Abstract:
Process for the production of 2,4,6-trimethyl pyridine wherein acetone or an acetone derivative is reacted under pressure with ammonia in the presence of a metallic catalyst to form mixture of products with a high preparation of 2,4,6-trimethyl pyridine and recovering the trimethyl pyridine.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of Ser. No. 793,890 filed Nov. 1, 1985, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention is a process for the production of 2,4,6-trimethyl pyridine wherein acetone or an acetone derivative is reacted with ammonia or aqueous solutions thereof to form a mixture containing 2,4,6-trimethyl pyridine. The mixture is then treated to recover 2,4,6-trimethyl pyridine in high yields. 
     Technical grade collidine or 2,4,6-trimethyl pyridine (TMP) is commercially available as a coal tar extract and contains a mixture of trimethyl and dimethyl pyridines which are difficult to separate due to their close boiling points. 
     There are many known synthetic methods to make 2,4,6-trimethyl pyridine as is illustrated by U.S. Pat. Nos. 3,781,292; 3,829,429, 4,140,690, and 4,220,783. 
     It is known from U.S. Pat. No. 2,796,421 to react ketones and ammonia over a catalyst to make trimethyl pyridines. However, this single pass process over silica-alumina gives low yields as is shown by the control set forth herein. 
     SUMMARY OF THE INVENTION 
     It now has been discovered that 2,4,6-trimethyl pyridine can be made in high yields and high purity by a process wherein acetone or an acetone derivative can be reacted with ammonia at a relatively high temperature to make a crude mixture of products containing 2,4,6-trimethyl pyridine which is then purified and 2,4,6-trimethyl pyridine is isolated. 
     The essential steps in the process of this invention are: 
     (A) reacting acetone or an acetone derivative with ammonia in the presence of an inorganic dehydrogenation catalyst containing one or more metals from Groups IVB to VIII of the Periodic Table or their compounds at a temperature in the range from about 300° to about 475° C. under a pressure in the range from about 2 to about 50 atmospheres with a liquid hourly space velocity 0.01 reciprocal hours and a mole ratio of ammonia to acetone or acetone derivatives equal to or greater than 0.2:1 to form a mixture of products containing a high proportion of TMP and 
     (B) recovering TMP from said mixture. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the process of this invention acetone is reacted with ammonia. While acetone is the preferred starting material, other compounds such as mesityl oxide and diacetone alcohol can be used. 
     The process is carried out with an ammonia to acetone or acetone derivative mole ratio in the range 0.2:1 to 14:1 with the preferred range being 4:1 to 8:1. Higher mole ratios give no advantage while lower mole ratios lead to decreased yields of trimethyl pyridine. 
     The temperature should be in the range from 300° to 475° C. and the preferred range is 360° to 390° C. 
     The liquid hourly space velocity of the reactants through the catalyst should be in the range 0.01 to 5.0 reciprocal hours and preferably in the range 0.2 to 2.0. 
     The pressure range should be in the range from about 2 to about 50 atmospheres. 
     The reaction product of the reaction is recovered and purified. The light products i.e. acetone, ammonia, acetone imine, mesityl oxide and mesityl imine can be flashed off and recycled to the reactor. The remainder can be distilled preferably under a nitrogen atmosphere and under a sub-atmospheric pressure of approximately 100 mm Hg and a temperature range from 45° to 140° C. 
     Examples of catalysts useful herein are activated alumina, silica-alumina or activated zeolite substrates impregnated with catalytic material processing relatively high dehydrogenation activity or properties. In general, the appropriate dehydrogenation catalytic material within the scope of this invention include the Group IVB to Group VIII metals of the Periodic Table. Still another group of these dehydrogenation materials comprise the oxides, halides, sulfides, selenides, molybdates, chromates, and manganates, of the above class of metals. 
     Any one or a plurality of the above metal or metal compounds possessing dehydrogenation activity may be used in admixture or as a deposit on the surface of the activated alumina, silica-alumina, or activated zeolite catalysts. 
     The preferred dehydrogenation materials for use in the scope of this invention include any one or a plurality of the following metals or their oxides: nickel, molybdenum, cobalt, tungsten, rhodium, rhenium, palladium, and platinum. 
     The following examples and controls are presented to further illustrate, but not limit the invention set forth in the claims. 
    
    
     EXAMPLE 1 
     Acetone was reacted with ammonia to produce 2,4,6 trimethylpyridine in a single-pass, fixed bed reactor (1&#34; diameter). The reactor held 250 ml of catalyst and ammonia and acetone were fed into the top of the reactor via separate lines. The product exiting the reactor was condensed in a stainless steel watercooled heat exchanger. Samples were analyzed by gas chromotography and H 2  O analyses were performed using the Karl Fischer titration technique. Acetone was passed over 6.7% NiO/27.0% MoO 3  on an alumina based catalyst at a rate of 1 ml/min (0.24 hr -1  LHSV). A 4/1 ammonia/acetone molar ratio was maintained while operating at 65 psig and 350° C. A sample of the reactor product gave the following results: 
     
         ______________________________________Product             Weight %______________________________________2,4,6-TMP           25.2Acetone             8.6Unknown Lights      13.7Mesityl Oxide       0.6Mesitylene          13.8Picoline            1.1Acetonin            0.7Diacetone Alcohol   1.4Phorone             0.4Isophorone          0.1Unknown Heavies     18.4H.sub.2 O           16.0% Yield to 2,4,6-TMP               39.7Based on consumed acetone% Acetone Conversion               91.4______________________________________ 
    
     EXAMPLE 2 
     Utilizing the same equipment mentioned in Example 1, the ammonia/acetone reaction was conducted using 0.5% palladium oxide on alumina catalyst under the following conditions and resulting in the following products: 
     
         ______________________________________Temperature °C.              379Pressure psig       89LHSV hr.sup.-1     0.13NH.sub.3 /Acetone mole ratio              7:1______________________________________ 
    
     
         ______________________________________Product             Weight %______________________________________2,4,6-TMP           18.2Acetone             27.5Unknown Lights      8.3Mestyl Oxide        1.7Mesitylene          0.7Tetrapyre           2.9Acetonin            13.1Isophorone          8.7Unknown Heavies     4.9Water               14.0% Yield to 2,4,6-TMP               36.1Based on consumed acetone% Acetone Conversion               72.5______________________________________ 
    
     EXAMPLE 3 
     Utilizing the same equipment mentioned in Example 1 the ammonia/acetone reaction was conducted using 0.5% palladium oxide on alumina catalyst under the following conditions and resulting in the following products: 
     
         ______________________________________Temperature °C.              378Pressure psig       56LHSV hr.sup.-1     0.27NH.sub.3 /Acetone mole ratio              4:1______________________________________ 
    
     
         ______________________________________Product             Weight %______________________________________2,4,6-TMP           16.4Acetone             38.4Unknown Lights      0.2Mestyl Oxide        1.0Mesitylene          0.3Tetrapyre           0.1Acetonin            21.9Diacetone Alcohol   2.5Picoline            0.1Isophorone          4.7Unknown Heavies     5.4Water               9.0% Yield to 2,4,6-TMP               38.3Based on consumed acetone% Acetone Conversion               61.6______________________________________ 
    
     EXAMPLE 4 
     Ammonia and acetone were also reacted over a 0.3% platinum/alumina catalyst utilizing the same equipment mentioned in Example 1. The following conditions were used resulting in the following products: 
     
         ______________________________________Temperature °C.              375LHSV hr.sup.-1     0.24NH.sub.3 /Acetone mole ratio              4:1Pressure psig       95______________________________________ 
    
     
         ______________________________________Product             Weight %______________________________________2,4,6-TMP           15.7Acetone             40.2Unknown Lights      8.5Mesityl Oxide       2.1Mesitylene          0.8Tetrapyre           0.6Acetonin            3.0Isophorone          5.5Unknown Heavies     8.5H.sub.2 O           15.0% Yield to 2,4,6-TMP               37.7Based on consumed acetone% Acetone Conversion               59.8______________________________________ 
    
     Control 1 
     An ammonia/acetone reaction was run over a SiO 2  /Al 2  O 3  catalyst in order to reproduce the prior state-of-the-art process which is shown in U.S. Pat. No. 2,796,421. The following conditions were used resulting in the following products: 
     
         ______________________________________Temperature °C.              360Pressure psig       45LHSV hr.sup.-1     0.24NH.sub.3 /Acetone mole ratio              4:1______________________________________ 
    
     
         ______________________________________Product             Weight %______________________________________2,4,6-TMP           14.3Acetone             14.4Lights              5.7Mesityl Oxide       0.7Mesitylene          8.0Tetrapyre           1.3Acetonin            1.1Diacetone Alcohol   0.3*Isophorone         9.6*Unknown Heavies    29.6H.sub.2 O           15.0% Yield to 2,4,6-TMP               24.0Based on consumed acetone% Acetone Conversion               85.6______________________________________ 
    
     Large losses to unrecyclable heavies and isophorone.