US2512570A - Desulfurization of hydrocarbon oils - Google Patents

Description

Patented June 20, 1950 UNITED STAT 55 PATENT oFnc DESULFURIZATIOgflgF HYDROCABBO Albin F. Sartor, Pasadena, Tex., assignor to Shell Francisco 3 Claims. (Cl. 196-24) 1 This invention relates to the catalytic desulfurization of hydrocarbon oils by hydrogenation. More particularly the invention relates to the desulfurization of hydrocarbon oils by hydrogenation with the aid 01 an improved catalyst which is particularly adapted to this process.

The desulfurization of hydrocarbon oils presents a problem of 'ever increasing importance which has in the past been given considerable attention. Although various methods have been devised for the removal of sulfur from crude petroleum and its various products, none of them are as satisfactory as would be desired. 0f the available types of desulfurization processes those involving the removal of sulfur by hydrogenation are the most effective and most eiiicient. These processes have, however, the drawbacks (1) that they are relatively costly to operate and (2) that the desulfurization is accompanied by undesired cracking and/or hydrogenation of aromatics and/or olefins in the oil which not only increases the consumption of costly hydrogen, but also reduces the quality of the product in other respects.

In the desulfurization of hydrocarbon oils by hydrogenation it is, of course, necessary that the desulfurization be eiiected with the aid of a hydrogenation catalyst. Oi the many available hydrogenation catalysts, however, only a very few are of sumcient usefulness to come into practical consideration for this particular purpose. Although certain other catalysts have been developed which are fairly good catalysts for desulfurization of certain types of oils, e. g. the known nickel sulfide-timgsten sulfide catalyst and the known molybdenum sulfide-cobalt sulfide-alumina. catalyst, nickel sulfide is considered to be the most suited for the purpose because of its excellent activity and superior selectivity of action. In desulfurization by hydrogenation the matter of selectivity of action is of prime importance not only because a highly selective catalyst allows the process to be carried out more economically, but primarily because desulfurization with a catalyst of good selectivity can effect the'desired desulfurization and at the same time improve the 2 quality of the oil in other sulfurization with a catalyst of poor selectivity can materially degrade the oil.- For example, in

' the desulfurization of a cracked gasoline a selective catalyst will give a product having an octane number equal to or better than the original feed, whereas a catalyst of lesser selectivitywill reduce the octane number by several points. It is not known w t properties or characteristics of the catalyst uence or determine its selectivity of action in desulfurization. It isknown, however, that the selectivity is a property distinct from the overall activity.

For catalytic desulfurization nickel sulfide is preferably employed in combination with a relatively inert carrier or supporting material. A fairly selective catalyst for desulfurization is obtained when the nickel sulfide is combined with a diatomaceous earth. One of the best catalysts presently known in the art for this purpose is one prepared with diatomaceous earth in the manner described in detail in U. '8. Patent No. 2,298,346 (which patent relates to the desu1fur ization of hydrocarbon oils) and by Ellis, Hydrogenation of Organic Substances, page 140, sec-- tion 1141, D. Van Nostrand Company, 1930. This method of catalyst preparation which it will'be seen is substantially the method developed for the highly active nickel-diatomaceous earth catalyst for use in the Fischer-Tropschprocess, involves precipitation of nickel carbonate upon the diatomaceous-support. Catalysts prepared with diatomaceousearth through impregnation and precipitation methods although not as active as some of the above-mentioned catalysts, e. g. the tungsten sulfide nickel sulfide catalyst, molybdenum sulfide-cobalt sulfide-alumina catalyst and sulfided Raney nickel catalyst, are more selective in their action and more active and selective than nickel sulfide catalysts prepared by other methods such as direct mixing of the sulfide and carrier.

In illustration-the characters of some of the better-known hydrogenation catalysts in the catalytic desulfurization of hydrocarbon oils by hydrogenation are shown in the following Table I.

respects, whereas de- Table I Cetel st sumaelri ty Selectivity Pb Supported upon activealumina Verypoor.-- BL- (in do Cl do (in Supported upouactivealumlna Good-- Poor. Without carrier do D (in do Do. Supported upon silica vel do Do.

Supported upon active alumin Poor- Fair.

dn dn" Do, Without carrier do Do. Supported upon active alumina fln p (in D0.

Supported upon alumina gel. Feir Fair. Supported upon active alumina do Do. Sulfided Raney cataly do Do. On alumina gel by impregnation -do- Do. On diatomite by pptation ex-CO: .do Do. On silica gel by impregnation do Do. Pelleted with dlatom on Do. Pigleted with diatomite by impregnado Do.

It has now been found that the desuliurization Table H of. hydrocarbon oils by hydrogenation using a nickel sulfide catalyst may be materially improved it a, catalyst is used which has been pre-- f g: gagg pared in the particular manner now to be deg u- (03 13 scribed. This catalyst combines a good activity Liquid Hourly coupled with a good selectivity. space v lodty an The catalyst is prepared starting with preformed nickel carbonate, 1. e. the normal car- In 55 66 bon'ate or the basic carbonate. This material may 1 3 be obtained from any source. but it is usually 40 42 58 prepared by precipitation with or without an 0 a 3? a excess of carbonic acid. The material may be 3 3 56 in either the hydrated or dessicated form. Comm g mercial nickel carbonate generally contains the basic carbonate and also appreciable amounts of cobalt as an impurity. The presence of some 45 The moistened plastic mass (paste) may be cobalt in the nickel carbonate is in no way detrimental and may be of some slight advantage.

The nickel carbonate in powdered form is mixed with a suitable amount of a powdered, relatively inert carrier, e. g. diatomaceous earth. The amount of nickel carbonate is adjusted such that the percentage of nickel in the finished catalyst, on the reduced basis, lies between about 25% and 75% and preferably between and 72%. The mixture is then moistened with an aqueous solution of ammonium hydroxide to form a thick paste. Sufficient ammonium hydroxide should be added that the powder upon pressing in the hand forms a friable lump. 0n the other hand the paste is preferably sufllciently thick that it does not flow or show a separate liquid phase. A concentrated aqeuous ammonium hydroxide solution having a gravity of at least 20 B., is preferred. In order to decrease the volatility of the ammonia the ammonium hydroxide solution may be partly neutralized with an acid, e. g. nitric acid, acetic acid, or hydrochloric acid, thus forming the corresponding vaporizable ammonium salt.

The following table illustrates the efiect of the concentration of nickel in nickel sulfide-diatomaceous earth catalysts under mild conditions at difierent throughput rates of oil.

extruded, for instance with a conventional auger extrusion machine, and the extrudate may then be dried. On the other hand. the plastic mass may be dried directly without extruding. The dried material is broken up or ground to a fineness suitable for pelleting, e. g. passing a 30 mesh sieve, and then formed into pellets of the desired size and shape. A minor amount of a lubricant suchas stearic acid, graphite, aluminum flakes, starch. or the like, may be added to aid in the pelleting operation. In some cases where pellets of considerable mechanical strength are not required, e. g. when the catalyst is eventually to be used in powdered form, the extruded product mentioned above may be further treated without pellcting.

The dried pellets (or the extrudate or powder) are calcined to convert the nickel carbonate (and/or basic nickel carbonate) to nickel oxide. The recommended calcination temperature is about 700-800 F., but temperatures down to about 500 F. or up to about 900 F. may be used. The catalyst may at this point he partially'reduced by a conventional treatment with hydrogen at, for example, 800 F., but this step is not essential. The catalyst, whether reduced or not, is finally sulflded by treatment with hydrogen sulfide or one of the known equivalent sulflding agents. In effecting the sulildlng of the catalyst the temperature should preferably be maintained below 900 F. while temperatures as low as about 300 F. can be applied it is preferable to maintain a temperature between about 400' F. and 800 F. The sulilding treatment is preferably carried out only to completion since treatment with hydrogen sulfide beyond this point has been found to lower the activity of the catalyst somewhat. Thus, if the catalyst pellets are charged to the reactor and sulfided therein by a stream of hydrogen sulfide while controlling the flow of hydrogen sulfide such that; the hot zone of reaction (which moves from the inlet towards the outlet) is maintained within the stated temperature range, the sulfiding is preferably stopped as soon as appreciable amounts of hydrogen sulfide appear at the exit end of the reactor. In the sulfided catalyst the atomic ratio of nickel to sulfur is found to be somewhat above 1.32 to l which corresponds to a composition intermediate between NiaS: and N18 or NizS. Small variations in' this ratio do not appear to materially affect the activity of the catalyst from which it is concluded that the detrimental effect of overtreating is due to some other cause than the lowering of this ratio. It may be pointed out, however, that the desired ratio of at least 1.32 to 1 is above that generally produced by reducing the catalyst and then allowing it to become sulfided through use in the desulfurization of a sulfur-bearing hydrocarbon oil. During use of the catalyst it is'found that this ratio gradually decreases and is accompanied by a parallel decline in the activity. This decline in the activity of the catalyst may be largely prevented by operating in such a way that there is an appreciable amount of hydrogen sulfide in the hydrogen gas applied. This condition may be easily maintained by recycling to the reaction zone a- Table III Approximate Percent of Temperature Original Sulfur of Sulfiding Retained in Step, F. Oil

While in the above various important details regarding the method of preparation are pointed out these are mainly of importance in insuring the production of a catalyst of high activity. It is the described mixing of the dry nickel carbonate and carrier material followed by moistening the mixture with a small amount of aqueous ammonium hydroxide (or ammonium salt) to form a plastic mass and'the drying that is responsible for the superior selectivity of the finished catalyst. Catalyst pellets of the same composition prepared by other methods (while observing the other important features of the preparation), such as pelleting a mixture moistened with water. direct mixing of nickel sulfide and carrier. various impregnation methods, and the mentioned precipitation method, may in some 6 cases have an equal activity, but do not have the selectivity of the catalyst prepared in the described manner.

Example Twenty-five part of diatomite (Johns-Manville grade FC diatomaceous earth) were intimately mixed in the dry state with 117 parts of nickel carbonate (NiCOa) containing 0.4% of cobalt. After thorough mixing, the mixture was I moistened with an aqueous solution of ammonium hydroxide (28% NHa) to form a thick plastic paste. The paste was then dried at about 250 F. and the dried cake was broken up and ground to pass a 30 mesh sieve. A small amount of stearic acid was mixed into the powder and the mixture was formed into it inch cylindrical pellets in a conventional pelleting machine. The pellets were calcined at '750800 F. to convert the nickel carbonate to the oxide. The calcined pellets were then placed in a reactor and sulfided by passing a controlled stream of hydrogen sulfide over the pellets while maintaining the temperature at about 800 F. The resulting catalyst contained about 70% nickel, calculated on the reduced basis.

A catalyst prepared in the following manner may be used for comparison. One hundred and seventeen parts of ammonium carbonate were added to 372 parts of aqueous ammonium hydroxide (28%). One hundred and seventeen parts of the above-mentioned nickel carbonate was added; This solution was then used to impregnate 25 parts of the above-mentioned diatomaceous earth. After drying at about 250 F. and grinding the material to pass a 30- mesh sieve, the catalyst was completed as described above. The finished catalyst contained about 70% nickel on the reduced basis. 1

The above catalysts were used in the desulfurization of a Dubbs pressure distillate gasoline of about 370-400 F. end point having the following 7 inspection data.

Bromine number Sulfur, per cent by weight 0.363 Maleic anhydride value 30 Octane number, clear 70.2

The conditions of operation were substantially identical and were as follows:

First Comparison Catalyst Catalyst Temperature, F 602 508 Pressure, p. s. i. g 75 75 Liquid hourly space velocity. 8. 0 8. 3 Mol ratio, rn oin... l. 74 2. 00

The results obtained in the two cases are shown It will be seen that the catalyst prepared in the described manner removed 44% of the original sulfur, reduced the maleic anhydride value to l and increased the clear octane number by 1.5 points without hydrogenating the olefins, even though the space velocity wasvery high.(8.0) and the pressure was very low (75 p. s. i. g.). While under the conditions employed in the given example the reduction in the concentration of sulfur was only 44% it is possible to remove up to at least 92% of the sulfur with only a nominal hydrogenation, e, g. 17%, of the olefins by the use of a lower throughput rate. The ability of the catalyst to hydrogenate sulfur compounds more or less selectively is increased. rather than decreased, by operating at low space velocities.

The comparison catalyst having the same composition and prepared by an accepted method removed only 3196 of the sulfur, reduced the maleic anhydride value to only and increased the clear octane number by only 0.5 point. If the severity of the conditions were increased using the sec- 0nd catalyst in order to obtain the same degree of removal of sulfur and reduction in maleic anhydride value an appreciable amount of the olefins would be hydrogenated and the clear octane number would be reduced.

It is to be noted that the comparison catalyst is one having a fair activity and a fairly good selectivity as indicated in the above Table 1. Thus, for comparison a cobalt sulfide-molybdenum sulfide-alumina catalyst frequently recommended for use in catalytic desulfurization gave the following results when treating a very similar pressure distillate gasoline from the same source under the same conditions.

Per cent oleflns retained 84 Per cent sulfur retained 50 Maleic anhydride value of product 1 Change in clear octane number 2.5

Upon inspection of Table I it may be noticed that the hydrogenation catalysts having\ the highest activity (designated as good) have a poor selectivity whereas some of the catalysts having a poor activity have a fairly good selectivity. This relationship, however, holds only in a very general way since, as can be seen in the above example, some catalysts are more active as well as more selective than others. The activity as this term is herein used refers to the ability of the catalyst to catalyze the hydrogenation of the sulfur compounds in the oil and not to the activity of the catalyst in catalyzing hydrogenation of olefins or other compounds.

While in the above attention has been focused primarily on a nickel sulfide catalyst prepared with diatomaceous earth, this is because this particular carrier has been found to give catalysts which are for some unknown reason somewhat superior to other common carrier materials. Other relatively inert carrier materials such as the aluminas, silica gels, magnesia, certain clays and the like do however give catalysts which are sufllciently good to be applied commercially and these likewise may be improved by preparing them in the manner described. The described and claimed method of preparation is for this reason not to be considered limited to the preparation of nickel sulfide catalysts with diatomaceous earth.

In the catalytic desulfurization of hydrocarbon oils using a catalyst prepared as just described the oil to be desulfurized is contacted with the catalyst in the presence of hydrogen or a gas consisting predominantly of hydrogen at a temperature in the order of 450 to 850 F. The oil to be desulfurized may be in the vapor phase, liquid phase, or mixed phase. The pressure is preferably at least 75 pounds per square inch (gage) and preferably above 150 pounds per square inch. In general the desulfurization and maintenance of the catalytic activity are improved with increasing pressure. In practice, however, this improvement must be weighed against the much greater plant costs for operation at higher pressures. An additional advantages of the described catalyst is that it allows the desulfurization to be carried out quite satisfactorily at pressures considerably lower than those generally considered practicable with the previously known catalysts. Thus, as pointed out, the desuli'urization may be carried out at pressures below 200 pounds per square inch and even below 100 pounds per square inch. The rate of throughput of the oil may vary from about 0.3 up to about 16 volumes of oil per volume of catalyst bed per hour and is preferably adjusted for each individual case to effect the desired degree of desulfurization.

When desulfurizing lower boiling hydrocarbon oils such as olefinic cracked gasolines and fractions thereof boiling below about 500 IF. it is usually desired to operate with the oil in the vapor phase, and when desulfurizing higher boiling oils such as cracked gas oils and the like it isv usually preferable to operate with the oil at least partly in the liquid phase. One particularly suitable method which is applicable both with lower and higher boiling oils is to trickle the liquid oil down over a bed of the catalyst countercurrent to a small stream of the hydrogen gas. When desulfurizing very heavy or dirty oils a particularly suitable method is to dilute the oil with suflicient lower boiling napthenic hydrocarbons to lower the critical temperature of the mixture to within the preferred temperature range and then to work with very small amount of hydrogen under a pressure above the critical pressure of the mixture. The high solvent power of the dense pseudo liquid phase in this method of operation prevents contamination of the catalyst with tarry deposits which otherwise tend to form when treating oils of this character.

I claim as my invention:

1. in a process for the removal of sulfur from a sulfur-bearing hydrocarbon oil by catalytic hydrogenation with a nickel sulfide catalyst, the

improvement which comprises contacting the oil to be desulfurized under hydrogenation conditions with a nickel sulfide catalyst which has been prepared by mixing nickel carbonate with powdered relatively inert carrier material, adding aqueous ammonium hydroxide to form the mix ture into a paste, drying, calcining, and sulflding.

2. In the removal of sulfur from a sulfur-bearing hydrocarbon oil by catalytic hydrogenation 3. A process for the removal of sulfur from a I sulfur-bearing hydrocarbon oil which comprises contacting the oil to be desulfurized with a hydrogen under hydrogenation conditions with a nickel sulfide-diatomaceous earth catalyst prepared by mixing performed nickel carbonate with diatomaceous earth in the dry state, forming the mixture into a paste by the addition of an aqueous solution 01 ammonium hydroxide, drying, calcin- REFERENCES CITED The following references are of record in the tile 01 this Patent:

10 UNITED STATES PATENTS Number I Name Date Arnold May 8, 1923 Muhlenberg Mar. 11, 1930 Gaus et a1 Oct. 24; 1933 Rosenstein Sept. 25, 1934 Szeyna Feb. 17, 1942 Corson et a1 Oct. 13, 1942

Claims (1)

1. IN A PROCESS FOR THE REMOVAL OF SULFUR FROM A SULFUR-BEARING HYDROCARBON OIL BY CATALYTIC HYDROGENATION WITH A NICKEL SULFIDE CATALYST, THE IMPROVEMENT WHICH COMPRISES CONTACTING THE OIL TO BE DESULFURIZED UNDER HYDROGENATION CONDITIONS WITH A NICKEL SULFIDE CATALYST WHICH HAS BEEN PREPARED BY MIXING NICKEL CARBONATE WITH POWERED RELATIVELY INERT CARRIER MATERIAL, ADDING AQUEOUS AMMONIUM HYDROXIDE TO FORM THE MIXTURE INTO A PASTE, DRYING, CALCINING, AND SULFIDING.