Method and apparatus for steam dealkylation in a plant for the catalytic reforming of hydrocarbons

Abstract

A method and apparatus for treating a fraction consisting predominantly of hydrocarbons having at least six carbon atoms (C 6+ fraction) as produced in a plant for the catalytic reforming of hydrocarbon-containing feedstock, is disclosed. The C 6+ fraction is taken for steam dealkylation where the useable products benzene and hydrogen are produced.

1 . A method for treating a fraction consisting predominantly of hydrocarbons having at least six carbon atoms (C 6+  fraction) as produced in a plant for catalytic reforming of hydrocarbon-containing feedstock, wherein the C 6+  fraction undergoes steam dealkylation, where two usable product materials benzene and hydrogen are produced in addition to reaction products such as carbon monoxide and carbon dioxide.  
   
   
       2 . The method according to  claim 1 , wherein the C 6+  fraction contains: 
 a) aromatic hydrocarbons having six to ten carbon atoms;    b) cyclic paraffins (cycloalkenes) having five to ten carbon atoms;    c) iso- and n-paraffins having five to ten carbon atoms;    d) alkenes having six to ten carbon atoms; or    any mixture of the aforementioned.    
   
   
       3 . The method according to  claim 1 , wherein the hydrocarbons from the C 6+  fraction react with water in a gas phase with addition of heat to a solid catalyst.  
   
   
       4 . The method according to  claim 1 , wherein heat required for the dealkylation reaction is generated by combustion of a starting material with air.  
   
   
       5 . The method according to  claim 1 , wherein gaseous reaction products from the steam dealkylation are separated following compression by way of pressure swing adsorption into gaseous hydrogen and gaseous reaction by-products, specifically carbon monoxide, carbon dioxide and methane.  
   
   
       6 . The method according to  claim 5 , wherein the gaseous reaction by-products from the steam dealkylation, specifically carbon monoxide and methane, are used as starting material for the combustion with air.  
   
   
       7 . The method according to  claim 1 , wherein flue gases generated during combustion are cooled by a heat exchanger while heating starting materials for the steam dealkylation.  
   
   
       8 . The method according to  claim 1 , wherein the C 6+  fraction and the steam are conducted in pipes, from top to bottom, past a solid catalyst, where the catalyst is on an inside of the pipes.  
   
   
       9 . The method according to  claim 8 , wherein heat is brought to the pipes from outside.  
   
   
       10 . The method according to  claim 9 , wherein the heat required for the dealkylation reaction is transferred to the pipes by electromagnetic radiation, thermal radiation and/or convection.  
   
   
       11 . The method according to  claim 1 , wherein a solid catalyst of a porous carrier material is used, specifically γ-Al 2 O 3 , MgAl spinel and/or Cr 2 O 3  and an active component on a surface of the carrier material, in particular Rh with 0.1-1.0% loading by weight and/or Pd with 0.2.-2.0% loading by weight.  
   
   
       12 . The method according to  claim 1 , wherein the steam dealkylation is performed at a temperature of 400° C. to 600° C., preferably 450° C. to 550° C., particularly preferably 480° C. to 520° C.  
   
   
       13 . The method according to  claim 1 , wherein the steam dealkylation is performed at a pressure from 1 to 15 bar, preferably 1.2 to 10 bar, particularly preferably 1.5 to 8 bar.  
   
   
       14 . The method according to  claim 1 , wherein the steam dealkylation is performed at a molar quotient of steam to hydrocarbons in a range from 1 to 20, preferably from 2 to 15, when it enters a reactor.  
   
   
       15 . The method according to  claim 1 , wherein the steam dealkylation is performed at a molar quotient of steam to hydrocarbons which is in a range from 3 to 12, preferably from 5 to 10, when it enters a reactor.  
   
   
       16 . The method according to  claim 1 , wherein the C 6+  fraction undergoes a process prior to the steam dealkylation to convert dienes and styrenes where in particular hydrating methods are employed involving consumption of hydrogen.  
   
   
       17 . The method according to  claim 1 , wherein the C 6+  fraction undergoes a process prior to the steam dealkylation to convert and to remove components containing sulfur, nitrogen and/or oxygen, in which specifically hydrating processes involving consumption of hydrogen are employed.  
   
   
       18 . The method according to  claim 1 , wherein the reaction products from the steam dealkylation are cooled and separated into gaseous reaction products, hydrocarbons and water in a 3-phase separation.  
   
   
       19 . The method according to  claim 16 , wherein the hydrogen produced in the steam dealkylation of the C 6+  fraction is fed completely or partially into a starting material for the processes involving the consumption of hydrogen.  
   
   
       20 . The method according to  claim 17 , wherein the hydrogen produced in the steam dealkylation of the C 6+  fraction is fed completely or partially into a starting material for the processes involving the consumption of hydrogen.  
   
   
       21 . The method according to  claim 1 , wherein the hydrogen produced in the steam dealkylation of the C 6+  fraction is fed as starting material to a process consuming hydrogen in an oil refinery, preferably into a process to convert and remove components containing sulfur or a process to split hydrocarbon-containing starting material via hydrogen.  
   
   
       22 . The method according to  claim 1 , wherein a sulfur content in the C 6+  fraction is reduced to below 10 ppm, preferably below 3 ppm, particularly preferably below 1 ppm prior to the steam dealkylation.  
   
   
       23 . The method according to  claim 1 , wherein the benzene is separated from the hydrocarbons by way of rectification of the reaction products.  
   
   
       24 . The method according to  claim 23 , wherein the benzene undergoes adsorptive fine cleaning following rectification to dry and remove trace components, where the benzene is passed across an adsorbent on which the trace components are adsorbed.  
   
   
       25 . The method according to  claim 1 , wherein components boiling close to benzene or forming azeotropes in the C 6+  fraction are converted by steam dealkylation.  
   
   
       26 . The method according to  claim 23 , wherein all heavier boiling reaction products than benzene from rectification, consisting predominantly of non-converted feedstocks from the steam dealkylation are returned to the steam dealkylation as feedstock via optional hydration.  
   
   
       27 . The method according to  claim 23 , wherein all heavier boiling reaction products than benzene from rectification consisting predominantly of non-converted feedstocks from the steam dealkylation are returned prior to steam dealkylation for hydration of the C 6+  fraction or for hydration of a fraction consisting predominantly of hydrocarbons having at least five carbon atoms.  
   
   
       28 . The method according to  claim 1 , wherein linear hydrocarbons are separated from the C 6+  fraction prior to steam dealkylation by means of liquid-liquid extraction.  
   
   
       29 . The method according to  claim 1 , wherein a fraction consisting predominantly of hydrocarbons having at least eight carbon atoms (C 8+  fraction) is separated by distillation from the C 6+  fraction prior to steam dealkylation where the C 8+  fraction is taken as feedstock to a process to extract paraxylene.  
   
   
       30 . The method according to  claim 29 , wherein following separation of the C 8+  fraction, benzene is separated from the C 6+  fraction prior to the steam dealkylation.  
   
   
       31 . An apparatus for treating a fraction consisting predominantly of hydrocarbons having at least six carbon atoms (C 6+  fraction) as produced in a plant for catalytic reforming of hydrocarbon-containing feedstock, wherein the apparatus includes an oven with a furnace and pipes located in the furnace.  
   
   
       32 . The apparatus according to  claim 31 , wherein the pipes are mounted vertically in the furnace and have heat expansion compensating elements at a lower and/or an upper end.  
   
   
       33 . The apparatus according to  claim 31 , wherein each pipe has a supply for the C 6+  fraction and the steam and an outlet for the reaction products.  
   
   
       34 . The apparatus according to  claim 31 , wherein each pipe is filled on an inside with a catalyst, where the catalyst consists of a porous carrier material, specifically γ-Al 2 O 3 , MgAl spinel and/or Cr 2 O and an active component on a surface of the carrier material, in particular Rh with 0.1-1.0% loading by weight and/or Pd with 0.2.-2.0% loading by weight.  
   
   
       35 . The apparatus according to  claim 31 , wherein the oven has at least one burner on a wall, a ceiling and/or a floor.  
   
   
       36 . The apparatus according to  claim 31 , wherein the pipes are suitable for an internal pressure of 1 to 15 bar, preferably 1.2 to 10 bar, particularly preferably 1.5 to 8 bar, and for use in an oven with flame temperatures of up to 1400° C.  
   
   
       37 . A method of extracting benzene from a hydrocarbon having at least six carbon atoms, comprising the steps of: 
 producing the hydrocarbon having at least six carbon atoms in a plant for catalytic reforming of hydrocarbon-containing feedstock;    subjecting the hydrocarbon having at least six carbon atoms to steam dealkylation; and    producing benzene from the steam dealkylation.    
   
   
       38 . The method according to  claim 37 , further comprising the step of producing hydrogen from the steam dealkylation.