The invention features methods for producing isoprene from cultured cells wherein the cells in the stationary phase. The invention also provides compositions that include these cultured cells and/or increased amount of isoprene. The invention also provides for systems that include a non-flammable concentration of isoprene in the gas phase. Additionally, the invention provides isoprene compositions, such as compositions with increased amount of isoprene or increased purity.

Methods for the selective hydrogenation of acetylenic compounds in a product stream that includes isoprene. A method of selectively hydrogenating an acetylenic hydrocarbon in the presence of isoprene may include obtaining a hydrocarbon mixture comprising an acetylenic hydrocarbon, isoprene, and butadiene or cyclopentadiene, or both. If cyclopentadiene is present, the hydrocarbon mixture may comprise greater than 2 wt. % cyclopentadiene. The method may further include contacting the hydrocarbon mixture and hydrogen (H.sub.2) with a hydrogenation catalyst under reaction conditions that are more selective to the hydrogenation of the acetylenic hydrocarbon than the isoprene.

Methods for the selective hydrogenation of acetylenic compounds in a product stream that includes isoprene. A method of selectively hydrogenating an acetylenic hydrocarbon in the presence of isoprene may include obtaining a hydrocarbon mixture comprising an acetylenic hydrocarbon, isoprene, and butadiene or cyclopentadiene, or both. If cyclopentadiene is present, the hydrocarbon mixture may comprise greater than 2 wt. % cyclopentadiene. The method may further include contacting the hydrocarbon mixture and hydrogen (H.sub.2) with a hydrogenation catalyst under reaction conditions that are more selective to the hydrogenation of the acetylenic hydrocarbon than the isoprene.

Systems and methods for recovering cyclopentadiene and/or isoprene from a mixture comprising C.sub.5 hydrocarbons are disclosed. A C.sub.5 mixture comprising cyclopentadiene and/or isoprene is flowed into a dimerization unit to form dimers. The dimers are then separated from the unreacted C.sub.5 hydrocarbons. The separated dimers are monomerized to form a stream comprising cyclopentadiene and/or isoprene, which is subsequently separated to form a first product stream comprising primarily isoprene and a second product stream comprising primarily cyclopentadiene.

Systems and methods for recovering cyclopentadiene and/or isoprene from a mixture comprising C.sub.5 hydrocarbons are disclosed. A C.sub.5 mixture comprising cyclopentadiene and/or isoprene is flowed into a dimerization unit to form dimers. The dimers are then separated from the unreacted C.sub.5 hydrocarbons. The separated dimers are monomerized to form a stream comprising cyclopentadiene and/or isoprene, which is subsequently separated to form a first product stream comprising primarily isoprene and a second product stream comprising primarily cyclopentadiene.

A method for producing a conjugated diene, including a step A of allowing an α-olefin and formaldehyde to react with each other to produce a γ,δ-unsaturated alcohol in the presence of an alcohol; and a step B of subjecting the γ,δ-unsaturated alcohol to a dehydration reaction at 135 to 210° C. in the presence of an aqueous solution of an acidic catalyst.

A method for producing a conjugated diene, including a step A of allowing an α-olefin and formaldehyde to react with each other to produce a γ,δ-unsaturated alcohol in the presence of an alcohol; and a step B of subjecting the γ,δ-unsaturated alcohol to a dehydration reaction at 135 to 210° C. in the presence of an aqueous solution of an acidic catalyst.

A hydrocarbon production method for producing hydrocarbons from a hydrocarbon mixture includes: a first extractive distillation step of performing extractive distillation of an extractive distillation target to obtain a fraction (A) in which isoprene and piperylene are enriched and a fraction (B) in which a linear hydrocarbon and a branched hydrocarbon are enriched; a first distillation step of obtaining a fraction (C) in which isoprene is enriched and a fraction (D) in which piperylene is enriched from the fraction (A); a dehydrogenation step of performing dehydrogenation or oxidative dehydrogenation of either or both of the linear hydrocarbon and the branched hydrocarbon contained in the fraction (B) to obtain a dehydrogenated product; and a recovery step of supplying the dehydrogenated product to an extractive distillation column or a distillation column and obtaining isoprene and/or piperylene from the dehydrogenated product.

A hydrocarbon production method for producing hydrocarbons from a hydrocarbon mixture includes: a first extractive distillation step of performing extractive distillation of an extractive distillation target to obtain a fraction (A) in which isoprene and piperylene are enriched and a fraction (B) in which a linear hydrocarbon and a branched hydrocarbon are enriched; a first distillation step of obtaining a fraction (C) in which isoprene is enriched and a fraction (D) in which piperylene is enriched from the fraction (A); a dehydrogenation step of performing dehydrogenation or oxidative dehydrogenation of either or both of the linear hydrocarbon and the branched hydrocarbon contained in the fraction (B) to obtain a dehydrogenated product; and a recovery step of supplying the dehydrogenated product to an extractive distillation column or a distillation column and obtaining isoprene and/or piperylene from the dehydrogenated product.

A zeolite membrane composite includes a porous support and a zeolite membrane formed on at least one surface of the porous support. The zeolite membrane of the zeolite membrane composite is formed of an X-MOR-type zeolite, where X includes at least one type of transition metal ion.