Methane Conversion to C_2 Hydrocarbons in Solid State Oxide Electrolyte Membrane Reactor

Provskite-type catalysts, Ln0.6 Sr0.4 FexCo1-x O3 (Ln = Nd,Pr, Gd, Sm, La, 0＜x＜1) and Ln0.8Na0.2CoO3(Ln= La,Gd, Sm) were synthesized, their catalytic properties in the oxidative coupling of methane (OCM) were examined in a fixed-bed reactor. The former group presented higher activity in the OCM, but the main product was carbon dioxide. While the later group showed lower activity but much higher selectivity to C2 hydrocarbons compared with the former. Electrochemical measurements were conducted in a solid oxide membrane reactor with La0.8 Na0.2CoO3 as catalyst. The results showed that methane was oxidized to carbon dioxide and ethane by two parallel reactions. Ethane was oxidized to ethene and carbon dioxide. A fraction of ethene was oxidized deeply to carbon dioxide. The total selectivity to C2 hydrocarbons exceeded 70%. Based on the experimental results, a kinetic model was suggested to describe the reaction results.

Heterogeneous dynamic modeling and simulation of an industrial ethylene oxide reactor experiencing catalyst deactivation

This paper investigates steady-state and dynamic simulation of an industrial fixed-bed ethylene oxide reactor. A mathematical heterogeneous one-dimensional model is developed for simulation of reactor performance in the presence of long term deactivation of silver/a-alumina catalyst. In this paper, steady-state model of the reactor is solved and results of steady state simulation are fed to dynamic simulator as initial condition. When results of dynamic simulation are compared with industrial reactor data, it is found that there were good agreements between simulation results and industrial data. The proposed model is also validated by industrial process data for a period of 1100 operating days.

Ozonation of o-phenylenediamine in the presence of hydrogen peroxide by high-gravity technology

The study herein investigated the effectiveness of simultaneous use of ozone and hydrogen peroxide(O_3/H_2O_2 process) to degrade o-phenylenediamine(o-PDA) in a simulated wastewater. A rotor–stator reactor(RSR) was employed to create a high-gravity environment in order to enhance ozone-liquid mass transfer rate and possibly improve the degradation rate of o-PDA. The degradation efficiency of o-PDA(η) as well as the overall gas-phase volumetric mass transfer coefficient(KGa) were determined under different operating conditions of H_2O_2 concentration, initial o-PDA concentration, temperature of reaction, initial p H and rotation speed of RSR in attempt to establish the optimal conditions. Chemical oxygen demand reduction rate(rCOD) of wastewater treated at a particular set of conditions was also analyzed. Additionally, the intermediate products of degradation were identified using a gas chromatography-mass spectrometer(GC/MS) to further evaluate the extent of o-PDA degradation as well as establish its possible degradation pathway. Results were validated by comparison with those of sole use of ozone(O_3 process), and it was noted that η, KGa and rCODachieved by O_3/H_2O_2 process was 24.4%,31.6% and 25.2% respectively higher than those of O_3 process, indicating that H_2O_2 can greatly enhance ozonation of o-PDA. This work further demonstrates that an RSR can significantly intensify ozone-liquid mass transfer rate and thus provides a feasible intensification means for the ozonation of o-PDA as well as other recalcitrant organics.

NUMERICAL SIMULATION OF SWIRLING FLOWS IN OXIDATION REACTORS FOR TiO_2 MANUFACTURE

The oxidation reactor plays a key role in producing rutile titanium dioxide （TiO2） from vapor-phase titanium tetrachloride （TiCl4） by employing a swirling flow operation for enhanced gas mixing. This work aims to understand the effect of reactor configuration on the 3-D swirling flow field using computational fluid dynamics （CFD） simulation. Considering the anisotropic turbulence involved, the Reynolds stress model is applied to describe the complex swirling flow together with the cross-flow mixing of gases. The results show significant effect of the flow angle between the wall jet of air stream （representing TiCl4 in practice） and the axial direction on the initial flow field of cross-flow mixing, where 60° gives smooth profiles of axial velocity development while 90° may provide the fastest mixing between the jet and the axial bulk flow. The pipe shape for the reaction and developing zone, i.e., straight, expanding and shrinking, shows slight influence on the hydrodynamics.

Atmospheric photochemistry and secondary aerosol formation of urban air in Lyon,France

Photochemical aging of volatile organic compounds(VOCs)in the atmosphere is an important source of secondary organic aerosol(SOA).To evaluate the formation potential of SOA at an urban site in Lyon(France),an outdoor experiment using a Potential Aerosol Mass(PAM)oxidation flow reactor(OFR)was conducted throughout entire days during JanuaryFebruary 2017.Diurnal variation of SOA formations and their correlation with OH radical exposure(OHexp),ambient pollutants(VOCs and particulate matters,PM),Relative Humidity(RH),and temperature were explored in this study.Ambient urban air was exposed to high concentration of OH radicals with OHexp in range of(0.2-1.2)×10^12 molecule/(cm^3·sec),corresponding to several days to weeks of equivalent atmospheric photochemical aging.The results informed that urban air at Lyon has high potency to contribute to SOA,and these SOA productions were favored from OH radical photochemical oxidation rather than via ozonolysis.Maximum SOA formation(36μg/m^3)was obtained at OHexp of about 7.4×10^11 molecule/(cm^3·sec),equivalent to approximately 5 days of atmospheric oxidation.The correlation between SOA formation and ambient environment conditions(RH&temperature,VOCs and PM)was observed.It was the first time to estimate SOA formation potential from ambient air over a long period in urban environment of Lyon.