TITANIA CATALYST, METHOD OF MAKING SAME, AND ITS USE IN THE PREPARATION OF LINEAR POLYETHYLENEPOLYAMINES

Abstract: A catalyst compositions based on titania pellets on which a minor amount of tungstophosphoric acid or molydbophosphoric acid is deposited is useful in a process for preparing predominantly linear polyethylenepolyamines from ethylenediamine and monoethanolamine.

Description: This invention relates to a catalyst composition prepared by depositing a minor amount of tungstophosphoric acid or molybdophosphoric acid on titania and a process which utilizes the catalyst composition for the preparation of predominantly linear polyethylenepolyamines from ethylenediamine and monoethanolamine. Heretofore, polyethylenepolyamine compounds such as diethylenetriamine, triethylenetetramine and the higher homologs have been produced by the reaction of an alkyl halide such as ethylene dichloride with an amine such as ammonia or ethylenediamine at elevated temperatures and pressures. Normally, relatively high yields of predominantly non-cyclic polyethylenepolyamine compounds are obtained from this process with varying yields of heterocyclic amines. The large amounts of energy required to produce the reactants as well as the difficult separation procedures required to recover the more valuable linear polyethylenepolyamines diminish the usefulness of the ethylene dichloride process. The hydrohalide salts of ammonia and the polyethylenepolyamine products must also undergo difficult and time consuming caustic neutralization to yield the free polyethylenepolyamines. It has heretofore been known that phosphates can be used to catalyze reactions to produce predominantly heterocyclic rather than linear products. Thus, US-A-3297701 reaches the use of aluminium phosphate to catalyze the reaction of ethanolamines and polyethylenepolyamines to yield cyclic compounds. US-A-3342820 discloses the use of aluminium phosphate for the preparation of heterocyclic compounds such as triethylenediamine. As another example, US-A-4103087 also discloses the use of aluminium phosphate catalysts for producing heterocyclic product compounds. More recently, investigators have found that more linear products can also be obtained in a catalyst conversion. US-A-4463193 -4578517 are directed to the reaction of an alkanolamine with an alkyleneamine and ammonia in the presence of a catalytically effective amount of a group IIIB metal acid phosphate to give primarily noncyclic polyalkylene polyamine products. Thus, Table 4 of US-A-4463193 discloses the reaction of monoethanolamine with ethylenediamine and amminia using catalysts such as lanthanum acid phosphate and praseodymium acid phosphate at conversions of 11 to 43% of monoethanolamine to give a noncyclic selectivity of 67% to 92%. In US-A-4503253 phosphoric acid incorporated onto an inert support (silica) was used as a catalyst and in Table 1 of the patent, use of this type of catalyst was shown to provide monoethanolamine conversions of 34% to 68% with a selectivity to noncyclics of 62% to 86%. EP-A-0073520 disclosed that the reaction of monoethanolamine with ethylenediamine and ammonia can be catalyzed with acidic metal phosphates, phosphoric or phosphorous acid or their anhydrides and alkyl or aryl esters (e.g., boron phosphate, ferric phosphate, aluminum phosphate, etc.). US-A-4314083 discloses the reaction of ethylenediamine with monoethanolamine to prepare noncyclic polyalkylenepolyamines using, as a catalyst, a salt of a nitrogen or sulfur-containing compound. In inventions originating in our laboratories, US-A-4036881 discloses the use of phosphorus-containing catalysts to catalyze the reacti on of ethylenediamine with monoethanolamine. Excellent results were obtained when the reaction was conducted in an autoclave. However, when the phosphorus compound was supported on silica or diatomaceous earth, good results were obtained only at comparatively low conversions. US-A-4044053 is also relevant in this regard. US-A-4448997 is directed to an alumina phosphate-type catalyst composition wherein the novel feature is the method of preparing a catalyst from alumina phosphoric acid, ammonium hydroxide and water. Excellent results were obtained using a catalyst of this nature in batch-type reactions. More recently, a series of U.S. Patents (US-A-4540822, -4578518, -4578519, -4584406, and -4588842) have disclosed that the reaction of monoethanolamine with ethylenediamine to provide essentially noncyclic polyethylenepolyamine reaction products can be effectively promoted with catalysts composed of a minor amount of phosphorus thermally, chemically bonded to a group IVb metal oxide support such as titania or zirconia. Also, US-A-4555582 discloses use of a zirconium silicate catalyst to promote this reaction. US-A-2921081 discloses catalysts for use in the conversion of olefins that are prepared by reacting a zirconium halide with a designated class of phosphoric acids. US-A-4164519 discloses a process for the oxidative dehydrogenarion of hydrocarbons using a catalyst of the formula Ti Mo x P y O z where x and y are 0.01 to 5, and z is determined by the valence requirements of Ti, Mo and P. US-A-2824073 is concerned with the manufacture of a titanium-phosphoric acid catalyst that can be prepared by mixing titania with triphosphoric acid to form a doughy mixture which is thereafter dried and heated. According to a first aspect of the invention, there is provided catalytically activated titania characterised in that the titania carries a deposit of from 0.1 to 10 wt.% phosphorus and 0.1 to 30 wt.% of tungsten or molybdenum, or a mixture thereof, and present as tungstophosphorus or molybdophosphorus groups chemically bound to the said titania. According to a second aspect of the invention, there is provided a method of making the catalytically activated titania, comprising the steps of impregnating titania with an aqueous solution of a tungstophosphoric acid or salt or a molybbdosphosphoric acid or salt, or a mixture thereof, the amount of said aqueous solution being such as to provide 0.1 to 10 wt % of phosphorous and 0.1 to 30 wt % of tungsten or molybdenum, or of a mixture thereof, in the final product, drying the impregnated titania, and calcining the titania. According to a third aspect of the invention, there is provided a process for the preparation of predominantly linear polyethylenepolyamines by reacting monoethanolamine with ethylenediamine in a reaction zone in the presence of a phosphorus-containing catalyst characterised by: a. using the above-described catalyst; and b. continuously contacting a mixture of said ethylenediamine and said monoethanolamine in a molar ration to from 1 to 5 moles of ethylenediamine per mole of monoethanolamine with said catalyst at a temperature of from 250° to 400°C and a gauge pressure of from 34.47 to 206.8 bar (from 3.55 to 20.78 MPa [500 to 3000 psig]). Thus, catalysts prepared by depositing a minor amount of tungstophosphoric acid or molybdophosphoric acid on titania can be used effectively to catalyze the reaction of monoethanolamine with ethylenediamine, and in this way improve the production of predominantly linear polyethylenepolyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine from the reaction of ethylenediamine and monoethanolamine. The present catalyst compositions catalyze the reaction of ethylenediamine with monoethanolamine at a temperature of from 250°C to 400°C, preferably from 270°C to 320°C and a pressure of from 34.47 to 206.8 bar (from 3.55 to 20.78 MPa [500 to 3000 psig]) and preferably from 68.9 to 137.8 bar gauge (from 6.99 to 13.89 MPa [1000 to 2000 psig]). Higher temperatures and pressure can be used, if desired, but there is no particular advantage in using such higher temperatures and/or pressures. The pelleted catalyst compositions of the present invention are preferably employed as a fixed bed of catalyst in a continuous reaction system. In a continuous process of this nature, the time of contact of the reactants with the catalyst is one of the interrelated factors that those skilled in the art will adjust, along with temperature, pressure, bed geometry, pellet size, etc. in order to obtain a desired rate of reaction and, hence, a desired percentage of conversion of the reactants. In a continuous process, it is not necessary to drive the reaction to completion because unreacted feedstock components can be recycled to the reactor. It is customary to use cylindrically-shaped catalyst pellets having a diameter essentially equal to the length thereof, such as diameters and lengths ranging from 0.794 mm (1/32 inch) to 9.525 mm (3/8 inch). It will be understood that the shape and dimensions of the pellets are not critical to the present invention and that pellets of any suitable shape and dimensions may be used as desired, by one wishing to practise the process of the present invention. When cylindrical pellets of catalyst of the type described above are used, the weighted hourly space velocity may be varied within wide limits (e.g. 0.1 to 5 w/hr/w i.e. weight of reactants per hour per unit weight of catalyst), in order to obtain a desired rate of conversion, as explained above. Normally, space velocities of 0.5 to 2 w/hr/w will be employed. Catalyst life is an important factor in conducting a continuous reaction. For example, if a catalyst is easily poisoned, or if catalyst pellets do not have good structural properties, the economics of the process will be seriously and adversely affected. The catalysts of the present invention are not particularly susceptible to poisoning so this normally does not present a problem. However, under the reaction conditions employed, amines of the type used and formed herein have the potential capability of leaching or otherwise adversely affecting the structural integrity of the pellets. In an extreme instance, catalysts pellets having good initial crush strength and surface hardness will be reduced to fines very rapidly when used under reaction conditions such as those employed herein. As a consequence, the catalyst compositions of the present invention are advantageously used for a continous process for the continuous production of essentially linear polyethylenepolyamine reaction products from monoethanolamine and ethylenediamine. Such catalyst compositions can be used for prolonged periods without the need for regeneration (e.g., 1,000 hours or more). Nevertheless, with the passage of time deactivation will tend to slowly occur. Deactivation can be measured qualitatively as the increase of temperature required to maintain an essentially constant conversion rate for the monoethanolamine and ethylenediamine. The catalyst compositions of the present invention are prepared by depositing a minor amount of a molybdophosphoric acid or a tungstophosphoric acid on titania. Titania pellets can be prepared by extrusion or by compaction in conventional pelleting apparatus using a pelleting aid such as graphite. It is also within the scope of the present invention to deposit the molybdophosphoric or tungstophosphoric acid on titania followed by pelleting and calcination. Any appropriate molybdophosphoric acid or tungstophosphoric heteropoly acid, or their salts, may be used to p repare the catalyst compositions of this invention. Suitable examples include 12-tungstophosphoric acid, having the general formula H₃(PM₁₂O₄₀), where M = Mo or W, other heteropolymolybdates and tungstates having the structure (P₂M₁₈)₆₂) 6⁻ , where the ratio of P to Mo or W is 2:18, (PM₁₁O₃₉) 5⁻ where the P:Mo ratio is 1:11, as well as phosphomolybdates (PMo₁₀O x ) n⁻ and (P₂Mo₁₇O x ) m , where n, m and x are integers. The heteropolymolybdates and tungstates may be employed in their acid form or as their salts, such as sodium 12-molybdate, Na₃(PMo₁₂O₄₀), and potassium 12-tungstophosphate. Both the heteropoly acids and their salts may be used as their hydrates. The preferred phosphomolybdate is 12-molybdophosporic acid and the preferred heteropoly phosphotungstate is 12-tungstophosphoric acid. These acids are preferably used in the form of an aqueous solution containing 1% to 50% of the acid. It is within the scope of the present invention to use an aqueous solution of two or more tungstophosphoric acids or two or more molybdophosphoric acids or a mixture of a tungstophosphoric acid with a molybdophosphoric acid. As a matter of convenience, the normal practice is to use only one chemical as an acid source. Preferably the catalyst composition is prepared by impregnating a preformed pellet. A suitable procedure to be used is to immerse titania pellets in an aqueous solution of the acid, preferably at ambient temperature. Higher temperatures in a range of from 100° to 150°C can be used, if desired. This treatment should be continued, preferably with agitation, for a period of from 0.1 to 5 hours sufficient to permit the aqueous solution to penetrate the pores of the titania pellet. Suitably, the amount of aqueous solution of the acid that is used should be adequate to permit full immersion of the titania pellets. Larger amounts of the aqueous solution can be used, if desired, but there is no particular advantage in doing so. At the end of the immersion step, the excess aqueous solution can be evaporated from the treated pellets or the pellets can be removed from the aqueous solution and permitted to dry (e.g., in a drying oven). Only a minor amount of tungstophosphoric acid or molybdophosphoric acid will be permanently deposited on the titania pellets by this procedure, such that the treated titania pellets will have only 0.01 to 10 wt.% of phosphorus deposited thereon, and normally 1 wt.% or less (e.g. 0.1 to 1 wt.%). A small but significantly larger percentage of tungsten or molybdenum will be co-deposited on the titania, such as 0.1 to 30 wt.% and normally from 1 to 10 wt.% of tungsten or molybdenum. It will be understood that the phosphorus and tungsten or molybdenum that are present on thus-treated titania pellets are not present as elemental compounds, but rather as tungstophosphorus or molybdophosphorus groups that are chemically bound, normally as an oxide, to the titania support. The exact nature of the bonding is not completely understood, The pelleted catalyst compositions of the present invention should be calcined. They can be calcined prior to use or calcined in situ when used as catalysts at temperatures in excess of 100°C. When the catalysts are to be calcined prior to use, calcination is suitably conducted for 2 to 24 hours at a temperature of 100°C but below the temperature at which thermal destruction of the chemical bonding occurs. This can be determined by routine experimentation for a particular catalyst. Temperatures above 900°C should be avoided. A suitable calcining temperature range is normally 200° to 800°C and, more preferably, 300° to 600°C. Alternatively, the titania can be treated in powdered form with the aqueous acidic solution and the powder can thereafter be pelleted. If the pelleting treatment is conducted at a temperature of 100°C or more, thermal activation will normally have been obtained and it will not be absolutely necessary to perform a calcining operation before use. If lower treating temperatures are used, calcining is normally a desired operation before use. The calcining operation can be conducted prior to or subsequent to the pelleting step. In any event, in-situ calcining will occur when the pelleted compositions are used to catalyze the reaction of monoethanolamine with ethylenediamine at 250° to 400°C. There are many compounds which can be formed from the reaction of ethylenediamine and monoethanolamine besides the preferred linear polyethylenepolyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. Less desirable cyclics and other compounds, such as piperazine, N-(2-aminoethyl) ethanolamine and N-(2-aminoethyl)piperazine, are also formed. The more desired linear polyethylenepolyamines can be easily recovered from the reaction product mixture by conventional methods such as distillation. Such distillation recovery methods are well known in the art. An outstanding advantage of the present invention is that the lower molecular weight polyethylenepolyamines recovered from the reaction mixture can be further reacted with monoethanolamine to produce a larger percentage of the higher molecular weight linear polyethylenepolyamines. Ammonia may also be added as a reactant in the generation of the preferred linear polyethylenepolyamines from ethylenediamine and monoethanolamine using the tungstophosphoric acid and molybdophosphoric acid on titania catalysts of this invention. The following illustrative Examples will further illustrate the preparation of predominantly linear polyethylenepolyamines from ethylenediamine and monoethanolamine by the use of the catalyst compositions of the present invention. It will be understood that reactants, proportions of reactants, and time, temperature and pressure of the reaction steps may be varied with much the same results achieved. For purposes of convenience and brevity, the reactant compounds employed and the products obtained have been abbreviated in the following Examples and Tables. The abbreviations employed for these various compounds are: EDA - ethylenediamine MEA - monoethanolamine PIP - piperazine DETA - diethylenetriamine TETA - triethylenetetramine TEPA - tetraethylenepentamine AEEA - N-(2-aminoethyl)ethanolamine AEP - N-(2-aminoethyl)piperazine HEP - N-(hydroxyethyl)piperazine I. Tungstophosphoric Acid Titania Catalyst Preparations A series of pelleted catalysts were prepared by depositing tungstophosphoric acid on a titania support. Example 1 Preparation of 12-Tungstophosphoric Acid-on-Titania To a 125-cm³ of titania extrudates with diameter 3mm (1/8") and a 51 m²/g surface area, provided by the Norton Company, is added a solution of 10.0g of 12-tungstophosphoric acid in 50 ml of water. The mixture is stirred to absorb the liquid into the pores of the solid, excess liquid is recovered by slow rotary evaporation, and 127.5g of white extrudates are isolated. Analysis of the extrudates shows the presence of 0.13% phosphorus and 5.4% tungsten. Example 2-7 Additional 12-Tungstophosphoric Acid on Titania Catalysts The procedure of Example 1 was repeated using 3mm (1/8") titania extrudates impregnated with differing quantities of tungstophosphoric acid. The amount (in grams) of tungstophosphoric acid used and the amount of tungsten and phosphorus deposited on the titania pellets is set out below: (1) 125 ml of pellets having a surface area 120 m²/g. (2) 125 ml of pellets having a surface area of 51 m²/g. (3) 125 ml of pellets having a surface area of 60 m²/g. (a) Not determined. Example 8 Preparation of 12-Molybdophosphoric Acid-on-Titania To a 125-cm³ of titania extruders (as used in Example 1) is added a solution of 10.0g of 12-molybdophosphoric acid in 50 ml of water. The mixture is stirred to absorb the liquid into the pores of the solid, excess liquid is removed by slow evaporation, and 110.3g of yellow extrudates are recovered. Analysis of the extrudates shows the presence of 0.13% phosphorus and 3.4% molybdenum. Example 9 Polyethylenepolyamine Synthesis To a 125-cm³ tubular, fixed bed reactor is charged 100 cm³ of the 12-tungstophosphoric acid-on-titania catalyst of Example 1. The catalyst bed is calcined in place at 350°C for 2 hours under a stream of nitrogen. A mixture of ethylenediamine and monoethanolamine (2:1 weight ratio) is then run through the reactor bed, in the upflow mode, at a series of amination temperatures ranging from 270° to 310°C. Pressure within the reactor system is maintained at 1034 bar (10.44 MPa/ 1500 psig), the LHSV=1.0. The liquid effluent from the reactor, under steady state conditions is sampled and analyzed by glc (gas liquid chromatography. The data are summarized below: a = Insufficient TETA to calculate this number. Examples 10-15 Example 9 was repeated using the catalysts of Examples 2-7. The results obtained are summarized below. Examples 10 Example 11 Example 12 a) Insufficient material in the TETA range to determine this number Exmple 13 Example 14 Example 15 a) Insufficient material in the TETA range to determine this number. From the foregoing Examples it is seen that the tungstophosphoric acid-on-titania catalysts of the present invention provide reaction products that are wholly linear or predominantly linear insofar as the reaction of monoethanolamine with ethylenediamine is concerned. Thus, in Example 9, good conversions of MEA to highly linear products was obtained at reaction temperatures of 290° to 310°C. In Example 10, wholly noncylic products were obtained at 273° and 282°C at moderate MEA conversaions of about 35 to 45%. Equivalent results were obtained in Examples 11-15. Example 16 Polyethylenepolyamine Synthesis To the 125-cm³ tubular reactor of Example 9 is charged 100 cc of the 12-molybdophosphoric acid-on-titania catalyst of Example 8. The catalyst bed is calcined in place at 350°C, then at 2:1 EDA/MEA mix is run through the reactor bed, in the upflow mode, at a series of amination temperatures. Pressure within the reactor system is maintained at 10.44 MPa (1500 psig), the LHSV=1.0. the liquid effluent from the reactor, under steady state conditions, is sampled and analyzed by glc. The data are summarized below:

Claims: Catalytically activated titania characterised in that the titania carries a deposit of from 0.1 to 10 wt.% of phosphorus and 0.1 to 30 wt.% of tungsten or molybdenum, or a mixture thereof, and present as tungstophosphorus or molybdophosphorus groups chemically bound to the said titania. Catalytically activated titania as claimed in claim 1, in the form of pellets. A method of making catalytically activated titania, according to claim 1 comprising the steps of impregnating titania with an aqueous solution of a tungstophosphoric acid or salt or a molybdophosphoric acid or salt, or a mixture thereof, the amount of said aqueous solution being such as to provide 0.1 to 10 wt % of phosphorus and 0.1 to 30 wt % of tungsten or molybdenum, or of a mixture thereof, in the final product, drying the impregnated titania, and calcining the titania. Method according to claim 3 wherein the tungstophosphoric acid is 12-tungstophosphoric acid. Method according to claim 3 or 4 wherein the molybdophosphoric acid is 12-molybdophosphoric acid. A method according to claim 2, 3, 4 or 5 wherein the salt is a sodium or potassium salt. A method according to any one of claims 3 to 6 wherein the said aqueous solution contains from 1 wt.% to 50 wt.% of solute, wherein the titania is immersed in the said solution for a period of from 0.1 to 5 hours at a temperature of up to 150°C, and wherein the steps of drying and calcining the thus-treated titania are conducted at a temperature of from 200° to 800°C and for a period of from 2 to 24 hours. A method according to any one of claims 3 to 7, including the step of pelleting the titania A method according to claim 8 wherein the step of pelleting is carried our prior to the step of impregnating. The use of catalytically activated titania as claimed in claim 1 or 2 to catalyse the reaction between monoethanolamine and ethylenediamine to yield polyethylenepolyamines. A process for the preparation of predominantly linear polyethylenepolyamines by reacting monoethanolamine with ethylenediamine in a reaction zone in the presence of a phosphorus-containing catalyst characterised by: a. using activated titania according to claim 1 or 2 as the said catalyst, and b. continuously contacting a mixture of said ethylenediamine and said monoethanolamine in a molar ratio to from 1 to 5 moles of ethylenediamine per mole of monoethanolamine with said catalyst at a temperature of at least 250°C and a gauge pressure of at least 34.47 bar (500 psig [3.55 MPa]). A process according to claim 11 wherein the contacting step is performed at a temperature of from 270°C and 320°C and a gauge pressure of from 68.9 to 137.8 bar (from 1000 to 2000 psig [6.99 to 13.89 MPa]). A process according to claim 11 or 12 wherein the said titania is present as pellets.

Inventors: GRICE, NEAL JOHN, KNIFTON, JOHN FREDERICK
Applicants: TEXACO DEVELOPMENT CORPORATION
Application year: 1987
Main classification: B01J27
IPC codes: C07C209, C07C67, C07C211, C08G73, B01J27