Antioxidant properties of engine oil detergent additives

The antioxidant properties of engine calcium sulphonate, phenate and salicylate detergent additives were investigated. Their influence on engine oil oxidation both in the presence of metallic copper, oil-soluble copper compounds, and without any catalyst, was studied. The influence of the detergent type and its basicity on oil antioxidant properties was determined. The specific influence of the co-operative action of detergent additives and zinc dithiophosphate on the antioxidant properties of engine oil formulations with these additives was established. The results obtained revealed various new patterns concerning the oil oxidation process, and allowed us to characterise the process of depletion of detergent additives during oil ageing.     

Investigation of long-term engine oil performance using lab-based artificial ageing illustrated by the impact of ethanol as fuel component

The effect of ethanol and its combustion products on the lubrication system is not very well understood. In this paper, a novel lab-based artificial ageing method for the evaluation of engine oils for bio-fuelled automotives and the results thereof are presented. Artificial ageing of three fully formulated engine oils with addition of ethanol, acetaldehyde, and acetic acid was carried out. The oil formulations chosen represent a consequent series of optimisation steps based on the engine oil performance in terms of preservation of typical oil parameters, e.g. base reserve and oxidation, observed during the artificial ageing procedure. It was shown that ethanol as well as acetaldehyde has almost no effect on the oil degradation especially in the case that advanced additive technology was used. On the contrary, acetic acid significantly affected the formulated oil showing influence on the detergent chemistry and even caused sludge formation. The use of the novel artificial ageing method proved to clearly differentiate the impact of the respective compounds added with the possibility to simulate enhanced stress conditions without the need of time-consuming and expensive engine bench tests. Hence, the novel setup offers valuable input for the formulation and the pre-selection of future engine oils suitable for bio-fuel.     

不同氧化条件下柴油机油的氧化降解研究

为探讨氧化温度、时间以及金属催化氧化等因素对柴油机油性能的影响,采用高温烘箱以及氧化测试仪模拟不用的氧化条件,研究柴油机油氧化前后部分理化性能、摩擦学性能的变化,分析不同氧化条件对柴油机油的氧化过程及性能的影响规律.结果表明:高温烘箱试验后发动机油的理化性能、抗氧化性能以及摩擦学性能会有一定程度的劣化,但变化幅度不大,...     

Factors affecting the dissolution of copper in transformer oils

The effect of addition of acids, peroxides and model N‐containing compounds to the oils on the rate of the copper dissolution from a copper strip into the oils was studied. The oils used were poly‐alpha‐olefin 2 (PAO‐2) and a highly refined naphthenic oil. Acids and peroxides were found to increase the copper dissolution into the oil, whereas the model nitrogen‐containing compounds exhibited a surface passivatory effect. The presence of the oil's partial oxidation products was found to increase the dissolution of the copper into the oil. The reasons for these observations are discussed. The relative contribution of the electrochemical and chemical processes to the copper corrosion is discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

油酸甲酯对柴油机油热氧化性能影响研究

为研究生物柴油对柴油机油的影响,在柴油机油中分别加入质量分数10%和20%油酸甲酯,研究氧化前后油酸甲酯对柴油机油黏度、酸值和正戊烷不溶物含量的影响,量化了不同油酸甲酯含量对柴油机油各理化性能的影响百分比,从而得到不同油酸甲酯含量对柴油机油热氧化性能影响的总体百分比。结果表明:油酸甲酯的加入加快了柴油机油样品中高分子聚合物、酸性物质和正戊烷不溶物的生成,导致黏度和酸值增加;油酸甲酯对柴油机油酸值的影响最大,对黏度的影响其次,对不溶物含量的影响最小,说明加入油酸甲酯后,易较快地生成酸性物质是其诱导柴油机油氧化变质的主要原因;加入油酸甲酯越多,油酸甲酯对柴油机油热氧化性能的影响越大,这是因为随着油酸甲酯的逐渐加入,它的稀释作用会使柴油机油的性能衰减加剧。     

甲醇汽油对汽油机油氧化和硝化的影响

应用红外光谱技术,根据不同物质在红外光谱仪中的吸光度不同,研究了在汽油机油中加入不同配比和含量的甲醇、甲醛和甲酸对汽油机油的抗氧化性和抗硝化性的影响。结果表明,加入甲醇、甲醛和甲酸后的油样和汽油机油相比,氧化和硝化程度都增大了;加入甲醇汽油的油样和加入甲酸或甲醛的油样相比,硝化值和氧化值都比较大,表明甲醇汽油对汽油机油的抗氧化性和抗硝化性的影响最大,甲醛和甲酸的影响较小。     

菜油乙酯作为润滑油基础油的研究

菜籽油或菜籽油与矿物油混合作为润滑油其抗氧性特差,易产生大量油泥。采用菜籽油酯交换生成乙酯的方法改善了菜籽油的抗氧抗油泥性,考察了菜油酯化物氧化老化性能和主要理化指标,分析了不同酯交换程度对菜油乙酯流变性能以及摩擦学性能的影响。氧化老化试验表明,氧化后的乙酯油泥含量比菜油大为减少,这是由于菜油乙酯初步氧化生成的为油溶性的线型聚合物,避免了油泥的产生。菜籽油酯交换生成的菜油乙酯的粘度指数高,将菜油乙酯和矿物油混合可大大改善矿物油(尤其对低的粘度指数基础油)的粘温性能和生物降解能力。     

Effect of worn metals on the oxidation of lubricating oils

Worn metals (copper, iron, Ni-Cr and aluminium) are found in used motor oils as a result of the friction of movable engine parts. Their effect on the deterioration rate of these oils was studied.Although iron and Ni-Cr were found to exist at lower concentrations than copper, their effect on the deterioration in the detergency power of the oils was stronger. This effect can be attributed to the high reactivity of their ions, which form complex compounds with the polar groups of the detergent additives tested.Copper was found to increase the oils' oxidation rate substantially and this can be attributed to its being a heterogeneous oxidizing catalyst, which resulted in the high oil deterioration. However, because copper has a low propensity to form complex compounds, its effect on the detergency power was relatively weak.When combinations of these metals were present the same characteristics were exhibited.     

Studies on boundary lubrication properties of oxidised coconut and soy bean oils

Vegetable oils are a potential source of base oils for biodegradable lubricants, with limited oxidative stability. This study focuses on the effect of long‐term ageing and the influence of oxidation products on the boundary lubrication performance of coconut and soy bean oils, by subjecting them to accelerated ageing in a dark oven at elevated temperature. The samples were collected at regular intervals and analysed for the changes in viscosity, percentage of free fatty acid and peroxide number compared to fresh oil samples. The boundary lubrication properties of these samples were evaluated using a four‐ball tester. Increased wear observed with aged oil samples was linked to the destruction of triglyceride structure and formation of peroxides. The difference in the wear properties of soy bean oil to coconut oil was accounted by its high content of unsaturated fatty acids and its susceptibility to undergo oxidation. It was concluded that the coconut oil can perform as a better lubricant and has got a better storage life compared to soy bean oil. Copyright © 2009 John Wiley & Sons, Ltd.     

Oxidation of mineral base oils of petroleum origin: The relationship between chemical composition,thickening, and composition of degradation products

The aim of this study was to improve understanding of high-temperature oxidation of base oils used in automobile engine oil formulations. Various oils were investigated: oils from the Middle East and the North Sea, with high and low aromatic and sulphur contents respectively; a hydro-isomerised polyalphaolefin oil with no aromatic or sulphur content; and a hydrocracked oil of intermediate composition. The influence of the aromatic and sulphur content and composition of the oils on thermo-oxidative degradation is investigated. These compounds give base oils natural protection from oxidation, but, under severe oxidation conditions, in the presence of a catalyst such as iron, which is always present in an engine, they become precursors of deposits. The action of two types of additive, radical inhibitors and hydroperoxide decomposers, was studied through oxygen consumption and thin-film oxidation tests. The oxidation products were identified; these provide insight into the degradation processes of the compounds during oxidation. They show too the influence of these processes on the formation of oxidised volatile species, on the increase in viscosity of the oil, and on the formation of oxidised species of high molar mass which, as they condense, contribute to the formation of insoluble compounds and deposits.     

Findings from a fleet test on the performance of two engine oil formulations in automotive CNG engines

This work presents a comparative assessment of engine oil performance on field test using urban transport vehicles powered by compressed natural gas engines using two different mineral oil formulations approved by engine manufacturer. The first one is considered as a baseline reference, and the second one is a higher quality formulation in terms of base stock refining and additive content. Higher quality oil has shown a significant enhanced lubricant performance, leading to reach the oil drain interval defined by engine manufacturer on these engines without penalties in maintenance costs. In order to assess oil performance, an oil analysis programme has been established for oil samples collected from vehicles operated under real service conditions in an urban transport fleet. Monitored parameters include oxidation, nitration, aminic anti‐oxidant additives depletion, anti‐wear additives depletion, total acid number, total basic number and remaining useful life number (as an estimation of anti‐oxidant additive depletion including aminic and zinc dialkyldithiophosphate). Results obtained in more than 90 samples from 15 different vehicles have shown higher degradation rates for low quality lubricant oil formulation. This deviation can be explained taking into account factors related with lower anti‐oxidant additives content and lower thermal stability that can be mainly related with the base stock quality. This lower oil performance can be finally converted into higher vehicle maintenance cost and lower engine reliability. Copyright © 2013 John Wiley & Sons, Ltd.     

Assessment of the useful life of current long‐drain and future low‐phosphorus engine oils

The assessment of engine oil useful life is an important step in the development of future low‐phosphorus, catalyst‐compatible, and long‐drain engine oils. This paper describes the development and application of a new laboratory screening test, the Ford oil ageing test (FOAT), for the assessment of engine oil useful life. FOAT simulates the Sequence IIIE engine dynamometer test and evaluates oils on the basis of viscosity increase. It correlates well with both single‐ and double‐length Sequence IIIE test results. FOAT allows for inexpensive screening of candidate oils prior to engine tests and is currently being used in the evaluation of future low‐phosphorus engine oils. This comparative study has demonstrated that low‐phosphorus, catalyst‐compatible engine oils can be formulated to provide a similar useful life to current commercial long‐drain oils.     

船舶柴油机油质量劣化规律研究

对船舶柴油机油劣化规律进行模拟氧化试验和船舶行驶试验研究,运用红外光谱和理化指标分析所取样品的酸值、碱值、闪点、氧化值等.结果表明,模拟样品和跟踪样品随着氧化时间和航程的增加,呈黏度增加、酸值升高、碱值降低,氧化值、硝化值增大的变质趋势,且理化指标和红外指标有很好的相关性.模拟氧化试验和跟踪取样的样品的红外和理化数据变化一致,因此可以用模拟试验的数据来预测实际样品的衰变.应用模拟氧化试验可以快速研究柴油机油的劣化规律,采取红外和理化相结合的方法能够评价柴油机油的质量变化程度,实现按质换油.     

Oil Degradation in a Diesel Engine with Dual-Loop Lubricating System

A common lubricating oil sump is used in most modern internal combustion engines for cooling, wear protection, and friction reduction. This requires compromises during base oil and additive selection as a result of differing needs for lubricant performance in engine subsystems. The use of a dual lubricating loop, providing separate oil sumps for the power cylinder and valve train subsystems, was investigated experimentally to determine the effect of system segregation on oil degradation. A small diesel engine was modified, installed in a commercial generator unit, and operated for one oil drain cycle. Oil sampling was tailored to assess base and acid numbers, oxidation, soot concentration, water content, and viscosity changes. The experiment complemented an earlier study that investigated the fuel economy benefits of such a lubricating configuration. These include longer drain intervals for the cylinder head and power cylinder subsystems, improved wear performance for the valve train, and opportunities for alternative material selection during engine design. The experiment demonstrated protection of the valve train subsystem from soot contaminants in the power cylinder. Lower total acid number and oxidation tendency was also observed in the valve train.     

Interactions of Engine Oil Additives

Modern engine oil formulations usually contain many kinds of additives, such as detergent-dispersants, antioxidants, VI improvers, rust inhibitors, and friction modifiers. However, what these additives do in the crankcase is not yet fully understood. As a first step in clarifying the complex mechanisms of engine oil performance in the crankcase, the interaction of engine oil additives was studied on the basis of surface chemistry.

Metallic detergents form rigid micelles in oil, whereas ashless dispersants associate moderately and form small micelles in oil. No interaction was found between metallic detergents and zinc dithio-phosphate (ZDP), but there were strong interactions between ashless dispersants and metallic detergents and between ashless dispersants and ZDP. The adsorption onto an iron surface, the solubilization of sludge, and oxidation inhibition by engine oil additives are strongly influenced by the state of solution of these mixed systems.     

有机铜盐抗氧剂及其作用机理

由于为了降低汽车尾气催化剂转化器的中毒而减少磷含量,以及满足更长时间的运行和高温条件,润滑油需要在越来越苛刻的条件下使用。ZDDP已不能满足这些条件,特别是P的浓度限制在0．(15～0．08％的情况下。这就需要新的无P高温抗氧剂来补充ZDDP的作用。近来,有文献报道,过渡金属盐类,特别是铜能够抑制润滑油的氧化,比传统抗氧剂芳胺和酚具有更好的抗氧能力。但对有机铜盐高温抗氧剂的作用机理研究,是近几年来才进行的,时止今日对有机铜盐高温抗氧剂的作用机理仍没有统一的认识,特别是对一价铜与二价铜的作用机理的认识存在很大的差别,甚至是相反的结论。本文拟就有机铜盐高温抗氧剂的类型及作用机理作一简述。     

基于红外光谱技术的两用燃料发动机油抗劣化性研究

应用红外光谱技术,根据润滑油组分中各官能团的红外光谱吸收峰的出现和变化,研究了开发的CNG/汽油两用燃料发动机润滑油与参比油在运行期间,润滑油的氧化值、硝化值、硫化值的变化程度,发现CNG/汽油两用燃料发动机润滑油运行18 000 km后,其氧化值变化范围为2.45(ABS/0.1 mm)、硝化值变化范围为2.03(ABS/0.1 mm)、硫化值变化范围为3.85(ABS/0.1 mm)。结果表明CNG/汽油两用燃料发动机润滑油有着良好的抗劣化性能,红外光谱技术是研究润滑油抗劣化性的有效方法之一。     

Composition and oxidation stability of SAE 15W-40 engine oils

The modified IP 48 procedure was used for testing the oxidation stability of engine oils for ignition engines of the SAE 15W-40 and minimum API SG/CD specifications. Eight engine oils, such as Agip, BP, Esso, Mogul, ÖMV, Petro-Canada, Shell, and Total, were collected and oxidised. Oils were also fractionated by using chromatographic methods, and group composition of base oils, amount of VI improvers and other additives were determined. Several differences in the oxidation stability were found between the collected oils. Viscosity characteristics, carbon residue, acid number, amount of pentane insolubles and mass losses during the test were chosen as parameters for evaluation of the oxidation stability of the oils. The most stable engine oil was blended from a hydrocracked base oil whereas most of the other oils were based on the solvent refined oils.     

Electrochemical mechanisms of the dissolution of metals and the concomitant oxidation of lubricating oils under high temperature friction conditions

In used motor oils worn and dissolved metals (e.g. copper, iron, Ni-Cr and aluminium) are found as a result of erosion and/or corrosion of the movable engine parts. These suspended and dissolved metals cause an oxidative deterioration of the motor oil, as indicated by its increase in viscosity and acidity, and a decrease in its detergency etc. The recent work of Abou El Naga and Salem, carried out under controlled laboratory conditions, provides excellent data for examining various mechanistic proposals.It is shown here that the oxidation of the oil occurs through a peroxide route involving electrochemical (on open circuit) reduction of oxygen with metal dissolution (i.e. corrosion) as its conjugate anodic reaction. In fact, it is found that the amount of oil oxidized is proportional to the amount of metal corroded, irrespective of the nature of the metal. Electrochemical reactions appropriate for this situation are suggested; it is pointed out that the proposed mechanism is consistent with the modern theory of corrosion and electrocatalysis.     

Proposal of an FTIR Methodology to Monitor Oxidation Level in Used Engine Oils: Effects of Thermal Degradation and Fuel Dilution

This article describes a procedure, based on ASTM standards D7214 and E2412, that has been defined to improve quantification of oil oxidation in used engine oils. Taking into account typical problems that can be found in this type of sample, including thermal oxidation and fuel dilution, Fourier transform infrared (FTIR) spectra were analyzed also considering the effect of the oil formulation. Two zones were considered inside the typical wavenumber range for quantification of oxidation, where those problems can be detected and assessed more easily: zone A between 1725 and 1650 cm^?1, where the main oxidation products, such as aldehydes, carboxylic acids, and ketones, occur due to thermal degradation of the oil; and zone B between 1770 and 1725 cm^?1, where esters due to potential biodiesel dilution problems are detected.