Detal process

Alkylation of benzene with linear monoolefms is industrially preferred. The Detal process (Figure 10-9) combines the dehydrogenation of n-paraffins and the alkylation of benzene. Monoolefms from the dehydrogenation section are introduced to a fixed-bed alkylation reactor over a heterogeneous solid catalyst. Older processes use HF catalysts in a liquid phase process at a temperature range of 40-70°C. The general alkylation reaction of benzene using alpha olefins could be represented as ... 

Figure 10-9. The UOP (Detal) process for producing linear alkylbenzene (1) pacol dehydrogenation reactor, (2) gas-liquid separation, (3) reactor for converting diolefins to monoolefins, (4) stripper, (5) alkylation reactor, (6,7,8) fractionators.

FIG. 16 UOP DETAL process. BC, benzene column PC, paraffin column RR, rerun column Rx, reactor VE, vacuum ejector. (From Ref. 10.)... 

An alkene mixture of industrial source (equal amounts of C9-C13 alkenes and alkanes) was used in the alkylation of benzene on three Nafion-silica catalysts with 5%, 13%, and 20% loadings.195 20% Nafion-silica showed high and stable activity and its performance exceeded that of a Y-zeolite-based material. The selectivity to 2-phenylalkanes (25%) was higher than in the Detal process using fluorinated silica-alumina but decreased somewhat with increasing Nafion content. 

Linear alkylbenzenes are made from linear terminal olefins and benzene and are important precursors of biodegradable anionic surfactants (LAS, linear alkylbenzenesulfonates). The conventional catalyst is HF, first to be replaced by a fluorinated silica-alumina in the DETAL process. The DETAL process is safer than the HF process and also more cost-effective because no special metallurgy is required and no calcium fluoride waste stream exists.52 Zeolites such as Beta may come to the fore here because they display a higher selectivity to the desired 2-phenyl isomers.55... 

Application The Detal process uses a solid, heterogeneous catalyst to produce linear alkylbenzene (LAB) by alkylating benzene with linear olefins made by the Pacol process. 

Commercial plants Twenty-nine UOP LAB complexes based on the Pacol process have been built. Four of these plants use the Detal process. 

An exisiting LAB producer can increase production by using UOPs new Pacol catalyst and Molex adsorbent, adding a PEP unit to remove aromatics and increase the alkylation reaction efficiency, revamping the Pacol unit to apply TCR reactor technology and/or revamping to add a Detal process unit. 

Friedel-Crafts alkylation processes were traditionally operated at 65-70°C with AICI3 and at 40-60°C with HF. A variety of solid acid catalysts have been developed at the laboratory level, mainly based on zeolites, heteropolyacids or sulfated zirconia (zirconia treated with sulfuric acid). The most recent industrial achievement is the Detal process (UOP-CEPSA) which is based on silica-alumina impregnated with HF. The selectivity towards linear alkylbenzenes exceeds 95%. The cymene processes use AICI3 in the liquid phase or supported phosphoric acid as catalysts. 

Typical yields for complexes using HF and solid-bed alkylation routes are shown in Table 1. This table illustrates that the yields for the two routes are similar. For constant production of LAB, paraffin use is approximately equal for both the routes. The HAB byproduct stream consists of heavy alkylate (discussed in more detail in later sections). The HAB by-product is formed in both routes and depending on the properties, may be used in applications, such as heat transfer fluids, or as enhanced oil recovery surfactants in a sulfonated form. Both routes also produce some light products in the form of off-gas and cracked product from the dehydrogenation unit. The solid-bed alkylation route also produces an aromatic by-product stream (PEP Extract in Table 1), which consists of aromatics produced in the dehydrogenation unit. While aromatics removal is possible for the HF route, it is typically not practiced. Instead, the HF route has an acid regenerator bottoms stream, which consists of by-products extracted from purification of the HF acid. Both of these by-products are typically recovered for fuel value. In the table Case-1 represents an LAB complex that includes the Pacol , DeFine , PEP, and Detal processes all licensed by UOP LLC and hereafter referred to as Pacol/DeFine/PEP/Detal complex. Case-2 represents the Pacol, DeFine, and UOP HF detergent alkylation processes, all licensed by UOP LLC and hereafter referred to as Pacol/ DeFine/HF Alky complex. ... 

The flow scheme of the Detal process is presented in Fig. 10. The olefin feed and recycle benzene are... 

Fig. 10 UOP/CEPSA Detal process for the production of LAB. (View this art in color at www.dekker.com.)...

Because the Detal process eliminates the need for HF, carbon steel metallurgy can be used in vessel and piping construction. Also, the special equipment required for HF handling is no longer needed. 

The DetaF process, jointly developed by UOP and Compania Espanola de Petroleos, S.A., uses a solid heterogeneous acid catalyst. Since its commercial introduction in 1995, 75% of all new unit capacity additions have been based on this process technology. As of 2006, the installed capacity of Detal process units represents -18% of the 3.5 million metric tons per annum total world production of LAB and by 2011, it is expected to surpass 22% of the world production capacity. A typical flow scheme for the Detal process is shown in Figure 2.6. 

In the Detal process, a solid catalyst is used instead of liquid HF acid catalyst or an AICI3 catalyst in slurry. The feedstock combines with makeup and recycled benzene and flows through a reactor, which contains a fixed bed of solid catalyst. Reactor effluent then flows directly to a fractionation section that is essentially the same as that used in the HF or AICI3 alkylation processes. As is the case for the other alkylation processes, the number of distillation columns in the fractionation section for the Detal process is determined in large part by the feedstock used. The standard fractionation scheme consists of colunms to (i) separate and recycle benzene, (ii) separate and recycle paraffins, and (iii) finally separate the LAB product from the HAB. 

The Detal process is much simpler in design and construction because by-product neutralization and waste-stream treatment are not required. The elimination of equipment otherwise needed as part of the other two processes and use of much simpler metallurgy due to the lack of a corrosive environment results in a plant that is safe and easy to operate, as well as having much lower maintenance costs. 

As of 2004, most dodecylbenzenes were produced using HF as the catalyst (44). Several years previous to 2004, the Detal process was developed jointly by UOP and Compania Espanol de Petrolesos SA (CEPSA) three Detal units have already been commercialized. The catalyst used has apparently not been reported. A fixed bed of catalyst is employed using mild operating conditions. The quality of the product obtained is claimed to be superior to those produced in HF or AICI3 units. The Detal process is claimed to have a 15% lower plant investment plus lower operating costs. Safety concerns of this process are of course much reduced as compared with especially HF-type processes. 

---