Olefin and btx production using aliphatic cracking and dealkylation reactor

Abstract

A process and apparatus for making olefins and aromatics are described. The process includes reforming a naphtha stream in a reforming unit to produce a reformer effluent stream comprising aromatic compounds and aliphatic compounds, wherein at least a portion of the aromatic compounds contain alkyl groups. A cracking feed stream is taken from the reformer effluent stream, heated and passed to a cracking reactor. The aliphatic compounds are selectively cracked and at least a portion of the alkyl groups on the aromatic compounds are selectively dealkylated in the presence of a cracking catalyst to produce a cracked reformer effluent stream comprising aromatic compounds and cracked olefins.

1 . A process for making aromatics and olefins comprising:
 reforming a naphtha stream in a reforming unit under reforming conditions to produce a reformer effluent stream comprising aromatic compounds and aliphatic compounds, wherein at least a portion of the aromatic compounds contain alkyl groups;   taking a cracking feed stream from the reformer effluent stream;   passing the cracking feed stream at a temperature of at least 500° C. to a cracking reactor comprising a cracking catalyst particles, more than 90 wt % of the cracking catalyst particles in the cracking reactor include a zeolite having a maximum pore diameter of greater than 5 Angstroms;   selectively cracking the aliphatic compounds and selectively dealkylating the alkyl groups on the aromatic compounds in the presence of the cracking catalyst in the cracking reactor under cracking conditions to cracked olefins and aromatic compounds in a cracked reformer effluent stream.   
     
     
         2 . The process of  claim 1  wherein the cracked reformer effluent stream comprises a molar ratio of olefins to paraffins of at least 0.1. 
     
     
         3 . The process of  claim 1  wherein the zeolite comprises MFI zeolite. 
     
     
         4 . The process of  claim 1  wherein the zeolite comprises a silicalite catalyst having a zeolite silica to alumina molar ratio of greater than about 250. 
     
     
         5 . The process of  claim 1  further comprising:
 separating the cracked reformer effluent stream into an aromatic lean fraction comprising the cracked olefins and an aromatic rich fraction comprising the aromatic compounds; and 
 recovering the aromatic rich fraction. 
 
     
     
         6 . The process of  claim 5  further comprising:
 passing at least about 75 wt % of the recovered aromatic rich fraction directly to an aromatics complex. 
 
     
     
         7 . The process of  claim 5  further comprising:
 cracking the aromatic lean fraction in a downstream cracking reactor to form additional olefins, the additional olefins comprising at least one of ethylene, propylene, and butylene; and 
 recovering the additional olefins. 
 
     
     
         8 . The process of  claim 1  wherein the cracking conditions include at least one of a temperature in the range of about 500° C. to about 700° C., a pressure in a range of about 30 kPa (g) to about 750 kPa (g), a hydrogen to C 5+  hydrocarbon mole ratio at an inlet to the cracking reactor of at least about 0.5:1 to about 6:1, and a weight hourly space velocity (WHSV) of about 0.1 hr −1  to about 6 hr −1 . 
     
     
         9 . The process of  claim 1  wherein the catalyst may comprise 0 to about 0.1 wt-% transition metals in IUPAC Groups 5 to 12 of the Periodic Table. 
     
     
         10 . The process of  claim 1  further comprising:
 introducing a naphtha feed stream into a naphtha splitter column to produce at least two streams, the first stream having a T5 boiling point in a range of about 0° C. to about 34° C. and a T95 boiling point in a range of about 25° C. to about 82° C. and the second stream having a T5 boiling point in a range of about 20° C. to about 82° C. and a T95 boiling point in a range of about 140° C. to about 215° C.; 
 passing the second stream to a naphtha hydrotreating reactor to produce a hydrotreated naphtha stream; and 
 wherein reforming the naphtha stream comprises reforming the hydrotreated naphtha stream. 
 
     
     
         11 . The process of  claim 10  further comprising:
 passing at least a portion of the first stream to the cracking reactor and selectively cracking the hydrocarbons in the first stream. 
 
     
     
         12 . The process of  claim 1  further comprising:
 introducing a naphtha feed stream into a naphtha hydrotreating reactor to produce a hydrotreated naphtha stream; 
 passing the hydrotreated naphtha stream to a naphtha splitter column to form at least two streams, the first hydrotreated stream having a T5 boiling point in a range of about 0° C. to about 34° C. and a T95 boiling point in a range of about 25° C. to about 82° C. and the second hydrotreated stream having a T5 boiling point in a range of about 20° C. to about 82° C. and a T95 boiling point in a range of about 140° C. to about 215° C.; and 
 wherein reforming the naphtha stream comprises reforming the second hydrotreated stream. 
 
     
     
         13 . The process of  claim 1  further comprising:
 introducing an additional stream comprising hydrocarbons to the cracking reactor and selectively cracking the hydrocarbons in the additional stream. 
 
     
     
         14 . A process for making aromatics, and at least one of ethylene, propylene, and butylene comprising:
 reforming a naphtha stream in a reforming unit under reforming conditions to produce a reformer effluent stream comprising aromatic compounds and aliphatic compounds, wherein at least a portion of the aromatic compounds contain alkyl groups;   taking a cracking feed stream from the reformer effluent stream;   passing the cracking feed stream at a temperature of at least 500° C. to a cracking reactor comprising a cracking catalyst particles, more than 90 wt % of the cracking catalyst particles in the cracking reactor include a zeolite having a maximum pore diameter of greater than 5 Angstroms;   selectively cracking the aliphatic compounds and selectively dealkylating the alkyl groups on the aromatic compounds in the presence of the cracking catalyst in the cracking reactor under cracking conditions to cracked and dealkylated olefins and aromatic compounds in a cracked reformer effluent stream, wherein the cracked olefins comprise at least one of ethylene, propylene, and butylene;   separating the cracked reformer effluent stream into an aromatic lean fraction comprising the cracked olefins and an aromatic rich fraction comprising the aromatic compounds; and   passing the aromatic rich fraction to an aromatics complex.   
     
     
         15 . The process of  claim 14  wherein the cracking conditions include at least one of a temperature in the range of about 500° C. to about 700° C., a pressure in a range of about 30 kPa (g) to about 750 kPa (g), a hydrogen to C 5+  hydrocarbon mole ratio at an inlet to the cracking reactor of at least about 0.5:1 to about 6:1, and a weight hourly space velocity (WHSV) of about 0.1 hr −1  to about 6 hr −1 . 
     
     
         16 . The process of  claim 14  further comprising:
 introducing a naphtha feed stream into a naphtha splitter column to form at least two streams, the first stream having a T5 boiling point in a range of about 0° C. to about 34° C. and a T95 boiling point in a range of about 20° C. to about 82° C. and the second stream having a T5 boiling point in a range of about 20° C. to about 82° C. and a T95 boiling point in a range of about 140° C. to about 215° C.; 
 passing the second stream to a naphtha hydrotreating reactor producing a hydrotreated naphtha stream; and 
 wherein reforming the naphtha stream comprises reforming the hydrotreated naphtha stream. 
 
     
     
         17 . The process of  claim 14  further comprising:
 introducing a naphtha feed stream into a naphtha hydrotreating reactor to produce a hydrotreated naphtha stream; 
 passing the hydrotreated naphtha stream to a naphtha splitter column to produce at least two streams, the first hydrotreated stream having a T5 boiling point in a range of about 0° C. to about 34° C. and a T95 boiling point in a range of about 25° C. to about 82° C. and the second hydrotreated stream having a T5 boiling point in a range of about 20° C. to about 82° C. and a T95 boiling point in a range of about 140° C. to about 215° C.; and 
 wherein reforming the naphtha stream comprises reforming the second hydrotreated stream. 
 
     
     
         18 . An apparatus comprising:
 a reforming reactor;   a cracking reactor being in downstream communication with the reforming reactor;   a fractionation column having an inlet, an overhead outlet, and a lower outlet, the fractionation column being in downstream communication with the cracking reactor; and   an aromatics complex being in downstream communication with the lower outlet of the fractionation column.   
     
     
         19 . The apparatus of  claim 18  further comprising:
 a naphtha splitter column having an inlet, an overhead outlet and a lower outlet, 
 a naphtha hydrotreating reactor being in downstream communication with the lower outlet of the naphtha splitter column, and the reforming reactor being in downstream communication with the naphtha hydrotreating reactor. 
 
     
     
         20 . The apparatus of  claim 18  further comprising:
 a downstream cracking reactor being in downstream communication with the overhead outlet of the fractionation column.