Stability of Methacrolein and Methacrylic Acid in Vapour Phase Catalytic Oxidation of Methacrolein

Stability of methacrolein and methacrylic acid was studied prior to inquiry into new effective catalysts for synthesis of methacrylic acid by the vapour phase catalytic oxidation of methacrolein. It is necessary to use a reactor designed to avoid mixing of methacrolein with oxygen before catalyst zone, because autoxidation of methacrolein occurs remerkably at the reaction temperature of above 320°C in the empty tube.More than 29% of methacrylic acid was cracked over the Mo-Co catalyst at the temperature of above 350°C in the presence of oxygen, forming acetone and carbon dioxide as by products. It was found that the lower selectivity of methacrylic acid in the catalytic oxidation of methacrolein was attributable to successive oxidation as affected by the forming method of catalyst, reaction temperature, contact time and concentration of oxygen and methacrylic acid in feed gas.