Abstract: The present invention relates to a process for reducing the Bromine Index of a hydrocarbon feedstock having at least 50 wt. % of C8 aromatics, comprising the step of contacting the hydrocarbon feedstock with a catalyst at conversion conditions, wherein the catalyst includes a molecular sieve having a zeolite structure type of MWW.

Abstract: The invention is an adsorptive separation process for producing a para-xylene product from a feed stream comprising para-xylene, at least one other C8 aromatic, and a C9 aromatic. An adsorbent comprising X or Y zeolite and a desorbent comprising para-diethylbenzene (p-DEB) are used in an adsorptive separation zone to produce an extract stream comprising para-xylene, p-DEB, and the C9 aromatic and a raffinate stream comprising the at least one other C8 aromatic, the C9 aromatic, and p-DEB. The extract stream is separated in an extract distillation zone to produce a second desorbent stream comprising the C9 aromatic and p-DEB and the raffinate stream is separated in a raffinate distillation zone to produce a third desorbent stream comprising the C9 aromatic and p-DEB. At least a portion of at least one of the second desorbent stream and the third desorbent stream is further separated in a desorbent distillation zone to produce a stream comprising the C9 aromatic.

Abstract: This invention relates to a process for reducing the Bromine Index of a hydrocarbon feedstock having less than 5 wppm oxygenates-oxygen, comprising the step of contacting the feedstock with a catalyst at conversion conditions to form a first effluent, wherein the catalyst includes a molecular sieve having a zeolite structure type of MWW.

Abstract: A process for continuously removing a target product X in the form of fine crystals from a liquid phase P comprising the target product X and constituents other than the target product X by cooling suspension crystallization in an indirect heat transferer, in which the crystal suspension formed is conducted out of the heat transferer first into a mixed buffer tank and, from there, fed to an apparatus for separating the crystal suspension into crystals and liquid phase, and wherein external measures dissipade the oversaturation of the crystal suspension fed to the buffer vessel with target product X.

Abstract: Provided is a process for crystallization separating p-xylene, comprising: a) feeding a mixed xylenes stream comprising greater than or equal to 60% by weight, of p-xylene, such as 60% to 98% by weight of p-xylene, to a crystallization unit to perform cooling crystallization, to obtain a slurry comprising p-xylene crystals; and b) feeding the slurry to a filtration and purification unit, to obtain a mother liquor, washings, and p-xylene, wherein the filtration and purification unit uses a simulated moving bed or a combination of multiple moving beds.

Abstract: The process includes at least two adsorptive separation zones to separate para-xylene from a feed stream comprising C8 aromatic hydrocarbons and at least one C9 aromatic hydrocarbon component. An adsorbent comprising X or Y zeolite and a heavy desorbent are used in the first adsorptive separation zone to produce an extract stream comprising para-xylene and a raffinate stream comprising para-xylene depleted C8 aromatic hydrocarbons, the C9 aromatic hydrocarbon, and the desorbent. The raffinate stream is separated in a raffinate distillation zone to produce a stream comprising the first desorbent component and the C9 aromatic hydrocarbon which stream is further separated in a second adsorptive distillation zone to produce a stream comprising the desorbent and a C9 aromatic hydrocarbon stream.

Abstract: A process for co-producing para-xylene and styrene from a feed (1) of hydrocarbons containing xylenes and ethylbenzene is described, the process comprising the following succession of steps: a step for separating the feed in a simulated moving bed in an adsorption column (6) containing beds of an adsorbent, from which an extract that is rich in para-xylene (7a) of at least 99.7% purity and at least one raffinate (7b) containing ethylbenzene, ortho-xylene, meta-xylene and a very small quantity of para-xylene is withdrawn; a step for dehydrogenating (10) the ethylbenzene contained in the raffinate (7b) to styrene; at least one step for primary separation of the stream (11) from the dehydrogenation step (10), to eliminate by-products; a step for separating the purified mixture (18) derived from the stream (11) containing styrene, unconverted ethylbenzene, meta-xylene and ortho-xylene, from which a stream (21a) that is rich in styrene of at least 99.

Abstract: A process for fractionating a starting mixture of two or more components by extractive distillation using a selective solvent in a dividing wall column aligned in the longitudinal direction of the column and extending to the upper end of the column and dividing the column interior into a first region, a second region, and a lower combined column region. The starting mixture is fed into the first region, a first top stream is taken off from the first region, and a second top stream is taken off from the second region, each stream having a prescribed specification. The selective solvent is introduced in the upper part of the first region and/or in the upper part of the second region, and solvent flow into the first region and/or solvent flow into the second region are set so that each of the prescribed specifications for the top streams are met.

Abstract: A process for continuously removing a target product X in the form of fine crystals from a liquid phase P comprising the target product X and constituents other than the target product X by cooling suspension crystallization in an indirect heat transferee, in which the crystal suspension formed is conducted out of the heat transferer first into a mixed buffer tank and, from there, fed to an apparatus for separating the crystal suspension into crystals and liquid phase, and wherein external measures dissipade the oversaturation of the crystal suspension fed to the buffer vessel with target product X.

Abstract: The invention concerns a process for separating meta-xylene from a hydrocarbon feed comprising isomers containing 8 carbon atoms, comprising: a step for bringing said feed into contact with a faujasite type zeolite adsorbant, the water content of the adsorbant being in the range 0 to 1% by weight and the adsorption temperature being from 160° C. to 180° C.; a desorption step employing a solvent selected from toluene, indane and mixtures thereof.

Abstract: Process for reduction of bromine index in aromatics, comprising the steps of feeding an aromatics feed stream which contains olefin impurities to a distillation column; withdrawing an overhead stream from the distillation column; subjecting at least a portion of the overhead stream to a treatment for the alkylation or polymerization of olefin in a clay treater to provide a purified overhead stream which is then injected to the aromatics feed stream.

Abstract: Recent experimental work with currently available adsorbents indicates that operating the adsorption section at lower temperatures improves the para-xylene productivity. As a result, an aromatics complex and heat recovery network for a low temperature adsorptive separation-isomerization loop is disclosed resulting in adsorbents savings in combination with higher capacity thereby enabling smaller adsorbents chambers, a smaller total heat exchanger area and a lower heat exchanger shell count.

Abstract: Processes are disclosed for production of purified products from a fluid mixtures of C8 aromatics by means of integration of perm-selective separations with purified product recovery operations. The perm-selective separations of the invention comprise of one or more devices using polymeric perm-selective membrane devices to separate a meta-xylene enriched stream from fluid mixtures of C8 aromatics thereby producing a fluid comprising the remaining aromatic compounds which advantageously includes para-xylene. Processes of the invention are particularly useful for recovery of very pure meta-xylene and para-xylene co-products from liquid mixtures even containing ethylbenzene as well as the three xylene isomers.

Abstract: Processes and apparatus are disclosed for recovery of purified products from a fluid mixture by means of integrated perm-selective separations with purified product recovery operations. More particularly, integrated processes of the invention comprise separations by means of one or more devices using polymeric membranes coupled with recovery of purified products by means of fractional crystallization and/or selective sorption. Processes of the invention are particularly useful for recovery of a very pure aromatic isomer when processing aromatic starting materials, for example, a pure para-xylene product from liquid mixtures even containing ethylbenzene as well as the three xylene isomers.

Abstract: Apparatus and processes are disclosed for economical separation of fluid mixtures utilizing perm-selective membranes. Broadly, apparatus of the invention comprises a plurality of membrane modules comprising a solid perm-selective membrane and equipment for controlling enthalpy of selected fluids within the apparatus. Advantageously, the membrane modules are disposed in a first product group, a second product group, and at least one intermediate group. Apparatus of the invention is particularly useful for simultaneous recovery of a very pure permeate product, and/or a desired non-permeate stream, from fluid mixtures of two or more compounds which when subjected to appropriately altered conditions of temperature and/or pressure exhibit a bubble point.

Abstract: Bromine reactive hydrocarbon contaminants are removed from aromatic streams by first providing an aromatic feedstream having a negligible diene level. The feedstream is contacted with an acid active catalyst composition under conditions sufficient to remove mono-olefins. An aromatic stream may be pretreated to remove dienes by contacting the stream with clay, hydrogenation or hydrotreating catalyst under conditions sufficient to substantially remove dienes but not mono-olefins.

Abstract: A pressure swing adsorption process to separate para-xylene and ethylbenzene from C8 aromatics which uses a para-selective, non-acidic, medium pore molecular sieve of the MFI structure type and is operated isothermally in the vapor phase at elevated temperatures and pressures is integrated with simulated moving bed adsorption (SiMBAC) to produce para-xylene product. A fixed bed of adsorbent is saturated with pX and EB, which are preferentially adsorbed, the feed is stopped, and lowering the partial pressure desorbs the pX and EB. The process effluent, which is rich in pX and EB, is subjected to SiMBAC to obtain para-xylene product.

Abstract: An improved process for the recovery of aromatic compounds from a mixture containing aromatic and non-aromatic compounds and method for retrofitting existing equipment for the same is provided. The improved process comprises the steps of recovering aromatic compounds via parallel operation of a hybrid extractive distillation/liquid-liquid extractor operation and variations thereof. Methods of quickly and economically retrofitting existing recovery process equipment for use with the improved aromatic recovery process are also disclosed.

Abstract: A process for co-production of paraxylene, metaxylene and/or orthoxylene from a hydrocarbon feedstock (1) that comprises [1] a separation stage of the feedstock in a simulated moving bed in a chromatographic column (9) that contains a number of beds of an adsorbent, interconnected in a loop, is described, whereby said column comprises an injection (3) of the feedstock, a draw-off (10) of an extract that consists of paraxylene and desorbent, an intermediate fraction (11) (extract or raffinate) that contains ethylbenzene, and a raffinate (12) that contains a mixture of metaxylene and orthoxylene that is virtually free of ethylbenzene and paraxylene and [2] a crystallization stage (27) of the metaxylene and/or orthoxylene fraction. Upstream from the adsorption zone and/or upstream from the crystallization zone, it is possible to distill the entering mixture to produce an orthoxylene-enriched fraction at the bottom and a metaxylene-enriched fraction at the top.

Abstract: A process for the removal of hydrocarbon contaminants, such as dienes and olefins, from an aromatics reformate by contacting an aromatics reformate stream with a hydrotreating catalyst and/or a molecular sieve. The hydrotreating catalyst substantially converts all dienes to oligomers and partially converts olefins to alkylaromatics. The molecular sieve converts the olefins to alkylaromatics. The process provides an olefin depleted product which can be passed through a clay treater to substantially convert the remaining olefins to alkylaromatics. The hydrotreating catalyst has a metal component of nickel, cobalt, chromium, vanadium, molybdenum, tungsten, nickel-molybdenum, cobalt-nickel-molybdenum, nickel-tungsten, cobalt-molybdenum or nickel-tungsten-titanium, with a nickel molybdenum/alumina catalyst being preferred. The molecular sieve is an intermediate pore size zeolite, preferably MCM-22. The clay treatment can be carried out with any clay suitable for treating hydrocarbons.

Abstract: Apparatus, methods and systems useful for removing phenylacetylene from crude styrene feedstock are disclosed. Generally the processes and systems comprise the catalytic reduction of phenylacetylene to produce styrene via injection of a phenylacetylene reducing agent, such as hydrogen. A phenylacetylene reduction catalyst preferred herein comprises palladium on a calcium aluminate carrier, wherein the catalyst comprises less than 0.3 weight percent palladium.

Abstract: A process for producing 99.5+ wt. % para-xylene by selective alkylation has been discovered. A mixure of isomers of para-xylene having at least about 90.0 wt. % purity may be reacted with an alkylating agent having at least one tertiary butyl moiety in the presence of an acidic catalyst under conditions where the catalyst is in good molecular contact with the non-para-xylene isomers. The catalyst may be a high surface area acidic heterogeneous catalyst such as a proton-exchanged zeolite. Upon distillation, para-xylene is recovered in 99.5 wt. % purity or higher. The selective alkylation gives little or no alkylation of the para-xylene, the most predominant species, and very little or no isomerization to the other, non-desirable isomers.

Abstract: Process for the separation of light olefins from paraffins contained in mixtures, optionally also containing hydrogen, comprising bringing said mixtures into contact with an aqueous solution of one or more compounds of silver, preferably silver nitrate, and one or more ferric compounds, preferably ferric nitrate.

Abstract: The present invention relates to agglomerated zeolite adsorbents based on faujasite with an Si/Al ratio such that 1≦Si/Al≦1.15, at least 70% exchanged with barium and optionally with potassium, and on a binder, preferably a zeolitizable binder. They are obtained by agglomerating zeolite powder with a binder, followed by exchange of the zeolite ions for barium ions and activation of the adsorbents thus exchanged. These adsorbents are particularly suitable for the adsorption of the para-xylene contained in aromatic C8 hydrocarbon fractions in the liquid phase, in processes of simulated fluid-bed type.

Abstract: The system and method for optimizing para-xylene production from a feed stream containing para-xylene, ortho-xylene, meta-xylene, ethylbenzene and non-aromatics propose directing the feed stream into an isomerization unit of the system rather than to a separator of the system to avoid causing a bottleneck at the separator and to initially remove ethylbenzene and non-aromatics from the feed stream. This system and method may further provide a reactor in the feed stream used in a pretreatment step, the reactor containing an isomerization catalyst in an amount sufficient to convert substantially all the ethylbenzene in the feed stream to benzene, which is immediately removed and to convert and remove non-aromatics therefrom to optimize equilibrium isomer concentration in the isomerization unit and substantially eliminate coking therein.

Abstract: A process for the production of at least one isomer of xylenes comprising a simulated moving-bed adsorption (8) of a C8-aromatic feedstock (1) that delivers a paraxylene-rich fraction (9) that is optionally purified after a distillation (16) by at least one high-temperature crystallization (5) and a fraction (10) that is low in paraxylene is described. Fraction (10) is distilled and then isomerized (21) in the presence of an EUO-structural-type catalyst. The lightest hydrocarbons are removed from the isomerization effluent in a first distillation (23) then naphthenes in a second distillation (26), and distilled isomerization effluent (2) that results therefrom is recycled at least in part in adsorption (8). A mother liquor (3) that results from the crystallization stage is recycled at least in part in adsorption (8).

Abstract: This invention relates to a process and a chemical plant for the production primarily of paraxylene. In particular the process and chemical plant utilise zeolite membranes for enhanced paraxylene production.

Abstract: A continuous process for integrated processing of a C8+ aromatic hydrocarbon stream is disclosed for recovery of a high purity meta-xylene product in conjunction with efficient separation and recovery of purified para-xylene and, optionally, purified ortho-xylene products.

Abstract: A process for co-production of paraxylene and ethylbenzene comprises: (A) an adsorption stage of a feedstock of xylenes and ethylbenzene in a simulated moving bed that produces an extract of pure paraxylene and an ethylbenzene-rich raffinate; (B) an adsorption stage in a simulated moving bed, of raffinate from which desorbent has been removed that supplies an essentially pure ethylbenzene extract and an orthoxylene and metaxylene raffinate that contains desorbent; (C) a recover stage for the desorbent; (D) an isomerization stage for the orthoxylene and metaxylene raffinate in the presence of a catalyst that comprises an EUO-type zeolite; and (E) a stage for recycling the isomerate that is produced with adsorption.

Abstract: For co-production of metaxylene and paraxylene from a feedstock (line-4) of hydrocarbons, there is employed a simulated moving bed chromatographic column 5 having at least five zones and which delivers an extract, a raffinate and an intermediate raffinate. The feedstock has an ethylbenzene content of less than 5% by weight, and the chromatographic column comprises at least twenty-five beds, of which at least five beds are in zone 3B. The raffinate is distilled (31) to recover the metaxylene at a purity of at least 99% and orthoxylene. The extract is distilled (7, 10) to recover the paraxylene at a purity of at least 99.6%. The recovered isomers can be synthesized into isophthalic acid and terephthalic acid.

Abstract: The present invention is directed to an apparatus and method for the distillation of a readily polymerizable vinyl aromatic compound employing a polymerization inhibitor. The vinyl aromatic compound is subjected to distillation in at least one fractionation column having at least one reboiler for maintaining the bottoms of said column at a proper temperature. The reboiler includes a heating section and a vapor phase section. The bottoms fraction from the fractionation column is cycled to the reboiler and subjected to heat to vaporize at least a portion of the bottoms fraction to form a vapor phase in the vapor section, A slip stream of the bottoms fraction is introduced to the vapor phase section of the reboiler. The slipstream contains polymerization inhibitor that had been added to the process at the fractionation column. The invention reduces fouling at the reboilers. The slipstream is optionally introduced to the reboiler using one or more spray nozzles.

Abstract: An apparatus and process for regulating the flow rate of at least one fluid or effluent circulating in a simulated moving bed comprises a plurality of beds disposed in a closed loop in at least one chromatographic column (1) and comprising at least one means for recirculating fluid and comprising at least two lines for injecting fluid at a controlled flow rate and at least two lines for withdrawing fluid, one of said withdrawal (extract or raffinate) lines being under flow rate control, the other (60) being under pressure control via at least one control valve (6), and is characterized in that said pressure controlled withdrawal line (60) comprises, in addition to the control valve, comprises at least one restriction means (201) enabling the pressure downstream of at least one of the beds to be reduced. One embodiment of the use of the invention is for separating a xylene isomer.

Abstract: Paraxylene and ethylbenzene are produced from an aromatic hydrocarbon feedstock by using adsorption zones in a simulated fluid bed. The feedstock is first passed into a first adsorption zone to produce a first paraxylene-rich fraction and a second ethylbenzene-rich fraction. The second fraction is then passed into a second adsorption zone to produce a third fraction containing essentially pure ethylbenzene and a fourth fraction containing a majority of orthoxylene and metaxylene. The fourth stream is then passed into an isomerization zone to produce an isomerate which is then recycled back to the first adsorption zone.

Abstract: Apparatus and process are disclosed for the distillation separation of styrene monomer from ethylbenzene utilizing a split feed to two distillation columns in conjunction with cascade reboiling utilizing thermal energy from the overhead of one column to supply heat to the second.

Abstract: The propylene oxide and styrene co-production process generates a heavy residue byproduct containing metals, mainly sodium, which previously was adequate for use only as low quality fuel. According to the invention, the heavy residue is dehydrated in the presence of a strong inorganic acid at temperatures of 150-250.degree. C. and pressures below the atmospheric pressure to yield styrene and recover 2-phenylethanol, a compound used in the perfume industry, and a heavy residue substantially free of metals that may be used as fuel.

Abstract: An apparatus and process for regulating the flow rate of at least one fluid or effluent circulating in a simulated moving bed comprises a plurality of beds disposed in a closed loop in at least one chromatographic column (1) and comprising at least one means for recirculating fluid and comprising at least two lines for injecting fluid at a controlled flow rate and at least two lines for withdrawing fluid, one of said withdrawal (extract or raffinate) lines being under flow rate control, the other (60) being under pressure control via at least one control valve (6), and is characterized in that said pressure controlled withdrawal line (60) comprises, in addition to the control valve, comprises at least one restriction means (201) enabling the pressure downstream of at least one of the beds to be reduced. One embodiment of the use of the invention is for separating a xylene isomer.

Abstract: Para-xylene is produced from a paraselective toluene disproportionation reactor, effluent (3) is distilled to eliminate toluene and benzene in at least 2 distillation columns (C1), (C2), and the xylenes (8) are crystallized at least once (10) at between +10.degree. C. and -30.degree. C. The separated mother liquor (14) is adsorbed on a zeolitic sieve in the presence of toluene in a simulated moving bed (15). This latter produces a raffinate (16) containing toluene which is depleted in para-xylene which is distilled in a distillation column (C4), and an extract which is enriched in para-xylene and contains toluene, which is recycled to columns (C1, C2). The para-xylene crystals are purified by washing with toluene and distillation or by partial melting (30) followed by washing with molten high purity para-xylene.

Abstract: A process is provided for producing high purity benzene and high purity paraxylene from a hydrocarbon feed. In one aspect, the process comprises: (a) reforming a hydrocarbon feed using either a monofunctional catalyst or a bifunctional catalyst to provide one or more reformate streams; (b) fractionating the reformate stream to provide a toluene stream, a benzene stream, and a xylene stream; (c) subjecting the toluene stream to disproportionation; (d) purifying the benzene stream by extraction followed by distillation to provide a high purity benzene product; and (e) purifying the xylene stream by simulated moving bed countercurrent adsorption followed by crystallization to provide a high purity paraxylene product.

Abstract: In a process for the separation of p-xylene from a feed to be treated containing a mixture of xylenes and olefinic impurities, at least a portion of the feed is circulated in an enrichment zone (14) to enrich a first fraction (15) in p-xylene and provide a second fraction (18) which is depleted in p-xylene. The second fraction is circulated in an isomerisation zone (19) and an isomerate (20) is recovered which is recycled to the enrichment zone. At least a portion of the feed to be treated, the isomerate, or a mixture thereof is circulated in at least one selective hydrogenation zone (3) to partially remove the olefinic impurities and thereafter in at least one clay tretment zone (8) to remove additional olefinic impurities. An effluent is recovered which is sent to the enrichment zone.

Abstract: A method for recovering crystalline 2,6-dimethylnaphthalene comprising crystallizing in a scraped-wall crystallizer apparatus at crystallization temperature T, a mixture of low melting components, LM, having melting points of 70.degree. F. and below, and high melting components (HM), including 2,6-dimethylnaphthalene, having melting points above 70.degree. F, such that: ##EQU1## where HM is the total weight percent of high melting components, including 2,6-dimethylnaphthalene, in the mixture, and LM is the total weight percent of low melting components in the mixture, and where T is the temperature of the crystallization in degrees Fahrenheit, and where A is at least 1.0.

Abstract: A process for separating para-xylene from a C.sub.8 feed in a simulated moving bed comprises a step for adsorption on a zeolite and desorption using a desorbent delivering an extract and a raffinate, and an extract crystallization step. A stream of water is introduced into the feed, into the desorbent and/or into the stream for recycling one flux in the column, such that the weighted average of the amounts of water measured in the extract and in the raffinate is in the range 1 to 200 ppm. The ratio S/F of the desorbent flow rate to that of the feed during the adsorption and desorption step is in the range 0.6 to 2.5.

Abstract: This invention relates to a catalytic reaction of an aromatic stream wherein a guard bed for the removal of nitrogen compounds from the aromatic hydrocarbon stream comprising the nitrogen compounds is provided to contact the hydrocarbon stream with a selective adsorbent having an average pore size less than about 5.5 Angstroms to produce a treated feedstream essentially free of the nitrogen compound. The selective adsorbent is a molecular sieve selected from the group consisting of pore closed zeolite 4A, zeolite 4A, zeolite 5A, silicalite, F-silicalite, ZSM-5 and mixtures thereof. The invention provides significant cost advantages when the feedstream is subject to slugs or surges in levels of nitrogen compounds which can be detrimental to downstream acid catalysts as found in aromatic conversion reactions.

Abstract: A process for the removal of trace quantities of polynuclear aromatic compounds from the vapor effluent of a hydrocarbon dehydrogenation zone containing normally gaseous olefinic hydrocarbons, trace mononuclear aromatic compounds and trace polynuclear aromatic compounds by contacting the vapor effluent of a hydrocarbon dehydrogenation zone with a lean liquid absorption stream comprising at least one alkylated mononuclear aromatic compound to absorb at least a portion of the trace mononuclear aromatic compounds and the trace polynuclear aromatic compounds to produce a rich liquid absorption stream and a gaseous olefin-containing hydrocarbon stream having a reduced concentration of mononuclear aromatic compounds and polynuclear aromatic compounds. The rich liquid absorption stream is separated to produce a stream rich in mononuclear aromatic compounds, a stream rich in alkylated mononuclear aromatic compounds and a stream comprising polynuclear aromatic compounds.

Abstract: To continuously produce and separate high purity p-xylene from a C.sub.8 aromatic hydrocarbon charge, successive use is made in combination of (1) a stage of separating low-purity p-xylene (75 to 98%) by simulated moving bed adsorption chromatography; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25 to +10.degree. C.); (3) a stage of catalytic isomerization of the charge which has been p-xylene-depleted by the separating stage (1); and recovering an isomerate which is then recycled to the charge. The solvent for desorption in stage (1) and washing in stage (2) is advantageously toluene.

Abstract: Para-xylene is produced from a paraselective toluene disproportionation reactor, effluent is distilled to eliminate toluene and benzene in at least 2 distillation columns, and the xylenes are crystallized at least once at between +10.degree. C. and -30.degree. C. The separated mother liquor is adsorbed on a zeolitic sieve in the presence of toluene in a simulated moving bed. This latter produces a raffinate containing toluene which is depleted in para-xylene which is distilled in a distillation column, and an extract which is enriched in para-xylene and contains toluene, which is recycled. The para-xylene crystals are purified by washing with toluene and distillation or by partial melting followed by washing with molten high purity para-xylene.

Abstract: Improved process and apparatus for purifying paraxylene from mixed C8-aromatic feedstocks are disclosed in which the use of at least two crystallization stages operated at different temperatures in combination with a final product separator improves purity and recovery while reducing capital and energy costs.

Abstract: A mixed aromatic stream is hydrotreated to remove olefins and fractionated to separate C.sub.9 + heavies in a distillation column reactor and the C.sub.8 and lighter material is fed to a selective adsorption unit where the para-xylene is removed. The para-xylene depleted raffinate therefrom may be subjected to isomerization to form additional para-xylene. The effluent from the isomerization can be fed to the distillation column reactor for hydrogenation of any olefins formed during the isomerization or directly to the adsorption unit.

Abstract: This invention relates to a process for the removal of nitrogen compounds from an aromatic hydrocarbon stream comprising the nitrogen compounds by contacting the hydrocarbon stream with a selective adsorbent having an average pore size less than. about 5.5 Angstroms. The selective adsorbent is a molecular sieve selected from the group consisting of pore closed zeolite 4A, zeolite 4A, zeolite 5A, silicalite, F-silicalite, ZSM-5 and mixtures thereof. In one embodiment, the present invention comprises a combination of a fractionation zone and an adsorption zone wherein the feedstream is passed to the fractionation zone to provide a dry bottoms product stream essentially free of the nitrogen compounds and an overhead stream. The overhead stream is condensed to provide an aqueous stream and a hydrocarbon stream. The hydrocarbon stream is passed to an adsorption zone and a treated effluent recovered therefrom is returned to the fractionation zone.

Abstract: A mixture of aromatic hydrocarbons, comprising ethylbenzene and at least one xylene, is isomerized using a two reactor system to convert the ethylbenzene to compounds that may be removed from the aromatic hydrocarbon stream and to produce a product stream wherein the para-xylene concentration is approximately equal to the equilibrium ratio of the para-isomer. The catalyst present in the first reactor is one that is effective for ethylbenzene conversion with minimal xylene loss when operated under suitable conversion conditions, e.g., a catalyst comprising silica bound ZSM-5 that has been selectivated by one or more silicon impregnations or that has been coke selectivated. The catalyst present in the second reactor is one which is effective to catalyze xylene isomerization when operated under suitable conditions. Each of the catalysts of this invention may contain one or more hydrogenation or dehydrogenation components.

Abstract: A mixture of aromatic hydrocarbons, comprising ethylbenzene and at least one xylene, is treated to convert the ethylbenzene to compounds that may be removed from the aromatic hydrocarbon stream and to isomerize any xylenes present. The ethylbenzene conversion catalyst is one that is effective for ethylbenzene conversion with minimal xylene loss, e.g., a silica bound intermediate pore size zeolite that has been selectivated. The xylene isomerization catalyst is one which is effective to catalyze xylene isomerization. Each of the catalysts of this invention may contain one or more hydrogenation or dehydrogenation components.