Linear alkylbenzene sulfonates biodegradation

During the early 1960s, linear aliphatic olefins, such as a olefins produced via ethylene oligomerization or linear internal olefins produced via catalytic dehydrogenation of linear paraffins, replaced the use of propylene tetramers ia iadustrialized countries, and production of more biodegradable linear alkylbenzene sulfonates (LABS) began (see ADSORPTION, LIQUID SEPARATION) (70). Except ia a few parts of the world, the use of DDES was phased out by 1980. 

Taylor, P. W., G. Nickless, Paired-ion HPLC of partially biodegraded linear alkylbenzene-sulfonate.y. Chromatogn, 1979,178, 259-269. 

Linear paraffins in the C q to range are used for the production of alcohols and plasticizers and biodegradable detergents of the linear alkylbenzene sulfonate and nonionic types (see Alcohols Plasticizers Surfactants). Here the UOP Molex process is used to extract / -paraffins from a hydrotreated kerosine (6—8). 

BIODEGRADATION OF LINEAR ALKYLBENZENE SULFONATES IN THE MARINE ENVIRONMENT... 

Although the marine environment can generally be considered the final destination of industrial and urban wastewater effluents, studies of biodegradation of linear alkylbenzene sulfonates (LAS) in this compartment have been scarce until recently [1—8]. The removal of LAS from the marine medium seems to be an efficient process, as shown by the low levels of LAS detected in samples of both water and sediment [9—11]. High values have only been found in zones close to the direct wastewater effluent discharge points of urban areas [11]. 

The three transitions mentioned above, replacement of branched alkylben-zene sulfonates by linear alkylbenzene sulfonates, replacement of alkylphenol ethoxylates by alcohol ethoxylates and substitution of ester quats for stable quats are all driven by environmental concerns. Rate of biodegradation and aquatic toxicity are the major parameters taken into account, and, in order to pass the regulations that the European Union has adopted, a surfactant must pass the criteria of showing ... 

It is common practice to put the experimentally obtained values for biodegradation and aquatic toxicity into a kind of matrix, as is illustrated by Fig. 2. The shaded areas in the matrix are the approved areas . Out of the six product types discussed above linear alkylbenzene sulfonates, alcohol ethoxylates, and ester quats lie within the shaded areas, while branched alkylbenzene sulfonates, alkylphenol ethoxylates and stable quats do not. 

The production of LAB involves the liquid-phase alkylation of benzene with linear monoolefins or alkyl chlorides. Liquid HF is used as catalyst for linear monoolefins. And the A1C13 is used as the catalyst for alkyl chlorides. Nowadays, acidic zeolite catalyst is used for olefin alkylation which generates less waste and reduces manufacture cost. The alkylate is then sulfonated to produce linear alkylbenzene sulfonate for biodegradable detergents. The manufacture of detergents is described in detail in Chapter 27. 

In the mid-1960s, commercial processes were developed for the production of linear paraffins. These could be used as feedstock to produce linear alkylbenzene sulfonates (LAS), a biodegradable alternative to SDBS. " The majority of synthetic detergent plants built after the 1970s were for the production of LABs rather than DDB. Reformulation with LAS started the phaseout of DDB, and by the end of the 1990s, most DDB plants were no longer in operation or had been converted to production of LAB. 

The separation of linear and branched alkanes is also of importance in the process known as dewaxing, in which the removal of normal alkanes makes the product hydrocarbon less viscous and reduces the so-called pour point temperature. Such processes can be combined with catalytic isomerisations to optimise the value of oil fractions (Chapter 8). Linear paraffins are also separated using a zeolite-based process from kerosene fractions to give reactants for the synthesis of linear alkylbenzene sulfonate anionic surfactants, which are both cost effective and biodegradable. 

It should be noted that continuous sulfation is widely used today, with the mixture of SOj/air in reactors such as Chemithon, Allied, or Ballestra. Moreover, alcohol sulfates are preferably used in alkaline formulations because of their low stability in acid medium. However, they are completely biodegradable and compete with petrochemical-derived linear alkylbenzene sulfonates (LAS). 

The dilemma in discussing environmental acceptability of petroleum sulfonates is (1) the dearth of environmental data on this class and (2) the diversity of chemical structures which makes biodegradation and toxicity information difficult to interpret. A logical approach is to look at the environmental properties of a prototypical structure that represents petroleum sulfonates, This structure would be an alkyl aryl sulfonate, and the best candidate is linear alkylbenzene sulfonate. Linear alkyl-benzene sulfonate (LAS) has been the focus of more environmental studies than any other surfactant, and it is a good surrogate for understanding the fate and effects of alkyl aryl sulfonates and petroleum sulfonates. 

Description. Today, the linear alkylbenzene sulfonate is the most important surfactant used. Linear chains are preferred over the branched ones due to their improved biodegradability. The reaction of linear olefins or chlorinated straight-chain paraffins with benzene in the presence of Friedel-Crafts-type catalysts (AICI3 or HF) yields linear alkylbenzene (LAB), the precursor of LAS this raw material can be procured under very attractive commercial conditions. The LAB isomer distribution depends on the type of catalyst selected. Isomers with the phenyl in the 2-position are present at about 20% and 30% in the mixture resulting from HF- and AlCls-catalyzed processes, respectively. 

Particularly important members of this family are the alkylbenzene sulfonates (ABS) and the linear alkylbenzene sulfonates (LABS). The ABS family, as mentioned earlier, is based on highly branched tetrapropylene alkyl groups that resist biodegradation processes, something that is less of a problem with the linear alkyl analoges. 

Alkylbenzene. Alkylbenzene is an intermediate for the production of alkylbenzene sulfonate. Alkylbenzene consists of a mixture of phenyl substituted n-alkanes of 9 to 14 carbon atoms. Prior to 1965, alkylbenzene was synthesized from propylene tetramer, obtained by oligomerization of propylene. The resulting hard alkylate was a highly branched chain compound. However, the slow biodegradability of propylene tetramer-based materials soon became apparent and by 1965, most of the detergent industry had switched over to linear alkylbenzene. Extensive research has demonstrated... 

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