| Linear alkylbenzene | |
|---|---|
|
Other names
LAB, linear alkyl benzene |
|
| Properties | |
| Molecular formula | C6H5CHR1R2 where R1 = CnH2n+1 and R2 = CmH2m+1 m,n are integers m≥0, n≥1 (typically 10-16) |
| Appearance | colourless oily liquid |
| Density | 0.8628 g cm-3 |
| Boiling point |
282-302 °C |
| Hazards | |
| MSDS | MSDS |
| Main hazards | flammable, relatively non-toxic |
| Flash point | 145 °C |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| Infobox references | |
Linear alkylbenzene is a family of organic compounds with the formula C6H5CnH2n+1. Typically, n lies between 10 and 16, although generally supplied as a tighter cut, such as C12-C15, C12-C13 and C10-C13, for detergent use[1]. The CnH2n+1 chain is unbranched. They are sometimes called LAB's. They are mainly produced as intermediate in the production of surfactants, for use in detergent. Since the 1960s resulted in LAB emerging as the dominant precursor of biodegradable detergents.[2]
Contents |
Hydrotreated kerosene is a typical feedstock for high purity linear paraffins, which are subsequently dehydrogenated to linear olefins:
Alternatively, ethylene can be oligomerized (partially polymerized) to produce linear alkenes. The resulting linear mono-olefins react with benzene in the presence of a catalyst to produce the LABs. Hydrogen fluoride (HF) and aluminum chloride (AlCl3) are the two major catalysts for the alkylation of benzene with linear mono-olefins. The HF-based process is commercially dominant; however, the risk of releasing HF (a poisonous substance) into the environment became a concern particularly after the Clean Air Act Amendment. In 1995, a solid catalyst system (the DETAL process) became available. The process eliminates catalyst neutralization and HF disposal. Consequently, most LAB plants built since then have utilized this process.[3]
Given the large scale applications of LAB-derived detergents, a variety routes have been developed to produce linear alkylbenzenes:[3]
Each process generates LAB products with distinct features. Important product characteristics include the bromine index, sulfonatability, amount of 2-phenyl isomers (2-phenylalkane), the tetralin content, amount of non-alkylbenzene components, and the linearity of the product.
The production of n-paraffins often occurs as part of an integrated LAB plant where the producers start from kerosene as raw material. The UOP process for producing normal paraffin includes a kerosene prefractionation unit, a hydrotreating unit and a Molex unit.[4] The ExxonMobil Chemical technology includes a recovery process and can produce LAB grade n-paraffins from most medium to low sulfur kerosene without the use of a hydrotreater stage upstream. A desulfurization process is needed to reduce the sulfur content of some n-paraffins.
Linear alkylbenzene is sulfonated to produce linear alkylbenzene sulfonate (LAS), a biodegradable surfactant. LAS replaced branched dodecylbenzene sulfonates, which were phased out because they biodegrade more slowly.
LAB is currently used as a liquid scintillator in neutrino detectors (SNO+ for example[5] ) due to of its good optical transparency (~20 m), its high light yield, its low amount of radioactive impurities, and its high flash point (140 °C) which makes safe handling easier. The material performs well in deep underwater environments.[6] One study suggested LAB as a suitable material to be employed in a Secret Neutrino Interactions Finder (SNIF), a type of antineutrino detector designed to detect the presence of nuclear reactors at distances of between 100 and 500 km.[7]
LAB has been subject to concern about its effect on the environment and human health. European Council Regulation (EC) 1488/94[8] led to it being extensively evaluated. The life-cycle analysis considered the emissions and resulting environmental and human exposures. Following the exposure assessment, the environmental risk characterization for each protection target in the aquatic, terrestrial and soil compartment was determined. For human health the scenarios for occupational exposure, consumer exposure and human exposure indirectly via the environment have been examined and the possible risks identified.
The report concludes that there are no concerns for the environment or human health. There is no need for further testing or risk reduction measures beyond those currently practiced. LAB was therefore de-classified and was removed from Annex 1 in the 28th ATP (Directive 2001/59).