Aromatics transalkylation to ethylbenzene and xylenes

Abstract

The use of transalkylation catalysts to react heavy aromatic compounds of carbon number nine (and heavier carbon numbers) with benzene to form carbon number eight aromatics is disclosed. The catalyst system preserves ethyl-group species on the heavier aromatics that are otherwise de-ethylated over most gas-phase transalkylation catalysts to form undesired ethane gas with benzene or toluene. The catalyst system also promotes methyl-group species transalkylation at selected conditions. Thus, by using the transalkylation system, a greater yield of para-xylene or other carbon number eight aromatics may be achieved overall within an integrated aromatics complex.

1 . A process for transalkylation of aromatic hydrocarbons comprising providing a stream including benzene and C 9   +  alkylaromatics, contacting the provided stream with a transalkylation catalyst under at least partial liquid-phase transalkylation conditions, and recovering a product stream comprising ethylbenzene and at least 1 wt-% xylene calculated on a net effluent basis; wherein the transalkylation catalyst comprises a zeolitic aluminosilicate component and an inorganic oxide binder component.  
   
   
       2 . The process of  claim 1  wherein the zeolitic aluminosilicate component is selected from the group consisting of MTW, MFI, type Y, beta, and mordenite.  
   
   
       3 . The process of  claim 2  wherein the component is type Y or beta.  
   
   
       4 . The process of  claim 1  wherein the C 9   +  alkylaromatic stream comprises C 10   +  aromatics present in an amount less than about 50 wt-% of the stream.  
   
   
       5 . The process of  claim 1  wherein the transalkylation conditions comprise a temperature from about 1000 to about 540° C., a pressure from about 1 to about 60 kg/cm 2 , and a weight hourly space velocity from about 0.1 to about 20 hr 1 .  
   
   
       6 . The process of  claim 5  wherein the transalkylation conditions comprise a temperature from about 2000 to about 300° C., a pressure from about 10 to about 50 kg/cm 2 , and a weight hourly space velocity from about 0.5 to about 15 hr −1 .  
   
   
       7 . The process of  claim 1  wherein the product stream comprises at least 3 wt-% xylene calculated on a net effluent basis.  
   
   
       8 . The process of  claim 1  wherein the benzene stream is combined with the C 9   +  alkylaromatic stream in a molar ratio of benzene to C 9   +  alkylaromatic from about 0.5 to about 10.  
   
   
       9 . The process of  claim 8  wherein the molar ratio of benzene to C 9   +  alkylaromatic is from about 1 to about 6.  
   
   
       10 . The process of  claim 1  wherein the provided stream comprises a maximum of 5 wt-% ethylbenzene.  
   
   
       11 . The process of  claim 1  further characterized in that the transalkylation conditions include the substantial absence of hydrogen.  
   
   
       12 . A process for conversion of aromatic hydrocarbons into para-xylene comprising: 
 a) providing a stream including benzene and C 9   +  alkylaromatics, wherein the molar ratio of benzene to C 9   +  alkylaromatic is from about 0.5 to about 10;    b) passing the stream of step (a) to an at least partial liquid-phase transalkylation unit, wherein said streams are contacted with a transalkylation catalyst comprising a zeolitic aluminosilicate component selected from the group consisting of MTW, MFI, type Y, beta, and mordenite, and an inorganic oxide binder component, under transalkylation conditions without substantially added hydrogen to produce a transalkylation product stream comprising ethylbenzene and at least 1 wt-% xylene calculated on a net effluent basis;    c) separating the product streams of step (b) in a fractionation zone comprising at least one column to produce a fractionated-benzene stream and a xylene-plus stream;    d) separating the xylene-plus stream in a xylene column to produce a xylene enriched stream and a C 9   +  alkylaromatic-enriched stream; and    e) passing the xylene enriched stream to a para-xylene production unit to produce para-xylene, which is recovered as a product from the process.    
   
   
       13 . The process of  claim 12  wherein the molar ratio of benzene to C 9   +  alkylaromatic in step (a) is from about 1 to about 6.  
   
   
       14 . The process of  claim 12  wherein the transalkylation conditions comprise a temperature from about 100° to about 540° C., a pressure from about 1 to about 60 kg/cm 2 , and a weight hourly space velocity from about 0.1 to about 20 hr 1 .  
   
   
       15 . The process of  claim 12  wherein the zeolitic aluminosilicate component is present in an amount from about 5 to about 99 wt-% of the catalyst.  
   
   
       16 . The process of  claim 12  wherein the fractionation zone of step (c) produces a fractionated-toluene stream.  
   
   
       17 . The process of  claim 12  further comprising the step of recycling at least part of the fractionated-benzene stream of step (c) back to the benzene stream of step (a).  
   
   
       18 . The process of  claim 12  further comprising the step of recycling at least part of the C 9   +  alkylaromatic-enriched stream of step (d) back to the C 9   +  alkylaromatic stream of step (a).