Thermochimica Acta 434 (2005) 27–36 Flow calorimetric and thermal gravimetric study of adsorption of thiophenic sulfur compounds on NaY zeolite Ming Jiang, Flora T.T. Ng ∗ , Ataur Rahman, Viral Patel Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ont., Canada N2L 3G1 Received 9 October 2004; received in revised form 26 November 2004; accepted 5 January 2005 Available online 30 January 2005 Abstract A study of adsorption of thiophenic sulfur compounds (thiophene, benzothiophene, dibenzothiophene and 4,6-dimethyl benzothiophene) in normal alkane solvents (octane, dodecane and hexadecane) on NaY zeolite has been performed by using flow calorimetry technique and thermogravimetric analysis. The measured heat of adsorption of sulfur compounds includes the heat from the displacement of the adsorbed solvent molecules by sulfur compounds and it is therefore much lower than that obtained by gas phase adsorption of sulfur compounds in the zeolite. The apparent heat of adsorption of sulfur compounds per gram of sorbent decreases when the solvent changes from octane, dodecane to hexadecane, but the heat of adsorption per mole of sulfur compound calculated based on the sorption data does not vary significantly with the solvent used. The measured heat of adsorption per gram of sorbent is also influenced by the molecular size of the sulfur compound and decreases in the order: thiophene > benzothiophene > dibenzothiophene due to the higher sorbent capacity for the smaller sulfur compound. Thermogravimetric analysis of the adsorbed sulfur compounds under combustion condition used for the sulfur elimination from the sorbent indicates that the combustion of the refractory sulfur compounds occurs at higher temperatures. Analysis of the effluent from the calorimeter could be used to estimate the breakthrough characteristics of the sorbent. This indicates that the flow calorimetry is a promising technique for establishing the relationship between sorption capacity and heat of adsorption of sulfur compounds. The information obtained from the flow calorimetry and thermogravimetry could be used for the development of selective sorbents for the production of ultra-clean fuels. © 2005 Published by Elsevier B.V. Keywords: Flow calorimetry; Thermogravimetry; Sulfur adsorption; NaY zeolite 1. Introduction Deep removal of sulfur-containing compounds in fuels has become an ever more important subject of environmental pro- tection due to the required lower limit of sulfur content in fuel products set by the government legislation. US Environmen- tal Protection Agency mandates a reduction of sulfur content of gasoline from the current 300 to 30 parts per million (ppm) by weight and diesel from 500 to 15 ppm by 2006 [1–3]. Eu- ∗ Corresponding author. Tel.: +1 519 888 4567x3979; fax: +1 519 746 4979. E-mail address: fttng@cape.uwaterloo.ca (F.T.T. Ng). ropean legislation also calls for a reduction of sulfur content to less than 50 ppm for gasoline and diesel fuels by 2005 [4]. On-board or on-site reforming of the fuels to produce hydro- gen for fuel cells also requires ultra-clean fuels since traces of sulfur will poison the reforming and electrode catalysts [2,3,5]. Conventional hydrodesulfurization process has been used in the refineries worldwide to remove sulfur compounds from the liquid fuels. This process is very effective to remove light sulfur compounds such as thiophene and bezothiophene, but it is difficult to remove refractory sulfur compounds such as dibenzothiophene and, especially, 4,6-dimethyl dibenzoth- iophene. Furthermore, hydrodesulfurization also reduces the octane number of the fuels due to the saturation of olefins 0040-6031/$ – see front matter © 2005 Published by Elsevier B.V. doi:10.1016/j.tca.2005.01.006