NOx Removal over Modified Carbon Molecular Sieve Catalysts Using a Combined Adsorption-Discharge Plasma Catalytic Process

Structure-activity relationships, product species distribution and the mechanism of effect of multi-component flue gas on Hg0 adsorption and oxidation over CuO/ACs

A series of Cu-doped activated cokes (CuO/ACs) were synthesized via an impregnation method and applied for the removal of elemental mercury (Hg0). Structure-activity relationships between Hg0 removal and CuO/AC surface characteristics were identified. Hg0 removal over CuO/AC occurs through a combination of physisorption and chemisorption and is mainly dominated by chemisorption. It was found that 1 nm micropores facilitate Hg0 physisorption. Hg0 could weakly adsorb onto an O-terminated crystal layer, whereas strongly adsorb onto Cu-terminated single highly dispersed, clustered and bulk CuO (110) crystal planes via the Mars-Maessen mechanism. Product distributions and mechanisms of Hg0 adsorption and oxidation over the CuO/AC catalyst under multi-component flue gases are also discussed. O2 enhances both physisorption and chemisorption toward Hg0 by 38%. Inhibition of Hg0 removal by SO2 originates from the competitive adsorption and deactivation of CuO cation vacancies, whereas the impact is weakened by O2 through generating 20% of physically adsorbed mercury product species. NO and O2 promote Hg0 chemisorption efficiency by 93% to form Hg(NO3)2. HOCl and/or Cl2 produced by HCl can oxidize 100% of Hg0 to HgCl2, and the catalytic oxidation efficiency is approximately 29%, but O2 slightly lowers the Hg0 catalytic oxidation efficiency by 8%. The affinity ability between various flue gases and Hg0 follows the order O2 < NO < HCl.

Activation and characterization of environmental catalysts in plasma-catalysis: Status and challenges

Plasma-catalysis has attracted great attentions in environmental/energy-related fields, but the synergetic mechanism still suffers intractable defects. Key issues are that what kind of catalysts are applicable for plasma system, how are they activated in plasma, and how to characterize them in plasma. This review systematically gives a comprehensive summarization of the selection of catalysts and its activation mechanism in plasma, based on the character of plasma, including physical effects containing the enhancement of discharge intensity and adsorption of reactants, and the utilization of plasma-generated active species such as·O, heat, O₃, ultraviolet light and e* . Focus is given to the illumination of the activation mechanisms of catalysts when placed in plasma zone. Subsequently, the novel characterization techniques for catalysts, which may associate properties to performance, are critically overviewed. The challenges and opportunities for the activation and characterizations of catalysts are proposed, and future perspectives are suggested about where the efforts should be made. It is expected that a bridge between catalysts design and character of plasma can be built to shed light on the synergetic mechanism for plasma-catalysis and design of new plasma-catalysis systems.

A Review about the Recent Advances in Selected NonThermal Plasma Assisted Solid-Gas Phase Chemical Processes

Plasma science has attracted the interest of researchers in various disciplines since the 1990s. This continuously evolving field has spawned investigations into several applications, including industrial sterilization, pollution control, polymer science, food safety and biomedicine. nonthermal plasma (NTP) can promote the occurrence of chemical reactions in a lower operating temperature range, condition in which, in a conventional process, a catalyst is generally not active. The aim, when using NTP, is to selectively transfer electrical energy to the electrons, generating free radicals through collisions and promoting the desired chemical changes without spending energy in heating the system. Therefore, NTP can be used in various fields, such as NOx removal from exhaust gases, soot removal from diesel engine exhaust, volatile organic compound (VOC) decomposition, industrial applications, such as ammonia production or methanation reaction (Sabatier reaction). The combination of NTP technology with catalysts is a promising option to improve selectivity and efficiency in some chemical processes. In this review, recent advances in selected nonthermal plasma assisted solid-gas processes are introduced, and the attention was mainly focused on the use of the dielectric barrier discharge (DBD) reactors.

Diesel engine exhaust denitration using non-thermal plasma with activated carbon

A diesel engine de-NO_x system combining non-thermal plasma and activated carbon was set up. The de-NO_x efficiency reaches 91.8% and 92.5% for simulated gas and real exhaust gas, respectively. It has good potential to replace vanadium-based SCR.

Using CuO-MnOx/AC-H as catalyst for simultaneous removal of Hg° and NO from coal-fired flue gas

A series of CuO-MnO_x modified catalysts were prepared, and proposed for simultaneous removal of Hg° and NO from flue gas. As Mn loading value was 5%, the high value of 90% Hg and 60% NO_x were removed efficiently. With gradual increasing of reaction temperature, the mercury removal efficiency (Mercury RE) first increased to 92% then decreased slightly, while NO_x removal efficiency (NO_x RE) exhibited a trend of continuous increase. O₂ had promotional effect on the double pollutants removal, while NH₃ had slightly negative effect on Hg° removal. As 5% O₂ was added into system, the removal efficiency of Hg and NO_x rose by 30% and 47%, respectively. Unfortunately, Mercury RE decreased to 90% in the presence of 500 ppm NH₃. Overall, superior Mercury RE (>90%) and NO_x RE (78%) were performed over 8%CuO-5%MnO_x/AC-H at 200 °C. XRD results revealed calcination affected catalysts activity by playing a role in active components formation at different temperature. In XPS spectra, new formation of HgO and Hg° adsorption on spent catalysts revealed the possible reaction processes that the conversion of CuO and MnO₂ on fresh catalyst to other species benefited HgO formation. The removal mechanism might be a combination of Langmuir-Hinshelwood and Mars-van-Krevelen mechanism.

Hydroisomerization of n-hexadecane over a Pd–Ni2P/SAPO-31 bifunctional catalyst: synergistic effects of bimetallic active sites

The Pd-Ni2P/SAPO-31 catalyst shows excellent performance in n-hexadecane hydroisomerization due to the synergistic effects of Pd–Ni2P and improved metal/acid balance.