CA2415064A1 - Selective chemical binding for olefins/paraffins separation - Google Patents
Selective chemical binding for olefins/paraffins separation Download PDFInfo
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- CA2415064A1 CA2415064A1 CA 2415064 CA2415064A CA2415064A1 CA 2415064 A1 CA2415064 A1 CA 2415064A1 CA 2415064 CA2415064 CA 2415064 CA 2415064 A CA2415064 A CA 2415064A CA 2415064 A1 CA2415064 A1 CA 2415064A1
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- olefins
- diolefins
- chemical binding
- binding agent
- process according
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
- C07C7/152—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound by forming adducts or complexes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/72—Organic compounds not provided for in groups B01D53/48 - B01D53/70, e.g. hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
- C07C7/173—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound with the aid of organo-metallic compounds
Abstract
The present invention provides a process for the production of high purity olefin and diolefin components employing a separation system based on the separation of olefins and diolefins from non-olefinic materials using selective chemical binding reactions of olefins and diolefins, the release of the olefins and diolefins through a reverse chemical reaction, and separation of the olefins and diolefins into higher purity components by distillation, overcoming the drawbacks of the prior cryogenic separation processes.
Description
FIELD OF THE INVENTION
The present invention relates to the separation of olefins from a stream of mixed cracked gases. More particularly the present invention relates to the separation of Gower olefins and particularly C2_3 olefins from cracked gases from an ethylene cracker.
BACKGROUND OF THE INVENTION
Cryogenic separation systems of the prior art have suffered from various drawbacks. In conventional cryogenic recovery systems, the cracked gas is typically compressed to about 450-550 prig, requiring 4-6 stages of compression. Additionally, in conventional cryogenic recovery systems, three fractionators (distillation tower systems) are required to separate the ethylene from the other components of the cracked gas stream: demethanizer, deethanizer, and C2 splitter. Because the separation of ethane from ethylene involves close boiling compounds, the splitters generally require very high reflux ratios and a large number of trays, typically on the order of 100 to 250 trays each. The conventional cryogenic separation technology also requires multi-level cascaded propylene and ethylene refrigeration systems, as well as complicated hydrogen and methane turboexpanders and recompressors or a methane refrigeration system, adding to the capital and operation cost and complexity of the conventional cryogenic separation technology.
Much work has been done with solutions of silver (I), and to a lesser degree copper (I), compounds as alternatives to cryogenic separation of olefins and paraffins. Silver and copper in their +1 valent states are known to selectively and reversibly bind olefins. While these M:\Trevor\TTSpec19254can.doc 2 materials have had some success in simple separation of olefins from paraffins, their application has been limited due to their reactivity with the hydrogen, carbon monoxide, and acetylenes normally found in olefin-containing cracked gas streams. To date, n~o known commercial application of this phenomenon has been developed.
Recently, Wang and Steifel (U.S. Patent 6,120,692, WO 00/61528) reported that dithiolene nickel complexes can selectively and reversibly bind olefins. It was further observed that these complexes were not reactive with coproducts found in commercial olefin streams, specifically parafFins, hydrogen, carbon monoxide, and acetylene. Further, the metal dithiolenes were observed to be unreactive to low concentrations of hydrogen sulfide. It was found that the bound olefins could be readily released either physically, through a change in temperature or pressure, or electrochemically by altering the oxidation state of the metal complex.
The present invention seeks to provide a simple process for the recovery of high purity olefins, including ethylene, from a cracked gas stream, preferably without the need for distillation separation of close boiling olefins and paraffins.
The present invention further seeks to provide a process for the recovery of C3 and higher olefins and diolefins with low levels of non-olefinic impurities.
Additionally, the present invention seeks to separate olefins and diolefins from paraffins, acetylenes, hydrogen, and carbon monoxide in a single processing step.
M:lTrevorlTTSpec19254can.doc The present invention also seeks to provide a process for the recovery of high purity olefins that reduces refrigeration requirements.
SUMMARY OF THE IN'1~ENTION
The present invention provides a process foir the separation of C2_6 olefins and C4_6 diolefins from a mixed gas stream also containing one or more members selected from the group consisting of paraffins, acetylenes, hydrogen, and carbon monoxide comprising:
(i) compressing said mixed gas stream to a pressure from 100 to 450 psig;
(ii) caustic washing said compressed mixed gas stream to remove acidic gases including hydrogen sulphide to a level of less than 5,000 ppm;
(iii) drying said washed compressed mixed gas stream to a dew point of from -100°C to -130°C;
(iv) contacting said dried washed compressed mixed gas stream with reversible chemical binding agent which preferentially complexes one or more olefins, diofefins or both to form complexed olefins diolefins or both;
(v) separating said dried washed compressed mixed gas stream from said stream of complexed olefins, diolefins or both; and (vi) treating said complexed olefins, diolefins or both to release said olefins, diolefins or both and regenerate said reversible chemical binding agent.
M:lTrevorlTTSpec19254can.doc 4 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic flow chart of a cryogenic process of the prior art.
Figure 2 is a schematic flow chart of the process of the present invention.
DETAILED DESCRIPTION
The present invention uses selective chemical binding reactions to separate high purity streams of olefins and dioiefins from mixed streams through a reversible chemical reaction.
The present invention may be used in the separation of olefins and diolefins from paraffins, acetylenes, hydrogen, and carbon monoxide without resorting to distillation or cryogenic liquefaction. The olefins and diolefins are first separated from the other cracked gas components in a chemical binding process. The olefins are then relatively easily separated from each other using conventional distillation due to their relatively wide boiling point differences.
Typically the olefins may be C2_6 olefins, preferably linear olefins preferably C2_4, most preferably Cz_3 olefins, most preferably alpha olefins.
(i.e. ethylene and propylene).
The diolefins may be C4_6 diolefins, preferably C4_5 diolefins which may be straight chained or branched and unsubstituted or substituted by one or more C~_4 alkyl radicals. The diolefins may include butadiene and isoprene.
M:lTrevorlTTSpec19254can.doc 5 The mixed gases may also include paraffins such as C~-10 hydrocarbons that are straight chained or branched and which may be unsubstituted or substituted by one or more C~_4 alkyl radicals.
In a typical conventional cryogenic separation process, as shown in Figure 1, a mixed gas stream from a source,. preferably cracked gas from a cracker such as an ethylene cracker is fed by line 2 to a compressor 4.
The compressed gas leaves compressor 4 by line 6 and is fed to a caustic washer 8. In caustic washer 8 acidic gases including hydrogen sulphide are reduced to a level of less than 5,000 ppm, preferably less than 500, most preferably less than 100 ppm. The washed compressed gas is fed by line 10 to dryer 12 where the gas is dried by a conventional drying means such as a molecular sieve. The compressed dried gas is then fed by line 14 to the chilling train 16. Hydrogen and methane are separated from the cracked gas by liquefying a portion of the methane and essentially all of the heavier components in the chilling train 16 typically using propylene and ethylene refrigeration. The gaseous components (e.g. hydrogen and some of the methane) are removed from the chilling train 16 by line 20 which feeds into line 28 and ultimately into turboexpander 30.
The liquids from the chilling train 16 are removed via a line 18 and fed to a demethanizer tower 22. The methane is removed from the top of the demethanizer tower 22 in a line 24, and is combined with the hydrogen and methane in a line 20 to form a single stream in a line 28. The hydrogen and methane in a line 28 is fed to expander 30 and returned to the chilling train 16 as a refrigerant via a line 32 and removed from the M:lTrevor\TTSpec\9254can.doc chilling train 16 by line 34 to be recompressed in a compressor 36 and recovered in a line 38.
The C2+ components are removed from the bottom of the demethanizer tower 22 by line 26 and fed to a deethanizer tower 40. The C2 components are removed from the top of the deethanizer tower 40 by line 42 and passed to an acetylene hydrogenation reactor 46 for selective hydrogenation of acetylenes. The effluent from the reactor 46 is then fed by a line 48 to a C2 splitter 50 for separation of the ethylene, removed from the top of splitter 50 in line 52, and ethane, removed from the bottom of splitter 50 in a line 54.
The C3+ components are removed from the bottom of the deethanizer tower 40 in line 44 and may be subjected to further separation and purification steps which are well known to those skilled in the art.
In the invention process depicted in Figure 2 the cracked gas in line 102 is compressed in a compressor 104. The compressed gas is fed by line 106 to a caustic washer 108 and fed via a line 110 to dryer 112. The dried gas is fed by line 114 chemical separating unit 116 which separates a stream containing ethylene and higher olefins and diolefins in line 120 from a stream consisting primarily of non-olefins (e.g. paraffins and acetylenes, C02, CO and other products in the mixed gas stream) in a line 118. The primarily non-olefins stream in a line 118 may be subjected to further separation and purification using methods well known to those skilled in the art.
The olefin-containing stream in line 120 is fed to a deethylenizer tower 122. The ethylene is removed from the top of the deethylenizer M:\Trevor\TTSpec\9254can.doc tower 122 in a line 124. The C3+ olefins and diolefins are removed from the bottom of the deethylenizer tower 122 in line 126 and may be subjected to further separation and purification.
The present invention provides a novel process for the recovery of olefins and diolefins from cracked gases cornprising the steps of (a) contacting the cracked gas stream with a metal complex capable of selectively reacting and binding with olefins and diolefins to produce a stripped paraffin-rich gaseous stream, (b) recovering the bound olefins and diolefins from the metallic complex by reversing the binding reaction, and (c) separating the resulting olefin and diolefin stream into an ethylene and a mixed-olefin and diolefin stream.
The cracked gas streams useful as feedstocks in the process of the present invention can typically be any gas stream which contains light olefins, namely ethylene and propylene, in combination with other gases, particularly hydrogen and saturated hydrocarbons. Typically, cracked gas streams for use in accordance with the practice of the present invention will comprise a mixture of butane, butenes, propane, propylene, ethane, ethylene, acetylene, methyl acetylene, propadiene, butadienes, methane, hydrogen, and carbon monoxide.
The cracked gas stream is preferably first compressed to a pressure ranging from about 100 psig to about 450 psig, preferably from about 200 psig to about 400 psig, in the compressing step to produce a compressed cracked gas stream. The compression may be effected in any compressor or compression system known to those skilled in the art.
This relatively low compression requirement represents a significant M:lTrevorlTTSpec\9254can.doc improvement over the prior art cryogenic processes. In the prior art cryogenic process, the cracked gas is typically required to be compressed to about 450-550 psig and requires 4-6 stages of compression. In the present process, the compression requirements are significantly reduced thereby representing a significant savings.
The compressed gas is then caustic washed to remove hydrogen sulfide and other acid gases, as is well knov~rn to those skilled in the art.
Any of the caustic washing processes known to those skilled in the art may be employed in the practice of the present invention. However, in the practice of the present invention which includes a chemical binding step, complete removal of hydrogen sulfide is not necessary because the olefins and diolefins will be selectively removed from the hydrogen sulfide in the selective chemical binding system and because traces of hydrogen sulfide are not known to adversely affect the metal complex used in the selective chemical binding process.
The washed and compressed gas is then dried, such as over a water-absorbing molecular sieve to a dew paint of from about -150°F
(about -100°C) to about -200°F (about -128°C) to produce a dried stream.
The dried process stream may then be passed directly to the selective chemical binding system of the present invention.
In a preferred embodiment of the invention, the dried process stream may then be purified to remove some higher hydrocarbons prior to introduction in the selective chemical binding unit.
M:\Trevor\TTSpec\9254can.doc More preferably, the dried process stream may be debutanized to recover C5+ and heavier components from the stream prior to removal of olefins and diolefins. This process is well known to those skilled in the art.
The bottoms from the debutanizer comprises substantially all of the C5+
hydrocarbons and may be separated into its component parts for pentene recovery, and recycling of paraffins to the steam cracker, as desired. The overhead from the debutanizer comprises substantially all of the C4 and lighter hydrocarbons and is then passed to the selective chemical binding system of the present invention.
In the selective chemical binding section the olefin-containing vapour stream is contacted with a metal-containing complex to separate the olefins and diolefins from the bulk of the stream. Through such contacting, the olefins and diolefins are chemically reacted with the metal complex and are selectively separated (removed) from the paraffinic components (typically C~_1o paraffins which are straight chained or branched and are unsubstituted or substituted by one or more C,_4 alkyl radicals including methane, ethane, propane and butane). The scrubbed gases, mainly paraffins, hydrogen, acetylenes, and carbon monoxide, are removed from the top of the binding reactor. The olefins and diolefins bound with the metal complex are then recovered through a reversal of the binding chemical reaction to generate a stream containing essentially olefins and diolefins.
This contacting system may be chosen from any of several methods well known in the art, including but not limited to liquid absorption (e.g. passing through a liquid pool or co or counter current adsorption in M:lTrevor\TTSpec\9254can.doc 1 Q
for example a tower), solid-phase adsorption passing through a fixed adsorption bed), and contacting through polymeric membranes.
(e.g. membranes which may be doped with the reversible chemical binding agent).
Olefin andlor diolefin recovery (and regeneration of the reversible chemical binding agent) may be effected by a physical method, such as reduction in temperature or pressure of the stream, or by an electrochemical method whereby the oxidation state of the metal complex is changed to release the bound olefins or diolefins.
The metal complex used may be selected from any number of compounds that possess the following properties:
1 ) the metal complex reacts with olefins and diolefins to bind the olefin or diolefin in a single molecule;
The present invention relates to the separation of olefins from a stream of mixed cracked gases. More particularly the present invention relates to the separation of Gower olefins and particularly C2_3 olefins from cracked gases from an ethylene cracker.
BACKGROUND OF THE INVENTION
Cryogenic separation systems of the prior art have suffered from various drawbacks. In conventional cryogenic recovery systems, the cracked gas is typically compressed to about 450-550 prig, requiring 4-6 stages of compression. Additionally, in conventional cryogenic recovery systems, three fractionators (distillation tower systems) are required to separate the ethylene from the other components of the cracked gas stream: demethanizer, deethanizer, and C2 splitter. Because the separation of ethane from ethylene involves close boiling compounds, the splitters generally require very high reflux ratios and a large number of trays, typically on the order of 100 to 250 trays each. The conventional cryogenic separation technology also requires multi-level cascaded propylene and ethylene refrigeration systems, as well as complicated hydrogen and methane turboexpanders and recompressors or a methane refrigeration system, adding to the capital and operation cost and complexity of the conventional cryogenic separation technology.
Much work has been done with solutions of silver (I), and to a lesser degree copper (I), compounds as alternatives to cryogenic separation of olefins and paraffins. Silver and copper in their +1 valent states are known to selectively and reversibly bind olefins. While these M:\Trevor\TTSpec19254can.doc 2 materials have had some success in simple separation of olefins from paraffins, their application has been limited due to their reactivity with the hydrogen, carbon monoxide, and acetylenes normally found in olefin-containing cracked gas streams. To date, n~o known commercial application of this phenomenon has been developed.
Recently, Wang and Steifel (U.S. Patent 6,120,692, WO 00/61528) reported that dithiolene nickel complexes can selectively and reversibly bind olefins. It was further observed that these complexes were not reactive with coproducts found in commercial olefin streams, specifically parafFins, hydrogen, carbon monoxide, and acetylene. Further, the metal dithiolenes were observed to be unreactive to low concentrations of hydrogen sulfide. It was found that the bound olefins could be readily released either physically, through a change in temperature or pressure, or electrochemically by altering the oxidation state of the metal complex.
The present invention seeks to provide a simple process for the recovery of high purity olefins, including ethylene, from a cracked gas stream, preferably without the need for distillation separation of close boiling olefins and paraffins.
The present invention further seeks to provide a process for the recovery of C3 and higher olefins and diolefins with low levels of non-olefinic impurities.
Additionally, the present invention seeks to separate olefins and diolefins from paraffins, acetylenes, hydrogen, and carbon monoxide in a single processing step.
M:lTrevorlTTSpec19254can.doc The present invention also seeks to provide a process for the recovery of high purity olefins that reduces refrigeration requirements.
SUMMARY OF THE IN'1~ENTION
The present invention provides a process foir the separation of C2_6 olefins and C4_6 diolefins from a mixed gas stream also containing one or more members selected from the group consisting of paraffins, acetylenes, hydrogen, and carbon monoxide comprising:
(i) compressing said mixed gas stream to a pressure from 100 to 450 psig;
(ii) caustic washing said compressed mixed gas stream to remove acidic gases including hydrogen sulphide to a level of less than 5,000 ppm;
(iii) drying said washed compressed mixed gas stream to a dew point of from -100°C to -130°C;
(iv) contacting said dried washed compressed mixed gas stream with reversible chemical binding agent which preferentially complexes one or more olefins, diofefins or both to form complexed olefins diolefins or both;
(v) separating said dried washed compressed mixed gas stream from said stream of complexed olefins, diolefins or both; and (vi) treating said complexed olefins, diolefins or both to release said olefins, diolefins or both and regenerate said reversible chemical binding agent.
M:lTrevorlTTSpec19254can.doc 4 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic flow chart of a cryogenic process of the prior art.
Figure 2 is a schematic flow chart of the process of the present invention.
DETAILED DESCRIPTION
The present invention uses selective chemical binding reactions to separate high purity streams of olefins and dioiefins from mixed streams through a reversible chemical reaction.
The present invention may be used in the separation of olefins and diolefins from paraffins, acetylenes, hydrogen, and carbon monoxide without resorting to distillation or cryogenic liquefaction. The olefins and diolefins are first separated from the other cracked gas components in a chemical binding process. The olefins are then relatively easily separated from each other using conventional distillation due to their relatively wide boiling point differences.
Typically the olefins may be C2_6 olefins, preferably linear olefins preferably C2_4, most preferably Cz_3 olefins, most preferably alpha olefins.
(i.e. ethylene and propylene).
The diolefins may be C4_6 diolefins, preferably C4_5 diolefins which may be straight chained or branched and unsubstituted or substituted by one or more C~_4 alkyl radicals. The diolefins may include butadiene and isoprene.
M:lTrevorlTTSpec19254can.doc 5 The mixed gases may also include paraffins such as C~-10 hydrocarbons that are straight chained or branched and which may be unsubstituted or substituted by one or more C~_4 alkyl radicals.
In a typical conventional cryogenic separation process, as shown in Figure 1, a mixed gas stream from a source,. preferably cracked gas from a cracker such as an ethylene cracker is fed by line 2 to a compressor 4.
The compressed gas leaves compressor 4 by line 6 and is fed to a caustic washer 8. In caustic washer 8 acidic gases including hydrogen sulphide are reduced to a level of less than 5,000 ppm, preferably less than 500, most preferably less than 100 ppm. The washed compressed gas is fed by line 10 to dryer 12 where the gas is dried by a conventional drying means such as a molecular sieve. The compressed dried gas is then fed by line 14 to the chilling train 16. Hydrogen and methane are separated from the cracked gas by liquefying a portion of the methane and essentially all of the heavier components in the chilling train 16 typically using propylene and ethylene refrigeration. The gaseous components (e.g. hydrogen and some of the methane) are removed from the chilling train 16 by line 20 which feeds into line 28 and ultimately into turboexpander 30.
The liquids from the chilling train 16 are removed via a line 18 and fed to a demethanizer tower 22. The methane is removed from the top of the demethanizer tower 22 in a line 24, and is combined with the hydrogen and methane in a line 20 to form a single stream in a line 28. The hydrogen and methane in a line 28 is fed to expander 30 and returned to the chilling train 16 as a refrigerant via a line 32 and removed from the M:lTrevor\TTSpec\9254can.doc chilling train 16 by line 34 to be recompressed in a compressor 36 and recovered in a line 38.
The C2+ components are removed from the bottom of the demethanizer tower 22 by line 26 and fed to a deethanizer tower 40. The C2 components are removed from the top of the deethanizer tower 40 by line 42 and passed to an acetylene hydrogenation reactor 46 for selective hydrogenation of acetylenes. The effluent from the reactor 46 is then fed by a line 48 to a C2 splitter 50 for separation of the ethylene, removed from the top of splitter 50 in line 52, and ethane, removed from the bottom of splitter 50 in a line 54.
The C3+ components are removed from the bottom of the deethanizer tower 40 in line 44 and may be subjected to further separation and purification steps which are well known to those skilled in the art.
In the invention process depicted in Figure 2 the cracked gas in line 102 is compressed in a compressor 104. The compressed gas is fed by line 106 to a caustic washer 108 and fed via a line 110 to dryer 112. The dried gas is fed by line 114 chemical separating unit 116 which separates a stream containing ethylene and higher olefins and diolefins in line 120 from a stream consisting primarily of non-olefins (e.g. paraffins and acetylenes, C02, CO and other products in the mixed gas stream) in a line 118. The primarily non-olefins stream in a line 118 may be subjected to further separation and purification using methods well known to those skilled in the art.
The olefin-containing stream in line 120 is fed to a deethylenizer tower 122. The ethylene is removed from the top of the deethylenizer M:\Trevor\TTSpec\9254can.doc tower 122 in a line 124. The C3+ olefins and diolefins are removed from the bottom of the deethylenizer tower 122 in line 126 and may be subjected to further separation and purification.
The present invention provides a novel process for the recovery of olefins and diolefins from cracked gases cornprising the steps of (a) contacting the cracked gas stream with a metal complex capable of selectively reacting and binding with olefins and diolefins to produce a stripped paraffin-rich gaseous stream, (b) recovering the bound olefins and diolefins from the metallic complex by reversing the binding reaction, and (c) separating the resulting olefin and diolefin stream into an ethylene and a mixed-olefin and diolefin stream.
The cracked gas streams useful as feedstocks in the process of the present invention can typically be any gas stream which contains light olefins, namely ethylene and propylene, in combination with other gases, particularly hydrogen and saturated hydrocarbons. Typically, cracked gas streams for use in accordance with the practice of the present invention will comprise a mixture of butane, butenes, propane, propylene, ethane, ethylene, acetylene, methyl acetylene, propadiene, butadienes, methane, hydrogen, and carbon monoxide.
The cracked gas stream is preferably first compressed to a pressure ranging from about 100 psig to about 450 psig, preferably from about 200 psig to about 400 psig, in the compressing step to produce a compressed cracked gas stream. The compression may be effected in any compressor or compression system known to those skilled in the art.
This relatively low compression requirement represents a significant M:lTrevorlTTSpec\9254can.doc improvement over the prior art cryogenic processes. In the prior art cryogenic process, the cracked gas is typically required to be compressed to about 450-550 psig and requires 4-6 stages of compression. In the present process, the compression requirements are significantly reduced thereby representing a significant savings.
The compressed gas is then caustic washed to remove hydrogen sulfide and other acid gases, as is well knov~rn to those skilled in the art.
Any of the caustic washing processes known to those skilled in the art may be employed in the practice of the present invention. However, in the practice of the present invention which includes a chemical binding step, complete removal of hydrogen sulfide is not necessary because the olefins and diolefins will be selectively removed from the hydrogen sulfide in the selective chemical binding system and because traces of hydrogen sulfide are not known to adversely affect the metal complex used in the selective chemical binding process.
The washed and compressed gas is then dried, such as over a water-absorbing molecular sieve to a dew paint of from about -150°F
(about -100°C) to about -200°F (about -128°C) to produce a dried stream.
The dried process stream may then be passed directly to the selective chemical binding system of the present invention.
In a preferred embodiment of the invention, the dried process stream may then be purified to remove some higher hydrocarbons prior to introduction in the selective chemical binding unit.
M:\Trevor\TTSpec\9254can.doc More preferably, the dried process stream may be debutanized to recover C5+ and heavier components from the stream prior to removal of olefins and diolefins. This process is well known to those skilled in the art.
The bottoms from the debutanizer comprises substantially all of the C5+
hydrocarbons and may be separated into its component parts for pentene recovery, and recycling of paraffins to the steam cracker, as desired. The overhead from the debutanizer comprises substantially all of the C4 and lighter hydrocarbons and is then passed to the selective chemical binding system of the present invention.
In the selective chemical binding section the olefin-containing vapour stream is contacted with a metal-containing complex to separate the olefins and diolefins from the bulk of the stream. Through such contacting, the olefins and diolefins are chemically reacted with the metal complex and are selectively separated (removed) from the paraffinic components (typically C~_1o paraffins which are straight chained or branched and are unsubstituted or substituted by one or more C,_4 alkyl radicals including methane, ethane, propane and butane). The scrubbed gases, mainly paraffins, hydrogen, acetylenes, and carbon monoxide, are removed from the top of the binding reactor. The olefins and diolefins bound with the metal complex are then recovered through a reversal of the binding chemical reaction to generate a stream containing essentially olefins and diolefins.
This contacting system may be chosen from any of several methods well known in the art, including but not limited to liquid absorption (e.g. passing through a liquid pool or co or counter current adsorption in M:lTrevor\TTSpec\9254can.doc 1 Q
for example a tower), solid-phase adsorption passing through a fixed adsorption bed), and contacting through polymeric membranes.
(e.g. membranes which may be doped with the reversible chemical binding agent).
Olefin andlor diolefin recovery (and regeneration of the reversible chemical binding agent) may be effected by a physical method, such as reduction in temperature or pressure of the stream, or by an electrochemical method whereby the oxidation state of the metal complex is changed to release the bound olefins or diolefins.
The metal complex used may be selected from any number of compounds that possess the following properties:
1 ) the metal complex reacts with olefins and diolefins to bind the olefin or diolefin in a single molecule;
2) the binding of olefin or diolefin to the metal complex can be readily reversed by one or more of a) a reduction in pressure, b) increase in temperature, andlor c) a change in the oxidation state of the metal-complex; and
3) the metal complex does not react with paraffins, hydrogen, carbon monoxide, or acetylenic compounds not containing a carbon-carbon double bond.
Examples of this type of metal complex include but are not limited to the metal dithiolene complexes discussed by Wang and Steifel (U.S.
Patent No. 6,120,692).
Dithiolene is a commonly used name for 1,2-enedithiolate or benzene-1,2-dithiolate and related dithiolates.
M:lTrevorlTTSpec19254can.doc 1 1 The transition metal dithiolene complexes which may be useful in accordance with the present invention rnay be selected from the group of complexes of the formulae:
MLS2 ~2 (R1 R2)~2 Rl S
M\
L - z and M~S2 ~6 (R3 R4 R6 R7~~2 \s Rs The preparation of complexes of the formulae (i) and (ii) is disclosed in United States Patent 6,120,692 referred to above.
In the formulae M is a transition metal, preferably a Group VIII
metal, R' and R2 may be the same or different, and are independently selected from a hydrogen atom, electron-withdrawing groups including those that are or contain heterocyclic, cyano, carboxylate, carboxylic ester, keto, nitro, and sulfonyl groups, and hydrocarbyl groups, including C~_6, preferably C~_4 alkyl groups, C5_$, preferably C6_$ cyclo alkyl groups, C2_$, M:\TrevorlTTSpec\9254can.doc 12 preferably C2_4 alkenyl groups and C6_$ aryl groups, unsubstituted or fully or partly substituted, preferably those substituted with electron-withdrawing groups. Preferably the groups are cyano groups or halo substituted C~~. alkyl groups, more preferably the halo substituents on the carbon atoms are fluoro groups. Most preferably R~ and R2 are CF3 or CN.
The benzene dithiolato compounds, represented by the structure in the formula (ii) above. In the formula (ii), M also is a transition metal, preferably a Group VIII metal, R3, R4, R5, and R6 may be the same or different and are independently selected from the group consisting of a hydrogen atom; electron-withdrawing groups as described above, and hydrocarbyl groups, including C~_~, preferably C~_4 alkyl groups, C5_$, preferably C6_$ cyclo alkyl groups, C2_$, preferably C2_4 alkenyl groups and C6_$ aryl groups, unsubstituted or fully or partly substituted, preferably those substituted at the carbon atoms of the hydrocarbyl group that are electron-withdrawing groups such as a halide atom, preferably a fluorine atom.
Mueller-Westerhoff, U. T., "Dithiolene and Related Species", Comprehensive Coordination Chemistry, Vol. 2, 595-631 (1987);
McCleverty, J. A., "Metal 1,2-Dithiolene and Related Complexes", Prog.
Inorg. Chem., Vol. 10, 49-221 (1968)) disclose more complex forms of the dithiolenes that also may be used.
The transition metals are preferably Fe, Co, Ni, Cu, Pd and Pt, preferably Ni. Thus the complex can be any metal bis(1,2-enedithiolate), preferably a group VIII metal bis(1,2-enedithiolate), more preferably M:\TrevorlTTSpec19254can.doc 13 substituted 1,2-enedithiolate with electron withdrawing groups, and most preferably the bis[1,2-bis(trifluoromethyl)ethylene-1,2-dithiolato] metal complex.including but not limited to bis-cis(1,2-perfluoromethylethylene-1,2-dithiolato)nickel and bis-cis(1,2-cyanoethylene-1,2-dithiolato)nickel.
The recovered olefins and diolefins from the selective chemical binding unit may then be further purified in a deethylenizer tower to separate the ethylene from the C3 and higher olefins and diolefins. This stream may require compression to a pressure ranging from about 250 psig to about 300 psig, preferably about 300 psig, if a reduction in pressure was used to reverse the selective chemical binding with the metal complex. Any means of compression known to those skilled in the art may be employed. It is further understood that this stream may require a solvent removal step if the bound metal complex was dissolved in a volatile solvent. If a temperature change is required the temperature differential between the complexed and free reversible chemical bonding agent (complex) should be at least about 25°C, preferably at least about 30°C, most preferably at least about 50°C.
The mixed separated olefins would be fed to a deethylenizer tower that operates at a pressure ranging from about 250 psig to about 300 psig, generally about 275 psig. Typically, Bow level propylene refrigeration is sufficient for feed chilling and to condense the overheads in the deethylenizer. High purity ethylene is taken at or near the top of the deethylenizer. A mixed olefins and diolefins stream is removed from the bottom of the deethylenizer.
M:\TrevorlTTSpec19254can.doc 14 Conventionally, the recovery of high-purity ethylene by distillation is a very expensive proposition due to the difficulty of separating low- and close-boiling compounds via distillation. In the demethanizer, methane is separated from C2 and heavier components.. In the deethanizer, ethane, ethylene, and acetylene are separated from C3 and heavier components.
In the C2 splitter, ethylene is separated from ethane. A large number of trays and high reflux ratios are required for these separations, particularly for the separation of ethylene from ethane, vvhere about 100-250 trays are required. Additionally, large quantities of energy in the form of steam, hat water, refrigeration and cooling water are required for the operation of these towers. Further, the capital required for these towers as well as the required complex ethylene, propylene, and turbo-expanded hydrogen and methane refrigeration systems is extremely high.
However, the present invention employing the selective chemical binding system, enables the separation of olefins and diolefins from paraffins, acetylenes, hydrogen, and carbon monoxide without resorting to distillation or cryogenic liquefaction. Thus, the olefins and diolefins are first separated from the other cracked gas components in a chemical binding process. The olefins are then relatively easily separated from each other using conventional distillation due to their relatively wide boiling point differences. Further, the level of refrigeration required within the condensers of these distillation towers are significantly lower due to the absence of difficult to condense components such as hydrogen, methane, and carbon monoxide. Thus, low reflux ratios, small number of trays, and M:lTrevorlTTSpec19254can.doc 15 minimal and low-level refrigeration are sufficient to produce high-purity ethylene and higher olefin products.
M:\TrevorlTTSpec\9254can.doc 16
Examples of this type of metal complex include but are not limited to the metal dithiolene complexes discussed by Wang and Steifel (U.S.
Patent No. 6,120,692).
Dithiolene is a commonly used name for 1,2-enedithiolate or benzene-1,2-dithiolate and related dithiolates.
M:lTrevorlTTSpec19254can.doc 1 1 The transition metal dithiolene complexes which may be useful in accordance with the present invention rnay be selected from the group of complexes of the formulae:
MLS2 ~2 (R1 R2)~2 Rl S
M\
L - z and M~S2 ~6 (R3 R4 R6 R7~~2 \s Rs The preparation of complexes of the formulae (i) and (ii) is disclosed in United States Patent 6,120,692 referred to above.
In the formulae M is a transition metal, preferably a Group VIII
metal, R' and R2 may be the same or different, and are independently selected from a hydrogen atom, electron-withdrawing groups including those that are or contain heterocyclic, cyano, carboxylate, carboxylic ester, keto, nitro, and sulfonyl groups, and hydrocarbyl groups, including C~_6, preferably C~_4 alkyl groups, C5_$, preferably C6_$ cyclo alkyl groups, C2_$, M:\TrevorlTTSpec\9254can.doc 12 preferably C2_4 alkenyl groups and C6_$ aryl groups, unsubstituted or fully or partly substituted, preferably those substituted with electron-withdrawing groups. Preferably the groups are cyano groups or halo substituted C~~. alkyl groups, more preferably the halo substituents on the carbon atoms are fluoro groups. Most preferably R~ and R2 are CF3 or CN.
The benzene dithiolato compounds, represented by the structure in the formula (ii) above. In the formula (ii), M also is a transition metal, preferably a Group VIII metal, R3, R4, R5, and R6 may be the same or different and are independently selected from the group consisting of a hydrogen atom; electron-withdrawing groups as described above, and hydrocarbyl groups, including C~_~, preferably C~_4 alkyl groups, C5_$, preferably C6_$ cyclo alkyl groups, C2_$, preferably C2_4 alkenyl groups and C6_$ aryl groups, unsubstituted or fully or partly substituted, preferably those substituted at the carbon atoms of the hydrocarbyl group that are electron-withdrawing groups such as a halide atom, preferably a fluorine atom.
Mueller-Westerhoff, U. T., "Dithiolene and Related Species", Comprehensive Coordination Chemistry, Vol. 2, 595-631 (1987);
McCleverty, J. A., "Metal 1,2-Dithiolene and Related Complexes", Prog.
Inorg. Chem., Vol. 10, 49-221 (1968)) disclose more complex forms of the dithiolenes that also may be used.
The transition metals are preferably Fe, Co, Ni, Cu, Pd and Pt, preferably Ni. Thus the complex can be any metal bis(1,2-enedithiolate), preferably a group VIII metal bis(1,2-enedithiolate), more preferably M:\TrevorlTTSpec19254can.doc 13 substituted 1,2-enedithiolate with electron withdrawing groups, and most preferably the bis[1,2-bis(trifluoromethyl)ethylene-1,2-dithiolato] metal complex.including but not limited to bis-cis(1,2-perfluoromethylethylene-1,2-dithiolato)nickel and bis-cis(1,2-cyanoethylene-1,2-dithiolato)nickel.
The recovered olefins and diolefins from the selective chemical binding unit may then be further purified in a deethylenizer tower to separate the ethylene from the C3 and higher olefins and diolefins. This stream may require compression to a pressure ranging from about 250 psig to about 300 psig, preferably about 300 psig, if a reduction in pressure was used to reverse the selective chemical binding with the metal complex. Any means of compression known to those skilled in the art may be employed. It is further understood that this stream may require a solvent removal step if the bound metal complex was dissolved in a volatile solvent. If a temperature change is required the temperature differential between the complexed and free reversible chemical bonding agent (complex) should be at least about 25°C, preferably at least about 30°C, most preferably at least about 50°C.
The mixed separated olefins would be fed to a deethylenizer tower that operates at a pressure ranging from about 250 psig to about 300 psig, generally about 275 psig. Typically, Bow level propylene refrigeration is sufficient for feed chilling and to condense the overheads in the deethylenizer. High purity ethylene is taken at or near the top of the deethylenizer. A mixed olefins and diolefins stream is removed from the bottom of the deethylenizer.
M:\TrevorlTTSpec19254can.doc 14 Conventionally, the recovery of high-purity ethylene by distillation is a very expensive proposition due to the difficulty of separating low- and close-boiling compounds via distillation. In the demethanizer, methane is separated from C2 and heavier components.. In the deethanizer, ethane, ethylene, and acetylene are separated from C3 and heavier components.
In the C2 splitter, ethylene is separated from ethane. A large number of trays and high reflux ratios are required for these separations, particularly for the separation of ethylene from ethane, vvhere about 100-250 trays are required. Additionally, large quantities of energy in the form of steam, hat water, refrigeration and cooling water are required for the operation of these towers. Further, the capital required for these towers as well as the required complex ethylene, propylene, and turbo-expanded hydrogen and methane refrigeration systems is extremely high.
However, the present invention employing the selective chemical binding system, enables the separation of olefins and diolefins from paraffins, acetylenes, hydrogen, and carbon monoxide without resorting to distillation or cryogenic liquefaction. Thus, the olefins and diolefins are first separated from the other cracked gas components in a chemical binding process. The olefins are then relatively easily separated from each other using conventional distillation due to their relatively wide boiling point differences. Further, the level of refrigeration required within the condensers of these distillation towers are significantly lower due to the absence of difficult to condense components such as hydrogen, methane, and carbon monoxide. Thus, low reflux ratios, small number of trays, and M:lTrevorlTTSpec19254can.doc 15 minimal and low-level refrigeration are sufficient to produce high-purity ethylene and higher olefin products.
M:\TrevorlTTSpec\9254can.doc 16
Claims (12)
1. A process for the separation of C2-6 olefins and C4-6 diolefins from a mixed gas stream also containing one or more members selected from the group consisting of paraffins, acetylenes, hydrogen, and carbon monoxide comprising:
(i) compressing said mixed gas stream to a pressure from 100 to 450 psig;
(ii) caustic washing said compressed mixed gas stream to remove acidic gases including hydrogen sulphide to a level of less than 5,000 ppm;
(iii) drying said washed compressed mixed gas stream to a dew point of from -100°C to -130°C;
(iv) contacting said dried washed compressed mixed gas stream with reversible chemical binding agent which preferentially complexes one or more olefins, diolefins or both to form complexed olefins diolefins or both;
(v) separating said dried washed compressed mixed gas stream from said stream of complexed olefins, diolefins or both; and (vi) treating said complexed olefins, diolefins or both to release said olefins, diolefins or both and regenerate said reversible chemical binding agent.
(i) compressing said mixed gas stream to a pressure from 100 to 450 psig;
(ii) caustic washing said compressed mixed gas stream to remove acidic gases including hydrogen sulphide to a level of less than 5,000 ppm;
(iii) drying said washed compressed mixed gas stream to a dew point of from -100°C to -130°C;
(iv) contacting said dried washed compressed mixed gas stream with reversible chemical binding agent which preferentially complexes one or more olefins, diolefins or both to form complexed olefins diolefins or both;
(v) separating said dried washed compressed mixed gas stream from said stream of complexed olefins, diolefins or both; and (vi) treating said complexed olefins, diolefins or both to release said olefins, diolefins or both and regenerate said reversible chemical binding agent.
2. The process according to claim 1, wherein said mixed gas stream is a stream of cracked gas.
3. The process according to claim 2, wherein said cracked gas comprises a mixture of butane, butenes, propane, propylene, ethane, ethylene, acetylene, methyl acetylene, propadiene, butadienes, methane, hydrogen, and carbon monoxide.
4. The process according to claim 3, wherein the cracked gas is compressed to a pressure from 200 to 400 prig.
5. The process according to claim 4, wherein the acidic gases including hydrogen sulphide in the cracked gas is reduced to a level of less than 100 ppm.
6. The process according to claim 5, wherein the dried washed compressed cracked gas stream is debutanized to recover the C5+
components from the stream prior to contact with the reversible chemical binding agent.
components from the stream prior to contact with the reversible chemical binding agent.
7. The process according to claim 6, wherein the dried washed compressed cracked gas stream is contacted with said reversable chemical binding agent using a process selected from the group consisting of liquid absorption, solid-phase adsorption, and permeation through polymeric membranes doped with said chemical binding agent.
8. The process according to claim 7, wherein olefin and/or diolefin recovery and regeneration of the reversible chemical binding agent is effected by a method selected from the group consisting of reduction in temperature or pressure, an electrochemical method alteration of oxidation state of the metal complex, and a mixture thereof.
9. The process according to claim 8, wherein the reversible chemical binding agent has the following properties:
(i) the reversible chemical binding agent reacts with olefins and diolefins to form a single molecule;
(ii) the bond between the reversible chemical binding agent and the olefin or diolefin can be readily reversed by one or more of a) a reduction in pressure, b) increase in temperature, and/or c) a change in the oxidation state of the metal-complex; and (iii) the reversible chemical binding agent does not react with paraffins, hydrogen, carbon monoxide, or acetylenic compounds not containing a carbon-carbon double bond.
(i) the reversible chemical binding agent reacts with olefins and diolefins to form a single molecule;
(ii) the bond between the reversible chemical binding agent and the olefin or diolefin can be readily reversed by one or more of a) a reduction in pressure, b) increase in temperature, and/or c) a change in the oxidation state of the metal-complex; and (iii) the reversible chemical binding agent does not react with paraffins, hydrogen, carbon monoxide, or acetylenic compounds not containing a carbon-carbon double bond.
10. The process according to claim 9, wherein said olefins are selected from the group consisting of ethylene and propylene and said diolefins are selected from the group consisting of butadiene and isoprene.
11. The process according to claim 9, wherein the reversible chemical binding agent is a metal dithiolene selected from the group of complexes of the formulae:
(i) M[S2 C2(R1 R2)]2;
(IMG) and (ii) M[S2 C6(R3 R4 R6 R7)]2.
(IMG) wherein M is selected from the group consisting of Fe, Co, Ni, Cu, Pd and Pt; and R1, R2, R3, R4, R5, and R6 are independently selected from the group consisting of a hydrogen atom, electron-withdrawing groups including those that are or contain heterocyclic, cyano, carboxylate, carboxylic ester, keto, nitro, and sulfonyl groups, hydrocarbyl radicals selected from the group consisting of C1-6, alkyl groups, C5-8, alkyl groups, C2-8, alkenyl groups and C6-8 aryl groups which hydrocarbyl radicals are unsubstituted or fully or partly substituted, preferably those substituted by halogen atoms.
(i) M[S2 C2(R1 R2)]2;
(IMG) and (ii) M[S2 C6(R3 R4 R6 R7)]2.
(IMG) wherein M is selected from the group consisting of Fe, Co, Ni, Cu, Pd and Pt; and R1, R2, R3, R4, R5, and R6 are independently selected from the group consisting of a hydrogen atom, electron-withdrawing groups including those that are or contain heterocyclic, cyano, carboxylate, carboxylic ester, keto, nitro, and sulfonyl groups, hydrocarbyl radicals selected from the group consisting of C1-6, alkyl groups, C5-8, alkyl groups, C2-8, alkenyl groups and C6-8 aryl groups which hydrocarbyl radicals are unsubstituted or fully or partly substituted, preferably those substituted by halogen atoms.
12. The process according to claim 11, wherein the reversible chemical binding agent is selected from the group consisting of bis-cis(1,2-perfluoromethylethylene-1,2-dithiolato)nickel and bis-cis(1,2-cyanoethylene-1,2-dithiolato)nickel.
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| CA 2415064 CA2415064A1 (en) | 2002-12-23 | 2002-12-23 | Selective chemical binding for olefins/paraffins separation |
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| CA 2415064 CA2415064A1 (en) | 2002-12-23 | 2002-12-23 | Selective chemical binding for olefins/paraffins separation |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016059518A1 (en) | 2014-10-15 | 2016-04-21 | Nova Chemicals (International) S.A. | High conversion and selectivity odh process |
| WO2017079004A1 (en) * | 2015-11-06 | 2017-05-11 | Uop Llc | Reactor effluent wash to remove aromatics |
| CN111185079A (en) * | 2019-12-04 | 2020-05-22 | 大连百傲化学股份有限公司 | Resourceful treatment method for acid gas in incineration flue gas |
-
2002
- 2002-12-23 CA CA 2415064 patent/CA2415064A1/en not_active Abandoned
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016059518A1 (en) | 2014-10-15 | 2016-04-21 | Nova Chemicals (International) S.A. | High conversion and selectivity odh process |
| US10626066B2 (en) | 2014-10-15 | 2020-04-21 | Nova Chemicals (International) S.A. | High conversion and selectivity ODH process |
| WO2017079004A1 (en) * | 2015-11-06 | 2017-05-11 | Uop Llc | Reactor effluent wash to remove aromatics |
| CN108349837A (en) * | 2015-11-06 | 2018-07-31 | 环球油品公司 | Reactor effluent is washed to remove aromatic compounds |
| US10272359B2 (en) | 2015-11-06 | 2019-04-30 | Uop Llc | Reactor effluent wash to remove aromatics |
| CN108349837B (en) * | 2015-11-06 | 2021-06-11 | 环球油品公司 | Reactor effluent scrubbing to remove aromatics |
| CN111185079A (en) * | 2019-12-04 | 2020-05-22 | 大连百傲化学股份有限公司 | Resourceful treatment method for acid gas in incineration flue gas |
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