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Union Carbide Corporation

Union Carbide Chemicals & Plastics Technology Corporation

Paulino Forte

Jose A Vidueira

Stanley Joseph Frey

George S Somekh

Kenneth F Butwell

Leo Ernest Hakka

Craig Norman Schubert

John Wayne Dean

The present invention provides a process for removing sulfur compounds including sulfur in the (&minus;2) oxidation state such as mercaptans, dialkyl sulfides, carbonyl sulfide, hydrogen sulfide, thiophenes and benzothiophenes, from liquid or gas feed streams, particularly hydrocarbon feed streams such as, for example, natural gas and refinery process streams. According to the process, such a feed stream including these sulfur impurities is contacted with an absorbent which includes a metal ion-containing organic composition such as, for example, iron, copper, lead, nickel, tin, zinc or mercury cation-containing phthalocyanine or porphyrin to thereby form sulfur-metal cation coordination complexes in which the oxidation state of the sulfur and the metal cation remains essentially unchanged. The complexes are separated from the feed stream, and the absorbent is regenerated by disassociating the sulfur compound from the complexes.

Process for removing sulfur compounds from gas and liquid hydrocarbon streams

An absorbent composition for the removal of acid gases, such as CO , H S and COS, from gas streams is provided. The absorbent composition comprises an aqueous solution comprising: 1) greater than 1 mole piperazine per liter of aqueous solution; and 2) about 1.5 to about 6 moles methyldiethanolamine per liter of aqueous solution.

Absorbent compositions for the removal of acid gases from gas streams

A process is directed to the removal of impurities such as sulfur compounds, oxygenates, and/or olefins from a light paraffin hydrocarbon feedstock such as a C.sub.4 -C.sub.6 fraction, which may be used subsequently in an isomerization process in an integrated complex for the production of ethers such as MTBE and TAME. The hydrocarbon feedstream is passed to a removal zone wherein the hydrocarbon feedstream is contacted with a selective solvent for the removal of the impurities comprising at least one of sulfur compounds, oxygenates and olefins to provide a rich solvent stream and a treated hydrocarbon stream. The rich solvent comprising the trace impurities is contacted with a stripping medium stream to regenerate the selective solvent in a stripping zone. The removal zone may be a liquid-liquid extraction zone or a gas absorption zone. The selective solvent comprises a water miscible organic liquid having a low molecular weight preferably less than about 400 and more preferably having a molecular weight of less than about 200. The process is particularly useful in removing impurities such as sulfur, oxygenates and/or olefins which are harmful to the isomerization catalyst. The process replaces separate olefins, oxygenate, and sulfur removal processes resulting in simplified processing schemes.

Process for removal of impurities from light paraffin isomerization

A process is disclosed for the removal of sulfur from petroleum fractions such as FCC gasoline by employing a solvent selected from the group consisting of a polyalkylene glycol, polyalkylene glycol ether, and mixtures thereof and having a molecular weight less than 400. The process is useful for saving energy, saving hydrogen consumption, and retaining octane. By requiring only the mild hydrotreatment of an extracted or absorbed stream concentrated with the sulfur impurities, the sulfur impurities are removed without the loss of octane resulting from conversion of either high octane olefins or aromatic components. In addition, the extract stream is a significantly smaller stream than the original feedstream.

Process for the removal of sulfur from petroleum fractions

Process for removal of impurities from etherification feedstocks

The invention relates to a process for separating aromatic hydrocarbons from a mixed hydrocarbon feed employing a selective solvent which exhibits a low critical solution temperature of the solvent with a solute. The mixed hydrocarbon feed is passed to an extraction zone wherein the feed is contacted with a lean solvent to provide a raffinate stream comprising non-aromatics and a rich solvent stream comprising aromatics and solvent. Both the raffinate stream and the rich solvent stream are admixed with a sufficient amount of a solute at a temperature which is at or below a low critical solution temperature with the solvent to separate the raffinate and aromatic phases from the solvent/solute mixture. The solvent/solute mixture is heated to a separation temperature which is above the low critical solution temperature to provide a solvent phase which is essentially free of solute at energy levels significantly lower than conventional processes.

Separation of aromatic hydrocarbons from a mixture of aromatic and

A process is disclosed for the purification of natural gas in which the reduction of the nitrogen content of a natural gas stream is achieved by a combination of absorption, purification, flashing, and reflux steps. More specifically, the process achieves the rejection of inert components such as nitrogen from natural gas without operating in the cryogenic temperature range. The process uses a lean solvent to absorb the non-rejected components in a recovery zone of an absorber and uses a portion of the off-gas from the flashing zone to purify the rich solvent in a purification zone of the absorber. In a further embodiment, solvent entrained in off-gases from low and medium pressure flash zones is recovered in a high pressure flash zone by washing the off-gases with recovered lean solvent.

Process for the purification of gases

A continuous solvent extraction process for the separation of aromatic hydrocarbons from a feedstock comprising aromatic and non-aromatic hydrocarbons provides more efficient heat utilization by using a lean solvent stream to heat the rich solvent stream as it passes from a primarily extractive stripping section to a section that primarily provides steam stripping. The feed stream is contacted with a lean solvent stream in an extraction zone to separate it into a raffinate stream comprising non-aromatic hydrocarbons and a first rich solvent stream comprising solvent, aromatic hydrocarbons and non-aromatic hydrocarbons. The first rich solvent stream passes to a first stripping zone section from which a first vapor stream is recovered and a second rich solvent stream is discharged. As the second rich solvent stream is passed to a second section of the stripping zone it is heated by heat exchange with the lean solvent stream that is recovered from the second stripping zone section. Heat exchange of the rich solvent with the lean solvent between stripping sections removes substantially more heat from the lean solvent stream than was previously removed when the lean solvent stream was used to heat stripping steam. The additional heat made available by this invention reduces the overall heat input and permits the use of low pressure steam to heat the stripping stream.

Process for the separation of aromatic hydrocarbons with energy

A process is disclosed for the purification of natural gas in which the reduction of the nitrogen content of a natural gas stream is achieved by a combination of absorption, purification, flashing, and reflux steps. More specifically, the process achieves the rejection of inert components such as nitrogen from hydrocarbon gas streams without operating in the cryogenic temperature range. The process uses a lean solvent to absorb the non-rejected components in a recovery zone of an absorber and uses a cooled light gas stream to purify the rich solvent in a purification zone of the absorber. The process can be employed to reject hydrogen and recover C.sub.3 +hydrocarbons from a dehydrogenation reaction zone integrated with an etherification zone for the production of ethers to improve recovery and lower operating costs.

A method is provided for the recovery of aromatic hydrocarbons from the extract phase of aromatic-selective solvent extraction process which involves withdrawing a vapor side-cut fraction containing aromatic hydrocarbons and solvent from a stripping zone and passing the side-cut fraction to a rectification zone which can be refluxed with an aqueous condensate. The benefits of the invention are that the introduction of the rectification zone bottoms to the bottom of the stripping section provides an aromatic product comprising less than 100 wt. ppm. solvent, provides improved stripping over prior schemes, and reduces the flowrate of stripping medium throughout the stripping zone which results in energy saving.

Method for aromatic hydrocarbon recovery

A continuous solvent extraction process for the separation of aromatic hydrocarbons from a feedstock comprising aromatic and non-aromatic hydrocarbons provides more efficient heat utilization by using a lean solvent stream to heat the rich solvent stream as it passes from a primarily extractive stripping section to a section that primarily provides steam stripping. The feed stream is contacted with a lean solvent stream in an extraction zone to separate it into a raffinate stream comprising non-aromatic hydrocarbons and a first rich solvent stream comprising solvent, aromatic hydrocarbons and non-aromatic hydrocarbons. The first rich solvent stream passes to a first stripping zone section from which a first vapor stream is recovered and a second rich solvent stream is discharged. As the second rich solvent stream is passed to a second section of the stripping zone it is heated by heat exchange with the lean solvent stream that is recovered from the second stripping zone section. Heat exchange of the rich solvent with the lean solvent between stripping sections removes substantially more heat from the lean solvent stream than was previously removed when the lean solvent stream was used to heat stripping stream. The additional heat made available by this invention reduces the overall heat input and permits the use of low pressure steam to heat the stripping steam stream.

In a combined solvent extraction/steam distillation process for the separation of aromatic hydrocarbons from a mixture of aromatic and non-aromatic hydrocarbons, there are three major thermal and material cycles: the solvent cycle, the hydrocarbon cycle, and the water cycle. The process is improved by redistributing the energy use between the three cycles to minimize the internal recycle within the process and to reduce the overall energy requirements. One means of the redistribution includes cooling of a lean solvent stream with liquid in a recovery or stripping column. Cooling of the lean solvent reduces flashing within an extract column and the resulting reflux of hydrocarbons to the extract column.

Processes are provided for the recovery of aromatic hydrocarbons from feeds comprising mixtures of aromatic and non-aromatic hydrocarbons using a mixed aromatic extraction solvent at extraction temperature of less than 250.degree. F. The mixed extraction solvent is comprised of a solvent component containing low molecular weight polyalkylene glycols and a cosolvent component containing glycol ethers. Extractive distillation and steam distillation operations are employed to separate the hydrocarbon components from the rich solvent extract. Low temperature extraction followed by subsequent heating of the rich solvent stream results in improved solvent selectivity, reduced solvent to feed ratios, improved thermal stability and energy savings.

Aromatic extraction process using mixed polyalkylene glycol/glycol ether

Methods are provided for the recovery of aromatic hydrocarbons from the extract phase of aromatic-selective solvent extraction processes which involve withdrawing a vapor side-cut fraction containing aromatic hydrocarbons and solvents from a stripping zone and passing the side-cut fraction to a rectification zone which can be refluxed with aromatic hydrocarbons or aqueous condensate.

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Yonkers, NY, United States of America

Paulino Forte