Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
  • C07C51/36—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by hydrogenation of carbon-to-carbon unsaturated bonds

Definitions

• the present invention relates to a catalytic process for the hydrogenation of terephthalic acid to hexahydroterephthalic acid.
• esters of terephthalic acid are hydrogenated to esters of hexahydroterephthalic acid in good yield by conducting the hydrogenation in the molten state at an elevated temperature and pressure in the presence of a metal hydrogenation catalyst.
• the metal hydrogenation catalyst may comprise nickel, platinum or palladium or compounds of these metals
• the preferred catalyst is said to be a nickel catalyst, such as Raney nickel or nickelon-kieselguhr.
• the present invention provides a process for the hydrogenation of terephthalic acid to hexahydroterephthalic acid which comprises subjecting terephthalic acid to the action of hydrogen at an elevated temperature and pressure in the presence of a catalyst selected from the group consisting of palladium and ruthenium and in the presence of an inert liquid medium in which terephthalic acid is at least partially soluble under reaction conditions.
• Example 1 Terephthalic acid in the amount of 55 parts was placed in a stainless steel rocking type autoclave along with 5.5 parts of a commercial 5% palladium-on-activated charcoal catalyst and 200 parts of water.
• the air in the autoclave was displaced with nitrogen, the nitrogen with hydrogen and the autoclave was then pressured to 5,000 p.s.i.g. with hydrogen.
• the autoclave was next vented to 2,500 p.s.i.g. and, while agitating the reaction mixture, the temperature was raised over a period of minutes to a temperature of 180 C. and held there for 35 minutes.
• the autoclave was then cooled and the hydrogen released.
• the product was taken up in aqueous sodium hydroxide, filtered, and the clear, colorless solution diluted with water to-a total weight of about 1,600 parts.
• the solution was reacted dropwise with stirring to pH 2 with concentrated hydrochloric acid to give an odorless, colorless suspension. Since the strong charac teristic odor of hexahydrobenzoic acid was completely lacking, mono-decarboxylation during hydrogenation did not occur.
• the product was cooled to about 5 0., collected on a sintered funnel, washed four times with cold water and dried in a vacuum oven at 50 C.
• Example 2 The procedure of Example 1 was repeated with the exception that the autoclave was charged with parts of terephthalic acid and 10 parts of catalyst, the reaction pressure was 3,000 p.s.i.g., the temperature 200 C., and the reaction time 2 hours. Analysis of the product showed that the yield of mixed cis and trans-hexahydroterephthalic acids was greater than 83.5% at a terephthalic acid conversion of 100%.
• Example 3 The procedure of Example 2 was repeated with the exception that the reaction pressure was 5,000, the reaction temperature 180" C., and the reaction time 35 minutes. The yield of hexahydroterephthalic acid (a mixture of cis and trans isomers) was greater than 93% at a terephthalic acid conversion of 100%.
• Example 4 The procedure of Example 2 was repeated with the exception that the reaction pressure was 5,000 p.s.i.g. and the reaction temperature C. The yield of hexahydroterephthalic acid (a mixture of cis and trans isomers) was approximately 92% at 100% conversion of terephthalic acid.- I v
• Example 5 The procedure of Example 2 was followed with the exception that the reaction pressure was 5,000 p.s.i.g., the reaction temperature 250 C., and the reaction time 30 minutes. The yield of hexahydroterephthalic acid (a mixture of cis and trans isomers) was approximately 92% at 100% conversion of terephthalic acid.
• Example 6 The procedure of Example 2 was followed with the exception that the reaction pressure was 5,000 p.s.i.g., the reaction temperature 195 C., and the reaction time two hours. The yield of hexahydroterephthalic acid (a mixture of cis and trans isomers) was approximately 98.5% at 100% conversion of terephthalic acid.
• Example 7 One hundred parts of terephthalic acid was placed in a stainless steel rocking type autoclave with two parts of a commercial 20-64 mesh 5% palladium-onsilica gel catalyst and 200 parts of water. The autoclave was flushed twice with nitrogen and twice with hydrogen and pressured to 3,000 p.s.i.g. with hydrogen. Starting at this pressure the autoclave was heated to 240 C. over the course of 1 /2 hours. When the temperature reached 240 C. the pressure was raised to 5,000 p.s.i.g. and was maintained at 5,000-i200 p.s.i.g. for 1.8 hours. Work-up and analysis of the product showed that 100% of the terephthalic acid had been converted and the yield of mixed cis and trans-hexahydroterephthalic acids was greater than 92.5%.
• Example 8 Following the procedure of Example 2, 75 parts of terephthalic acid was hydrogenated at 140 C. and 5,000 p.s.i.g. in the presence of 300 parts of water and parts of a powdered 1.25% ruthenium-on-activated charcoal catalyst for 9 hours. The yield of hexahydroterephthalic acid (mixture of trans and cis isomers) was approximately 98% at 100% conversion of terephthalic acid. Essentially the same results were obtained in a repetition of this example in which the temperature was raised to 200 C. and the reaction time decreased to 4 /2 hours.
• the hydrogenation of terephthalic acid can be carried out under variable reaction conditions to provide high yields of hexahydroterephthalic acid as a mixture of cis and trans isomers provided a palladium or ruthenium catalyst is employed and the reaction is carried out in an inert liquid medium in which terephthalic acid is at least partially soluble under reaction conditions.
• the reaction involved is specific to palladium and ruthenium catalysts, the physical structure and composition of the catalyst can be widely varied without effect on the operability of the process.
• the cataiyst is one in which metallic palladium or ruthenium is distributed on a support of high surface area.
• Catalysts of this description are well known to the art and include palladium-on-charcoal, palladium-on-silica, palladium-on-alumina, and palladium-on-rutile and the corresponding ruthenium catalysts. These supported catalysts are effective whether in the form of pellets or powder or otherwise.
• Unsupported catalysts are also useful as, for example, powdered palladium or ruthenium, although, as a general rule, the efiicacy of the catalyst, on a terephthalic acid basis, is proportionate to the exposed surface area of palladium or ruthenium which explains the preference for supported catalysts.
• the quantity of catalyst to be used in the invention varies widely. It has been found that rapid reactions and good yields are obtainable when the amount of palladium or ruthenium is as low as 0.003 part per parts of terephthalic acid although, on a practical basis, it is desirable to employ at least about 0.025 part of palladium or ruthenium per 100 parts of terephthalic acid. There is, of course, no upper limit on the ratio of catalyst to terephthalic acid that can be used, this being entirely an economic consideration.
• the conditions of temperature and pressure can also be varied widely in carrying out the invention but, in general, temperatures within the range of to 300 C. are preferred with a temperature of 200 to 300 C. being most preferred as resulting in the most desirable reaction rates.
• the initial reaction mixture is prepared simply by charging terephthalic acid and the inert liquid medium to the reaction vessel either separately or in admixture with each other.
• terephthalic acid and the inert liquid medium In most cases, especially in continuous operation, it is desirable to feed to the reactor a slurry of terephthalic acid in the inert liquid medium and this consideration imposes the practical limitation of employing sufficient medium to form a fiowable slurry. In general, this amount of inert liquid medium corresponds to about 2 to 5 times the weight or" terephthalic acid employed.
• a greater amount of the inert liquid medium can, of course, be employed without detriment to the process but in order to avoid too dilute a reaction mixture it is preferred to have present not more than about 20 parts of the inert liquid medium per part of terephthalic acid.
• a process for the production of hexahydroterephthalic acid which comprises subjecting tere'phthalic acid to the action of hydrogen at an elevated temperature within the range of ISO-300 C. and at a pressure of at least 1000 p.s.i.g. in the presence of a palladium catalyst and in the presence of an inert liquid medium in which terephthalic acid is at least partially soluble under reaction conditions.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24740507

Family Applications (1)

Country Status (4)

Cited By (41)

Families Citing this family (4)

Citations (1)

Family Cites Families (1)

• 0
  • NL NL103362D patent/NL103362C/xx active
  • BE BE571022D patent/BE571022A/xx unknown
  • DE DENDAT1072620D patent/DE1072620B/de active Pending
• 1957
  • 1957-09-09 US US682632A patent/US2888484A/en not_active Expired - Lifetime

Patent Citations (1)

Also Published As

Similar Documents