No abstract

Besides organic pollutants, coke production generates emissions of toxic heavy metals. However, intensive studies on heavy metal emissions from the coking industry are still very scarce. The current work focuses on assessing the emission characteristics of heavy metals and their behavior during coking. Simultaneous sampling of coal, coke, residues from air pollution control devices (APCD), effluent from coke quenching, and fly ash from different processes before and after APCD has been performed. The total heavy metal concentration in the flue gas from coke pushing (CP) was significantly higher than that from coal charging (CC) and combustion of coke oven gases (CG). Emission factors of heavy metals for CP and CC were 378.692 and 42.783 μg/kg, respectively. During coking, the heavy metals that were contained in the feedstock coal showed different partitioning patterns. For example, Cu, Zn, As, Pb, and Cr were obviously concentrated in the inlet fly ash compared to the coke; among these metals Cu, As, and Cr were concentrated in the outlet fly ash, whereas Zn and Pb were distributed equally between the outlet fly ash and APCD residue. Ni, Co, Cd, Fe, and V were partitioned equally between the inlet fly ash and the coke. Understanding the behavior of heavy metals during coking processes is helpful for the effective control of these heavy metals and the assessment of the potential impact of their emissions on the environment.

The activation of C–H bonds at low temperatures has attracted widespread interest in heterogeneous catalysis, which involves complex thermocatalytic and photocatalytic reaction processes. Herein, we systematically investigate the photothermal catalytic process of C–H bond activation in C2H6 dehydrogenation on rutile TiO2(110). We demonstrate that the photochemical activity of the C2H6 molecule adsorbed on TiO2(110) is site-sensitive and that C2H6 is more easily adsorbed at the Ti5c site with a lower dehydrogenation energy barrier. The first C–H bond activation of the C2H6 adsorbed at the Ti5c site tends to occur in the ground state, whereas Obr-adsorbed C2H6 is more photoactive during the initial adsorption. During the dehydrogenation of C2H6, the photogenerated electrons are always located at the Ti4+ sites of the TiO2 substrate while the photogenerated holes can be captured by C2H6 to activate the C–H bond.

No abstract