Room Temperature Adsorptive Removal of Thiophene over Zinc Oxide-Based Adsorbents
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JMEPEG https://doi.org/10.1007/s11665-018-3192-2
Room Temperature Adsorptive Removal of Thiophene over Zinc Oxide-Based Adsorbents Sohan Bir Singh and Mahuya De (Submitted April 19, 2017; in revised form December 18, 2017) This study investigated the room temperature adsorptive removal of thiophene over zinc oxide adsorbents in the presence of hydrogen. The bulk zinc oxide was prepared by precipitation method and calcined at different temperatures in the range of 300-550 °C. Supported zinc oxide was prepared by co-precipitation of 30 wt.% ZnO with alumina and calcined at 550 °C. Properties of the adsorbents were determined by various characterization techniques such as surface area and pore volume analysis, XRD, FESEM, EDX and TPR. The desulfurization process was carried out in a down-flow packed bed reactor at room temperature (30 °C). The BET surface area of bulk zinc oxide adsorbents decreased with the increase in calcination temperature from 300 to 550 °C. The surface area of bulk zinc oxide adsorbents was 30.5 and 14.6 m2/g when calcined at 300 and 550 °C, respectively. The surface are of supported zinc oxide adsorbents was 177 m2/g. The highest average pore size was obtained for bulk ZnO calcined at 550 °C (45 nm) compared to that calcined at 300 °C (42 nm) and supported ZnO (27 nm). The XRD peaks corresponded to the hexagonal structure of zinc oxide. The removal of thiophene was most significant for bulk ZnO calcined at 550 °C. The higher removal efficiency for this adsorbent in spite of lower surface area may be attributed to its higher percentage of larger pores and higher average pore size. Keywords
adsorption, desulfurization, thiophene, ZnO adsorbents
1. Introduction The residue sulfur in transportation fuels is one of the major sources of air pollution. The stringent environment laws have necessitated the production of cleaner fuels (Ref 1). The worldwide allowed sulfur levels are different in different countries. In USA, the accepted sulfur level is 15 ppm for highway diesel since 2006 (Ref 2), while for Europe it is 10 ppm sulfur (Ref 3). Other developed countries such as Japan and Canada also follow similar regulations. In India, there is a two-tier system for fuel quality called Bharat Stage specifications (BS). The BS-IV grade diesel has been introduced in 13 major cities since April 2010, which requires a reduction of sulfur from the earlier 350 ppm level (BS-III) to 50 ppm (BSIV) (Ref 4). Currently, sulfur is removed from diesel fuel by the conventional hydrodesulfurization process, in which the This article is an invited paper selected from presentations at ‘‘ICETINN-2017, International Conference on Emerging Trends in Nanoscience and Nanotechnology,’’ held March 16-18, 2017, in Majitar, Sikkim, India, and has been expanded from the original presentation. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11665-018-3192-2) contains supplementary material, which is available to authorized users. Sohan Bir Singh and Mahuya De, Department of Chemical Engin
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