Method of removing sulfur-containing impurities from hydrocarbons

Sulfur-containing impurities are removed from a refined hydrocarbon feed by contact thereof with a porous sulfur-reactive agent having a pore volume of at least 0.15 cc per cc of which at least 5% is in pores having a diameter in the range 0.1 to 15 microns. The agent contains at least one sulfur-reactive material from the group copper, iron, zinc and compounds thereof.

BACKGROUND OF THE INVENTION 
This invention relates to a process for removing sulfur-containing 
impurities from a refined hydrocarbon feed. More particularly it relates 
to removing such impurities by contacting the feed with a novel material 
containing a sulfur-reactive agent and having a pore volume of at least 
0.15 cc per cc of which 5% is in pores having a diameter in the range 0.1 
to 15 microns. 
In the refining of crude oil, product streams are obtained which contain a 
relatively minor amount of sulfur-containing impurities, for example 
thiols, thiophenes, hydrogen sulfide, organic sulfides, sulfur-containing 
heterocyclic organic compounds and the like. Such impurities reduce the 
desirability of a stream for many uses and may even make it unacceptable, 
for example as a feed to a naphtha reformer unit and the like. 
Contemporary anti-pollution standards greatly limit the amount of sulfur 
which may be present in any form in hydrocarbon fuels. 
It is known to reduce the sulfur content of a refined hydrocarbon by 
contacting it with a material comprising a sulfur-reactive agent such as 
one comprising copper, iron, zinc and compounds thereof, especially where 
these materials are disposed upon an inert carrier material (see for 
example U.S. Pat. Nos. 2,755,226; 2,769,764; 3,192,152; 3,382,044; 
3,441,370; and 3,660,276). A serious limitation of these materials is that 
the desired sulfur-removing reactions resulting from the contacting of the 
feed with the material are subject to diffusion limitations. In order to 
make a more effective use of the contact material in such a case, it is 
necessary to reduce the space velocity of the feed. This is 
disadvantageous because it lowers the capacity of the process unit 
involved. 
SUMMARY OF THE INVENTION 
An improved process has now been found for removing an impurity comprising 
sulfur from a refined hydrocarbon feed by contacting the feed with a 
sulfur-reactive agent under hydrocarbon sulfur-removing conditions. The 
improvement comprises employing a solid sulfur-reactive agent having a 
pore volume of at least 0.15 cc per cc of which at least 5% is in pores 
having diameters in the range of from about 0.1 to 15 microns. 
In a more particular aspect, the sulfur-reactive agent is a novel 
composition comprising a rigidly interconnected pack of irregularly shaped 
particles, the pack having a pore volume of at least 0.15 per cc and 
having access channels among said particles throughout the pack, said 
channels comprising interconnected macropores having diameters 
corresponding to values as determined by mercury porosimetry in the range 
of from about 0.1 to about 15 microns, and said macropores contributing at 
least 5 percent of the pore volume; said particles being (1) of the same 
or different materials and (2) sized in the average diameter range below 
about 0.15 mm; and said particles comprising at least one material 
selected from the group consisting of (1) sulfur-reactive agents, (2) 
composites of said agents and at least one refractory oxide selected from 
the oxides of the metals of Groups II, III and IV of the Periodic Chart of 
the Elements, and (3) at least one of said refractory oxides; said 
composition containing at least about 1 weight percent of said 
sulfur-reactive agent and having a surface area in the range of from about 
2 to 700 square meters per gram. 
PREATION OF CONTACT MATERIAL 
The contact material required for the process of the invention may be 
obtained by any suitable way. In a preferred method this material is 
prepared by a unique process in which (1) the material in finely divided 
form (particles of diverse sizes having diameters in the range below 0.04 
mm) is admixed with a hydrocolloid-forming organic compound, for example 
wheat flour, and water to form an extrudable dough-like mass, (2) the mass 
is then extruded, for example by using a 2.5 mm orifice and (3) dried. 
Broadly, the drying may be effected by any suitable means for removing 
water from the composite. Heating thereof at an elevated temperature, for 
example in the range of between 50.degree. to 700.degree. C. in an 
oxygen-containing gas, for example air, or in an inert atmosphere, for 
example, nitrogen gas, is, in general, satisfactory. When the heating is 
at a temperature below about 200.degree. C. or with the composite 
blanketed by an inert atmosphere in the range 200.degree. C. to 
700.degree. C., the resulting composite usually contains residual 
carbonaceous material. The latter composite is a preferred contact 
material because of its usually superior crush strength relative to the 
case where the drying is effected in air or an oxygen-containing gas under 
a combusting temperature in the range above 200.degree. C. to 700.degree. 
C. 
Based upon the finely divided material, about 2-10 weight percent of the 
organic compound and sufficient water to form an extrudable mass are used 
in the preparation. The resulting product has an appreciable pore volume 
of which at least 5% is in pores sized in the 0.1 to 15 micron diameter 
range. Pores of these dimensions are excellent access pores for the 
hydrocarbon feed. 
EMBODIMENT 
In a preferred embodiment a naphtha boiling range fraction obtained from 
the hydrocracking of a suitable distillate feed is treated by the process 
of the invention. A representative hydrocrackate feed has a boiling point 
in the range 93.degree. C. to 177.degree. C. and has a sulfur content, 
calculated as elemental sulfur, in the range 15 to 250 ppm. Such a 
hydrocrackate, because of its sulfur content, is undesirable for many 
purposes, for example as a feed to a reformer employing a 
platinum-rhenium-containing reforming catalyst. In the treatment, the 
hydrocrackate feed is contacted at an elevated temperature of about 
165.degree. C. at a liquid hourly space velocity of about 10 with a 
contact mass comprising a mixture of copper chromite and fluid catalytic 
cracking (FCC) catalyst fines, for example electrostatically precipitated 
fines normally recovered in a hydrocarbon catalytic cracking process. 
These fines are normally submicron sized and usually, but not necessarily, 
are a composite of an amorphous silica-alumina matrix and a crystalline 
aluminosilicate, i.e., zeolitic molecular sieves, suitable as a cracking 
catalyst component. In the preparation of the contact mass as described 
above, proportion, in parts by weight, as follows are desirably used: 
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FCC fines 27 
Copper Chromite (powdered) 27 
Wheat Flour 10 
Water 36 
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The resulting product stream has a sulfur content of less than 0.1 ppm and 
is an excellent feed for a reformer unit. 
In a further embodiment, a porous copper-containing contact material herein 
is used as a guardbed for a hydrocarbon reformer unit, for example where a 
hydrotreated hydrocarbon feed stream is stripped in a gas stripping unit 
for the removal of hydrogen sulfide prior to use as feed to the reformer. 
Normally, the stripping procedure is effective. However, inadvertent 
upsets and misadventures are known to have occured with serious 
consequences in the operation of the reformer unit, for example 
temperature excursions, impairment of catalyst selectivity and activity 
and as a result reduced aromatic content in the product. The bottom 
effluent from the stripper unit is normally a liquid at a temperature in 
the range 20.degree. to 50.degree. C. This liquid is introduced into 
contact with the porous contact material herein in a fixed bed at a liquid 
hourly space velocity (LHSV) of at least 10. Even at the relatively low 
temperatures noted above any hydrogen sulfide present in the stripper 
bottom effluent is effectively removed from the feed streams. Because of 
the relatively high content of 0.1 to 15 micron macropores in the contact 
mass, relatively high LHSV's may be advantageously used with guardbed unit 
without diffusion limitation problems and without risk of hydrogen sulfide 
carryover into the reformer unit. 
PROCESS FEED 
Refined hydrocarbons having a sulfur-containing impurity content, 
calculated as elemental sulfur, in the range of from about 1 to 2000 ppmw 
are especially satisfactory for use as process feeds herein and such use 
is contemplated. 
By refined hydrocarbons as used herein, is meant by definition liquid and 
gaseous hydrocarbons and mixtures thereof normally obtained as primary or 
secondary products in the processing of sulfur-containing petroleum oils 
and gas in a petroleum refinery or the like and containing, calculated as 
elemental sulfur, at least about 1 ppm (weight) of sulfur-containing 
impurities and less than about 2000 ppm thereof. Larger relative amounts 
of the impurity may be present and are effectively removed. However, there 
are usually more economic means for treating such than by the process 
herein. 
Representative refined hydrocarbons include distillate fractions such as 
gas oil, hydrocrackate and cat-cracker oils, gasoline, kerosene, jet and 
diesel fuels and fractions thereof, and the like which have a 
sulfur-containing impurity content in the range from 1 to about 2000, 
preferably 5 to 500 ppmw. 
CONTACT MASS 
A contact mass satisfactory for use in the process of the invention and 
contemplated for use herein must be a solid comprising a sulfur-reactive 
agent which has at least an appreciable (at least 0.15 cc per cc) pore 
volume of which at least 5% is in access pores, that is, in pores having a 
diameter in the 0.1 to 15 micron range. 
By a sulfur-reactive agent as used herein is meant by definition the metals 
copper, iron and zinc, mixtures thereof and compounds of the metals which 
react with hydrogen sulfide and alkyl mercaptans under the process 
conditions herein to form the corresponding metal sulfide and metal 
mercaptide and their composites with refractory metal oxides. Preferably, 
the contact solid comprises at least one sulfur-reactive agent selected 
from the group consisting of the metals copper, iron, and zinc, their 
sulfide- and mercaptide-forming compounds, and their composites comprising 
the agent(s) and at least one refractory oxide selected from the oxides of 
the metals of Groups II, III and IV of the Periodic Chart of the Elements. 
Representative sulfur-reactive agents include copper, iron and zinc; 
copper, iron and zinc oxides; copper, iron and zinc salts, such as copper 
chloride, copper acetate, copper carbonate, copper chromite and the like 
copper salts; and iron and zinc carbonate and the like salts. The metals 
and metal oxides and composites thereof with one or more refractory metal 
oxides are preferred sulfur-active agents, especially in the form of the 
particle packs described supra. 
Where the contact mass is a composite of a sulfur-reactive agent and a 
refractory oxide, the amount of the agent present in the composite mass 
may vary widely depending in general upon the service in which it is to be 
employed. In general, a satisfactory amount, based upon the refractory 
oxide and calculated as the metal fraction of said agent, will be in the 
range from about 1 to 25 weight percent. Best results are believed to 
obtain when the amount is in the range 5 to 20 weight percent. Contact 
masses containing a refractory oxide component as herein may be prepared 
by any suitable method. Again, the preferred method is pursuant to the 
process described above in which a particle pack is produced and in which 
(1) the finely divided refractory oxide solid contains the sulfur-active 
agent disposed therein; (2) both the refractory oxide and the 
sulfur-active agent are finely divided solids of the described dimensions; 
or (3) finely divided refractory oxide material in the absence of a 
sulfur-active agent is converted to suitable porous material which is then 
impregnated with the sulfur-active agent or a suitable precursor thereof 
by customary impregnation methods, for example by immersion of the porous 
solid in an aqueous solution of a copper salt followed by drying and 
calcination. 
A contact mass suitable for use herein must have a substantial pore volume, 
for example at least 0.15 cc per cc and a substantial surface area for 
effective utilization of the sulfur-reactive agent. Pore volume and 
surface area characteristics vary depending in the main upon the sizing of 
the pores constituting the pore volume. In general, a satisfactory contact 
mass will have a pore volume in the range 0.15 to 0.8 cc per cc and higher 
and a suface area in the range of from about 2 to 700 m.sup.2 per gram, 
preferably 20 to 300 m.sup.2 /g. 
In order to provide effective access of the hydrocarbon feed to the 
sulfur-reactive agent and to avoid diffusion limitation problems, the 
contact mass must contain a substantial fraction of its pore volume in 
access pores having diameters in the range of from about 0.1 to 15, 
preferably 1 to 10 microns. In general, a satisfactory fraction will be in 
the range of from about 5 to 45% of the pore volume. The lower relative 
amounts of access pores relate to solid contact masses having relatively 
high pore volumes, and the higher relative amounts correspond to masses 
having relatively lower pore volumes. 
The contact mass herein may have any suitable size. Desirable sizing 
varies, in general, depending upon whether the contacting is carried out 
in a fixed bed, fluid bed or slurry of liquid and solid, for example for 
fixed bed usage in the usual average diameter range of from about 0.8 to 
13 mm, and for fluid a slurry usage in the average diameter range below 
about 0.8 mm. 
SULFUR-REMOVING REACTION CONDITIONS 
Satisfactory sulfur-removing reaction conditions vary widely, depending 
upon the particular contact mass employed, the particular kind and amount 
of the sulfur-containing impurity involved, upon the pore volume and pore 
size distribution of the contact mass and the like factors. In general, 
these conditions include: 
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Condition Broadly Preferred 
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Temperature, .degree. C 
10 to 425 50 to 350 
Pressure, atm 1 to 100 1 to 10 
LHSV, V/V/hr 1 to 25 5 to 20 
Hydrogen Pressure, 
atm 0 to 100 0 to 50 
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The following examples are provided for the further illustration of the 
process of the invention but not the limitation thereof.