1. A method for purification of acrylic acid, which comprises the steps of:
a) providing a crude acrylic acid having a concentration ratio of furfural to acrolein by weight that is adjusted so as to satisfy the following equation:
3\u2266(furfural concentration by weight)(acrolein concentration by weight)\u2266100;
then
b) charging the crude acrylic acid with an aldehyde treatment chemical, with the aldehyde treatment chemical comprising a hydrazine compound; then
c) reacting the hydrazine compound with aldehydes of the crude acrylic acid such that, after said step of reacting and prior to a step of distilling the crude acrylic acid, a concentration of said hydrazine compound in said crude acrylic acid is not more than 100 ppm by weight; and then
d) distilling the crude acrylic acid containing said furfural and acrolein as impurities.
2. A method according to claim 1, wherein the concentration ratio of furfural to acrolein by weight in said crude acrylic acid is adjusted so as to satisfy the following equation:
3\u2266(furfural concentration by weight)(acrolein concentration by weight)\u226630.
3. A method according to claim 2, wherein the amount of said aldehyde treatment chemical is not more than 8.0 mole per mole of furfural existing in said crude acrylic acid.
4. A method according to claim 1, wherein the amount of said aldehyde treatment chemical is not more than 8.0 mole per mole of furfural existing in said crude acrylic acid.
5. A method for purification of acrylic acid, comprising the steps of:
a) providing a crude acrylic acid containing furfural and acrolein as impurities;
b) determining a ratio of a concentration of furfural to a concentration of acrolein;
c) determining whether the ratio of the concentration of furfural to the concentration of acrolein is within a preset range and, if so, continuing with said method;
d) determining whether the ratio of the concentration of furfural to the concentration of acrolein is outside said preset range and, if so, adjusting the ratio of the concentration of furfural to the concentration of acrolein to fall within said preset range;
e) charging said crude acrylic acid with a chemical that treats aldehydes and selecting, as said chemical that treats aldehydes, a hydrazine compound, with said step of charging taking place after said steps of determining and after said step of adjusting and prior to a step of distilling said crude acrylic acid; then
f) reacting the hydrazine compound with aldehydes of the crude acrylic acid such that, after said step of reacting and prior to a step of distilling the crude acrylic acid, a concentration of said hydrazine compound in said crude acrylic acid is not more than 100 ppm by weight; and then
g) distilling said crude acrylic acid.
6. A method according to claim 5, wherein said preset range is: (furfural concentration by weight)(acrolein concentration by weight)\u2266100.
7. A method according to claim 5, wherein said preset range is: 2\u2266(furfural concentration by weight)(acrolein concentration by weight)\u226630.
8. A method according to claim 5, wherein said preset range is: 3\u2266(furfural concentration by weight)(acrolein concentration by weight)\u2266100.
9. A method according to claim 5, wherein said preset range is: 3\u2266(furfural concentration by weight)(acrolein concentration by weight)\u226630.
10. A method of claim 5, and further comprising the step of selecting an amount of said chemical that treats aldehydes to be not more than 8.0 moles per mole of furfural in said crude acrylic acid.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for polishing a substrate comprising ruthenium and silicon dioxide, the method comprising abrading a surface of the substrate comprising ruthenium and silicon dioxide with a CMP composition comprising about 1 to about 10 percent by weight of a particulate abrasive selected from the group consisting of alumina, titania, and a combination thereof, suspended in an aqueous carrier containing about 0.01 to about 0.5 percent by weight of a nitroxide compound; wherein, in the presence of hydrogen peroxide, the nitroxide compound is capable of preventing the deposition of ruthenium species having an oxidation state of IV or higher on the surface of the substrate, and concomitantly forming a soluble Ru(II) nitroxide coordination complex with oxidized ruthenium formed during CMP of the substrate.
2. A method for polishing a substrate comprising ruthenium and silicon dioxide, the method comprising abrading a surface of the substrate comprising ruthenium and silicon dioxide with a CMP composition comprising a particulate abrasive selected from the group consisting of (a) colloidal silica or (b) a combination of colloidal silica and titania, suspended in an aqueous carrier containing a nitroxide compound wherein, in the presence of an oxidizing agent, the nitroxide compound is capable of preventing the deposition of ruthenium species having an oxidation state of IV or higher on the surface of the substrate, and concomitantly, forming a soluble Ru(II) N\u2014O coordination complex with oxidized ruthenium formed during CMP of the substrate.
3. A chemical-mechanical polishing (CMP) method for selectively removing ruthenium from the surface of a substrate in preference to silicon dioxide, the method comprising the steps of
(a) contacting a surface of a substrate comprising ruthenium and silicon dioxide with a polishing pad and an aqueous CMP composition in the presence of an oxidizing agent; and
(b) causing relative motion between the substrate and the polishing pad while maintaining a portion of the CMP composition and oxidizing agent in contact with the surface between the pad and the substrate for a period of time sufficient to abrade at least a portion of the ruthenium present in the substrate from the surface;
wherein the CMP composition contains a particulate abrasive selected from the group consisting of alumina, titania, and a combination thereof; the particulate abrasive being suspended in an aqueous carrier containing a ruthenium-coordinating oxidized nitrogen ligand (N\u2014O ligand), the N\u2014O ligand comprising a nitroxide compound; wherein, in the presence of the oxidizing agent, the N\u2014O ligand is capable of preventing the deposition of ruthenium species having an oxidation state of IV or higher on the surface of the substrate, and concomitantly is capable of forming a soluble Ru(II) N\u2014O coordination complex with oxidized ruthenium formed during CMP of the substrate.
4. The method of claim 3 wherein the particulate abrasive is present in the composition at a concentration in the range of about 1 to about 10 percent by weight.
5. The method of claim 3 wherein the N\u2014O ligand is present in the composition at a concentration in the range of about 0.01 to about 0.5 percent by weight.
6. The method of claim 3 wherein the particulate abrasive is alpha-alumina.
7. The method of claim 3 wherein the N\u2014O ligand comprises a nitroxide compound selected from the group consisting of 2,2,6,6-tetramethylpiperidinel-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, an imino nitroxide, a nitronyl nitroxide, and a combination thereof.
8. The method of claim 3 wherein the composition further comprises ascorbic acid.
9. The method of claim 8 wherein the ascorbic acid is present in the composition in an amount that is about equimolar to the amount of N\u2014O ligand in the composition.
10. The method of claim 3 wherein the oxidizing agent comprises hydrogen peroxide.
11. The method of claim 10 wherein the hydrogen peroxide is present at a concentration in the range of about 1 to about 5 percent by weight, based on the combined weight of the composition and hydrogen peroxide.
12. A chemical-mechanical polishing (CMP) method for selectively removing dioxide from the surface of a substrate in preference to ruthenium, the method comprising the steps of:
(a) contacting a surface of a substrate comprising ruthenium and silicon dioxide with a polishing pad and an aqueous CMP composition in the presence of an oxidizing agent; and
(b) causing relative motion between the substrate and the polishing pad while maintaining a portion of the CMP composition and the oxidizing agent in contact with the surface between the pad and the substrate for a period of time sufficient to abrade at least a portion of the ruthenium present in the substrate from the surface;
wherein the CMP composition contains a particulate abrasive comprising colloidal silica suspended in an aqueous carrier containing a ruthenium-coordinating oxidized nitrogen ligand (N\u2014O ligand), the N\u2014O ligand comprising a nitroxide compound; and, in the presence of the oxidizing agent, the N\u2014O ligand is capable of preventing the deposition of ruthenium species having an oxidation state of IV or higher on the surface of the substrate, and concomitantly is capable of forthing a soluble Ru(II) N\u2014O coordination complex with oxidized ruthenium formed during CMP of the substrate.
13. The method of claim 12 wherein the particulate abrasive further comprises titania.
14. The method of claim 12 wherein the particulate abrasive is present in the composition at a concentration in the range of about 1 to about 10 percent by weight.
15. The method of claim 12 wherein the N\u2014O ligand is present in the composition at a concentration in the range of about 0.01 to about 0.5 percent by weight.
16. The method of claim 12 wherein the N\u2014O ligand comprises a nitroxide compound selected from the group consisting of 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, an imino nitroxide, a nitronyl nitroxide, and a combination thereof.
17. The method of claim 12 wherein the composition further comprises ascorbic acid.
18. The method of claim 17 wherein the ascorbic acid is present in the composition in an amount that is about equimolar to the amount of N\u2014O ligand in the composition.
19. The method of claim 12 wherein the oxidizing agent comprises hydrogen peroxide.
20. The method of claim 19 wherein the hydrogen peroxide is present at a concentration in the range of about 1 to about 5 percent by weight, based on the combined weight of the composition and the hydrogen peroxide.