Abstract: A plurality of catalyst assemblies each have a plurality of sheet catalysts which are arranged in parallel to each other with distances thereby to define a plurality of gas passages. The catalyst assemblies are stacked in a catalytic reactor so that the width direction of the sheet catalysts of one of the catalyst assemblies will traverse the width direction of the sheet catalysts of each of the immediately adjacent assemblies, whereby leading edges of the sheet catalysts of each assembly are exposed to a gas to be treated rising upward in the gas passages.

Abstract: A waste gas containing sulfur oxides is contacted with an adsorbent comprising an intimate mixture of an iron oxide and/or a copper oxide and a titanium oxide at a temperature of 250.degree.-500.degree. C. The sulfur oxides thus adsorbed are desorbed with a reducing gas and recovered as sulfur material.The efficiency of the adsorbent is not reduced even after many repetitions of the adsorption-desorption cycle. Since the adsorbent exhibits a high resistance to sulfuric acid mist (SO.sub.3) contained in the waste gas.

Abstract: Waste water issued from a wet type desulfurization apparatus and containing thionic acid ions is introduced into ion-exchange towers filled with weak-basic anion-exchange which has to effect anion exchange therein. The weak-basic anion-exchange resin which has adsorbed the thionic acid ions is desorbed by contacting an alkaline solution. The thionic acid ions included in the desorbing solution are decomposed by heating them in the presence of acid. A decomposed solution is issued out of the system after its neutralization.

Abstract: Nitric acid is added to an aqueous solution of organic acid salts of metals to be included in a resulting complex oxide powder, into which an aqueous solution of an inorganic salt of other metal component has been incorporated according to need, and the resulting solution is heated until the organic acid salts are decomposed and the decomposition product is heated, whereby a intended complex powder which is very fine and highly bulky and has a large specific surface area is obtained.

Abstract: The present invention relates to a process for removing nitrogen oxides contained in a gaseous mixture such as combustion flue gas, etc. by reduction of the nitrogen oxides with ammonia, and a cuprous or cupric halide is used as a catalyst to carry out the reduction in a low temperature range. As a result, nitrogen oxides can be satisfactorily removed by the reduction even at about 150.degree. C.

Abstract: A contaminant, such as sulfur dioxide, is removed from a fluid, such as hot exhaust gas, by passing it through beds of material for removing the contaminants, such as activated carbon for adsorbing the sulfur dioxide as sulfur trioxide; periodically, the bed is regenerated by discontinuing the passage of process fluid therethrough and passing through the bed a regenerating fluid, such as water, with quantities of the regenerating fluid being successively passed through the bed with corresponding decreasing amounts of contaminants, such as sulfuric acid within the water, in the respective quantities of regenerative fluid. At least one further bed of material is regenerated with substantially the same regenerative fluid in substantially the same succession of concentrations, but out of phase so that a quantity of regenerative fluid of one contaminant concentration is passed completely through only one bed of material prior to its passing through another bed of material.

Abstract: An ammonia gas to be determined, and an oxidative gas containing nitrogen oxides in moles more than those of the ammonia are brought into contact with an analytical catalyst capable of forming nitrogen and water from ammonia and nitrogen oxides.Concentrations of nitrogen oxides of the gas before and after the contact with the analytical catalyst are determined, and an ammonia concentration of the gas is determined by converting the difference between the concentrations of nitrogen oxides to the ammonia concentration by calculation.

Abstract: A catalyst composition for reducing nitrogen oxides, which is characterized in that the same contains, as its chief ingredient,A. tin (Sn) as the component A, andB. at least one metal selected from the group consisting of molybdenum (Mo), tungsten (W), and iron (Fe), as the component (B).in the form of their oxides, and a process for reducing nitrogen oxides to nitrogen, which comprises contacting a gaseous mixture containing nitrogen oxides and molecular oxygen and a reducing gas with aforesaid catalyst composition at elevated temperatures.