MXPA00004057A - Process for the production of n-butanol - Google Patents

Abstract

Disclosed is the use of a Raney cobalt catalyst in the hydrogenation process for the production of n-butanol. A process for the production of purified n-butanol comprising contacting in a hydrogenation zone n-butyraldehyde and hydrogen with an active porous cobalt catalyst under hydrogenation conditions of temperature and pressure for the production of alcohols from aldehydes, either in the substantial absence of water, or in the presence of water in an amount up to about 6 wt.%based on the weight of the liquid hydrogenation reaction product to produce said reaction product comprising n-butanol, and purifying said reaction product by fractional distillation in the presence of about 0.01 to about 6 wt.%of water, based on the total weight of feed to the fractionating column.

Description

PROCEDURE FOR THE PRODUCTION OF N-BUTANOL ANTECENT OF THE INVENTION FIELD OF THE INVENTION The present invention relates to an improved process for the production of n-butanol purified by the hydrogenation of n-butyraldehyde and the fractional distillation of the resulting crude n-butanol.

RELATED TECHNIQUE It is known that n-butanol is produced by the hydrogenation of n-butyraldehyde obtained, for example, by the hydroformylation of propylene by reaction with carbon monoxide and hydrogen. However, in order to be suitable for various applications, for example, as a solvent for fats, waxes and resins, and in the manufacture of rayon, detergents and various butyl compounds, n-butanol must have a high degree of purity including a specified low level of various impurities produced by the hydroformylation and hydrogenation reactions. To solve this problem, the crude n-butanol produced by the hydrogenation reaction must be purified, generally by fractional distillation. One of the impurities intended to be removed by distillation is di-n-butyl ether (DBE) which has an atmospheric boiling point of 142 ° C, but in the absence of water forms a binary azeotrope with n-butanol having an atmospheric boiling point of about 117.6 ° C. The above approximates the boiling point of pure n-butanol at about 117.2 ° C, making it difficult to separate the DBE from n-butanol when there is no water. However, in the presence of water, a ternary azeotrope of water, n-butanol and DBE is formed having a boiling point of about 90.6 ° C which can be exploited in the separation of the DBE from the volume of the n-butanol product . Other impurities produced during the catalytic hydrogenation of n-butyraldehyde to form n-butanol are the so-called "heavy ends", which have a relatively high boiling and tend to break during purification by distillation to form "permaganate time consumers" (PTCs), that is, certain unsaturated and chromophoric compounds such as olefins, aldehydes and ketones, during distillation. PTCs, like other impurities such as DBE, can also have an adverse effect on end-use applications if they are present in the n-butanol product, and similar DBE, their separation of the n-butanol product is facilitated by the presence of water in the distillation column. When any of certain catalysts such as nickel Raney is used for the hydrogenation of n-butyraldehyde to n-butanol, a large amount of water, for example, of about 8-15 percent by weight (% by weight), is added to the aldehyde supplied to reduce the amount of DBE otherwise formed as a side reaction of the hydrogenation of the aldehyde in the absence of said amount of water, and to ensure that the volume of DBE that is formed can be separated from the n-butanol product as the ternary azeotrope described above, and It also facilitates the removal of PTCs that are formed from the heavy ends in the fractionation column. However, the presence of such a large amount of water in the fractionation column results in a substantial expenditure of energy, generally through steam consumption, to vaporize the water present, and may also need a column larger than necessary to carry out purification. In this way, any change in the procedure is desirable, which results in a reduced amount of water needed in the reactor and in the fractionation column and thus a reduction in energy consumption and possibly the size of the column, without any increase in the amount of DBE and PTCs present in the product. The following references of the prior art can be considered as material for the claimed invention. The patent of E.U.A. No. 4, 263,449, issued April 21, 1981 to Saito et al, discloses a process for producing alcohols, for example butanol, by hydroformylating an alkenyl compound, for example propylene, and hydrogenation of the resulting aldehyde in the presence of a catalyst of hydrogenation, for example Raney cobalt. Water is added at a ratio of 0.5 to 30 times by weight based on the aldehyde produced by the hydroformylation prior to hydrogenation. The patent of E.U.A. No. 4,826,799, issued May 2, 1989 to Cheng et al. Teaches a catalyst manufacturing process by the Raney process including the pelletizing steps of a Raney process metal alloy, e.g., cobalt and aluminum, in a polymer matrix and plasticizers, followed by the removal of the plasticizer and polymer, and the leaching of aluminum with caustic.

The catalyst can be used to hydrogenate an aldehyde for the corresponding alkanol, for example butanol.

BRIEF DESCRIPTION OF THE INVENTION According to this invention, the purified n-butanol is produced by a process comprising the contact in a hydrogenation zone of n-butyraldehyde and hydrogen with an active porous cobalt catalyst under hydrogenation conditions of temperature and pressure for the production of alcohols from aldehydes, either in the substantial absence of water, or in the presence of water in an amount of up to about 6% by weight based on the weight of hydrogenation reaction product of resulting crude n-butanol, and purification of the reaction product by fractional distillation in the presence of about 0.01 to about 6% by weight of water, based on the total weight of the fraction fractionation feed.

The use of an active porous cobalt catalyst in the hydrogenation process surprisingly results in the production of significantly smaller amounts of most impurities, including DBE and heavy ends, than when using a catalyst such as Raney nickel, The above allows the use of a substantially lower amount of water in the fractionation column in which the n-butanol product is purified from the hydrogenation process, although less water is required for the formation of the ternary azeotrope necessary to separate the DBE from the n-butanol, and the removal of PTCs. The above in turn reduces the energy, for example in the form of vapor, necessary to vaporize the water in the column, and also allows the use of a smaller column, or larger production of n-butanol with an existing column.

DETAILED DESCRIPTION OF THE INVENTION The n-butylaldehyde supplied from the process of this invention can be obtained from any source, for example, by catalyzed hydroformylation of the noble metal-phosphine propylene ligand. If the supply is obtained from this last procedure, it is not usually necessary to subject it to an extensive purification before using it in the hydrogenation, although said supply is generally treated to remove the phosphine ligand.

Active porous cobalt catalysts suitable for use in the hydrogenation reaction of this invention are prepared by treating a cobalt alloy and at least one other metal, for example, aluminum with a chemical agent, for example sodium hydroxide, to extract the other metal from the alloy and obtain the cobalt in a highly porous form. Such active cobalt catalysts are known in the art as "Raney cobalt" catalysts. The above can be obtained commercially, for example, from W.R. Grace & Co. and are typically listed under the trade name "Raney". These can be unsupported or supported, for example in a porous carrier such as alumina or silica, with the metal portion containing, for example, at least about 80% by weight cobalt, and any remaining metal being, for example, aluminum , iron, nickel and / or chromium, with chromium, if present, possibly acting as a promoter for cobalt. For purposes of illustration only, the unsupported catalysts may have an average particle size of, for example, from about 15 to about 60 microns, and a specific gravity of, for example, from about 6.5 to about 7.5, and a volume density of, for example, about 6.36 to 8.172 kg / 3.78 liters based on the weight of a catalyst mixture of 56% solids in water. The hydrogenation is generally carried out under hydrogenation conditions for the production of alcohols from aldehyde, for example, at a temperature of from about 100 to about 160 ° C, at a hydrogen pressure of about 7.03 to about 49.21 kg / cm2, and a catalyst load of from about 2 to about 20% by weight, preferably from about 8 to about 10% by weight, based on the weight of the liquid supply. In addition, the liquid supply, for example, must substantially not contain water, or must contain an amount of water, for example up to about 6% by weight, preferably from 2 to about 6% by weight, and more preferably from about 0.1 to about 3% by weight, based on the weight of the crude hydrogenation reaction product. "Substantially without water" refers to the fact that no water is added to the reactor, and the reaction liquid contains only the water that is produced during the formation of butyraldehyde. The hydrogenation reaction can be carried out continuously, semicontinuously or by batch, preferably with some backmixing during the reaction, for example a continuous mixing bed system operating between the sealing flow and the backmixing. A rotating mixing element is not necessary, but if used, it can operate at a rotational speed, for example, from about 1000 to 2000 rpm. The residence time of the remaining hydrogenation in the reaction zone can be on the scale, for example, of about 10 to 120 minutes. In several cases, the hydrogenation reaction product will contain no more than about 100 ppm of di-n-butyl ether (DBE) significantly lower than the amount usually obtained when the hydrogenation is carried out with a Raney nickel catalyst, other conditions being equal.

As stated above, the purification in crude n-butanol from the hydrogenation zone is carried out by fractional distillation in the presence of about 0.01 to about 6% by weight of water, preferably about 0.1 to about 3% by weight, based on the weight of supply to the fractionation column. Although a quantity of water within this scale may not be present in the hydrogenation effluent, water may be added to said effluent before it is supplied to the fractionator, if it is necessary to place the water level in the fractionation column to the concentration desired. In this connection, it should be noted that water can act as a cooling agent within the column as it is necessary to form the necessary azeotrope for efficient separation of DBE, and act as an agent for the removal of heavy ends. To achieve a cooling effect, most of the water is circulated inside the column by internal reflux where the water vapor condenses to the surface of the column and back-flushes where it absorbs heat and revaporizes to start new the cycle, or external reflux where the liquid streams containing water for example, the ternary azeotrope the heavy ends containing water previously described, are removed from the column, most of the water in the stream is separated from the organic , for example, by decanting, and the liquid water is returned to a point in the upper portion of the column. The preferred distillation is carried out at atmospheric pressure, although it is possible to operate at subatmospheric or superatmospheric pressures, if desired under certain circumstances. In general, the number of trays in the column and the amount of heat transferred to the material being purified in the column are sufficient to produce a liquid stream of purified n-butanol containing at least about 99.5% by weight of n-butanol. butanol. Typically, a liquid or vapor stream comprises n-butyraldehyde having an atmospheric boiling point of 75.7 ° C and, the source of n-butyraldehyde is the hydroformylation of propylene, about 9-10% by weight of iso-butyraldehyde having an atmospheric boiling point of about 64 ° C, based on the total weight of the aldehyde, is removed at or near the top of the column; ternary azeotrope condensed water, n-butanol and DBE containing essentially the total DBE impurity in the hydrogenation effluent and having an atmospheric boiling point of about 90.6 ° C is removed in the upper portion of the column at a point below that of n-butyraldehyde; and the purified n-butanol having an atmospheric boiling point of about 117 ° C is removed at a point below the removal of the condensed ternary azeotrope. The remaining significant impurities, which boil substantially higher than n-butanol, are removed as single compounds or mixtures at points below the purified n-butanol. Although the amounts of DBE impurity and most of the heavy ends in the hydrogenation effluents are substantially lower when an active porous cobalt catalyst is employed instead of a catalyst such as Raney nickel, all other conditions remain the same, the amount of water that must be present in the column to form a ternary azeotrope that contains substantially all of the DEB impurity and to remove the PTCs produced by the heavy ends is significantly reduced, resulting in a lower energy cost to evaporate said water, and possibly a higher production of n-butanol and / or a requirement for a smaller column. The following non-limiting examples further illustrate the invention.

EXAMPLE 1 In Example 1, a stream of crude n-butyraldehyde obtained in the catalyzed hydroformylation of the noble metal-propylene phosphine ligand containing about 9-10% by weight of iso-butyraldehyde based on the total weight of pure aldehydes is used. in the hydrogen current using an unsupported active porous cobalt catalyst sold by the Grace Davison Division of WR Grace &; Co., as "Raney Cobalt 2700" with a composition of at least 93.0% by weight of cobalt and not more than 6.0% by weight of aluminum, 0.7% by weight of iron and 0.8% by weight of nickel, a size of average particle on the scale of 20 to 50 microns, and specific gravity of about 7 and a volume density of 6.81-7.718 kg / 3.78 liters based on the weight of the catalyst mixture of 56% solids in water. Prior to hydrogenation, the crude n-butyraldehyde was not treated except for the removal of the phosphine ligand used for the hydroformylation. The hydrogenation is carried out continuously in a fully stirred back-mixing reactor at a temperature of 135-138 ° C, a hydrogen pressure of 28.12 kg / cm2 and a stirring speed of 1750 rpm. The catalyst loading is about 8-10% by weight based on the weight of the liquid reaction mixture in the reactor, the water content of the liquid hydrogenation effluent is controlled 2. 80 and 3.60% by weight based on the weight of the hydrogenation reaction product of crude n-butanol by the addition of water to the hydrogenation, and the flows to and from the reactor are controlled to provide a residence time in the reactor. around 40 minutes. The stain samples of the hydrogenation reaction product are removed after the times of the total process in the stream of about 2 to 15 hours intervals between the removal of the samples of about 1.2 to 3 hours, and are analyzed for the percent by weight of water (H2O) by the Karl-Fischer trituration and for the parts per million of the following impurities by gas chromatography: n-butyraldehyde (n-BuH); di-n-butyl ether (DBE); butylbutyrate (BBt); butylbutyral (BB1); butyric acids (BA); and the following heavy ends: Texanol (Tex), which is composed of trimers, esters of iso-butyraldehyde; 2-ethyl-4-methylpentanediol (EMP); 2-ethylhexanol (EH); 2-ethyl-1,3-hexanediol (EHD); trimer of C.2 (T C-12), which is composed of trimers of esters of i- and n-butyraldehyde; and 2,2,4-trimethylpentanediol (TMP). It is also assumed that about 9-10% by weight of n-butyraldehyde based on the total weight of ne i-butyraldehyde and about 9-10% by weight of i- is present in the crude hydrogenation reaction product. butanol based on the total weight of n- and i-butanol.

COMPARATIVE EXAMPLE A In Comparative Example A the procedure of Example 1 is generally followed, except that the Raney nickel hydrogenation catalyst sold by the Grace Davison Division of W.R. Grace & Co., as "Raney 3300 Nickel", that is to say a porous nickel promoted from unsupported molybdenum in which the metal component comprises from about 90.0-99.1% by weight of nickel, from about 0.5-1.5% by weight of molybdenum, no more than about 8.0% by weight of aluminum, and no more than about 0.8% by weight of iron, and having the average particle size of about 25 to about 65 microns, a specific gravity of about of 7, and a volume density of about 6.81-7.718 kg / 3.78 liters, based on the weight of the catalyst mixture of 56% solids in water; the water content is controlled between 3. 50 and 4.40% by weight based on the weight of the hydrogenation reaction product of crude n-butanol; and the stain samples of the hydrogenation reaction product are removed and analyzed after the total process times between about 1.8 and 15 hours with intervals between sample withdrawals of about 0.5 to 3.2 hours. The results of the analysis of impurities as the experiment progresses are shown in table 1. The table also includes the rate of supply to the hydrogenation reactor (supply speed = total supply rate of the aldehyde), the speed of the product (Prod. Speed), ie the effluent velocity from the reactor, and the residence time (Res. Time) of the reactants in the reactor, measured or calculated for the interval between the samples.

TABLE 1 Comparative examples of Ranev Co-catalyzed hydrogenation versus Ranev Ni of crude butyraldehyde at 3-4% by weight addition of water.

* In time is from the start of the procedure As shown in the values in Table 1, the procedure of Example I of the invention, the use of an active porous cobalt hydrogenation catalyst (Raney cobalt), produced a reaction product of crude hydrogenation containing much less di-n-butyl ether (DBE) and, particularly as the total reaction time of about 15 hours, a much smaller amount of heavy ends than the procedure of Comparative Example A employing a hydrogenation catalyst by conventional Raney nickel. In view of the foregoing, the hydrogenation product of example 1, when purified in a fractionating column, requires a relatively small amount of water, ie, no more than about 6% by weight based on the weight of supply for the column to form a ternary azeotrope amount of water, n-butanol and sufficient DBE to remove substantially all the DBE in the hydrogenation reaction product, and also enough to remove the PTCs. In contrast, the hydrogenation product of Comparative Example A, in view of its much higher content of DBE and heavy ends, requires a significantly greater amount of water in the fractionating column, ie, above about 8% by weight , to remove substantially all of the DBE, and PTCs produced in the column. Alternatively, the amount of DBE and heavy ends produced in the hydrogenation reaction when a conventional Raney nickel catalyst is employed, as shown in the results of Comparative Example A, can be reduced by the addition of a larger amount of water, for example, at least about 8% by weight, to the liquid hydrogenation reaction mixture. However, the amounts of such impurities produced when larger amounts of water are used are still generally greater than when an active porous cobalt hydrogenation catalyst with a substantially lower amount of water in the hydrogenation reactor is employed. In addition, much of any water added to the hydrogenation catalyzed by Raney nickel to reduce impurity formation is finally transferred to the fractionation column when the hydrogenation product of crude n-butanol is purified. In this way, a larger amount of water is inevitably present in the fractionation column when the Raney nickel is used than when the active porous cobalt catalyst (Raney cobalt) is used. The use of this latter catalyst of the invention results therefore in a lower energy cost and higher production of n-butanol and / or the need for a smaller column. The above is due to the requirement of less water in the column to achieve the desired degree of purification than when a conventional Raney nickel hydrogenation catalyst is employed.

EXAMPLE 2 The procedure of Example I is followed except that no additional water is added to the hydrogenation reaction, which effluent therefore contains only water, if any, present in the propylene hydroformylation effluent and / or formed in the hydrogenation reaction; and the procedure is continued for more than 200 hours. Table 2 shows the results of the analyzes of the samples withdrawn at intervals of approximately 20 hours as well as the rate of supply of hydrogenation, product speed and residence time in time of each sample withdrawal.

TABLE 2 The time is from the beginning of the procedure The comparison of the results of examples 1 and 2 as shown in tables 1 and 2 indicate that when no additional water is added to the hydrogenation reaction, as in example 2, even smaller amounts of DBE and such heavy ends as Texanol, 2-ethyl-4-methylpentanediol, 2-ethylhexanol and trimer of C.2, are formed when the additional water is added to the hydrogenation reaction as in example 1; in this way, when no additional water is added to the hydrogenation reactor, even less water is required in the fractionating column to remove the DBE by forming the ternary azeotrope as described above, and the PTCs produced from the heavy ends present in the column. Therefore, even greater savings can be achieved due to a lower energy requirement for the vaporization of the water in the column.

Claims (12)

NOVELTY OF THE INVENTION CLAIMS

1. - A process for the production of purified n-butanol comprising the contact in a hydrogenation zone of n-butyraldehyde and hydrogen with an active porous cobalt catalyst under conditions of temperature and pressure hydrogenation for the production of alcohols from aldehydes either in the substantial absence of water, with the presence of water in an amount of up to about 6% by weight based on the weight of the liquid hydrogenation reaction product to produce said reaction product comprising n-butanol, and purification of said reaction product by fractional distillation in the presence of about 0.01 to about 6% by weight of water, based on the total weight of supply to the fractionation column.

2. The process according to claim 1, further characterized in that said hydrogenation reaction product does not comprise more than about 100 ppm of di-n-butyl ether.

3. The process according to claim 1, further characterized in that said n-buteraldehyde is obtained from the hydroformylation of propylene.

4. The process according to claim 1, further characterized in that the metallic portion of said active porous cobalt catalyst contains at least about 80% by weight of cobalt.

5. The process according to claim 4, further characterized in that said catalyst is prepared by treating a cobalt alloy and at least one other metal with a chemical agent to extract the other metal from the alloy and obtain the cobalt in a highly porous form.

6. The process according to claim 5, further characterized in that said other metal is aluminum and said treatment agent is sodium hydroxide.

7. The process according to claim 5, further characterized in that said catalyst is not supported and has a particle size of about 15 to about 60 microns, a specific gravity of about 6.5 to about 7.5, and a volume density of about 6,356 to 8,172 kg / 3.78 liters based on a weight of catalyst mixture of about 56% solids in water.

8. The process according to claim 1, further characterized in that said hydrogenation is carried out continuously with at least some backmixing at a temperature of about 100 to about 160 ° C, a hydrogen pressure of about 7.03 at about 49.21 kg / cm2, and a catalyst load of about 2 to about 20% by weight, based on the weight of the liquid supply.

9. - The process according to claim 1, further characterized in that said fractional distillation is carried out in such a way that a ternary azeotrope of water, n-butanol and di-n-butyl ether (DBE) which contain substantially all of the DBE in the hydrogenation effluent is removed in the upper portion of the column, the purified n-butanol is removed at a point below said azeotrope, and the upper boiling impurities are removed in points below the removal of said purified n-butanol.

10. The process according to claim 9, further characterized in that said purified n-butanol contains at least about 99.5% by weight of pure n-butanol.

11. A process for the production of purified n-butanol comprising the contact in a hydrogenation zone of n-buteraldehyde and hydrogen with an active porous cobalt catalyst under conditions of temperature and pressure hydrogenation for the production of alcohols from of aldehydes in the substantial absence of water to produce n-butanol, and the purification of said n-butanol by fractional distillation in the presence of about 0.01 to about 6% by weight of water, based on the weight total supply in the fractionation column.

12. A process for the production of purified n-butanol comprising the contact in a hydrogenation zone of n-buteraldehyde and hydrogen with an active porous cobalt catalyst under the conditions of temperature and pressure hydrogenation for the production of alcohols a from aldehydes in the presence of water in an amount of up to about 6% by weight based on the weight of the liquid hydrogenation reaction product to produce n-butanol, and the purification of said n-butanol by fractional distillation in the presence of about 0.01 to about 6% by weight of water, based on the total weight of the supply to the fractionation column.