Process for making dialkyl carbonates

Abstract

A process for producing dialkyl carbonates, such as dimethyl carbonate, from the reaction of a primary alcohol with urea in the presence of a novel organotin catalyst complex with a high boiling electron donor compound acting as solvent which are (1) materials having the general formula RO[CH 2 (CH 2 ) k CH 2 O] m R, wherein each R is independently selected from C 1-12 alkyl, alkaryl or aralkyl moieties, k=0,1, 2 or 3 and m=1, 2, 3, 4 or 5 and (2) bidentate ligand which form 1:1 bidentate and/or 1:2 monodentate adducts with R′ 2 SnX 2 (X═Cl, R′O, R′COO or R′COS), R′ 3 SnX, R′SnO, Ph 3-n R′SnX n or Ph 4-n SnX n (wherein R′=C q H 2q-1 n=0, 1 or 2 and q=2 1 to 12) and mixtures thereof, such as materials having the general formula RO[CH 2 ( CH 2 ) x CH 2 O] m R, wherein each R is independently selected from C 1-12 alkyl, alkaryl or aralkyl moieties, k=0,1, 2 or 3 and m=1, 2, 3, 4, or 5.

The invention claimed is:  
     
       1. A process for the production of dialkyl carbonates comprising the steps of: 
       (a) feeding urea and a primary alcohol to a reaction zone;  
       (b) feeding an organotin compound selected from the group consisting of R′ 2   SnX   2  ( X═Cl, R′O, R′COO or R′COS ) , R′   3   SnX, R′   2   SnO, Ph   3-n   R′SnX   n    or Ph   4-n   SnX   n  ( wherein R′=C   q   H   2q-1   , n= 0 ,  1  or  2  and q= 1  to  12   )  and mixtures thereof  and a high boiling electron donor atom containing solvent comprising bidentate ligands which form  1 : 1  bidentate and/or  1 : 2  monodentate comprising materials having the general formula RO[CH 2 ( CH   2 ) k   CH   2   O]   m   R, wherein each R is independently selected from C   1-12    alkyl, alkaryl or aralkyl moieties, k= 0 ,  1 ,  2  or  3  and m= 1 ,  2 ,  3 ,  4 , or  5  and mixtures thereof,  to said reaction zone; and  
       (c) concurrently in said reaction zone  
       (i) forming an adduct of said organotin compound and said bidentated ligands,  
       ( ii ) reacting a portion of the primary alcohol and urea in the presence of said organotin compound and said high boiling electron donor atom containing solvent to produce dialkyl carbonate; and  
       (ii)( iii ) removing the dialkyl carbonate and from said reaction zone as a vapor mixture; and  
       ( iv )  recovering the dialkyl carbonate from said vapor mixture by condensation.    
     
     
       2. The process according to claim  1  wherein ammonia and a portion of said alcohol are removed from said reaction zone as vapor and withdrawn along with said dialkyl carbonate as overheads. 
     
     
       3. The process according to claim  2  wherein said overheads are partially condensed to separate said ammonia as a vapor from said dialkyl carbonate and said alcohol as a liquid. 
     
     
       4. The process according to claim  1  wherein said organotin catalyst is dibutyltin dimethoxide. 
     
     
       5. The process according to claim  1  wherein said high boiling electron donor atom containing solvent comprises polyglycol ether. 
     
     
       6. The process according to claim  1  wherein said high boiling electron donor atom containing solvent comprises (1) materials having the general formula RO[CH 2 (CH 2 ) k CH 2 O] m R, wherein each R is independently selected from C 1-12  alkyl, alkaryl or aralkyl moieties, k=0, 1, 2 or 3 and m=1, 2, 3, 4 or 5 and (2) bidentate ligands which form 1:1 bidentate and/or 1:2 monodentate adducts with R′ 2 SnX 2 (X=Cl, R′O, R′COO or R′COS), R′ 3 SnX, R′SnO, Ph 3-n R′SnX n  or Ph 4-n SnX n  (wherein R′=C q H 2q-1  n=0, 1 or 2 and q=2 to 12) and mixtures thereof. 
     
     
       7. The process according to claim  6   1 wherein said high boiling electron donor atom containing solvent comprises triethylene glycol dimethyl ether. 
     
     
       8. The process according to claim  1  wherein said high boiling electron donor atom containing solvent comprises materials having the general formula RO[CH 2 (CH 2 ) k CH 2 O] m R, wherein each R is independently selected from C 1-12  alkyl, alkaryl or aralkyl moieties, k=0,1, 2 or 3 and m=1, 2, 3, 4 or 5 and mixtures thereof. 
     
     
       9. The process according to claim  1  wherein said high boiling electron donor atom containing solvent comprises bidentate ligand which form 1:1 bidentate and/or 1:2 monodentate adducts with R′ 2 SnX 2 (X=Cl, R′O, R′COO or R′COS), R′ 3 SnX, R′SnO, Ph 3-n R′SnX n  or Ph 4-n SnX n  (wherein R′=C q H 2q-1 , n=0, 1 or 2 and q=2 to 12) and mixtures thereof. 
     
     
       10. The process according to claim  1  wherein said primary alcohol is methanol and said dialkyl carbonate is dimethyl carbonate. 
     
     
       11. A process for the production of dimethyl carbonate comprising the steps of: 
       (a) feeding urea and methanol to the reboiler of a distillation still;  
       (b) feeding dialkyltin catalyst and triethylene glycol dimethyl ether solvent/cocatalyst to said reboiler;  
       (c) concurrently in said reboiler;  
       (i) forming an adduct of said organotin compound and said bidentated ligands,  
       ( ii ) reacting a portion of said methanol and urea in the presence of said dibutyltin catalyst and said triethylene glycol dimethyl ether cocatalyst adduct to finally produce dimethyl carbonate; and  
       (ii)( iii ) removing the dimethyl carbonate and ammonia from said reboiler as a vapor mixture; and  
       ( iv )  recovering the dimethyl carbonate from said vapor mixture by condensation.    
     
     
       12. The process according to claim  11  wherein a portion of said methanol is removed from said reboiler as vapor and withdrawn from said distillation column along with said dimethyl carbonate as overheads. 
     
     
       13. The process according to claim  12  wherein said overheads are partially condensed to separate said dimethyl carbonate and said methanol as a liquid. 
     
     
       14. The process according to claim  1  wherein said organotin compound comprises R′ 2   SnX   2 .  
     
     
       15. The process according to claim  1  wherein said organotin compound comprises R′ 3   SnX.    
     
     
       16. The process according to claim  1  wherein said organotin compound comprises R′ 2   SnO.    
     
     
       17. The process according to claim  1  wherein said organotin compound comprises Ph 3-n   R′SnX   n .  
     
     
       18. The process according to claim  1  wherein said organotin compound comprises Ph 4-n   SnX   n .