US2225847A - Hydrocarbon oil treatment - Google Patents

Description

Dec. 24. 1940. -w. B. sHANLEY ETAL HYDROCARBON OIL TREATMENT- Filed July 50. 1938 Patented Dec. 24, 1940 PATENT OFFICE HYDROCARBON OIL TREATMENT William B. Shanley and Robert E. Sutherland, Chicago, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application July 30, 1938, Serial No. 222,155

Claims.

This invention relates particularly to processes aimed at sweetening sour distillates such as those produced in either the straight-run or cracking distillation of crude petroleums or their fractions respectively.

It is more specifically concerned with a particular method of operation in which granular sweetening reagents are employed in a highly effective manner from a practical and commercial standpoint.

The petroleum refining industry is familiar With numerous processes and reagents applicable to the conversion of the mercaptans present in low boiling hydrocarbon fractions into relatively nonodorous di-alkyl di-suldes by reactions involving overall oxidation. The so-called doctor treating reagent is Well-known as Well as other processes involving the use of cupric or other ic salts which are produced during the sweetening stage then reactivated by controlled oxidation for further service. Some of the disadvantages of the plumbite method of treatment are concerned with emulsion formation, the time required for the break when sulfur is added to the primarily formed lead mercaptides to cause a separation of lead sulfide and the formation of the di-alkyl di-sulfides, and the tendency to use an excess of sulfur to hasten the break which increases the `sulfur content of the gasoline or naphtha undergoing treatment and form polysuldes which have a very deleterious effect on the anti-knock properties of the gasoline.

Cupric and other salts of metals having higher and lower valences are employed in various ways to eect the oxidation of mercaptans to di-alkyl di-suldes, sometimes in solution and sometimes as constituents of granular composites through which the sour distillates are percolated. The present process involves a specilic method of utilizing granular sweetening composites containing salts of metals at one of their higher valences which have been found commercially practical particularly in plants of relatively small capacity as measured by oil renery standards.

In one specific embodiment the present invention comprises a process for the sweetening of sourv hydrocarbon distillates which comprises adding a xed amount of a granular sweetening reagent to a body of sour distillate, pumping the suspension in admixture with regulated amounts of air or other oxidizing gas through a filter to build up a cake thereon, recycling a portion of the filter effluent to further contact with the sweetening reagent, separating residual gases, further contacting the distillate with stationary beds (C1. ISB- 29) of granular materials comprising reagents eiective in removing dissolved salts and continuing the process until the treating efficiency of the filter cake has dropped below a practical level.

The more important features of the present process will now be described inv connection with the attached diagrammatic drawing which shows ingeneral side elevation Without regard to absolute or relative dimensions an arrangement of interconnected units in which the process may be conducted. f

Referring to the drawing any distillate which is presumably thoroughlyv washed with caustic soda or other alkalis to remove hydrogen sulfide is introduced to the treating plant through a line I containing a valve 2 and pumped by a pump 3 through a line 4 containing a valvev 5 through a heating element 6 disposed to receive heat from a furnace 1. During passage through heating element 6 which lmay take the form of va heat exchanger if hot process fluids are conveniently available, the temperature is preferably brought to about 85 F. which is the optimum when employing sweetening composites containing Cupric salts cfa character to be presently described. ln case of prevailingatmospheric temperatures oi the order of 85 F. or higher, the heating Will obviously be dispensed with. The present method of operation is'appilcable to the sweetening of sour distillates with any type of granular composite containing salts of metals at a higher state of valence, and temperature of treatment will be varied according to the oxidizing and treating eiciency of the particular compound or mixture of compounds chosen.

The incoming charge at the optimum temperature of treatment passes through line 8 containing valve 9 to slurry tank I0 to which a xed amount of granular sweetening composite is added in one portion or in a number of small portions as the treatment may require. The tank may be provided with any type of agitating or mixing device although these are not shown in the drawing. The suspension of granular treating reagent inoil passes through line I I containing valve I2 to pump I3 which discharges through line I4 containing control valve I5 at a rate dependent upon the level in slurry tank IIJ as controlled by float I6 and transmission line Il. The slurry passes through a mixer 29 which may contain lilling or bailling material or any arrangement of perforated plates to insure thorough mixing and contacting of the oil and the treating reagent, after which the materials pass through line 30 containing valve 3l to a lter press 32 which may be of any suitable type of construction. According to the present process the sweetening reagent is permitted to build up a filter cake on the plates of a press and the sour oil is pumped through the lter cake at an optimum rate depending upon the effectiveness of the reagent and the sourness of the distillate until sweetening is effected. Line 33 containing valve 34 permits the withdrawal of any amount of liquid at this point and branch line 35 containing Valve 36 permits the return ofl the filter efliuent to the slurry tank I9 in case sweetening is not effected by a single passage through the bed of reagent. Line 31 containing valve 38 is provided for the returnl of a mixture of oil and air to an air separator 39 from which the air is withdrawn through line 40 containing valve 4I and the liquid passes back to slurry tank l0 through line 42 containing valve 43.

Prior to the passage of the slurry to mixer 29 a regulated amount of dry air at the approximate rate of 10 ou. ft./bbl. of sweetened distillate is added. This in effect causes a partial concurrent reactivation of the cupric or other ic salts and permits much longer periods of operation before reactivation is necessary. Thus air under pressure may be introduced through line I6 containing valve I1' to ,water knock-out drum I8 which may contain filling or baiiiing material supported on perforated false bottom I9. In this treatment any mechanically entrained water will be `removed and Withdrawn through line 20 containing valve 2|. The air at substantially 100% humidity at the temperature of operation then i passes through line 22 containing valve 23 to air drier 24 which may have adsorbent or chemical drying materials such as fullers earth or calcium chloride respectively within the upper and lower perforated plates 25 and 26. 'I'he function of this drier is to reduce the Water content of the incoming air to a low point since apparently best results are obtained when substantially no moisture is present. The dry air passes through line 21 containing valve 28 to line I4 already described.

When thecake of sweetening material which is permitted to build up on the plates of iilter press 32 becomes too far spent for practical purposes, the stream of slurry may be diverted to other presses connected in parallel and the filter cake then removed from the press into a hopper 44 and reactivated in separate apparatus or disposed of in a manner suitable to its composition. By the use of filter presses in parallel the present process may be made substantially continuous.

The sweetened distillate, which inthe case of `copper salts frequently contains traces of color, due possibly to copper mercaptides, passes through line 45 containing valve 46 to an air Aseparator 41 from which any entrained air may be vented through line 48 containing Valve 49. Line 50 containing valve 5|v permits the withdrawal of distillate or sedimentary materials at this point for test or other purposes.

The sweetened distillate then passes through line 52 containing valve 53 tov pump 54 which discharges through line 55 containing control Valve 56 which is actuated by float 51 through transmission 58 inaccordance with the level in the air separator.

The distillate then passes through a bed of granular material in secondary treater 59 to improve color and remove dissolved salts. The materials'putilizable in the secondary treater comprise various metal suliides, alone or on relatively inert supports, such as sodium sulfide, iron sulvcontaining cupric salts.

iide, zinc sulfide, etc. Zinc sulfide or composites containing the same have been found especially effective for use in the secondary step of the treatment. Secondary treater 59 is provided with line BEI containing valve 6| for the removal of liquid or sedimentary material and line 62 con taining valve 63 for the withdrawal of sweetened and decolorized distillate.

While the present process may employ any type of granular sweetening reagent comprising metal salts at their higher degree of valence it is particularly suitable for the utilization of composites The following table shows the limit range of composition of composites which have been found particularly eiiective:

Limit compositions of sweetem'ng reagent l Per cent by weight* Ammonium chloride (NI-i401) 25 5 Copper sulfate (CuSOaHzO) 25 5 Adsorbent, 6-30 mesh 50 90 *Calculated on a dry basis except for the water of composition of the crystalline copper sulfate.

Among the adsorbent materials which may be employed alternatively in the treating composites, crushed silica, crushed rebrick, and fullers earth may be mentioned, these materials being utilized in particle sizes between approximately 6 and 30 mesh. It has been found essential to the proper functioning of the treating reagent in the sweetening of sour gasolines to maintain the water content of the composite reagent Within rather narrow limits. Experiments have shown that there is a denite shortening of the life of the reagent if there is not sufiicient water present to provide the necessary iive moles of crystallization for the copper sulfate. The reactions which occur more or less simultaneously in treatment of the present character are given below:

(1) Sweetening reaction:

2CuCl2+RSH 2C`uCl+2HCl-l-RzSz (2) Reactivation reaction:

While the above equations do not represent the total of the reactions occurring, they may be taken asI typical. It will be seen from the first equation that cupric chloride has been assumed to be the active reagent which is reduced to cuprous chloride and then simultaneously regenerated by the combined action of hydrochloric acid and the oxygen of the air. One of the net results of these reactions is the generation of considerable quantities of Water depending upon the amount of mercaptans present.

Composite treating reagents of the present character are preferably made by the following general series of steps. The required amount of the copper sulfate pentahydrate is reduced to a fine state of subdivision in some sort of grinding device such asv a ball mill until it is approximately 200 mesh. An equal weight of ammonium chloride is added to the same mill without removing the copper sulfate and the pulverizing is continued until the total material is of approximately 200-mesh in iineness; The ground and intimately commingled ammonium and copper compounds are then removed and mixed in other apparatus with the required amount of ad, sorbent which has been separately ground and sized to approximately 6-30 mesh. This final mixing is done in such a manner that there is substantially no further reduction in particle sizes and the solid ammonium and copper salts are adsorbed on the inert granular material to form a surface coating thereon. The nal step in the process involves the addition of approximately 3% water by weight of the dry materials after which the mixing is continued until a'uniform composition is obtained. We have found that the addition of this amount of Water is sufficient to counterbalance the losses suffered by the copper sulfate crystals during their grinding and to add a slight excess which is still on the safe side of the point corresponding to actual wetting.

One of the important features of the present process which constitutes an improvement in the older processes employing granular sweetening reagents is that by the use of thin layers of reagent on the plates of a filter press, there is substantially no tendency to the channeling observed When the same reagents are used in relatively tall cylindrical treating towers. In the present instance sweetening will proceed until the water generated in the sweetening reagent has caused the solution and removal of the active copper at which time the press is dumped and fresh granular treating reagent is added. Operations are also more rapid on account of the extended surface presented and the reduced pressure drop.

The following characteristic example is illustrative of the results normally obtainable in sweetening sour gasolines by the process of the invention although not with the intention of limiting its scope in exact correspondence therewith.

A plant of the character described with reference to the drawing was used on a sour cracked gasoline produced from Mid-Continent residual charging stock. The plant was operated to treat 1200 bbl. gasoline per day using a copper sulfateammonium chloride-fullers earth composite as described in the foregoing Specification, and the yield of gasoline per pound of sweetening reagent composite was 50 bbls. The gasoline from the cracking plant stabilizer was washed With 15 B. caustic soda to remove hydrogen sulfide and heated to .a temperature of 85 F. before mixing With the copper-containing sweetening reagent.

v Air was used in an amount of cu. ft./bbl. of net sweetened product, and a recycle ratio from the filter press back to the slurry tank of approximately 1:1 was maintained. The air was dried by passing through clay and calcium chloride. A secondary treating reagent used to remove dissolved copper compounds consisted of finely divided zinc sulfide mixed with fullers earth.

We claim as our invention:

1. A process for sweetening sour hydrocarbon distillate which comprises mixing a solid granular sweetening agent With a portion of the distillate, forcing the mixture through a filter press to build up a cake of the sweetening agent on the filter press, vcontinuously passing additional quantities of the sour distillate through the cake of sweetening agent deposited on the filter press, repeatedly recirculating a portion of the filter press effluent back through the filter press and effecting the major portion of the sweetening of the distillate during its passage through the filter press, and maintaining the continuous passage of sour distillate through 4the filter press until the cake of sweetening agent deposited thereon has substantially lost its sweetening activity.

2. 'I'he process as defined in claim 1 further characterized in that an oxygen-containing gas is commingled with said additional quantities of sour distillate prior to the passage thereof through the filter press.

3. The process as defined in claim 1 further characterized in that said sweetening agent comprises a cupric salt.

`Li. A process for sweetening sour hydrocarbon distillate which comprises mixing a solid granular sweetening agent comprising a cupric salt with a portion of the distillate, forcing the mixture through a filter press to build up a cake of the sweetening agent on the filter press, continuously passing additional quantities of the sour distillate through the cake of sweetening agent deposited on the filter press, repeatedly recirculating a portion of the filter press effluent back through the filter press and effecting the major portion of the sweetening of the distillate during its passage through the filter press, continuously passing the remainder of the lter press efliuent to a treating zone and therein treating the same with a reagent capable of removing dissolved copper compounds therefrom, and maintaining the continuous passage of sour distillate through the filter press until the cake of sweetening agent deposited thereon has substantially lost its sweetening activity.

5. The process as defined in claim 4 further characterized in that air is commingled with said additional quantities of sour distillate prior to the passage thereof through the filter press and residual air separated from said remainder of the filter vpress eflluent prior to the introduction of the latter to said treating zone.

WILLIAMB. SHANLEY. ROBERT E. SUIT-IERLAND.

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