PROCESS FOR THE PRODUCTION OF ALKYLAMINES

Abstract: This invention relates to a process for preparing an alkylamine by contacting an alcohol and at least one of ammonia, a primary amine, a secondary amine or a tertiary amine with a non-zeolitic molecular sieve under conditions effective to produce the alkylamine. The selectivity for the production of monoalkylamines by reacting lower alcohols with ammonia is good.

Description: This invention relates to a process for the production of alkylamines. More specifically, this invention relates to a process for the reaction of an alcohol with ammonia by contacting the alcohol and ammonia with a silicoaluminophosphate (SAPO) molecular sieve. The process of this invention is particularly, though not exclusively, intended for the reaction of methanol with ammonia to selectively produce monomethylamine. Lower aliphatic alkylamines, that is methyl-, ethyl- and propylamines, are large volume commodity chemicals. Processes for their manufacture include, for example, the reaction of methanol and ammonia over an acidic dehydration catalyst and the reaction of ethanol or propanol and ammonia over either an acidic dehydration catalyst or a reductive amination catalyst. These processes suffer from the disadvantage that the alkylamine products generally are not produced in relative amounts corresponding to market demands. For example, the reaction of methanol with ammonia gives monomethylamine as the primary product. Monomethylamine, however, is more reactive than ammonia so it reacts readily with methanol to give dimethylamine. Similarly, dimethylamine reacts with methanol to give trimethylamine. This tends to favor production of di- and trimethylamine to a larger extent than the market demands. Many catalysts give an equilibrium distribution of alkylamine products. When utilizing these processes known in the art, it is possible to increase the yield of monomethylamine by (i) running the reaction with a large excess of ammonia, (ii) running the reaction at low conversion, and (iii) recycling di- and trimethylamine to force the production of monomethylamine. Various processes are known which describe the production of alkylamines from ammonia and alcohols using aluminosilicate zeolites. For example, US-A-4,254,061 discloses a catalytic process for producing monomethylamine from methanol and ammonia by reacting methanol and ammonia in such amounts so as to provide a carbon/nitrogen (C/N) ratio from the methanol and ammonia reactants of 0.5-1.5 over a catalyst selected from: (a) mordenite wherein the primary cation is Li, Na, HNa having at least 2% Na by weight, K, Ca, Sr, Ba, Ce, Zn or Cr; (b) ferrierite wherein the primary metal cation is Li, Na, K, Ca, Sr, Ba, Ce or Fe; (c) erionite ore; (d) calcium erionite; and (e) clinoptilolite ore; at a temperature of 250°-475°C, a pressure of 7-7000 kPa, a contact time normalized to 7 kPa of 0.1 to 60 seconds and a methanol conversion of 15-95%. EP-A-0183423 describes a process for producing dimethylamine by reacting methanol and/or dimethylether and ammonia in amounts sufficient to provide a carbon/nitrogen (C/N) ratio of from 0.2 to 1.5 at a temperature from about 250°C to about 450°C in the presence of a catalytic amount of zeolite catalyst selected from: (a) acidic zeolite rho; (b) acidic zeolite zk-5; and (c) acidic natural, H-exchanged and M-exchanged chabazites, each having a geometric selectivity index greater than about 3, wherein M is one or more alkali metal ions selected from the group consisting of Na, K, Rb and Cs. EP-A-064380 discloses amorphous aluminosilicate catalysts containing 0.1-6% by weight of Na, K, Li, Ba or Sr which are useful for the preparation of monomethylamine, dimethylamine and trimethylamine from methanol or dimethylether and ammonia. It is disclosed that such catalysts allow the monomethylamine: dimethylamine: trimethylamine weight ratio (normally 15: 23: 62) to be altered at will. US-A-4,434,300 describes a process for improving the methanol conversion rate in the reaction of methanol and ammonia to produce methylamines by effecting the reaction in the presence of a macroporous, highly acidic aluminosilicate catalyst. Macroporous H-chabazite-erionite is described as the preferred catalyst. US-A-4,398,041 discloses a process for converting a C₁-C₄ alcohol to a non-equilibrium controlled distribution of mono-, di- and trialkylamines. A mixture of the alcohol and ammonia is reacted in a first conversion reactor containing a shape selective crystalline aluminosilicate zeolite catalyst to yield a first product stream comprising the mono- and disubstituted alkylamines and substantially no trisubstituted alkylamine. A predetermined fraction of the first product stream is removed and the remainder of the stream is reacted in a second conversion reactor containing a catalyst which yields a second product stream comprising an equilibrium controlled distribution of the mono-, di- and trisubstituted alkylamine. The fraction of the first product stream and the second product stream are combined to yield an alkylamines stream comprising a non-equilibrium controlled alkylamines distribution. EP-A-0180983 discloses a catalytic process for the amination of C₂₋₈ alkanols, the catalyst being a dealuminized zeolite having an increased Si: Al molar ratio over the original zeolite. A dealuminized H-mordenite catalyst is described as particularly effective for the amination of ethanol to give selectively mono- and diethylamine without the formation of triethylamine. EP-A-0101921 describes an improvement in the vapor phase catalytic production of an amine by the reaction of a mixture comprising a C₂₋₄ olefin and ammonia. The improvement which provides for high conversion and selectivity to the amine resides in the use of an acidic offretite as the catalyst. EP-A-0039918 discloses the vapor phase catalytic production of an amine by the reaction of a mixture comprising an olefin having from 2 to 8 carbon atoms and ammonia or ammonia type compound. The formation of polymers is prevented by applying a temperature ranging from 200° to 500°C, a pressure of from 300 to 6,000 psig and an aluminosilicate zeolite catalyst. EP-A-0107457 describes a process for producing methylamines from methanol and/or dimethylether and ammonia by reaction over a synthetic levynite-type zeolite. It is disclosed that such catalysts give a good yield of monomethylamine in preference to dimethylamine and very little trimethylamine. EP-A-0076034 discloses a process for the manufacture of methylamines which involves reacting a feed containing methanol and/or dimethylether and ammonia over a binderless zeolite A catalyst, preferably a binderless zeolite 5A catalyst. Use of binderless zeolite 5A makes the process selective to dimethylamine in preference to mono- and trimethylamine. It is disclosed that if the catalyst is essentially free of alkali metal it is not only more active than similar catalysts containing alkali metal but also more selective. US-A-4,082,805 describes a process for the production of aliphatic amines by reaction of a C₁-C₅ alcohol or ether with ammonia in the presence of a catalyst comprising a crystalline aluminosilicate having the structure of ZSM-5, ZSM-11 or ZSM-21, said reaction being effected at a temperature between 300° and 500°C, a pressure between atmospheric and 1000 psig with the relative feed rates, expressed in grams per hour, of (1) alcohol or ether and (2) ammonia being within the approximate range of 1: 1 to 5: 1. EP-A-0130407 and JP-A-59227841 disclose a process for producing dimethylamine by the gas phase reaction of ammonia and methanol over a zeolite catalyst (mordenite, clinoptilolite, erionite) treated with an atmosphere containing steam at 250°C-700°C. EP-A-0125616 describes a process for producing dimethylamine with high selectivity by reaction between (a) methanol and ammonia; (b) methanol, a mixture of methylamines and ammonia; or (c) a mixture of methylamines and ammonia; in gas phase over a solid catalyst which is a mordenite type zeolite. The catalyst has a sodium content of 0.2-3.9 grams per 100 grams of catalyst and an alkali metal total content of 0.01-0.20 mole per 100 grams of catalyst. The alkali metal is sodium, potassium or lithium. JP-A-57169444 describes the preparation of methylamine by reacting methanol and ammonia in the presence of a mordenite type zeolite, preferably naturally occurring mordenite or a synthetic small pore mordenite with a part of its alkali metal ions displaced with a hydrogen ion or a di- or trivalent metal. It is disclosed that a mordenite type zeolite inhibits formation of trimethylamine (TMA) which is of low commercial value and has a specific selectivity to dimethylamine (DMA) which is of high commercial value. Mochida, I., Yasutake, A., Fujitsu, H. and Takeshita, K., Journal of Catalysis 82, 313-321 (1983) disclose the selective production of dimethylamine (DMA) from methanol and ammonia over some zeolites and metal oxides at a temperature range of 300° to about 450°C under ambient pressures. Proton or alkali-earth ion-exchanged zeolites were found to show considerable selectivity around 50% (product mole base) at 400°C. The selectivity for the sum of DMA and monomethylamine (MMA) which can be recycled again for DMA production was over 85% at the conversion level of 90%, indicating suppression of trimethylamine (TMA) formation over the zeolite. The selectivity is discussed in terms of the type, strength, and steric environment of the acidic active sites. The activation of ammonia, desorption of DMA, and the shape selective discrimination of the pore structure for TMA are discussed as factors for the selectivity. It has now been discovered that the reaction of methanol with ammonia to selectively produce monomethylamine can be efficiently conducted using non-zeolitic molecular sieves as catalysts. The same catalysts can be used for the reaction of other alcohols with ammonia to produce alkylamines. This invention relates to a process for the reaction of an alcohol with at least one of ammonia, a primary amine, a secondary amine or a tertiary amine by contacting the alcohol and at least one of ammonia, a primary amine, a secondary amine or a tertiary amine with a silicoaluminophosphate (SAPO) molecular sieve under conditions effective to produce alkylamines. In particular, this invention relates to a process for the reaction of methanol with ammonia by contacting methanol and ammonia with a silicoaluminophosphate molecular sieve under conditions effective to selectively produce monomethylamine. US-A-4440871 describes the preparation and structure of silicoaluminophosphate molecular sieves and indicates the possibility of using them as absorbants and catalysts. As indicated above, this invention relates to a process for preparing an alkylamine, which process comprises contacting an alcohol and at least one of ammonia, a primary amine, a secondary amine or a tertiary amine with a silicoaluminophosphate molecular sieve under conditions effective to produce the alkylamine. In a preferred embodiment, this invention relates to a process for selectively producing monomethylamine, which process comprises contacting methanol and ammonia with a non-zeolitic molecular sieve under conditions effective to selectively produce monomethylamine. The process of this invention represents a highly desirable route to alkylamines. In particular, the process of this invention represents a highly desirable route to monomethylamine in high selectivities. Alcohols suitable for use as reactants in the process of this invention have the general formula R₁OH wherein R₁ is an alkyl radical, straight or branched chain, having from 1 to 12 carbon atoms. Illustrative alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol. Methanol is the preferred alcohol for use in the process of this invention. Ammonia and the primary, secondary and tertiary amines are used as reactants in the process of this invention and have the formula: wherein the R₂ groups can be the same or different and are hydrogen or an alkyl (C₁ to C₁₂) radical, preferably a lower alkyl (C₁ to C₄) radical such as methyl or ethyl. Illustrative primary and secondary amines include monomethylamine, dimethylamine, monoethylamine, diethylamine. The alcohol: ammonia (C/N) mole ratio utilized in the process of this invention can vary over a wide range depending on the mix of mono-, di- and trialkylamines desired. For example, in the preparation of methylamines, a high C/N ratio will give a product high in trimethylamine while a low C/N ratio will give a product high in monomethylamine. C/N ratios above 2.0 will give predominantly di- and trimethylamine. C/N ratios below 0.1 will give predominantly monomethylamine. Intermediate C/N ratios will give intermediate product mixes. There is generally no incentive to use C/N ratios much above 5.0 as little extra di- and trimethylamines are formed but the cost of recycling the methanol increases. Similarly, there is generally no incentive to use C/N ratios much below 0.05 as little extra monomethylamine is formed but the cost of recycling the ammonia increases. The optimum C/N ratio depends not only on the product ratio desired but also on the other reaction conditions. At high pressure, the cost of recycling ammonia or methanol increases. Since the product ratio changes with changing methanol conversion, the optimum C/N ratio for any desired product mix will change with pressure or temperature or anything else that affects the conversion. The alkylamines which can be produced by the process of this invention include, for example, methylamines, ethylamines, n-propylamines, i-propylamines, and n-butylamines. The monosubstituted: disubstituted: trisubstituted alkylamine ratio can be controlled; for example, high selectivities of monomethylamine versus dimethylamine and trimethylamine can be obtained by the process of this invention. The molecular sieves used as catalysts in the process of this invention include a large number of silicoaluminophosphates having a variety of crystal structures, which may include one or more other elements in addition to aluminum, phosphorus and silicon. Accordingly, the manner in which the molecular sieves are used as catalysts in the process of this invention will first be described, and thereafter the chemical nature and methods for the preparation of the molecular sieves will be described. As already mentioned, in the process of this invention an alcohol and ammonia are contacted with a silicoaluminophosphate molecular sieve under conditions effective to produce alkylamines. As is well known to those familiar with the use of molecular sieves as catalysts, the reaction rate and product distribution of a molecular sieve catalyzed reaction is strongly influenced by the pore size of the molecular sieve, since the catalytic activity of molecular sieves appears to depend upon the ability of the reactants and products to diffuse through the pores of the molecular sieve. The pore sizes of the molecular sieves vary over a wide range and, since amination of alcohols such as methanol with ammonia to give alkylamines such as monomethylamine involves the diffusion of molecules of moderately small size through the molecular sieve, the molecular sieve used as catalyst in the process of this invention should be selected to provide a sufficient pore size to accommodate these molecules. The molecular sieves may be divided into small, medium and large pore materials. The small pore materials are those having, in their calcined form, an adsorption of isobutane of less than 2 percent by weight of the molecular sieve at a partial pressure of 66,7 KPa (500 torr) and a temperature of 20°C. The medium pore materials are those having, in their calcined form, an adsorption of isobutane of at least 2 percent, and preferably at least 4 percent, and an adsorption of triethylamine of less than 5 percent by weight of the non-zeolitic molecular sieve at a partial pressure of 0,35 KPa (2.6 torr) and a temperature of 22°C. The large pore materials are those having, in their calcined form, an adsorption of isobutane of at least 2 percent, and an adsorption of triethylamine of at least 5 percent, by weight of the molecular sieve at a partial pressure of 0,35 KPa (2.6 torr) and a temperature of 22°C. Empirically, it appears that in the reaction of methanol with ammonia, small pore materials tend to give better selectivities to monomethylamine than medium pore materials. As synthesized by the methods described below, the molecular sieves normally contain within their internal pore systems at least one form of the organic templating agent employed in their formation. Before being used in the process of this invention, the molecular sieves need to have this templating agent removed. Preferably, the templating agent is removed by calcining the as-synthesized molecular sieve at an elevated temperature, normally at least 500°C, before the molecular sieve is used in the process of the present invention. Alternatively, if the process of this invention is to be conducted under conditions (especially temperature) which are sufficient to remove the templating agent from the as-synthesized molecular sieve, the molecular sieve may be placed in the reactor to be used for the process and the templating agent thus removed in situ during the process. However, such in situ removal of the templating agent is usually less desirable than prior calcination of the molecular sieve. Specific preferred silicoaluminophosphate molecular sieves for use in the process of this invention are SAPO-11 and SAPO-34 (for descriptions of these SAPO materials see the information given below, and the fuller description set out in US-A-4440871. Characteristics of these materials are also set out below in the section of the Description headed "SILICOALUMINOPHOSPHATE MOLECULAR SIEVES.") Selection of the temperature at which the process of this invention is to be conducted involves a compromise between selectivity to the desired alkylamine product and conversion of the alcohol used as starting material. It is recommended that the process of this invention be conducted at a temperature in the range of 250°C to 500°C; below this temperature range, the reaction tends to proceed too slowly, while at very high temperatures, the selectivity to the desired monomethylamine product tends to decrease. The preferred temperature range is from 300°C to 450°C. For obvious reasons, it is desirable to adjust the temperature and other reaction parameters discussed below so as to ensure that the reaction is run at a methanol conversion of at least 10%, and preferably at least 20%, and at a selectivity to monomethylamine of at least 40%, and preferably at least 50%. It should be noted that the conversion and selectivity achieved with a given material may vary considerably with its exact composition and the procedure and raw materials used to prepare a given specimen of the material. The process of this invention can be run over a wide range of pressures ranging from sub-atmospheric pressures to 1000 psig (6.9 MPa.) or more. However, since the use of very high pressures does not confer any significant advantages but increases equipment costs, it is recommended that the process of the present invention be carried out at a pressure of from about atmospheric pressure to 500 psig (0.7 MPa.). It has been found that satisfactory conversions and selectivities can be achieved by running the process of the invention under atmospheric pressure. Because the rate of reaction should increase at higher pressures, it may be advantageous to run at somewhat elevated pressures. But this advantage is offset by the higher cost of equipment required for high pressure operations. The process of the present invention can also be carried out over a wide range of weight hourly space velocities of the alcohol. For example, weight hourly space velocities of from 0.1 to 50 may be employed, with the preferred range of weight hourly space velocity being from 0.5 to 10. At high weight hourly space velocities the conversion tends to decrease, and at low weight hourly space velocities the catalyst productivity tends to be low. The optimum weight hourly space velocity will depend on the temperature and pressure of the reaction. The silicoaluminophosphate molecular sieve catalysts used in the process of this invention enable the reaction to be carried out at high selectivities. As illustrated in the Examples below, the process of this invention can be carried out with a selectivity to monoethylamine of at least about 60%. As with some reactions catalyzed by molecular sieves, the conversion achieved in the process of the present invention may fall as the time for which the molecular sieve catalyst has been used in the process increases. If the molecular sieve catalysts become deactivated, the deactivated catalyst can readily be regenerated by heating in air at an appropriate temperature (typically about 500°C) and for an appropriate period (typically one hour). The molecular sieve may be modified by depositing or impregnating the non-zeolitic molecular sieve with cations, anions or salts so as to improve its efficacy as a catalyst in the process of this invention. Techniques which may be employed to effect the deposition or impregnation of a molecular sieve are generally known in the art. Such techniques may involve such procedures as (1) impregnating the molecular sieve with a solution comprising a solvent or solubilizing agent of one or more such modifying materials in an amount sufficient to deposit the desired weight of such materials in the molecular sieve and/or (2) exchanging the molecular sieve with a solution containing the modifying material. The impregnation or deposition of the modifying materials may generally be accomplished by heating the molecular sieve at an elevated temperature to evaporate any liquid present to effect deposition or impregnation of the modifying material on to the interior and/or exterior surface of the molecular sieve, or by the exchange of cations present in the molecular sieve with cations that provide for the desired properties (provided of course that the molecular sieve is one having a significant ion-exchange capacity). Alternatively, the modifying material may be formed on the molecular sieve from a solution or an emulsion or a slurry containing the modifying material by conventional methods known in the art. Impregnation or exchange procedures are generally the preferred techniques because they utilize and introduce the modifying material more efficiently than other procedures such as coating procedures since a coating procedure is generally not able to effect substantial introduction of the modifying material on to the interior surfaces of the molecular sieve. In addition, coated materials are more generally susceptible to the loss of the modifying materials by abrasion. Suitable modifying materials include alkali metals, alkaline earth metals, transition metals and the salts thereof including inorganic and organic salts such as nitrates, halides, hydroxides, sulfates and carboxylates. Other modifying materials generally employed in the art are also believed to be employable in the molecular sieves. In carrying out the process of this invention, the molecular sieves may be admixed (blended) or provided sequentially to other materials which may provide some property which is beneficial under process conditions, such as improved temperature resistance or improved catalyst life by minimization of coking, or which are simply inert under the process conditions used. Such materials may include synthetic or naturally-occurring substances such as clays, silicas, aluminas, metal oxides and mixtures thereof. In addition, the molecular sieves may be formed with materials such as silica, alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-berylia, and silica-titania, as well as ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia and clays present as binders. The relative proportions of the above materials and the molecular sieves may vary widely with the molecular sieve content ranging between 1 and 99 percent by weight of the composite. The process of this invention may be carried out using, for example, a fixed bed reactor, a fluid bed reactor, or a slurry reactor. The optimum size and shape of the catalyst particle will depend on the type of reactor used. In general, for fluid bed reactors, a small, spherical catalyst particle is preferred for easy fluidization. With fixed bed reactors, larger catalyst particles are preferred so the back pressure within the reactor is kept reasonably low. The process of this invention can be conducted in a batch or continuous fashion. The reaction can be conducted in a single reaction zone or in a plurality of reaction zones, in series or in parallel or it may be conducted batchwise or continuously in an elongated tubular zone or series of such zones. The materials of construction employed should be inert to the reactants during the reaction and the fabrication of the equipment should be able to withstand the reaction temperatures and pressures. Means to introduce and/or adjust the quantity of reactions or ingredients introduced batchwise or continuously into the reaction zone during the course of the reaction can be conveniently utilized in the process especially to maintain the desired molar ratio of the reactants. The process may be conducted in either glass lined, stainless steel or similar type reaction equipment. The reaction zone may be fitted with one or more internal and/or external heat exchanger(s) in order to control undue temperature fluctuations, or to prevent any possible "runaway" reaction temperatures. The following is a description of the chemical nature and methods for preparation of the molecular sieves used as catalysts in the process of this invention. The "SAPO" molecular sieves are described in No. 4,440,871 and U.S. Serial No. 575,745, filed January 31, 1984. The nomenclature employed herein to refer to the members of the aforementioned SAPOS is consistent with that employed in the aforementioned applications or patents. A particular member of a class is generally referred to as a "-n" species wherein "n" is an integer, e.g. SAPO-11. In the following discussion set forth hereinafter the mole fraction of the SAPOS are defined as compositional values which are plotted in phase diagrams in US-A-4440871. SILICOALUMINOPHOSPHATE MOLECULAR SIEVES The silicoaluminophosphate molecular sieves of US-A-4440871 and the aforementioned application Serial No. 575,745, are disclosed as microporous crystalline silicoaluminophosphates, the pores of which are uniform and have nominal diameters of greater than 3 Angstroms and whose essential empirical chemical composition in the as-synthesized and anhydrous form is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Si x Al y P z )O₂ and has a value of from 0.02 to 0.3; "x", "y" and "z" represent the mole fractions of silicon, aluminum and phosphorus, respectively, present as tetrahedral oxides, said mole fractions being such that they are within the pentagonal compositional area defined by points A, B, C, D and E of the ternary diagram of FIG. 5 of the aforementioned US-A-4440871, and are preferably within the pentagonal compositional area defined by points a, b, c, d and e of FIG. 6 of the patent. The SAPO molecular sieves of US-A-4440871 and the aforementioned application Serial No. 575,745 are also described as silicoaluminophosphates having a three-dimensional microporous framework structure of PO₂⁺, AlO₂⁻ and SiO₂ tetrahedral units, and whose essential empirical chemical composition on an anhydrous basis is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the mole of "R" present per mole of (Si x Al y P z )O₂ and has a value of from zero to 0.3; "x", "y" and "z" represent, respectively, the mole fractions of silicon, aluminum and phosphorus present in the oxide moiety, said mole fractions being within the compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the aforementioned patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below in any one of Tables I, III, V, VII, IX, XIII, XVII, XXI, XXIII, or XXV of US-A-4440871. Further, the as-synthesized crystalline silicoaluminophosphates of US-A-4440871 may be calcined at a temperature sufficiently high to remove at least some of any organic templating agent present in the intracrystalline pore system as a result of such synthesis. The silicoaluminophosphates of US-A-4440871 are generally referred to therein as "SAPO", as a class, or as "SAPO-n" wherein "n" is an integer denoting a particular SAPO as its preparation is reported in US-A-4440871. The preparation of the SAPOs is disclosed in US-A-4440871. Medium pore (MP)-SAPOs include SAPO-11, SAPO-31, SAPO-40 and SAPO-41. The species SAPO-11 as referred to herein is a silicoaluminophosphate material having a three-dimensional microporous crystal framework structure of PO₂⁺, AlO₂⁻ and SiO₂ tetrahedral units, and whose essential empirical chemical composition on an anhydrous basis is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Si x Al y P z )O₂ and has a value of from zero to 0.3; "x", "y" and "z" represent, respectively, the mole fractions of silicon, aluminum and phosphorus present in the oxide moiety, said mole fractions being within the compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the patent, and preferably within the area bounded by points a, b, c, d and e on the ternary diagram which is FIG. 6 of the patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: The species SAPO-31 as referred to herein is a silicoaluminophosphate having a three-dimensional microporous crystal framework structure of PO₂⁺, AlO₂⁻ and SiO₂ tetrahedral units, and whose essential empirical chemical composition on an anhydrous basis is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Si x Al y P z )O₂ and has a value of from zero to 0.3; "x", "y" and "z" represent, respectively, the mole fractions of silicon, aluminum and phosphorus present in the oxide moiety, said mole fractions being within thy compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the patent, and preferably within the area bounded by points a, b, c, d and e on the ternary diagram which is FIG. 6 of the patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: The species SAPO-40 as referred to herein is a silicoaluminophosphate material having a three-dimensional microporous crystal framework structure of PO₂⁺, AlO₂⁻ and SiO₂ tetrahedral units, and whose essential empirical chemical composition on an anhydrous basis is: mR: (Si x Al y P x )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Si x Al y P z )O₂ and has a value of from zero to 0.3, "x", "y" and "z" represent respectively, the mole fractions of silicon, aluminum and phosphorus present in the oxide moiety, said mole fractions being within the compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the patent, or preferably within the area bounded by points a, b, c, d and e on the ternary diagram which is FIG. 6 of the patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: The species SAPO-41 as referred to herein is a silicoaluminophosphate having a three-dimensional microporous crystal framework structure of PO₂⁺, AlO₂⁻ and SiO₂ tetrahedral units, and whose essential empirical chemical composition on an anhydrous basis is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Si x Al y P z )O₂ and has a value of from zero to 0.3; "x", "y" and "z" represent, respectively, the mole fractions of silicon, aluminum and phosphorus present in the oxide moiety, said mole fractions being within the compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the patent, or preferably within the area bounded by points a, b, c, d and e on the ternary diagram which is FIG. 6 of the patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: Large pore(LP)-SAPOs include SAPO-5 and SAPO-37. The species SAPO-5 as referred to herein is a silicoaluminophosphate material having a three-dimensional microporous crystal framework structure of PO₂⁺, AlO₂⁻ and SiO₂ tetrahedral units, and whose essential empirical chemical composition on an anhydrous basis is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Si x Al y P z )O₂ and has a value of from zero to 0.3, "x", "y" and "z" represent respectively, the mole fractions of silicon, aluminum and phosphorous present in the oxide moiety, said mole fractions being within the compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the patent, or preferably within the area bounded by points a, b, c, d and e on the ternary diagram which is FIG. 6 of the patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: The species SAPO-37 as referred to herein is a silicoaluminophosphate having a microporous crystalline framework structure and whose essential empirical chemical composition in the as-synthesized form and on an anhydrous basis is: mR: (Si x Al y P z )O₂ wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" has a value of from 0.02 to 0.3, "x", "y" and "z" represent respectively, the mole fractions of silicon, aluminum and phosphorus present in the oxide moiety, said mole fractions being within the compositional area bounded by points A, B, C, D and E on the ternary diagram which is FIG. 5 of the patent, or preferably within the area bounded by points a, b, c, d and e on the ternary diagram which is FIG. 6 of the patent, said silicoaluminophosphate having a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: The adsorption characterization of the molecular sieves employed in this invention relates to a characterization that is carried out on a molecular sieve which has been subjected to a post synthesis treatment, e.g., calcination or chemical treatment, to remove a substantial portion of the template "R" which is present as a result of synthesis. Although a particular molecular sieve is characterized herein by reference to its adsorption of isobutane as being to the adsorption characteristics of the molecular sieve in its calcined form, this invention necessarily includes the use of a non-calcined or modified molecular sieve which may be characterized by such adsorption in its calcined form, since upon use of such a non-calcined molecular sieve in the instant process at effective isomerization process conditions the molecular sieve may be calcined or hydrothermally treated in situ so as to have the characteristic adsorption of isobutane. Thus, the molecular sieve may be rendered in situ to a form characterized by the aforementioned adsorption characteristics. Thus, reference to a molecular sieve having a particular adsorption characteristic in its calcined or anhydrous form is not intended to exclude the use of the molecular sieve in its as-synthesized form which upon in-situ calcination, hydrothermal treatment and/or other treatment, e.g., ion exchange with suitable atoms, would have such adsorption characteristics. The following Examples are provided to further illustrate the process of the present invention. The molecular sieve catalysts used in the following Examples were calcined in air following synthesis to remove the organic templating agent. Unless otherwise specified, all parts, proportions etc. are by weight. Example 1 This experiment illustrates the use of SAPO-34 as a non-zeolitic molecular sieve catalyst in the process of this invention. SAPO-34 was prepared as described hereinabove and then heated for one hour under nitrogen at a temperature of 400°C prior to use. SAPO-34 has a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: This experiment was conducted using a reactor consisting of a 20.3 cm (8 inch) length by 6.35 mm (0.25 inch) diameter stainless steel tube. Approximately 0.5 grams of the SAPO-34 catalyst as a powder was dispersed among about 2.5 grams of 0.595 to 0.841 mm (20-30 U.S. mesh) quartz chips. This mixture was charged to the reactor and the reactor was then immersed in a sand bath and heated to a temperature of 400°C. Connected to the inlet of the reactor was a source of ammonia which was fed at a rate of 15 cubic centimeters/minute in the gas phase at about atmospheric pressure. Also connected to the inlet of the reactor was a liquid feed line of methanol connected to a high pressure liquid chromatography (HPLC) type solvent pump. The methanol was fed as a liquid at a rate of 1.6 milliliters/hour. The methanol: ammonia (C: N) mole ratio was 1.0 and the weight hourly space velocity of methanol was 2.8. The liquid products of the reaction were collected immediately downstream from the reactor in a cold trap at a temperature of 0°C and the gaseous products were sampled directly to a gas chromatograph. The material collected in the cold trap and the gaseous products were analyzed by gas chromatography on a 3.05 m (10 foot) length by 0.32 cm (1/8 inch) diameter column containing 4% Carbowax® 20M + 0.6% KOH on Carbopack B (Supelco). Analysis of the products of the reaction (samples taken from 3 to 4 hours into the run) showed a 50% methanol conversion, a 29% yield of dimethylether and a methylamine distribution as follows: monomethylamine 41%, dimethylamine 17% and trimethylamine 42%. Example 2 This experiment illustrates the use of SAPO-11 as a non-zeolitic molecular sieve catalyst in the process of this invention. SAPO-11 was prepared as described hereinabove and then heated for one hour under nitrogen at a temperature of 400°C prior to use. SAPO-11 has a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth below: This experiment was conducted using a reactor consisting of a 20.3 cm (8 inch) length by 6.35 mm (0.25 inch) diameter stainless steel tube. Approximately 0.5 grams of the SAPO-11 catalyst as a powder was dispersed among about 2.5 grams of 0.595 to 0.841 mm (20-30 U.S. mesh) quartz chips. This mixture was charged to the reactor and the reactor was then immersed in a sand bath and heated to a temperature of 400°C. Connected to the inlet of the reactor was a source of ammonia which was fed at a rate of 15 cubic centimeters/minute in the gas phase at about atmospheric pressure. Also connected to the inlet of the reactor was a liquid feed line of methanol connected to a high pressure liquid chromatography (HPLC) type solvent pump. The methanol was fed as a liquid at a rate of 1.6 milliliters/hour. The methanol: ammonia (C: N) mole ratio was 1.0 and the weight hourly space velocity of methanol was 2.8. The liquid products of the reaction were collected immediately downstream from the reactor in a cold trap at a temperature of 0°C and the gaseous products were sampled directly to a gas chromatograph. The material collected in the cold trap and the gaseous products were analysed by gas chromatography on a 3.05 m (10 foot) length by 0.32 cm (1/8 inch) diameter column containing 4% Carbowax® 20M + 0.6% KOH on Carbopack B (Supelco). Analysis of the products of the reaction (samples taken from 3 to 4 hours into the run) showed a 50% methanol conversion, a 27% yield of dimethylether and a methylamine distribution as follows: monomethylamine 32%, dimethylamine 17% and trimethylamine 51%. Example 3 This experiment illustrates the use of SAPO-34 as a non-zeolitic molecular sieve catalyst in the process of this invention. SAPO-34 was prepared as described hereinabove and then heated for one hour under nitrogen at a temperature of 400°C prior to use. SAPO-34 has a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth in Example 1. This experiment was conducted using a reactor consisting of a 20.3 cm (8 inch length) by 6.35 mm (0.25 inch) diameter stainless steel tube. Approximately 0.5 grams of the SAPO-34 catalyst as a powder was dispersed among about 2.5 grams of 0.595 to 0.841 mm (20-30 U.S. mesh) quartz chips. This mixture was charged to the reactor and the reactor was then immersed in a sand bath and heated to a temperature of 400°C. Connected to the inlet of the reactor was a source of ammonia which was fed at a rate of 30 cubic centimeters/minute in the gas phase at about atmospheric pressure. Also connected to the inlet of the reactor was a liquid feed line of methanol connected to a high pressure liquid chromatography (HPLC) type solvent pump. The methanol was fed as a liquid at a rate of 1.6 milliliters/hour. The methanol: ammonia (C:N) mole ratio was 0.5 and the weight hourly space velocity of methanol was 2.8. The liquid products of the reaction were collected immediately downstream from the reactor in a cold trap at a temperature of 0°C and the gaseous products were sampled directly to a gas chromatograph. The material collected in the cold trap and the gaseous products were analyzed by gas chromatography on a 3.05 m (10 foot) length by 0.32 cm (1/8 inch) diameter column containing 4% Carbowax® 20M + 0.6% KOH on Carbopack B (Supelco). Analysis of the products of the reaction (samples taken 4.5 hours into the run) showed a 47% methanol conversion, a 20% yield of dimethylether and a methylamine distribution as follows: monomethylamine 58%, dimethylamine 21% and trimethylamine 21%. Example 4 This experiment illustrates the use of SAPO-31 as a non-zeolitic molecular sieve catalyst in the process of this invention. SAPO-34 was prepared as described hereinabove and then heated for one hour under nitrogen at a temperature of 325°C prior to use. SAPO-34 has a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth in Example 1. This experiment was conducted using a reactor consisting of a 20.3 cm (8 inch) length by 0.95 cm (3/8 inch) diameter stainless steel tube encased in a 2.5 cm (1 inch) diameter stainless steel sheath. Approximately 1.5 grams of the SAPO-34 catalyst as a powder was dispersed among about 4.5 grams of 0.595 to 0.841 mm (20-30 U.S. mesh) quartz chips. This mixture was charged to the reactor and the reactor was then heated to a temperature of 325°C with a split furnace heater. Connected to the inlet of the reactor was a source of ammonia which was fed at a rate of 18 cubic centimeters/minute in the gas phase at about atmospheric pressure. Also connected to the inlet of the reactor was a liquid feed line of methanol connected to a high pressure liquid chromatography (HPLC) type solvent pump. The methanol was fed as a liquid at a rate of 1.8 milliliters/hour. The methanol: ammonia (C: N) mole ratio was 1.0 and the weight hourly space velocity of methanol was 1.0. The liquid products of the reaction were collected immediately downstream from the reactor in a cold trap at a temperature of 0°C and the gaseous products were sampled directly to a gas chromatograph. Gas chromatography analysis of the reactor off gas downstream from the cold trap indicated that virtually all the products of the reaction and the unreacted methanol were collected in the cold trap. The material collected in the cold trap was analysed by gas chromatography on a 3.05 m (10 foot) length by 0.32 cm (1/8 inch) diameter column containing 4% Carbowax® 20M + 0.6% KOH on Carbopack B (Supelco). Analysis of the products of the reaction (samples taken 3 hours into the run) showed a 65% methanol conversion, a 13% yield of dimethylether and a methylamine distribution as follows: monomethylamine 63%, dimethylamine 32% and trimethylamine 5%. Example 5 This experiment illustrates the use of SAPO-11 as a non-zeolitic molecular sieve catalyst in the process of this invention. SAPO-11 was prepared as described hereinabove and then heated for one hour under nitrogen at a temperature of 400°C prior to use. SAPO-11 has a characteristic X-ray powder diffraction pattern which contains at least the d-spacings set forth in Example 2. This experiment was conducted using a reactor consisting of a 20.3 cm (8 inch) length by 6.35 mm (0.25 inch) diameter stainless steel tube. Approximately 0.5 grams of the SAPO-11 catalyst as a powder was dispersed among about 2.5 grams of 0.595 to 0.841 mm (20-30 U.S. mesh) quartz chips. This mixture was charged to the reactor and the reactor was then immersed in a sand bath and heated to a temperature of 400°C. Connected to the inlet of the reactor was a source of ammonia which was fed at a rate of 15 cubic centimeters/minute in the gas phase at about atmospheric pressure. Also connected to the inlet of the reactor was a liquid feed line of ethanol connected to a high pressure liquid chromatography (HPLC) type solvent pump. The ethanol was fed as a liquid at a rate of 1.6 milliliters/hour. The liquid products of the reaction were collected immediately downstream from the reactor in a cold trap at a temperature of 0°C and the gaseous products were sampled directly to a gas chromatograph. Gas chromatography analysis of the reactor off gas downstream from the cold trap indicated that virtually all the products of the reaction and the unreacted methonal were collected in the cold trap. The material collected in the cold trap was analysed by gas chromatography on a 3.05 m (10 foot) length by 0.32 cm (1/8 inch) diameter column containing 4% Carbowax® 20M + 0.6% KOH on Carbopack B (Supelco). Analysis of the products of the reaction showed that monoethylamine was formed.

Claims: 1. A process for preparing an alkylamine by contacting an alcohol with a compound of the formula in which each R₂, which can be the same or different, represents hydrogen or C₁-C₁₂ alkyl, in the presence of a catalyst, characterized in that the catalyst is a silicoaluminophosphate (SAPO) molecular sieve. 2. A process according to Claim 1 characterized in that the silicoaluminophosphate molecular sieve comprises any one or more of SAPO-5, SAPO-11, SAPO-31, SAPO-34 and SAPO-41 as defined in the Description. 3. A process according to Claim 1 or 2 characterized in that the alcohol has the formula R₁OH wherein R₁ is straight or branched chain alkyl having 1 to 12 carbon atoms. 4. A process according to any one of Claims 1 to 3 characterized in that the alcohol and the compound of the formula are reacted at a temperature of 250 to 500°C. 5. A process according to Claim 4 characterized in that the temperature is 300 to 450°C. 6. A process according to any one of Claims 1 to 5 characterized in that the alcohol and the compound of the formula are reacted at a pressure from atmospheric pressure to 500 psig (0.7 MPa).

Inventors: KAISER, STEVEN WILLIAM, OLSON, KURT DAMAR
Applicants: UOP
Application year: 1988
Main classification: C07C209
IPC codes: C07C209, C07C67, C07C211, B01J29, C07B61