Determination of Traces of Nickel and Vanadium in Petroleum Distillates An X-Ray Emission Spectrographic Method Based on a New Rapid-Ashing Procedure JOHN
E.
SHOTT, Jr., THOMAS J. GARLAND, and RALPH 0. CLARK
Gulf Research & Development Co., Pittsburgh, f a .
b A rapid method for the determination of nickel and vanadium in petroleum and related products has been developed. By burning the sample in the presence of benzenesulfonic acid, the metals are retained as effectively as in a sulfuric acid-coking method, and the ashing can b e completed in a fraction of the time. The analytical procedure i s based on the use of this ashing technique followed b y measurement of the x-ray line intensities of the metals directly from the ash. An internal standard, cobalt, i s added to the oil prior to ashing. To obtain the ash in a form suitable for x-ray measurement, it i s washed onto the surface of a filter disk. The procedure requires less than 1.5 hours for a complete analysis. The new technique i s especially valuable in the concentration range below 2 p.p.m., although it can be employed up to several hundred parts per million.
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the major analytical problems in the petroleum industry has been the determination of trace quantities of metals, especially nickel and vanadium, in various oil products such as crudes, charge stocks, residua, and other similar materials. With the current trend toward computer-controlled refining processes, rapid methods of analysis are mandatory, with continuous analytical monitoring of process streams as the ultimate goal. While this has been accomplished in several analytical procedures, such as viscosity measurement and the determination of certain functional groups by infrared spectroscopy, the determination of less than 1 p.p.m. of both nickel and vanadium apparently must remain, a t least for the present, as a representative sampling process. Most current techniques for determining nickel and vanadium in oils require ashing the sample followed by photometric or spectrographic determination of the metals in the ash. Due to the difficulties involved in the ashing step, these procedures are lengthy NE OF
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ANAlYTlCAL CHEMISTRY
and subject to many variables nhich can affect the accuracy, especially in the
