Process for the manufacture of dichloropropanol

Abstract

A process for manufacturing dichloropropanol in which glycerol and/or monochloropropanediol are reacted with hydrogen chloride, in a liquid reaction medium, which is in contact with a gaseous phase, in at least two reactors arranged in a loop, and under a partial pressure of hydrogen chloride in the first reactor which is greater than the partial pressure of hydrogen chloride in the second reactor. This process is suitable for recovering dichloropropanol free from hydrogen chloride and the recovered dichloropropanol may be used in subsequent reactions while avoiding overconsumption of basic agent and loss of recoverable hydrogen chloride, and corrosion during transfer and storage of dichloropropanol will be limited.

1 . A process for manufacturing dichloropropanol wherein glycerol and/or monochloropropanediol are reacted with hydrogen chloride, in a liquid reaction medium, which is in contact with a gaseous phase, in at least two reactors arranged in a loop, and under a partial pressure of hydrogen chloride in the first reactor which is greater than the partial pressure of hydrogen chloride in the second reactor. 
     
     
         2 . The process according to  claim 1 , comprising at least two separation operations, including one in at least one evaporator in which the value of the partial pressure of hydrogen chloride is between the partial pressure of hydrogen chloride in the second reactor and the partial pressure of hydrogen chloride in the first reactor and including another in at least one distillation column , according to which:
 the first reactor is supplied with a first gas flow containing hydrogen chloride and the second reactor with a first liquid flow containing glycerol and optionally water and hydrogen chloride, and a second liquid flow containing a catalyst;   drawn off from the first reactor is a third liquid flow and the evaporator is supplied with this third liquid flow;   drawn off from the evaporator is a second gas flow in which the weight ratio of hydrogen chloride with respect to water is greater than that of the azeotropic water/hydrogen chloride composition at total pressure in the evaporator and the second reactor is supplied with this second gas flow, drawn off from the evaporator is a fourth liquid flow of which the hydrogen chloride content is less than the hydrogen chloride content in the liquid reaction medium of the first reactor, and the first distillation column is supplied with this fourth liquid flow;   drawn off from the second reactor is a fifth liquid flow which supplies the first reactor; and   drawn off from the first distillation column is a third gas flow which mostly contains dichloropropanol and a sixth liquid flow which mostly contains reaction intermediates such as monochloropropanediol, the catalyst and reaction by-products such as partially chlorinated glycerol oligomers, and drawn off from the sixth liquid flow is a seventh liquid flow which constitutes a purge.   
     
     
         3 . The process according to  claim 2 , comprising an additional separation step in at least a second distillation column which is supplied with a fourth gas flow drawn off from the second reactor, and drawn off from which is a fifth gas flow which mostly contains water and dichloropropanol and an eighth liquid flow which supplies the second reactor. 
     
     
         4 . The process according to  claim 2 , comprising two additional separation steps, including one step in a second evaporator and including another step in a second distillation column, which second evaporator is supplied with the fifth liquid flow and from which a sixth gas flow is drawn off and a ninth liquid flow which supplies the first reactor, which second distillation column is supplied with the sixth gas flow and from which an eighth liquid flow is drawn off which supplies the reactor. 
     
     
         5 . The process according to  claim 4 , wherein the second distillation column is supplied with a fourth gas flow drawn off from the second reactor. 
     
     
         6 . The process according to  claim 2 , wherein drawn off from the sixth liquid flow is a tenth liquid flow which supplies the second reactor. 
     
     
         7 . The process according to  claim 2 , wherein drawn off from the sixth liquid flow is an eleventh liquid flow which supplies the first reactor. 
     
     
         8 . The process according to  claim 2 , wherein drawn off from the second distillation column is a twelfth liquid flow which supplies the first reactor. 
     
     
         9 . The process according to  claim 1 , wherein the reaction is carried out in the presence of a catalyst. 
     
     
         10 . The process according to  claim 9 , wherein the reaction is carried out in the presence of adipic acid as the catalyst. 
     
     
         11 . A process for producing epichlorohydrin, the method comprising
 (a) in a liquid reaction medium containing water, which is in contact with a gaseous phase, glycerol is reacted with hydrogen chloride under a partial pressure of hydrogen chloride in the gaseous phase greater than 0.2 bar absolute to produce dichloropropanol;   (b) at least part of the liquid reaction medium and optionally part of the gaseous phase from step a) is (are) subjected to at least one separation operation and, prior to said separation operation, the part of the liquid reaction medium and the part of the gaseous phase from step a) are subjected to:
 i. at least one treatment for reducing the weight ratio between the hydrogen chloride and the water in the part of the liquid reaction medium so as to attain a ratio less than or equal to the weight ratio between the hydrogen chloride and the water in the binary azeotropic hydrogen chloride/water composition at total pressure of the separation operation; and/or 
 ii. at least one treatment for reducing the weight ratio between the water and the dichloropropanol in the part of the liquid reaction medium so as to attain a ratio less than or equal to the weight ratio between the water and the dichloropropanol in the ternary water/dichloropropanol/hydrogen chloride azeotrope at total pressure of the separation operation; and 
   (c) reacting the dichloropropanol obtained to produce epichlorohydrin.