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 C3 to C5 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.

Description

FIELD OF INVENTION

This invention relates to a simple reactor/mixer design for the sulfuric acid alkylation process where C₃, C₄ and C₅ olefins are reacted with isobutane to produce alkylate in the presence of Sulfuric acid catalyst. The conventional process has been practiced for a long time with mechanical propeller mixers and complex seals. The internal mixer and seals are working in a hostile environment (strong sulfuric acid which is used as catalyst for the process) which is demanding. To provide the mixing and tight emulsion one needs reasonable energy being provided to each contactor/reactor and has been cause of lot of maintenance. The process is practiced at certain temperature so as to keep the viscosity low and is not working at optimum temperature. Conventional process works at higher temperature so as to keep the viscosity reasonable for mixing. The Opex of the present conventional application together with complicated mixing device which has been known to require higher maintenance can be improved and more specifically present device of an Eductor is being suggested. The total Capital and Operating costs can be reduced by the new device of Eductor by a factor.

Additionally a new concept of recovering the C₃/C₄ vapors from the auto refrigeration is being introduced which additionally saves capital cost by either not having the compressor or in the case of revamps additional equipment for absorption and desorption can be introduced which reduces the cost of revamp by a large margin.

The alkylate product normally has reasonably good ROI based on the conventional process, but still the units require high investment. The HF alkylation does not require refrigeration and acid regeneration so it is marginal better in that respect but is much more hazardous due to HF acids and is not readily acceptable environmentally and still capital cost is little better.

BACKGROUND OF THE INVENTION

RHT alkylation process (RHT-Alkylation) of C₃/C₄/C₅ Olefins or mix carbon number stream with these olefins, react with Isobutane in the presence of Strong sulfuric acid as a catalyst to produce Alkylate (TMP), the reaction chemistry is similar to the conventional process, except the low cost contacting device providing optimum conditions for better product quality and low acid consumption without needing excessive maintenance. The process operates essentially at isothermal conditions. The art of the reactor mixing device together with normal refinery equipment makes it a simple operating system. The art of the invention with eductor mixing device (or equivalent as a sparger and nozzles or similar in configuration) is able to operate at low temperature with auto refrigeration at isothermal conditions. The advantages of art has been already mentioned but will be summarized in the Claims. The contacting device is unique that it can work with viscous fluids under operating conditions and without having any moving parts in the hostile environment in the reactor which makes it very cost effective. It does not have any other complex packing material which has to be changed frequently and could be problem as regards to integrity of the system. The some of the reactor with internals as packed systems have to obtain from a single source which is major drawback for any process and are installed through a manway.

The reactor effluent is taken partly after settling as alkylate/C₄ mix and entrained acid. Due to the art in this embodiment utilized in the process, the unique mixing device in the reactor which is an Eductor, allows that the entrained acid can be removed from the hydrocarbon by successive Coalescing devices as manufactured by York or equivalent to remove the acid from the hydrocarbon to ppm level as has been described in Stratco articles in recent years they have been able to reduce the acid carry over to by three fold to few ppm to about <15 ppm. RHT have gone ahead and made the coalescing system to provide lower than 1 ppm level of sulfur in hydrocarbon product by changing and improving the design of Coalescers and also doing the coalescing under better conditions i.e. higher temperature. This acid free hydrocarbon is sent to conventional alkylate recovery section after heat integration. The heat integration system where hydrocarbons are heated to flash of C₄'s hydrocarbon from alkylate between the coalescing stages, so that one can get better coalescing at higher temperature before the second or successive stages of coalescing and separation. This location of this flash drum is an important art employed to provide an efficient acid separation at slightly elevated temperature of 40 to 300 F and heat integration so as to reduce the load on compressor and are some of the claims of this process.

The vapor from this flash drum can be sent to compressor intermediate stage or if the flash is done at higher pressure than can be condensed separately and recycled to the reactor with olefin feed and isobutane recycle after cooling with the cold alkylate. Alkylate is one of most desirable gasoline component as it is free of sulfur, aromatics and olefins Refiners are always looking at improving this alkylation process so as to reduce the acid consumption and utilities together with maintenance costs. Due to the side reactions taking place due to the impurities, during the alkylation process, acid soluble oils (conjunct Polymers; ASO) are produced which reduce the acid concentration and fresh acid make up is provided to overcome this requirement. The acid soluble oil is sent to the acid regeneration unit. The cost of acid regeneration for low acid consumption unit is about 20% of the operating cost of the alkylation unit. The RHT-Alkylation process at low temperature reduces the acid consumption and provides lower cost of acid regeneration apart from the major cost benefits of process mentioned above.

SUMMARY OF THE INVENTION

This invention describes the alkylation of C₃, C₄ and C₅ mix streams with isobutane and claims in the embodiment that the process uses a unique mixing device in the form of Mixing Eductor, or any similar device like sparger or nozzles to mix the hydrocarbon stream with sulfuric acid to provide a much simpler and reliable process which can operate at optimum temperature at just about isothermal conditions. The mixing device is a paradigm shift from the existing technologies which either have impeller and use excessive energy or complicated packing which has to be changed every so often. The eductor does not have any mechanical moving parts in the reactor and can be scaled to 15,000 b/d in one reactor and even with field erected reactor the equipment can essentially be of any unit capacity with one train. But most of the Clients would want a shop erected reactor and also for easier mobility for the unit. This provides scale of economy by a factor compared to the existing art. As process can work at lower temperature with multiple eductors, it has multiple advantages compared to present art being practiced or being offered which will be illustrated in the claims, and is low Capex, low Opex option.

Another alternate can be provided with no C₄ compression system, which can be replaced with absorption system. As regards to Eductor it does not have to come from a single source, like internals and also has low maintenance costs. The unique concept of C4 auto refrigeration vapors can be increased in pressure by Isobutane from the Deisobutanizer overhead by the use of an ejector. This can be further increased in pressure by absorbing liquid, could be Iso-Octane product, heavy Naphtha or any other solvent which will absorb this C4 vapor stream. This vapor and the absorbing liquid can be separated by conventional distillation and C4 separation. This is major breakthrough of the process and is an art of the embodiment.

It has already been published in the literature and art of alkylation of olefins with isobutane, and sulfuric acid as a catalyst under low temperature conditions (U.S. Pat. No. 5,095,168) and its benefits e.g. better product quality, low acid consumption. The present art of invention provides a low capex and opex based on the eductor patented mixing device.

As has been published in the articles that in the papers by Stratco that the sulfuric acid has been reduced by three fold by the use of coalescers in the range of 5 to 7 wppm in hydrocarbon/alkylate stream, i.e. raw mix alkylate. The present embodiment with the help of major improvements in the design of coalescer have brought the sulfuric acid to below 1 wppm in the product going to de-isobutanizer and removed the alkyl sulfates as well. The process is shown in FIG. 3 but the coalescrs can be horizontal or vertical (preferably Vertical) and design under improved conditions as explained earlier claims this as one of art of the process. If need be a small polishing absorber will be provided but we do not find that necessary. Note that the vertical coalescers system for both the coalescers is preferred design and is being claimed as art of this patent.

As explained the chemistry is being used the same as by the conventional process but major improvements are in:

• a) Mixing device of Eductor
• b) The operating parameters of the reactor, low temperature, isothermal conditions.
• c) Scaling of reactor
• d) Absorption and desorption of auto refrigeration vapors which removes the need for additional moving item the compressors reducing cost.
• e) Mixing with the eductor by putting the hydrocarbon at the pump discharge in all proportions or putting in the side port and other port for the reactor mixing is art of this embodiment and is. Claimed by this patent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrates the Novel Mixing device, Eductor (or any equivalent device as sparger or nozzles for mixing the reactants and catalyst) or multiple eductors to agitate the reactants and catalyst, so as to get the reaction complete in shortest possible time and provides adequate interfacial area for the reaction. The art of mixing with the eductor in the embodiment of this invention by using recycle acid as motive fluid for the eductor and Olefin Feed, recycle hydrocarbons, condensed C₄'s and recycle isobutane and contents of the reactor are pulled into the side chamber to mix the liquids, or can also be mixed with the acid at the pump discharge using a inline mixer. The acid line is put in through the bottom of the reactor so as to keep it inside (essentially acid is kept in reactor with minimum lines outside the reactor) as shown in the FIGS. 1 and 2 and this is part of the reactor internal design and is claimed by this invention and eductor as mixing device is exclusive claim. The advantages of operating the reactor between 20 to 50 F, the art of low temperature operation has already been described in the U.S. Pat. No. 5,095,168.The present invention will work at about 20 to 35 F, preferably at 25 to 27 F as close to isothermal conditions as possible due to inherent design of reactor and mixing device.

FIG. 3 describes the art of acid separation with Coalescer pads as has been practiced by Conventional Licensers essentially for expansion/revamp, with York or equivalent Coalescer pads in separation of acid and hydrocarbon. The hydrocarbon from the Primary Coalescer vessel could be 5 to 50 wppm, the hydrocarbon from the primary Coalescing step is sent to Finishing Coalescer after heating and flashing some of the hydrocarbons. The higher temperature will enhance the coalescing of acid from hydrocarbon in the Finishing Coalescing step and liquid product will have sulfur less than 1 wppm or lower. This coalescer concept as has been experienced by York and Licensers can reduce the acid in the hydrocarbon and is being taken further to dry process concept based on the multiple coalescers and better separation new design concept as a vertical Coalescer preferably but horizontal can also be used, which provides reasonable saving in Capital cost and no caustic waste. In the present art the claim of having the coalescing at the finishing stage at higher temperature provides benefits of easier acid separation and this temperature can be 50 to 300 F but close to 80 to 300 F so as to take advantage of the vaporization and reducing the compressor load or can be condensed with water if lashed at higher pressure, and will have better efficiency as well. The major claim as stated above is to have the flash drum either before the finishing Coalescer or after, but to be at the optimum condition will be in between the coalescer stages so as to enhance acid separation from hydrocarbon at higher temperature, and this practice is one of the claim of this process together with vertical coalescing step is a major concept of this claim.

FIG. 4 is a block Flow diagram of the whole process and describes the process completely, including the auto refrigeration step. The possibility of condensing the vapor from auto refrigeration in an absorber is described in the FIGS. 5 and 6 as novel C₄ recovery system from auto refrigeration. The back end after the reactor effluent flash drum downstream of the polishing coalescer is similar to conventional alkylation process for recovery of alkylate by distillation and recycling the isobutane and removing the n-butane and light ends/propane from the unit.

FIGS. 5 and 6 is an alternate to the refrigeration vapor recovery via compression of C4 auto refrigeration vapor (could be C3/C4 and C5 in any proportion in the mixture) vapor absorption system. The vapor absorption system will be cheaper and could be novel capex saving option and will be an advantage in expansion of the unit where compressor is a bottle neck C₄'s can be absorbed in heavy Naphtha or in a special solvent or alkylate product. In the next column the C₄'s recovered and are recycled back to the alkylation reactor and the heavy hydrocarbon is recycled to the absorber. The FIG. 4 shows unique utilization of ejectors to increase the pressure of C₄ stream so as to have the absorption done at 1 to 60 psig pressure ranges, preferably at 1 to 30 psig and preferably close to 15 psig as higher as practical to be cost effective. The unique Ejector used to increase the pressure and absorption and desorption system for C₄ recovery is one of novel claims of this patent. The motive fluid for the ejector could be liquid as shown in Figure or any other gas like isobutane from deisobutanizer or nitrogen.

DETAILED DESCRIPTION OF INVENTION

An aspect of this disclosure in this patent describes the process to alkylate C₃, C₄ and C₅ mixed olefins and isobutane stream is mixed vigorously in the presence of Sulfuric acid catalyst with novel eductor device. Internal acid piping is provided to the ejector for the motive fluid. The alkylate is produced at low temperature which has a better quality than the conventional process. The Capex and Opex are lower than any other technology and it does not have any non reliable internals and also installation of any internals in not time consuming. Essentially the process works under similar acid concentration as conventional process in the range 89 to 95% but preferably around 90 to 92% to provide the best quality product and low acid consumption, but at lower temperature than conventional process at about 20 to 50 F but preferably at 25 to 27 F in essentially isothermal conditions. The low temperature is obtained by auto refrigeration by flashing the C₄ hydrocarbons. Acid to olefin molar ratio is kept around 45 to 180, preferably in the range of 45 to 60, to provide the desired alkylate reaction and quality. The Isobutane to olefin molar ratio of 6 to 15 is desired. These ratio's are very important and are controlled to provide the optimum conditions at the low Opex. To provide the good mixing all the hydrocarbon streams are mixed and sent to the eductor where motive fluid of acid mixes all the streams with acid catalyst and reactants to provide good selectivity, and undesirable reactions are minimized.

The disclosed methods and apparatuses can be understood by referring to the attached figures, which are described in detail herein. It should be understood that the pipelines are being designated when streams are being identified and that streams are intended, if not stated, when materials are mentioned. Moreover, flow control valves, temperature/pressure regulating devices, pumps, compressors, exchangers, drums and the like are understood as installed and operating in conventional relationships to the major equipment items which are shown in Figures/drawings and discussed hereinafter with reference to the continuously operating process of the this invention. All of these valves, devices, pumps, compressor and exchangers and the like, are included in the term auxiliary equipment. It is in the ability of one of the ordinary skill in the art to implement such auxiliary equipment, as needed in view of the present disclosure.

FIGS. 1 and 2 discloses an embodiment of the disclosed the part of reactor and Eductor system in the process. The reactor is a standalone item 1 and Eductor item 2 are the main part of this system. The acid settles in the bottom of reactor, which is recycled by the pump back through line 8, where as the Olefin mixed stream (which includes all the C4 streams recovered and the olefin feed) are fed through line 6 to Eductor to provide vigorous nixing of the acid and hydrocarbon. Packing and Demister pads are provided for obvious reason, which are clear to the person who is accomplished in this art. As the reactor operates in the range 1 to 10 psig range there is auto refrigeration due to evaporation of C3/C4 and some C5 hydrocarbons, which are taken out by the line 3 from the Top. The reaction products together with some entrained acid and other components are taken for processing to other equipment by line 7 as shown in the FIG. 1.

In the embodiment of this invention, following arts are being specifically practiced:

Operating the reactor at low temperature with unique reactor design where mixing is being done by the Eductor. Acid is supplied as motive fluid by an internal pipe in the reactor. The eductor provides adequate mixing so as to have reaction completed. The vapor is generated de to auto refrigeration and heat of reaction which is taken as vapor stream from the top of the reactor. The reactor effluent products which have 20 45% alkylate is taken as a side draw with entrained acid which is separated down stream.

The reactor is operated at about 1 to 10 psig pressure and 25 to 27 F temperature.

FIG. 3 illustrates the stream 7, which is the reactor effluent and contains alkylate, C4 hydrocarbons and entrained acid is separated from the acid with multiple coalescers item 11 and 14 so as to have dry process. These coalescers are York type or equivalent to meet the product separation requirements. The Finishing Coalescer can be kept at the optimum temperature to have better separation of acid and hydrocarbon in the range of 80 to 300 F. Recovered acid through line 9 is recycled to the Reactor item 1 after separation in first coalescer item 11. Where as line 10 takes the raw mix alkylate product through heat exchangers and is flashed to remove some of C4's in item 12 flash drum, through line 13 the C4 stream is taken for recovery. The bottom of the item 12 Flash drum is sent to item 14 where all the residual acid is removed by finishing coalescer. The recovered acid is recycled to the reactor item 1 where as raw mix alkylate stream is sent to conventional recovery system where alkylate is separated from Isobutane and n-butane.

FIG. 4 illustrates an embodiment having the Block flow diagram of the whole process. Some of the reactor and separation of acid/Hydrocarbon stream have been already described but one shows the full process by this Figure. Acid strength is kept at about 90 to 92% and for that acid make up made through line 24. Some the adjunct polymers (ASO) formed is taken out through the line 25, which is sent for acid regeneration. As shown C4 Vapor from line 3 is sent to compressor or New absorption system. Mixed Olefin Feed is mixed with all the other C4 streams from the unit before sending it to the reactor. The Reactor effluent from Item 14 is sent for true alkylate recovery and is taken through line 20 and line 21 separates the normal butane which is sent to OSBL, whereas Isobutane is recycled through line 22 to the reactor. Part of the C4 auto refrigeration vapor after recovery is sent for lights/propane removal through item 19, line 26 and is sent to OSBL.

The process in this embodiment uses reactor effluent cold energy is used to condense the De-Isobutanizer overhead and, or compressor discharge after cooling the total hydrocarbon stream recycled back to the reactor. This art has already been described in the U.S. Pat. No. 4,130,593 of 1978.

FIGS. 5 and 6 in this embodiment provides option to absorb C₄'s produced from the auto refrigeration in the reactor through line 3 in Heavy Naphtha, special solvent or alkylate product. In this embodiment it is shown that the C4 streams pressure can increased to 15 psig or higher through line 33 by using Ejector with a motive fluids of Isobutane line 32 and absorption liquid line 31 so as to make the absorption possible. In the next column the through line 35 the absorbed are sent for recovery. The C4's are recovered through line 30 from Heavy Naphtha/Solvent or Alkylate (what ever is used for absorption of C4 vapors) and C4 stream is recycled back to the reactor. The vent through line 36 is used to control the absorption column control. The second column can be reboiled with LP steam and will be cheaper alternate to Compressor option and can also be used when revamping any unit where the compressor is a bottleneck The back end of the unit is simple de-isobutanizer as one column system or two column system to separate the Isobutane and n-butane from Alkylate. The straight chain olefins provide the slightly higher octane Alkylate from the Sulfuric acid alkylation compared to branched chain olefins, and the acid consumption for branched chain olefins is higher as well. So straight chain olefins C₃, C₄ and C₅ are the preferred Olefin species.

REACTIONS

The reaction of olefins with isobutane provides Tri methyl Pentanes (TMP) which is the desired reaction products. The C₃ olefins provide more of di methyl Pentane (DMP) in the Alkylate and C₅ provide more of C9 alkylate component giving lower octane product compared to C₄ olefins. The straight chain olefins provide the slightly higher octane Alkylate from the Sulfuric acid alkylation compared to branched chain olefins, and the acid consumption for branched chain olefins is higher as well. So straight chain olefins C₃, C₄ and C₅ are the preferred Olefin species.

In the Sulfuric Acid alkylation process, olefins and isobutane are reacted in the presence of Sulfuric acid catalyst at 20 to 60 F to form essentially TMP and some other products like Di methyl Hexanes (DMH) and DMP.

Alkylation Chemistry
Butylenes+Isobutane→TMP
Propylene+Isobutane→DMP
It should be noted that even though in C₄ alkylation TMP has high concentration over 60 to 70% in the alkylate product, but other components are e.g. DMH and DMP, which are formed in the alkylation reaction.
The side reactions can be postulated as follows:
Polymerization olefin+olefin →Polymer C₆, C₈ and C₁₂ etc
Cracking
In the reaction larger compounds are made which crack to make smaller compounds:
C₁₁H₂₄ →C₆H₁₂+C₅ H₁₂
Hydrogen Transfer reactions
This reaction takes place by transferring hydrogen to olefin to make paraffin. Essentially Isopentane is made in the reaction.
2 C₄H₁₀+C₅ H₁₀ →C₈H₁₈ +C₅ H₁₂
Esterification reaction
Sulfuric acid reacts with olefins to form small amount of di-butyl sulfate, which is unstable at high temperature and is removed in the coalescer so as to produce good quality product.
Disproportionation
This takes place by rearrangement of the hydrocarbons to form different molecules from a larger hydrocarbon molecule.
2 C₁₀H₂₂ →C₈HIs+C₁2H₂₆
The relative reaction rates of olefins influence the product quality and relative conversion rates can be postulated as follows:
n-butene >i-butene>isopentenes>n-pentenes>propylene

From above one can deduce that one needs lower space velocity for pentenes and even lower for propylene compared to butylenes. In the present embodiment the novel reactor mixing device for alkylation where mixed olefins stream and other recycle streams and excess of isobutene is fed to the eductor and is mixed by acid being recycled as the motive fluid is new concept. The mixing is done in the eductor and in the reactor where predominantly TMP mixture, and 20 to 35% of other DMH, DMP and heavy compounds e.g. nonanes are produced.

As it has already been illustrated by prior art U.S. Pat. No. 5,095,168 that working at lower temperatures around 10 to 50 F preferably at 25 to 28 F, the selectivity to TMP is better providing better octane and also lower acid consumption, the art here is being practiced under low temperature conditions. RHT-Alkylate process works at most desired temperature conditions, at isothermal conditions, which provide even better results for selectivity. RHT-Alkylate process has much better advantage on Capex and Opex compared to competitive technologies and is less complex due to essentially reactor internal being just eductor.

Example

Feed,             wt %
Propane/Propylene 0.6
Isobutane         15.5
Isobutylene       14.7
2-butene          38.5
1-Butene          14.6
N-butane          15.8
C5's              0.3
Total             100.0

The above feed was used to produced alkylate and the results were very good. The Road Octane was observed to be 94.5 to 95.0 with RON clear to be 95.5 to 96.0 and MON Clear to be 93.5 to 94.0.

Based on flow sheet, the estimated total Installed cost of the unit is expected to be 40 to 45% lower than the conventional process. The Opex is expected to be 35 to 40 lower than the conventional process. The capital cost saving can be realized even higher if auto refrigeration compression is deleted and absorption of the C4's (lower molecular weight hydrocarbons) is done in heavy Naphtha, any solvents or alkylate.

Claims

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( C3/C4 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.