Font Size: a A A

Recycling Dimethyl Siloxane Cyclics From Waste Silicone Oil By Catalytic Cleavage Reaction

Posted on:2014-09-13Degree:MasterType:Thesis
Country:ChinaCandidate:M D WangFull Text:PDF
GTID:2251330398983309Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
The products of organosilicone have been widely utilized in various industries like aerospace, medical treatment, and daily cosmetics. However, it is unavoidable that large amounts of byproducts and wastes of organosilicone have emerged during industrial production and daily using. On the view of efficient utilization of resource and environment-protection, it is necessary to recycle those wastes via effective approaches.Presently, mostly used pathway for recycling waste organosilicone is decomposition under acid’s or alkali’s catalytic equilibrium. Generally, under conditions of150~160℃and of reduced pressure distillation, wastes can be decomposed through using acid-base catalyst like tetramethyl ammonium hydroxide silicon alkoxide. Afterwards, dehydration and deprivation of catalysts processes are proceed and dimethyl siloxane cyclics mixture (DMC) is obtained, which can be used for the production of new organosilicone like silicon oil, silicon rubber by means of ring opening polymerization. But, because of decomposition reaction’s equilibrium limits, treatments mentioned have not received high recovery rate and it is likely that waste liquids after reation would bring secondary pollution due to the existence of acid-base. In addition, new products directly made from recycled DMC possess low quality and purity. In order to more efficiently use wastes, electron-donating solvents reaction system is adopted and method of decomposing silicon oil under vacuum with different catalysts is used to extract DMC, including octamethylcyclotetrasiloxane(D4), hexamethylcy(D3).In this paper, butanone function as electron-donating solvent; H2O, methanol, ethanol are used for chain transfer agent; KOH as base catalyst is used for decomposing dimethicone. That polar solvent can enhance the concentration of active center for siloxane’s cracking, and offer a polar reaction environment for KOH to accelerate the generation of cyclic compounds from rearrangement reaction catalyzed by alkali. Chain transfer agent can not only weaken silicon oxygen bond, but also react with generated cyclic compounds so that they would not reduce through ring opening polymerization. Therefore, the equilibrium can be pushed to be good for the decomposition reaction. Affluence on treatment to silicon oil from different reaction time, different chain transfer agents and different dosage of KOH, different volum butanone of are respectly studied. Products are detected by GC-2010and conversion rate of silicon is figured out from data of GC.Moreover, lewis acid containing A1C13, FeCl3, CuCl2, CrCl3,(CH3CH3CHO)4Ti, ZnCl2and (CH3)4NC1, and protonic acid including methanesulfonic acid, phosphotungstic acid, and other bases are used to decompose silicon oil under vacuum. Despite an overall conversion rate greater than40%, mass of D3and D4obtained is less than1.3g(from lOg silicon oil) after5h, which means a quite percentage of high polymer.Hydroxide radical-containing ion liquids like hydrogen oxidation of methyl butyl imidazole are synthesized for decoposing reaction. Those ILs have strong alkalinity and can be recycled used, with advantages like easy separation with reaction system. However, due to their high viscosity and low stability, the treatment effection to silicon oil does not meet expected levels. Further research is needed to promote their function.
Keywords/Search Tags:WASTE OIL, DIMETHYL SILOXANE CYCLICSMIXTURE, ACID-BASE CATALYSIS
PDF Full Text Request
Related items