Metal-based coatings for inhibiting metal catalyzed coke formation in hydrocarbon conversion processes

Abstract

A coating applied to at least a portion of the surfaces of reactors, reactor internals, other reactor components, and/or heater tubes is provided in order to minimize the formation of metal catalyzed coke in hydrocarbon conversion processes operating at temperatures at about 350° C. (662° F.) or greater and in reducing environments. These coatings may comprise Nickel coatings or complexes thereof, such as Ni—Al, Ni—Cr/Cr carbide, as well as aluminum painted coatings that are applied in a reduction cure process (e.g., application temperatures of about 600° C. (1112° F.)). Additionally, where H 2 S is necessary for the process, such as to minimize thermal cracking, the coatings also reduce corrosion of base metal due to sulfidation attack and eliminate the requirement of continuous replacement of reactor internals and other components.

1 . A coating for metal alloy surfaces comprising complexes of nickel and aluminum, complexes of nickel, chromium and chromium carbide, sintered aluminum, or sintered aluminum applied over complexes of nickel and aluminum, the coating metallurgically bonded to the metal alloy surfaces and providing an exposed surface resistant to metal catalyzed coke formation in the presence of a hydrocarbon feed stream under reducing conditions. 
   
   
       2 . The coating of  claim 1 , wherein the nickel and aluminum complexes, and the nickel, chromium and chromium carbide complexes are metallurgically bonded to the metal alloy surfaces and are applied as a plasma spray to metal alloy surfaces that are at about ambient temperatures. 
   
   
       3 . The coating of  claim 2 , wherein the nickel and aluminum complexes and the nickel, chromium and chromium carbide complexes are in an amount effective to inhibit metal catalyzed coke formation in the presence of a hydrocarbon stream containing sulfur compositions, under reducing conditions and to resist corrosion of the metal alloy surfaces in contact with the feed stream due to sulfidation attack at temperatures greater than about 350° C. (662° F.) and less than about 650° C. (1200° F.). 
   
   
       4 . The coating of  claim 1 , wherein the sintered aluminum provides an exposed surface resistant to metal catalyzed coke formation in the presence of a hydrocarbon stream under reducing conditions at temperatures greater than 350° C. (662° F.). 
   
   
       5 . The coating of  claim 4 , wherein the sintered aluminum coating comprises a sintered aluminum with an oxidized surface. 
   
   
       6 . The coating of  claim 1 , wherein the sintered aluminum coating is applied as aluminum particles suspended in a carrier and cured under reducing conditions at temperatures effective to sinter the aluminum coating, the sintered aluminum coating having a thickness of at least about 20 microns. 
   
   
       7 . The coating of  claim 1 , wherein the coating is in an amount effective to resist sulfidation corrosion of the metal alloy surface in the presence of sulfur compounds in the feed stream. 
   
   
       8 . The coating of  claim 1 , wherein the sintered aluminum coating is in an amount effective to prevent substantial sulfidation corrosion of the metal alloy surfaces in contact with a hydrocarbon feed stream containing sulfur compositions. 
   
   
       9 . The coating of  claim 8 , wherein the coating is in an amount effective to prevent substantial coke formation on and sulfidation corrosion of the metal alloy surfaces after repeated thermal cycling. 
   
   
       10 . The coating of  claim 9 , wherein the sintered aluminum coating is in an amount effective to resist substantial coke formation and sulfidation corrosion of the metal alloy surfaces after repeated thermal cycling relative to the coke formation and corrosion of the metal alloy surfaces without the sintered aluminum coating exposed to repeated thermal cycling under the same conditions. 
   
   
       11 . The coating of  claim 1 , wherein the metallurgically bonded coating of a complex of nickel and aluminum, and the complex of nickel, chromium and chromium carbide are enriched with compounds of chromium in amounts effective to increase corrosion resistance of the coated metal alloy surface. 
   
   
       12 . The coating of  claim 1 , wherein the coating of sintered aluminum over a layer of the complex of nickel and aluminum comprises sintered aluminum in an amount effective to form a protective sealing layer over the metallurgically bonded nickel and aluminum complex. 
   
   
       13 . A system for converting a hydrocarbon feed stream under reducing conditions, the system including metal alloy components with surfaces of the metal alloy components exposed to the hydrocarbon feed stream having a coating applied thereto, the coating comprising a complex of nickel and aluminum, a complex of nickel, chromium and chromium carbide, sintered aluminum, or sintered aluminum applied over a complex of nickel and aluminum, the coating metallurgically bonded with the metal alloy surfaces providing an exposed surface resistant to metal catalyzed coke formation in the presence of the hydrocarbon feed stream under reducing conditions. 
   
   
       14 . The system of  claim 13 , wherein the metal alloy components are provided with an amount of the coating effective to resist sulfidation corrosion of the exposed metal alloy component surfaces in the presence of the hydrocarbon feed stream containing sulfur compounds, under reducing conditions at temperatures greater than about 350° C. (662° F.) and less than about 650° C. (1200° F.). 
   
   
       15 . The system of  claim 14 , wherein the coating is formed from a plasma spray composition containing the nickel complexes applied to the metal alloy surfaces. 
   
   
       16 . A method for the reduction of metal catalyzed coke formation on metal alloy component surfaces exposed to a hydrocarbon feed stream under reducing conditions comprising:
 applying a coating containing complexes of nickel and aluminum, complexes of nickel, chromium and chromium carbide, or sintered aluminum to the metal alloy surfaces in contact with the feed stream;   forming a metallurgical bond between metal complexes of the coating and the metal alloy surfaces in contact with the coating;   the metal alloy component surfaces provided with an amount of the coating effective to inhibit coke formation on the exposed metal alloy surfaces.   
   
   
       17 . The method of  claim 16 , wherein the coating is applied in an amount effective to inhibit sulfidation corrosion of the metal alloy surfaces the presence of the hydrocarbon feed stream containing sulfur compounds under reducing conditions at temperatures greater than about 350° C. (662° F.) but less than about 650° C. (1202° F.). 
   
   
       18 . The method of  claim 17 , wherein the coating is effective to prevent substantial metal catalyzed coking after repeated thermal cycling. 
   
   
       19 . The method of  claim 18 , wherein the coating is formed from a plasma spray composition comprising the nickel aluminum complexes or the nickel, chromium and chromium carbide complexes applied to metal alloy surfaces that are at or about ambient conditions. 
   
   
       20 . The method of  claim 19 , wherein the coating of sintered aluminum is applied by coating the metal alloy surface with a media containing aluminum and sintering the coating under reducing conditions at temperatures of less than about 800° C. (1472° F.) and applied in an amount to provide a layer comprising aluminum with a thickness of at least about 20 microns.