Fluid coking with the addition of dispersible metal compounds

A fluid hydrocoking process is provided in which certain metal compounds are dispersed in the coker chargestock. Preferred compounds are molybdenum compounds, for example, molybdenum naphthenate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an improvement in a fluid hydrocoking process. 
More particularly, this invention relates to a fluid hydrocoking process 
in which certain metal compounds are added to the chargestock. 
2. Description of the Prior Art 
Fluid coking is a well known process which may be carried out with or 
without recycle of the heavier portion of the fluid coking zone effluent. 
As is well known in the art, the fluid coking process, as shown, for 
example, in U.S. Pat. No. 2,881,130, which is hereby incorporated by 
reference, uses a fluid coking vessel and an external heating vessel. A 
fluid bed of solids, preferably coke particles produced by the process 
having a size in the range from about 40 to about 1000 microns is 
maintained in the coking zone by the upward passage of fluidizing gas, 
usually steam, injected at a superficial velocity usually between 0.3 and 
5 feet per second. The temperature in the fluid coking bed is maintained 
in the range of from about 850.degree. to about 1400.degree. F., 
preferably between 950.degree. and 1100.degree. F. by circulating solids 
(coke) to the heating vessel and back. The heavy oil to be converted is 
injected into the fluid bed and upon contact with the hot solids undergoes 
pyrolysis evolving lighter hydrocarbon products in vapor phase, including 
normally liquid hydrocarbons, and depositing a carbonaceous residue (coke) 
on the solid. The turbulence of the fluid bed normally results in 
substantially isothermal reaction conditions and thorough and rapid 
distribution of the heavy injected oil. Product vapors, after removal of 
entrained solids, are withdrawn overhead from the coking zone and sent to 
a scrubber and fractionator for cooling and separation. The end boiling 
point of distillate fraction obtained from the process is usually 
1,050.degree. to about 1,200.degree. F. and the remaining heavy ends are 
usually recycled to extinction. 
It is known to add hydrogen to a fluid coking zone, see, for example, U.S. 
Pat. Nos. 2,888,395 and 2,888,393. 
It is also known to use oil soluble organometallic compounds in thermal 
cracking or in destructive hydrogenation of hydrocarbons, see, for 
example, U.S. Pat. No. 1,876,270. 
It is also known to conduct cracking or destructive hydrogenation in the 
presence of oil soluble salts of acid organic compounds selected from the 
group consisting of carboxylic acids and phenol with a metal of Group VI 
and Group VIII of the Periodic Table, see, for example, U.S. Pat. No. 
2,091,831. 
A slurry hydrocracking process is also known in which an oil soluble 
compound of Groups IV to VIII is added to a heavy oil feed, see, for 
example, U.S. Pat. No. 3,131,142. It has now been found that the addition 
of a minor amount of certain metal compounds to the chargestock of a fluid 
coking process will provide advantages that will become apparent in the 
ensuing description. 
SUMMARY OF THE INVENTION 
In accordance with the invention, there is provided, in a fluid coking 
process comprising the steps of contacting a carbonaceous chargestock 
having a Conradson carbon content of at least 5 weight percent with hot 
fluidized solids in a fluidized coking bed contained in a coking zone 
maintained in a fluidized state by the introduction of a 
hydrogen-containing fluidizing gas and operated at coking conditions, 
including a total pressure ranging from about 20 to about 150 psig to 
produce a vapor phase product and a solid carbonaceous material which 
deposits on said fluidized solids, the improvement which comprises adding 
to said chargestock a metal compound selected from the group consisting of 
metal salts of organic acids, metal phenolates, metal halides, inorganic 
heteropoly acids and mixtures thereof wherein the metal constituent is 
selected from the group consisting of Groups IVB, VB, VIB, VIIB and VIII 
of the Periodic Table of Elements and mixtures thereof, the hydrogen 
pressure in said coking zone being at least about 20 psig.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the FIGURE, a carbonaceous material having a Conradson carbon 
content of at least 5 weight percent is passed by line 10 into a coking 
zone 1 in which is maintained a fluidized bed of solids (e.g. coke 
particles of 40 to 1000 microns in size) having an upper level indicated 
at 14. Suitable carbonaceous chargestocks for the present invention 
include heavy hydrocarbonaceous oils, heavy and reduced petroleum crudes, 
atmospheric residuum, vacuum residuum, pitch; asphalts; bitumen; other 
heavy hydrocarbon residues; coal; slurries of coal and oil; slurries of 
coal and water; liquid products derived from coal liquefaction processes 
and mixtures thereof. Typically such carbonaceous chargestocks have a 
Conradson carbon content of at least 5 weight percent, generally from 
about 5 to about 50 weight percent, preferably above 7 weight percent (as 
to Conradson carbon residue, see ASTM test D-189-65). A metal compound is 
added to the carbonaceous chargestock by line 12. Preferably, the metal 
compound is an oil soluble compound or an oil dispersible compound. 
Suitable metal compounds to be added to the chargestock of the present 
invention include metal salts of organic acids, such as acyclic and 
alicyclic aliphatic carboxylic acids containing 2 or more carbon atoms 
(e.g. naphthenic acids); metal phenolates; metal halides; inorganic 
heteropoly acids (e.g. phosphomolybdic acid) and mixtures thereof wherein 
the metal constituent is selected from the group consisting of Groups IVB, 
VB, VIB, VIIB and VIII of the Periodic Table of Elements, in accordance 
with the table published by E. H. Sargent and Co., copyright 1962, Dyna 
Slide Co. The preferred metal constituent of the added metal compound is 
selected from the group consisting of molybdenum, vanadium and chromium. 
The more preferred metal constituent of the metal compound is molybdenum. 
The preferred metal compounds are molybdenum naphthenate and 
phosphomolybdic acid. The added metal compound is dissolved or dispersed 
in the carbonaceous chargestock. When coal is used as the feed, the coal 
particles may be slurried in the hydrocarbonaceous oil to which the metal 
compound is added. 
The metal compound is added to the carbonaceous chargestock in an amount 
ranging from about 10 to about 950 wppm, preferably from about 50 to about 
500 wppm, more preferably from about 50 to about 200 wppm, said weight 
being calculated as if the compound existed as the elemental metal, based 
on the initial carbonaceous chargestock. 
A hydrogen-containing fluidizing gas is admitted in the coking reactor 1 by 
line 16 in an amount sufficient to maintain a superficial gas velocity in 
the range of about 0.3 to about 5 feet per second. The hydrogen-containing 
fluidizing gas may also include steam, gaseous hydrocarbons, vaporized 
normally liquid hydrocarbons, or mixtures thereof. Typically, the 
hydrogen-containing fluidizing gas used will comprise steam. The 
fluidizing gas comprises added hydrogen in an amount sufficient so as to 
maintain a hydrogen pressure in the coking zone of at least about 20 psig, 
preferably about 30 to about 150 psig, including any hydrogen that may be 
produced in situ during the coking reaction. Coke at a temperature above 
the coking temperature, for example, at a temperature of 100 to 800 
Fahrenheit degrees in excess of the actual operating temperature of the 
coking zone is admitted to coker 1 by line 26 in an amount sufficient to 
maintain the coking temperature in the range of about 850.degree. to about 
1400.degree. F., preferably in the range of about 950.degree. to 
1100.degree. F. The total pressure in the coking zone is maintained in the 
range of about 20 to about 150 pounds per square inch gauge (psig), 
preferably in the range of about 30 to about 150 psig. The lower portion 
of the coking reactor serves as a stripping zone to remove occluded 
hydrocarbons from the solids. A stream of solids is withdrawn from the 
stripping zone by line 20 and circulated to heater 2. The vaporous product 
includes gaseous hydrocarbons and normally liquid hydrocarbons as well as 
other gases which were introduced into the coking reactor as fluidizing 
gas. The vapor phase product is removed from coker 1 by line 18 for 
scrubbing and fractionation in a conventional way. If desired, at least a 
portion of the vaporous effluent may be recycled to the coker as 
fluidizing gas. A stream of heavy material condensed from the vaporous 
coker effluent may be recycled to the coker or the coker may be operated 
in a once-through manner, that is, without recycle of the heavy material 
to the coker. 
A stream of stripped coke (commonly called cold coke) is withdrawn from the 
coker by line 20 and introduced to a fluid bed of hot coke having a level 
30 in heater 2. The heater can be operated as a conventional coke burner 
such as disclosed in U.S. Pat. No. 2,881,130, which is hereby incorporated 
by reference. When the heater is operated as burner, an oxygen-containing 
gas, typically air, is introduced into heater 2 by line 22. The combustion 
of a portion of the solid carbonaceous deposition on the solids with the 
oxygen-containing gas provides the heat required to heat the colder 
particles. The temperature in the heating zone (burning zone) is 
maintained in the range of about 1200.degree. to about 1700.degree. F. 
Alternatively, heater 2 can be operated as a heat exchange zone such as 
disclosed in U.S. Pat. Nos. 3,661,543; 3,702,516 and 3,759,676, the 
teachings of which are hereby incorporated by reference. Hot coke is 
removed from the fluidized bed in heater 2 and recycled to the coking 
reactor by line 26 to supply the heat thereto. 
While the process has been described for simplicity of description with 
respect to circulating coke as the fluidized solids, it is to be 
understood that the fluidized seed particles on which the coke is 
deposited may be silica, alumina, zirconia, magnesia, calcium oxide, 
alundum, mullite, bauxite or the like. 
The following example is presented to illustrate the invention. 
EXAMPLE 
Comparative experiments were made in a stirred coking vessel with and 
without the use of molybdenum naphthenate as the added metal compound. The 
feed utilized in these experiments was a Tia Juana vacuum residuum having 
a Conradson carbon residue of 20.7 weight percent and an API gravity of 
7.7. The conditions used and resulting products are summarized in the 
following table. 
TABLE 
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Run No. 1 2 
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Molybdenum naphthenate 
None 460 wppm 
Temperature, .degree. F. 
950 950 
H.sub.2 Pressure, psig.sup.(1) 
30 30 
Feed rate 
Oil, gm/min. 30.9 24.2 
H.sub.2, 1/min. 6.8 6.9 
Product Yields, wt. % 
C.sub.4.sup.- gas 9.9 11.0 
Liquids 
C.sub.5 /430.degree. F. 
11.1 11.5 
430/650.degree. F. 10.9 10.9 
650/975.degree. F. 23.9 29.3 
955.degree. F..sup.+ 
17.1 17.9 
TOTAL 63.0 69.6 
Coke 22.1 19.1 
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.sup.(1) This hydrogen pressure was also the total pressure. 
As can be seen from the data in the table, Run No. 2, which is a run in 
accordance with the present invention, yielded less coke and more liquid 
products than comparative Run 1.