Hydrogenation of high boiling hydrocarbons

Abstract

.[.In a hydrogenation operation employing an ebullated catalytic bed, recycle is recovered from the hydrogenated product with at least 25%, by volume, of the recycle boiling above 950° F. The recycle is cooled to a temperature of from 350° to 600° F. to separate coke precursors, prior to recycle to the hydrogenation. Higher conversion levels can be achieved by effecting recycle in such manner..]..Iadd.Disclosed is a hydrogenation process using at least one fluidized catalytic stage and a recycle material of heavy hydrogenated effluent. The heavy effluent material is cooled to a temperature within 350°-600° F. to separate toluene and heptane insoluble coke precursors prior to recycle. This separation may be enhanced by the use of centrifugation, filtration or a bed of particulate material (e.g. calcined coke). .Iaddend.

We claim: 
     
       1. In a process for upgrading high boiling hydrocarbon materials to valuable lower boiling materials .[.is.]. .Iadd.in .Iaddend.a hydrogenation operation including at least one expanded bed catalytic hydrogenation zone to produce an upgraded hydrogenated product, the improvement comprising: recovering from the upgraded hydrogenation product a recycle liquid having a 5-volume percent distillation temperature of at least 450° F. with at least 25 -volume percent thereof boiling above 950°F.; cooling the liquid recycle to a temperature of at least 350° F. and no greater than 700° F. to .[.separate.]. .Iadd.precipitate coke precursors; .Iaddend..Iadd.removing essentially only .Iaddend.coke precursors from the .Iadd.cooled .Iaddend.liquid recycle; and subsequent to .[.separation.].  .Iadd.removal .Iaddend.of said coke precursors providing the liquid recycle to an expanded bed catalytic hydrogenation zone.   
     
     
       2. The process of claim 1 wherein the cooled liquid recycle is passed through a bed of particulate solids to deposit separated coke precursors on the solids. 
     
     
       3. The process of claim 2 wherein the recycle liquid is a 600° F. +  fraction. 
     
     
       4. The process of claim 1 wherein the recycle liquid is a 1000° F. +  fraction. 
     
     
       5. The process of claim 1 wherein the recycle is cooled to a temperature of at least 400° F. 
     
     
       6. The process of claim 1 wherein the recycle is cooled to a temperature of no greater than 600° F. .Iadd.7. The process of claim 1 wherein the cooled liquid recycle is centrifuged to enhance separation and removal of coke precursors. .Iaddend. .Iadd.8. The process of claim 7 wherein the 
     
     
        recycle liquid is a 600° F. +  fraction. .Iaddend. .Iadd.9.  The process of claim 7 wherein the recycle is a 1000° F. +  fraction. .Iaddend. 10. The process of claim 7 wherein the recycle is cooled to a temperature of no greater than 600° F.