Patent EP-0203651-A3 (EP)
IPC: C10L10/14
Filed: 1986-05-14
Abstract: A cryogenic process is disclosed for the selective 
removal of acidic gases from natural gases or from syn­
thesis gases by adsorption in two towers and cooling of 
the gas outcoming from the first tower to the purpose of 
condensing a portion of CO₂ contained in the same gas, 
which is characterized in that in it a mixture is used 
constituted by one or more selective solvents selected 
among low molecular weight esters, alcohols and ethers of 
the following classes:  
- esters of alcohols of general formula R₁COOR₂,  
wherein R₁ and R₂ are alkyl groups of from 1 to 4 
carbon atoms, equal to or different from each other, 
wherein one or more hydrogen atoms can be substituted 
by alcoholic groups;  
- esters of glycols of general formula 
  
 
 
  
wherein R₁ and R₂ are alkyl groups having from 1 to 3 
carbon atoms, equal to or different from each other, 
R₃, R₄, R₅, R₆, equal to or different from each other, 
are either alkyl groups containing from 1 to 3 carbon 
atoms or hydrogen atoms,  m  and  n  are integers which can 
have the value 0 or 1;  
- cyclic esters (lactones) of formula 
  
wherein R₂, R₃, R₄, R₅, equal to or different from each 
other, are alkylene groups wherein one or more hydrogen 
atoms can also be substituted by alkylic, alcoholic or 
ether groups;  
- alcohols of general formula 
  
wherein R₁, R₂, R₃, R₄, R₅, R₆, equal to or different 
from each other, are alkyl groups having from 1 to 3 
carbon atoms or hydroxy groups or hydrogen atoms, and  m  
 
 
 n  are integers which can assume the values 0 and 1;  
- cyclic ethers such as 
  
wherein R₂, R₅, R₆, equal to or different from each 
other, are alkyl groups wherein hydrogen can also be 
substituted by alkyl or methoxy groups, R₃ is either an 
oxygen atom or an alkylene group wherein hydrogen can 
also be substituted by alkyl or methoxy groups, R₄ is 
either equal to R₃ or can be absent in case of a 
pentaatomic ring;  
- ethers of general formula  
R₁-O-CH₂-(R₃) n -CH₂-O-R₂  
wherein R₁ is an alkyl group of from 1 to 4 carbon 
atoms, R₂ is either an alkyl group of from 1 to 4 
carbon atoms or a hydrogen atom , R₃ is either an 
alkylene group or (CH₂-O-CH₂),  n  is an integer which 
can have the value 0 or 1;  
- ethers of general formula  
R₁-O-R₂  
wherein R₁ and R₂, either equal to or different from 
each other, are alkyl groups of from 1 to 4 carbon 
atoms, wherein one or more hydrogen atoms can be sub­
stituted by alcoholic groups;  
- ester-ethers, compounds containing both the functions, 
of formula:  
(R₄-O) n  - R₁ - COOR₂ (OR₃) m    
wherein R₃ and R₄, equal to or different from each 
other, are alkyl groups having from 1 to 4 carbon 
 
 
atoms, R₂ is an alkylene group having from 1 to 4 
carbon atoms, R₁ is either equal to R₂ or equal to R₃, 
 m  and  n  are integers which can have the value 0 or 1,  
and by one or more organic compounds selected from:  
- heptane,  
- fractions of natural gasolines containing hydrocarbons 
having a number of carbon atoms comprised within the 
range of from 5 to 8;  
- monoaromatic compounds having a number of paraffinic 
carbon atoms comprised within the range of from 2 to 4, 
bound to the benzene ring either separately or as one 
or more linear or branched side chains;  
- dimethylethers of polyglycols having the glycolic unit 
-CH₂-CH-O- repeated from once to five times;  
- methoxy- and/or ethoxyalcohols, wherein the alcoholic 
group is a radical having from 1 to 4 carbon atoms in 
either linear or branched chain.