Systems and processes for producing isomerized alkenes are disclosed. The systems mainly include an isomerization unit, a dehydrogenation unit, and a MTBE synthesis unit. A hydrocarbon stream is fed into the isomerization unit to form iso-alkanes in a sulfur free hydrocarbon stream. The sulfur free hydrocarbon stream is heated and then combined with a sulfur-containing hydrocarbon stream comprising sulfur containing compounds to form a reactant feed stream to the dehydrogenation unit. The iso-alkanes is dehydrogenated to form iso-alkenes. The formed iso-alkenes comprising isobutylene can be used as a feed stock for the MTBE synthesis unit.

A method of producing methanol is disclosed. The method involves adding alkali to crude methanol and distilling the crude methanol in one or more distillation columns. The method also includes flowing a vapor side draw from one of the distillation columns, where the vapor side draw comprises fusel oil substantially free from alkali The fusel oil is recycled to a methanol synthesis reactor and/or a MTBE synthesis reactor.

A method of producing methanol is disclosed. The method involves adding alkali to crude methanol and distilling the crude methanol in one or more distillation columns. The method also includes flowing a vapor side draw from one of the distillation columns, where the vapor side draw comprises fusel oil substantially free from alkali The fusel oil is recycled to a methanol synthesis reactor and/or a MTBE synthesis reactor.

Systems and methods for producing MTBE without using a catalytic distillation column or a super fractionator have been disclosed. An optimum volume of methanol stream required to maximize MTBE production and reduce slippage of isobutylene to minimum acceptable values together with a crude C4 stream are flowed into a primary reaction unit that comprises a first reactor and a second reactor in parallel configured to produce maximum values of final MTBE volumes under higher or equal established purity commercial quality specifications levels. The combined effluent from the first reactor and the second reactor is split to form a first portion, a second portion and a third portion. The first portion is flowed to a third reactor configured to produce additional MTBE. The second portion is combined with an effluent from the third reactor for further separation. The third portion is recycled to the first reactor and/or second reactor.

Systems and methods for producing MTBE without using a catalytic distillation column or a super fractionator have been disclosed. An optimum volume of methanol stream required to maximize MTBE production and reduce slippage of isobutylene to minimum acceptable values together with a crude C4 stream are flowed into a primary reaction unit that comprises a first reactor and a second reactor in parallel configured to produce maximum values of final MTBE volumes under higher or equal established purity commercial quality specifications levels. The combined effluent from the first reactor and the second reactor is split to form a first portion, a second portion and a third portion. The first portion is flowed to a third reactor configured to produce additional MTBE. The second portion is combined with an effluent from the third reactor for further separation. The third portion is recycled to the first reactor and/or second reactor.

Processes for producing olefins include introducing a hydrocarbon feed to a high-severity fluidized catalytic cracking system, contacting the hydrocarbon feed with a cracking catalyst under high-severity conditions in the high-severity fluidized catalytic cracking system to produce a cracking reaction effluent comprising butene, and passing at least a portion of the cracking reaction effluent, which includes at least butene, to a metathesis system. The processes further include contacting the portion of the cracking reaction effluent with a metathesis catalyst in the metathesis system, which causes at least a portion of the butene in the cracking C4 effluent to undergo a metathesis reaction to produce a metathesis reaction effluent comprising at least one of ethylene, propene, or both. The processes may further include separating a metathesis C5+ effluent from the metathesis reaction effluent and passing the metathesis C5+ effluent back to the high-severity fluidized catalytic cracking unit.

Processes for producing olefins include introducing a hydrocarbon feed to a high-severity fluidized catalytic cracking system, contacting the hydrocarbon feed with a cracking catalyst under high-severity conditions in the high-severity fluidized catalytic cracking system to produce a cracking reaction effluent comprising butene, and passing at least a portion of the cracking reaction effluent, which includes at least butene, to a metathesis system. The processes further include contacting the portion of the cracking reaction effluent with a metathesis catalyst in the metathesis system, which causes at least a portion of the butene in the cracking C4 effluent to undergo a metathesis reaction to produce a metathesis reaction effluent comprising at least one of ethylene, propene, or both. The processes may further include separating a metathesis C5+ effluent from the metathesis reaction effluent and passing the metathesis C5+ effluent back to the high-severity fluidized catalytic cracking unit.

Systems and methods for processing a C.sub.3 and C.sub.4 hydrocarbon mixture have been disclosed. The C.sub.3 and C.sub.4 hydrocarbon mixture is first processed in an isomerization unit to isomerize n-butane to form isobutane. The resulting effluent stream from the isomerization unit comprising primarily isobutane and C.sub.3 hydrocarbons, collectively, is flowed into a separation unit configured to separate the effluent stream to form a C.sub.3 stream comprising C.sub.1 to C.sub.3 hydrocarbons and a C.sub.4 stream comprising primarily isobutane. The isobutane in the C.sub.4 stream is further dehydrogenated to form isobutene, which is further flowed into an MTBE synthesis unit as a feedstock for producing MTBE.

Systems and methods for processing a C.sub.3 and C.sub.4 hydrocarbon mixture have been disclosed. The C.sub.3 and C.sub.4 hydrocarbon mixture is first processed in an isomerization unit to isomerize n-butane to form isobutane. The resulting effluent stream from the isomerization unit comprising primarily isobutane and C.sub.3 hydrocarbons, collectively, is flowed into a separation unit configured to separate the effluent stream to form a C.sub.3 stream comprising C.sub.1 to C.sub.3 hydrocarbons and a C.sub.4 stream comprising primarily isobutane. The isobutane in the C.sub.4 stream is further dehydrogenated to form isobutene, which is further flowed into an MTBE synthesis unit as a feedstock for producing MTBE.

Methods and systems for producing light olefins are disclosed. A feedstock comprising crude oil is distilled to produce a plurality of streams including a naphtha stream and a vacuum residue stream. The naphtha is fed to a steam cracking unit to produce light olefins, C.sub.4 hydrocarbons, pyrolysis gasoline and pyrolysis oil. The vacuum residue stream is hydrocracked to produce additional naphtha and heavy unconverted oil. The heavy unconverted oil and the pyrolysis oil from steam cracking unit can be deasphalted to produce deasphalted oil and pitch product. The deasphalted oil can be further hydrocracked to produce naphtha. The pitch product can be gasified to produce synthesis gas, which is further used to produce methanol. The methanol can be used to react with isobutylene of the C.sub.4 hydrocarbon stream from steam cracker to produce methyl tert-butyl ether (MTBE).