US2559457A - Hydrodesulfurization of petroleum hydrocarbons - Google Patents

Description

y 3, 19 c. w. MONTGOMERY ETAL 255954537 HYDRODESULFURIZATION OF PETROLEUM HYDROCARBONS Filed May 2, 1949 in r N H 0 THROUGH PUT WT.%Cu. x700) N pownBRme Rams: XNVENTORS cnmwss nun'raomrsnx .6 win-1AM 1- ILBER HQ STANLEZY M.B '5ZEN BY ka-EM, A TORNEY Patented July 3, 1951 UNITED STATES PATENT OFFICE HYDRODESULFUBIZATION OF PETROLEUM HYDROGARBONS Application May 2, 1949, Serial No. 90,864 Claims. (Cl. 196-28) This invention relates to the hydrodesulfurization of petroleum hydrocarbons and more particularly to a method of contacting sulfur-bearing petroleum hydrocarbons in the presence of hydrogen with a contact agent to remove the sulfur therefrom.

Amon the most eflicient methods of processing high sulfur petroleum hydrocarbons is the contact or absorption desulfurization process. This procedure is described in U. S. application Serial Nos. 699,671 and 699,672, filed September 27, 1946, by W. A. Home and J. F. Junge, now respectively Patent Nos. 2,516,876 and 2,516,877 of August 1, 1950, and comprises contacting high sulfur content petroleum hydrocarbons with a contact comprising iron group metals and/or metal oxides on a carrier in the presence of hydrogen. This process has proved to be highly successful and is believed to be the most eflicient type process for the removal of sulfur from high sulfur crude and gasolines; However, we have found that when the process is repeated and the contact regenerated for long periods, the contact tend to decrepltate. This problem assumes large proportions with the contact type hydrodesulfurization process in as much as it involves frequent regeneration of the contact due to the carbon lay down as a result of the action of the iron group metal or oxide. Due to this decrepitation the contact tends to lose its efficacy after repeated regeneration and use since the pulverization of the contact induces an excessive pressure drop across the contact bed. Ultimately this requires a shut-down of the process and corbquent replacement of the catalyst bed with concomitant expense and loss of production time.

This invention has as an object the provision of a contact hydrodesulfurization process in which there is a marked decrease in the amount of contact pulverization.

A further object of the present invention is to provide a contact hydrodesulfurization process in which numerous regenerations may be carried out without replacing the contact bed.

Other obj sets will appear hereinafter.

These and other objects are achieved by the process of the present invention which comprises removing sulfur from petroleum hydrocarbons by contacting vapors of sulfur containing petroleum hydrocarbons and hydrogen-containing gas with a contact comprising a carrier on which has been deposited a mixture of nickel and/or nickel oxide and copper and/or copper oxide with the weight per cent of copper to nickel in the mixture being between 5 and 11 per cent, absorbing sulfur from the vapors to form nickel and copper sulfide on the contact, and continuing said proces until regeneration of the contact proves necesary, then regenerating said contact to substantially itsoriginal form and again contactin the vapors of the petroleum hydrocarbon and lwdrogen cmtalning as with the regenerated contact.

As shown in the aforementioned Home and J unge applications the hydrodesulfurization is accomplished at v y g temperatures, pressures and space velocities with the optimum conditions depending on the type charge stock that is used. For example, with low boiling hydrocarbons such as those normally liquid peia-oleum fractions having an ASIM end point up to 600 P such as straight run or cracked gasolincs and naphtha, the temperature will usually lie between 600 and 800 F. At temperatures below 600 F. the desuliurizaiion activity of the contact diminishes whereas with temperatures higher than 800 F. excessive cracking reactions result in decreased product recovery and rapid coke formation which deactivates the contact. We have further found that the optimum pressures lie between and 500 p. s .i. g. At pressures below 100 p. s. Lg. the

partial pressure of hydrogen is not suflicient to maintain desulfurization activity nor to suppress cracking reactions which result in coke tonnation. Increasing the pressure above 500 p. s. i. 3. results in only a slight incremental gain in desalfurization, and a decrease in the bromine number of the end product gasoline and is thus not commercially desirable. The preferred space velocities lie between 0.2 and 6.0 liquid volmnes of charge per hour per volume of contact agent. Space velocities below 0.2 result in excessive cracking and olefin saturation reactions caused by the long contact time whereas at space velocities above 6.0 the contact time is too short to pmvide sufiicient desulfurization.

The foregoing conditions are applicable to the treatment of low boiling hydrocarbons. However this invention can be applied with excep tional success to high boiling petroleum hydrocarbon oil such as total crude as well as topped" or reduced crude. These terms may be defined as follows: total crude is defined as naturally occurring petroleum oil which has not been processed in any manner but has been or preferably should be separated from water or sediment and desalted. Topped or reduced crude is defined as the residual petroleum oil resulting from removal of all or some of the straight run fractions such as gas, gasoline, kerosene, naphtha, furnace oil, gas oil, etc. which are normally reboiling straight rim or cracked petroleum frac-' tions including gases are also included. Diluents of this kind may be required in processing low gravity crudes such as some of those from Mississippi as well as those from Kuwait. Diluents may also be necessary and preferred in desulfurizing topped orreduced crudes. The purpose of this diluent is to assist vaporization of the heavier constituents of the charge stock. In some cases it may be desirable to admix steam with the charge stock to assist vaporization. Preferred operating conditions for the aforementioned high boiling petroleum hydrocarbons may vary within certain ranges depending upon the charge stock.

We have found the optimum temperature .range to be from 750 to 950 F. for high boiling petroleum hydrocarbons. At temperatures below 750 F. the desulfurizing activity of the contact diminishes whereas at temperatures greater than 950 F. excessive cracking actions result in decreased product recovery'and rapid coke formation which deactivates the contact.

We have further ascertained the preferred pressure range to be-between 100and 1000 p. s. i. g.

- with pressures below 100 p. s. i. g. it appears that v the partial pressure of hydrogen is not sufficient.

the former causes excessive cracking reactions due to the long contact time, while space velocities above 6.0 are too short to allow suiiicient desulfurization. As shown in these aforementioned Horne and Junge applications the hydrogen to oil ratio should be above 300 SCF/bbl.

The copper-nickel-carrier contacts of this invention may comprise copper and nickel in their metallic state, or in the state of their oxides, or as a mixture of the metallic and oxide states. A suitable method for preparing the metallic type contact is to impregnate a carrier such as alumina, kieselguhr, silica gel, aluminum silicates, silica-aluminas, Alfrax, Magnesol, Porocel, bauxite, diatomaceous earth, etc., with a combination solution or solutions of soluble salts of nickel and copper. Suitable soluble salts of nickel include the acetates, nitrates and nitrites. Suitable copper salts include the acetates, nitrates and jnitrites. The concentration of these salts is ad- Justed so that the requisite amount of nickel and copper is deposited upon the carrier. The carrier is then dried, calcined and reduced by a suitable reducing gas such as a hydrogen-containing gas so that the nickel and copper are present on the contact.

The mixture of metallic and metal-oxide type contact is prepared by the identical treatment given for the preparation of the metallic type contact, except that the reduction is controlled so that but a portion of the nickel and copper is reduced to the metallic state.

It is to be understood that the above mentioned methods of preparing the contact are not to be considered as all-inclusive and that other methods such as repeated coimpregnation or coprecipitation, readily apparent to one skilled in the art may be employed.

The following examples illustrate a method of preparing a conventional contact, and also for preparing a contact useful in aplicants invention. Example I indicates a method of preparing a contact in which nickel alone is present while Example 11 illustrates a method of preparing a contact of the type utilized in the present invention containingboth nickel and copper.

Example I.Contact A was prepared using 4 to 10 mesh Alorco granular F-10 alumina which has a surface area of about 119 square meters-per gm. The alumina base was placed in an evacuated chamber and a solution of nickel nitrate containing 20 per cent nickel oxide as nitrate was. introduced so as to completely cover the alumina.

After 5 minutes of impregnation under vacuum,

the vacuum was broken and the alumina was 2.1-

lowed to stand for 10 more minutes in the nickel nitrate solution. At the end of this time, the nickel nitrate solution was drained from the contact. The contact was placed in anoven and dried in a stream of air at 248 F. for 46 hours. The temperature of the dried contact was then raised to 1000" F. over a period of about Shows and held at this temperature for an additional 10 hour period while a stream of air was passed over the contact. At this point the contact contained 13.3 per cent nickel oxide (or 10.8 percent nickel on' reduced basis). After cooling to room temperature, the above procedure was repeated, and, after calcining and cooling, the nickel oxide content was 22.1 per cent (or 18.25 per cent nickel on reduced basis). A third impregnation was carried out as above except that the nickel nitrate solution used for this impregnation contained 10 per cent nickel oxide as nitrate. After calcining and cooling, the contact was found to contain 25.1 per cent nickel oxide (or 20.8 per cent nickel on reduced basis). This is equivalent to 19.7 weight per cent nickel in the oxide form of the Example II.-Contact B'was prepared from Alorco granular alumina F-10 having a surface area of about 119 square meters per gm. and was 8 to 14 mesh in size. 350 cc. of the alumina base was calcined in a stream of nitrogen at 1000 F. for 2 hours. An aqueous solution of nickel nitrate containing 20 per cent nickel xide was mixed with an aqueous solution'of cop'per nitrate containing 20 per cent copper oxide so that the mole ratio of nickel oxide to copper oxide was 4 to 1. The calcined alumina base, after cooling to room temperature, was immersed for 15 minutes in the above nickel nitrate-copper nitrate solution. The solution was then removed from the contact and the contact was allowed to drain for 3 minutes. Vacuum was then applied for 5 minutes to further reduce the water content of the contact. The impregnated contact was placed in a furnace at 230 F. for 8 hours in a slow stream of nitrogen. After this drying period, the temperature of the contact in the furnace was brought to 1000 F. in 2 hours, while a slow stream of air was passed through the furnace. The contact was held at 1000 F. for 2 additional hours. After cooling to room temperature, the impregnated alumina was again immersed, drained, dried, and calcined as above. This procedure was carried out a third time, and after calcining, the nickel content of the contact was 17.6 per cent and the copper content was 1.4 percent, bothmetals being presentinthe form of the oxide.

In most cases the on-stream cycle should be terminated when hydrogen sulfide appears in substantial anemia in the eiliuent. This has beenfoundtooccurwhenabout30t060percent of the metallic content of the contact has been converted into sulfide. At this point the contact should be regenerated. In situations in which theeconomicsofthe processpermit the removal of relatively small amounts of hydrogen sulfide from the product the reaction may be continued until the metallic content of the contact has been completely converted into metallic sulfide before commencing regeneration.

The contacts of this invention may be regenerated by any of the well known prior art methods- However, this regeneration may best be accomplished by first purging the contact with aninert gas or steam in order to recover valuable hydrocarbons remaining in the contact bed. Following this purge the contact is regenerated through the use of an oxygen-containing gas such as air or oxygen- This forms sulfur dioxide gas which may be recovered by use of conventional methods, such as by solvent absorption and stripp The further treatment of the contact will be dependent upon the type of contact. with oxide type contacts no further treatment beyond the aforementioned oxidation step need be employed. However, when the contacts comprise copperandnickelinthemetallicstateorasa mixture of metallic and oxide states, a reducing treatment to restore the contact to its original form is The contacts of this invention may be used in numerousmethods. Multiple or single fixedbedsystemsmaybeutiliaedaswellasanart in which the contact is continuously chargedandremovedfromthereactionzoneand followed by external regeneration. Furthermore, the contact may be fragmentized into fine particles andutilized in a fluidized state.

lion runs were made to determine the relative hydrodesulfurizing activity of the contact containing nickel (contact A) as compared to the contact of the present invention containing both nickel and copper (contact B).

Example III.West Texas crude was passed over contact A (prepared in Example I) having 19.! per cent nickel, as nickel oxide, on alumina at a space velocity of 1.0 volume of charge per hour per volume of contact, and a temperature of850'1'.,apresmeof500poundspersquare inch, 9. hydrogen to oil ratio of 2000 SCF/bbl. for a throughput of 4.0. The sulfur content of thetreatedcrudewasllopercentlessthanthat of the Or in l crude.

A similar run was made under the identical conditions described above utilizing contact B (prepared in Example 11) having a content of 17.6 per cent nickel, as nickel oxide, and 1.4 per cent comer, as copper oxide on an alumina support. There was a desulfurization of about '70 per cent, as compared with the 80 per cent desulfurizafion obtained with contact A having no copper.

It can be seen that the presence of copper decreases the hydrodesuliurization activity to a certain extent but for practical purposes, the falling-off of hydrodesulfurization activity does not become a serious problem as long as the byrate is above about 50 per cent, and hence the contacts of this invention serve as excellent hydrodesulfurization contacts.

In order to compare the powdering rate of the contacts of this invention which contain both copper and nickel with contacts in which the copper is omitted, and in order to show the critical nature of varying the weight per cent of copper based on the nickel content, the following experimental runs were made.

Example IV.Applicants have found that the following test is an accurate method of determining the powdering rate of hydrodesulfurization contacts.

Normal heptane was passed with equimolar proportions of hydrogen over a bed of contact pellets. The apparatus that was utilized consisted of a 1%" 0D Pyrex tube surrounded by an electrically heated furnace. In the bottom of the tube was placed a plug of glass wool and on top of the glass wool 50 cc. of contact pellets of about 56" diameter. Above the pellets was placed cooled trap where the liquid products were acthrough a wet test meter.

cumulated. The gases passed out of the trap At the end of each run the Pyrex chips were removed from the tube and the total weight and volume of the contact were determined. The contact material was then screened to separate the fines from the pellets, and the weight and volume per cent fines were determined.

The temperature was 850 F., the gaseous space velocity being 590 cc./hr./cc. catalyst at standard temperature and pressure, with the actual flow rate of hydrogen being 9.9x10- ft. per

min. and that of the heptane being 1.7 cc./lnin.

'(liq.), or a value of 0.011 moi/ min. for both the hydrogen and the heptane. The amount of catalyst charge in each run was 50 cc.

The following table discloses the powdering rates for each contact, e. g. powdering rates wt. of fines in gms.X wt. of catalyst charge+deposited carbon minutes Percent metal reduced bases Percent Powder- Run Type Cu based ing Rate on Ni W Ni Cu 1 NiO-Alz03 22. 01 0 0 3. 37 2 NiO-CuO-AhO; 21. 62 1. 39 6. 44 2. 25 3. NiO-AhO: 10. 5 0 0 2. 076 4 NiO-CuO A: 8. 41 2. 32 27. 6 0 5. d 9. 13 1. l0 l2. 2 0

Figure 1 was prepared from data similar to runs 4, 5, 6, and 7 in order to reveal the variation of the powdering rate W with the change in weight per cent of copper based on the weight of nickel.

It should be noted that the absolute powdering rate will be a function of the total amount of metal present in the contact (as shown by a comparison of runs 1 and 2 with runs 3 to 7), as well as the weight per cent of copper based on nickel. However, for a given total metal content especially from accompanying Figure -1, it can clearly be seen that the powdering rate of contacts in which the copper is omitted is vastly greater than those in which it is present. In addition, it is apparent that the maximum change of slope of the powdering rate curve occurs at the value of about 5 weight per cent copper, and that the powdering rate increases rapidly when the percentage copper is reduced below this value. Thus, this value is to be regarded as the critical minimum value, that is the lowest value at which the addition of copper to the contact has a substantial effect on powdering rate; Also it is readily evident from Figure 1 that increasing the percentage of copper beyond 11 per 'cent has no effect on the powdering rate, since the powdering rate at the value of 11 weight per cent copper is nil.

Further hydrodesulfurization runs were conducted in order to determine the effect of adding additional copper to the contact. beyond that required to reduce the powdering rate.

Example V.--Utilizing conditions similar to those given'in Example III, hydrodesulfurization runs were conducted with contacts having varying weight per cent copper values based on nickel. The through-put at which hydrogen sulfide appeared, i. e. the volume of charge stock/volume of contact/cycle, and in which the cycle is defined as the duration of time from the point when the reaction was commenced till the time at which hydrogen sulfide appeared, was determined for each contact as follows:

Weight percent Through-put at Copper Based on which Hydrogen Nickel Sulfide Appears It will be seen that there is a decrease in the through-put on increasing the amount of copper. For this reason it is undesirable to use any more copper than is necessary to suppress powdering of the contact. Data similar to the foregoing were plotted and appear in accompanying Figure 2 wherein it is seen that with increasing amounts of copper the through-put decreases in a more or 8 contact agent. Thus, below the value of about 5 weight per cent copper based on nickel, the powdering rate of the contact is excessive, whereas above about the 11 per cent value it is nil; and

furthermore increasing the copper content above about 11 per cent causes the through-put to adversely decrease. It can therefore be seen that the range 5 to 11 weight per cent of copper based on nickel is a critical one comprising that at which the powdering rate is decreased to a point where it does not impair the efliciency of the process. and at which the decrease of the throughput is not sufliciently marked to hamper the onstream cycle.

In addition to the foregoing, it was also observed that on increasing the weight per cent of copper based on nickel the per cent hydrodesulfurization decreased.

Example VI.Utilizing conditions similar to those given in Example 111 hydrodesulfurization runs were conducted with the following contacts. In the following table the per cent hydrodesulfurization that was obtained with each contact is indicated. 1

Percent Ni Percent Cu Percent 011 Percent Based on Based on Based on Hydrodesul- Contact Contact Ni furization From the foregoing it is evident that the falling off of hydrodesulfurization concomitant with the increase in copper content does not result in a reduction to a value that would impede the commercial practicability of the process; because as heretofore stated contacts having above about 50 per cent hydrodesulfurization values are industrially serviceable. However, it can be seen that increasing the weight per cent of copper based on nickel causes the hydrodesulfurization activity of the contact to decrease and hence is undesirable.

I Thus, it is to be emphasized that while increasing the weight per cent of copper based on nickel beyond the 11 per cent value fails to produce a further beneficial decrease in the powdering rate, adverse effects upon the through-put and the hydrodesul'furization activity of the contact will be obtained. Accordingly, it is essential for the purposes of the present invention to limit the weight per cent copper based on nickel to a value of between about 5 and 11 per cent.

The results achieved by the present invention are a function of the ratio of the weight per cent of copper to nickel and will be more or less independent of the total amount of metal which may be present. However, we have found that for the present process to be commercially applicable the total weight of metal in the contact should be from between about 5 to about 25 per cent. In addition to the copper and nickel, minor amounts of other metals may be present, such as iron. cobalt, calcium, and magnesium.

We do not wish to be bound by any theory for the present invention, however, we believe that the powdering is caused by the deposition of carbon from the hydrocarbon compounds which are being treated. The copper evidently prevents the carbon from entering the metal crystal lattice of the contact and thereby prevents the powdering and decrepitation heretofore encountered with these contacts.

The present process permits an increase in the production time for which a given catalyst bed may be utilized, and furthermore will permit a given hydrodesulfurization contact to be regenerated more frequently than has heretofore been possible. This means a marked saving in both time and money when our contact hydrodesulfurization process is utilized, as well as ease of operation.

We claim:

1. In the process for desulfurizing a petroleum hydrocarbon by contacting vapors thereof and hydrogen-containing gas with a contact comprising a member of the group consisting of nickel and nickel oxide on a carrier, absorbing sulfur from the vapors to form nickel sulfide, regenerating the contact to substantially its original form and again contacting the petroleum hydrocarbon vapors and hydrogen with the regenerated contact, the improvement for reducing powdering of said contact as a result of repeated regeneration which comprises incorporating copper in said contact in an amount of between and 11 per cent by weight of the nickel whereby powdering is efiectively reduced.

2. In the process for desulfurizing a high boiling petroleum hydrocarbon by contacting vapors thereof and hydrogen-containing gas with a contact comprising a member of the group consisting of nickel and nickel oxide on a carrier, at a temperature between 750 and 950 F., absorbing sulfur from the vapors to form nickel sulfide, regenerating the contact to substantially its original form and again contacting the petroleum hydrocarbon vapors and hydrogen with the regenerated contact, the improvement for reducing powdering of said contact as a result of repeated regeneration which comprises incorporating copper in said contact in an amount of between 5 and 11 per cent by weight of the nickel whereby powdering is effectively reduced.

3. In the process for desulfurizing a petroleum hydrocarbon by contacting vapors thereof and hydrogen-containing gas with a contact comprising a member of the group consisting of nickel and nickel oxide on a carrier the per cent nickel in the entire contact being between 5 and 25 per cent, absorbing sulfur from the vapors to form nickel sulfide, regenerating the contact to substantially its original form and again contacting the petroleum hydrocarbon vapors and hydrogen with the regenerated contact, the improvement for reducing powder-ing of said contact as a result of repeated regeneration which comprises incorporating copper in said contact in an amount of between 5 and 11 per cent by weight of the nickel whereby powdering is eifectively reduced.

4. In the process for desulfurizing a high boiling petroleum hydrocarbon by contacting said hydrocarbon and hydrogen-containing gas with a contact comprising a member of the group consisting of nickel and nickel oxide on a carrier the per cent nickel in the entire contact being between 5 and 25 per cent, absorbing sulfur from the high boiling hydrocarbon to form nickel sulflde, regenerating the contact to substantially its original form and again contacting the high boiling petroleum hydrocarbon and hydrogen with the regenerated contact, the improvement for reducing powdering of said contact as a result of repeated regeneration which comprises incorporating copper in said contact in an amount of between 5 and 11 per cent by weight of the nickel whereby powdering is eflectively reduced.

5. In the process for desulfurizing a, high boiling petroleum hydrocarbon by contacting vapors thereof and hydrogen-containing gas with a contact comprising a. member of the group consisting of nickel and nickel oxide on a carrier the per cent nickel in the entire contact being between 5 and 25 per cent, absorbing sulfur from the vapors to form nickel sulfide, regenerating the contact to substantially its original form and again contacting the petroleum hydrocarbon vapors and hydrogen with the regenerated contact, the improvement for reducing powdering 01 said contact as a result of repeated regeneration which comprises incorporating copper in said contact in an amount of about 11 per cent by weight of the nickel whereby powdering is efl' tively reduced. 1

CHARLES W. MONTGOMERY.

I. GILBERT. STANLEY M. HAZEN.

REFERENCES CITED The following references are of record in the .file of this patent:

UNI'IIHJ STATES PATENTS Number Name Date 1,257,829 Evans Feb. 26, 1918 2,073,578 Gwynn Mar. 9, 1937 2,273,298 Szayna Feb. 17, 1942 2,337,358 Szayna Dec. 21. 1943

Claims (1)

1. IN THE PROCESS FOR DESULFURIZING A PETROLEUM HYDROCARBON BY CONTACTING VAPORS THEREOF AND HYDROGEN-CONTAINING GAS WITH A CONTACT COMPRISING A MEMBER OF THE GROUP CONSISTING OF NICKEL AND NICKEL OXIDE ON A CARRIER, ABSORBING SULFUR FROM THE VAPORS TO FORM NICKEL SULFIDE, REGENERATION THE CONTACT TO SUBSTANTIALLY ITS ORIGINAL FORM AND AGAIN CONTACTING THE PETROLEUM HY-

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