Montedison S.p.a.

Ministero Dell'universita E Della Ricerca Scientifica E Tecnologica

Istututo Guido Donegani S.p.a.

Franco Montino

Giuseppe Spoto

Luigi Balducci

Giampiero Basile

Guido Cogliati

Giancarlo Boero

Francesco Ferrero

Emiliano M Ceresa

Nicola Pernicone

Ariello Rolando Corradi

Erminio Nonato

The invention relates to high-porosity silica xerogels and a process for their preparation consisting of subjecting silica alcogels to thermal treatment in the presence of organic compounds containing amino and hydroxyl groups. The xerogels are characterised by a total pore volume .gtoreq.2 cc/g and a mean pore diameter .gtoreq.100 .ANG..

Process of preparing high-porosity silica xerogels using alkanolamines

A process for producing the precursor of a precipitated catalyst for the sub.3 synthesis, based on Fe, Al, Co and K oxides, which comprises the steps of:

Process for producing the precursor of a precipitated catalyst for the

Mixed oxides of alumina and zirconia having a controlled granulometric distribution, consisting essentially of spherical, submicronic particles, wherein zirconia is distributed uniformly in alumina and may reach 38% by weight, said zirconia being in the stabilized form at room temperature in the tetragonal phase, after having subjected the amorphous hydrated composite oxides to thermal treatments, wherein occurs the transition of zirconia to the tetragonal phase.

Mixed oxides of alumina and zirconia consisting essentially of spherical

A process for preparing hydrated alumina consisting essentially of spherical particles having a narrow granulometric distribution (polydispersion index dw/dn.ltoreq.2) starting from aqueous solution of aluminum sulphate, the molar ratio SO.sub.4.sup.= /Al.sup.3+ being greater than 1, by homogeneous precipitation in the presence of cationic polyelectrolytes, which are soluble under the reaction conditions and have a mean molecular weight higher than one million and an ionicity, deriving from the cationic groups present in the polyelectrolyte, of at least 3 milliequivalents/gram.

Process for preparing hydrated alumina consisting essentially of

A process for preparing titanium dioxide in the form of spherical particles having the particle size distribution indicated by dw/dn.ltoreq.2, by hydrolysis of strongly acid solutions of Ti(IV), wherein the molar ratio SO.sub.4.sup.= /Ti(IV) is at least 1.5, and in the presence of cationic polyelectrolytes having a molecular weight higher than 1 million and a ionicity of at least 3 milliequivalents per gram.

Process for preparing titanium dioxide in the form of spherical

This invention relates to a process for stabilizing ferromagnetic chromium dioxide in respect of water and oxidizable organic compounds which it may contact in magnetic tapes. The process is applicable to a starting CrO.sub.2 having good magnetic properties, i.e. a coercive force not lower than about 400 Oersted, a maximum magnetic induction B.sub.m not lower than about 2500 gauss, and a magnetic induction B.sub.r not lower than about 1600 gauss. The CrO.sub.2 is subjected to a heat treatment at a temperature ranging from 300.degree. to 390.degree. C. in the presence of a gas stream not exerting any oxidizing or reducing action on the compounds of trivalent, tetravalent and hexavalent chromium. Suitable gases are, for example, nitrogen, helium and argon.

Process for stabilizing ferromagnetic chromium dioxide

A process is disclosed for obtaining acicular magnetic particles of .gamma.-Fe.sub.2 O.sub.3 modified with Fe.sup.++ and Co.sup.++ ions. The product thus obtained and magnetic tapes containing said product are also disclosed. A suspension of acicular .gamma.-Fe.sub.2 O.sub.3 in an aqueous solution of soluble Fe.sup.++ and Co.sup.++ salts is prepared. NH.sub.3 is then added in such quantity that the molar ratio

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Novara, Italy

Franco Montino