A process and apparatus are disclosed for hydrocracking hydrocarbon feed in a hydrocracking unit and hydrotreating a diesel product from the hydrocracking unit in a hydrotreating unit. The hydrocracking unit and the hydrotreating unit share the same recycle gas compressor. A make-up hydrogen stream may also be compressed in the recycle gas compressor. A warm separator separates recycle gas and hydrocarbons from diesel in the hydrotreating effluent, so fraction of the diesel is relatively simple. The warm separator also keeps the diesel product separate from the more sulfurous diesel in the hydrocracking effluent, and still retains heat needed for fractionation of lighter components from the low sulfur diesel product.

A process and apparatus are disclosed for hydrocracking hydrocarbon feed in a hydrocracking unit and hydrotreating a diesel product from the hydrocracking unit in a hydrotreating unit. The hydrocracking unit and the hydrotreating unit share the same recycle gas compressor. A make-up hydrogen stream may also be compressed in the recycle gas compressor. A warm separator separates recycle gas and hydrocarbons from diesel in the hydrotreating effluent, so fraction of the diesel is relatively simple. The warm separator also keeps the diesel product separate from the more sulfurous diesel in the hydrocracking effluent, and still retains heat needed for fractionation of lighter components from the low sulfur diesel product.

Processes for the hydrogenolysis of butane are described. A process can include (a) introducing a butane feed and hydrogen to a first hydrogenolysis reactor comprising a hydrogenolysis catalyst, and (b) contacting the butane feed and hydrogen with the hydrogenolysis catalyst at conditions sufficient to produce a first hydrogenolysis product stream. The introduction of the butane feed stream and hydrogen to the first hydrogenolysis reactor can be controlled to maintain a hydrogen to butane molar ratio in the reactor inlet of 0.3:1 to 0.8:1.

Processes for the hydrogenolysis of butane are described. A process can include (a) introducing a butane feed and hydrogen to a first hydrogenolysis reactor comprising a hydrogenolysis catalyst, and (b) contacting the butane feed and hydrogen with the hydrogenolysis catalyst at conditions sufficient to produce a first hydrogenolysis product stream. The introduction of the butane feed stream and hydrogen to the first hydrogenolysis reactor can be controlled to maintain a hydrogen to butane molar ratio in the reactor inlet of 0.3:1 to 0.8:1.

Processes for the hydrogenolysis of butane are described. A process can include (a) introducing a butane feed and hydrogen to a first hydrogenolysis reactor comprising a hydrogenolysis catalyst, and (b) contacting the butane feed and hydrogen with the hydrogenolysis catalyst at conditions sufficient to produce a first hydrogenolysis product stream. The introduction of the butane feed stream and hydrogen to the first hydrogenolysis reactor can be controlled to maintain a hydrogen to butane molar ratio in the reactor inlet of 0.3:1 to 0.8:1.

The invention relates to a p-xylene separation process wherein at least a portion of ethylbenzene present in an aromatics-containing feed is removed prior to isomerization. Aspects of the invention provide a process for producing p-xylene. The process includes providing a first mixture comprising ≧5.0 wt. % of aromatic C.sub.8 isomers, the C.sub.8 isomers comprising p-xylene and ethylbenzene. A p-xylene-containing portion and an ethylbenzene-containing portion are separated from the first mixture in a first separation stage to form a p-xylene-depleted raffinate. The first separation stage can include at least one simulated moving-bed adsorptive separation stage. At least a portion the p-xylene-depleted raffinate in the liquid phase is reacted to produce a reactor effluent comprising aromatic C.sub.8 isomers. The first mixture can be combined with ≧50.0 wt. % of the reactor effluent's aromatic C.sub.8 isomers. The combining can be carried out before and/or during the separating of the p-xylene and ethylbenzene portions.

Systems and methods for producing 1,3-butadiene from a C.sub.4 hydrocarbon mixture are disclosed. The C.sub.4 hydrocarbon mixture comprising 1,3-butadiene, C.sub.4 acetylenes, and other C.sub.4 hydrocarbons is processed in an extractive distillation column to produce a crude 1,3-butadiene stream that comprises 1,3-butadiene, and C.sub.4 acetylenes including vinyl acetylene and ethyl acetylene. The crude 1,3-butadiene stream is subsequently distilled in the first distillation column, and the bottom stream of the first distillation column is further distilled in a second distillation column to produce an overhead stream comprising primarily 1,3-butadiene. A side stream comprising primarily C.sub.4 acetylenes is withdrawn from the second distillation column and processed in a selective hydrogenation unit to produce additional 1,3-butadiene.

Systems and methods for producing 1,3-butadiene from a C.sub.4 hydrocarbon mixture are disclosed. The C.sub.4 hydrocarbon mixture comprising 1,3-butadiene, C.sub.4 acetylenes, and other C.sub.4 hydrocarbons is processed in an extractive distillation column to produce a crude 1,3-butadiene stream that comprises 1,3-butadiene, and C.sub.4 acetylenes including vinyl acetylene and ethyl acetylene. The crude 1,3-butadiene stream is subsequently distilled in the first distillation column, and the bottom stream of the first distillation column is further distilled in a second distillation column to produce an overhead stream comprising primarily 1,3-butadiene. A side stream comprising primarily C.sub.4 acetylenes is withdrawn from the second distillation column and processed in a selective hydrogenation unit to produce additional 1,3-butadiene.

A method for producing para-xylene (PX) includes introducing a C.sub.8 aromatic-containing composition to a xylene rerun column to separate the C.sub.8 aromatic-containing composition into a xylene-containing effluent and a heavy effluent and passing the xylene-containing effluent to a PX processing loop that includes a PX recovery unit operable to separate a PX product from the xylene-containing effluent, a membrane isomerization unit operable to convert a portion of the MX, OX, or both from the xylene-containing effluent to PX, an EB dealkylation unit operable to dealkylate EB from the xylene-containing effluent to produce benzene, toluene, and other C.sub.7− compounds, and a membrane separation unit operable to produce a permeate that is PX-rich and a retentate that is PX-lean. The permeate is passed to the PX recovery unit for recovery of PX, which the retentate is bypassed around the PX recovery unit circulated through the xylene processing loop.

A method for producing para-xylene (PX) includes introducing a C.sub.8 aromatic-containing composition to a xylene rerun column to separate the C.sub.8 aromatic-containing composition into a xylene-containing effluent and a heavy effluent and passing the xylene-containing effluent to a PX processing loop that includes a PX recovery unit operable to separate a PX product from the xylene-containing effluent, a membrane isomerization unit operable to convert a portion of the MX, OX, or both from the xylene-containing effluent to PX, an EB dealkylation unit operable to dealkylate EB from the xylene-containing effluent to produce benzene, toluene, and other C.sub.7− compounds, and a membrane separation unit operable to produce a permeate that is PX-rich and a retentate that is PX-lean. The permeate is passed to the PX recovery unit for recovery of PX, which the retentate is bypassed around the PX recovery unit circulated through the xylene processing loop.