Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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Subject: search.filters.subject.Lignite

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  • Article
    Citation - WoS: 98
    Citation - Scopus: 108
    Capacity and Mechanism of Phenol Adsorption on Lignite
    (Elsevier Ltd., 2006) Polat, Hürriyet; Molva, Murat; Polat, Mehmet
    A raw lignitic coal from Soma, Turkey was investigated to determine its potential as an adsorbent for phenol removal from wastewaters. Kinetic batch tests demonstrated that phenol could be completely removed from solution given sufficient solids loading and reaction time. The adsorption capacity of 10 mg/g obtained with the lignite is low compared to those achievable with activated carbons (around 300 mg/g). However, when normalized for the surface area, the adsorption capacity was much larger for the lignite (1.3 mg/m2) than that generally observed with activated carbons (0.05-0.3 mg/m2). Hydrogen-bonding of the phenolic -OH with the oxygen sites on the lignite surface is the most likely mechanism for adsorption. Though water molecules also have affinity for the same oxygen sites, lateral benzene ring interactions make phenol adsorption energetically more favorable. Since phenol molecules adsorbed in this fashion would project their benzene rings into solution, formation of a second layer through the action of the dispersive π-π interactions between the benzene rings is very likely. Residual water quality with respect to major elements and heavy metals was within acceptable limits defined by the ASTM standards. Dissolution of organic matter from the lignite was also observed to be negligible.
  • Article
    Citation - WoS: 23
    Citation - Scopus: 28
    Direct Liquefaction of High-Sulfur Coals: Effect of the Catalyst, the Solvent, and the Mineral Matter
    (American Chemical Society, 2002) Gözmen, Belgin; Artok, Levent; Erbatur, Gaye; Erbatur, Oktay
    Two low-rank coals with high sulfur contents (Gediz subbituminous coal: 7.6 wt % S:dry basis. Çayirhan lignite: 5.7 wt% S:dry basis.) were subjected to hydroliquefaction. Liquefaction conditions included dry or solvent mediated runs under pressurized hydrogen without added catalyst or with the impregnated catalyst precursor ammonium heptamolybdate (AHM). Gediz coal having higher sulfur content gave 90% conversion in the absence of catalyst and solvent. Maximum conversion (98%) and maximum oil + gas yield (70%) from this coal were obtained by impregnating AHM onto coal and carrying out liquefaction in H 2/tetralin system at 450 °C for 30 min. Under the same conditions, Çayirhan lignite gave 85% conversion and 70.5% oil + gas yield. The superior hydrodesulfurization effect of impregnated AHM on the oil fraction when used in the absence of solvent (less than 0.1% S in lignite's oil and less than 1% S in subbituminous coal's oil following one-stage hydrogenation) is a promising finding of this work. AHM was found to be much more effective in liquefaction of Çayirhan lignite and this has been ascribed to the well-dispersion of AHM throughout this lignite's structure via a cation-exchange mechanism through oxygen functionalities. Strong evidence for the catalytic effect of clay minerals in coal structure on char-forming reactions during liquefaction was observed by making use of liquefaction reactions of demineralized coal samples. It was also observed that tetralin had a retarding effect on the condensation and subsequent cross-linking reactions.