US3347779A - Manufacture of petroleum distillates by hydrodesulfurization and hydrogenation - Google Patents

Description

United States Patent 3,347,779 MANUFACTURE OF PETROLEUM DISTILLATES BY HYDRODESULFURHZATION AND HY DRO- GENATION Willem Groenendaal, The Hague, and Willem H. Logrnan,

Amsterdam, Netherlands, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No drawing. Filed Apr. 23, 1965, Ser. No. 450,516 Claims priority, application Netherlands, Apr. 28, 1964, 644,715 7 Claims. (Cl. 208-89) The invention relates to a process for the preparation of a petroleum distillate with an improved smoke point. More particularly, it relates to a process of making low smoke point by the application of desulfurization and dearomatization.

In the case of petroleum fractions whose burning properties are of interest, such as illuminating kerosene and kerosene-type jet engine fuels, these properties can be characterized by such factors as the smoke point, which is the height in mm. of the flame just before it becomes smoky. This smoke point is known to be dependent, inter alia, upon the aromatics content of the petroleum fraction. It is also known that the aromatics content can be reduced, and thereby the smoke point raised, by hydrogenation. It is likewise known that, in this hydrogenation of aromatics to naphthenes, the catalysts usually applied are sensitive to sulfur compounds occurring in petroleum fractions and that their hydrogenation activity drops considerably if such sulfur compounds constitute more than a few thousandths percent of the petroleum fraction to be hydrogenated. British patent specification 794,809, for example, states that in the preparation of petroleum fractions with a high smoke point, the hydrogenation of the aromatics can be effected with the aid of platinum on eta-alumina catalyst and that, if the feed contains sulfur compounds, the latter are first removed by hydrodesulfurization over a cobalt-molybdenum catalyst. From British patent specification 838,751 it is known that petroleum distillates with a high smoke point can be prepared by first desulfurizing the distillate with the aid of hydrogen and a sulfur-insensitive catalyst to a sulfur content of at most 0.002 percent by weight and subsequently hydrogenating it over a nickel catalyst to an aromatic content of at most 1 percent by weight.

The processes known from these two patent specific-ations yield petroleum fractions with a very high smoke point. If, however, only a moderate rise in smoke point of the feed is needed, it is not economical to subject the entire feed to the above-mentioned combined process of desulfurization and dearomatization. It would then be more advantageous to restrict this treatment to a part of the feed and to mix the product with untreated feed in order thus to obtain the desired smoke point. However, applicant has found that this solution is not a suitable one, because of the presence of sulfur compounds in the untreated feed portion of the mixture.

Applicant has now found that the problem can be solved in a suitable manner by partly desulfurizing the feed, splitting up the resultant product into at least two parts, refining one part and mixing the refined product with another part of the partly desulfurized product.

The invention therefore relates to a process for the preparation of a petroleum distillate with an improved smoke point by the application of desulfurization and dearomatization, characterized in that the feed is partly desulfurized with the aid of hydrogen and a catalyst, that the product of this stage is split up into two or more streams, that one of the streams is refined applying hydrogenation for the removal of aromatics and that the 3,347,779 Patented Oct. 17, 1967 product resulting from this stream is blended With one or more of the other streams.

As a result of the reduction in aromatics content obtained by applying the process according to the invention the cetane number becomes higher, so that the process is also suitable for the preparation of fuels for diesel engines.

The-aromatic contents s'tated hereinafter have been determined according to the method ASTM D 1319.

The process according to the invention is very flexible in that smoke point of the final product can be adapted to a wide range of requirements by Varying the ratio of the streams wihch are blended. However, the smoke point of the final product depends not only on the ratio of the blend components, but also on the smoke point of the feed. The maximum increase in smoke point resulting from the dearomatization may vary with the type of starting material. For example, it has been found experimentally that when the starting material is a feed with a smoke point varying between 20 and 26 mm, the hydrogenation step yielded component streams with a smoke point varying between 32 and '45 mm., so that in this example products with smoke points between 20 and 45 mm. can be obtained by blending.

In general, the smoke point of the mixture obtained by blending the two streams is not equal to the weighted arithmetic mean of the smoke points of the two streams. The smoke point which is obtained by blending has to be determined experimentally. In other words, the mixing ratio required to obtain a certain smoke point is determined by trial and error.

Suitable feedstocks are petroleum distillates with final boiling points up to 375 C. and particularly those boiling essentially completely within the kerosene boiling range, i.e. from to 300 C., and more particularly those boiling from to about 290 C. Owing to the application of partial desulfurization which in the process according to the invention precedes the separation of the feed into two or more streams, it is possible to choose a feed whose initial and final boiling points need not be adapted to those of the final product to be prepared. When, for example, one aims at the preparation of a lamp kerosene, one can take a 350 C.-minus fraction containing gas oil components as the starting material, introduce this fraction into the desulfurization unit and after partial desulfurization split it up into a gasoline fraction, a kerosene fraction and a gas oil fraction by distillation. The kerosene fraction is then split up into two stream-s, one of which is refined and mixed with the other. Owing to this possibility, the process according to the invention may easily be incorporated into existing refinery processing schemes.

Partial desulfurization of the feed is effected with the aid of hydrogen and a catalyst. For this purpose any known technique may be used. For instance, desulfurization can be carried out in the gase phase, or in the liquid phase with gas recycle, as, for instance, in the trickle operation, in which a very thin film of oil flows over a catalyst bed. The trickle process, which is very suitable, is described, for example, in British patent specification 657,521.

By the partial desulfurization, the sulfur compounds present are partly converted into hydrocarbon and hydrogen sulfide. The conditions are preferably chosen so that the sulfur content of the petroleum distillate drops at least to 100 parts by weight sulfur per million parts by weight of petroleum distillate, and preferably to a sulfur content of 50 parts by weight of sulfur per million parts by weight of petroleum distillate, or less.

Suitable catalysts for this partial desulfurizatio-n are metals and oxygenor sulfur-containing compounds of metals of the sixth and eighth-groups of the Periodic Systerm, for example, oxides and sulfides of these metals. Preference is given to a catalyst which contains both a metal of the sixth group or a compound of this metal and a metal of the eighth group of the Periodic System or a compound of this metal. They can be supported on a carrier, such as activated carbon, fullers earth, kieselguhr, silica or alumina, for instance, alumina in the form of bauxite or sintercd clay. Preference is given to a carrier consisting, at least substantially, of alumina.

In particular, catalysts are preferred which are insensitive to hydrogen sulfide, such as cobalt compounds and molybdenum compounds together on alumina as carrier, and tungsten sulfide and nickel sulfide together on alumina as carrier.

The partial desulfurization can be effected at pressures which may vary within wide limits. As an example a pressure of from 20 to 80 kg./cm. abs. may be mentioned. A pressure of from 35 to 60 kg./cm abs. is preferred.

As a hydrogen source, use can be made of pure hydrogen or of hydrogen-containing mixtures, such as, for instance, the end gases of catalytic reforming processes.

For the temperature a value may be chosen of, for example, from 275 to 360 C., temperatures of from 300 to 350 C. being preferred.

For the space velocity, which may vary within wide limits, values may be chosen of, for example, from 0.5 to 12 tons of oil per m of catalyst per hour. The hydrogen/hydrocarbon ratio may be varied between, for instance, 10 and 250 m3 (measured at C. and 760 mm. mercury pressure) per ton of oil, but quantities smaller than and larger than 250 m. per ton of oil are also suitable.

The separation of the partly desulfurized product into two or more streams may be carried out as desired, either in such a way that the properties of the component streams from which the final product is prepared are similar or in such a way that they are dissimilar to each other. In the latter case there is, for instance, an installation in which the light components formed during the partial desulfurization are distilled off, the residue being split up into two or more streams by distillation in the same installation or in another.

The procedure is then preferably carried out in such a way that a stream consisting of one or more of the lighter fractions is refined and the product obtained from this stream is blended with a heavier fraction, for example, the bottom product of the distillation. For example, the product of the partial desulfurization of a feed consisting of a kerosene minus fraction is split up by distillation into a gasoline fraction boiling below 155 C., a light kerosene fraction boiling in the range of 155 to 200 C., and a bottom product boiling above 200 C., the light kerosene fraction is refined and the raflinate is blended with the bottom product.

If the starting material is a feed consisting of a 350 C.-minus fraction, which therefore contains gas oil components, and the desired final prfoduct is a kerosene with an increased smoke point, the distillation may be conducted, for example, such that a gasoline fraction, a light kerosene fraction, a heavy kerosene fraction and, as the bottom product, a gas oil fraction are obtained. The light kerosene fraction is then refined and blended with the heavy kerosene fraction.

The term refining as it has been used hereinabove refers to the removal of aromatics by hydrogenation, i.e. hydrogenative dearomatization. In this hydrogenation step, which uses hydrogen and a hydrogenating catalyst, the degree of dearomatization can be varied as desired. However, in order to obtain the highest possible smoke point of the final product from the smallest possible quantity of component stream, the hydrogenation is preferably carried out such that at least 75% of the aromatics is converted into non-aromatic compounds. Hydrogenation products containing 3% w. of aromatics or less are even more preferred.

Dearomatization can, of course, also be effected by the application of an extraction process with the aid of solvents suitable for this purpose such as furfural, liquid sulfur dioxide, sulfolane, etc. However, hydrogenative dearomatization converts the aromatics into saturates with better burning properties. Therefore this manner of dearomatization is preferred.

Hydrogenative dearomatization is well known in the art and can be carried out in a number of ways such as operation in the gas phase or in the liquid phase with gas recycle.

Suitable catalysts for the dearomatization are, for instance, the commercially available hydrogenation catalysts. Examples of very suitable catalysts are those containing nickel or metals of the platinum group or compounds of these metalls. Mostly, the active components are supported on a carrier. Examples are a nickel-kieselguhr catalyst with 40-65% w. of nickel, a rhodium-onalumina catalyst with, for instance, 0.5% Rh, or a platimum-alumina catalyst containing, for example, 0.l2% w. of platinum. Catalysts based on platinum often contain 01-10% w. of halogen, for instance, fluorine or chlorine, and in addition alkaline-earth oxides or alkali oxides as contaminants.

The dearomatization may be carried out at a pressure varying within wide limits, for instance, a total pressure of 2090 kg./crn. abs. At this pressure a partial hydrogen pressure of 5 kg./cm. may already be sufficient, but as a rule this value is higher, for instance, 1050 kg./cm. In the hydrogenation with gas recycle a reactor pressure of 60-70 kg./cm. is preferably applied.

The hydrogenation temperature may be chosen, for example between and 350 C., a temperature between 200 and 300 C. being preferably chosen.

The space velocity may vary within wide limits. An example is a space velocity of 05-10 tons of oil per m. of catalyst per hour. The gas/oil ratio amounts to, for instance, 25300 111. (measured at 0 C. and 760 mm. mercury pressure, which standard conditions are denoted by the prefix N") per ton of oil, but in general lower and higher values for the gas/ oil ratio are also suitable.

As a hydrogen source pure hydrogen may be used or hydrogen-containing mixtures, such as, for instance, end gases of catalytic reforming processes. As a rule mixtures will be used with a hydrogen content of 50% or higher. For catalyst life it is very desirable and therefore preferred that the mixture should contain essentially no hydrogen sulfide.

Applicant has found that the smoke point of the component stream can be further improved, if before the removal of the aromatics by hydrogenation a deep desulfurization is applied. This deep desulfurization need not immediately precede the dearomatization. For example, it may already be applied to the product of the partial desulfurization before the latter product is split up into two or more streams. However, when this is not necessary, for example, to reach a low sulfur content of the final product, the deep desulfurization is preferably applied to the component stream which is refined.

The deep desulfurization is also carried out with the aid of hydrogen and a catalyst. For this purpose any of several well known techniques can be used, for instance, desulfurization in the gas phase or in the liquid phase with gas recycle, as, for example, in trickle operation as mentioned hereinbefore. This trickle process is very suitable.

The deep desulfurization is preferably carried out under such conditions that the sulfur content becomes equal to or lower than 10 parts by weight per million parts by weight of petroleum distillate; in particular a desulfurization process is preferred which reduces the sulfur content to 1 p.b.w. per million p.b.w. of petroleum distillate, or less.

Examples of suitable catalysts for this deep desulfurization are the catalysts mentioned hereinbefore in the description of the partial desulfurization. Preference is given to a catalyst which contains both a metal of the sixth group, or a compound of this metal, and a metal of the eighth group of the Periodic System, or a compound of this metal. They may be supported on a carrier, such as activated carbon, fullers earth, kieselguhr, silica or alumina, for instance, alumina in the form of bauxite or sintered clay. Preference is given to a carrier consisting, at least substantially, of alumina.

Preference is given to catalysts that are insensitive to hydrogen sulfide, such as cobalt compounds and molybdenum compounds together supported on alumina as a carrier, nickel compounds and molybdenum compounds together on alumina as a carrier, and tungsten sulfide and nickel sulfide on alumina as a carrier.

The deep sulfurization can be carried out at pressures varying within wide limits, for example, a pressure of 20-80 kg./cm. abs., preferably 35-60 kg./cm. abs.

As a hydrogen source pure hydrogen may be used or hydrogen-containing mixtures, such as, for example, platformer end gas. As a rule mixtures with a hydrogen content of 40% or higher will be used and are preferred.

The temperature may be chosen between 350 and 400 C., for instance. For the space velocity, which may vary within wide limits, values may be chosen of, for example, from 0.5 to 12 tons of oil per m of catalyst. A space velocity of from 1 to 3 tons of oil per m. of catalyst per hour is preferably applied. The hydrogen/hydrocarbon ratio may vary, for example, from 10 to 250 m. (measured at C. and 760 mm. mercury pressure) per ton of oil; quantities smaller than 10 and larger than 250 m. of oil may also be used.

The invention will be better understood by reference to the following examples:

EXAMPLE I A kerosene with a smoke point of 22 mm. was prepared as follows: A petroleum distillate with a boiling range of 150 to 290 C. ASTM, a sulfur content of 0.25% W., an aromatic content of 18% W. and a smoke point of 20 mm., obtained by distillation of a crude oil originating from South America, was partly desulfurized according to the trickle procedure under the following conditions: Reactor pressure 25 kg./cm. abs., temperature 340 0, space velocity tons of oil per m of catalyst per hour, gas/oil ratio 100 Nm. hydrogen per kg. of oil. As a hydrogen source pure hydrogen was used. The catalyst was a commercial product which, when fresh, consisted of cobalt oxide and molybdena on an alumina carrier. The content of cobalt oxide and molybdena of this catalyst amounted to 3.5% W., and 13.5% w., respectively; the catalyst was in the form of cylinders with a diameter of 1.5 mm. and a length of 3-5 mm.

The partly desulfurized product had a sulfur content of 0.008% w. and a smoke point of 20 mm. This product was split up into three streams, A, B and C, in a distillation column. Stream A was a gasoline fraction boiling below 155 C., stream B a light kerosene fraction boiling in the range of 155 to 200 C., and stream C was the bottom product. The sulfur content of stream B was 0.003% w. Stream B was dearomatized in the liquid phase with gas recycle. The catalyst used was a commercial product which, when fresh, consisted of nickel oxide supported on kieselguhr as carrier, the nickel content being 44% w. The conditions applied were as follows: reactor pressure 63 kg./cm. hydrogen partial pressure 35 kg /cm. temperature 275 C. space velocity 4 tons of oil per in. of catalyst per hour, gas/oil ratio 100 Nm. per ton of oil. The product of this dearomatization step had an aromatic content of 0.9% w. and a smoke point of 32 mm.

The hydrogenated stream B was blended with stream C in the ratio of 1:3 (v./v.). The smoke point of the mixture obtained was 22 mm.

6 EXAMPLE 11 From a petroleum distillate with a boiling range of 150 to 250 C. ASTM and a smoke point of 20 mm. a kerosene with a smoke point of 22 mm. was prepared as follows:

The petroleum distillate which had a sulfur content of 0.20% w. and an aromatic content of 18% w. and had been obtained by distillation of a crude oil originating from South America, was partly desulfurized according to the trickle procedure under the following conditions: reactor pressure 25 kg./om. abs., temperature 340 C., space velocity 5 tons of oil per m. of catalyst per hour, gas/oil ratio Nm. of hydrogen per kg. of oil. As a hydrogen source pure hydrogen was used. The catalyst was a commercial product which, when fresh, consisted of cobalt oxide and molybdena on alumina as carrier. The contents of cobalt oxide and molybdena of this catalyst were 3.5% w. and 13.5% w., respectively; the catalyst was in the form of cylinders with a diameter of 1.5 mm. and a length of 3-5 mm.

The partly desulfurized product had a sulfur content of 0.005% w. and a smoke point of 20 mm. This product was split up into two streams, A and B, the ratio of stream A to stream B being 1:3 (v./v.).

Stream A was desulfurized deeply by means of the trickle procedure under the following conditions: reactor pressure 50 kg./cIn. abs., temperature 370 C., space velocity 3 tons of oil per 111. of catalyst per hour, gas/oil ratio 100 Nm. of hydrogen per kg. of oil. As a hydrogen source pure hydrogen was used. The catalyst was the same commercial product as that applied in the partial desulfurization. The deeply desulfurized product had a sulfur content of 0.0001% w.

The deeply desulfurized stream A was dearomatized in the liquid phase with gas recycle. The catalyst used was a commercial product which, when fresh, consisted of nickel oxide supported on kieselguhr as carrier, the nickel content being 44% w.

The conditions applied were as follows: reactor pressure 63 kg./cm. partial hydrogen pressure 35 kg./cm. temperature 275 0., space velocity 4 tons of oil per m. of catalyst per hour, gas/oil ratio 100 Nm. per ton of oil. The product of this dearomatization step had an aromatic content of 0.9% w. and a smoke point of 32 mm.

The deeply desulfurized hydrogenated stream A was blended with stream B. The smoke point of the mixture obtained was 22 mm.

EXAMPLE III A kerosene with a smoke point of 22 mm. was prepared as follows: A petroleum distillate with a boiling range of to 290 C. ASTM, a sulfur content of 0.25% w., an aromatic content of 18% w. and a smoke point of 20 mm. obtained by distillation of a crude oil originating from South America, was partly desulfurized according to the trickle procedure under the following conditions: Reactor pressure 25 kg./cm. abs. temperature 340 C. space velocity 5 tons of oil per m of catalyst per hour gas/oil ratio 100 Nm. hydrogen per kg. of oil. As a hydrogen source pure hydrogen was used. The catalyst was a commercial product which when fresh consisted of cobalt oxide and molybdena on an alumina carrier. The content of cobalt oxide and molybdena of this catalyst amounted to 3.5 w. and 13.5% w., respectively; the catalyst was in the form of cylinders with a diameter of 1.5 mm. and a length of 3-5 mm.

The partly desulfurized product had a sulfur content of 0.008% w. and a smoke point of 20 mm. This product was split up into three streams, A, B and C, in a distillation column. Stream A was a gasoline fraction boiling below C., stream B a light kerosene fraction boiling in the range of 155 to 200 C., and stream C was the bottom product. The sulfur content of stream B was 0.003% w.

Stream B is then desulfurized deeply by means of the trickle procedure under the following conditions: reactor pressure 50 kg./crn. abs; temperature 370 (1., space velocity 3 tons of oil per m? of catalyst per hr., gas/oil ratio 100 Nm. of hydrogen per kg. of oil. As a hydrogen source pure hydrogen is used. The catalyst is the same as that applied in the partial desulfurization. The deeply desulfurized product has a sulfur content of 1 ppm. by weight.

The deeply desulfurized stream B is dearomatized in the liquid phase with gas recycle. The catalyst used is a commercial product which, when fresh, consists of nickel oxide supported on kieselguhr as carrier, the nickel content being 44% W. The conditions applied are as follows: reactor pressure 63 kg./cm. hydrogen partial pressure 35 kg./cm. temperature 275 C., space velocity 4 tons of oil per m of catalyst per hour, gas/ oil ratio 100 Nm. per ton of oil. The product has an aromatic content below 1% w. and a smoke point above 30.

The dearomatized stream B when blended with stream C in the ratio of 1:3 (v./v.) produces a kerosene boiling range distillate having a smoke point greater than 22 mm.

We claim as our invention:

1. A process for the preparation of a petroleum distillate having an improved smoke point comprising the sequential steps:

(a) partially hydrodesulfurizing a petroleum distillate fraction having a smoke point lower than desired;

(b) fractionating the partially desulfurized petroleum distillate into two fractions of diiTerent boiling ranges, both of which have atmospheric boiling ranges at least as high as the boiling range of kerosene, and at least one of which boils substantially within the kerosene boiling range;

(c) hydrogenatively dearomatizing said fraction boiling substantially within the kerosene boiling range; and

(d) blending the dearomatized kerosene boiling range fraction with the remaining un-dearomatized fraction having an atmospheric boiling range at least as high as the boiling range of kerosene to recover a petroleum distillate having a higher smoke point than the feed.

2. The process hydrogenatively dearomatized is deeply prior to dearomatization.

3. The process of claim 2 in which the fraction to be hydrogenatively dearomatized is desulfurized to a sulfur content of no more than 10 ppm. by weight, prior to dearomatization.

4. The process of claim 1 in which the partial desulfurization of the petroleum distillate feed to the process is carried out to a sulfur level of no more than 100 ppm. by Weight, basis the partially desulfurized product.

5. The process of claim 1 in which at least 75% by Weight of the aromatics contained in the feed to the hydrogenation dearomatization step are converted into non-aromatic compounds.

6. The process of claim 1 in which division of the partially desulfurized petroleum distillate is carried out by fractionation to recover a fraction boiling below about 200 C. and a fraction boiling above about 200 C.

7. The process of claim 6 in which the fraction boiling below about 200 C. is desulfurized to a sulfur content of no more than 10 ppm. by weight prior to dearomatization.

of claim 1 in which the fraction to be desulfurized References Cited UNITED STATES PATENTS 2,865,849 12/1958 Van Loon et al 208-212 3,044,955 7/1962 de Groot et a1. 2082l2 3,256,175 6/1966 Kozlowski et al. 260-667 DELBERT E. GANTZ, Primary Examiner. S. P. JONES, Assistant Ex'aminer.

Claims (1)

1. A PROCESS FOR THE PREPARATION OF A PETROLEUM DISTILLATE HAVING AN IMPROVED SMOKE POINT COMPRISING THE SEQUENTIAL STEPS: (A) PARTIALLY HYDRODESULFURIZING A PETROLEUM DISTILLATE FRACTION HAVING A SMOKE POINT LOWER THAN DESIRED; (B) FRACTIONATING THE PARTIALY DESULFURIZED PETROLEUM DISTILLATE INTO TWO FRACTIONS OF DIFFERENT BOILING RANGES, BOTH OF WHICH HAVE ATMOSPHERIC BOILING RANGES AT LEAST AS HIGH AS THE BOILING RANGE OF KEROSENE, AND AT LEAST ONE OF WHICH BOILS SUBSTANTIALLY WITHIN THE KEROSENE BOILING RANGE; (C) HYDROGENATIVELY DEAROMATIZING SAID FRACTION BOILING SUBSTANTIALLY WITHIN THE KEROSENE BOILING RANGE; AND (D) BLENDING THE DEAROMATIZED KEROSENE BOILING RANGE FRACTION WITH THE REMAINING UN-DEAROMATIZED FRACTION HAVING AN ATMOSPHERE BOILING RANGE AT LEAST AS HIGH AS THE BOILING RANGE OF KEROSENE TO RECOVER A PETROLEUM DISTILLATE HAVING A HIGHER SMOKE POINT THAN THE FEED.