The issue of gums in oils

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I. The impact of gums on the actual use of petroleum products: Gums present in petroleum products are important indicators used to assess the stability of gasoline, to determine its tendency to form gums within engines, and to decide whether the gasoline can be used or continued to be stored. When the actual gum content of the gasoline added is too high, gum and carbon deposits are formed during combustion. A viscous gel-like substance forms in the fuel tank, filters, and carburetor; in severe cases, it can clog the fuel injectors and disrupt fuel supply. The gumy deposits that accumulate on the spark plugs can form carbon buildup at high temperatures, leading to short circuits. Coking on the intake and exhaust valves can cause them to close improperly, or even jam, resulting in complete failure of those valves. Carbon deposits that accumulate on the cylinder head, cylinder walls, and pistons can lead to poor heat dissipation in the engine, cause surface combustion or knocking, reduce the engine’s power, and increase fuel consumption. In severe cases, the engine produces abnormal noises whether the vehicle is cold or warm, there is idle vibration, significant loss of power, and in some instances the engine fails to start. II. Main causes of gum formation (1) Internal factors: Gasoline components produced by different processing methods vary greatly, and their stability also differs. Naturally distilled gasoline, hydrotreated gasoline, and reformed gasoline contain almost no olefins, and there are also few non-hydrocarbon compounds, so they have good stability. Catalytic cracking gasoline, thermal cracking gasoline, and coking gasoline contain a high amount of olefins and a small amount of dienes, as well as many non-hydrocarbon compounds; therefore, they have poor stability. In addition to unsaturated hydrocarbons, sulfur-containing compounds in gasoline, particularly thiophenes and thiolues, can also promote the formation of gums. The presence of nitrogen-containing compounds likewise leads to gum formation, causing the color of gasoline to turn red and darker upon contact with air, and even resulting in the formation of gel-like precipitates. Distilled gasoline fractions contain no unsaturated hydrocarbons, so they have excellent stability ； The gasoline fractions produced through secondary processing (such as cracked gasoline, etc.) have poor stability due to their high content of unsaturated hydrocarbons and other non-hydrocarbon compounds. (2) External factors: The influence of external conditions on the stability of gasoline. The deterioration of gasoline is not only closely related to its inherent chemical composition but also depends on various external factors, such as temperature, the effect of metal surfaces, and the size of the surface area in contact with air. Temperature has a significant impact on the oxidative degradation of gasoline. At higher temperatures, the oxidation rate of gasoline increases, the induction period shortens, and the tendency to form gums grows. Experiments show that for every 10°C increase in storage temperature, the rate of gum formation in gasoline increases by approximately 2.4 to 2.6 times. Gasoline inevitably comes into contact with various metal surfaces during storage, transportation, and use. Experiments have shown that under the action of a metal surface, gasoline not only tends to darken in color, but the accumulation of gums also accelerates. Among various metals, copper has the greatest impact, as it can reduce the induction period of gasoline samples by 75%; other metals such as iron, zinc, aluminum, and tin can also reduce the stability of gasoline. III. The main solutions for reducing gums, from a production process perspective, involve the use of hydrogenation units that enable direct saturation through hydrogenation, thereby eliminating unsaturated hydrocarbons that tend to form gums. This reduces the amount of such substances in the mixture, and as a result, the level of gums in the oil is decreased. But doing this not only reduces the gums, but it also **lowers the octane rating. Some oil treatment companies increase the induction period as a solution; the advantage of this is that it helps to raise the induction period and also effectively suppresses the growth of gums. However, it cannot deal with gums that have already formed, nor can it reduce the amount of gums in the oil, so it fails to address the root cause of the gum problem.