Obtaining multimetallic oxides derived from hydrotalcite type compounds

A process of purifying exhaust gas, comprising the steps of:

• contacting an SOx-containing exhaust gas with a mixed multimetallic oxide absorbent for sufficient time to remove SOx from the exhaust gas, wherein the mixed multimetallic oxides are hydrotalcite type compounds having four metallic cations, forming part of sheets of the hydrotalcite type compounds represented by the following formula:
• [M(II)1−x−y−zM(II)′xM(III)yM(III)′z(OH)2](An−y+z/n).mH2O, where:
• [M(II)+M(II)′]/[(M(III)+M(III)′], is the molar relationship between divalent cations and trivalent cations, and is between 0.5 and 10;
• M(II) represents an element of group 2, 6-12 of the periodic table with a valence equal to two;
• M(II)′ represents an element of group 2, 6-12 of the periodic table with a valence equal to two or three, which can be the same as M(II) but with different valence;
• M(III) represents an element of group 4-8, 13 with a valence equal to 3 and different from M(II) and M(II)′;
• M(III)′ represents an element of group 4-8, 13 with a valence equal to 3 and different from M(II) and M(III) or the same as M(III) but with a different valence;
• A, represents an interlaminar anion located between the sheets;
• n−, represents the negative electronic charge of the interlaminar anion, and may be from −1 to −8);
• x=0.01 up to 0.99;
• y=0.01 up to 0.99;
• and
• z=0.01 up to 0.99;
• and where the multimetallic hydrotalcites are prepared by a process comprising:
• (1) preparing an aqueous or organic solution containing three or more cations from precursor compounds selected from the group consisting of oxides, hydroxides, chlorides, nitrates, acetates and mixtures thereof;
• (2) preparing an alkaline solution of 0.5 to 10 molarity from at least one selected from the group consisting of KOH, K2CO3, (NH4)2CO3, NH4(OH), urea, an alkaline compound, except a sodium compound, and mixtures thereof;
• (3) slowly combining solutions (1) and (2) to cause co-precipitation of the cations at a pH between 7 and 12 at a temperature between 293 and 373 K to obtain a precipitate containing hydrotalcites;
• (4) washing the precipitate containing the hydrotalcites with water to remove non-precipitated ions;
• (5) drying the precipitate between 333 and 473K in an atmosphere selected from the group consisting of air, oxygen, nitrogen, under vacuum, or mixtures thereof;
• and
• (6) calcining the dried hydrotalcites between 573 and 1273K in a stream selected from the group consisting of air, oxygen, nitrogen, or mixtures thereof.

A catalyst for removing SOx from an SOx-containing exhaust gas, said catalyst comprising a mixed multimetallic oxide absorbent, the mixed multimetallic oxides being hydrotalcite type compounds having four metallic cations, forming part of sheets of the hydrotalcite type compounds represented by the following formula:

• [M(II)1−x−y−zM(II)′xM(III)yM(III)′z(OH)2](An−y+z/n).mH2O, where:
• [M(II)+M(II)′]/[M(III)+M(III)′], is the molar relationship between divalent cations and trivalent cations, and is between 0.5 and 10;
• M(II) represents an element of group 2, 6-12 of the periodic table with a valence equal to two;
• M(II)′ represents an element of group 2, 6-12 of the periodic table with a valence equal to two or three, which can be the same as M(II) but with different valence;
• M(III) represents an element of group 4-8, 13 with a valence equal to 3 and different from M(II) and M(II)′;
• M(III)′ represents an element of group 4-8, 13 with a valence equal to 3 and different from M(II) and M(III) or the same as M(III) but with a different valence;
• A, represents an interlaminar anion located between the sheets;
• n−, represents the negative electronic charge of the interlaminar anion, and may be from −1 to −8);
• x=0.01 up to 0.99;
• y=0.01 up to 0.99;
• and
• z=0.01 up to 0.99.