Process For The Removal Of Nitrogen-Containing Compounds From A Hydrocarbon Feed

Abstract

Process for the removal of nitrogen-containing compounds from a hydrocarbon feed comprising at least one olefin selected from the C3, C4, C5 and optionally C6 olefins and mixtures thereof comprising solvent extraction comprising monitoring the degradation of the solvent.

1 . A Process for the removal of nitrogen-containing compounds from a hydrocarbon feed comprising at least one olefin selected from the C3, C4, C5 and optionally C6 olefins and mixtures thereof comprising the steps of:
 a) contacting the hydrocarbon feed with an extracting solvent containing propylene carbonate to obtain a hydrocarbon phase of reduced nitrogen-containing compounds content and a solvent phase containing dissolved nitrogen-containing compounds;   b) separating the hydrocarbon phase of reduced nitrogen-containing compounds content from a solvent phase containing dissolved nitrogen-containing compounds;   c) subjecting the hydrocarbon phase from step (b) to a distillation step to separate a heavy phase containing the solvent and optionally heavy hydrocarbon compounds from a light hydrocarbon fraction containing the C3, C4 and C5 olefins;   d) optionally subjecting the light fraction to further processing; and   e) subjecting the solvent phase from step (b), optionally with the heavy phase from step (c), to a regeneration step; and   f) recycling the regenerated solvent back to step (a),   said process further comprising monitoring the degradation of the solvent by
 keeping the content of the propylene carbonate present in recycled solvent above 94% by weight relative to the solvent as measured by gas chromatography; 
 keeping the Total Acid Number (TAN) of the recycled solvent measured according to ISO 1843/2 below 0.1 mg KOH/g 
 keeping the distribution coefficient of the nitrogen-containing compounds between the recycled solvent and the hydrocarbon feed above 50% of the value measured with fresh solvent; 
 keeping the settling time of the recycled solvent in the hydrocarbon feed below 200% of the settling time of the raw propylene carbonate; or 
 maintaining the surface tension of the recycled solvent as measured by the Ring Tear Off method above 25 mN/m or the interfacial tension measured by the Du Nouy Ring method above 6 mN/m. 
   
     
     
         2 . The process according to  claim 1 , wherein the accumulation of solvent degradation products and heavy hydrocarbons in the recycling loop can be avoided or at least minimize by one or more of the following steps
 filtration of the solvent before feeding it back to step (a);   depending on the monitoring results purging an appropriate amount of solvent and replacing by fresh solvent;   operating the regeneration step in such a way that the heavy hydrocarbon compounds and the solvent degradation products are removed at said regeneration step, for example by decreasing the reflux ratio in the stripper or adapting the regeneration temperature; and   adding a distillation step between the regeneration and the extraction steps.   
     
     
         3 . The process according to  claim 1 , wherein the regeneration step (e) is operated in a stripping column by using an inert gas or a light hydrocarbon having from 1 to 7 carbon atoms. 
     
     
         4 . The process according to  claim 1 , wherein the solvent comprise propylene carbonate. 
     
     
         5 . The process according to  claim 1 , wherein the hydrocarbon feed is a C5 olefin feeds including FCC Light Naphtha streams, steam cracker C5 rich streams that have been treated for diene removal, C5 olefin containing streams from Gas to Olefin (GTO) Units, or Fisher-Tropsch Units. 
     
     
         6 . The process according to  claim 1 , wherein the stripping column is equipped with an overhead reflux resulting in a column configuration comprising a stripping portion in the bottom and a distillation portion at the top. 
     
     
         7 . The process according to  claim 1 , wherein, depending on the monitoring results, an appropriate amount of solvent is purged at step (e) and replaced by fresh solvent. 
     
     
         8 . A process for converting a hydrocarbon feed comprising at least one olefin selected from the C3, C4, C5 and optionally C6 olefins and mixtures thereof contaminated with at least one nitrogen-containing compound into a hydrocarbon product; said process comprising the steps of:
 i) providing a hydrocarbon feed contaminated with at least one nitrogen-containing compound;   ii) removing the nitrogen-containing compounds from the feed to produce a hydrocarbon feed stream having a reduced level of nitrogen-containing compounds; and   contacting said hydrocarbon feed stream having a reduced level of nitrogen-containing compounds with a catalyst in order to convert the feed stream into a hydrocarbon product,   wherein nitrogen-containing compounds are removed from the feed by using the process as defined in any one of the preceding claims.   
     
     
         9 . The process according to  claim 8  wherein step (iii) is an isomerization, an alkylation, a hydrogenation, an aromatization or an oligomerization step. 
     
     
         10 . The process according to  claim 9 , wherein step (ii) is an oligomerisation step using an oligomerization catalyst comprising a material selected from the group consisting of zeolites, phosphoric acids, supported metal oxides and combinations thereof. 
     
     
         11 . The process according to  claim 10 , wherein the oligomerization catalyst comprises a zeolite, in particular a zeolite selected from the group consisting of ZSM-5, ZSM-11, ZSM-1, ZSM-18, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-50, ZSM-57, ITQ-39 and mixtures thereof.