KR100340637B1 - Improved propylene oxide and styrene monomer co-production procedure - Google Patents

Abstract

The combined process for the production of propylene oxide and styrene produces by-products, which are heavy residues containing metals, mainly sodium, which were previously only suitable for use as low quality fuels. According to the present invention, the heavy residue can be dehydrated in the presence of a strong inorganic acid at a temperature of 150 to 250 ° C. and a pressure below atmospheric pressure to obtain styrene and be used as fuel and 2-phenylethanol, a compound used in the perfume industry. Recover heavy residues substantially free of metal present.

Description

Method for jointly preparing propylene oxide and styrene monomers {IMPROVED PROPYLENE OXIDE AND STYRENE MONOMER CO-PRODUCTION PROCEDURE}

The present invention relates to a process for jointly preparing propylene oxide and styrene monomers.

U. S. Patent No. 5,210, 354 relates to a process for jointly producing propylene oxide and styrene. The improvement lies in reassessing the sodium-containing heavy residue stream obtained as a by-product. According to this method, the sodium-containing heavy residue is mixed with an aqueous acid, preferably sulfuric acid, at relatively mild conditions, for example 20 to 100 ° C, preferably 40 to 90 ° C. The resulting mixture is separated into an immiscible phase, ie an aqueous phase containing sodium and an organic phase having a limited sodium content. A compatible acid catalyst, such as p-toluenesulfonic acid, is added to the organic phase and the resulting mixture is decomposed at high temperatures to produce 1-phenylethanol and styrene monomer, which products can be separated by distillation from residual heavy compounds. have. Temperatures below 70-300 ° C., preferably 120-220 ° C. and pressures below atmospheric pressure, such as 100-400 mm Hg, suitable for evaporating the light compounds are used for the decomposition. Degradation products, 1-phenylethanol and styrene involve increased performance of styrene during the manufacturing process in that 1-phenylethanol is a precursor of styrene. Moreover, heavier decomposition products are useful as fuels with a low sodium content. The most preferred variant of the process is the vacuum evaporation of the organic phase after acid treatment in a membrane evaporator designed to separate about 40% by weight of the volatile compound fraction. This upper fraction can be taken directly into the dehydration zone of a conventional propylene oxide / styrene co-production process where certain components of the hard header fraction are converted to styrene under conditions that are generally applied to 1-phenylethanol dehydration. Membrane evaporator residue is used as a reevaluated fuel because of its low sodium content.

The acid is used in an amount sufficient to react with all the sodium present in the heavy residues. If sulfuric acid is used, less than 0.5 mole of sulfuric acid is used to produce sodium sulfate with a sufficient amount of acid, i.e., sodium of each gram atom, preferably one mole of sulfuric acid per sodium of each gram atom It is used to produce sodium.

U. S. Patent No. 5,276, 235 relates to improvements in the method disclosed in that patent. An important point in this invention is that the acid used to react with sodium present in the heavy residues is used at a molar concentration corresponding to the salt concentration in the aqueous solution produced above the solubility limit. Thus, the salts produced by the reaction create a suspension in the phase mixture, maximizing the density difference between the phases, facilitating separation, and reducing organic contamination in the aqueous phase.

The method disclosed in the above patents has the problem that the yield of styrene is relatively low and produces an aqueous stream with a high salt content contaminated by organic compounds that require purification, for example, by biodegradation.

It is an object of the present invention to obtain a fraction of the styrene yield higher than that of the conventional method and to have a high content of 2-phenylethanol, which is a compound used in the perfume industry, at the same time, producing no water contaminated with metal salts and organic compounds, and suitable It is an object of the present invention to provide an improved process for the co-production of propylene oxide and styrene monomers in which a residue is obtained which is substantially free of non-volatile metals which can be used as fuel.

Known methods for co-producing propylene oxide and styrene are, for example, Spanish Patents 314,229, 314,231, 307,877, 320,168, 323,754, 331,818, 334,098, 335,098 , 343,579 and 365,624. In the first step, ethyl benzene is reacted with molecular oxygen at high temperature to produce ethyl benzene hydroperoxide. Ethyl benzene hydroperoxide is reacted with propylene to produce propylene oxide and 1-phenylethanol. The mixture obtained from the epoxidation reaction is usually alkaline washed and subjected to a series of distillations to separate various components: propylene oxide, unreacted ethyl benzene and 1-phenylethanol, and heavy residues with low content of sodium and other metals. Is left. The 1-phenylethanol stream is dehydrated by a known method such as, for example, disclosed in Japanese Patent Application Laid-Open No. 8019247, for example, using p-toluenesulfonic acid as a catalyst to produce a styrene monomer.

According to the present invention, a heavy residue having a low sodium content has a relatively high content of fractions of 2-phenylethanol, which is a compound used in the styrene and perfume industry, without prior removal of metals, especially sodium, and sodium content used as fuel. It can be used directly as raw material for the production of low heavy residues.

According to the invention, in the presence of a strong inorganic acid serving as a catalyst the heavy residues containing sodium and other metals are dehydrated at a temperature of about 150 to 250 ° C. and under atmospheric pressure, preferably at a pressure of 50 to 400 mmHg. , Light compounds, mainly styrene produced in the reaction, and 2-phenylethanol are evaporated, and then this organic distillate, which represents about 30 to 50% by weight of the heavy residue, is classified by a known method such as distillation to obtain pure styrene and Fractions containing a relatively large amount of 2-phenylethanol are recovered. This fraction can be used as a raw material for preparing perfume grade 2-phenylethanol by known methods. The nonvolatile residue of the reaction consists of heavy organic products, sodium salts and other inorganic acid metals and trace amounts of excess inorganic acid. The metal salt can be easily separated from the organic product, for example by filtration, to obtain a nonvolatile organic residue that is substantially free of sodium and other metals suitable for fuel.

Clearly, according to the present invention, heavy residues in which most sodium and other metals have been removed by known methods such as treatment with aqueous acids and subsequent phase separation can be used as raw material. However, this method is generally undesirable in the context of the present invention because of the inconvenience associated with the form of treatment in question.

The strong inorganic acid used to treat heavy residues containing sodium and other metals is preferably sulfuric acid. Other inorganic acids that can be used within the scope of the present invention include phosphoric acid, pyrophosphoric acid, polyphosphoric acid and fluorophosphoric acid, as well as V ₂ O ₅ solutions in polyphosphoric acid. Moreover, the mixture of the said inorganic acid can also be used.

Strong inorganic acids should be used in amounts above stoichiometric amounts to react with all sodium and other metals present in the heavy residues. Acids per gram atom of sodium and other metals should be used in amounts greater than 1 equivalent. Exceeding the stoichiometric amount is not critical. In general, the strong acid is preferably used in an amount sufficient to provide a free acid concentration in the reaction medium of about 0.001 to 1% by weight after reacting with sodium and other metals. When using a smaller amount, the reaction is relatively slow, while using a larger amount has no further benefit.

Example 1

The dehydration reaction of the heavy residue was carried out in a 50 liter glass reactor equipped with agitation means and connected with a water-cooled condenser at the top. The vacuum was obtained using a water pump providing a constant pressure of 220 mm Hg. 30 kg of heavy residue (1.0 wt% sodium) and 0.7 kg 96% sulfuric acid were initially added. Vacuum was applied at 220 mm Hg and the mixture was slowly heated to 220 ° C. Subsequently, the heavy residue (1.0% by weight sodium) and 96% sulfuric acid were continuously fed at a flow rate of 10 kg / h and 0.23 kg / h, respectively, to give 5.68 kg / of nonvolatile residue containing sodium sulfate and other metals. Obtained from the bottom at an average flow rate of h and organic distillate from the top at an average flow rate of 4.32 kg / h. The organic distillate comprises 44.4% styrene, 12.9% 2-phenylethanol, 1.8% acetophenone and 0.7% 1-phenylethanol, the remainder being mainly oxidized such as water and propylene oxide condensation products, ethers Compounds and the like.

In practical application of the present invention, the styrene production rate is increased by 2.09%. Thus, when the present invention is applied to a commercial manufacturing facility capable of producing 500,000 tons of styrene per year, it is possible to expect an added value of 888,000,000 peseta when calculated from the current styrene price.

Example 2

The reaction was carried out in a similar apparatus as in Example 1, except using a 1 L reactor. Reaction temperature was 193 degreeC, and the pressure was 140 mmHg. 302 gr / h of heavy residue (1.0% by weight of sodium) and 9.0 gr / h of 75% sulfuric acid were continuously added to the reactor. 127.3 gr / h (42.2% by weight of the heavy residues fed) organic distillate and 18.5 gr / h of water were obtained from the top of the reactor and 165.2gr / h of nonvolatile residues (54.7 weights of the heavy residues fed) %) Flow was obtained from the bottom of the reactor. The organic distillate is 66.2 weight percent styrene, 22.0 weight percent 2-phenylethanol, 2.2 weight percent acetophenone, 1.8 weight percent 1-phenylethanol and 7.8 weight percent other oxidation products, such as propylene oxide condensation products. , Ether and the like.

Comparative Example 2

Instead of using a strong inorganic acid stream according to the invention, i.e. 9.0 gr / h, at 21.9 gr / h p-toluenesulfonic acid, an organic acid stream generally proposed for 1-phenylethanol dehydration, under the exact same conditions Example 2 was repeated. The yield was obtained at 49.8% by weight relative to the amount of heavy residues fed, the composition being 0.6% by weight styrene, 25% by weight 2-phenylethanol, 2.2% by weight acetophenone, 18.0% by weight 1-phenylethanol And 54.2% by weight of other oxidation products, such as propylene oxide condensation products, ethers and the like.

This example illustrates the advantages of the heavy residue treatment according to the present invention.

Example 3

The organic distillate stream obtained in Example 1 was fractionated by distillation to recover a stream containing 99.3% rich styrene and 24.7% 2-phenylethanol, the flow being perfume grade 2-phenyl according to a known process. It can be effectively used as a raw material for recovering ethanol.

Example 4

The non-volatile residue containing sodium sulfate and other metals obtained in Example 1 was filtered through a fourth porous glass plate at 80 ° C., and filtered material containing less than 0.1% sulfate ash, which can be used as a reevaluated fuel. Obtained.

The above examples are intended to illustrate the present invention and do not limit the scope of the present invention.

According to the method for the purpose of the present invention, a fraction of styrene yield is higher than that of the conventional method and a high content of 2-phenylethanol, a compound used in the perfume industry, is obtained simultaneously, and water contaminated with metal salts and organic compounds is not produced at all. And a residue free of nonvolatile metals that can be used as a suitable fuel is obtained.

Claims (7)

Oxidation of ethyl benzene with molecular oxygen yields ethyl benzene hydroperoxide, propylene is epoxidized with ethyl benzene hydroperoxide to form propylene oxide and 1-phenylethanol, and then the epoxidation product is alkali washed and distilled. Isolating propylene oxide, excess ethyl benzene and 1-phenylethanol, alkali washing one or more process streams to produce a heavy residue containing sodium and other metals, and dehydrating 1-phenylethanol to yield styrene. In the method for jointly producing a propylene oxide and styrene monomer, A heavy residue containing sodium and other metals in the presence of a strong inorganic acid as a catalyst, at a temperature of 150 to 250 ° C. and a pressure below atmospheric pressure, the stoichiometry of the strong inorganic acid to the sodium and other metals contained in the residue. A method characterized by dehydration using an amount in excess of the theoretical amount. The method of claim 1 wherein the strong inorganic acid is sulfuric acid. 3. Process according to claim 1 or 2, characterized in that the amount of strong inorganic acid is higher than the amount corresponding to the stoichiometric ratio for sodium and other metals present in the heavy residues. A process according to claim 1, characterized in that the dehydration reaction of heavy residues containing sodium and other metals in the presence of strong inorganic acids is carried out at an absolute pressure of 50 to 400 mmHg. The process according to claim 1, wherein the organic distillate obtained by dehydrating the sodium-containing heavy residue with a strong inorganic acid is distilled to obtain a fraction having a relatively high content of pure styrene and 2-phenylethanol. The non-volatile residue obtained by dehydrating the heavy residue containing sodium and other metals in the presence of a strong inorganic acid is filtered to remove the inorganic salts and sodium and other metals which can be suitably used as fuels. Obtaining a residue which is virtually non-existent. 4. The process according to claim 3, wherein the amount of strong inorganic acid is selected such that excess free inorganic acid remains at a concentration of 0.001 to 1% by weight after reacting with sodium and other metals present in the heavy residues.