Process and zeolitic materials for the separation of gases

Abstract

The present invention relates to a process for the separation of gases which comprises putting a mixture of gases in contact with a zeolite of the ESV type to obtain the selective adsorption of at least one of the gases forming the gaseous mixture. The present invention also relates to particular zeolitic compositions suitable as adsorbents.

1 . A process for the separation of gases which comprises putting a mixture of gases in contact with a zeolite for selectively adsorbing at least one of the gases forming the mixture, characterized in that the zeolite is a zeolite of the ESV type. 
     
     
         2 . The process according to  claim 1  comprising a desorption step of the gases adsorbed. 
     
     
         3 . The process according to  claim 1  or  2 , wherein the zeolite is an ERS-7 zeolite. 
     
     
         4 . The process according to  claim 3 , wherein the zeolite is a zeolite of the ERS-7 type having in the calcined and anhydrous form the following general formula (I):
   M 2/n O.Al 2 O 3   .x SiO 2      
       wherein M is a cation having a valence n selected from H + , metallic cations of the IA group, metallic cations of the IIA group and their mixtures, n=1 or 2, and x has a value ranging from 15 to 30. 
     
     
         5 . The process according to  claim 4 , wherein M is at least a cation selected from H + , Li + , Na + , K + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ . 
     
     
         6 . The process according to  claim 5 , wherein M is Na +   +  or Na and H + , optionally mixed with one or more cations selected from Li + , Na + , K + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ . 
     
     
         7 . The process according to  claim 6 , wherein the zeolite of the ERS-7 type is in the form directly deriving from the synthesis, after drying and calcination, containing sodium ions and H +  ions. 
     
     
         8 . The process according to  claim 4 ,  5 ,  6  or  7  wherein M is at least partly a sodium ion and is in a quantity ranging from 0.2 and 1 expressed as a molar ratio Na/Al. 
     
     
         9 . The process according to  claim 1 , wherein the zeolite is used in bound form with an inorganic binder selected from inorganic materials such as clays, oxides of silicon, aluminum, titanium, zirconium and mixtures thereof. 
     
     
         10 . The process according to  claim 9 , wherein the zeolite is used in bound form and in a quantity ranging from 50 to 95% by weight with respect to the total weight of the product formed by the zeolite and binder. 
     
     
         11 . The process according to  claim 10 , wherein the zeolite is in a quantity ranging from 60 to 90% by weight. 
     
     
         12 . The process according to  claim 1 , wherein the ESV zeolite is contained in a membrane. 
     
     
         13 . The process according to  claim 1  or  2 , effected by means of adsorption cycles. 
     
     
         14 . The process according to  claim 13 , effected by means of adsorption cycles of the pressure swing adsorption (PSA), thermal swing adsorption (TSA), vacuum swing adsorption (VSA), pressure-thermal swing adsorption (PTSA), or pressure-vacuum swing adsorption (PVSA. type. 
     
     
         15 . The process according to  claim 14 , wherein the process is effected by means of adsorption cycles of the PSA or PTSA type. 
     
     
         16 . A process of the PSA type according to  claim 15  comprising the following steps:
 a. putting a mixture of gases in contact at a high pressure with a zeolite of the ESV type, to selectively adsorb at least one of the gases forming the mixture and collecting or discharging the remaining gaseous components of the mixture; 
 b. interrupting the flow of gaseous mixture and optionally reducing the pressure; 
 c. desorbing the gas or gases adsorbed in step a), by partial pressure reduction of the gas or gases adsorbed, and collecting or discharging them; 
 d. repressurizing the system with the mixture of gases fed. 
 
     
     
         17 . A process of the PTSA type according to  claim 15  comprising the following steps:
 a. putting a mixture of gases in contact at a high pressure with a zeolite of the ESV type to selectively adsorb at least one of the gases forming the mixture and collecting or discharging the remaining gaseous components of the mixture; 
 b. interrupting the flow of gaseous mixture and optionally reducing the pressure; 
 c. desorbing the gas or gases adsorbed in step a), by raising of the temperature of the zeolite and partial pressure reduction of the gas or gases adsorbed, and collecting or discharging them; 
 d. repressurizing the system with the mixture of gases fed. 
 
     
     
         18 . The process according to  claim 1 , wherein the gaseous mixture is natural gas containing one or more pollutants selected from nitrogen, CO 2 , H 2 S, water, which are adsorbed. 
     
     
         19 . The process according to  claim 1 , wherein the gaseous mixture is hydrogen containing carbon dioxide, carbon monoxide and hydrocarbons which are adsorbed. 
     
     
         20 . The process according to  claim 16  or  18  for the separation of carbon dioxide, and, if present, H 2 S, from a gaseous mixture containing them together with methane comprising the following steps:
 a. putting said gaseous mixture in contact, at a high pressure, with a zeolite of the ESV type, to selectively adsorb carbon dioxide and, if present, H 2 S, and collecting the remaining gaseous component containing methane; 
 b. interrupting the flow of gaseous mixture and optionally reducing the pressure; 
 c. desorbing the carbon dioxide and, if present, H 2 S, adsorbed in step (a), by partial pressure reduction of the gas or gases adsorbed, and collecting or discharging them; 
 d. repressurizing the system with the mixture of gases fed. 
 
     
     
         21 . The process according to  claim 17  or  18  for the separation of carbon dioxide, and, if present, H 2 S, from a gaseous mixture containing them together with methane comprising the following steps:
 a. putting said gaseous mixture in contact, at a high pressure, with a zeolite of the ESV type, to selectively adsorb carbon dioxide and, if present, H 2 S, and collecting the remaining gaseous component containing methane; 
 b. interrupting the flow of gaseous mixture and optionally reducing the pressure; 
 c. desorbing the carbon dioxide and, if present, H 2 S, adsorbed in step (a), by raising the temperature of the zeolite and partial pressure reduction of the gas or gases adsorbed, and collecting or discharging them; 
 d. repressurizing the system with the mixture of gases fed. 
 
     
     
         22 . The process according to  claim 1 ,  16 ,  17 ,  20  or  21 , wherein the adsorption is carried out at a temperature ranging from 0 to 40° C. and a pressure ranging from 10 to 90 bara. 
     
     
         23 . The process according to  claim 22 , wherein the adsorption is carried out at an adsorption pressure ranging from 10 to 40 bara. 
     
     
         24 . The process according to  claim 2 ,  16  or  20 , wherein the desorption step is carried out at a pressure ranging from 0.5 to 10 bara and a temperature ranging from 0 to 40° C. 
     
     
         25 . The process according to  claim 2 ,  17  or  21 , wherein the desorption step is carried out at a pressure ranging from 0.5 to 10 bara and a temperature ranging from 50 to 200° C. 
     
     
         26 . The process according to  claim 25 , wherein the temperature ranges from 60 to 100° C. 
     
     
         27 . The process according to  claim 16 ,  17 ,  20  or  21  wherein the zeolite is ERS-7. 
     
     
         28 . The process according to  claim 2 ,  16  or  17 , wherein the desorption step is followed by washings with a gas selected from N 2 , CH 4 , air or hydrogen. 
     
     
         29 . Zeolites of the ERS-7 type having in the calcined and anhydrous form the following general formula (I):
   M 2/n O.Al 2 O 3   .x SiO 2      
       wherein M is at least a cation having a valence n selected from Li, Mg, Ca, Sr, Ba, optionally mixed with one or more cations selected from H +  and Na + , n=1 or 2, and x has a value ranging from 15 to 30. 
     
     
         30 . A process for preparing zeolites of the ERS-7 type having in the calcined and anhydrous form the following general formula (I):
   M 2/n O.Al 2 O 3   .x SiO 2      
       wherein M is a cation having a valence n selected from H + , metallic cations of the IA group, metallic cations of the IIA group and their mixtures, n=1 or 2, and x has a value ranging from 15 to 30, which comprises:
 a. reacting sodium silicate, aluminum sulfate, N,N-dimethylpiperidinium halide or hydroxide, under hydrothermal conditions, so that there are the following molar ratios in the reagent mixture: 
 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   SiO 2 /Al 2 O 3   
                   15-30 
                 
                     
                   R/SiO 2   
                   0.2-0.4 
                 
                     
                   H 2 O/SiO 2   
                   30-50 
                 
                     
                   Na/Al 2 O 3   
                   10-30 
                 
                     
                   OH − /SiO 2   
                   0.3-0.6 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
               
            
           
         
       
       wherein R is N,N-dimethylpiperidinium, at a temperature ranging from 150 to 200° C. for a period of time varying from 5 to 15 days;
 b. discharging the resulting mixture from which a solid is separated, by means of filtration, which, after washing with demineralized water and drying at a temperature ranging from 120 to 150° C. has the following composition (II):
     y R 2 O. m M 2 O.Al 2 O 3   .x SiO 2   (II)
 
 
 
       wherein 0<y≦1, 0<m≦1, R is N,N-dimethylpiperidinium, M is sodium, x has a value ranging from 15 to 30;
 c. calcining at a temperature ranging from 500° to 700° C. for 5-18 hours, in a stream of air; 
 d. optionally partially or totally exchanging with an aqueous solution containing at least one reagent selected from an acid, an organic ammonium salt, a salt of a cation selected from metallic cations of group IA, metallic cations of group IIA, and their mixtures, drying and optionally calcining. 
 
     
     
         31 . The process according to  claim 29 , wherein the templating agent N,N-dimethylpiperidinium halide is prepared in situ by reaction between 1,5-pentyldihalide, dimethylamine and NaOH, in a relative molar ratio 1:1.15:1.