Additives for controlling DVB crosslinking and insoluble polymer formation in styrene processes

Abstract

A method for reducing fouling in a styrene production process, the method comprising the steps of introducing an additive into a stream containing styrene and a byproduct, divinylbenzene (DVB), wherein the additive comprises at least one compound comprising one or more functional groups selected from the group consisting of amines, alcohols, aminoalcohols, labile C-C, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogen, and combinations thereof, and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C, or ±60°C of the boiling point of divinylbenzene (DVB), which is 195°C, wherein the at least one compound is effective in inhibiting crosslinking of the divinylbenzene (DVB). A system for performing the method is also provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 62 / 814,659, filed on March 6, 2019, which is hereby incorporated by reference in its entirety for all purposes.

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] none.

[0005] References to Microfilm Appendix

[0006] none. Technical Field

[0007] The present disclosure relates to the production of styrene monomer. More specifically, the present disclosure relates to reducing styrene fouling that occurs during styrene monomer production. More specifically, the present disclosure relates to reducing the amount of insoluble polystyrene polymer during styrene production by an additive comprising at least one chemical component having a boiling point close to that of divinylbenzene (DVB) and having sufficient chemical activity to inhibit DVB crosslinking of styrene. Background Art

[0008] Styrene is a raw material for major polymer products (e.g., polystyrene, acrylonitrile-butadiene-styrene, styrene-butadiene rubber, etc.), consumed in significant quantities annually, and is one of the most representative general-purpose monomer products. It is well known that styrene can be produced by dehydrogenating ethylbenzene (EB) over a dehydrogenation catalyst bed in a reactor in the presence of superheated water vapor (i.e., steam). Styrene manufacturing plants typically utilize a reaction system consisting of two or three adiabatic reactors connected in series, along with multiple furnaces and heat exchangers.

[0009] Conventional production of styrene (e.g., by EB dehydrogenation) produces a crude styrene stream that typically contains about 60% styrene. Purification by distillation presents challenges because thermal autoinitiation of styrene polymerization can occur at significant rates above 80°C. Styrene boils at 145°C, so distillation is typically performed at lower pressures and temperatures with the addition of polymerization inhibitors (also known as anti-polymerization agents or inhibitors). In order to control unwanted monomer degradation and / or unwanted polystyrene polymer formation during styrene production, inhibitors are typically added to the process. Typical products used for this purpose are dinitrophenols [such as DNOC (dinitro-o-cresol) or DNBP (dinitro-sec-butylphenol)] and true inhibitors (such as substituted tetramethylpiperidin-1-oxyl substances). Although effective in controlling styrene polymerization, these inhibitors can be highly toxic and / or quite expensive. True inhibitors are rapidly consumed and may be ineffective in certain regions.

[0010] Another complication is the ubiquitous byproduct divinylbenzene (DVB). DVB is a potent crosslinking agent that can result in the production of insoluble DVB-crosslinked polystyrene polymers (also referred to herein as insoluble polymers and / or DVB-crosslinked polymers). Significant amounts of insoluble polymer are often observed in styrene distillation systems, even with the use of conventional distillation inhibitors. Insoluble polymer fouling in styrene production plants can lead to problems such as flow restrictions, reduced heat exchange, and loss of distillation column performance. Modern anti-polymerization inhibitors / inhibitors can eliminate insoluble polymer formation, even at high dosages. DVB, with a boiling point of 195°C, can concentrate as a hot liquid in areas where styrene and EB are still in the gas phase. These areas are potential sites for insoluble polymer initiation. Clumps of crosslinked polymer free radicals can form at these locations. Once formed, these insoluble polymer "seeds" can migrate to other areas where, over time, they can settle and form large insoluble polymer deposits. Therefore, insoluble polymer deposition is a problem in conventional styrene production.

[0011] Therefore, there is a need for improved styrene production and / or purification processes whereby the formation of insoluble polymers is suppressed.

[0012] Overview

[0013] Disclosed herein is a method for reducing fouling in a styrene production process, the method comprising introducing an additive into a stream comprising styrene and a byproduct, divinylbenzene (DVB), wherein the additive comprises at least one compound comprising one or more functional groups selected from the group consisting of amines, alcohols, aminoalcohols, labile CC, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogen, and combinations thereof, and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C, or ±60°C of the boiling point of divinylbenzene (DVB), which is 195°C, wherein the at least one compound is effective in inhibiting crosslinking of the divinylbenzene (DVB).

[0014] Also disclosed herein is an additive for reducing fouling in a crude styrene purification process, the crude styrene comprising styrene and a by-product divinylbenzene (DVB), the additive comprising: at least one compound comprising one or more functional groups effective to inhibit crosslinking of divinylbenzene (DVB) and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C or ±60°C of the boiling point of DVB of 195°C; and a polymerization inhibitor having a boiling point greater than the boiling point of the at least one compound.

[0015] Also provided herein is a composition comprising: a crude styrene stream comprising styrene and byproduct divinylbenzene (DVB); and an additive comprising one or more functional groups effective to inhibit crosslinking of the DVB and having a boiling point of 170°C to 270°C, 170°C to 230°C, 170°C to 220°C, or 170°C to 195°C.

[0016] Also disclosed herein is a system for producing styrene by dehydrogenating ethylbenzene (EB), the system comprising: one or more dehydrogenation reactors operable to contact EB and steam with a dehydrogenation catalyst under dehydrogenation conditions to produce a crude styrene effluent comprising styrene and a by-product, divinylbenzene (DVB); a heat exchange device for reducing the temperature of the crude styrene effluent; a separation device configured to separate off-gas and condensate from the cooled crude styrene effluent, thereby providing a dehydrogenated mixture; a distillation section operable to separate the dehydrogenated mixture into a stream comprising benzene, toluene, ethylbenzene, or a combination thereof, a coke stream, and a condensate stream; and a condensate separation device. an oil stream and one or more streams comprising styrene; an oxidation unit configured to produce, by oxidation of the tar stream, at least one compound comprising one or more functional groups effective to inhibit crosslinking of divinylbenzene and having a boiling point greater than or equal to 170° C. and within ±10° C., ±20° C., ±30° C., ±40° C., ±50° C., or ±60° C. of the boiling point of DVB of 195° C.; and one or more recovery lines whereby the at least one compound can be fed to, recovered from, or refluxed from a crude styrene effluent, a cooled crude styrene effluent, a dehydrogenation mixture, a distillation column of a distillation section, or a combination thereof.

[0017] Also disclosed herein is a method for reducing fouling in a styrene production process, the method comprising the steps of generating at least one compound effective in inhibiting divinylbenzene (DVB) crosslinking by oxidation of crude styrene, a styrene tar stream, or a combination thereof, the compound comprising one or more functional groups selected from amines, alcohols, amino alcohols, labile CC, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogen, and combinations thereof, and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C, or ±60°C of the boiling point of divinylbenzene (DVB), which is 195°C; and introducing the at least one compound into a stream comprising styrene and by-product divinylbenzene (DVB), thereby inhibiting divinylbenzene (DVB) crosslinking.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The detailed description will refer to the drawings which are briefly described below, wherein like reference numerals represent like parts / portions.

[0020] Figure 1 is a process flow diagram of a styrene production system according to an embodiment of the present disclosure.

[0021] Figure 2 is a process flow diagram of a styrene production system according to another embodiment of the present disclosure.

[0022] Figure 3 Graph showing the percentage (%) change in DVB and the percentage of soluble polymer growth in batch tests of the additive of Example 1 and selected reference materials.

[0023] Figure 4 is a graph of the percentage of soluble polystyrene (PS) polymer formed versus the percentage (%) of DVB for selected additives of Example 1.

[0024] Figure 5 Schematic diagram of the crude styrene condensate test equipment of Example 2.

[0025] Figure 6 is a bar graph of the DVB percentage (%) of the condensation test structures of Example 2.

[0026] Detailed description

[0027] Overview

[0028] First, it should be understood that although illustrative embodiments of one or more embodiments are provided below, the disclosed additives, compositions, systems, and methods can be implemented using any number of currently known or currently unavailable technologies. The present disclosure should not be limited to the exemplary embodiments, drawings, and techniques shown below, but may be modified within the scope of the appended claims and their equivalents. Although the dimensional values ​​of various components / elements are disclosed, the drawings may not be drawn to scale.

[0029] As mentioned above, styrene produced by high-temperature dehydrogenation of ethylbenzene (EB) contains small amounts of byproducts, such as divinylbenzene (DVB), which can cause insoluble polymer fouling. The deposition of insoluble DVB cross-linked polymers can be a serious problem for styrene plants. The fact that the plant's operating time may last for more than three years exacerbates the problem. Disclosed herein are additives that can reduce or inhibit the formation of such insoluble polymers and the accompanying fouling (e.g., DVB fouling effect), compositions comprising the additives, and methods for reducing fouling that occurs during styrene production and / or purification. The additives include one or more components having a boiling point close to that of DVB and having sufficient chemical activity to inhibit the formation of insoluble polymers from DVB (e.g., inhibiting the formation of DVB cross-linked polystyrene).

[0030] Standard polymerization inhibitors appear to inhibit DVB reactions when present, however, such polymerization inhibitors are typically expensive, toxic, and have high boiling points (e.g., boiling points above 200° C. at atmospheric pressure). It has been discovered that additives as described herein comprising at least one compound having a boiling point close to that of DVB (also referred to herein as a “chemical component”) can effectively address potential sites of DVB condensation and reaction. By having a boiling point close to that of DVB (and lower than that of conventional polymerization inhibitors), the chemical component can remain with the DVB (or “follow” the DVB) during styrene purification. Without wishing to be bound by theory, such DVB condensation sites can be a source of “seed” polymer that leads to insoluble polymer deposition, and the additives described herein comprising a chemical component having the appropriate properties to interact with and follow the DVB (i.e., remain with the DVB during the majority of the styrene purification / post-production processing) can reduce this seeding and the resulting insoluble polymer fouling.

[0031] Unless otherwise stated, the boiling points listed herein are standard boiling points at 1 atmosphere. In some embodiments, the boiling point of at least one compound having a boiling point close to DVB is within ±5°C, ±10°C, ±20°C, ±30°C, ±40°C, ±50°C, or ±60°C of the DVB boiling point (which is 195°C), and is sufficiently higher than the boiling point of styrene (e.g., 170°C) to achieve effective separation from styrene. That is, in some embodiments, the boiling point range of at least one chemical component is 190°C to 200°C, 185°C to 205°C, 175°C to 215°C, 170°C to 225°C, 170°C to 235°C, 170°C to 245°C, or 170°C to 255°C. In some embodiments, the boiling point of at least one chemical component is lower than or equal to the DVB boiling point, i.e., lower than or equal to 195°C. In some embodiments, at least one chemical component has a boiling point greater than or equal to the boiling point of styrene, i.e., greater than or equal to 145° C., and ideally greater than 170° C., to allow for efficient separation by distillation. In some embodiments, at least one compound has a boiling point less than or equal to about 260° C., 250° C., 240° C., 230° C., 220° C., 210° C., 200° C., or 195° C., and a boiling point greater than or equal to about 170° C., 180° C., 190° C., 200° C., 210° C., 220° C., or 230° C., or some ranges therein.

[0032] At least one chemical component also comprises one or more functional groups, thereby is effective in inhibiting DVB crosslinking. As used herein, if the crude styrene comprising styrene and DVB is purified in the presence of the chemical component and produces less insoluble polymer (in some cases, this can be represented by a reduction in DVB) compared to the same process in the absence of the at least one chemical component, then the chemical component is 'effective in inhibiting DVB crosslinking'. For example, this analysis can be performed by the techniques described in Example 1 below. The method according to the present disclosure can provide reduced fouling during styrene production / purification. Relative to the same process in the absence of the additive, the reduction in fouling can include a reduction in the formation of insoluble polystyrene and / or soluble polystyrene.

[0033] Several different chemical moieties (e.g., labile C—H and C—C bonds, oxygen and nitrogen functional groups) have been found to have the ability to inhibit adverse reactions of DVB and delay crosslinking of DVB. In some embodiments, the chemical component contains a significant amount of reactive oxygen, such as provided by, but not limited to, alcohols, aldehydes, ketones, esters, and carbonates. In some embodiments, the chemical component contains a reactive hydrogen functional group, such as, but not limited to, strained rings with β-hydrogen and carbonyl groups. In some embodiments, one or more functional groups are selected from: amines, alcohols, amino alcohols, labile C—C, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogens, diols, or combinations thereof. In some embodiments, at least one compound is selected from amines, diols, benzoates, carbamates, or combinations thereof. Without wishing to be bound by theory, a key chemical property, in addition to the boiling point described above, may be chemical instability sufficient to interfere with free radical chain polymerization. In addition, certain substances may be able to react chemically with DVB under typical styrene distillation conditions.

[0034] Suitable compounds include, but are not limited to, ethyl lactate, tetralin, acetophenone, propylene glycol, dipropylene glycol, dipropylene glycol methyl ether, transtilbene, N,N-diethyl-1,4-phenylenediamine, phenylethanol (e.g., 1-phenylethanol), benzaldehyde, benzaldehyde dimethyl acetal, diphenyl carbonate, methyl carbamate, ethyl carbamate, methyl benzoate, ethyl benzoate, ethyl acetoacetate, diethylaminoethanol, biphenyl, diethanolamine, 3-amino-1-propanol, terpineol, or a combination thereof.

[0035] Without wishing to be bound by theory, at least one component may be effective in inhibiting DVB crosslinking by consuming DVB (e.g., causing it to be incorporated into a soluble polymer or otherwise react with DVB), preventing its incorporation into free radical polymerization, or some other mechanism. For example, as shown in Example 1 below, benzaldehyde can react with DVB and thus effectively remove it from the process stream, while alkyl benzoates appear to inhibit DVB reactivity by another mechanism. Addition reactions (including, but not limited to, Diels-Alder reactions) can occur to remove DVB from the process.

[0036] The additives disclosed herein may include more than one chemical component that is effective in inhibiting DVB crosslinking and has a boiling point close to DVB. For example, in some embodiments, the additive includes one such chemical component with a boiling point lower than DVB (i.e., lower than 195°C) and another such chemical component with a boiling point higher than DVB (i.e., higher than 195°C). This additive mixture can operate across a range of vapor pressures and thus provide broad coverage for retarding DVB reactivity. For example, such a mixture comprising materials with boiling points higher than and lower than DVB can provide broad coverage in the condensation zone and distillation column.

[0037] When used together with a conventional polymerization inhibitor, the additive can further improve the overall performance. In some embodiments, the additive of the present disclosure therefore also includes a conventional polymerization inhibitor. Typically, the boiling point of the conventional polymerization inhibitor is much higher than the chemical components described herein. For example, the boiling point of a conventional polymerization inhibitor may be higher than 195°C, 200°C, 250°C or 300°C. The polymerization inhibitor includes, but is not limited to, dinitrophenols (e.g., DNOC (dinitro-o-cresol) or DNBP (dinitro-sec-butylphenol)) available from multiple commercial suppliers, TMPO compounds (e.g., 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, (2,2,6,6-tetramethylpiperidin-1-yl)oxy or (2,2,6,6-tetramethylpiperidin-1-yl) oxidanyl free radical (oxidanyl)), oximes (e.g., alternative polymerization inhibitors), etc.

[0038] According to some embodiments, a method for reducing fouling in a styrene production process according to the present disclosure comprises introducing an additive as described above into a stream comprising styrene and a byproduct, divinylbenzene (DVB). In some embodiments, the stream comprising styrene and DVB is crude styrene formed in a reactor configured to produce styrene. Crude styrene can be a product of dehydrogenation of ethylbenzene (EB), whereby EB is dehydrogenated in the presence of superheated water vapor (i.e., steam) according to equation (1):

[0039]

[0040] The system and method for producing this crude styrene product is known in the art, and in some embodiments, crude styrene is produced by any such known system and method.For example, multi-stage EB dehydrogenation system and method are described in the U.S. Patent Application No. 62 / 436653 submitted on December 20, 2016, and this document is included in this paper in full by reference, for the purpose not conflicting with the present disclosure.The system and method for producing this crude styrene is described in more detail hereinafter.

[0041] In some embodiments, the additive is introduced at a concentration of 0.001%, 0.01% or 0.1% by weight of the stream comprising styrene and DVB. In some embodiments, the stream containing styrene into which the additive is introduced can be the crude styrene reactor effluent of an EB dehydrogenation reactor. In some embodiments, the stream containing styrene into which the additive is introduced is a feed stream, a recovery stream or a reflux stream to a distillation column (or other purification unit) that enters a styrene purification / recovery section downstream of a reactor (e.g., an EB dehydrogenation reactor) that produces crude styrene. As described below with reference to Figure 2 Discussed in more detail, the distillation column can include a distillation column configured to separate an overhead product comprising EB from a bottoms product comprising styrene, a distillation column configured to separate an overhead product comprising benzene and toluene from a bottoms product comprising EB and styrene, or a distillation column configured to separate an overhead product comprising styrene from a bottoms product comprising tar.

[0042] Also disclosed herein is a composition comprising a crude styrene stream containing styrene and by-product DVB and an additive as described above.

[0043] Systems for styrene production / purification

[0044] Now refer to Figure 1 A process for producing styrene employing the additives disclosed herein is described. Figure 1 is a process flow diagram of a styrene production system 1 according to an embodiment of the present disclosure. The styrene production system 1 includes a crude styrene production apparatus 100 disclosed in this patent; a cooling, exhaust and condensate removal apparatus 110; a separation or "distillation" apparatus 120; and an oxidation apparatus 130. The crude styrene production apparatus 100 is any apparatus operable to produce crude styrene comprising styrene and DVB from reactants. The reactants may be introduced via one or more reactant supply lines. For example, in Figure 1In some embodiments, the first reactant line 101 and the second reactant line 102 are combined to produce a reactant supply inlet line 103, which is fluidically connected to the crude styrene production equipment 100. In some embodiments, the reactant supply can provide approximately equal EB and steam mass flow rates. Alternatively, the first reactant line 101 and the second reactant line 102 can both introduce reactants directly into the crude styrene production equipment 100. Crude styrene is removed from the crude styrene production equipment 100 via a crude styrene discharge line 105. As described below with reference to Figure 2 Further discussed, in some embodiments, crude styrene is produced by EB dehydrogenation.Systems and methods for producing crude styrene by EB dehydrogenation are known in the art, and can be used for providing crude styrene in some embodiments.For example, in some embodiments, the multi-stage EB dehydrogenation as described in U.S. Patent Application No. 62 / 436,653 can be adopted.

[0045] The cooling, off-gas and / or condensate removal apparatus 110 is operable to cool the crude styrene effluent of the crude styrene production facility 100 (which is introduced into the crude styrene effluent via the crude styrene effluent line 105) by heat exchange and may be referred to herein as simply the "cooling apparatus" or "condensation zone" 110. The cooling, off-gas and / or condensate removal apparatus 110 may also be used to separate waste and / or condensate from the crude styrene, thereby providing crude styrene that has been degassed and from which condensate (e.g., water) has been removed. An off-gas line 112 may be fluidly connected to the cooling apparatus 110 so that off-gas may be removed therefrom, and a condensate line 111 may be fluidly connected to the cooling apparatus 110 so that condensate may be removed therefrom. In some embodiments, the off-gas line 112 is associated with a separation apparatus 120. A separation supply line 113 may fluidly connect the cooling apparatus 110 to the separation apparatus 120 so that the cooled crude styrene mixture (which may also be degassed and / or dehydrated) may be introduced into the separation apparatus 120.

[0046] Separator 120 is any equipment that can be operated to remove one or more by-products, unreacted reactant and heavy residue (for example, tar) from cooling styrene mixture, thereby provides the styrene monomer stream of purification.For example, separator 120 can be configured to separate the unreacted reactant stream (for example, EB) that can be removed from separator 120 via unreacted reactant outlet line 122, one or more by-product streams that can be removed from separator 120 via one or more by-product outlet lines 121 and the tar that can be removed from purified styrene monomer stream via tar outlet line 125, it can be removed from separator 120 via styrene monomer (SM) outlet line 123.In some embodiments, the styrene monomer of purification comprises and is lower than, 150,100 or 75PPM EB.Unreacted reactant outlet line 122 can for example make separator 120 be connected with crude styrene production equipment 100 fluids via pipeline 101 and / or 103, thus recyclable unreacted reactant is to produce extra crude styrene.

[0047] When the crude styrene production facility 100 includes one or more EB dehydrogenation reactors, the unreacted reactants may include EB, which may be recycled to the crude styrene production facility 100, for example, via an unreacted reactant outlet line 122, and the by-products may include benzene and / or toluene, which may be removed from the separation facility 120 via one or more by-product outlet lines 121.

[0048] In some embodiments, tar recovery is utilized, whereby at least a portion of the tar in the tar outlet line 125 (and / or the oxidation residue outlet line 136) is recovered via one or more tar recovery lines 128. In this embodiment, the one or more tar recovery lines 128 may be configured to recycle the tar / heavy residue to the separation feed line 113, or to any individual column within the separation or distillation apparatus 120.

[0049] All or a portion of the styrene tar stream in the tar outlet line 125 can be used to feed a tar oxidation unit operation, wherein components in the tar stream can be oxidized to hydrocarbon oxides (oxygenates), which can be recycled back to the separation section to provide the insoluble polymer reduction additive. For example, without limitation, styrene in the styrene tar can be oxidized to benzaldehyde, acetophenone, or phenylethyl alcohol; these substances can effectively reduce insoluble polymer fouling. Other substances in the tar can also form such oxides and provide the same or similar effects. Therefore, in some embodiments, the tar outlet line 125 is fluidly connected to an oxidation unit or device 130. The oxidation unit or device 130 is any oxidation device that is operable to oxidize at least a portion of the tar introduced thereto via the tar outlet line 125 into at least one chemical component described above for use in the additives disclosed herein. For example, the tar may contain some latent styrene monomer and / or other monomers / compounds that can be converted (i.e., oxidized) to form the desired oxygenated chemical components of the additives described herein, such as, but not limited to, acetophenone, phenylethyl alcohol, and / or benzaldehyde. In an exemplary embodiment, a laboratory batch reactor at 120° C. showed that 1.4% benzaldehyde, 0.9% acetophenone, and 50 ppm phenylethanol could be produced using a plant stream sample. It should be noted that the oxidation unit operation can be used on styrene tar and / or another stream from separation section 120, provided that the stream contains an oxidizable species.

[0050] The one or more additive component outlet lines 137 can be configured to remove at least one additive component from the oxidation unit 130, which can be reintroduced as an additive component at another location in the styrene production system 1. The additive component stream in the additive component outlet line 137 from the oxidation reaction in the oxidation unit 130 can be recycled back to the feed stream for separation (e.g., separation feed line 113) and / or recycled back to another point within the separation section within the separation device 120. For example, as further described below, the one or more additive component outlet lines 137 can be configured to be used in the effluent as is, or to remove at least one oxidation compound from the tar oxidation device 130, which can be combined with other additive components and / or introduced into the crude styrene effluent in the crude styrene effluent line 105, the cooled (and / or degassed and / or dehydrated) crude styrene effluent in the separation feed line 113, a distillation column that is fed, recycled, and / or refluxed to the separation device 120, or a combination thereof. The oxidation residue can be used as is in the effluent or removed from the oxidation unit or apparatus 130 via oxidation residue outlet line 136. Although not shown in the figure, in some embodiments, a portion of the styrene monomer (e.g., in purified styrene monomer outlet line 123 (or elsewhere)) is introduced into the oxidation unit (with or without EB tar) to produce oxidation chemical components for use in the additives described herein.

[0051] As mentioned above, styrene, with a boiling point of 145°C, thermally self-initiates polymerization in the liquid state (styrene polymerization does not occur in the gas phase), and the polymerization rate can be greater at temperatures above 80°C. DVB has a boiling point 50°C higher than that of styrene and can also thermally self-initiate polymerization. Therefore, there may be areas in styrene production plants where DVB accumulates in high concentrations through condensation. This area may be the location where insoluble polymer formation is initiated. Two main areas of potential concern have been identified, and it is precisely in these areas that the introduction (and / or presence) of the disclosed additives may be particularly useful. The first area is where the gaseous crude styrene in the styrene production reactor first condenses to a liquid. In this area, the high-boiling-point DVB may liquefy before the styrene liquefies, providing a location for exposure to hot liquid DVB. The second potential initiation zone may be in the distillation column of the downstream separation / purification equipment, where DVB vapor can condense in the absence of inhibitors / retarders. Once produced, the insoluble polymer can attach and grow over time, with attachment occurring at the initiation point and / or somewhere downstream. The insoluble polymer can absorb and retain styrene, promoting its growth. Thus, in some embodiments, the method for reducing fouling in the styrene production process of the present disclosure comprises introducing an additive (as described above) into one or more streams comprising styrene and byproduct divinylbenzene (DVB) in the first zone (via one or more additive inlet lines A1), in the second zone (via one or more additive inlet lines A2), and / or into another zone (via one or more additive inlet lines A3).

[0052] For example, Figure 1 As shown, before the crude styrene effluent is cooled in the cooling device 110, the additive according to the present disclosure can be introduced into the crude styrene effluent line 105 through the additive inlet line A1, thereby allowing the additive to be present in the first zone described above, wherein the gaseous crude styrene from the styrene production reactor of the crude styrene production device 100 is first condensed into a liquid. Alternatively or additionally, the additive according to the present disclosure can be introduced before or during the purification of the cooled crude styrene, such as Figure 1 In this way, the additive will be present in the relevant second area of ​​interest in the distillation column of the downstream separation / purification device 120, where the DVB vapor can condense in the absence of inhibitors / retarders.

[0053] Alternatively or additionally, the disclosed additives may be introduced at other locations, such as, but not limited to, into a tar recovery stream, such as Figure 1In this embodiment, the one or more additive inlet lines A3 may be configured to introduce the additives of the present disclosure into one or more tar recovery lines 128, which are configured to recover tar / heavy residue from the tar outlet line 125 (and / or the oxidation residue outlet line 136 discussed below) to the separation feed line 113 and / or any individual column in the separation section.

[0054] In some embodiments, since the temperature of the first zone (i.e., the zone where the gaseous crude styrene is first condensed into liquid within the cooling device 110) is generally higher than the distillation column of the separation device 120, the additive introduced into the first zone via the additive inlet line A1 may be different from the additive introduced into the second zone via the additive inlet line A2 and / or the additive introduced into another zone via the additive inlet line A3.

[0055] Production of crude styrene in a crude styrene production plant

[0056] In some embodiments, the crude styrene containing styrene and DVB is produced in crude styrene production equipment 100 by EB dehydrogenation.This EB dehydrogenation can be carried out in a conventional manner known to the art, including steam dilution, reduced pressure operation and adiabatic reactor.For endothermic reaction, regenerator (reheater) is located between adiabatic reactor.Dehydrogenation reaction can be carried out under low pressure, so reactor is usually operated under reduced pressure (that is, vacuum condition) by installing compressor (such as vacuum compressor) on effluent line.Conventional three-bed reactor system is arranged in series mode, and is the common transformation option that improves plant capacity.

[0057] In some embodiments, as described in U.S. Patent Application No. 62 / 436,653, the first two EB dehydrogenation reactors of a multi-stage dehydrogenation application can be operated in parallel, and their combined product streams fed to a common third reactor, thereby enabling reductions in overall reactor pressure, reduced energy requirements, and / or increased product selectivity while maintaining desired conversion.

[0058] In some embodiments, crude styrene is produced by a conventional styrene manufacturing process using a reaction system comprising two or three adiabatic reactors connected in series and a plurality of furnaces and heat exchangers. Styrene can be prepared by dehydrogenating EB on a dehydrogenation catalyst bed in a reactor in the presence of superheated water vapor (i.e., steam). In this process, EB is mixed with a gas phase having a volume of 6 to 12 times that of the EB in high-temperature steam and passed through a solid bed of catalyst. Most ethylbenzene dehydrogenation catalysts are based on iron oxide and are promoted by a few percent of potassium oxide or potassium carbonate.

[0059] During the dehydrogenation process, high ethylbenzene conversion and high selectivity for styrene are required to suppress the production of by-products such as benzene and toluene. Process parameters that influence dehydrogenation performance include reaction temperature, reaction pressure, space velocity, and the mixing ratio of steam to hydrocarbons (e.g., ethylbenzene).

[0060] Since the ethylbenzene dehydrogenation reaction is an endothermic reaction, a higher reaction temperature is beneficial for the reaction. However, when the reaction temperature is too high, the selectivity for styrene decreases, and side reactions that produce benzene, toluene, or other by-products become dominant. Due to the considerable amount of reaction heat, the outlet temperature of the reactor is significantly lower than the inlet temperature of the reactor. To compensate for the temperature drop, conventional dehydrogenation processes use multiple reactors and provide interstage energy addition between the reactors.

[0061] Water is a catalytic poison in many reactions, but it is well known that water plays an important role in the dehydrogenation of ethylbenzene. Steam reacts with potassium and iron to create active centers, providing latent heat for powering the endothermic reaction and removing carbon deposits (i.e., coke) that often form on the iron oxide catalyst by the water gas shift reaction. The potassium promoter of the catalyst enhances this decoking reaction. Steam also dilutes the reactants and products, shifting the position of chemical equilibrium toward the products. Since a lot of energy is required to maintain steam above 600°C, it is preferred to use a process that uses minimal energy. When excess steam is used at high temperatures, an important active component of the dehydrogenation catalyst (i.e., potassium) dissolves and elutes through the reactor outlet. This is the main cause of catalyst deactivation.

[0062] Because the number of product molecules produced is more than the number of reactants, the conversion rate of ethylbenzene dehydrogenation decreases with the increase of pressure. That is to say, lower pressure (or ethylbenzene partial pressure) is conducive to the production of styrene by promoting product equilibrium. Therefore, it may be necessary to operate EB dehydrogenation at a pressure as low as possible without applying too large a capacity load on the compressor. When the pressure is reduced, due to the reduction of catalyst coking, stability increases, and due to the relative reduction of the side reaction (which produces the by-products mainly composed of benzene and toluene) degree, the selectivity to styrene is also improved. Therefore, decompression is also considered to be very advantageous in this process, and conversion rate and selectivity can be improved. Dehydrogenation reactor can be operated under vacuum to improve conversion rate and selectivity. The typical total conversion rate of two reactors running in series is about 60-63%, and the typical total conversion rate of three reactors running in series is about 63-70%. The selectivity to styrene is generally 92-97 mol %.

[0063] Since styrene and ethylbenzene have similar boiling points, their separation requires large distillation columns and high return / reflux ratios.Thus, the desired conversion can be maintained within the dehydrogenation reactor, thereby reducing the amount of EB that must be separated from the product stream.

[0064] Now refer to Figure 2 Describing a styrene production system according to another embodiment of the present disclosure, Figure 2 is a process flow diagram of a styrene production system II. The styrene production system II includes an EB dehydrogenation 200; a cooling, off-gas and condensate removal device 210 (also referred to as a 'condensing section 210'); a styrene separation / distillation section 220; and a tar oxidation section 230. An EB dehydrogenation system 200 according to the present disclosure may include any number of dehydrogenation reactors in series and / or in parallel. In some embodiments, the EB dehydrogenation system 200 includes three dehydrogenation reactors in series as described above, while in other embodiments, the dehydrogenation system 200 includes two dehydrogenation reactors in series upstream of and in parallel with a downstream dehydrogenation reactor. In Figure 2 In an embodiment, a crude styrene production system includes an EB dehydrogenation system 200, which includes a first EB dehydrogenation reactor DR1 connected in series with a second EB dehydrogenation reactor DR2. The EB dehydrogenation reactors DR1 and DR2 are configured to convert EB into styrene by dehydrogenation. During EB dehydrogenation, styrene is produced as shown in Equation 1 above and the schematic diagram in Equation 2 below:

[0065] Ethylbenzene → styrene + hydrogen (2).

[0066] Additionally, some benzene and toluene are produced via equations 3 and 4:

[0067] Ethylbenzene → Benzene + Ethylene (3)

[0068] Ethylbenzene + hydrogen → toluene + methane (4).

[0069] The EB in the EB reactant line 201 is combined with the steam in the steam reactant line 202 and introduced into the first EB dehydrogenation reactor DR1 through the reactant supply inlet line 203. In the first EB dehydrogenation reactor DR1, the EB is dehydrogenated in the presence of a suitable dehydrogenation catalyst under dehydrogenation conditions to produce styrene and hydrogen. The product of the first EB dehydrogenation reactor DR1 is introduced into the second EB dehydrogenation reactor DR2 through the first dehydrogenation reactor outlet line 204. In the second EB dehydrogenation reactor DR2, unreacted EB (and / or EB directly introduced into the second EB dehydrogenation reactor DR2) is removed. Figure 2 (not shown in the embodiment)) is converted into styrene monomer in the presence of a dehydrogenation catalyst.

[0070] Dehydrogenation reactors DR1 and DR2 can be any dehydrogenation reactor known to those skilled in the art. As mentioned above, a three-reactor system is an equally viable option. In some embodiments, dehydrogenation reactors DR1 and DR2 are adiabatic reactors. Dehydrogenation reactors DR1 and DR2 contain a dehydrogenation catalyst therein, which is suitable for catalyzing the dehydrogenation of hydrocarbons in a hydrocarbon supply into dehydrogenated products. In some embodiments, the dehydrogenation catalyst is a catalyst that can be operated to dehydrogenate ethylbenzene in a hydrocarbon supply to produce a dehydrogenated product containing styrene. Suitable dehydrogenation catalysts and conditions are known in the art and will not be described in detail herein. For example, the conditions may include a temperature of about 600° C., a reduced pressure at the outlet (e.g., 7 PSIA (48 kPa)) and a large steam dilution (e.g., a molar ratio of steam to EB of 6-9). It is obvious to those skilled in the art that a suitable dehydrogenation catalyst is selected based on given reactor conditions. In some embodiments, the dehydrogenation catalyst includes iron (III) oxide, promoted by potassium oxide or potassium carbonate, rare earth oxides and other inorganic performance promoters. In some embodiments, the dehydrogenation catalyst comprises a heterogeneous catalyst system adapted to operate under steam dilution, reduced pressure, and elevated temperature to overcome equilibrium limitations and endothermic reactions.

[0071] The crude styrene effluent from the EB dehydrogenation unit 200 is introduced into a cooling, off-gas and / or condensate removal unit 210 via a crude styrene effluent line 205. The cooling, off-gas and / or condensate removal unit 210 is configured to cool the hot dehydrogenation reactor crude styrene effluent from the EB dehydrogenation unit 200 and may also be configured to remove off-gas and / or condensate therefrom. Figure 2 In some embodiments, the heat exchanger 206 is configured to reduce the temperature of the crude styrene effluent in the crude styrene effluent line 205 by exchanging heat with a cooling medium introduced into the heat exchanger 206 via a coolant inlet line 207. The cooled crude styrene is withdrawn from the heat exchanger 206 via a cooled crude styrene outlet line 209, and the heated heat exchange medium is withdrawn from the heat exchanger 206 via a heat exchange outlet line 208. In some embodiments, a separator may be used to separate gas and / or condensate from the cooled crude styrene. For example, in Figure 2 In an embodiment, the separator 214 is configured to separate gas and condensate (e.g., including condensed water) from the cooled crude styrene introduced via the cooled crude styrene outlet line 209. Gas from the separator 214 can be introduced into the gas compressor 215 via the gas line G, and the compressed liquid is returned to the separator 214 via the liquid line L. Exhaust gas can be removed from the compressor 215 via the exhaust gas outlet line 212. Condensate can be removed from the separator 214 via the condensate outlet line 211. Additives of the present disclosure can be introduced into the condensing section 210, such as the heat exchanger 206, via one or more additive inlet lines A1.

[0072] The cooled crude styrene, from which off-gases and / or condensates have been removed, may be introduced into a styrene separation / distillation unit 220 (also referred to herein as a styrene purification unit 220) via separation or "dehydrogenation mixture" or "DM" supply line 213. The styrene purification unit 220 may include any suitable number of distillation columns, as known in the art. Typically, a separation system may be used to separate one or more by-products (e.g., benzene and / or toluene), unreacted reactants (e.g., EB), and heavy residue (also referred to herein as "tar") to provide a purified styrene monomer stream. In some embodiments, the styrene separation system 220 includes: one or more distillation columns configured to separate a bottoms product comprising EB and styrene and an overhead product comprising benzene and toluene, one or more distillation columns configured to separate an overhead product comprising benzene from a bottoms product comprising toluene, EB, and styrene, one or more distillation columns configured to separate an overhead product comprising toluene from a bottoms product comprising EB and styrene, one or more distillation columns configured to separate an overhead product comprising EB from a bottoms product comprising styrene, one or more distillation columns configured to separate an overhead product comprising styrene from a bottoms product comprising tar, or a combination thereof.

[0073] Figure 2The styrene separation / distillation apparatus 220 of the embodiment includes four distillation columns, including a first distillation column D1, a second distillation column D2, a third distillation column D3, and a fourth distillation column D4. The first distillation column D1 is configured to separate cooled crude styrene introduced therein via the separation or DM supply line 213 into an overhead product comprising benzene (withdrawn therefrom via a benzene outlet line 221A) and a bottom product comprising toluene, EB, and styrene (withdrawn therefrom via a first distillation column bottoms outlet line 223A). The second distillation column D2 is configured to separate the first distillation column bottoms product introduced therein via the first distillation column bottoms outlet line 223A into an overhead product comprising toluene (withdrawn therefrom via a toluene outlet line 221B) and a bottom product comprising styrene and EB (withdrawn therefrom via a second distillation column bottoms outlet line 223B). As described herein, in some embodiments, the first and second distillation columns D1 and D2 may be combined into a single column to remove a mixed stream of benzene and toluene from the overhead space. The third distillation column D3 is configured to separate the second distillation column bottoms product introduced therein via the second distillation column bottoms product outlet line (223B) into an overhead product comprising EB (which is withdrawn therefrom via the EB outlet line 222) and a bottoms product comprising styrene (which is withdrawn therefrom via the third distillation column bottoms outlet line 224). The fourth distillation column D3 is configured to separate the third distillation column bottoms product introduced therein via the third distillation column bottoms product outlet line (224) into an overhead product comprising styrene monomer (which is withdrawn therefrom via the purified styrene outlet line 223) and a bottoms product comprising tar (which is withdrawn therefrom via the fourth distillation column bottoms or "tar" outlet line 225). Optionally, an additional column may be used to remove latent monomers from the tar stream.

[0074] In some embodiments according to the present disclosure, the additive A2 is introduced into the feed stream, the recycle stream, or the reflux stream or is introduced together with the feed stream, the recycle stream, or the reflux stream into the distillation column downstream of the EB degassing reactor. For example, the additive inlet line A2 may be configured to introduce the additive into the first distillation column D1 alone or in combination with the cooled crude styrene in the DM feed line 213. Alternatively or additionally, the additive of the present disclosure may be introduced into the reflux line of one of the distillation columns, for example, in some embodiments, the additive of the present disclosure may be introduced into the top reflux R1A and / or the bottom reflux R1B of the first distillation column D1, into the top reflux R2A and / or the bottom reflux R2B of the second distillation column D2, into the top reflux R3A and / or the bottom reflux R3B of the third distillation column D3, and / or into the top reflux R4A and / or the bottom reflux R4B of the fourth distillation column D4. For example, in Figure 2In the embodiment of the present invention, the additive inlet line A2' is configured to introduce the additive of the present disclosure into the third distillation column D3 (which is configured to separate the top product containing EB and the bottom product containing styrene) by introducing the bottom product of the second distillation column D2 thus extracted through the bottom of the second distillation column and the outlet line 223B. (Although in Figure 2 In some embodiments, the additive supply line A2' may be directly introduced into the third distillation column D3. Figure 2 In an embodiment, the additive inlet line A2" is configured to introduce the additive of the present disclosure into the third distillation column D3 (which is configured to separate an overhead product comprising EB and a bottom product comprising styrene) by introducing the overhead reflux thus introduced via the overhead reflux line R3A.

[0075] As mentioned above Figure 1 As described in the embodiment of the present disclosure, the styrene production system according to the present disclosure may further include an oxidation device 230, wherein the oxidation device 230 is configured to oxidize at least one component of the tar introduced therein via the fourth distillation column outlet line 225. The oxidation device 230 may be configured to produce at least one oxidation chemical component suitable for the additive of the present disclosure and an oxidation residue, which may be used as it is in the effluent or removed from the tar removal device 230 via the additive component outlet line 237, and the oxidation residue may be removed from the tar oxidation device 230 via the oxidation residue outlet line 236. The additive component outlet line 237 allows the tar oxidation device 230 to be fluidically connected to an upstream device, thereby allowing the oxygen-containing chemical component produced in the oxidation device 230 to be introduced into the upstream device as an additive or additive component. Alternatively, as described above with reference to Figure 1 As described in the embodiment of FIG. 2 , if desired, oxidation device 230 can be located at another location within separation system 220 and the oxidation stream in additive component outlet line 237 can be recycled to any suitable point in the separation section.

[0076] Despite Figure 2In the embodiment of the present invention, one arrangement of distillation columns is described, but it will be understood that other combinations and / or sequences of distillation columns can be used to separate styrene monomer from crude styrene, and such alternative arrangements are included within the scope of the present disclosure. For example, another styrene separation / distillation section may include a first distillation column configured to separate a bottom product comprising EB and styrene from an overhead product comprising toluene and benzene; a second distillation column configured to separate the bottom product comprising EB and styrene from the first distillation column into an overhead product comprising EB (which can be recycled to the EB dehydrogenation section) and a bottom product comprising styrene and tar; and a third distillation column configured to separate the bottom product comprising styrene and tar from the second distillation column into an overhead product comprising styrene monomer and a bottom product comprising tar. In this embodiment, the additives according to the present disclosure may be added to any combination of feed, recycle, and / or reflux to the distillation columns, for example, added to the crude styrene feed to the first distillation column and / or added to the reflux to the second distillation column. In other embodiments, multiple distillation columns may be used to achieve a given separation. As a non-limiting example, in some embodiments, multiple distillation columns are used to separate the crude styrene stream from which benzene, toluene, and EB have been removed into a purified styrene monomer product and a tar stream (i.e., separation of styrene from tar). In addition, various other components (e.g., heaters) can be used in systems known in the art (e.g., to maintain flowable tar). Other configurations are suitable and will be apparent to those skilled in the art.

[0077] As described above, the additive disclosed herein introduced via additive inlet line A1 in the first zone (i.e., the zone in the styrene production reactor where the gaseous crude styrene is first condensed into a liquid) may be different from the additive introduced via additive line A2 into the second zone (i.e., in the distillation column of the downstream separation / purification equipment where the DVB vapor may condense in the absence of an inhibitor / retarder), which itself may be the same as or different from the additive introduced elsewhere (e.g., into the tar recovery stream) via additive inlet line A3. One skilled in the art can determine by routine experimentation which additive disclosed herein is most effective for a given injection / introduction location. However, for example, additives introduced into the first zone (e.g., via additive inlet line A1) may comprise higher boiling point chemical components and / or different chemical reactivity (e.g., different functional groups) than additives introduced into the second zone (e.g., via additive inlet line A2, A2', A2"). Similarly, additives introduced into the first zone (e.g., via additive inlet line A1) and / or (e.g., via additive inlet lines A2, A2', A2") may comprise lower boiling point chemical components and / or different chemical reactivity than additives introduced into the third zone (e.g., via additive inlet line A3). For example, benzoates may be more suitable as an additive or additive component for introduction into the second zone, but may not be suitable for use in the first zone due to decomposition in the presence of steam.

[0078] In some embodiments, an additive is injected into the cooling, exhaust, and / or condensate removal equipment 110 / 210 (e.g., via additive line A1) to inhibit or prevent the formation of insoluble polymers due to DVB liquefaction and initiation. The additive can be injected neat or as a solution at a dosage of 1 to 1000 ppm (0.0001 wt% to 0.1 wt%) relative to the organic portion of the process stream. Without limitation, in this embodiment, the additive can be selected from the group consisting of phenylethyl alcohol, terpineol, propylene glycol, ethyl carbamate, acetophenone, benzaldehyde, tetralin, diethanolamine, 3-amino-1-propanol, or combinations thereof. In some embodiments, the additive introduced into the first zone exhibits high functionality at higher temperatures, is not disturbed by steam, has a reactivity suitable for condensation conditions, or a combination thereof.

[0079] In some embodiments, an additive is injected into any column of the feed or separation section or apparatus 120 / 220 (e.g., via additive lines A2, A2', A2", or other) to prevent insoluble polymer formation due to DVB liquefaction and initiation. The additive can be injected neat or as a solution at a dosage of 1 to 1000 ppm (0.0001 wt% to 0.1 wt%) relative to the organic portion of the process stream. Without limitation, in this embodiment, the additive can be selected from the group consisting of propylene glycol, dipropylene glycol, methyl benzoate, benzaldehyde, diethylaminoethanol, acetophenone, DPGME (dipropylene glycol methyl ether), tetralin, ethyl acetoacetate, terpineol, biphenyl, or a combination thereof. In some embodiments, the additive introduced into the second zone provides a suitable boiling point, sufficient reactivity for high styrene / DVB concentrations, acceptable physical properties, or a combination thereof.

[0080] In some embodiments, the additive introduced into the third zone via additive inlet line A3 has properties suitable for its injection point back into the system.

[0081] In some embodiments, the additive is prepared (partially or entirely) from a crude stream or styrene tar stream containing an appropriate oxidizable component by a tar oxidation unit 130 / 230. The oxidized gas stream (in the additive component outlet line 137 / 237) may contain a mixture of oxidation products of the tar or crude gas stream components as an additive combination at a concentration of about 10 ppm to 100,000 ppm (0.001 wt% to 10 wt%). In some embodiments, the additive in the oxidized stream may be injected into the feed stream 113 / 213 to the separation section 120 / 220 or anywhere else therein. Without limitation, in this embodiment, the additive may be selected from the group consisting of acetophenone, benzaldehyde, phenylethyl alcohol, and combinations thereof.

[0082] Features / Potential Advantages of the Additives, Compositions, Systems, and Methods Disclosed herein

[0083] The additive described herein comprises one or more chemical components, whose boiling point is close to DVB, and can also suppress the formation of insoluble polymers by its reactive functional groups. Because crude styrene contains DVB, which is an effective cross-linking agent that forms insoluble polymers present during styrene polymerization, the additive disclosed herein can be used to minimize the amount of insoluble polymers (i.e., polystyrene) formed during styrene production (e.g., during the purification of styrene monomer by crude styrene stream). The one or more chemical components comprise one or more reactive functional groups, which comprise reactive organic substances with oxygen, hydrogen, nitrogen and / or similar active sites. The organic matter includes, but is not limited to, alcohols, aldehydes, ketones, acids and unstable hydrogen. Insoluble polymer structures can reduce output, shorten operating time and extend turnaround time. Therefore, in some embodiments, the additive, composition, system and method of the present invention can provide increased output, longer operating time and / or shortened turnaround time. Example

[0084] Example 1: Performance of Additives to Reduce Insoluble Polymers

[0085] Various additives were tested for their ability to control the formation of insoluble polymers. Performance evaluations were performed in the liquid phase using a 6-port test system. A conventional heating block with six ports was used that accommodated 25 (D) x 150 (H) mm tubes, allowing for simultaneous operation of six different solutions. Each tube was sealed with a septum cap and each tube was purged using a conventional nitrogen head. The nitrogen purge was introduced into the tubes using 1 / 16" tubing extending through the septum cap. The purge gas was expelled using a syringe needle.

[0086] A test solution containing about 60 weight percent (wt%) styrene was collected from a laboratory insulation pilot unit as a crude styrene sample. Crude styrene was added to DVB to produce a 0.1 wt% concentration. The additive was used at the same concentration, i.e., 0.1 wt%. Crude styrene with 0.1 wt% DVB was used as a reference sample. In order to evaluate, 10 g of the solution was placed in a test tube and purged with nitrogen at room temperature. The heating module was set to 120 ° C and stabilized before introducing the test solution. After purging each solution, each test tube was moved into the heating module port. Samples were taken after 15 minutes and 30 minutes. A method for measuring low levels of DVB and quantitatively analyzing common crude styrene substances was used to analyze each sample by gas chromatography (GC), and the common crude styrene substances included benzene, toluene, EB, styrene, DVB, ethyl vinyl benzene, and phenylacetylene. The test solution was also subjected to a gravimetric analysis test of polymers and heavy substances using a solid analyzer, which included an electronic balance and a high-intensity infrared lamp operable to evaporate the monomer. Changes in DVB concentration (a decrease in this concentration can be associated with insoluble polymer formation) and soluble polymer formation were recorded.

[0087] Table 1 lists the additives tested in this example. The substances tested were selected based on their boiling points (higher than styrene and closer to DVB). The boiling points of the additives tested are also shown in Table 1; styrene and DVB and their boiling points are included for reference.

[0088]

[0089]

[0090] After 30 minutes at 120°C, the results of adding 1000 ppm of the additive to the crude styrene to which 1000 ppm of DVB was given are as follows: Figure 3 As shown, this is a bar graph of the percent change in DVB and percent polymer growth for the additive of Example 1. Figure 3 In the formula (Bzald is benzaldehyde, PhE is 1-phenylethanol, BZDMA is benzaldehyde dimethyl acetal, DPC is diphenyl carbonate, ET Lactate is ethyl lactate, Etaceto acetate is ethyl acetoacetate, AcPhen is acetophenone, dpgme is dipropylene glycol methyl ether, DiET-amino-EtOH is diethylaminoethanol, DiPG is dipropylene glycol, PG is propylene glycol, and N,N-diEt PDA is N,N-diethyl-1,4-phenylenediamine.)

[0091] The additives tested included N,N-diethylphenylenediamine, methyl carbamate, ethyl carbamate, methyl benzoate, ethyl benzoate, dipropylene glycol, diethylaminoethanol, biphenyl, cyclohexanol, and ethyl acetoacetate; the functional groups of the active substances tested included amines, amino alcohols, labile C-C bonds, esters, and carbamates. Amines, diols, benzoates, and carbamates produced particularly good results.

[0092] Most of the additives evaluated showed a correlation between their % PS formation and the change in % DVB, suggesting that they act by inhibiting the initiation and / or propagation of styrene polymerization. This is expected because DVB is consumed by free radical polymerization; once polymerization occurs, DVB will be incorporated into the polymer. However, as discussed below, there are some exceptions to this correlation. The results for all additives tested are summarized in Figure 4 middle, Figure 4 Graph showing the percentage of soluble polystyrene (PS) polymer formed as a function of the percentage of DVB in the Example 1 additive.

[0093] Without wishing to be bound by theory, it is believed that benzaldehyde reacts with DVB, resulting in high DVB consumption during the test period. Benzaldehyde also inhibited polymer formation. The two benzoate species also showed inconsistent correlations with the other species. Methyl benzoate and ethyl benzoate showed little change in DVB %. Ethyl benzoate showed no ability to inhibit polymer formation, while methyl benzoate showed moderate inhibition. Again, without wishing to be bound by theory, this suggests that some other interaction with DVB prevents it from participating in free radical polymerization and crosslinking of the polymer, and also suggests that benzoate derivatives can be mixed with standard anti-polymerization inhibitors to prevent DVB crosslinking by selectively inhibiting its reaction.

[0094] Example 2: Study on fouling in the crude styrene condensation area

[0095] As mentioned above, the first major area of ​​a styrene production plant with respect to potential insoluble polymer formation is the heat exchanger area, where the condensate from the vapor-phase reactor effluent is cooled and liquefied. This condensation zone has sufficient temperatures to initiate styrene polymerization and sufficient concentrations of DVB to form insoluble polymers. DVB, with its higher boiling point of 195°C, liquefies before styrene during condensation; it can also thermally initiate polymerization. Therefore, a test apparatus was designed to simulate the conditions under which crude styrene in the vapor phase and vapor condenses to a liquid.

[0096] The crude styrene feed was prepared from the EB dehydrogenation lab reactor effluent, which contained approximately 55-65 wt% styrene, 35-45 wt% EB, 2 wt% benzene / toluene, and trace amounts of byproducts (to which an additional 500 ppm DVB was added). Figure 5 Schematic diagram of the crude styrene concentration test equipment of Example 2. ISCO syringe pumps 301 and 302 are used to add crude styrene and water to the system to generate steam, respectively. The main container 309 consists of a horizontal tube 310, which has the dimensions of 1 / 2" inner diameter (ID) by 15" length, wrapped in heat tape 311 set at 130°C and powered by an independent controller 312. Water is supplied through a 1 / 8" tube 304 to a preheated vaporization zone 306 set at 135°C controlled by an independent controller 307 to heat the heat tape 305 connected to the inlet 308 of the horizontal tube 310. The crude styrene passes through a 1 / 8" tube 303 with steam at the inlet 308 of the horizontal tube 310. The effluent 313 passes through a water-cooled condenser (not shown) and enters a sample collection or effluent bottle 314. Nitrogen was introduced through a 90 PSI nitrogen utility line, regulator 315, and tube 316 to purge the horizontal tube 310 between tests. Nitrogen was used to remove oxygen before testing and to clean the equipment between tests.

[0097] Individual tests were conducted by adding selected additives to crude styrene. The dosages listed are based on the hydrocarbon portion only and do not include steam / water. The hot tapes 305 and 311 were first started and allowed to reach the set point (i.e., 135°C and 130°C, respectively). The water pump was started at 0.25 ml / min and run until the system stabilized with only steam. The crude styrene pump was then started at 0.5 ml / min. The piping 310 of the main container 309 was maintained in the temperature range of 110°C to 140°C. Most tests were conducted at 110°C or 130°C. The data from the 130°C tests were used to select acceptable additives. After four hours, a composite effluent sample was collected and analyzed by GC along with the crude styrene feed sample. The change in DVB (weight percentage loss by GC) concentration from the feed to the effluent was recorded; the greater the DVB loss, the more insoluble polymer was presumably formed. The formation of insoluble polymer was confirmed by inspecting the horizontal tubes after the test was conducted.

[0098] Several candidates with suitable physical properties were evaluated using the crude styrene condensation test equipment described above. The condensation additive test data obtained are shown in Tables 2 and Figure 6 As shown, Figure 6 It is a bar graph of the DVB percentage change of the condensation test results of Example 2.

[0099] The additives were tested at a dose of 200 ppm. PhE (phenylethyl alcohol), terpineol, and PG (propylene glycol) showed higher performance, while urethane, acetophenone, biphenyl, and benzaldehyde showed intermediate performance. Tetralin was less active in the first test area (A1) and was used primarily for comparison.

[0100]

[0101] This embodiment studies the performance of additive in the condensation zone (gaseous reactor effluent is converted into liquid) of styrene production plant under high temperature.In this (" first zone ") position, there is steam, and finds steep temperature gradient.The main reason that finds that fouling is suspected in this area is that the boiling point of DVB is higher, may cause hot liquid DVB to condense before styrene / EB, thereby triggers the formation of insoluble polymer.The boiling point of commercially available polymerization inhibitor is very high, and can condense before DVB, but if temperature is higher (as the temperature encountered here), many polymerization inhibitors may have thermal instability.And the cost of use of this commercially available product in this application may be very high.Have chemical activity and the ready-made cheap compound (for example additive of the present invention) that boiling point is close to DVB provides the attractive selection of solving this problem.

[0102] Additional Notes

[0103] The specific embodiments disclosed above are illustrative only, and those skilled in the art will understand, after reading the teachings herein, that the present disclosure can be modified and implemented in many different but equivalent ways. In addition, except as described in the appended claims, there is no intention to limit the details of construction or design shown herein. Therefore, it is obvious that changes or modifications can be made to the specific illustrative embodiments disclosed above, and all such changes are considered to be within the scope and spirit of the present disclosure. Alternative embodiments produced by combining, integrating and / or omitting features of the embodiments are also within the scope of the present disclosure. Although compositions and methods are described in broader terms such as "having", "comprising", "containing" or "including" various components or steps, the compositions and methods can also be "essentially composed of components / parts and steps" or "composed of components / parts and steps". The use of the term "optionally" with respect to any element of a claim means that the element is required, or the element is not required, and both options are within the scope of the claim.

[0104] The above disclosed numbers and ranges may be different. Whenever a numerical range with a lower limit and an upper limit is disclosed, any numerical value and any included range falling within the range are specifically disclosed. In particular, the various ranges of numerical values ​​disclosed herein (in the form of "about a to about b", or equivalently "about a to b", or equivalently "about ab") should be understood as enumerating various numbers and ranges included in the wider range of numerical values. Moreover, unless otherwise clearly and clearly defined by the patentee, the terms in the claims have their general, usual meanings. In addition, the indefinite article "a" or "an" used in the claims defined herein represents one or more than one element introduced therein. If there is a conflict in the use of words or terms in this specification and one or more patents or other documents, the definition consistent with this specification should be adopted.

[0105] The following are non-limiting embodiments according to the present disclosure:

[0106] A: A method for reducing fouling in a styrene production process, the method comprising: introducing an additive into a stream comprising styrene and a by-product divinylbenzene (DVB), wherein the additive comprises: at least one compound comprising one or more functional groups selected from amines, alcohols, amino alcohols, labile CC, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogen, and combinations thereof, and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C, or ±60°C of the boiling point of divinylbenzene (DVB), which is 195°C, wherein the at least one compound is effective in inhibiting crosslinking of divinylbenzene (DVB).

[0107] B: An additive for reducing fouling in a crude styrene purification process, the crude styrene comprising styrene and a by-product divinylbenzene (DVB), the additive comprising: at least one compound comprising one or more functional groups effective in inhibiting crosslinking of divinylbenzene (DVB) and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C or ±60°C of the boiling point of DVB of 195°C; and a polymerization inhibitor having a boiling point higher than the boiling point of at least one compound.

[0108] C: A composition comprising: a crude styrene stream comprising styrene and byproduct divinylbenzene (DVB); and an additive comprising one or more functional groups effective to inhibit crosslinking of DVB and having a boiling point of 170°C to 270°C, 170°C to 230°C, 170°C to 220°C, or 170°C to 195°C.

[0109] D: A system for producing styrene by dehydrogenating ethylbenzene (EB), the system comprising: one or more dehydrogenation reactors operable to contact EB and steam with a dehydrogenation catalyst under dehydrogenation conditions to produce a crude styrene effluent comprising styrene and a by-product divinylbenzene (DVB); a heat exchange device for reducing the temperature of the crude styrene effluent; a separation device configured to separate off-gas and condensate from the cooled crude styrene effluent to provide a dehydrogenated mixture; and a distillation section operable to separate the dehydrogenated mixture into a stream comprising benzene, toluene, ethylbenzene, or a combination thereof, a tar stream, and a mixture of the styrene and divinylbenzene streams. and one or more streams comprising styrene; an oxidation unit configured to produce, by oxidation of the tar stream, at least one compound comprising one or more functional groups effective to inhibit crosslinking of divinylbenzene and having a boiling point greater than or equal to 170° C. and within ±10° C., ±20° C., ±30° C., ±40° C., ±50° C., or ±60° C. of the boiling point of DVB of 195° C.; and one or more recovery lines whereby the at least one compound can be fed to, recovered from, or refluxed from a crude styrene effluent, a cooled crude styrene effluent, a dehydrogenation mixture, a distillation column of a distillation section, or a combination thereof.

[0110] E: A method for reducing fouling in a styrene production process, the method comprising the steps of: producing at least one compound effective in inhibiting divinylbenzene (DVB) crosslinking by oxidation of crude styrene, a styrene tar stream, or a combination thereof, the compound comprising one or more functional groups selected from amines, alcohols, amino alcohols, labile CC, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogen, and combinations thereof, and having a boiling point greater than or equal to 170°C and within ±10°C, ±20°C, ±30°C, ±40°C, ±50°C, or ±60°C of the boiling point of divinylbenzene (DVB), which is 195°C; and introducing the at least one compound into a stream comprising styrene and by-product divinylbenzene (DVB), thereby inhibiting divinylbenzene (DVB) crosslinking.

[0111] Each of Embodiments A, B, C, D, and E may have one or more of the following additional elements: Element 1: wherein the at least one compound has a boiling point less than or equal to about 250°C, 240°C, 230°C, 220°C, 210°C, 200°C, or 195°C and a boiling point greater than or equal to about 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, or 230°C, or a combination thereof. Element 2: wherein the at least one compound is selected from an amine, a diol, a benzoate, a carbamate, or a combination thereof. Element 3: wherein the at least one compound comprises ethyl lactate, tetralin, acetophenone, propylene glycol, dipropylene glycol, dipropylene glycol methyl ether, trans-stilbene, N,N-diethyl-1,4-phenylenediamine, phenylethanol (e.g., 1-phenylethanol), benzaldehyde, benzaldehyde dimethyl acetal, diphenyl carbonate, methyl carbamate, ethyl carbamate, methyl benzoate, ethyl benzoate, ethyl acetoacetate, diethylaminoethanol, biphenyl, diethanolamine, 3-amino-1-propanol, or a combination thereof. Element 4: wherein the additive is introduced at a concentration of 0.001 wt%, 0.01 wt%, or 0.1 wt% of the stream comprising styrene and DVB. Element 5: wherein the process for producing styrene comprises an ethylbenzene (EB) dehydrogenation process. Element 6: wherein the stream comprising styrene and DVB to which the additive is introduced is the crude styrene effluent from the EB dehydrogenation reactor. Element 7: The stream containing styrene and DVB to which the additive is introduced is a feed stream, a recycle stream, or a reflux stream entering a distillation column downstream of the EB dehydrogenation reactor. Element 8: The distillation column comprises a distillation column configured to separate an overhead product containing EB from a bottom product containing styrene, a distillation column configured to separate an overhead product containing benzene and toluene from a bottom product containing EB and styrene, or a distillation column configured to separate an overhead product containing styrene from a bottom product containing tar. Element 9: Reducing fouling comprises reducing the formation of insoluble polystyrene and / or soluble polystyrene by at least 1%, 10%, 50%, or 100% relative to an identical process without the additive. Element 10: The polymerization inhibitor has a boiling point greater than 195°C, 200°C, 250°C, or 300°C. Element 11: wherein the polymerization inhibitor is selected from the group consisting of: dinitrophenols (e.g., DNOC (dinitro-o-cresol) or DNBP (dinitro-sec-butylphenol)), TMPO compounds (e.g., 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), oximes (e.g., alternative polymerization inhibitors), or combinations thereof. Element 12: wherein the polymerization inhibitor has a boiling point greater than 195°C, 200°C, 250°C, or 300°C. Element 13: wherein the one or more functional groups are selected from the group consisting of: amines, alcohols, amino alcohols, labile C—C groups, esters, carbamates, aldehydes, ketones, acids, acetates, benzoates, labile hydrogens, diols, or combinations thereof.Element 14: wherein the at least one compound has a boiling point less than or equal to about 250°C, 240°C, 230°C, 220°C, 210°C, 200°C, or 195°C and a boiling point greater than or equal to about 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, or 230°C, or a combination thereof. Element 15: wherein the crude styrene is a product of ethylbenzene (EB) dehydrogenation. Element 16: wherein the crude styrene stream further comprises a polymerization inhibitor having a boiling point greater than the boiling point of the at least one compound. Element 17: wherein the crude styrene stream comprises a crude styrene effluent from an ethylbenzene (EB) dehydrogenation reactor. Element 18: wherein the crude styrene stream comprises a feed stream, a recycle stream, or a reflux stream to a distillation column downstream of the ethylbenzene (EB) dehydrogenation reactor. Element 19: wherein the at least one compound comprises benzaldehyde, acetophenone, phenylethyl alcohol, or a combination thereof.

[0112] While preferred embodiments of the present invention have been shown and described, various modifications may be made thereto by those skilled in the art without departing from the spirit and content of the present invention. The embodiments described herein are illustrative only and are not intended to be limiting. Many variations and modifications of the embodiments disclosed herein are within the scope of the present invention.

[0113] Once the above disclosure is fully understood, many other modifications, equivalents and alternatives will become apparent to those skilled in the art. It is intended that the following claims be interpreted as covering all such modifications, equivalents and alternatives, where applicable. Therefore, the scope of protection is not limited by the description listed above, but is limited only by the appended claims, the scope of which includes all equivalents of the subject matter of the claims. Each claim is incorporated into the specification as an embodiment of the present disclosure. Therefore, the claims are further descriptions and supplement the detailed description of the present invention. The disclosures of all patents, patent applications and publications listed herein are incorporated herein by reference, and they provide exemplary, procedural or other detailed supplements to the contents set forth herein.

Claims

1. A method for reducing fouling in a styrene production process, the method comprising: An additive is introduced into a stream comprising styrene and byproduct divinylbenzene, wherein the additive comprises: at least one compound comprising one or more functional groups selected from the group consisting of glycols, carbamates, benzoates, and combinations thereof, and having a boiling point greater than or equal to 170°C and within ±60°C of the boiling point of divinylbenzene, 195°C.

2. The method according to claim 1, wherein At least one compound has a boiling point within ±30°C of the boiling point of divinylbenzene.

3. The method according to claim 1, wherein At least one compound has a boiling point within ±10°C of the boiling point of divinylbenzene.

4. The method according to claim 1, wherein At least one compound has a boiling point lower than or equal to 250°C and a boiling point higher than or equal to 210°C.

5. The method according to claim 1, wherein At least one compound has a boiling point lower than or equal to 230°C and a boiling point higher than or equal to 180°C.

6. The method of claim 1, wherein: At least one compound has a boiling point lower than or equal to 200°C and a boiling point higher than or equal to 170°C.

7. The method according to any one of claims 1 to 6, wherein The at least one compound includes propylene glycol, dipropylene glycol, dipropylene glycol methyl ether, methyl carbamate, ethyl carbamate, methyl benzoate, ethyl benzoate, or a combination thereof.

8. The method according to any one of claims 1 to 6, wherein The additive was introduced at a concentration of 0.001%, 0.01% or 0.1% by weight of the stream.

9. The method according to any one of claims 1 to 6, wherein The process used to produce styrene involves the dehydrogenation of ethylbenzene.

10. The method of claim 9, wherein: The stream containing styrene and divinylbenzene into which the additive is introduced is the crude styrene effluent of the ethylbenzene dehydrogenation reactor.

11. The method of claim 9, wherein: The stream containing styrene and divinylbenzene into which the additive is introduced is a feed stream, a recovery stream or a reflux stream entering a distillation column downstream of the ethylbenzene dehydrogenation reactor.

12. The method of claim 11, wherein: The distillation column includes a distillation column configured to separate an overhead product containing ethylbenzene from a bottom product containing styrene, a distillation column configured to separate an overhead product containing benzene and toluene from a bottom product containing ethylbenzene and styrene, or a distillation column configured to separate an overhead product containing styrene from a bottom product containing tar.

13. The method according to any one of claims 1 to 6, wherein Reducing fouling includes reducing the formation of insoluble polystyrene and / or soluble polystyrene by at least 1% relative to the same process without the additive.

14. The method of any one of claims 1 to 6, wherein the additive further comprises: Polymerization inhibitors with a boiling point above 195°C.

15. The method of claim 14, wherein: The polymerization inhibitor is selected from the group consisting of: dinitrophenol, TEMPO compound, oxime, or a combination thereof.

16. An additive for reducing fouling during the purification of crude styrene in the method according to any one of claims 1 to 15, wherein the crude styrene comprises styrene and a by-product, divinylbenzene, the additive comprising: at least one compound comprising one or more functional groups selected from the group consisting of glycols, carbamates, benzoates, and combinations thereof, and having a boiling point greater than or equal to 170° C. and within ±60° C. of the boiling point of divinylbenzene at 195° C.; and A polymerization inhibitor having a boiling point higher than the boiling point of at least one compound.

17. The additive according to claim 16, wherein At least one compound has a boiling point within ±30°C of the boiling point of divinylbenzene.

18. The additive according to claim 16, wherein The polymerization inhibitor has a boiling point higher than 195°C.

19. The additive according to claim 16, wherein The polymerization inhibitor has a boiling point higher than 250°C.

20. The additive according to any one of claims 16 to 19, wherein The polymerization inhibitor is selected from the group consisting of: dinitrophenol, TEMPO compound, oxime, or a combination thereof.

21. The additive according to any one of claims 16 to 19, wherein At least one compound has a boiling point lower than or equal to 250°C and a boiling point higher than or equal to 210°C.

22. The additive according to any one of claims 16 to 19, wherein At least one compound has a boiling point lower than or equal to 230°C and a boiling point higher than or equal to 180°C.

23. The additive according to any one of claims 16 to 19, wherein At least one compound has a boiling point lower than or equal to 200°C and a boiling point higher than or equal to 170°C.

24. The additive according to any one of claims 16 to 19, wherein The at least one compound includes propylene glycol, dipropylene glycol, dipropylene glycol methyl ether, methyl carbamate, ethyl carbamate, methyl benzoate, ethyl benzoate, or a combination thereof.

25. The additive according to any one of claims 16 to 19, wherein Crude styrene is the product of dehydrogenation of ethylbenzene.

26. A composition comprising: a crude styrene stream comprising styrene and by-product divinylbenzene; and The additive according to any one of claims 16 to 25.

27. The composition of claim 26, wherein The polymerization inhibitor has a boiling point higher than 195°C.

28. The composition of claim 26, wherein The polymerization inhibitor has a boiling point higher than 250°C.

29. The composition of claim 26, wherein The polymerization inhibitor is selected from the group consisting of: dinitrophenol, TEMPO compound, oxime, or a combination thereof.

30. The composition of claim 26, wherein The crude styrene stream comprises the crude styrene effluent from an ethylbenzene dehydrogenation reactor.

31. The composition of claim 26, wherein The crude styrene stream comprises the feed stream, the recovery stream, or the reflux stream that enters the distillation column downstream of the ethylbenzene dehydrogenation reactor.

32. The composition of claim 31, wherein The distillation column includes a distillation column configured to separate an overhead product containing ethylbenzene from a bottom product containing styrene, a distillation column configured to separate an overhead product containing benzene and toluene from a bottom product containing ethylbenzene and styrene, or a distillation column configured to separate an overhead product containing styrene from a bottom product containing tar.

Images