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Linear alkylbenzene

BY

TECHNOLAB EL-BAHAA GROUP

GENERAL.DR

BAHAA BADR

01229834104

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)

Hazards

Main hazards flammable, relatively non-toxic

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 LABs.

They are mainly produced as intermediate in the production of surfactants, for use in detergent.

LABs have emerged as the dominant precursor of biodegradable detergents.

[2]

Hydrotreated kerosene is a typical feedstock for high purity linear paraffins, which are subsequently dehydrogenated to linear olefins:

CnH2n+2 → CnH2n + H2

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 aluminium 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]

Production details

the large scale applications of LAB-derived detergents, a variety routes have been developed to produce linear alkylbenzenes:

[3]
The HF/n-paraffins process involving dehydrogenation of n-paraffins to olefins, and subsequent reaction with benzene using hydrogen fluoride as catalyst.

This process accounts for the majority of the installed LAB production in the world.

It includes a PACOL Stage where n-paraffins are converted to mono-olefins (typically internal mono-olefins),

a DEFINE Unit whose primary function is to convert residual diolefins to mono-olefins, a PEP Unit which is essentially an aromatic removal unit - introduced before the alkylation step to improve LAB yield and quality,

an alkylation step where mono-olefins, both internal and alpha olefins, are reacted with benzene to produce LAB in the presence of HF catalyst.

The DETAL process involving dehydrogenation of n-paraffins to olefins, and subsequent reaction with benzene using a fixed bead catalyst.

This is newer technology and has several of the stages depicted in the HF/n-paraffins process, but it is principally different in the benzene alkylation step, during which a solid-state catalyst is employed.

There is a developing transalkylation (TA) stage to the Detal process wherein any higher alkylated benzenes (HAB) are contacted with additional benzene over a transalkylation catalyst.

The Friedel-Crafts alkylation process involves chlorination of n-paraffins to monochloroparaffins followed by alkylation of benzene using aluminum chloride (AlCl3) catalyst.

This method is one of the oldest commercial routes to LABs.

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 ALKYL BENZENE 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.

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.

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.

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–PHYSICAL AND CHEMICAL PROPERTIES

Appearance Clear Colourless liquid

Odour Odourless

Solubility in water Slightly soluble

Relative Density (H2O=1) 0.858 – 0.868 @ 15.5 °C

Boiling Point °C 278 – 314 °C

Melting Point °C < -70°C

Relative Vapour Density (Air=1) 8.4

Flash point °C 140°C

Auto ignition °C NA

Vapour pressure (hPa) @ 25 °C 0.013

Molecular weight 239-245

Explosive limits in air % by volume NA

pH NA
Viscosity cst @37.7 °C 4.4

Pour point °C <-50

Evaporation rate (water=1) NA

Octanol/water partition coefficient log Kow 7.5 – 9.12 @ 25 °C

% volatile NA

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