Systems and processes herein improve the conversion of propylene to ethylene via metathesis. On a mass basis, embodiments herein may be used to convert greater than 40% propylene, on a mass basis, to ethylene, such as 43% to 75%, on a mass basis. In one aspect, processes for the conversion of propylene to ethylene herein may include introducing a propylene feed stream to a metathesis reactor, and contacting the propylene with a metathesis catalyst in the metathesis reactor to convert the propylene to ethylene and 2-butene. An effluent from the metathesis reactor may be recovered, the effluent including ethylene, 2-butene, and unconverted propylene. The effluent may then be separated in a fractionation system to recover an ethylene fraction, a propylene fraction, a c4 fraction, and a C5+ fraction. The propylene fraction and the C4 fraction may then be fed to the metathesis reactor to produce additional ethylene.

Systems and processes herein improve the conversion of propylene to ethylene via metathesis. On a mass basis, embodiments herein may be used to convert greater than 40% propylene, on a mass basis, to ethylene, such as 43% to 75%, on a mass basis. In one aspect, processes for the conversion of propylene to ethylene herein may include introducing a propylene feed stream to a metathesis reactor, and contacting the propylene with a metathesis catalyst in the metathesis reactor to convert the propylene to ethylene and 2-butene. An effluent from the metathesis reactor may be recovered, the effluent including ethylene, 2-butene, and unconverted propylene. The effluent may then be separated in a fractionation system to recover an ethylene fraction, a propylene fraction, a c4 fraction, and a C5+ fraction. The propylene fraction and the C4 fraction may then be fed to the metathesis reactor to produce additional ethylene.

Mixed pentenes may be converted to propylene by feeding an alcohol, linear pentenes, and isopentenes to an etherification reactor. The alcohol and isopentenes may be reacted in the etherification reactor to convert isopentenes to tertiary amyl alkyl ether, which may be separated from the linear pentenes, recovered as a linear pentene fraction. The tertiary amyl alkyl ether may be fed to a decomposition reactor to convert at least a portion of the tertiary amyl alkyl ether to alcohol and isopentenes. The alcohol and isopentenes may then be separated to recover an isopentene fraction and an alcohol fraction. The isopentene fraction is then fed to a skeletal isomerization reactor to convert at least a portion of the isopentenes to linear pentenes, the effluent from which may be recycled to the etherification reactor. Ethylene and the linear pentene fraction may then be fed to a metathesis reactor to produce propylene.

Mixed pentenes may be converted to propylene by feeding an alcohol, linear pentenes, and isopentenes to an etherification reactor. The alcohol and isopentenes may be reacted in the etherification reactor to convert isopentenes to tertiary amyl alkyl ether, which may be separated from the linear pentenes, recovered as a linear pentene fraction. The tertiary amyl alkyl ether may be fed to a decomposition reactor to convert at least a portion of the tertiary amyl alkyl ether to alcohol and isopentenes. The alcohol and isopentenes may then be separated to recover an isopentene fraction and an alcohol fraction. The isopentene fraction is then fed to a skeletal isomerization reactor to convert at least a portion of the isopentenes to linear pentenes, the effluent from which may be recycled to the etherification reactor. Ethylene and the linear pentene fraction may then be fed to a metathesis reactor to produce propylene.

A method includes brominating a butanes feed stream including i-butane in a bromination reactor to form a bromination effluent stream including t-butyl bromide. The method includes dehydrobrominating the t-butyl bromide to form isobutylene. Another method includes brominating a mixed pentanes feed stream including i-pentane and n-pentane in a bromination reactor to form a bromination effluent stream including t-pentyl bromide. The method includes dehydrobrominating the t-pentyl bromide to form isoamylene and HBr.

A method includes brominating a butanes feed stream including i-butane in a bromination reactor to form a bromination effluent stream including t-butyl bromide. The method includes dehydrobrominating the t-butyl bromide to form isobutylene. Another method includes brominating a mixed pentanes feed stream including i-pentane and n-pentane in a bromination reactor to form a bromination effluent stream including t-pentyl bromide. The method includes dehydrobrominating the t-pentyl bromide to form isoamylene and HBr.

Embodiments of processes and multiple-stage catalyst systems for producing propylene comprising introducing a hydrocarbon stream comprising 2-butene to an isomerization catalyst zone to isomerize the 2-butene to 1-butene, passing the 2-butene and 1-butene to a metathesis catalyst zone to cross-metathesize the 2-butene and 1-butene into a metathesis product stream comprising propylene and C.sub.4-C.sub.6 olefins, and cracking the metathesis product stream in a catalyst cracking zone to produce propylene. The isomerization catalyst zone comprises a silica-alumina catalyst with a ratio by weight of alumina to silica from 1:99 to 20:80. The metathesis catalyst comprises a mesoporous silica catalyst support impregnated with metal oxide. The catalyst cracking zone comprises a mordenite framework inverted (MFI) structured silica catalyst.

Embodiments of processes and multiple-stage catalyst systems for producing propylene comprising introducing a hydrocarbon stream comprising 2-butene to an isomerization catalyst zone to isomerize the 2-butene to 1-butene, passing the 2-butene and 1-butene to a metathesis catalyst zone to cross-metathesize the 2-butene and 1-butene into a metathesis product stream comprising propylene and C.sub.4-C.sub.6 olefins, and cracking the metathesis product stream in a catalyst cracking zone to produce propylene. The isomerization catalyst zone comprises a silica-alumina catalyst with a ratio by weight of alumina to silica from 1:99 to 20:80. The metathesis catalyst comprises a mesoporous silica catalyst support impregnated with metal oxide. The catalyst cracking zone comprises a mordenite framework inverted (MFI) structured silica catalyst.

Embodiments of methods of synthesizing a metathesis catalyst system, which include impregnating tungsten oxide on silica support in the presence of a precursor to produce a base catalyst; calcining the base catalyst; impregnating a metal oxide co-catalyst comprising a metal oxide onto the surface of the base catalyst to produce a doped catalyst; and calcining the doped catalyst to produce a metathesis catalyst system. Further embodiments of processes for the production of propylene, which include contacting a hydrocarbon feedstock comprising a mixture of 1-butene and 2-butene with embodiments of the metathesis catalyst system to produce, via metathesis conversion, a product stream comprising propylene.

Embodiments of methods of synthesizing a metathesis catalyst system, which include impregnating tungsten oxide on silica support in the presence of a precursor to produce a base catalyst; calcining the base catalyst; impregnating a metal oxide co-catalyst comprising a metal oxide onto the surface of the base catalyst to produce a doped catalyst; and calcining the doped catalyst to produce a metathesis catalyst system. Further embodiments of processes for the production of propylene, which include contacting a hydrocarbon feedstock comprising a mixture of 1-butene and 2-butene with embodiments of the metathesis catalyst system to produce, via metathesis conversion, a product stream comprising propylene.