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1
REMOVAL OF IMPURITIES FORMED DURING THE PRODUCTION OF 1, 3-PROPANODIOL
FIELD OF THE INVENTION The present invention relates to a process for the production of 1, 3-propanediol (PDO) wherein an aqueous solution of 3 -hidroxipropanal (HPA) is formed, and neutralized HPA is hydrogenated to produce a mixture of PDO that is distilled to produce purified PDO. BACKGROUND OF THE INVENTION Numerous companies have developed technologies for the preparation of PDO starting with ethylene oxide as the main raw material. The ethylene oxide is reacted with a synthesis gas (syngas), a mixture of carbon monoxide and hydrogen, which can be obtained by steam reforming the natural gas or by partial oxidation of hydrocarbons. The idealized reaction of ethylene oxide (EO) with syngas to give PDO is shown below: OE + CO + 2H2? PDO US Patents 4,873,378, 4,873,379, and 5,053,562 to Hoechst Celanese describe a reaction in one step using 2: 1 (molar) syngas at 110 to 120 ° C and about 6900 kPa (1000 psig) to give 65 to 78 percent molar PDO performance and its precursors. He
Ref.s 163652 2
The catalyst system used consists of rhodium, various phosphines, and various acids and water as promoters. U.S. Patent Nos. 5,030,766 and 5,210,318 to Union Carbide describe the reaction of OE with syngas in the presence of rhodium-containing catalysts. A 110 ° C and 6900 kPa (1000 psig) of syngas 2: 1 molar selectivity was achieved up to 47 mole percent but the rate of combined formation of PDO and 3-hydroxy propanal was quite low at 0.05 to .07 moles liter per hour. Better results were achieved by increasing the ratio of the phosphoric acid promoter to the rhodium catalyst. US Patents 5,256,827, 5,304,686, and 5,304,691 from Shell Oil described the production of PDO from OE and syngas using cobalt carbonyl catalysts in tertiary phosphine complexes. The reaction conditions of 90 to 105 ° C and from 9650 to 10.340 kPa (1400-1500 psig) of syngas (1: 1 molar ratio) for selectivities produced in three hours in the range of 85 to 90 mole percent and the conversion OE was found in the range of 21 to 34%. Later work reported a higher selectivity and OE conversion. US Patent 5,527,973 discloses a method for the purification of PDO containing carbonyl by-products including acetals. An aqueous solution of carbonyl-containing PDO is formed with a pH less than 7 and then a sufficient amount of base is added to this solution to increase the pH to values above 7. The solution is then heated to distill most of the water of the same and then the remaining basic solution is heated to distill most of the PDO from the basic solution obtaining a PDO composition with a lower carbonyl content than the initial composition. This process has several stages and it would be a commercial advantage to provide a method that decreases the carbonyl content in less reaction stages. Acetate MW132 of PDO is formed as an undesired by-product in the hydroformylation and hydrogenation reactions. It is difficult to separate the MW 132 from the PDO by simple distillation because it has a volatility similar to that of the PDO. Its formation decreases the overall recovery of PDO as well as its purity. Thus, it would be very advantageous to have a process in which acetal W132 will react chemically with other materials that are more easily separated from the PDO. The present invention presents this chemical method. Summary of the Invention In one embodiment, the present invention is an improvement of the process for the production of 1,3-propanediol (PDO) in which an aqueous solution of 3-hydroxypropanal (HPA) is formed, and the HPA is subjected to hydrogenation to produce a crude PDO mixture comprising PDO, water, acetal MW176 4
(so-called because it is an acetal and has a molecular weight of about 176), and high and low volatility materials, in which the raw PDO mixture is dried, generally by distillation, to produce a first top stream that includes water and some high volatility materials, such as ethanol and / or process solvents, and a crude mixture of dry PDO as a first stream of distillation bottoms including PDO, acetal MW176, and low volatility materials, and in the that the crude mixture of dry PDO is distilled to produce a second top stream that includes some high volatility materials, an intermediate stream that includes PDO and acetal MW176, and a second stream of distillation bottoms that includes PDO and low volatility materials. Most of the recoverable PDO is in the intermediate stream that constitutes up to 99.9% by weight of PDO. The second stream of distillation bottoms may contain up to 50% by weight of PDO but this PDO is difficult to separate from low volatility materials. Trace concentrations of acetal MW176 may be present in the bottom stream. In this embodiment, the improvement includes contacting: 1) the crude PDO mixture before drying and / or 2) the dry crude PDO mixture before the distillation and / or 3) the intermediate stream (with this third embodiment, another distillation would be required to remove the reaction products of the more volatile MW176 acetal of the PDO) with an acidic zeolite (eg mordenite clay) at 40 to 150 ° C to convert the cyclic acetal MW176 to alternative chemical species that can be more easily separated from the PDO by distillation, in a process in which the production of other heat generating impurities and PDO oligomers is minimized. In another embodiment of this invention, 1) and / or 2) and / or 3) are contacted with a cation exchange resin of acid form, typically of the sulphonic acid type, at temperatures between ambient and 150 ° C. In another aspect, soluble acids, such as H2SO4, are used to treat the streams, preferably in a corrosion resistant column, at a temperature of 20 to 100 ° C. The contact of the crude PDO mixture with the solid acid purifier is carried out as a continuous process, or batch process, using standard methods and practices for the contact of a liquid stream with a catalyst or a solid adsorbent. In this way, the impurities that present difficulties in their separation, such as the acetal MW176, are largely eliminated, so that the PDO can be distilled until obtaining it in high degrees of purity with high recovery efficiency. In another embodiment, this invention provides a 6
process for the production of 1,3-propanediol which includes the steps of: a) forming an aqueous solution of 3-hydroxypropanal, b) hydrogenating the 3-hydroxypropanal to form a first crude mixture of 1,3-propanediol including 1, 3-propanediol, water, and cyclic acetal M 132, c) distill the first crude mixture of 1,3-propanediol to remove water and low boiling impurities and form a second crude mixture of 1,3-propanediol, d) put in contact the second mixture of crude 1,3-propanediol with a cation exchange resin of acid form at a temperature of 50 to 150 ° C to convert the cyclic acetal MW132 to more volatile cyclic acetals and / or other degradation products, and e) separating the more volatile cyclic acetals and / or other degradation products of 1,3-propanediol by distillation or gas extraction. In the most preferred mode of this embodiment, steps d) and e) are carried out together (in the same vessel or column) in such a way that the volatile cyclic acetals and / or other degradation products are separated from the 1, 3 - propane diol as they are formed. In another variant of this embodiment, an acidic zeolite can be used in place of the cationic acid exchange resin. In this case, the temperature is preferably 80 to 200 ° C.
7
BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a very simple schematic diagram representing an example of a simplified distillation scheme. DETAILED DESCRIPTION OF THE INVENTION The aqueous solution of 3-hydroxypropanal (HPA) which is the starting material of the present invention, can be produced by a number of different processes. US patent 4,873,378 aforementioned, 4,873,379, 5,053,562, 5,030,766, 5,210,318, 5,256,827, 5,304,686, and 5,304,691, which are incorporated herein by reference, describe different methods for producing aqueous solutions of HPA. HPA can also be produced by hydration of acrolein in the presence of acid catalysts. Processes to achieve these results are described in U.S. Patents 5,426,249, 5,015,789, 5,171,898, 5,276,201, 5,334,778, and 5,364,987, which are incorporated herein by reference. A preferred method for carrying out the entire process of the present invention is described in U.S. Patent No. 5,786,524, which is incorporated herein by reference, and is generally as follows. The ethylene oxide (EO) is hydroformylated in a reactor such as a bubbling column or a stirred tank at 1380 to 34,500 8
kPa (200 to 5000 psi) of syngas with a radius of hydrogen and carbon monoxide from 1: 5 to 25: 1 at 50 to 110 ° C in the presence of a hydroformylation catalyst at a concentration of 0.05 to 15 weight percent , more preferably from 0.05 to 1 percent. The effluent from the hydroformylation reaction is preferably extracted with a small amount of water at water-solvent ratios in the range of 2: 1 to 1:20 at 5 to 55 ° C in an atmosphere greater than 350 kPa (50 psi) of carbon monoxide. The solvent layer containing more than 90% of the catalyst in active form is recycled to the hydroformylation reactor. The HPA is extracted in the water layer at a concentration of 10 to 45% by weight. The catalyst can be removed from this aqueous HPA solution by any known means including first an oxidation of the catalyst and then its removal using an acidic ion exchange resin. The ion exchange resin can be a weak or strong acid ion exchange resin. Examples include: AMBERLYST resins 15, 35, and XN-1010, AMBERLITE IR-118, IRC76, A1200, DOWEX 50 x 2-100 and 5 x 8-100, XL-383 and -386, plus BIO RAD AG50W-X2 and AMBERSEP 252H, or other strong (sulfonic) acid or weak (carboxylic) acid resins (AMBERLYST, AMBERLITE, DOWEX, BIO RAD and AMBERSEP are trademarks).
9
After neutralization of the aqueous solution of 3-hydroxypropanal, the aqueous solution is hydrogenated. This can be carried out by hydrogenation over a fixed bed of hydrogenation catalyst generally at 690 to 13,800 kPa (100 to 2000 psi) of hydrogen. The hydrogenation catalyst may be any of those described in U.S. Pat. 5,786,524, which is included herein by way of reference, including catalysts of a Group VIII metal such as nickel, cobalt, ruthenium, platinum, or palladium. The initial hydrogenation is preferably carried out at 40 to 80 ° C and the temperature is preferably increased from 120 to 175 ° C to promote the reaction of reactive components such as cyclic acetals to revert to PDO. Finally, the water and light solvents (low-boiling) and impurities (low boiling) entrained high volatility (higher current) distilling the PDO crude and components less volatile separated during distillation as the bottoms stream distillation . Acetal MW132 To carry out the second embodiment of this invention, the dry crude product stream (from the distillation), with M 132 acetal and PDO, is treated as described below to recover PDO at high yield levels and with a high degree of purity. The crude PDO as described above may present high levels of
impurity levels of cyclic MW132 acetal. This impurity is undesirable and limits the recovery efficiency of the PDO during the subsequent distillation. It can be formed by reaction of the PDO with HPA. Reaction Scheme No. 1
PDO HPA Acetal MW 132
It is known that the cyclic acetal 2-ethylene-1,3-dio: < Anus (EDCA) formed by decomposition of acetal M 132 catalyzed by acid is much more volatile than PDO. The following formula explains the dehydration of acetal M 132 to form the cyclic acetal 2-ethylene-1,3-dioxane (EDCA) which can be rapidly separated from the PDO by distillation. Acidic zeolites and acidic cation exchange resins (such as those used for the removal of cobalt) can be used to purify PDO via the reaction of acetal MW132 to form EDCA: Reaction Scheme
Acetal 132 EDCA 11
Therefore, the dry crude PDO stream with unwanted cyclic acetal MW132 is contacted with an acidic cation exchange resin or with an acid zeolite under conditions that favor the reaction scheme shown above for the conversion of acetal MW132 to EDCA . This step is combined with the removal of EDCA via concerted distillation or via the use of an extraction gas such as nitrogen or steam. Distillation and concerted reaction, in which the distillation and reaction are combined in the same processing unit to separate the reactants from the products as they are formed, can employ any of the well-known methods for carrying out a "distillation" reactive. " Alternatively, an inert gas such as nitrogen can be used to extract the reaction mixtures (extraction and concerted reaction) of the most volatile degradation product of the acetal MW132 (EDCA), and thus avoid the reformation of MW132 by chemical equilibrium. The use of steam (steam) is a common commercial practice to provide process heat and an inert gas extraction. In this case, again the elimination is carried out in the same processing unit as the acetal reaction MW132. The reaction products are removed as they were formed to direct the chemical equilibrium towards the elimination or reduction of the presence of MW132 acetal. Of 12
thus, the acid-catalyzed reaction combination plus the extraction in the same processing step leads to the separation of reactant and product in the same way as "reactive distillation" combination of acid-catalysed reaction and distillation. In general, it was found that water suppresses the reversal and removal of acetal MW132. However, small amounts of water are usually present due to incomplete removal, adsorption on the solid catalyst, or due to the dehydration reaction itself (reaction scheme No. 1 above) and may allow it to be carried out. the removal of a portion of MW132 via the reversion of reaction No. 1. If HPA is formed in this way, it can be further dehydrated to high volatility acrolein, which is quickly extracted or distilled from the reaction mixture. Regardless of which mechanism, the acid catalyzed reaction with separation (distillation or extraction) of volatile reaction products results in a reduction of the impurity of MW132 of the PDO product. Concerted distillation or extraction of inert gases is required to displace the chemical equilibrium of the thermodynamically favored cyclic acetal MW132. An acid-form zeolite can be used during the process described above to catalyze the degradation of M 132 acetal.
13
The use of the cation exchange resin in acid form with the concerted separation results in virtually complete conversion of the M 132 acetal. The reaction is preferably carried out at a temperature of about 50 to 150 ° C, more preferably 80 to 120 °. C. The contact with the resin catalyst is carried out either batchwise, or in a continuous column, using well-known reactor design methods to ensure virtually complete conversion of M 132 acetal. Batch contact of 80 to 120 ° C can be carried out from 1 to 5 hours with 10% acidic resin. percent by weight, for example, to effect the complete conversion. Alternatively, the contact can be made in a continuous reaction vessel, preferably a column, with a space velocity per hour by weight "(weight of impure feed of PDO pox" weight of acid resin per hour - "WHSV") of 0.1 to 1 per hour. With zeolites, the activity for the reversal of acetal is lower, so that higher temperatures or longer contact time with the zeolite are required. The reaction with acid zeolite is preferably carried out at a temperature of 70 to 250 ° C, more preferably 90 to 170 ° C, by batch or continuous contact. Similar contact times or space speeds per hour in weight could be used. For any of the systems, the 14
combination of temperature and contact time with the solid acid purifier (cation exchange resin of acid form or acid zeolite) should be optimized to limit the production of undesirable impurities imparting color and to minimize the production of dimer and oligomers greater than the PDO. Preferred catalysts are ion exchange resins with strongly acid cation exchange (cation exchange resins of acid form). These include gel-type or macroreticular (macroporous) ion exchange resins with sulfonic acid functional groups in which the sulfonic acid function is attached directly or indirectly to an organic polymer backbone. Examples include AMBERLITE or AMBERLYST resins A200, A252, IR-118, IR120, A15, A35, XN-1010, or particle size unifoxme A1200 Rohm and Haas; resins of MSC-1, M-31, or of the DOWEX 50 series of Dow, SYBRON C-249 resins, 'C-267, CFP-110; PUROLITE C-100 or C-150 resins; RESINTECH CG8; IWT C-211, SACMP; IWT C-381; or other commercially comparable strong acid cation exchange resins. Another example of cation exchange resins is the acidified perfluorinated polymer of NAFION sulfonic acid (SYBRO, PUROLITE, RESINTECH and NAFION are trademarks). Suitable zeolite catalysts contain one
or more zeolites modified preferably in the acid form. These zeolites should contain pore dimensions large enough to allow the entry of the acyclic or aliphatic compounds. Preferred zeolites include, for example, zeolites of the structural types MFI (e.g., ZSM-5), MEL (e.g., ZSM-11), FER (e.g., ferrierite and ZSM-35), FAU (e.g. zeolite Y), BEA (for example, beta), MFS (for example, ZSM-57), NES (for example, NU-87), MOR (for example, mordenite), CHA (for example, chabasite), MTT (for example, morphite). for example, ZSM-23), WW (for example, CM-22 and SSZ-25), EUO (for example, EU-1, ZSM-50, and TPZ-3), OFF (for example, offretite), MTW (eg, ZSM-12) and zeolites ITQ-1, ITQ-2, MCM-56, MCM-49, ZSM-48, SSZ-35, SSZ-39 and zeolites of the crystalline phase mixtures, such as, for example, zeolite PSH- 3. Structural types and references in regard to the synthesis of various zeolites can be found in the "Atlas of Zeolite Structure Types" (published on behalf of the Structures Commission of the International Zeolite Association), by WM Meier, D.H. Olson and Ch. Baerlocher, published by Butterworth-Heinemann, fourth revised edition, 1996. The structural types and references to the zeolites mentioned above are available online at www.iza-structure.org. These zeolites are available 16
commercially from Zeolyst International Inc., and ExxonMobil Corporation. Additional examples of suitable zeolite catalysts can be found in U.S. Patent Nos. 5,762,777; 5,808,167; 5,110,995; 5,874,646; 4,826,667; 4,439,409; 4,954,325; 5,236,575; 5,362,697; 5,827,491; 5,958,370; 4,016,245; 4,251,499; 4,795,623; 4,942,027 and WO99 / 35087 which are incorporated herein by reference. Acetal MW176 As shown by the exemplified simplified distillation scheme of Figure 1, which is useful in the description of the first embodiment of the invention, the aqueous PDO containing acetal MW176 flows into the drying distillation column 2. remove water and some high volatility materials in the upper stream 3 and the dry PDO with acetal MW176 from the distillation bottom stream flows into the distillation column 5. More high volatility materials are separated and exit through the upper stream 6 and distillation bottom stream 8 contains low volatility materials and some PDO as well as trace quantities of acetal MW176. The recoverable PDO comes out in the intermediate stream. Containers 1, 4, and 7 are optional acid treatment vessels (although at least one is required in the system shown in the figure). The treatment with acid catalyst can 17
It can be carried out before drying in the container 1 or it can be carried out after drying in the container 4 but before the distillation or it can take place after the distillation in the container 7. When the last mode is carried out, a additional distillation to separate the more volatile W176 acetal reaction products from the PDO. The crude PDO described above sometimes presents high levels of cyclic acetal impurities MW176. It was found that this impurity is marginally less volatile than the PDO, which limits the recovery efficiencies of PDO. Due to the difficulty in the separation of the PDO, a batch distillation was carried out in the laboratory to evaluate the relative volatilities of MW176 and PDO. Approximately 85 grams of PDO contaminated with this impurity and also C5 diol were refluxed at a nominal pressure of 1.3 kPa (10 m Hg) and 143 ° C bottom temperature. The ethylene glycol (EG) and butanediol markers were added in approximately 1% by weight to aid in the assignment of relative volatilities. The results (Table 1) show that the acetal MW176 and C5 diol are heavier than the PDO. A good correlation was obtained between the measured relative volatility vs. the reported EG vs. PDO indicating that the balance was actually reached for these measurements.
18
Table 1: Relative Volatility BATCH DISTILLATION DATOD: Species Distillation Ratio Domes Funds Distillation% volatility: Weight% by weight t / b2
PDO 97.88 98.09 1.00
Ethylene glycol 0.369 0.824 2.233 C5 diol 0.326 0.280 0.859
Acetal MW176 0.055 0.047 0.855 Butanediol 1.375 0.762 0.554
1 Reported relative volatility EG / PDO at 230 ° F (110 ° C) 2.16 2 t = distillation "domes" or "superior product" b = distillation "bottoms"
Acetal MW102 formed by acid-catalyzed decomposition of acetal MW176 is known to be much more volatile than PDO and therefore can be easily separated from PDO with high efficiency. This result was expected based on the absence of hydroxyl groups in MW102 due to condensation removal. Although it is not desired to be limited by a specific mechanism, the following reaction scheme may explain the degradation of the W176 acetal and the formation of the W176 acetal.
acetal MW102 (which can be easily separated from? D0 by distillation) and also the formation of acetal W132 as observed in the experiments. Reaction Scheme 3:
Aldehido mU Acetal 102
It is known that "detoxification" occurs under acidic conditions. The aldehydes are easily condensed with PDO under acidic conditions to form thermodynamically favored cyclic acetals, in this case, acetal MW102. A cation exchange resin of acid form or an acid zeolite also facilitates the removal of acetal MW132 by conversion to cyclic acetal 2-ethi len-1,3-dioxane (EDCA) which is a material of substantially higher volatility.
twenty
Acetal 132 EDCA The crude PDO stream containing the acetal
Unwanted MW176 is treated with a cationic exchange resin of acid form or an acidic zeolite or soluble acid under conditions that favor the reaction schemes shown above. The batch or continuous flow processes can be used in any way for an intimate contact of the liquid stream with the solid acid purifier or the soluble acid. In general, continuous contact would be preferred commercially in a fixed, fluid, or expanded bed, either in downflow or upflow operation or through a horizontal contactor. While the optimum bed size will depend on the particle size and the nature of the solid acid purifier used, the typical design includes a "space velocity in weight per hour" (WHSV) of 0.1 to 10, WHSV being expressed as the flow velocity of Raw PDO mass per mass of solid acid purifier per hour. The optimum bed size and operating temperatures are selected to carry out a high conversion level of acetal MW176 acetal, while minimizing oligomerization of PDO to other components of fraction 21
heavy. When acidic zeolites are used as the solid acid purifier, a temperature in the range of 40 to 150 ° C, preferably 60 to 120 ° C is typically desired. Temperatures from ambient to 150 ° C or lower (from room temperature to 100 ° C) can be used with acid-cation exchange resins, which are indicated as more active in the removal of M 176 impurities. When soluble acids are used, the Temperature can be from 20 to 100 ° C. Preferred zeolite catalysts contain one or more modified zeolites, preferably in the acid form. These zeolites should contain sufficiently large pore dimensions to allow the entry of acyclic or aliphatic compounds. Preferred zeolites include, for example, zeolites of the structural types MFI (e.g., ZSM-5), MEL (e.g., ZSM-11), FER (e.g., ferrierite and ZSM-35), FAU (e.g. zeolite Y), BEA (for example, beta), MFS (for example, ZSM-57), NES (for example, NU-87), MOR (for example, nordeni a), CHA (for example, chabazite), MTT (for example, ZSM-23), MWW (for example, MCM-22 and SSZ-25), EUO (for example, EU-1, ZSM-50, and TPZ-3), OFF (for example, offretite), MTW (for example, ZSM-12) and zeolites ITQ-1, ITQ-2, MCM-56, MCM-49, ZSM-48, SSZ-35, SSZ-39 and zeolites of mixed crystalline phases as per 22
example, zeolite PSH-3. The structural types and the reference to the synthesis of various zeolites can be found in the "Atlas of Zeolite Structure Types" (published on behalf of the Structures Commission of the International Zeolite Association), by W.M. Meier, D.H. Olson and Ch. Baerlocher, published by Butterworth-Heinemann, fourth revised edition, 1996. The structural types and references to the zeolites mentioned above are available on the Internet at www.iza-structure.org. These zeolites are commercially available from Zeolyst International, Inc. and ExxonMobil Corporation. Additional examples of suitable zeolite catalysts can be found in U.S. Patent Nos. 5,762,777; 5,808,167; 5,110,995; 5,874,646; 4,826,667; 4,439,409; 4,954,325; 5,236,575; 5,362,697; 5,827,491; 5,958,370; 4,016,245; 4,251,499; 4,795,623; 4,942,027 and WO99 / 35087 which are incorporated herein by reference. Other suitable catalysts include acrylic-type cation exchange resins. These include ion-exchange resins of the gel-type or macro-reticular (macroporous) type with sulfonic acid functional groups in acid form, in which the sulfonic acid function. binds directly or indirectly to a main structure of organic polymer. Examples include: AMBERLITE or 23
A BERLYST A200, A252, IR-118, IR120, A15, A35, XN-1010, or A1200 resins from Rohm and Haas of uniform particle size; resins of the MSC-1 or DOWEX 50 series from Dow; SYBRON C-249, C-267, CFP-110 resins; PUROLITE C-100 or C-150 resins; RESINTECH CG8; IWT C-211; SACMP; IWT C-381; and other comparable commercial resins. Another example of these cation exchange resins is acidified perfluorinated polymer of NAFION sulfonic acid. Soluble acids that can be used include H 2 SO 4, H 3 PO 4, HCl, and soluble sulfonic acids such as para-toluene sulfonic acid, benzene sulfonic acid, and methane sulfonic acid, etc. H2S04 and soluble sulfonic acids are preferred. If these soluble acids are used, corrosion-resistant columns are highly preferred. The acid is removed with the heavier components (heavy fractions). The concentration of the acid is preferably 0.1 to 1.0% by weight. EXAMPLES Examples MW176 Example 176-1 The results in Table 2 show that the room temperature treatment of a sample of PDO contaminated with M 176 acetal with acidic type USY zeolite acid was not effective in the reversal of acetal MW176. It was shown that the reversion at room temperature 24
using strong A15 acid resin (AMBERLYST 15 from Rohm and Haas). Treatment at high temperature with zeolite at 150 ° C overnight resulted in the removal of MW176 with the formation of 2-methyl-1,3-dioxane. However, the formation of poly PDO (di-1,3-propylene glycol) and higher oligomers occurred at higher concentrations than that of the original MW176 acetal. Therefore, the purity and overall yield was reduced, despite the fact that the more difficult to separate M 176 acetal was eliminated. Studies were carried out at other times at 100 ° C using the zeolite USY H +. These results show a reactive conversion of acetal MW176, especially the first ge peak (gas chromatograph) MW176-1 that reacted for virtual completion at 5 hours (acetal MW176 shows three peaks in gc analysis / mass spectrometer; the dominant MW176-1 peak described in Table 2 quickly faded during the acid treatment experiments, while the second "isomer" appeared to be non-reactive). Unlike the previous test at 150 ° C, at 100 ° C the reversion was selective without the measurable formation of di or tri-1,3-propylene glycol via PDO condensation. Unintentionally, a sample of mordenite in sodium form was first tested overnight at 150 ° C, 25
allowing to obtain large quantities of new secondary products of heavy fractions, presumably due to degradation of the PDO. A sample of acid-form mordenite heated with the same PDO overnight at 60 ° C showed, however, an essentially complete removal of the acetal MW176 acetal, with formation of the same 2-methyl-1,3-dioxane (acetal MW102 ) and impurities of M 132 acetal as observed with the USY type zeolite. The reversion was selective since no additional by-products were observed. The performance of the acid form mordenite was then comparable to that of the USY zeolite acid form. These results indicate an optimum temperature for the complete or partial removal of acetal MW176, with minimal degradation of PDO to other secondary products.
Table 2: Purification in solid acid of PDO contaminated with MW176 TiemTemp CataMW176 M 132 W102 RT26.8 di- Other fractions% in% in% in MW176- PDO% PDO% fracciohoras C tai i zador dor weight weight 1 in in weight weights% in weight weight in weight weight new weight%
0 none 25 0.0 0.240 0.050 0.000 0.168 0.000 0.000 0.0 (at the inlet) 24 Acid Resin 25 4.0 0.010 0.290 0.100 0 0.000 0.000 0.0 A35 24 Zeolite USY H + 25 4.0 0.240 0.050 0.000 na 0.000 0.000 0.0
24 Zeolite USY H + 150 4.0 0.010 0.041 0.124 0.002 0.545 0.514 0.0
0 inguna 25 0.0 0.237 0.093 0.000 0.161 0.000 0.000 0.0 (feed) 18 Acid resin 25 10.0 0.005 0.402 0.161 0.002 0.000 0.000 0.0 A15
18 acid A15 + 15% 25 10.0 0.01 0.111 0.048 0.005 0.000 0.000 H20 27 Mordenite Na 150 10.0 0. 016 0. 084 0. .018 0. 013 0., 000 0 .000 20 .5
22 Mordenite H + 60 3.6 0. 017 0. 431 0. .143 0. 005 0., 000 0 .000 0. 0
0 none 100 0.0 0. 237 0. 093 0., 000 0. 161 0., 000 0 .000 0. 0
(feed) 1 Zeolite USY H + 100 10.0 0. 136 0. 209 0., 075 0. 082 0. .000 0 .000 0. 0
3 Zeolite USY H + 100 10.0 0. 048 0. 330 0., 127 0. 018 0., 000 0 .000 0. 0
5 Zeolite USY H + 100 10.0 0. 033 0. 371 0. .142 0. 004 0. .000 0 .000 0. 0
27 Zeolite USY H + 100 10.0 0. 030 0. 351 0. .147 0. 003 0. .000 0 .000 0. 0
Zeolite USY H + = CBV-500-X16 LR22765 (4/2/2000) H-mordenite = LR23768-128 (1/28/2000)
28
Example 176-2 Impurity of M 176 acetal with a strong cation acid ion exchange resin (AMBERLYST A35 from Rohm and Haas) at room temperature. The results of Table 3 show the degradation of acetal MW176, with the formation of acetal MW102, MW18 (H2O), and acetal MW132.
Table 3: Preliminary PDO treatment on A35 resin at room temperature
Treatment with solid PDO acid with MW176 acetal can degrade this impurity to lighter components 29
(non-hydroxylated acetal MW102) which are easily separated by distillation. Strong cationic acid ion exchange resins can reverse acetal MW176 at room temperature. The acid zeolites can also revert to acetal MW176 at a higher temperature. Even at higher temperatures (as demonstrated, for 150 ° C), PDO is condensed by means of the acid zeolites to poly 1,3-propylene glycols, obtaining losses in yields and lower purity.
Examples MW 132 Example 132-1 (comparative) Treatment with acid resin before distillation This experiment included the treatment of 1500 grams of crude PDO followed by water removal, by distillation, with 43.5 grams of cation exchange resin of strong acid A15 dry (Amberlyst A15 resin) under nitrogen atmosphere for 3 hours at 100 ° C with minimum separation (extraction). The treated material was bright yellow. Acetal MW 132 was reduced from only 3.2% by weight to 2.6% by weight. The treated material was distilled and the successive distillation cuts showed reduction in MW 132 acetal from 11% to 2% by weight but with formation of up to 2700 ppm of acrylate by the final cut. Excessive acrylate formation can be expected due to treatment with strong acid that releases acid 3-30
hydroxypropionic, with which there is a maximum formation of acrylate and finally of ester. This example illustrates that no significant removal of acetal MW132 was observed for the resin treatment in the absence of a concerted separation (extraction or distillation) of the volatile impurities. Example 132-2 Acid resin treatment with concerted removal to remove acetal: The results of this experiment are shown in Table 4. 1 gram of strong acid resin A15 dried in vacuum was added to 10 grams of PDO distillate containing 1.38% by weight of cyclic acetal MW 132 from which the greater amount of water was removed by distillation. The sample was heated by means of a metal block heater at 100 ° C with vigorous nitrogen extraction (concerted extraction) as shown by the liquid expansion of approximately 10% by volume. Acetal MW 132 acetal was easily removed with formation of significant amounts of di and tri-PDO by direct self-condensation of PDO.
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Table 4
PDO weight
56 34 97
This study was repeated with different distillates. 1 gram of dried A15 resin was used for 12 grams of PDO distillate. MW 176 (a higher boiling cyclic acetal) and MW 132 acetals were eliminated. Di- and tri-PDO are formed in significant amounts. The results are shown in Table 5.
Table 5: Dry resin removal TiemEG RtJ = 21.69 Acetal MW 176 rtl = = 24.6 rtl = = 29.4% po in Acrylate "M 132 rt = 26.18 di - PDO tri-PDO
Shows hours weight% by weight% by weight% by weight% by weight% by weight
High feed of acetal 197-3 0 0.142 0.416 2.409 0.421 0 0
20b 1 0.126 0.175 1.032 0 0. 615 2. 559
20d 0.122 0.078 0.282 0 3. 004 3. 938
20f 5 0.084 0.031 0.067 0 5. 929 3. 535
Low feed of acetal 192-5 0 0 0.023 0.3 0.051 0 0
20a 1 0 0 0.077 0 0. 557 0. 138
20c - 0 0 0.044 0 2. 027 0. 156
20e 5 0 0 0.028 0 4. 486 0. 206
1 rt is the chromatographic retention time. 2 3-hydroxypropyl acrylate.
Another similar experiment was carried out using 5% by weight of M31 strong acid cation exchange resin (macroreticular resin). As in the previous experiments, the concentration of KYS 132 acetal decreased and the PDO dimer was produced by being in contact with the acid catalyst and by the concerted extraction with nitrogen. The results are shown in Table 6. Table 6: Acid Resin + N2 Extraction 5% Resin Acetal MW Catalyst Time in 132 di-PDO at 100 ° C hours% by weight% by weight
None 12 2, 865 0
A15 12 1, 509 10, 427
M31 12 1, 024 10, 316
Example 132-3 Dry Extraction in Acid Resin with Subsequent Redistillation A sample of PDO double-distillation product of visibly light yellow color when tested for color body precursors was contacted with 5% by weight of strong acid cation exchange resin dry A15 with nitrogen extraction for 4 hours at 105 ° C. The acetal MW 132 was virtually eliminated while 1.7% by weight of di-PDO was formed (Table 7), obtaining a purity of ge 34.
(gas chromatography) of 97.9 ¾ by weight. The treated sample was redistilled to 1.3 kPa (9 mm Hg) in a concentric tubular column of 0.6 meters (2 feet) with background temperature of 121 to 123 ° C. The distillation showed an easy di-PRO separation from the PDO distillate. The distillate cuts were substantially reduced in acetal MW 132 to a 99.9% by weight purity of ge. The color test now gave a slightly yellow tint, indicating a reduction in the precursors of colored bodies. Table 7: Acid removal with redistillation MW 13: PDO di-PDO grams ppm by weight% by weight
Feed 160. 4 n. d. 97,933 1,713 No. cut 17.34 500 99.766 0 distillate 43.15 200 99.910 0 51.19 0 99.894 0 43.41 0 99.846 0
Total 155.09
A less pure sample containing 132 MW 3% acetal, which exhibited a significant color when analyzed to determine colored body precursors, was treated similarly with 5% by weight of strong acid resin (A15) during the nitrogen extraction. The resulting PDO does not
contained acetal MW 132 after 4 hours, but contained 2.9% by weight of di-PDO. Redistillation at 1.3 kPa (8 mm Hg) and 122 to 129 ° C bottom temperature in a 0.6 meter (2 foot) concentric tubular column gave the distillation cuts shown in Table 8. Again, the extraction with resin acid removed a significant portion of the acetal MW 132 in such a way that higher distillation products free of this impurity could be produced. The Di-PDO formed during the resin treatment was easily removed by distillation. The purities of the final distillation cuts would have been relatively high were it not for the progressive formation of acetal MW 102 (2-methyl-1,3-dioxane), which is known to be more volatile than PDO, during distillation. However, another distillation would have eliminated this impurity from the product. Table 8: Acid extraction with redistillation
Source Cutoff number of 1 distillation 2 36
3 45. 87 0 99 106 0 0 .505 4 52. 60 0 99 329 0 0 .606 5 10. 57 0 98 579 0 1 .186 Total 175 .45
Example 132-4 Solid inorganic acids such as silica-aluminas or zeolites are more adaptable for commercial use in an extraction tower with nitrogen or steam. However, their activity in the desirability of beta hydroxy cyclic acetals such as M 132 is poorer than the activity of the strong acid ion exchange resins under comparable conditions (Table 9). Highly active resins, on the other hand, form more di and tri-PDO by-products. However, these oligomers are not believed to be color precursors, and they are more easily separated by distillation than the original acetal 132. The temperature and reaction times (contact) are preferably optimally adjusted so that the cation exchange resin acid form vs. the acid zeolite maximizes the reversal of acetal MW132 to PDO while minimizing the production of other heavy impurities.
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Table 9: Solid inorganic acids vs. Interchange resin for acid elimination
38
10. 3
It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.