Cuiqin Li

Synthesis and Demulsification of Two Lower Generation Hyperbranched Polyether Surfactants

A lower generation hyperbranched molecular skeleton R12-1.0G was synthesized with methanol as solvent by means of Michael addition and amidation condensation reaction with C12 fatty amine, acrylate, and ethylenediamine as raw materials. The structure was characterized by IR and 1H NMR spectrum. Two lower generation hyperbranched polyethers were further synthesized by means of a skeleton as raw materials through addition reaction with epoxyethane and epoxypropare, respectively. The surface tension, cloud point, and HLB value of the hyperbranched polyethers were determined systematically. On this basis, the demulsification of two hyperbranched polyethers for simulated emulsion was studied in this paper. The results showed that two hyperbranched polyethers are typical surfactants, and they show different demulsification for the simulated emulsion. The structure of polyethers can influence the demulsification performance, and the main factor is the molecular block structure. The demulsification mechanism of two hyperbranched polyethers was studied using the single-droplet protocol, and the dynamic data of drainage time, half life time, and rupture rate constant obtained are consistent with the demulsification law of the hyperbranched polyethers. This study may be helpful in accounting for the demulsification mechanism and for developing effective demulsifiers with new structure.

Scavenging ability of dendritic PAMAM bridged hindered phenolic antioxidants towards DPPH˙ and ROO˙ free radicals

Antioxidant activities of first generation and the second generation dendritic antioxidants (1.0G and 2.0G dendritic antioxidants) with a hindered phenolic group and a tertiary amine group at the same molecule were evaluated using the DPPH˙ method and the oxygen uptake method. It was found that two dendritic antioxidants had good scavenging abilities on DPPH˙ and ROO˙ free radicals and their scavenging abilities were superior to Irganox 3114 with only hindered phenol groups. The antioxidant abilities of dendritic skeletons which only contained the tertiary amine groups were evaluated and they might scavenge DPPH˙ and ROO˙ free radical. The results of dendritic skeletons showed that dendritic antioxidants were the intramolecular complex primary antioxidants with hindered phenolic group and tertiary amine group, and they have good synergistic effect.

Synthesis and application of bidentate nickel complexes bearing hyperbranched salicylaldimine ligands in ethylene oligomerization

Abstract Three bidentate salicylaldimine nickel complexes containing different long-chain alkyl groups in their ligand backbone were synthesized in good yield. All the bidentate salicylaldimine ligands and their nickel complexes were fully characterized by FT-IR, 1H NMR, UV spectroscopies, and mass spectrometry. Three bidentate nickel complexes were evaluated as catalyst precursors in ethylene oligomerization. Upon activation with methylaluminoxane (MAO), the catalytic activity was 5.75 × 105 g/(mol Ni·h) and the oligomers were mainly butenes (52.10%) and octenes (32.63%) for bidentate nickel complex with 1-tetradecyl as core in the ligand backbone (R14-complex) using toluene as solvent. However, bidentate nickel complex with 1-octadecyl as core in the ligand backbone (R18-complex) produced mainly octenes (59.38%) and C10 + olefins (29.01%) and the catalytic activity was 2.23 × 105 g/(mol Ni·h). After activation with ethylaluminum sesquichloride (EASC) in toluene, three nickel complexes yielded mainly C10 + products which contained Friedel-Craft alkylated-toluene, and their catalytic activities were above 1.5 × 106 g/(mol Ni·h). For the bidentate salicylaldimine nickel catalysts with hyperbranched molecules as ligand backbones, the solvent and the reaction conditions had a large effect on catalytic activity as well as oligomerization distribution except the structure of the catalyst and the co-catalyst.

Novel dendrimer-based nickel catalyst: synthesis, characterization and performance in ethylene oligomerization

A novel nickel metallodendrimer was synthesized with poly(amidoamine), 3,5-di-tert-butyl-2-hydroxy-benzaldehyde and nickel chloride via the Schiff’s base and the complexation reactions. Structures of the dendritic ligand and its nickel complex were characterized by IR, NMR, UV, ESI-MS and elemental analyses. This new nickel metallodendrimer as a catalyst precursor, together with methylaluminoxane as an activator, was evaluated in the ethylene oligomerization. Under the conditions of 0.5 h, 0.5 MPa, 25°C and Al/Ni mole ratio 500: 1 employed for the nickel complex, the catalytic activity showed a maximum value of 4.93 × 105 grams per mole of Ni catalyst per hour. Substituents on the benzene ring seem to have a negative influence on the catalytic activity of the complex.

Interfacial activity and de-emulsification performance of some new amphiphilic cardanol-based phenol-amine resin block polyethers

ABSTRACT Four amphiphilic cardanol-based phenol-amine resin block polyethers (CPAE) with different contents of ethylene oxide and propylene oxide were prepared and were characterized by FTIR and 1H NMR. The surface tension and the interfacial tension of four CPAE block polyethers were measured, and series of surface active parameters were also calculated. The surface activity and the interfacial activity of the CPAE block polyethers were correlated with their chemical structure. The cmc, γcmc, Гmax, and values decreased with an increase of the branching number and the molecular weight, but the Amin value increased. The equilibrium interfacial tension decreased with the increase of the concentration and the molecular weight of the CPAE block polyethers. The results of de-emulsification revealed that the CPAE block polyethers showed interesting de-emulsification efficiency towards the simulated emulsions used in our work. The structure of the CPAE block polyethers could influence the de-emulsification performance, especially the molecular block. The de-emulsification mechanism of the CPAE block polyethers was studied using a single-droplet protocol and the dynamic data of drainage time, half-life time, and rupture rate constant obtained were consistent with the de-emulsification efficiency of the CPAE block polyethers. GRAPHICAL ABSTRACT

Interface Activity and Thermodynamic Properties of Cardanol Polyoxyethylene Ether Carboxylates

Abstract A series of saturated cardanol polyoxyethylene ether carboxylates was synthesized using renewable saturated cardanol originating from Cashew Nut Shell Liquid as raw material. The structures were characterized by hydrogen nuclear magnetic resonance spectroscopy. The studies of their surface activity and interface activity were carried out to analyze the influence of the chemical structures of the series of cardanol surfactants on the adsorption and micellization. Results showed that saturated cardanol polyoxyethylene ether carboxylates had a good surface activity and interface activity, and the interface activities of the Gemini cardanol surfactants were better than those of the corresponding monomer cardanol surfactants. The critical micelle concentrations (CMC) of all investigated cardanol surfactants, obtained from surface tension measurements, were low in the order of 10−5 mol/L. The CMCs decreased and the oil-water interface tension for the same cardanol surfactants increased with the increase of the oxyethylene number. The process of micellization became easier with increasing the oxyethylene number. The ΔGθm values of the Gemini cardanol surfactants were more negative than those of the corresponding monomer cardanol surfactants. The micellization for all cardanol surfactants was a spontaneous process and exhibited enthalpy-entropy compensation. The micellization of all the cardanol surfactants was entropy-driven.

Physicochemical properties of series of cardanol polyoxyethylene ether carboxylates with different ethoxylation unit at the interface

Abstract Series of cardanol polyoxyethylene ether carboxylates were synthesized with biomass cardanol as material to study their physicochemical properties at the interface. The surface tensions of the cardanol nonionic-anionic surfactants were measured at 25 °C and the thermodynamic parameters of adsorption were also calculated. The surface activity and thermodynamic properties of the cardanol nonionic-anionic surfactants were correlated to their chemical structures. With increasing of the number of the ethoxylation unit in the hydrophilic group, a decrease in adsorption efficiency and an increase in surface tension at critical micelle concentration and thermodynamic free energy of adsoption were observed and were attributed to a decrease in adsorption of the cardanol nonionic-anionic surfactants at the interface. Series of the cardanol nonionic-anionic surfactants have good wettability and foaming property. The foaming capacity and the foaming stability of the solution of the cardanol nonionic-anionic surfactants increase by decreasing in the ethoxylation unit and by increasing the double bond of the hydrophobic group. The physicochemical properties of the cardanol nonionic-anionic surfactants at the interface are correlated to the chemical structures of the investigated surfactants, and there is the synergy effect between the nonionic hydrophilic group and the anionic hydrophilic group at the interface. GRAPHICAL ABSTRACT

Kinetics and structure-activity relationship of dendritic bridged hindered phenol antioxidants to protect styrene against free radical induced peroxidation

A series of dendritic poly(amido-amine) (PAMAM) bridged hindered phenols antioxidants were synthesized. The active antioxidant group (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) was attached to two generations of PAMAM dendrimers, and their structure was verified by nuclear magnetic resonance (NMR) and fourier transform infrared spectra (FT-IR). The antioxidant abilities of the dendritic phenols to inhibit the oxidation of styrene were evaluated and the relationships between the length of core, the generation of dendrimers and the antioxidant activities were established. The reaction kinetics of scavenging peroxyl radicals was followed by oxygen consumption. The inhibition time (tinh) values showed the dendritic phenols had the ability of scavenging peroxyl radicals, and that the antioxidant ability increased with the increasing length of the core and the generation. The kinetic analysis demonstrated that dendritic phenols could slow the rate of styrene peroxidation induced by AIBN, as shown by the number of trapping ROO· (n), and this role was in accordance with that of the tinh values.

Synthesis of short straight-chain alkylamine based hyperbranched nickel complexes and their catalytic performance of ethylene oligomerization

ABSTRACT Short straight-chain alkylamine based hyperbranched molecules and their corresponding salicylaldimine nickel complexes have been synthesized in high yield and characterized by FTIR, 1H-NMR and mass spectrometry. The optimal reaction parameters were determined under the catalytic system of methylaluminoxane (MAO) as co-catalyst and toluene as solvent. Under these conditions, the effect of catalyst structure, solvent and co-catalyst were determined. Upon activation of MAO in toluene, ethylene oligomerization products were homogeneous distribution of butene, hexene and octene with trace higher olefin. The same catalytic system under cyclohexane and methyl cyclohexane as solvent, however, produced majority of butene. Under the activation of EtAlCl2, Et2AlCl and EASC as co-catalyst in toluene, ethylene oligomerization reaction was tandem with Friedel-Crafts reaction in catalytic system.