The method of purification of propylene oxide

 

(57) Abstract:

The invention relates to a method of improving the quality of propylene oxide contaminated with poly(propylene oxide), which includes the following stages: (a) interaction of liquid propylene oxide powder of the adsorbent in an amount of from 0.05 to 15 wt.% in relation to the mass of liquid propylene oxide consisting of a silicate of magnesium and/or calcium silicate, with taking the suspension, where the average particle size of the specified powder is from 1 to 100 μm, or deletion of contaminated propylene oxide over at least one layer of the extrudates of the same adsorbent, and (b) isolation of the pure product of propylene oxide. The propylene oxide is widely used to obtain polyether polyols which in interaction with compounds MDI give polyurethanes. The technical result - the increase of the purity of propylene oxide to improve the quality polyurethane foams based on it. 5 C.p. f-crystals, 2 PL.

This invention relates to a method of improving the quality of propylene oxide.

The propylene oxide is widely used as a precursor to obtain polyether polyols which in interaction with compounds MDI give polyurethanes. About the active hydrogen atoms with propylene oxide, optionally together with one or more other acceleratedly, such as ethylene oxide or butylenes. Suitable starting compound include polyfunctional alcohols, typically containing from 2 to 6 hydroxyl groups. Examples of such alcohols are glycols, glycerine, pentaerythritol, trimethylolpropane, triethanolamine, sorbitol, mannitol, and so forth. Usually in reactions of this type as a catalyst using a strong base, such as potassium hydroxide.

The quality of the propylene oxide used to obtain polyetherpolyols has a significant impact on the quality of the resulting polyurethane foams. Especially, it is known that the presence of poly(propylene oxide) causes adverse effects in the formation of polyurethane foams. Examples of such adverse effects is the occurrence of voids when blowing, low rise foam and even the destruction of the obtained foam. Especially when molding, the presence of poly(propylene oxide) in the propylene oxide used for initial polyetherpolyols, can cause problems with quality polyurethane foam.

The term “poly(propylene oxide) used in the context of this description, refers to poly(impregnated what langille gel chromatography.

The methods of industrial production of propylene oxide are well known in the art. In industrial production typically use the chlorohydrin process or hydroperoxide process. In the last process propene is subjected to interaction with an organic hydroperoxide. This hydroperoxide is either tert-butyl hydroperoxide or ethylbenzene hydroperoxide. In the first case as a by-product is formed tert-butyl alcohol (which is then converted into methyl tert-butyl ether), in the second case, as a by-product is formed styrene. In the chlorohydrin process chlorine, propene and water is subjected to interaction with obtaining propylchloride, which is then dehydrochlorinated calcium hydroxide with obtaining propylene oxide. For the purposes of this invention it does not matter what method of obtaining used. Namely, in all the ways of poly(propylene oxide) is formed in undesirable high quantities. Moreover, it is known (for example, from US 4692535), poly(propylene oxide) with high molecular weight can be formed during storage or transportation, for example, by contact with metal, such as carbon steel.

Sponichi. Some adsorbents are described as useful for this purpose. For example, in US 4692535 describes the use of activated carbon, charcoal or attapulgite as suitable adsorbents. In EP-A 0601273 not calcined diatomaceous earth is named as adsorbent for the removal of poly(propylene oxide). In JP-A 08/283253 zeolites and magnesia are named as adsorbents. Suitable zeolites have a pore diameter of from 3 to 10 angstroms, and magnesium should preferably contain at least 90 wt.% magnesium oxide.

Although known adsorbents, especially activated carbon, operate satisfactorily when removing poly(propylene oxide) from propylene oxide, there is scope for further improvement. This invention provides a method of improving the quality of propylene oxide adsorption, where the used adsorbent has at least the same efficiency for the removal of poly(propylene oxide), as activated charcoal.

According to US 5493035 there are various difficulties associated with the use of activated carbon as adsorbent for the purification of propylene oxide, especially during the initial phase or phases of the startup processing activated carbon. Namely, adsorbtion temperature during this run. Such an action may have unintended consequences, one of which is the evaporation of propylene oxide and a transition layer, which, in turn, gives a secondary exothermic effect with very high temperatures. This is very dangerous and can even lead to the destruction of the reactor, as specified in US 5493035. The solution proposed in US 5493035 is the pre-treatment of activated carbon, consisting in contact specified activated carbon with a glycol such as propylene glycol.

Predictably, is that the adsorbent used in the method in accordance with this invention, should not carry the above risks associated with the use of activated charcoal. On the other hand, the cleaning efficiency of the used adsorbent must be at least equivalent efficacy of activated charcoal.

Accordingly, this invention relates to a method of improving the quality of propylene oxide contaminated with poly(propylene oxide), comprising the following stages:

(a) interaction of liquid propylene oxide with an adsorbent consisting of a silicate of magnesium and/or calcium silicate in such conditions that the amount of poly(propylene oxide) she indicated above, the method, which are propylene oxide, it does not matter for the present invention. Can be used any known method of obtaining. The propylene oxide processed by the method in accordance with this invention, may be a product directly obtained by known methods of obtaining. Alternative specified directly obtained propylene oxide may also be processed by the usual methods of purification and extraction to processing in accordance with this invention. For example, if the propylene oxide obtained using hydroperoxides of the process, these methods of cleaning and selection usually include removing unreacted propene and organic hydroperoxide, by-products (such as propane, aldehydes and alcohol) and other processing agents. In General, the flow of propylene oxide processed by the method in accordance with this invention, consists of at least 95 wt.% of propylene oxide.

The adsorbent is magnesium silicate, calcium silicate or a mixture thereof. In principle, there can be used known commercially available silicates of magnesium and calcium silicates. The preferred silicates of magnesium are synthetic, for example, obtained in staticheskie calcium silicates. Usually, silicates of magnesium and calcium is used in the form of their hydrates, although can also be used dehydrogenated or not containing water silicates. The use of magnesium silicate as adsorbent preferably.

The adsorbent can be used in powder form to obtain a suspension with or propylene oxide can be used in extruded form in the layer through which pass the propylene oxide.

Accordingly, stage (a) in the first embodiment may include the interaction of liquid propylene oxide with finely ground powder of the adsorbent. The average particle size of this powder is usually from 1 to 100 μm, preferably from 2 to 40 μm. Appropriate adsorbent is dispersed in the liquid propylene oxide to obtain a suspension. In the described embodiment of the present invention stage (b) is mainly a stage filtration with obtaining permeate (or filtrate) containing the purified product of propylene oxide. Withheld substance, therefore, contains the adsorbent with adsorbed therein poly(propylene oxide). Filtering can be performed by microfiltration method known in the art. Filter used should be about the nd filter used, therefore, depending on the size of particles used powder of the adsorbent. Suitable filters, for example, are glass filters, plate filters and mnogohramie filters, such as filters Fundabac or filters Contibac (Fundabac and Contibac are trademarks). Mnogohramie filters typically include a vessel filled with vertically arranged filter elements, distributed over many departments, where each filter element is a tube of porous material surrounded by a filter cloth. The suspension is passed through the vessel and liquid purified propylene oxide under pressure is passed through the filter cloth and the walls of the porous tube in the specified tube and separated at the end of the specified tube.

The amount of the adsorbent when the adsorbent is used in powder form, usually ranges from 0.01 to 20 wt.% in relation to the number of processing liquid propylene oxide. Preferably the amount of adsorbent is from 0.05 to 15 wt.% with respect to the liquid propylene oxide. Usually when using the adsorbent powder is preferably used in an amount of not more than necessary for effectivecriteria not more than 5 wt.% absorbent powder. Absorbent powder may have a surface area of from 10 to 1000 m2/g, but preferably the surface area is at least 50 m2/g, more preferably at least 200 m2/g and even more preferably at least 400 m2/year

In an alternative variant of the method in accordance with this invention stage (a) comprises passing the contaminated propylene oxide over a layer of molded particles of the adsorbent. Such particles can be of any commonly used shape, including spheres, cylinders, stars, trekhgrannykh, tetrahedra, hollow cylinders, or monoliths. The size (diameter) is typically of the order of several millimeters, for example, from 0.1 to 5 mm Cylinders typically have a ratio of length/diameter of from 2 to 6, preferably from 3 to 5. Porosity and surface area of such molded particles should be such that poly(propylene oxide) could be properly absorbed. The preferred porosity, expressed as pore volume is from 0.1 to 3 ml/g, more preferably from 0.2 to 2 mg/g, most preferably from 0.5 to 1.2 ml/g, determined by adsorption of nitrogen. The surface area appropriately can ranged the2/g determined by the BET method (ISO 9277: 1995 (E)).

If the particles of absorbent material, i.e., the magnesium silicate or calcium silicate molded using extrusion, the extrudates typically contain a binder and an adsorbent material. Suitable binder materials include inorganic oxides such as silica, magnesia, titanium dioxide, aluminum oxide, zirconium dioxide and a mixture of silicon dioxide - aluminum oxide, among which preferred is silicon dioxide. The weight ratio of binder to adsorbent may vary from 10:90 to 90:10, preferably from 20:80 to 50:50.

The extrudates can be obtained by conventional extrusion methods known in the art. Typically, the extrusion of the mixture obtained from powders solids (adsorbent and binder) and water mixing and plasticization of ingredients and passing the resulting mixture in the extruder. The mixture typically looks like pasta. How optimizatsii methods of mixing/unit to obtain an extrudable paste, and select the most suitable conditions of extrusion is in the competence of the person skilled in the art. In addition to the absorbent material properties yield strength. Such extrusion additives known in the art and include, for example, aliphatic monocarboxylic acids, polyvinylpyridine and connections sulfoxide, sulfone, phosphonium and Idonia, alkylated aromatic compounds, acyclic monocarboxylic acids, fatty acids, from sulphonated aromatic compounds, sulphates, alcohol, ether alcohol sulfates, sulfated fats and oils, salts of phosphonic acids, polyoxyethyleneglycol, polyoxyethylene alcohols, polyoxyalkylene, polyoxyethylenated, polyacrylamides, polyacrylamide, polyols, polyvinyl alcohols, acetylene glycols, and graphite. To improve the porosity of the final extrudate can also be used burnable materials. Examples of burnable materials include polyethylene oxide, methylcellulose, ethylcellulose, latex, starch, nut shell or flour, polyethylene or any polymeric microspheres or micrococci.

After the extrusion, the extrudates are dried and calicivirus. Drying may be conducted at elevated temperature, preferably up to 300°C, more preferably up to 200°C. the drying Period can vary, but is typically up to 5 hours, more Pyromania usually carried out at elevated temperature, preferably up to 1000°C, more preferably from 200 to 800°C, most preferably from 300 to 700°C. the Calcination of the extrudates is usually carried out for up to 5 hours, preferably from 30 minutes to 4 hours.

After calcination of the extrudates may be treated to neutralize any catalytically active acid sites, which are still present after calcination, or possibly formed on the surface of the catalyst during calcination. Such acid sites can potentially contribute to the formation of poly(propylene oxide). This processing includes, for example immersion calcinatory extrudates water or steam treatment. For purposes of this invention, the preferred steam treatment. The steam treatment can be carried out by conventional methods, such as the interaction calcinatory extrudates with a stream of steam under low pressure at a temperature of 120 to 180°C for 30 minutes to 48 hours, preferably from 2 to 24 hours. If you carry out immersion in water or steam treatment, conduct stage drying under mild conditions (i.e., at a temperature of 30 to 100°C).

The extrudates appropriately placed in a still from the C cycle of propylene oxide over a layer of adsorbent or transmission of propylene oxide through the adsorption column, containing a cascade of two or more rigid layers are combined in series. The purified product of propylene oxide is separated in time, when the lower thread exits adsorbing layer, or out of adsorbing layer for the last time (during the cycle), or leaves the final layer (using a cascade of adsorption layers).

One of the suitable processing modes is the use of two adsorption columns, where one column is used as the replacement string. In this processing mode is one adsorption column, while the other is switched off from the process, for example, to replace the absorbent material. As soon as the adsorption efficiency of the existing adsorption column drops to an undesirable low level, connect the second adsorption column with fresh adsorbent, while the column with (partial) “deactivated” by the adsorbent is removed from the process for replacement of the adsorbent. Under this regime, the adsorption can be carried out very efficiently. Alternatively, use a single adsorption column, which temporarily withdrawn from the process, when you need to replace the layer. Given the fact that above the layer of miss a huge amount of propylene oxide,the second degree is diluted with a large volume of propylene oxide. From the point of view of the economy of the process the last mode is preferred because it requires only a single adsorption column.

The adsorbent on the basis of magnesium silicate or calcium silicate may be pre-treated with an organic liquid to minimize the heat of adsorption released during the adsorption of poly(propylene oxide) adsorbent. Although the heat of adsorption is much lower than when using activated carbon, a further reduction is useful, because it allows you to save on cooling in the production on an industrial scale. Usually the cooling equipment is very expensive and, therefore, it is preferable, if there is an opportunity to save money on this expensive equipment. Suitable organic liquids which can be used for this purpose include a glycol, such as propylene glycol, as described in US 5493035 (mentioned above), but preferably the organic liquid is selected from ethylbenzene, 1-phenylethanol (methylphenylcarbinol), methylvinylketone or use a mixture of two or more of these liquids. Pre-processing usually involves the interaction of the adsorbent with an organic liquid for a time sufficient to adsorbtion preferably to be such, to the concentration of poly(propylene oxide) was decreased to 0.5 mg/l or less, more preferably up to 0.2 mg/l or less. Moreover, the conditions must be such that the propylene oxide remained in the liquid state. Thus, it can be applied atmospheric pressure at a temperature of from 0 to 34°C. Appropriate stage (a) is conducted at a temperature in the range from 5 to 30°C. Pressure is not critical and can generally be from 0.5 to 10 bar (50 to 1000 kPa), more preferably from 0.5 to 4 bar (from 50 to 400 kPa). Usually the most preferred work at atmospheric pressure. The contact time of the adsorbent and of propylene oxide should be sufficient to achieve the required level of poly(propylene oxide) in the final product of propylene oxide. Typically, the contact time is from 1 minute to several hours, but for practical reasons preferably the contact time is from 5 minutes to 2 hours. When working with a fixed layer average hourly feed rate of the liquid is preferably from 0.5 to 10 h-1.

Further, the invention is illustrated in the following examples, without limiting the scope of the invention data specific options.

Examples

In a 250 ml glass th bath with a temperature of about 15°C. The propylene oxide inside the reactor is stirred at 320 rpm Sample of 5 g of the crude propylene oxide selected through the filter of the P5 silicate of boron (i.e., glass) (1-1,6 μm), when the propylene oxide takes the desired temperature of about 15°C, and the obtained sample to measure the concentration of poly(propylene oxide) having a molecular weight of 2000 and more ([CEA control], in mg/l).

The concentration of poly(propylene oxide) is determined using the combined gel chromatography and evaporative optical scattering detection (GPC-IRO). Used the RBI detector is an ALTECH 500 (ALTECH is a trademark), which is used at a temperature of 55°C with a stream of nitrogen 1.9 ml/min According to the method GPC-IRO poly(propylene oxide) having a molecular weight of 2000 and more separated from the material having a lower molecular weight using GPC and then pass in the RBI detector, where it is sprayed in a mist consisting of small droplets using nitrogen as a sputtering gas. Thus obtained droplets passed through the evaporator tube, where they are partially evaporated, leaving spots of small non-volatile particles. These particles pass through the light beam and the b is calculated from the square of YORO peak found using the equation:

Y=a·b

where Y is the peak area of YORO, WITH the concentration of poly(propylene oxide) and a and b are constants. Constants a and b determined using a series of standard solutions of poly(methyl methacrylate) (molecular weight 24400 Yes) with known concentrations.

Example 1

Charged to the reactor, the crude propylene oxide and define middleware control, as described above.

Next, powdered magnesium silicate with a molar ratio of SiO2/MgO 1,5 containing 17 to 30 wt.% H2O and having the average particle size of 15 microns and a surface area of 500 m2/g is added to the crude propylene oxide in an amount of 0.1% relative to its mass under stirring to obtain a suspension. Stirring is continued for 6 minutes. Then out of the reactor through P5 filter select about 10 grams of the treated propylene oxide, after which the content of poly(propylene oxide) having a molecular weight of 2000 Da or more ([CEA], in mg/l), determined by GPC-IORO, as described above.

The results are presented in table 1 (example 1).

Comparative example 1

Repeat the procedure of example 1 except that instead of silicate MAGN is estaline in table 1.

Example 2

Extrudates of magnesium silicate cylindrical shape having a diameter of 0.8 mm and the ratio length/diameter of from 3 to 4, was obtained as follows.

Extrusion paste obtained by mixing and plasticization of 51 grams powder of silicon dioxide having a surface area of 200 m2/g, 136 grams powder of magnesium silicate having a surface area of 500 m2/g, 145 g of water and 9 grams of conventional extrusion additives. The resulting paste is then ekstragiruyut and obtained from the extruder filament with a diameter of 0.8 mm is cut into cylinders with a length of 2.5 to 3 mm. Obtained extrudates calicivirus at a temperature of 490°C for 7 hours and then exposed to steam under low pressure with a temperature of 160°C for 18 hours. Steamed extrudates are dried at a temperature of 60°C for 5 hours. The extrudates have a surface area of 348 m2/g (BET method according to ISO 9277) and pore volume of 0.9 ml/g, determined according to the method of nitrogen adsorption.

Charged to the reactor, the crude propylene oxide and the CEA control determines, as described above.

Next, the formed extrudates of magnesium silicate, obtained as described above, is added to the crude propylene oxide in kolichestvo. Then out of the reactor through P5 filter select about 10 grams of the treated propylene oxide, after which the content of poly(propylene oxide) having a molecular weight of 2000 Da or more ([CEA], in mg/l), determined by GPC-IORO, as described above.

The results are presented in table 1 (example 2).

Comparative example 2

Repeat the procedure of example 2 except that instead of magnesium silicate add extrudates of activated carbon in the amount of 1% relative to the mass.

The results are presented in table 1 (cf. example 2).

From table 1 one can see that the use of magnesium silicate as an adsorbent in very small quantities (only 0.1 wt.%) gives deleting all of the poly(propylene oxide) of the crude propylene oxide (example 1), while using the same amount of activated charcoal gives less efficiency of adsorption for the removal of poly(propylene oxide) (comparative example 1). When using magnesium silicate in extruded form in the amount of 1 wt.% (example 2) the efficiency of adsorption is comparable with the efficiency of adsorption when using the same amount of activated carbon extrudates (srmi of magnesium silicate is carried out in adiabatic conditions to determine the effect of the used adsorbent for the heat of adsorption.

In the apparatus of the Dewar under adiabatic pressure, equipped with a calorimeter (AISI-304 ADC II from Chilworth) load 140 g of extrudates of magnesium silicate used in example 2, and create an atmosphere of nitrogen. The propylene oxide is supplied from steel 160-ml container at room temperature (20°C) using nitrogen at a pressure of 4 bar (400 kPa). The total pressure in the Dewar up to 2 bar (200 kPa). The amount of propylene oxide corresponds to the total free volume and the volume of pores present in the extrudate of magnesium silicate, thus simulating a fully filled with the absorbent layer.

thermocouple is located in the center of the absorbent layer for temperature measurement. Dewar was incubated for 24 hours.

Number of added components and registered the temperature difference (T) is shown in table 2.

Examples 4 and 5 and comparative example 3

Repeat the procedure of example 3 except that:

the extrudates of magnesium silicate pre-treated with 100 g of ethylbenzene (example 4) or 117 g 70/30.about. a mixture of methylvinylketone and methylphenylcarbinol (example 5), or

- 0.8 mm extrudates of activated charcoal (NORIT RO 0.8 a; NORIT is overpopulated (ON) and registered the temperature difference (T) is presented in table 2.

Table 2 shows that when using adsorbent-based activated carbon is allocated the greatest amount of heat of adsorption which, therefore, gives the greatest increase in temperature. When using extrudates of magnesium silicate obviously stands out much less heat compared to extrudates of activated charcoal. The heat of adsorption in the environment even more reduced when the pre-treatment of the silicate of magnesium ethylbenzene or a mixture of methylvinylketone and methylphenylcarbinol. I believe that this phenomenon is also caused by the fact that the solvent acts as an absorber of heat of reaction and, in the case of example 5, an additional endothermic effect due to mixing of the used solvent with propylene oxide. It is clear that the main advantage of low or minimum allocation of the heat of reaction is that can be minimized or even completely eliminated cooling. This is very attractive from the point of view of the efficiency of the process.

1. The method of purification of propylene oxide contaminated with poly(propylene oxide), comprising the following stages: (a) interaction of liquid is Licata magnesium and/or calcium silicate, with the receipt of the suspension, where the average particle size of the specified powder is from 1 to 100 μm, or deletion of contaminated propylene oxide over at least one layer of the extrudates of the same adsorbent and (b) isolation of the pure product of propylene oxide.

2. The method according to p. 1, wherein stage (b) includes a step of filtering with obtaining a permeate containing the purified product of propylene oxide.

3. The method according to p. 1 or 2, wherein the absorbent material is pre-treated organic liquid.

4. The method according to p. 3, in which the organic liquid is selected from ethylbenzene, methylphenylcarbinol, methylvinylketone or a mixture of two or more of these liquids.

5. The method according to any of paragraphs.1-4, in which the conditions applied in stage (a) is such that the concentration of poly(propylene oxide) was decreased to 0.5 mg/l or less.

6. The method according to any of paragraphs.1-5, in which stage (a) is conducted at a temperature of from 5 to 30°C.



 

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