Summary
Chemical looping hydrogen generation based on iron is an innovative method to produce high purity hydrogen and capture CO2 simultaneously. However, carbon deposition of iron ore limits the development. The iron ore modified by K and Cu was employed to suppress the carbon deposition. Experiments were carried out to investigate the effects of the additive amount on carbon deposition and hydrogen purity via carbon release characteristics in a batch fluidized bed. The carbon deposition ratio decreased monotonically with the increasing amount of potassium, but the excess copper loading led to a rise in the ratio of carbon deposition instead. The carbon deposition ratio decreased by up to 84% after adding K and Cu, which is speculated to be closely related to the weight ratio of Fe on the oxygen carrier surfaces. The experimental results at different temperatures demonstrated that 850°C was suitable for the inhibition of carbon deposition and sintering. In addition, the mechanism of inhibition of carbon deposition was proposed in detail and illustrated that it was correlated to the covering of active sites and the reactivity enhancement. Moreover, the carbon deposition ratio of the modified oxygen carrier maintained stable during the cyclic experiments. Therefore, it is feasible to employ the iron ore modified by K and Cu as oxygen carrier to suppress carbon deposition in the chemical looping hydrogen generation.
Normal
temperature catalytic ozonation (NTCO) is a promising yet
challenging method for the removal of volatile organic compounds (VOCs)
because of limited activity of the catalysts at ambient temperature.
Here, we report a series of Pt/FeO
x
catalysts
prepared by the co-precipitation method for NTCO of gaseous methanol.
All samples were found to be active and among them, the Pt/FeO
x
-400 (calcined at 400 °C) catalyst with
a Pt cluster loading of 0.2% exhibited the highest activity, able
to completely convert methanol into CO2 and H2O at 30 °C. Extensive experimental research suggested that the
superior catalytic activity could be attributed to the highly dispersed
Pt clusters and an appropriate molar ratio of Pt0/Pt2+. Furthermore, electron paramagnetic resonance and density
functional theory computational studies revealed the mechanism that
the Pt/FeO
x
-400 catalyst could activate
O3 and water effectively to produce hydroxyl radicals responsible
for the catalytic oxidation of methanol. The findings of this work
may foster the development of technologies for normal temperature
abatement of VOCs with low energy consumption.
Hematite
has become a promising oxygen carrier (OC) due to its
abundance and low cost for chemical looping hydrogen generation (CLHG).
However, the poor redox reactivity, low yield, and purity of hydrogen
are the main issues using hematite as an OC. In order to solve the
problems, a synthesized OC based on iron ore comodified by copper
and potassium was first proposed for CLHG to increase the reduction
reactivity and hydrogen yield. Experiments were conducted in a batched
fluidized bed reactor to evaluate the performance of the synthesized
OC. The results demonstrated that the adding of potassium and copper
elevated the reduction reactivity. The reduction reactivity was in
the sequence of 5Fe1.67Cu10K > 5Fe1Cu10K > 5Fe0.625Cu10K >
5Fe1Cu5K
> 5Fe1Cu0K > hematite. As compared with hematite, the oxygen
transport
conversion increased 70.11% using 5Fe1.67Cu10K. The reduction reactivity
enhancement was attributed to the self-diffusion and pores formation
via adding potassium as well as the high reactivity and oxygen transport
conversion of copper loading. K2Fe4O7 and CuFe2O4 were detected in the synthesized
OCs by XRD analysis, which were active phases for reduction. Moreover,
the high oxygen transport conversion and reactivity revealed the deep
reduction of iron oxides. The hydrogen yield increased 2.1 times on
account of the existence of potassium and copper. Meanwhile, the hydrogen
production rate was improved. Additionally, 850 °C was suitable
for CLHG in consideration of the reaction rate and the low melting
point of the additive. The hydrogen purity was up to 99.9%, indicating
that copper and potassium play significantly synergistic roles on
suppressing carbon deposition. Therefore, the synthesized oxygen carrier
based on iron ore comodified by potassium and copper was suitable
for CLHG.
We herein report a visible-light photoredox-catalyzed regioselective sulfonylation of alkenes with sulfonyl hydrazides assisted by oximes at room temperature, which affords a variety of sulfones in good yields. The initial mechanistic experiments demonstrate that the hydroxyl group within oximes plays a crucial role in this sulfonylation.
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