Processes Pacol

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.

Apart from the UOP Pacol process, today s only other meaningful economic process is the Shell higher olefin process (SHOP) in which /z-olefins are produced by ethylene oligomerization. Until 1992 Hiils AG used its own technology to produce -60,000 t/year of /z-olefins by the chlorination of /z-paraffins (from Molex plant) and subsequent dehydrochlorination [13]. In the past, the wax cracking process (Shell, Chevron) played a certain role. In the Pacol and Hiils processes, olefins are obtained as diluted solutions in paraffin (Pacol to max. 20%, Hiils about 30%) without further processing these are then used for alkylation. In contrast, the SHOP process produces pure olefins. 

Since the mid-1960s C10/13 /z-paraffins have been used as the starting material for the manufacture of the corresponding C10/13 n-olefin (required as alkylation reagent in the manufacture of LAB, e.g., Hiils, Pacol process). 

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. 

Should pure olefin be used for alkylation (Shell process), the organic phase consists of benzene, LAB, and heavy alkylate and is fractionally distilled, after which the remaining HF is usually removed by stripping. When using olefin as a solution in paraffin (Pacol and Hiils process) for alkylation, the organic phase contains additional large quantities of paraffin which have to be separated out by distillation and used again in the production of olefin. 

All of these points contribute to a better process economy than the classical process offers. UOP estimates the cost of a plant (50,000 t/a LAB capacity) with Pacol plant, DeH-9 as catalyst, DeFine- and Detal step at around 45 million. Compared to the first plants with similiar capacities of the early 1980s, in which... 

The color of the derivative alkylbenzenesulfonic acid is clearly better. The solubility characteristics remain good. An olefin from the Pacol-Olex process (C, 0/13 olefin) is used as a starting olefin. The DeFine step is employed to reduce the diolefin content to <0.5%. With such an olefin an LAB is obtained over an aluminum chloride catalyst with a linear content of >99% and from which the sulfonation product has a biodegradability (DOC) comparable to that of other LABs[122,123].Table 25 gives typical physical-chemical data about different LAB types. 

The formation of DATs results from the presence of dichloroparaffins or diolefins in the alkylation process. In the chloroparaffin/AlCl3 process the ratio of dichloroparaffin to monochloroparaffin is about 1 10, and this results in a level of about 6-10% DAT in the product LAB. However, in the Pacol/HF process the ratio of diolefin to monoolefin is lower, resulting in a DAT level of about 1-2% [12]. When a DeFine unit is coupled to the Pacol olefin stream to further reduce diolefins, the level of DAT can be less than 1% [13]. 

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... 

Olex A version of the Sorbex process for separating olefins from paraffins in wide-boiling mixtures. It can be used for hydrocarbons in the range C6 - C20. Based on the selective adsorption of olefins in a zeolite and their subsequent recovery by displacement with a liquid at a different boiling point. Mainly used for extracting Cn - C14 olefins from the Pacol... 

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. 

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. 

PEP [Pacol Enhancement Process] A process for selectively removing aromatic hydrocarbons from hydrocarbon mixtures. See Pacol. 

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. 

Table 2.32 provides economic data concerning the production of propylene and n-butenes by the Catofio and Oleilex processes, and the production of long-chain olefins by the Pacol Olex technique. 

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