Desulfurization and hydroconversion of residua with alkaline earth metal compounds and hydrogen

Sulfur-containing petroleum oil feedstocks which include heavy hydrocarbon constituents undergo simultaneous desulfurization and hydroconversion by contacting such feedstocks with alkaline earth metal hydrides or alkaline earth metal oxides, particularly barium hydride or barium oxide, in the presence of hydrogen, and at elevated temperatures. The mixtures of reaction products resulting from the above procedure can be separated to give a petroleum oil product which has been substantially desulfurized and demetallized and significantly upgraded as demonstrated by reduced Conradson carbon content, and increased API gravity and which includes alkaline earth metal sulfide salts from which the alkaline earth metal hydrides or oxides may be regenerated.

CROSS-REFERENCE TO RELATED APPLICATION 
This application is a continuation-in-part of application Ser. No. 571,904, 
filed June 2, 1975, now abandoned. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the combined desulfurization and hydroconversion, 
and consequent upgrading, of sulfur-bearing hydrocarbon feedstocks by 
contacting the feedstock with an alkaline earth metal hydride or oxide in 
the presence of hydrogen and at elevated temperatures. 
2. Description of the Prior Art 
The problem of air pollution, particularly with regard to sulfur oxide 
emissions, has been of increasing concern to refiners. As a consequence, 
the development of efficient as well as economic means for the removal of 
sulfur from sulfur-bearing fuel oils has become a primary research goal in 
this industry. Presently, the most practical desulfurization process is 
the catalytic hydrogenation of sulfur-containing molecules in petroleum 
hydrocarbon feeds to effect the removal of these sulfur molecules as 
hydrogen sulfide. The process generally requires relatively high hydrogen 
pressures, e.g., from about 700 to 3000 psig and temperatures in the range 
of about 650.degree. F to 800.degree. F depending on the feedstock and the 
degree of desulfurization. Also, these processes do not effect the 
simultaneous desulfurization and hydroconversion of the feedstocks 
employed, and particularly not without a high degree of coke make during 
same. 
The catalytic process is thus generally quite efficient in the handling of 
distillates, but becomes more complex and expensive and less efficient as 
the feedstock becomes increasingly heavier, e.g., whole or topped crudes 
and residua. Thus, for example, a residuum feedstock is often times 
contaminated with heavy metals, e.g., nickel, vanadium, iron, and 
asphaltenes which tend to deposit on and deactivate the catalyst. Also, 
the sulfur is generally contained in high molecular weight molecules that 
can be broken down only with the aid of severe operating conditions. Such 
operating conditions, however, tend to accelerate catalyst deactivation 
due to the accelerated depositions of coke and metal on the catalyst 
surfaces. 
It has also long been known that alkali and alkaline earth metals, as well 
as their corresponding hydrides, hydroxides and oxides, exhibit 
desulfurization activity for residua, but even so suffer from distinct 
drawbacks, such as poor desulfurization efficiency, a tendency to produce 
oil insoluble sludges, the inability to upgrade the feedstock by 
demetallization, and the formation of salt-oil mixtures that are 
exceedingly difficult to resolve by conventional means. Furthermore, 
again, none of these materials has ever been employed to obtain the 
simultaneous desulfurization and substantial hydroconversion of the 
feedstocks being treated. 
As an example of such a prior art process, U.S. Pat. No. 1,865,235 to Cross 
discloses the use of sodium, calcium, potassium, magnesium, strontium, 
barium and lithium in their metallic form or as hydrides thereof by 
contacting such materials with oils to be desulfurized at relatively low 
temperatures. Furthermore, U.S. Pat. No. 2,002,747 to Morrell discloses a 
method for the desulfurization of hydrocarbon oils wherein metals of the 
alkali or alkaline earth groups, preferably in a molten state, together 
with gases such as ammonia, steam and air react with cracked hydrocarbon 
vapors to produce sulfides of the metals involved, hydrogen sulfide and 
hydrogen in a state sufficiently reactive to substantially saturate the 
olefinic constituents of the vapors. The above reaction is generally 
carried out at a temperature of the order of 750.degree. to 1000.degree. 
F, under a pressure of the order of 100 to 500 psig. U.S. Pat. No. 
3,633,433 to Fraini relates to a process for reducing the sulfur content 
of hydrocarbon oils by reacting such feedstocks in a hydrogen atmosphere 
with finely divided magnesium, at a temperature in the range of 
600.degree. to 850.degree. F under a pressure of 100 to 200 psig and 
employing a hydrogen flow rate of 0.5 to 1.5 moles hydrogen per mole of 
feedstock per hour. Once again, however, none of these processes employ 
the materials of the present invention in order to obtain simultaneous 
desulfurization and hydroconversion. 
While these techniques have thus proven successful with regard to 
desulfurization, the search has continued for improved desulfurization 
processes which are capable of effecting significant simultaneous 
hydroconversion, and for improved methods for regenerating the products 
produced by the contact of the desulfurization agent in the reaction zone. 
It has now been found that when alkaline earth metal hydrides, oxides and 
mixtures thereof, especially barium hydride and barium oxide, are 
contacted to react with sulfur-bearing, heavy petroleum oil feedstocks, in 
the presence of hydrogen, at elevated temperatures, the feedstock 
undergoes desulfurization and demetallization while, simultaneously, heavy 
constituents of the feedstock undergo hydroconversion to lighter, lower 
boiling components. Thus, in effect the use of alkaline earth metal 
hydrides or oxides in conjunction with the hydrogen as described herein 
results in a combined and simultaneous desulfurization and hydroconversion 
of the feedstock which may be effected in an efficient and economical 
manner. In the past it has not been known to subject such feedstocks to 
such hydroconversion in the presence of such materials. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an efficient desulfurization, 
hydroconversion and feed upgrading process is provided, wherein 
sulfur-bearing, heavy hydrocarbon feedstocks, for example whole or topped 
crudes and residua, and hydrogen are contacted in a reaction zone with 
said feedstock being substantially in the liquid phase in said reaction 
zone, with a reagent selected from the group consisting of alkaline earth 
metal hydrides, alkaline earth metal oxides and mixtures thereof, at 
elevated temperatures ranging from about 500.degree. F to 2000.degree. F, 
and wherein the hydrogen partial pressure is within the range of from 
about 500 to 5000 psig. The reaction product produced as a result of the 
above process comprises an alkaline earth metal sulfide phase and a 
desulfurized, upgraded petroleum oil having a sulfur and Conradson carbon 
content lower than that of the feedstock. 
In one embodiment of the invention, the feedstock is contacted with barium 
oxide at a temperature and under a hydrogen partial pressure in the upper 
extremes of the temperature and hydrogen partial pressure ranges set out 
above to provide substantial desulfurization and demetallization while 
simultaneously hydroconverting heavy constituents of the feedstock to 
lighter, lower boiling components. Irrespective of the temperature and 
hydrogen pressure employed, barium sulfide is formed in the reaction zone 
and barium oxide may be regenerated therefrom as will be described below. 
In another embodiment of the invention, the alkaline earth metal hydrides, 
and preferably barium hydride, are supplied as preformed reagents. 
DETAILED DESCRIPTION OF THE INVENTION 
The process of this invention is generally applicable to any sulfur-bearing 
feedstock. Thus, while the process is also applicable to lighter 
distillates, it is particularly effective when utilized to treat heavy 
hydrocarbons, e.g., those containing residual oils. Preferably, therefore, 
the process of the invention is utilized for the treatment of whole or 
topped crude oils and residua. Crude oils obtained from any area of the 
world such as the Middle East, e.g., Safaniya, Arabian heavy, Iranian 
light, Gach Saran, Kuwait, etc., the U.S. or Venezuelan, e.g., 
Laquinallas, Tia Juana, Bachaquero, etc., as well as heavy gas oils, shale 
oils, heavy catalyst cycle oils, tar sands or synthetic crudes derived 
from tar sands, coal oils, bitumen derived from tar sands, and 
asphaltenes, can be treated by the process of this invention. 
Additionally, both atmospheric residuum (boiling above about 650.degree. 
F) and vacuum residuum (boiling above about 1050.degree. F) can be 
treated. Preferably, the feedstock is a sulfur-bearing heavy petroleum oil 
having at least about 10 wt.% of materials boiling above about 
1050.degree. F and more preferably at least about 25 wt.% of materials 
boiling above about 1050.degree. F. Where the feedstock is a whole crude 
it will generally contain between 1 and 3 wt.% sulfur therein, and when a 
residual feedstock, from between 2 and 7 wt.% sulfur therein, based upon 
the total feedstream. 
The feedstock may be directly introduced into the reaction zone for 
combined desulfurization and hydroconversion, without pretreatment. It is 
desirable, however, to desalt the feedstock in order to prevent NaCl 
contamination of the alkaline earth metal products of the desulfurization 
reaction. Desalting is well known in the refining industry and may be 
effected by the addition of small amounts of water to the feedstock to 
dissolve the salt followed by the use of electrical coalescers. The oil is 
then dehydrated by conventional means. 
The alkaline earth metal hydrides and alkaline earth metal oxides which may 
be employed for the process of the invention generally include the 
hydrides and oxides of the metals of Group IIA of the Periodic Table. 
Thus, hydrides and oxides of berylium, calcium, magnesium, strontium, and 
barium are suitable for use in the present process. The hydrides of barium 
and calcium are preferred due to their commercial availability as well as 
the ease with which they may be regenerated and recycled for further use. 
Furthermore, barium oxide is preferred over the other mentioned alkaline 
earth metal oxides inasmuch as it is substantially more effective as a 
desulfurizing and hydroconverting agent as compared to such other oxides. 
The alkaline earth metal hydrides or oxides can be charged in a granular 
form ranging from powders (10+ microns) to particles (14 to 35 mesh range) 
or may be blended in a powder form with the feedstock prior to charging. 
Powders are preferred, however, in order to maximize reaction rate and 
minimize the need for mechanical agitation beyond the point of initial 
blending of powders and feedstock. The alkaline earth metal hydrides or 
oxides may also be employed as a dispersion in the feedstock itself prior 
to being charged into the reaction zone. 
The amount of alkaline earth metal hydride or oxide employed may generally 
range from about 1 to about 40% by weight of the feedstock, and preferably 
from about 1 to about 25% by weight thereof, depending on the sulfur 
content of the feedstock. Thus, from about 0.1 to about 8.0 moles of 
alkaline earth metal hydride or oxide per mole sulfur in the feedstock can 
be employed, and preferably from about 0.5 to about 4, and more preferably 
from about 0.5 to about 2.0 moles of hydride or oxide per mole of feed 
sulfur. 
In preferred embodiments of the process of the invention, barium oxide will 
be employed in an amount within the range of from about 12 to about 40% by 
weight of the feedstock; barium hydride will be employed in an amount 
within the range of from about 10 to about 35% by weight of the feedstock; 
and calcium hydride will be employed in an amount within the range of from 
about 3 to about 15% by weight of the feedstock. Barium hydride and/or 
barium oxide are particularly preferred reagents. 
A hydrogen-containing gas is introduced into the reaction zone as either 
pure hydrogen (for example, from a steam reforming process) or as a 
diluted hydrogen gas stream (for example, that from refinery discard 
streams, e.g., subsequent to hydrotreating processes, gas effluent from 
cat cracker or reformer light ends streams, naphtha reformer recycle 
hydrogen streams, and the like). 
Contact of the alkaline earth metal hydride and/or oxide reagent, hydrogen 
and the feedstock is carried out at reaction conditions designed to 
maintain the feedstock substantially in the liquid phase in the reaction 
zone and to effect simultaneous desulfurization and hydroconversion of the 
feedstock. Thus, the reaction of the feedstock, reagent and hydrogen may 
be carried out at a temperature within the range of from about 500.degree. 
F to 2000.degree. F and at a hydrogen partial pressure within the range of 
from about 500 to 5000 psig. The actual conditions of temperature and 
pressure maintained within the reaction zone are important depending upon 
whether only desulfurization is desired, or combined desulfurization and 
hydroconversion of the feedstock is required. Thus, in the preferred 
embodiment of the invention wherein it is desired to simultaneously effect 
desulfurization, demetallization and substantial hydroconversion of heavy 
constituents of the feedstock to lighter, lower boiling components, the 
feedstock, reagent, preferably barium oxide or barium hydride, and 
hydrogen are contacted at a temperature within the range of from about 700 
to 1500.degree. F, preferably within the range of from about 750 to 
1000.degree. F, and under a hydrogen partial pressure ranging from about 
1500 to 3000 psig. Typical reaction holding times will range from about 15 
minutes to 90 minutes and preferably about 60 minutes. Increasing the 
temperature and/or the hydrogen partial pressure results in increasing 
hydrogen consumption by the feedstock with concomitant increasing product 
quality, including increased demetallization, substantial desulfurization, 
a substantial reduction of Conradson carbon content and a substantial 
increase in API gravity. 
It has been found that operating the reaction zone outside of these ranges 
does not yield the highly desirable simultaneous desulfurization and 
hydroconversion of the invention. In addition, in the absence of the 
hydrogen required in the reaction zone of this invention, severe cracking 
and coking of the feed occur where the oxide reagent is employed, whereas 
poor product quality is obtained where the hydride reagent is employed. 
It will also be appreciated that the process of the invention may be 
operated in a staged manner by successive treatments of feed with fresh 
charges of the reagent and hydrogen. 
The simultaneous desulfurization and hydroconversion can be conducted as a 
batch or continuous type operation. The apparatus used in carrying out the 
desulfurization and hydroconversion is of a conventional nature and can 
comprise a single reactor or multiple reactors equipped with shed rows or 
other stationary devices to encourage contacting; orifice mixers; 
efficient stirring devices such as mechanical agitators, jets of 
restricted internal diameter, turbomixers, and the like; or a packed bed, 
or other such means as described in U.S. Pat. No. 3,787,315 all of which 
is incorporated herein by reference thereto. 
The feedstock and reagent can be passed through one or more reactors in 
concurrent, crosscurrent, or countercurrent flow, etc. It is preferable 
that oxygen and water be excluded from the reaction zones; therefore, the 
reaction system is normally purged with dry nitrogen and the feedstock 
dried prior to introduction into the reactor. It is understood that trace 
amounts of water, i.e., less than about 0.5 wt.%, preferably less than 
about 0.1 wt.% based on total feed, can be present in the reactor. The 
resulting oil dispersion is subsequently removed from the desulfurization 
zone and resolved by conventional means. 
The salt produced in the above reaction generally comprises an alkaline 
earth metal sulfide in admixture with small amounts of coke and 
demetallization products. These salts are conveniently separated from the 
desulfurized feedstock by filtration, centrifugation, decantation, etc. 
In accordance with the present invention the desired alkaline earth 
reagent, i.e., hydride or oxide, can be regenerated from the alkaline 
earth metal sulfides formed in the reaction zone by the well known, 
commercially practiced reactions shown below, and described for barium 
salts in Volumes 3 and 11 of the Encyclopedia of Chemical Technology, 2nd 
Edition, from Interscience Publishers, New York (1964). 
______________________________________ 
STEP-A CONVERSION OF ALKALINE EARTH 
SULFIDES TO CARBONATES 
##STR1## 
where M = Ba or Ca 
STEP-B CONVERSION OF CARBONATES TO OXIDES 
##STR2## 
STEP-C CONVERSION OF OXIDE TO METAL 
##STR3## 
STEP-D CONVERSION OF METAL TO HYDRIDE 
##STR4## 
Alternatively, the metal oxide may be converted to the metal hydride by 
reaction with phenol, followed by hydrogenation of the phenolate salt, as 
described in U.S. Pat. No. 2,392,545, which is also incorporated herein by 
reference thereto. 
Barium and calcium hydrides may also be regenerated by reaction of the 
metal sulfides with hydrochloric acid to provide the metal chlorides and 
release hydrogen sulfide. The metal chlorides are subsequently reduced by 
hydrogen and ammonia, or by hydrogen and zinc, to provide the metal 
hydrides, as described in British Pat. No. 496,294.