DE2344509A1 - HYDRATION PROCESS - Google Patents

Description

DIAIiOND SHAMROCK CORPORATION, Cleveland, Ohio, V.St.A. 1100 Superior Avenue

The invention relates to a hydrogenation process in which a non-reduced ruthenium salt and aluminum oxide mixed together or combined can be used as a hydrogenation catalyst to unsaturated carbocyclic and heterocyclic To convert compounds into the corresponding saturated derivatives, in particular to convert unsaturated compounds such as benzene, pyridine and substituted pyrroles and pyrrolines.

The invention provides an improved method to obtain saturated cyclic compounds from related unsaturated Make connections. The invention particularly relates to a low pressure hydrogenation process in which a combination from a non-reduced ruthenium salt, for example ruthenium chloride, and alurainium oxide used as a catalyst will.

As Morris Freefeld reports in Practical Catalytic Hydrogenation, John Wiley and Sons, New York (1971), are platinum oxide or rhodium on support materials have long been the preferred catalysts to produce aromatic compounds, for example Benzene,

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and to saturate heterocyclic compounds such as pyridine and in particular pyrroles, pyrrolines and the like at a low hydrogen pressure in an acidic medium. For example, Evans reports in JACS, 73,5231 (1951) that cis-2,5-dimethylpyrrolidine can be produced by catalytic reduction of 2,5-dimethylpyrrole at a hydrogenation pressure of about 3.1 atmospheres (45 psig) using Adams- Catalyst (platinum dv) oxide) can be produced in glacial acetic acid. Later, Overberger et al in JACS, 22 »^ ⁰² (1955) reported that cls-2,5-dimethylpyrrolidine by catalytic reduction of 2,5-dimethylpyrrole at a hydrogen pressure of 2.8 atmospheres (40 psig) Using 5 $ igera rhodium on alumina as a catalyst in glacial acetic acid can be produced.

US Pat. No. 2,675,390 describes the hydrogenation of pyrrole using 5% rhodium as the catalyst on aluminum oxide and glacial acetic acid and water as solvents.

In US Pat. No. 3,177,258, the hydrogenation of Pyrrole using the catalyst, the ruthenium

along with another platinum group metal, proposed. Similarly, ruthenium was found as a dioxide or as a metal on a support, such as on carbon or alumina, with considerable success as a catalyst the reduction of a number of ring systems at moderately high pressures and temperatures, for example at saturation of aromatic compounds such as benzene or of heterocyclic compounds such as pyridine.

It has now been found that unsaturated carboxyclic hydrocarbons and heterocyclic hydrocarbons readily convert into their saturated derivatives at moderate temperature and moderate pressures can be converted if one is used as a hydrogenation catalyst a non-reduced ruthenium salt and aluminum oxide are used in combination.

The invention is an improved method for

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the catalytic hydrogenation of aromatic hydrocarbons, for example benzene and heterocyclic hydrocarbons, such as pyridine and in particular for 2,5-dialkylpyrroles and 2,5-dialkyl-1-pyrrolines in their corresponding saturated derivatives, being a simple combination of non-reduced ruthenium salt and aluminum oxide is used as a catalyst. Hydrogen pressures ranging from about 7.03 to about 105 atmospheres (100 to about 1500 psig) can generally be used and, if desired, an inert liquid reaction medium such as water or cyclohexane can also be used. The process gives high conversions to the desired saturated products, for example 2,5-dialkyl pyrrolidines which typically have cis-isomer contents of about 85 to about 98 % .

According to the process of the invention, any carbocyclic or heterocyclic compounds which can be used in their related saturated products can be transferred, can be effectively reduced in good yields under moderate hydrogen pressure if the combined catalyst is used Unreduced ruthenium salt and aluminum oxide catalyst used. One can in particular BenzoIUPyridin and particularly preferably dialkylpyrroles and dialkyl-1-pyrrolines hydrogenate effectively and well, giving the desired saturated cyclic compounds obtained.

In general, one can use the catalyst combination according to the invention use any water-soluble non-reduced ruthenium salt such as the nitrate or chloride. Since that Chloride is readily available and costs relatively little. the most preferred ruthenium salt. For this reason, the following will mainly focus on the Reference ruthenium chloride.

The mechanism according to which unreduced ruthenium chloride and alumina combined together in the present

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Invention to act as a catalyst is not known. However, this mixture, as made, is an active one Hydrogenation catalyst, so that no special activation treatments which one usually has to carry out in the catalyst field, are required.

The activity of the ruthenium chloride-aluminum oxide catalyst combination according to the invention is very surprising. Although it was found that the unreduced ruthenium chloride even with the hydrogenation of many unsaturated compounds and especially with 2,5-dimethylpyrrole and 2,5-Dimethyl-1-pyrroline shows catalytic properties, it is not sufficiently active to act as a hydrogenation catalyst to have any practical value. Hydrogenations using ruthenium chloride alone will proceed very slowly and are completed long before the hydrogenation is complete, i.e. the hydrogenation ceases. Aluminum oxide is even similar at the moderate temperature and pressure used in the hydrogenation of the present invention will not be a hydrogenation catalyst of practical value. The catalytic effectiveness of the ruthenium chloride-aluminum oxide combination according to the invention was therefore not with knowledge of the properties of ruthenium chloride or aluminum oxide predictable.

Any unreduced ruthenium chloride which is soluble in water can be used. Ruthenium chloride hydrate of the formula RuCl, .xH ₂ O, in which χ = 2.5 to 3.5 and which contains 35-40 percent by weight of ruthenium, is particularly satisfactory and currently preferred. In general, any finely divided activated alumina powder can be used, such as the Catapal aluminas manufactured by the Continental Oil Company.

The catalyst system according to the invention can be according to various Procedures are effectively combined. If so desired

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ORIGINAL INSPECTED

the ruthenium chloride can first be dissolved in a solvent such as water, and the aluminum oxide is then converted into slurried this solution. Alternatively, the catalyst mixture in situ in the reactor by adding the aluminum oxide and ruthenium chloride to the reactor, or the chloride solution can be introduced separately into the reactor. Similarly, the catalyst components can be combined externally and then with the compound that reduces is to be mixed in the reactor. If desired, the ruthenium chloride and aluminum oxide can with the Compound to be reduced, for example with the pyrrole or the dialkyl-1-pyrroline together with any liquid medium, which is optionally used in the process, are mixed, and this mixture can be introduced into the reactor. The process for the production of the coordination from ruthenium chloride and aluminum oxide doesn’t seem to be critical at all.

The amount of ruthenium chloride used in the catalyst based on the weight of the unsaturated compound to be reduced can generally range from about 0.01 % to about 2 % ruthenium chloride calculated as ruthenium metal. The concentration of alumina can similarly vary generally from about 0.1% to 4 % based on the weight of the unsaturated compound. It has been found that concentrations of ruthenium chloride, calculated as ruthenium metal and of alumina, range from about 0.02 percent by weight to 0.50 percent by weight and from about 0.20 to 0.60 percent by weight, based on the compound to be reduced, are typical and optimal overall conversions to the desired saturated product are obtained. In particular, these concentrations of the catalyst components additionally result in optimal yields of the desired cis isomers thereof in the conversion of, for example, 2,5-dialkylpyrrole. Hydrogenation pressures can vary from about 7.03 to 105 atmospheres (100 to 1500 psig) and reaction temperatures

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ORIGIN INSPECTED

can vary from about 40 ° C to 200 ° C. The response times can typically be in the range of 0.5 msec 20 hours. As previously described, you can optionally inert reaction media, such as water or cyclohexane, which do not interact either with the starting materials or with the saturated one Product react, be used. /

After the hydrogenation is complete, the catalyst is separated from the hydrogenation mixture and the mixture by vapor phase chromatography using an Amin 220 column (Supelco, Inc., Beliefonte, Pennsylvania) analyzed. If 2,5-dimethylpyrrole is hydrogenated, the Content of the cis isomers in the resulting pyrrolidime product generally in the range of about 85 to 98 percent by weight.

When carrying out the process according to the invention, if water is used as the reaction medium, the product, namely dimethylpyrrolidine in particular, is soluble therein and forms an azeotrope during the distillation. In order to reduce the water content, the pyrrolidine-water azeotrope is mixed with a relatively low-boiling organic solvent for the product, for example pentane, hexane and similar compounds. Sufficient caustic (ie alkali see) compounds in flakes or pellet form are added to the resulting mixture of solvent and water to produce a 20% caustic solution, based on the water content. The entire two-phase system is heated to 50 ° C. with stirring. It is then cooled with stirring and separated into two phases. The lower phase (the aqueous caustic solution) is removed and discarded. The upper phase is the solvent solution from the product, namely the dimethylpyrrolidine, and usually contains less than 2 % water. In order to further reduce the water content of the product solution, the treatment with caustic compounds can be repeated. The product solution can be used in reactions in which the solvent does not react, or the solvent can optionally be used

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ORIGINAL INSPECTED

strip from the product by distillation in a known manner.

The inventive method is easy to carry out and represents a technically usable process to achieve optimal yields of, for example, cyclohexane, piperidine, or cis-2,5-dialkyl-pyrrolidines from the related unsaturated compounds. In the method according to the invention becomes a simple mixture of aluminum oxide and a non-reduced ruthenium salt as a hydrogenation catalyst used in place of the previously used catalysts made of reduced ruthenium metal with supports. Inert liquid media, such as cyclohexane can be effectively used in the method of the present invention, and it is not necessary as in the known method to use acetic acid. This creates difficulties in handling the acetic acid and avoided in their extraction.

The following examples illustrate the invention without restricting it.

example 1

A solution of 0.10 g of ruthenium chloride hydrate (RuCT ^ .x ^ O content of ruthenium metal 37 %) in 15 g of water is filled into a 250 ml stainless steel autoclave, 0.25 g of aluminum oxide being mixed well in the solution with stirring. 44 g of freshly distilled 2,5-dimethylpyrrole are then introduced into the autoclave (the concentration of ruthenium, based on the weight of the dimethylpyrrole, is 0.084% and that of the aluminum oxide is 0.57 %) .

The autoclave is tightly closed and flushed several times with nitrogen and hydrogen and finally is Hydrogen up to a pressure of. 28.1 atti (400psig) filled. The reaction mixture is then heated to approximately 140 ° C at a rate of 2 - 4 ° C per hour, during this time the pressure was increased to 36.6 atmospheres (520 psig)

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increases. As the absorption progresses, the pressure drops to 28.1 atmospheres (40 opsig). The reaction occurs at approximately 140 ° C and 28.1 atmospheres (400 psig) continued until conversion is complete based on hydrogen consumed (determined due to the pressure drop in the hydrogen reservoir). The reaction is complete in about 3 1/2 hours.

The reactor is cooled and the gases are vented. The reaction mixture is removed and filtered to remove the Separate catalyst. The filtrate is determined by vapor phase chromatography analyzed. The chromatograph contains a 0.47 cm χ 15.2 cm (3/16 "6 ·) column filled with 5% amine 220 on Chromosorb G High Performance 80 - 100 mesh (corresponding to sieves with clear mesh sizes of 0.175 0.147 mm) is packed. It is used at a temperature of 70 to 90 ° C in the quantitative analysis of cis and trans-2,5-dimethylpyrrolidine and a temperature of 150 - 160 ° C operated in the quantitative analysis of 2,5-dimethylpyrrole. The cis isomer is eluted first, followed shortly after by the trans isomer. Then the column temperature immediately to 150-160 ° C. The pyrrole will post the pyrrolidine isomer approximately 3 minutes at these conditions eluted. The percentage conversion is determined from the remaining amount of pyrrole.

Using this procedure, the product in this example is obtained in 99% theoretical yield, greater than 91 percent by weight of which are cis isomers. In order to obtain essentially anhydrous product, the Filtrate mixed with heptane and then caustic dehydration (= caustic water removal) as described above subject.

Examples 2-6

Using the same apparatus and procedure as described in Example 1 above, 2,5-dimethylpyrrole hydrogenated, the amounts of catalyst

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mixture and the reaction conditions are used, which are listed in the table below and where water is optionally used as the inert reaction medium. 44g of dimethylpyrrole are used in each experiment. After the reaction mixture has been cooled and filtered, the filtrate is analyzed for the total conversion and the percentages by weight of cis- and trans-2,5-diraethylpyrrolidine in each experiment by vapor phase chromatography.

A comparative experiment is carried out using only ruthenium chloride used. The following results are obtained:

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example CatalvsatormischunK Wassei 0.18 19 Table I. Print time % conversion
kg / cm (psi) hours 37 % cis isomer I. Ruthenium aluminum %
Wt% wt % 0.58 31 28.1 (400) 7.5 82 97 _i
O
I. 2 0.03 ¹ 0.58 0 28.1 (400) 12 94 92 3 0.03 ¹ 0.25 0 • Dimethvlpvrrolidine reaction conditions 28.1 (400) 3 92 91 4th 0.082 ² 0 55 Tgmp. 28.1 (400) 6 25th 92 5 O, O3 ² 141 28.1 (400) 13 The addition of the mixed catalyst components and the
took place as described in Example 1. 93 O
cc 6th O, 16 ³ 150 Pyrrole OC
NJ 1 141. Ruthenium salt and aluminum oxide are mixed in a mortar
grind and then put directly into the reactor. Then will
introduced the dimethylpyrrole into the reactor. ro
-P-
KJ 2 153 η
. ■> 135

RuCl ₃ .xHpO (37% ruthenium) is slurried in the water in the reactor before the dimethylpyrrole is added.

cn O CD

The procedure of Example 5 above is repeated using different temperatures and hydrogen pressures. It is found that the reaction occurs at a considerable reaction rate, ie an approximate 0.5% conversion per minute at the low reaction temperature of 50 ° and a mini]
(300 psi) takes place.

of 50 ° and a minimum hydrogen pressure of 21.1 kg / cm

Example 7

The general procedure described in Example 1 is followed and 44 g of 2,5-dimethyl-1-pyrroline are hydrogenated using 0.30 g of a combined catalyst which is prepared by adding 0.5 g of aluminum oxide and 0.5 g. 16 g RuCl ^ .xPL, 0 (37 % ruthenium metal) ground. The amount of combined catalyst used gives 0.027 percent by weight ruthenium, based on the dialkyl-1-pyrroline. The reaction is run "at 132 ° C, 28.1 atmospheres (400 psig) hydrogen pressure and is complete in about 30 minutes.

The product, namely 2,5-dimethylpyrrolidine, is obtained in 99% theoretical yield. More than 91 % of the product obtained is the cis isomer.

Example 8

As described in Example 1, 44 g of pyridine are hydrogenated using 0.30 g of a catalyst mixture prepared from 1.0 g of aluminum oxide and 0.32 g of RuCl -, xHpO (this gives 0.061 percent by weight of ruthenium metal, based on the Pyridine). The reaction is carried out at 166 ° with a constant hydrogen pressure of 28.1 atmospheres (400 psig) and is complete in approximately 3 1/2 hours.

The saturated product piperidine is obtained in a yield of over 99 % .

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Example 9

Benzene as described in the previous examples hydrogenated _t wherein one 0.60 g of the catalyst mixture described in Example 8 is used. The reaction mixture is heated at a hydrogen pressure of 28.1 atmospheres (400 psig) for 30 minutes at 104 ° C., after which the reaction stops at an approximate 40% conversion to cyclohexane, determined by the uptake of hydrogen. The reaction temperature is increased to 193 ° C and the pressure is maintained at 28.1 atmospheres (400 psig). The reaction continues for about 7 1/2 hours and stops at about 95 % conversion. The reaction mixture is filtered and analyzed by vapor phase chromatography (the total area is analyzed). The product contains approximately 95 % cyclohexane and approximately 5 % of the starting benzene.

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Claims (9)

Claims Hydrogenation process to convert an unsaturated carbocyclic or heterocyclic compound into the related to convert saturated carbocyclic or heterocyclic compound, characterized in that the hydrogenation catalyst a non-reduced ruthenium salt and aluminum oxide are used in combination. 2. The method according to claim 1, characterized in that the non-reduced ruthenium salt ruthenium chloride, which contains 35 to 40 percent by weight ruthenium is used. 3. The method according to claim 1, characterized in that there is 2,5-dimethylpyrrole as the unsaturated heterocyclic compound hydrogenated and that the product obtained is mainly cis-2,5-dimethylpyrrolidine. 4. The method according to claim 1, characterized in that that pyridine is hydrogenated as the unsaturated heterocyclic compound, piperidine being obtained as the saturated product. 5. The method of claim 1, characterized in that the method is carried out at a hydrogen pressure in the range of about 7.03-105 kg / cm ² (100-1500 psi) and at a temperature of 40-200 ° C. 6. The method according to claim 1, characterized in that ruthenium chloride is used as the non-reduced ruthenium salt component of the catalyst mixture and that the ruthenium chloride is used in an amount which is from about 0.01 to about 2 % ruthenium metal, based on the weight of the unsaturated compound, which is to be hydrogenated results. 7. The method according to claim 1, characterized in that the alumina component is used in the catalyst mixture in an amount in the range from about 0.10 to about 4 % _t based on the weight of the unsaturated compound to be hydrogenated. 8. The method according to claim 1, characterized in that it is carried out in the presence of an inert liquid reaction medium which is a solvent for the hydrogenation product. 9. The method according to claim 8, characterized in that that water is used as the inert liquid reaction medium, Ü a ö I 2 / i 2 4 2