Synthesis And Performance Of Branched Vicinal Diol Polyoxyethylene Ethers

Branched surfactants have potential applications in the industrial cleaning field because of their low surface tension,low foaming and fast defoaming properties,and good wetting ability.Currently,typical branched surfactants are synthesized using Guerbet alcohol with"Y"branch structure as hydrophobes.As we all know,Guerbet alcohol was synthesized by Guerbet condensation reaction of two molecules of alcohol.However,this reaction would be accompanied by a series of rather complicated side reactions,leading to the formation of other compounds such as aldehydes,ketones,acids,etc.,which makes the yield of the target product low,thereby affecting its use in the synthesis of branched surfactants.Therefore,it is of great necessity to find new alternative raw materials that can synthesize branched surfactants.In modern coal chemical production,α-olefins（1-hexene and 1-octene）produced by Fischer-Tropsch synthesis could be selectively dimerized to synthesize 2,2-dialkylethylene（2-butyl-1-octene and 2-hexyl-1-decene）.2,2-Dialkylethylene not only has a"Y"type branched structure,but also has carbon-carbon double bonds,which is the alternative hydrophobes for synthesis of branched surfactants.In organic synthesis reactions,a variety of methods have been reported to modify carbon-carbon double bonds.Among them,the hydroxylation reaction catalyzed by HCOOH and H₂O₂ is an effective method to synthesize vicinal diols.Therefore,2,2-dialkylethylene（2-butyl-1-octene and 2-hexyl-1-decene）was used as raw material to synthesize branched vicinal diol polyoxyethylene ethers through hydroxylation and ethoxylation in this study,and determining them surfactant properties.The main research contents and conclusions include:（1）Using 2-butyl-1-octene or 2-hexyl-1-decene as the raw material,branched vicinal diols was generated via hydroxylation reaction catalyzed by HCOOH and H₂O₂.The distribution of the products were measured,the chemical structure of each product were determined,and a high-purity target product was obtained through optimizing the reaction conditions.The results showed that the hydroxylated product not only contained the target product branched vicinal diols,but also included branched epoxides,by-product ketones and other products.By optimizing the process parameters,the optimized reaction conditions for the synthesis of 2-butyl-1,2-octanediol were obtained as follows:H₂O₂/2-butyl-1-octene=1.5,HCOOH/2-butyl-1-octene=3.5,the reaction temperature is 30°C,the reaction time is 6 h,and the optimized reaction conditions for the synthesis of 2-hexyl-1,2-decanediol were obtained as follows:H₂O₂/2-hexyl-1-decene=1.5,HCOOH/2-hexyl-1-decene=4.0,reaction temperature is 50°C,reaction time is 10 h.In the end,the conversion of the raw materials is close to 100%,and the selectivity of branched vicinal diols is greater than 70%.（2）In the solvent-containing reaction system,branched vicinal diol polyoxyethylene ethers（2-butyl-1,2-octanediol polyoxyethylene ether or 2-hexyl-1,2-decanediol polyoxyethylene ether）were synthesized via the ethoxylation catalyzed by KOH.The product distribution was determined,products structure was characterized,and the synthesis of 2-hexyl-1,2-decanediol polyoxyethylene ethers was taken as an example to study the effect of various conditions on the reaction,in order to obtain optimized reaction conditions.Since branched vicinal diol polyoxyethylene ethers are a mixture of"homologs"with similar polarity,different products in the HPLC spectrum did not show significant differences.Mass spectrometry analysis showed that the branched vicinal diols successfully reacted with ethylene oxide,and products are a mixture of different ethylene oxide addition numbers.The optimized reaction conditions were obtained as follows through adjusting the process parameters:the reaction temperature was 140°C,the reaction pressure was 0.15 MPa,and the amount of catalyst was 1.5‰.（3）Through the surface performance test,the surfactant performance of six branched vicinal diol polyoxyethylene ethers were investigated.The surface tension test shows that the six branched vicinal diol polyoxyethylene ethers have the ability to reduce the surface tension of water.Especially 2-hexyl-1,2-decanediol polyoxyethylene ethers,that has better surface activity due to longer hydrophobic alkyl chain,which can reduce the surface tension of water to 27 m N/m.The contact angle test shows that the contact angle of 2-butyl-1,2-octanediol polyoxyethylene ethers is relatively large and can not wet the paraffin film well.The contact angle of 2-hexyl-1,2-decanediol polyoxyethylene ethers decreased significantly with the increase of the concentration,especially the 1.000 g/L B-C8EO-6 aqueous solution,the contact angle on the paraffin film changed from 53.5°to 38.5°within 30 s,and showing good wetting ability.The foam performance test shows that these branched vicinal diol polyoxyethylene ethers has lower foam volume and defoaming ability.Therefore,they have typical branched surfactant properties.This research provides new raw materials for the synthesis of branched non-ionic surfactants,and also opens up a new way for the utilization of coal resources to synthesize fine chemicals.