Study On The Photolysis Of Ester Lubricants Catalyzed By Semiconductor Catalyst

With the widespread use of lubricants and society is paying daily attention to environment, people take more and more concern about the environmental pollution of the lubricating oil. Photocatalytic oxidation is a pollution control technology arising in recent years.it can oxidize and decompose the recalcitrant organic pollutants, reaction at normal temperatures and pressures, it's easy to operate and low energy consumption. The TiO₂ catalyst is nontoxic and innoxious, it presents great stability and recoverable. more and more researchers given great attention of this technology.This paper is according to anatase nano TiO₂ as photocatalyst to photodegrade dipentaerythritol hexa-caproate and trimethylolpropane tri-heptylate under the UV source of 1000W high-pressure mercury lamp. Study on photocatalytic degradation of the different dosage of titanium dioxide, concentration of H₂O₂ and different reaction time,different PH, different organic solvents, and analysis of reaction kinetics. The research results as follows:The results show that: Using iso-octane as organic solvents, dipentaerythritol six heptanoic acid ester (di-PEHECA), trimethylolpropane tri-heptylate has the best peak shape after Photolysis, as the best solvent of UV-analysis test. Compared with the comparison, the significant was effects of anatase nano TiO₂ for dipentaerythritol hexa-caproate and trimethylolpropane tri-heptylate, With di-PEHECA concentration was 50.2 mg·mL^-1, ultraviolet radiation time was 20 min, when Nano TiO₂ dosage was 1.26g·L^-1 ,the degradation rate was 93.07%, the rate of photodegradation increase about 61%. and the trimethylolpropane tri-heptylate concentration was 51.3 mg·mL^-1.ultraviolet time was 20 min when the dosage of Nano TiO₂ was 1.24g·L^-1, photodegradation rate was 95.8%, the rate of photodegradation increase about 48%. The degradation of two types of lubricants catalytic has obvious implications for Acidity, It is closely related to pH.In di-PEHECA concentration of 50.2 mg·mL^-1 condition, ultraviolet radiation time was 20 min, The best effect of di-PEHECA in acid and neutral conditions, the degradation rate was 93.0%～98.0%; when the pH is 3.5, the degradation rate was 97.93%; when the pH is 7.0, the degradation rate was 96.67%. The drop of less effective was the conditions of weak acid and alkaline, the degradation rate was 85%～89%. When the trimethylolpropane tri-heptylate concentration was 51.3 mg·mL^-1 ultraviolet time was 20 min, The degradation rate was lower than acid conditions, the degradation rate was 60%～70%,when the pH is 7.5⁸.0, The best degradation is 95.8%, the most suitable pH of trimethylolpropane tri-heptylate is neutral and weak alkaline. H₂O₂ can promote photodegradation of di-PEHECA and trimethylolpropane tri-heptylate.Compared with the comparison,The rate was higher than the comparison of adding a certain concentration of H₂O₂ for di-PEHECA, When the concentration of H₂O₂ is less than 2 mo·L^-1, The efficiency of photodegradation increase to a certain extent, When the concentration of H₂O₂ is 2mol·L^-1～3 mol·L^-1, The efficiency of photodegradation sharp rise .reached 95.92%. Compared with the comparison, The rate of photodegradation increase about 23%, The degradation rate increased. less on H₂O₂ of trimethylolpropane tri-heptylate, When concentration of H₂O₂ is 3 mol·L^-1,the degradation rate was 92.07 %, the rate of photodegradation increase about 9%.When trimethylolpropane tri-heptylate concentration was 51.3mg·mL^-1, di-PEHECA concentration was 50.2 mg·mL^-1, With the light of the changes of time,the result show that: the rate of degradation increasing with the light of the increased time,Within the first 20 min, the effects of photodegradation is significant, With the rate of time-almost a straight line up,The time of 20 min, the degradation rate of di-PEHECA was 75.26%, the degradation rate of trimethylolpropane tri-heptylate was 91.97%. After 20 minutes of photodegradation, the rate of degradation increase in the extension of time, increasing greater extent of degradation rates for di-PEHECA,When the time of photodegradation is reaching 50 min, The photolysis rates were parting as high as 90% and 99% of di-PEHECA and trimethylolpropane tri-heptylate. The effect of degradation on organic solvents for di-PEHECA and trimethylolpropane tri-heptylate was sigmficantly.The photodegradation on the di-PEHECA order of four organic solvents is: isooctane>acetone>ethanol>dichloromethane, and photolysis results of the order of the trimethylolpropane tri-heptylate: alcohol solution>methanol>isooctane>xylene>acetone. Thus, the best photodegradation solvents of di-PEHECA is isooctane, the best photodegradation solvents of trimethylolpropane tri-heptylate is the alcohol solution.The dynamics of the experimental results of Nano-TiO₂ dosage, pH value, H₂O₂ concentration of di-PEHECA show that:Adopting exponential draft gained dynamic equation of different dosage of Nano-TiO₂,The decision coefficient,R²>0.96, The dosage of nanometer TiO₂ for di-PEHECA follow a one-order dynamics rules.lt is kept to one-order dynamics rules on Acid(pH=5.10) neutral(pH=7.02) alkaline(pH=9.02). The decision coefficienti is more than 0.975. The photodegradation of the di-PEHECA has obvious influence for pH, The degradation was the best in neutral conditions. The photodegradation of the di-PEHECA has obvious influence for H₂O₂ concentration,When the H₂O₂ concentration add to 1.96～2.61mol·L^-1, Compared with the comparison,the half life shorten 5～6 times, This shows that H₂O₂ accelerates photodegradation of the di-PEHECA.The dynamics of the experimental results of Nano-TiO₂ dosagean, pH value,differt organic solvent and H₂O₂ concentration of the trimethylolpropane tri-heptylate show that: The dosage of nanometer TiO₂ for rimethylolpropane tri-heptylate follow a one-order dynamics rules,When the dosage of nanometer TiO₂ is from 0.76g·L^-1 add to 2.99g·L^-1,The half life is from 128.4min drop to 10.4min, The half life is shorten 12.8 times.The photodegradation of the trimethylolpropane tri-heptylate has obvious influence for H₂O-2 concentration. Compared with the comparison, the concentration H₂O₂ is in the range of 0.65～1.96mol·L^-1,It promoted photodegradation of trimethylolpropane tri-heptylate,The speed constant were greater than the comparison, The half life is lower the comparison.In the acid(pH=5.10) condition, The speed constant is lower, .In the neutral (pH=7.06) condition and alkaline(pH=9.02) condition, The speed constant is more. The half-life is abbreviater twice in the neutralcondition and alkalinecondition than in the acid condition/The order of influence of dynamics on trimethylolpropane tri-heptylate for four organic solvent was Acetone> isooctane> ethanol> methanol. This shows that the acetone more favorable photodegradation of trimethylolpropane tri-heptylate.