Preparation Of Low-temperature Castor Oil-based Luricant And Its Properties Characterization

With the gradual depletion of petroleum resources and the increasing awareness of environmental protection,traditional petroleum-based lubricants will eventually be replaced due to pollution and unsustainability.So,to cater the sustainable development of mankind,research and development of green and renewable lubricant base oil should be urgently carried out.Differing from using edible oils,i.e.soybean oil and rapeseed oil,as raw materials to prepare vegetable oil-based lubricating base oil,this paper chosed non-edible oil castor oil as the research object,and a systematical exploration was conducted to prepare castor oil-based lubricating base oil.Moreover,to generate castor oil-based lubricating base oil with low temperature fluidity the molecular structure of castor oil was further designed and modified.1.Composition analysis of castor oil and the optimization of bio-enzymatic synthesis of epoxy castor oil.Firstly,GC-MS was utilized to analyse the composition of castor oil,then the results showed that the content of ricinoleic acid could reach 86.16%,and the total unsaturated fatty acid content was 93.39%.Secondly,with Novozyme435 as catalyst,single factorial optimization and response surface methodology?RSM?were sequently employed to optimize the process for synthesis of epoxy castor oil.The obtained optimal reaction conditions were:reaction temperature 42°C,toluene concentration 43 wt%,enzyme loading 5 wt%,reaction time 18 h,ricinoleic acid quantity 8 wt%,and the molar ratio of hydrogen peroxide to double bond 2:1.At these conditions,the epoxy value of the epoxy castor oil was 5.20%,and the epoxy conversion rate attained 97.93%.Furthermore,the structure of the obtained epoxy castor oil was verified via infrared spectroscopy?FTIR?and 1H-nuclear magnetic resonance?¹H-NMR?.2.The molecular structure of the synthesized epoxy castor oil was further designed and then modified to improve its low temperature performence.First,the epoxy ring was opened with 6 different molecular structure fatty alcohols?ethanol,butanol,isobutanol,hexanol,octanol and isooctanol?.Then,the hydroxyl groups on the structure of the derived6 ring-opening products wer esterified with 2 different acid anhydrides?butyric anhydride and hexanoic anhydride?.Therefore,12 groups of original castor oil based-lubricant base oil?OCLBO?with different molecular structures were finally obtained.Additionally,the pour point,kinematic viscosity?40°C and 100°C?and thermal oxidation stability of these12 OCLBOs were tested and compared.It revealed that the low temperature fluidity of the treated oils was greatly improved,the pour point all fell between-64°C and-25°C;their viscosity index were very high,all between 129 and 176;their thermal oxidation stability was fairly good,and their thermal weight loss of 10%were all beyond 200°C,and the deposits generated during thermal oxidation were very tiny,all bellow 5%.Among them,12#OCLBO?isooctanol,hexanoic anhydride?exhibited the best comprehensive performance,its pour point was-64°C,V_40°C=32.80 mm²/s,V_100°C=6.109 mm²/s,and the viscosity index was 136.3.12#OCLBO was further modified by adding antioxidant Vanlube 7723 to foster its application.When antioxidant Vanlube 7723 was added into 12#OCLBO at 0.2 wt%,the test sample exhibited the best thermal oxidation stability.At this time,the flash point was226°C and the viscosity index was 128,V_40°C=30.52 mm²/s,V_100°C=5.67 mm²/s,pour point was totally below-54°C,and all of the above parameters meet the requirement of US Military Aviation Lubricant Standard MIL-PRF-7808L.In addition,compared with the mineral oil VG 46,the castor oil based-lubricant base oil?CLBO?had better extreme pressure ability?P_B=863 N?,and its wear resistance perfomence?WSD=0.54 mm?and oxidation stability?24min?were both super to the mineral oil VG 46?P_B=804 N,WSD=0.67 mm,T=20 min?.