Large heat duty for amine regeneration in absorptionbased CO 2 capture is one of the major drawbacks of this process. Along with a highly endothermic carbamate breakdown reaction in the stripper, the difficulty of proton transfer from protonated amines to water in the amine regeneration process is also considered a basic reason for high heat duty. Transition metal oxide catalysts can play a vital role in decreasing the required thermal energy for amine regeneration in the stripper by providing Bronsted acids and Lewis acids that would help break down the carbamate by direct attack. MEA saturated with CO 2 at 35 °C, with initial loading of 0.56 mole CO 2 /mole amine, was used in this study. The performance of five different transition metal oxide catalysts, V 2 O 5 , MoO 3 , WO 3 , TiO 2 , and Cr 2 O 3 , was studied separately to investigate the effects of these catalysts on amine regeneration in the temperature range of 35−86 °C. It has been observed that MoO 3 performance is much better as it regenerated almost double of the MEA solvent than noncatalytic amine regeneration systems, whereas other catalysts also showed considerable differences in amine regeneration in this temperature range. The amine regeneration performance trend was MoO 3 > V 2 O 5 > Cr 2 O 3 > TiO 2 > WO 3 > blank test. The application of this work would mean that metal oxide catalysts could be used in strippers for a faster CO 2 desorption rate at lower temperature, which would cause a significant reduction of the heat duty.
CO 2 capture from flue gas using the amine-based postcombustion technique is costly because of the high energy requirement for solvent regeneration. The addition of catalyst to the regeneration step can overcome this drawback. In this study, we investigate the regeneration performance of CO 2 -rich MEA solution without and with two solid metal oxide catalystsZrO 2 and ZnOwithin a temperature range of 40−86 °C. The solvent regeneration performance was evaluated in terms of CO 2 desorption rate, total amount of desorbed CO 2 , solvent cyclic capacity, and CO 2 -lean loadings achieved from the catalytic solutions in comparison with the noncatalytic MEA solution.To understand and support the obtained results BET, NH 3 −TPD, pyridine−FTIR, and 13 C NMR characterization techniques are performed. The obtained results suggest that both catalysts are capable of optimizing the solvent regeneration by desorbing up to 32% greater amounts of CO 2 , improving the CO 2 desorption rate up to 54%, and increasing the solvent cyclic capacity up to 56%. On the basis of the obtained experimental and characterization results, a possible mechanism for metal oxide catalyst-aided MEA regeneration process is proposed. The stabilities of both catalysts are confirmed by 5 cyclic solvent regeneration experiments. Additionally, by studying the CO 2 absorption in MEA in the presence of catalyst, it has been investigated if the catalysts induce any undesired activity in the CO 2 absorption step. Catalytic regeneration of amine solvent can pace up the construction of largescale CO 2 capture plants by economizing the process.
Dry
reforming of methane (DRM) is an attractive route to simultaneously
consume both methane (CH4) and carbon dioxide (CO2) for the production of valuable syngas. Although nickel catalysts
are considered to be the most promising in both cost and activity,
catalysts having high stability with low coke formation are highly
coveted for commercialization. Here, we report a one-pot synthesis
for mesoporous supported nickel catalysts with high activity and stability
in a DRM reaction by using a spray pyrolysis-assisted evaporation-induced
self-assembly (EISA) method. Two different strategies were introduced
to prepare the catalysts of mesoporous alumina supports with highly
dispersed active nickel sites from one pot of precursor solutions.
One is phase segregation of nickel from alumina supports already in
the self-assembly step by using a hydrophobic nickel oleate precursor,
a hydrophilic alumina precursor, and an amphipathic triblock copolymer,
which was achievable owing to the unique characteristics of spray
pyrolysis, especially its fast drying-pyrolysis-mediated kinetic quenching,
which was used to form catalysts with highly dispersed active sites
of nickel (3 nm). The other strategy is exsolution, entailing the
release and anchoring of nickel from the bulk to the surface of the
alumina phase in the reduction step while using a hydrophilic nickel
precursor. Compared with nickel catalysts prepared by conventional
wet impregnation, the one-pot catalysts, especially the nickel oleate-based
catalyst, showed high coke resistance, maintaining conversion for
30 h with 92% CH4 conversion and 97% CO2 conversion,
which originated from the smaller well-dispersed nickel particles,
the strong metal–support interaction, and the suppressed particle
agglomeration. We envisage the development, by the one-pot processing
of multicomponent precursor solutions, of heterogeneous supported
catalysts with superior performances for a wider range of applications.
The worldwide large-scale deployment
of the state-of-the-art CO2 capture technique is being
delayed due to the overwhelmingly
high energy consumption in the stripper. Here, we reveal an efficient
Ag2O–Ag2CO3 catalytic cycle
and analyze its activity in the amine solvent regeneration step which
is capable of greatly minimizing the energy requirement by desorbing
greater amounts of CO2 at up to 1000% higher desorption
rate, at low temperature, e.g. 80 °C. After substantially improving
the CO2 desorption, the Ag2O converts into Ag2CO3 which is even more efficient. The Ag2CO3 ultimately decomposes into Ag2O in the
amine regeneration step, and this cycle continues. The validity of
the cyclic catalytic behavior was tested for ten cycles. Furthermore,
the mechanism of Ag2O/Ag2CO3 facilitated
CO2 desorption was elucidated using 1H and 13C nuclear magnetic resonance spectroscopy.
This study focuses on identifying the CO2 absorption
mechanism in an aqueous potassium carbonate (K2CO3)/homopiperazine (homoPZ) solution, at various CO2 loading. 1H nuclear magnetic resonance (NMR) and 13C NMR
measurements were conducted at 295 K within the absorbent concentration
of homoPZ 7.5 wt % and K2CO3 15 wt %/homoPZ
7.5 wt %. The CO2-loaded absorbents were prepared by using
vapor–liquid equilibrium (VLE) apparatus at 333 K. The results
show that the amount of carbamate and bicarbamate in the CO2-loaded K2CO3/homoPZ solution was larger than
in the homoPZ solution. The free homoPZ that is able to react with
CO2 increases in the aqueous K2CO3/homoPZ solution because the K2CO3 serves as
a buffer. It was found that the NMR method can be used to determine
the CO2 absorption mechanism of the absorbents.
Catalytic amine regeneration has recently emerged as an effective strategy to improve CO 2 desorption at low temperatures. In this work, we synthesized inexpensive M-montmorillonite (M = Cr, Fe, and Co) catalysts via a facile metal ionexchange process and used these to optimize the CO 2 desorption rate of a 30 wt % monoethanolamine (MEA) solution at a moderate temperature (∼86 °C). The metal ion-exchange process led to Si and Al leaching from the aluminosilicate layers and cation removal from the Mont interlayers, resulting in an increase in the surface acidity, mesoporosity, and total surface area of the ion-exchanged Mont catalysts. The prepared catalysts introduce acid sites to amine solution that can attach with the carbamate, carbonate, and bicarbonates, to favor the CO 2 desorption at low temperatures. Overall, the CO 2 desorption rate and the total amount of released CO 2 were improved up to 315 and 82.5%, respectively, whereas the regeneration energy penalty was reduced by 40%, in comparison with the noncatalytic MEA solution. The impact of various physicochemical catalytic properties on the CO 2 desorption performance was also evaluated. The stability of the prepared catalysts was verified in five cyclic uses and no change in the catalytic activity or structure was detected. In addition, the catalysts were readily separable by simple filtration. This work introduces an effective strategy to design abundant and cost-effective catalysts for energy-efficient CO 2 capture.
Highly efficient photothermal layers were developed based on a commercially available low-cost material, activated carbon, which demonstrates the potential for practical desalination application with upscalability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.