Integrated Butane Isomerization And Ionic Liquid Catalyzed Alkylation Processes

CATEGORY: IONIC LIQUIDS
PATENT
Integrated Butane Isomerization And Ionic Liquid Catalyzed Alkylation Processes
Pub. No.:    WO/2013/039566    International Application No.:    PCT/US2012/031165
Publication Date:  21.03.2013 International Filing Date:  29.03.2012
Applicants:  CHEVRON U.S.A. INC. [US/US]; 6001 Bollinger Canyon Road San Ramon, California 94583 (US) (For All Designated States Except US).
Inventors:  TIMKEN, Hye Kyung Cho; (US) 
Abstract:  
Integrated isomerization and ionic liquid catalyzed alkylation processes may comprise integrating ionic liquid alkylation and n-butane isomerization using a common distillation unit for separating an n-butane containing fraction from at least one of an alkylation hydrocarbon phase from an ionic liquid alkylation reactor and an isomerization hydrocarbon stream from an isomerization unit. The n-butane containing fraction may undergo isomerization to provide an isomerization reactor effluent comprising the isomerization hydrocarbon stream. An isobutane containing fraction, separated from at least one of the alkylation hydrocarbon phase and the isomerization hydrocarbon stream, may be recycled from the distillation unit to the ionic liquid alkylation reactor.
TECHNICAL FIELD
The present invention relates to integrated butane isomerization and ionic liquid catalyzed alkylation processes.
BACKGROUND
Conventional paraffin-olefm alkylation plants may be used in conjunction with a
conventional n-butane isomerization plant in order to provide additional feedstock
(isoparaffin) for the alkylation plant. Conventional n-butane isomerization processes use AICI3 catalyst or a Pt-alumina catalyst plus HCl. Since the isomerization catalyst is sensitive to moisture, conventional n-butane isomerization processes require extensive feed drying.
Hydrofluoric acid (HF) is used as a catalyst in conventional alkylation processes for the production of high-octane gasoline, distillate, and lubricating base oil. The hazards of HF, e.g., related to HF volatility, are well documented. The use of additives to reduce HF volatility is expensive and does not eliminate the need for large quantities of HF in the plant. Efforts to develop safer, alternative catalysts have encountered serious challenges. The conversion of HF alkylation units to use sulfuric acid (H2SO4) as catalyst requires significant added capital and operating expense, and at the same time introduces the hazards associated with highly corrosive concentrated H2SO4. Further, solid alkylation catalysts have proved difficult to commercialize due to rapid fouling and deactivation.
The quest for alternative catalytic systems to replace conventional HF and H2SO4 catalysts in alkylation processes has been researched by various groups in both academic and industrial institutions. Thus far, no alternative catalyst for performing such processes has been commercialized.
Recently there has been considerable interest in metal halide ionic liquid catalysts as alternatives to HF and H2SO4 catalysts. As an example, the ionic liquid catalyzed alkylation of isoparaffins with olefins is disclosed in U.S. Patent No. 7,432,408 to Timken, et al.
Further, U.S. Patent No. 7,572,943 to Elomari, et al. discloses the ionic liquid catalyzed oligomerization of olefins and the alkylation of the resulting oligomers(s) with isoparaffins to produce alkylated olefin oligomers.
Figure 1A schematically represents a conventional n-butane isomerization plant lOaccording to the prior art. Conventional n-butane isomerization plant 10 includes a feed dryer 12, an isomerization reactor 14, a gas/liquid separation unit 16, a distillation unit 18, and a caustic (KOH or NaOH) treating unit 20. Dried n-butane or a mixed butane stream containing a significant amount of n-butane is co-fed with dried H2 to isomerization reactor 14. The H2 and HC1 are removed from the reactor effluent via gas/liquid separation unit 16. The resultant hydrocarbon effluent (isomerized butane mixture) is sent to distillation unit 18 to separate n-butane from the isobutane product. The isobutane stream is treated in caustic treating unit 20 to remove residual chloride in the isobutane product stream before being sent to a conventional HF or H2S04 alkylation plant (see, e.g., Figures IB and 1C).
Figure IB schematically represents a conventional HF alkylation plant 30, in relation to a conventional butane isomerization plant, according to the prior art. HF alkylation plant 30 may include a feed treatment unit 32, an HF alkylation reactor 34, an HF settler 36, an HF heat exchanger 38, an HF regeneration unit 40, a fractionation unit 42, and a product treatment unit 44. An olefin containing stream is fed to HF reactor 34 together with an isobutane containing stream from a conventional butane isomerization plant (see, e.g., Figure 1 A). The effluent from HF reactor 34 is separated via HF settler 36 into a hydrocarbon phase and an HF phase. The HF phase is recycled to HF reactor 34 via HF heat exchanger 38. The hydrocarbon phase is fractionated via fractionation unit 42, and one or more fractions treated via product treatment unit 44 to provide one or more products.
Figure 1C schematically represents a conventional H2S04 alkylation unit 30', in relation to a conventional butane isomerization plant, also according to the prior art. H2S04 alkylation plant 30' may include an H2S04 alkylation reactor 34', an acid settler 36', an acid wash vessel 24, an alkaline water wash vessel 26, a refrigeration unit 28, a fractionation unit 42', and a product treatment unit 44'. An olefin containing stream is fed to H2S04 reactor 34' together with an isobutane containing stream from a conventional butane isomerization plant (see, e.g., Figure 1 A). The effluent from H2SO4 reactor 34' is separated via acid settler 36' into a hydrocarbon phase and an acid phase. A portion of the acid phase is recycled to H2SO4 reactor 34'. A further portion of the acid phase may be removed for acid regeneration.
Fractionation unit 42' fractionates the hydrocarbon phase to provide one or more products for treatment by product treatment unit 44 ' .
Conventional processes for both n-butane isomerization and HF/H2SO4 catalyzed alkylation are well known in the art.
U.S. Patent No. 7,439,410 to Rice et al. discloses an integrated isomerization-alkylation process that uses a common distillation zone, in which the isomerization reaction zone effluent is passed to a depropanizer, either directly or via a chloride treater. In an alternative embodiment of the '410 patent, the isomerization reaction zone effluent is cooled and then undergoes gas-liquid phase separation before the liquid phase is passed to the depropanizer via the chloride treater. During alkylation according to the '410 patent, the reactants may be in the vapor-, liquid-, or mixed liquid-vapor phase when contacted with the catalyst particles.
There is a need for efficient, integrated ionic liquid catalyzed alkylation-butane isomerization processes.
SUMMARY
In an embodiment of the present invention there is provided an integrated ionic liquid alkylation and n-butane isomerization process comprising contacting at least one isoparaffm and at least one olefin with an ionic liquid catalyst in an ionic liquid alkylation zone under ionic liquid alkylation conditions; separating an alkylation hydrocarbon phase from an alkylation reactor effluent of the ionic liquid alkylation zone; fractionating, via a distillation unit, an internal hydrocarbon feed to provide an n-butane containing fraction, wherein the internal hydrocarbon feed comprises the alkylation hydrocarbon phase; isomerizing at least a portion of the n-butane in the n-butane containing fraction to provide isobutane; and recycling the isobutane to the ionic liquid alkylation zone.
In another embodiment, there is provided an integrated ionic liquid alkylation-butane isomerization process comprising contacting at least one isoparaffm and at least one olefin with an ionic liquid catalyst in an ionic liquid alkylation zone under ionic liquid alkylation conditions; separating an alkylation hydrocarbon phase from an alkylation reactor effluent of the ionic liquid alkylation zone; fractionating, via a distillation unit, an internal hydrocarbon feed to provide an n-butane containing fraction, wherein the internal hydrocarbon feed comprises the alkylation hydrocarbon phase; contacting the n-butane containing fraction with an isomerization catalyst in an isomerization zone under butane isomerization conditions; separating an isomerization reactor effluent of the isomerization zone into a gas phase and an isomerization hydrocarbon stream, wherein the isomerization hydrocarbon stream comprises isobutane, and the internal hydrocarbon feed further comprises the isomerization hydrocarbon stream; fractionating, via the distillation unit, the internal hydrocarbon feed to further provide an isobutane containing fraction; and recycling the isobutane containing fraction to the ionic liquid alkylation zone.
In a further embodiment, there is provided an integrated ionic liquid alkylation and n-butane isomerization process comprising contacting at least one isoparaffm and at least one olefin with an ionic liquid catalyst in an ionic liquid alkylation zone under ionic liquid alkylation conditions; separating an alkylation hydrocarbon phase from an alkylation reactor effluent of the ionic liquid alkylation zone; fractionating, via a distillation unit, an internal hydrocarbon feed to provide an n-butane containing fraction, wherein the internal hydrocarbon feed comprises the alkylation hydrocarbon phase and an isomerization hydrocarbon stream;
contacting the n-butane containing fraction with an isomerization catalyst in an isomerization reactor under butane isomerization conditions to provide an isomerization reactor effluent comprising the isomerization hydrocarbon stream; separating the isomerization hydrocarbon stream from the isomerization reactor effluent; recycling the isomerization hydrocarbon stream to the distillation unit; separating, via the distillation unit, an isobutane containing fraction from the internal hydrocarbon feed; and recycling the isobutane containing fraction to the ionic liquid alkylation zone.
As used herein, the terms "comprising" and "comprises" mean the inclusion of named elements or steps that are identified following those terms, but not necessarily excluding other unnamed elements or steps.
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