heating a support material to form a calcined support material; (b) contacting the calcined support material with an alkali metal to form a catalyst precursor mixture of alkali metal and calcined support material; and (c) contacting the catalyst precursor mixture with an activating gas at a temperature of from about 55° to about 300°C. The invention also includes an isomerization process utilizing the high temperature activated catalyst. This process for catalytically isomerizing an alkenyl bridged ring compound to the corresponding alkylidene bridged ring compound comprises: (a) preparing an isomerization catalyst by heating a support material to form a calcined support material, contacting the calcined support material with an alkali metal to form a catalyst precursor mixture of alkali metal and calcined support material, and contacting the catalyst precursor mixture with an activating gas at a temperature of from about 55°C to about 300°C to form an activated catalyst; and (b) contacting an alkenyl bridged ring compound with the activated catalyst. A feature of this invention is the high level of VNB conversion and the high selectivity to ENB. Another feature of this invention is the stability of the catalyst used to effect isomerization. An object of the invention is to provide an isomerization catalyst which combines high selectivity and conversion efficiency and yet remains non-explosive on contact with air or water. Accordingly, these and other features of this invention will become apparent from the following detailed description, wherein reference is made to the Figures in the accompanying drawings. IN THE DRAWINGS Figure 1 is an X-ray diffraction pattern for alumina. Figure 2 is an X-ray diffraction pattern for a catalyst made according to the invention. Figure 3 is an X-ray diffraction pattern for a catalyst made according to the prior art. Figure 4 is a graph showing the relationship between catalyst activity and the surface area of the support. Figure 5 is a graph showing the relationship between the amount of oxygen used to activate the catalyst and the activity of the catalyst. DETAILED DESCRIPTION OF THE INVENTION The isomerization of olefins described herein relates to th movement of the olefinic double bond from its initial position in the olefini molecule. It is often necessary to change the location of the double bond i order to provide the proper reactant for a desired chemical synthesis. F instance, linear alpha olefins such as 1-butene, 1-pentene, 1-hexene, 1-hepten and 1-octane may be isomerized to yield internal olefins such as 2-butene, pentene, 2-hexene, 3-hexene, 2-heptene, 3-heptene, 2-octene, 3-octene and octene. Additionally, branched alpha olefins such as 2-methyl-l-butene and 3 methyl- 1-pentene may be isomerized to 2-methyl-2-butene and 3-methyl-2-pentene respectively. Internal olefins and branched internal olefins may also b isomerized according to the invention which may be used to isomerize any olefi with three or more carbon atoms. The invention is particularly useful in the production of ENB fro VNB which may be produced by a Diels-Alder reaction. The Diels-Alde reaction is an additive reaction of an olefin with a conjugated diene. The Diels Alder reaction proceeds without a catalyst at temperatures ranging from abou 50° to 25(fC. Alkenyl bridged ring compounds may be produced by the Diels Alder reaction of cyclodienes with aliphatic dienes. VNB is produced by th Diels-Alder reaction of 1,3-butadiene with cyclopentadiene. The conditions necessary to bring about the Diels-Alder reaction of 1,3-butadiene with cyclopentadiene are well known in the art. In particular, butadiene may be contacted with cyclopentadiene in the liquid phase at temperatures of from 100° to 200°C and a pressure of from 150 to 300 lbs/square inch. It is not necessary to use a catalyst to advance the Diels-Alder reaction. The reaction is generally completed in 0.1 to 100 hours and is usually conducted under an inert atmosphere. Preferably, the reaction may be conducted in a liquid state, most preferably in a liquid-full reaction vessel -7- The preferred reaction occurs between 1.3-butadiene a cyclopentadiene, however, undesirable polymerization reactions may also occ For example, 1,3-butadiene monomers may react with other 1,3-butadie monomers to form polymers. Similar polymerization reactions may occur betwe cyclopentadiene monomers, and between 1,3-butadiene and cyclopentadie Certain compounds are known which suppress or inhibit the undesir polymerization reactions. Any one or combination of these inhibitor compou may be added to the reactants in order to produce more VNB from the sa amount of starting material and to avoid plugging certain parts of the reacti apparatus with the high molecular weight polymers which might otherwise formed. Many inhibitor compounds are known in the art includi 2,6-di-t-butyl-p -cresol, diphenylnitrosamine, and N-substituted p-phenylenediamin The reaction product mixture may be passed directly to t isomerization process, however, it is preferred to purify the reaction product order to yield a stream predominately containing VNB. The reaction prod stream may be purified by fractional distillation under increased pressu atmospheric pressure or preferably at reduced pressures. Extractive distillati techniques may also be used and some of the known extractive distillati solvents are acetonitrile, water, sulfolane and N-methylpyrrolidone (NMP). T reaction product may also be purified by extraction, extraction followed distillation, or crystallization. The Diels-Alder reaction product or preferably the purified VNB then isomerized in order to convert VNB to ENB. The VNB stream to isomerized may be 90% or more by volume VNB or the VNB stream may diluted with a solvent that is inert during the isomerization process. Appropri solvents include aliphatic compounds such as hexane, heptane, octane a isooctane, and aromatic compounds such as benzene, toluene, xylene a ethylbenzene. Many other solvents are acceptable and within the scope of t invention; however, certain types of compounds are isomerization catalyst pois and should not be used as solvents. These poisons include water, alcohols, acid compounds and conjugated diene compounds. The isomerization catalyst of the invention is comprised of an alkali metal on a calcined support material, the combination being further treated with a gas containing oxygen. The alkali metal may be selected from the group of lithium, sodium, potassium, rubidium, cesium and mixtures thereof. The alkali metal consists essentially of the metal in its elemental state, for example, if potassium is the alkali metal, it should be added as pure potassium and not in combination with another element, i.e., potassium hydroxide. Two or more alkali metals may be combined in the same catalyst. Sodium is the preferred alkali metal. The catalyst may be prepared by dispersing 1-40 wt% alkali metal on a calcined support material at temperatures of from 100-600°C under an atmosphere of dry, inert gas. The alkali metal dispersed on the support material is then subjected to oxidation by contact with a gas having an oxygen content of 0.1 to 25 mole% at temperatures of 0-300°C. The material of the support upon which the alkali metal should be dispersed may be any normally solid material which has large pores and a surface area ranging from 125 to 195 πr/g after calcination, but the support material may not be a hydrotalcite compound as described in U.S. Patent 4,675,307. The support material should remain in the solid state at the elevated temperatures required during calcination and alkali metal dispersion. Preferably, the support material has a surface area ranging from about 130 to 190 square meters per gram (m 2 /g) more preferably from about 140 to 180 m 2 /g and most preferably from about 150 to 180 m 2 /g. In fact, some surprisingly active catalysts have been prepared from support material with a surface area of about 170 m 2 /g. Catalysts with a surface area of about 180 m 2 /g are also good. Calcination, as described herein, at temperatures below 400°C does not significantly change the surface area of the support The surface area of the alumina is measured by the BET (Brunauer, Emmett, Teller) method of nitrogen adsorption and desorption. The pore size of the support material may range from about 5 1,000 Angstroms more preferably from 10 to 300 Angstroms and most preferab from 10 to 100 Angstroms. The support material used for preparing the cataly may be in powder, pelletized, or extruded form. The support material should calcined under a dry atmosphere, and it should be free of water and entrain oxygen after calcination. Alumina, silica, and oxides of metals of Groups 3A, 4A and 4B the Periodic Table may be used as the support material. The Periodic Tab referred to is the table as reproduced in the CRC Handbook of Chemistry a Physics, 53rd edition. Other examples of specific support materials inclu carbon, graphite, magnesia, titania, zirconia, calcium oxide, magnesium oxid sodium oxide and barium oxide. Alumina is the preferred support material a in a most preferred embodiment, the support material consists essentially alumina. Alumina consists of mostly A1 2 0 3 and small amounts of Na 2 0, Si0 2 a Fe 2 0 3 . The form of alumina utilized in the most preferred embodiment gamma alumina. The support should be calcined prior to contact with the alka metal. Calcination is effected by heating the support material at temperatur of from 100° to 1,000°C, more preferably from about 200° to about 800°C an most preferably from about 200° to about 400°C. The calcination may conducted at atmospheric pressure or higher, however, reduced pressures a preferred. Preferably an inert gas is purged through the calcination vessel order to sweep away any water or oxygen molecules which may be driven o from the support material by the heat. The calcination should last for fro about 0.1 to 100 hours preferably from about 1 to 20 hours. The heat calcination drives water from the support material, and provides an essentially d support material. After calcination, the support material should be kept und a dry atmosphere so that water does not become associated with the suppo material. SUBSTITUTE SHEET As mentioned above, calcination at temperatures below 400°C f less than 20 hours does not significantly change the surface area of alumin However, calcination at temperatures above 500°C may result in a decrease i the alumina surface area. In fact, high temperature calcination may be used t reduce the surface area of aluminas from values above 195 m 2 /g to values withi the desired range of 125-195 m 2 /g. For example, an alumina with a surface are of 240 m 2 /g may be calcined at 600°C for 1 to 2 days to yield an alumina wit a surface area of 170 πr/g. The catalytic combination of alkali metal and support material i prepared by first contacting the calcined support material with the alkali meta under a dry, inert, oxygen free atmosphere thus forming a catalyst precurso mixture. The alkali metal is preferably in the molten state during at least portion of the contact and the contact occurs by physically blending the calcine support material with the alkali metal under the dry, inert, oxygen fre atmosphere. In the most preferred embodiment, the catalyst precursor mixture consists essentially of the alkali metal and the support material. The alkali metal may be in the solid, liquid or gaseous state when initially contacted with the calcined support material. Usually, the initial contact occurs at a temperature of from about 0° to about 500°C, preferably from about 10° to about 40°C under an inert atmosphere. Gasses such as nitrogen, argon, helium and kiypton will provide an inert atmosphere. If the alkali metal is in the solid state when initially contacted with the support material, the temperature of the mixture should be raised enough to melt the alkali metal, and the mixture should be stirred for initial dispersion of the alkali metal on the support material. The resulting mixture is then heated to a temperature of from about 100° to about 600°C, preferably 100°C to 300°C, more preferably 120° to 200°C under constant agitation. The mixing agitation may be discontinued after the alkali metal is roughly dispersed on the support material, however, it is preferable to continue SUBSTITUTE SHEET mixing until the alkali metal is evenly distributed on the surface of the calcined support material. In the case of a mixture of sodium on alumina, a visual indication of a blue black or blue gray evenly distributed color over the surface of the alumina indicates uniform distribution of sodium. If large amounts o materials are to be mixed or slow mixing speeds are used, complete uniform dispersion will take longer, however, mixing is often complete within about two hours when a rotary mixer is used to produce 100 grams of catalyst. The amount of alkali metal which should be distributed upon the calcined support material is in the range of from about 1 to about 40 wt% based upon the total weight of the mixture comprising both alkali metal and calcined support material. Preferably the range of alkali metal is from about 5 to about 20 wt% and most preferably from about 10 to about 15 wt%. After the alkali metal has been dispersed upon the calcined suppor material to form a catalyst precursor mixture, the mixture should be contacted with an activating gas containing oxygen. Since a violent reaction between the alkali metal and oxygen will occur if oxygen is added too quickly, care should be taken to avoid exposing the mixture to excessive oxygen initially. If the temperature of the mixture exceeds about 300°C during the activation, the rate of oxygen contact with the mixture should be reduced. The rate of oxygen contact may be reduced by lowering the flow rate of oxygen containing gas or by reducing the concentration of oxygen in the oxygen containing gas. Some inert gas flow should be maintained in order to reduce the temperature of the catalyst mixture to a safe level. Alternatively, pure oxygen at reduced pressure may be used as the activating gas. In one embodiment of the invention, the catalyst mixture is contacted with the activating gas at a temperature within the range of from abou 0° to about 300°C preferably about 20° to 150°C and most preferably about 25 to about 50°C. The catalyst mixture may be agitated while the contact with th activating gas occurs. In another embodiment of the invention, the catalyst mixture is contacted with the activating gas at high temperatures. Typically, t temperatures should be about 55° to about 300°C, preferably about 65° to abo 300°C and most preferably about 100° to about 300°C. The activating gas may comprise a single type of gaseous compou containing oxygen or a mixture of an inert gas with another gas containi oxygen. Examples of activating gases include nitric oxide, nitrous oxide, sulf dioxide, dry air, ozone, and mixtures of oxygen with nitrogen, helium, argo krypton, xenon, or radon. Mixtures of these gases or mixtures may also be use In a preferred embodiment a mixture of oxygen (0 2 ) in nitrogen (N 2 ) may b used as the activating gas. The amount of oxygen in the activating gas shoul be from about 0.1 to about 25 mole %. Preferably the amount of oxygen in th activating gas mixture is from about 2 to about 10 mole % and most preferabl about 5 mole Ψc. If pure oxygen (100 mole % 0 2 ) is used as the activating ga the pressure should be reduced to between about 0.001 and 0.25 atmosphere. If oxygen is only part of an oxygen containing molecule, such as N or NO j , the oxygen content of the gas is calculated by dividing the atomic weigh of oxygen in the molecule by the molecular weight of the gas. The contact between the oxygen containing gas and the mixture ma be continued until all of the alkali metal has been oxidized; however, it i preferable to stop the contact when the total contact oxygen to alkali meta atomic ratio is within the range of from about 0.005 to about 1.0 moles o oxygen per atom of alkali metal. Preferably the ratio is within the range of fro about 0.01 to 0.2, more preferably 0.03 to 0.18 and most preferably 0.05 to 0.1 moles of oxygen per atom of alkali metal. These ranges reflect the total mole of oxygen contacted with the alkali metal. At these ranges most, usually all, o the oxygen contacted with the alkali metal reacts with the alkali metal. This i apparent in Figure 5 where contact of more than 0.5 moles of oxygen per ato of sodium does not result in further change in catalyst activity. The catalyst prepared as described above is then used to isomeri olefins. For example, the catalyst may be used to isomerize alkenyl bridged ri compounds, such as VNB, to alkylidene bridged ring compounds, such as EN Alkenyl bridged ring compounds are of the general formula (I): 5 wherein R\R 2 and R 3 are each hydrogen or alkyl having 1 to 8 carbon ato R 4 is hydrogen or alkyl having 1 to 4 carbon atoms, and n is 1 or 2 and where a double bond may be present at the place between the 2- and 3-positions indicated by the dotted line. Specific examples of some alkenyl bridged ring compounds are: 10 5-vinylbicyclo[2,2,l]heptane; 5-(l '-propenyl)-bicyclo[2,2,l]heptane; 5-(r-butenyl)-bicyclo[2,2,l]heptane; 5-isopropenylbicyclo[2,2,l]heptane; 5-(2 '-methyl- 1 '-propenyl)bicyclo[2,2, ljheptane; _ - 6-methyl-5vinylbicyclo[2,2, ljheptane; 6-methyl-5-isopropenyl[bicyclo[2,2,l]heptane; 6 _thyl-5-vinylbicyclo[2,2, ljheptane; 5-vinylbicyclo[2,2, 1 Jhepta-2-ene; 5-(l '-propenyl)-bicyclo[2,2,lJhepta-2-ene; 20 5-(l '-butenyl)-bicyclo[2,2,lJhepta-2-ene; 5-isopropenylbicyclo[2,2,lJhepta-2-ene; 5-(2'-methyl-l-propenyl)-bicyclo[2,2,lJhepta-2-ene; 5-(l '-octenyl)-bicyclo[2,2,l]hepta-2-ene; 6-methyl-5-vinylbicyclo[2,2,l]hepta-2-ene: 6-methyl-5-isopropenylbicyclo[2,2,lJhepta-2 -ene; 6-ethyl _-vinylbicyclo[2,2,l]hepta-2-ene; 5-vinylbicyclo[2,2,l]octane; 5-( 1' -propenyl )-bicyclo[2,2,2]octane; 5-isopropenylbicyclo[2,2,2]octane; 5-(l'-butenyl)-bicyclo[2,2,2Joctane; 6-methyl-5-vinylbicyclo[2,2,2]octane; 6-methyl-5-isopropenylbicyclo[2,2,2]octane; 5-vinylbicyclo[2,2,2]octane; 5-(l '-propenyl)-bicyclo[2,2,2]octa-2-ene; 5-isopropenylbicyclo[2,2,2]octa-2-ene; 5-(l '-butenyl)-bicyclo[2,2,2Jocta-2-ene; 5-(2'-methyl-l '-propenyl) __cyclo[2,2,2]octa-2-ene; 6-methyl-5-vinylbicyclo[2,2,2]octa-2-ene; and 6-methyl-5-isopropenylbicyclo[2,2,2Jocta-2-ene. The compounds represented by formula I can be produced by subjecting a cyclic diene such as cyclopentadiene or cyclohexadiene and an aliphatic 1,3-diene to a Diels-Alder reaction or by subjecting the corresponding bridged ring compound bearing a hydroxyl group at the 1'- or 2 ' - position to dehydration. Isomerization of an alkenyl bridged ring compound shifts the double bond from r -2' position to the 5-1 ' position of formula I thereby forming the alkylidene bridged ring compound. The isomerization is effected by contacting an alkenyl bridged ring compound, for example, a VNB stream, with the catalyst at temperatures of from about -50° to about 200°G Preferred temperatures of isomerization range from about 0° to about 150°C most preferably from about 20° to about 100°C; however, a temperature of at least 80°, preferably about 100°C provides unique advantages if the VNB is contaminated with catalyst SUBSTITUTE SHEE poisons such as cyclopentadiene. The high temperature isomerization embodime of the invention is particularly useful for isomerizing chemical plant strea comprising a substantial amount of alkenyl bridged ring compounds, but furth comprising isomerization catalyst poisoning compounds. This is because of th surprising and unexpected discovery that this particular catalyst is resistant t catalyst poisons. The catalyst is especially effective at higher temperatur isomerization conditions. The amount of catalyst used is not critical although the use of mor catalyst will reduce the time necessary to bring about a given level of conversio at the same temperature. Generally, the weight of alkali metal utilized pe weight of alkenyl bridged ring compound ranges from 1 part alkali metal pe 10,000 parts of alkenyl bridged ring compound to 1 part alkali metal per 50 parts of alkenyl bridged ring compound. In fixed bed processes, the weigh average space velocity expressed in terms of weight of feed per hour divided b the weight of the supported catalyst in the fixed bed should range between 0. to 500 Hr 1 . The isomerization process may be conducted at any pressur however, pressures of from about 0 to about 100 psig are preferred. Th reaction may be conducted in liquid phase or gas phase. Reaction time varie depending on the reaction temperature, and the amount of catalyst used, b generally ranges from 5 minutes to 6 hours. The isomerization reaction i generally conducted in the absence of oxygen and water. Use of the above described catalyst of the invention in th isomerization of VNB to ENB usually results in nearly complete conversion t ENB and therefore no product purification is necessary. The resulting ENB ma be transferred directly to a polymerization process to make EPDM rubber. If fo some reason the conversion rates are lower, the ENB may be purified of VN by distillation. SUBSTITUTE SHEET Although the isomerization of VNB to ENB has been described in more detail, the catalyst is also useful in the isomerization of olefins in general in the same way as described in reference to VNB isomerization. Conversion percentages herein are determined by subtracting the weight amount of compound 5 remaining after isomerization from the beginning amount of the compound and dividing the result by the beginning amount of the compound. The resulting quotient is multiplied by 100% to express the term in percent. Selectivity is determined by dividing the amount of material converted into desired product by the total amount of material converted and multiplying the result by 100%. 0 Particular aspects of the invention may be further understood by reference to the examples below. While these examples are provided to fully illustrate and describe specific features of the invention, they should not be construed as limitations on the scope of the invention, which is fully described above. 5 Example 1 This example demonstrates a method of preparing a catalyst according to the invention. The following procedures were conducted in a N 2 dry-box. Fifteen grams of calcined, 50/100 mesh alumina powder and 1.5g of fresh -cut sodium (65.2 mg-atom) were placed in a 300 mL 3-neck flask equipped o with a stir shaft with a glass paddle, a "Y'-adapter, a hose nipple, a gas addition tube, and a stopper. The flask was subjected to a vacuum for 30 minutes, and then the flask was filled with nitrogen. The flask was taken from the dry-box, and filled with dry nitrogen. The contents were stirred, and heated with an electric heating mantle to a skin temperature of 400°C for 2 hours to form an 3 evenly dispersed mixture of sodium on alumina. Afterwards, the skin temperature was reduced to 150°C, and an activating gas of 5% 0 2 and 95% N 2 was added at 0.07 IJmin via the gas addition tube. The activating gas addition continued for 90 min with good stirring. The resulting catalyst was then allowed to cool to room temperature under a N 2 atmosphere. Two grams of the catalyst prepared as noted above were placed al at once into a vessel containing water. There was no indication of gas evolutio or any strong exothermic reaction. Example 2 This example demonstrates isomerization of VNB to ENB at lo temperatures according to one embodiment of the invention. In a N 2 dry-box 25g of VNB (208 mmole) and 2g decane were placed into a 50 mL Erlenmeye flask equipped with a teflon coated spin-bar. Then, 0.5g of the catalyst prepare according to Example 1 was added, and the mixture was stirred vigorously a room temperature. After 3 hours, the VNB conversion was 99.6% and th selectivity to ENB was 99.7%. Example 3 This example demonstrates isomerization of VNB to ENB a relatively high temperatures according to one embodiment of the invention Under nitrogen, 50g of dry VNB (417 mmole) and 5g of decane, as a G standard, were placed into a 300 mL round-bottomed flask equipped with paddle stirrer. The VNB mixture was heated to 120°C, and l.Og of catalys prepared according to Example 1 was added while vigorous stirring wa maintained. After 60 minutes, the VNB conversion was 98%, and the selectivi to ENB was 99.7%. Example 4 This example illustrates a high temperature activation of the catalyst Fifteen grams of alumina powder with a surface area of 90 m 2 /g was calcine for one hour at 500°C under a nitrogen atmosphere. The calcined alumina wa then cooled to room temperature and subjected to a vacuum for 30 minutes an thereafter blanketed with nitrogen. 1.5g of sodium was added to the calcine SUBSTITUTE SHEET alu ina, and the mixture was heated at a rate of 6°C/min with stirring until a temperature of 400°C was reached. The stirring of the mixture continued while the temperature of the mixture was held at 400°C for one hour. After the mixture cooled to a temperature of 150°C, an activating gas comprising 5% 0 2 and 95% N, by volume was passed through the mixture for 90 minutes at a rate of 0.07L/min. Example 5 X-ray diffraction patterns for three solids were measured and are compared in the Figures 1-3. The X-ray diffraction pattern for the raw alumina from Example 4 is represented by Figure 1. The X-ray diffraction pattern for the sodium catalyst made according to Example 4 is represented at Figure 2. The X-ray diffraction pattern for a catalyst made according to U.S. Patent 3,928,485 using the same alumina used in Example 4 is represented by Figure 3. The catalyst made according to U.S. 3,928,485 was prepared as follows. Fifteen grams of dried alumina and 1.5g NaOH were ground together, and then mixed under nitrogen for 2 hours at a temperature of 330°C. The temperature was then lowered to 90°C and 0.83g of sodium was added to the mixture. Thereafter the mixture was stirred and heated to a temperature of 400°C. Stirring continued for 2 hours while the temperature was maintained at 400°C. Example 6 This example demonstrates isomerization in the presence of an isomerization catalyst poison. 0.25g of a catalyst made according to Example 1 was stirred at 120°C with 25g of VNB which contained 0.03% cyclopentadiene, a known isomerization catatyst poison. After one hour of stirring, 60% of the VNB had been converted and all of the cyclopentadiene had been converted. SUBSTITUTE SHEET 4.0g of a catalyst prepared in accordance with Example 1 was stirre at 25°C with 200g VNB which contained 0.06% cyclopentadiene. After one hou of stirring, the cyclopentadiene concentration was reduced to 0.03% and the VN conversion was 10%. This example shows that the negative effects o cyclopentadiene are less pronounced at higher temperature isomerization. Th example also shows that the cyclopentadiene may be removed by the highe temperature isomerization reaction. Example 7 This example demonstrates the extra safety of using an activate catalyst. An alumina with a surface area of 210 πr/g was calcined at 400°C fo one hour and then held under a vacuum at 200°C for one hour. 4.5g of sodiu metal was added to two separate 30g portions of the calcined alumina. Th resulting mixtures were stirred at 210°C for one hour after which the temperatur was increased to 410°C and mixing continued for one more hour. The mixture were then cooled to room temperature. The first portion was contacted wit water resulting in a very violent exothermic reaction. The second portion wa first treated with an activating gas of 5 volume % O 2 and 95 volume % N 2 . Th second activated catalyst portion was treated with water in a manner similar t the first portion but only a very mild exothermic reaction resulted. Example 8 This example demonstrates that the activated catalyst has superio resistance to catalyst poisons. The activating gas treated catalyst prepare according to Example 7 was stirred for one hour at 25°C in a solution of VN with 0.06% cyclopentadiene. The amount of catalyst used was 4 wt% of the tota weight of the solution and the conversion of VNB was 40%. When the sam amount of catalyst prepared according to Example 7 without the activating ga treatment was similarly contacted with the same solution of VNB wit cyclopentadiene, the conversion of VNB was 25%. SUBSTITUTE SHEET Example 9 This example demonstrates that the activated catalyst has an activi equivalent to a more dangerous non-activated catalyst. The activated and non activated catalysts prepared in Example 7 were contacted with purified VNB For each contact, 2 wt% of catalyst was used based on the weight of purifie VNB. The conversions after one hour were 52% for the activated catalyst an 58% for the non-activated catalyst. Example 10 This example demonstrates the reactivity of sodium on alumina with water. Sodium materials are difficult to handle because of their explosive reactivity with air and water and therefore require special care in shipping and processing. Twenty grams of alumina powder and 3 grams of Na (0.13 gram- atom) were mixed at 300°C for 1 hour under a nitrogen atmosphere. The mixture was cooled, and then carefully mixed with kerosene. Addition of water to this slurry set off an exothermic reaction that was accompanied by evolution of large quantities of gas from the mixture. Example 11 This example demonstrates various catalysts prepared on alumina with different surface areas. For each catalyst prepared, the alumina was calcined at 400°C in air for 1 hour. Thereafter, the air was removed and the temperature reduced to 200°C. The alumina was maintained under vacuum at 200°C for 1 hour. Thirty grams of the alumina prepared as noted above were then mixed with 4.5 g of sodium under a nitrogen atmosphere at 210°C. The mixing continued for 1 hour after which the temperature was increased to 410°C. SUBSTITUTE SHEET Mixing continued at 410°C for 1 more hour under the nitrogen atmospher resulting in an evenly distributed mixture of sodium on alumina. The mixture was cooled to room temperature (25°C) and the contacted with a gas consisting of 5% oxygen and 95% nitrogen. The gas flo rate was maintained at 126 mL/min while the mixture was continuously stirre for 152 minutes. VNB was contacted with 2 wt% of the catalyst prepared as note above. The VNB/catalyst solution was stirred at room temperature for 1 hou A sample of the resulting solution was taken and the conversion of VNB wa measured. The 11-A alumina was supplied as AL-0171P by Engelhard and ha a surface area of 210 m 2 /g. The VNB conversion for 11-A was 55%. The 11- alumina was supplied by Engelhard designated AL-1040P and had a surface are of 172 m 2 /g. The VNB conversion for 11-B was 99.8%. The 11-C alumina wa supplied by Engelhard as AL-3916P and had a surface area of 155 m 2 /g. Th conversion level for 11-C was 99.8%. Example 12 Figure 4 shows the activity rate constant for the isomerization o VNB to ENB at room temperature over catalysts prepared according to th invention. The surface area of the alumina support material used to prepare th catalysts varied from less than 10 square meters per gram to more than 225 m 2 / before calcination, as indicated by the horizontal axis of Figure 4. The activi rate constant was calculated according to the following formula: [ln(VNB VNB f )] ÷ [(catalyst wt% Na)(reaction time in hours)J, where VNB ; i the initial concentration of VNB, and VNB f is the concentration of VNB at th designated reaction time. The figure clearly shows that when alumina suppo material is selected to have a surface area within the range of 125-195 m 2 /g, th SUBSTITUTE SHEET activity of the catalyst for this reaction can be significantly improved ove activities of catalysts outside of the desired surface area range. More preferabl the surface area of the alumina should be between 130 and 190 m 2 /g, 140 to 18 nr/g and most preferably 150 to 180 m 2 / g. The most active catalyst is prepare from alumina with a surface area of about 170 m /g. Example 13 This example shows the preparation of a catalyst from an alumin support with a surface area outside of the preferred range. Alumina powde (30g) having a surface area of 200 πr/g was placed in a round bottom flask under a nitrogen blanket at room temperature along with 4.5g sodium meta which had been cut into small pieces. The mixture inside the round bottom flask was stirred and heated to 150°C for 30 minutes. The sodium metal disperse onto the alumina resulting in a blue-gray powder. That mixture was then heated to a temperature of 300°C and stirring was continued for 60 minutes. The sodium/alumina mixture was cooled to room temperature after which, a gaseous stream of 5% O 2 in N 2 was passed through the flask at a rate of 126 mL/min until the molar ratio of 0 2 to the initial amount of Na was 0.2:1. Analysis of the catalyst showed that 6 wt% of the initial amount of Na remained unreacted with 0 2 . The activity rate constant of this catalyst for isomerization of VNB to ENB at room temperature was measured as 31. Example 14 This example describes the preparation of a catalyst from alumina support material that had a surface area within the preferred range. The catalyst was prepared following the same procedure as outlined in Example 13, except that the alumina had a surface area of 136 m 2 /g. Analysis of the catalyst showed that 25 wt% of the initial Na remained unoxidized. The activity rate constant SUBSTITUTE SHEE of this catalyst for the isomerization of VNB to ENB at room temperature was measured as 52. Example 15 This example describes the results achieved using a catalyst prepare from an alumina within the preferred range of surface area. The catalyst was prepared according to the same procedure as outlined in Example 13 except that the alumina support material had a surface area of 178 m 2 /g. Analysis of the catalyst prepared showed that 5 wt% of the initial Na remained unoxidized. The activity rate constant of this catalyst for the isomerization of VNB to ENB at room temperature was 87. Example 16 This example shows the preparation and activity of a catalyst within the most preferred range of alumina surface area. The catalyst was prepared according to the same procedure outlined in Example 13 except that the alumina had a surface area of 170 πr/g. Analysis of the resulting catalyst showed that 19 wt% of the initial Na metal remained unoxidized. The activity rate constant of this catalyst for the isomerization of VNB to ENB at room temperature was measured as 158. Example 17 This example describes the preparation of a catalyst at a lower maximum dispersion temperature than was used in Examples 12-16. Alumina powder (30g) with a surface area of 178 m 2 /g, and 4.5g Na metal, cut into pieces, were placed in a round bottom flask under a nitrogen atmosphere at room temperature. The mixture was stirred and heated to a temperature of 150°C for 30 minutes. After this step the sodium was dispersed on the alumina yielding a blue-gray powder. The temperature of the mixture was maintained at 150°C for SUBSTITUTE SHEET an additional 60 minutes with continuous stirring. After that, the mixture was cooled to room temperature. A stream of nitrogen containing 5 wt% voI% 0 2 was passed through the flask at a rate of 126 mUmin until the or molar ratio of 0 2 to initial Na was 0.2:1. Analysis of the resulting catalyst showed that 11 wt% of the initial sodium remained unoxidized. The activity rate constant of this catalyst for isomerization of VNB to ENB at room temperature was measured as 189. The activity rate constant of the catalyst of this Example 17 is much higher than the 87 reported for the same catalyst prepared at a higher mixing temperature of 300°C as in Example 15. This Example 17 indicates that mixing at a lower temperature of 150°C improves the activity of the finished catalyst by a factor of 2.17 compared to a catalyst prepared with mixing at 300°C. Example 18 The steps described in Example 17 were repeated except that the mixing temperature was maintained at 220°C instead of 150°C in the second step described above. Analysis of the resulting catalyst showed that 12 wt% of the initial sodium remained unoxidized. The activity rate constant of this catalyst for isomerization of VNB to ENB at room temperature was measured as 285. Comparison of the results from Examples 15, 17 and 18 show that there is an optimum temperature for performing the mixing of sodium with alumina. The following Table 1 indicates the differences obtained. Table 1 Example 19 This example shows the preparation of a catalyst prepared from a alumina with a surface area outside of the preferred range. Alumina powde (30g) with a surface area of 200 m 2 /g and 4.5g sodium metal, cut into pieces, o placed into a round bottom flask under a nitrogen atmosphere at roo temperature. The mixture was stirred and heated to 150°C for 30 minutes During this step, the sodium metal was dispersed onto the alumina resulting i a bluish-gray powder. The stirring was continued while the temperature wa maintained at 150°C for 60 minutes. The mixture was then cooled to roo temperature. A gaseous stream of nitrogen containing 5 mol % oxygen wa passed through the round bottom flask at a rate of 126 mL min until the mola ratio of 0 2 to initial sodium was 0.2:1. The activity rate constant for this catalyst for isomerization of VNB to ENB at room temperature was measured as 15. Comparison of the results from this Example 19 with the results o Example 12 shows that the temperature of mixing sodium and alumina leads t different catalytic activity even for catalysts with surface areas outside of th ranges preferred in the invention. Example 20 This example shows the preferred amounts of 0 2 added to a catalys during catalyst preparation. Figure 5 graphically shows the relationship betwee the activity rate constant and the ratio of 0 2 to initial sodium. In each of four separate preparations of catalysts, 30 g alumi powder with a surface area of 178 πr/g, and 4.5 g sodium metal, cut into piec were placed in a round bottom flask under a nitrogen atmosphere at roo temperature. The mixture was stirred and heated to a temperature of 150°C f 30 minutes. After 30 minutes, the sodium metal was dispersed onto the alumi and the powder had changed in color to bluish-gray. The temperature of t mixture was then raised to 300°C for 60 minutes while stirring continued. T mixture was then cooled to room temperature. A nitrogen stream containing vol % oxygen was then passed through the flask at 126 mL min until the rati of O, to initial sodium was 0.1:1. The catalyst preparation was repeated exce that the nitrogen stream containing 5 vol % O, was passed through the flask unt the ratio of 0 2 to initial sodium was 0.2:1. A third catalyst was prepared in similar manner so that the ratio of 0 2 to initial sodium was 0.5:1. A fourt catalyst was prepared in the same manner except that no oxygen was added t the mixture of sodium dispersed on alumina. The results of an analytical test t determine the amount of unreacted sodium on the catalyst is set forth below i Table 2. Table 2 The isomerization activity of the four catalyst prepared above was measured and is set forth in Figure 5. These results show that the most preferred ratio of 0 2 to sodium is 0.1:1. As can be seen from the conversion levels above, the alumina wit a surface area of about 180 m 2 /g performed better than aluminas with surfac areas of either 155 or 210 m 2 /g. Aluminas with surface areas of about 170 πr/ are most preferred. The examples set forth above illustrate aspects of the invention an are not limitations on the scope of the invention which is set forth in the claim below. Many other variations and modifications may be made to the process an catalyst described above without departing from the concept of the prese invention. Accordingly, it should be clearly understood that the methods referre to in the foregoing description are illustrative only and are not intended a limitations on the scope of the invention. SUBSTITUTE SHEET

Claims: Claims: 1. A process for isomerizing an olefin comprising contacting the olefin with an isomerization catalyst which comprises an alkali metal dispersed on a calcined support having a surface area of 125 to 195 m 2 /g wherein the isomerization catatyst is activated with an oxygen containing gas before contact with the alkenyl bridged ring compound. 2. A process in accordance with Claim 1 wherein the support consists essentially of alumina. 3. A process in accordance with Claim 2 wherein the alkali metal is sodium. 4. A process in accordance with Claim 3 wherein the calcined support has a surface area of 140 to 180 m 2 /g. 5. A process in accordance with Claim 4 wherein the oxygen containing gas is a mixture of oxygen and nitrogen and wherein the olefin is an alkenyl bridged ring compound. 6. A process in accordance with Claim 5 wherein the alkenyl bridged ring compound is 5-vinyl-2-norbornene. 7. A process in accordance with Claim 5 wherein the temperature at which the sodium is dispersed on the calcined support is 100°C to 300°C. 8. A process in accordance with Clai 5 wherein the ratio of total moles of activating oxygen to total atoms of sodium is in the range of 0.005:1 to 1:1. 9. A process for catatyticaily isomerizing a stream comprising an alkenyl bridged ring compound which comprises contacting the stream comprising an alkenyl bridged ring compound with an activated catalyst, wherein the activated SUBSTITUTE SHEET catalyst is prepared by heating a support material having a surface area of 125 195 πr/g to form a calcined support material, contacting the calcined suppo material with an alkali metal to form a catalyst precursor mixture of alkali met and calcined support material, and contacting the catalyst precursor mixture wit an activating gas. 10. A process in accordance with Claim 9 wherein the support material consist essentially of alumina. 11. A process in accordance with Claim 10 wherein the alkali metal is sodium 12. A process in accordance with Claim 11 wherein the sodium is contacte with the activated alumina at temperatures of from about 100 to about 300° and mixed to form a uniform dispersion of sodium on alumina. 13. A process in accordance with Claim 12 wherein the catalyst precurso mixture is contacted with an activating gas at temperatures of from about 20 t about 150°C wherein the activating gas is a mixture of oxygen and nitrogen. 14. A process in accordance with Claim 13 wherein the alkenyl bridged rin compound is 5-vinyl-2-norbornene and the contact between the stream comprisin an alkenyl bridged ring compound and the activated catalyst occurs at temperature of about 100°C. 15. A process in accordance with Claim 14 wherein the stream comprising a alkenyl bridged ring compound further comprises an isomerization catalyst poiso 16. A process in accordance with Claim 10 wherein the contact between th stream comprising an alkenyl bridged ring compound and the activated catalys occurs at a temperature from about 20° to about 100°C. 17. A process for catalyticaUy isomerizing an alkenyl bridged ring compound to the corresponding alkyladiene bridged ring compound which comprises: (a) preparing an isomerization catalyst by heating a support material to form a calcined support material having a surface area of 125 to 195 πr/g, contacting the calcined support material with an alkali metal to form a catalyst precursor mixture of alkali metal and calcined support material, and contacting the catalyst precursor mixture with an activating gas at a temperature of from about 55°C to about 300°C to form an activated catalyst; and (b) contacting an alkenyl bridged ring compound with the activated catalyst. 18. A process in accordance with Claim 17 wherein the catalyst precursor mixture is contacted with the activating gas at a temperature of from about 100° to about 300°C. 19. A process in accordance with Claim 18 wherein the support material consists essentially of alumina. 20. A process in accordance with Claim 19 wherein the alkali metal is selected from sodium, potassium, cesium and mixtures thereof. 21. A process in accordance with Claim 20 wherein the contact between the activated catalyst and the alkenyl bridged ring compound occurs at a temperature of about 100°C. 22. A process in accordance with Claim 21 wherein the alkenyl bridged ring compound is 5-vinyl-2-norbornene. 23. A process in accordance with Claim 22 wherein the activating gas comprises nitrogen and from about 2 to about 10 mole percent oxygen. 24. An activated catalyst prepared by: (a) heating a support material to form a calcined support material having a surface area of 125 to 195 nr/g; (b) contacting the calcined support material with an alkali metal to form a catalyst precursor mixture of alkali metal and calcined support material; and (c) contacting the mixture with an oxygen containing activating gas. 25. An activated catalyst prepared according to Claim 24 wherein the contact of the catalyst precursor mixture with the activating gas occurs at a temperature of from about 55°C to about 300°C. 26. An activated catalyst prepared according to Claim 25 wherein the support material consists essentially of alumina. 27. An activated catalyst prepared according to Claim 26 wherein the contact between catalyst precursor mixture and the activating gas occurs at a temperature of 100°C to 300°C. SUBSTITUTE SHEET

Inventors: SMITH ROBERT SCOTT, SMITH, ROBERT, SCOTT
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1992
Main classification: B01J23
IPC codes: B01J23, C07B61, C07C5, C07C13