Process for producing (meth)acrylic acids

Abstract

A process for producing (meth)acrylic acid or (meth)acrylic acid esters, which comprises a reaction step comprising vapor phase catalytic oxidation of propylene, propane or isobutylene and, if necessary, a reaction step comprising an esterification step, characterized in that at the time when a high boiling mixture (hereinafter referred to as a high boiling material) containing a Michael addition product, is decomposed in a decomposition reactor to recover (meth)acrylic acids, while forcibly imparting a liquid flow in the circumferential direction to a liquid reaction residue in the decomposition reactor, the liquid reaction residue is discharged. In a process for recovering a valuable substance by thermally decomposing the high boiling material containing the Michael addition product of (meth)acrylic acids, it is possible to transfer the decomposition residue from the decomposition reactor to the storage tank without clogging, whereby a long-term continuous operation is possible.

1 - 31 . (canceled)  
     
     
         32 . A method for installing a liquid level meter in a case where a liquid level meter is installed at a place where a liquid containing an easily polymerizable compound is stored, in an installation for production of the easily polymerizable compound, characterized in that a high pressure side detection line of the liquid level meter is connected to a discharge line for the liquid stored.  
     
     
         33 . The method according to  claim 32 , wherein the connection angle α between the high pressure side detection line and the liquid discharge line is from 5 to 90°.  
     
     
         34 . The method according to  claim 32 , wherein the dimensional ratio D 2 /D 1  is from 1 to 20 where D 1  is the pipe diameter of the high pressure side detection line and D 2  is the pipe diameter of the liquid discharge line.  
     
     
         35 . The method according to  claim 32 , wherein the liquid discharge line is connected to a distillation column, a reflux tank of the distillation column, a decomposition reaction column, a thin film evaporator, a column top gas condensed liquid tank, a vertical storage tank, a horizontal storage tank or a tank.  
     
     
         36 . The method according to  claim 32 , wherein the high pressure side detection line and/or the low pressure side detection line of the liquid level meter, is heated or warmed.  
     
     
         37 . The method according to  claim 32 , wherein the high pressure side detection line and/or the low pressure side detection line of the liquid level meter, is connected with an inlet for a gas and/or a liquid.  
     
     
         38 . The method according to  claim 32 , wherein the easily polymerizable compound is (meth)acrylic acid or its ester, and the liquid to be measured by the liquid level meter, contains at least one member selected from an acrylic acid dimer, β-(meth)acryloxypropionic acid esters, β-alkoxypropionic acid esters, β-hydroxypropionic acid and β-hydroxypropionic acid esters, formed as byproducts when (meth)acrylic acid or its ester is produced.