Cerium doped copper/ZSM-5 catalysts used for the selective catalytic reduction of nitrogen oxide with ammonia

The CuCe/ZSM-5 catalysts with different cerium loadings (0, 0.5, 1.0, 1.5 and 2.0wt.%) was investigated to evaluate the correlation between structural characteristics and catalytic performance for the selective catalytic reduction (SCR) of NO by NH3. It was found that the addition of cerium increased copper dispersion and prevented its crystallization. According to the results of X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H2-TPR), copper species were enriched on the ZSM-5 grain surfaces and part of copper ions was incorporated into the cerium lattice. Addition of cerium improved the redox properties of the CuCe/ZSM-5 catalysts, owing to the higher valence of copper and mobility of lattice oxygen than those of Cu/ZSM-5 catalyst. Hence the introduction of cerium in Cu/ZSM-5 improved significantly NO conversion. On the one hand, the cerium introduction into Cu-Z enhances their low-temperature activities. 95% NO conversion is reached around 197°C for Cu-Z while the corresponding temperature value decreases to 148°C for CuCe4-Z. On the other hand, the temperature range of efficient NO reduction (95%) also extends to higher temperature when the cerium are added to Cu/ZSM-5. Among the Cu-Ce/ZSM-5 catalysts tested, the CuCe4-Z sample exhibits the highest catalytic activity with the temperature range for 90% NO removal of 148-427°C

Characterization of self-adjoint domains for regular even order C-symmetric differential operators

Let $C$ be a skew-diagonal constant matrix satisfying $C^{-1}=-C=C^{\ast}$. We characterize the self-adjoint domains for regular even order $C$-symmetric differential operators with two-point boundary conditions. Thepreviously known characterizations are a special case of this one

Characterization of self-adjoint domains for regular even order C-symmetric differential operators

Let C be a skew-diagonal constant matrix satisfying C −1 = −C = C . We characterize the self-adjoint domains for regular even order C-symmetric differential operators with two-point boundary conditions. The previously known characterizations are a special case of this one

A torsion balance as a weak-force testbed for novel optical inertial sensors

Torsion balances (TBs) are versatile instruments known for their ability to measure tiny forces and accelerations with high precision. We are currently commissioning a new TB facility to support the development and testing of novel optical inertial sensor units for future gravity-related space missions. Here, we report on the status of our apparatus and present first sensitivity curves that demonstrate acceleration and torque sensitivities of 5 ⋅ 10 − 11 m s − 2 and 1 ⋅ 10 − 12 N m H z − 1 at frequencies around 4 m H z , respectively. Capacitive sensors and optical levers measure the dynamics of the system with a displacement sensitivity of down to 9 ⋅ 10 − 10 m H z − 1 for the former and 2 ⋅ 10 − 11 m H z − 1 for the latter. Combining the readout of the suspended inertial member (IM) with environmental sensor signals, the system is characterized, and limiting noise sources are identified. We find that, in particular, the coupling of ambient seismic motion is limiting over a broad frequency range and show that due to its high susceptibility to ground motion, our TB is also a promising platform for exploring ground motion sensing in multiple degrees of freedom. Future upgrades will focus on mitigating seismic noise by controlling the torsion fiber suspension point using piezoelectric actuators and the integration of precision interferometric readout of the IM. These improvements will further increase the sensitivity towards the thermal noise limit which constrains the performance to 1 ⋅ 10 − 13 m s − 2 H z − 1 at 4 m H z

A facilitated synthesis of hierarchically porous Cu-Ce-Zr catalyst using bacterial cellulose for VOCs oxidation

Highly active CuO-CeO2-ZrO2 catalysts were prepared by sol-gel method, using environmentally friendly bacterial cellulose (BC) as structure directing regent. The catalyst designed with commercial BC (Com-BC) exhibited catalytic performances in toluene (T100 =220 oC) and ethyl acetate oxidation (T100 =170 oC) superior to the catalysts prepared by traditional methods. Furthermore, excellent stability was obtained and no deactivation was observed during the 100 h on stream in toluene and ethyl acetate oxidation at T100. The excellent activity and stability of Com-BC can be explained by the hierarchically porous structure, abundant oxygen vacancies, and good reducibility

Characterization of Self-Adjoint Domains for Two-Interval Even Order Singular C-Symmetric Differential Operators in Direct Sum Spaces

This paper is concerned with the characterization of all self-adjoint domains associated with two-interval even order singular C-symmetric differential operators in terms of boundary conditions. The previously known characterizations of Lagrange symmetric differential operators are a special case of this one

Characterization of self-adjoint domains for regular even order CC-symmetric differential operators

Let $C$ be a skew-diagonal constant matrix satisfying $C^{-1}=-C=C^{\ast}$. We characterize the self-adjoint domains for regular even order $C$-symmetric differential operators with two-point boundary conditions. Thepreviously known characterizations are a special case of this one

Plasma-catalytic oxidation of toluene over MCeZrO_<i>x</i>/TiO₂ (M = Cu, Mn, Ni and Co) catalysts using a dielectric barrier discharge reactor

Plasma catalysis is recognized as a promising technology for the elimination of diluted volatile organic compounds (VOCs). In this study, a hybrid process was carried out using dielectric barrier discharge (DBD) and MCeZr/TiO2 (M = Cu, Mn, Ni, and Co) catalysts for the degradation of VOCs. The plasma-catalytic system demonstrated a substantial improvement in toluene conversion and CO2 selectivity compared to the plasma-only system owing to the synergistic effects of plasma and thermal catalysis on toluene degradation. The performance of toluene removal follows the sequence of CuCeZr/T > NiCeZr/T > CoCeZr/T > MnCeZr/T in plasma catalysis. The CuCeZr/T catalyst demonstrated the highest toluene conversion of 99.0% and a CO2 selectivity of 91.0% at a discharge power of 30 W. Energetic electrons and reactive species generated by plasma actively participate in toluene activation in the gas phase and facilitate adsorption on the catalyst surface. The redox properties between Ce4+/Ce3+ and Cu+/Cu2+ species dictated the reducibility of the CuCeZr/T catalyst, promoting oxygen cycling during toluene oxidation and leading to enhanced catalytic performance. The pathways of toluene destruction in the plasma-catalysis system are discussed based on the analysis results of GC-MS, optical emission spectroscopy and calculations of the electron-impact reactions