Number Of Sulphonic Acid Groups Research Articles

Reduced surface sulphonic acid concentration Alleviates carbon-based solid acid catalysts deactivation in biodiesel production

In this study, esterification of oleic acid with methanol using solid acid catalysts synthesised from different waste biomasses (bamboo, wheat straw, and peanut shells) using the carbonisation–sulphonation method was investigated. The results showed that biomass with higher lignin content had a lower optimum carbonisation temperature and the corresponding catalyst contained more acidic groups. All three catalysts catalyzed esterification reactions under optimum reaction conditions (10 wt% catalyst loading, 8:1 methanol/oleic acid, at 75 °C for 8 h) with >96% conversion. The oleic acid conversion decreased with catalyst cycles, reaching approximately 80% after four cycles. In addition to the leaching of active groups during the reaction, the reaction of the sulphonic acid on the catalyst surface with excess methanol (i.e., sulphonic ester formation) is an important cause of catalyst deactivation. The high concentration of sulphonic acid groups on the catalyst surface was the major cause of sulphonic ester formation during esterification. Therefore, reducing the concentration of sulphonic acid groups by increasing the catalyst volume and specific surface area is an effective way to avoid reduction in the catalyst activity while maintaining a constant total number of sulphonic acid groups.

Decoloration of acid dye effluent with ozone: effect of pH, salt concentration and treatment time

A study of the ozone treatment of textile effluent containing acid dyes has been carried out to explore the influence of their chemistry, and the pH, salt concentration, ozone dose and time of treatment. The experiments were constructed using a Box-Hunter second-order composite design for three variables. The study has demonstrated that the type of aromatic rings and the number of sulphonic acid groups in the dye have a marked effect on decoloration. The pH, salt concentration and treatment time are also found to have a predictable influence. The ozone oxidation of acid dye effluent results in a reduction in pH and total organic carbon content.

Statistical analysis of the effect of aromatic, azo and sulphonic acid groups on decolouration of acid dye effluents using advanced oxidation processes

In the present study, the effect of advanced oxidation processes such as ozone/UV, ozone/H 2O 2 and ozone/UV/H 2O 2 on decolouration of Acid Red 88, Acid Orange 7, Acid Orange 10 and Acid Red 73 dye effluents in the presence of sodium sulphate salt were considered. Studies were carried out to analyse and compare the effect of aromatic, azo and sulphonic acid groups on decolouration of acid dye effluents. Among the advanced oxidation processes, ozone/UV/H 2O 2 treatment is more efficient for decolouration than other treatments in all the dye effluents except in Acid Red 88, where ozone/UV treatment shows better decolouration than the other processes. Acid dyes possessing only naphthalene rings in its structure undergo faster decolouration than the dyes with the combination of benzene and naphthalene rings. Among the dyes studied, those with higher number of sulphonic acid groups in its structure are easier to decolour. But on increasing the azo groups in its structure, increasing decolouration time was observed. It was also found that acidic pH and lower salt concentration in the effluents are more efficient for decolouration in all the treatment processes.

Studies on decolouration, toxicity and the possibility for recycling of acid dye effluents using ozone treatment

Investigations carried out to study the feasibility of application of ozone technology for decolouration, toxicity and towards recycling of acid dye effluents for dyeing of silk fabric are reported in this paper. The dyes Acid Red 88, Acid Red 18, Acid Orange 7, Acid Orange 10 and Acid Red 73 were used in this study. The used dye baths were treated with ozone till complete colour removal and reused. For all the dyes two successive recycling processes were carried out. Characteristics of effluents and ozone treated effluents were assessed in terms of total dissolved solids (TDS) and chemical oxygen demand (COD). Gambusia affinis was used for the bioassay tests to find the LC 50 value of the treated effluents. The effect of recycling on quality of dyeing was determined using colour difference (Δ E*) and relative unlevelness index (RUI). This study reveals that treatment of acid dye effluents with ozone does not have an effect on TDS reduction. But it reduces the COD of effluents including the effluents obtained in recycling processes. The toxicity of the ozone treated effluents increases with increasing time. A dye having a greater number of sulphonic acid groups in its structure reveals higher toxicity. Resulting effluents from the application of Acid Red 88 and Acid Red 73 on silk fabric can be recycled twice and those from Acid Red 18 and Acid Orange 10 can be recycled once with acceptable Δ E* values. Acid Orange 7 effluent is found to be unsuitable for recycling because of its higher colour difference values. The levelness of the shade determined on the basis of RUI, produced on the silk fabric in the recycling processes, is either excellent or good in all the cases, which include those producing higher colour difference.

The catalytic performance of sulphonated cross-linked polystyrene beads in the formation of isobornyl acetate

The use of three sulphonated cross-linked polystyrene resins (Dowex 50WX8, Amberlyst 15 and Purolite MN500) is reported as heterogeneous Bronsted acid catalysts in the solvent-free liquid-phase hydro-acyloxy-addition reaction of acetic acid ( 1a) to camphene ( 2), giving the pine-fragrance isobornyl acetate ( 3a). As a homogeneous reference catalyst p-toluene sulphonic acid monohydrate was employed. Prior to use, the hygroscopic resins were dried in vacuo, followed by swelling with glacial acetic acid vapour. Since Karl Fischer titrations showed that the drying procedure did not remove all adsorbed water, acetic anhydride was used to eliminate traces of residual water. Ion-exchange reactions provided the number of sulphonic acid groups per gram of resin, while the accessibility of the acid groups was assessed from acid–base titrations and SEM/EDAX. The number of resin beads to be suspended to achieve a desired number of acid sites determined the rate of the reaction. It was demonstrated that transport within the pores of the beads did not affect the rate of the reaction. The conformation of the polystyrene chains determines the accessibility of the acid groups as well as the presence of liquids as dimethylsulfoxide that are able to establish hydrogen bonds with the acid sites. With both the resin catalysts and the homogeneous reference catalyst, the rate of the reaction increased upon addition of small aliquots of water to the reaction mixture. A rise of the proton mobility near the sulphonic acid moieties rationalises the increase of the rate of the reaction by addition of water. The specific absorption of water in the resins also decreased the agglomeration of the sulphonic acid groups of the resins and the shielding of the acid groups by the polystyrene chains, which proceeds with the more flexible (less cross-linked) Dowex 50WX8. The other two resins gave similar reaction rate constants as p-toluene sulphonic acid monohydrate. Since the conversion of camphene ( 2) completely stopped after separation of the resin beads from the reaction mixture, the three different types of resin beads can be effectively applied as heterogeneous solid acid catalysts. By application of a fixed-bed reactor and re-circulating the reactants, the equilibrium is quantitatively shifted to the product isobornyl acetate ( 3a).

Biological activities of phthalocyanines. XIV. Effect of hydrophobic phthalimidomethyl groups on the in vivo phototoxicity and mechanism of photodynamic action of sulphonated aluminium phthalocyanines.

Aluminium phthalocyanines substituted to different degrees with hydrophilic sulphonic acid and hydrophobic phthalimidomethyl groups were investigated in vivo as new agents for the photodynamic therapy of malignant tumours. Parameters studied included the photodynamic action on EMT-6 mammary tumours in BALB/c mice, the therapeutic window and the potential for direct cell killing, assayed via an in vivo/in vitro test. Although the efficiency of photoinactivation of the EMT-6 tumour increases by a factor of ten with reduction of the number of sulphonic acid groups from four to two, no further effect was seen with the addition of the hydrophobic phthalimidomethyl groups. Addition of the latter groups however increased the potential for direct cell killing by a factor of two and expanded the therapeutic window by a factor of four, thus improving the usefulness of the dye as a photosensitiser for the photodynamic therapy of cancer.

Sulphonic Acid Groups in Monoazo Acid Dyes and Their Effect on Lightfastness on Nylon 66

This paper discusses the measurement of the increase in lightfastness of some monoazo acid dyes on nylon 66 obtained by increasing the number of sulphonic acid groups in the dye molecules. The increase may be attributed to decreasing surface activity of dye molecules and also to increased strength of dye-fiber bonding caused by an enhanced likelihood of ionic links forming between dye and fiber.

Dyeing of Water Swollen, Solvent Exchanged Cotton with Anionic Dyes from Dimethylformamide-Trichloroethylene Solvent Mixtures

Attempts have been made to study the equilibrium adsorption at 40°C of three acid dyes having the same structure but a varying number of sulphonic acid groups on water swollen, solvent exchanged cotton from different ratios of dimethylfor mamide-trichloroethylene solvent mixtures. The equilibrium adsorption of the dyes in general increased with decrease in dye solubility in the solvent mixture and increase in the number of sulphonic acid groups in the dye molecule. To understand the dyeing mechanism, the adsorption isotherms were plotted and interpreted in terms of distribution of dye between the dye bath and the solvent closely associated with the fiber, followed by Langmuir adsorption on cotton. The affinity values were cal culated using the Langmuir equation and were consistent over a wide range of dye concentrations. The dye affinity increased with the increase in trichloroethylene con tent in the solvent mixture and with the increase in sulphonic acid groups in the dye molecule.

DIFFUSION OF ACID DYES IN SILK

The penetration of acid dyes in silk fibroin gut with circular cross section was studied. The dye penetration coefficient (p) was determined by measuring the penetration distance (X) in dyed gut section by means of a microspectrophotometer using the following equation, where t is the dyeing time.The results obtained were as follows:(1) The penetration distance was proportionate to the square root of dyeing time except for prolonged dyeing.(2) The penetration distance was affected remarkably by dyeing temperature, and also was very much dependent on dye species. However, in the apparent activation energy of penetration, there was no large difference among the dyes giving 6-8kcal/mol.(3) The penetration coefficients of A. Orange 7, A. Food Yellow 3 and A. Red 18 increased with the decrease in dye-bath pH, but the coefficient of A. Red 88 remained unchanged. The penetration coefficient of A. Red 18 increased with the dye concentration in the dye-bath.(4) For dyes having the same sulphonic acid group number, the penetration coefficients decreased with increasing molecular weight or the number of atoms, or with decreasing inorganic/organic ratio of the dyes.Comparison of the penetration coefficients of the dyes with the same bone structure, indicated that the coefficient decreased with the number of sulphonic acid groups, the extent of which were much different for pH above or below 4.0.(5) If great care is taken in uniform thickness of cross sections, it was found possible to obtain the diffusion coefficient D(c) through this experimental technique. The diffusion coefficient of A. Red 18 was observed to be dependent on dye concentration within the gut.