Extension of catalyst cycle length in residuum desulfurization processes

Abstract

Solvent injection in amounts no greater than 2 wt % can favorably alter the way heavy metals, such as vanadium, are normally deposited in catalyst particles. Heavy metals may be stored on the catalyst in a more compact form, saving catalyst pore volume. Consequently catalyst cycle length is improved, since capacity for deposition is increased. The instant invention has also been demonstrated to control the rate of catalyst fouling by deposition of coke, or microcarbon residue (MCR). In the past, attempts to increase catalyst activity led to increased rates of catalyst fouling and shorter catalyst life. In the instant invention the rate of deposition of microcarbon residue is decreased, resulting in slower fouling of pores and increased cycle length.

What is claimed is:  
     
         1 . A process for the extension of catalyst cycle length in the hydrodesulfurization of feeds containing heavy metal contaminants, said process occurring in one or more reaction zones, where the feed is contacted with the hydrodesulfurization catalyst, whereby no more than 2 wt % of a solvent is mixed with the feed prior to its entry into the initial reaction zone or is subsequently added to the initial reaction zone or a succeeding reaction zone.  
     
     
         2 . The process of  claim 1 , wherein the solvent is a compound comprising oxygen which is selected from the group consisting of water, alcohol, either and other water precursors.  
     
     
         3 . The process of  claim 1 , wherein a heavy metal contaminant is nickel, vanadium, or a mixture of the two.  
     
     
         4 . The process of  claim 1 , wherein no more than 1.5 wt % of a solvent is mixed with the feed prior to its entry into the initial reaction zone or is subsequently added to the initial reaction zone or a succeeding reaction zone.  
     
     
         5 . The process of  claim 4 , wherein no more than 0.75 wt % of a solvent is mixed with the feed prior to its entry into the initial reaction zone or is subsequently added to the initial reaction zone or a succeeding reaction zone.  
     
     
         6 . The process of  claim 1 , wherein the solvent is injected during the first 200 hours of the operational cycle.  
     
     
         7 . The process of  claim 1 , wherein the feed is selected from the group consisting of crude oils, petroleum residua, tar sand bitumen, shale oil, or liquefied coal or reclaimed oil.  
     
     
         8 . The process of  claim 7 , whereby petroleum, residua is selected from the group consisting of crude oil atmospheric distillation column bottoms or vacuum distillation column bottoms.  
     
     
         9 . The process of  claim 8 , crude oil atmospheric distillation column bottoms. is selected from the group consisting of reduced crude oil or atmospheric column residuum.  
     
     
         10 . The process of  claim 1 , whereby at least one reaction zone is designed for onstream catalyst regeneration.  
     
     
         11 . The process of  claim 1 , whereby the operating conditions for hydrodesulfurization processes include a reaction zone temperature in the range from 600° F. to 900° F., a pressure in the range of from 200 to 3000 psig, and a hydrogen feed rate of 500 to 15000 SCF per barrel of oil feed.  
     
     
         12 . The process of  claim 10 , in which at least one catalyst in one or more of the reaction zones is a macroporous catalyst suitable for onstream catalyst regeneration.