TECHNICAL FIELD

The various embodiments of the disclosure relate generally to methods for making and compositions of hydrophobic sorbents. It is particularly useful for preparing sorbents for CO2/H2O displacement desorption processes, in which the sorbent has been made more hydrophobic by the including of silicon sources.

BACKGROUND

Fossil fuels currently supply the majority of world's energy needs and their combustion is the largest source of anthropogenic carbon dioxide emissions. Carbon dioxide is a greenhouse gas and is believed to contribute to global climate change. Concern over global climate warming has led to interest in capturing CO2emissions from the combustion of fossil fuels. The quantities of combustion gas produced in electric power generation are large because of the scale of furnaces and turbines utilized. One measure of the scale of these operations is the amount of CO2produced in a typical 500 Megawatt power plant, for coal fired power generation, the rate of CO2production is on the order of 100 kg per second; for gas fired power production it is more like 50 kg per second.

CO2can be removed from combustion flue gas streams by various methods, often referred to a carbon capture and sequestration (CCS.) The challenge for CO2capture from flue gas is to do it efficiently to minimize the cost. All post-combustion CO2capture technologies suffer from the disadvantages that the CO2in the flue gas is present at low pressure (1 atmospheric pressure) and in low concentrations (3 to 15%). A large amount of energy is needed to separate CO2. Developing methods that minimize the amount of energy and other costs will be necessary if CO2removal from flue gas is to be economical. Methods for the removal of CO2from flue gas streams include adsorption with a solvent, adsorption with a sorbent, membrane separation, and cryogenic fractionation and combinations thereof. In absorption/adsorption processes to capture CO2, the energy needed to regenerate the sorbent or solvent is also a large cost element.

CO2displacement desorption process uses a competitive adsorption of H2O to drive off adsorbed CO2on sorbent. During CO2capturing step, CO2of the flue gas displaces the adsorbed H2O on the sorbent. Displacement desorption swings the concentrations of H2O and CO2. It is an isothermal process and has no need for pressure swing.

BRIEF SUMMARY

The various embodiments of the disclosure relate generally to methods for preparing and compositions of silicon-modified sorbents.

An embodiment of the disclosure can be a silicon-modified CO2/H2O displacement desorption sorbent, comprising an aluminum compound support; an alkali metal salt; and a silicon source capping hydroxyl positions on the aluminum compound support.

In some embodiments, the silicon source can be 5% to 20% by weight of silica impregnated on the aluminum support. The silicon source can be 7% to 15% by weight of silica impregnated on the aluminum support.

In some embodiments, the silicon source comprises an organosilyl moiety. The organo silyl moiety can be a triorganosilyl halide or triflate. In some embodiments, the organo silyl moiety can be a trialkyl silyl moiety. The alkyl fragment of the trialkylsilyl moiety can be methyl, ethyl, or propyl, or combinations thereof. In some embodiments, the trialkyl silyl moiety is a trialkylsilyl halide or triflate. The organosilyl moiety can be trimethylsilyl chloride.

An embodiment of the disclosure can be a method for reducing parasitic water sorption/desorption for CO2/H2O displacement desorption sorbents, comprising surface modifying a sorbent with a silicon source. The sorbent can be an aluminum compound impregnated with an alkali metal; and the silicon source can be either an organosilyl moiety added to the sorbent after impregnating with the alkali metal; or a silica added to the aluminum compound prior to impregnating with the alkali metal.

In some embodiments, the silicon source comprises an organosilyl moiety. The organo silyl moiety can be a triorganosilyl halide or triflate. In some embodiments, the organo silyl moiety can be a trialkyl silyl moiety. The alkyl fragment of the trialkylsilyl moiety can be methyl, ethyl, or propyl, or combinations thereof. In some embodiments, the trialkyl silyl moiety is a trialkylsilyl halide or triflate. The organosilyl moiety can be trimethylsilyl chloride.

In some embodiments, the silicon source can be 5% to 20% by weight of silica impregnated on the aluminum support. The silicon source can be 7% to 15% by weight of silica impregnated on the aluminum support.

An embodiment of the disclosure can be a method for preparing a hydrophobic CO2/H2O displacement desorption sorbent, including the steps of impregnating an aluminum compound support with silica; drying and then calcining the silica-impregnated support; depositing an alkali metal salt on the silica-aluminum support; and calcining the support to form the sorbent.

In some embodiments, the silicon source can be 5% to 20% by weight of silica impregnated on the aluminum support. The silicon source can be 7% to 15% by weight of silica impregnated on the aluminum support.

In some embodiments, the aluminum compound can be aluminum oxide, aluminum oxide hydroxide, aluminum hydroxide, boehmite, or pseudoboehmite. In some embodiments, the alkali metal salt can be a potassium salt, a sodium salt, or a lithium salt, or a combination thereof. In some embodiments, the alkali metal salt can be greater than about 5 weight % of the sorbent as M2O, or can be greater than about 8 weight % of the sorbent as M2O.

An embodiment of the disclosure can be a method for preparing a hydrophobic CO2/H2O displacement desorption sorbent, including the steps of preparing an aluminum compound mixture; drying and then calcining the mixture to form a support; depositing an alkali metal salt on the support; and calcining the support to form the sorbent, and treating the sorbent with an organo silyl moiety.

In some embodiments, the silicon source comprises an organosilyl moiety. The organo silyl moiety can be a triorganosilyl halide or triflate. In some embodiments, the organo silyl moiety can be a trialkyl silyl moiety. The alkyl fragment of the trialkylsilyl moiety can be methyl, ethyl, or propyl, or combinations thereof. In some embodiments, the trialkyl silyl moiety is a trialkylsilyl halide or triflate. The organosilyl moiety can be trimethylsilyl chloride.

In some embodiments, the aluminum compound can be aluminum oxide, aluminum oxide hydroxide, aluminum hydroxide, boehmite, or pseudoboehmite. In some embodiments, the alkali metal salt can be a potassium salt, a sodium salt, or a lithium salt, or a combination thereof. In some embodiments, the alkali metal salt can be greater than about 5 weight % of the sorbent as M2O, or can be greater than about 8 weight % of the sorbent as M2O.

