Abstract: A boehmite having an orthorhombic crystal form in which the ratio of the maximum length in the direction of the a-axis of the crystal to the distance between the opposing crystal faces perpendicular to the c-axis of said crystal is at least 10, said maximum length in the direction of the a-axis of the crystal is at least 2500 .ANG. and said distance between the opposing faces perpendicular to the c-axis of said crystal is 250-900 .ANG..

Abstract: A boehmite having a crystal form wherein the ratio of the maximum length in the direction of the a-axis to the distance between the opposing crystal faces perpendicular to the c-axis is at least 10.

Abstract: A calcium silicate shaped product comprises heat-resistant particles having a radiation energy absorptivity of at least 20% throughout the entire range of the wavelength of from about 2 to about 5.mu., as measured by a 0.1 wt. % KBr disc method.

Abstract: A process for producing a boehmite shaped product comprises slurrying a mixture of a gibbsite powder and at least one powder selected from the group consisting of powders of pseudo-boehmite, amorphous aluminum hydroxide, alumina cement and .rho.-alumina, molding the slurry thereby obtained and subjecting the molded product to hydrothermal treatment.

Abstract: A process for preparing a calcium silicate shaped product comprises heat-reacting a calcareous source and a siliceous source dispersed in water to obtain an aqueous slurry containing a calcium silicate hydrate having a molar ratio of CaO/SiO.sub.2 being more than 1, adding a siliceous source to the aqueous slurry to bring the molar ratio of CaO/SiO.sub.2 to a level of from 0.85 to 1, and pressfilter-molding the aqueous slurry thereby obtained, followed by steam-curing and drying.

Abstract: A calcium silicate shaped product is produced by forming an aqueous slurry of calcium silicate hydrate obtained by reacting a calcareous source with a siliceous source dispersed in water under heating; molding said aqueous slurry and heat-treating said molded product under the condition providing the equations (I) and (II);100.ltoreq..theta..multidot.T (I)50.ltoreq..theta..ltoreq.300 (II)wherein .theta. represents a temperature of the inner part of the molded product (.degree.C.) and T represents a time (hour) and providing a percent water loss of the treated molded product of less than 25 wt. %, before drying or steam-curing and drying the molded product.

Abstract: A calcium silicate shaped product is prepared by forming an aqueous slurry of calcium silicate hydrate by reacting a calcareous source with a siliceous source in water as a dispersion under heating; molding said aqueous slurry to form a molded product having a bulk density of less than 0.6 g/cm.sub.3 ; curing said molded product, in a closed tank having a capacity of 1.5 to 30 times of the volume of said molded product at 140.degree. to 300.degree. C. by dry-heating without feeding steam, and drying the product.

Abstract: An aqueous slurry of calcium silicate hydrate which is formed by heating a siliceous source and a calcareous source in water to react them and which has the specific property is shaped with a press filter molding and cured by a steam curing under steam pressure to cause a transformation of the calcium silicate hydrate whereby a calcium silicate shaped product having low bulk density and high mechanical strength is obtained. The calcium silicate shaped product is suitable as a lagging product or a heat insulator.

Abstract: Nitrogen oxides in exhaust gases are catalytically reduced in the presence of oxygen and ammonia at 200.degree. to 600.degree. C. over a catalyst of at least one catalyst component selected from the group consisting of compounds of metals of Groups 1B, 5A, 6A, 7A and 8 of the periodic table, and lanthanides and tin which is supported on a specific carrier comprising a main component of calcium silicate.

Abstract: An aqueous slurry of calcium silicate hydrate which is formed by heating a siliceous source and a calcareous source in water to react them and which has the specific property is shaped with a press filter molding and cured by a steam curing under steam pressure to cause a transformation of the calcium silicate hydrate whereby a calcium silicate shaped product having low bulk density and high mechanical strength is obtained. The calcium silicate shaped product is suitable as a lagging product or a heat insulator.