A catalyst for treating an exhaust gas comprising SO.sub.2, NO.sub.x and elemental mercury in the presence of a nitrogenous reductant comprises a composition containing oxides of: (i) Molybdenum (Mo) and optionally Tungsten (W); and (ii) Vanadium (V); and (iii) Titanium (Ti); and(iv) Phosphorus (P), wherein, with respect to the total metal atoms in the composition, the composition comprises: (i) Mo in an amount of less than 2 at. %, and optionally up to 9 at. % W; (ii) from 2.5 to 12 at. % V; (iii) from 85 to 96 at. % Ti, and wherein the composition comprises (iv) P in an atomic ratio to the sum of atoms of Mo, W and V of from 1:2 to 3:2. The values expressed must total 100%.

A catalyst for treating an exhaust gas comprising SO.sub.2, NO.sub.x and elemental mercury in the presence of a nitrogenous reductant comprises a composition containing oxides of: (i) Molybdenum (Mo) and/or Tungsten (W); (ii) Vanadium (V); (iii) Titanium (Ti), and (iv) an MFI zeolite, wherein the composition comprises, based on the total weight of the composition: (i) 1 to 6 wt % of MoO.sub.3 and/or 1 to 10 wt % WO.sub.3; and (ii) 0.1 to 3 wt % V.sub.2O.sub.5, and (iii) 48.5 to 94.5 wt % TiO.sub.2; and (iv) 35 to 50 wt % MFI zeolite.

Shippable modular units configured for use in sequestering CO.sub.2 are provided. Aspects of the units include a support having one or more of: a CO.sub.2 gas/liquid contactor subunit, a carbonate production subunit and an alkali enrichment subunit; associated therewith. Also provided are systems made up of one or more such modular units, and methods for using the units/systems in CO.sub.2 sequestration protocols.

The gas separation membrane includes a separation layer containing a silsesquioxane compound, and a protective layer, in which a composition of the separation layer in a thickness direction is uniform.

A protective-layer-covered gas separation membrane has a gas separation membrane that satisfies specific conditions such as having a resin layer containing a compound having a siloxane bond, a protective layer located on the resin layer containing a compound having a siloxane bond of the gas separation membrane, and a porous layer on the protective layer. The protective-layer-covered gas separation membrane is produced. A gas separation membrane module and a gas separation apparatus have the protective-layer-covered gas separation membrane.

A method for producing a protective-layer-covered gas separation membrane includes forming a gas separation membrane having a resin layer containing a compound having a siloxane bond and satisfying a particular condition by surface oxidation treatment of a resin layer precursor containing a siloxane bond; and providing a protective layer on the resin layer before winding. A protective-layer-covered gas separation membrane is produced by the method for producing a protective-layer-covered gas separation membrane. A gas separation membrane module and a gas separation apparatus are produced by the method for producing a protective-layer-covered gas separation membrane.

A calcium-containing composition with fixed CO.sub.2 is produced by contacting a mixture of a calcium-containing composition before CO.sub.2 fixation and water with a CO.sub.2-containing gas. The calcium-containing composition, liquid water, and the CO.sub.2-containing gas having a temperature between 20 degree Celsius and 300 degree Celsius and a CO.sub.2 concentration between 1 volume % and 100 volume % are supplied to a reactor. By the supplied CO.sub.2-containing gas, the calcium-containing composition and water are made to flow in the reactor. Alternatively, the calcium-containing composition and water are in the reactor. Thus, CO.sub.2 is fixed in the calcium-containing composition and simultaneously the calcium-containing composition is dried to a water content of 5 mass % or less.

A system and a method for converting captured carbon dioxide (CO.sub.2) into hydrogen (H.sub.2) by using metallic iron or metallic magnesium in anaerobic process are described. In a first step, the CO.sub.2 can be absorbed in an alkaline solution such as NaOH and a soluble bicarbonate is formed. In a second step, the soluble bicarbonate HCO.sub.3 is converted into H.sub.2 by reacting it with zero valent metal, like metallic Fe (powder) or scrap Fe or Magnesium ribbon in anaerobic ambient conditions. Metal carbonate, like siderite, is created on the outer surface of Fe(.sup.0) and can be separated by the alkaline solution, which is recycled in the first reaction to be used for CO.sub.2 absorption. Exposing the separated siderite to weak acid, either citric acid or oxalic acid, zero valent metal is obtained, which is recycled in the second reaction. Alternatively, the siderite can be used as a raw material in the steel industry or cement industry or commercialized as an iron scrap. The generated H.sub.2 can be directly used for energy purposes or can be directed to another reactor comprising also bicarbonate solution and mix hydrogenotrophic methanogens to be converted into methane (CH.sub.4) or to a bioreactor comprising homoacetogenic bacteria to be converted into carboxylic acids, like acetic acid (CH.sub.3COOH). Alternatively, the reaction with Fe(.sup.0) or Mg(.sup.0), bicarbonate solution, CO.sub.2 and hydrogenotrophic methanogens for the production of CH.sub.4 can take place in one and same bioreactor.

Disclosed is a bypass system for use with off gases that have exited a cement kiln utilized in a cement making process. The bypass system is adapted to remove both NOx and volatile components that are present in the off gases while the off gases are in the bypass duct.

Calcium hydroxide-containing compositions can be manufactured by slaking quicklime, and subsequently drying and milling the slaked product. The resulting calcium hydroxide-containing composition can have a size, steepness, pore volume, and/or other features that render the compositions suitable for treatment of exhaust gases and/or removal of contaminants. In some embodiments, the calcium hydroxide-containing compositions can include a D.sub.10 from about 0.5 microns to about 4 microns, a D.sub.90 less than about 30 microns, and a ratio of D.sub.90 to D.sub.10 from about 8 to about 20, wherein individual particles include a surface area greater than or equal to about 25 m.sup.2/g.