Process for preparation of sulphonates

Details Process for preparation of sulphonates Process for preparation of sulphonates

1995-04-06

1997-11-04

Conrad, Joseph

Organic compounds -- part of the class 532-570 series

Organic compounds

Sulfonic acids or salts thereof

C07C30302, C07C30931

Patent

active

056841841

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a method for the preparation of basic or neutral sulphonates and in particular to a method for the preparation of basic or neutral sulphonates which are essentially chloride free.
Basic or neutral sulphonates may be used as additives for lubricating oils such as passenger car, diesel and marine engine lubricants. Basic sulphonate additives are generally known as either low base number sulphonates or high base number sulphonates. Neutral and low base number sulphonates function primarily as surfactants, detergents and rust inhibitors. High base number sulphonates primarily function to neutralise acids produced in the oil during use. These sulphonates also help to inhibit corrosion and reduce sedimentation during use.
Neutral and low base number sulphonates for use as oil additives are usually prepared by the neutralisation of a sulphonic acid with a basic salt such as a basic calcium salt e.g. calcium oxide or hydroxide in a suitable diluent oil. The sulphonate product may be a mixture of a number of species; when calcium hydroxide is used these species may include the following: ##STR1## (ii) A basic calcium sulphonate ##STR2## (iii) A calcium sulphonate ##STR3## (iv) A calcium sulphonate hydrate ##STR4## wherein R is an organic moiety and x denotes at least one molecule of water of hydration.
In addition dispersed calcium hydroxide may be present.
When preparing low base number sulphonates the basic salt is added in stoichiometric excess to that required for complete neutralisation of the sulphonic acid so that the resulting product is basic.
EP-A-135920 describes the preparation of alkaline-earth metal salts of alkaryl sulphonic acids containing from 1.5 to less than 3 wt. % water without requiring azeotropic distillation using a polar solvent and by limiting the water in the reaction mixture. Preferably the sulphonic acid is "proportioned" into the reaction mixture (i.e. added at a rate to give the required rate of salt formation). The small amount of water may be introduced as a sulphonate solution. Basic materials such as amines are added at completion of the reaction to make the product basic.
High base number sulphonates are generally prepared by a process of neutralisation and carbonation. The sulphonic acid is first neutralised with excess basic metal oxide or hydroxide in a suitable diluent. Some of the excess basic metal oxide or hydroxide is then converted to metal carbonate via carbonation. Typically the reaction is carried out in the presence of a hydrocarbon and/or polar solvents such as toluene or methanol; the solvent is subsequently removed. The resulting product is a colloidal dispersion, in a diluent oil, of sub-micron particles of CaCO.sub.3 and CaOH.sub.2 which are sterically stabilised by the calcium sulphonate species produced by the reaction.
Whether neutral or overbased, it is desirable that the sulphonates for use in engine lubricants should be low in sediment and/or rapidly filterable, clear rather than hazy, not unduly viscous, and stable on storage, particularly against sedimentation.
Sulphonates have been prepared from natural sulphonic acids which in turn have been prepared by the sulphonation of a suitable oil fraction with sulphuric acid. Excess sulphuric acid in the reaction mixture is neutralised with sodium hydroxide and the sodium sulphonates formed are convened to calcium sulphonates by treatment with calcium chloride. The final products contain residual chloride from the calcium chloride treatment.
Sulphonates have also been prepared from synthetic sulphonic acids which have in turn been prepared for example by the sulphonation of C.sub.12 -C.sub.60 alkyl substituted benzene and/or C.sub.12 -C.sub.60 alkyl substituted xylene compounds. These sulphonic acids can be used to produce sulphonates which do not have residual chloride present. It has been found, however, that some synthetic sulphonic acids cannot be satisfactorily neutralised with calcium hydroxide or lime to produce calcium sulphonates; the attempted neutralisation results i

REFERENCES:
patent: 4891155 (1990-01-01), Fernley et al.

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