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: 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: Method for controlling with precision a permanent in-line process for separating constituents of a mixture in a simulated moving bed separation system from concentration and flow rate measurements.The system comprises a set of columns forming a closed loop comprising several zones between fluid injection and draw-off points. Control of the process (linear or nonlinear) is performed from a knowledge model and from a certain number of operating variables at a plurality of measuring points along the loop (concentrations and flow rates for example) and characteristic measurements of the fluids injected and drawn off. Ratios respectively indicative of the ratio, in each of the different zones, between the fluid flow rates and the simulated adsorbent material flow rates, are determined from actual values of controlled variables depending on the measured operating variables (purity of the constituents, system yield, etc.).

Abstract: An apparatus and process are described for simulated moving bed separation in which line containing fluid containing the desired product is flushed at least once by a secondary fluid entering each distribution plate or by a fluid leaving each of said plates during at least a portion of a period of time between two successive permutations of the principal supply lines and the principal extraction lines, or during the entirety of said periods, the secondary fluid being selected from the group formed by the solvent, the fluid containing the desired product and the fluid containing the desired product freed of at least a portion of the solvent.

Abstract: A chromatographic simulated moving bed separation process is most generally characterized by a recycling pump which successively adopts the flow rate characteristics of 4 or 5 zones of the process. The invention describes the method by which a conventional simulated moving bed separator process can be adapted to a simulated moving bed process in which the recycling pump is operated at an optimal constant flow rate. In order to achieve this, throughout the cycle all the introduction and extraction circuits are shifted using independent means, such that the eluted volume at the outlet to each zone remains substantially constant, zone by zone, between two successive shifts throughout the cycle.

Abstract: A process for regulating at least one flow of at least one fluid or effluent circulating in a simulated moving bed comprising columns which form a closed loop containing at least one device such as a recycling pump introducing a pressure anisotropy. Every time an injection or extraction point passes from one part of the pump to the other, a control device which controls a fluid flow regulating means for the fluid under consideration, regulated about a set value, is caused to stop regulation temporarily, and substantially simultaneously the regulating means is placed in a position which allows it to approach the desired value, preferably to reach the desired flow rate and to begin to regulate the flow rate about the desired set value, to keep the flow rates in all the zones in a simulated moving bed constant. The process is especially applicable Application to the separation of para-xylene from a mixture of xylenes.

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, with a ratio for the solvent to charge flow rates of 1.2 to 2.5; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25.degree. 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: In a simulated mobile bed separation process, perturbations are corrected in the compositions of an extract (EA) or raffinate (RB) due to the dead volume introduced by at least one recycling pump (P) or compressor for a liquid, supercritical or gaseous mixture in a closed circuit of columns.

Abstract: In a simulated mobile bed separation process, perturbations are corrected in the compositions of an extract (EA) or raffinate (RB) due to the dead volume introduced by at least one recycling pump (P) or compressor for a liquid, supercritical or gaseous mixture in a closed circuit of column sections. The volume of the section immediately upstream of the dead volume is reduced by an appropriate value when said dead volume is located downstream of this section and upstream of the extraction streams of said section, or the volume of the section immediately downstream of the dead volume is reduced by an appropriate value when the dead volume is located downstream of the injection streams into said section and upstream of this section.The invention is applicable to the separation of isomers of aromatic hydrocarbons containing 8 carbon atoms.

Abstract: A monochromatic light signal of a wavelength of between 400 and 1300 nanometers is simultaneously passed by a source 1, a beam splitter 2 and optical fibers 3, 3a to at least two points of a zone 9 for the separation of a mixture of isomers and aromatic hydrocarbons having from 8 to 10 carbons atoms. A polychromatic signal is recovered corresponding to the Raman effect between 400 and 3500 cm.sup.-1 by optical receiving fibers 5, 5a connected to sensors 4 at the locations of said points. The chemical composition of the mixture is determined from the Raman spectra obtained by a spectrometer 6. The analysis sequence is repeated, the profiles with respect to the concentration of the isomers in the mixture are reconstituted and by comparison with reference concentration profiles, action is taken on at least on operational variable 11, 12 of the separation process.

Abstract: A description is given of a process for the separation of at least one constituent from a mixture containing at least two polyglycerols having consecutive degrees of polymerization from 2 to 10, in which said mixture is passed into at least one column lined with an adsorbent particular phase through which flows a liquid eluent, said phase consisting of a cationic organic resin such as a styrene-divinyl benzene copolymer or an anionic resin, or a mineral phase chosen from among silicas, aluminas and zeolites in normal form or modified by grafting, said liquid eluent consisting of an aqueous phase to which is optionally added a strong acid. The process described can be performed continuously or batchwise and in simulated counter-current (SCC) or simulated cocurrent manner.

Abstract: An apparatus and process for fractionation of component mixtures by chromatography or adsorption on a simulated mobile bed comprising three, four or five zones is described. A compressed gas is injected as eluent (IE, IR) using a compressor or pump, the pressure being lower than the critical pressure of the gas. At any point in at least one zone and preferably at any point in at least two zones from the eluent injection point (IR), the gas has a compressibility coefficient substantially different to 1. A supercritical fluid or a subcritical liquid may equally be injected as the eluent. The pressure between each zone may be altered.

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, with a ratio of the solvent to charge flow rates of 1.2 to 2.5; (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: For the at least partial separation of aliphatic paraffins into at least one effluent comprising the least branched paraffins and at least one effluent comprising the most branched paraffins, use is made of at least one adsorbent bed comprising at least one grafted microporous solid. A preferred use of the invention relates to the treatment of a charge obtained from an isomerization zone, whereby at least one adsorbent bed makes it possible to separate the charge into a first effluent comprising the normal paraffins and a second effluent, and at least one adsorbent bed on which passes the second effluent, comprising at least one grafted microporous solid, making it possible to obtain a third effluent comprising the monomethyl branched paraffins and a fourth effluent comprising the polymethyl branched paraffins.

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, with a ratio of the solvent to charge flow rates ob 1.2 to 2.5; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25.degree. 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 si then recycled to the charge. The solvent for desorption in stage (1) and washing in stage (2) is advantageously toluene.

Abstract: A process and a device are described for the continuous separation, in the fluid phase, of a mixture of at least three constituents into three fractions.A so-called simulated countercurrent technique is used in a separation column packed with a sorbent having five zones 6, 5, 4, 3 and 2 with different functions, and the following sequence of steps is performed: so-called strong solvent S.sub.2 is introduced, a strong solvent extract E.sub.2 is removed, the same solvent is introduced but at a lower temperature and/or at a lower pressure (so-called weak solven S.sub.1), weak solvent extract E.sub.1 is drawn off, the mixture to be separated is introduced, weak solvent raffinate R is drawn off and a stream Roy is recycled alternately to the feed for strong solvent S.sub.2 and then to the feed for weak solvent S.sub.1. A stream coming from zone 6 is sent alternately to an outlet for storng solvent extract E.sub.2 and then to the inlet of the fifth zone.

Abstract: A description is given of a process and an apparatus for continuous separation in fluid phase of a mixture of at least three constituents into three fractions. A technique is used, known as the simulated countercurrent technique, in a separation column which is filled with sorbent and has 6 zones 6, 5, 4, 3, 2 and 1 which have different functions, and the following sequence of steps is carried out: strong solvent S.sub.2 is introduced, an extract E.sub.2 with strong solvent is removed, weak solvent S.sub.1 is introduced. The extract with weak solvent E.sub.1 is drawn off, the separating mixture is introduced, refined substance is drawn off with weak solvent R, rinsing solvent (S.sub.1) is introduced, a current Rcy is recycled alternatingly towards the feed of strong solvent S.sub.2 and then towards the feed of weak solvent S.sub.1. A current coming from zone 6 is sent alternatingly to an outlet for the extract with strong solvent E.sub.2, then towards the intake of the fifth zone.

Abstract: In a deasphalting process wherein the deasphalted oil is separated from the deasphalting solvent, the invention consists of performing said separation in at least two separate steps, differing by their temperatures, and of recovering heat from the deasphalted oil.The oil to be deasphalted (26) passes through an extractor (1), then through heat recuperators (3) and (4). The oil-solvent separation is achieved in two steps (5) and (11), under supercritical conditions, at different temperatures. The process has the particular advantage of saving power since external heat is provided (10) to only part of the charge.

Abstract: Process for hydrodesulfurizing and deoxygenating a gas (A) comprising methane, oxygen and at least one organic sulfur compound, said process comprising contacting a mixture of said gas (A) with a hydrogen-containing gas (B) first with a palladium-containing catalyst, at a temperature of 300.degree.-450.degree. C., and then with a second catalyst comprising molybdenum and at least one of nickel and cobalt, at a temperature of 300.degree.-450.degree. C.