CS97591A3 - Process of sulfurized styrene residues regeneration - Google Patents

Description

- 1 -

Method, regeneration of sulfurized 3> TJ X - o * Γ> O o <c- o GO □ · “o» - O i oo - <m iO J 00 • w. N cn - styrene residues £

Technical Field · i! ♦ i * 1

The invention relates to a process for the regeneration of sulfurized ester residues. In particular, the invention relates to a process for the regeneration of sulfurized styrene residues obtained by producing styrene by catalytic dehydrogenation of ethylbenzene.

Background Art

It is known that styrene obtained by catalytic dehydrogenation of ethylbenzene carried out at high temperatures can be recovered from the crude reaction liquid by fractionated desalting using a series of fractionation columns.

Since the styrene has a tendency to polymerize at a relatively low distillation temperature, it is well known that some monomer conversion to the polymeric compound manifests itself in this process, causing product loss. Corrosion inhibitors are generally used to prevent such losses. A highly effective inhibitor, preferably used in industry, is sulfur. In fact, this element, aligning with other known organic compounds, such as dinitrophenols, mononitrophenols and dinitrophenols containing alkyl substituents in the core, phenols with nitrogen and the like, provides considerable technological, manufacturing and economic advantages. It is a known fact that, in addition to being more expensive and having higher toxicity, organic compounds can lead. the corrosion of the equipment due to the contents of the oxygen-residue residues may still be explosive in the off-state.

However, the use of sulfur as a styrene polymerization inhibitor results in the presence of this element in the residual material in the final distillation column. Therefore, the residual material obtained from the distillation column contains; - low boiling hydrocarbons boiling below 200 ° C, i · .1. i · 1 - 2 - such as, styrene, cumene, ¢ (, - methylstyrene, methylethylbenzenes, methylvinylbenzenes, butylhenzenes and the like, - high boiling hydrocarbons boiling above 200 QC, formed in the dehydrogenation section as polynucleic compounds, - poles materials such as polystyrene, sulfurized polystyrene and sulfur total sulfur content is generally 5 to 3.0%, preferably 10 to 20% f based on the total residues, and have a very low commercial value and technique. it is known that their elimination is associated with great difficulty.

In fact, the combustion of these residues brings environmental and corrosion problems due to sulfur dioxide emissions. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for obtaining styrenudestillation of residual sulfur-containing materials as a polymerization inhibitor having the aforementioned drawbacks. Now with. surprisingly, it has been found that blending such sulphurized residual materials with gas oil and subjecting the obtained mixture to thermal cracking at temperatures above 400 GC and fractional distillation and hydrodesulphurization of medium fractions having a boiling point of 140 to 390 is achieved.

SUMMARY OF THE INVENTION

The principle of the process for the regeneration of sulfur residues, which is obtained in the purification of styrene in the process of catalytic dehydrogenation of ethylbenzene, according to the invention, in the case of the process according to the invention. b) the gas mixture is added to the sulfur residues, b) the mixture obtained is subjected to a thermal cracking at a temperature above 400 ° C, c) the mixture thus obtained is subjected to fractionated distillation, d) a distillation fraction boiling at 440-390 ° C. is the hydrosulfurization process and e) sulfur is obtained from the sulfurized hydrogen thus obtained.

The sulfur thus obtained is either. reused as an inhibitor of polymerization. styrene or is used in conventional fields of its use,

It will be apparent to those skilled in the art the importance of this method of the invention, since the process allows the regeneration of sulfur-containing styrene residues without air contamination or of technological problems with regard to a considerable amount of styrene produced. In fact, styrene is another used monomer for the production of resins, plastics, elastomers, synthetic rubbers, and the like.

The process of the invention is used to obtain and regenerate sulfur residues resulting from the purification of styrene in which ethyl benzene is obtained by conventional catalytic dehydrogenation; however, the applicability of the method of the invention is not limited by the manner in which styrene is obtained. In other words, the process according to the invention is applicable to any styrene-containing feedstock which is contaminated with various higher-boiling-polymeric or non-polymeric materials and which in particular contains sulfur as a polymerization inhibitor.

The gaseous oil used in the process of the invention is an oil typically produced by vacuum distillation processes for oil products and generally has a boiling point of 390 to 550

The amount of sulfur residues obtained during the purification of the styrene, which may be added to the gas oil, is not of decisive importance: it is generally preferred to use 0.1% by weight with respect to the gas oil; 0.5 to 10% by weight. In the process according to the invention, the gas oil and sulfur residue mixture is subjected to a thermal cracking process in which the mixture is heated to a temperature of 465-500 ° C in a furnace equipped with an internal heating coil.

The residence time of the mixture in the furnace is 1 to 15 minutes.

The cracking reaction is preferably terminated in the following period where the residence time of the mixture is 10 to 30 minutes. Upon leaving the vessel, the mixture is cooled to 480-400 ° C and then passed to a conventional fractionation column where individual product fractions are separated from each other. ? - I Separate the column from the head. they remove light gases generally containing hydrogen, ethane, propene and butane together with the sulphurized hydrogen, the light gases are compressed and introduced into a known amine washing machine to obtain the sulfurized water and then the sulfur.

The fractions boiling in the gasoline range (70-140 ° C) can be washed and blended with other gasoline components or introduced into catalytic hydrodesulfurization units where in the presence of hydrogen and carbonate. a cobalt-molybdenum-based or nickel-amolybdenite-based lyser at 250 to; 350 ° C and at a pressure of 2 to 8 µM and first cleaned from. foreign admixtures and then introduced into the octane conversion unit (where isomerization and reforming are carried out).

The intermediate distillates boiling at 140 DEG-390 DEG C. and containing kerosene (b.p. 140 DEG-240 DEG C.) and gas oil (boiling point 240 DEG-390 DEG C.) are subjected to catalytic hydrodesulfurization.

Catalytic dehydrodesulfuration process; It consists of admixing medium distillates to hydrogen and heating the resulting mixture to a temperature of 350 to 420 ° C and a pressure of 2 to 8 MPa, in the presence of a catalyst, preferably cobalt and molybdenum for 1 to 60 minutes. After this time, the unreacted hydrogen and the hydrogenated hydrogen formed by the reaction are separated from the mixture. The residual product obtained is used in mixtures usually sold for combustion in diesel engines or for heating purposes.

Sulfurized hydrogen is obtained by amine washing and converted to elemental sulfur by methods known in the art, for example

Cleus process. The remainder, not transferred in the thermal cracking process, removed from the fractionation column - from its bottom, boiling above 390 ° C - is subjected to stripping and is used as a heavy fuel by conventional means. Adding residual sulfurized styrene materials to the gas oil and subjecting the obtained heat-boiling process mixture to numerous surprising and unexpected advantages In fact, it has been found that pyrolysis reaction is promoted during the cracking step to produce useful products. Therefore, by adding styrene residues and working at the same temperature and under the same pressure conditions it is possible to obtain an increase in pyrolysis reaction with a subsequent higher yield of useful fractions or the yield of useful fractions is the same, but the reduction reaction can be carried out at lower temperatures of about 14 to 15 GC, thereby reducing Cleaning of the cracking furnace hyhřívacíchhadů 60%, causing great-elongation working time. without stopping the process to by purification of the heating coils in a cracking furnace.

A further advantage of using styrene sulphurized residues in the gas oil cracking process is the conversion of high-boiling products contained therein into an oil fraction having a higher additional value.

In addition, the process of the present invention allows the suppression of sulfur dioxide missions occurring in the combustion of the sticky resins obtained in the process of producing styrene, which entails great ecological benefits and also a significant reduction or even suppression of consumption. sulfur used as a styretyl polymers inhibitor. the following examples illustrate the invention but do not limit it in any way. By way of example, reference is made to the accompanying drawing, which illustrates the method; of the invention. ii ?; What? £ ώ iš

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EXAMPLES Example 1. Ť

1200 t / day vacuum oil distillation gas is introduced through the pipeline, boiling point 390-320 ° C, with a sulfur content of 2.3% by weight and a density (15/4 ° / 0.928 kg / l). To this, the styrene residues, obtained by the catalytic dehydrogenation, are fed through a line 2 of 3% by weight of styrene residues. ethylbenzene. Styrene residues have the following composition: - hydrocarbons boiling below 200 ° C 20% - hydrocarbons boiling above 200 ° C. 35% - polymer products 33% - sulfur? 12%

The gas oil mixture is heated to about 300 ° C and fed to a furnace equipped with a heating coil 4. The mixture is heated to 495 ° C and kept at that temperature for about 7 minutes.

The pressure at the outlet of the heating coil 4 is kept constant at 1.5 MPa, while the inlet pressure at the beginning of the operation with the clean coil is 2.5 MPa. The mixture leaving port 2 is then fed into a 1.5MPa vessel with a residence time of about 15 minutes. As a result of the endothermic cracking reaction, the temperature dropped from 495 at the inlet to 440 ° C. output.

The mixture is then cooled to about 390 ° C and fed into a normal fractionation column 6. The non-condensed light gas is removed from the head 7 of the fractionation column 6, compressed and fed into the amine scrubber to obtain the sulfated hydrogen, which is subsequently converted to sulfur in a manner known per se.

The liquid gasoline obtained in the upper portion 8 of the fractionating column 6 is fed to the de-sulphurization unit of the gasoline and then subjected to the known isomerization and reforming processes. O

Kerosene having a boiling point of 140 to 240 ° C; is diverted - 7 - from the upper middle section. And a gas oil. The fractionation wheel I 6 is removed from the lower middle portion 10, mixed with each other, and passed to the desulfurization reactor 13 after the addition of hydrogen via line 12 in an amount of about 0.3% by weight of the mixture of petroleum and gas mixture. oils. In the desulfurization reactor 13, kerosene and gas oil in the form of a mixture are heated to a temperature of 370 ° C under a pressure of 5.7-5.8 MPa and in the presence of a catalyst based on cobalt and molybdenum. The gaseous hydrogen-containing gases leaving the reactor 13 through the conduit 14 undergoing the mashing process and from these gases to obtain sulfurized hydrogen are converted to elemental sulfur by the Cl &amp;amp;

Desulfurized mixture. leaving the desulfurization reaction via line 15 is stored. Residues from bottom 11 of fractionation column 1d are used as fuel. During the experiment, the furnace inlet pressure gradually increases to 3.8 MPa after 61 days of operation. At this point, the pxprocess is interrupted and the heating coil 4 is cleaned in a manner known per se for removing coke deposits. The experimental results are shown in Table I. Example 2 / Comparative Test /

AND

The procedure of Example 1 was repeated without adding 3% of atyrene residues. The results of this test are also shown in Table I. ‘2 values shown in Table I clearly show that the presence of styrene residues leads to a significant increase in unit productivity, operating under otherwise identical conditions.

Table 1 Example 1 Example 2 Column A / Gas% by weight results A 1.4 8 / petrol% by weight 4 / * 3.1 C / petroleum% by weight '6.5 *' 5.0 D / gas oil% weight 23.1 14.9 E / residues% 64.9 -; 76.0 Heated Snake Lifetime Days 4 6Ί 85 Total Component Production B + C + D from the Heating Hose Lifetime / Tons / 25400 23460 Example 3

In the method of Example 1, a mixture of gas oil and styrene residues in furnace X was treated at 485 ° Ga under the same inlet and outlet pressures. The results are shown in Table II »Example 4 / Comparative Example /

The procedure of Example 3 was repeated but without the addition of 3% styrene residues. The results are shown in Table II.

Table II Column Outlet Results Example 3 1.1. 0.8 A / gas weight 8 / petrol% weight 3.4 2.4 C / kerosene weight 4.9 4.9 - n / gas-oil -% - weight ——-— 1-7- , -6 ——— E / residues. % by weight 73.0 79.8 Heated Snake Lifetime .4 106 • 140 Total Snapper Production 8 + C + D over Heater Lifetime / Tons / 33930 32600 - 9

Industrial usability.

The method of refining the sulphurized styrene residues obtained in the production of styrene by catalytic dehydrogenation ethylbenzene, in which these residues are mixed with gas oil and subjected to cracking, fractional desalting and hydrodesulphurization of heavy fractions having a boiling point: greater than 140 ° C. In the process, the sulfur dioxide and the sulfur consumption used as the polymerization inhibiting agent in the styrene production process are not significantly reduced. * * £ * í 'I,' ·

Claims (8)

A process for the regeneration of styrene-treated sulfurized styrene residues, characterized in that the sulfurized residues are added to the gas oil, the mixture obtained is subjected to a thermal cracking at a temperature above 400 ° C, the treated mixture is subjected to fractional distillation, the temperature distillate fraction boiling point 140 DEG-390 DEG C. is subjected to catalytic-hydrodesulphurization, and elemental sulfur is obtained from the sulfurized hydrogen thus obtained. 2. Process according to claim 1, characterized in that the gas oil used is a gas oil obtainable by vacuum distillation of the products having a boiling point of from 390 to 550 ° C. 3. Process according to claim 1 or 2, characterized in that the added amount of sulfur residues obtained during the purification of the oil according to the gas oil is greater than 0.1% by weight and preferably is 0.5 to 10% by weight. %, based on the weight of the gas oil. ( 4. Process according to claim 1, characterized in that the thermal cracking is carried out at a temperature of 465 to 500 ° C. at a pressure of 1 to 5 MPa. 5 ;. 4. Process according to claim 4, characterized in that the thermal cracking is carried out for 1 to 15 minutes in a furnace equipped with a heating coil and is completed in a further vessel at a time of 10 to 30 minutes. 6. A method according to claim 1, wherein the heat-cracking mixture is cooled to a temperature of about 380 to about 400 and introduced into a fractionation column. 7. Process according to claim 1, characterized in that the distillation fractions with a boiling point of 140 DEG-390 DEG C. are mixed with hydrogen and then maintained at 350 DEG to 420 DEG C. under a pressure of 2 to 8 .mu.g in the presence of catalyst. preferably the catalyst comprises cobalt and molybdenum. 8. The process of claim 17 wherein the sulfur is recovered from the sulfurized hydrogen by a process. and