A series of AOT (aerosol-OT) analogue surfactants (sodium salt of dibutyl-2-sulfosuccinate, sodium salt of dipentyl-2-sulfosuccinate, sodium salt of dihexyl-2-sulfosuccinate, and sodium salt of dioctyl-2-sulfosuccinate) were synthesized and characterized by 1H NMR and elemental analysis. A static method coupled with gravimetric analysis is developed to measure the solubility of the surfactants in 1,1,1,2-tetrafluoroethane (HFC-134a) and supercritical CO2 (scCO2). The solubilities of the surfactants in HFC-134a and scCO2 are affected by the temperature, pressure, and carbon atom number of the surfactant. The solubility of the same surfactant in HFC-134a solvent is approximately two times that in the most commonly used supercritical solvent CO2. The pressuretemperature phase diagrams for water/HFC-134a microemulsions stabilized by the surfactants were determined using cloud-point measurements for a concentration range of the surfactant from (1.85 _ 10-3 to 5.60 _ 10-3) M, temperature up to 338 K, and pressure up to 40 MPa in a high-pressure vessel. At a fixed temperature, the cloud-point pressure increased with increasing water-to-surfactant molar ratio (Wo). At a fixed Wo, the cloudpoint pressure decreased with increasing temperature. The surfactant with the longest hydrocarbon chain has the highest cloud-point pressure even at lower surfactant concentrations.

zing cellulose acetate particles from ramie fiber was developed. The optimum conditions for preparing cellulose acetate (CA) by reaction of ramie fiber with acetic anhydride under an acidic condition were determined. Reaction was carried out in a ratio of ramie fiber to acetic anhydride of 1:6 (w/w) at 80 _C for 0.5–1 h. When CA was added to a mixture of water and acetone, CA particles with a well-distributed diameter ranging from 5 to 15 lm were obtained. The difference of the CA particle surface was resulting from different washing methods of CA particles with water or aqueous sodium bicarbonate. The highest degree of substitution (DS) of 2.50 for CA by titration method was achieved. A new adsorbent was prepared from CA, which is an excellent sorption regent for organic waste in water. The scanning electron microscopy (SEM) and particle size distribution results showed that the average size of CA particles is about 5–15 lm in diameter. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to determine the stability of ramie fiber and CA particle. 2006 Elsevier B.V. All rights reserved.

The catalytic synthesis of methyl acrylate by hydroesteri cation of acetylene with methyl formate was studied under various conditions. Mixtures of nickel acetate tetrahydrate, copper sulfate pentahydrate and sodium iodide dihydrate were used as catalysts, and N,N-dimethylformamide as solvent. The experimental results concerning the effects of the reaction condition on selectivity to methyl acrylate, methanol and methyl propionate suggested the synthesis of methyl acrylate through the carbonylation reaction of acetylene. When the reaction was carried out under the total initial pressure of 6.0 Mpa and the CO initial partial pressure of 3.0 MPa at the temperature of 1808C with the catalyst composition of 0.040 M Ni(OAc)2_4H2O and 0.054 M NaI_2H2O, 86% selectivity to methyl acrylate and 64% conversion of methyl formate were achieved. # 1998 Elsevier Science B.V. All rights reserved.

The surface hydrophobicity/hydrophilicity of ramie fiber was regulated through the atom transfer radical polymerization of methyl methacrylate from initiators immobilized on the fiber. The optimal reaction conditions for preparing the macroinitiated ramie fiber were determined to be a temperature of 608C and a reaction time of 24 h. The grafted copolymers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive analysis of X-rays, gel permeation chromatography, and thermogravimetric analysis. The results indicate that poly (methyl methacrylate) was covalently bonded onto the surface of the ramie fiber, and the polymerization of methyl methacrylate was a living/controlled process under the investigated conditions. The results of the contact angle measurements indicate that the wettability of the ramie fiber could be widely regulated by control of the grafted ratios of poly(methyl methacrylate) from 26 to 33 wt %.

The effects of pretreatment conditions, including the addition of a phase-transfer catalyst, on the benzylation of ramie fiber were investigated in this study. Raw and benzylated ramie fibers were dyed in supercritical carbon dioxide, and the color strength (K/S) of the ramie fiber was measured by ultraviolet–visible spectroscopy. An obviously improved dyeing capability of the benzylated ramie fiber, that is, a better level-dyeing property and a higher K/S, was achieved. Moreover, the color strength of the ramie fiber, indexed as the value of K/S, increased significantly with the degree of substitution of the benzylated ramie fiber. The raw and modified ramie fibers were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry.