TECHNICAL FIELD

This invention relates to catalysts and more particularly to catalysts for producing alkyl substituted pyrrolidones from alcohols and 2-pyrrolidone.

BACKGROUND OF THE INVENTION

Presently, N-substituted 2-pyrrolidones are produced by the reaction of butyrolactone with the corresponding amine. However, amines are more costly than corresponding alcohols since they are prepared from the alcohols, requiring an extra processing step. Also, the amines are produced in less than quantitative yields due to the formation of secondary and tertiary amines. Consequently, it would be economically desirable- to prepare N-substituted pyrrolidones directly from alcohols and 2- pyrrolidone, providing the yields are sufficiently high.

In Japanese unexamined Patent Application No. 117,459, a method is disclosed which utilizes copper catalysts in a hydrogen atmosphere at temperatures of 180 to 450°C to react various alcohols with 2-pyrrolidone. The catalysts discussed are copper, copper-chromium, copper- rhenium, copper-silver, copper-nickel, copper-molybdenum, copper-manganese, copper-tungsten, and a copper-chromium- manganese catalyst. These were found to provide

satisfactory selectivity relative to alcohol and pyrrolidone, however the yields were fairly low.

In a Journal of Molecular Catalysis article, 55(1989) p. 241 to 246, a catalyst for the n-alkylation of amides and lactams using alcohols is discussed with the catalyst being homogenous ruthenium. However _r ruthenium is quite expensive and difficult to recover. Also, it appears that tri-substituted phosphine is needed to carry out the reaction, thus making the process even more expensive.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel catalyst for producing N-substituted 2- pyrrolidones from alcohols and 2-pyrrolidone. It is a further object to provide a novel catalyst of relatively low cost and high selectivity which produces the N-substituted pyrrolidones in economic yields.

These and other objects of the present invention are achieved by providing a catalyst for converting various alcohols and cyclic lactams to N-substituted cyclic lactams in a hydrogen environment. The catalyst comprises from 10 to 15% cooper, 0.01 to 0.15% palladium disposed on a carrier. Utilizing a copper-palladium catalyst produces noticeable improvements in yield and selectively over other catalysts, including those disclosed in the Japanese Application, particularly in the production of N-octyl 2- pyrrolidone.

DETAILED DESCRIPTION OF THE INVENTION

The active catalytic components according 'to the present invention are copper and palladium deposited on a substrate support material. While various substrates could be used, a manganese silicate support substrate is preferred.

The active catalytic material, copper and palladium, are deposited on the substrate material by any conventional method. Generally, metal salts are dissolved in either aqueous or organic solvents and dried on a substrate and then treated with hydrogen to form metal crystallites. While metal deposition from the nitrates is preferred, any acceptable route to form the metal crystallites on the substrate material may be used, such as hydrogen reduction of the salt to form the metal crystallites or oxidation of the salt in air followed by reduction in hydrogen. The amounts of copper and palladium used may vary somewhat but are generally used in amounts based on catalyst plus support materials of 10 to 15% by weight copper, 0.01 to 0.15% palladium. Preferably, 10 to 12% copper and 0.09 to 0.13% palladium are used. The catalyst is usable at temperatures of from about 150° to 400°C.

The inventive catalyst provides improved conversion and selectively in the conversion of alcohols and cyclic lactams of the Formula I to produce N-substituted lactams of the Formula II:

where m is an integer from 2 to 5 and n is an integer from 2 to 20.

Preferably 2-pyrrolidone of Formula III is used, to produce the N-substituted pyrrolidones of Formula IV:

R' ' R

where R', R" and R ¹ " are H or lower alkyl, R ^IV is

H, alkyl, alkoxyl, cycloalkyl or aralkyl, and n is 2 to 20.

EXAMPLE 1

800 millimeters of water and 3.25 grams of concentrated nitric acid were combined and then 65 grams of copper nitrate hemipentahydrate was dissolved in the mixture which was combined with 130 grams of manganese silicate (SILPREC) with heating at 50°C for about an hour. 52 grams of sodium carbonate dissolved in 200 milliliters of water was then added slowly to the mixture to neutralize the acid. After stirring for another hour, the solution was filtered and the filter cake washed 3 times with distilled water. The filter cake was then dried at 200°C and then calcined overnight at 450°C. The calcined powder was broken up and combined with a solution of palladium nitrate which comprised 0.375 grams in 200 milliliters of water. After mixing, the material was dried at 200°C and

again calcined overnight at 450°C. The dry powder was then passed through a No. 30 sieve.

The reactions described in the example can be varied to alter the characteristics of the catalyst. Longer reaction times and higher temperatures may produce catalysts which have an increase in effectiveness as it was found that during the initial reaction with copper nitrate, the longer reaction times, higher temperatures and higher acid levels may result in the production of a catalyst which has copper disposed deeper in the substrate. This tends to induce a stronger interaction of the copper with the substrate which increases the efficiency of the catalyst when used in the reaction of the invention.

EXAMPLE 2

170 grams (2 moles) of 2-pyrrolidone _f 195 grams

(1.5 moles) of 1-octanol and 18 grams (5% by weight) of the catalyst of example 1 were added to a 1 liter autoclave.

After purging the reactor with nitrogen to remove air, the nitrogen pressure was lowered to atmospheric pressure and 100 psig of hydrogen gas was introduced. The reactor was then sealed and heated to 275°C and held for 10 hours while temperature and pressure readings were recorded. The mixture was then cooled, discharged and filtered to remove the catalyst. The remaining material was analyzed by gas chro atography. Calculations were made to determine the selectivity, conversion and yield of the reaction based

upon the recovered weight of product and 1 octanol. 1- octanol was the limiting material, and thus the selectively and yield are based on 1-octanol rather than on conversion of the 2-pyrrolidone. Yield was calculated as the amount of product formed relative to the maximum amount of product possible based on reaction stoichiometry assuming a complete reaction. For a mole ratio of 2 moles of 2- pyrrolidone to 1.5 moles of 1-octanol, the following equations apply:

Yield = % octyl pyrrolidone formed x 100

81.0

% Selectively — 66 x (% octyl pyrrolidone) x 100 53.43 - (% 1-octanol remaining)

% Conversion = n-(% 1-octanol remaining)] x 100

53.43 For example, in the reaction of Example 2, the amount of 2-pyrrolidone in excess was 0.5 moles or 42.5 grams. The maximum amount of water that can be formed in the reaction was 1.5 moles or 27 grams for a total of 69.5 grams. Since the total weight introduced is 195 grams of 1-octanol and 170 grams of 2-pyrrolidone, the total weight exclusive of catalyst is 365 grams. The proportion of 2- pyrrolidone in excess plus the amount of water in the material that adds weight to the crude product but which could not be product. These constitute 19% [(69.5/365) x 100] of the weight, leaving 81% of the crude product which could be the desired octyl pyrrolidone. Consequently, the yield is given by the equation which includes division by

81. The equations for selectivity and conversion are derived in a similar fashion from these definitions ^* . The results are shown in Table II. Table I shows the reaction using the catalyst of Example 1 at 100 psi of hydrogen pressure producing average results of 68.8% yield and selectivity of 82.8%.

COMPARATIVE EXAMPLE 1

A reaction was also carried out as described in example 2 using copper chromite and ruthenium catalysts as described in Table II which follows. Conditions such as pressure, temperature and time were also varied. The best results were obtained at a hydrogen pressure of 1,000 psi

where the selectively was 50% and the yield was 39.7%. In addition, Raney copper, and copper-bismuth were also utilized, none of which were as effective as even the copper chromite catalyst.

Various branched and unbranched C ₂ -C ₂ o alcohols were tested to determine whether these would also be reactive with the inventive catalyst and 2-pyrrolidone to produce various alkyl pyrrolidones. For example, 1 butanol was reacted with 2-pyrrolidone and the copper-palladium catalyst of the invention to produce butylpyrrolidone with a yield estimated at 60% and selectivity at greater than 80%. Similarly, branched and cyclic alcohols such as 2 ethylhexanol and cyclohexanol were converted into the corresponding pyrrolidones, N-2-ethylhexyl pyrrolidone and

N-cyclohexyl pyrrolidone. The reaction was also under taken between 1-octanol and caprolactam to produce N-octyl- caprolactam.

Utilizing the inventive catalyst, economic conversion of alcohols and 2-pyrrolidone or cyclic lactams to corresponding alkyl pyrrolidones and alkyl substituted lactams are achieved. With the inventive process, processing costs are reduced through the reduction in cost of raw materials for producing the finished product. For example, octylamine sells for approximately $2.50/pound while octyl alcohol sells for approximately $.83/pound. Thus, the invention offers significant improvements over the prior art processes for producing N-substituted pyrrolidones. While preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes and modifications could be made without varying from the scope of the present invention.