US2889272A

US2889272A - Catalytic desulfurization of petroleum hydrocarbons in a two stage autofining process

Info

Publication number: US2889272A
Application number: US572785A
Authority: US
Inventors: Moy John Arthur Edgar; Rowland John
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1955-03-22
Filing date: 1956-03-21
Publication date: 1959-06-02
Anticipated expiration: 1976-06-02
Also published as: DE1074182B; FR1144451A; BE546109A; GB792496A

Description

CATALYTIC DESULFURIZATION F TETROIJEUM HYDROCARBONS IN A IW0 STAGE AUTOFIN- ING PROCESS John Arthur Edgar May and John Rowland, 'Snnbury-on- 5.5

Thames, England, assignors to The British Petroleum Company Limited, London, England, a British jointstockcorporation N0 Drawing. Application March 21, 1956 Serial No. 572,785

Claims priority, applica'tionGreat BritainM'arch 22, 1955 '6 Claims. or. 208-210) This invention relates to the catalytic dcsulfurization of petroleum hydrocarbons by means of the autofining process, the nature of which is described inter alia in United States Patents Nos. 2,573,726, 2,574,445-51 and 2,540,802. As set forth in these patents the autofining operation is carried out under a temperature selected between about 650-800 F. and a pressure selected between 25-500 p.s.i. ga. with the temperature and pressure being correlated with respect to one another to insure a net production of hydrogen.

Almost complete desulfurization of the .lower boiling petroleum distillates, such as naphtha and kerosene, is effected by once-through treatment of the distillate in the autofining zone, at a pressure of 100 lb./sq. in.

In order to achieve adequate desulfurization on a once-through basis of the higher boiling petroleum distillates, such as gas oils, however, it is generally necessary. to carry out the process and. operate the plant under the equilibrium pressure method described in United States Patent No. 2,648,623. The equilibrium pressure obtainable with any particular feedstock depends upon the particular catalyst employed, the temperature and the space velocity. For a given catalyst, temperature and space velocity, the equilibrium pressure gradually falls from the maximum obtainable with fresh catalyst to a lower value, with decrease in the catalyst activity. As set forth in Patent No. 2,648,623 in equilibrium pressure autofim'ng, the temperature is selected between 65-0800 F. and the pressure is permitted to rise above 100 psi. ga. until the amount of hydrogen produced equals the amount of hydrogen consumed at which point the system is in pressure equilibrium.

Plants suitable for the autofining of the lower boiling feedstocks may not necessarily be adapted for operation at the higher pressures reached when autofining under equilibrium pressure conditions, but it would nevertheless be desirable if the higher boiling petroleum distillates could be adequately desulfurized in such plants.

It has now been found that higher boiling petroleum distillates that are not adequately desulfurized by autofining on a once-through basis at pressures below the equilibrium autofining pressure of the distillate under the autofining conditions of catalyst, temperature and space Velocity obtaining in the autofining zone, be further desulfurized by recycling or reprocessing the product obtained from the first treatment under substantially the same conditions.

According to the present invention therefore, a process for the catalytic desulfurization of a petroleum distillate, particularly of a higher boiling petroleum distillate that cannot be adequately desulfurized by autofining alt pressures below the equilibrium autofining pressure, comprises autofining the distillate at a pressure below the equilibrium pressure and recycling the treated distillate to the reaction zone, or reprocessing the treated distillate,

preferably under the same conditions, over a flesh charge of catalysts 'The invent-ion is particularly applicable to the autofining of gas oils.

The catalyst employed is preferably 'of the kind comprising the oxides of cobalt and molybdenum either as such or in combined form incorporated with a metal oxide support, usually alumina. The catalyst may with advantage comprise a small amount, preferably between 0.1% and 6.0% by weight, of fluorine as described in United States patent application Ser. No. 311,429, filed September 25, 1952, now US. :Patent No. 2,800,429. "The use of .such a catalyst does not increase the degree of :desulfurization unless equilibrium pressure operation is employed, but even .at lower pressures it has the effect of producing a greater net yield of hydrogen which may with advantage be used in other processes in the refinery. The invention will now -be described with reference to the followingexamples:

Example 1 t A Kuwait gas oil was autofined in a pilot plant having a mlncatalyst capacity under the following conditions:

The liquid product was washed with caustic soda solution and water to remove dissolved hydrogen sulfide and then reprocessed under the same conditions over a fresh charge of catalyst. Two types of catalyst were used, a catalyst consisting of the oxides of cobalt and molybdenum supported on alumina and a catalyst of similar composition but activated with aluminum fluoride.

The results were as follows:

Mixed oxides Mixed Oxides of Cobalt and of Cobalt and Molybdenum Catalyst Molybdenum on alumina on alumina activated with aluminium fluoride Chemical Analysis, g./100 g. of material stable 1,020" F.:

M00 15.75 14. 4 C00 3. 2 3. 2 F 0 3. 36 Liquid Product inspection data After First Processing:

S.G. 60 F/60 F 0.8365 0.8390 13.1. (ASTM), C. 104 F.B.P. (ASTM), 0. 354 355 Bromine No 10. 2 10.7 Aromatics (ASTM D875), percen v01 13. 5 12. 5 Sulfur content, percent wt 0.54 0.55 Sulfur removal, percent.-- 57 56 Gross Hydrogen make, s.c.f./b 136 Liquid Product inspection data After Second Processing:

S.G. 60 F/60 F"..- 0. 8350 0. 8375 I.B.P. (ASTM), C. 89 94 F.B.P. (ASTM), C. 355 359 Bromine No 9. 8 11. 3 Aromatics (ASTM D875), percent vol 14.0 16.0 Sulfur content, percent wt- 0. 40 0. 44 Sulfur removal, percent 26 22 Gross Hydrogen make, s.c.i./b 28 41 3 Example 2 The same feedstock as in Example 1 was processed under the same conditions as in Example 1, using the catalyst that. did not contain fluorine,for five-processing periods, at the end of which the sulfur content of the product had been reduced to 0.17% wt. The results obtained were as follows:

Run number 1 2 s 4 5 Duration, hours 25 22 21 21 20 Sulfur content of product, ercent w 0. 17 Gross hydrogen make, s.c.f./b 133 34 26 14 12 We claim: Q '1. A process for the catalytic 'desulfurization under autofining conditions of a petroleum distillate that cannot be adequately desulfurized under autofining conditions on a once-through basis at pressures below the equilibrium autofining pressure of the distillate obtainable under the autofining conditions of catalyst, temperature,

and space velocity existing in an autofining zone, which comprises contacting the distillate in a reaction zone with a dehydrogenation-hydrogenation catalyst and hydrogen derived solely from the distillate at a temperature between about 650-800 F., and at a pressure below 25-500 p.s.i. ga., and recovering a distillate of still further reduced sulfur content from the product of the second operation.

.2. A process in accordance with claim 1 wherein the autofining conditions of the second stage reaction zone are substantially the same as the first stage reaction zone.

3. A process in accordance with claim 1 wherein the dehydrogenation-hydrogenation catalyst is oxides of cobalt and molybdenum on alumina.

4. A process in accordance with claim 3 wherein the catalyst contains about 0.1% and 6.0% of fluorine.

5. A process in accordance with claim 1 wherein the distillate is a gas oil.

6. A process for the catalytic desulfurization under autofining conditions of a petroleum distillate that cannot be adequately desulfurized under autofining conditions on a once-through basis at pressures below the equilibrium autofining pressure of the distillate obtainable under the autofining conditions of catalyst, temperature, and space velocity existingin the autofining zone, which comprises contacting the distillate in a reaction zone with a dehydrogenation-hydrogenation catalyst and hydrogen derived solely from the distillate at a temperature between about 650800 F. and at a. pressure below the equilibrium 'autofining pressure obtainable under the selected operating conditions, recovering a distillate of reduced sulfur content, recycling the recovered" distillate back to the first reaction zone as the sole feedstock therein and in contact'with a fresh dehydrogenation hydrogenation catalyst and in the presence of hydrogen derived solely from the recovered distillate, and under substantially the same conditionsof tempera- "ture and pressure as the initial treatment, and recovering a.distillate of still further reduced sulfur content from the product of the second operation.

: I References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A PROCESS FOR THE CATALYTIC DESULFURIZATION UNDER AUTOFINING CONDITIONS OF A PETROLEUM DISTILLATE THAT CANNOT BE ADEQUATELY DESULFURIZED UNDER AUTOFINING CONDITIONS ON A ONCE-THROUGH BASIS AT PRESSURES BELOW THE EQUILIBRIUM AUTOFINING PRESSURE OF THE DISTILLATE OBTAINABLE UNDER THE AUTOFINING CONDITIONS OF CATALYST, TEMPERATURE AND SPACE VELOCITY EXISTING IN AN AUTOFINING ZONE, WHICH COMPRISES CONTACTING THE DUSTILLATE IN A REACTION ZONE WITH A DEHYDROGENATION-HYDROGENATION CATALYST AND HYDROGEN DERIVED SOLELY FROM THE DISTILLATE AT A TEMPERATURE BETWEEN ABOUT 650-800* F,, AND AT A PRESSURE BELOW THE EQUILIBRIUM ATUOFINING PRESSURE OBTAINABLE UNDER THE SELECTED OPERATING CONDITIONS, RECOVERING A DISTILLATE OF REDUCED SULFUR CONTENT, PASSINT THE RECOVERED DISTILLATE THROUGH A REACTION ZONE AS THE SOLE FEEDSTOCK THEREIN AND IN CONTACT WITH A DEHYDROGENATION-HYDROGENATION CATALYST AND IN THE PRESENCE OF HYDROGEN DERIVED SOLELY FROM THE RECOVERED DISTILLATE, AND AT A TEMPERATURE BETWEEN ABOUT 650-800 F,. AND AT A TEMPERATURE BETWEEN ABOUT REDUCED SULFUR CONTENT FROM THE PRODUCT OF THE SECOND OPERATION.