Molecular Design,synthesis And Structure-Performance Investigation Of Dodecylbenzyl Ethoxylates

Nonylphenol ethoxylate(NPEOn)was the second largest nonionic surfactants in the world,with excellent emulsification,solubilization,wetting and washing properties.NPEOn was widely used in civil and industrial cleaning,fine chemical and other fields.However,due to the poor biodegradability and environmental toxicity,NPEOn has been banned or restricted worldwide in recent years,so finding NPEOn green alternative has become the focus urgent problem of surface active agent production and related application industry.However,the current study remains the use of existing surfactants to replace some properties of NPEOn,lacking a full range of structure and performance alternative studies.In this paper,a novel nonionic surfactant dodecylbenzyl ethoxylate(DBEOn)with similar molecular structure to NPEOn was studied by molecular design.The phenoxy fragment in NPEOn was replaced by benzyloxy fragment and the structure-performance of DBEOn was also investigated.Further,whether DBEOn can retain NPEOn excellent surface activity and application performance or not and both good biodegradability were explored.For structural identification and structure-performance relationship research,in this paper,DBEOn with monodistribution of alkyl and ethoxy groups(EO)were prepared by n-dodecylbenzene(DB)through chloromethylation and Williamson etherification.N-dodecylbenzyl chloride(DBCl)was synthesized from DB by chloromethylation.DBEOn with different number of ethylene oxide(EO)units(n = 2,4,6,8,10,or 12)were synthesized from DBCl by multi-step alternating group activation reaction and Williamson etherification.The surface activity and application performance of DBEOn were determined and the structure-performance relationship of DBEOn was studied.The primary biodegradability of DBEO8,a representative member of DBEOn,was also determined.The results of biodegradation showed that the primary biodegradability of DBEO8 was close to 100% based on a seven-day,which completely overcome the drawback that NPEOn was not easy to biodegradable.The experimental results also showed that the cloud point of DBEOn rised,the critical micelle concentration(cmc)increased,cmc/c20 decreased,the saturated adsorption capacity(Γm)increased,the saturated adsorption area(Am)decreased,solubilization,emulsification and wetting performance all reduced with the EO number increasing.Compared DBEOn series and TX-10,the representative variety of NPEOn,DBEO8 and TX-10 had similar cloud point and cmc,but better solubilization for benzene and much better emulsification for mineral oil,vegetable oil,silicone oil.Therefore,DBEO8 was expected to become an environmentally friendly alternative to TX-10 in many applications.In order to explore the feasibility of industrial production,in this paper,linear laurylbenzyl ethoxylate(LBEOn)with multi-distribution of alkyl and EO was prepared by industrial linear laurylbenzene(LB)through chloromethylation,hydrolysis and ethoxylation.Laurylbenzyl chloride(LBCl)was synthesized from LB by chloromethylation and laurylbenzyl alcohol(LBA)was synthesized from LBCl by two-step hydrolysis reaction.LBEO9 was synthesized from LBA and ethylene oxide by ethoxylation,and the surface activity and application performance were determined.Compared to TX-10,the results showed that LBEO9 had lower cloud point,smaller cmc and Πcmc,larger γcmc,cmc/c20 and Am,better solubilization for benzene,better emulsification for mineral oil and vegetable oil,slightly worse emulsification for silicone oil.Compared with DBEOn series,the cloud point,γcmc,Πcmc,Am,solubilization,emulsification,wetting and other performance of LBEO9 and TX-10 were closer,so LBEO9 had more potential to replace TX-10.In order to simplify the hydrolysis process,in this paper,one-step hydrolysis of DBCl under alkaline or acidic conditions was explored.The hydrolysis of DBCl was preliminarily investigated by means of mixed solvent method,ultrasonic-microwave assisted method,emulsion method,hydrothermal method or phase transfer catalysis,and finally the hydrothermal-assisted phase transfer catalysis made the hydrolysis completed.The optimum process conditions were as follows: when the molar fraction of dodecyl dimethyl benzyl ammonium chloride(1227)was 5.6%,a high yield of n-dodecylbenzyl alcohol(DBA)of 93.6% by alkaline hydrolysis of n-dodecylbenzyl chloride was obtained under hydrothermal condition at 130 ℃ for 16 h.Since the molecular structure unit of phase transfer catalyst 1227 is similar to the structure of reactant and product,the affinity of the phase transfer catalyst to reactant and product is improved,so that the alkaline hydrolysis of DBCl is carried out with high hydrolytic selectivity and no byproduct benzyl ether.The hydrothermal condition is conducive to further increase the compatibility of DBCl and water,thereby increasing the yield of hydrolysis reaction.