Process for the production of a microporous body having heat insulation properties

A process for the production of a microporous body having heat insulation properties which is based on highly dispersed oxides of the elements silicon and/or aluminum, which process comprises

• (a) mixing to prepare a mixture of
• (I) 0.5%-60% by weight of a mixture selected from the group consisting of magnesium carbonate/calcium carbonate, and magnesium carbonate/calcium hydroxide;
• (II) 5%-95% by weight of pyrogenically prepared SiO.sub.2 with a content of 0%-20% by weight of Al.sub.2 O.sub.3 (based on the SiO.sub.2 employed);
• (III) 0%-60% by weight of an opacifying agent having at least one absorption maximum in the wavelength range of 1.5-10 .mu.m;
• and
• (IV) 0.1%-10% by weight of an organic fiber, selected from the group consisting of cellulose fibers and carbon fibers;
• (b) compressing the mixture prepared to form a shaped article;
• and
• (c) heating the shaped article under oxidizing conditions produced at a temperature between 750.degree. C. to 950.degree. C. to oxidize the organic fibers and to produce the microporous body.