Selective Conversion of Paraffinic Naphtha to Propylene in the Presence of Hydrogen

Abstract

The invention relates to a process of catalytic conversion by hydrocracking of paraffinic and naphthenic hydrocarbons from a naphtha feedstock (1) to propylene, the process comprising the steps of providing a naphtha feedstock (1) containing one or more paraffins comprising 4 to 10 carbon atoms; and contacting said naphtha feedstock (1) with a catalyst composition in the presence of hydrogen in a reaction zone under hydrocracking conditions; wherein the catalyst composition consists of one or more zeolite catalysts comprising acid 10-membered ring channels.

1 .- 15 . (canceled) 
     
     
         16 . A process of catalytic conversion by hydrocracking of paraffinic and naphthenic hydrocarbons from a naphtha feedstock to propylene, the process being characterized in that it comprises the following steps:
 a) providing a naphtha feedstock containing one or more paraffins comprising 4 to 10 carbon atoms; and   b) submitting said naphtha feedstock to a hydrocracking step by contacting said naphtha feedstock with a catalyst composition in the presence of hydrogen in a reaction zone under hydrocracking conditions to produce an effluent;   c) submitting the effluent to a separation step to recover propane; and   d) submitting said propane to a step of dehydrogenation into propylene in a propane dehydrogenation reactor;   e) collecting hydrogen produced in the step of dehydrogenation into propylene, and recycling said hydrogen back to the hydrocracking reaction zone in order to perform the hydrocracking step;   and in that the catalyst composition of the hydrocracking step comprises one or more zeolite catalysts comprising one or more acid 10-membered ring channels.   
     
     
         17 . The process according to  claim 16 , characterized in that the naphtha feedstock comprises at least 10 wt % of naphthenes as based on the total weight of the naphtha feedstock. 
     
     
         18 . The process according to  claim 16 , characterized in that the one or more zeolite catalysts have a Si/Al molar ratio ranging from 10 to 100. 
     
     
         19 . The process according to  claim 16 , characterized in that the hydrocracking conditions of the hydrocracking step comprise:
 a. the naphtha feedstock being contacted with the catalyst composition at a temperature ranging from 200 to 600° C., and/or   b. the naphtha feedstock being contacted with the catalyst composition at a pressure ranging from 1 to 10 MPa.   
     
     
         20 . The process according to  claim 16 , characterized in that the catalyst composition contains no added noble metal and no added transition metals. 
     
     
         21 . The process according to  claim 16 , characterized in that the catalyst composition contains at most 50 ppm wt of noble metal and less than 0.05 wt % of transition metals as based on the total weight of the catalyst composition. 
     
     
         22 . The process according to  claim 16 , characterized in that the hydrocracking conditions of the hydrocracking step comprise the naphtha feedstock being contacted with the catalyst composition at a WHSV (feed) of at least 0.1 h −1    
     
     
         23 . The process according to  claim 16 , characterized in that, in the hydrocracking step, hydrogen is provided to the naphtha feedstock at a molar ratio H 2 /Naphtha ranging from 1000:1 to 1:1. 
     
     
         24 . The process according to  claim 16 , characterized in that the catalyst composition comprises at least 60 wt % of one or more zeolite catalysts comprising one or more acid 10-membered ring channels. 
     
     
         25 . The process according to  claim 16 , characterized in that the catalyst composition comprises one or more zeolite catalysts selected from the list comprising ZSM-5, silicalite-1, ZSM-11, silicalite-2, SSZ-46, MCM-68, CIT-1, SSZ-33, ZSM-8, Ferrierite, FU-9, ZSM-35, ZSM-23, ZSM-22, Theta-1, NU-10, ZSM-50, EU-1, ZSM-57, SAPO-11 and ZSM-48. 
     
     
         26 . The process according to  claim 16 , characterized in that the one or more zeolite catalysts comprising one or more acid 10-membered ring channels comprise or are zeolites catalysts of the MFI-type. 
     
     
         27 . The process according to  claim 16 , characterized in that the catalyst composition comprises a binder selected from silica, alpha-alumina, gamma-alumina, clays, alumina phosphates, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, iron, bronze and stainless steel, glass, and carbon. 
     
     
         28 . The process according to  claim 16 , characterized in that the step of dehydrogenation into propylene is performed at a temperature ranging from 500 to 800° C. and a partial pressure of propylene below one atmosphere. 
     
     
         29 . The process according to  claim 16 , characterized in that the separation step comprises recovering a C4 paraffins fraction from the effluent of step b) and a step of recycling back the C4 paraffins fraction to the hydrocracking reaction zone, and/or the separation step comprises recovering a C5+ hydrocarbon fraction from the effluent of step b) and a step of valorization of said C5+ hydrocarbon fraction as gasoline. 
     
     
         30 . The process according to  claim 16 , characterized in that it comprises a step of recovering the unconverted propane after the step of dehydrogenation into propylene and recycling it to the propane dehydrogenation reactor to be submitted to a further step of dehydrogenation into propylene. 
     
     
         31 . The use of one or more zeolite catalysts comprising the one or more acid 10-membered ring channels in a process according to  claim 16  of catalytic conversion by hydrocracking of paraffinic and naphthenic hydrocarbons from a naphtha feedstock to propane, and further dehydrogenation of said propane to propylene, characterized in that the zeolite catalysts contains at most 50 ppm wt of noble metal and less than 0.05 wt % of transition metals as based on the total weight of the catalyst composition.