Low temperature low cost sulfuric acid alkylation process

Abstract

Novel reactor design allows to provide a new and optimum sulfuric acid alkylation process which is operated at low temperature to provide all the benefits, with no complex mixing devices and cumbersome internals which have to be installed through manways. The novel art provided in this embodiment, provides novel Eductor mixing device, and auto refrigeration absorption rather than compression, and makes alkylate product which has a better octane, lower acid consumption and lower capital and operating costs. The reaction of C 3 to C 5 Olefins with Isobutane in the presence of 90 to 95% sulfuric acid concentration in this novel reactor design provides the low temperature (essentially under isothermal conditions) operation which has advantages over conventional processes of good product quality band low acid consumption. The process described in this embodiment has lower capital and operating cost by 40% compared to the conventional process and about 10% compared to new process/patents and provide much better flexibility and reliable equipment.

1 ) Novel reactor design for mixing the reactants and the catalyst with the Eductor, providing good interfacial area which makes the reaction to go to completion fast and provides good selectivity. 
 A) The Eductor device and any equivalent device like sparger or mixing nozzles are covered by Eductor mixing.    B) Provide internal Acid pipe in the vessel entering from the bottom and taking suction from the bottom as well as shown in the  FIG. 1  and  2 .    C) Operate the reactor at 20 to 50 F preferably at 25 to 27 F temperatures by having the auto refrigeration by evaporating the Light C4 components( C 3 /C 4  and C5.components), and providing isothermal conditions for the reaction which provide better selectivity.    D) Olefin Mix Feed, together with reactants, condensed hydrocarbons from the Refrigeration system, Isobutane recycle, Isobutane make up are fed to the side chamber of the eductor and Acid is used as motive fluid to mix the reactants and acid catalyst.    E) Reactor scaling is easy and can be provided to larger scale from low capacity to large capacity of 1,000 b/d or less to 50,000 b/d depending on fabrication of the reactor size in a single train system.    
     
     
         2 ) Well tested Coalescer system (York or Equivalent) to remove acid from the hydrocarbon to less than 1 ppm. No caustic or acid wash required. Coalescer system designed to run in specific separation conditions so that all sulfur is removed. The Vertical Coalescers are preferred to horizontal and are claimed one of the process invention. 
 A) Feed to the de-isobutanizer flashed after heating, to reduce the load on de-isobutanizer. The flash drum to be installed preferably in between coalescer stages so as to provide better acid separation after heating the hydrocarbon Flash drum can be installed at most convenient location after the coalescing or in between the coalescer stages depending on the requirements. The claim in this art of having the finishing or multiple Coalescing stage at temperatures of 40 to 350 F and most probably at 60 to 300 F is desired for better acid and hydrocarbon separation. The art of Coalescing above 45 F is being claimed as an art practiced by this patent for improving the hydrocarbon acid separation efficiency.    B) If required, flash drum can be operated at a pressure where the hydrocarbons can be condensed with cooling water without loss of alkylate. Optimum case to be used for each operation.    C) The reactor effluent to be used for cooling the hydrocarbon stream to the reactor and after this the cold energy from this stream should be used to cool other stream or to condense De-isobutanizer overhead. This has already been stated in the art of U.S. Pat. No. 4,130,593.    
     
     
         3 ) Auto refrigeration vapor generated in the reactor either can be compressed and condensed or preferably adsorbed in the Heavy Cat naphtha at the reactor pressure or after using an ejector to raise the C4 vapor hydrocarbon pressure to about 1 to 50 psig preferably at 1 to 10 psig. This is shown in the  FIGS. 5 and 6  and this art is claimed by this patent and is cheaper than compressor capex and Opex option. This novel idea is one of the major claim and paradigm shift in the technology. The absorption system can work at lower pressure or at about 30 psig by increasing the C4 stream pressure by ejector, and by using motive fluid as absorption liquid which could be Alkylate product, HCN, or any suitable solvent. The same fluid is used for enhancing the C4 stream pressure through the ejector and facilitate the absorption process. The art of this patent also claims that the vapor motive fluids can also be used for the ejector to raise the pressure of C4 stream vapor generated by the auto refrigeration, these Vapor streams could be De-isobutinizer, or De-butanizer overhead product, or any other vapor like nitrogen etc. The concept of absorption in lieu of compression by all these means is covered by this art which is illustrated in this claim and has been shown in the  FIGS. 5 and 6 .  
     
     
         4 ) The Isobutane to olefin molar ratio is to be kept between 6 to 15 to provide the optimum conditions for best quality product and selectivity. The best ratio is around 8 to 11. This includes recycling some of the reactor effluent to the reactor with the entire hydrocarbon recycle stream and feed olefin, as mentioned in the patent above. 
 A) Acid to olefin molar ratio is kept around 10 to 300, preferably in the range of 45 to 60, to provide the desired alkylate reaction, selectivity and quality.    B) As has been practiced in the art of alkylation one or two fractionation columns are used to separate the product. The de-isobutanizer as a single column system or two column system, where isobutane, alkylate and N-butane can be fractionated to the desired specification is normally practiced.    C) The unit Coalescing system will remove the acid and any di-alkyl sulfate formed but small bauxite or similar sulfur adsorption system may be provided for polishing the sulfur removal system.    D) The cold energy available from the auto refrigeration absorption liquid can be used to Condense De-Isobutanizer and De-butanizer overhead product, provided major saving cooling water. As mentioned earlier this saves major capital for compression and all the associated equipment with the compressor. This is one of the major paradigm shifts in the art to save the capital cost by absorption technique.    E) RHT-Alkylation process in this invention provides easy revamp solutions in the Following area: 
 Capacity by adding a Reactor.  
 By using absorption system where Compressor is a bottle neck.  
   
     
     
         5 ) In this patent, the art of part of the mix hydrocarbon feed (including olefin) can be split before feeding it to the side port of the Eductor, and is mixed with motive fluid at the pump discharge by installing an inline mixer to provide enhanced mixing.  
     
     
         6 ) This art of putting some or all the hydrocarbon feed feeding to motive fluid pump discharge is especially desired for the propylene alkylation to provide higher over all space velocity (OSV).  
     
     
         7 ) The art in this patent also takes care of the best practices of Coalescing of Acid/Hydrocarbon in a preferably horizontal coalescer, but not limiting it to that option, so to optimize if the Vertical coalescer provides best option than one will be using the optimum option for this application.  
     
     
         8 ) Provide the auto refrigeration vapors absorbed in alkylate Heavy naphtha or any solvent (claiming the absorption application instead of compressor if so required and is cheaper).  
     
     
         9 ) Provide the flash from item  12  to the de isobutanizer at a high enough pressure so as to condense the C4 hydrocarbons either with water or with cold process fluid if available, this will save compressor energy, and is claimed by this patent and art as described here.