Background on Sodium Sulfonate Problem
by Bill Sluhan, Master Chemical Corp, Perrysville, OH
News Item in News Fax Vol 7 No. 6
In the latter part of the 19th century some refineries began producing a highly refined mineral oil called "white oil" which was originally used to make Vaseline and a number of other specialty lubricants (these days white oil is used primarily in making numerous kinds of plastic and rubber compounds). White oil was originally made by taking certain napthenic crude oils and reacting them with fuming sulfuric acid (called "oleum" in the trade); somewhere between 1.5 and 3.0% of the crude oil would react with the acid and would separate from the crude stream. The reacted crude would be sent onto the still (or these days to the cracking tower) and different fractions were separated for different uses. The reaction product of the acid and the crude oil is a dark, viscous mass that had no uses. However, if the excess sulfuric acid was removed and the reaction product was neutralized with caustic soda the result was still a dark viscous mass (called "mahogany soap", so called because it had the color of mahogany wood and was found to have the ability to emulsify mineral oils in water.) About 1890 someone discovered that if you mixed about 6-7% mahogany soap with refined mineral oil and the result was mixed with water you had a relatively stable dispersion of oil in water. Further, it was found this "water soluble oil" had some of the lubricating and rust inhibiting properties of mineral oils typically used as cutting and grinding lubricants at the time, but also had some of the cooling properties of water.
This neutralized mahogany soap is more properly called sodium petroleum sulfonate and over the years numerous uses have been developed for it. It has been widely used as the (or at least part of) the emulsifier package in soluble oils and semi-chemical (semi-synthetic) cutting and grinding fluids. They are also used to make the WWII GI's favorite rust inhibitor, Cosmoline as well as being used in solvent cut-back thin film rust inhibitors typified by WD-40 and similar products. If the sodium petroleum sulfonate is further reacted with calcium hydroxide you produce a material referred to as "over based" calcium sulfonate. This material is widely used in motor oils to disperse dirt and to neutralize acids that contaminate the oil as the result of the blow-by of combustion products into the crankcase; in today's engines blow-by occurs primarily when an engine is started cold.
As you stated in your note, the Shell facility has been producing about 80% of the petroleum sulfonate produced in the US today. However, you should be aware that about half of what Shell has been producing has been converted into over-based calcium sulfonate that goes primarily into motor oils. The balance of their sodium sulfonate goes into soluble oils, semi-chemical fluids, rust preventatives, etc., etc. Now there are a couple of other producers of sulfonates in North America and they will be expanding their production to some degree. In addition, there are several sources in Europe for synthetic sulfonates (which have the potential to provide better and more uniform quality emulsifiers) as well as some natural sulfonate production in the old Soviet Union (pretty poor quality, as you would expect) in India, Indonesia and even in Venezuela (if they can ever solve their political "squabbling").
You will recall that Shell experienced a problem with sulfonate production in 1993 when there was an explosion and fire at the Rhone-Poulenc waste acid reprocessing facility adjacent to Shell's Martinez refinery. Because there was no place to send their acid waste from the sulfonation plant Shell had to shut down and go into intermittent sulfonate production. There were shortages of sulfonate and what sulfonate that Shell could produce was of much poorer quality than was normal. Producers of soluble oils could not get all they needed and the users of these products found that they were having emulsion instability problems, corrosion problems and a much higher incidence of bacterial growth because of the poor quality. In the years since most formulators learned what was causing these problems and most have searched for alternative sources of supply and for alternative emulsifier systems.
Most of us recognized that in spite of Shell's stated commitment to the continued production of natural sulfonates at some point they would make a decision to shut down the Martinez, CA sulfonation plant. The reasons for that are:
1.The environmental regulations in California make it a terrible location for a refinery.
2. The sources of the napthenic crudes suitable for the production of natural petroleum sulfonates are running out.
3. There are alternative processes for the production of white oils today that produce better quality white oils at lower cost than does sulfonation. As a result of that
4. The production of sodium petroleum sulfonate had become an end in itself rather than a saleable by-product. The Shell sulfonation plant has far more capacity than is needed to meet demand for sulfonate. (Running any portion of a refinery at less then full capacity is a big money looser for the operating company.)
With the present recession in manufacturing in the US, the demand for cutting and grinding fluids, rust preventatives, etc. is down from three years ago. At that time Shell "swore on a stack of Bibles" before a group of us formulators that "they were in the sulfonate business for the long haul". They made an economic decision for Shell and while the decision is no doubt a wise one for Shell, their decision will have consequences for all of us who formulate or use products based on natural petroleum sulfonates.
1. Sulfonates are used in soluble oils and "semi-synthetic" fluids.
2. They are NOT used in the "straight synthetic" fluids
3. There are alternatives to natural sulfonates but (a.) They are generally more costly (b).They are generally not "drop-ins" so there will be time required to develop replacement products (c.) They have somewhat different emulsification properties and so formulations will become more complex.
I will predict that over the long term the products that will be developed will ultimately prove to be better performing products with longer useful lives. (The alternative emulsifiers will prove to have higher, more uniform quality and will, therefore, have better, more predictable performance.) In the interim however those who are used to using truly cheap soluble oils (based on re-refined oils and minimal percentages of emulsifiers) will find their costs for these products will "jump" dramatically (if they can buy them at all). And, I think that they will find that the performance of these products will give them "fits" in the near term. (People still get what they pay for.)
|