Research of oxidation influence on the properties of biological base oils ; Oksidacijos įtakos biologinės kilmės bazinų alyvų savybėms tyrimas
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ALEKSANDRAS STULGINSKIS UNIVERSITY Raimondas Kreivaitis RESEARCH OF OXIDATION INFLUENCE ON THE PROPERTIES OF BIOLOGICAL BASE OILS Summary of the Doctoral Dissertation Technological Sciences (T000) Environmental Engineering and Land Management (04T) Akademija, 2011 Dissertation was performed in 2007–2011 at Aleksandras Stulginskis University (former Lithuanian University of Agriculture). This work was supported by the State Science and Studies Foundation of the Republic of Lithuania. Scientific supervisor Prof. dr. Juozas PADGURSKAS (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management – 04T) Scientific adviser Prof. dr. Violeta MAKAREVI ČIEN Ė (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management – 04T) Council of Environmental Engineering and Land Management: Chairman: Prof. dr. Egidijus ŠARAUSKIS (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management – 04T) Members: Prof. habil. dr. Ramutis Petras BANSEVIČIUS (Kaunas University of Technology, Technological Sciences, Mechanical Engineering – 09T) Prof. dr. Gintaras DENAFAS (Kaunas University of Technology, Technological Sciences, Environmental Engineering and Land Management – 04T) Assoc. prof. dr.
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ALEKSANDRAS STULGINSKIS UNIVERSITY Raimondas Kreivaitis
RESEARCH OF OXIDATION INFLUENCE ON THE PROPERTIES OF BIOLOGICAL BASE OILS
Summary of the Doctoral Dissertation Technological Sciences (T000) Environmental Engineering and Land Management (04T)
Akademija, 2011
Dissertation was performed in 20072011 at Aleksandras Stulginskis University (former Lithuanian University of Agriculture). This work was supported by the State Science and Studies Foundation of the Republic of Lithuania. Scientific supervisor Prof. dr. Juozas PADGURSKAS (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management 04T) Scientific adviser Prof. dr. Violeta MAKAREVIČIENĖ Stulginskis University, (Aleksandras Technological Sciences, Environmental Engineering and Land Management 04T) Council of Environmental Engineering and Land Management: Chairman: Prof. dr. Egidijus ARAUSKIS (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management 04T) Members: Prof. habil. dr. Ramutis Petras BANSEVIČIUS (Kaunas University of Technology, Technological Sciences, Mechanical Engineering 09T) Prof. dr. Gintaras DENAFAS (Kaunas University of Technology, Technological Sciences, Environmental Engineering and Land Management 04T) Assoc. prof. dr. Eglė JOTAUTIENĖ (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management 04T) Dr. Antanas Sigitas ILEIKA (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management 04T) Opponents: Prof. habil. dr. Vladislovas KATINAS (Lithuanian Energy Institute, Technological Sciences, Environmental Engineering and Land Management 04T) Prof. dr. Gvidonas LABECKAS (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering and Land Management 04T) The official defence of the dissertation will be held at the open meeting of the doctoral council at 11 a.m. on 28 October, 2011 in the room 261, central building of the Aleksandras Stulginskis University. Address: Aleksandras Stulginskis University, Studentų11, Akademija LT-53361 Kauno r., Lithuania. The send out date of the Dissertation Summary is 28 of September 2011. The Dissertation is available at the library of Aleksandras Stulginskis University.
ALEKSANDRO STULGINSKIO UNIVERSITETAS Raimondas Kreivaitis
OKSIDACIJOSĮTAKOS BIOLOGINĖS KILMĖS BAZINŲ ALYVŲSAVYBĖMS TYRIMAS
Daktaro disertacijos santrauka Technologijos mokslai (T000) Aplinkos ininerija ir kratotvarka (04T)
Akademija, 2011
Disertacija rengta 20072011 metais Aleksandro Stulginskio universitete (buvęs Lietuvos emėsūkio universitetas). DarbąrėmėLietuvos Valstybinis mokslo ir studijųfondas. Mokslinis vadovas Prof. dr. Juozas PADGURSKAS (Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Mokslinėkonsultantė Prof. dr. Violeta MAKAREVIČIENĖ(Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Disertacija ginama Aleksandro Stulginskio universiteto Aplinkos ininerijos ir kratotvarkos mokslo krypties taryboje. Pirmininkas: Prof. dr. Egidijus ARAUSKIS (Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Nariai: Prof. habil. dr. Ramutis Petras BANSEVIČIUS (Kauno technologijos universitetas, technologijos mokslai, mechanikos ininerija 09T) Prof. dr. Gintaras DENAFAS (Kauno technologijos universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Doc. dr. Eglė JOTAUTIENĖ (Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Dr. Antanas Sigitas ILEIKA (Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Oponentai: Prof. habil. dr. Vladislovas KATINAS (Lietuvos energetikos institutas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Prof. dr. Gvidonas LABECKAS (Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos ininerija ir kratotvarka 04T) Disertacija bus ginama vieame Aplinkos ininerijos ir kratotvarkos mokslo krypties tarybos posėdyje 2011 m. spalio 28 d. 11. val. Aleksandro Stulginskio universiteto centriniųrūmų261 auditorijoje. Adresas: Aleksandro Stulginskio universitetas, Studentų11, Akademija LT-53361, Kauno r., Lietuva. Disertacijos santrauka isiųsta 2011 m. rugsėjo 28 d. Disertacijągalima periūrėti Aleksandro Stulginskio universiteto bibliotekoje.
INTRODUCTION Relevance of the topic. Depleting petroleum resources are the point of contradictory discussions a few decades. Continuously increasing environmental pollution forces to find effective solutions to solve such kind of problems. One of the solution is the use of renewable energy and renewable raw materials. Recently it becomes one of the priorities in energetic and scientific research. Millions tones of lubricants are consumed in the World annually. Half of them get in the environment polluting the ground and surface water by various ways. The use of biodegradable non-toxic environmentally friendly bio lubricant can greatly decrease the negative impact on environment. The use of environmentally friendly lubricants which meet the Eco Labels is essential in the forestry and agriculture as well as water transport. In this case readily biodegradable base lubricants based on renewable resources should be used. Pure and additives modified vegetable and animal fats as well as various esters based on mentioned materials are promising raw materials for environmentally friendly base lubricants. Vegetable oils have good tribological and viscosity properties together with excellent biodegradability and non-toxicity. Moreover their price is low comparing to synthetic esters. Unfortunately there wider usage is restricted by pure oxidation stability and low temperature properties. Nevertheless vegetable oils remain attractive base oil for production of environmentally friendly lubricants. Durability of vegetable oil based lubricants depends mainly on oxidation. This problem is analysed in many research works. Nevertheless scientists agree, that still remain many unanswered questions. One of them how rapeseed oil oxidation influence tribological properties and biodegradability. Hypothesis. Rapeseed oil modified with natural antioxidant is suitable raw material for production of environmentally friendly lubricants. Research goal and objective. Research goal is the investigation of potential of vegetable and animal origin stocks according to tribological properties for production of environmentally friendly base lubricants, determination of the influence of oxidation on properties of chosen stock and estimation of its biodegradability. The following tasks were performed in order to achieve the goal of the study: o Investigation of the potential of vegetable and animal origin stocks according to tribological properties for production of environmentally friendly base lubricants;
o Investigation of the influence of accelerated oxidation on tribological and physicochemical properties of rapeseed oil; o Investigation of the influence of natural antioxidants on oxidation properties of rapeseed oil; o Investigation of the influence of ageing on tribological and physicochemical properties of pure and natural antioxidants modified rapeseed oil; o Investigation of the influence of oxidation on corrosiveness of rapeseed oil; o Investigation of the influence of oxidation on biodegradability of pure and natural antioxidants modified rapeseed oil. Scientific innovation. The influence of oxidation on physicochemical, tribological and biodegradability properties of rapeseed oil were compositely studied for the first time. It was determined that the biggest influence on tribological properties have peroxides and high molecular weight compounds. The natural antioxidants were produced and their effectiveness to increase oxidation stability of rapeseed oil was studied. The influence of oxidation on corrosiveness of rapeseed oil was investigated. It was determined that even much oxidized rapeseed oil not influences the corrosiveness essentially. The influence of oxidation and modification with natural antioxidants on biodegradability was studied too. It was determined that neither pure nor natural antioxidant modified rapeseed oils oxidation has no essential influence on its biodegradability. Practical value of research. The possibility of manufacturing environmentally friendly base lubricants from vegetable oils produced in Lithuania was studied. The investigated lubrication, physicochemical and corrosiveness properties and their variation during oxidation allow effectively predict the changes in the oil during the exploitation. The investigated natural antioxidants can be used in production of environmentally friendly total loss lubricants. Validation and publication of the study results. The presentations on the topic of the thesis work were presented at the following international scientific conferences: Balttrib (2007 and 2009), OTG Symposium (2008), Mechanika 2009, Aplinkos ininerija (2011) and EcoTrib (2011). The topic of the thesis work has been published in 15 journals: 2 in journal, included into the list of reviewed scientific papers in ISI data basis with a citation index, 6 in other journals, included into the list of reviewed scientific papers in ISI data basis, 1 publication in reviewed scientific Journals, referred in other databases, 5 publications in other reviewed scientific publications, 1 in other journals.
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Structure and content. Dissertation consist the following parts: Introduction, Literature Review, Materials and Methods, Results and Discussion, Conclusions, list of 139 cited Literature sources, and Appendix. Dissertation has 94 pages including 5 tables and 54 figures. Statements of the dissertation to be defended: The results of the work allow defending the following important statements: o Oxidation of rapeseed oil regarding the structural changes reduces its physicochemical and tribological properties. The intensive reduction begins after induction period; o Natural sage and thyme extracts greatly increase the oxidation induction period of rapeseed oil. The increase is proportional to concentration of extract in the oil; o down the ageing of rapeseed oil, andNatural antioxidants slow danp the tribological and physicochemical properties; o Oxidation has no significant influence on corrosiveness of pure and natural antioxidants modified rapeseed oil; o Oxidation of pure and natural antioxidants modified rapeseed oil has no significant influence on its biodegradability. 1. MATERIALS AND METHODS The accelerated oxidation tests of rapeseed oil conducted by using Rancimat 743 apparatus. Samples of 20 ml heated to 100 and 120oC in the glass vessels (no metal catalyze). Dry air with the 10 l/hr flow rate was blown through the sample. In odder to determine the influence of oxidation products on tribological and other properties of rapeseed oil the tests were carried out in all three stages of oxidation. The oxidation stability for both pure and antioxidants modified rapeseed oil was evaluated according to induction period (IP). Increasing the induction period leads to better oxidation stability and efficiency of antioxidants. Four natural antioxidants were investigated: attars of thyme and sage, and extracts of thyme and sage. The influence of natural antioxidants concentration in the rapeseed oil on oxidation stability was investigated increasing concentration from 0.1 to 0.6 % (by wt.). The results were compared with 3 different certificated environmentally friendly lubricants. The tests were performed in accordance with ISO 6886:2006 standard. The amount of sample was 2.5 g. The test temperature was 100oC, the dry air with 10l/hr flow rate was blown through the sample. Pure and natural antioxidants modified rapeseed oil was aged according to standard AOCS Cg 5-97 Oven Storage Test for Accelerated Aging of Oils.
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The closed jars with capacity of 250 ml were held in dark environment with 100 ml of investigated sample. The test temperature was 70oC. Physicochemical changes occurred in pure and natural antioxidants modified rapeseed oil during accelerated and ageing oxidation tests were determined according to density (LST EN ISO 12185:1999), kinematic viscosity (LST EN ISO 3104+AC:2000), viscosity index (ISO 2909:2002), acid number (LST EN ISO 660:2000) and peroxide value (LST EN ISO 3960:2001). Spectral properties of samples were investigated using Ocean Optics spectrometer USB 4000 together with pulsed xenon lamp PX 2. Measurements were conducted in 350700 nm wavelength interval with 200 ms integration time. The average of 10 measurements was taken as the result. Non oxidized rapeseed oil sample was used as 100 % transmitting reference. The tribological properties were investigated using four ball tribometer in accordance with standard DIN 51 350, part 3. The load of 150 N was used. Test duration was 1 hr. The lubricity evaluation parameters were wear scar diameter (WSD) and mean torque. WSD was measured using optical microscopy MBI 6. The variation in torque during the test was estimated too. For better understanding the rules of wear, the wear scars were analyzed using optical (MBI 6) and scanning electron (JEOL JSM 5600) microscopy. The magnification of optical microscope was 160 x, and SEM 100, 150, 1500 and 2000 x. The profiles of wear scars were measured using profilometer MarSurf GD 25. The biodegradability of fresh and oxidized specimens was determined in accordance with requirements of CEC L-33-A-93 standard. Non-treated bacterial culture received from JSC Kauno Vandenys after the first (mechanical) treatment stage was used for the test. The amount of bacteria in the used water according to standard should be 104107CFUo/ml. In current study the amount was monitored using Dip Slide indicators. After the preparation of samples for the biodegradability part of them were extracted getting the biodegradability of 0 day. The second part was hold in the dark environment with the temperature of 25oC, for 21 day. After this period these samples extracted getting the biodegradability of 21 day. The corrosion tests were performed in accordance with standard LST EN ISO 2160:1998. The prepared plates of copper were hold in investigated base lubricant with the temperature of 100oC. The test duration was 3 hr. To avoid any fatty residues on the specimens surfaces they were washed with n-heptane before and immediately after the test. The obtained results were estimated using standard reference plates, comparing them with those obtained during the tests. The obtained results of the experimental studies are presented in the form of charts ant tables. All experiments were performed using at least 3 repeats. The averages, standard deviations, error bars and least significant differences (LSD) for obtained results were measured.
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2. RESULTS AND DISCUSSION 2.1. Tribological properties of potential raw materials for environmentally friendly base lubricants The good lubricity of vegetable oils is well known. In current study the rapeseed and flaxseed oils planted and produced in Lithuania were investigated. Their tribological properties compared with soybean and sunflower oils which are common in foreign countries. The obtained results show that all investigated vegetable oils have similar wear and friction reduction properties (Fig. 2.1). 0.8 R.050.044 0.6 0.4 0.2 0.0
Rapeseed Falxseed Soybean Sunflower Vegetable Oils a
80 .058.78 R 60 40 20 0 Rapeseed Falxseed Soybean Sunflower Vegetable Oils b Fig. 2.1Tribological properties of vegetable oils: a wear of lubricated surfaces; b friction between contacting surfaces expressed by torque Slightly better wear and friction reduction properties show flaxseed oil. The flaxseed oil has a lot of unsaturated fatty acids which can form tribopolymers in the contact. It can be stated that in Lithuania planted rapeseed and flaxseed oils have sufficient tribological properties which are necessary for base oil. Whereas rapeseed oil is much more common in Lithuania in comparison with flaxseed oil, it was chosen for the further investigations. Tribological properties of esters obtained from vegetable and animal origin fats are presented in Fig. 2.2. Because of the different molecular size and 9
much more expressed fatty acid saturation tribological properties of esters varying more then that of vegetable oils. The best wear reduction properties have Rapeseed oil fatty acid Methyl Ester (RME) and Lard oil fatty acid Butyl Ester (LBE), the worst Lard oil fatty acid Methyl Ester (LME) and Rapeseed oil fatty acid Butyl Ester (RBE). Methyl esters, particularly RME showed the worst friction properties. They had the highest friction torque. Such properties are determined by short chain molecules which do not ensure separation of lubricating surfaces. 1.2 1.0 R.050.099 0.8 0.6 0.4 0.2 0.0
Rapeseed RME LME TME Oil Test Oils a
RBE
LBE
80 R058.45 . 60 40 20 0 Rapeseed RME LME TME RBE LBE Oil Test Oils b Fig. 2.2Tribological properties of rapeseed oil and various esters: a wear of lubricated surfaces; b friction between contacting surfaces expressed by torque Where: RME Rapeseed oil fatty acid Methyl Ester; LME Lard oil fatty acid Methyl Ester; TME Tallow oil fatty acid Methyl Ester; RBE Rapeseed oil fatty acid Butyl Ester; LBE Lard oil fatty acid Butyl Ester Hence these short chain esters have worse tribological properties comparing vegetable oils. Besides, the esters have a very low kinematic viscosity. Therefore they should be additionally modified with viscosity modifiers. At the same time low viscosity ensures lower drop point temperature what is advantage in comparison to vegetable oils. Regarding the mentioned properties tested esters are more likely to be additives for the base oil. 10
Despite that vegetable oils have good tribological properties their wider usage is restricted by pure oxidation properties. Influence of oxidation on tribological, corrosion and environmental properties of oils will be discussed in further research. 2.2. Accelerated rapeseed oil oxidation The accelerated rapeseed oil oxidation causes significant changes in physicochemical, tribological and other properties (Fig. 2.3 and 2.4). 6 700 5 Acid number 600 4 Peroxide value 500 400 3 300 2200 1100 0 0 0 5 10 15 20 25 30 35 40 45 Oxidation time, hr a 250 250 Kinematic viscosity 200 Viscosity Index 200 150 100 150 50 0 100 0 5 10 15 20 25 30 35 40 45 Oxidation time, hr b Fig. 2.3properties during the accelerated oxidation atChanges in rapeseed oil 100oC: a change in peroxide value and acid number; b change in kinematic viscosity and viscosity index The IP of oxidized (100o In the hr.C) rapeseed oil is approximately 18 primary oxidation stage (018 hr) an increasing number of peroxides indicate the growing quantity of alkylradicals (Fig. 2.3 a). A slight increase in acidity makes it possible to assume that in this stage almost no free fatty acids are formed (Fig. 2.3 a). Rapeseed oil thermal oxidation, which proceeds to the end of IP, has no influence on kinematics viscosity, because the compounds, which increase the viscosity, have not formed yet (Fig. 2.3 b). 11
