Abstract: Procedure for the preparation of a solid carrier for olefin polymerization catalysts comprising the steps:

Abstract: A catalyst for purification of exhaust gas includes a carrier, and a catalyst layer containing an alkali metal and/or an alkaline earth metal as an NOx-adsorbing component, the catalyst layer being loaded on the carrier, in which catalyst the carrier-composing material contains Si in an amount of 0.5 to 10.0% by weight as expressed as an oxide. Since the inclusion of Si can suppress the deterioration of the carrier caused by the alkali metal and/or the alkaline earth metal during the use of the catalyst, the catalyst can be used over a long period.

Abstract: Frangible, spray dried agglomerate catalyst supports are provided, e.g. of silica gel, which possess a controlled morphology of microspheroidal shape, rough, scabrous appearance, and interstitial void spaces which penetrate the agglomerate surface and are of substantially uniform size and distribution. The agglomerates also possess a 1-250 micron particle size, 1-1000 m2/gm. surface area, and an Attrition Quality Index (AQI) of at least 10. The agglomerates are derived from a mixture of dry milled inorganic oxide particles, e.g. silica gel, and optionally but preferably wet milled inorganic oxide particles, e.g. silica gel particles, (which preferably contain a colloidal segment of <1 micron particles) slurried in water for spray drying. The high AQI assures that the agglomerates are frangible and that polymerization performance is improved.

Abstract: A method of making frangible, spray dried agglomerate catalyst supports is provided, e.g. of silica gel, which possess a controlled morphology of microspheroidal shape, preferably a rough, scabrous appearance, and interstitial void spaces which penetrate the agglomerate. The agglomerates also possess a 4-250 micron particle size, 1-1000 m2/gm. surface area, and an Attrition Quality Index (AQI) of at least 10. The method comprises dry milling inorganic oxide particles, e.g. silica gel, wet milling the dry milled inorganic oxide particles (to preferably impart a colloidal segment of <1 micron particles), and spray drying the particles. The high AQI assures that the agglomerates are frangible and that polymerization performance is improved. The controlled morphology is believed to permit the constituent particles of the agglomerates to be more uniformly impregnated or coated with conventional olefin polymerization catalysts.

Abstract: This invention relates to a preparation process of a catalyst which comprises a noble metal and a metal as catalysis promoter in combination with an alkali or alkaline earth metal compound, supported on the outer surface of a carrier. The preparation process comprises impregnating the carrier with a solution containing an oxidative state noble metal as the main catalyst and an oxidative state metal as catalysis promoter, reducing the oxidative state metals into the metallic state in gaseous phase with a gaseous reducing agent under certain temperature, pressure, moisture and gas concentration, then impregnating the reduced carrier with a solution of an alkali or alkaline earth metal compound. The metal components-supporting catalyst prepared by the process according to the present invention has a high surface area and exhibits high catalytic activity, which leads to increase the catalytic efficiency and life of this heterogeneous catalyst.

Abstract: Catalyst systems of the Ziegler-Natta type comprise as active constituents

Abstract: Aluminum-magnesium silicate- or fluorinated magnesium silicate- aerogels which may be calcined, chemically modified, ion-exchanged, agglomerated, used as a component of a catalyst composition for an addition polymerization; supported versions thereof; and processes for polymerization are disclosed.

Abstract: A catalyst for purifying an exhaust gas includes amorphous and homogeneous composite oxide particles, a catalytic noble metal element, and metallic oxide particles. The metallic oxide particles interpose among the composite oxide particles to connect them with each other at least. The catalyst has good heat resistance, sulfur-poisoning resistance, and durability. The catalyst is produced as follows. A slurry is prepared by mixing an organosol with a suspension, or by mixing a solution with a suspension. The slurry is deposited on a support substrate to form a coating layer thereon. The suspension includes a precursor powder, and a solvent. The precursor powder includes the composite oxide particles, and the catalytic noble metal element. The composite oxide particles include a support component, and an NOx storage element. The solvent is free from elution of the NOx storage element. The organosol includes an organic solvent, and an oxide sol.

Abstract: An electron accepting developer useful for producing visible images by reaction with an electron donor in carbonless paper and photo-imaging systems, the developer comprising an acid-treated, water insoluble alkali metal-modified, inorganic oxide or an acid-treated molecular sieve.

Abstract: An additive catalyst for the cracking of heavy oil, characterized in that the additive catalyst includes: (i) a mixed metal oxide composed of an acidic metal oxide and a basic metal oxide, in which the proportion of the basic metal oxide is from 5 to 50 mole %, (ii) clay, and (iii) silica.

Abstract: The invention relates to a method of producing a catalyst comprising a porous support and a catalytically active metal deposited thereon comprising the steps of treating the porous support with a solution of a salt of the catalytically active metal and a reducing agent to achieve electroless deposition of the catalytically active metal on the support. The invention also relates to a catalyst obtainable by the method and a process of producing hydrogen peroxide.

Abstract: Disclosed are certain catalysts and catalyst support materials and processes for the preparation of the catalyst support materials and for the selective hydrogenation of 3,4-epoxy-1-butene (EpB) to 1,2-epoxy-butane (butylene oxide—BO). The catalyst support materials have micropores filled with one or more inorganic oxides and the supported catalysts comprise one or more Group VIII metals deposited on the support materials. The rhodium-containing supported catalysts are especially useful for the selective hydrogenation of EpB to BO.

Abstract: A honeycomb structure in which partitioning walls comprising, as a chief component, cordierite of a chemical composition containing 45 to 55% by weight of SiO.sub.2, 33 to 42% by weight of Al.sub.2 O.sub.3, and 12 to 18% by weight of MgO are formed in the shape of a honeycomb. The partitioning walls have a thickness of not larger than 250 .mu.m and a porosity of from 45 to 80%.

Abstract: The present invention relates to amorphous microporous mixed oxides, characterized by having, in dried form, a narrow pore size distribution (half width <.+-.10% of the pore diameter) of micropores with diameters in the range of <3 nm and a total surface area of between 20 and 1000 m.sup.2 /g, containing a fraction of from 0.1 to 20% by weight of non-hydrolyzable organic groups, and to a process for the preparation of such oxides.

Abstract: Procedure for the preparation of a solid carrier for olefin polymerization catalysts, comprising the steps:a) impregnating a silica with a solution of Mg-chloride in the presence of electron donors,b) drying the impregnated silica obtained in (a) and impregnating it with a solution of Mg-alkyls in SiCl.sub.4 at a temperature from -10 to 20.degree. C., optionally adding a further amount of electron donors,c) subsequently treating the slurry obtained in (b) at a temperature from 40.degree. C. to reflux temperature,d) drying the carrier obtained in (c).

Abstract: The present invention provides a methanol reforming catalyst having the following general formula on a dry basis:X.sub.a Y.sub.b Z.sub.c O.sub.d, whereinX is a metal selected from the group consisting of zinc, cadmium, mercury, rubidium, cesium, silver, and combinations thereof, Y is a metal selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, and combinations thereof, Z is a material selected from the group consisting of boron, silicon, aluminum, silicoaluminate, zirconium, titanium, hafnium, gallium, lanthanum, scandium, and yttrium, and combinations thereof, and O is the element of oxygen. The claimed methanol reforming catalyst contains neither copper oxide nor chromium oxide.

Abstract: A catalyst composition, a process for producing the composition, and a hydrotreating process for converting a hydrocarbon stream such as, for example, gasoline, to olefins and C.sub.6 to C.sub.8 aromatic hydrocarbons such as toluene and xylenes are disclosed. The catalyst composition comprises a zeolite, a clay, and a promoter. The process for producing the composition comprises the steps: (1) combining a zeolite with a clay and a promoter under a condition sufficient to bind the clay to the zeolite to produce a clay-bound zeolite; and (2) heating the clay-bound zeolite to produce a modified zeolite. The hydrotreating process comprises contacting a hydrocarbon stream with the catalyst composition under a condition sufficient to effect the conversion of a hydrocarbon to an olefin and a C.sub.6 to C.sub.8 aromatic hydrocarbon.

Abstract: Compacts produced from a pyrogenically produced oxide, magnesium stearate, methyl cellulose and urea are mixed together in the presence of water, compacted, dried, comminuted to a powder, and the powder is pressed with an isostatic press to compacts and the compacts tempered. The resulting compacts have an outside diameter of 16 to 100 mm.

Abstract: The present invention provides a process for producing an alkyl ether of a phenol from a phenol and an alcohol at a selectivity and a yield higher than in conventional processes, stably over a long period of time. The process is characterized by alkyl-etherifying a phenol with an alcohol in the presence of an oxide catalyst comprising an alkali metal as a constituent element.

Abstract: A process of producing supported olefin polymerization catalysts in which the support is a porous silica material containing specified amounts of alkali and alkaline metal cations, and olefin polymerization catalysts produced thereby.

Abstract: Dehydroxylated oxide (e.g. silica) particles are obtained by reacting oxide particles, having surface hydroxyl groups, with a dialkylcarbonate or diarylcarbonate. The resulting products have surface alkoxy or aryloxy groups and significantly reduced hydroxyl content. The treated oxide particles are especially suitable for use as catalyst supports, and especially as polyolefin catalyst supports.

Abstract: A catalyst member for use in processes for the catalytic combustion of gaseous carbonaceous fuels is made from a stabilized carrier having a plurality of gas flow passages extending therethrough defined by channel walls and a catalyst material disposed on the channel walls, wherein the carrier is stabilized against interaction with the catalyst material. The stabilized carrier may be prepared from a monolith comprising silica, magnesia and alumina that has a coating of alumina on the channel walls and by subjecting the coated monolith to stabilizing conditions. The stabilizing conditions may include exposure to high temperature steam.

Abstract: The present invention relates to a process for making novel catalysts, catalyst supports, and adsorbers comprising synthetic hydrotalcite-like binders, having a sheet-like morphology and a sheet broadness to thickness ratio of at least 50 and a formula Mg.sub.1-x Al.sub.x (OH).sub.2.xA.sup.-. mH.sub.2 O where A.sup.- is a mono carboxylic anion of the form RCOO.sup.- where R is C.sub.n H.sub.2n+1 and n=0-5, and x and m are numbers satisfying the following conditions:0.2<=x<=0.40.0<=m<=4This hydrotalcite-like material is combined with an inorganic material to form shapes which have good mechanical strength. The process includes starting with a synthesis mixture having magnesium (divalent cation) to aluminum (trivalent cation) molar ratio between 1:1 and 10:1, mono carboxylic anion to aluminum (trivalent cation) molar ratio between 0.1:1 to 1.2:1 and optionally added other anions.

Abstract: A porous material composed of many SiO.sub.4 tetrahedra sheets having interlayer bridges of SiO.sub.2. It has pores having a diameter of 10 .ANG. or above, and possesses the properties of a solid acid formed by the isomorphous substitution of metal atoms for Si of SiO.sub.4 frameworks. It is made by a process including introducing an organic substance into interlayer space of crystals of layered silicates to expand the spacing between crystal layers, as well as forming bridges of SiO.sub.2 therebetween, bringing the intercalated compounds into contact with a metal salt to link metal atoms to the SiO.sub.4 frameworks, and firing the products. The material can withstand a temperature of 800.degree. C., has a pore diameter larger than that of zeolites, etc., and is useful in making an adsorbent or catalyst for molecules having a high molecular weight, such as a catalyst for the catalytic cracking of petroleum.

Abstract: Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

Abstract: Microbeads of aerogels of one or more oxides are characterised by a high porosity and the fact that at least 90% of the pores present have a diameter lying within a very narrow range. The surface area exceeds 300 m.sup.2 /g and more frequently exceeds 500 m.sup.2 /g, the total pore volume exceeding 1 ml/g.

Abstract: A catalyst member for use in processes for the catalytic combustion of gaseous carbonaceous fuels is made from a stabilized carrier having a plurality of gas flow passages extending therethrough defined by channel walls and a catalyst material disposed on the channel walls, wherein the carrier is stabilized against interaction with the catalyst material. The stabilized carrier may be prepared from a monolith comprising silica, magnesia and alumina that has a coating of alumina on the channel walls and by subjecting the coated monolith to stabilizing conditions. The stabilizing conditions may include exposure to high temperature steam.

Abstract: A catalyst for catalytic reduction of nitrogen oxide using at least one reducing agent selected from the group consisting of a hydrocarbon and an oxygen-containing organic compound is described, which includes an oxide represented by formula (V):A.sup.5.sub.x B.sup.3.sub.3-x C.sup.4.sub.3 O.sub.7 (V)wherein A.sup.5 represents at least one element selected from the group consisting of La, Y, Ce, Pr, Nd, Sm, Eu, and Gd; B.sup.3 represents at least one element selected from the group consisting of Ba, Sr, Ca, Mg, Pb, Zn, and Ag; C.sup.4 represents at least one element selected from the group consisting of Mn, Co, Fe, Ni, Cr, Cu, V, Mo, W, Ti, Zr, Nb, Pd, Rh, Ru, and Pt; and x is a number of from 0 to 1, supported on a solid acid carrier.

Abstract: The present invention concerns a heterogeneous catalyst particularly suited to the metathetic reactions of olefins in liquid or gas phase. Such a catalyst generally includes catalytically active species of tungsten on an inorganic support. The catalyst in accordance with the invention is prepared by vaporizing a precursor of tungsten, such as tungsten oxychloride or hexachloride and then routing the vapor of the tungsten-containing reagent into a reaction space, where the vapor is brought to interaction with the support material at approximately 160.degree. to 500.degree. C. The vapor pressure of the tungsten-containing reagent is kept sufficiently high, and the duration of interaction with the support sufficiently long, to keep the amount of the reagent at least equal to the number of available bonding sites of the support, whereby the bonding of the tungsten-containing reagent to the support surface is determined by the surface properties of the support.

Abstract: Multimetal oxide compositions of the formula I[X.sup.1.sub.a X.sup.2.sub.b O.sub.x ].sub.p [X.sup.3.sub.c X.sup.4.sub.d X.sup.5.sub.e X.sup.6.sub.f X.sup.7.sub.g X.sup.2.sub.h O.sub.y ].sub.q(I)whereX.sup.1 is bismuth, tellurium, antimony, tin and/or copper,X.sup.2 is molybdenum and/or tungsten,X.sup.3 is an alkali metal, thallium and/or samarium,X.sup.4 is an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and/or mercury,X.sup.5 is iron, chromium, cerium and/or vanadium,X.sup.6 is phosphorus, arsenic, boron and/or antimony,X.sup.7 is a rare-earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and/or uranium,a is from 0.01 to 8,b is from 0.

Abstract: A catalytic system for the production of synthesis gas by reacting light hydrocarbons, preferably methane, with CO.sub.2 is described formed from:one or more compounds of metals of the platinum group, preferably chosen from rhodium, ruthenium and iridium;a support consisting of inorganic compounds chosen from oxides and/or spinels of aluminium, magnesium, zirconium, silicon, cerium and/or lanthanum, possibly in the presence of alkali metals,in which the weight percentage of the metal or metals of the platinum group in the catalytic system is between 0.01 and 20%, and preferably between 0.1 and 5%.

Abstract: A method for producing a polyolefin is disclosed which comprises polymerizing an .alpha.-olefin in the presence of a catalyst composition comprising (A) a solid catalyst component prepared by contacting (a) a solid component comprising a magnesium alkoxide and/or a magnesium salt of a fatty acid supported on an inorganic oxide composed of at least one member selected from the group consisting of oxides of elements belonging to Groups II, III and IV of the periodic table and/or a composite inorganic oxide containing at least one member selected from the group consisting of oxides of elements belonging to Groups II, III and IV of the periodic table, the inorganic oxide or composite inorganic oxide having a surface hydroxide concentration of 3 .mu.mol/m.sup.2 or less, (b) an electron donating compound and (c) a titanium halide, (B) an organic metal compound, and (C) an electron donating compound.

Abstract: The process for activating a catalytic composition for paraffin dehydrogenation containing gallium, alumina, possibly silica and/or one or more alkaline or alkaline-earth metals, comprises thermal activation in air followed by post-activation effected by the following stages:oxidation with air and/or oxygen or a mixture containing oxygen and inert gas;purging with inert gas;reduction with hydrogen or a mixture of hydrogen and an inert or reducing gas.The catalytic composition activated by said process contains gallium, alumina, silica and possibly one or more alkaline or alkaline-earth metals, the alumina being in .delta. or .theta. phase or in .delta.+.theta. or .delta.+.theta.+.alpha. phase mixture.

Abstract: A method for incorporating diverse Varieties of intercalants or templates directly during hydrothermal synthesis of clays such as hectorite or montmorillonite-type layer-silicate clays. For a hectorite layer-silicate clay, refluxing a gel of silica sol, magnesium hydroxide sol and lithium fluoride for two days in the presence of an organic or organometallic intercalant or template results in crystalline products containing either (a) organic dye molecules such as ethyl violet and methyl green, (b) dye molecules such as alcian blue that are based on a Cu(II)-phthalocyannine complex, or (c) transition metal complexes such as Ru(II)phenanthroline and Co(III)sepulchrate or (d) water-soluble porphyrins and metalloporphyrins. Montmorillonite-type clays are made by the method taught by U.S. Pat. No. 3,887,454 issued to Hickson, Jun. 13, 1975; however, a variety of intercalants or templates may be introduced.

Abstract: A silica-containing bayerite alumina is prepared by reacting aluminum sulfate, sodium aluminate and sodium silicate at a pH of about 10.5 to 11.5, preferably in the presence of finely divided magnesium hydroxide "seeds". The silica-containing bayerite is heated to obtain a hydrothermally stable silica "stabilized" eta alumina which may be used in the preparation of catalytic compositions.

Abstract: A process for producing a denitration catalyst comprising the following steps of immersing a base material composed of an inorganic fiber cloth in an aqueous slurry containing 5 to 20% by weight of at least one sol-form substance selected from the group consisting of silica sol, titania sol and zirconia sol, as a first component, 20 to 70% by weight of at least one inorganic oxide fine powder selected from the group consisting of those of titania, zirconia and cordierite, as a second component, and 1 to 3% by weight of at least one organic binder selected from the group consisting of polyvinyl alcohol, polyvinyl acetate and carboxymethyl cellulose, as a third component, removing superfluous liquid from the resulting base material, drying the base material, coating catalyst components onto the surface of the dried base material, and drying and calcining the resulting material, are proposed.

Abstract: An improved supported chromium oxide catalyst, a process for preparing the catalyst and a process for polymerizing olefin monomers utilizing the catalyst are provided. In accordance with the preparation process, chromium oxide and a support containing one or more of silica, titania, thoria, alumina, zirconia or aluminophosphates are combined, impregnated with a metal salt and activated. The metal salt is selected from the group consisting of alkali metal salts, alkaline earth metal salts and mixtures thereof.

Abstract: The present invention relates to rare earth complex oxide combustion catalysts wherein perovskite-type rare earth complex oxide active components are carried on a support using mullite as the main phase. The present invention relates also to a process for preparing a rare earth complex oxide combustion catalyst which comprises impregnating the support with the solution of the metallic ions prepared by the ABO.sub.3 stoichiometry and then drying and calcining it. Furthermore, the present invention relates to the use of the said catalyst as a combustion catalyst for CO in the fluid catalytic cracking (FCC) process of petroleum refining.

Abstract: H.sub.2 S formation by three-way catalyst is suppressed by incorporating nickel, manganese or iron oxides into an undercoat layer disposed on a substrate, such as a monolith substrate. A topcoat overlying the undercoat is comprised of a three-way catalyst material which includes one or more of platinum, rhodium and palladium as catalytic metals.

Abstract: A process of preparing a mixture of polyalkylenepolyamines and alkanolpolyamines comprising contacting a difunctional aliphatic alcohol with a primary or secondary aliphatic amine in the presence of a metal silicate catalyst wherein the metal is selected from the group consisting of Groups IIA, IIIB, and the lanthanide and actinide metals. For example, monoethanolamine reacts with diethylenetriamine in the presence of magnesium silicate to yield a mixture of higher molecular weight linear and branched polyethylenepolyamines and their corresponding alkanolpolyamines. These product mixtures are useful in the formation of specialty polyurethanes.

Abstract: Pressed parts based on pyrogenically produced silicon dioxide with the following physicochemical characteristic data:______________________________________ Outer diameter 2 to 15 mm BET surface 50 to 400 m.sup.2 /g Pore volume 0.6 to 1.3 ml/g Breaking strength 50-150 N Pore distribution no pores <5 mn diameter only meso and macropores Composition >99% by weight SiO.sub.2 Abrasion <1.0% Bulk weight: 400-500 g/l ______________________________________are produced by homogenizing pyrogenically produced silicon dioxide with urea, methyl cellulose and/or magnesium stearate, graphite and aluminum stearate with the addition of water, dried at a temperature of 80.degree. to 120.degree. C., comminuted to a powder, pressing the powder to pressed parts and tempering the pressed parts for a period of 0.5 to 8 hours at a temperature of 400.degree. to 1200.degree. C.

Abstract: A composition useful for processing hydrocarbonaceous feedstocks is disclosed comprising a mixture of a calcium/magnesium-containing material and a magnesium-containing material. The preferred calcium/magnesium-containing material is dolomite and the preferred magnesium-containing material is sepiolite.

Abstract: There is provided an improved catalyst for purifying exhaust gases comprising a carrier carrying alumina, zirconium oxide and a noble metal catalyst. The improvement resides in the fact that the carrier carries the alumina as a layer having dispersed therein the zirconium oxide particles, the zirconium oxide particles carrying said noble metal catalyst. The dispersibility of the noble metal catalytic component is thereby improved and the sintering prevention effect on the noble metal catalytic component by the zirconium oxide is effectively exhibited. Thus, the heat-proof property of the catalyst is improved and the cooperation between the noble metal catalytic component and alumina is effectively enhanced, improving longevity of the catalyst.

Abstract: A solid composition is prepared by mixing water, a hydraulic cement, aluminum metal powder, and a catalyst composition comprising (a) an inorganic support, (b) Pt and/or Pd metal (c) and Fe metal and/or oxide, followed by maintaining the obtained mixture under such conditions as to affect hardening of the hydraulic cement. Preferably, the hydraulic cement is a Type III portland cement and/or a Class H well cement. The thus-prepared solid compositon can be used as a CO oxidation catalyst.

Abstract: A solid composition is prepared by mixing water, a hydraulic cement, sodium silicate, and a catalyst composition comprising (a) an inorganic support, (b) Pt and/or Pd metal and (c) Fe metal and/or oxide, followed by maintaining the obtained mixture under such conditions as to affect hardening of the hydraulic cement. Preferably, the hydraulic cement is a Type III portland cement and/or a Class H well cement. A solid composition comprising hydraulic cement, sodium silicate and the above-described catalyst composition is provided. This solid composition can be used as a CO oxidation catalyst.

Abstract: Disclosed is a catalyst support material comprised of alumina and a modifier comprised of about 100 to 500 wppm Si and at least 10 wppm of one or more alkaline earth metals selected from Ca, Mg, Ba, and Sr wherein the total amount of modifier does not exceed 5000 wppm.

Abstract: A catalytic cracking process is disclosed employing a dual component cracking catalyst system comprising zeolite as a first component and a mixture of a calcium/magnesium-containing material and a magnesium-containing material as a second component. The preferred calcium/magnesium-containing material is dolomite and the preferred magnesium-containing material is sepiolite.

Abstract: A silica-magnesia cogelled material is usable as a base for petroleum cracking catalysts based on zeolites. Invention described provides cogel base in which the silica and magnesia components are intimately mixed. This feature is achieved by controlling the pH during the mixing procedure.

Abstract: A dual component cracking catalyst system is disclosed comprising zeolite as a first component and a mixture of a calcium/magnesium-containing material and a magnesium-containing material as a second component. The preferred calcium/magnesium-containing material is dolomite and the preferred magnesium-containing material is sepiolite.

Abstract: This invention relates to a catalyst support structure, methods of preparing the support structure and a process for using the support structure. The catalyst support structure is composed of a substantially polycrystalline cordierite phase having a chemical composition by weight of 6-15% MgO, 33-40% Al.sub.2 O.sub.3 and 45-56% SiO.sub.2 and characterized in that it has a surface area of at least 2.7 m.sup.2 /g and preferably 8 m.sup.2 /g, a compressive strength of at least 31 MPa, a thermal expansion coefficient smaller than 5.2.times.10.sup.-6 m/m/.degree.C. and a porosity of at least 20%.