Synthesis And Application Of Muti-head Amphoteric Surfactants In Coal Water Slurry

The problem of air quality caused by coal combustion is becoming more and more serious,therefore,clean and efficient utilization of coal should be realized.The research of coal water slurry?CWS?has attracted much attention due to its stable combustion,low pollution emission,continuous improvement of CWS technology and cost reduction.The hydrophobicity of coal powder makes it difficult to be moistened by water,so as to be hardly combined with water,while the surfactant can reduce the interfacial tension of coal water and produce homogenous high concentration CWS.The key to improve the performance of CWS is to select the appropriate surfactant.In this thesis,three kinds of amphoteric surfactants with different structures were synthesized from the perspective molecular design.In this paper,biphenyldibenzyl chloride was first reacted with tertiary amines of different chain lengths?8,16?and then sulfonated with chlorosulfonic acid to obtain the first kind of Gemini amphoteric surfactants C_n-B-C_n with the same coupling group and different alkyl chain lengths.TBS and TTS were synthesized from triethanolamine,dichlorosulfoxide,N,N-dimethyl benzyl amine,N,N-dimethyl dodecyl tertiary amine.The third kind of amphoteric surfactants CTSAC and CSSAC,which are easy to be biodegradable,were prepared by using citric acid,dimethyl dodecyl tertiary amine,dimethyl hexadecyl tertiary amine and chlorosulfonic acid as the main raw materials.The molecular structure of the six products were characterized by FT-IR and ¹H NMR.The surface tension of the three surfactants was determined by surface tension meter,and the surfactant emulsification and foam properties were determined.The contact angle and Zeta potential of coal water interface before and after surfactant modification were measured by contact angle measuring instrument and Zeta potential meter.The adsorption of surfactants on the surface of coal particles was studied by XPS and TOC.The six surfactants were separately mixed with Yulin coal pulping and naphthalene series for pulping.The viscosity change,pulping concentration and rheological characteristics of CWS after pulping were measured by viscometer.The stability of coal water slurry before and after modification was determined by stability analyzer.Results showed that the contact angle of coal-water interface after modification of the first amphoteric surfactant C₈-B-C₈ and C₁₆-B-C₁₆ can be reduced from 74.98°of original coal to 33°and 25.42°,respectively,the zeta potential of coal particles were increased from 21.8 mV to 30.31 mV and 33.03mV.The isothermal adsorption amounts on the surface of coal particles at 25°C were 3.8 mg/g and 3.89 mg/g.The slurry showed shear thinning tendency after slurry was formed alone,and the maximum slurry after C₁₆-B-C₁₆ and naphthalene compounding The maximum slurry concentration was up to 70.5%,and the stability of the C_n-B-C_n modified slurry was much higher than that of the original coal or naphthalene.The second multi-head amphoteric surfactant's own performance is optimal,TTS in its critical micelle concentration aqueous solution corresponding to the surface tension of 32.88 mN/m at 25?,TBS,TTS in coal particles on the surface of the saturated adsorption capacity were 3.39 mg/g,4.07 mg/g,conform to the Langmuir monolayer adsorption,thermodynamics in different temperature of?G value was less than zero,?S=0.658,dynamic aspect with level 2dynamic model.TTS modified coal sample was pulped,coal water slurry concentration could reach more than 64%,after added naphthalene and TTS at the same time,coal water slurry concentration was up to 72%.When slurry concentration was 70%,the apparent viscosity of CWS was 740 mPa·s.The surface tension at the critical micelle concentration of CSSAC and CTSAC were 34.81 mN/m and 35.26 mN/m,respectively.The slurry prepared separately by CTSAC and CSSAC was a pseudoplastic fluid,and the slurry was consistent with Herschel-Bulkley model.When the optimal dosage of CSSAC and naphthalene series was 0.4%respectively,the maximum slurry concentration after compounding was 67.2%,and after the slurry with 62%modified CSSAC was set for 7 days,the minimum water extraction rate of CSSAC was 2.24%,the stability level was level 1,and the fluidity was A.