Silicates with high ion exchange capacity derived from sepiolite and processes for their production

Claim 2

A process for obtaining a silicate derived from a sepiolite comprising reacting said sepiolite with a base selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides and ammonium hydroxide, in the presence of a polar liquid selected from the group consisting of water, alcohols and mixtures thereof, at a temperature in the range from about 100° C. to about 400° C. and for a period sufficient to increase the ion exchange capacity of the sepiolite to at least 100 meq. per 100 g with respect to potassium or magnesium, and recovering a silicate with said ion exchange capacity.

Claim 3

A process as claimed in claim 1 wherein the base is an alkali metal hydroxide.

Claim 4

A process as claimed in claim 1 wherein the weight ratio of sepiolite to polar liquid is between about 0.01:1 and about 1:1, and the weight ratio of sepiolite to said hydroxide is between about 0.25:1 and about 40:1.

Claim 5

A process as claimed in claim 3 wherein the weight ratio of sepiolite to polar liquid is between about 0.05:1 and about 0.5:1 and the weight ratio of sepiolite to said hydroxide is between about 1.5:1 and about 15:1.

Claim 6

A process as claimed in claim 1 wherein said temperature is about 100° C. to about 200° C.

Claim 7

A process as claimed in claim 1 carried out above the boiling point of the polar liquid in an autoclave.

Claim 8

A process as claimed in claim 1 wherein the reaction time is between about 5 minutes and about 20 days.

Claim 9

A process as claimed in claim 7 wherein said time is about 2 hours to about 8 days.

Claim 10

A process as claimed in claim 1 carried out in the presence of agitation.

Claim 11

A process as claimed in claim 1 carried out in the presence of a member selected from the group consisting of alkali metal carbonates, alkaline earth metal carbonates, alkaline earth metal carbonates, and ammonium carbonate, said member being added to the reaction mixture.

Claim 12

A process as claimed in claim 1 carried out in an agitated batch reactor.

Claim 13

A process as claimed in claim 1 wherein the starting material sepiolite is a natural sepiolite pretreated with a pretreatment agent selected from the group consisting of mineral acids, organic acids and ammonium salts.

Claim 14

A process as claimed in claim 1 including the steps of filtering, washing and calcining the product silicate.

Claim 15

A silicate having an ion exchange capacity with respect to magnesium of at least about 100 meq. per 100 g and conforming to the general formula Si.sub.y W.sub.w M.sub.x A.sub.z O.sub.30 (OH).sub.4 wherein W is selected from the group consisting of aluminum, magnesium, iron, nickel, manganese and mixtures thereof; M is a divalent metal selected from the group consisting of the alkaline earth metals, and mixtures thereof; A is selected from the group consisting of alkali metals, ammonium ion and mixtures thereof; y is from about 10 to about 12; w is from about 3.5 to about 8; x is from about 0 to about 2; z is from greater than zero up to about 4; and the molar ratio w:y is from about 0.29:1 up to about 0.8:1.

Claim 16

A silicate having an ion exchange capacity with respect to magnesium of at least about 100 meq. per 100 g and conforming to the general formula Si.sub.y W.sub.w M.sub.x A.sub.z O.sub.30 (OH).sub.4 wherein W is selected from the group consisting of aluminum, magnesium, iron, nickel, manganese and mixtures thereof; M is a divalent metal selected from the group consisting of the alkaline earth metals, and mixtures thereof; A is selected from the group consisting of alkali metals, ammonium ion and mixtures thereof; y is from about 10 to about 12; w is from about 3.5 to about 8; x is from about 0 to about 2; z is from greater than zero up to about 4; and the molar ratio w:y is from about 0.29:1 up to about 0.8:1.

Claim 17

A silicate as claimed in claim 14 wherein A is an alkali metal.

Claim 18

A silicate as claimed in claim 15 wherein A is sodium.

Claim 19

A silicate as claimed in claim 14 wherein z is from about 1 to about 2.

Claim 20

A silicate in sodium form having been calcined at 250° C. and having the formula Si y W x M x Na z O 30 (OH) 4 , wherein W is selected from the group consisting of aluminum, magnesium, iron, nickel, manganese and mixtures thereof; M is a divalent metal selected from the group consisting of alkaline earth metals, and mixtures thereof; y is from about 10 to about 12, w is from about 3.5 to about 8; x is from about 0 to about 2; and z is from greater than zero up to about 4; and having the following X-ray difractogram: ______________________________________ 20 d(A) I.sub.obs hkl ______________________________________ 6.9 12.80 s 110 19.7 4.50 w 060 20.4 4.34 i 131 26.5 3.35 i 080 34.4 2.60 w 441,281 35.2 2.54 w 371,191 36.5 2.45 w 202,042 ______________________________________ wherein the relative intensities are ms=strongest, s=strong, i=intermediate and w=weak.

Claim 21

A silicate in sodium form having been calcined at 250° C. and having the formula Si y W x M x Na z O 30 (OH) 4 , wherein W is selected from the group consisting of aluminum, magnesium, iron, nickel, manganese and mixtures thereof; M is a divalent metal selected from the group consisting of alkaline earth metals, and mixtures thereof; y is from about 10 to about 12, w is from about 3.5 to about 8; x is from about 0 to about 2; and z is from greater than zero up to about 4; and having the following X-ray difractogram: ______________________________________ 20 d(A) I.sub.obs hkl ______________________________________ 6.9 12.80 s 110 19.7 4.50 w 060 20.4 4.34 i 131 26.5 3.35 i 080 34.4 2.60 w 441,281 35.2 2.54 w 371,191 36.5 2.45 w 202,042 ______________________________________ wherein the relative intensities are ms=strongest, s=strong, i=intermediate and w=weak.

Claim 22

A silicate in nickel form having been calcined at 250° C. and having the formula Si y Ni w M x A z O 30 (OH) 4 , wherein M is a divalent metal selected from the group consisting of alkaline earth metals, and mixtures thereof; A is selected from the group consisting of alkali metals, ammonium ion and mixtures thereof; y is from about 10 to about 12, w is from about 3.5 to about 8, x is from about 0 to about 2, and z is from greater than zero up to about 4, and having the following X-ray difractogram: ______________________________________ 20 d(A) I.sub.obs hkl ______________________________________ 7.10 12.44 s 110 17.54 5.05 w 150 19.64 4.51 i 060 20.50 4.32 i 131 23.60 3.76 w 260 26.46 3.36 i 080 27.70 3.21 w 331 34.60 2.59 i 371,191 36.50 2.45 w 202,042 ______________________________________ wherein the relative intensities are ms=strongest, s=strong, i=intermediate and w=weak.

Claim 23

A silicate in nickel form having been calcined at 250° C. and having the formula Si y Ni w M x A z O 30 (OH) 4 , wherein M is a divalent metal selected from the group consisting of alkaline earth metals, and mixtures thereof; A is selected from the group consisting of alkali metals, ammonium ion and mixtures thereof; y is from about 10 to about 12, w is from about 3.5 to about 8, x is from about 0 to about 2, and z is from greater than zero up to about 4, and having the following X-ray difractogram: ______________________________________ 20 d(A) I.sub.obs hkl ______________________________________ 7.10 12.44 s 110 17.54 5.05 w 150 19.64 4.51 i 060 20.50 4.32 i 131 23.60 3.76 w 260 26.46 3.36 i 080 27.70 3.21 w 331 34.60 2.59 i 371,191 36.50 2.45 w 202,042 ______________________________________ wherein the relative intensities are ms=strongest, s=strong, i=intermediate and w=weak.

Claim 24

A process as claimed in claim 12 wherein said pretreatment agent is EDTA.