Pacol™ process dehydrogenation

By catalytic dehydrogenation of suitable n-paraffin cuts, important /z-olefms are obtained for the synthesis of surfactants. The process is known as the Pacol process. The UOP developed process embraces the following process steps, which are described in more detail in this chapter (Fig. 9) ... 

The catalytic system used in the Pacol process is either platinum or platinum/ rhenium-doped aluminum oxide which is partially poisoned with tin or sulfur and alkalinized with an alkali base. The latter modification of the catalyst system hinders the formation of large quantities of diolefins and aromatics. The activities of the UOP in the area of catalyst development led to the documentation of 29 patents between 1970 and 1987 (Table 6). Contact DeH-5, used between 1970 and 1982, already produced good results. The reaction product consisted of about 90% /z-monoolefins. On account of the not inconsiderable content of byproducts (4% diolefins and 3% aromatics) and the relatively short lifetime, the economics of the contact had to be improved. Each diolefin molecule binds in the alkylation two benzene molecules to form di-phenylalkanes or rearranges with the benzene to indane and tetralin derivatives the aromatics, formed during the dehydrogenation, also rearrange to form undesirable byproducts. 

DeFine [Di-olefine saturation] A process for converting di-olefins to mono-olefins by selective dehydrogenation. Developed by UOP for use with its Pacol process. First commercialized in 1986 and now incorporated in all new Pacol plants. Six units were operating in... 

The PACOL process (paraffin conversion to olefin) produces n-olefins by dehydrogenation of paraffin over a heterogeneous platinum catalyst. The Pacol process is more selective than thermal cracking and produces smaller amounts of byproducts. 

The UOP Paeol process for selective long-chain paraffin dehydrogenation to produee linear mono-olefins is shown in Fig. 15 in combination with the UOP detergent alkylation process. The Pacol process consists of a radial-flow reactor and a product recovery section. Worldwide, more than 2 million metric tons per year of linear alkyl benzene is produced employing this process. 

Normal Paraffin-Based Olefins, Detergent range -paraffins are currently isolated from refinery streams by molecular sieve processes (see ADSORPTION, LIQUID separation) and converted to olefins by two methods. In the process developed by Universal Oil Products and practiced by Enichem and Mitsubishi Petrochemical, a -paraffin of the desired chain length is dehydrogenated using the Pacol process in a catalytic fixed-bed reactor in the presence of excess hydrogen at low pressure and moderately high temperature. The product after adsorptive separation is a linear, random, primarily internal olefin. Shell formedy produced olefins by chlorination—dehydrochlorination. Typically, C —C14 -paraffins are chlorinated in a fluidized bed at 300°C with low conversion (10—15%) to limit dichloroalkane and trichloroalkane formation. Unreacted paraffin is recycled after distillation and the predominant monochloroalkane is dehydrochlorinated at 300°C over a catalyst such as nickel acetate [373-02-4]. The product is a linear, random, primarily internal olefin. 

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.

Application To produce linear alkylbenzene (LAB) from C10 to C14 linear paraffins by alkylating benzene with olefins made by the Pacol dehydrogenation and the DeFine selective hydrogenation processes. The alkylation reaction is carried out over a solid, heterogeneous catalyst in the Detal process unit. 

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. ... 

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