The invention relates to a catalyst system suitable for hydrogenating aromatic nitro compounds (I) to form the corresponding aromatic amines (II), the catalyst system containing, as essential constituents: a component A selected from the group consisting of silicon carbide, corundum (alpha-Al.sub.2O.sub.3) and slightly porous to non-porous zirconium oxide (ZrO.sub.2); and a component B, containing B1—a carrier substance selected from the group consisting of silicon dioxide, gamma-, delta- or theta-aluminum oxide Al.sub.2O.sub.3, titanium dioxide, zirconium dioxide and graphite, B2—a metal or a plurality of metals selected from the group consisting of copper, nickel, palladium, platinum and cobalt, and optionally B3—an additional metal selected from the group consisting of at least one metal selected from main group I, main group II, main group IV and sub-groups II, V, VI and VIII of the periodic table of the elements, the proportion of component A being in the range of 5 to 60 wt %, in relation to the total weight of the catalyst system, and the aromatic nitro compounds (I) being those of the general formula R—(NO.sub.2).sub.n, (I), and the aromatic amines (II) being those of the general formula R—(NH.sub.2).sub.n, (II), and the moieties R and indices n in formulas (I) and (II) having the following meaning: R is a substituted or unsubstituted aromatic C.sub.6-C.sub.10 moiety and n is an integer from 1 to 5.

Described herein is a gaslight multilayered composite tube having a heat transfer coefficient of >500 W/m.sup.2/K which in its construction over the cross section of the wall of the composite tube includes as an inner layer a nonporous monolithic oxide ceramic surrounded by an outer layer of oxidic fiber composite ceramic, where this outer layer has an open porosity of 5%<ε<50%, and which on the inner surface of the composite tube includes a plurality of depressions oriented towards the outer wall of the composite tube. Also described herein is a method of using the multilayered composite tube as a reaction tube for endothermic reactions, jet tubes, flame tubes or rotary tubes.

Described herein is a gaslight multilayered composite tube having a heat transfer coefficient of >500 W/m.sup.2/K which in its construction over the cross section of the wall of the composite tube includes as an inner layer a nonporous monolithic oxide ceramic surrounded by an outer layer of oxidic fiber composite ceramic, where this outer layer has an open porosity of 5%<ε<50%, and which on the inner surface of the composite tube includes a plurality of depressions oriented towards the outer wall of the composite tube. Also described herein is a method of using the multilayered composite tube as a reaction tube for endothermic reactions, jet tubes, flame tubes or rotary tubes.

A porous material includes aggregate particles and a binding material. In the aggregate particles, oxide films containing cristobalite are provided on surfaces of particle bodies that are silicon carbide particles or silicon nitride particles. The binding material binds the aggregate particles together in a state where pores are provided therein. The porous material contains at least one of copper, calcium, and nickel as an ancillary component.

A porous material includes aggregate particles and a binding material. In the aggregate particles, oxide films containing cristobalite are provided on surfaces of particle bodies that are silicon carbide particles or silicon nitride particles. The binding material binds the aggregate particles together in a state where pores are provided therein. The porous material contains at least one of copper, calcium, and nickel as an ancillary component.

A composite sintered body contains a silicon phase, a cordierite phase, and a high-resistance silicon carbide phase. The content of silicon in the composite sintered body to the composite sintered body is not lower than 30 mass % and not higher than 50 mass %. The content of cordierite in the composite sintered body to the composite sintered body is not lower than 10 mass % and not higher than 50 mass %. The content of high-resistance silicon carbide in the composite sintered body to the composite sintered body is not lower than 20 mass % and not higher than 50 mass %.

A composite sintered body contains a silicon phase, a cordierite phase, and a high-resistance silicon carbide phase. The content of silicon in the composite sintered body to the composite sintered body is not lower than 30 mass % and not higher than 50 mass %. The content of cordierite in the composite sintered body to the composite sintered body is not lower than 10 mass % and not higher than 50 mass %. The content of high-resistance silicon carbide in the composite sintered body to the composite sintered body is not lower than 20 mass % and not higher than 50 mass %.

An exhaust gas treatment system (1) comprises a catalyst article (5) for the treatment of an exhaust gas, the catalyst article (5) comprising a non-metallic substrate (20) comprising a plurality of catalytically-active transition-metal-doped iron oxide magnetic particles (45), and an inductive heater (70) for inductively heating the plurality of catalytically-active magnetic particles by applying an alternating magnetic field.

The present invention relates to a method of preparing ultra-pure silicon carbide in which a super-porous spherical silica aerogel is used as a silica raw material. By preparing the silica aerogel particles using low-cost water glass, a reaction area with respect to a carbon raw material is increased to enable low-temperature synthesis of silicon carbide, the size and shape of silicon carbide powder may be uniformly controlled to prepare ultra-pure silicon carbide, and economic efficiency and productivity of the silicon carbide synthesis may be improved. Thus, it is expected that the silicon carbide powder prepared by the preparation method of the present invention may be provided as an optimized raw material for the preparation of silicon carbide sintered body and single crystal (ingot).

The present invention relates to a method of preparing ultra-pure silicon carbide in which a super-porous spherical silica aerogel is used as a silica raw material. By preparing the silica aerogel particles using low-cost water glass, a reaction area with respect to a carbon raw material is increased to enable low-temperature synthesis of silicon carbide, the size and shape of silicon carbide powder may be uniformly controlled to prepare ultra-pure silicon carbide, and economic efficiency and productivity of the silicon carbide synthesis may be improved. Thus, it is expected that the silicon carbide powder prepared by the preparation method of the present invention may be provided as an optimized raw material for the preparation of silicon carbide sintered body and single crystal (ingot).