JPS6342747B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method and apparatus for measuring the amount of oxygen consumed by oxidation of petroleum products as a method for measuring the oxidation stability of petroleum products.

The conventional method for testing the oxidation stability of petroleum products is to measure the amount of oxygen consumed by oxidation of petroleum products by bringing the petroleum product into contact with oxygen at a constant pressure in a reaction vessel, and reducing the amount of oxygen consumed by the absorbed oxygen. This equipment uses an oxygen supply device to maintain a constant internal pressure, which requires a complex combination of glassware, an electrolyzer to supply the oxygen necessary to maintain a constant internal pressure, and a mercury manometer. etc., making the equipment more complex and larger.Also, for petroleum products with high vapor pressure, a cold trap is required, making the equipment even more complicated. Moreover, it has drawbacks such as low accuracy in measuring oxidation stability at an early stage when the amount of oxygen absorbed is small.

An object of the present invention is to provide a method for measuring oxidation stability and a simplified device for use therein, which eliminates the above-mentioned drawbacks and allows rapid and reliable results to be obtained with relatively simple operations. It is in.

That is, the present invention involves bubbling a standard gas with a known oxygen concentration through an inorganic heat-resistant reaction vessel containing a petroleum product sample at a constant rate, and quantifying the amount of oxygen consumed by reaction with the sample. This invention relates to a novel oxidation stability measurement method for calculating oxygen absorption rate and an apparatus used therefor.

The apparatus of the present invention will be explained with reference to FIG. A constant flow rate of standard oxygen gas, for example one diluted with an inert gas such as nitrogen or helium, from a standard oxygen gas cylinder 1 with a known concentration is measured by a flowmeter 2, and then the inorganic heat resistant It is introduced into the reaction vessel 3. A petroleum product as a sample is placed in the reaction vessel 3, and is kept at a constant temperature by a constant temperature bath 4. The gas that has passed through the reaction vessel 3 is stored in a sample measuring tube 7, sampled at fixed time intervals by an automatic sample switching tank 6, and introduced into an analytical instrument 10 through a vapor removal column 9. 5 is a stirrer of the constant temperature bath, and 8 is an integrated flowmeter for accurately measuring the flow rate of gas. The vapor removal column 9 is a column for removing vapor generated from petroleum products other than standard oxygen gas components, and is intended to improve the accuracy of oxygen determination of the analytical instrument 10 and ensure long-term stable use of the analytical instrument 10. .

Next, a method for measuring oxygen absorption rate using the embodiment of the apparatus of the present invention shown in FIG. 1 will be described. A clean and weighed sample is taken into the reaction vessel 3, and standard oxygen gas is introduced into it and bubbled therein. After the amount of oxygen dissolved in the sample reaches equilibrium with the amount of oxygen in the standard gas, a catalyst is added from the top of the reactor to start the reaction. The gas whose oxygen concentration has been reduced due to the reaction is sampled at regular time intervals by an automatic switching device 6. The sampled gas passes through a vapor removal column 9 to remove gases generated from the petroleum product (sample) other than standard oxygen gas components, and then is introduced into an analytical instrument 10, where the amount of oxygen in the gas is measured. Ru. The oxygen absorption rate is calculated from the amount of decrease in oxygen content in the gas. The analytical instrument 10 is, for example, a gas chromatograph or an oxygen gas concentration meter, but is not limited to these as long as it can continuously measure the oxygen concentration.

FIG. 2 shows the results of time changes in the oxygen absorption rate of a sample measured by the method of the present invention.

Insulating oil equivalent to JIS No. 2 was used as the sample, and the amount of gas sampled at one time by the automatic sample switching device was set to 1.00 ml, and the standard oxygen gas contained 3% by volume of oxygen diluted with nitrogen. used gas. The volumetric flow rate is 25.0±0.2ml/min,
The temperature of the constant temperature bath was set to 95±1°C. Under these conditions, copper was used as the added catalyst, and the amount added was 800 ppb.
(A), 400ppb(B), 300ppb(C), 200ppb(D), 100ppb(E)
and the oxygen absorption rate was measured as 50 ppb(F).
As is clear from FIG. 2, it can be seen that differences in initial reaction rates due to differences in catalyst amount can be measured with high accuracy. Furthermore, when using the method of the present invention, differences in reaction rates due to differences in petroleum product types and lots can also be measured with high precision.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an embodiment of the apparatus for measuring oxidation stability of petroleum products of the present invention, and Figure 2 is a diagram showing the time change in the oxygen absorption rate of petroleum products measured using the measuring method of the present invention. It is a graph showing the results. (Main symbols in the drawing), 1: Standard oxygen gas cylinder,
3: Inorganic heat-resistant reaction vessel, 6: Automatic switching pot, 9: Vapor removal column, 10: Analytical equipment.

Claims (1)

[Claims] 1. A standard oxygen gas with a known oxygen concentration diluted with an inert gas is bubbled through an inorganic heat-resistant reactor containing a petroleum product at a constant speed, and the standard oxygen gas after the reaction is heated for a certain period of time. 1. A method for measuring the oxidation stability of petroleum products, which comprises sampling each sample and measuring the amount of oxygen that has not been consumed in reaction with the petroleum product. 2. An inorganic heat-resistant reaction vessel for bubbling petroleum products with standard oxygen gas of known oxygen concentration diluted with an inert gas, an automatic switching device for sampling the standard oxygen gas after bubbling at regular intervals, and a gas other than the standard gas. Oxidation stability measuring device for petroleum products, which is equipped with a column for removing gas.