Lubricant Base Stocks Research Articles

Properties of naphthalene oligomers polyalkylated with linear 1‐alkenes

AbstractStar‐shaped alkylaromatic hydrocarbons consisting of oligomeric naphthalene cores and long straight‐chain alkyl arms have been synthesised using a one‐pot method:magnified imageWhere 1‐alkene is 1‐hexene, 1‐octene, 1‐decene, 1‐dodecene, 1‐tetradecene, 1‐hexadecene, and 1‐octadecene, respectively. Different linear 1‐alkenes with increasing chain length have been reacted with naphthalene oligomers in an identical way, and the properties of the total products compared and related to the chain length of the alkylating normal 1‐alkene. Consequent to this, increases in M̌n, (= 550–1900), viscosity indexes (90–161), pour points (—24 to + 17°C), flash points (210–330°C), and oxidation resistance, could be observed. These products exhibited properties good enough to be suitable for use as lubricant base stocks and/or additives.

Synthetics versus vegetable oils: Applications, options, and performance

AbstractEnvironmental concerns have brought forward vegetable oils as alternatives to more expensive synthetic lubricant base stocks, in moderate operating conditions. The contents of various acids, such as oleic and linoleum, can be changed by selective breeding to produce more desirable lubricating properties and less oxidation vulnerability.Different tests are needed for such lubricants, and the Baader test has been modified to show the ageing stability of rapeseed oil raffinate, TMP trioleate, dioctyl adipate, and HOSO. Such oils can also be modified with additive packages.

Nonequilibrium Molecular Dynamics Simulation of the Rheology of Linear and Branched Alkanes

Liquid alkanes in the molecular weight range of C20–C40 are the main constituents of lubricant basestocks, and their rheological properties are therefore of great concern in industrial lubricant applications. Using massively parallel supercomputers and an efficient parallel algorithm, we have carried out systematic studies of the rheological properties of a variety of model liquid alkanes ranging from linear to singly branched and multiply branched alkanes. We aim to elucidate the relationship between the molecular architecture and the viscous behavior. Nonequilibrium molecular dynamics simulations have been carried out for n-decane (C10H22), n-hexadecane (C16H34), n-tetracosane (C24H50), 10-n-hexylnonadecane (C25H52), and squalane (2, 6, 10, 15, 19, 23-hexamethyltetracosane, C30H62). At a high strain rate, the viscosity shows a power-law shear thinning behavior over several orders of magnitude in strain rate, with exponents ranging from −0.33 to −0.59. This power-law shear thinning is shown to be closely related to the ordering of the molecules. The molecular architecture is shown to have a significant influence on the power-law exponent. At a low strain rate, the viscosity behavior changes to a Newtonian plateau, whose accurate determination has been elusive in previous studies. The molecular order in this regime is essentially that of the equilibrium system, a signature of the linear response. The Newtonian plateau is verified by independent equilibrium molecular dynamics simulations using the Green–Kubo method. The reliable determination of the Newtonian viscosity from non-equilibrium molecular simulation permits us to calculate the viscosity index for squalane. The viscosity index is a widely used property to characterize the lubricant's temperature performance, and our studies represent the first approach towards its determination by molecular simulation.

Alkylated petroleum hydrocarbons as base stocks for lubricants

Alkylated petroleum hydrocarbons as base stocks for lubricants

Ester base stocks for synthetic lubricants

AbstractThis paper reports on work on the synthesis and characterisation of mixtures of aliphatic adipates with complex esters based on polyols, adipic acid, and monohydroxy alcohols, in order to formulate new synthetic base stocks. The viscosity and pour point values of these mixtures are higher than those of adipates. Both of these physical properties become greater with the increasing molecular weight of the complex ester or of the ester's concentration in the mixture.

FT‐NMR and FTIR applications in lubricant distillates and base stocks characterisation

AbstractLubricant distillates undergo different stages of refining in order to produce the quality required of base stock for lubricating oil formulations, incorporating different additives in various doses. It is essential to monitor the degree of refining at different stages and additive response in base stocks, using fast and accurate techniques. FT‐NMR and FTIR techniques offer a new dimension to the monitoring and characterisation of lubricant distillates and base stocks.In the present paper, an attempt is made to demonstrate the application of these techniques to deriving some average structural parameters and to correlate them with various physico‐chemical characteristics of lubricant distillates and base stocks. These correlations could be used to optimise various process parameters during the refining of lubricant distillates. If the process parameters are constant, such correlations could be used to predict the quality of the base stocks obtained from any change in the composition of the lubricant distillates. Various applications of FTIR in base oil characterisation and its processing are also reviewed.

Biodegradability of lubricant base stocks and fully formulated products

AbstractIncreasing awareness of the environmental impact of consumer and industrial products has produced a demand for lubricants that biodegrade. There is a number of biodegradation tests that can be used on lubricants, although not all are always appropriate, as this paper explains. The CEC test is among the best known and is in use for both conventional and synthetic oils. There will, in future, be a greater movement to biodegradable oils in Europe, perhaps extending to all oils.

Vegetable oils as a component of lubricant base stocks

Vegetable oils as a component of lubricant base stocks

Investigation of biomass formation during the biodegradation of ester base lubricants

AbstractComparative studies were performed to assess the biodegradation of the synthetic lubricant base stock, Priolube 3999, by P. putida using the CEC test method and manometric respirometry. Supplementary analyses demonstrated the production of a non‐readily biodegradable metabolite, trimethylol‐propane, the alcohol group of the candidate fluid. Evidence was obtained that indicated that a significant fraction of carbon added as test substance remained incorporated in the biomass. The implications of these results are discussed and modifications to the CEC test proposed.

A new high‐stability synthetic phosphate ester

AbstractNeutral phosphate esters are used as fire‐resistant basestocks in several applications including hydraulic systems, turbines, and compressors. They are also used as grease basestocks, and in hydrocarbon‐based lubricants and synthetic fluids as antiwear additives.Development aspects of a new synthetic triaryl phosphate ester is presented in this paper. This product provides superior hydrolytic stability and lower volatility than existing commercial phosphate esters. Additionally, it has excellent oxidative stability and is fire resistant. The performance characteristics of the fluid suggest use of this phosphate ester as a high stability antiwear additive or lubricant basestock, and in any application where stability is of primary importance.

Synthesis and properties of naphthalene oligomers polyalkylated with 1-octadecene and 1-hexadecene

A one-pot method is described for the synthesis of naphthalene oligomers polyalkylated with 1-octadecene and 1-hexadecene. The synthesis involves two steps: 1) oligomerization of naphthalene using an AlCl3/CuCl2 catalyst/oxidant system, and 2) polyalkylation with a 1-olefin. Characterization studies include1H- and13C-NMR spectroscopy, GPC and testing methods for lubricants. The degree of alkylation, variations in the alkyl groups, and the position of the substituent on the naphthalene ring were established by13C NMR spectroscopy. The purified products possess excellent properties for being suitable as a lubricant base stock, lubricant additives and functional fluids.

The design of fuel efficient automotive hypoid gear lubricants

Synthesised lubricant base stocks and the performance additives used in hypoid gear lubricants can both be chemically designed to give improved hypoid gear efficiency and, therefore, better vehicle fuel economy than provided by conventional lubricants In this paper, the authors review, relative to a widely used SAE 90 grade mineral oil-based lubricant, the changes in gear efficiency which have been documented using certain classes of synthesised lubricants. These advantages are described in terms of (a) EPA City and Highway Cycle efficiencies, (b) absolute data over a wide temperature range under four selected speed/torque combinations, and (c) absolute changes in inefficiency compared to the mineral oil product. Newtonian and non-Newtonian fluids have been studied. The bulk oil temperature at which a specific lubricant gives maximum efficiency is dependent on both gear operating conditions and on the chemical composition of the lubricant.

Investigation of the biodegradation process of a synthetic lubricant base stock

The biodegradation of the synthetic lubricant base stock PRIOLUBE 3999 was examined using several methods. The mineralization rate, the degradation determined by IR-spectroscopy (disappearance of CH 3 CH 2-groups), the formation of polar metabolites by DOC and the increase of the microbial biomass indicated by the DNA-content were measured. Differences of 33 – 40 % were found in the determinations of the degradation by mineralization and IR-spectroscopy. These differences can be explained by the formation of polar metabolites and of microbial biomass. The suitability of several standardized test methods dependent on the test substance is discussed.

Olefin oligomerization via zeolite catalysis

Oligomerization of terminal and internal long-chain, linear olefins has been successfully demonstrated using large pore zeolites with high silica-to-alumina ratios as catalysts. Both reactant and product selectivities have been demonstrated using 12-membered ring zeolites for the oligomerization of C12–C18 olefins. The catalytic activity of these zeolites decreases in the order faujasite > mordenite > pentasil; the activity of the Y-zeolites depends primarily upon the silica-to-alumina molar ratio, but not on the total acidity. 1-tetradecene oligomerization, followed by oligomer hydrogenation, yields synthetic lubricant base stocks with excellent physical characteristics.

Prediction of Viscosities Using Chemical Graph Theory

The viscosities of three groups of lubricant basestock molecules are predicted using chemical graph theory. Alkyl diphenylphosphates, trimethyloethane esters, and oligomers of chlorotrifluoroethylene are modeled. These compounds are similar for graph theoretical modeling purposes in that all are aliphatic in nature or vary only by aliphatic substituents. The graph theoretical approach for the modeling of these compounds uses summations of the shortest topological distances between atoms in the molecule. A new topological index is introduced that weights chlorine molecules in the chlorotrifluoroethylene oligomers. For each group modeled, the coefficient of determination r2 was in excess of 0.99 with a standard error of estimate well below five percent of the average value modeled.

Performance comparisons of synthetic and mineral oil crankcase lubricant base stocks

AbstractThe physical and performance characteristics of representative synthetic base stocks are compared with those of mineral oils. Comparisons of the base stocks alone and as fully formulated crankcase lubricants are presented.Bench test results and physical properties of unformulated synthetic and mineral oil base stocks are compared. The volatility characteristics of synthetic base stocks are superior to typical mineral oil base stocks. All the synthetic base stocks displayed greater viscosity indices than did mineral oils. Bench tests designed to measure thermal and oxidative stabilities are used to compare synthetic with mineral oil base stocks. Although synthetics appeared no more resistant to oxidation than did mineral oils, fewer sediments, deposits and fluid viscosity increases were observed with synthetic base stocks. No one type of synthetic base oil showed a distinct advantage in these evaluations.Fully formulated mineral oil‐based lubricants are compared with commonly used synthetic‐based lubricants containing identical additive treatments. The synthetic lubricants showed superior engine cleanliness, and resistance to viscosity increased in these tests, but were directionally less effective in wear prevention than mineral oil‐based lubricants. Proper formulation or addition of an antiwear supplement overcame this deficiency.These comparisons demonstrated that synthetic base stocks are available with a wide range of physical properties. Available synthetic base stocks offer performance advantages at an increased cost over mineral oils, but proper formulation of the synthetic lubricant is necessary to ensure totally acceptable lubricant performance.

Use of replication and signal‐to‐noise ratios in the identification and estimation of the composition of lubricant basestock mixtures using 13C nuclear magnetic resonance spectroscopy and projection into principal component/canonical variates space

AbstractThe theory of experimental error in analysis of mixture experiments by abstract factor analysis or target transformation factor analysis is considered. The theoretical implications of using signal‐to‐noise ratios (as weights) or canonical variates analysis to reduce the level of imbedded error in the factor model are examined. The approach is illustrated by application to 13C NMR spectra of lubricant basestock mixtures.

Effect of ashless additives on antifriction and antiwear properties of mineral oil

The lubricating properties of oils containing amidothiophosphates, two non-Soviet ashless additives designated 1 and 2 for test purposes, and a molybdenum-containing dithiophosphate are evaluated. Additive 1 did not contain any heteroatoms; additive 2 contained 9.1% phosphorus. The additives were separately dissolved in M-11 lubricating base stock at a concentration of 2% by weight and the oils were tested for wear and friction reduction at 20-300 C and 2100 MPa. Dependence of lubricity on temperature and on the structures of the additives were determined. The amidothiophosphates were found to be equal to the molybdenum-containing additive for friction reduction. Additives 1 and 2 tested at much poorer friction reduction coefficients. Results are graphed and tabulated.

Antiwear properties of alkylnaphthalene lubricating fluids

Technical sec-alkylnaphthalenes, which are complex mixtures of higher sec-alkylnaphthalenes and olefin oligomers, show promise as base stocks for lubricants [i]. As reported in [2], a method has been developed for single-stage production of either pure sec-alkylnaphthalenes or mixture of these compounds with olefin oligomers in predetermined ratios. The composition of the products can be varied by adjusting the conditions of s~thesis and cataly~ preparation, thus obtaining lubricating fluids with predetermined lubricating properties.

The relationships between structure and rheological properties of hydrocarbons and oxygenated compounds used as base stocks

AbstractThe growing interest shown by industry in synthetic lubricants for severely stressed engines and machines has led the author's organisation to investigate the best hydrocarbon and oxygenated structures which serve to achieve a good compromise between viscosity index and pour point. Several analyses of structure and property relationships have been published. The American Petroleum Institute's project 421 has given the characteristics of many light hydrocarbons from C10 to C35 belonging to different chemical families. During the Second World War, American and German research centres investigated a large number of esters and selected the best diacid and polyol ester structures.The compromise between the viscosity index and pour point has been studied for hydrocarbons and oxygenated products as to their prospects for use as base stocks. With hydrocarbons having a long main chain which is substituted either by a very branched chain, or by a chain ending with a saturated ring, it is possible to reach a viscosity index of around 160 for a pour point of −20°C. The introduction of ester functions in a hydrocarbon chain improves the compromise between viscosity index and pour point. Diacid esters constituted of linear diacids and branched monoalcohols are very favourable, but the best compromise is achieved by polyalkoxy ‐ether‐esters and polyalkoxy diesters. Unhappily these are miscible to hydrocarbons only if the hydrocarbon chains are sufficiently long. Of course for formulation of lubricants, other properties also linked to chemical structure should be taken into account, such as thermal and oxidative stability, antiwear behaviour, hydrolytic stability, and compatibility with additives.The data presented here and other data derived from research projects conducted in the author's laboratory, some jointly with Produits Chimiques Ugine Kuhtmann, have been analysed to determine the possibilities for main synthetic lubricant base stocks.