Catalytically active amorphous silica

A method for preparing amorphous silica gel comprising forming a hydrogel in a reaction mixture comprising water, silicate anions, and quaternary ammonium cations having a nitrogen atom bonded to four carbon atoms, and dehydrating the hydrogel to yield a product containing a substantial proportion of amorphous silica gel.

A method for preparing amorphous silica gel wherein said method comprises acidifying a reaction mixture comprising sodium silicate, water, and a quaternary ammonium cation having a nitrogen atom bonded to four carbon atoms, allowing a hydrogel to form in the reaction mixture, separating the hydrogel from the reaction mixture, removing one or more metals from said hydrogel, and dehydrating said hydrogel to produce a product containing a substantial proportion of amorphous silica gel.

A method for preparing silica gel wherein said method consists essentially of acidifying a reaction mixture comprising sodium silicate, water, and a quaternary ammonium cation having a nitrogen atom bonded to four carbon atoms, said acidification resulting in a pH between 8 and 12 and said carbon atoms each being members of alkyl groups containing between 1 and 6 carbon atoms, allowing a hydrogel to form in the reaction mixture maintained at a temperature below 95.degree. C., recovering the hydrogel from the remainder of the reaction mixture, removing sodium from the hydrogel by washing, and dehydrating said hydrogel to produce a product containing a substantial proportion of silica gel.

An amorphous silica useful in the catalysis of hydrocarbon conversion reactions prepared by a method comprising acidifying a reaction mixture comprising water, sodium silicate, and a quaternary ammonium cation having a nitrogen atom bonded to four carbon atoms, said acidifying resulting in a pH between about 8 and 12, allowing the reaction mixture to stand under conditions sufficient to produce a hydrogel therein from which an essentially amorphous silica gel is produced in the dehydrating step hereinafter defined, separating the hydrogel from the remainder of the reaction mixture, washing the hydrogel so as to reduce the sodium content thereof, and dehydrating the washed hydrogel to yield a silica product consisting essentially of an amorphous silica gel.

An amorphous silica having catalytic activity for isomerizing ortho-xylene to para-xylene and meta-xylene at 900.degree. F. and atmospheric pressure at a rate of at least 1.0.times.10.sup.10 molecules of ortho-xylene converted per second per square centimeter of surface area of said amorphous silica.

A composition consisting essentially of amorphous silica gel having catalytic activity for isomerizing ortho-xylene to para-xylene plus meta-xylene at 900.degree. F. and atmospheric pressure at a rate of at least 4.0.times.10.sup.10 molecules of ortho-xylene converted per second per square centimeter of surface area of said composition.

An amorphous silicon-containing hydrogel produced from a reaction mixture comprising water, silicate anions, and an organic reactant selected from the group consisting of amines having a pK.sub.a value above 10.0, quaternary ammonium cations wherein a nitrogen atom is bonded to four alkyl groups containing between 1 and 6 carbon atoms, quaternary phosphonium ions wherein a phosphorus atom is bonded to four alkyl groups containing between 1 and 6 carbon atoms, precursors of the foregoing, and mixtures thereof.