US2378064A - Catalytic desulphurization process - Google Patents

Description

June 12, 1945. M. w. coNN CATALYTIC DESULPHURIZATION PROCESS Filed Feb. 12, 1942 aolvwnwnoov ancload md@ I mDL HOLVCIVdBS .LlNn

NOIiVZIHfLIInSBO l minvws INVENTOR MILLER W. CONN BM ATTO NEY m23@ Ommm Dumm Patented June 12, 19145 i 2,378,064 v CATALYTIC DESULIHURJZA'IIONA PROCESS Miller Wade ConnQBartlesville.' Okla., assignor to Phillips Petroleum` Company, a'corporation of Delaware Application February 12, 1942,Serial No. 430,686

4 claims. (c1. 19e-27)` This invention relates to a process of treating hydrocarbons and relates more4 particularlyl to desulphurization of hydrocarbon oils, particularly petroleum, shale oil and other mineral oils, and their products.

There are various types of sulphur compounds present in mixtures of hydrocarbons comprising petroleum, coal tar, shale oils and the like. These types of sulphur compounds maybe gen-4 erally classied as (1) 'I'he aliphatic and aromatic mercaptans, sulphides and disulphides, which for the sake of brevity are termed nonheterocyclic sulphur compounds, and (2) Heterocyclic sulphur compounds, such as thiophenes and thiophanes.

The presence of the aforementioned sulphur compounds and the like in hydrocarbon oils are known to be detrimental to automotive fuels, aviation iuels,'solv,ent naphthas, and the like, and oftentimes it is highly essentialto remove as nearly as completely all sulphur-bearing bodies from such oils. In recent years many processes have been advancedv for the removal oi organic sulphur compounds from hydrocarbon oils and` bauxite (as described by James E. Pew and A. E. Buell under the title yci Catalytic desulphurization solves problem in high-sulphur distillates in National Petroleum News for October 2, 1940) has been found to be a very eiective catalytic desulphurization catalyst. It is believed that the mechanism of the catalytic reaction may proceed according to Equation 1 below which is typied by butyl .mercaptan in the presence of bauxite catalyst under proper conditions of temperature and pressure:

( CH: CH: CH| CHI-SH am@ Mercapton cmcrncmom xfi I have discovered that, probably inasmuch as Equation 1 is promoted by the catalytic action of the bauxite under elevated temperatures and moderate pressures, a reversal o! this chemical equation takes place considerabLv at normalconditions of temperature and pressure to an extent that will result in onlya partially desulphurized oil. The reversal oi Equation 1 may be exemplifled by Equation 2 to show the recombination of hydrogen sulphide and olenic hydrocarbons to form mercaptans at normal conditions of temperature and pressure:

Oleiin Hydrogen sulphide cmomonsomsn Mel-captan According to chemical theory, Equation 1 and I Equation 2 as set Iorthfabove will proceed until chemical equilibrium is established according to Equation 3 hereinafter set forth:

v 3) cmomcmcmsn:'omomcmcm His tent of the desulphurized hydrocarbon oils.

A principal object of this inventionis to provide an improved method of catalytic desulphurization of hydrocarbon oils, and particularly the removal of hydrogen sulphide and vother sulphurous bodies yto anextentto obtain greater 'degrees of catalytic desulphurization than -hitherto known and/or practiced.

A further object oithis invention is to provide a new and novel means for curtailing and reducing the extent of the reverse 'reaction shown in Equation 3 in order to secure and obtain a `more completely desulphurized oil and one which will meet -the so-called Doctor test and the most rigid corrosion test specifications.

Numerous other objects and advantages will appear from the following description taken in .conjunction with the accompanying drawing which portrays diagrammatically one -iorm of apparatus which may be used in carrying out the present invention. r

In accordance with my invention a hydrocarbon oil containing organic sulphur compounds, and especially mercaptans, as impurities, is .vaporized and brought to from about 650 to about 800 F. and passed, in the presence or absence of added hydrogen at this temperature and at a pressure of from about atmospheric to about 100 pounds-per square inch gauge into intimate contact with a solid desulphurization catalyst to effect catalytic desulphurization.

Examples of such catalysts are:-fullers earth, bauxite, other catalysts of the clay type, as described in U. S. 1,895,081 and 2,016,271; chromium ore (U. S. 2,016,272); vanadium ore (U. S. 2,075,171); tungsten ore (U. S. 2,075,172); molybdenum ore (U. S. 2,075,173); cadmium ore (U. S. 2,075,174) porous alumina (U. Si. 2,112,931) zinc ore (U. S. 2,098,943); the catalysts described in U. S. 2,162,319; zirconium oxide (U. S. 2,206,- 921); and any other known or suitable solid desulphurization catalyst capable of converting, under the above conditions, the organic sulphur compounds and especially the mercaptans to hydrogen sulphide, and preferably adapted to be arranged in pervious beds of granular catalyst. The effluent from the desulphurization step at essentially the temperatureprevailing in the desulphurization unit is continuously withdrawn and while still at this temperature treated to remove the free hydrogen sulphide therefrom in order to prevent re-combination thereof with the hydrocarbon' content and especially with the olefins. This removal of hydrogen sulphide should be effected before, or atv the latest simultaneously with, any appreciable cooling of the eilluent. This may be accomplished in accordance with my invention in a number of ways among which are those set forth Vspecifically below. The removal is effected under conditions such that the temperature of the entering eilluent vapors is maintained for at least the beginning of the contact with the removal agent and preferably during a substantial portion of said contact. The conditions should be such that throughout the removal unitthe concentration of free hydrogen sulphide lis so low and the temperature of the mixture is such as to preclude any substantial reaction of said free hydrogen sulphide, having due regard for the law of mass action.

In one mode of sulphur removal, the hot vapors are passed through a bed or solid reagent capable of removing the hydrogen sulphide. Numerous solid reagents capable of reacting with and removingIhS are well known to the art and need not be enumerated here. The temperature throughout the removal zone is preferably maintained at essentially that prevailing in the catalytic desulphurization tower.

Another mode of, accomplishing the HgS removal is to scrub the hot gases with a liquid medium adapted to dissolve, either by solution or reaction, the hydrogen sulphide in the eilluent. Examples of such liquids are water, aqueous solutions of lower aliphatic alcohols such as methanol, ethanol, etc., aqueous 'solutions of alkales such as alkali metal hydroxides, ammonium hydroxide, etc. In this way, by supplying the scrubbing medium in sufficient volume and at a sufciently low temperature, the vapors are condensed at the same time as the hydrogen sulphide is removed, and at no time are conditions; of HzS concentration and temperature of effluent such that Krereaction of the hydrogen sulphide'can occur.

Referring to the drawing, the sulphur-bearing oil is charged to the system by line IA and feed pump I through line 2 to heat exchanger 3, thence via line 4 to the tube bank 5, said tube bank being disposed in heater 6, wherein' the hydrocarbon oil is vaporized and super heated t0 temperatures in excess of 650 Iii-'100 F. say to about 750 F. From the tubular heater the super-heated hydrocarbon vapors pass through line 'I to catalyst towers 8 which may or may not be operated in parallel. In catalyst towers 8, under the conditions of temperature as speciiied above and pressures in the range of from about to about 50 pounds gauge, the reaction expressed by Equation 1 set forth above proceeds to substantial completion with many sulphurbearing hydrocarbon oils and particularly light straight run and natural gasolines. As the desulphurized hydrocarbon oils containing equivaient; molecular quantities of oleflnic hydrocarbons and hydrogen sulphide emerge from cattalyst towers 8 through treating zone I5 in line 9 and thence in heat exchange relationship with the incoming charge in heat exchanger 3 there is appreciable recombination of hydrogen sulphide and olefinic hydrocarbons taking place as exemplied by Equation 2 set forth above.

The principal object of this invention is to provide for the addition of an agent to the hot sulphurous gases, such agent to exert a greater ailinity for hydrogen sulphide than the olenic hydrocarbons in order to reduce to a negligible quantity the chemical recombination of olelnic hydrocarbons and hydrogen sulphide as exemplied by Equation 2 set forth above.

The numerous agents employed within the scope of this invention may be roughly divided into two classes, namely, 'those exerting purely chemical anity for hydrogen sulphide and those exerting physical and preferably solvent eiects on hydrogen sulphide and at the same time being immiscible with the hydrocarbon oils. Among those agents exerting chemical anity for hydrogen sulphide may be any of the well known metallic substances and their compounds such as iron, alkali metals and alkaline earth metals and others well known to the art. Among those substances known to exert a, solvent effect on hydrogen sulphide and at the same time being substantially immiscible with the hydrocarbon oils are water and aqueous mixtures of some of the-lighter alcohols and the like. These aqueous mixtures are not necessarily limited to solutes exerting purely a physical influence on HzS, but

`may be capable of chemically reacting therewith such as alkales, ammonia, etc.

In the practice of this invention any one or more of theabove enumerated agents and the like may be disposed in zone I5 into which the superheated sulphur-bearing hydrocarbon vapors pass from the catalyst towers 8 while still subjected to substantially the conditions of temperature and pressure to which they were subjected in towers 8. In intimate contact with the said agents the eiliuent may be allowed to reach normal condition of temperature and pressure and thereby produce a desulphurized hydrocarbon oil substantially free of any recombined hydrogen sulphide and olefinic hydrocarbons which may be to such an extent to produce a product giving a positive Doctor` test and exhibiting severe corrosion properties. From the inuence and direct and intimate relationship with the said agent disposed within unitv I5 the hot or cold hydrocarbon vapors may proceed via line I6 through heat exchanger 3, through line I to condenser II andV thence through line I2 to an accumulator tank I3 for further processing if desiredfsuch as sweetening, etc., (in equipment not shown).V i y t Treating unit I5 is designed for th rapid re` moval of the hydrogen sulphide formed in towers 8-by ,the desulphurization reaction, before'the effluent has had a chance to cool to any material extent. 'By removing the hydrogen sulphide from the effluent before it has cooled to temperatures at which re-reaction can take place to any substantial degree, the occurrence of such re-reaction is'eifectively prevented.

Preferably unit I5 is located in such close proximity to the exit point of towers 8 that no apreciable cooling of the effluent can take place between towers 8 and the inlet to `unit I5. Desirably the line 9 may be lagged to prevent heat loss. Also the unit I5 may advantageously be lagged to maintain the temperature therein by preventing loss of heat therefrom.

Unit I5 may take any form which will accomplish essentially complete removal of free HzS from the catalytic desulphurization effluent before or, at the latest simultaneously with the cooling of the eilluent to a point at which appreciable re-reaction might occur.

In one form, unit I5 may be a chamber or tower, preferably lagged, filled with a pervious or porous mass of granular solid material which is adapted -to react with the hydrogen sulphide and x the same. In such case the unit I5 may be maintained throughout at essentially the same temperature as that prevailing in towers 8, and the effluent from unit I5 will be at substantially the same temperature as that in towers 8. Or the temperature may gradually lower as the vapors pass through the unit, the reduction in concentration of free hydrogen sulphide by the reaction with the solid reagent being such that as to effectively counteract any tendency for Reaction 2 to occur due to the progressively lower temperature encountered. It will be understood that the tendency for Equation 2 to proceed depends on the concentration of hydrogen sulphide as well as the temperature of the reaction mixture.

The pressure in unit I5 may be substantially that in towers 8, namely from aboutatmospheric to about 100 pounds per square inch gauge. Usually substantially atmospheric pressure is preferred.

In another embodiment, unit `I5 may take the form of a scrubbing tower in which the hot effluent from the desulphurization catalyst intimately contacts, as in countercurrent relationship, a liquid medium capable of reacting with and/or dissolving the hydrogen sulphide content thereof. In such case the hot effluent is condensed at the same time as it is freed of hydrogen sulphide, and thereby converted to liquid form, its temperature being rapidly brought to well below the point at which any re-combination with any free hydrogen 'sulphide might occur. A volume of relatively cold liquid medium sufficient to eiect complete condensation of all of the hydrocarbons in the eiiiuent should be used. Where the liquid medium boils at temperatures well below that of the effluent vapors, it is necessary to introduce a sufliciently large volume of liquid medium at a sufficiently low temperature that the entire eluent is condensed while the liquid medium remains in the liquid phase. In some cases maintenance of the desulphurization tower and the HzS removal unit at an elevated pressure may be resorted to in order to raise the boiling point of theliquidmedium and lower the volume thereof necessary to be supplied.

When practicing the invention in accordance with the embodiment just described, thehydrocarbon condensate 'from scrubbing unit I5 may' be passedl via linev I1 directly to accumulating tank I3'. i If desired a unitv I8 maybe interposedY in line IIk for the removal of any' last traces of the scrubbing medium employed in unit I5.

Two examples describing the practice of this invention will be set forth:

Example 1 At some point in line 9, preferably as close to the exit from towers 8 as possible, a, tower I5 of suitable size may be placed through which the sulphur-bearing hydrocarbon vapors may pass at greatly reduced linear velocities, there being disposed in said tower any of the well known chemical agents exerting a greater affinity for hydrogen sulphide than the oleiinic hydrocarbons resulting from the catalytic action in towers 8. Alternate towers I5may be provided for vuse while towers I5 containing spent reagents may be regenerated in order to obtain continuous operation. The chemical agents used in the towers I5 may be any of the well known chemical reagents known to be corroded by hydrogen sulphide or to react therewith and to have a much greater ailinity for hydrogen sulphide than the olefinic hydrocarbons produced as a result of the catalytic action taking place in catalyst chambers 8.

Example 2 will enter the lower end of the scrubber, whichl may be of any of the well known types and pass in counter current ow in intimate contact with the hydrogen sulphide solvent such as water or methanol. Theaction of the solvent lwill be twofold,

' that'is, to dissolve the hydrogen sulphide from the hydrocarbon vapors and/or liquid hydrocarbons and to simultaneously cool and condense the hydrocarbon vapors to condition of temperature at which no recombination of the olenic hydrocarbons and hydrogen sulphide will occur as exemplifled by Equation 2 set forth above.

Many other applications of the present disclosure will be obvious to those skilled in the art of catalytic desulphurization and general chemical refining. I

I claim: I

1. The Iprocess of desulphurizing hydrocarbon oil containing organic sulphur compounds as impurities which comprises vaporizing the cil and heating to a temperature within the range of from about 650 to about 800 F., contacting the vapors at substantially said temperature with a solid desulphurization catalyst adapted to convert said sulphur compounds to hydrogen sulphide, removing the elliuent vapor from said contacting step, directly scrubbing said eiliuent while at substantially said temperature at the beginning of the scrubbing step by suddenly, rapidlyl and thoroughly contacting the eilluent vapor with `a sufficient quantity lof relatively cold liquid medium adapted to dissolve substantially all of the hydrogen sulphide therefrom and simultaneously cool the emuent vapor before said hydrogen sulphide has had an opportunity to re-react with the hydrocarbon in the emuent due to cooling before thoroughly contacting, said scrubbing step taking place under conditions that the hydrocarbon content of said eilluent is substantially condensed to liquid phase, and recovering the resulting liquid substantially free from hydrogen sulphide.

2. The process of claim 1 in which said liquid medium is water. l

3. The process of claim 1 in which said liquid medium is an aqueous solution of a lower aliphatic 5 alcohol.

4. The process of claim 1 in which said liquid medium is an aqueous solution of methyl alcohol.

MIILER WADE CONN.

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