CA1168614A - Demetalation of hydrocarbonaceous feeds with h.sub.2s - Google Patents

Abstract

ABSTRACT

Metallic contaminants, such as selenium, arsenic, iron and sodium are removed from a hydrocarbonaceous fluid feed stream by contacting the feed stream with a gas comprising substantially pure hydrogen sulfide (H2S) or a mixture of hydrogen sulfide and hydrogen (H2).

Description

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rhis invention relates to demetalation of hydrocarbonaceous feeds. More particularly, this invention relates to an improved method of non-catalytic demetalation of hydrocarbonaceous fluid feeds using a pressurized guard bed or a heat soak zone upstream from hydroprocessing units.
Increasing worldwide demand for petroleum products combined with continuously increasing prices for petroleum and products recovered therefrom, has prompted a renewed interest in the sources of hydrocarbons which are less accessible than crude oil of the Middle East and other countries. Alternative sources of energy have been known for a long time, however, the methods of exploration and processing of these sources have not thus far been economically competitive with the traditional sources of petroleum. However, increasing demand for petroleum products, and the resulting continuous increases in prices thereof, makes it apparent that formerly noncompetitive sources of energy will become competitive in the near future and therefore will supply a substantial amount of our energy needs. One of the more promising sources of hydrocarbons that will be used in the future to supply our growing demand are synthetic hydrocarbonaceous fluids obtained from oil shale, normally solid coal, tar, including tar sands, etc. These hydrocarbonaceous fluids are generally referred to by generic terms, such as "synthetic crude oil" or "synthetic oil fractions." The term hydro-~5 carbonaceous fluids as used herein is not limited to synthetically-derived hydrocarbons. The term refers to hydrocarbon fluids derived from conventional sources, e.g., petroleum, and from the alternative sources of energy, e.g., shale oil, tar sands and coal fluids.
One of the problems encountered in processing the afore-mentioned hydrocarbonaceous fluids resides in the presence of heavy metal contaminants therein which affect the ease of processing of such fluids into satisfactory sources of energy and into precursors for the synthesis of other desired materials, e.g., plastics, resins, etc. For example, shale oil contains appreciable quanti-ties of iron, selenium and arsenic, which are potential poisons of 9~

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- 3~6~4 F-07s8 -2-hydrotreating catalysts. Accordingly, such impurities must be removed from shale oil and cther sources of hydrocarbons prior to processing the shale oil in unit operations containing catalysts which may be poisoned by the impurities contained therein.
Attempts have been made in prior art to remove such contaminants by means of catalytic or noncatalytic methods. Thus, for example, catalytic methods of removal of arsenic are disclosed in U. S. Patents 3,622,498 and 3,496,09g, while noncatalytic methods are disclosed in U. S. Patent 2,778,779. In addition, U. S. Patent 4,029,571 discloses the thermal "heat soak" demetalation method, whereby arsenic and heavy metal contaminants are precipitated from shale oil in the presence of hydrogen, with or without the use of a separate hydrogenation step. A similar process is also disclosed by Sullivan et al in Catalytic Hydroprocess_n~ of Shale Oil to Produce Distillate Fuels, ADVANCES IN CHEMISTRY, Vol. 179, pages 25-51 (1979~.
However, the prior art methods of removing heavy metal and other contaminants from shale oil and other hydrocarbonaceous fluids have met only with partial success because a substantial portion of contaminants remained in the hydrocarbonaceous fluid feeds.
Accordingly, it is the primary object of the present inven-tion to provide an improved process for removal of heavy metals and other contaminants from hydrocarbonaceous fluid feed streams.
It is an additional object of the present invention to provide an improved non-catalytic process for removing heavy metals contaminants from shale oil.
These and othar objects have been met by providing a non-catalytic process for removal of heavy metals, e.g., selenium, arsenic, and iron, from a hydrocarbonaceous fluid feed stream by contacting the stream with a gas comprising hydrogen sulfide (H2S)-or a mixture of hydrogen sulfide and hydrogen. In one embodiment, the gas contacts the hydrocarbonaceous fluid feed stream in a heater and the mixture is then passed to a heat soak zone where the mixture resides for sufficient time to cause the metallic contaminants to 8 ~

precipitate out of the feed. The precipitate can then be removed by physical separation means (e.gO, a centrifuge or decanting after settling).
In an alternative embodiment, the gas contacts hydro-carbonaceous fluid feed stream in a guard bed filled with a porous inert material, e.g., alumina. The thus-formed metals-containing precipitate can be completely removed by the porous material or it can be partially removed by the porous material and partially by a suitable physical separation means depending on the sur~ace area of the poraus material.
The Figure is a schematic representation of the process of this invention.
The process of this invention can best be described by referring to a schematic illustration thereof in the appended figure.
In the figure, the hydrocarbonaceous fluid feed stream is introduced into the process through a feed conduit 1, which then conducts it to a heater 2. A pressurizing gas (either a substan-tially pure hydrogen sulfide or a mixture of hydrogen sulfide and hydrogen, as set forth in detail below) is introduced into the process through a make-up conduit 10 and through a recycle conduit 13. The pressurizing gas is combined with the feed stream so that it is thoroughly admixed therewith. The combined stream of feed and of the pressuri~ing gas is heated to a desired temperature and under desired pressure conditions in the heater 27 from which it is removed via a conduit 3. The heated stream is then passed to a heat soak zone (or thermal holding zone) 4, which is sized to provide sufficient residence time to allow the heated hydrocarbonaceous fluid feed stream to be maintained at the desired temperature and pressure conditions to allow for the formation o~ a precipitate. In 3~ some instances, the operating temperature and pressure conditions o~
the heater 2 are such that they allow for the formation of the precipitate of heavy metals, in which case, the thermal holding zone 4 can be reduced in size or even totally eliminated. Following the desired residence time in the heat soak zone 4, the treated hydro-carbonaceous fluid is withdrawn as a liquid through the conduit 5 ~1~8~
F-0758 ~4 and conducted to a suitable separation means 6, such as a centri-fuge, gravity settlers; filtering through a high surface area material such as clay, manganese nodules, metal oxides, etc. which is insoluble in the oil and separates from the oil or any other con-ventional separating means well known in the art, wherein at least a portion of the precipitate Formed in the heat soak zone 4 is removed through a conduit 7. The product oil containin~ a fraction of metallic contaminants contained in the hydrocarbonaceous fluid feed stream is withdrawn through a product conduit 8. If desired, the lo thermal holding zone 4 can be equipped with an overhead vapor conduit 9 to remove vaporized oil and the pressurizing gas. The conduit 9 passes the mixture of the pressurizing gas and the vaporized oil to a gas separation means 12, commonly known in the art, e.g., high-pressure gas-liquid separator followed by a low pressure gas-liquid separator, wherein the vaporized hydrocarbons are withdrawn by a conduit 11 and the pressurizing gas is recycled to the process through a conduit 13. A make-up pressurizing gas may be added to the process through the conduit 10, as discussed above.
In an alternative embodiment, discussed in detail below, the heat soak zone is replaced by a guard chamber filled with a porous inert material which is capable of removing the metal contaminants from the hydrocarbonaceous feed. Suitable porous inert materials are refractory oxides selected from the group consisting of the oxides of the elements of Groups IIA, IIB, IIIA, IIIB, IVA
and IVB of the Periodic Table, andtor naturally occurring high surface area inert materials, e.g., clays, coals, sands, and manganese nodules. The guard bed can be filled with any one of the aforementioned porous materials or with any suitable combination thereof. The guard chamber is of a conventional design well known 3~ in the art and it is operated in a conventional manner and acts as a medium for the deposition of contaminant metals. The alternative embodiment of this invention is operated in identical manner as the embodiment using the heat soak zone. Accordingly, all of the process conditions and parameters discussed herein in connection 1 ~8~1 ~

with the operation of ~he process containing heat soa~
zone also apply to the alternative embodiment using the inert material-filled guard chamber.
The hydrocarbonaceous fluids that can be treated in accordance with the process of this invention are hydro-carbonaceous fluids obtained from oil shale and coal-derived liquids.
The hydrocarbonaceous fluids are known to contain arsenic, selenium and iron impurities or metal-contaminants and other impurities, e.g., sodium and calcium~ The pro-cess of the present invention provides a relatively simple and effective method of removal of such metal contaminants by forming a precipitate which can be removed from the feed fluids by any well known physical separation means.
The term metal contaminants as used herein encompasses any metal components present in the hydrocarbonaceous fluids, for example, iron, sodium, calcium, arsenic, selenium, or other metals capable of ~orming metal sulfides under the reaction conditions. The term precipitate, as used herein, refers to any solid or semisolid material capable of being physically separated from the fluid portion of the heat treated hydrocarbonaceous fluid. The precipitate may be in the form of hard particles or soft waxy or tarry materials which are easily separated from the liquid portion of the heat treated hydrocarbonaceous fluid by any well known physical separation means. Such physical separation means include separation means wherein the precipitate can be separated from the ~ 1~8~ 1 4 liquid portion of the heat treated hydrocarbonaceous fluid by well known size or gravity separation principles and techniques, including settling, followed by decantation, filtration, centri-fugation and the like. The precipitate obtained in the process of this invention contains significant amounts o~ the arsenic, sodium, calcium and iron contaminants originally present in the hydro-carbonaceous fluid feed. In particular, it has been found that the use of pressurizing gas comprised of a substantially pure hydrogen sulfide or a mixture of hydrogen sulfide and hydrogen results in the 1~ removal of about 88% of the metallic contaminants, as compared to only about 71% for the processes of the prior art which use sub-stantially pure hydrogen gas.
In heat treating the hydrocarbonaceous fluids according to this invention, any conventional method for applying heat to the fluids can be utilized. Thus, conventional heat exchangers (optionally utilizing the heat carried by various process streams oF
this process), directly and indirectly heated furnaces, and other vessels can be utilized to supply the necessary heat to the hydro-carbonaceous fluids for the heat treating step of this invention.
The heat soak zone (thermal holding zone) of this invention can be a conventional vessel, substantially horizontal in shape, or a coiled tube.
In an alternative embodiment, the heat soak zone can be replaced by a conventional guard bed or guard chamber containing alumina or any other porous inert material of moderate surface area te.9., generally greater than 10 m /9 with more efficient demetal-lation occurring as surface area increases) which is generally used upstream (i.e., before) from hydroprocessing units to remove metals ~rom hydrocarbonaceous feeds. If the inert material in the guard bed has a high surface area (e.g., alumina of 50-3ûO m2g), the inert material will be sufficient to remove the metals. Conversely, i~ the inert material has a low surface area (e.g., Vycor of 1-10 m /9), then the metals will be partially removed by the inert material and partially by other physical separation means, e.g., separation means 6, as would be obvious to those skilled in the ~.168~ ~

art. The porous material in the guard bed removes a portion of the precipitate in a conventional manner as described in detail in U.S.
4,141,820, or in a manner similar to U.S. 4,003,829 (but without the addition of transition metal containing materials to the inert S material in the guard bed). The porous material is usually alumina,but can also be other high surface area materials such as metal oxides (SiO2, TiO2, etc.) In the embodiment wherein the heat soak zone without the inert material is used, the contaminan~s-containing precipitate is removed by any conventional physical separation means, e.g., centri-fugation, settling followed by decantation, filtration, etc. The heat treatment of the hydrocarbonaceous fluid in accordance with this invention is conducted at a temperature of at least 316C
(600F). The maximum temperature of the heat treating step is a ~unction of the length of time the fluid is maintained at that temperature and of the amount of cracking or coking which can be tolerated during the heat treating step. The heat treating step can be normally carried out at a temperature of from 316C to 540C
(600F to 1000F) preferably at the temperature of 4ûOC to 455C
(750CF to 850F).
The pressure of the heat treating step is preferably a pressure at which a substantial portion (e.g., from 1% to 99%, preferably 80~ to 90Y0, most preferably 84% to 88%) of the hydro-carbonaceous fluid being processed is maintained in a liquid phase.
Generally, the pressure of the heat treating step is at least 205 kPa (15 psig), and preferably 205 kPa (15 psig) to 34575 kPa (5000 psig), most preferably 1480 kPa (200 psig) to 13890 kPa (20ûO psig).
~s noted above, the process of this invention can be carried out either with a substantially pure (lOO~o by volume) stream 3~ of gaseous hydrogen sulfide (H2S), or with a gas comprising a combination of H25 and hydrogen (H2) as the pressurizing gas for the guard chamber or the heat soak zone. When the pressurizing gas comprises a mixture of H2S and H2, it generally contains about 1% to 95~, preferably 10% to 40% and most preferably 18% to 2Z%
H2S, the remainder being substantially pure hydrogen.

F-~758 It has been found that the use of either substantially pure hydrogen sulfide gas or a mixture of hydrogen sulfide and hydrogen, as set forth above, results in the removal of about 88% of the sum of all metal contaminants (As, Na, Ca and Fe), as compared to only about 71% removal rate when substantially pure hydrogen is used under identical process conditions (i.e., maintaining the synthetic hydrocarbonaceous fluids in the guard bed in the presence of the pressurizing gas for about one hour).
The length of time the hydrocarbonaceous fluids are main-lo tained at the elevated temperature in the thermal holding zone, the guard chamber, and/or in the heater (the residence time) will vary, in a manner apparent to those skilled in the art, depending on the temperature and pressure conditions thereof, as well as on the amount of cracking and coking that can be tolerated during the heat treating step. When the temperature and pressure conditions in the thermal holding zone or in the guard bed are relatively mild, for example, about 399~ (750F) and about 3549 kPa (500 psig), the residence time is relatively long, for example, 30-60 minutes.
Conversely, at more severe conditions, such as 450C (850F) and 3549 kPa (500 psig), the residence time is relatively short, for example, less than .~0 minutes.
Generally, the residence time of the hydrocarbonaceous fluid is at least 1 second to 360 minutes, preferably 5 minutes to 100 minutes, and most preferably 40 minutes to 80 minutes. It will ~5 be apparent to those skilled in the art that the hydrocarbonaceous fluids may be maintained for the entire residence time in the thermal holding zone or in the guard chamber or in the heater, or the residence time may be apportioned in any desired manner between the heater, the guard chamber, and the thermal holding zonP, depending on the desired end result, so lons as the sum of residence times falls within the time limits specified above.
Following the heat treating and separation steps to remove at least a portion of the metallic contaminants, the hydro-carbonaceous fluid, having reduced impurity levels, can be refined, treated or used in any desirable manner. Because of the low levels of arsenic and selenium contamination, the treated products produced : .
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with this învention are particularly applicable to subsequent refining and/or treatment steps wherein operations would be impaired if the arsenic and selenium contaminants were present.
An additional advantage of the present invention resides in that the conversion of the hydrocarbonaceous feed material to the hydrocarbons boiling in the range commonly referred to as the "gasoline boiling range" of about 230C ~45ûF) is about 13.5%, as compared to a conversion of only about 9.5% in a prior art process conducted under identical conditions but using substantially pure hydrogen (H2).
Another advantage of the present invention involving the use of H2S resides in the greater pour point reduction achieved with the H2S treated hydrocarbonaceous feeds as compared to H2-treated feeds. Without wishing to be bound by any theory of 1~ operability, the pour point reduction is probably achieved by generation of sulfur containing pour point depressants derived from the added H~S (A. Schilling, Motor Oils and Engine Lubrication, Scientific Publ., ~reat Britain, 1968, Chapter 2). This is also consistent with the higher sulfur content of the liquid product.
Thermal treatment alone with H2 gives only a slight pour point decrease.
H2S treated oils have lower molecular weights than H2 treated oils. Lower molecular weight oils are easier to processO
The following examples illustrate specific non-limitative embodiments of the invention. All temperatures are in degrees centigrade (C), all pressures in both kilopascals (kPa) and atmospheres (atm), and all percent proportions in percent by weight, unless otherwise indicated.

3~ A Paraho Shale ûil was heated in the presence of either lOOX H25 or 100% H2 pressurizing gases in a stirred autoclave.
After quenchiny the reaction and cooling, the oil from the autoclave was centrifuged at 8000 rpm for 1/2 hour, decanted ~rom the centrifuge cans, and analyzed.
The autoclave was heated at a constant rate and held at the temperature of 399C (750F) either for O hours or 1 hour. Table 1 shows analysis of the treated centrifuged oils and of the feed.

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TAaLE 1 Analysis of Centrifuged Shale Oil Treated With Heat in the Presence of H2 or H25 Example No.
~ 1 2 Temp. (C) 399 399 399 Pressure (kPa/atm) 1692/16.72128/21 2482/24.5 Time, hrs. 0 Pressurizing Gas Used H2S+He H2 H2S~He Material Balance 98% 98% 97%
Mole Ratio H/C 1.55 1.54 1.59 1.59 % N, Total 2.27 2.08 2.23 2 16 % N, Basic 1.33 1.31 1.32 1 30 % S 0.84 1.08 0.79 1.18 % 0 1.03 1.04 0.92 0.5 As ppm 32 9 2 2 Na ppm 14 6.512 4.9 Ca ppm 2.5 0.84 0.49 0.47 Fe pp 46 6.513.0 4.0 Total ppm metal 94.5 2~ 7~~ Lr.4 % Demetalation 76 71 88 deN (Total N~ 8.41.8 4.8 Mol. wt. 637 341 442 389 Wt. % residue 0 1.1 0 Wt. % gases 0.40.7 1.6 1~8~

Boiling Point Conversions (% by volume) Conversion Example Ambient 216- 343~ 454- to 216C BP
No. Gases-216C 343C 454C 579C579C~ Fraction Paraho Shale 7.5 28.2 34.315.8 14.2 13990C, o hrs, 3.5 9.2 25.7 26.6 21.516.7 5.6 H2S + He 2399~C, 1 hr., 0.715.5 21.3 27.2 12.223.1 9.4 3399C, 1 hr., 1.618.3 26.~ 26.5 9.917.2 13.4 H2S + He Formula for Conversion to 216C: (216C liq. gas) - 7.5 Helium (He) was used with H2S in Examples 1 and 3 to provide a relatively easily compressible pressurization gas.
However, the helium is inert to the reactants and it did not chemically react with H2S or the shale oil.
As can be seen from Table 1, pressurization of the auto-clave with H2S at 399C (750F) for 1 hour removes 88% of the metals (iron, Fe; arsenic, As; calcium, Ca; and sodium, Na), while pressurization with H2 under the same conditions removes only 71%. The H25-treated oil has lower molecular weight, less total N
and conversion to 216C (420F) material has occurred as well.
The boiling point conversion to the gasoline range (216C
boiling point - ~P) is 13.4% when H2S and He at 399C for one (1) hour is used, as compared to 9.4% conversion for the treatment with H2 alone.

2ûO grams of Paraho Shale Oil was charged to a stirred autoclave (300 cc volume), which was then flushed with helium.
Hydrogen (H2) or hydrogen sulfide (H2S) gas at 791 kPa (100 psig) was added to the autoclave. The autoclave was heated to 427C
(800F) and held at that temperature for one (1) hour, followed by immediate ice-water quench. The oil was centrifuged, decanted from the centrifuge cans and analyzed.

Table II summarizes the conditions and results of the experiments.

Ana Heat in the Presence of H2 or H2S

Example No.
~ 4 5 Temp. (C) 427 427 Pressure (kPa/atm) 4377/43.2 4722/46.6 Time J hrs.
Pressuri~ing Gas Used H2 H25 Mole Ratio H/C 1.551.56 1.51 % N, Total 2.272.05 2.16 % N, Basic 1.331.29 1.30 % S 0.840.48 0.68 % û 1.031.93 0.89 As ppm 32 Na ppm 14 5.2 5.2 Ca ppm 2050.98 1.0 Fe pp 45 3.5 ~ 2.5 Total ppm metal ~5 1~7- ~7~
% Demetalation 89% go~
Mol. wt. 637 423 369 Residue:
M.W. 240 444 ppm As 17 29 Wt. % 11.0 13.0 Wt. ~ gases 4.0 3.5 Conversion Example Ambient 216- 343- 454- to 216C BP
No~ Gases-216C 343C 454C 579C579C~ Fraotion Paraho Shale 7.5 2802 34.315.8 14.2 4 427C, 1 hr., 3.622.2 22.9 21.4 5.425.9 19.8 427C, 1 hr., 3.121.5 24.0 17.8 3.631.6 18.5 , 1~8~

As seen above, pressurization of the autoclave with H2S
for one (1) hour at 427C (800F) results in greater demetalation of the feed shale oil than the identical treatment with H2.
Examples 6-7 s Runs were conducted on the Paraho shale oil in a 0.64 cm ~1/4 in.) coiled stainless steel tube reactor having a length of 3.66 m (144 in.). In the thermal runs, the reactor was packed wlth 50 cc o~ 20/30 mesh vycor and heated by a fluidized bath to 39~C
(750F). The LHSV was 0.6 based on the volume of the empty tube.
The vycor-filled tube reactor had a sur~ace area of approxlmately 0.4-1.0 meter-square. This surface area was at least 40-100 times greater than the previous autoclave used in Examples 1 through 5.
The oil was fed into the reactor by an Isco pump through heated lines (130C). A 15.2 cm (6-inch), 0.64 cm (1/4-inch) stainless steel preheater section, maintained at 260C (~00F), was placed immediately before the reactor. Each run was conducted in a fresh reactor.
The H2 flow was 534 Nl/l (3000 SCF/9BL) and the pressure was 4928 kPa (700 psig). H2S was added to the H2 stream by using a liquid H2S bubbler system maintained at 11C to give 40 H2S in H2.
Table III summarizes the results of these experiments. In these examples, the product oils were analyzed as received from the reactor. The metals levels of the product oil in Example 7 are lower because H2S + H2 gases give higher levels o~ demetallation than H2 alone (Example 6). The As and Fe metals in the oil in Example 7 deposit on the walls of the reactor and vycor glass, mostly as metal sulfide species. Greater pour point reduction is also achieved with H2S + H2.
A higher surface area component in the tube reactor than 20/30 mesh vycor would give better results.

TAB E III

Shale Oil EXAMPLE NO
Feed 6 GASES USED: H2 H2S+H2 (40 mol % H~S and 60 mol ~ H2) Processed at:
Pressure (kPa/psig) 4928/700 4928/700 LHSV 0.6 0.6 Temp.( C) 399 399 Pour point 80 72 59 CCR 2.78 --* 2.51 Analysis:
Basic N 1.33 1.33 1.28 Total N 2012 2.09 1.87 0 1.53 1.07 1.01 S 0.81 0.39 1.32 C 84.25 85.13 84.93 H 11.03 11.26 11 24 g9.74 99.94 100 37 Mole ratio H/C 1.57 1.59 1.59 %deN 1.4 11.8 %deO 30.0 %deS 51.9 0 Trace elements:
As ppm 26 5 1.5 Fe ppm 26 11 5 Hydrogen:
Consumption 28/159 26/145 (Nl/l SCF/BBL) Wt~ gas make 0.4 0-9 (Cl-C5 gases) Insufficient sample for analysis.

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Boilin~ Range Distribution Ambient 216 343- 454- 579C
Gases -216C 3430C 454C 579C 579~F Conversion Shale Oil Feed 7.5 28.2 34.3 15.8 14.2 ~~~
EX. 6 }99C, 4928 kPa treated 0.14 10.5 19.2 31.8 18.~ 20.3 0 EX. 7 H2S + H2 treated 0.89 7.6 18.6 24.8 2~.9 19.1 0 It will be apparent to those skilled in the art that the above examples can be successfully repeated with ingredients equivalent to those generically or specifically set ~orth above and under variable process conditions.
From the foregoing specification one skilled in the art can readily ascertain the essential features of this invention and without departing from the spirit and scope thereo~ can adopt it to various diverse applications.

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Claims (10)

Claims:

1. In a noncatalytic process for removing at least one metal contaminant from a hydrocarbonaceous fluid feed stream selected from shale oils and coal-derived liquids by contacting the hydrocarbonaceous fluid feed stream with a gas at a pressure of at least 205 kPa (15 psig) and at a temperature of at least 316°C (600°F), the improvement wherein the gas comprises hydrogen sulfide.

2. A process according to claim 1 wherein the gas com-prises a hydrogen sulfide and hydrogen.

3. A process according to claim 2 wherein the gas comprises at least 50% by volume of hydrogen.

4. A process according to claim 1, 2 or 3 wherein the gas comprises at least 80% by volume of hydrogen.

5. A process according to claim 1, 2 or 3 wherein the gas contacts the hydrocarbonaceous fluid feed stream at a temperature of at least 399°C (750°F).

6. A process according to claim 1, 2 or 3 wherein the gas contacts the hydrocarbonaceous fluid feed stream at a pressure of 205 kPa (15 psig) to 34575 kPa (5000 psig).

7. A process according to claim 1, 2 or 3 wherein the gas contacts the hydrocarbonaceous fluid feed stream for at least 1 second.

8. A process according to claim 1, 2 or 3 wherein the hydrocarbonaceous fluid feed stream is contacted with the as in a guard chamber containing a porous inert material.

9. A process according to claim 1, 2 or 3 wherein at east one metal contaminant is iron, sodium, calcium, arsenic or selenium.

10. A process according to claim 1, 2 or 3 wherein the hydrocarbonaceous fluid feed stream is contacted with the gas in a heat soak zone.