Process for the hydrogenation of MDA

Abstract

A process for continuous heterogeneous catalytic hydrogenation of MDA. The process occurs in a reactor cascade including n serially connected reaction spaces, R.sub.i, that are each filled with catalyst and can be filled or emptied independently of one another where 1in, in the order in which they are connected. R.sub.1 is temporarily disconnected from the cascade as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree. The reconfigured reactor cascade R.sub.i, includes i reaction spaces where 1i(n1), in the order in which they are connected. Each reaction space R.sub.i where 2in becomes a reaction space R.sub.i where 1i(n1). The catalyst in R.sub.1 is replaced and/or regenerated and R.sub.1 is subsequently connected as reaction space R.sub.i where i=n.

Claims

1. Process for the continuous heterogeneous catalytic hydrogenation of MDA, characterized in that a) the process is carried out in a reactor cascade comprising n serially connected reaction spaces that are each filled with catalyst and can be filled or emptied independently of one another, which are respectively given the designation R.sub.i, where 1in, in the order in which they are connected, b) and R.sub.1 is temporarily disconnected from the cascade as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree, resulting in a reconfigured reactor cascade comprising i reaction spaces, which are given the designation R.sub.i, where 1i(n1), in the order in which they are connected, wherein each reaction space R.sub.i where 2in becomes a reaction space R.sub.i where 1i(n1), c) the catalyst in R.sub.1 is replaced and/or regenerated and d) R.sub.1 is subsequently connected as reaction space R.sub.i where i=n.

2. Process according to claim 1, characterized in that the MDA used comprises at least 70% by weight of 4,4-diaminodiphenylmethane and 0.01% to 2% by weight of N-methyl compounds, in each case based on the total mass of compounds having aromatic rings.

3. Process according to claim 1, characterized in that the process is a fixed-bed process for continuous catalytic hydrogenation.

4. Process according to claim 1, characterized in that the catalyst is a supported catalyst.

5. Process according to claim 4, characterized in that the catalyst contains, applied on a support, active metal in an amount of 0.01% to 20% by weight based on the supported catalyst, and the active metal thereof is ruthenium alone or ruthenium and at least one metal of subgroups I, VII or VIII [groups 7-11] of the periodic table of the elements.

6. Process according to claim 1, characterized in that each reaction space R.sub.i consists of x parallel-connected subreactors where x=1 to 250 that are spatially separated by catalyst-free plant components from one another and from the other reaction spaces.

7. Process according to claim lany of the preceding claims, characterized in that the catalytic hydrogenation of MDA in the reactor cascade takes place essentially isothermally.

8. Process according to claim 1, characterized in that the point at which an undesirable degree of deactivation is reached is determined by monitoring the activity of the catalyst in R.sub.1 while in operation and comparing this with the initial catalyst activity.

9. Process according to claim 8, characterized in that the normalized activity of the catalyst present in R.sub.1 is determined and R.sub.1 is temporarily disconnected from the cascade as soon as the normalized activity of the catalyst present in R.sub.1 falls below a defined value.

10. Process according to claim 9, characterized in that the normalized activity of the catalyst present in R.sub.1 is less than 0.7.

11. Process according to claim 1, characterized in that the hydrogenation is continued during the replacement or regeneration of the catalyst.

12. Process according to claim 1, characterized in that a) the process is carried out in a reactor cascade comprising two serially connected reaction spaces that are each filled with catalyst and can be filled or emptied independently of one another, which are respectively given the designation R.sub.1 and R.sub.2 in the order in which they are connected, b) and R.sub.1 is temporarily disconnected from the cascade as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree, so that the reaction is carried out only in R.sub.2, wherein R.sub.2 is from then on designated reaction space R.sub.1, c) the catalyst in R.sub.1 is replaced and/or regenerated and R.sub.1 is subsequently connected as reaction space R.sub.2.

13. Process according to claim 1, characterized in that the reaction in the reactor cascade is followed by a reaction in a finisher.

14. Process according to claim 13, characterized in that the reaction is carried out essentially isothermally in the reactor cascade and essentially adiabatically in the finisher.

Description

Process for the Hydrogenation of MDA

[0046] The process of the invention is a process for the hydrogenation of MDA. MDA is an acronym for methylenedianiline and refers to a diaminodiphenylmethane-containing composition. It usually originates from the reaction of aniline and formaldehyde. The employed diaminodiphenylmethane-containing composition preferably comprises 4,4-diaminodiphenylmethane as its principal constituent or consists thereof. Further preferably, the employed diaminodiphenylmethane-containing composition comprises 4,4-diaminodiphenylmethane as its principal constituent and 2,4-diaminodiphenylmethane and 2,2-diaminodiphenylmethane as secondary constituents. However, in addition to 4,4-diaminodiphenylmethane, 2,4-diaminodiphenylmethane and 2,2-diaminodiphenylmethane there may also be present further reaction products having three or more aromatic rings that are formed in the reaction of aniline and formaldehyde, in particular ones having three or more phenyl rings (multiring compounds).

[0047] Preference is given to using in the present process an MDA comprising at least 70% by weight of 4,4-diaminodiphenylmethane and 0.01% to 2% by weight of N-methyl compounds (2,2-, 2,4- and/or 4,4-N-methyl-methylenedianiline, in particular 2,4- and 4,4-N-methyl-methylenedianiline), in each case based on the total mass of compounds having aromatic rings. Even further preference is given to using an MDA consisting of 74-85% by weight of 4,4-MDA, 3-20% by weight of 2,4-MDA, less than 1% by weight of 2,2-MDA and up to 1% by weight of N-methyl compounds. With the cited mixtures, a hydrogenation mixture can be particularly readily obtained that has a trans/trans content of the 4,4 isomers of 10% to 30%.

[0048] Because of the high proportion of 4,4-diaminodiphenylmethane in the MDA used, the methylenebis(cyclohexylamine) obtainable in the hydrogenation of the invention is mostly 4,4-diaminodicyclohexylmethane or bis(para-aminocyclohexyl)methane. The potential presence of the corresponding 2,4-and 2,2-diaminophenylmethane isomers in the MDA means that 2,4-diaminodicyclohexylmethane and 2,2-diaminodicyclohexylmethane may likewise be present in methylenebis(cyclohexylamine). In addition, hydrogenated MDA can also contain (sometimes partially) hydrogenated multiring compounds besides methylenebis(cyclohexylamine).

[0049] The hydrogenation results in the formation of diastereoisomers. The 4,4-diaminodicyclohexylmethane product derived from 4,4-diaminodiphenylmethane can be in the form of trans/trans, cis/cis and cis/trans isomer and is therefore generally a mixture of these isomers in varying proportions. The process of the invention is especially well suited to the production of 4,4-diaminodicyclohexylmethane mixtures having high trans/trans contents, particularly when using the abovementioned MDA grades.

[0050] The process of the invention for the hydrogenation of MDA is further preferably a fixed-bed process for continuous catalytic hydrogenation. Further preferably, MDA is thus hydrogenated by means of a catalytic fixed-bed process in the presence of hydrogen.

[0051] The material stream introduced per tonne of catalyst in the reactor cascade is preferably 0.1-10 t/h, further preferably 0.5-8 t/h, even further preferably 0.75-5 t/h. The material stream further preferably consists of a solution containing 5-50% by weight, further preferably 7.5-30% by weight, even further preferably 10-20% by weight, of MDA.

[0052] The hydrogen (H.sub.2) required for the hydrogenation is preferably added stoichiometrically to marginally superstoichiometrically with respect to the desired reaction. For the process for the hydrogenation of MDA, the hydrogen (H.sub.2) required for the hydrogenation is added in a molar ratio of 300-350 mol %, further preferably 300-330 mol %, further preferably 300-310 mol %, based on the phenyl rings present in the MDA.

[0053] The hydrogenation preferably takes place at temperatures between 50 and 200 C., preferably between 80 and 170 C., particularly preferably between 85 and 135 C. The hydrogen pressure here is preferably between 1 and 30 MPa, preferably between 5 and 15 MPa, particularly preferably between 7 and 10 MPa.

[0054] The process of the invention is thus preferably a liquid-phase hydrogenation process, i.e. a hydrogenation process carried out in the liquid phase.

[0055] A solvent can in principle be present in the hydrogenation, but does not have to be. It is however preferable to add MDA in a solvent. The proportion of the solvent is further preferably between 50% and 95% by weight, more further preferably between 70% and 92.5% by weight, even further preferably between 80% and 90% by weight, of solvent. Preferred solvents can be selected from the group consisting of primary, secondary and tertiary monohydric or polyhydric alcohols (in particular methanol, ethanol, n- and i-propanol, 1-, 2-, i- and tert-butanol, ethylene glycol and ethylene glycol mono(C1-C3)alkyl ethers), linear ethers (in particular ethylene glycol di(C1-C3)alkyl ethers), cyclic ethers (in particular tetrahydrofuran and dioxane) and alkanes (in particular n- and isoalkanes having 4-12 carbon atoms, further preferably n-pentane, n-hexane and isooctane, and cyclic alkanes, further preferably cyclohexane and decalin). Whereas alcohols can result in alkylation of the amino groups, ethers do not have this disadvantage and are thus particularly preferred. A very particularly preferred solvent is tetrahydrofuran.

[0056] However, solvent can also likewise preferably be the hydrogenation product itself.

[0057] The hydrogenation can preferably also be carried out in the presence of ammonia, a primary, secondary or tertiary amine, or a polycyclic amine having a bridging nitrogen atom.

[0058] The process of the invention is preferably a fixed-bed process for continuous catalytic hydrogenation, i.e. it is carried out in the presence of at least one heterogeneous catalyst immobilized in the fixed bed. The fixed-bed process is further preferably a process in which the reactants flow once through the reactor cascade (single-pass process).

[0059] Heterogeneous catalysts may be either unsupported catalysts or supported catalysts. In principle, both an unsupported catalyst and a supported catalyst can be used in the process of the invention.

[0060] It is possible to use just one catalyst or a mixture of catalysts. Preference is however given to using just one catalyst.

[0061] In particular, catalysts containing active metals selected from nickel, cobalt, palladium, platinum, ruthenium and/or rhodium have been found to be particularly suitable.

[0062] To increase activity, selectivity and/or service life, the catalysts may additionally comprise doping metals or comprise or have been treated with other modifiers. Preferred doping metals may be selected from the group consisting of Mo, Fe, Ag, Cr, V, Ga, In, Bi, Ti, Zr, Mn and the rare earths. Preferred modifiers are ones that allow the acid-base properties of the catalysts to be influenced, in particular alkali metals, alkaline earth metals, phosphoric acid and sulfuric acid, and compounds and salts thereof.

[0063] The catalysts can preferably be used in the form of powders or shaped bodies, for example extrudates or compressed powders. It is possible to employ unsupported catalysts, Raney-type catalysts or supported catalysts.

[0064] Preference is given to using a supported catalyst.

[0065] Preferred support materials for supported catalysts are activated carbons and inorganic oxides, particularly Al.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, ZrO.sub.2, ZnO and MgO, and also bentonites, aluminosilicates, kaolins, clays, kieselguhrs and lithium aluminates. The active metal can be applied to the support material in a manner known to those skilled in the art, for example by impregnation, spray application or precipitation. Depending on the method of catalyst production, further preparation steps known to those skilled in the art are necessary, for example drying, calcining, shaping and activation. For shaping, it is optionally possible to add further auxiliaries, for example graphite or magnesium stearate.

[0066] Preference is given to using supported catalysts containing ruthenium, rhodium or Rh/Ru combinations as essential active metals. Preferred support materials are ones based on Al.sub.2O.sub.3 and SiO.sub.2.

[0067] Preference is given to using catalysts known to be employable for production of a methylenebis(cyclohexylamine) having a trans/trans content of the 4,4-isomer of between 10% and 30% by weight, in particular between 15% and 25% by weight. Suitable catalysts are described for example in documents EP 1 366 812 A1, EP 0 066 211 A1, DE 100 54 347 A1, EP 0 392 435 A1, EP 0 630 882 A1, EP 0 639 403 A2 and U.S. Pat. No. 5,545,756 A.

[0068] Very particularly preferably, the hydrogenation is carried out in the presence of a supported catalyst that contains, applied on a support, active metal in an amount of 0.01% to 20% by weight based on the supported catalyst, and the active metal thereof is ruthenium alone or ruthenium and at least one metal of subgroups I, VII or VIII [groups 7-11] of the periodic table of the elements. This catalyst allows particularly low trans/trans contents of 4,4-diaminodicyclohexylmethane to be achieved.

a) Reactor Cascade

[0069] The process of the invention is carried out in a reactor cascade consisting of a plurality of reaction spaces. The reactor cascade is characterized in that 50-100 mol %, preferably 50-95 mol %, further preferably 70-90 mol %, of the hydrogen required for the hydrogenation of MDA undergoes reaction therein. In addition, it comprises n serially connected reaction spaces that are each filled with the same catalyst and can be filled or emptied independently of one another. The number n is here an integer greater than or equal to 2 that indicates how many reaction spaces that can be filled or emptied independently of one another there are. Preferably, n is a value between 2 and 10. Further preferably, n is a number selected from the range of 2 to 6; even further preferably, n=2, 3 or 4. Very particular preferably, n=2 or 3.

[0070] The individual reaction spaces are respectively given the designation R.sub.i, where 1in, in the order in which they are connected. The expression in the order in which they are connected is here considered to be synonymous with in the order of through-flow of the reactant (MDA). This means that the first reaction space through which the employed MDA is introduced for reaction is designated R.sub.1, the second is designated R.sub.2, and so on. The final reaction space is designated R.sub.n. Where there are three reaction spaces, the final reaction space of the reactor cascade that is entered by the employed MDA is thus R.sub.3.

[0071] A reaction space is in the present case understood as meaning a catalyst-filled spatial unit that is spatially separated by catalyst-free plant components from the other reaction spaces of the reactor cascade in which hydrogenation of MDA takes place at an earlier or later stage with respect to the progress of the reaction. A reaction space can thus be a subreactor that is spatially separated by catalyst-free plant components from the other subreactors of the reactor cascade in which hydrogenation takes place at an earlier or later stage with respect to the progress of the reaction. It is however also possible for the reaction space to consist of a plurality of parallel-connected subreactors in which hydrogenation of MDA takes place at the same time with respect to the progress of the reaction. Preferably, each reaction space R.sub.i consists of x parallel-connected subreactors where x=1 to 250 that are spatially separated by catalyst-free plant components from one another and from the other reaction spaces. In the case of parallel-connected subreactors, this can for example be the x parallel-connected tubes of a tube-bundle reactor. Further preferably, the number x of parallel-connected subreactors is x=2 to 250, preferably x=50 to 250, further preferably x=150 to 250.

[0072] Preferably, the catalytic hydrogenation of MDA in the reactor cascade takes place essentially isothermally, i.e. with reaction enthalpy drawn off by means of an external cooling circuit at essentially even temperature.

[0073] Preferably, the reactants flow through the reactor cascade only once, i.e. the reactor cascade is operated in single-pass mode.

[0074] Likewise preferably, the reactor cascade is a trickle-bed cascade.

b) Removal of R.SUB.1

[0075] During the hydrogenation of MDA, the activity of the catalyst in the individual reaction spaces of the reactor cascade changes and over time declines. It was found here that the activity of a freshly introduced catalyst decreases most sharply in the first reaction space and the least in the final reaction space. R.sub.1 is accordingly temporarily disconnected from the cascade, with the aim of replacing and/or regenerating the catalyst present therein, as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree.

[0076] The core of the present invention is thus that it is sufficient to replace and/or regenerate the catalyst in R.sub.1 as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree,

[0077] Preferably, the point at which an undesirable degree of deactivation is reached is determined by monitoring the activity of the catalyst in R.sub.1 while in operation and comparing this with the initial catalyst activity. Even further preferably, this is achieved by determining the normalized activity of the catalyst present in R.sub.1 and temporarily disconnecting R.sub.1 from the cascade as soon as the normalized activity of the catalyst present in R.sub.1 falls below a defined value.

[0078] Preference is therefore given to a process for the continuous heterogeneous catalytic hydrogenation of MDA, in which: [0079] a) the process is carried out in a reactor cascade comprising n serially connected reaction spaces that are each filled with catalyst and can be filled or emptied independently of one another, which are respectively given the designation R.sub.i, where 1in, in the order in which they are connected, [0080] b) the normalized activity of the catalyst present in R.sub.1 is determined and R.sub.1 is temporarily disconnected from the cascade as soon as the normalized activity of the catalyst present in R.sub.1 falls below a defined value, [0081] resulting in a reconfigured reactor cascade comprising i reaction spaces, which are given the designation R.sub.i, where 1i(n1), in the order in which they are connected, [0082] wherein each reaction space R.sub.i where 2in becomes a reaction space R.sub.i where 1i(n1), [0083] c) the catalyst in R.sub.1 is replaced and/or regenerated and [0084] d) R.sub.1 is subsequently connected as reaction space R.sub.i where i=n.

[0085] The activity of the catalyst in R.sub.1 is preferably monitored while in operation.

[0086] This can be done for example by continuous or occasional online monitoring of the catalyst or by withdrawing samples of the catalyst with subsequent external analysis in a laboratory-scale reference investigation at various times t.sub.x. The normalized activity a of the catalyst can be determined as the ratio of the conversion at time t=t.sub.x (dividend) and the conversion at time t=0 (divisor), the conversion being determined at a reaction temperature of 100 C., a hydrogen pressure of 80 bar and an inverse mass-related residence time of 0.330 kg (MDA)/(kg (catalyst).Math.h) of MDA per total mass of catalyst of all reaction spaces of the reactor cascade.

[0087] The preferred position for determining conversion in order to monitor the activity of the catalyst in R.sub.1 is always in the same place. Further preferably, the activity of the catalyst is determined directly at the outlet of the reaction space R.sub.1.

[0088] The actual conversion based on hydrogen consumption is calculated by evaluating the area percent values for methylenebis(cyclohexylamine) in the gas chromatogram with a factor of 1, adding 0.5 times the area percent values for the methylene(aminocyclohexyl)aniline components thereto and dividing the resulting total by the total of the area percent values for all MDA, methylene(aminocyclohexyl)aniline and methylenebis(cyclohexylamine) compounds.

[0089] As soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree, a change is made to the connection of the individual reaction spaces. The change to the connection is preferably made as soon as the normalized activity of the catalyst present in R.sub.1 falls below a defined value. After the change to the connection, the catalyst in R.sub.1 is replaced and/or regenerated.

[0090] Quantification of the degree of deactivation or the actual numerical value for the normalized activity has little bearing on the practicability of the present invention and the achievement of the advantages of the invention. As soon as MDA conversion falls to within an undesirable range, this alone indicates that the catalyst has become deactivated or that its normalized activity has decreased and action is required.

[0091] However, it is preferable that R.sub.1 is disconnected from the cascade once the normalized activity of the catalyst present in R.sub.1 is less than 0.7, particularly preferably less than 0.5, even further preferably less than 0.3.

[0092] As soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree, particularly when the normalized activity of the catalyst present in R.sub.1 falls below a defined undesirable value, a change is made to the connection of the individual reaction spaces, whereby R.sub.1 is temporarily disconnected from the cascade. This is preferably done by redirecting the reactant and product streams. For this, the inflowing streams of unreacted MDA and hydrogen are supplied directly to reactor R.sub.2. The streams flowing into and out of R.sub.1 are on the other hand closed.

[0093] Disconnecting R.sub.1 from the cascade of n reaction spaces results in a reconfigured reactor cascade comprising one reaction space fewer, i.e. (n1) reaction spaces. This can now be redesignated on the basis of the altered configuration now present: Disconnecting R.sub.1 from the reactor cascade comprising n reaction spaces results, from the remaining reaction spaces R.sub.i where 2in, in a number of reaction spaces (n1), which are given the designation R.sub.i, where 1i(n1), in the order in which they are connected.

c) Replacement/Regeneration of the Catalyst

[0094] The catalyst present in R.sub.1 is replaced and/or regenerated, i.e. the catalyst is partly or completely (preferably completely) replaced or regenerated. It is also conceivable that a portion of the catalyst is partly or completely (preferably completely) regenerated and another portion of the catalyst is partly or completely (preferably completely) replaced.

[0095] This is preferably done by releasing the pressure and emptying the residual contents of the reactor into a slop container. Any solvent still present can then be washed off the catalyst with water and the catalyst can be dried at elevated temperature in a stream of nitrogen. The catalyst can subsequently be removed and replaced with fresh catalyst.

[0096] Alternatively, the catalyst can also be regenerated. Preferred regeneration processes are described for example in CN 117654548 A, CN 110204447 B and CN 113893866 B.

[0097] After replacement and/or regeneration of the catalyst originally present in R.sub.1, this reaction space is subsequently connected as reaction space R.sub.i where i=n. This means that the reaction space is connected as the final reaction space in the reactor cascade. Thus, once the reaction space formerly designated R.sub.1 has been connected as new reaction space R.sub.n, the reactor cascade again comprises n serially connected reaction spaces that are each filled with catalyst and can be filled or emptied independently of one another. The reconfigured reactor cascade comprising n reaction spaces can of course undergo the process of the invention again as soon as the catalyst now present in R.sub.1 is no longer sufficiently active.

[0098] The present invention is based on a reactor concept in which the reactor consists of two or more reaction spaces arranged in series with respect to one another. Such an arrangement allows the individual reaction spaces to be replaced without reprocessing or replacing the portion of the catalyst that is still active.

[0099] During replacement or regeneration of the catalyst, the hydrogenation can in principle be halted or continued. Operation of the hydrogenation is preferably continued during the replacement or regeneration, since this is better for the space-time yield of the plant. Further preferably, the operation of the hydrogenation is continued with reduced load, since this allows particularly good results to be achieved.

[0100] In a preferred embodiment of the process n=2, i.e. the reactor cascade consists of two reaction spaces R.sub.1 and R.sub.2 that can be filled or emptied independently of one another and are respectively given the designation R.sub.1 and R.sub.2 in the order in which they are connected. R.sub.1 is temporarily disconnected from the cascade as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree. The reaction is thus carried out only in R.sub.2, and R.sub.2 is from then on designated reaction space R.sub.1. The catalyst in R.sub.1 is replaced and/or regenerated. R.sub.1 is subsequently connected as reaction space R.sub.2.

[0101] Further preferably, the point at which an undesirable degree of deactivation is reached is determined by monitoring the activity of the catalyst in R.sub.1 while in operation and comparing this with the initial catalyst activity. Even further preferably, the normalized activity of the catalyst present in R.sub.1 is determined and R.sub.1 is temporarily disconnected from the cascade as soon as the normalized activity of the catalyst present in R.sub.1 falls below a defined value.

[0102] The continuous hydrogenation of the invention can only be carried out in the abovementioned reactor cascade. It is however preferable that the reaction in the reactor cascade is followed by a reaction in a finisher (which can optionally comprise two or more sub-finishers). In said unit, preferably in the presence of at least one different catalyst, the conversion for the hydrogenation of MDA is increased further. This finisher (downstream reactor) is not part of the reactor cascade.

[0103] The material stream introduced into the finisher per tonne of catalyst in the reactor cascade is preferably 0.15-25 t/h, further preferably 0.75-20 t/h, even further preferably 1-15 t/h.

[0104] Particularly good results can be achieved when the reaction is carried out essentially isothermally (i.e. with reaction enthalpy drawn off by means of an external cooling circuit at essentially constant temperature) in the reactor cascade and essentially adiabatically (i.e. without cooling and with little heat loss) in the finisher.

[0105] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

[0106] In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

[0107] The entire disclosures of all applications, patents and publications, cited herein and of corresponding European application No. 24191090, filed Jul. 26, 2025, are incorporated by reference herein.

[0108] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0109] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.