Polyhydroxy-Polyalkylene-Polyamine Salts of Maleic Amide Acids as Corrosion Inhibitors in Water-in-Oil Emulsions

1. Field of the Invention

This invention relates to the corrosion inhibition of iron or metal containing iron in contact with water-in-oil emulsions.

2. Description of the Prior Art

In technical processes where iron or metals containing iron come in contact with aqueous systems, the problem of corrosion is encountered. These problems are particularly serious when the aqueous system is based on salt water as is normally the case in numerous natural oil recovery and treatment processes.

From German published application No. 24 37 920 adducts of maleic anhydride to longer chained unsaturated fatty acids are known which are used as corrosion inhibitors for salt water-in-oil emulsions. In some cases, however, these substances are not sufficiently effective.

From German Application No. 11 49 843 amine salts of amide acids are known which are obtained by reaction of, for instance, maleic anhydride with alkyl amines containing 4 to 30 carbon atoms per alkyl group and subsequent neutralization with such amines and which act among other things as rust preventives even in the presence of sea water.

However, these substances are either not water soluble or if they are in the form of lower amine salts are very difficult to dissolve in water, which prevents their use in water-in-oil emulsions which are to be separated later since the substances will then be present only in the oil phase thus allowing the salt water to freely corrode the iron which is present in the lines and in the vessels used.

The purpose of this invention was to determine substances which are effective as corrosion inhibitors in those petroleum-containing liquids which come in contact with iron or metals containing iron in the recovery, processing, transport, and storage of petroleum. That is, they must be soluble and/or dispersible in the water as well as in the oil phase of said liquids in order to uniformly protect the corrosion prone metals. Another goal of this invention consisted of finding such corrosion inhibitors which can be uniformly distributed at least in a colloidially dispersed form even in concentrated salt solutions.

Salts of maleic amide acids are effective corrosion inhibitors for iron and iron-containing metals in the presence of water-in-petroleum oil emulsions. The salts of the invention have the formulas: ##STR1## in which R.sup.1 represents C.sub.7 to C.sub.20 alkyl radical, R.sup.2 stands for hydrogen or R.sup.1 and A.sup.+ represents the protonized radical of an amine of formula II ##STR2## in which B stands for hydrogen or the radical (C.sub.2 H.sub.4 O).sub.x, wherein x is an integer of 1-3 provided that the total number of the C.sub.2 H.sub.4 O radicals in the molecule is 3-18 and m stands for 1 or 2.

Salts with similar structures, namely, alkanolamine salts of specially defined maleic amide acids, that is, substances which are based on ammonia, which was ethoxylated once or several times are known from German published Application No. 27 58 123. They are used as corrosion inhibitors in technical cleaning and cooling processes where emphasis is placed on pronounced low foaming properties in addition to the corrosion protection effect. They are less suited for oil processes since these materials are not very soluble in the oil phase.

The maleic amide acids upon which the salts are based have the formula: ##STR3## wherein R.sup.1 represents an alkyl radical having 7 to 20 carbon atoms and R.sup.2 represents hydrogen or R.sup.1.

Preferred representatives are compounds having the formula III, in which R.sup.2 represents hydrogen. Among these formulas, in turn, those are preferred where the amide acid is derived, for instance from C.sub.10 to C.sub.18 primary alkyl amines. Of particular technical interest are maleic amide acids such as maleicoctyl-, -decyl, -dodecyl-, -tridecyl-and/or -octadecylamide acid, containing straight chained or branched alkyl groups. These maleic amide acids can also be used as mixtures. The amines upon which the amide components are based can be derived, for instance, also from C.sub.9 to C.sub.11, also from C.sub.13 to C.sub.15, or C.sub.17 to C.sub.19 oxoalcohol mixtures.

The salt components of the maleic amide acids are derived from the ethoxylated polyalkylene polyamines as defined by formula II. In this formula m represents 1 or 2, that is, the basic materials are diethylenetriamine, triethylenetetramine, or mixtures thereof. Higher or lower polyalkylene polyamines display a reduction in their effectiveness. Preferred are compounds having 5 to 10 ethoxyl groups in the amine cation since when combined with the maleic amide acid, these best display the solubility properties corresponding with the goals of this invention.

The salts according to this invention may be used in all systems based on crude oil and (salt) water emulsions. They display good effectiveness, for instance, in crude oil demulsification processes and during the transport of such crude oil emulsions. The corrosive attack of the salt water separated during the emulsifying processes, which is also removed by pipelines containing iron, is inhibited by the addition of the salts according to the invention. The salts are added to the water-in-oil emulsions in quantities of 50 to 500 ppm.

The following examples illustrate various aspects of the invention but are not intended to limit its scope. Where not otherwise specified throughout this specification and claims, temperatures are given in degrees centigrade and parts, percentages, and proportions are by weight.

The following compounds were used as corrosion inhibitors.

(1) Maleic iso-tridecylamide acid as salt of the fivefold ethoxylated diethylenetriamine.

(2) Maleic iso-tridecylamide acid as salt of the tenfold ethoxylated diethylenetriamine

(3) (Control) Maleic iso-tridecylamide acid-triethanolamine salt (according to German published Application No. 27 58 123).

A 5 percent aqueous solution of (1) was added in in different quantities to a mixture of test gasoline and a 3 percent NaCl solution under a CO.sub.2 atmosphere. Steel sheet (carbon steel) was placed in these mixtures and was left in the mixture for twenty-one days. Following this period, the corrosive material reduction was determined. The material reduction is listed in percent of the blank value.

The same mixture was tested but under a H.sub.2 S atmosphere.

In this case a salt water-in-oil emulsion (Reitbrook Crude Oil) was used and the remaining procedure was that described in Example 1.

The results are listed in the following table:

While this invention has been described with reference to certain specific embodiments, it will be recognized by those skilled in this art that many variations are possible without departing from the scope and spirit of the invention.