苄基化疏水改性淀粉的合成及水煤浆分散性能

采用氧化淀粉和羟乙基淀粉为原料,氯化苄为疏水剂,引入一定量的疏水基团苄基,制备出两种新型苄基化改性淀粉(氧化苄基化淀粉(OBS)和羟乙基苄基化淀粉(HBS))。将OBS和HBS作为分散剂应用于神华煤制备水煤浆,探讨改性淀粉对浆体的表观黏度、制浆浓度、稳定性和流变性的影响。结果表明:OBS和HBS的最佳添加量为0.50%(质量分数,下同),最大制浆浓度为65%;苄基化疏水改性后制得的淀粉分散剂均具有较好的分散效果,含苄基和羧基更多的OBS分散剂性能更佳,浆体表观黏度为842 mPa·s,7 d析水率为4.3%,煤颗粒表面Zeta电位降至-36.2 mV,体现出较好的稳定性和流变特性。OBS分散剂通过结构中的疏水基团苄基与煤中的硫水区域通过π电子极化作用力结合,形成平躺的线性折叠链式吸附。

Synthesis of Benzylated Hydrophobic Modified Starch and Dispersion Property of Coal Water Slurry

Oxidized starch and hydroxyethyl starch as raw materials and benzyl chloride as hydrophobic reagent,two new benzylated modified starches(oxidized benzylated starch(OBS)and hydroxyethyl benzylated starch(HBS))were prepared by introducing a certain amount of hydrophobic group benzyl into the starch structure.The effect of modified starch on the apparent viscosity,pulping concentration,stability and rheological properties of coal water slurry prepared from Shenhua coal was discussed.The results show that the optimum addition of OBS and HBS is 0.50%and the maximum pulping concentration is 65%.The dispersants prepared with starch by benzylation and hydrophobic modification have good dispersing effect.The OBS dispersant with more benzyl and carboxyl groups has better performance.The apparent viscosity of the slurry is 842 mPa·s,which is in line with the national standard.The water evolution rate is 4.3%after 7 d,and the Zeta potential on the surface of coal particles decreases to-36.2 mV,reflecting better stability and rheological properties.The OBS dispersant combines the hydrophobic group benzyl in the structure with the hydrophobic region in the coal throughπeletron polarization force,forming a linear folded chain adsorption.