Font Size: a A A

Study On The Green Oxidation Of Alcohols

Posted on:2016-05-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:J ZhuFull Text:PDF
GTID:1221330482967718Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
The selective oxidation of primary and secondary alcohols into the corresponding aldehydes or ketones is one of the most important and challenging transformations in modern organic chemistry. The study on oxidation of alcohols, especially the development of novel catalytic systems, is always of great interest. Recengly, researches usually centre on subjects including improving the selectivity of oxidation products, ameliorating oxidation conditions, reducing or even eliminating environmental pollutions suffered from oxidation reactions. In this work, several novel, green catalytic systems were developed and applied for selective oxidation of alcohols with O2 or H2O2 as green oxidants.Two types of TEMPO catalysts with ionic liquids as supports including [Imim-PEG6oo-TEMPO][OMS] and Fe3O4/MPS/PIL/TEMPO were synthesized and used for oxidation of alcohols. With O2 as oxidant, aldehyde or ketone was obtained as the only product, exhibiting both high conversion and selectivity. For TEMPO functionalized imidazolium salt [Imim-PEG600-TEMPO][OMS], a temperature-dependent system was achieved together with cyclohexane/CCl4 mix solvent. Under a pseudo homogeneous process, high conversion of 98% was obtained for benzyl alcohol with selectivity of 99%. Fe3O4/MPS/PIL/TEMPO was a recoverable catalyst with magnetic Fe3O4 nanoparticles coated by TEMPO and sulfonic acid funcitonalized polymeric ionic liquids.Different from the general TEMPO/NaNO2 system, addition of conventional acid was avoided due to the existence of HSO4- anion in the catalyst. After 4 hours’ reaction, conversion of benzyl alcohol achieved 98% with yield of 97% for benzaldehyde. Due to their temperature-dependent and magnetic property respectively, catalysts could be efficiently recovered by simple decantation after reaction without any apparent loss of catalytic activity and little loss of weight.Two polyoxometalate catalysts were designed and prepared:IL/SMNP combining TEMPO based ionic liquid and polyoxometalate moieties and metal-organic framework supported polyoxometalates. With H2O2 as green oxidant, the two catalysts could be used for oxidation of alcohols. In IL/SMNP, polyoxometalate moieties served as co-catalyst for TEMPO which avoided the loss of co-catalyst for TEMPO. After reaction of 5 h, yield of benzaldehyde reached 97%. For MOF-POMs, ordered structure and high surface area were displayed. The nano-sized MOF-POMs which offered organized multiple porosity and high surface area, were proved to be efficient catalyst for various alcohol oxidations in micellar solutions. Cationic surfactant CTAB gave the best results due to its attractability of Keggin anion. With MOF-HPW as model catalyst, the yield of benzaldehyde reached 98% after 3 h. A wide set of aliphatic; allylic, heterocyclic and benzylic alcohols could be oxidized into their corresponding carbonyl compounds with good to excellent yields.A novel catalyst with metal organic framework supported gold nanoparticles was synthesized for selective oxidation of benzyl alcohol. The reactions were performed under solvent-free conditions with O2 as oxidant, and thus a green and environmental process was achieved. TOF reached the highes value of 9130 h-1 at 10 h, with conversion of benzyl aocohol reached 53.8% and selectivity of benzaldehyde exceeded 99%. The catalyst with uniform gold nanoparticles (about 5 nm) showed great dispersion which ensured the excellent catalytic performance. It was found that addition of water could improve the reaction efficiency and its optimized amount was 0.5% of substrate (volume ratio). The promotion effect of water was also facilitated due to the hydrophilic character of the inner surface of UiO-66. Also, it was confirmed that the control factor of the oxidation process was oxidation speed rather than the mass transfer effect.Glycerol was treated seeking for its additional values. With MOF supported POM as catalyst and under green and mild conditions (water solvent, H2O2 oxidant,40℃), esters was generated as one of the major products which could serve as biodiesel again. The regeneration of biodiesel from its by-product GLY was achieved through a one-pot oxidative esterification process. Benefiting from the pore limitation effect of MOFs and catalytic performance of POMs, no other reagents were needed during this process, and all of the intermediates were produced by glycerol itself, exhibiting a green and efficient process.The highest efficiency was obtained with loaing amount of 8 wt.% and pH=8. The conversion of glycerol reached 48.6% with selectivity of esters of 34.5%. The oxidative esterification reaction was further studied in detail including the role of MOFs, the influence of POM type, the mechanism and so on.
Keywords/Search Tags:Oxidalion, Alcohols, Selective, Catalysis, Green
PDF Full Text Request
Related items