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las production

Linear alkylbenzene sulphonate is a component of laundry detergents and other cleaning products that was created in the early 1960s to help put an end to foaming in rivers and streams caused by the poorly degradable product used until then called BABS (Branched Alkylbenzene Sulphonate) was the traditional surfactant of choice for detergents until the 1960s, when alternatives were sought that would prevent foaming of rivers and streams. The focus became biodegradability. And LAS was selected because of its high rate of biodegradability.

LAS graph 01

Linear alkylbenzene (LAB), the material used to produce LAS, is derived exclusively from petroleum derivatives: benzene and linear paraffins. The total world LAB production capacity in 2002 was estimated at 2.5 million tons, with 300 000 tons being consumed in Western Europe. LAS currently represents one-third of the active ingredients in detergents worldwide. Virtually all LAB is transformed into LAS.

processing steps

LAS is produced by sulphonation of LAB with a variety of sulphonating agents. In the past, oleum (fuming sulphuric acid) as well as sulphuric acid were the predominant agents used either in batch reactors or in the so-called "cascade" systems. The sulphonation technology, however, has been considerably improved since the mid 60s and nowadays, although oleum is still used, modern falling film reactors (FFR) (mono-tube or multi-tube) and SO3 gas are the state-of-the-art technology in most of the sulphonation facilities in Europe. These modern plants generally sulphonate LAB and fatty alcohols directly on site.

LAB, the precursor of LAS, is manufactured in large scale industrial processes by 1) Alkylating benzene with linear mono-olefins or alkyl halides such as chloro-paraffins by using HF or AlCl3 as the alkylation catalyst(Cavalli et al., 1999-b), and 2) recently also over heterogeneous solid super-acids in a fixed-bed reactor (Erickson et al., 1996). LAB production quality, as measured by its bromine and color indeces, by impurities and alkyl chain linearity, has been enhanced over time following significant technological improvements (Marr et al., 2000). Alkylation with AlCl3 was the first commercial process used in the mid 60s when branched dodecylbenzene (DDB) was replaced by LAB. At the end of the 60s the HF technology was applied for the first time and immediately it became the preferred technology to be used around the world to produce LAB.
In the mid 90s a new alkylation technology based on a heterogeneous catalyst in a fixed-bed reactor, Detal®, appeared on the market (Berna et al., 1994) and was rapidly adopted, as testified by several new units recently installed with this technology. The new technology offers considerable advantages over the old ones, namely: process simplification, elimination of acid handling and disposal (HF, HCl) as well as an overall production yield improvement. Production of commercial LAS involves a series of processes illustrated in the above scheme.

Total LAB world production capacity in the year 2000 is estimated to be near 3 million tons, with a split by technology as follows: 80% HF, 10% AlCl3, and 10% fixed-bed. In Europe, in the year 2000, the estimated installed LAB capacity was around 600 kton/y with a corresponding demand of more than 300 kton/y (ECOSOL, 2001). The balance is usually exported out of the European market.
The result of sulphonating LAB is the formation of alkylbenzene sulphonic acid, which has the consistency of a liquid with a high active content (>97%), containing about 1% of unsulphonated matter and 1-2% of H2SO4 (IUCLID, 1994; Schönkaes, 1998). It represents commercially the most important supply form. The acid is then neutralized with a base to give the final LAS surfactant salt. Sodium neutralized LAS is by far the predominant grade. As salt, it can also be supplied in various forms and active contents, for example as paste (50-75%) and powder (80-90%)(Schönkaes, 1998).

LAS is almost exclusively used as a surfactant ingredient in detergents. Because of LAS's environmental safety, cleaning effectiveness and cost competitiveness, LAS has experienced more than 30 years of ever-increasing use around the world.