Stability studies of coal liquid products using high performance liquid chromatography

The storage stability of coal liquids is of great importance if coal liquefaction products are to replace petroleum products. It has been reported that gum formation occurs in coal-derived liquids during storage to a level at which it becomes a handling problem. The aging of coal hydropyrolysis liquids has been studied. Coal liquid products were placed in preweighed sample vials and stored under light, in the presence of air, at different storage temperatures (2, 21, and 32°C). The weight of gum formed was determined at specified sampling times. High performance liquid chromatography (HPLC) was used to monitor the changes in hydrocarbon class composition with storage time. The changes in boiling point distribution were also determined using simulated distillation with an evaporative light-scattering detector.;Results show that the rate of gum formation is fastest at the highest storage temperature and slowest at the lowest storage temperature. The gum formed increased significantly at the early stage of storage and then remained constant with time. It was found that the saturate compound class remained constant with time at all storage conditions. However, both the polar and aromatic compound classes decreased significantly at the early stage of storage and then remained constant with time. The polar compounds were separated from the aromatic and saturate compound classes using solid phase extraction. No gum formation was observed for both the polar compounds and the aromatic-saturate mixture. Results from HPLC and simulated distillation method show no signs of changes in their chemical composition and boiling point distribution. It was concluded that the main reactants in gum formation in coal liquids are the aromatic and polar compound classes. Results from GC/MS and FTIR show that the polar compounds consist mainly of phenols. The affects of inert gas on the stability of coal liquids were determined by storing coal liquid samples in the presence of argon gas. It was then concluded that the presence of inert gas does not prevent the formation gum; instead, it slows down the rate of gum formation. A kinetic model was developed that describes the experimental data

Removal of Acid Yellow 25 from Aqueous Solution by Chitin Prepared from Waste Snow Crab Legs

Acid Yellow 25 (AY25) is used in the textile industry for dyeing of natural and synthetic fibers, and is also used as a coloring agent in paints, inks, plastics, and leathers. Effluents from such industries are major sources of water pollution. Hence, it is important to find simple, efficient, and inexpensive ways to remove these dyes from wastewater. Here, we determined the suitability of chitin extracted from waste crab legs as an adsorbent for removing AY25 dye. The adsorption kinetics was modeled using pseudo-first order, pseudo-second order, and intraparticle diffusion equations to determine the rate controlling step. Results showed that the pseudo-second order adsorption mechanism is predominant, and the overall rate of the dye adsorption process is therefore controlled by an adsorption reaction. Adsorption isotherms were analyzed by utilizing the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models at 23˚C, with data collected by using various initial dye concentrations with different chitin dosages. Our results show the highest correlation with the Langmuir model, consistent with the fact that chitin contains both a monolayer and homogeneous adsorption sites. Based on the D-R model, the adsorption of AY25 dye onto chitin is via chemisorption. Furthermore, we have concluded that the rate constants of both pseudo-second order adsorption and film diffusion are correlated to the initial dye concentrations and chitin dosages. In conclusion, chitin from waste crab legs is a very suitable adsorbent material that is capable of rapidly removing up to 95% of the initial concentration of AY25 dye at a pH of 2 and room temperature