Claims
- 1. In a process for preparing methacrylic acid by the vapor-phase catalytic oxidation of methacrolein or a methacrolein-containing mixture with molecular oxygen in the presence of an oxidation catalyst; the improvement wherein said process comprises a first-stage oxidation step of oxidizing methacrolein or a methacrolein-containing mixture as a starting material,
- a first-stage separating step of separating the resulting methacrylic acid from the reaction product obtained in the first-stage oxidation step, to form a mixture containing unreacted methacrolein,
- a second-stage oxidation step of oxidizing said mixture containing the unreacted methacrolein, and
- a second-stage separating step of separating the resulting methacrylic acid from the reaction product obtained in the second-stage oxidation step, and
- with or without at least one additional oxidation step and separating step subsequent to the second-stage separating step,
- and wherein the conversion of methacrolein in the first-stage oxidation step is adjusted to 30-85 mole% and the final conversion of methacrolein is adjusted to at least 90 mole%.
- 2. The process of claim 1 wherein the starting methacrolein-containing mixture is the reaction product obtained by the vapor-phase catalytic oxidation of isobutylene, tertiary butanol or a mixture of these.
- 3. The process of claim 1 wherein the conversion of methacrolein in the first-stage oxidation step is 40-80 mole%.
- 4. The process of claim 1 wherein the methacrylic acid is separated in each separating step by using an absorbing solvent.
- 5. The process of claim 1 wherein the catalyst contains (a) P and Mo or (b) P and Pd as essential ingredients.
- 6. The process of claim 1 wherein the starting methacrolein-containing mixture is the reaction product obtained by catalytically oxidizing isobutylene, tertiary butanol or a mixture of these in the vapor phase in the presence of a catalyst containing as essential ingredients (a) Mo, (b) Bi, (c) Fe, (d) Co and/or Ni and (e) at least one of alkali metals, alkaline earth metals or T1.
Priority Claims (1)
Number |
Date |
Country |
Kind |
51-128665 |
Oct 1976 |
JPX |
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Parent Case Info
This application is a continuation-in-part application of application Ser. No. 843,691 filed Oct. 19, 1977 now abandoned.
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
3686294 |
Ito et al. |
Aug 1972 |
|
3976688 |
Akiyama et al. |
Aug 1976 |
|
4031135 |
Engelbach et al. |
Jun 1977 |
|
4035418 |
Okada et al. |
Jul 1977 |
|
4129600 |
Childress et al. |
Dec 1978 |
|
Foreign Referenced Citations (4)
Number |
Date |
Country |
2547536 |
Apr 1976 |
DEX |
49-92006 |
Sep 1974 |
JPX |
50-37719 |
Apr 1975 |
JPX |
50-12410 |
May 1975 |
JPX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
843691 |
Oct 1977 |
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