Synthesis And Properties Of Sodium Carboxylate Of Glyceryl Monooleate Succinic Acid Monoester

Waste cooking oils are low-quality oils discarded in production and daily life.Direct emissions and illegal processing of waste cooking oils pose serious threats to the ecological environment and food safety.As a potential renewable resource,waste cooking oils are supposed to be“turned into waste”to achieve the resource utilization.Accordingly,use of waste oils as renewable raw materials for preparation of the important fine chemicals such as biodiesel,biolubricants,and surfactants,has become a focus of research in academia and industry.As one of the indispensable functional materials,surfactants play an important role in the national economy.It is one of the important areas to use waste cooking oil as a renewable raw material for synthesis of green surfactants.Meanwhile,it is in line with the concept of greenization and sustainable development of the modern surfactant industry.Monoglyceride is one of the important products during the conversion and utilization of waste cooking oils.It is known that monoglyceride itself can be used as an emulsifier.Due to the presence of hydroxyl group in the molecule,the monoglyceride can be grafted onto the hydrophilic group through hydroxyl functionalization to synthesize a novel surfactant with excellent water solubility.Maleic anhydride is an important organic chemical raw material that can be used for synthesis of surfactants by esterification reaction with hydroxyl-containing compounds.In view of the above,maleic anhydride and glyceryl monooleate were used as raw materials to synthesize glyceryl monooleate succinic acid monoester by grafting carboxylic acid groups through hydroxyl functionalization,and subsequent neutralization with sodium bicarbonate solution to synthesize sodium carboxylate of glyceryl monooleate succinic acid monoester.The research content and conclusions are as follows:（1）The thermodynamic data of the esterification reaction of glyceryl monooleate with maleic anhydride in the temperature range of 298⁴28 K was studied using the group contribution method and thermodynamic empirical formula.the results show that:In the temperature range of 298⁴28 K,the two enthalpies（?H_r^?）of glyceryl monooleate succinic acid monoester and diesters are less than zero,meaning the esterification reactions are an exothermic reactions;the entropy changes（?S_r^?）are greater than zero,demonstrating the esterification reactions are irreversible;the Gibbs free energy（?G_r^?）is less than zero,namely,the esterification reaction can occur spontaneously;The equilibrium constant（k^?）is much greater than 1,indicating the esterification reaction can be completed in the forward reaction.According to the variation of thermodynamic parameters with temperature,it is found that monoglyceride monoester is favored in the temperature range of 298³70 K.（2）Sodium carboxylate of glyceryl monooleate succinic acid monoester was synthesized by esterification of glyceryl monooleate（GMO）with maleic anhydride（MA）and subsequent neutralization with sodium bicarbonate solution.The esterification reaction parameters with sodium propionate catalyst were optimized in terms of the acid value of the prepared product via single factor variable experiment method.The optimum operating conditions were as follows:a maleic anhydride/glyceryl monooleate molar ratio of 2:1,a reaction time of 1 h,a reaction temperature of 90°C,and a catalyst loading of 10%（with respect to glyceryl monooleate）.The structure of the prepared products was identified by fourier transform infrared spectroscopy（FT-IR）,electrospray ionization mass spectrometry（ESI-MS）methods.（3）Some properties of sodium carboxylate of glyceryl monooleate succinic acid monoester（MGSC）were measured,such as Krafft point,surface properties,foaming properties,emulsifying properties,solubilization lime soap dispersibility,salt-tolerance and hard water resistance.The experimental results show that:MGSC has low Krafft points of less than 0oC,exhibiting excellent low temperature solubility;MGSC has good performance of reducing surface tension,CMC=0.137 mmol·L^-1,γ_cmc=33.90 mN·m^-1.By studying the surface parameters,MGSC has demonstrated excellent surface tension reducing ability and efficiency;the initial foaming volume of MGSC was 300 mL.After 5minutes,the foam volume was 290 mL.Its foam stability was 96.7%,which revealed MGSC exhibited excellent foaming ability and foam stability;The emulsification time of liquid paraffin for MGSC was 114 s,meaning its emulsifying capacity is normal;.MGSC has a calcium soap dispersion index of45%and exhibits good calcium soap dispersion;MGSC showed turbidity in 8%aqueous solution of NaCl,implying its salt-tolerance is normal;MGSC has a milky color in an aqueous solution with a calcium hardness of 12 mmol·L^-1 and an average stability of 4 grades.It has good anti-hard water properties.In summary,sodium carboxylate of glyceryl monooleate succinic acid monoester exhibits excellent surfactant performance.