Abstract: A process for preparing N-ethyldiisopropylamine by reacting acetaldehyde with diisopropylamine and hydrogen at elevated temperature and under pressure in the presence of a heterogeneous hydrogenation catalyst, the catalyst being a supported transition metal catalyst comprising Pd and/or Pt as catalytically active metal, wherein the diisopropylamine used has a purity of 58% to 94% by weight and impurities as follows: 3% to 20% by weight of water, 3% to 20% by weight of isopropanol, 0% to 2% by weight of others.

Abstract: A system and method for processing unconditioned syngas first removes solids and semi-volatile organic compounds (SVOC), then removes volatile organic compounds (VOC), and then removes at least one sulfur containing compound from the syngas. Additional processing may be performed depending on such factors as the source of syngas being processed, the products, byproducts and intermediate products desired to be formed, captured or recycled and environmental considerations.

Abstract: An aluminum-halogen fuel cell has a positive electrode (2), a negative electrode (3), and an electrolyte (4) containing an ionic liquid represented by formula (1) or the like. In formula (1), R1 represents an unsubstituted or substituent-containing C1 to C20 alkyl group, R2 represents a C1 to C4 alkyl group or the like, each of R3 and R4 independently represents a hydrogen atom or the like, X represents AlCl4 or the like, and Y represents Al2Cl7 or the like.

Abstract: Disclosed are a process and an apparatus for concentrating an organic acid by using a nitroalkane as an entrainer for the azeotropic removal of water from an aqueous organic acid solution. The nitroalkane may be the same as a nitroalkane that is the product of a high pressure nitration process that produces nitroalkanes and aqueous organic acid.

Abstract: The disclosure relates to a process for separating propylene oxide for a crude propylene oxide stream, for example an intermediate stream from a PO/TBA process. The crude propylene oxide stream can be passed through an extractive distillation column. The distillation column is operated at a pressure in a range of greater than 25 up to 50 psig, and/or at a temperature in a range of from 70 to 150 degrees Celsius using C8-C20 paraffin as extractive solvent with an overhead distillate water wash drum. The crude propylene oxide stream include from 0.001 to 0.1 wt % methanol, based on the total composition of the crude propylene oxide stream. The systems, methods, and apparatuses can produce a propylene oxide stream having less formaldehyde and acetaldehyde than the prior art.

Abstract: A process for separating ethylene glycol and 1,2-butanediol. A material flow containing ethylene glycol and 1,2-butanediol gets into the lower-middle part of the azeotropic rectification column C3 after the light components are removed by the separating columns C1 and C2, wherein the ethylene glycol and the azeotropic agent added from the top of the column form azeotrope which is distilled out from the top of the column and gets into the phase separator D1 after being condensed, the upper phase enriched with azeotropic agent after the phase was separated returns to the top of the column to continue to participate in azeotropy, and the lower phase enriched with ethylene glycol gets into the fourth separating column C4 to be refined to obtain the ethylene glycol product.

Abstract: Systems and processes for improving quality and yield of one or more distillate products generated in a distillation column are disclosed. The system comprises a feed inlet distributor that reduces the amount of liquid entrained in vapor rising from the feed zone of the distillation column, a wash zone collection apparatus having an improved design for collecting slop wax falling from a liquid/vapor contacting structure provided in the wash zone, a recirculation subsystem for recirculating at least a portion of the collected slop wax to the top of the wash zone for distribution as wash oil, and a control subsystem. The feed inlet distributor ensures a horizontal fluid flow path free of transverse surfaces thereby minimizing atomization of liquid droplets entrained in vapor in the feed stream.

Abstract: High temperatures and oxygen exposure during extractive distillation can result in polymerization of vinyl aromatic compounds. In various embodiments, the present disclosure relates to methods for inhibiting polymerization of vinyl aromatic compounds during extractive distillation. In various embodiments, the methods include a) providing a mixture containing at least one vinyl aromatic compound, b) adding at least one dinitrophenol inhibitor to the mixture, and c) after step b), performing an extractive distillation on the mixture to isolate the at least one vinyl aromatic compound. Purified styrene can be isolated by the methods described herein. In some embodiments, the dinitrophenol inhibitor is 2-sec-butyl-4,6-dinitrophenol (DNBP).

Abstract: Disclosed herein are processes for separation of 2,3,3,3-tetrafluoropropene and hydrogen fluoride using azeotropic distillation. Additionally, disclosed are processes for separating mixtures of 2,3,3,3-tetrafluoropropene, hydrogen fluoride and 1,1,1,2,3-pentafluoropropane (HFC-245eb) and/or 1,1,1,2,2-pentafluoropropane (HFC-245cb) by azeotropic distillation.

Abstract: The present invention relates to a process for separating ethylene glycol and 1,2-butanediol. A material flow containing ethylene glycol and 1,2-butanediol gets into the lower-middle part of the azeotropic rectification column C3 after the light components are removed by the separating columns C1 and C2, wherein the ethylene glycol and the azeotropic agent added from the top of the column form azeotrope which is distilled out from the top of the column and gets into the phase separator D1 after being condensed, the upper phase enriched with azeotropic agent after the phase was separated returns to the top of the column to continue to participate in azeotropy, and the lower phase enriched with ethylene glycol gets into the fourth separating column C4 to be refined to obtain the ethylene glycol product.

Abstract: A method is described for controlling instability of operation in a de-ethanizer tower (13) in the gas recovery unit in fluid catalytic cracking units and delayed coking units. The method comprises the step of intervening in the de-ethanizer tower (13) when instability occurs in it, and adjusting the material balance of water in such a way that the excess of water in the feed load stream (9) is removed only as an azeotrope. The intervention is performed by introducing into the feed load stream (9) of the de-ethanizer tower (13) a volume fraction (18) of a flow of hydrocarbon, which may be either dry hydrocarbons or hydrocarbons with a low level of water content.

Abstract: Disclosed are a process and an apparatus for concentrating an organic acid by using a nitroalkane as an entrainer for the azeotropic removal of water from an aqueous organic acid solution. The nitroalkane may be the same as a nitroalkane that is the product of a high pressure nitration process that produces nitroalkanes and aqueous organic acid.

Abstract: A process for recovering ethylene is disclosed, the process including: recovering a ethylene-containing stream comprising methane, ethylene, and nitrogen oxides from at least one of an ethylene production process and an ethylene recovery process; separating the ethylene-containing stream via extractive distillation using at least one C2+ hydrocarbon absorbent to produce an overheads fraction comprising methane and nitrogen oxides and a bottoms fraction comprising the at least one C2+ hydrocarbon absorbent and ethylene; wherein the separating comprises operating the extractive distillation at temperatures and pressures sufficient to prevent any substantial conversion of nitrogen oxides to N2O3.

Abstract: The invention relates to a method and a device with the aid of which hydrogen halide and water are removed from biomass hydrolyzates containing halogen acid. The core of the invention is an evacuated container (B1), which is continuously supplied with a heat-transfer medium and which is completely filled with the heat-transfer medium in a part. In said evaporation chamber, the biomass hydrolyzate is likewise continuously introduced. In the container (B1), heat is transferred from the heat-transfer medium to the hydrolyzate, wherein hydrogen halide and water are continuously evaporated. The remaining hydrolyzate particles are continuously discharged with the cooled heat-transfer medium and continuously removed by means of the heat-transfer medium and continuously separated from said heat-transfer medium. The invention described can also be used to treat other mixtures or solutions for the purpose of evaporation.

Abstract: Process for separating propane and propylene using a distillation column and at least one membrane separation unit constituted by one or more modules operating in series, said membrane separation unit being placed either upstream, or downstream, or upstream and downstream of the distillation column.

Abstract: The present disclosure relates to a process for separating a fluoroolefin from a mixture comprising hydrogen fluoride and fluoroolefin, comprising azeotropic distillation both with and without an entrainer. In particular are disclosed processes for separating any of HFC-1225ye, HFC-1234ze, HFC-1234yf or HFC-1243zf from HF.

Abstract: A process and system for removing bound water from bio-oil by azeotropic distillation. The process includes combining a bound-water-containing bio-oil with an azeotrope agent and subjecting the resulting treated bio-oil to azeotropic distillation under reduced pressure. The azeotropic distillation removes a substantial portion of the bound water from the bio-oil, thus producing a water-depleted bio-oil that is less corrosive, more stable, and more readily miscible with hydrocarbons.

Abstract: Disclosed herein are processes for separation of 2,3,3,3-tetrafluoropropene and hydrogen fluoride using azeotropic distillation. Additionally, disclosed are processes for separating mixtures of 2,3,3,3-tetrafluoropropene, hydrogen fluoride and 1,1,1,2,3-pentafluoropropane (HFC-245eb) and/or 1,1,1,2,2-pentafluoropropane (HFC-245cb) by azeotropic distillation.

Abstract: A process for extractively removing homogeneously dissolved catalysts from a reaction effluent of a hydrocyanation of unsaturated mononitriles to dinitriles with a hydrocarbon H, including performing the steps of a) concentrating the reaction effluent before step b) by distillation at pressures of from 0.1 to 5000 mbar and temperatures of from 10 to 150° C., b) adding a hydrocarbon H to the concentrated reaction effluent to obtain a stream I, and c) feeding stream I, without prior separation of the liquid phases, into an extraction apparatus and extracting it at a temperature T with the hydrocarbon H to obtain a stream II comprising the hydrocarbon H enriched with the catalyst and a stream III having a low catalyst content.

Abstract: The invention relates to methods for separating mixture components such as reactor effluent components. In particular, the invention relates to the use of an extractive agent such as a hydrocarbon in an extractive distillation process to separate monomers such as a C4-C7 isoolefins such as isobutylene from mixtures such as reactor effluents including one or more hydrofluorocarbon(s) (HFC).

Abstract: The present invention provides a process for removing methyl acetylene and/or propadiene from a propylene stream and/or a butylene stream by two step fractionation. Methyl acetylene and/or propadiene avoids the use of a hydrogenation reactor and makes the methyl acetylene and/or propadiene recoverable from the process.

Abstract: The present invention provides extractive distillation processes for removing difluoromethane (HFC-32) from a mixture comprising HFC-32 and at least one of chlorodifluoromethane (CFC-12), 1,1,1-trifluoroethane (HFC-143a), chloropentafluoroethane (CFC-115), and pentafluoroethane (HFC-125) using hydrocarbon, chlorocarbon, and oxygen-containing extractive agents.

Abstract: A process for purifying propylene oxide characterized by subjecting a liquid reaction mixture containing propylene oxide, and water, hydrocarbons and oxygen-containing organic compounds as impurities obtained by reacting cumene hydroperoxide with propylene to extractive distillation using an extractant of a hydrocarbon having 7 to 20 carbon atoms with an extractive distillation column, and controlling a concentration of propylene glycol in the extractant supplied to the extractive distillation column to 20% by weight or less.

Abstract: Apparatus and processes are disclosed for economical separation of fluid mixtures. Broadly, apparatus of the invention is an integrated fractional distillation and perm-selective membrane separation apparatus. More particularly, the integrated apparatus comprises a fractional distillation column and one or more membrane device utilizing solid perm-selective membranes. Processes of the invention are particularly useful for simultaneous recovery of a very pure permeate product, a desired non-permeate stream, and one or more distillate products from a fluid mixture containing at least two compounds of different boiling point temperatures.

Abstract: The invention provides a method for producing purified N-vinyl-2-pyrrolidone free of odorous components. The method is composed of distilling with a distillation column a liquid, which is formed by adding to an odorous components-containing liquid having a N-vinyl-2-pyrrolidone purity of not lower than 90 wt %, a compound having boiling point lower than that of N-vinyl-2-pyrrolidone, and whereby removing the odorous components together with said low-temperature boiling compound as the distillate.

Abstract: Cyclic esters of hydroxy organic acids can be produced and recovered via azeotropic distillation. In certain embodiments cyclic esters, such as glycolide and lactide, can be produced from a fermentation broth or other feed stream that contains a hydroxy organic acid, an ammonium salt of a hydroxy organic acid, an amide of a hydroxy organic acid, or an ester of a hydroxy organic acid using azeotropic distillation. The hydroxy organic acid of the feed stream or the hydroxy organic acid derived from the feed stream by decomposition is reacted to produce the cyclic ester. In other embodiments a crude composition of a cyclic ester of an organic ester can be purified using azeotropic distillation.

Abstract: Disclosed herein are methods for the recovery of at least one of an organic acid or an organic acid amide, such as a heat stable lactic acid or lactamide, from a feed stream which contains the organic acid and/or organic acid amide. The feed stream is mixed with at least one azeotroping agent. The azeotroping agent is a hydrocarbon capable of forming at least one heteroazeotrope with the organic acid or the organic acid amide in the feed stream. The mixture of the feed stream and the azeotroping agent is heated to produce a vapor stream. The heteroazeotrope is a component of that vapor stream. The vapor stream can be heated further to separate components or it can be condensed into a liquid stream. The liquid stream is capable of being separated into a first phase and a second phase. The first phase contains the highest concentration of the organic acid and/or the organic acid amide and the azeotroping agent is part of the second phase.

Abstract: Disclosed herein are methods for the recovery of an organic acid, such as a heat stable lactic acid, from a feed stream which contains at least one of an organic acid amide, an organic acid ammonium salt, or an alkylamine-organic acid complex. The feed stream is mixed with at least one azeotroping agent. The azeotroping agent is a hydrocarbon capable of forming at least one azeotrope with the organic acid that is produced by the thermal decomposition of the amide, ammonium salt, or complex in the feed stream. Preferably the azeotrope is a heteroazeotrope. The mixture of the feed stream and the azeotroping agent is heated to produce a vapor stream. The azeotrope is a component of the vapor stream. The vapor stream can be condensed to a liquid stream, and the organic acid is recovered in the liquid stream that is produced. When the azeotrope is a heteroazeotrope, the vapor stream can be condensed into a liquid stream, which can be separated into a first phase and a second phase.

Abstract: A process is described for purifying propylene oxide, which includes the step of distilling propylene oxide containing impurities in the presence of a hydrocarbon having 5 carbon atoms or less. According to the present invention, a process is provided for purifying propylene oxide which has a feature that impurities contained in a solution containing propylene oxide to be purified can be efficiently removed. Oxygen-containing impurities, in particular, can be very efficiently removed.

Abstract: A method and apparatus for isolation of a barely volatile organic compound in a sample suspected to contain the same, e.g. a dioxin, which includes continuously adding superheated steam and a volatile and hardly water-soluble/water-insoluble solvent to a liquid or solid sample suspected to contain said organic compound to be isolated, a solid sample being dissolved in said solvent which can dissolve said organic compound to be isolated, distilling off an azeotropic mixture of said organic compound and said solvent by steam distillation, separating a solvent phase of said solvent dissolving said organic compound and said water phase, and recovering quantitatively said organic compound from said solvent. The dioxins are then further subjected to analysis, for example, GC, HRGC-MS and the like.

Abstract: A method and an apparatus for treating gasoline vapor by bringing gasoline vapor within a fuel tank into contact with a fluid gasoline and making the fluid gasoline absorb the gasoline vapor, in order to improve absorptivity of the gasoline vapor and to reduce the amount of the gasoline vapor introduced into a canister, thereby attaining a canister downsizing. The method and apparatus comprise a separation device of introducing the liquid gasoline within the fuel tank and separating it into a low boiling point component and a high boiling point component, and a gas-liquid contact device of bringing the gasoline vapor within the fuel tank into contact with an extractive gasoline composed of the high boiling point component separated by the separation device, whereby when contacting the gasoline vapor with the extractive gasoline, a part of the gasoline vapor is absorbed to the extractive gasoline, and a residual of the gasoline vapor not absorbed to the extractive gasoline is introduced into a canister.

Abstract: A process for reducing the level(s) of water and/or other impurities from cyclosiloxanes by either azeotropic distillation, or by contacting the cyclosiloxane compositions with an adsorbent bed material. The purified cyclosiloxane material is useful for forming low-dielectric constant thin films having dielectric constants of less than 3.0, more preferably 2.8 to 2.0.

Abstract: A process for purifying propylene oxide, which comprises distilling propylene oxide containing impurities in the presence of a hydrocarbon having 5 carbon atoms or less. According to the present invention, a process for purifying propylene oxide which has a feature that impurities contained in a solution containing propylene oxide to be purified can be efficiently removed, especially, oxygen-containing impurities can be very efficiently removed, is provided.

Abstract: Disclosed herein are methods for the recovery of at least one of an organic acid or an organic acid amide, such as a heat stable lactic acid or lactamide, from a feed stream comprising the organic acid and/or organic acid amide. The feed stream that comprises the organic acid and/or organic acid amide is mixed with at least one azeotroping agent. The azeotroping agent is a hydrocarbon capable of forming at least one heteroazeotrope with the organic acid or the organic acid amide. The mixture comprising the feed stream and the azeotroping agent is heated to produce a vapor stream that comprises the heteroazeotrope. The vapor stream can be heated further to separate components or it can be condensed into a liquid stream. The liquid stream is capable of being separated into a first phase and a second phase. The first phase contains the highest concentration of the organic acid and/or the organic acid amide and the second phase comprises the azeotroping agent.

Abstract: Disclosed herein are methods for the recovery of an organic acid, such as a heat stable lactic acid, from a feed stream comprising at least one of an organic acid amide, an organic acid ammonium salt, or an alkylamine-organic acid complex. The feed stream that comprises the organic acid amide, organic acid ammonium salt, or alkylamine-organic acid complex is mixed with at least one azeotroping agent. The azeotroping agent is a hydrocarbon capable of forming at least one azeotrope with the organic acid that is produced by the thermal decomposition of the amide, ammonium salt, or complex in the feed stream. Preferably the azeotrope is a heteroazeotrope. The mixture comprising the feed stream and the azeotroping agent is heated to produce a vapor stream that comprises the azeotrope. The vapor stream can be condensed to a liquid stream, and the organic acid is recovered in the liquid stream that is produced.

Abstract: A mixture of propylene oxide and methanol is separated by liquid/liquid extraction using water and a hydrocarbon such as n-octane as extractive solvents.

Abstract: A modular solvent recovery device (30) includes an enclosure (34) mounted to a frame (32) to enclose a tank (70) having a solvent section (72) and a waste fluid section (73), a still (40) in which waste photopolymer fluid is distilled by application of heat and vacuum pressure to the waste photopolymer fluid to distill a solvent from the waste photopolymer fluid and reduce the waste photopolymer fluid to a coalescing concentrated residue, and a flash-point-increasing agent delivery system (95) to supply a flash-point-increasing agent to the concentrated residue in an amount sufficient to raise the flash point temperature of the coalescing concentrated residue to a predetermined temperature. The still has a manhole device (46) comprising a pivotally and telescopically mounted closure (47) having wheels (51) rotatably mounted thereto and tracks (52) mounted to the still to engage the wheels and raise the closure vertically above a manhole (42) of the still upon pivotal movement of the closure.

Abstract: Cyclic esters of hydroxy organic acids can be produced and recovered via azeotropic distillation. In certain embodiments cyclic esters, such as glycolide and lactide, can be produced from a fermentation broth or other feed stream that comprises a hydroxy organic acid, an ammonium salt of a hydroxy organic acid, an amide of a hydroxy organic acid, or an ester of a hydroxy organic acid using azeotropic distillation. The hydroxy organic acid of the feed stream or the hydroxy organic acid derived from the feed stream by decomposition is reacted to produce the cyclic ester. In other embodiments a crude composition of a cyclic ester of an organic ester can be purified using azeotropic distillation.

Abstract: A method of removing water from wet organoborane by dissolving the wet organoborane in an organic solvent in which water is incompletely soluble, decanting any insoluble water, and distilling the organic phase to remove water which may be contained therein.

Abstract: Nitrogen trifluoride (NF3) containing less than 10 parts-per-million molar impurities, e.g., tetrafluoromethane (PFC-14), is disclosed. Azeotropic and extractive distillation processes using entraining agents for separating NF3 and PFC-14 from each other and from mixtures with other electronics industry materials are disclosed.

Abstract: A process for the recovery and purification of cyclobutanone from a crude product mixture obtained from an oxidation product mixture resulting from the oxidation of cyclobutanol to cyclobutanone in the presence of water. The process provides for the recovery of cyclobutanone in a purity of at least 90 weight percent by a combination of distillation steps.

Abstract: A method of separating methanol and acetone, and methanol and methyl acetate involves distilling a mixture of the components by an extractive distillation process in the presence of an extractive distillation solvent. The extractive distillation solvent may be an amine, a chlorinated hydrocarbon, a brominated hydrocarbon, a paraffin, and an alkylated thiopene.

Abstract: A method of separating ethanol and ethyl acetate, and ethanol and water involves distilling a mixture of the components by an extractive distillation process in the presence of an extractive distillation solvent. The extractive distillation solvent may be an amine, an alkylated thiopene, and paraffins.

Abstract: A method and apparatus for removing a contaminant from a fluid feed stream containing the contaminant. The method includes the steps of providing a feed stream (10) and heating it in a first step (18) to at least partially remove some of the contaminants and recover energy from a concentrate and distillate generated. Further heating the feed stream in a second heating step (20) in a heated separator generates a saturated vapor fraction (30) and a concentrated liquid contaminant fraction. The vapor fraction (30) may be compressed (32) to generate a temperature differential in the reboiler exchanger (34) with the vapor fraction being passed into contact with a reboiler exchanger (34) to provide a stream of condensed vapor from the reboiler. The stream may be circulated through the reboiler exchanger (34) and the heated separator to maintain from about 1% to about 50% by mass vapor in the stream.

Abstract: A process is disclosed for manufacturing a concentrated residue from a photopolymer fluid which includes photopolymer and photopolymer solvent. The photopolymer fluid may be derived by chemically etching a photopolymer layer of a printing plate with a solvent. The process includes distilling the photopolymer fluid to recover the solvent and concentrate the photopolymer fluid to form a concentrated photopolymer residue, and mixing a flash-point-increasing agent with the concentrated photopolymer residue in an amount sufficient to raise the flash point temperature of the concentrated photopolymer residue to a pre-selected temperature to form the concentrated residue. The flash-point-increasing agent may be mixed with the waste photopolymer fluid prior, during, or after distillation. Also, the flash-point-increasing agent includes oils, such as paraffinic and naphthenic oils and a blend thereof.

Abstract: For the fractionation of viscous silicones, oily or polymeric diorganosilicones with a chain length of between 2 and 10 000 are separated into a top and a bottom product, preferably continuously in an extracting column, using compressed hydrocarbons such as ethane, propane and n- or i-butane, or mixtures thereof, at temperatures of between 25 and 250° C., pressures of between 20 and 500 bar and a gas density >160 kg/m3. To avoid viscosity problems, either an organic solvent in the form of a C5-8 alkane or up to 85 wt. % of the compressed gas (mixture) can be added to the starting materials prior to fractionation. With this process, high-quality viscous silicone fractions are obtained, which have a chain length of 200 to 10 000 and/or a viscosity of 100 to 500 000 mPas, and whose total oligomer content D4 to D20 is less than 0.05 wt. %.

Abstract: Gamma-Butyrolactone (GBL) is recovered from a mixture containing GBL and other heavy organics by a process of azeotropic distillation in the presence of a C8-C 10 hydrocarbon as an azeotroping agent, wherein an azeotrope of GBL and the hydrocarbon is obtained as a distillate, which forms immiscible GBL-rich and hydrocarbon-rich phases, and the hydrocarbon-rich phase is decanted or isolated from the GBL-rich phase. By this process GBL can be efficiently separated from a large proportion of various compounds having boiling points close to that of GBL, e.g., the methyl-&ggr;-butyrolactones (MeGBL's).

Abstract: Inhibition of the formation of unsaturated carbon compounds during the heating of 141b involving the addition of various inhibitors such as dialkylhydroxylamine and/or the use of a vessel made of a nickel alloy.

Abstract: The invention relates to a method for purifying a crude 1,1,1,3,3-pentafluoropropane (HFC-245fa) containing HFC-245fa and 1-chloro-3,3,3-trifluoro-trans-1-propene (HCFC-1233zd(t)), by distillation. This method is characterized in that the distillation is conducted in the presence of a solvent having a boiling point which is higher than that of HCFC-1233zd(t), thereby to substantially remove HCFC-1233zd(t) from the crude HFC-245fa. This solvent may be selected from carbon chlorides, chlorohydrocarbons, fluorochlorohydrocarbons, saturated hydrocarbons, and mixtures thereof. With the use of this solvent, it becomes possible to substantially easily separate HFC-245fa from HCFC-1233zd(t).

Abstract: A process for the separation of propylene from an input stream of C3 hydrocarbons containing propylene and methyl acetylene and/or propadiene and, optionally, C4 and/or higher hydrocarbons is described. The process includes subjecting the input stream to fractional distillation to separate propylene as an overhead stream leaving a bottoms stream containing the methyl acetylene and/or propadiene and the C4 and/or higher hydrocarbons, when present. A propane-containing stream is added to said input stream whereby propane is separated as part of the bottoms stream. The propylene content of the bottoms streams is maintained at less than 10% weight. The amount of propane added to the input stream is such that the weight of propane, propylene, and C4 and/or higher hydrocarbons, when present, in the bottoms stream is greater that the total weight of methyl acetylene and propadiene in the bottoms stream.