MXPA04008139A - Improved process for producing alkanolamines. - Google Patents

Abstract

The present invention refers to an improved process for producing alkanolamines, which consists of at least two or three Reaction Systems with a liquid phase. The First Reaction System is useful for reacting an epoxide with a mixture of water and ammonia in order to form alkanolamines, in the Second or Third Reaction System the aforesaid epoxide reacts with an alkanolamine or a mixture of water and ammonia in order to form alkanolamines; in the Second or Third Reaction System the aforesaid epoxide reacts with an alkanolamine or a mixture of alkanolamines in liquid phase, virtually in the absence of ammonia or water so as to form more alkanolamines. The invention further comprises a system for Preparing Ammonia Water, a Column for isolating Ammonia, a Column for Drying vacuum alkanolamines; optionally a Column for Concentrating Monoalkanolamine and a system for purifying alkanolamines, which consists of a plurality of vacuum distillation columns. The improved process of the present inv ention is useful for obtaining alkanolamines with a wide range of products distribution without requiring recycling pure amines with regard to the First Reaction System. Moreover, the selection of particular operating conditions of said improved process and the thermal integration among certain sections of the process are carried out in such a manner that a substantial reduction of the energy consumption is achieved, in comparison with conventional processes, thereby producing the same amount of products. Said improved process can be used in the construction of novel unities for producing alkanolamines, as well as in the modification of former unities, which require changing the distribution of the obtained products and increasing the production capacity or reducing the energy consumption.

Description

PROCESS PERFECTED POPE THE PRODUCTION OF ALCANOLAMINES BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a process for the production of alkanolamines. Alkanolamines, particularly ethanolamines, have wide industrial applications, for example, in the removal of acid gases such as CO2 and H2S from natural gas or gas from petroleum refineries, in the formulation of corrosion inhibitors, in the production of alkanolamides used as surfactants, in the neutralization of anionic surfactants used in cleaning products and in cosmetics, in the preparation of biocides, as additives in the manufacture of cement, as intermediates in the synthesis of various chemical compounds, etc. There are two families of alkanolamines with more commercial interest, which are ethanolamines and isopropanolamines. The alkanolamines have the chemical formula Rn H3-n where n can be equal to 1, 2 or 3. In the case of ethanolamines, the group R is H0 (C2ÍÍ4) -; for isopropanolamines, R is HO (C3He) -. The alkanolamines are obtained from the reaction of an epoxide with ammonia, to form the monoalkanolamine. The latter reacts with the new epoxide molecule, forming the dialkanolamine. Finally the dialkanolamine reacts with a third epoxide molecule forming the trialkanolamine. The reactions are: CH2OCHR1 + NH3 - HO (C2H3R1) NH2 (monoalkanolamine) CH2OCHR1 + H0 (C2H3R1) NH2? [HOÍCaHs 1)] 2NH (dialkanolamine) CH2OCHR1 + HO (C2H3R1) NH? [HO (C2H3R1)] 3N (trialkanolamine) When R1 is hydrogen, then the epoxide CH2OCHR1 is ethylene oxide; when R1 is the radical CH3, then the epoxide CH2OCHR1 is propylene oxide. These reactions are all exothermic. The distribution of the products depends mainly on the ammonium / epoxide ratio and the initial molar reactions of monoalkanolamine / epoxide and dialkanolamine / epoxide present in the mixture. In the industrial processes of production of alkanolamines, the reactions of the epoxide with ammonia are conducted in liquid phase, generally when there is water, since the water: 1) acts as a catalyst of the reaction; 2) serves as a heat reserve, limiting and controlling the temperature; 3) keeps the ammonia in liquid state (aqueous solution) without there being the need to maintain high pressures in the system.

The reactions indicated above are accompanied by secondary reactions, which occur in small proportions, forming undesirable byproducts, which may affect the quality of the alkanolamines or decrease the yield in useful products. One of these parallel reactions is the reaction between the epoxide and the hydroxy groups of the alkanolamines, forming alkoxylated alkanolamines. The other important secondary reaction is the reaction between epoxide and water, forming glycol. These side reactions are considerably accelerated by temperature, so that it is always desirable to maintain relatively low temperatures in the reaction systems, especially when there is the presence of water. The alkanolamine consuming markets demand the three products of each family (derived from the same epoxide), monoalkanolamine, dialkanolamine and trialkanolamine, in variable proportions over time. In certain situations it may happen that the demand for one of the products is much higher than the demand of the other two. Depending on the alkanolamine whose production is to be maximized or minimized, process conceptions optimized in production and / or investment costs may be very different for each case. However, in practice it is more convenient to have productive units that provide maximum flexibility with respect to the distribution of products, always considering the minimization of production costs. The conventional processes of alkanolamin production generally have few variations in their basic conception. Such processes are described, generally, by MÜLLINS in Volume 1 of the Kirk-Othmer Encyclopedia of Chemical Technology, pages 944-967, edited in 1978 by John Wiley & amp; amp;; Sons. For a good evaluation of the improvements that are the object of this invention, we describe below the characteristics of the conventional processes of alkanolamines production: A mixture of ammonia and water is continuously obtained in the bottom of an absorption column that receives water in the top and amonia for replacement, together with ammonia recovered from the process in a region near the bottom. The absorption of ammonia in water is exothermic so that it is necessary to remove heat to maintain the correct temperature. The removal of heat from the system is carried out by recirculating the water / ammonia mixture, called ammonia water, from a cooler operated with cooling water. The ammonia water is pumped to the reaction system, and there it is mixed with the epoxide. The epoxide leak is adjusted so that the ammonium / epoxide molar reaction is between 2 and 30 or usually between 3 and 15, depending on the desired distribution for the products. Another possibility of adjusting the final distribution of the products is to recycle monoalkanolamine or dialkanolamine for the reaction system, when it is desired to obtain more dialkanolamine or trialkanolamine, respectively. The effluent from the reaction system goes to a distillation column where some of the water and all ammonia used in excess are removed. The water / ammonia mixture is partially condensed and returns to the absorption column where the ammoniacal solution is prepared. The condenser of the water / ammonia mixture usually operates with cooling water, so that the condensation heat is lost to the environment. From the bottom of the ammonia distillation column a drying column is fed, whose function is to remove virtually all the remaining water, by the top, and a mixture of dry alkanolamines by the bottom. This column, called the drying column, is usually operated in a vacuum. The dry alkanolamines are then sent to the purification system. Generally this purification system is composed of three columns of vacuum distillation. The first column, called the monoalkanolamine purification column, isolates the pure monoalkanolamine at the top, leaving a mixture of di and trialkanolamines and heavy by-products in the bottom. In a second column, called the dialkanolamine purification column, the dialkanolamine is removed through the stop, leaving the trialkanolamine and heavy residues at the bottom. In the third column, called the trialkanolamine purification column, the trialkanolamine is isolated at the top leaving a mixture of trialkanolamine and heavy by-products in the bottom.

Description of the Previous Technique The main variations of the conventional processes mentioned above are in the reaction system and in the ammonia recovery system. Some of them are described below. COCÜZZA and TOREGGIANI, in the US patent number US4169856 of October 2, 1979"Process for the preparation and the recovery of ethanolamines", describe a continuous process whose reaction system consists of an isothermal reactor followed by an adiabatic reactor and system of ammonia recovery formed by a column of ammonia absorption of dishes that make bubbles derived from internal cooling. CELEGHIN et al., In the Brazilian patent number 8003904, filed on June 23, 1980: "Continuous process for the production of alkanolamines" (Continuous process for the production of alkanolamines), describe a process whose reaction system consists of several Adiabatic phases, with external cooling between each intermediate phase and epoxide injection before the first and before each intermediate phase. Maybe this system works with ammonia concentrations between 5 and 50%. The examples presented indicate that when the reaction system is fed with ammonia water containing high concentrations of ammonia maintaining high ammonium / epoxide ratios, monoalkanolamine is formed in proportionally higher amounts. However, when a larger proportion of dialkanolamine and / or trialkanolamines is desired, it is necessary to operate with lower ammonium / epoxide molar ratios, which requires the reduction of the ammonia concentration and the leakage of ammonia water to a minimum value from which too much glycol is formed by virtue of the possibility of the large temperature rise in the adiabatic phases. H &MMER and WERNER indicate an alternative solution to this problem, described in U.S. Patent No. U.S. 5545757 of August 13, 1996"Production of ethanolamines". In this alternative, a multitube reactor with indirect cooling is used as the first phase, followed by a set of adiabatic reactors, as described by CELEGHIN and his collaborators. AHMED et al., In U.S. patent number U.S. 4845296 of July 4, 1989"Process for preparing alkanolamines" and GIBSON and co-workers in U.S. patent number Ü.S. 4847418 of July 11, 1989"Continuous process for preparing alkanolamines" describe processes in which an epoxide reacts with ammonia in the presence of catalytic amounts (less than 5%) of water under very critical conditions, between 100 and 180 ° C and pressures between 170 and 240 atmospheres, with ammonium / epoxide molar ratio between 15: 1 to 50: 1, to generally form more than 75% of monoalkanolamine and small amounts of dialkanolamine (15 to 20%) and trialkanolamine (approximately 5%). Although the processes described by AH ED and GIBSON are capable of producing monoalkanolamine in high proportions, they require high investments because they operate at high pressures and temperatures. In addition to that, because of the very high ammonium / epoxide ratios, the energy consumption can be larger than the consumption required by processes using ammonia solutions. In addition to the possibility of varying the ammonium / epoxide ratio, the adjustment of the distribution of the products can also be carried out by the recycling of monoalkanolamine and / dialkanolamine directly for the first reaction phase, as described by CELEGHIN et al. Or for the second phase of a reaction system with two phases, as described by NYGAARD and DiGUILIO in the US patent number US 6063965 of May 16, 2000"Production of diethanolamine". Another way was described by DiGUILIO and co-workers in the U.S. patent number U.S. 6075168 of June 13, 2000"Selective production of diethanolamine" in which ethylene oxide is injected together with monoethanolamine into a reactive distillation column, operated in vacuum. Although the authors claim a selectivity of at least 85% of diethanolamine, it is necessary to consider that, in vacuum and at high temperatures, ethylene oxide is a gas, which can impose limitations determined by mass transfer. In addition to that, the system will depend on safety devices carefully designed and operated to prevent the ethylene oxide, which is too toxic, reaching the top of the column without reacting, reaching the vacuum system and then the atmosphere. Regarding the ammonia recovery system, there are few variations of the conventional process. One of those variations was described by WILLIS AND HENRY in U.S. Patent No. U.S. 4355181 of October 19, 1982"Process for ethanolamines" in which a pre-evaporation of the ammonia of the stream coming from the reaction system is proposed. That ammonia would be condensed and returned to the reaction system, without going through the absorption system.

BRIEF DESCRIPTION OF THE INVENTION The main deficiencies inherent to the conventional processes described above are related to the limited flexibility with respect to the distribution of the products and the high consumption of energy. Thus, an improved process for the production of alkanolamines, which is more flexible in relation to the distribution of products and with less energy consumption, compared with conventional processes, is the subject of this invention. Attending these objectives a process was developed for the production of alkanolamines that uses at least two Reaction Systems in liquid phase, being that in the First Reaction System an epoxide reacts with a mixture of water and ammonia to form alkanolamines and in a second and / or in a Third Reaction System the same epoxide reacts with one or more alkanolamines, in liquid phase, virtually in the absence of ammonia or water to form more alkanolamines, an Ammoniacal Water Preparation System, one or more Isolation Columns of Ammonia, one or more Drying Columns of Alkanolamines at reduced pressure, optionally one or more Monoalkanolamine Concentration Columns and an alkanolamine purification system consisting of one or more Monoalkanolamine Purification Columns, one or more Purification Columns of Dialkanolamine and, optionally, one or more Trialcanolamine Purification Columns, or even according to the figures 1 and 2 attached.

This invention relates to a process for the manufacture of alkanolamines by reaction in liquid phase between an epoxide and excess aqueous ammonia solution in a first reaction phase, completed by at least one other reaction system and, optionally, a third system of reaction in which a further quantity of epoxide reacts with the mixture of alkanolamines obtained in the first reaction system, after the isolation of excess ammonia and water or, optionally, with part of an alkanolamine isolated from said mixture of alkanolamines . This invention still relates to an advantageous way of isolating the excess ammonia and water of the alkanolamines derived from the first reaction phase, as well as by the choice of certain operating conditions of this perfected process and the thermal integration between certain sections. of the process, achieving in this way obtain advantageous reduction of energy consumption when compared with conventional processes producing the same quantities of products. The improved process object of this invention is based on the following inter-related characteristics: 1. a First Reaction System in which part of the epoxide reacts with a concentrated solution of ammonia water (containing about 20 to about 65% by weight of ammonia) ), under such conditions that the ammonium / epoxide molar ratio is between about 4 and about 20, preferably between about 5 and about 12. The objective of this First Reaction System is to produce monoalkanolamine in the largest ratio to the other alkanolamines; alternatively, operating conditions can be selected such that a maximum optimized ratio of monoalkanolamine plus dialkanolamine is obtained when it is desired to produce more di or trialkanolamine. The First Reaction System is composed of one or a set of reactors of various types, such as those already described in the prior art. Preferably the epoxides used are ethylene oxide or propylene oxide. The alkanolamines obtained are preferably from the family of ethanolamines or isopropanolamines. Multitubular reactors with external cooling or adiabatic tubular cooling with intermediate cooling or a combination of those types of reactors can be used in the First Reaction System. 2. An Ammonia Recovery System divided into two sections: an Antonia Isolation Subsystem, operated at high pressure and an Ammoniacal Water Preparation Subsystem, operated in lower pressure. -in the Ammonia Recovery Subsystem, all ammonia (and part of the water) is isolated from the alkanolamines and the rest of the water at the top of a distillation column. Ammonia and water are then partially condensed at relatively high temperatures, taking advantage of the heat of condensation and dissolution of ammonia in a useful way in the production unit of alkanolamines. The Ammonia Recovery Subsystem can, optionally, add a compressor to raise the pressure of the water / ammonia mixture to suitable levels, allowing its condensation at higher temperatures. Warmed liquid water can be added to the gaseous mixture of water and ammonia to ensure partial condensation at higher temperatures, when necessary. The gaseous mixture of ammonia and water, as well as the aqueous solution of ammonia, obtained after the partial condensation of the mixture are sent to the Subsystem of Preparation of Ammoniacal Water. -The Ammoniacal Water Preparation Subsystem consists of an Ammonia Absorption Column and an Ammonia Water Container. The Ammonia Absorption Column receives water at the top and the ammonia and water currents recovered in the Ammonia Recovery Subsystem. The final mixture is accumulated in the Ammoniacal Water Container. This subsystem may also be of an external heat exchanger used with the objective of maintaining the temperature of the ammonia water below a certain limit. The isolation of a mixture of water and ammonia from the effluent of the First Reaction System, which occurs in this Ammonia Insulation Column, can then be partially condensed so that it uses the heat of condensation in a useful way, preferably used by the unit itself of the production process of alkanolamines. The operation of the Ammonia Insulation Column can be conducted at an absolute pressure chosen between about 700 and about 1200 kPa. A compressor can be used to raise the pressure of the ammonia mixture and water withdrawn at the top of the Ammonia Insulation Column to a discharge pressure chosen between about 800 and about 1800 kPa, preferably between about 1000 and close of 1400 kPa. It is added to the water and ammonia mixture before it is condensed, thus increasing the condensation temperature and facilitating the useful recovery of the condensation heat. 3. A Drying Column of alkanolamines, operated under reduced pressure. Once monoalkanolamine is always in larger proportions than in conventional processes, the bottom temperature of this column may be sufficiently low to allow partial condensation of the ammonia / water mixture produced in the high pressure ammonia subsystem, decreasing or eliminating the energy consumption coming from external sources. 4. a Second and / or a Third Reaction System (optional), whose objective is to complete the production and adjust the desired distribution of the products, when necessary. In this Second and / or Third Reaction Systems, the remainder of the epoxide reacts with a concentrated stream of monoalkanolamine, dialkanolamine or a mixture of alkanolamines. The alkanolamin mixture may be the bottom stream of the Dry Column or the bottom stream of the Monoalkanolamine Purification Column, depending on the desired product distribution. Agitated tank reactors followed by multitubular reactors with external cooling or adiabatic tubular reactors with intermediate cooling or a combination of those types of reactors in the Second and / or the Third Reaction System, and / or using a Second Reaction System can be used. fed with the same epoxide used in the First Reaction System and the mixture of dry alkanolamines from the bottom of the vacuum drying column of alkanolamines, and / or using a second system of Reaction fed with the same epoxide used in the First Reaction System and the concentrated monoalkanolamines from a Concentration Column of Monoalkanolamines. A Second or a Third Reaction System fed with the same epoxide used in the First Reaction System and the mixture of dry alkanolamines from the bottom of the Purification Column in vacuum of monoalkanolamines can be used. The Second and / or the Third Reaction System may be constituted by any type of reactors or their combinations already described in the literature for similar cases, such as: -a set of multitubular reactors ("plug-flow") with external cooling, or adiabatic, with cooling between each reactor, with a single or with multiple injections of epoxide. -a continuous reactor, stirred tank type, with or without cooling, followed by one or a set of tubular reactors ("plug-flow") with external cooling, or adiabatics with cooling between each reactor, used to complement the reaction, with a only epoxide injection only in the first phase, or with multiple epoxide injections. Preferred are systems consisting of two or more adiabatic reactors with multiple epoxide injections, with cooling between each. Once there is no more water in the mixture, there is no possibility of the reaction of the epoxide with water to form glycol. In this way, the temperature limit is determined by the possibility of the reaction of the epoxide with hydroxyl groups of the alkanolamines, which can lead to the formation of unwanted byproducts, or to thermal degradation of the alkanolamines. The cooling of the reactors of this according to the reaction system can be done using process currents and in this way take advantage of the heat released by the reactions that are exothermic. One of these streams may be the effluent from the first reaction phase, which would thus be pre-heated before it was introduced into the ammonia removal column. The same reaction system may be aligned to operate with any of the loading options, ie concentrated monoalkanolamine, when it is desired to maximize the production of dialkanolamine, the bottom stream of amine drying column, when the three alkanolamines are desired, or the bottom stream of the isolation and purification column of monoalkanolamine, when it is desired to maximize the production of trialkanolamine. This second reaction phase can be dispensed, or not used, when the maximum production of monoalkanolamine is desired. 5. A System of Alkanolamines Purification, similar to those that are used by the conventional technique, but that includes a Second and / or a Third System of Reaction of amines with epoxide. The second Reaction system can be located before the Alkanolamines Purification System or, optionally, after a Monoalkanolamine Concentration Column, when it is used. The Third Reaction System, when necessary, is located between the Monoalkanolamine Purification Column and the Dialkanolamine Purification Column. In addition, the Second and Third Reaction Systems as well as the Alkanolamines Purification System can be thermally integrated with the rest of the unit, taking advantage of the heat that must be removed from its hot currents. According to the invention, a varied distribution of alkanolamines is obtained without the use of recycle of any purified alkanolamine for the First Reaction System. The improved process object of this invention has the advantage of substantially reducing energy consumption and providing even greater flexibility with respect to the distribution of products. In this way it is possible to obtain a final distribution of products that can vary greatly within certain limits. Some of the títopes cases that can be taken as illustrative examples are presented: -Maximal production of monoalcanolamine, or typically 70% of monoalcanolamina, approximately 20% of dialcanolamina and less than 10% of trialcanolamine; -Maximum production of dialkanolamine, or typically from zero to 15% of monoalkanolamine, from 60 to 85% of dialkanolamine and from 10 to 40% of trialkanolamine; -Maximum production of trialkanolamine, or typically from zero to 15% monoalkanolamine, up to 15% dialkanolamine and more than 70% trialkanolamine; -Many other combinations are possible, respecting the maximum and minimum limits of each individual alkanolamine that can be obtained without too much cost of production and investment in equipment. It should be underlined that with this perfected process, said flexibility of products is obtained without the need to recycle amines already purified for the first reaction system, as is the most common practice in conventional processes. The improved process object of this invention can be applied for the construction of new alkanolamines producing units as well as for the modification of existing units, when it is desired to change the distribution of the obtained products, increase the production capacity or reduce the energy consumption. A typical manner of the process object of this invention is shown with Figure 1 and is complemented with Figure 2, considering that the two models are integrated in a single process, but they are presented separately for convenience, to facilitate their analysis .

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a model of the First Reaction System, the Ammonia Recovery Subsystem, the Ammoniacal Water Preparation Subsystem, and the Alkanolamin Drying Column, integrated with the Ammonia Recovery System in a way that takes advantage of the heat of condensation absorption of ammonia. Figure 2 shows the Alkanolamines Purification System as well as the Second and Third Reaction Systems, in their possible ways to optimize the distribution of products. The process model depicted with Figure 1 and supplemented with Figure 2 is illustrative only and should not be construed as restricting the merit of this invention. Many other variations can be used, mainly with respect to the combinations used for the integration of the process currents for the use of energy. Description of Figure 1 According to the attached Figure 1, the Ammoniacal Water Preparation System, which is formed by an Ammonia Absorption Column (1), an Ammoniacal Solution Container (2), and a solution cooling system of ammonia water, which is not shown in Figure 1), receives ammonia and water from the Partial Condenser (3), from the pipeline (4), which is fed to the bottom of the Absorption Column (1). That column also receives, through the pipe (5), recycle water that is fed to the top, after cooling in the heat exchanger (6), and a mixture of water is ammonia, through the pipe ( 7) obtained as condensate in the Ammonia Recovery System, after being cooled in the heat exchangers (8) and (9). The Ammoniacal Water Preparation System operates with an absolute pressure chosen between 400 and 900 kPa. The ammoniacal solution collected with the container (2) coupled to the Ammonia Absorption Column (1) is pumped by the Pump (10) through the pipe (11), then receiving the replacement ammonia through the pipe ( 12), forming the final mixture of ammonia water that will feed the First Reaction System (13). The first Reaction System (13), which operates with an absolute pressure chosen between 800 and 3500 kPa, receives the mixture of ammonia water and a first portion of epoxide, which is introduced through the pipe (14). The epoxide can be introduced with a single or with many points, according to the set of reactors chosen (in Figure 1, Reaction System 13 is shown in a simplified form with only one introduction point). The effluent of the First Reaction System (13), hereinafter simply referred to as the effluent of (13), is formed by a mixture of alkanolamines, ammonia and water. The conversion of the epoxide is practically complete and therefore is virtually absent in this stream. The effluent mixture of (13) follows through the pipe (15) and is preheated in the Heat Exchanger (8), by thermal exchange with the ammonia mixture and water coming from the container (20). Then the effluent from (13) is fed by means of the pipe (16) with the preheater (17) (optional) and then, through the pipe (18) to the heat exchanger (19) (also optional), where you can change heat with the gaseous mixture of water and ammonia from the Insulation Vessel (20). Finally, the effluent of (13) is fed to the Ammonia Insulation Column (21) in an intermediate region, preferably close to the stop. The column (21) receives backflow of water in the stop through the pipe (22). The vaporized ammonia, part of the water and eventually small amounts of monoalkanolamine are removed at the top of the Ammonia Insulation Column (21), through the pipe (23). This column is operated with maximum pressure, chosen between 700 and 1200 kPa (absolute), limited only by the background temperature, which generally should not exceed 185 ° C to avoid thermal degradation of the amines. A Compressor (24) (optional) can be used to compress the water / ammonia mixture to a convenient pressure to condense the largest part of the mixture at a temperature high enough to take advantage of the heat of condensation and mix in a useful manner. That pressure usually does not need to exceed 1800 kPa (absolute). It is possible to condense the water / ammonia mixture at a pressure of approximately 1200 kPa (absolute), obtaining a condensate containing about 24% ammonia, effecting condensation at approximately 133 ° C or about 15% ammonia if condensation is carried out at 139 ° C. If the pressure is about 850 kPa (absolute) it is possible to obtain a condensate containing about 17% or 11% ammonia, respectively, at temperatures of 133 or 139 ° C. The effluent of the heat exchanger (25) is a mixture composed of a liquid phase and a vapor phase. This mixture is conducted to the Insulation Vessel (20) where the gaseous part, formed mainly by ammonia, is sent to the Absorption Column (1), optionally passing first through the Heat Changer (19) and then through the partial condenser. (3), preferably operated with cooling water. The bottom product of the Ammonia Insulation Column (21) is a mixture composed of water and alkanolamines. This mixture flows by pressure difference for the Drying Column (26), through the pipe (27), passing, optionally, through the Preheater (17). The Drying Column (26) is operated with the lowest possible pressure, chosen between 6 and 25 kPa (absolute), limited only by the stop temperature necessary to condense the water withdrawn from the amines mixture. With these conditions, using a low load loss filler it is possible to obtain background temperatures between 115 and 130 ° C in the Dry Column (26). Note that under these conditions there are sufficient temperature differences to promote the change of heat between the condensation of the water / ammonia mixture from the Ammonia Insulation Column (21), and the bottom product of the column (26) by means of of the heat exchanger (25), thereby providing much of the heat required by that column. Depending on the design and operation conditions of the system, the heat exchanger (25) can supply all of the thermal load required by the column (26), and can be completely dispensing the heat eventually suppressed by the heat exchanger (28) . At the top of the Drying Column (26) all the water fed with the alkanolamines is removed, following for the top condenser. A part of the condensed water returns as reflux. A vacuum unit is used to maintain the desired pressure in the column. The capacitor and the vacuum unit are represented generically by the assembly (29). The water removed from the assembly (29). The water removed from the assembly (29), called recycle water, is pumped by the pump (30) for three different destinations: a) for the Ammonia Absorption Column (1), by means of the pipes (31), ( 32) and (5); b) As reflux of the Ammonia Insulation Column (21), through the pipes (31) and (22); c) for the high pressure water / ammonia condenser, heat exchanger (25), by means of the pipes (33) and (34), through the equipment (37) or optionally by means of the pipe ( 35) to the heat exchanger (36) and to the pipe (34). The equipment (37) represents in a generic way an equipment of the Alkanolamines Purification System where the preheating of the water takes place taking advantage of the heat of hot currents of said System. The bottom product of column (26), consisting of a mixture of dry alkanolamines, passes for the alkanolamines purification system, by means of pipe (38), where a second (and optionally a third) system is also indicated. Reaction used to adjust the final production and the desired distribution of each product. That system is represented with Figure 2, the description of which is made below. Description of Figure 2 According to the attached Figure 2, the stream of dry amines, coming from the bottom of the Drying Column (26) shown in Figure 1, is transferred, by means of the pipe (38), and optionally fed to the Second Reaction system (39) where, after adjusting the temperature, it receives the other part of the epoxide, by means of the pipeline (55), producing more dialkanolamine and trialkanolamine and adjusting the desired distribution of products. The reaction system used with this Second Reaction System (39) can be any of the types described with the literature for similar cases, such as: a) a set of "plug-flow" reactors with cooling or adiabatic , with cooling between each phase, with a single or with multiple injections of epoxide b) a continuous reactor, tank type stirred, with or without cooling, followed by one or a set of tubular reactors ("plug-flow") with adiabatic cooling with cooling between each phase, used to supplement the reaction with epoxide injection alone in the first phase, or with multiple epoxide injections. A system of adiabatic reactors with multiple injections of epoxide, with cooling between phases is preferred. The effluent from this reaction system (39) can be sent directly to the Monoalkanolamine Purification Column, (40). Optionally, the mixture of dry amines, coming from Drying Column (26), can be sent, by means of the pipe (41) to the Concentration Column of Monoalcanolamina (42), of vacuum distillation, whose function is to produce concentrated monoalkanolamine as a top product. That current, withdrawn in liquid form by means of the pipe (43) can be fed to the Second Reaction system (39). The effluent of the second Reaction system (39) can be fed directly to the Monoalkanolamine Column (40) or it can be returned to the Column (42) by means of the pipe (44). In this case, the bottom product of the Column (42), withdrawn through the pipe (45) feeds the Monoalkanolamine Purification Column (40). The preference for this option occurs when a maximized product distribution in dialkanolamine is desired. The use of Column (42) allows to increase the monoamine / epoxide ratio beyond that which is possible by directly using the stream of dry amines from the Dry Column (26). The larger the monoalkanolamine / epoxide ratio, the greater the production of dialkanolamine in relation to the trialkanolamine, for the same epoxide consumption. When it is desired to maximize the production of monoalkanolamine, Column (42) and Second Reaction System (39) may not be used with this case, the mixture of dry amines coming from the Drying Column (26) is directed to the pipe (46) and directly feeds the Monoalkanolamine Purification Column (40). The background product of the Monoalkanolamine Purification Column (40), withdrawn by means of pipe (47) is composed of a mixture of dialkanolamine, trialkanolamine and small amounts of heavy by-products. When the ratio between dialkanolamine and trialkanolamine is within what the market expects, the mixture can be directly sent to the Dialkanolamine Purification Column (48). When it occurs, with the case that a larger amount of trialkanolamine is desired, then the mixture may be sent, via line (49), for a Third Reaction System, (50), similar to the Second Reaction system ( 39). An additional amount of epoxide, fed by means of the pipe (51) is added to the Third Reaction System (50) by adjusting the desired product distribution. When it is desired to maximize the production of trialkanolamine relative to dialkanolamine, part of the dialkanolamine removed at the top of the Dialkanolamine Purification Column, (48), may be recycled for the Third Reaction System, (50), by means of the pipe (52). When it is desired to maximize the production of trialkanolamine relative to the monoalkanolamine + dialkanolamine, then part of the dialkanolamine removed at the top of the Dialkanolamine Purification Column, (48), may be recycled for the Second Reaction System, (39), by means of the pipe (53). Note that it is not always necessary for the two Reaction Systems (39) and (50) to be added in the same unit. When they are included, the aforementioned Reaction Systems can be operated simultaneously or one of them can be used while keeping the other disconnected. The Reaction Systems and the chosen operating modes will depend on the desired distribution of products, the cost of the necessary investments for each case and the operational costs. The Reaction systems (39) and (50) normally operate at considerably higher temperatures than the Reaction System (13) and may require cooling to avoid too much temperature rise. To take advantage of the heat of reaction it is possible to use cold process currents, which need heating. This is the case, for example, of the stream of alkanolamines, water and ammonia effluent from the Reaction System (13), which must be preheated before entering the Ammonia Insulation Column (21). That current, therefore, can be used to coil the Reaction Systems (39) and / or (50). Optionally, the recycled water returned, transferred by the pipe (33) (shown in Figure 1) can also be heated, totally or partially, by the heat of reaction produced in the Reaction Systems (39) and / or ( fifty) . The option for each case will depend on each specific case, becoming an engineering option, without affecting the success of the present invention. The bottom product of the Dialkanolamine Purifying Column (48), containing practically Trialcanolamine and heavy, is sent to the Trialcanolamin Purification Column (54), where Trialcanolamine product is removed by the top by means of the pipe (58) and a mixture containing Trialcanolamine and heavy is removed by the bottom by the pipe (59 ).

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES ? t molo 1 As this example we used a unit similar to that described above and represented with Figures 1 and 2. A First Reaction System (13) and a Second Reaction System (39) were used. The Third Reaction System (50) was not used. Specifically with this example, the First Reaction System (13) consisted of five adiabatic tubular reactors. (5 phases) containing a cooler between each phase and the Second Reaction system (39) consisted of two adiabatic reactors (2 phases) with cooling between the first and second phase. The epoxide was ethylene oxide, forming ethanolamines in that way. A solution of ammonia water was used, fed at 35 ° C, containing 59% by weight of water, 40% by weight of ammonia and 1% by weight of monoethanolamine before receiving the replacement ammonia. The mixture was fed to the First Reaction System (13), making an injection of ethylene oxide before each phase, resulting in a molar ratio 6 between the ammonia contained in the inlet of (13) and the total ethylene oxide fed. The effluent of each phase was cooled to 35 ° C before it received the respective injection of ethylene oxide. The pressure with (13) was maintained at 2500 kPa, ensuring that the mixture was always in the liquid state. The temperatures observed with the output of each phase were: 54 ° C with the output of the first phase, 6 ° C with the output of the second phase, 61 ° C with the output of the third phase, 60 ° C at the output of the fourth phase and 61 ° C at the start of the fifth phase. The effluent from the last phase had the following approximate composition: 32% by weight of ammonia, 11% by weight of monoethanolamine, 7% by weight of diethanolamine, 3% by weight of triethanolamine. No significant amounts of ethylene oxide or heavy by-products have been detected. The stream containing the efletarus mixture of the fifth reaction phase, with the composition indicated above was heated in the heat exchanger (8) and then further heated in the second Reaction system (39), not shown in Figure 1, and finally in the heat exchanger (17) until it reaches a temperature of 150 ° C. In this example, the Heat Changer (19) was not used. Then that current was fed to the Ammonia Insulation Column (21) operated with an absolute stop pressure equal to 930 kPa. The vapors removed at the top of the Column (21) have presented 51% by weight of ammonia, 47% by weight of water and 2% by weight of monoethanolamine, where a temperature of 151 ° C has been noted. These vapors were mixed with 75% of the water removed at the top of the Drying Column (26) and partially condensed in the heat exchanger (25), which acted as the Column's heater (26). A mixture composed of ammonia, water and monoethanolamine was obtained at 132 ° C. This mixture was conducted to the Insulation Vessel (20) where a liquid phase containing 78% by weight of water, 20% by weight of ammonia and 2% by weight of monoethanolamine and a vapor phase containing 19% was obtained. by weight of water and 81% by weight of ammonia. These two streams returned to the Ammoniacal Water Preparation System as presented in Figure 1. The bottom stream of the Ammonia Insulation Column (21) was cooled in the exchanger (17) to 140 ° C, then in the Heat Changer (36) to 116 ° C, finally being fed to the Drying Column (26). That column, with which low load loss filling was used, was operated with a top pressure of 11.3 kPa. The stop temperature was 48 ° C and the background temperature was 125 ° C. The water removed at the top of the Drying Column (26) was divided into two streams. One of these currents was preheated in the Heat Changer (36) and mixed with the vapors coming from the top of the Column (21), before introducing it into the heat exchanger (25). The other stream was cooled in the heat exchanger (6) and fed to the top of the Ammonia Absorption Column (1). The mixture of amines from the Drying Column (26) was fed to the Second Reaction System (39) formed by a set of two adiabatic reactors (two phases) provided with an intermediate cooler. Ethylene oxide was fed to the first phase so that the outlet temperature was limited to 170 ° C. The reactor effluent was then cooled to 125 ° C, then receiving new ethylene oxide feed, observing that the exit temperature of the second phase also did not exceed 170 ° C. The conversion of ethylene oxide in this Reaction System was practically complete. The composition of the amines removed at the outlet of the second reaction phase was 30% by weight of monoethanolamine, 39% by weight of diethanolamine, about 30% by weight of triethanolamine and about 1% by weight in heavy byproducts . A consumption of water vapor was observed in the proportion of 2.6 kg for each kg of total ethanolamines produced. For the same distribution conditions of the products, the conventional processes have a steam consumption between 4.5 and 5.5 kg per kg of total amines produced, the considerable advantage of energy consumption of the improved process being demonstrated, object of this invention. . Example 2 In this example a unit similar to that described above was used and schematically represented in Figures 1 and 2. A First Reaction System (13), a Monoalkanolamine Concentration Column (42) and a Second Reaction System were used. (39). The Third Reaction System (50) was not used. Specifically in this example, the First Reaction System (13) consisted of six adiabatic tubular reactors (6 phases) provided with a cooler between each phase and the Second Reaction System (39) consisted of two adiabatic reactors (2 phases) with cooling between the first and second phases, installed after the Monoalkanolamine Concentration Column. The epoxide was ethylene oxide, forming ethanolamines in that way. An ammonia water solution was used, fed at 35 ° C, containing 57.8% by weight of water, 41.5% by weight of ammonia and 0.7% by weight of monoethanolamine after receiving the ammonia. spare. The mixture was fed to the First Reaction System (13), making an injection of ethylene oxide before each phase, resulting in a 4.2 molar ratio between the ammonia contained in the entry of (13) and the total ethylene oxide. fed. The effluent of each phase was cooled to 35 ° C before it received the respective injection of ethylene oxide. The pressure in (13) was maintained above 2500 kPa, thus ensuring that the reaction mixture was always in the liquid state. The temperatures observed at the exit of each stage were: 44 ° C at the exit of the first phase, 63 ° C at the exit of the second phase, 66 ° C at the exit of the third phase, 64 ° C at the exit of the fourth phase, 69 ° C at the exit of the fifth phase and 64 ° C at the exit of the sixth phase. The effluent of the last phase had the following approximate composition: 28% by weight of ammonia, 11.2% by weight of monoethanolamine, 9.2% by weight of diethanolamine, and 5.6% by weight of triethanolamine and less than 0.1% ethoxylated ethanolamines. No significant amounts of ethylene oxide were detected. The effluent stream of the sixth reaction phase, with the composition indicated above was fed to the Ammonia Insulation Column (21) without being preheated in the Second Reaction System (39), not shown in Figure 1. The rest from the processing to the Drying Column was done in a manner similar to that described in Example 1. The amines mixture from the Drying Column (26) was fed to a Monoalkanolamine Concentration Column (42), where a stop current concentrated in monoethanolamine was produced. This current was fed, by means of the pipe (43), at a temperature of 63 ° C for the Second Reaction System (39) formed by a set of two adiabatic reactors (two phases) supplied with an intermediate cooler. Ethylene oxide was fed to the first phase so that the ratio between monoethanolamine and ethylene oxide would be 7.5: 1. The reactor effluent was then cooled to 90 ° C, receiving a new feed of ethylene oxide equal to 2/3 of that fed in the first phase. The exit temperature of the second phase was 114 ° C. The conversion of ethylene oxide in this Reaction System was practically complete. The effluent from the second phase of the Second Reaction System returned to the feed of the Monoalkanolamine Concentration Column (42). The bottom product of this column, formed by crude ethanolamines, was sent to the Purification System. The approximate composition of the amines removed at the bottom of the Monoalkanolamine Concentration Column (42) was 8.2% by weight of monoethanolamine, 68.3% by weight of diethanolamine, 22.5% by weight of triethanolamine and 1% by weight in heavy by-products, which corresponded approximately to the distribution of the final products. The model described in this example can be used to reduce the production of monoalkanolamine to virtually zero. A consumption of water vapor was observed in the proportion of approximately 3 kg for each kg of total ethanolamines produced. Example 3 In this example, a unit similar to that described in Example 1 was used, represented schematically in Figures 1 and 2. A First Reaction System (13) and the Third Reaction System (50) were used. The Second Reaction System (39) was not used. Specifically in this example, the First Reaction System (13) consisted of six adiabatic tubular reactors (6 phases) provided with a cooler between each phase and the Third Reaction System (50) consisted of three adiabatic reactors (3 phases) with cooling between each phase. The epoxide was ethylene oxide, forming ethanolamines in that way. The reaction conditions maintained in the First Reaction System (13), as well as the conditions in the Ammonia Insulation Column (21) and in the Drying Column (26) were similar to those described in Example 2. The mixture of amines from the Drying Column (26) was fed to a Monoalkanolamine Purification Column (40), where pure monoethanolamine (final product) was obtained. The bottom stream of the Monoalkanolamine Purification Column (40), together with a portion of the recycled diethanolamine at the top of the Dialkanolamine Purification Column (48), was fed to the Third Reaction System (50). Ethylene oxide was fed to the first phase so that the molar ratio between the diethanolamine and the ethylene oxide would be about 3: 1. The conversion of ethylene oxide to (50), measured in the effluent of the third phase, was practically completed. The effluent from the third phase of (50) was fed to the Column Purification of Dialkanolamine (48). The top product of this column was partly removed as product diethanolamine and the remainder returned for the (50) feed. The bottom product of the colmna (48) was fed to the Trialcanolamin Purification Column (54) where product triethanolamine was removed by the top, by means of the pipe (58) and residue by the bottom, by means of the pipeline (59). The final production of ethanolamines presented the following approximate distribution: 39% of monoethanolamine, 9% of diethanolamine, 50% of triethanolamine and 2% of heavy products. Example 4 In this example a unit similar to that described in Example 1 was used., represented schematically in Figures 1 and 2. A First Reaction System (13) and the Second Reaction System (39) were used. The Third Reaction System (50) and the Monoalkanolamine Concentration Column (42) were not used. Specifically in this example, the First Reaction System (13) consisted of six adiabatic tubular reactors (6 phases) provided with a cooler between each phase and the Second Reaction System (39) consisted of three adiabatic reactors (3 phases) with cooling between each phase. The epoxide was ethylene oxide, forming ethanolamines in that way. the reaction conditions maintained in the First Reaction System (13), as well as the conditions in the Ammonia Isolation Column (21) and in the Drying Column (26) were similar to those described in Example 2. The mixture of amines from the Drying Columa (26), by means of the pipe (38), together with a part of the recycled diethanolamine at the top of the Dialkanolamine Purification Column (48), by means of the pipe (53) ), was fed to the Second Reaction System (39). The ethylene oxide was fed before each phase. The conversion of ethylene oxide to (39), measured in the effluent of the third phase was practically completed. The effluent from (39) was fed to the Alkanolamines Purification System. Monoethanolamine was removed as top product of the Monoalkanolamine Purification Column (40), diethanolamine as top product of the Dialkanolamine Purification Column (48) being part of this recycling for the Second Reaction System (39) and triethanolamine as top product of the Triethanolamine Purification Column (54). The heavy products were removed at the bottom of this last column. The final production of ethanolamines presented the following approximate distribution: 20% of monoethanolamine, 20% of diethanolamine, 58% of triethanolamine and 2% of heavy products.

Claims (13)

1. Process perfected for the production of alkanolamines CHARACTERIZED by the use of at least two Reaction Systems with liquid phase, being that with the First Reaction System an epoxide reacts with a mixture of water and ammonia to form alkanolamines and with a Second and / o Third Reaction System the same epoxide reacts with one or more alkanolamines, with liquid phase, with virtually no ammonia or water to form more alkanolamines, an Ammoniacal Water Preparation System, one or more Ammonia Isolation Columns, one or more Drying Columns of alkanolamines at reduced pressure, optionally one or more Concentration Columns of onoalkanolamine and an alkanolamin purification system consisting of one or more Monoalkanolamine Purification Columns, one or more Dialkanolamine Purification Columns and, optionally , one or more Trialcanolamine Purification Columns, or even according to Figures 1 and 2 ad together

2. Process perfected for the production of alkanolamines according to claim 1 CHARACTERIZED by using a mixture of water and ammonia with the First Reaction Phase with which the ammonia concentration is selected between about 20 and 65% by weight of ammonia.

3. Process perfected for the production of alkanolamines according to claim 1 CHARACTERIZED to be used more ammonium / epoxide molar ratio with the First Reaction Phase between about 4 and 20. Process perfected for the production of alkanolamines according to claim 3 CHARACTERIZED by using molar ammonia / epoxide in the First Reaction Phase preferably between about 5 and 12, chosen so as to increase the production of monoalkanolamine or monoalkanolamine plus dialkanolamine. 5. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact that the epoxide is ethylene oxide and alkanolamines with ethanolamines. 6. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact that the epoxide is propylene oxide and the alkanolamines are the isopropanolamines. 7. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by using multitubular reactors with external cooling or adiabatic tubular with intermediate cooling or a combination of those types of reactors in the First Reaction System. 8. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact of the ammonia recovery system can present one or more sections, one of them being equivalent to an ammonia isolation subsystem operating at high pressure and one of to a subsystem of water and ammonia preparation operating under lower pressure. 9. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact of being possible the use of stirred tank reactors followed by multitubular reactors with external cooling or adiabatic tubular with intermediate cooling or a combination of those types of reactors in the Second and / or in the Third Reaction System. 10. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact of being possible a Second Reaction system fed with the same epoxide used in the First Reaction System and the mixture of dry alkanolamines coming from the bottom of the Column Vacuum drying of alkanolamines. 11. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact of being able to use a Second Reaction System fed with the same epoxide used in the First Reaction System and concentrated monoalkanolamines coming from a Concentration Column of Monoalcanolaminas . 12. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the fact that it is possible to use the Second or Third Reaction System fed with the same epoxide used in the First Reaction System and the mixture of dry alkanolamines from the bottom of the Purification Column to the vacuum of monoalkanolamines. 13. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by obtaining a varied distribution of alkanolamines without the use of recycle of any purified alkanolamine for the First Reaction System. 1 . Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the isolation of mixture of water and ammonia from the effluent of the First Reaction System, using an Ammonia Insulation Column, which mixture will be partially condensed, using the heat of condensation in a useful way, preferably taken advantage of by the own unit production process of alkanolamines. 15. Process further developed for the production of alkanolamines according to claim 14, CHARACTERIZED by the operation of the Ammonia Insulation Column occurring at an absolute pressure chosen between about 700 and 1200 kPa. 16. Process perfected for the production of alkanolamines according to claim 14, CHARACTERIZED by being able to use a compressor to raise the pressure of the ammonia mixture and water withdrawn at the top of the Ammonia Insulation Column up to a chosen discharge pressure between of 800 and 1800 kPa, preferably between about 1000 and 1400 kPa. 17. Process perfected for the production of alkanolamines according to claim 14, CHARACTERIZED by the addition of water to the mixture of water and ammonia before it is condensed, thus increasing its condensation temperature and facilitating the useful recovery of the condensation heat. 18. Process perfected for the production of alkanolamines according to claim 1, CHARACTERIZED by the use of one or more Drying Columns of Alkanolamines operated at an absolute stop pressure chosen between 6 and 25 kPa. 19. Process perfected for the production of alkanolamines according to claims 1 and 16, CHARACTERIZED by the condensation of the mixture of water and ammonia in a changer that is, at the same time, a harvester of the vacuum drying column of alkanolamines. SUMMARY The present invention is an improved process for the production of alkanolamines with which at least two or up to three Reaction Systems with liquid phase are used, being that with the First Reaction System an epoxide reacts with a mixture of water and ammonia to form alkanolamines and in a Second or Third Reaction System the same epoxide reacts with an alkanolamine or a mixture of alkanolamines, in liquid phase, virtually in the absence of ammonia or water to form more alkanolamines, an Ammoniacal Water Preparation System, a Ammonia Insulation Column, a Vacuum Alkanolamine Drying Column, optionally a Monoalkanolamine Concentration Column and an alkanolamin purification system formed by a set of vacuum distillation columns. By means of the improved process object of the present invention it is possible to obtain alkanolamines with a wide range of product distribution without the need to recycle pure amines for the First Reaction System. In addition, the choice of certain operating conditions of this perfected process and the thermal integration between certain sections of the process is done in such a way that it is possible to obtain a considerable reduction of the energy consumption, when compared with the conventional processes producing the same quantities of energy. products. The improved process object of this invention can be applied for the construction of new alkanolamine producing units as well as for the modification of existing units, when it is desired to change the distribution of the obtained products, expand the production capacity or reduce the energy consumption.