An efficient chemical absorption method capable of
cyclic fixed-bed operations under moist
conditions for the recovery of carbon dioxide from flue gases has been
proposed employing K2CO3-on-carbon. Carbon dioxide was chemically absorbed by the reaction
K2CO3 + CO2 +
2KHCO3 to form potassium hydrogencarbonate. Moisture,
usually contained as high as 8−17%
in flue gases, badly affects the capacity of conventional adsorbents
such as zeolites, but the
present technology has no concern with moisture; water is rather
necessary in principle as shown
in the equation above. Deliquescent potassium carbonate should be
supported on an appropriate
porous material to adapt for fixed-bed operations. After
breakthrough of carbon dioxide, the
entrapped carbon dioxide was released by the decomposition of
hydrogencarbonate to shift the
reaction in Eq.1 in reverse on flushing with steam, which could be
condensed by cooling to afford
carbon dioxide in high purity. Among various preparations of
alkaline-earth carbonates (X2CO3,
X = Li, Na, K) on porous materials,
K2CO3-on-activated carbon revealed
for the present purpose. Preparation and characterization of
fixed-bed operations under flue gas conditions in laboratory columns
and a bench-scale plant
The aims of this study were to improve the mechanical and chemical properties of conventional restorative glass ionomer cement (GIC) by adding hydroxyapatite (HAp) preparations with different characteristics, and to investigate the underlying reaction mechanisms. Fuji IX GP ® was used as the control GIC. The experimental GICs consisted of four HAp-particles with different characteristics added at 8 mass% to Fuji IX-powder. All cements were prepared by mixing with Fuji IX-liquid (P/L=3.6). Four HApparticles were analyzed, and then the mechanical strengths and the fluoride-ion-release-recharge-behaviors of five GIC groups were evaluated. The results of this study demonstrate that the addition of HAp particles with highly reactive properties such as high specific surface area can enhance the flexural strength and fluoride ion release properties of conventional restorative GIC. Our results further indicate that HAp functions as an adsorbent and an ion exchangeable agent, resulting in improved mechanical and chemical properties of GIC.
Potassium carbonate supported on an activated carbon has been proposed as an efficient sorbent to recover CO 2 from moist flue gases. As a characteristic of the present CO 2 sorption process, which can be described as K 2 CO 3 ‚1.5H 2 O + CO 2 ) 2KHCO 3 + 0.5H 2 O, moisture in the feed gases had no influence on the CO 2 sorption. By the temperature-swing operation of a fixed-bed, the CO 2 recovery was achieved as follows: carbon dioxide in moist flue gases at around 363 K was sorbed by the K 2 CO 3 sorbent, followed by steam flushing at 433 K to release the CO 2 , and then cooling the sorbent for the next CO 2 sorption. In the present study employing a bench-scale apparatus, the material (CO 2 and H 2 O) balances, together with those of heat during each step, were measured to elucidate the CO 2 sorption/release and the cooling behaviors. To evaluate the practical adaptability of this process, the heat consumption for the CO 2 recovery on a commercial-scale was estimated. When compared with that for other processes such as the conventional amine process, it provided a remarkable energy-conservative effect. The cost for the CO 2 recovery by K 2 CO 3 -on-activated carbon is also discussed.
We report single molecular sheets of niobate prepared by a simple bottom-up approach using hydrothermal synthesis of niobium ethoxide with the aid of triethanolamine as a structural modifier: the high kinetic stability of these molecular entities against self-assembly allows them to mix well with other colloids and facilitates their extensive electronic interactions and thus photocatalytic hydrogen evolution activity from water is much enhanced over composite of single niobate sheets with graphene and MoS2 due to efficient electron transfer and charge separation.
The oxidative dehydrogenation of sodium lactate to sodium pyruvate in an aqueous phase proceeded favorably using Pd/C and that doped with Te at 358 K with no adjustment in solution pH under pressurized oxygen, although previous reports had stated that this reaction would not proceed using Pd/C while Pd/C doped with either Pb, Bi or Te showed the activity at atmospheric pressure, 363 K, and a pH of 8.
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