Process and apparatus for alkylation (UOP)

CATEGORY: ALKYLATION
Process and apparatus for alkylation (UOP)

Type	Patent
Inventor	Daniel K. Aiken
Inventor	Kurt A. Detrick
Inventor	Andrey Kuzmin
URL	Free Full Text Source:  http://www.google.com/patents/US20140163293
Assignee	Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, UOP
Patent Number	US20140163293 A1
Issue Date	Jun 12, 2014
Abstract	One exemplary embodiment can be a process. The process can include obtaining a hydrocarbon phase having one or more hydrocarbons and an alkylation catalyst from a first vessel, swirling the hydrocarbon phase to separate the alkylation catalyst, and recycling the alkylation catalyst to an alkylation reactor. DESCRIPTION OF THE RELATED ART Typically, motor fuels are produced with sufficient octane to ensure the efficient and reliable operation of a motor vehicle. One process that can be used to improve motor fuel octane is an alkylation process. Generally, an alkylation process can combine light alkenes, which are usually mixtures of propene and butenes, with one or more alkanes, such as isobutane. The alkylation reaction generally takes place in the presence of a catalyst, which may include an acid, such as hydrofluoric or sulfuric acid, under conditions typically selected to maximize alkylate yield and quality. Usually, the product can possess anti-knock properties and high octane due to the presence of branched alkanes. In such processes, the reaction product may form a suspension with an alkylation catalyst and be transferred to downstream equipment, typically a large vessel for separating the alkylation catalyst from the reaction product as well as any unreacted hydrocarbons. Usually, the reaction product is subsequently separated into various fractions often using one or more distillation towers. Generally, the vessel or settler that is used to separate the acid phase from the hydrocarbon phase is designed for laminar flow conditions to minimize the entrainment or carryover of the acid phase in the hydrocarbon exiting the large vessel. For existing liquid acid alkylation units, feed capacity typically is limited by the downstream separation volume available. Exceeding this limit may result in acid carryover to downstream fractionation units, potentially risking increased corrosion. Moreover, each unit volume increase in alkene feed to the unit typically corresponds to an eight-to-twelve fold increase in isoalkane flow to maintain optimum reaction conditions and product quality. This increased volumetric flow of isoalkanes to the large vessel with respect to the acid flow volume can increase the amount of liquid acid catalyst entrained in the hydrocarbon phase as it exits the vessel. This excess entrained acid carried to the fractionation section can accelerate equipment corrosion. Accelerated equipment corrosion may negatively impact the reliability and safety of the unit and increase shutdowns of the unit to repair the corrosion damage. Increasing unit capacity often requires installing a larger vessel to minimize acid carryover to facilitate the higher feed rates. Alternatively, a parallel reactor-settler combination may be added in parallel to accommodate the increased flow. Unfortunately, either option involves increased capital investment, such as greater acid and hydrocarbon inventories, and equipment down time to implement the modifications. Moreover, lowering inventories can improve safety by reducing the potential risk of system failures. Thus, it would be desirable to provide a unit or process that minimizes the corrosion and wear of the downstream vessels due to alkylation catalyst carry over.