KR20050074504A - Removal of impurities formed during the production of 1,3-propanediol - Google Patents

Abstract

This invention describes improvements upon a process for the production of 1,3-propanediol (PDO) wherein an aqueous solution of 3-hydroxypropanal (HPA) is formed and the HPA is subjected to hydrogenation to produce a crude PDO mixture. One improvement on this process comprises treating the crude PDO mixture with an acidic zeolite, an acid form cation exchange resin, or a soluble acid to convert the MW176 cyclic acetal to more volatile materials which can be easily separated from PDO by distillation. Another improvement involves removing water from the crude 1,3-propanediol mixture, contacting the resulting mixture with a solid acid purifier at a temperature of from about 50 to about 250 °C to convert the MW 132 cyclic acetal to more volatile cyclic acetals, and separating the more volatile cyclic acetals from the 1,3-propanediol by distillation or gas stripping.

Description

REMOVAL OF IMPURITIES FORMED DURING THE PRODUCTION OF 1,3-PROPANEDIOL}

The present invention provides a 1,3-propane comprising forming an aqueous solution of 3-hydroxy propanal (HPA), hydrogenating neutralized HPA to produce a PCO mixture, and distilling to produce purified PDO. It relates to a process for preparing diols.

Several companies have developed PDO manufacturing techniques that initiate with ethylene oxide as the main raw material. Ethylene oxide reacts with syngas, a mixture of carbon monoxide and hydrogen, obtainable by steam reforming of natural gas or partial oxidation of hydrocarbons. The ideal reaction of ethylene oxide (EO) and syngas to yield PDO is as follows:

EO + CO + 2H ₂ → PDO

Hoechst Celanese's U.S. Patents 4,873,378, 4,873,379, and 5,053,562 use a single gas to give PDO and its precursors at 65 to 78 mol% yield using a 2: 1 (molar ratio) syngas at 110-120 ° C. and about 1000 psig (6900 kPa). Step reactions are described. The catalyst system used consists of rhodium, various phosphines, and various acids and waters as promoters.

U.S. Patents 5,030,766 and 5,210,318, assigned to Union Carbide, describe the reaction of EO with syngas in the presence of a rhodium containing catalyst. Selectivity up to 47 mol% was obtained at 110 ° C. and 1000 psig (6900 kPa) of syngas at 2: 1 molar ratio, but the complex rate of PDO and 3-hydroxy propanal formation was significantly lower, from 0.05 to 0.07 mol per liter per hour. Increasing the ratio of phosphate promoter to rhodium catalyst yielded better results.

U.S. Patents 5,256,827, 5,304,686, and 5,304,691, assigned to Shell Oil, describe a process for preparing PDO from EO and syngas using tert-phosphine complex cobalt carbonyl catalysts. The selectivity ranged from 85 to 90 mol% and the EO conversion ranged from 21 to 34% under reaction conditions of 90 to 105 ° C. and synthesis gas (molar ratio 1: 1) 1400 to 1500 psig (9650 to 10340 kPa) for 3 hours. Increased selectivity and EO conversion were reported from later work.

U.S. Patent 5,527,973 describes a process for purifying PDO containing carbonyl by-products including acetals. An aqueous solution of carbonyl containing PDO was prepared to have a pH of less than 7, and then a sufficient amount of base was added to the solution to raise the pH to above 7. The solution was then heated to distill most of the water and then the remaining basic solution was heated to distill most of the PDO from the basic solution to provide a PDO composition having a lower carbonyl content than the starting composition. This method has the commercial advantage of providing a method of lowering the carbonyl content in fewer process steps by including only a few steps.

MW132 acetal of PDO is formed as an undesirable by-product of hydroformylation and hydrogenation reactions. Since MW132 exhibits similar volatility to PDO, it is difficult to separate from PDO by simple distillation. This formation lowers not only the purity of the PDO but also the overall recovery. Therefore, it would be very advantageous to be able to chemically react MW132 acetal with other materials that are more readily separated from PDO. The present invention provides such a chemical method.

Summary of the Invention

The present invention comprises the steps of forming an aqueous solution of 3-hydroxy propanal (HPA), hydrogenating HPA to give PDO, water, MW176 acetal (so called because it is an acetal having a molecular weight of about 176), and high volatility and low volatility material Preparing a crude 1,3-propanediol mixture comprising, the crude 1,3-propanediol mixture is generally dried by distillation to provide water and somewhat highly volatile substances such as ethanol and / or process solvents. Producing a dried crude PDO mixture as a first overhead stream comprising PDO, a first distillate bottoms stream comprising PDO, MW176 acetal, and low volatility, and distilling the dried crude PDO mixture to somewhat Produce a second overhead stream comprising a highly volatile material, an intermediate stream comprising PDO and MW176 acetal, and a second distillate bottoms stream comprising PDO and a low volatile material Relates to improvements in 1,3-propanediol (PDO) manufacturing method comprising the steps: Most of the recoverable PDO is in the middle stream, which contains about 99.9 wt% of PDO. The second distillate bottoms stream may contain up to 50 wt% PDO, but this PDO is difficult to separate from the low volatility material. There may be traces of MW176 acetal in the bottoms stream.

In such embodiments, improvements include: 1) crude PDO mixture before drying and / or 2) dried crude PDO mixture before distillation and / or 3) middle stream (in this third embodiment, the more volatile MW176 acetal reaction product). Another distillation step will be required to remove the PDO from the PDO, by contacting the acidic zeolite (e.g. Conversion of acetals to alternative species that can be more easily separated from PDO by distillation is included. In another embodiment of the present invention, 1) and / or 2) and / or 3) are contacted with a cation exchange resin in acid form, typically sulfonic acid type, at temperatures from ambient to 150 ° C. In another embodiment, a soluble acid such as H ₂ SO ₄ is used to treat the stream at a temperature of 20 to 100 ° C., preferably in a corrosion resistant column.

The process of contacting the crude PDO mixture with a solid acid purifier is performed as a continuous process or batch using standard methods and practices for contacting the liquid stream with a solid catalyst or adsorbent. In this way, since the difficulty of separating impurities such as MW176 acetal is largely eliminated, high recovery can be obtained by distilling PDO with high purity.

In another embodiment the invention,

a) forming an aqueous solution of 3-hydroxy propanal,

b) hydrogenating 3-hydroxy propanal to form a first crude 1,3-propanediol mixture comprising 1,3-propanediol, water, and MW132 cyclic acetal,

c) distilling the first crude 1,3-propanediol mixture to remove water and low boiling impurities and to form a second crude 1,3-propanediol mixture,

d) contacting the second crude 1,3-propanediol mixture with a cationic exchange resin in acid form at a temperature of 50 to 150 ° C. to convert the MW132 cyclic acetal into a more volatile cyclic acetal and / or other degradation products. Converting, and

e) providing a process for preparing 1,3-propanediol, comprising separating volatile acetals and / or other degradation products from 1,3-propanediol by distillation or gas stripping.

In the most preferred mode of this embodiment, 1,3-propanediol is formed when volatile cyclic acetals and / or other degradation products are formed by performing steps d) and e) together (eg using the same vessel or column). Separate from. In another mode of this embodiment, acidic zeolites can be used in place of cationic acid exchange resins. In this case, the temperature is preferably 80 to 200 ° C.

1 is a very simple schematic diagram showing an example of a simplified distillation system.

Aqueous 3-hydroxy propanal (HPA) aqueous solution, which is the starting material of the present invention, can be prepared by a number of different methods. The aforementioned US Pat. Nos. 4,873,378, 4,873,379, 5,053,562, 5,030,766, 5,210,318, 5,256,827, 5,304,686, and 5,304,691, all of which are incorporated herein by reference, describe different methods of making HPA aqueous solutions. HPA can also be prepared by hydration of acrolein in the presence of an acidic catalyst. Methods for achieving these results are described in US Pat. Nos. 5,426,249, 5,015,789, 5,171,898, 5,276,201, 5,334,778, and 5,364,987, all of which are incorporated herein by reference.

Preferred methods for carrying out the entire process of the invention are described in US Pat. No. 5,786,524, which is incorporated herein by reference, generally as follows. 200 to 5000 psi (1380 to 34500 kPa) of ethylene oxide (EO) in a hydrogen to carbon monoxide ratio of 1: 5 to 25: 1 in the presence of a hydroformylation catalyst having a concentration of 0.05 to 15 wt%, more preferably 0.05 to 1 wt% And hydroformylation in a reactor such as a bubble column or stirred tank at 50-110 ° C.

The hydroformylation reaction effluent is preferably extracted with a small amount of water having a water-solvent ratio in the range of 2: 1 to 1:20 at an atmosphere of greater than 50 psi (350 kPa) carbon monoxide at 5 to 55 ° C. The solvent layer containing more than 90% of the active catalyst is recycled to the hydroformylation reactor. HPA is extracted in the aqueous layer at a concentration of 10 to 45 wt%.

The catalyst can be removed from the HPA aqueous solution by any known means such as first oxidizing the catalyst and then removing it using an acid ion exchange resin. The ion exchange resin may be a weak acid or strong acid ion exchange resin. Examples include AMBERLYST 15, 35, and XN-1010, AMBERLITE IR-118, IRC76, A1200, DOWEX 50 x 2-100 and 5 x 8-100, XL-383 and -386, and BIO RAD AG50W-X2 and AMBERSEP 252H resins, or other strong (sulfonic) or weak (carboxy) acid resins (AMBERLYST, AMBERLITE, DOWEX, BIO RAD, and AMBERSEP are trademarks).

After neutralization of the aqueous 3-hydroxy propanal solution, the aqueous solution is hydrogenated. This can be done by hydrogenating with hydrogen, typically 100-2000 psi (690-13800 kPa), in the immobilized bed of the hydrogenation catalyst. The hydrogenation catalyst may be any of those disclosed in US 5,786,524 (incorporated herein), including a Group VIII metal catalyst such as nickel, cobalt, ruthenium, platinum, or palladium. Initial hydrogenation is preferably carried out at 40-80 ° C. and promotes a reaction which reversely converts reactive components such as cyclic acetals to PDO by increasing the temperature to preferably 120-175 ° C. Finally, the light (low boiling) solvent and highly volatile (high boiling) impurities entrained with water are distilled from the PDO (overhead stream) and the crude PDO and low volatile components are also separated as bottoms stream during distillation. .

MW132 Acetal

To carry out the second embodiment of the present invention, the dried crude product stream (distilled) containing MW132 acetal and PDO is treated as follows to recover PDO in high yield and high purity. The crude PDO described above can exhibit high levels of MW132 cyclic acetal impurities. This impurity is undesirable and limits PDO recovery during subsequent distillation. This can be formed by the reaction of PDO with HPA.

Reaction # 1

2-ethylene-1,3-dioxane cyclic acetal (EDCA) formed by acid catalysis of MW132 acetal is known to be much more volatile than PDO. The following scheme illustrates the dehydration of MW132 acetal to form 2-ethylene-1,3-dioxane cyclic acetal (EDCA) which can be easily separated from PDO by distillation. PDO can be purified through the reaction of MW132 acetal to form EDCA using acidic zeolites and cationic exchange resins in acid form (such as those used for cobalt removal).

Reaction # 2

That is, the dried crude PDO stream containing the undesirable MW132 cyclic acetal is contacted with an acidic cationic exchange resin or acid zeolite under conditions prevailing above the reaction regime for conversion of MW132 acetal to EDCA. This step is combined with the removal of EDCA through cooperative distillation or through the use of a stripping gas such as nitrogen or steam.

Cooperative distillation and reactions (which are combined in the same processing unit to separate them from the product when the reactants are formed) can use any well known method for carrying out "reactive distillation". Alternatively, an inert gas such as nitrogen can be used to strip the reaction mixture of the more volatile decomposition products (EDCA) of MW132 acetal (cooperative stripping and reaction) to prevent reforming of MW132 through chemical equilibrium. . The use of steam (steam) is a common commercial practice for providing treatment heat and inert stripping gas. In this case, stripping is again carried out in the same processing unit as the reaction of MW132 acetal. The reaction product is removed when formed to exclude chemical equilibrium or reduce the presence of MW132 acetal. In this way, the combination of acid catalyzed reaction and stripping into the same treatment step affects reactant-product separation in the same way as the "reactive distillation" bond of acid catalyzed reaction and distillation.

In general, water has been shown to inhibit the reverse conversion and removal of MW132 acetal. In general, however, small amounts of water present due to incomplete removal, sorption in solid catalysts, or their own dehydration reaction (# 1 described above) can remove a portion of MW132 via a reverse reaction of reaction # 1. HPA (if formed in this manner) can then be further dehydrated with highly volatile acrolein, which is easily stripped or distilled from the reaction mixture. Regardless of which mechanism prevails, the acid catalyzed reaction in conjunction with the separation (distillation or stripping) of the volatile reaction products reduces the MW132 impurities of the PDO product. Cooperative distillation or inert gas stripping requires keeping the chemical equilibrium away from the thermodynamically predominant MW132 cyclic acetal. Acid forming zeolites may also be used during the above-described process to promote MW132 acetal removal.

Use of the acidic cationic exchange resin with cooperative separation yields a substantially complete MW132 acetal conversion. The reaction is preferably carried out at a temperature of 50 to 150 ° C, more preferably 80 to 120 ° C. Contact with the resin catalyst is carried out in a batch or continuous column using well known reactor design methods that ensure substantially complete MW132 acetal conversion. Batch contact at 80 to 120 ° C. may be effective for complete conversion, for example, with 1 to 5 hours of 10 wt% acid resin. Alternatively, the contact may be effective in a continuous reaction vessel, preferably a column, having a "weight space velocity per hour" (weight of crude PDO feedstock per weight of acid resin per hour minus "WHSV") of 0.1 to 1 per hour. Can be.

To lower the activity for acetal reverse conversion by zeolites, higher temperatures or increased contact times with the zeolites are required. The reaction with the acidic zeolite is preferably carried out via batch or continuous contact at a temperature of 70 to 250 ° C, more preferably 90 to 170 ° C. Similar contact times or hourly space velocity can be used. For any system, the combination of contact time and temperature with a solid acid purifier (cation exchange resin or acid zeolite in acid form) limits the formation of undesirable chromogenic impurities and prevents the production of dimers and higher oligomers of PDO. It should be optimal to minimize.

Preferred catalysts are ion exchange resins with strong acidic cation exchange (acidic cationic exchange resins). These include gel type or macroreticular (macroporous) ion exchange resins with sulfonic acid functionalities, where the sulfonic acid functional groups are directly or indirectly bound to the organic polymer backbone. Examples include Rohm and Haas AMBERLITE or AMBERLYST A200, A252, IR-118, IR120, A15, A35, XN-1010, or uniform particle size A1200 resins; Dow MSC-1, M-31, or DOWEX 50 series resins, SYBRON C-249, C-267, CFP-100 resins; PUROLITE C-100 or C-150 resins; RESINTECH CG8; IWT C-211, SACMP; IWT C-381; Or other commercially strong acid cationic exchange resins equivalent thereto. Another example of a cation exchange resin is an acidified perfluorinated polymer of NAFION sulfonic acid (SYBRON, PUROLITE, RESINTECH and NAFION are trade names).

Suitable zeolite catalysts contain one or more modified zeolites, preferably in acid form. These zeolites should contain pores with dimensions large enough to allow for the penetration of acyclic or aliphatic compounds. Preferred zeolites include, for example, structured zeolite MFI (e.g. ZSM-5), MEL (e.g. ZSM-11), FER (e.g. ferrierite and ZSM-35), FAU (e.g. For example, zeolite Y), BEA (e.g. beta), MFS (e.g. ZSM-57), NES (e.g. NU-87), MOR (e.g. mordenite), CHA (e.g. For example, carbazite), MTT (eg ZSM-23), MWW (eg MCM-22 and SSZ-25), EUO (eg EU-1, ZSM-50 and TPZ-3) ), OFF (e.g., Opretite), MTW (e.g., ZSM-12) and Zeolite ITQ-1, ITQ-2, MCM-56, MCM-49, ZSM-48, SSZ-35, SSZ Zeolites such as -39 and mixed crystalline phases such as, for example, zeolite PSH-3. Structural forms and synthesis of various zeolites are described in W. M. Meier, D. H. Olson and Ch. See Baerlocher's "Atlas of Zeolite Structure Type" (published on behalf of the Structure Commission of the International Zeolite Association), 4th edition (1996). Structural types and the above-mentioned zeolites may be referred to the World Wide Web www.iza-structure.org. Such zeolites are available from Zeolyst International, Inc. And ExxonMobil Corporation. Further examples of suitable zeolite catalysts are described in US Pat. No. 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, all of which are incorporated herein by reference.

MW176 Acetal

As shown in the exemplary simplified distillation scheme of FIG. 1 to aid in understanding the first embodiment of the present invention, aqueous PDO containing MW176 acetal flows into dry distillation column 2. Water and somewhat highly volatile material are removed in overhead stream 3, and MW176 acetal and dried PDO from the distillation bottoms stream flow into distillation column 5. Higher volatility material is separated and removed through overhead stream 6, and distillation bottoms stream 8 contains low volatility and some PDO as well as trace amounts of MW176 acetal. Recoverable PDO flows out to the middle stream. Vessels 1, 4, and 7 are optional (although at least one is required in the system shown) acid treated vessels. The acid catalyst treatment may be carried out before drying in vessel 1, after drying in vessel 4 and before distillation, or after distillation in vessel 7. When carrying out the last embodiment, further distillation is required to separate the more volatile MW176 acetal reaction product from the PDO.

The crude PDO described above sometimes exhibits high levels of MW176 cyclic acetal impurities. This impurity has been found to be only slightly less volatile than PDO, limiting PDO recovery. Since difficulties were given for separation from PDO, laboratory batch distillation was performed to evaluate the relative volatility of MW176 impurities and PDO. Approximately 85 g of PDO was contaminated with this impurity, and the C ₅ diols were also refluxed at nominal 10 mmHg (1.3 kPa) pressure and 143 ° C. bottoms temperature. About 1 wt% of ethylene glycol (EG) and butanediol markers were added to assist in indicating relative volatility. The results (Table 1) show that both MW176 acetal and C ₅ diol are heavier than PDO. Good agreement between relative volatility measurements versus reported values of EG versus PDO indicates that equilibrium has actually been reached in these measurements.

Table 1: Relative Volatility ¹

¹ Relative volatility reported value of EG / PDO at 230 ° F (110 ° C) = 2.16

² t = distillation "supernatant" or "overhead product"

  b = distillation "bottom water"

MW102 acetals formed by acid catalysis of MW176 acetals are known to be much more volatile than PDOs and can be easily separated from PDOs with high efficiency. This result was expected based on the absence of hydroxyl groups in MW102 due to condensation removal. While not wishing to be limited to any particular mechanism, the following reactions will explain the decomposition of MW176 acetal and the formation of MW102 acetal, which can be easily separated from PDO by distillation, and also the formation of MW132 acetal as observed in the experiment. Can be.

"Deethoxylation" is known to occur under acidic conditions. Aldehydes are easily condensed with PDO under acidic conditions to form thermodynamically cyclic acetals, in this case MW102 acetals.

Acid form cation exchange resins or acid zeolites also promote the removal of MW132 acetal through conversion to substantially higher volatility 2-ethylene-1,3-dioxane cyclic acetal (EDCA).

The crude PDO stream containing the undesirable MW176 acetal is treated with acidic cation exchange resins or acidic zeolites or soluble acids under conditions prevailing in the reaction system. Batch or continuous flow processes can be used in any manner that provides intimate contact of the liquid stream with the solid acid purifier or the soluble acid. Typically continuous contact in a fixed, flow, or expansion bed will be commercially desirable, and may be carried out via a horizontal contactor or operation in the downstream or upstream direction. The optimal bed size will depend on the particle size and nature of the solid acid purifier used, but a typical design will involve a "weight hourly space velocity" (WHSV) of 0.1 to 10 (WHSV is unknown per mass of solid acid purifier per hour). The mass flow rate of the first PDO). The optimal bed size and operating temperature are chosen to be effective for high levels of MW176 acetal conversion while minimizing the PDO's small polymerization to other heavy bottom components.

When acidic zeolites are used as solid acid purifiers, temperatures in the range from 40 to 150 ° C., preferably from 60 to 120 ° C., are typically preferred. Acid type cation exchange resins indicated to be more active for MW176 impurity removal can be used at temperatures from ambient to 150 ° C. or lower (ambient to 100 ° C.). The temperature when using soluble acid may be 20 to 100 ° C.

Preferred zeolite catalysts contain one or more modified zeolites, preferably in acid form. These zeolites should contain pores with dimensions large enough to allow for the penetration of acyclic or aliphatic compounds. Preferred zeolites include, for example, structured zeolite MFI (e.g. ZSM-5), MEL (e.g. ZSM-11), FER (e.g. ferrierite and ZSM-35), FAU (e.g. For example, zeolite Y), BEA (e.g. beta), MFS (e.g. ZSM-57), NES (e.g. NU-87), MOR (e.g. mordenite), CHA (e.g. For example, carbazite), MTT (eg ZSM-23), MWW (eg MCM-22 and SSZ-25), EUO (eg EU-1, ZSM-50 and TPZ-3) ), OFF (e.g., Opretite), MTW (e.g., ZSM-12) and Zeolite ITQ-1, ITQ-2, MCM-56, MCM-49, ZSM-48, SSZ-35, SSZ Zeolites such as -39 and mixed crystalline phases such as, for example, zeolite PSH-3. Structural forms and synthesis of various zeolites are described in W. M. Meier, D. H. Olson and Ch. See Baerlocher's "Atlas of Zeolite Structure Type" (published on behalf of the Structure Commission of the International Zeolite Association), 4th edition (1996). Structural types and the above-mentioned zeolites may be referred to the World Wide Web www.iza-structure.org. Such zeolites are available from Zeolyst International, Inc. And ExxonMobil Corporation. Further examples of suitable zeolite catalysts are described in US Pat. No. 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, all of which are incorporated herein by reference.

Other suitable catalysts include cation exchange resins in acid form. These include gel-type or macroreticular (macroporous) ion exchange resins with sulfonic acid functional groups in acid form, where the sulfonic acid functional groups are bonded directly or indirectly to the backbone of the organic polymer. Examples include Rohm and Haas AMBERLITE or AMBERLYST A200, A252, IR-118, IR120, A15, A35, XN-1010, or uniform particle size A1200 resins; Dow MSC-1, M-31, or DOWEX 50 series resins, SYBRON C-249, C-267, CFP-100 resins; PUROLITE C-100 or C-150 resins; RESINTECH CG8; IWT C-211, SACMP; IWT C-381; Or other commercial resins equivalent thereto. Another example of these cation exchange resins is the 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, methane sulfonic acid and the like. Preference is given to H ₂ SO ₄ and soluble sulfonic acids. When using these soluble acids, corrosion resistant columns are very preferred. Acid is removed as the heaviest component (heavy bottoms). The concentration of the acid is preferably 0.1 to 1.0 wt%.

MW176 Example

Example 176-1

From the results in Table 2, it can be seen that ambient temperature treatment of PDO samples contaminated with MW176 acetal with USY zeolite in acid form is ineffective for MW176 acetal reverse conversion. Room temperature reverse conversion using strong acid resin A15 (Rohm and Haas AMBERLYST 15) was demonstrated. High temperature treatment with zeolite overnight at 150 ° C. removed MW176 by the formation of 2-methyl-1,3-dioxane. However, poly PDO (di-1,3-propylene glycol) and higher oligomers were formed at higher concentrations than originally MW176 acetal. Thus, overall purity and yield decreased, and it became more difficult to separate the removed MW176 acetal.

Further time studies were performed using USY H + type zeolites at 100 ° C. The results showed reactive conversion of MW176 acetal, in particular the first gc (gas chromatograph) peak MW176-1 which reacts to substantial completion within 5 hours (MW176 acetal shows three peaks in gc / mass specificity analysis, The potent MW176-1 peak shown in 2 easily disappears during acid treatment experiments, while the second "isomer" is believed to be non-reactive). Unlike the previous test at 150 ° C., reverse conversion at 100 ° C. was selective because no condensation of PDO formed di- or tri-1,3-propyl glycol to a measurable degree.

The mordenite samples were first tested by chance in the sodium form overnight at 150 ° C., presumably through the decomposition of PDO, giving a large amount of new heavy bottom by-products. However, the modenite samples in acid form heated at 60 ° C. overnight with the same PDO were essentially formed by the formation of the same 2-methyl-1,3-dioxane (MW102 acetal) and MW132 acetal impurities as observed in USY zeolites. As shown complete MW176 acetal removal. Reverse conversion was selective because no additional byproducts were observed. Thus, the performance of acid form mordenite was comparable to that of USY acid form zeolite. These results indicate the optimum temperature for complete or partial removal of MW176 acetal while minimizing degradation of PDO into other byproducts.

Table 2: Solid Acid Purification of PDO Contaminated with MW176

USY H + Zeolite = CBV-500-X16 LR22765 (4/2/2000)

H-mordenite = LR23768-128 (1/28/2000)

Example 176-2

MW176 acetal impurities were treated with strong cation acid ion exchange resin (Rohm and Haas AMBERLYST A35) at room temperature. From the results shown in Table 3, it can be seen that MW176 acetal was decomposed by the formation of MW102 acetal, MW18 (H ₂ O), and MW132 acetal.

Table 3: Preliminary PDO Treatment with A35 Resin at Room Temperature

Solid acid treatment of PDO contaminated with MW176 acetal can decompose this impurity into a lighter component (MW102 monohydroxylated acetal) that can be easily separated through distillation. Strong cation acid ion exchange resins can reverse MW176 acetal at room temperature. Acidic zeolites can also reverse MW176 acetal at higher temperatures. At much higher temperatures (as evidenced for 150 ° C.), PDO was condensed with poly 1,3-propylene glycol by acidic zeolites, resulting in yield loss and lower purity.

MW132 Example

Example 132-1 (Comparative Example)

Acid resin treatment before distillation

This experiment was carried out using a cationic exchange resin in the form of a strong acid, 43.5 g of dry A15 (Amberlyst A15 resin) at 100 ° C. under nitrogen atmosphere for 3 hours after distillation of water, and 1500 g with minimal separation (striping). Accompanied with the steps of processing the crude PDO. The treated material was light yellow. MW132 acetal was reduced from only 3.2 wt% to 2.6 wt%. The treated material was distilled and a series of distillation cuts showed a decrease from 11 wt% to 2 wt% of MW132 acetal, but up to 2700 ppm of acrylate formed until the final cut. The excess formation of acrylates can be expected to be due to the strong acid treatment which gives the maximum ester by removing 3-hydroxypropionic acid and ultimately forms the acrylate. This example demonstrated that no significant MW132 acetal removal was observed in the resin treatment in the absence of cooperative separation (striping or distillation) of volatile impurities.

Example 132-2

Acid resin treatment with cooperative stripping to remove acetal:

The results of this experiment are presented in Table 4. 1 g of vacuum dried A15 strong acid resin was added to 10 g of PDO distillate containing 1.38 wt% MW132 acetal from which most of the water was distilled off. Samples were heated to 100 ° C. through a metal block heater with active nitrogen stripping (cooperative stripping) specified with liquid expansion up to about 10 vol%. MW132 acetal was easily removed by significant amounts of di- and tri-PDO formation via direct PDO self-condensation.

Table 4

This study was repeated for different distillates. 12 g of PDO distillate was treated using 1 g of dry A15 resin. MW176 (high boiling cyclic acetal) and MW132 acetal were removed. Di- and tri-PDO were formed in significant amounts. The results are shown in Table 5.

Table 5: Resin Dry Stripping

¹ rt is chromatography retention time.

² 3-hydroxypropyl acrylate

Another similar experiment was performed using 5 wt% M31 strong acid form cationic exchange resin (macroreticular resin). As in the previous experiments, the amount of MW132 acetal was reduced and PDO dimers were formed by contact with the acid catalyst and by cooperative nitrogen stripping. The results are shown in Table 6.

Table 6: Acid Resin + N ₂ Stripping

Example 132-3

Acid Resin Dry Stripping with Subsequent Redistillation

Samples of two distilled PDO products that exhibited apparently bright yellow in the test for chromogenic precursors were contacted with 5 wt% dry A15 strong acid form cationic exchange resin with nitrogen stripping at 105 ° C. for 4 hours. MW132 acetal was substantially removed (Table 7) while 1.7 wt% of di-PDO was formed, giving 97.9 wt% of gc (gas chromatography) purity. The treated sample was re-distilled at 9 mmHg (1.3 kPa) in a 2-ft (0.6 m) small concentric tube column with a bottoms temperature of 121-123 ° C. Di-PDO was easily separated from the PDO distillate by distillation. Distillate cuts showed a substantially reduced MW132 acetal with gc purity approaching 99.9%. The color test now only showed a weak yellow color, indicating that the amount of chromophore precursor was reduced.

Table 7: Acid Stripping with Redistillation

Less pure samples containing 3 wt% MW132 acetal showing significant color in the analysis for chromogenic precursors were similarly treated with 5 wt% strong acid resin (A15) with nitrogen stripping. The PDO produced after 4 hours did not contain MW132 acetal, but contained 2.9 wt% of di-PDO. Re-distillation at 8 mmHg (1.3 kPa) and 122-129 ° C. in a 2-ft (0.6 m) concentric tube column gave a distillation cut as shown in Table 8. Again, by removing the significant portion of MW132 acetal with acid resin stripping it was possible to produce a distillation overhead product free of these impurities. Di-PDO formed during the resin treatment was easily separated by distillation. The purity of the final distillate cut would have been significantly higher, except for the progressive formation during the distillation of MW102 acetal (2-methyl-1,3-dioxane), which is known to be more volatile than PDO. However, this impurity will be removed from the product by another distillation.

Table 8: Acid Stripping with Redistillation

Example 132-4

Inorganic solid acids such as silica-alumina or zeolites are more suitable for commercial use in nitrogen or vapor strippers. However, the activity in dehydration of beta-hydroxy cyclic acetals such as MW132 was worse than the strong acid ion exchange resin activity under comparable conditions (Table 9). Highly active resins, on the other hand, produced more di- and tri-PDO as by-products. However, these oligomers are not considered to be chromogenic precursors, and were easily separated from the original MW132 acetal by distillation. The temperature and reaction (contact) time were optimally adjusted for acidic cationic exchange resins to acidic zeolites, preferably to maximize the reverse conversion of MW132 acetal to PDO while minimizing the formation of other heavy impurities.

Table 9: Inorganic Solid Acid to Ion Exchange Resin for Acid Stripping

Claims (10)

a) forming an aqueous solution of 3-hydroxy propanal (HPA), b) hydrogenating 3-hydroxy propanal to form a crude 1,3-propanediol mixture comprising 1,3-propanediol, water, and MW132 cyclic acetal and / or MW176 cyclic acetal, c) distilling (drying) the crude 1,3-propanediol mixture to remove water, and a second crude 1 comprising 1,3-propanediol and MW132 cyclic acetal and / or MW176 cyclic acetal; Forming a 3-propanediol mixture (first distillate bottoms stream), d) contacting the stream containing MW132 cyclic acetal and / or MW176 cyclic acetal with an acidic cationic exchange resin or acidic zeolite or soluble acid, and e) removing MW132 cyclic acetal and / or MW176 cyclic acetal from 1,3-propanediol. The method of claim 1, wherein the step of forming an aqueous solution of 3-hydroxy propanal, hydrogenating 3-hydroxy propanal to form 1,3-propanediol, water, MW176 cyclic acetal, and high and low volatility materials. Preparing a crude 1,3-propanediol mixture comprising, drying the crude 1,3-propanediol mixture to form a first overhead stream comprising water, 1,3-propanediol, MW176 cyclic acetal, And producing a first distillate bottoms stream comprising high and low volatility materials, and distilling the first distillate bottoms stream to produce a second overhead stream comprising 1,3-propanediol and Generating an intermediate stream comprising MW176 acetal and a second distillate bottoms stream comprising 1,3-propanediol and low volatility, the crude 1,3-propanediol mixture or first distillation bottom; Stream of water or either By contacting at least one of the streams with an acidic zeolite or a cationic exchange resin in acid form or a soluble acid prior to drying, the MW176 cyclic acetal can be readily separated from the 1,3-propanediol by distillation into a more volatile material. Method for producing 1,3-propanediol, characterized in that the conversion. 3. The method of claim 2, wherein the crude 1,3-propanediol mixture is contacted with an acidic zeolite at 40 to 150 DEG C, preferably 60 to 120 DEG C prior to drying, thereby dimerizing chromogenic impurities and dimers of 1,3-propanediol. MW176 cyclic acetals are distilled by minimizing the production of higher oligomers or by contacting the cationic exchange resin in acid form with ambient temperatures at 150 ° C., preferably at 100 ° C., or with soluble acids at 20-100 ° C. A process for producing 1,3-propanediol, characterized in that it is converted to a more volatile substance which can be easily separated from, 3-propanediol. 3. The higher oligomer according to claim 2, wherein the first distillate bottoms stream is contacted with acidic zeolite at 40 to 150 [deg.] C., preferably 60 to 120 [deg.] C. prior to distillation to obtain dimers and higher oligomers of chromogenic impurities and 1,3-propanediol. 1,3- by distillation of the MW176 cyclic acetal by minimizing the formation or by contacting the cationic exchange resin in acid form with ambient temperature at 150 ° C, preferably at 100 ° C, or with soluble acid at 20-100 ° C. A process for producing 1,3-propanediol, characterized in that it is converted to a more volatile substance that can be easily separated from propanediol. The method of claim 2, wherein the intermediate stream is contacted with an acidic zeolite at 40-150 ° C., preferably 60-120 ° C. to minimize the formation of chromogenic impurities and dimers of 1,3-propanediol and higher oligomers, MW176 cyclic acetals are easily separated from 1,3-propanediol by distillation by contacting the cationic exchange resin in acid form with ambient temperature at 150 ° C, preferably at 100 ° C, or with soluble acid at 20-100 ° C. A process for producing 1,3-propanediol, characterized by converting it into a more volatile substance. The method of claim 1, a) forming an aqueous solution of 3-hydroxy propanal, b) hydrogenating 3-hydroxy propanal to form a first crude 1,3-propanediol mixture comprising 1,3-propanediol, water, and MW132 cyclic acetal, c) distilling the first crude 1,3-propanediol mixture to remove water and low boiling impurities and to form a second crude 1,3-propanediol mixture, d) the second crude 1,3-propanediol mixture is reacted with the cationic exchange resin in acid form at a temperature of 50 to 150 ° C., preferably 80 to 120 ° C., or about 70 to 250 ° C., preferably with an acidic zeolite. Converting the MW132 cyclic acetal into a more volatile cyclic acetal and / or other degradation product by contacting at a temperature of 90-170 ° C., and e) separating the more volatile acetal and / or other decomposition products from 1,3-propanediol by distillation or gas stripping. 7. 1,3-propane, according to claim 6, characterized in that by carrying out steps d) and e) together, volatile cyclic acetals and / or other degradation products are formed, which are separated from 1,3-propanediol. Diol preparation method. The method of claim 6, wherein the second crude 1,3-propanediol mixture is contacted with the cationic exchange resin or zeolite in a batch for about 1 to about 5 hours. 7. The 1,3-propagation of claim 6 wherein the second crude 1,3-propanediol mixture is contacted with a cationic exchange resin or zeolite at a weight hourly space velocity of about 0.1 to about 10 in a continuous reactor. Propanediol Preparation Method. The method of claim 6, further comprising distilling the 1,3-propanediol to separate the 1,3-propanediol from the high boiling impurities formed as a result of step d).