Reactor design, commercial alkylation

Although the choice of catalyst, reaction conditions, and reactor design aU allow control over byproduct formation and isomer selectivity in an acid-catalyzed alkylation reaction the type of the alkylating agent is also a major contributor in isomer selectivity as already discussed. A para-substituted, monoalkylated final product accounts for nearly 85% of all commercial alkylphenol manufacture. 

Stepan was the first to develop and conunercialize a continuous falling film SO3 sulfonation process. The design is a multitubular unit. The company operates about 12 falling film SO3 sulfonation units in the United States, not only for the production of linear alkyl benzene sulfonates, but substantial amounts of fatty alcohol and fatty alcohol ethoxylates are also sulfated. Other key commercial reactor designs are by Chemithon, Ballestra SpA, Lion, Mazzoni SpA, and Meccaniche Modeme. Several features are common to all falling-film systems. Fatty alcohol and alcohol ethoxylates are reacted at a rate of about 0.3 kg/h/mm with SO3 concentration at about 2-3%. Liquid residence times are estimated at 10-30 s and most units operate with gas velocities in the range of hurricane wind velocities (121-322 km/h). ° Linear alcohols and linear alcohol ethoxylates are by far the easiest to sulfate. Caution is required with branched alcohols as color and conversion can suffer. 

For purposes of plant design and for optimum operation consistent with feed stock availability, it is necessary to be able to predict accurately the octanes of the alkylate produced under varying operating conditions. Such a correlation developed from several hundred pilot plant and commercial plant tests is presented in Figures 7, 8, and 9. This correlation is applicable to sulfuric acid alkylation of isobutane with the indicated olefins, and was developed specifically for the impeller-type reaction system, although it also appears to be satisfactory for use with some other types of reactors. 

Relatively low temperatures are required in alkylation reactors using sulfuric acid catalyst. They are necessary in order to slow down polymerization reactions and reduce the formation of undesirable acid soluble and hydrocarbon soluble by-products. Typically, most commercial units operate with reaction temperatures in the range of 35 F. to 65 F. Design temperatures are usually set at 50 F. For minimum acid make-up the reactor section should be operated as cold as possible. This means operating... 

Because the main alkylation reactions occur at the interface, both isobutane and olefins in the dispersed droplets are transferred to the interface, and the resulting C5-C16 isoparaffins are transferred from the interface back into the dropletJ Experimental data indicate that such transfer steps are in part at least rate controlling steps. In any case, each droplet acts as a different reaction zone (basically a separate minireactor). As droplets of different compositions and sizes occur in all commercial reactors, the alkylation results differ in various droplets, i.e., different alkylates, RONs, yields, amounts of by-products, etc. Improved results would occur if alkylation reactors could be designed and operated so that all the alkylate was produced only at optimal conditions. 

Similar to the B/E in the alkylation reactor section, the first liquid phase plants were designed and operated with Bz/PEB close to 10 or higher. Over time, transalkylation catalyst system stability has been improved and the Bz/PEB has steadily decreased and in 2004 plants are typically designed with Bz/PEB in the range of 2.0-4.0. Generally, a commercial plant is operated at or very close to its design Bz/PEB and the operating Bz/PEB is not frequently adjusted. 

The CDTECH EB process is based on a mixed liquid-vapor phase alkylation reactor section. The design of a commercial plant is similar to the liquid phase technologies except for the design of the alkylation reactor, which combines catalytic reaction with distillation into a single operation. ... 

Construction of an AlkyClean process demonstration unit at Fortum s facilities in Porvoo, Finland, was completed in 2002. Figure 12.14 shows the process flow schematic of the demo unit, which contains all of the key elements of our proposed commercial design. Three reactors are included - two under cyclic operation (i.e., alternating between alkylation and mild regeneration) allowfor continuous production... 

Fixed bed and liquid riser type reactors are found in the majority of the proposed commercial solid acid alkylation processes, as will be detailed hereinafter. Nevertheless, other reactor configurations have been proposed for alkylation processes employing solid catalysts. For instance, a spouted bed reactor is constituted by a gas flow propelled riser, an annular downcomer where part of the solid and liquid are recycled to the reactor inlet and a hydrocyclon in which the solid catalyst is collected to be regenerated in continuous at a neighboring unit. Recently, a spouted bed reactor equipped with a fluidized-bed catalyst regenerator has been designed to be used in solid alkylation processes, employing a Pt/S0x(Zr-Ti)02... 

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