High energy duty restricts the application of amine-based absorption
in CO2 capture and limits the achievement of carbon neutrality.
Although regenerating the amine solvent with solid acid catalysts
can increase energy efficiency, inactivation of the catalyst must
be addressed. Here, we report a robust metal–organic framework
(MOF)-derived hybrid solid acid catalyst (SO4
2–/ZIF-67-C@TiO2) with improved acidity for promoting amine
regeneration. The TiO2 coating effectively prevented the
active components stripping from the surface of the catalyst, thus
prolonging its lifespan. The well-protected Co–N
x
sites and protonated groups introduced onto the
TiO2 surface increased the amount and rate of CO2 desorption by more than 64.5 and 153%, respectively. Consequently,
the energy consumption decreased by approximately 36%. The catalyzed
N–C bond rupture and proton transfer mechanisms are proposed.
This work provides an effective protection strategy for robust acid
catalysts, thus advancing the CO2 capture with less energy
duty.
Using a K2CO3/piperazine (PZ) mixture as
a typical phase-change absorbent has promising applicability for carbon
dioxide (CO2) capture in coal-fired power plants that would
contribute to low energy consumption for solvent regeneration. In
this study, the reaction rate of CO2 with a concentrated
K2CO3/PZ mixture was measured in a wetted-wall
column. At a CO2 loading close to saturation absorption,
correlative physical parameters were calculated. The effects of operating
conditions, including gas flow rate, slurry flow rate, PZ concentration,
CO2 loading, K2CO3 mass fraction,
and temperature, on the absorption rate of CO2 were investigated.
The results showed that the absorption rate was sensitive to the effects
of the gas flow rate and CO2 loading. The PZ concentration
and K2CO3 mass fraction also substantially influenced
the CO2 absorption rate. However, minor changes in the
CO2 absorption rate were observed when the slurry flow
rate and temperature were increased. On the basis of a pseudo-first-order
model, the absorption rate determined in this study was found to be
controlled by mass transfer in both the gas film and the liquid film.
The results can serve as a useful reference for designing CO2 removal systems using K2CO3/PZ mixtures.
Hexavalent chromium (Cr(VI)) is a highly toxic substance
in wastewater,
triggering grievous detriment to aquatic life and human health. Magnesium
sulfite is spawned along with the desulfurization process in coal-fired
power plants, which is usually disposed of as solid waste. Here, a
“waste control by waste” method was proposed upon the
redox of Cr(VI)–sulfite, in which highly toxic Cr(VI) is detoxicated
and sequent enriched on a novel biochar-induced cobalt-based silica
composite (BISC) due to the forced electron transfer from chromium
to surface hydroxyl. The immobilized Cr on BISC gave rise to the reconstruction
of catalytic active sites “Cr–O–Co”, which
further enhance its performance in sulfite oxidation by elevating
O2 adsorption. As a result, the sulfite oxidation rate
increased by 10 times compared with the non-catalysis benchmark together
with the maximum chromium adsorption capacity being 120.3 mg/g. Therefore,
this study provides a promising strategy to simultaneously control
highly toxic Cr(VI) and sulfite, achieving high-grade sulfur resource
recovery for wet magnesia desulfurization.
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