Abstract: A process for the separation of metaxylene from aromatic C.sub.8 hydrocarbons, particularly from ethylbenzene and paraxylene, wherein a first phase is provided in which the mixture of aromatic hydrocarbons is selectively adsorbed, in vapor phase, into a catalytic bed consisting of zeolite of the Y type, preliminarily exchanged with potassium, and in a second phase a desorption is effected with a suitable solvent. The process, carried out at a temperature of 150.degree. to 200.degree. C. and preferably at atmospherical pressure, permits the recovery of metaxylene, substantially pure and at a concentration much higher than that of the starting mixture.

Abstract: A process for separating a normal paraffin from a mixture of the same with another structural class of hydrocarbon selected from the cyclic hydrocarbons having greater than six carbons per molecule and the branched chain hydrocarbons. The process comprises contacting the mixture at adsorption conditions with an adsorbent comprising silicalite. The normal paraffin is selectively adsorbed and will preferably be recovered from the adsorbent by desorption with a desorbent material.

Abstract: A continuous, cyclic, vapor-phase adsorption process for the separation of normal paraffins from a hyrocarbon feed mixture, providing improved efficiency of separation and continuity of product flows. For purposes of this process, a continuous flow of the feed mixture and a continuous flow of an eluent are passed in repetitions of a particular sequence of six process steps to at least three molecular sieve adsorbent beds.

Abstract: A continuous, cyclic, vapor-phase adsorption process for the separation of normal paraffins from a hydrocarbon feed mixture, providing improved efficiency of separation and/or continuity of product flows. For purposes of this process, a continuous flow of the feed mixture and a continuous flow of an eluent are passed in repetitions of a particular sequence of six process steps to at least three adsorbent beds.

Abstract: Normal paraffins are separated from a gas oil-containing hydrocarbon vapor feed stream having 16 to 25 carbon atoms per molecule in a constant pressure process employing a molecular sieve adsorbent and n-hexane for purging and for dilution of gas oil-containing feedstock. Cocurrent purge effluent is used to provide a source of such n-hexane diluent, thereby reducing the equipment size and energy consumption for processing of the n-hexane purge recycle stream and increasing adsorbent utilization or the efficiency of the adsorption process.

Abstract: Normal paraffins are separated from a gas oil-containing hydrocarbon vapor feed stream having 16 to 25 carbon atoms per molecule in a constant pressure process employing a molecular sieve adsorbent and n-hexane for purging and for dilution of gas oil-containing feedstocks. Countercurrent purge effluent is used to provide a source of such n-hexane diluent, thereby effecting a savings in the amount of energy necessary to process the purge recycle stream and the size of the equipment used therefor.

Abstract: This invention comprises an adsorptive separation process for separating polar organic compounds containing sulfur, oxygen or nitrogen atoms from a naphtha feed mixture which process comprises contacting the feed mixture with an adsorbent comprising a crystalline aluminosilicate, selectively adsorbing the polar organic compounds and thereafter recovering relatively high-purity naphtha. A desorption step may be used to desorb the adsorbed compounds.

Abstract: In the separation of cyclohexene from a feed which contains cyclohexene and cyclohexane, the feed is contacted with a type X and/or type Y aluminosilicate zeolite, thereby adsorbing cyclohexene selectively on the zeolite, and then the zeolite which adsorbed cyclohexene is contacted with a trimethylbenzene to desorb cyclohexene.

Abstract: A process for separating three components from a feedstream employing an adsorbent and desorbent material which in combination have selectivities for the components in descending order of magnitude. The process uses a simulated-moving bed counter current flow system with an intermediate raffinate stream taken off the column at about the midpoint of the adsorption zone in addition to the usual extract and raffinate product streams. In a preferred embodiment the first component is para-xylene, the second component is ethyl benzene, and the third component is a mixture of meta and ortho-xylene.

Abstract: Improved hydrocarbon separation processes by the selective sorption properties of a novel class of zeolites are provided. The novel class of zeolites is characterized by a silica to alumina mole ratio greater than 12 and a constraint index within the approximate range of greater than about 2 to about 12. The separations encompassed by this invention include paraffins from aromatics, olefins from aromatics, olefins from paraffins, linear paraffins from branched paraffins, linear olefins from branched olefins, methyl branched hydrocarbons from more highly branched hydrocarbons, higher molecular weight components from lower molecular weight components within an homologous series, n-paraffins or methylparaffins from cycloparaffins, n-alkyl or methyl alkyl substituted aromatics from more highly branched isomers, mixed paraffins from aromatics (dewaxing), and non-aromatic methyl-branched hydrocarbons from aromatics.

Abstract: Impregnated silica is manufactured by passing a substantially anhydrous solution of a polar organic compound in a non-polar organic diluent through a bed of substantially anhydrous silica particles, under a pressure of at least 200 bars so as to modify the adsorbent properties of the silica particles with the selective properties of the polar compound without impairing the silica particle adsorbing efficiency.

Abstract: An adsorptive separation process is disclosed for separating para-aromatic isomers from a hydrocarbon feed containing a mixture of aromatic isomers, using a crystalline aluminosilicate adsorbent which has been treated with an alkyl amine preferably an alkyl amine hydrochloride. The alkyl amine treatment substantially increases the selectivity of the adsorbent for the para-xylene isomer, relative to the heavy desorbent p-DEB, thereby improving the efficiency of the separation process.

Abstract: An adsorbent for separating para-xylene from C.sub.8 aromatic hydrocarbons, specifically a faujasite zeolite which contains potassium, zirconium and proton or ammonium as cation, process for separating para-xylene, and process for making the adsorbent.

Abstract: A process is disclosed for separation of straight chain paraffins from a mixture of paraffinic hydrocarbons by selective adsorption on a molecular sieve followed by desorption of the straight chain paraffins with gaseous hydrogen.

Abstract: Process for increasing the concentration of normal cis olefins in a hydrocarbon composition with pre-treated molecular sieves which have been heated to a temperature of from 400.degree. to 500.degree. F. for a period of about 1 to 6 hours to reach the water-zeolite equilibrium at said temperature range in the presence of water.

Abstract: Normal paraffins are isolated from a feedstock mixture of normal and non-normal paraffins in the vapor phase at superatmospheric pressure using an adsorption system comprising at least four fixed adsorption beds containing a 5 Angstrom molecular sieve adsorbent, each of which cyclically undergoes the stages of (a) adsorption-fill, (b) adsorption, (c) void space purging, and (d) purge desorption. The improvement of the present process comprises recycling in the vapor phase in combination with feedstock the mixture of isoparaffins and normal paraffins purged from one bed of the system during stage (c) to another bed of the system undergoing stage (b). In conventional practice the void space contained hydrocarbons purged from each bed during stage (c) was cooled, separated from the purging gas, pumped to a holding tank in the liquid phase and thereafter reheated to form the vapor phase before being admixed with fresh feedstock for further treatment.

Abstract: A new composition of matter, a method for the preparation of a rubidium exchanged Type X structured zeolite and a separation process employing the same. The zeolite adsorbent is prepared by a procedure employing the aqueous ion exchange step and a final activation step including contacting a sodium-X zeolite with a rubidium salt in aqueous solution. The process involves the selective separation of ethylbenzene from a C.sub.8 aromatic isomer mixture containing ethylbenzene and employs the use of the rubidium exchanged type X structured zeolite in an adsorption separation process.

Abstract: A process for treating a hydrocarbon composition containing both straight chain and non-straight chain hydrocarbons in which said hydrocarbon composition is separated into a straight chain hydrocarbon-rich fraction and a non-straight chain hydrocarbon-rich fraction, non-aromatics in said non-straight chain hydrocarbon-rich fraction are converted to aromatics, and at least a portion of the straight chain hydrocarbon-rich fraction is passed in combination with steam over a steam active catalyst comprising at least one Group VIII metal and a tin modified Group II metal aluminate under conditions such that aromatics are produced.

Abstract: A hydrocarbon mixture is fed to a system of adsorbents in a plug flow so as to form at least one displacement boundary in the system to accumulate the composition in the vicinity of the boundary. The process is simple to operate and suitable for separation of a hydrocarbon mixture containing components with similar physical and chemical properties such as a mixture of hydrocarbon isomers.

Abstract: A C.sub.8 -aromatic hydrocarbon mixture containing para-xylene is subjected to adsorption-separation in contact with a crystalline aluminosilicate adsorbent which selectively retains para-xylene. Raffinate therefrom, being a para-xylene deficient C.sub.8 -aromatic concentrate, is isomerized in contact with a catalytic composite containing a Group VIII noble metal component to form additional para-xylene. Isomerization conditions employed to produce the para-xylene, also effect the formation of olefinic material. To prevent the adverse effect which olefins exhibit toward the efficiency and capacity of the zeolitic adsorbent, the isomerization effluent is subjected to hydrotreating at conditions which provide a liquid-phase operation and saturate olefins without saturation of the C.sub.8 -aromatics. The hydrotreating is effected in contact with a substantially non-acidic catalytic composite comprising a Group VIII noble metal component.

Abstract: A hydrocarbon conversion apparatus is dried as a preliminary step of a startup procedure by the circulation of a superheated vapor stream which is formed in one of two reboilers attached to a fractionation column used in the process. Preferably this vapor stream is formed on the tube side of the reboiler, with normal on-stream operation comprising the generation of the vapors fed to the column on the shell side of the reboiler.

Abstract: An adsorptive separation process for separating ethylbenzene from a feed mixture comprising ethylbenzene and a plurality of xylene isomers which process comprises contacting the feed mixture with an adsorbent comprising strontium and potassium exchanged type X or type Y zeolite, selectively adsorbing substantially all of the said xylene isomers to the substantial exclusion of the ethylbenzene and thereafter recovering high-purity ethylbenzene. A desorption step may be used to desorb the adsorbed xylene isomers. The process can be either in the liquid or vapor phase.

Abstract: A cyclic, vapor-phase, pressure swing process for the separation of n-paraffins from a mixture with non-straight chain hydrocarbons comprises the steps of adsorption purge and desorption. Purge effluent is recycled through a bed of a 5 A molecular sieve in an adsorption stage and an effluent of reduced n-paraffin content is recovered. The bed is purged to remove surface adsorbed and interstitial matter by reducing the pressure in the bed by direct contact condensation with fresh feed introduced at or near ambient temperature. A purge effluent is recovered for recycle to stage (1). The bed is then desorbed to recover n-paraffins by further reducing the pressure in the bed.

Abstract: Molecular sieve pressure swing separating process is modified by stopping the feed before the end of the adsorption stage and passing a mixture richer in n-paraffins than the feed through the sieve bed. Suitable mixtures include purge effluent and desorpting effluent. This enhances the purity of the product.

Abstract: A process for the separation of the para-isomer from a hydrocarbon feed mixture comprising at least two bi-alkyl substituted monocyclic aromatic isomers, including the para-isomer, said isomers having from 8 to about 18 carbon atoms per molecule, which process employs an adsorbent comprising a X or a Y zeolite containing selected cations at exchangeable cationic sites to preferentially adsorb the para-isomer. The para-isomer thereafter is removed from the adsorbent by contacting it with a desorbent material and is recovered as a product stream. In a preferred embodiment the process uses a simulated-moving-bed counter-current flow system.

Abstract: A process for the separation of a para-isomer from a hydrocarbon feed stock containing alkyl-aromatic hydrocarbons having more than eight carbon atoms per molecule which employs a crystalline aluminosilicate adsorbent containing a particular cation or cations to selectively adsorb either a para-, meta-, or ortho- isomer from the feed stock. A feed stock contacts an adsorbent which allows one or more isomers from the feed stock to be selectively adsorbed by the adsorbent. The selectively adsorbed component is thereafter recovered from the adsorbent in a more pure form as compared to the other isomers in the feed stock. The process can be performed in both the liquid or vapor phase.

Abstract: A zeolite of type 5A, which has been used to separate normal paraffins from a hydrocarbon mixture containing normal paraffins by bringing the hydrocarbon mixture into contact with the zeolite whereby the zeolite absorbs the normal paraffins and then desorbing the normal paraffins from the zeolite by contacting the zeolite with water-containing ammonia vapour, is reactivated by first contacting the zeolite with at least one of water, aqueous solutions and water-containing gases at a temperature below 350.degree. C and then heating the zeolite to a temperature above 350.degree. C.

Abstract: An improved process for the separation of olefins from a hydrocarbon feed mixture comprising olefins and saturates which process uses an adsorbent comprising sodium type X or sodium type Y zeolite to selectively adsorb the olefins. The improvement comprises employing an adsorbent produced by the steps of: contacting a precursor mass comprising type X or type Y zeolite having a Na.sub.2 O/Al.sub.2 O.sub.3 ratio less than about 0.7 with an aqueous sodium hydroxide solution at ion exchange conditions to effect the addition of sodium cations to the mass and the removal of a small amount of silica and alumina, washing the mass with water to remove excess sodium hydroxide solution; and, at least partially dehydrating the mass at dehydrating conditions thereby producing an adsorbent which has both increased capacity for olefins and decreased catalytic activity.

Abstract: An improved process for separating normal paraffins from a feed stream containing a mixture of normal paraffins, isoparaffins and aromatic hydrocarbons to produce a normal paraffin product stream having a reduced concentration of contaminant aromatic hydrocarbons. The general process comprises the steps of contacting the feed stream with an adsorbent comprising a crystalline aluminosilicate wherein normal paraffins are adsorbed within the pores of the adsorbent and contaminant aromatics are adsorbed on the surface of the adsorbent and subsequently contacting the adsorbent with a desorbent material to remove both adsorbed normal paraffins and contaminant aromatics. The improvement resides in using a two-stage desorption step in which a first desorbent material contacts the adsorbent and removes surface-adsorbed aromatic contaminants and then a second desorbent material contacts the adsorbent to remove normal paraffins adsorbed within the pores of the adsorbent.

Abstract: Dual desorbent composition and/or dual temperature technique, when employed in a simulated moving-bed adsorption-desorption separation system embedded with a solid sorbent comprising certain sieves, e.g., Rb-exchanged Type X crystalline aluminosilicate sieve, which preferentially adsorb ethylbenzene, entails an improved separation and recovery of ethylbenzene from C.sub.8 aromatic feedstreams as sorbate product. Further, certain specific sieves, which preferentially adsorb xylene isomers, i.e., orthoxylene, metaxylene and paraxylene, may also be employed, in said simulated process utilizing the dual desorbent composition and/or the dual temperature concept, in order to effect the improved separation and recovery of ethylbenzene from its C.sub.8 aromatic isomers as raffinate product.

Abstract: Dual desorbent composition and dual temperature techniques are provided as improvements for a simulated moving bed adsorption-desorption separation process which help reduce total desorbent requirements. The invention describes a process for continuously separating, in a liquid phase, components of a C.sub.8 aromatic feed mixture by contacting said feed mixture with a solid sorbent and utilizing a simulated countercurrent flow system wherein a liquid stream flows through serially and circularly interconnected desorption, rectification and sorption zones. One of the embodiments envisioned in the present improved process is directed to the employment of two desorbent streams of different strengths. This embodiment minimizes total amount of desorbent requirements by using a strong desorbent stream in the desorption zone and a suitable weaker desorbent stream in the rectification zone to achieve the desired separation.

Abstract: Dual desorbent composition and dual temperature techniques as improvements for simulated moving-bed adsorption-desorption separation processes whereby certain hydrocarbons can be separated from mixtures containing various unsaturated and/or saturated aliphatic and/or aromatic hydrocarbons. The dual desorbent composition technique is implemented by employing a strong desorbent stream in the desorption zone and a weaker desorbent stream in the rectification zone of a simulated moving-bed countercurrent adsorption-separation system; while the dual temperature concept envisions the temperature differentiation between the desorption zone and the remaining zones of said separation system in order to both minimize the desorbent requirement and enhance the purity of the separation products. A combined use of both the dual desorbent composition and the dual temperature techniques can further improve the performance of said simulated moving-bed system.

Abstract: Simulated moving bed processes for the separation of C.sub.8 aromatic isomers using molecular sieve adsorbents are improved by the use of meta-diisopropylbenzene as the eluting agent. The invention describes a process for continuously separating, in a liquid phase, components of the feed mixture by contacting said feed mixture with a solid sorbent and utilizing a simulated countercurrent flow system wherein a liquid stream flows through serially and circularly interconnected desorption, rectification and sorption zones.

Abstract: Selective adsorption of one cyclic compound from a fluid mixture with a structurally similar cyclic compound can be obtained with molecular sieves (crystalline aluminosilicate zeolites) which have been partially dehydrated at a temperature in the range of 80.degree.-300.degree.C. Preferably the Al/Si ratio in the zeolite framework is in the range of 0.2-0.65. For example, m-xylene can be separated from p-xylene by selective adsorption of the m-xylene on NaY zeolite which was partially dehydrated at 125.degree. C. and contains about 12 wt % water by ignition analysis.

Abstract: A more economical method of removing materials adsorbed on solid adsorbents used to treat hydrocarbon streams is presented. The method comprises removing a liquid hydrocarbon stream from a distillation column, vaporizing the liquid stream and superheating the vapors which are formed, passing the superheated vapor through the adsorbent and effecting the removal of the adsorbed material, and then returning the vapor to the fractionation column and utilizing the vapor as stripping media within the column. In the preferred embodiment, water is removed from alumina.

Abstract: An improved process for separating normal paraffins from a feed stream containing a mixture of normal paraffins and isoparaffins. The general process comprises the steps of contacting the feed stream with an adsorbent comprising a crystalline aluminosilicate thereby adsorbing normal paraffins and subsequently contacting the adsorbent with a desorbent material to remove the adsorbed normal paraffins. The improvement resides in a method of fractionating and recycling a desorbent material for re-use in the process in a manner that reduces total fractionation energy requirements. The method is particularly suitable when two desorbent materials are used in the process.

Abstract: In a 5A molecular sieve separation process for the production of n-paraffins the amount of feed required to produce a given amount of n-paraffins is reduced by recycling all of the effluent from the adsorber for a certain period during the adsorption stage.

Abstract: A process for separating para-xylene in high purity and at high recovery from a feed stream comprising para-xylene and at least one other C.sub.8 aromatic isomer which employs an adsorbent comprising a type X or a type Y zeolite containing barium and strontium at the exchangeable cationic sites in a weight ratio of barium to strontium of from about 1:1 to about 15:1 to selectively adsorb para-xylene from the feed stream and a desorbent material comprising para-diethylbenzene to remove the adsorbed para-xylene from the adsorbent.

Abstract: An adsorptive separation process for separating ethylbenzene from a feed mixture comprising ethylbenzene and a plurality of xylene isomers, which process comprises contacting the feed mixture with a crystalline aluminosilicate adsorbent comprising a sodium-type Y zeolite having a SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio greater than about 4.5, selectively adsorbing substantially all of the said xylene isomers to the substantial exclusion of the ethylbenzene and recovering high-purity ethylbenzene. A desorption step may then be used to desorb the adsorbed xylene isomers. The process can be either in the liquid or vapor phase.

Abstract: A process for the separation of the para-isomer from a hydrocarbon feed mixture comprising at least two bi-alkyl substituted monocyclic aromatic isomers, including the para-isomer, said isomers having from 8 to about 18 carbon atoms per molecule which process employs an adsorbent comprising a type Y zeolite essentially completely exchanged with a single cation selected from the group consisting of potassium, cesium, and rubidium. The feed mixture is passed through a bed of the adsorbent wherein the para-isomer is preferentially adsorbed within the adsorbent and thereafter recovered from the adsorbent.

Abstract: There is a drastic change in the composition of the effluent streams of a fixed bed adsorption column when the feed and withdrawal points are periodically advanced in order to simulate moving-bed operation. These effluents are fractionated to recover a desorbent which is recycled to the adsorption column. The claimed process improves the efficiency of this fractionation by changing the locations at which the effluents enter the fractionators to correlate the compositions of the effluents and the material in the fractionators at these locations.

Abstract: An improved process for the separation of olefins from a hydrocarbon feed mixture comprising olefins and saturates which process uses a zeolite adsorbent to selectively adsorb the olefins. The improvement comprises employing a zeolite adsorbent produced by the steps of: contacting a precursor mass containing type X structured zeolite and amorphous material as a binder with an aqueous caustic solution to effect the addition of alkali metal cations to the crystalline structure; washing the mass with water to remove therefrom excess caustic solution; and, at least partially dehydrating said mass at dehydrating conditions thereby producing an adsorbent which has both increased capacity for olefins and decreased catalytic activity.

Abstract: A process for separating the para-isomer from a feed mixture containing at least two bi-alkyl substituted monocyclis aromatic isomers, including the para isomer, said isomers having from 8 to about 18 carbon atoms per molecule which process comprises contacting said mixture with an adsorbent prepared by the steps of: contacting a base material comprising type X or type Y zeolite with a fluoride-containing aqueous sodium hydroxide solution at first ion exchange conditions to effect the addition of sodium to and the extraction of alumina from said base material; treating the sodium-exchanged base material at second ion exchange conditions to effect the essentially complete exchange of sodium cations; and, drying the material at conditions to reduce the LOI at 900.degree. C. to less than about 10 wt. % thereby selectively adsorbing at adsorption conditions said para isomer.

Abstract: An adsorptive separation process for separating ethylbenzene from a feed mixture comprising ethylbenzene and at least one xylene isomer, which process comprises contacting the feed mixture with a crystalline aluminosilicate adsorbent comprising type X structured zeolite containing at the exchangeable cationic sites at least one cation selected from the group consisting of cations of elements of Group I-A of the Periodic Table of Elements to effect the selective adsorption of ethylbenzene. The ethylbenzene adsorbed by the adsorbent is thereafter recovered as a purified product. The process can be either in the liquid or vapor phase.

Abstract: A process for the separation of the para-isomer from a hydrocarbon feed mixture comprising at least two bi-alkyl substituted monocyclic aromatic isomers, including the para-isomer, said isomers having from 8 to about 18 carbon atoms per molecule using a specially prepared adsorbent comprising a Y zeolite containing at the exchangeable cationic sites one or more selected cations. The feed mixture is passed through a bed of the adsorbent wherein the para-isomer is preferentially adsorbed within the adsorbent and thereafter recovered from the adsorbent. Novel feature of the process is the use of the specially prepared adsorbents which have faster adsorption-desorption rates for the desired para-isomer.