Linear Alkylbenzene   

Linear alkylbenzene (LAB) is an alkylation product of benzene used to produce biodegradable anionic detergents. The alkylating agents are either linear C₁₂–C₁₄ mono-olefins or monochloroalkanes. The linear olefins (alpha olefins) are produced by polymerizing ethylene using Ziegler catalysts or by dehydrogenating n-paraffins extracted from kerosines. Monochloroalkanes, on the other hand, are manufactured by chlorinating the corresponding n-paraffins. Dehydrogenation of nparaffins to monoolefins using a newly developed dehydrogenation catalyst by UOP has been reviewed by Vora et al.16 The new catalyst is highly active and allows a higher per-pass conversion to monoolefins. Because the dehydrogenation product contains a higher concentration of olefins for a given alkylate production rate, the total hydrocarbon feed to the HF alkylation unit is substantially reduced.

Alkylation of benzene with linear monoolefins is industrially preferred. The Detal process (Figure 1.1) combines the dehydrogenation of n-paraffins and the alkylation of benzene. Monoolefins 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 1.1. 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.

Typical properties of detergent alkylate are shown in Table 1.1.

Table 1.1 Typical properties of detergent alkylate

 Detergent manufacturers buy linear alkylbenzene, sulfonate it with SO₃, and then neutralize it with NaOH to produce linear alkylbenzene sulfonate (LABS), the active ingredient in detergents: