Preparation And Performance Study Of Plant-Based Lubricants

With the requirement of sustainable development and the progress of industrial machinery,high performance and strong biocompatible lubricants are the inevitable trend for future lubricant development.Some non-edible oils such as cottonseed oil（CSO）are excellent raw materials for the production of bio-lubricants,but there are some defects in performance due to natural structure,which need to be chemically modified to enhance and give some properties.Therefore,in this study,CSO is used as a raw material to develop high value-added products and high-performance bio-based lubricants through various modifications.Oxidative cracking of fatty acids from CSO to prepare high value-added short and medium chain fatty aldehydes:The hydrolysis of cottonseed oil was catalyzed by the lipase Candida sp.99-125,and then purified by molecular distillation and concentrated by urea embedding,and the yield of unsaturated fatty acids reached 98.69%.It was epoxidized using the green oxidant H₂O₂ catalyzed by the lipase Novozym 435.The tungsten carbide catalyst with catalytic H₂O₂ oxidative cleavage of epoxide was developed using phosphotungstic acid and ZIF-8 as raw materials and applied to the oxidative cleavage of epoxidized fatty acids.The optimal cleavage process:the ratio of epoxidized oleic acid to H₂O₂ was 1:2,the optimal temperature was 80℃,and the catalyst addition was 1%of the substrate mass.Under the optimal process,the 2 h cracking rate reached 95.7%,the selectivity reached 81.2%,and the catalyst still maintained strong catalytic activity within 6 batches.Glycerol carbonate derived from CO₂ and glycerol was combined with a variety of fatty acids（including CSO fatty acid groups whose oxidative cleavage products）to overcome the solubility of glycerol carbonate in water and to overcome the high freezing point of fatty acids to produce bio-based lubricants.The optimal transesterification process was carried out using the lipase Novozym 435 as the transesterification catalyst:the temperature was 50℃,the ratio of the amount of glycerol carbonate to fatty acid was 1:1.1,the amount of lipase added was 2%of the system mass,the stirring speed was 300 r/min,and a certain amount of dry air was continuously passed to remove water.However,the reaction time varied with the fatty acid composition.The lipase could be used in five batches.The obtained fatty acids of glycerol carbonate all had low pour points（-39～-19℃）and high viscosity indices（131～243）,but there were some gaps in viscosity,which could meet the requirements of unused working conditions.Finally,CSO was modified by hydrolysis,esterification,epoxidation and ring-opening branched steps,and a process for synthesizing high-viscosity and low-pour-point bio-lubricants combining the lipase Candida sp.99-125,the lipase Novozym 435 and the recoverable ionic liquid[HMIm]PF₆ as green catalysts was developed.The developed bio-based lubricant has excellent low-temperature fluidity and viscosity-temperature properties（pour point=-47℃;kinematic viscosity at 40℃=200.3 mm²/s;viscosity index=141）,in addition to excellent thermal oxidation stability（oxidation onset temperature:307.21℃;rotational oxygen bomb:21 min）,and its lubricity properties are far superior to those of SN grade lubricants（average friction coefficient:0.07;average mottling diameter:132μm;oil film coverage:100%）.