The aggregation of nanoparticle catalysts is one of the main problems in catalytic reactions. In this study, a series of TiO 2 nanoparticle catalysts with various dispersions were prepared and applied in the catalytic oxidation of dibenzothiophene (DBT) systems. Compositions and structures of the as-prepared samples were analyzed by means of wide-angle X-ray diffraction, Raman and X-ray photoelectron spectroscopies. The dispersions of TiO 2 nanoparticles were controlled by calcining at various temperatures and verified using transmission electron microscopy. It was found that the activities of TiO 2 nanoparticles in the catalytic oxidation of DBT were positively correlated with the dispersions. TiO 2 nanoparticles calcined at 500°C (500-TiO 2 ) showed the best catalytic activity and the oxidation of DBT reached 99.8% under mild conditions. Based on the results of GC-MS analysis, radical trapping experiments and electron spin resonance spectra, • O 2 − radicals were proved to be the main active species in the oxidation process, and a mechanism is proposed. Meanwhile, the recycling performance of 500-TiO 2 was investigated, and no obvious decrease was observed after six recycles.

Among nitrogen-containing cationic electrolytes, diallyl quaternary ammonium salt is a typical monomer with the highest positive charge density, which has attracted the most attention, especially in the research on homopolymers and copolymers of dimethyl diallyl ammonium chloride (DMDAAC), which occupy a very unique and important position. In order to improve the lipophilicity of substituted diallyl ammonium chloride monomers under the premise of high cationic charge density, the simplest, most direct, and most efficient structure design strategy was selected in this paper. Only one of the substituents on DMDAAC quaternary ammonium nitrogen was modified by alkyl; the substituents were propyl and amyl groups, and their corresponding monomers were methyl propyl diallyl ammonium chloride (MPDAAC) and methyl amyl diallyl ammonium chloride (MADAAC), respectively. The effect of substituent structure on the homopolymerization activity of methyl alkyl diallyl ammonium chloride was illustrated by quantum chemical calculation and homopolymerization rate determination experiments via ammonium persulfate (APS) as the initiator system. The results of quantum chemistry simulation showed that, with the finite increase in substituted alkyl chain length, the numerical values of the bond length and the charge distribution of methyl alkyl diallyl ammonium chloride monomer changed little, with the activation energy of the reactions in the following order: DMDAAC < MPDAAC < MADAAC. The polymerization activities measured by the dilatometer method were in the order DMDAAC > MPDAAC > MADAAC. The activation energies Ea of homopolymerization were 96.70 kJ/mol, 97.25 kJ/mol, and 100.23 kJ/mol, and the rate equation of homopolymerization of each monomer was obtained. After analyzing and comparing these results, it could be easily found that the electronic effect of substituent was not obvious, whereas the effect of the steric hindrance was dominant. The above studies have laid a good foundation for an understanding of the polymerization activity of methyl alkyl diallyl ammonium chloride monomers and the possibility of preparation and application of these polymers with high molecular weight.

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The source of dyeing wastewater and the composition of pollutants are very complex, direct discharge will bring great harm to living environment, and cause waste of water resources. For the treatment of reactive dyeing wastewater, this work developed and synthesized a novel cationic flocculant called Poly (DMDAAC-co-DAMBAC), which was made by copolymerizing dimethyl-diallyl-ammonium chloride (DMDAAC) and methyl-benzyl-diallyl-ammonium chloride (DAMBAC). To assess its flocculation effects, flocculation decolorization studies with 3RF reactive yellow, KNÀ R reactive blue, and 3BF reactive red were conducted. The copolymers' lipophilicity considerably increased once atyl groups were added. The experimental results showed that Poly(DMDAAC-co-DAMBAC) had an optimal decolorization rate of over 94 % for three reactive dyes and a maximum decolorization rate of roughly 80 % for COD Mn , both of which were significantly higher than those of PDMDAAC and nearly on par with those of PDAMBAC with a comparable viscosity. Instead, Theoretical calculations of the binding energy of the results demonstrated the accuracy of the findings. The study illustrated the flocculation mechanism and laid the foundation for further application of Poly(DMDAAC-co-DAM-BAC).

Utilizing the copolymerization modification of dimethyl diallyl ammonium chloride (DMDAAC), the high positive charge density of the copolymer could be maintained, thereby facilitating the deficiency of its monomer in the application. In this paper, poly (DMDAAC-co-DAMBAC) (9:1) was synthesized with an aqueous polymerization method using DMDAAC and methyl benzyl diallyl ammonium chloride (DAMBAC) as monomers and 2,2’-azobis [2-methylpropionamidine] dihydrochloride (V50) as an initiator. Targeted to the product’s weight-average relative molecular mass (Mw), the response surface methodology (RSM) was used to optimize the preparation process. The optimal process conditions were obtained as follows: w (M) = 80.0%, m (V50):m (M) = 0.00700%, m (Na4EDTA):m (M) = 0.00350%, T1 = 50.0 °C, T2 = 60.0 °C, and T3 = 72.5 °C. The intrinsic viscosity ([η]) of the product was 1.780 dL/g, and the corresponding double bond conversion (Conv.) was 90.25 %. Poly (DMDAAC-co-DAMBAC) (9:1) revealed a highest Mw of 5.637 × 105, together with the polydispersity index d (Mw/Mn) as 1.464. For the demulsification performance of simulated crude oil O/W emulsions, the demulsification rate of poly (DMDAAC-co-DAMBAC) (9:1) could reach 97.73%. Our study has illustrated that the copolymerization of DMDAAC and a small amount of DAMBAC with poor reactivity could significantly improve the relative molecular weight of the polymer, enhance its lipophilicity, and thus the application scope of the polymer.