A method for preparing ethylene including: feeding a thermally cracked compressed stream to a first distillation apparatus selectively operating as a first deethanizer or a depropanizer; and feeding an overhead discharge stream of the first distillation apparatus to a second distillation apparatus. When the first distillation apparatus is operated as the first deethanizer, a bottom discharge stream of the second distillation apparatus is fed to a C2 separator. When the first distillation apparatus is operated as the depropanizer, the bottom discharge stream of the second distillation apparatus is passed through a third distillation apparatus and fed to the C2 separator.

A method for preparing ethylene including: feeding a thermally cracked compressed stream to a first distillation apparatus selectively operating as a first deethanizer or a depropanizer; and feeding an overhead discharge stream of the first distillation apparatus to a second distillation apparatus. When the first distillation apparatus is operated as the first deethanizer, a bottom discharge stream of the second distillation apparatus is fed to a C2 separator. When the first distillation apparatus is operated as the depropanizer, the bottom discharge stream of the second distillation apparatus is passed through a third distillation apparatus and fed to the C2 separator.

A process increases the concentration of non normal paraffins in a feed stream comprising separating a naphtha feed stream into a normal paraffin rich stream and a non-normal paraffin rich stream. The non-normal paraffin rich stream is isomerized over an isomerization catalyst to convert non-normal paraffins to normal paraffins, hydrocrack C5+ hydrocarbon to C2-C4 paraffins and produce an isomerization effluent stream. The isomerization effluent stream is separated into a C3− off gas, C4 rich stream and C5+ stream that is recycled to the naphtha feed stream. A depentanizer column may be positioned to either remove C6+ from the naphtha feed stream or from a bottoms stream from a stabilizer column. The amount of C2-C4 paraffins that are provided is increased from about 55% to as much as 77% and even more with further modifications including operating at higher temperatures or increasing the volume of catalyst.

An object of the present invention is to provide a gas refining apparatus which can produce a product gas with high purity and high yield at low cost and can produce a plurality of types of gas as a product gas without changing an adsorbent, and the present invention provides a gas refining apparatus (10) including a first derivation line (L3) connected to the second adsorption towers (2a, 2b) and through which the first gas flows, a second derivation line (L4) connected to the second adsorption towers (2a and 2b) and through which the second gas flows, a regeneration line (L5) connected to the first adsorption towers (1a, 1b), through which a regeneration gas for regenerating a first adsorbent in the first adsorption towers (1a, 1b) flows, and a pump (P) provided in the second derivation line (L4) and configured to desorb the second gas from a second adsorbent in the second adsorption towers (2a and 2b), and the regeneration line (L5) is connected to each of the first derivation line (L3) and the second derivation line (L4).

An object of the present invention is to provide a gas refining apparatus which can produce a product gas with high purity and high yield at low cost and can produce a plurality of types of gas as a product gas without changing an adsorbent, and the present invention provides a gas refining apparatus (10) including a first derivation line (L3) connected to the second adsorption towers (2a, 2b) and through which the first gas flows, a second derivation line (L4) connected to the second adsorption towers (2a and 2b) and through which the second gas flows, a regeneration line (L5) connected to the first adsorption towers (1a, 1b), through which a regeneration gas for regenerating a first adsorbent in the first adsorption towers (1a, 1b) flows, and a pump (P) provided in the second derivation line (L4) and configured to desorb the second gas from a second adsorbent in the second adsorption towers (2a and 2b), and the regeneration line (L5) is connected to each of the first derivation line (L3) and the second derivation line (L4).

An apparatus and process for separating a gas mixture is disclosed. The apparatus includes a first membrane stage, a second membrane stage, and a third membrane stage. The first membrane stage includes a first gas separation membrane configured to separate the gas mixture into a first retentate stream and a first permeate stream. The second membrane stage includes a second gas separation membrane configured to separate the first permeate stream into a second retentate stream and a second permeate stream. The second retentate stream of the second membrane stage is recycled back to connect with the first retentate stream to form a mixed fluid stream. The third membrane stage includes a third gas separation membrane configured to separate the mixed fluid stream into a third retentate stream and a third permeate stream, and the third retentate stream is configured to be withdrawn as a product or discarded.

An apparatus and process for separating a gas mixture is disclosed. The apparatus includes a first membrane stage, a second membrane stage, and a third membrane stage. The first membrane stage includes a first gas separation membrane configured to separate the gas mixture into a first retentate stream and a first permeate stream. The second membrane stage includes a second gas separation membrane configured to separate the first permeate stream into a second retentate stream and a second permeate stream. The second retentate stream of the second membrane stage is recycled back to connect with the first retentate stream to form a mixed fluid stream. The third membrane stage includes a third gas separation membrane configured to separate the mixed fluid stream into a third retentate stream and a third permeate stream, and the third retentate stream is configured to be withdrawn as a product or discarded.

A method for separating classes of hydrocarbon compounds from a feed stream including a hydrocarbon mixture is disclosed. The method includes the steps of passing a feed stream through a plurality of separation units arranged in a series in any order, wherein each separation unit has an adsorbent material; and separating classes of hydrocarbon compounds from the feed stream. When one of the plurality of separation units comprises an adsorbent material that is a metal organic framework selected from a zirconium, hafnium, cerium, or titanium-based metal organic framework, then another plurality of separation units includes an adsorption material that is different from the metal organic framework. The method is conducted in a liquid phase. The method can also use a single separation unit with a continuous cyclic bed apparatus. The method can be combined with refining and downstream processes.

A system and a method for separating C.sub.4 and recovering 1,3-butadiene are disclosed. The system includes a main washer column, a rectifier column for separating a bottom stream from the main washer column, an after washer column for purifying 1,3-butadiene from a side stream of the rectifier column comprising acetylenes and butadienes, a degasser column for separating a bottom stream from the rectifier column to produce a lean solvent stream. The lean solvent stream comprises primarily the solvent and about 8.3% water used in the main washer column and after washer column. A reboiler for the rectifier column includes one or more heat exchange units. At least one of the heat exchange units of the reboiler for the rectifier column uses steam as heating medium.

A system and a method for separating C.sub.4 and recovering 1,3-butadiene are disclosed. The system includes a main washer column, a rectifier column for separating a bottom stream from the main washer column, an after washer column for purifying 1,3-butadiene from a side stream of the rectifier column comprising acetylenes and butadienes, a degasser column for separating a bottom stream from the rectifier column to produce a lean solvent stream. The lean solvent stream comprises primarily the solvent and about 8.3% water used in the main washer column and after washer column. A reboiler for the rectifier column includes one or more heat exchange units. At least one of the heat exchange units of the reboiler for the rectifier column uses steam as heating medium.