Reprinted from the JOlJ"RNAL OF THE AMERICAN GIL CHEMISTS' SOCIETY, Vol. 48, No.6, Pages: 265-2iO (.June 19i1) Purchased by Agricultural Research Ser,ice, U.S. Dept. of Agriculture, for official use. Catalytic Effects in the Ammonolysis of Vegetable Oils 1 W.L. KOHLHASE, E.H. PRYDE and J.C. COWAN, Northern Regional Research Laboratory,Z Peoria, Illinois 61604 ABSTRACT (19), also promote ammonolysis. Catalysts for the ammonolysis of soybean oil are, Our study was undertaken to develop a practical method in order of decreasing overall effectiveness, for rapid ammonolysis of vegetable oils under mild ammonium acetate, sodium methoxide, 9-amino­ conditions. A variety of known and new catalysts and nonanoic acid, sodium soyate, ammonium nitrate, reaction conditions were compared at 100-150 C; excess alanine, sodium acetate and glycerol. At 125 C, a anhydrous ammonia was the solvent. reaction time of 1 hr and a 30: 1 mole ratio of ammonia to ester, ammonium acetate achieved EXPERIMENTAL PROCEDURES ammonolysis in 16%,61% and 84% conversions at the Materials respective concentrations of 0.0, 0.1 and 1.0 mole per mole ester groups. Conversion was 98% complete in 4 Crude soybean oil (A.E. Staley Mfg. Co.) contained hr with 1.0 mole. The ammonolysis generally 0.43% free fatty acid. Alkali-refined soybean oil (Archer exhibited the expected first order kinetics up to Daniels Midland Co.) had 0.03% free fatty acid. USP olive about 80% reaction. oil (Mario's Food Products, Detroit, Mich.) had an iodine value of 83 and n'b° = 1.4647. Methyl oleate from Applied Science Laboratories contained 99% monoene (95% .6,9). INTRODUCTION All catalysts were commercial reagent grade materials used Higher fatty amides are useful industrial chemicals as as supplied unless noted otherwise in Table 1. Moisture well as intermediates for several laboratory processes, for sensitive catalysts were handled in a dry atmosphere. example, the synthesis of nylon-9 (1). Commercially, fatty Ammonolysis Procedure amides are made by reaction between fatty acids and excess ammonia at 150-300 C and 1 atm (2); reaction time is Catalyst was placed in the autoclave (Table I, footnote typically 10 hr at 150~200 C (3). High temperatures and a), which was flushed with dry Nz and kept under Nz long reaction times significantly dehydrate the amides to thereafter; the lower half was cooled in dry ice for 1 hr. nitriles. For example, reaction of stearic acid and ammonia With HzO-absorbing catalysts (Runs 3,4, 16, 18 and 19, at 300 C produces stearonitrile (4). Table I), the autoclave was first dried at 150 C and cooled Alkyl esters, including triglycerides, of fatty acids are under dry Nz before charging. The ester was then charged, also suitable starting materials for amide preparations by the head secured to the autoclave and the entire autoclave 'eaction with excess anhydrous ammonia under autogenous cooled in dry ice for 1 to 1 1/2 hr. Commercial 99.99% pressure. Temperatures needed are lower than with fatty pure anhydrous NH 3 was condensed to ±3 ml of the desired acids; although slow ammonolysis occurs even at 25 C (2), volume into a graduated cold trap that had been oven dried temperatures above 150 C are required for practical at 125 C and cooled under dry Nz. The NH 3 was then reaction rates (5). Nitrile formation begins about 175 C (6), transferred to the open autoclave under Nz. The autoclave becomes significant above 190 C and causes discoloration was sealed and heated to the desired operating temperature and lower amide yield (5). A 1.5% conversion of stearamide within 30-50 min, the exact period depending upon the to stearonitrile occurs in 7 hr at 190 C (7). autoclave and temperature. At the end of the reaction, NH 3 A catalyst is necessary to give practical rates for ester was slowly vented through an appropriate manifold system. ammonolysis at temperatures well below the amide dehy­ With rocker bombs, which were first cooled to dry ice dration point and to permit operation below the critical temperature, the NH 3 was allowed to evaporate from the temperature of ammonia (133 C). Ammonium salts are opened bomb as it warmed to room temperature. There was reported to be catalysts in anhydrous ammonia (2,7-9) but no problem with foaming during the NH 3 boil-off except in not in methanol solution (10). The rate of ammonolysis of Runs 18 and 19 with CH 3 0Na. seed oils in excess anhydrous ammonia was doubled at For the rate studies (Table I, Runs 1-20), samples were 165 C by adding 17% NH4 Cl; in 2 hr, the reaction with obtained by means of a 1.2 mm bore tube extending to the soybean oil was 32% complete and with olive oil, 55% bottom of the autoclave; the line was flushed with 2-3 ml complete (8). Other inorganic ammonium salts (11), reaction mixture before collecting each 0.5-1.5 ml sample. ammonium benzoate (11) and about 5% of the ammonium Some stress corrosion caused by the anhydrous NH 3 salt of the corresponding free fatty acid (7) have served as vapor occurred at the top of the solenoid housing of the 0.5 catalysts. The relative activity of four ammonium salts as liter stainless steel (type 316) autoclave; pitted fissures were catalysts for the ammonolysis of ethyl benzoate in observed. anhydrous ammonia was in the order (11) of benzoate> Amide Purification chloride>bromide>perchlorate, the reverse of their relative degree of ionization in water. The crude ammonolysis product was freed of glycerol The effectiveness of strong bases as catalysts is unclear. and catalyst by washing in the molten state five to seven Although a Russian patent (12) ascribes activity to metal times with 5-6 vol hot Hz 0, or by dissolving in 3-4 vol hot amides, their high base strength causes extensive proton acetone and adding to 4-5 solution vol Hz 0 at 0 C, filtering abstraction at the a-carbon and little ammonolysis in liquid the precipitated solids and washing the solids with 1-2 vol ammonia (13,14). Alkoxides have been used as ammonoly­ Hz O. Certain runs required that these procedures be sis catalysts in lower alcohols (10) and as aminolysis modified. The amides from Runs 3 and 17 were separated catalysts (15,16). Hydroxyl compounds, particularly from catalyst by dissolving in CH zClz , filtering or centri­ glycols (17), as well as acetonitrile (18) and neutral salts fuging and finally evaporating the solvent before Hz 0­ washing. The basic catalyst in Runs 18 and 19 was 1Presented at the ISF-AGCS Meeting, Chicago, September 1970. neutralized by addition of a slight excess of HCOOH or ZNo. Market. Nutr. Res. Div., ARS, USDA. NH4 Cl solution before work-Up; severe emulsion problems 265 tv 0\ 0\ TABLE I Ammonolysis of Fatty Esters Chargeb,C Reaction conditionsd Per cent ammonolysise Catalyst First order NH3' Maximum Graphs kat 50% Run Ester moles Moles/ Temperature Time, pressure, Final reaction ...... number Reactora wt,g RCOO- Identity RCOO- C hr psig I hr 4 hr product (In-I) c:0 ::tl If M RS,79 30 0 0 150 6.0 2100 19 (2.4) 70 (3.0) 89 0.28 Z 2 M RS,79 30 0 0 125 5.0 1250 16(3.7) 60 (3.6) 74 0.22 ;J> 3 M RS,79 30 -COOH resing 0.10 125 6.0 1400 3 (2.4) 31 (3.0) 53 0.12 r' h 0 4 M RS,79 30 Glycerol 0.50 125 7.0 1300 16 (2.5) 68 (3.3) 91 0.25 "I'j 5 M RS,79 30 NH4N03 0.10 125 6.5 1350 35 (2.7) 86 (4.4) 96 0.5 I ..., 6 M RS, 79 30 NH40Ac 0.10 125 5.8 1375 6 I (3.0) 89 (4.6) 96 0.92 ::r:: 7 i M RS, 79 30 NH40Ac 0.20 125 6.0 1125 65 (4.2) 95 (4.6) 96 1.11 tTJ 8i M RS, 79 30 NH40Ac. 0.20 125 7.0 1300 66 (3.3) 95 (5.0) 98 1.5 I ;J>s:: 9 M RS, 79 30 ex HOAc! 0.20 125 6.0 1300 73 (2.6) 93 (4.2) 98 1.39 tTJ 10 M RS, 79 30 NH40Ac 0.50 125 5.8 1325 75 (3.2) 96 (4.5) 96 1.65 :;0 II M RS,79 30 NH40Ac 1.00 125 5.8 1200 84 (4.7) 98 (6.8) 98 1.92 n 12 M RS, 198 3 NH40Ac 0.14 125 6.1 400 10(3.6) 66 (3.7) 91 0.24 ;J> 13 M RS,79 30 NH40Ac 0.20 100 4.7 810 32 (3.4) 84 (4.7) 91 0.45 Z 14 M RS,79 30 CH3CH(NH2)COOH 0.10 125 5.5 1310 32 (3.2) 84 (4.7) 97 0.41 0 15 M RS,79 30 H2N(CH2)8COOHk 0.10 125 5.8 1225 49 (2.4) 60(3.9) 92 0.65 t=: l () 16 M RS, 80 30 NaOAc 0.20 125 6.0 1425 19 (2.5) 72 (3.7) 94 0.28 ::r:: 17 M RS, 63 37 Na soyatem 0.25 125 6.0 1500 46 (2.4) 82 (4.1) 86 0.57 tTJ 18 M RS, 79 30 NaOCH3 0.20 125 6.0 1325 61 (3.5) 85 (4.4) --- 1.00 s:: 19 M RS, 79 30 NaOCH3n 0.20 125 5.0 1210 80 (6.0) 80 (5.8) 79 3.65 ...,v; 20 M CS,79 30 0 0 125 1225 18 (3.7) 58 (4.1) 65 0.21 U; 0.5 400 --- --- v.> 21 R CS,44 30 0 0 ~72 -- 0 125 4.0 1200 --- --- 84 0 22 R CS, 44 30 NH40Ac 0.20 125 4.0 1200 --- --- 91 ...,tTJ 23 R CS, 44 30 NH40Ac 1.00 125 4.0 1200 --- --- 93 -< 0.5 400 24 L CS, 200 24 NH40Ac 0.90 ~ 75 125 3.8 1210 --- --- 98 ~ 0.2 290 25 L OL,IOO 68 NH40Ac 0.90 10060 1.0 775 125 4.8 1250 --- --- 98 1.0 730 26 L MO,50 52 NH40Ac 1.10 { 90 125 3.0 1225 --- --- 86 6 r' -l>­ 00 JUNE, 1971 KOHLHASE.