Procede d'hydrotraitement et/ou d'hydrocraquage de charges azotees avec stripage a l'hydrogene

Abstract

The invention relates to a process for hydrotreatment and/or hydrocracking of nitrogen feedstocks in which a portion of the hydrotreated and/or hydrocracked effluent is recycled to the hydrotreatment and/or hydrocracking stage after having been subjected to stripping with hydrogen or any other inert gas. The invention is particularly well suited for the processes that are performed in the absence of gaseous hydrogen circulating through the catalytic bed.

1 . Process for hydrotreatment and/or hydrocracking of nitrogen feedstocks in which a portion of the hydrotreated and/or hydrocracked effluent is recycled to the hydrotreatment and/or hydrocracking stage after having been subjected to stripping with hydrogen or another inert gas. 
     
     
         2 . Process according to  claim 1 , in which the hydrogen that enters into the stripper exhibits a purity (expressed in terms of volume) of at least 80%, preferably at least 90%, and also preferably at least 95%, and even at least 99%. 
     
     
         3 . Process according to  claim 1  in which the nitrogen feedstock and optionally the recycled portion is brought into contact with the gaseous hydrogen, and then it is subjected to a flash separation and is sent to the hydrotreatment and/or hydrocracking stage. 
     
     
         4 . Process according to  claim 1 , in which the nitrogen feedstock has a nitrogen content that is greater than 100 ppm and preferably between 500 and 5,000 ppm by weight, in a more preferred manner between 700 and 4,000 ppm by weight, and in an even more preferred manner between 1,000 and 4,000 ppm; the sulfur content is between 0.01 and 5% by weight, and more generally between 0.2 and 4%. 
     
     
         5 . Process according to  claim 1 , in which the feedstock is selected from the group that is formed by the atmospheric or vacuum distillates that are obtained from the direct distillation of crude or conversion processes, the deasphalted oils (DAO), the oils that come from units for extraction of aromatic compounds from lubricating oil bases or that are obtained from dewaxing of lubricating oil bases, by themselves or in a mixture. 
     
     
         6 . Process according to  claim 1 , in which the hydrogen stripping is implemented only on the recycled portion. 
     
     
         7 . Process according to  claim 1 , in which before separation of the gaseous phase, at least one portion of the effluent that is obtained from the hydrotreatment and/or hydrocracking stage is separated to be recycled to said stage, whereby said portion is subjected to a hydrogen stripping separation. 
     
     
         8 . Process according to  claim 1 , in which the effluent that is obtained from the hydrotreatment and/or hydrocracking stage is subjected to a flash separation, and a portion of the liquid phase that is obtained from the flash separation is subjected to a hydrogen stripping separation before being recycled to said stage. 
     
     
         9 . Process according to  claim 1 , in which the effluent in its entirety is subjected to hydrogen stripping; a portion is recycled to the hydrotreatment and/or hydrocracking stage. 
     
     
         10 . Process according to  claim 1 , in which the stripping is implemented with a pressure drop of at most 5 bar (0.5 MPa), generally between 0.5 and 5 bar, and the stripping temperature is 320-450° C.; the quantity of hydrogen is 0.2-1% by weight relative to the fresh feedstock (without the recycling), and preferably 0.5-0.7%. 
     
     
         11 . Process according to  claim 1 , in which the gaseous phase that exits from the stripping undergoes a treatment that comprises a low-temperature high-pressure separation with injected water and a cooling of the gaseous phase; the hydrogen having a purity of at least 90%, and most often at least 95%, is at least partially recycled, and after compression, optionally with supply of make-up hydrogen, to the stripping. 
     
     
         12 . Process according to  claim 1 , in which the gaseous phase that is obtained from this separation is subjected to washing with at least one amine; the hydrogen having a purity of at least 90%, and most often at least 95%, is at least partially recycled and after compression, optionally with supply of make-up hydrogen, to the stripping. 
     
     
         13 . Process according to  claim 1 , in which the gaseous phase that exits from the stripping undergoes a treatment that comprises a low-temperature, high-pressure separation with the injected water and a cooling of the gaseous phase, whereby the gaseous phase that is obtained from this separation is optionally subjected to washing with at least one amine; the hydrogen having a purity of at least 90%, and most often at least 95%, undergoes a purification treatment, preferably selected from the group that is formed by membrane separation, separation in a PSA, or a separation by cryogenics; hydrogen that is obtained with a purity of at least 99% is at least partially recycled after compression to the stripping. 
     
     
         14 . Process according to  claim 1 , in which the catalyst contains at least one element of group VIII and at least one element of group VIB that are deposited on an acid substrate, whereby the catalyst optionally contains phosphorus, and the hydrotreatment and/or hydrocracking stage is implemented at a temperature of more than 200° C., often between 250 and 480° C., advantageously between 320 and 450° C., preferably between 330 and 425° C., under a pressure of between 5 and 25 MPa, preferably less than 20 MPa, whereby the volumetric flow rate is between 0.1 and 20 h −1 , and preferably between 0.1 and 6 h −1 , preferably between 0.2 and 3 h −1 , and the quantity of hydrogen that is introduced is such that the volumetric ratio of liter of hydrogen/liter of hydrocarbon is between 10 and 5,000 l/l and most often between 50 and 2,000 l/l. 
     
     
         15 . Process according to  claim 1 , in which the hydrogen that is introduced to stripping has been compressed and reheated.