1. Shaanxi Key Laboratory of Chemical Additives for Industry, Shaanxi University of Science and Technology, Xi'an 710021, P. R. China
2. College of Chemisty and Materials Science, Weinan Normal University, Weinan 714099, P. R. China
3. Gong Cheng Ji Shu Guan Li Bu, Changqing Oil Field Branch Company, PetroChina, Xi'an 710018, P. R. China