PROCESS FOR PREPARING TERTIARY POLYALKYLENE AMINOETHER ALCOHOLS

Abstract: The present invention relates to a process for selectively preparing severely sterically hindered or cyclic tertiary polyalkylene aminoether alcohols by reacting (a) one or more secondary acyclic or heterocyclic amino compounds with (b) a polyalkylene ether glycol in the presence of a hydrogenation catalyst at elevated temperatures and pres­ sures. The resulting tertiary aminoether alcohols are useful in acid gas scrubbing processes, particularly in the selective removal of H₂S from gaseous streams containing CO₂ and H₂S.

Description: FIELD OF THE INVENTION The present invention relates to a process for selectively preparing tertiary polyalkenyl aminoether alcohols, some of which are severely sterically hindered, by reacting an acyclic or heterocyclic amino compound with a polyalkenyl ether glycol in the presence of a hydrogenation catalyst at elevated temperatures and pressures. BACKGROUND OF THE INVENTION Recently, it has been disclosed that tertiary aminoether alcohols are suitable agents for scrubbing acid gases from gaseous streams containing the same. Such compositions are disclosed in Belgium Pat. No. 769;797 as well as in Goodridge, Trans Faraday Society, 51, 1703-9 (1955). The art teaches that these compounds may be prepared by reacting the appropriate secondary amine or heterocyclic nitrogeneous compound with a haloalkoxyalkane or sulfonate ester of a glycolic ether under conditions such that the haloacid or sulfonic acid is eliminated. Disadvantages of such a process include relatively expensive raw materials and product isolation. That is, the initially formed product is an amine salt which requires caustic treatment as part of-the product isolation procedure. Consequently, there exists a need in the art for methods of preparing such tertiary aminoether alcohols which would not be limited by such disadvantages. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a process for preparing cyclic and severely sterically hindered acyclic tertiary polyalkenyl aminoether alcohols which comprises reacting (a) one or more secondary acyclic or heterocyclic amino compounds respectively represented by the formulas: EMI2.1 where R1 and R2 are independently selected from the group consisting of primary, secondary and tertiary alkyl radicals having 1 to 8 carbon atoms and cycloalkyl radicals having 3 to 8 carbon atoms with the proviso that at least one of R1 and R2 is a secondary or tertiary alkyl radical, q is the number, from 2 to 10, of carbon atoms in the heterocyclic ring, and R3, which is optional, is selected from the group consisting of alkyl and cycloalkyl radicals which may be pendent on one or more of the carbon atoms of the ring; with (b) a polyalkenyl ether glycol having the general formula: EMI2.2 where R4, R5, R6, and R7 are each independently selected from the group consisting of hydrogen, C1 to C4 alkyl radicals, and C3-Cg cycloalkyl radicals with the proviso that if only one of Rland R2 directly attached to the nitrogen atom is a secondary alkyl radical and neither of them is a tertiary alkyl radical, at least one of R4 and R5 directly bonded to the carbon which is bonded to the hydroxyl group is an alkyl or cycloalkyl radical, x and y are each positive integers independently ranging from 2 to 4, and z is a positive integer ranging from 1 to 10, said process being carried out in the presence of a catalytically effective amount of a supported Group VIII metal containing hydrogenation catalyst at elevated temperatures and pressures, wherein the mole ratio of amino compound employed to polyalkenyl ether glycol is less than 2:1 when z is greater than 1. In preferred embodiments of the present invention, R1 is a tertiary alkyl radical having 4 to 6 carbon atoms, R2 is an alkyl radical having 1 to 6 carbon atoms, R4, R5, R6, and R7 are hydrogen, x and y are 2 and z is from 1 to 10. In other preferred embodiments of the present invention, the amino compound is heterocyclic, preferably having 3 to 6 carbon atoms in the ring, R4, R5, R6 and R7 are hydrogen, x and y are 2, and z is from 1 to 10. DETAILED DESCRIPTION OF THE INVENTION As previously indicated, both secondary acyclic amino compounds and heretocyclic amino compounds may be used in the practice of the present invention. The preferred amino compound is N-methyl-tertiary-butyl amine and the preferred heterocyclic amino compounds are saturated and contain from 3 to 6 carbon atoms in the ring, more preferably 4 to 5 carbon atoms, and most preferably 4 carbon atoms. The amination process hereof is carried out under pressure at a temperature ranging from about 1600 to about 4250C, preferably from about 1800 to about 4000C, and most preferably from about 1900 to about 3500C. The pressures in the reactor may range from about 50 to about 3000 psig, preferably from about 100 to about 1000 psig, and most preferably from about 150 to about 750 psig. The reactor used may include any suitable vessel capable of withstanding the pressures necessary to carry out the amination process. Preferably, the amination process is carried out in a fixed bed reactor whereby the reactants are passed over a fixed bed of the catalyst, either concurrently or countercurrently. Other reactors suitable for use herein include moving bed reactors and continuous stirred reactors. For example, in a continuous stirred reactor the catalyst is circulated and the reactants and reaction product are passed through the reaction vessel at a controlled rate. The hydrogenation catalyst used in the amination process herein may include any of the known hydrogenation catalysts. Illustrative hydrogenation catalysts include platinum, palladium and other noble metals such as ruthenium, rhodium,osmium and iridium deposited on inert supports such as carbon, silica, alumina or other refractory oxides, Raney nickel, nickel-on-kieselguhr, nickel on inert support, massive nickel or nickel-cobalt or nickel-cobalt-copper coprecipitated with silicate and/or aluminum salts having alumina or kieselguhr supports. Preferred catalyst include coprecipitated nickel, nickel-cobalt, and nickel-cobalt-copper supported on silica, alumina or a mixture thereof. Also preferred is platinum supported on alumina. Still more preferred are catalysts having increasing concentrations of nickel, about 40% to 70% nickel, by weight. Since preferred catalysts include those massive-metal coprecipitated hydrogenation catalysts described in U.S. Patent Nos. 3,697,445; 4,251,394; 4,251,672; 4,263,173; 4,263,225; 4,273,680; 4,273,939; 4,307,248; 4,318,829; and the metal coprecipitated catalysts containing aluminum and silica disclosed and claimed in U.S. Serial Nos. 388,966 and 388,967, the disclosures of which are incorporated herein by reference. It is preferred that the catalyst be reduced or activated by a reductant, such as hydrogen prior to use in the amination reaction. This reduction or activation is typically carried out by passing hydrogen over the catalyst at temperatures ranging from 1750 to about 4000C, preferably 2000 to about 3500C. The concentration of the hydrogenation catalyst is that which is catalytically effective and that amount will generally range from about 0.1 to about 10 weight percent, preferably from about 2 to about 8 weight percent, based on the weight of the reactant charge. The normal pretreatment conditions and handling of the hydrogenation catalyst should be practiced as known to those skilled in the hydrogenation catalyst art. The theoretical equivalent mole ratio of amino compound to polyalkenyl ether glycol in the reac tion charge is 1:1. When the polyalkenyl ether glycol is diethylene glycol the mole ratio of amino compound to diethylene glycol can range from 0.5:1 to 6:1, pre ferably 1:1 to 4:1. When the polyalkenyl ether glycol is triethylene glycol or higher, the mole ratio of amino compound to glycol must be kept below 2:1 other wise the tertiary amino ether alcohol would not be favored. For purposes of this invention it may be desirable to include an inert solvent in the reaction medium. Preferably the solvent is a solvent such as cyclic or linear ether or a hydrocarbon containing compound in which the reactants will dissolve. The solvent should be of relatively low molecular weight to facilitate its removal from the product of the reaction. The amount of the solvent may vary, but will generally range from about 10 to 50 wt.%, preferably from 15 to 30 wt.%, based on the weight of the reactants used. Preferred solvents include tetrahydrofuran, dimethylether of ethylene glycol and toluene. Reduction of the catalyst may be carried out in situ while conducting the process by the presence of hydrogen. Hydrogen, however, is not essential to conducting the process but is preferably employed, for example, to minimize catalyst deactivation. Once the reaction has been completed, the reaction product can be conveniently recovered by known techniques such as solvent evaporation, distillation and the like. The invention is illustrated further by the following paper examples which, however, are not to be taken as limiting in any respect. All parts and percentages, unless expressly stated otherwise, are by weight. Example 1 N-Ethoxyethanol Pyrrolidine A mixture of 209 of pyrrolidine, 29g of diethylene glycol, 50ml of toluene and 6g of 1% platinum supported on graphite are heated at 2000C in a 300ml stirred steel autoclave at autogenous pressure. At the end of 24 hrs N-ethoxyethanol pyrrolidine will be obtained in a yield of about 40%. Example 2 N-Methyl-tertiarybutylaminoethoxyethanol A 300ml steel autoclave containing .5 moles of N-methyl-tertiarybutylamine, .5 mole of diethylene glycol and lg of a supported nickel catalyst (Harshaw Ni-5132P), are pressured with 100 psi of hydrogen and heated at 2000C until the diethylene glycol is completely consumed. Both the disappearance of diethylene glycol and the formation of N-methyl-tertiarybutylaminoethoxyethanol will be followed by the periodic withdrawal of samples from the autoclave, followed by G.C. analysis.

Claims: CLAIMS: 1. A process for producing tertiary polyalkylene aminoether alcohols comprising reacting: (a) one or more secondary acyclic or hete rocyclic amino compounds respectively represented by the formulas: EMI8.1 where R1 and R2 are selected from the group consisting of primary, secondary and tertiary alkyl radicals having 1 to 8 carbon atoms and cycloalkyl radicals having 3 to 8 carbon atoms with the proviso that at least one of R1 and R2 is a secondary or tertiary alkyl ra dical, q is the number, from 2 to 10, of carbon atoms in the heterocyclic ring, and R3, which is optional, is selected from the group consisting of alkyl and cycloalkyl radicals which may be pendent on one or more of the carbon atoms of the ring; with (b) a polyalkylene ether glycol having the general formula: EMI8.2 where R4, R5, R6 and R7 are each independently selected from the group consisting of hydrogen, C1 to C4 alkyl radicals, and C3-Cg cycloalkyl radicals, with the proviso that if only one of R1 and R2 directly attached to the nitrogen atom is a secondary alkyl radical and neither of them is a tertiary alkyl radical , at least one of R4 and R5 directly bonded to the carbon which is bonded to the hydroxyl is an alkyl or cycloalkyl radical, x and y are each positive integers in dependently ranging from 2 to 4, and z is a positive integer ranging from 1 to 10, said process being carried out in the presence of a catalytically effect ive amount of a supported Group VIII metal containing hydrogenation catalyst at elevated temperatures and pressures, and wherein the mole ratio of amino compound to polyalkylene ether glycol is less than 2:1 when z is greater than 1. 2. The process of claim 1 wherein R1 is an alkyl radical having 4 to 6 carbon atoms, R2 is an alkyl radical having 1 to 6 carbon atoms, R4, Rg, R6 and R7 are hydrogen, and x and y are both 2. 3. The process of anyone of the preceding claims wherein R1 is tertiary butyl, R2 is methyl, and z is 1. 4. The process of anyone of the preceding claims wherein the amino compound is a heterocyclic compound having 3 to 6 carbon atoms in the ring, R4, R5, R6 and R7 are hydrogen, and x and y are both 2. 5. The process of anyone of the preceding claims wherein the heterocyclic compound has 4 to 5 carbon atoms in the ring and z is 1. 6. The process of anyone of the preceding claims wherein the reaction is carried out at a temperature ranging from about 1600 to about 4250C. and at a pressure ranging from about 50 to about 3000 psig. 7. The process of anyone of the preceding claims wherein the reaction is carried out at a temperature ranging from about 1800 to about 4000C and at a pressure ranging from about 100 to about 1000 psig. 8. The process of anyone of the preceding claims wherein the reaction is carried out at a temperature ranging from about 1900 to about 3500C and at a pressure ranging from about 150 psig to about 750 psig. 9. The process of anyone of the preceding claims wherein the hydrogenation catalyst is a nickel, a cobalt, a nickel-cobalt, a nickel-cobalt-copper, or a platinum catalyst all of which are supported on alumina silica or a combination thereof.

Inventors: HO, WIN-SOW WINSTON, MONTAGNA, ANGELO ANTHONY, STOGRYN, EUGENE LEO
Applicants: EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1984
Main classification: C07C93
IPC codes: B01J23, C07C217, C07B61, C07D295, C07C213, C07C67