United States Patent Office Atented Sept

3,151,150 United States Patent Office atented Sept. 28, 1964 1. 2 cussed in Chemical Week (September 27, 1958), pp. 3,554,450 53-54, Chemical Engineering (June 1, 1957), pp. 42-44, PROCESS FOR THE MANUEFACTURE OF ACRYELONTRLE Chemical and Engineering News (December 1, 1958), pp. onas Karact, New York, N.Y.; Edna Yadven. Kamiet, 49 and 98, and by Sennewald and Steil in Chemie-In executrix of said Josias Kanet, deceased, assignor, by genieur-Technik, 30, #7, 440-446 (1958). mesne assign eats, to Edia Y. Kaanet, doing business It is the purpose of my invention to provide a process as The Kainie Laboratories, New York, N.Y. for the manufacture of acrylonitrile from acetaldehyde No Drawing. Fied Sept. 4, 1959, Ser. No. 839,570 and hydrogen cyanide which does not require reagents 4 Clains. (C. 260-465.9) other than acetaldeyhde and HCN and does not involve O by-product recovery, which does not require concentra This invention relates to a process for the manufacture tion and re-constitution of intermediates, and which gives of acrylonitrile. More particularly, this invention relates yields in excess of 90% of theory. to a process whereby acrylonitrile may be manufactured, The basis of my invention is the finding that acryloni in good yields, from cheap and readily available industrial trile may be obtained in excellent yield by the steps of: intermediates-acetaldehyde and hydrogen cyanide. (a) reacting lactonitrile (made from acetaldehyde and hy Acrylonitrile has become an extremely important chem drogen cyanide) with pre-formed acrylonitrile, in the ical article of commerce, widely used in the manufacture, presence of a basic catalyst, to form alpha,beta'-dicyano of synthetic rubbers, plastics, fibers, films, plasticizers, dye diethyl ether (alpha,beta'-oxydipropionitrile): stuffs, pharmaceuticals, solvents and other products. A tremendous technology has developed and several 20 thousand patents have issued on the manufacture of acry CH3CHOEICN -- CII-CEICN - CH-CH-ON9 lonitrile by the dehydration of ethylene cyanohydrin (from HCN and ethylene oxide) and by the reaction of CH2CH2CN acetylene with HCN. Lactonitrile (which is isomeric with (b) pyrolyzing the alpha,beta'-dicyanodiethyl ether, at ad ethylene cyanohydrin) made by the reaction of acetalde vanced temperatures, to form (for each mole of said hyde and hydrogen cyanide, cannot be dehydrated easily ether) two moles of acrylonitrile and one mole of water to form acrylonitrile and water, since it tends to decom pose into the original reagents at advanced temperatures. CH-CH-CN To obviate this tendency of lactonitrile to decompose o - 20EF2=CHCN -- HO into acetaldehyde and HCN, it has been proposed to acyl CHCHCN ate the lactonitrile and then to pyrolyze the resultant alpha-acyloxypropionic acid to obtain acrylonitrile and One mole of the acrylonitrile thus obtained is recycled the organic acid. Thus, lactonitrile is reacted with acetic to the first step of the process, for reaction with the lactoni. anhydride to form the alpha-acetoxypropionic acid, which trile to form the alpha,beta'-dicyanodiethyl ether. The is then pyrolyzed to form acrylonitrile and acetic acid. other mole of acrylonitrile is the salable end-product of (Ritchie, Jones and Burns, U.S. Patent 2,183,357 (1939); Said process. Miller and Groombridge, U.S. Patent 2,452,672 (1948).) Thus, the overall effect of the process is to form acry This process requires the use of an additional reagent lonitrile from acetaldehyde and hydrogen cyanide as sub acetic anhydride-and the recovery and recycling of the stantially the sole reagents. acetic acid formed. 40 Hansiey (in U.S. Patent #2,333,782 issued November More recently, a process has been developed for the 9, 1943) has shown that lactonitrile may be reacted with manufacture of acrylonitrile from acetaldehyde and hy acrylonitrile in the presence of an alkaline catalyst, to drogen cyanide which involves reacting these compounds form the alpha,beta'-dicyanodiethyl ether. to form lactonitrile, mixing the lactonitrile with phos I have found that this alphabeta'-dicyanodiethyl ether phoric acid (nitrile-acid ratio about 2:1) and then spray may be pyrolyzed over a very wide range of tempera ing this reaction mixture under pressure into a reac 45 ture, in the absence of catalysts as well as in the pres tion chamber, where it encounters pre-heated oxygen-free ence of dehydration catalysts, in the liquid phase and combustion gases, at a temperature of about 600 C. in the vapor phase and at subatmospheric, atmospheric Dehydration occurs in about 0.1 to 0.6 second. Reac and Super-atmospheric pressures, to give excellent overall tion products are cooled, condensed and separated. yields of acrylonitrile. It must be emphasized that, be The phosphoric acid is recovered in this process as 50 callse of the wide range and variety of operable reaction a solution of about 30% acid strength, which must then conditions, I do not wish to be limited in the scope of be concentrated to 80%-85% acid strength before it can this invention to any specific range of temperatures, cata be recycled to the process. About two-thirds of the lyst or reaction conditions. lactonitrile is thus dehydrated to acrylonitrile, the remain The lactonitrile for the process of my invention may der dissociating into acetaldehyde and HCN, which is 55 be made by any of the well-known methods of the prior recycled in the process. Part of the lactonitrile reacts art. Thus, for instance, liquid hydrogen cyanide is ad with the phosphoric acid and the water present to form justed to a pH between 6.0 and 8.0 with 20% aqueous Soda. Solution. The stoichiometric amount of acetalde lactic acid and primary ammonium phosphate hyde is then added with agitation at a temperature be -NHHPO 60 tWeen 10 C. and 25° C. to form actonitrile. About 7.5 kgs. of this ammonium phosphate is obtained The Iactonitrile thus obtained may then be reacted for every 100 kgs. of acrylonitrile formed. This salt with acrylonitrile, in the presence of an alkaline catalyst accumulates in the recycling phosphoric acid and must (e.g. alkali and alkaline earth metal hydroxides, alco be periodically separated from the system. This involves holates and cyanides, trialkyl amines, etc.), substantially a somewhat diminished yield of acrylonitrile, complicates 65 by the process of Hansley (U.S. Patent #2,333,782) to the phosphoric acid recovery, requires a concentration form the desired alpha,beta'-dicyanodiethyl ether. and recycle system and involves the consumption of addi It is also entirely feasible to react acetaldehyde, hydro tional phosphoric acid reagent. The overall yield of acry gen cyanide and acrylonitrile, in the presence of an alka lontrile by this process is about 90% of theory. This line catalyst, in a single step, to form the alpha,beta'. process is described in U.S. Patent #2,790,822 (issued 70 dicyanodiethyl ether. April 30, 1957, to Wolfram, Steil and Agunte) and dis The reaction of the acrylonitrile with the lactonitrile 3,151,150 s 4. (or with acetaldehyde and HCN if the reaction is effected active catalyst form and may be used as such for pro in a single step) is not quantitative. Thus, after the re longed periods of time. The preferred (but by no means action of the acrylonitrile with the lactonitrile is effected, solely effective) reaction temperature for the pyrolysis the reaction mixture is fractionated to recover the alpha employing phosphoric acid as a catalyst (or its dehydrated beta-dicyanodiethyl ether and to recover and recycle the forms-pyrophosphoric and metaphosphoric acid) is 300 various intermediates. Thus, the reaction product may C. to 400 C. first be fractionated at atmospheric pressure. Acetalde Alternately, the alphabeta'-dicyanodiethyl ether may hyde and hydrogen cyanide (formed by the dissociation be passed in the vapor state through a catalyst bed, or a of unreacted lactonitrile) distill over first (B. Pt. acetalde heated reaction zone containing the catalyst, or through hyde 21 C., hydrogen cyanide 26 C.). The unreacted 0 heated tubes filled with the catalyst. Catalysts suitable acrylonitrile (B. Pt. 78.5° C.) first distills over as an azeo for this purpose are activated alumina, pumice, dia trope with the water present in the system. This azeo tomaceous earth, fullers' earth, silica gel, Alundum, thoria, trope boils at 71° C. and contains 88% of acrylonitrile dehydrating clays, etc. as well as supported catalysts such and 12% of water. The fractionation of the reaction mix as phosphoric acid or ammonium phosphates on any solid ture is then continued under reduced pressure, e.g. at carrier, such as activated alumina, pumice, kaolin, clay, 18-20 mm. Hg. The unreacted lactonitrile distills over at firebrick, silica gel, zinc chloride on any solid carrier 90-100° C. at 18-20 mm. Hg, and the alphabeta'-dicy such as the above, etc. anodiethyl ether may be recovered at 145° to 155 C. at Alternately, the vaporized alpha,beta'-dicyanodiethyl 18-20 mm. Hg. However, in the practical application of ether may be passed, at advanced temperatures, through a this process, it is only necessary to recover the acetalde 20 turbulent bed of any of the catalysts above enumerated, hyde, hydrogen cyanide, acrylonitrile and lactonitrile frac in very finely divided form, by any of the technics now tions. The residue in the still, consisting of the alpha used in fluid bed catalyzed reactions, and well known to beta'-dicyanodiethyl ether, may be submitted directly to the art. pyrolysis for the formation of acrylonitrile, without prior The preferred temperature ranges when employing such fractionation or purification. The recovered acetaldehyde, 25 solid catalysts, with the alpha,beta-dicyanodiethyl ether hydrogen cyanide, acrylonitrile and lactonitrile fractions in the vapor state, is from 250° C.

Load more