Synthesis Of Dipropylene Glycol By Phase Transfer Catalysis

DPG is one of important industrial derivatives of propylene oxide, which is used widely in manufacture of plasticizer and unsaturated polyester resin,and production of cosmetics and perfume. With the increase of consumption, high-quality DPG will be in great need of. However, the technology of producing high-quality DPG has been monopolized by foreign countries, so there isn't industrial production in China. The orthodox method for synthesizing DPG was that propylene oxide was catalyzed by acid or base catalyst to open ring and then condensed propylene glycol, in which there were two professional ways: liquid acid and solid sodium methoxide catalysis. The orthodox ways, such as liquid acid or base catalysis, cauterized apparatus, demolished environment and complicated subsequent process, in which DPG yield and product selectivity could only reach 61.5%～67.3% and 69%～75%. Environment-friendly solid acids or bases, which can avoid the disadvantages of liquid acid or base catalyst, might cause severe solid-liquid phase effect that led to long reaction processes and high power consumption. So they are only studied in the lab, and merely used in industrial production.With the development of phase transfer catalysis (PTC), it will be a promising industrial catalysis in the near future because it can make the process react in mild circumstance, promote reaction rate and overcome the bottleneck of solid-liquid phase effect in solid acids or bases catalysis. As our country relies on import of DPG, we should develop new technology for synthesizing DPG which is cheap and adapt to conditions in China to promote agenda of producing DPG. So it is not only meaningful and promising but also economical and academic for our society, and can open up new areas for utilizing propylene oxide.The aim of the thesis is to synthesize high-quality DPG, and apply PTC in green synthesis of DPG to eliminate phase effect in acid or base catalysis on the basis of research on liquid acid and solid sodium methoxide catalysis so that high-yield, high-quality and low-contamination DPG.The technology of liquid acid catalysis was optimized by orthogonal and single factor experiments. The optimal conditions were as follows: amount of 85% sulfuric acid=4%wt, reaction temperature=42℃, molar ratio of PG and PO=0.7:1, dropping PG, feeding speed of PG=30g·h^-1, reaction time=4⁴.5h. The yield of DPG and conversion of PO were 65.3% and 71.5% respectively.Homemade SO₄^2-/Fe₂O₃ solid acid was used in reaction. The corresponding equation was set up by uniform design testing among objective function and molar ratio of PG and PO x (1), amount of catalyst x (2), reaction time x (3)and reaction temperature x (4). The regression analysis reached significant level. Regression correspondence equation was as follows:The optimal conditions for synthesizing DPG by solid acid catalyst on basis of correspondence equation were as follows: reaction temperature=150℃, molar ratio of PG and PO=0.9:1, amount of solid acid catalyst=4%wt, reaction time=14h. The yield of DPG was 68.7%.The technology of solid sodium methoxide catalysis was optimized by orthogonal and single factor experiments. The optimal conditions were as follows: amount of dissipating solid sodium methoxide=4%wt, reaction temperature=100℃, molar ratio of PG and PO=1.2:1, feeding speed of PO=90g·h^-1, reaction time=8h. The yield of DPG and conversion of PO were 70.3% and 80.5% respectively. The purity of DPG was 99.8% on basis of further purification. Further, based on researching on reaction mechanism, macro-kinetic model was established theoretically, and examined to second-order reaction experimentally, reaction kinetic equation was:PTC was used in solid acid and sodium methoxide catalysis and technology conditions were optimized by single factor experiments. The optimal conditions of PTC-solid acid catalysis were: TBAB as catalyst, amount of catalyst=4%mol, reaction time 8h, reaction temperature=120℃, stirring speed=460r·min^-1, yield of DPG=77.9%. The optimal conditions of PTC-solid sodium methoxide catalysis were: CE as catalyst, amount of catalyst=3%mol, reaction time 8h, reaction temperature=70℃, stirring speed=460r·min^-1, yield of DPG=82.2%. Result indicated that PTC was a green method for synthesizing high-quality DPG, which concluded not only high selectivity, environment-friendly character and simple subsequent process of solid acid but also high yield and simple process of solid sodium methoxide. It will be promising in industry.GC/MS and IR were used in the analysis of contents and characterization of DPG. GC/MS and IR were used in the analysis of contents and characterization of DPG. Specific Surface Instrument, IR and SEM were used in characterization of solid acid catalyst. Digital instrument of melting point, element analysis instrument and 1HNMR was used in characterization of homemade phase transfer catalyst.