United States Patent (11 3,630,676 72 Inventors George B. Davis (56) References Cited Creve Coeur; UNITED STATES PATENTS Earle C. Makin, Jr., St. Louis; Herbert J. Gebhart, Jr., Ferguson, all of Mo. 2,953,589 9/1960 McCaulay.................... 260/438.1 (21) Appl. No. 798,802 FOREIGN PATENTS (22) Filed Feb. 12, 1969 797,164 411936 France......................... 23/204 45) Patented Dec. 28, 1971 Primary Examiner-Oscar R. Vertiz (73) Assignee Monsanto Company Assistant Examiner-Hoke S. Miller St. Louis, Mo. Attorneys-M. N. Cheairs, Elizabeth F. Sporar and C. James Bushman (54) SELECTIVE COMPLEXFORMATION FOR THE REMOVAL AND RECOVERY OF CARBON ABSTRACT: A process for the separation of carbon monox MONOXDE FROMMXED GAS STREAMS ide from mixed gases comprising contacting said mixed gases 10 Claims, No Drawings with a first complex comprised of a cuprous salt selected from (52) U.S. Cl........................................................ 23/204M, the group consisting of cuprous fluoroborate and cuprous 23/2 R fluorophosphate together with a hydrocarbon selected from (51) Int. Cl......................................................... C01 b31/18, the group consisting of aromatic hydrocarbons, olefin B01j 1122 hydrocarbons and mixtures thereof to produce a second com 50 Field of Search............................................ 23/204 M, 2 plex containing the carbon monoxide and recovering carbon R,2S monoxide from the resulting second complex phase. 3,630,676 1. 2 SELECTIVECOMPLEXFORMATION FORTHE means of heating to thereby disassociate the carbon monoxide REMOVAL ANDRECOVERY OF CARBONMONOXDE from the complex, by displacement with other compounds FROMMIXED GAS STREAMS complexible with the cuprous fluoroborate or cuprous fluorophosphate, or by any other convenient means, BACKGROUND OF THE INVENTON The process of the present invention is highly selective for The present invention relates to a process for removing car the removal and separation of carbon monoxide from mixed bon monoxide from mixed gas streams. More particularly, the gases in which the carbon monoxide is an admixture with such present invention relates to a process for the removal of car gases as hydrogen, methane, ethane and/or carbon dioxide. In bon monoxide from mixed gas streams by selective complex addition to this selectivity and somewhat contrary to many formation. 10 conventional processes, the present process provides for a Many industrial gases contain carbon monoxide in com high loading of the carbon monoxide in the complex phase. bination with hydrogen and often, such light hydrocarbons as methane and ethane. In many instances, such industrial gases DESCRIPTION OF THE PREFERRED EMBODIMENTS are utilized primarily for the hydrogen content thereof. In OF THE PRESENT INVENTON such instances, however, quite frequently the catalysts em 15 ployed are readily poisoned by the presence of carbon monox In the process of the present invention, the separation and ide and therefore, it is necessary to remove the carbon monox removal of the carbon monoxide from mixed gas streams is ide from the mixed gas streamin order to prevent such poison obtained by the selective complexing of the carbon monoxide ing. Particularly, such processes as ammonia synthesis and 20 with a first complex which is one containing cuprous hydrofining generally require hydrogen substantially free of tetrafluoroborate or cuprous hexafluorophosphate. Generally, carbon monoxide. In other utilities, the industrial gases are these cuprous salts are referred to merely as cuprous utilized primarily for the carbon monoxide therein. Such utili fluoroborate and cuprous fluorophosphate. Both of these salts ties include phosgene and acrylate synthesis, and the like. In are relatively unstable and cannot be readily formed as the such utilization, it is necessary to substantially purify the car 25 salt. As a result, the usual practice is to form the salt in the bon monoxide of hydrogen and other impurities prior to its presence of an organic compound with which the cuprous salt S. will complex, thereby forming the salt and the complex of the A number of means have been proposed by the prior art for salt with the organic compound substantially concurrently. the separation of carbon monoxide from admixture with The organic compounds in which the cuprous salts may be hydrogen and other components of mixed gas streams. These 30 formed and with which such salts are immediately complexed means have included selective diffusion through palladium or may include any of a rather large number of such compounds. platinum tubes or membranes and the reversible chemical The choice of organic compound is often dictated by practical reaction of carbon monoxide with various compounds such as consideration in the particular operation of the present inven methanol to form compounds which may in turn be disas tion contemplated. Generally, however, the organic com sociated back to CO and the reactant compound. Addi 35. pounds will be aromatic hydrocarbons. Such aromatic tionally, it has been proposed to selectively absorb carbon hydrocarbons may contain a single aromatic ring or may con monoxide from gases by means of metal carbonyl complexes tain two or more aromatic rings, either condensed or noncon employing chromium, molybdenum or tungsten as the metal. densed. In addition, the aromatic hydrocarbons may have sub Also, certain ammonium complexes of aqueous cuprous salts stituents to the ring or may be condensed with one or more have been proposed for the selective absorption of carbon 40 other ring structures which are paraffinic or olefinic in nature. monoxide. However, none of these prior art techniques for the Nonlimiting examples of aromatic hydrocarbons suitable for separation of carbon monoxide from mixed gases have been use in preparing the cuprous salts of the present invention are found to be as successful as desired, particularly from the benzene, toluene, the xylenes, various other polymethyl commercial standpoint. benzenes, such as mesitylene, isodurene, tri-, tetra-, penta It is an object of the present invention to provide a new and 45 and hexamethylbenzenes, ethylbenzene and the various improved process for the separation of mixed gases containing polyethylbenzenes, isopropylbenzenes, propylbenzene and the carbon monoxide. An additional object of the present inven various polyisopropyl and polypropylbenzenes, the various tion is to provide a new and improved process for the separa butyl and pentylbenzenes and the like, the substituted tion of carbon monoxide from mixed gases which include benzenes containing two or more different substituents such hydrogen. Another object of the present invention is to pro 50 as ethyltoluene, isopropyltoluene, and ethylxylenes; vide a new and improved process for the separation of cabon naphthalene, the various methylnaphthalenes, and monoxide from mixed gases by means of selective complex polymethylnaphthalenes, ethylnaphthalene and the various formation. A remaining object of the present invention is to polyethylnaphthalenes, the naphthalenes containing propyl, provide a new and improved process for the separation of car isopropyl, butyl, and pentyl substituents; the substituted bon monoxide from mixed gases by means of selective com 55 naphthalenes containing two or more different substituents plex formation whereby greater selectivity for such carbon such as methylethylnaphthalene, methylpropylnaphthalenes, monoxide is obtained. Additional objects will become ap etc.; the various indanes such as methylindanes, ethylindanes, parent from the following description of the invention herein isopropylindanes, etc.; the dihydronaphthalenes such as disclosed. methyl, ethyl, propyl, and butyl substituted 60 dihydronaphthalenes; the tetrahydronaphthalenes and the SUMMARY OF THE INVENTION like. In the preferred practice of the present invention, the The present invention, which fulfills these and other ob aromatic hydrocarbons most often employed as the organic jects, is a process for the separation of carbon monoxide from compound in forming the complexes of the present invention mixed gases containing carbon monoxide, the process com 65 are benzene, naphthalene, partially hydrogenated prising contacting said mixed gases with a cuprous naphthalenes and the various alkyl substituted derivatives of fluoroborate or cuprous fluorophosphate containing complex these wherein the alkyl substituents have no more than four (hereinafter referred to as the "first complex' which contains carbon atoms per substituent. Within this group of preferred in addition to such cuprous fluoroborate or cuprous aromatic hydrocarbons are such compounds as benzene, fluorophosphate, aromatic and/or olefin hydrocarbons. Such 70 ethylbenzene, toluene, the xylenes, naphthalene and the contact results in the selective removal of carbon monoxide methylnaphthalenes, dihydronaphthalenes and the from the mixed gases by means of such carbon monoxide tetrahydronaphthalenes. A particularly useful group of aro being retained within the cuprous fluoroborate or cuprous matic hydrocarbons for use in forming the complexes is that fluorophosphate containing complex phase. The carbon including such compounds as toluene, ethylbenzene, ethyl monoxide may be recovered from the complex phase by 75 toluene, the xylenes and tetrahydronaphthalene. 3,630,676 3 4. The method of preparing the cuprous fluoroborate-aro often, the olefin hydrocarbons employed will be those con matic hydrocarbon containing complex which is used for the taining