PROBLEM TO BE SOLVED:

In an apparatus for synthesizing methane from carbon dioxide and hydrogen, a device which is capable to remove the reaction heat and lower the reaction temperature as the reaction progresses in order to increase the conversion ratio to methane has been desired.

SOLUTION:

In the present invention, powders of magnesium hydroxide and magnesium carbonate, which are chemical heat storage agents, are used as part of the fluidizing medium of the multi-stage fluidized bed in the temperature range where the methanation reaction proceeds. The heat generated during the methanation reaction can be absorbed and stored in the powder. At this time, carbon dioxide generated from magnesium carbonate can be used as a raw material gas for the methanation reaction. Furthermore, after discharging the magnesium oxide generated by endotherm, the powder can be regenerated with an external regenerating facility and then the storage heat can be released and recovered. The regenerated powder can be fed to the uppermost stage of the multi-stage fluidized bed at a temperature lower than the internal temperature of the reactor to lower inside temperature. This made it possible to lower the reaction temperature of ascending reaction gas in the reactor along with the reaction progress, and to increase the conversion ratio to the produced methane by this lowered temperature.

PROBLEM TO BE SOLVED:

In an apparatus for synthesizing methane from carbon dioxide and hydrogen, a device which is capable to remove the reaction heat and lower the reaction temperature as the reaction progresses in order to increase the conversion ratio to methane has been desired.

SOLUTION:

In the present invention, powders of magnesium hydroxide and magnesium carbonate, which are chemical heat storage agents, are used as part of the fluidizing medium of the multi-stage fluidized bed in the temperature range where the methanation reaction proceeds. The heat generated during the methanation reaction can be absorbed and stored in the powder. At this time, carbon dioxide generated from magnesium carbonate can be used as a raw material gas for the methanation reaction. Furthermore, after discharging the magnesium oxide generated by endotherm, the powder can be regenerated with an external regenerating facility and then the storage heat can be released and recovered. The regenerated powder can be fed to the uppermost stage of the multi-stage fluidized bed at a temperature lower than the internal temperature of the reactor to lower inside temperature. This made it possible to lower the reaction temperature of ascending reaction gas in the reactor along with the reaction progress, and to increase the conversion ratio to the produced methane by this lowered temperature.

Divalent ions are extracted from solids by leaching to form a divalent ion-containing solution. The divalent ion-containing solution is subjected to concentration to form a concentrated divalent ion-containing solution. Precipitation of a divalent ion hydroxide salt is induced from the concentrated divalent ion-containing solution. In other cases, the concentrated divalent ion-containing solution is exposed to carbon dioxide to induce precipitation of a divalent ion carbonate salt.

Divalent ions are extracted from solids by leaching to form a divalent ion-containing solution. The divalent ion-containing solution is subjected to concentration to form a concentrated divalent ion-containing solution. Precipitation of a divalent ion hydroxide salt is induced from the concentrated divalent ion-containing solution. In other cases, the concentrated divalent ion-containing solution is exposed to carbon dioxide to induce precipitation of a divalent ion carbonate salt.

The present disclosure relates to methods for producing hydrogen and calcium- or magnesium-bearing carbonates by capturing, converting, and storing carbon dioxide. The methods may include providing one or more calcium- or magnesium-bearing compounds; providing one or more water-soluble oxygenates; providing a plurality of catalysts; and reacting one or more calcium- or magnesium-bearing compounds and one or more water-soluble oxygenates with plurality of catalysts under conditions to produce hydrogen and calcium- or magnesium-bearing carbonates. The methods may include providing one or more calcium- or magnesium-bearing silicates; providing carbon monoxide; providing water vapor; and reacting one or more calcium- or magnesium-bearing silicates, carbon monoxide, and water vapor. The methods may include providing one or more calcium- or magnesium-bearing compounds; providing one or more water-soluble oxygenates; providing a catalyst; and reacting one or more calcium- or magnesium-bearing compounds and one or more water-soluble oxygenates with said catalyst.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

A method for producing mesoporous magnesium hydroxide nanoplates involving solvothermal treatment of a solution of a magnesium salt, a base, a glycol, and water is disclosed. The method does not use a surfactant or template in the solvothermal treatment. The method yields mesoporous nanoparticles of magnesium hydroxide having a plate-like morphology with a diameter of 20 nm to 100 nm, a mean pore diameter of 2 to 10 nm, a surface area of 50 to 70 m.sup.2/g, and a type-III nitrogen adsorption-desorption BET isotherm with a H3 hysteresis loop. An antibacterial composition containing the mesoporous magnesium hydroxide nanoplates is also disclosed. A method for reducing nitroaromatic compounds with a reducing agent and the mesoporous magnesium hydroxide nanoplates as a catalyst is also disclosed.