LUBRICANT TESTING AND DIFFERENTIATION IN LABORATORY BETWEEN MINERAL AND SYNTHETIC OIL Roberto Lava Region Reg ional al En Envir vironm onment ental al Protectio Prote ction n Agenc Agency y of Vene Veneto to
TAIEX Workshop on Quality Analy Ana lysis sis of Lubric Lubrican antt Oi Oill (60124) Cairo (Egypt) 11-12 April 2016
ARPA AR PAV V - Reg Region ional al Age Agenc ncy y for for Env Envir iron onme ment ntal al Pr Prot otec ectio tion n and Prev Prevent ention ion of Ven Veneto eto
The goal of the the Age Agency ncy is to cont control rol and pres preserv erve e the envi environm ronment ent in ord order er to help hel p the the identi identifica ficatio tion n and elim elimina inatio tion n of risk risks s to huma humans ns and to the the envir environme onment. nt. Mai ain n go goa als are: · Co Cont ntrol rolli ling ng of th the e env envir ironm onment ent in inclu cludin ding g so sourc urces es of po pollu llutio tion n (e.g. industrial emissions, waste, radiation); · Mon Monitor itoring ing of the the st state ate of of the the enviro environme nment, nt, particul part icularly arly the qual quality ity of air, air, water, water, and and soil; soil; · Pr Prev even enti ting ng ri risk sk fa fact ctor ors s an and d pr prom omot otin ing g an ed educ ucat atio ion n ai aime med d at fa favo vour urin ing g life styl styles, es, which resp respect ect the envi environm ronment. ent. ARPA RPAV V coo coordi rdina nate tes s its ac activ tiviti ities es clo closel sely y wit with h oth other ers s Pu Publ blic ic Bo Bodi dies es
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ARPA AR PAV V - Reg Region ional al Age Agenc ncy y for for Env Envir iron onme ment ntal al Pr Prot otec ectio tion n and Prev Prevent ention ion of Ven Veneto eto
The goal of the the Age Agency ncy is to cont control rol and pres preserv erve e the envi environm ronment ent in ord order er to help hel p the the identi identifica ficatio tion n and elim elimina inatio tion n of risk risks s to huma humans ns and to the the envir environme onment. nt. Mai ain n go goa als are: · Co Cont ntrol rolli ling ng of th the e env envir ironm onment ent in inclu cludin ding g so sourc urces es of po pollu llutio tion n (e.g. industrial emissions, waste, radiation); · Mon Monitor itoring ing of the the st state ate of of the the enviro environme nment, nt, particul part icularly arly the qual quality ity of air, air, water, water, and and soil; soil; · Pr Prev even enti ting ng ri risk sk fa fact ctor ors s an and d pr prom omot otin ing g an ed educ ucat atio ion n ai aime med d at fa favo vour urin ing g life styl styles, es, which resp respect ect the envi environm ronment. ent. ARPA RPAV V coo coordi rdina nate tes s its ac activ tiviti ities es clo closel sely y wit with h oth other ers s Pu Publ blic ic Bo Bodi dies es
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ARPAV ALPI (Dolomiti Mountains)
URBAN AREA (Verona, Padova)
UR!ACE "ATER (#arda La$e, Po%Adi&e% Brenta Rivers)
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PADANA PLAIN (rura (r urall an and d ind indust ustria rial) l)
VENICE and Veni'e La&oon
ADRIATIC EA
ARPAV
LABORATORY SERVICE 2012-2014: Re-organization of the laboratory network Two main regional laboratories: 1) ENVIRONMENT (air, water, soil and waste, REACH) 2) FOOD
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Organic Micro-Pollutants Unit
ADVANCED ANALYTICAL INSTRUMENTATIONS
AGENDA
09:30 - 10:30 Lubricant testing and their environmental impact Differentiation between mineral and synthetic oil in lab 10:30 – 10:45 Coffee break 10:45 - 12:00 Measurement of oil in produced water 12:00 – 12:15 Q&A. Discussion
OUTLINES
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Introduction Definition Test of the base stock Elemental and structural analysis Environmental Impact References and further readings
INTRODUCTION
LUBRICANT TESTING Physical and chemical tests / spectroscopic and chromatographic techniques used to establish the structural and compositional identity of lubricant.
LUBRICANT = BASE STOCK + ADDITIVES
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INTRODUCTION
LUBRICANT TESTING Physical and chemical tests / spectroscopic and chromatographic techniques used to establish the structural and compositional identity of lubricant.
LUBRICANT = BASE STOCK + ADDITIVES
TRIBOLOGICAL TESTs = tests (mostly mechanical) about the performances requirements of finished lubricant and their in-service condition monitoring
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MINERAL OIL
Purified and extracted from crude oil in refineries. Depending from the origin and separation processes used, the chemical composition can vary. - AROMATICS (high solubility) - NAPHTHENICS (good low-temperature properties) - PARAFFINS (high viscosity, low sulphur content, good oxidative stability) Variable distribution of chain length and ramification More complicated refinery processes (separation, degradation, hydrogenation, hydrocracking) produce a wider range of compounds, quite impossible to separate
Highly available on the market = INEXPENSIVE
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SYNTHETIC OIL
SYNTHETIC OIL Synthesised with industrial production - big advantage that can be customized chemical composition modified for the specific requirements (molecular structures more uniform). -Improved stability (viscosity) -Less internal fraction -Lower toxicity (less volatiles) -Compatibility with rubber and plastic -Lower environmental impact
Cost of the production higher
POLYALPHAOLEFINS (PAO) = hydrocarbon based polyglycols and esters saturated oligomers manufactured via catalytic oligomeration of alpha-olefins (Group IV) Group V = other types of synthetic oils
MINERAL VS SYNTHETIC I M S
K. Bannister, Machinery’s Handbook (lubrication chapters) and Lubrication for Industry, part of the ICML and ISO Domain of Knowledge
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Gandelli M, http://www.maconresearch.com/blog/olio-sintetico-e-olio-minerale-5-caratteristiche-a-confronto, 2014
MINERAL VS SYNTHETIC II
BIO-BASED LUBRICANT Attractive alternative to petroleum-based lubricant, biodegradable, mostly formulated from renowable agricoltural plant and animal resources. Lately cost competitive and their market is increasing
Synthetic fluid and bio-based lubricant market is growing (expected +13% for 2020) New products are continuously coming out in the market for very specific application NEW ADDITIVES/FORMULATIONS NEEDS OF SPECIFIC CONTROLS AND TARGET ANALYSES
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New performances specifications and test methods development as consequence
MINERAL VS SYNTHETIC III
Unfortunately there are no reliable ways or methods to exactly distinguish between mineral and synthetic oils. COLOR. Synthetic oil are TRANSPARENT, while mineral are DARKER (aromatics, sulphur). Not reliable for the use of colour additives and dyes (darkening or whitening) In LABORATORY Looking at the combination of the physical properties such as: - VISCOSITY INDEX - FLASH POINT - POUR POINT - ANILINE POINT - THERMAL STABILITY
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A mixture of synthetic and mineral oil become a very big analytical challenge study the composition of BASE STOCK and ADDITIVES.
BASE STOCK
Physical properties of the finished lubricants are primarily attributable to the structure and the properties if the lubricant base stock (bulk of the lubricant).
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Chemical properties, on the other hand, are due to the presence of the additives used to formulate them. - VISCOSITY - VAPOR PRESSURE - DENSITY - BULK MODULUS Properties that are evaluated - THERMAL PROPERTIES by the various physical and - SURFACE TENSION analytical tests: - GAS SOLUBILITY - FOAMING TENDENCY - ELECTRICAL PROPERTIES - THERMAL STABILITY - OXIDATION STABILITY
VISCOSITY SYNTHETIC OIL
MINERAL OIL
Gandelli M, http://www.maconresearch.com/blog/olio-sintetico-e-olio-minerale-5-caratteristiche-a-confronto, 2014
Measure of the resistance of a fluid to flow For a lubricant are reported at 40 C and 100 C, measured in Stroke (St = mm2/s) Viscosity decrease with the increase of temperature. HIGH VISCOSITY INDEX (VI) = BETTER OIL (more stable) Mineral oil = VI up to 100-120 Synthetic oil = >140 (140-170), >250 for silicone oil
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ASTM D445, kinematic viscosity at 100 C (most common method) The method specifies a procedure for the determination of kinematic viscosity of transparent and opaque oil by measuring the time for a volume of liquid to flow under gravity through a calibrated glass capillary viscometer ASTM D445-03 corresponds to the ISO 3104 range covered = 0.02 to 300000 mm2/s
FLASH POINT I
Measure of the ignitability of an oil. It is the lowest temperature at which vapours of a fluid ignite. Required an ignition source, a spark or flame (vs auto-ignition point of temperature) 2 methodologies (closed and open cup) ISO 2719, ASTM D93, EPA1010a: Pensky-Martens Closed Tester ASTM D92: Cleveland Open Cup (less used for oil) “It is a function of the apparatus design, the condition of the apparatus used, and the operational procedure carried out. Flash point can therefore only be defined in terms of a standard test method, and no general valid correlation can be guaranteed between results obtained by different test methods, or with test apparatus different from that specified” (ASTM D93)
In general event it is not a rule: flash point increase with the increase of the molecular weight (matter of volatility) E.g: an abnormal low flash point in a automotive oil - possible presence of gasoline
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Gear oil = 190-300 C Petroleum Oil = max 200-230
C
Motor Oil = 210-252 C Synthetic oil = > 230 C, up to 270
C
FLASH POINT II
Pensky-Martens Closed Tester 2 mL of lubricant Calibration with distilled water and n -decane Ignition source: flame burning butane
POUR POINT
Primary related to the low-temperature properties of a fluid
J. Wang Pour point, Encyclopedia of Tribology, 2013 Springer ed, pp 2673-2678
POUR POINT = is the temperature become semi-solid and loses flow characteristics (ASTM D97, ISO 3016) The lower is the temperature, the better quality is the oil. In a lubricant indicates the paraffinic content, to lower with additives. Synthetic oil contains no paraffins. They don’t need pour point depressant additives. Most petroleum lubricant: > -34 C even with additives Synthetic lubricant without additives: -45 C Synthetic lubricant with additives: -60 C
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CLOUD POINT = the temperature at which the oil loses its clarity, i.e. develops haze or cloudiness due to the start of crystal formation
ANILINE POINT
Defines the temperature at which equal volume if the lubricant and aniline are miscible. This temperature is indicative of the solvency characteristics of the oil. In general, the lower is the aniline point, the greater is the solvency of the oil ASTM D611 (last version 2012) “useful as an aid in the characterization of pure hydrocarbons and in the analysis of hydrocarbon mixtures. Aromatic hydrocarbons exhibit the lowest, and paraffins the highest values. Cycloparaffins and olefins exhibit values that lie between those for paraffins and aromatics. In homologous series the aniline points increase with increasing molecular weight. Although it occasionally is used in combination with other physical properties in correlative methods for hydrocarbon analysis , the aniline point is most often used to provide an estimate of the aromatic hydrocarbon content of mixtures.”
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THERMAL STABILITY Thermal stability = resistance of a lubricant to break down or to change its molecular structure (under influence of heat and absence of O2). ASTM D2879 - isoteniscope method ASTM E1131, ISO 11358 Thermogravimetric analysis ASTM E1782, E537 Differential Thermal Analysis (DTA) Significant decomposition (liquid decomposition and gas formation) MINERAL 340 - 380
SYNTHETIC (PAO) C
methane, ethane, ethylene
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310 - 340
C
more differentiated monomers
Aromatic compounds: more stable 450 - 480 C (PCB, PAH) Organic esters: (260 - 316 C) - the ester functional group the first degradation site A lot of additives has a low thermal stability OXIDATION STABILITY = resistance in presence of air or O 2. Good oxidation stability = highly desirable. Unlike thermal stability that is more inherent to the base stock, oxidation stability can be greatly improved by additives.
ELEMENTAL AND STRUCTURAL ANALYSIS On the other hand, chemical analysis can be applied also to the base stock Mineral oil contains a wide variety of elements (some at ppm levels) Refined process remove most of elements apart C, H, O, N, S. Trace elements: AAS, ICP-AES, ICP-MS, X-RF, micro-elemental analysis Not only to detect impurities, but also wear metals part and friction products (B, Ba, Ca, Cd, Cr, Cu, F, Hg, Mg, Mo, Ni, P, Pb, Sb, Se, Si, Sn, Zn) Micro-elemental analysis mostly for non-metal elements The sample is burn at the elementary form and analysed into gas product with different techniques
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C, H, N
ASTM D5291
IR or GC
Cl, organics
ASTM D4929b
microcoulometry
N
ASTM D4629/D5762
Chemioluminescence
O
ASTM D5622
Reductive Pyrolysis
S
ASTM D5453/D6667
UV Fluorescence
ISO TEST METHODS
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HYDROCARBON / ORGANIC ANALYSIS To identify the chemical structures that make the basis both of base stock and additives. MINERAL OIL: a challenge is the determination of the base stock composition because it is a complex mixture (various types, sizes and structures). SYNTHETIC OIL: structure determination is relatively straight forward for well-defined structures and purities, in known-unknown proportion. The challenge is done by the POLYDISPERSIVITY (wide molecular weight distribution).
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More complex techniques: -
GAS CHROMATOGRAPHY (GC, GCxGC) LIQUID CHROMATOGRAPHY (e.g. GPC) UV and IR SPECTROSCOPY NUCLEAR MAGNETIC RESONANCE (NMR) MASS SPECTROMETRY (MS)
GC-FID and GC-MS
www.chromatographyscience.it (2012)
Column: 15 - 105 m specific for mineral separation solvent: n -hexane or iso -octane injection: 0.5-1 uL on-column
W. Krasodomski and M. Krasodomski, Nafta-gaz 08-2010 ROK LXVI
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Carrier gas: Helium, Nitrogen, Hydrogen
typical oven program: 50 C to 300 C at 10 20 min hold time
C/min
GC-FID II
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K. Grob, Kantonales Labor Zurich (2011)
GC x GC
2 GC columns: one polar and the second non-polar
W. Krasodomski and M. Krasodomski, Nafta-gaz 08-2010 ROK LXVI
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INFRARED SPECTROSCOPY I
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Probably the most accepted test to obtain structure and composition of a lubricant Widely applied because non-destructive method (movement of molecules) Spectra range: 500-4000 cm-1 IR spectra are sufficiently unique to help identify structural features of many individual compounds
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Powerful if combined with different analytical techniques (GC, LC, MS) Easy to identify organic groups (heteroatoms: N, O, S, P) More difficult with all hydrocarbons (double bonds, aromatic rings)
INFRARED SPECTROSCOPY II
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Rizvi (2009)
EXAMPLE I: IR
R. Johnson, The case of the poorly blended fluid, Hydraulics & Pneumatics (2008)
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EXAMPLE II: GPC
Gooss W, Korn A. BMW Group Dep. Lab, Germany -Specific for automotive lubricants -Chemical composition important to meet high performance requirements -Analytical challenge from the analytical point of view, quantitative measurements It is nearly impossible in a mixed base oil to identify typical groups Chromatographic overlapped peaks Example of modern lubricant: mineral oil + PAO + synthetic esters 1) Pre-separation step via Solid Phase Extraction (SPE) to separate esters based components from PAO + mineral (POLARITY)
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2) GEL PERMEATION CHROMATOGRAPHY (GPC) = LC, fractionation in accordance to the size of solvated polymer clusters (porous separation matrix) + commercial deconvolution software to separate overlapped peak-area (separation of mineral oil from PAO)
EXAMPLE II: GPC
Gooss W, Korn A. BMW Group Dep. Lab, Germany
FULL SYNTHETIC
Differential molar mass distribution (UV-PDA detector at 280 nm)
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MINERAL
LUBRICANT AND THE ENVIRONMENT
Since there are limitation of the use of the lubricant (recycling is possible, but not a indefinite recondition), sooner or later used lubricant enter into the environment. It is necessary a specific regulation for environmental protection and occupational health & safety. Last generations of lubricant tent to be ENVIRONMENTALLY friendly, compatible, acceptable, harmless, responsible. GREEN FLUIDS like bio-base lubricant.
- BIODEGRADABILITY - TOXICITY (AQUATIC) In EUROPE an ECOLABEL for commercial lubricant
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REFERENCES and USEFUL READINGS
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S.Q.A. Rizvi, Lubricant Chemistry, Technology, Selection and Design (a comprehensive review), ASTM Publication MNL 59, 2009 ISBN 978-0-8031-7000-1
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L.R. Rudnick (eds), Synthetics, Mineral Oils, and Bio-Based Lubricants – Chemistry and Technology, 2nd ed, CRC Press, 2013 ISBN 978-1-4398-5538
