No abstract

In order to effectively remove mercury from raw natural gas, a preparation method of columnar sulfur-impregnated activated petroleum coke was proposed and mercury adsorption experiments were conducted under simulated natural gas processing operating conditions. The physicochemical properties of the adsorbents were discussed with the aid of characterization methods, including nitrogen adsorption/desorption and scanning electron microscopy (SEM) analysis, ultimate analysis, X-ray photoelectron spectroscopy (XPS) analysis, and thermalgravimetric (TG) analysis. The influence of different preparation procedures, KOH activation, sulfur impregnation, and the modification temperature, space velocity, and inlet Hg 0 concentration on mercury adsorption performance were investigated in a fixed bed reactor. The better preparation procedure of the adsorbent of columnar sulfurimpregnated activated petroleum coke was suggested by following the order of KOH activation, columnar shaping, and sulfur impregnation. Proper space velocity and inlet concentrations of Hg 0 can effectively improve mercury removal. The results showed that, compared with raw petroleum coke, the mercury removal efficiency of KOH activated petroleum coke increased by 20% and its specific surface area reached more than 1300 m 2 /g. After both KOH activation and sulfur impregnation, the bulk sulfur content reached more than 10 atom %, surface oxygen functional groups reached more than 24 atom %, and nonoxidized sulfur forms reached more than 8 atom %, which were most beneficial for mercury removal. It was found that the bonding of the short-chain S molecules to carbon matrix was fairly stable. Sulfur impregnation dominated the Hg 0 removal and the rich micropores were conducive to more sulfur loading and more active sites for mercury adsorption. The adsorbed mercury species of HgS and HgO were attributed to the surface nonoxidative sulfur forms and oxygen functional groups based on the temperature-programmed-desorption (TPD) and XPS results. Kinetic studies indicated that both external mass transfer and chemisorption played a more important role in mercury adsorption than intraparticle diffusion.

Mn/TiO2 (MT), Ce/TiO2 (CT), and Ce–Mn/TiO2 (CMT) for mercury removal were prepared by an impregnation method, and mercury adsorption tests were conducted in a fixed-bed reactor. Regeneration experiments were carried out in a thermal regeneration reactor, and the effects of temperature and atmosphere on the regenerability were investigated. Surface physicochemical characteristics of fresh, spent, and regenerated CMT were analyzed by means of N2 adsorption–desorption methods, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results showed that CMT had a higher resistance to SO2 poisoning than MT and CT and maintained a high mercury removal capability within a wide range of SO2 concentrations. Optimal thermal regenerability of spent CMT was obtained after thermal desorption at 400 °C followed by N2 + 50% O2 for 2 h. Ten cycles of mercury adsorption–regeneration demonstrated that there was no significant change in mercury removal capacity relative to fresh catalytic sorbent after multiple regeneration cycles. The regeneration of CMT was mainly attributed to the decomposition of mercury compounds and the restoration of Mn4+, Ce4+, and the chemisorbed oxygen on the catalytic sorbent surface. The procedure for the centralized control of mercury emissions from the flue gas by CMT was also analyzed for industrial application.

A series of Mn−V−W/TiO 2 (Mn−VWT) catalysts were synthesized by the impregnation method and calcinated at different temperatures (300−600 °C). To explore the effects of the reaction temperature, SO 2 , and H 2 O on the simultaneous removal performance of elemental mercury (Hg 0 ) and NO, Mn−VWT were investigated by a fixed-bed reaction system. Various techniques (scanning electron microscopy, Brunauer−Emmett−Teller, X-ray diffraction, H 2 -temperature-programmed reduction, NH 3 -temperature-programmed desorption, and X-ray photoelectron spectroscopy) were utilized to characterize the samples. The results showed that the catalytic activity of Mn−VWT first increased and then decreased with the increasing calcination temperature. The removal efficiency of Hg 0 and NO still had good performance even in low reaction temperature (200 °C), achieving 100 and 82%, respectively. Mn−VWT-400 had the best simultaneous removal performance because of the highest content of the Mn 4+ , V 4+ , and chemisorbed oxygen O α and the best reductive activity at low temperature. Furthermore, SO 2 irreversibly inhibited Hg 0 and NO removal ability due to the sulfate and sulfite generation on the surface of Mn−VWT-400. Especially, the inhibition effect was more serious if SO 2 and H 2 O coexisted because the rate of sulfate/sulfite was higher than that of the former. In addition, with the increase in reaction temperature, the effect of SO 2 and H 2 O on the removal of Hg 0 and NO over Mn−VWT was gradually reduced.

A Fe-pyridinedicaroxylate based nanoscale coordination polymer works as a Fenton catalyst to degrade pollutants by the formation of ˙OH and high-valent iron species.