Stability of hydrocarbons containing asphal tenes

Abstract

Heavy fuel oils or residual fuel oils can be stabilized with magnesium over-based compounds such as magnesium overbased carboxylates. It was surprisingly discovered that adding magnesium overbased carboxylates to the residual fuel oils shortly after thermal cracking gave much better results than can be achieved after the application of the carboxylates to the fuel oil after storage. Further, compounds containing at least about 21 wt % magnesium also give better results than compounds with 18 wt % or less, in one non-limiting embodiment. Magnesium overbased compounds can also be added to coker feedstocks to reduce coker furnace fouling. Treatment with the methods of this invention reduces asphaltene deposits and sludges.

1 . A method for stabilizing a hydrocarbon stream containing asphaltenes comprising: 
 heating the hydrocarbon stream containing asphaltenes; and    adding to the hydrocarbon stream a magnesium overbased compound selected from the group consisting of magnesium overbased carboxylates, magnesium overbased sulfonates, magnesium overbased phenates, and mixtures thereof, in an amount effective to improve the stability of the hydrocarbon stream, where the hydrocarbon stream is subjected to heat after the addition.    
     
     
         2 . The method of  claim 1  where the magnesium overbased compound is added in an amount ranging from about 25 to about 2000 ppm based on the hydrocarbon stream.  
     
     
         3 . The method of  claim 1  where the magnesium overbased compound contains at least 21 wt % magnesium.  
     
     
         4 . The method of  claim 1  where the adding is performed within 40 hours or less after the hydrocarbon stream is thermally cracked.  
     
     
         5 . The method of  claim 1  where the hydrocarbon stream is a coke drum feedstock and the magnesium overbased compound is added to the feedstock prior to storing the feedstock at an elevated temperature.  
     
     
         6 . The method of  claim 1  where the adding is performed within a temperature range of about 250 to about 490° C.  
     
     
         7 . A method for inhibiting coke furnace fouling comprising: 
 heating a coke drum feedstock containing asphaltenes;    adding to the coke drum feedstock a magnesium overbased compound selected from the group consisting of magnesium overbased carboxylates, magnesium overbased sulfonates, magnesium overbased phenates, and mixtures thereof; and    storing the coke drum feedstock at an elevated temperature.    
     
     
         8 . The method of  claim 7  where the magnesium overbased compound is added in an amount ranging from about 25 to about 2000 ppm based on the coke drum feedstock.  
     
     
         9 . The method of  claim 7  where the magnesium overbased compound contains at least 21 wt % magnesium.  
     
     
         10 . The method of  claim 7  where the adding is performed within a temperature range of about 250 to about 490° C.  
     
     
         11 . A method for stabilizing heavy fuel oils comprising: 
 thermally cracking a residual oil to provide a heavy fuel oil; and    adding to the heavy fuel oil a magnesium overbased compound selected from the group consisting of magnesium overbased carboxylates, magnesium overbased sulfonates, magnesium overbased phenates, and mixtures thereof, in an amount effective to improve the stability of the fuel oil, where the adding is conducted sufficiently soon after thermal cracking to improve stability.    
     
     
         12 . The method of  claim 11  where the magnesium overbased compound is added in an amount ranging from about 25 to about 2000 ppm based on the heavy fuel oil.  
     
     
         13 . The method of  claim 11  where the magnesium overbased compound contains at least 21 wt % magnesium.  
     
     
         14 . The method of  claim 11  where the adding is performed within 40 hours or less of the thermal cracking.  
     
     
         15 . The method of  claim 11  where the adding is performed within a temperature range of about 250 to about 490° C.  
     
     
         16 . The method of  claim 11  where the method is practiced in the absence of adding a co-promoter reaction product from a succinic anhydride and a lower carboxylic acid.  
     
     
         17 . The method of  claim 11  where the magnesium overbased compound is a magnesium overbased carboxylate.  
     
     
         18 . A method for stabilizing heavy fuel oils comprising: 
 thermally cracking a residual oil to provide a heavy fuel oil; and    adding to the heavy fuel oil a magnesium overbased carboxylate in an amount effective to improve the stability of the fuel oil, where the adding is conducted sufficiently soon after thermal cracking to improve stability, where the magnesium overbased carboxylate contains at least 21 wt % magnesium and the adding is performed within 2 hours or less of the thermal cracking.    
     
     
         19 . The method of  claim 18  where the magnesium overbased carboxylate is added in an amount ranging from about 25 to about 2000 ppm based on the heavy fuel oil.  
     
     
         20 . The method of  claim 18  where the adding is performed within a temperature range of about 250 to about 490° C.  
     
     
         21 . The method of  claim 18  where the method is practiced in the absence of adding a co-promoter reaction product from a succinic anhydride and a lower carboxylic acid.  
     
     
         22 . A stabilized heavy fuel oil comprising: 
 a heavy fuel oil prepared by thermally cracking a residual oil; and    a magnesium overbased compound in an amount effective to improve the stability of the fuel oil, where the magnesium overbased compound is added to the heavy fuel oil sufficiently soon after thermal cracking to produce the residual oil to improve stability, and where the magnesium overbased compound is selected from the group consisting of magnesium overbased carboxylates, magnesium overbased sulfonates, magnesium overbased phenates and mixtures thereof.    
     
     
         23 . The heavy fuel oil of  claim 22  where the magnesium overbased compound is present in an amount ranging from about 25 to about 2000 ppm based on the heavy fuel oil.  
     
     
         24 . The heavy fuel oil of  claim 22  where the magnesium overbased compound contains at least 21 wt % magnesium.  
     
     
         25 . The heavy fuel oil of  claim 22  where the magnesium overbased compound is added within 40 hours or less of the thermal cracking.  
     
     
         26 . The heavy fuel oil of  claim 22  where the magnesium overbased compound is added within a temperature range of about 250 to about 490° C.  
     
     
         27 . The heavy fuel oil of  claim 22  further comprises an absence of a copromoter reaction product from a succinic anhydride and a lower carboxylic acid.  
     
     
         28 . The heavy fuel oil of  claim 22  where the magnesium overbased compound is a magnesium overbased carboxylate.  
     
     
         29 . A stabilized heavy fuel oil comprising: 
 a heavy fuel oil prepared by thermally cracking a residual oil; and    a magnesium overbased carboxylate in an amount effective to improve the stability of the fuel oil, where the magnesium overbased carboxylate is added to the heavy fuel oil within 2 hours after thermal cracking to produce the residual oil to improve stability, and where the magnesium overbased carboxylate contains at least 21 wt % magnesium.    
     
     
         30 . The heavy fuel oil of  claim 29  where the magnesium overbased carboxylate is present in an amount ranging from about 25 to about 2000 ppm based on the heavy fuel oil.  
     
     
         31 . The heavy fuel oil of  claim 29  where the magnesium overbased compound is added within a temperature range of about 250 to about 490° C.  
     
     
         32 . The heavy fuel oil of  claim 29  further comprises an absence of a copromoter reaction product from a succinic anhydride and a lower carboxylic acid.