JEAN PAUL JONES – "SOLVENT EXTRACTION – EDELEANU AND ESPENHAIN."
J. P. Jones. Dr. Schroeder, the material that I am going to present is presented in greater detail in the two reports 1/ on the Edeleanu Company and on the A.G. Sachsischewerke at Espenhain, which is a small town south of Leipzig. During the war, the Edeleanu Company had its offices and research laboratories in Berlin, and the principal officers were moved to Altenburg, where we were able to find the head men. They had done a considerable amount of work on solvent dewaxing, and in that connection had developed a new filter 2/, which was known to them as "Bandzellen filter," or a "continuous band filter," as it was translated. They had also done a small amount of work on an optical method of determination of wax and oil, where the was content was between about 20 and 60 or 80 percent, and a small amount of work on catalytic cracking of Diesel oil to lower its pour point.
In studying solvent dewaxing, or solvent extraction of oils, they developed what they considered a new method of analysis. By extracting a given quantity of oil with various quantities of a given solvent at a constant temperature, and plotting the result of some additive physical qualities, such as the density, or the viscosity gravity constant, for the extract against that of the raffinate, it was found that the values would like along a straight line. If a different solvent was used for that same oil at that same temperature, with varying ratios, another straight line would be produced by plotting the resulting values. These two straight lines would intersect at a point and that point was common for the intersection of all such straight lines, regardless of the extraction temperatures or of the solvent, so that this point of intersection could be determined simply by four determinations on any one oil and was a characteristic of that oil, being what is called an "ultimate theoretical best extract." Such a theoretical extract could, of course, not be reached, but was useful in making various determinations of the properties of an oil and its ability to be satisfactorily solvent-extracted. These straight lines resulted only if the oil being so analyzed was a distillate. If the oil was a residual fraction, the line was not always straight, but did have a portion which was straight, so that determinations sufficient to determine that you were on the straight portion of the line, would give a smaller point for a residual fraction.
The optical method of wax determination was to measure the passage of polarized light through a very thin layer of the wax-containing oil. This was done by placing the oil in a small receptacle such as is used for making a blood count, so that the thickness was very accurately determined and reproducible. Measuring, in with a previously plotted standard, the amount of polarized light passed by the particular sample of oil, with suitable calibration and in the range of wax content of 20 to 60 percent, the wax content could be very quickly and readily determined.
In order to lower the pour point of Diesel oils, they found that catalytic cracking at a temperature of about 400oC over an alkaline catalyst gave satisfactory results and a yield of about 85 percent of a Diesel oil having a pour point lowered from about plus 5oC in the original, to about minus 10oC in the product, without marked change in the centane number of the oil. Two catalysts were used, bauxite impregnated with 5-10 percent KOH, and equimolar NaOH and Ca(OH)2.
The solvent dewaxing process had been developed to a commercial scale and was in actual operation at the Espenhain plant. The Espenhain plant was primarily a plant for getting electrical power by burning brown coal (lignite). It had been built just prior to the war so that it represented the best thoughts of German industry at that time, since it had been built from scratch. The hydrocarbon part of that plant came from the German economy; it was necessary to recover all the possible hydrocarbon material from the brown coal before it was used as a fuel under the boilers of the electrical power plant. The rather large installation was solely for that purpose. Hydrocarbons were obtained by briquetting the coal, subjecting it to low temperature carbonization and then treating the low-temperature-carbonization-tar which resulted. The solvent-treating plant had been installed in active competition with similar plants for treating similar hydrocarbon materials by hydrogenation. It was brought out that the hydrocarbons present are primarily aromatic. The process that Edeleanu had developed primarily for this plant, involved first a distillation to produce a gasoline in small residue. The wax fraction was redistilled with a small amount of cracking. The original wax was both hard wax and soft wax, and it was their opinion that soft wax was iso-paraffinic; by that I mean it had a small amount of branching, whereas the hard wax was composed primarily of normal paraffins. A small amount of cracking knocked off the side chain producing a normal white, hard wax. After the redistillation, the second distillation with this small amount of cracking, the wax-containing distillate was extracted with raffinate separated out and was separated from the extract by centrifugal separation. To the SO2-extract, without removal of the sulfur dioxide, the wax-free middle oil fraction was added, naphtha was added and an extraction resulted to produce a heating oil and a raffinate which could be used as a Diesel oil. From the centrifuge, the sulfur dioxide raffinate was freed from sulfur dioxide, and then subjected to a solvent dewaxing at about 5oC with ethylene dichloride. It was at this point that their "continuous band wax filter" was employed. This produced a hard wax containing less than 1 percent of oil and a filtrate which contained soft wax. The soft was separated at about minus 20oC, using a rotary drum filter, such as is standard in many refineries. The filtrate from that operation was the second Diesel oil which could be combined with the first Diesel oil.
The first commercial model of the band filter was in operation at Espenhain; a photograph of it is in the Espenhain report and has recently been published by National Petroleum News.3/ A later model of the filter was projected for use, and had been completely installed in the underground lubricating oil plant at Porta, near Minden, known as Dachs I. However, it had never been in operation there. The filter consisted of an endless series of filter pans attached to an endless chain moving in a horizontal path. The mixture of wax and oil and solvent was added to each filter pan at one end of the horizontal path. The filtrate was removed by suction through a hollow shoe which was sliding along a hollow rail. After the filtrate had been removed while the pan was traveling along its path, one or more wash liquids could be added and sucked away from the wax cake, so by the time the wax cake reached and end of the path it had been washed oil-free. The filter pan then went over the sprocket wheel at the end of the endless chain and when it was upside down a blast of air was passed through the filter pan, from another hollow rail along which this hollow shoe was sliding, and the wax cake was blown down into a trap from which it was removed by a screw conveyor. At Espenhain, the pans were about 6 feet long and suction was entirely from one end of the pan. In the previously-mentioned underground lubricating oil plant, the pans were about 12 feet long and suction was from each side of the pan. In each plant the pans were about 1.5 feet wide.
The British were very interested in this filter, particularly the one in the underground plant, since the one at Espenhain is now in the area occupied by Russians. There was considerable talk in London in the late summer of 1945, of removing one of the filters from the plant to Great Britain for testing there against other known and previously developed filtering methods. Such an operation might be desirable, but would be very difficult physically, since the filters are at the back of the mine in which the plant is located.
W. C. Schroeder. Thank you very much, Mr. Jones. Is there any discussion, any questions? That seems to cover the subject quite fully. Were you reading that, or was it from notes?
J. P. Jones. No, just a brief outline.
W. C. Schroeder. If there is no discussion on that, I think we will move on to the next paper, which is "Butane Dehydrogenation," by John G. Allen.
1/ This material is currently being published in National Petroleum News, see issues of Feb. 6, 1946, pages R-83 to R-88; March 6, 1946, pages R-181 to R-184; April 3, 1946, and May 1, 1946.
2/ See picture in National Petroleum News, December 5, 1945, page R-150.
3/ December 5, 1945, page R-950.