Alkylation unit

Typical feedstock, yields and product properties from an alkylation unit. 

C4 s that are inert with respect to the reaction constitute the raffinate. These can serve as feedstock to an alkylation unit. 

A simplified flow diagram of a modern H2SO4 alkylation unit is shown in Eigure 1. Excess isobutane is suppHed as recycle to the reactor section to suppress polymerization and other undesirable side reactions. The isobutane is suppHed both by fractionation and by the return of flashed reactor effluent from the refrigeration cycle. 

The H2SO4 catalyst produces a high octane product of similar composition from either 2-butene or 1-butene. This fact suggests that the isomerization of 1-butene to 2-butene is more complete than in the HF system. Isobutylene produces a slightly lower product octane than do the / -butenes. The location of a methyl tert-huty ether [1634-04-4] (MTBE) process upstream of the H2SO4 alkylation unit has a favorable effect on performance because isobutylene is selectively removed from the alkylation feed. 

A simplified flow diagram for a typical UOP linear detergent alkylation unit is shown in Figure 7. The design of this unit is similar to a unit that produces branched-chain detergent alkylate. 

The benzene—toluene fraction is further fractionated in a small column, not shown in Figure 5, to recover benzene for recycle to the alkylation unit and toluene for sale. This toluene can be converted to benzene by hydrodealkylation but the high selectivity catalyst has reduced the formation of toluene in the dehydrogenation reactor to the point where the cost of installing a hydrodealkylation unit is difficult to justify even in a large styrene plant. 

The Cy and Cg paraffias comprise about 90% of the alkylate Cg accounts for over 60%. Over 70% of the commercial alkylation processes employ sulfuric acid as the catalyst. Among the butylenes, 2-butene is superior to 1-butene. The C —fraction from the catalytic crackers is considered to be a superior feedstock to the alkylation unit. 

In the sulfuric acid process, the sulfuric acid removed must be regenerated in a sulfuric acid plant which is generally not a part of the alkylation unit and may be located off-site. Spent sulfuric acid generation is substantial typically in the range of 13 to 30 pounds per barrel of alkylate. Air emissions from the alkylation process may arise from process vents and fugitive emissions. 

Toxicity and Environmental Fate Information for Propylene CAS 115-07-1 Sourtes. Propylene (propene) is one of the light ends formed during catalytic and thermal cracking and coking operations, it is usually collected and used as a feedstock to the alkylation unit. Propylene is volatile and soluble in water making releases to both air and water significant. 

The primary process for separating the hydrocarbon components of crude oil is fractional distillation i.e. separation according to the boiling points of the components. These separated fractions are processed further by catalytic reformers, cracking units, alkylation units, or cokers which have there own fractional distillation towers for its products. 

I. Designate/instalt emergency isolation miIvcs in the alkylation unit and install remote switches in the alkylation unit control room so that operators can close ihcse valves during emergencies... 

Designate critical process alarms in the alkylation unit and ensure that these alarms are installed independent of equipment control loops... 

Evaluate making the alkylation unit control building a safe haven during hazardous material releases administrative action items... 

A large oil refinery had a failure in their alkylation unit resulting in a significant release of hydrofluoric acid (HF). This incident and others in refineries during recent years prompted members of the hydrocarbon processors to turn to HAZOP to better understand their risks. 

Figure 11.4-2 shows process flows for an HF alkylation unit. The three sections are 1) reaction, 2). settling and 3) fractionation. In the reaction section isobutane feed is mixed with the olefin feed (usually propylene and butylene) in approximately a 10 or 15 to 1 ratio. In the presence of the HF acid catalyst the olefins react to form alkylate for gasoline blending. The exothermic reaction requires water cooling. The hydrocarbon/HF mixture goes to the settling... 

Establish/enhance consistent programs lu periodically inspect and test the engineered defenses that are designed to protect against hazardous upsets in the alkylation unit... 

Investigate ways to improve the control of replacement materials installed in the alkylation unit during turnarounds and routine maintenance... 

Investigate ways to reduce the potential tor external impacts to damage process piping while the alkylation unit is operating... 

S. Evaluate the acid relief neutralization system in HE alkylation units to ensure its adequacy tor neutralizing design basis relief valve discharges and unit ventings... 

Figures 1-1 through 1-3 contain sketches of typical unit configurations offered by some licensers. Although the mechanical configuration of individual FCC units may differ, their common objective is to upgrade low-value feedstock to more valuable products. Worldwide, about 45% of all gasoline comes from FCC and ancillary units, such as the alkylation unit.

The overhead product is totally liquefied in the overhead condensers. A portion of the overhead liquid is pumped and returned to the tower as reflux. The remainder is sent to a treating unit to remove H2S and other sulfur compounds. The mixed Cj s and C s stream can then be fed to an ether or an alkylation unit. It can be fed to a depropanizer tower where the Cj s are separated from C4 s. The Cj s are processed for petrochemical feedstock and the C4 s are alkylated. 

Reformulated gasoline specifications require lower vapor pressure in the blended gasoline. It also requires maximum feed to the alkylation unit. This puts more pressure on the gas plant, particularly the debutanizer. Floating the tower pressure is often the best way to meet both constraints. 

An interesting development in this work was obtained when Gandini and Rieu-mont tried to activate the polymerization of vinyl 2-furoate with ZnCl2. It was found that oligomerization occurred and the products had a structure which contained a substantial amount of alkylated units of the type ... 

Recently, Bafquiren and Eddine have studied hindered Schiff base derivatives of fra/ s-l,2-diaminocyclohexane23 The differences in chemical shifts found for imino carbons have indicated the presence of anti- and syn-geometric configurations. The intense NOESY effects between protons of naphthyl and alkyl units have proved the anti-configuration of the major stereoisomer. 

---