Three stage hydroprocessing including a vapor stage

A three stage hydroprocessing process includes two liquid and one vapor reaction stages, with a hydrogen containing vapor effluent produced in both liquid stages. The second liquid stage vapor effluent comprises part of the first liquid stage feed and the first liquid stage vapor effluent is the feed for the vapor stage. At least a portion of the hydrogen for the first liquid stage and vapor stage reactions is respectively provided by the hydrogen in the second and first liquid stage vapor effluents.

BACKGROUND OF THE DISCLOSURE 
1. Field of the Invention 
The present invention relates to hydroprocessing hydrocarbonaceous feeds 
using two liquid and one vapor hydroprocessing reaction stages. More 
particularly the invention relates to catalytically hydroprocessing a 
hydrocarbonaceous feed in two liquid reaction stages with liquid and vapor 
separation after each stage and one vapor reaction stage, in which both 
liquid stages produce an effluent comprising a liquid and a 
hydrogen-containing vapor, with the hydrogen-containing first liquid stage 
vapor effluent hydroprocessed in the vapor stage using the hydrogen in the 
vapor and the second liquid stage vapor effluent providing the hydrogen 
for the first stage. Most of the hydroprocessing is achieved in the first 
stage, with the first stage liquid effluent comprising the second stage 
feed, and with fresh hydrogen used in the second stage to produce a 
hydroprocessed product. 
2. Background of the Invention 
As supplies of lighter and cleaner feeds dwindle, the petroleum industry 
will need to rely more heavily on relatively high boiling feeds derived 
from such materials as coal, tar sands, shale oil, and heavy crudes, all 
of which typically contain significantly more undesirable components, 
especially from an environmental point of view. These components include 
halides, metals, unsaturates and heteroatoms such as sulfur, nitrogen, and 
oxygen. Furthermore, due to environmental concerns, specifications for 
fuels, lubricants, and chemical products, with respect to such undesirable 
components, are continually becoming tighter. Consequently, such feeds and 
product streams require more upgrading in order to reduce the content of 
such undesirable components and this increases the cost of the finished 
products. 
In a hydroprocessing process, at least a portion of the heteroatom 
compounds are removed, the molecular structure of the feed is changed, or 
both occur by reacting the feed with hydrogen in the presence of a 
suitable hydroprocessing catalyst. Hydroprocessing includes hydrogenation, 
hydrocracking, hydrotreating, hydroisomerization and hydrodewaxing, and 
therefore plays an important role in upgrading petroleum streams to meet 
more stringent quality requirements. For example, there is an increasing 
demand for improved heteroatom removal, aromatic saturation and boiling 
point reduction. In order to achieve these goals more economically, 
various process configurations have been developed, including the use of 
multiple hydroprocessing stages as is disclosed, for example, in European 
patent publication 0 553 920 A1 and U.S. Pat. Nos. 2,952,626; 4,021,330; 
4,243,519; 4,801,373 and 5,292,428. 
SUMMARY OF THE INVENTION 
The invention relates to a three stage process for hydroprocessing a 
hydrocarbonaceous feed in which the feed is reacted with hydrogen in the 
presence of a hydroprocessing catalyst in two separate, liquid reaction 
stages to produce a hydroprocessed hydrocarbonaceous product liquid and 
hydrocarbonaceous vapors containing unreacted hydrogen, with vapor and 
liquid separation after each liquid stage, wherein the vapors from the 
first liquid reaction stage are hydroprocessed by reacting with hydrogen 
in a vapor reaction stage and wherein the hydrogen in the vapor effluents 
is used for the hydroprocessing. A mixture of the hydrocarbonaceous feed 
to be hydroprocessed and the hydrogen containing second stage vapor 
effluent comprises the first stage feed, with the partially hydroprocessed 
first stage liquid effluent and fresh hydrogen being the feed to the 
second stage. The first stage vapor effluent containing unreacted hydrogen 
is passed into the vapor stage in which it is hydroprocessed with the 
hydrogen in the vapor. The hydroprocessed vapor may be cooled to recover a 
portion (e.g., C.sub.4+ -C.sub.5+ material) as liquid which may be blended 
into the second stage product liquid. Sufficient fresh hydrogen in the 
form of either hydrogen or a hydrogen-containing treat gas is introduced 
into the second stage to insure that the hydrocarbonaceous vapor effluents 
from the second and first liquid stages contain sufficient hydrogen 
(unreacted hydrogen) to provide at least a portion or all of the hydrogen 
required for the first liquid stage and the vapor stage hydroprocessing. 
The term "hydrogen" as used herein refers to hydrogen gas. More 
particularly the invention comprises a hydroprocessing process which 
includes two liquid and one vapor reaction stages and which comprises the 
steps of: 
(a) reacting a hydrocarbonaceous feed comprising a mixture of liquid and 
vapor with hydrogen in a first hydroprocessing liquid reaction stage in 
the presence of a hydroprocessing catalyst to form a first stage effluent 
comprising a partially hydroprocessed hydrocarbonaceous liquid and a 
hydrogen-containing hydrocarbonaceous vapor, wherein said feed vapor 
comprises hydrogen-containing second stage hydrocarbonaceous vapor 
effluent which provides at least a portion of said hydrogen for said first 
stage reaction and for said vapor reaction stage and wherein said first 
stage vapor effluent contains unreacted hydrogen; 
(b) separating said first stage liquid and vapor effluent; 
(c) reacting said first stage liquid effluent with hydrogen in the presence 
of a hydroprocessing catalyst in said second hydroprocessing liquid 
reaction stage to produce a second stage effluent comprising a 
hydroprocessed hydrocarbonaceous product liquid and vapor, wherein said 
vapor contains unreacted hydrogen and wherein said second stage reaction 
hydrogen is provided by fresh hydrogen; 
(d) separating said second stage liquid and vapor effluent and recovering 
said hydroprocessed product liquid, and 
(e) reacting said hydrogen-containing first stage vapor effluent with 
hydrogen in said vapor in the presence of a hydroprocessing catalyst in 
said vapor reaction stage to form a hydroprocessed hydrocarbonaceous 
vapor, wherein at least a portion of said hydrogen for said reaction is 
provided by hydrogen in said first stage vapor effluent. 
The hydroprocessed vapor may then be cooled to condense out the higher 
boiling hydroprocessed material as liquid which may then be separated from 
gaseous contaminants and lower boiling material by simple separation 
means, such as a drum separator. 
The three reaction stages may be in a single reaction vessel or in two or 
three separate vessels. The catalyst used in each stage may be the same or 
different, depending on the feed and the process objectives. Further 
embodiments include stripping the recovered hydroprocessed product to 
remove undesirable reaction products, condensing the hydroprocessed vapors 
and stripping the resulting condensate and, optionally, combining the 
condensate with the hydroprocessed product liquid. The condensate 
comprises the lighter or lower boiling feed fraction. While in many cases 
is preferred that the second stage vapor effluent contain all of the 
hydrogen required for the first liquid stage hydroprocessing reaction and 
that the first liquid stage vapor effluent contain all of the hydrogen 
required for the vapor phase hydroprocessing reaction, this is not always 
possible. Therefore, in some cases fresh hydrogen or a hydrogen-containing 
treat gas may also be passed into either or both the first liquid stage 
and the vapor stage. 
In the practice of the invention, the fresh hydrocarbonaceous feed fed into 
the first stage reaction zone is mostly liquid and typically completely 
liquid. During the hydroprocessing, at least a portion of the lighter or 
lower boiling feed components are vaporized in each liquid stage. The 
amount of feed vaporization will depend on the nature of the feed and the 
temperature and pressure in the reaction stages and may range between 
about 5-80 wt. %. Thus, by liquid reaction stage is meant that some of the 
feed being hydroprocessed is in the liquid stage. In most cases the 
hydrocarbonaceous feed will comprise hydrocarbons. In an embodiment in 
which the process is a hydrotreating process for a sulfur and nitrogen 
containing distillate or diesel fuel fraction, the hydroprocessing forms 
H.sub.2 S and NH.sub.3, some of which is dissolved in the hydroprocessed 
product liquid and vapor condensate. Simple stripping removes these 
species from these liquids.

DETAILED DESCRIPTION 
By hydroprocessing is meant a process in which hydrogen reacts with a 
hydrocarbonaceous feed to remove one or more heteroatom impurities such as 
sulfur, nitrogen, and oxygen, to change or convert the molecular structure 
of at least a portion of the feed, or both. Non-limiting examples of 
hydroprocessing processes which can be practiced by the present invention 
include forming lower boiling fractions from light and heavy feeds by 
hydrocracking; hydrogenating aromatics and other unsaturates; 
hydroisomerization and/or catalytic dewaxing of waxes and waxy feeds, and 
demetallation of heavy streams. Ring-opening, particularly of naphthenic 
rings, can also be considered a hydroprocessing process. By 
hydrocarbonaceous feed is meant a primarily hydrocarbon material obtained 
or derived from crude petroleum oil, from tar sands, from coal 
liquefaction, shale oil and hydrocarbon synthesis. The reaction stages 
used in the practice of the present invention are operated at suitable 
temperatures and pressures for the desired reaction. For example, typical 
hydroprocessing temperatures will range from about 40.degree. C. to about 
450.degree. C. at pressures from about 50 psig to about 3,000 psig, 
preferably 50 to 2,500 psig. 
Feeds suitable for use in such systems include those ranging from the 
naphtha boiling range to heavy feeds, such as gas oils and resids. 
Non-limiting examples of such feeds which can be used in the practice of 
the present invention include vacuum resid, atmospheric resid, vacuum gas 
oil (VGO), atmospheric gas oil (AGO), heavy atmospheric gas oil (HAGO), 
steam cracked gas oil (SCGO), deasphalted oil (DAO), light cat cycle oil 
(LCCO), natural and synthetic feeds derived from tar sands, shale oil, 
coal liquefaction and hydrocarbons synthesized from a mixture of H.sub.2 
and CO via a Fischer-Tropsch type of hydrocarbon synthesis. 
For purposes of hydroprocessing and in the context of the invention, the 
terms "fresh hydrogen" and "hydrogen-containing treat gas" are synonymous 
and may be either pure hydrogen or a hydrogen-containing treat gas which 
is a treat gas stream containing hydrogen in an amount at least sufficient 
for the intended reaction plus other gas or gasses (e.g., nitrogen and 
light hydrocarbons such as methane) which will not adversely interfere 
with or affect either the reactions or the products. These terms exclude 
recycled vapor effluent from another stage which has not been processed to 
remove contaminants and at least a portion of any hydrocarbonaceous vapors 
present. They are meant to include either hydrogen or a 
hydrogen-containing gas from any convenient source, including the 
hydrogen-containing gas comprising unreacted hydrogen recovered from 
hydroprocessed vapor effluent, after first removing at least a portion and 
preferably most of the hydrocarbons (e.g., C.sub.4+ -C.sub.5+) or 
hydrocarbonaceous material and any contaminants (e.g., H.sub.2 S and 
NH.sub.3) from the vapor, to produce a clean, hydrogen rich treat gas. The 
treat gas stream introduced into a reaction stage will preferably contain 
at least about 50 vol. %, more preferably at least about 75 vol. % 
hydrogen. In operations in which unreacted hydrogen in the vapor effluent 
of any particular stage is used for hydroprocessing in a subsequent stage 
or stages, there must be sufficient hydrogen present in the fresh treat 
gas introduced into that stage for the vapor effluent of that stage to 
contain sufficient hydrogen for the subsequent stage or stages. 
The invention can be further understood with reference to FIG. 1 which is a 
schematic drawing of a hydroprocessing unit useful in the practice of the 
invention. In this particular embodiment the hydroprocessing process is a 
hydrotreating process and the reaction stages hydrotreating stages. For 
the sake of simplicity, not all process reaction vessel internals, valves, 
pumps, heat transfer devices etc. are shown. Referring to FIG. 1, a 
hydrotreating unit 10 comprises a reaction vessel 12, a heat exchanger 33, 
a simple drum type of gas-liquid separator 24 and, optionally, a stripper 
26 for interstage stripping shown in phantom. Vessel 12 contains three 
reaction stages or zones 14, 16, and 18, each comprising a fixed bed of 
hydrotreating catalyst and each having respective downstream gas-liquid 
separation means 20, 22 and 24, with 20 and 22 located in the reaction 
vessel and 24 external of the vessel, as shown. Each of the two gas-liquid 
separation means located in the reaction vessel may be a simple horizontal 
tray containing a plurality of chimneys or hollow tubes extending 
vertically therethrough, as is well known. Not shown are some of the gas 
and liquid flow distribution means above each catalyst bed for 
distributing liquid onto and horizontally across the catalyst bed below. 
Such means are well known to those skilled in the art and may include, for 
example, trays such as sieve trays, bubble cap trays, trays with spray 
nozzles, chimneys or tubes, etc., as is known. The hydrocarbon feed to be 
hydrotreated is passed via line 28 into vessel 12 above the first liquid 
stage 16 and down onto and across the catalyst bed below. In this 
particular illustration of the invention, the feed is a petroleum derived 
distillate or diesel fuel fraction containing heteroatom compounds of 
sulfur, nitrogen and perhaps oxygen. Fresh hydrogen or a 
hydrogen-containing treat gas is passed into the top of vessel 12 above 
the second stage via lines 30 and 32, with partially hydrotreated first 
stage liquid effluent recycled via line 34 from the first stage into the 
top of the reactor via line 32, as part of the second stage feed. The 
mixture of treat gas and feed passes down through the second liquid stage 
hydrotreating catalyst bed 14 in which a portion of the hydrogen reacts 
with the second stage feed to produce a second stage effluent comprising a 
hydrotreated product liquid and vapor, wherein the vapor comprises a 
mixture of unreacted hydrogen, some of the lighter or lower boiling feed 
components, and gaseous reaction products such as methane, H.sub.2 S and 
NH.sub.3. Most of the sulfur and other heteroatom compounds are removed 
from the feed in the first stage. In two stage hydrotreating processes, it 
is not unusual for 60%, 75% and even .gtoreq.90% of the heteroatoms (S, N 
and 0) to be removed from the liquid in the first stage. Therefore, the 
second stage catalyst can be a more active, but less sulfur tolerant 
catalyst for aromatics saturation which, in this embodiment comprises 
nickel-molybdenum or nickel-tungsten catalytic metal components on an 
alumina support. The second stage vapor effluent is separated from the 
hydrotreated second stage product liquid effluent by vapor and liquid 
separation means 20, with the hydrotreated product liquid removed via line 
36 and sent to a product stripper, not shown, to strip out any dissolved 
H.sub.2 S and NH.sub.3. The second stage vapor effluent containing 
unreacted hydrogen passes down through the gas and liquid separator 20 as 
indicated by the two arrows, into the first liquid reaction stage and down 
through the first stage catalyst bed 16, where it contacts the incoming 
feed to be hydrotreated. In the first reaction stage, at least a portion 
of the unreacted hydrogen in the second stage vapor effluent reacts with 
the fresh feed containing the sulfur, nitrogen and other undesirable 
compounds to form a first stage effluent comprising a mixture of partially 
hydrotreated liquid and a vapor comprising unreacted hydrogen, lighter 
feed components containing heteroatom compounds, H.sub.2 S and NH.sub.3. 
This mixture then passes down to the first stage gas and liquid separation 
means 22, from which the partially hydrotreated liquid is withdrawn via 
line 34 and passed, via lines 34 and 32 into the top of the reactor and 
through the second stage catalyst bed with the treat gas, to form the 
hydrotreated product liquid. Most (e.g., &gt;50%) of the heteroatom compounds 
are removed from the feed in the first stage, so that a relatively cleaner 
feed is recycled back into the second stage. The vapor effluent from the 
first stage reaction includes unreacted hydrogen, heteroatom-containing 
hydrocarbon vapors and H.sub.2 S and NH.sub.3 formed in the first and 
second stages, and passes down through the third or vapor stage reaction 
catalyst bed 18, in which at least a portion of the unreacted hydrogen 
remaining in the vapor reacts with any sulfur and nitrogen compounds in 
the gaseous feed components to form additional H.sub.2 S and NH.sub.3. The 
third stage vapor effluent passes down and out the bottom of the reactor 
vessel via line 31 and through a heat exchanger 33, in which the 
hydrotreated hydrocarbons are condensed to liquid, with the mixture of 
liquid and remaining gas passing into the separator vessel 24 via line 35. 
Typically the C.sub.4+ -C.sub.5+ hydrocarbons are condensed to liquid. 
The hydrotreating catalyst in the first stage must be suitable for 
processing fresh feed to the reactor which has higher levels of sulfur 
than the feed to the second stage. The more sulfur resistant catalyst in 
the first and third stages will typically comprise cobalt and molybdenum 
metal catalytic components supported on alumina. The gas-liquid separator 
24 may be a simple drum separator, with the sulfur and nitrogen reduced 
liquid removed via line 36 as light product liquid. The final H.sub.2 S 
and NH.sub.3 containing gas is removed via line 37 and sent to processing 
(e.g., scrubbing with an aqueous amine solution) for sulfur and ammonia 
removal. 
The liquid effluent from the first stage which is withdrawn via line 34, 
will contain small amounts of dissolved H.sub.2 S and NH.sub.3. This 
liquid is sent to the second stage which operates in a relatively clean 
reaction environment (i.e., the feed to the second stage is relatively low 
in heteroatom impurities relative to the first stage and the fresh 
hydrogen or hydrogen-containing treat gas to the second stage is 
essentially free of heteroatom species). In some cases it may be 
advantageous to further clean the liquid feed (the first stage effluent 
liquid) to the second stage by removing the relatively small amounts of 
H.sub.2 S and NH.sub.3 which may be dissolved in it. A cleaner feed to the 
second stage will boost the second stage kinetics, particularly if the 
second stage uses a high performance catalyst which may be sensitive to 
higher levels of H.sub.2 S and NH.sub.3. In such cases, at least a portion 
of the first stage hydrotreated liquid is optionally passed into stripping 
vessel 26 via lines 34 and 38, in which it flows down and meets an 
uprising, countercurrent stripping gas such as steam entering via line 40, 
which strips at least some of the dissolved H.sub.2 S and NH.sub.3 out of 
the treated liquid before it enters the second stage. The stripped liquid 
is removed from the bottom of the vessel via line 42 and passed into the 
top of the hydrotreating vessel 12, via lines 34 and 32. The stripper 
contains suitable medium such as packing, mesh, trays or other well known 
means for increasing the contact area between the stripping gas and the 
liquid, as is well known. The H.sub.2 S and NH.sub.3 containing stripping 
gas exits out of the top of the stripping vessel via line 44 and is sent 
to further processing. Thus, in this embodiment of the process of the 
invention, the hydrogen containing treat gas passes down through the 
reactor vessel 12 once, which eliminates the need for expensive 
inter-stage compression. With the only inter-stage recycle being the 
liquid recycle from the first stage reaction zone back up to the second 
stage, a simple and relatively inexpensive liquid pump (not shown) is all 
that is needed. The third or vapor stage hydrotreating zone which 
hydrotreats the sulfur and nitrogen containing vaporized feed components, 
permits the hydrotreated hydrocarbon vapor components to be condensed to 
liquid, which may then be blended directly into the final product liquid 
without further treatment. 
FIG. 2 is a brief schematic of another embodiment of a process of the 
invention similar in many respects to that of FIG. 1, but in which the two 
liquid and one vapor hydrotreating stages or zones are in separate vessels 
and wherein the first liquid stage gas and liquid separation means is in 
the bottom of the vessel containing the third or vapor reaction stage. 
Thus, a hydrotreating unit 50 comprises first and second liquid stage 
reaction vessels 52 and 54 containing respective fixed catalyst beds 56 
and 58 within, for hydrotreating a distillate or diesel feed. A third 
vessel 60 is a dual function vessel containing a gas/liquid separation 
zone 62 at the bottom and a vapor stage catalyst bed 64 in its upper 
portion for removing sulfur and nitrogen from the hydrocarbon vapors 
present in the vapor effluent from the first stage. Also shown are a 
liquid circulation pump 66, a heat exchanger 79 and a simple drum 
separator 68. A treat gas comprising hydrogen enters the second stage 
reaction vessel 54 via lines 70 and 72 and mixes with partially 
hydrotreated feed entering via line 74. Most (e.g., &gt;50%) of the feed 
hydrotreating is accomplished in the first stage hydrotreating vessel 52. 
The second stage is at a higher pressure than the first stage and most of 
the sulfur and nitrogen compounds have been removed from the feed in the 
first stage, so that a more active, and less sulfur tolerant, higher 
pressure hydrotreating catalyst can be used in the second stage. The 
liquid and treat gas pass down through the catalyst bed and the hydrogen 
reacts with the feed to remove sulfur and nitrogen compounds to form 
H.sub.2 S and NH.sub.3, with the hydrotreated product liquid and the vapor 
effluent from the second stage passing out through the bottom of the 
vessel via line 78, heat exchanger 79 and line 81, and into drum separator 
68 in which the gas and liquid phases are separated. The heat exchanger 79 
is optional and may be used to cool the mixed effluent down to a 
temperature sufficient to condense the heavier (e.g., C.sub.4+ -C.sub.5+) 
hydrotreated hydrocarbon vapors, if desired. If necessary and if desired, 
the reaction conditions are sufficiently severe to saturate aromatics 
present in the feed. The hydrotreated product liquid is removed from the 
separator via line 80. The vapor phase, containing vaporized hydrocarbons, 
unreacted hydrogen, gas reaction products, H.sub.2 S and NH.sub.3 is 
removed via line 82 and passed into line 84 where it mixes with the fresh 
incoming feed from line 86. The feed and vapor mixture passes down into 
vessel 52 and cocurrently down through the catalyst bed which contains a 
more sulfur tolerant catalyst as in the embodiment above in FIG. 1, in 
which the hydrogen reacts with the feed to remove sulfur and nitrogen 
compounds as H.sub.2 S and NH.sub.3 and also saturate olefins and 
aromatics, to form a partially hydrotreated liquid and a vapor containing 
vaporized feed components, some unreacted hydrogen, H.sub.2 S and 
NH.sub.3. The vapor and liquid effluent from the first stage is removed 
from the bottom of the vessel via line 88 and passed into the gas and 
liquid separation zone 62 in vessel 60. The liquid is removed from the 
bottom of 60 via line 90 and passed up into the top of the second stage 
reactor vessel 54, via pump 66, line 74 and line 72. The vapor phase 
passes up into hydrotreating catalyst bed 64 in which the remaining sulfur 
and nitrogen compounds are removed from the vaporized feed components by 
reacting with the hydrogen in the gas to convert any remaining sulfur and 
nitrogen compounds into H.sub.2 S and NH.sub.3 which are removed from the 
top of the vessel via line 92, along with the hydrotreated hydrocarbon 
vapor components. This hydrotreated gas is then passed via line 92 through 
a heat exchanger and knock-out or separation drum (not shown) as in FIG. 
1, and the recovered hydrotreated lighter hydrocarbon liquid optionally 
blended with the heavier hydrotreated product liquid recovered via line 
80. 
FIG. 3 is a schematic illustrating yet another embodiment of the process of 
the invention which, as with the illustrations above, will be explained 
with specific reference to hydrotreating a petroleum derived distillate or 
diesel fuel for simplicity. Thus, in FIG. 3 a hydrotreating unit 100 is 
shown which comprises first and second liquid stage reaction vessels 102 
and 104 containing respective fixed catalyst beds 106 and 108 within, for 
hydrotreating a raw distillate or diesel fuel feed. Also shown are a heat 
exchanger 114, gas and liquid separator 116, product stripper 118, gas 
scrubber 120, gas compressor 122 and liquid transfer pump 124. Below the 
fixed bed of hydrotreating catalyst 106 in the first reaction stage vessel 
102 is a gas and liquid separating means 110, followed by another fixed 
bed of hydrotreating catalyst 112 which comprises a vapor reaction stage 
for hydrotreating fractions of the liquid feed which have been vaporized 
to form part of the vapor stream during the reactions. Instead of a 
separate separator, the gas and liquid separating means for the second 
stage reaction effluent is the space 114 at the bottom of the reactor 104 
under the catalyst bed 108. Alternately, a separator vessel could be used 
to separate the second stage vapor and liquid effluents. In operation, 
fresh feed is passed into 102 via lines 126 and 128, along with 
hydrogen-containing second stage vapor effluent from line 130 recovered 
from the second stage reactor, as shown. The fresh feed and vapor pass 
cocurrently down through the first stage catalyst bed in which the 
hydrogen reacts with the heteroatom compounds and unsaturates to remove 
most (e.g., &gt;50%) of the sulfur and nitrogen compounds as H.sub.2 S and 
NH.sub.3, and saturate at least a portion of the aromatics. The first 
stage reaction effluent comprises a mixture of partially hydrotreated 
liquid and vapor. The vapor contains unreacted hydrogen, along with 
H.sub.2 S, NH.sub.3, and hydrocarbon vapors. This vapor passes down into 
the gas and liquid separator 110 to separate the liquid from the vapor. 
The partially hydrotreated liquid is removed from the separator via line 
132 and passed to liquid transfer pump 124. The hydrogen containing first 
stage vapor effluent passes from the gas and liquid separator 110, down 
through vapor hydrotreating catalyst bed 112, in which the vaporized feed 
components are hydrotreated with the unreacted hydrogen in the vapor to 
further remove sulfur and nitrogen to form hydrotreated hydrocarbons and 
additional H.sub.2 S and NH.sub.3. The hydrotreated vapor is removed from 
the bottom of vessel 102 via line 113 and then passed through a heat 
exchanger 114 in which it is cooled to condense some of the hydrocarbons 
(e.g., C.sub.4+ -C.sub.5+) to liquid. The resulting gas and liquid mixture 
is passed into gas and liquid separating drum 116 via line 115 in which 
the gas is separated from the condensed hydrocarbon liquid. The 
hydrocarbon liquid is removed from the separator via line 117 and passed 
into a stripper 118 in which the downflowing liquid is stripped by an 
upflowing stripping gas such as steam or nitrogen entering via line 133. 
The stripping gas removes H.sub.2 S and NH.sub.3 dissolved in the gas, 
with the heteroatom laden gas removed via line 135 from the top of the 
stripper and the stripped liquid removed from the bottom via line 134. The 
stripped hydrocarbon liquid may then be combined with the second stage 
stripped (not shown) product liquid. The gas phase is removed from 
separator 116 via line 136 and passed into the bottom of a scrubbing tower 
120, in which the uprising gas contacts a downflowing, aqueous amine 
solution entering near the top of the tower via line 138. The amine 
solution removes the H.sub.2 S and NH.sub.3 from the gas and passes out of 
the bottom of the tower via line 140 and sent to further processing. The 
cleaned gas, substantially reduced in H.sub.2 S and NH.sub.3, contains 
valuable and usable hydrogen, and passes out of the top of the tower via 
line 142 and is passed into compressor 122 which raises the gas pressure 
high enough for it to be recycled back into the first stage via lines 146, 
130 and 128 as treat gas. Purge line 144 prevents excess methane and other 
diluents from building up in the process. The mostly hydrotreated 
hydrocarbon liquid is pumped into the top of the second stage reactor via 
lines 125 and 103. Fresh hydrogen or a hydrogen-containing treat gas is 
also fed into the top of the second stage reactor via lines 101 and 103. 
The hydrocarbon liquid and fresh treat gas pass cocurrently down through 
second stage hydrotreating catalyst bed 108 in which the hydrogen reacts 
with and hydrotreats the hydrocarbon liquid to convert most of the 
remaining heteroatom compounds to H.sub.2 S and NH.sub.3 and saturate any 
remaining unsaturates to produce a hydrotreated product liquid which, in 
this example, is a light distillate or diesel fuel fraction. The vapor and 
liquid effluent from the second stage catalyst bed pass down into the 
bottom 114 of the reactor in which the vapor separates from the liquid. 
The liquid is removed from the bottom as hydrotreated product via line 15 
and sent to product stripping (not shown) to strip out dissolved H.sub.2 S 
and NH.sub.3. The hydrogen containing vapor effluent is removed from the 
reactor via line 130 and passed back into the top of the first stage 
reactor to provide at least a portion of the hydrogen for the first stage 
hydrotreating. This hydrogen containing vapor effluent in line 130 may 
also be cooled down to condense out some of the vaporized hydrocarbons in 
the second stage vapor effluent. As is the case for the embodiments 
illustrated above in FIGS. 1 and 2, the pressure in the second stage 
reactor in this embodiment is sufficiently higher than that in the first 
stage reactor to avoid the need for a compressor to pass the gas from the 
second to first stage. In all cases, and as illustrated in FIG. 3, recycle 
gas cleanup can be integrated into the hydroprocessing process if desired 
or if necessary. In a still further embodiment of the process of the 
invention, H.sub.2 S and NH.sub.3 can be scrubbed out of the vapor stage 
reaction gas effluent and recycled as part of the feed to the second stage 
liquid reaction zone, instead of to the first stage liquid reaction zone. 
This option applies to all of the embodiments described herein. 
Those skilled in the art will appreciate that the invention can be extended 
to more than two liquid and one vapor stages. Thus, one may also employ 
three or more liquid stages in which the partially processed liquid 
effluent from the first stage is the second stage feed, the second stage 
liquid effluent is the third stage feed, and so on, with attendant vapor 
stage processing in one or more vapor reaction stages. By reaction stage 
is meant at least one catalytic reaction zone in which the liquid, vapor 
or mixture thereof reacts with hydrogen in the presence of a suitable 
hydroprocessing catalyst to produce an at least partially hydroprocessed 
effluent. The catalyst in a reaction zone can be in the form of a fixed 
bed, a fluidized bed or dispersed in a slurry liquid. More than one 
catalyst can also be employed in a particular zone as a mixture or in the 
form of layers (for a fixed bed). Further, where fixed beds are employed, 
more than one bed of the same or different catalyst may be used, so that 
there will be more than one reaction zone. The beds may be spaced apart 
with optional gas and liquid distribution means upstream of each bed, or 
one bed of two or more separate catalysts may be used in which each 
catalyst is in the form of a layer, with little or no spacing between the 
layers. The hydrogen and liquid will pass successively from zone to the 
next. The hydrocarbonaceous material and hydrogen or treat gas are 
introduced at the same or opposite ends of the stage and the liquid and/or 
vapor effluent removed from a respective end. 
The term "hydrotreating" as used herein refers to processes wherein a 
hydrogen-containing treat gas is used in the presence of a suitable 
catalyst which is primarily active for the removal of heteroatoms, such as 
sulfur, and nitrogen, nonaromatics saturation and, optionally, saturation 
of aromatics. Suitable hydrotreating catalysts for use in a hydrotreating 
embodiment of the invention include any conventional hydrotreating 
catalyst. Examples include catalysts comprising of at least one Group VIII 
metal catalytic component, preferably Fe, Co and Ni, more preferably Co 
and/or Ni, and most preferably Co; and at least one Group VI metal 
catalytic component, preferably Mo and W, more preferably Mo, on a high 
surface area support material, such as alumina. Other suitable 
hydrotreating catalysts include zeolitic catalysts, as well as noble metal 
catalysts where the noble metal is selected from Pd and Pt. As mentioned 
above, it is within the scope of the present invention that more than one 
type of hydrotreating catalyst may be used in the same reaction stage or 
zone. Typical hydrotreating temperatures range from about 100.degree. C. 
to about 400.degree. C. with pressures from about 50 psig to about 3,000 
psig, preferably from about 50 psig to about 2,500 psig. If one of the 
reaction stages is a hydrocracking stage, the catalyst can be any suitable 
conventional hydrocracking catalyst run at typical hydrocracking 
conditions. Typical hydrocracking catalysts are described in U.S. Pat. No. 
4,921,595 to UOP, which is incorporated herein by reference. Such 
catalysts are typically comprised of a Group VIII metal hydrogenating 
component on a zeolite cracking base. Hydrocracking conditions include 
temperatures from about 200.degree. to 425.degree. C.; a pressure of about 
200 psig to about 3,000 psig; and liquid hourly space velocity from about 
0.5 to 10 V/V/Hr, preferably from about 1 to 5 V/V/Hr. Non-limiting 
examples of aromatic hydrogenation catalysts include nickel, 
cobalt-molybdenum, nickel-molybdenum, and nickel-tungsten. Noble metal 
(e.g., platinum and/or palladium) containing catalysts can also be used. 
The aromatic saturation zone is preferably operated at a temperature from 
about 40.degree. C. to about 400.degree. C., more preferably from about 
260.degree. C. to about 350.degree. C., at a pressure from about 100 psig 
to about 3,000 psig, preferably from about 200 psig to about 1,200 psig, 
and at a liquid hourly space velocity (LHSV) of from about 0.3 V/V/Hr. to 
about 2 V/V/Hr. 
It is understood that various other embodiments and modifications in the 
practice of the invention will be apparent to, and can be readily made by, 
those skilled in the art without departing from the scope and spirit of 
the invention described above. Accordingly, it is not intended that the 
scope of the claims appended hereto be limited to the exact description 
set forth above, but rather that the claims be construed as encompassing 
all of the features of patentable novelty which reside in the present 
invention, including all the features and embodiments which would be 
treated as equivalents thereof by those skilled in the art to which the 
invention pertains.