UM PROCESSO E APARELHO PARA PREPARAR UMA COMPOSIÇÃO DE ESTIRENO PURIFICADA A PARTIR DE MATÉRIA-PRIMA QUE CONTÉM ESTIRENO

Abstract

A PROCESS AND APPARATUS FOR PREPARING A PURIFIED STYRENE COMPOSITION FROM STYRENE-CONTAINING RAW MATERIAL. The present invention relates to a method for preparing a purified styrene composition with a styrene yield of at least 80%, wherein the method comprises providing a crude composition containing styrene and subjecting the crude composition to at least one crystallization step, wherein the at least one crystallization step comprises at least one static crystallization stage and at least one dynamic crystallization stage.

Description

1 / 46 “A PROCESS AND APPARATUS FOR PREPARING A PURIFIED STYRENE COMPOSITION FROM STYRENE-CONTAINING RAW MATERIAL”

[0001] The present invention relates to a method for preparing a purified styrene composition from a styrene-containing feedstock, such as pygas, from an ethylbenzene-styrene-containing stream produced in an ethylbenzene / styrene monomer (EBSM) process, from a styrene-containing stream produced by pyrolysis of polystyrene or similar. Furthermore, the present invention relates to an installation in which the method can be carried out. BACKGROUND OF THE INVENTION

[0002] Styrene is an important building block for polymers such as polystyrene, acrylonitrile-butadiene-styrene (ABS) / styreneacrylonitrile (SAN) resins, styrene-butadiene copolymer (SB) latex, unsaturated polyester resins, styrene-butadiene rubber (SBR) elastomers, and latex. It is one of the most widely traded basic chemicals, and over 30% of annual styrene production is traded internationally. Predominantly, styrene is produced from the feedstocks benzene and ethylene. Benzene is alkylated to produce ethylbenzene (EB), and EB is converted to styrene through the conventional dehydrogenation process or the ethylbenzene / styrene monomer (EBSM) process, respectively, or the propylene oxide / styrene monomer (POSM) process. Typically, styrene plants are located Petition 870220092366, dated 07 / 10 / 2022, page 11 / 244 2 / 46 near ethylene crackers due to the gaseous nature of ethylene, which makes it relatively difficult to transport compared to benzene.

[0003] In addition to the self-production route via EBSM / POSM, styrene is also present in hydrocarbon streams, such as pyrolysis gasoline obtained from the steam cracking of naphtha, hydrocarbon fraction obtained from the pyrolysis of polystyrene, gas oils, etc. The extraction of styrene from these hydrocarbon streams, although in much smaller quantities compared to EBSM / POSM, presents an attractive economic opportunity for the operator due to the low cost of the raw material. However, this separation is technically difficult due to the presence of near-boiling molecules and impurities from the initial raw material. The removal of near-boiling molecules, such as mixed xylenes, ethylbenzene, etc., from styrene by normal distillation is a process that consumes a lot of energy. Solvent-based extractive distillation techniques, as advocated in Patent No. US 5,849.In 1982, devices were developed and commercially deployed that remove nearby boiling molecules with reduced energy consumption.

[0004] Although producing high-purity styrene (>99.8% by weight), the extractive distillation route generally yields styrene that, compared to EBSM / POSM styrene, contains impurities such as chromophores, sulfur, oxygenates, etc. in the initial feedstock. These impurities affect the downstream polymerization process and, therefore, the properties of the polymer produced. Different methods for Petition 870220092366, dated 07 / 10 / 2022, page 12 / 244 3 / 46 Impurity removal methods were mentioned in the prior art based on chemical or adsorbent treatment. Chemical treatment may involve the use of dienophiles, nitric acid, alkali, etc. The use of adsorbents may involve clays, alumina, etc. These additional treatment steps can produce a marketable product that meets the ASTM specification for styrene monomer. However, styrene losses due to unwanted polymerization, polymer formation in adsorbent beds due to the inherent heat sensitivity of styrene, and the use of complex design precautions to prevent polymerization and complex equipment make these methods a nuisance for the owner / operator.

[0005] In addition, document JP S61-218,535 A describes a styrene preparation process comprising the steps of dehydrogenating ethylbenzene to obtain a mixture of styrene and ethylbenzene, distilling this mixture to obtain crude styrene having an ethylbenzene concentration of at most 4% by weight, and then subjecting the crude styrene to continuous crystallization. Continuous crystallization produces a purified styrene composition and a residual liquor stream containing impurities near and co-boiling along with styrene. Due to the continuous nature of the crystallization operation, a considerable amount of styrene is left in the residual liquor. Because of this, the residual liquor is recycled and mixed with the distillation column feed to recover the styrene as the bottom fraction, while the near-boiling impurities are removed in the top fraction. Thus, despite a low styrene yield Petition 870220092366, dated 07 / 10 / 2022, page 13 / 244 4 / 46 Comparable to the process, there is a heavy penalty in the distillation section, both from a capital and energy standpoint, to remove impurities from the overall system. Another disadvantage of this process is that co-boiling or very close-boiling impurities with styrene, such as phenylacetylene, can only be removed from the system by means of a styrene purge from the distillation section, in which the co-boiling or very close-boiling impurities are purged along with the styrene. This represents a loss of styrene in the overall system.

[0006] Considering the above, the underlying objective of the present invention is to provide a method for preparing a high-yield styrene-purified styrene composition from a styrene-containing feed composition, such as from pygas, from an ethylbenzene-styrene-containing stream produced in an EBSM process, from a styrene-containing stream produced by pyrolysis of polystyrene or similar, which reliably and efficiently removes impurities such as color-inducing species, sulfur and oxygenates, and in particular impurities with a boiling point close to that of styrene, such as phenylacetylene, ethylbenzene, mixed xylenes, propylbenzene, ethyltoluene, alpha-methylstyrene, etc., from styrene in an energy-efficient manner and requiring a low capital cost installation, even if impurities are contained in a comparable high quantity in the styrene-containing feed composition, in order to economically obtain a very pure styrene composition with a high styrene yield. SUMMARY OF THE INVENTION Petition 870220092366, dated 07 / 10 / 2022, page 14 / 244 5 / 46

[0007] According to the present invention, this objective is satisfied by providing a method for preparing a purified styrene composition with a styrene yield of at least 80%, wherein the method comprises providing a crude composition containing styrene and subjecting the crude composition to at least one crystallization step, wherein the at least one crystallization step comprises at least one static crystallization stage and at least one dynamic crystallization stage.

[0008] This solution is based on the surprising finding that subjecting a composition containing crude styrene to crystallization comprising at least one static crystallization stage and at least one dynamic crystallization stage, such as a falling film crystallization stage or a suspension crystallization stage, and preferably subjecting a composition containing crude styrene to molten material crystallization comprising at least one static molten material crystallization stage and at least one dynamic molten material crystallization stage, not only impurities such as color-inducing species, sulfur and oxygenates, and in particular impurities with a boiling point close to that of styrene, such as phenylacetylene, ethylbenzene, mixed xylenes, propylbenzene, ethyltoluene, alpha-methylstyrene, etc., are reliably and completely, or at least nearly completely, removed from styrene, even if the impurities are contained in a comparable high quantity in the styrene-containing composition, but the respective method is,. Petition 870220092366, dated 07 / 10 / 2022, page 15 / 244 6 / 46 additionally, it is energy efficient and is characterized by a high styrene yield of at least 80%. Thus, the method according to the present invention combines a high purity of the purified styrene composition with a high styrene yield and high energy efficiency. At least one dynamic crystallization step leads to a very large separation of impurities from the styrene, i.e., to a highly purified styrene composition, but requires a comparatively high concentration of styrene in the mother liquor of at least 90% by weight. Therefore, one or more dynamic crystallization steps alone do not allow obtaining a highly purified styrene composition with a high styrene yield.However, by performing at least one static crystallization step with mother liquor having a styrene content of less than 90% by weight, such as between 50% and less than 90% by weight, like the styrene-deficient mother liquor obtained with at least one dynamic crystallization step, additional styrene can be separated from this styrene-deficient mother liquor, since static crystallization does not require such high concentrations of styrene in the mother liquor for efficient styrene separation as dynamic crystallization. Consequently, the combination of at least one dynamic crystallization step and at least one static crystallization step allows for efficient styrene crystallization from mother liquors containing 50% to 99.9% by weight of styrene. This wide operating window, in turn, allows for a high styrene yield of at least 80%. Furthermore, as a consequence of the above, no. Petition 870220092366, dated 07 / 10 / 2022, page 16 / 244 7 / 46 any recycling of the styrene-deficient mother liquors obtained in the last crystallization step to a distillation step is entirely unnecessary. Thus, large distillation columns are not required, leading to low operating costs and low capital costs for large distillation columns. In short, the method according to the present invention allows economically and with a high styrene yield of at least 80% to purify a styrene-containing composition of impurities and even impurities with a boiling point close to that of styrene.For these reasons, the method according to the present invention is particularly suitable for the preparation of a purified styrene composition from styrene-containing compositions, which until now could not be economically reasonable to use for the preparation of pure styrene, such as in particular from pygas, a stream containing ethylbenzene and styrene produced in an EBSM process, a styrene-containing stream produced by pyrolysis of polystyrene and the like.

[0009] According to the present invention, the method is carried out in order to prepare a purified styrene composition with a styrene yield of at least 80%. Styrene yield means, in this context, the ratio of the amount of styrene included in the crude composition divided by the amount of styrene included in the purified styrene composition. Preferably, the styrene yield of the method is greater than 90%, more preferably greater than 95%, and most preferably greater than 98%.

[0010] As set forth above, the method according to the present invention comprises the step of providing a Petition 870220092366, dated 07 / 10 / 2022, page 17 / 244 8 / 46 crude composition containing styrene and subjecting the crude composition to at least one crystallization step. The step of providing a crude composition may comprise that a feed composition containing styrene is directly subjected to at least one crystallization step or that a feed composition containing styrene is processed first, for example, using one or more distillation steps or other steps, before the processed composition is subjected to at least one crystallization step.In order to make a strict distinction between the respective styrene-containing compositions, in this document “crude styrene-containing composition” or “crude composition” means the styrene-containing composition that is subjected to at least one crystallization step, while “styrene-containing feed composition” means a composition from which the “crude styrene-containing composition” can be prepared, and “purified styrene composition” means the styrene composition that is obtained after crystallization.

[0011] Furthermore, as is known in the art, crystallization processes or stages, respectively, can typically be carried out in multiple steps, that is, in several crystallization stages. In view of this, in the present application, a crystallization step is defined as comprising one or more crystallization stages.

[0012] As established above, the method according to the present invention is particularly suitable for removing impurities, and in particular impurities with a boiling point close to that of styrene, from a crude composition containing styrene. Therefore, it is preferable that the Petition 870220092366, dated 07 / 10 / 2022, page 18 / 244 9 / 46 crude composition used in the method contains one or more impurities selected from the group consisting of color-inducing species, sulfur species, meta- and ortho-xylenes, ethylbenzene, phenylacetylene, cumene, n-propylbenzene, alpha-methylstyrene, ethyltoluene, organochlorine species, organonitrogenous species and arbitrary mixtures of two or more of the aforementioned impurities.

[0013] Preferably, the crude composition contains as impurities one or more sulfur species and, preferably, one or more sulfur species selected from the group consisting of alkyl, naphthenes or aromatic mercaptans, alkyl, naphthenes or aromatic disulfides, alkyl, aromatic, naphthenes or vinylthiophenes (such as dimethylthiophenes or vinylthiophenes), hydrocarbon compounds containing oxygenated sulfur or any other hydrocarbon compound that includes at least one sulfur atom in its molecule and arbitrary combinations of two or more of the same, such as, for example, those with a boiling point of 130 to 150 °C, and arbitrary combinations of two or more of the same.

[0014] In addition, it is preferable that the crude composition contain as impurities one or more color-inducing species comprising at least one of the following: fulvenes, conjugated diolefins, oxygenated species, oxygenated sulfur species, styrene oligomers, alkynes, and hydrocarbon compounds comprising conjugated olefin and alkyne linkages, and any other compound that imparts to styrene a color greater than 10, as defined on the Pt-Co scale, such as, for example, those with a boiling point of 130 to 150 °C. For example, the species Petition 870220092366, dated 07 / 10 / 2022, page 19 / 244 10 / 46 oxygenated compounds can be water, an alcohol, a ketone, and / or an aldehyde, while fulvenes and their derivatives are suitable examples of diolefins.

[0015] With respect to the styrene content of the crude composition, the present invention is not particularly limited. For example, the styrene content of the crude composition may be not greater than 50% by weight or greater than 50 to 80% by weight or greater than 80 to 95% by weight or greater than 95 to 99% by weight or greater than 99% by weight, as well as greater than 99.8% by weight.

[0016] According to a particular preferred embodiment of the present invention, crystallization is carried out as molten material crystallization. Therefore, it is preferable that at least one static crystallization stage is at least one static molten material crystallization stage and that at least one dynamic crystallization stage is at least one dynamic molten material crystallization stage.

[0017] In particular, good results are obtained when at least one dynamic crystallization stage is a falling film crystallization stage and, more preferably, a falling film molten material crystallization stage. Alternatively, but less preferably, at least one dynamic crystallization stage is a suspension crystallization stage and, more preferably, a suspension molten material crystallization stage. Preferably, at least one dynamic crystallization stage is carried out before, i.e., upstream of, at least one static crystallization stage. Petition 870220092366, dated 07 / 10 / 2022, page 20 / 244 11 / 46

[0018] In a further development of the idea of ​​the present invention, it is suggested that the method comprises a crystallization step, which comprises one to ten static crystallization stages and one to ten dynamic crystallization stages. Even more preferably, the method comprises a crystallization step, which comprises one to five static crystallization stages and one to five dynamic crystallization stages. If the method comprises two or more dynamic crystallization stages and / or two or more static crystallization stages, each of the dynamic crystallization stages is fluidly coupled with one or two other dynamic crystallization stages, each of the static crystallization stages is fluidly coupled with one or two other static crystallization stages, and one of the dynamic crystallization stages is fluidly coupled with one of the static crystallization stages.In other words, the stages of dynamic crystallization are arranged in series with each other, and the stages of static crystallization are arranged in series with each other. The numbering starts from the static crystallization stage and the dynamic crystallization stage, which are fluidly coupled. Thus, if the crystallization comprises four stages of dynamic crystallization and four stages of static crystallization, the first dynamic crystallization stage and the first static crystallization stage are those that are coupled to each other. The first dynamic crystallization stage is fluidly coupled to the second dynamic crystallization stage, which is also coupled to the third dynamic crystallization stage, in. Petition 870220092366, dated 07 / 10 / 2022, page 21 / 244 12 / 46 that the third stage of dynamic crystallization is also coupled to the fourth stage of dynamic crystallization. Similarly, the first stage of static crystallization is fluidly coupled to the second stage of static crystallization, which is also coupled to the third stage of static crystallization, wherein the third stage of static crystallization is also coupled to the fourth stage of static crystallization. In both series, the first stage of crystallization is the most upstream stage of crystallization, wherein the second, third, and fourth stages of crystallization are located downstream of the first stage of crystallization.

[0019] According to a first particular preferred embodiment of the present invention, the method comprises a crystallization step, which comprises a static crystallization step and a dynamic crystallization step. In this variant, the crude composition is preferably fed into the dynamic crystallization step in order to produce a styrene-enriched crystallized fraction and a styrene-deficient residue fraction. The styrene-deficient residue fraction obtained in the dynamic crystallization stage mainly contains the styrene-deficient mother liquor and is fed into the static crystallization stage as feed. Also in the static crystallization stage, a styrene-enriched crystallized fraction and a styrene-deficient residue fraction are produced, wherein the styrene-enriched crystallized fraction obtained in the static crystallization stage is fed into the dynamic crystallization stage and mixed there with the composition. Petition 870220092366, dated 07 / 10 / 2022, page 22 / 244 13 / 46 crude is fed into the dynamic crystallization stage. The styrene-deficient residue fraction obtained in the static crystallization stage is removed, while the styrene-enriched crystallized fraction obtained in the dynamic crystallization stage is removed as the purified styrene composition. In principle, the crude composition can alternatively be fed to the above static crystallization stage, i.e., the static and dynamic crystallization stages can be arranged in reverse order to the description above. However, better results are obtained when the crude composition is fed into the dynamic crystallization stage. For completeness, it should be noted that the aforementioned terms "styrene-enriched crystallized fraction" and "styrene-deficient residue fraction" refer to the styrene content of the input to the respective crystallization stage and not to the styrene content of the crude composition.In other words, the styrene-enriched crystallized fraction obtained in the static crystallization step has a higher styrene content than the input to this static crystallization step (which is the styrene-deficient residue fraction fed from the dynamic crystallization step to the static crystallization step), and the styrene-deficient residue fraction has a lower styrene content than the input to this static crystallization stage.

[0020] According to a second preferred embodiment of the present invention, the method comprises a crystallization step, comprising two to five stages of static crystallization and two to five stages Petition 870220092366, dated 07 / 10 / 2022, page 23 / 244 14 / 46 of dynamic crystallization. Preferably, the crude composition is fed into the first of two to five stages of dynamic crystallization in order to produce a first crystallized fraction enriched with styrene and a first residue fraction deficient in styrene, wherein the first crystallized fraction enriched with styrene is fed into the second of the two to five stages of dynamic crystallization, wherein in any of the second and optional third to fifth stages of dynamic crystallization a crystallized fraction enriched with styrene and a residue fraction deficient in styrene are produced,wherein each of the styrene-enriched crystallized fractions produced in the second and third to fourth optional dynamic crystallization stages is fed into a downstream dynamic crystallization stage, and each of the styrene-deficient waste fractions produced in the second and third to fifth optional dynamic crystallization stages is fed into an upstream dynamic crystallization stage. The first styrene-deficient waste fraction is fed into the first of two to five static crystallization stages in order to produce a second styrene-enriched crystallized fraction and a second styrene-deficient waste fraction.where the second styrene-enriched crystallized fraction is fed into the first dynamic crystallization stage, and the second styrene-deficient residue fraction is fed into the second of two to five static crystallization stages. In any of the second and third to fifth static crystallization stages, Petition 870220092366, dated 07 / 10 / 2022, page 24 / 244 Optionally, a styrene-enriched crystallized fraction and a styrene-deficient residue fraction are produced, wherein each of the styrene-deficient residue fractions produced in the second and third to fourth optional static crystallization stages is fed into a downstream static crystallization stage, and each of the styrene-enriched crystallized fractions produced in the second and third to fifth optional static dynamic stages is fed into an upstream static crystallization stage. In principle, the crude composition can be fed into one of the static crystallization stages, i.e., the static and dynamic crystallization stages can be arranged in reverse order to the description above. However, better results are obtained when the crude composition is fed into one of the dynamic crystallization stages.

[0021] In an alternative variant to the variant described above, the crude composition is fed into the second of the two to five dynamic crystallization stages and not into the first dynamic crystallization stage, wherein the first to fifth is again viewed in the upstream to downstream direction. Again, the most upstream dynamic crystallization stage (i.e., the first dynamic crystallization stage) is the one that receives a styrene-enriched crystallized fraction from the first static crystallization stage and from which a styrene-deficient residue fraction is fed into the first static crystallization stage, while the most downstream dynamic crystallization stage is the one in which the Petition 870220092366, dated 07 / 10 / 2022, page 25 / 244 16 / 46 of the purified styrene composition is removed. Similarly, the most upstream static crystallization stage (i.e., the first static crystallization stage) is the one that receives a styrene-deficient residue fraction from the first dynamic crystallization stage and from which a styrene-enriched crystallized fraction is fed into the first dynamic crystallization stage, while the most downstream static crystallization stage (i.e., the second static crystallization stage) is the one from which the styrene-deficient residue fraction is removed.

[0022] For example, the method comprises a crystallization step, which comprises two static crystallization stages and four dynamic crystallization stages. In this embodiment, the crude composition is fed into the second of the dynamic crystallization stages in order to produce a second crystallized fraction enriched with styrene and a second residue fraction deficient in styrene. The second crystallized fraction enriched with styrene is fed into the third of the four dynamic crystallization stages in order to produce a third crystallized fraction enriched with styrene and a third residue fraction deficient in styrene, wherein the third crystallized fraction enriched with styrene is fed into the fourth of the dynamic crystallization stages in order to produce a fourth crystallized fraction enriched with styrene and a fourth residual fraction deficient in styrene.Although the fourth crystalline fraction enriched with styrene is removed as purified styrene composition, the fourth fraction of... Petition 870220092366, dated 07 / 10 / 2022, page 26 / 244 17 / 46 Styrene-deficient residue is fed into the third stage of dynamic crystallization, the third fraction of styrene-deficient residue is fed into the second stage of dynamic crystallization, and the second fraction of styrene-deficient residue is fed into the first stage of dynamic crystallization. In the first stage of dynamic crystallization, a first crystallized fraction enriched with styrene and a first fraction of styrene-deficient residue are produced. Although the first crystallized fraction enriched with styrene is fed into the second stage of dynamic crystallization, the first fraction of styrene-deficient residue is fed into the first of the two stages of static crystallization, where a fifth crystallized fraction enriched with styrene and a fifth fraction of styrene-deficient residue are produced.Although the fifth styrene-enriched crystallized fraction is fed into the first stage of dynamic crystallization, the fifth styrene-deficient residue fraction is fed into the second of the two static crystallization stages, where a sixth styrene-enriched crystallized fraction and a sixth styrene-deficient residue fraction are produced. Although the sixth styrene-enriched crystallized fraction is fed into the first stage of static crystallization, the sixth styrene-deficient residue fraction is removed.

[0023] In all the methods described above, preferably the production of a styrene-enriched crystallized fraction and a styrene-deficient residue fraction in one crystallization stage. Petition 870220092366, dated 07 / 10 / 2022, page 27 / 244 18 / 46 comprises the steps of removing the remaining liquid from the crystallization stage as a styrene-deficient residue fraction after the end of crystallization in the crystallization stage, melting the crystal layer obtained in the crystallization stage, and removing the molten crystal material obtained as a styrene-enriched crystallized fraction from the crystallization stage.

[0024] In order to increase the purity of the purified styrene product, it is preferable to carry out, at any stage of falling film and static crystallization, if present, at least one transpiration step before melting the crystal layers formed on the cooled surfaces of the crystallizer used in the simple crystallization stages. Transpiration means that the crystal layer deposited on the cooled surfaces is gently heated to a temperature close to the melting temperature of the purified substance in order to partially melt the crystals. The trapped and adhered molten material, which contains impurities, flows off during the partial melting of the crystals and is then removed from the crystallizer. In order to conduct such transpiration, the surface on which the crystals are deposited is heated with a heat transfer medium to the desired temperature.Transpiration can be performed one or more times before melting the crystal layers deposited on the cooled surfaces. Thus, transpiration leads to one or more transpiration fractions and a purified crystal layer. Preferably, at least a portion of the first transpiration fraction thus obtained is fed. Petition 870220092366, dated 07 / 10 / 2022, page 28 / 244 19 / 46 to the remaining liquid that was removed as a styrene-deficient residue fraction.

[0025] The crystallization temperature depends on the composition of the as-cast mix. However, good results are obtained when at least one, and preferably all, of the at least one static molten crystallization stage and at least one dynamic molten crystallization stage are carried out at a temperature of -200 °C and 30 °C, and more preferably at a temperature of -140 °C and 0 °C. In the case of static crystallization comprising one or more transpiration stages, and in the case of falling film crystallization comprising one or more transpiration stages, at least one, and preferably all, of the crystallization stages can be carried out at a temperature of -100 °C and -30 °C.

[0026] Depending on the composition of the feed composition, the feed composition may be fed directly as crude composition to at least one crystallization step or may be processed first with another technique before the processed feed composition is fed as crude composition to at least one crystallization step. For example, the step of providing the crude composition comprises subjecting a feed composition to one or more distillation steps and / or one or more extractive distillation steps, wherein the crude composition is obtained as a main stream, as a side stream or as a bottom stream from one or more distillation steps and / or one or more extractive distillation steps.

[0027] Preferably, the feed composition is Petition 870220092366, dated 07 / 10 / 2022, page 29 / 244 20 / 46 subjected to one or more extractive distillation steps using a polar solvent as the extractive solvent. Suitable polar solvents are solvents selected from the group consisting of propylene carbonate, sulfolane, tetramethylsulfolane, methyl carbitol, 1-methyl-2-pyrrolidinone, 2-pyrrolidinone and arbitrary combinations of two or more of the aforementioned solvents, but not including water. The extractive solvent may also be a two-part extractive solvent with one part being a solvent from the aforementioned group and the second part being water, wherein both parts of the extractive solvent are fed into the distillation column separately and independently of each other at different locations along the distillation column.

[0028] As set forth above, the method according to the present invention is particularly suitable for the preparation of a purified styrene composition from styrene-containing compositions, which until now could not be economically reasonable to use for the preparation of pure styrene. Therefore, it is preferable that the crude composition be derived from a pygas, a stream containing ethylbenzene and styrene produced in an EBSM process, or a styrene-containing stream produced by pyrolysis of polystyrene. Pygas is preferably a pyrolysis gasoline obtained from the steam cracking of naphtha. The method of the present invention allows for the efficient purification of styrene from such feed compositions, which is not possible with prior art methods. For example, the purification of styrene from a stream containing ethylbenzene and styrene produced in a Petition 870220092366, dated 07 / 10 / 2022, page 30 / 244 The 21 / 46 EBSM process via extractive distillation is very expensive because it requires an ethylbenzene styrene separation column, which is a large energy consumer.

[0029] According to a particular preferred embodiment of the present invention, the crude composition is derived from a pygas. In particular, the crude composition may originate from an extractive distillation process employed in the pyrolysis gasoline of the naphtha cracker. These pygases are known to contain impurities such as color-inducing species, C6-thiophene sulfur species, and oxygenates from the pygas feed, as well as air leaks in the vacuum equipment used in the process. In addition, they contain impurities with a boiling point close to that of styrene, such as ortho-xylene, which are difficult to remove completely by extractive distillation.In this embodiment, it is preferable that the crude composition be / have been prepared by distillation of a pygas feed composition to obtain a C8 fraction and subject the C8 fraction to an extractive distillation, in which the C8 fraction is treated with a polar solvent to obtain a styrene-containing fraction as a top stream, as a side stream or as a bottom stream. The styrene-containing fraction thus obtained can be processed into the crude composition, for example, by means of a distillation step, or, preferably, the styrene-containing fraction thus obtained is used as the crude composition, which is fed into the crystallization step.

[0030] In an alternative embodiment of the present invention, the crude composition is / was prepared by distillation Petition 870220092366, dated 07 / 10 / 2022, page 31 / 244 22 / 46 of a pygas feed composition to obtain a Cs fraction, feeding the Cs fraction into a hydrogenation reactor to hydrogenate, for example, phenylacetylene to obtain a hydrogenated gas, subjecting the hydrogenated gas to an extractive distillation, in which the hydrogenated gas is treated with a polar solvent to obtain a styrene-containing fraction as a top stream, as a side stream or as a bottom stream. The styrene-containing fraction thus obtained can be processed into the crude composition, for example, by means of a distillation step, or, preferably, the styrene-containing fraction thus obtained is used as the crude composition, which is fed into the crystallization step.

[0031] Preferably, hydrogenation is carried out in such a way that, while phenylacetylene is hydrogenated, the loss of styrene is less than 0.1% by weight.

[0032] To recover the solvent used in extractive distillation, it is preferable that the styrene-containing fraction be subjected to a distillation step in order to remove at least a portion of the polar solvent from the styrene-containing fraction, thus obtaining the crude composition.

[0033] The method according to the present invention results in a very pure styrene-containing composition. Preferably, the purified styrene composition has a styrene content of at least 99.00% by weight, more preferably at least 99.50% by weight, even more preferably at least 99.80% by weight, even more preferably at least 99.90% by weight, even more preferably at least 99.95% by weight, and most preferably at least 99.98% by weight. Petition 870220092366, dated 07 / 10 / 2022, page 32 / 244 23 / 46

[0034] In particular, the method according to the present invention allows for the complete or at least almost complete removal of color-inducing species from the crude styrene-containing composition. Therefore, in a further development of the idea of ​​the present invention, it is proposed that the purified styrene composition have a color of a maximum of 15 as defined by the Pt-Co scale according to ASTM D5386.

[0035] Furthermore, the method according to the present invention allows for the complete or at least almost complete removal of sulfur species from the crude styrene-containing composition. Consequently, it is particularly preferred when the purified styrene composition comprises less than 5 ppmw, more preferably less than 4 ppmw, even more preferably less than 3 ppmw and most preferably less than 2 ppmw of total elemental sulfur as contained in mercaptans, disulfides and thiophenes and / or less than 20 ppmw of oxygenates.

[0036] Furthermore, the method according to the present invention allows obtaining a purified styrene composition comprising less than 40 ppmw of impurities selected from the group consisting of phenylacetylene, mixed xylenes, ethylbenzene, cumene, ethyltoluene, n-propylbenzene and alpha-methylstyrene and / or having a polymer content of less than 10 ppmw.

[0037] Preferably, the purified styrene composition has a total organic chlorine content of less than 2 ppmw.

[0038] For example, the purified styrene composition may meet the following specifications.

[0039] Table 1 Petition 870220092366, dated 07 / 10 / 2022, page 33 / 244 24 / 46 Parameter Unit Specification Test Method Color Scale Pt / Co 15 max. ASTM D5386 Styrene Monomer Purity % by weight 99.8 min. ASTM D5135 or 7504 Aldehydes as benzaldehyde Weight ppm 75 max. ASTM D2119 Peroxides as H2O2 Weight ppm 15 max. ASTM D2340 Polymer Content Weight ppm 10 max. Test Method ASTM D2121 A Inhibitor (tert-butylcatechol) Weight ppm 10 max. ASTM D4590 Ethylbenzene Weight ppm 500 max. ASTM D5135 or D7504 Benzene Weight ppm 1 max. ASTM D6229 Phenylacethylene Weight ppm 150 max. ASTM D5135 Water Weight ppm 50 max. ASTM E1064 Total organic chlorides Weight ppm 2 max. ASTM D5808 Copper and Manganese Weight ppm 5 max. UOP 389 or 407 Viscosity at 25 °C cP 0.75 max. Petition 870220092366, dated 07 / 10 / 2022, page 34 / 244 25 / 46 Parameter Unit Specification Test Method Appearance — Clear and transparent liquid free of sediment and opacity at 18 to 25 °C

[0040] The residual mother liquor, that is, the styrene-deficient residue fraction obtained from crystallization, is discharged. Preferably, no styrene-deficient residue fraction obtained from crystallization is recycled in the method for an optional distillation step and, if so, a maximum of 50% by volume, more preferably a maximum of 20% by volume and even more preferably a maximum of 10% by volume of the styrene-deficient residue fraction obtained from crystallization are recycled.

[0041] According to another aspect, the present invention relates to an installation for preparing a purified styrene composition comprising at least one crystallization block, or at least one crystallization block comprising: at least one static crystallization section comprising one or more static crystallization stages, at least one dynamic crystallization section comprising one or more dynamic crystallization stages and at least two conduits that fluidly couple at least one of the one or more static crystallization stages with at least one of the one or more dynamic crystallization stages. Petition 870220092366, dated 07 / 10 / 2022, page 35 / 244 26 / 46

[0042] The term “crystallization block” refers to an apparatus for a purification process with one or more crystallizers. Furthermore, the term crystallization stage is not only used to denote a step or stage of the method, respectively, but also to denote an apparatus, that is, that part of a crystallizer, in which a crystallization stage is carried out. The crystallization stage as a feature of the apparatus may also be designated as a crystallizer, crystallization unit, or similar.

[0043] Preferably, one or more static crystallization stages are static molten material crystallization stages and one or more dynamic crystallization stages are dynamic molten material crystallization stages.

[0044] If the crystallization block comprises two or more dynamic crystallization stages and / or two or more static crystallization stages, preferably each of the dynamic crystallization stages is fluidly coupled with one or two other dynamic crystallization stages and each of the static crystallization stages is fluidly coupled with one or two other static crystallization stages.

[0045] Furthermore, it is preferable that at least one crystallization block comprises a static crystallization stage and a dynamic crystallization stage, wherein one of the at least two conduits fluidly couples the static crystallization stage with the dynamic crystallization stage so that a styrene-deficient residue fraction obtained in the stage of Petition 870220092366, dated 07 / 10 / 2022, page 36 / 244 27 / 46 dynamic crystallization can be fed into the static crystallization stage and wherein another of at least two conduits fluidly couples the static crystallization stage with the dynamic crystallization stage so that a styrene-enriched crystallized fraction obtained in the static crystallization stage can be fed into the dynamic crystallization stage.

[0046] Furthermore, it is preferable that at least one crystallization block comprises two to five static crystallization stages and two to five dynamic crystallization stages,wherein one of at least two conduits fluidly couples one of the static crystallization stages with one of the dynamic crystallization stages so that a styrene-deficient residue fraction obtained in the dynamic crystallization stage can be fed into the static crystallization stage, being fluidly coupled with the dynamic crystallization stage; and wherein one of at least two conduits fluidly couples the static crystallization stage with the dynamic crystallization stage, being fluidly coupled with the static crystallization stage so that a styrene-enriched crystallized fraction obtained in the static crystallization stage can be fed into the dynamic crystallization stage; wherein each of the two remaining static crystallization stages are fluidly coupled to each other by means of at least two conduits.and in which each two of the remaining stages of dynamic crystallization are fluidly coupled to one another by means of at least two conduits.

[0047] According to another preferred modality of Petition 870220092366, dated 07 / 10 / 2022, page 37 / 244 28 / 46 of the present invention, the installation further comprises at least one distillation column comprising two or more outlets, wherein at least one of these outlets is fluidly coupled to an inlet of the crystallization block.

[0048] In a further development of the idea of ​​the present invention, it is suggested that the installation additionally comprises at least one extractive distillation column comprising two or more outlets, wherein at least one of these outlets is fluidly coupled to an inlet of the crystallization block.

[0049] The installation may additionally comprise a solvent recovery distillation column, which is fluidly coupled to an outlet of the extractive distillation column.

[0050] According to another preferred embodiment of the present invention, the installation comprises at least one crystallization block, a distillation column, and an extractive distillation column, wherein the distillation column is fluidly coupled to the extractive distillation column by means of a conduit, and wherein the extractive distillation column is fluidly coupled to the inlet of the crystallization block by means of an inlet conduit. Preferably, the installation of this embodiment further comprises a hydrogenation reactor and an additional distillation column for solvent recovery, wherein the distillation column is fluidly coupled to the hydrogenation reactor by means of a conduit, wherein the hydrogenation reactor is fluidly coupled to the extractive distillation column by means of a conduit, wherein the extractive distillation column is coupled in a way Petition 870220092366, dated 07 / 10 / 2022, page 38 / 244 29 / 46 fluid to the additional distillation column for solvent recovery via a conduit and wherein the additional distillation column is fluidly coupled to the crystallization block via the inlet conduit.

[0051] According to a preferred alternative embodiment of the present invention, the installation comprises at least one crystallization block and three distillation columns, wherein the three distillation columns are fluidly coupled to each other and are arranged in series, wherein the last of the three distillation columns is fluidly coupled to the crystallization block by means of an inlet conduit. Preferably, the installation of this embodiment further comprises an alkylation unit and a dehydrogenation unit, wherein the alkylation unit is fluidly coupled to the dehydrogenation unit by means of a conduit and the dehydrogenation unit is fluidly coupled to the crystallization block by means of the inlet conduit.

[0052] According to yet another preferred alternative embodiment of the present invention, the installation comprises at least one crystallization block, two distillation columns and a pyrolysis reactor, wherein the pyrolysis reactor is fluidly coupled to the first of the two distillation columns, the first of the two distillation columns is fluidly coupled to the second of the two distillation columns and the second of the two distillation columns is fluidly coupled to the crystallization block by means of an inlet conduit.

[0053] The crystallization block comprises a line of Petition 870220092366, dated 07 / 10 / 2022, page 39 / 244 30 / 46 product outlet for discharging the purified styrene composition and a discharge line for discharging the residual mother liquor, i.e., the styrene-deficient residue fraction obtained during crystallization. Preferably, the installation does not include a recirculation line leading from the discharge line for discharging the styrene-deficient residue fraction obtained during crystallization to any of the optional distillation columns. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to achieve the aforementioned and other advantages and objectives of the invention, a more particular description of the invention briefly described above will be presented by way of reference to specific embodiments thereof, which are illustrated in the accompanying Figures. Understanding that these drawings represent only typical embodiments of the invention and, therefore, should not be considered limiting to its scope, the invention will be described with additional specificity and detail through the use of the accompanying drawings in which: Fig. 1a is a diagrammatic illustration of a crystallization block used in a method and installation according to an embodiment of the present invention. Fig. 1b is a diagrammatic illustration of a crystallization block used in a method and installation according to another embodiment of the present invention. Figure 2 is a diagrammatic illustration of an installation particularly suitable for purifying gasoline from naphtha-cracked pyrolysis according to Petition 870220092366, dated 07 / 10 / 2022, page 40 / 244 31 / 46 another embodiment of the present invention. Fig. 3 is a diagrammatic illustration of an installation particularly suitable for purifying an EBSM process stream according to another embodiment of the present invention. Fig. 4 is a diagrammatic illustration of an installation particularly suitable for purifying a styrene-containing stream produced from a polystyrene stream by means of pyrolysis according to another embodiment of the present invention. DESCRIPTION OF EXEMPLARY MODALITIES

[0055] Fig. 1a shows an embodiment of a crystallization block 10 for conducting the preparation process of a purified styrene composition according to an embodiment of the present invention. The crystallization block 10 includes a first dynamic molten material crystallization section 12 comprising a falling film crystallization stage or a falling film crystallizer 14, respectively as a dynamic molten material crystallization stage or crystallizer, respectively. In addition, the crystallization block 10 comprises a second static molten material crystallization section 16 having a static molten material crystallization stage 18 or a static melt crystallizer, respectively. The falling film crystallizer 14 is connected to an inlet conduit 20 for composition containing crude styrene that is suitable for feeding a crude styrene composition into the falling film crystallizer 14. Petition 870220092366, dated 07 / 10 / 2022, p. 41 / 244 32 / 46 Furthermore, the falling film crystallizer 14 has a discharge conduit 22 for discharging a purified styrene composition from the falling film crystallizer 14 and the crystallization block 10. The static melt crystallizer 18 is connected to the falling film crystallizer 14 via a transfer conduit 24 which is suitable for transferring a first styrene-deficient residue fraction obtained by crystallization in the falling film crystallizer 14 to the static melt crystallizer 18. In this respect, the transfer conduit 24 is in fluid communication with the falling film crystallizer 14 and the static melt crystallizer 18. The static melt crystallizer 18 comprises a discharge conduit 28 which serves to discharge a second styrene-deficient residue fraction, which is obtained by crystallization in the static melt crystallizer 18, from the static melt crystallizer 18 and the crystallization block 10.A recycling conduit 30 provides fluid communication between the static melt crystallizer 18 and the falling film crystallizer 14 and therefore allows at least a portion of the second styrene-enriched crystallization composition, which results from crystallization in the static melt crystallizer 18, to be recycled back into the falling film crystallizer 14.

[0056] Fig. 1b shows another embodiment of a crystallization block 10 for conducting the method for preparing a purified styrene composition according to the present invention. The first dynamic molten material crystallization section 12 comprises four stages. Petition 870220092366, dated 07 / 10 / 2022, page 42 / 244 Section 33 / 46 of falling film crystallization 14a, 14b, 14c, 14d and the second static molten material crystallization section 16 includes two static molten material crystallization stages 18a, 18b. Transfer conduits 32a, 32b, 32c are provided between the falling film crystallization stages 14a, 14b, 14c, 14d, through which a styrene-deficient residue fraction obtained by falling film crystallization in the simple falling film crystallization stages 14a, 14b, 14c, 14d can be transferred from one of the falling film crystallization stages 14b, 14c, 14d to the respective upstream falling film crystallization stages 14a, 14b, 14c.Furthermore, the falling film crystallization stages 14a, 14b, 14c, 14d are connected via recycling conduits 34a, 34b, 34c suitable for recycling at least a portion of the styrene-enriched crystallized fractions obtained by falling film crystallization in the simple falling film crystallization stages 14a, 14b, 14c, 14d from one of the falling film crystallization stages 14a, 14b, 14c to the respective downstream falling film crystallization stages 14b, 14c, 14d. An inlet conduit 20 is connected to the second falling film crystallization stage 14b so that a composition containing crude styrene can be introduced into the second falling film crystallization stage 14b. A discharge conduit 22 is provided in the most downstream descending film crystallization stage 14d to remove the purified styrene composition from the crystallization block 10. A transfer conduit 24 provides... Petition 870220092366, dated 07 / 10 / 2022, p. 43 / 244 34 / 46 a fluid communication between the most upstream falling film crystallization stage 14a of the first dynamic molten material crystallization section 12 and the most upstream static molten material crystallization stage 18b of the second static molten material crystallization section 16 so that the styrene-deficient residue fraction obtained by crystallization in the falling film crystallization stage 14a can be transferred to the static crystallizer 18b of the second static molten material crystallization section 16. The static molten material crystallization stages 18a and 18b are connected via a transfer conduit 36 ​​to transfer the styrene-deficient residue fraction obtained by crystallization from the static molten material crystallization stage 18b to the static molten material crystallization stage 18a.Furthermore, the static molten material crystallization stage 18a and the static molten material crystallization stage 18b are connected via a recycling conduit 38 allowing the transfer of the styrene-enriched crystallized fraction, resulting from crystallization in the static molten material crystallization stage 18a, to the static melt crystallizer of the crystallization stage 18b. Additionally, the static molten material crystallization stage 18a comprises a discharge conduit 28 to discharge the styrene-deficient residue fraction, obtained by crystallization in the static molten material crystallization stage 18a, from the crystallization block 10. A recycling conduit 30 provides communication. Petition 870220092366, dated 07 / 10 / 2022, page 44 / 244 35 / 46 fluid between the static melt crystallization stage 18b and the falling film crystallization stage 14a and therefore allows recycling at least part of the styrene-enriched crystallized fraction obtained in the static melt crystallization stage 18b from the second static melt crystallization section 16 back to the falling film crystallization stage 14a of the first dynamic melt crystallization section 12.

[0057] During the operation of device 10 shown in Fig. 1b a composition containing crude styrene is fed into the falling film crystallization stage 14b through the inlet conduit 20. In each of the falling film crystallization stages 14a, 14b, In steps 14c and 14d, a styrene-enriched crystallized composition and a styrene-deficient residue fraction are prepared. Each of the styrene-deficient residue fractions obtained in one of the falling film crystallization stages 14b, 14c, and 14d is transferred through transfer conduits 32a and 32b. 32c for the respective upstream falling film crystallization stage 14a, 14b, 14c. Furthermore, each of the styrene-enriched fractions obtained in one of the falling film crystallization stages 14a, 14b, 14c is at least partially recycled through recycling conduits 34a, 34b, 34c to the respective downstream falling film crystallization stage 14b, 14c, 14d. The styrene-deficient residue fraction obtained after crystallization in the falling film crystallization stage 14a of the first dynamic molten material crystallization section 12 is transferred through the Petition 870220092366, dated 07 / 10 / 2022, p. 45 / 244 Transfer conduit 24 to static molten material crystallization stage 18b of the second static molten material crystallization section 16. The styrene-deficient residue fraction obtained in static molten material crystallization stage 18b is transferred through transfer conduit 36 ​​to downstream static molten material crystallization stage 18a. Furthermore, the styrene-enriched crystallized fraction obtained in static molten material crystallization stage 18a is at least partially recycled through recycling conduit 38 to upstream static molten material crystallization stage 18b. The styrene-enriched crystallized fraction obtained after crystallization in static molten material crystallization stage 18b is recycled through recycling conduit 30 to the falling film crystallization stage 14a of the first dynamic molten material crystallization section 12.A finally purified styrene composition obtained in crystallization stage 14d is removed from apparatus 10 through discharge conduit 22, while the final styrene-deficient residue fraction is removed from static molten material crystallization stage 18a and from apparatus 10 through discharge conduit 28.

[0058] According to the present invention, Table 2 lists the different impurities that may typically be present in a crude styrene stream with their melting points. The reason for removing impurities from the crude styrene stream by block crystallization is twofold: a) some of the species have melting points lower than the Petition 870220092366, dated 07 / 10 / 2022, p. 46 / 244 37 / 46 styrene eb) During the crystallization process, impurities with higher melting points are more soluble in the mother liquor. Thus, despite having a higher melting point, these impurities can be removed from the styrene by crystallization. Therefore, crystallization offers a unique method of producing highly purified styrene compositions, as desired by the operator, from a crude composition containing styrene. The increase in product purity is directly correlated with an increasing number of crystallization stages. Recovery, on the other hand, is a function of the number of stages of the residue.

[0059] Table 2 COMPOUND MELTING POINT Water 0 °C (32 °C; 273 K) α-Methylstyrene -23 °C (-9.4 °F; 250 K) o-Xylene -25.2 °C (-13.4 °F; 248 K) Benzaldehyde -26 °C (-14.8 °F; 247 K) Styrene -30.6 °C (-23.1 °F; 243 K) Thiophene compounds with boiling points in the range of 130-150 °C -65 to -30 °C (-85 to -22 °F; 208 to 243 K) Phenylacethylene -45 °C (-49 °F; 228 K) Ethylbenzene -95 °C (-139 °F; 178 K) 3-Ethyltoluene (m-ethyltoluene) -95.5 °C (-140 °F; 177.6 K) Cumene -96 °C (-141 °F; 177 K) n-propylbenzene -99.5 °C (-147 °F; 173.7 K) Petition 870220092366, dated 07 / 10 / 2022, page 47 / 244 38 / 46

[0060] Fig. 2 schematically shows an installation particularly suitable for preparing a purified styrene composition from naphtha cracker pyrolysis gasoline. The installation 11 comprises a first distillation column 40, a second distillation column 42, a hydrogenation reactor 44, an extractive distillation column 46, a solvent recovery distillation column 48 and a crystallization block 10. The crystallization block 10 is composed as shown in FIG. 1b.

[0061] During the operation of the installation, a current of C7+-pygas is distilled in the first distillation column 40, and the bottom stream obtained in the first distillation column 40 is fed into the second distillation column 42 in order to obtain a C9+ stream as bottom product and a C8-rich stream as suspended product. The C8-rich stream thus obtained is fed into the hydrogenation reactor to hydrogenate phenylacetylene included in the stream by hydrogen, which is supplied to the hydrogenation reactor 44 through the hydrogen inlet conduit 50. The hydrogenation reactor 44 is operated under mild conditions to saturate phenylacetylene to produce styrene; however, this is accompanied by loss of styrene in the form of saturation which produces ethylbenzene. After hydrogenation, the hydrogenated C8 stream obtained in the hydrogenation reactor 44 consists mainly of ethylbenzene, mixed xylenes, etc., is fed into the extractive distillation setup comprising extractive distillation column 46 and solvent recovery distillation column 48. A polar solvent is used during extractive distillation to extract a stream containing styrene and solvent as . Petition 870220092366, dated 07 / 10 / 2022, page 48 / 244 39 / 46 bottom stream, which is then fed into the solvent recovery distillation column 48 to remove the solvent and obtain as top stream a styrene-enriched stream with a styrene content greater than 99.8% by weight. Despite being of high purity, this stream is of inferior quality due to the presence of color-causing species, sulfur molecules and oxygenates. However, during the crystallization carried out in the crystallization block 10 as described in detail above, impurities and, in particular, different impurities with a boiling point close to that of styrene, such as phenylacetylene, meta- and ortho-xylenes, ethylbenzene, cumene, n-propylbenzene, alpha-methylstyrene and ethyltoluene, are removed. This phenomenon can be exploited to minimize both the loss of styrene through the phenylacetylene hydrogenation reactor 44 and the utility consumption in the upstream distillation columns 40, 42, 46, 48.The removal of phenylacetylene via crystallization allows the phenylacetylene hydrogenation reactor 44 to be operated under low gravity conditions or even eliminated completely. The associated styrene loss during hydrogenation is thus minimized or nonexistent. The removal of near-boiling C9+ compounds, such as cumene, n-propylbenzene, etc., implies that the distillation column 42 or deoctanizer, respectively, in installation 11 can be relaxed to allow the slippage of C9+ compounds into the C8 cut. These C9+- compounds, by virtue of their polarity and boiling point, will predominantly land in the crude styrene stream and will eventually be removed through the block. Petition 870220092366, dated 07 / 10 / 2022, page 49 / 244 40 / 46 Crystallization 10. The removal of compounds with a boiling point close to that of styrene, such as ethylbenzene, orthoxylene, and meta-xylene, implies that the extractive distillation column 46 and the solvent recovery distillation column 48 can be designed with a lower solvent-to-feed ratio and lower extraction temperature at the bottom of the distillation column, thus reducing capital investment and utility consumption. The purified styrene composition is removed through the discharge conduit 22, while the styrene-deficient residue fraction obtained in the crystallization block 10 is removed through the discharge conduit 28 along with the raffinate C8 obtained as the head product of the extractive distillation column 46.

[0062] The crystallization block 10 removes, as described in detail above, impurities including color-causing species such as conjugated diolefins, sulfur species, which are mainly C6 thiophenes, and oxygenates such as water, ketones, aldehydes, and alcohols, etc. The crystallization block, due to the cryogenic nature of the process, prevents the undesirable formation of polymers in the styrene product. A common problem encountered in adsorbent styrene-based treatment is the undesirable formation of polymer due to localized exothermicity at the active sites, despite the insignificant temperature increase in the beds.

[0063] Fig. 3 depicts an installation 11 particularly suitable for purifying an EBSM process stream. The installation 11 comprises an alkylation unit 52, a dehydrogenation unit 54, a first distillation column 40, a second column of Petition 870220092366, dated 07 / 10 / 2022, page 50 / 244 41 / 46 distillation 42, a third distillation column 56 and a crystallization block 10. The crystallization block 10 is composed as shown in FIG. 1b.

[0064] During operation, benzene and ethylene are alkylated in the alkylation reactor 52 to produce ethylbenzene, which is fed into the dehydrogenation reactor 54. The effluent from dehydrogenation reactor 54 is fed into a separation block that includes the three distillation columns 40, 42, 56. The first distillation column 40 removes benzene and toluene from the effluent from dehydrogenation reactor 54, while the second distillation column 42 separates unreacted ethylbenzene from styrene and the third distillation column 56 distills the styrene stream. The bottom product of the third distillation column 56 is a styrene tar residue produced due to the unwanted polymerization of heat-sensitive styrene in the second distillation column 42. The second distillation column 42 is the largest energy consumer in this system.This occurs because the separation of ethylbenzene from styrene is difficult due to a) close boiling points and ii) styrene's heat sensitivity, which necessitate operating the column under vacuum and with a large number of distillation steps. Crystallization in crystallization block 10 not only affects energy efficiency but also reduces unwanted styrene polymerization at the bottom of distillation column 42. Distillation column 42 can be run in a relaxed mode, where small amounts of ethylbenzene (up to 3-5% by weight) can fall to the bottom of the column. This will not only result in lower utility consumption or theoretical stages but also less waste. Petition 870220092366, dated 07 / 10 / 2022, page 51 / 244 42 / 46 bottom temperature, which implies less unwanted styrene polymerization, thus increasing the styrene yield of the overall EBSM process. The ethylbenzene at the bottom of distillation column 42 will, by virtue of its boiling point, settle in the suspended product of the third column 56. This composition containing crude styrene, when fed into crystallization block 10, will result in the production of two streams, namely, i) the purified styrene composition withdrawn from crystallization block 10 through the discharge conduit 22 and ii) a residue liquor rich in ethylbenzene 28, which is discharged.

[0065] Fig. 4 shows an installation 11 particularly suitable for purifying a styrene-containing stream produced from a polystyrene stream by means of pyrolysis. The installation 11 comprises a pyrolysis reactor 60, a first distillation column 40, a second distillation column 42 and a crystallization block 10. The crystallization block 10 is composed as shown in FIG. 1b.

[0066] During operation, the pyrolysis of polystyrene is carried out in the pyrolysis reactor, which can be operated thermally or catalytically. The reactor effluent undergoes a series of fractionation steps in the first distillation column 40 and the second distillation column 42 in order to produce the composition containing crude styrene, which is fed into the crystallization block 10. The crystallization block 10 is applied at the end of the distillation step to produce a high-purity styrene product or VHPS, as desired by the Petition 870220092366, dated 07 / 10 / 2022, page 52 / 244 43 / 46 operator, with specific energy consumption and reduced capital expenditure.

[0067] The following example is provided to illustrate the invention and does not limit the scope of the claims. Example

[0068] Unless otherwise indicated, all parts and percentages are by weight.

[0069] A crude styrene stream containing various impurities was produced by an extractive distillation unit in pyrolysis gasoline and subsequently purified by a combination of falling film and static melt crystallization to prepare the final VHPS product and the final residue. The crystallization block used was as described above with reference to Fig. 1b, except that the static melt crystallization stage 18a was omitted.

[0070] Styrene recovery through the crystallization block was >95%. The styrene concentration of the single streams shown in Fig. 1b was as follows: Stream (no. in Fig. 1b) Fraction Styrene Concentration 20 Crude styrene, feed to falling film 98.89% by weight 22 Final product 99.94% by weight 24 Feed for static crystallization 96.94% by weight 36 Final residue 88.19% by weight

[0071] The term “at least one of” is intended to encompass Petition 870220092366, dated 07 / 10 / 2022, page 53 / 244 44 / 46 combinations of the listed elements, components, resources, and similar items, and the listed elements, components, resources, and similar items individually. For example, the phrase "at least one of A and B" is used to encompass modalities that comprise only A, which comprise only B and which include A and B, unless otherwise indicated. mode.

[0072] The term “which includes claims if intended to mean “that includes at least such that the list of elements cited in a claim is an open group.” The terms “a,” “an,” and other singular terms are intended to include plural forms of even unless specifically excluded. List of Numerical References 10 Crystallization Block 11 Installation 12 First section of dynamic molten material crystallization 14 Dynamic molten material crystallization / crystallizer stage (falling film) 14a, 14b, 14c, 14d Stages of crystallization of a film 16 Descending / dynamic molten material Second section of static molten material crystallization 18 Static molten material crystallization stage / crystallizer 18a, 18b Static molten material crystallization stages 20 Inlet conduit for composition Petition 870220092366, dated 07 / 10 / 2022, page 54 / 244 45 / 46 contains crude styrene. Discharge conduit for purified styrene compound (Transfer) conduit for feeding a styrene-deficient residue fraction from the dynamic crystallization section to the static crystallization section. Discharge pipe for styrene-deficient waste fraction (Recycling) pipe to feed a styrene-enriched fraction from the section of Static crystallization for the dynamic crystallization section 32b, 32c. Conduits for waste fractions lacking dynamic styrene crystallization in the section of 34b, 34c Pipes for styrene-enriched crystallized fraction in the dynamic crystallization section Pipes for styrene-deficient waste fractions in the static crystallization section Pipes for styrene-enriched crystallized fraction in the static crystallization section First distillation column Second distillation column Hydrogenation reactor Extractive distillation column Recovery distillation column Petition 870220092366, dated 07 / 10 / 2022, page 55 / 244 46 / 46 Solvent 50 Hydrogen inlet conduit 52 Alkylation unit 54 Dehydrogenation unit 56 Third distillation column 60 Pyrolysis reactor Petition 870220092366, dated 07 / 10 / 2022, page 56 / 244

Claims

1 / 2 CLAIMS 1. Installation (11) for preparing a purified styrene composition, characterized by comprising at least one crystallization block (10), wherein the crystallization block (10) comprises: at least one static crystallization section (16) comprising one or more static crystallization stages (18, 18a, 18b), at least one dynamic crystallization section (12) comprising one or more dynamic crystallization stages (14, 14a, 14b, 14c, 14d) and at least two conduits (24, 30) fluidly coupling at least one of the one or more static crystallization stages (18, 18b) with at least one of the one or more dynamic crystallization stages (14, 14a).

2. Installation (11), according to claim 1, characterized by further comprising at least one distillation column (40, 42, 56) comprising two or more outlets, wherein at least one of these outlets is fluidly coupled to an inlet of the crystallization block (10), or by further comprising at least one extractive distillation column (46) comprising two or more outlets, wherein at least one of these outlets is fluidly coupled to an inlet of the crystallization block (10).

3. Installation (11), according to claim 1 or 2, characterized by comprising: a) at least one crystallization block (10), at least one distillation column (42) and an extractive distillation column (46), wherein at least one distillation column (42) is fluidly coupled to the extractive distillation column (46) through a conduit and wherein the extractive distillation column (46) is fluidly coupled to the inlet of the crystallization block (10) through an inlet conduit (20); b) at least one crystallization block (10) and three distillation columns (40, 42, 56), wherein the three distillation columns (40, 42, 56) are fluidly coupled to each other and are arranged in series, wherein the last of the three distillation columns (56) is fluidly coupled to the crystallization block (10) by means of an inlet conduit (20);or c) at least one crystallization block (10), two distillation columns (40, 42) and a pyrolysis reactor (60), wherein the pyrolysis reactor (60) is fluidly coupled to the first of the two distillation columns (40), wherein the first of the two distillation columns (40) is fluidly coupled to the second of the two distillation columns (42) and the second of the two distillation columns (42) is fluidly coupled to the crystallization block (10) via an inlet conduit (20).

4. Installation (11), according to any one of claims 1 to 3, characterized by comprising a product outlet line (22) for discharging the purified styrene composition and a discharge line (28) for discharging the styrene-deficient residue fraction obtained from crystallization, wherein the installation (11) does not comprise a recirculation line leading from the discharge line (28) for discharging the styrene-deficient residue fraction obtained from crystallization to any of the optional distillation columns (40, 42, 56). Petition 870260060776, dated 22 / 06 / 2026, page 12 / 18

Images