DE1470533C - Process for reducing the content of sulfur, nitrogen, metal impurities and aromatic compounds as well as the coking tendency in high-boiling liquid hydrocarbons by two-stage treatment with hydrogen - Google Patents

Description

The invention relates to a method for reducing the content of sulfur, nitrogen, Metal impurities and aromatic compounds as well as the tendency to coke in high-boiling points liquid hydrocarbons through two-stage treatment with hydrogen. This procedure is thereby characterized in that the first stage at a temperature of 388 to 425 ° C and at a Pressure from 45.5 to 210 at, the second stage at a temperature that is 26 to 76 ° C below the temperature the first stage, and a pressure that is 5.9 to 9.8 at higher than the pressure in the first stage, performs, a fresh gas rich in hydrogen with a hydrogen content of at least 65 percent by volume in the second stage, the gaseous Hydrogen-containing fractions from the second stage as a hydrogen-containing gas in the first stage introduces and used as a catalyst for both stages a known cobalt molybdate catalyst.

• The high boiling points treated in this way liquid hydrocarbons are essentially sulfur-free and have only a low content of contaminating metals and aromatic compounds. The method according to the invention is accordingly particularly suitable for the pretreatment of feeds for catalytic cracking processes.

Contamination of the catalyst in the catalytic cracking process causes the formation of gases Hydrocarbons, which are unsuitable as motor fuels, also the formation of unsaturated Hydrocarbons, which are fickle when stored and in some cases less than motor fuels are suitable as saturated hydrocarbons, and the formation of coke, causing a loss Source material equals. -These disadvantages- ·. arise as soon as the starting materials for the Cracking processes contain the impurities mentioned above. It is therefore important to check the content of the The starting material to reduce impurities to a minimum. It is important to consider that the contamination of the catalyst with metals is cumulative, d. i.e., the metals are not burned during regeneration and removed from the catalyst, but must be used during the normal implementation of catalytic cracking processes are thereby kept at an acceptable level, that one continuously removes part of the catalyst and this by fresh, uncontaminated Replaced cracking catalyst. This measure is of course costly. By reducing the amount of metal impurities introduced with the starting material could also be the amount to be removed Amount of catalyst can be reduced.

According to the invention, the material to be fed to a catalytic cracking plant is in the manner pretreated so that sulfur can be formed from the sulfur compounds it contains of gaseous hydrogen sulfide, which can easily be separated from the liquid hydrocarbons, removed and replaced the removed sulfur with hydrogen. Usually these are the sulfur compounds contained in the starting material to thiophene compounds. By desulfurization however, other sulfur compounds are also removed with hydrogen. The crowd too the metal impurities contained in the hydrocarbons is reduced. These metallic ones Impurities are normally organometallic compounds that are soluble in the hydrocarbon material that cannot be removed by settling or filtering. The metals that make up the Contaminating the catalyst and being partially removed according to the invention include, among other things Nickel, vanadium and iron. The method according to the invention also produces a considerable amount

ίο those contained in the high-boiling hydrocarbons heavy aromatic compounds fully or partially hydrogenated to naphthenes.

The use of the hydrogen-containing gaseous components from a second stage as a hydrogen-containing reaction gas for a first reaction stage is known per se and is e.g. As described in British Patent 824,635. Cobalt molybdate catalysts are also known per se. In US Pat. No. 2,758,957, in which these catalysts are mentioned among others, however, certain Ni-Mo / Al ₂ O ₃ catalysts are proposed for the hydrogenation of aromatics and sulfur-containing hydrocarbons, which bring about a more effective hydrogenation of the aromatics supposed to be used as the cobalt molybdate catalysts. According to British patent specification 834 776, the more effective hydrogenation catalysts which are usually sensitive to sulfur are used for the hydrogenation, while catalysts which are insensitive to sulfur are used in the preceding desulphurisation stage.

In view of this state of the art, it was surprising that by using two process stages, but one and the same catalyst for both stages, while maintaining different reac- ■ tion conditions in the two stages an effective desulfurization and a hydrogenation of the aromatic Compounds and a reduction in metallic impurities in the high-boiling point Loading can be achieved.

The method according to the invention will now be explained with reference to the drawing. It shows the reactor 10 as the first stage and the reactor 12 as the second stage. The fresh batch is fed to the system via line 14. A hydrogen-rich gas is mixed with it via line 16. The mixture obtained is passed into the reactor 10 via line 18. Here, the desulphurisation with hydrogen takes place under relatively severe conditions. The product desulphurized by means of hydrogen is drawn off via line 20 and cooled in a cooling device 22, from where it passes via line 24 into a separator 26. In this, the light gases from the desulfurization stage are drawn off as the top fraction via line 28. These gases consist of light hydrocarbons and the hydrogen sulfide formed in reactor 10, and also unreacted hydrogen; "and the light hydrocarbons introduced via line 16. The liquid product flows out of the separator through line 30 and _: " becomes fed into the reactor 12 by means of the pump 32 via the lines 34 and 38. Before entering this reactor, fresh, heated hydrogen is added via line 36. In reactor 12, the reaction with hydrogen is carried out under relatively mild conditions. The resulting product is drawn off via line 40 and in

a separator 42 is passed in which the liquid material is separated and then considered to be essentially Sulfur-free product with significantly reduced levels of metallic and aromatic impurities Connections' is removed. At least some of those withdrawn from the separator 42 The gas phase is fed via line 16 to the fresh feed mixed in. If necessary, part of the gaseous phase can also be passed via line 44 and the valve 46 can be removed from the system. the Liquid phase emerging from separator 42 is fed via line 48 to a catalytic cracking plant 50 supplied, which can be a system with fluidized bed or quiescent bed. She can too fed to another catalytic process in the presence of a catalyst which is sensitive to the above-mentioned impurities is carried out.

As an alternative to the preferred method described above, in which the liquid is pumped and the Gas is passed through the application of pressure, it can be expedient under certain conditions both the liquid material from the first stage from the separator 26 in the reactor 12 as well as the gas from the separator 42 into the reactor 10 of the first stage.

In the first stage reactor 10, in which the feed is mixed with the gaseous, hydrogen-rich fractions from the reaction in the second stage, severe desulfurization conditions also prevail. Temperatures between 388 and 425 ° C. and a pressure of 45.5 to 210 at. The space flow rate used in the reaction vessel of the first stage is between 1.0 and 4.5 parts by volume of charge per part by volume of catalyst per hour. In the reaction vessel of the first stage, an amount of hydrogen of 6.24 to 26.8 m ³ / hl of charge is expediently used, the hydrogen content in the charge gas normally being between 65 and 85 percent by volume, but can also be only 60 percent by volume about 2.14 to 4.46 m ^{3 of} hydrogen per hectolitre of oil charge is consumed The sulfur content of the feedstock is normally 0.5 to 3 percent by weight.

In the reactor 12 of the second stage, a relatively mild desulfurization with hydrogen is carried out at 315 to 385 ° C., ie at a temperature which is 26 to 76 ° C. below the temperature of the first stage. The pressure in the second stage is 5.9 to 9.8 at higher than the pressure in the first stage and is between 53.5 and 211 at: the space flow velocity in the second stage expediently corresponds to that in the first stage . In the reaction vessel of the second stage, the amount of hydrogen required for treatment can be between 7.14 and 26.8 m ³ per hectolitre of charge, the hydrogen concentration being about .5 to 15% higher than in the first stage, i.e. preferably 70 to 90 ° / o. The hydrogen consumption in the second stage can be between 0.36 and 2.14 m ³ per hectolitre of charge: The lower hydrogen consumption in this stage is due to the pretreatment in the first stage, in which the majority of the hydrogenating desulfurization takes place. Depending on the degree of desulfurization achieved in the first stage, the sulfur content is'. in the feed for the second stage 0 to 2 percent by weight.

In contrast to the two-stage process according to the invention, in which the fresh hydrogen in a second stage and the gaseous hydrogen-containing components passed from the second stage into the first stage are, you have so far carried out the hydrogenative desulphurization in one pass. The The method according to the invention offers significant advantages over this method.

For comparison, a series of experiments was made

carried out, including three test series in the manner according to the invention (A, B, C) with changing the

■ temperatures used in the first and second stage, and a series of tests in a known manner with a single throughput. In order to achieve the same reaction times, the space flow rate for the hydrocarbon feed was kept about twice as high in the experiments carried out according to the invention as in the experiment carried out in a known manner. The pressure and the hydrogen and H ₂ S ratios were kept essentially at the same value in both types of experiment. The process conditions are summarized in Table I:

Table I.
Procedural conditions

In a familiar way

carried out

attempt

row
B.

Space velocity,

Vol / Vol / h .. · ... _v .., .. r _;

Temperature, ⁰ C ..............

Pressure, at ...-. :

H ₂ amount, m ³ / hl ...... ....

H ₂ S amount, m ³ / hl

0.98

374
57
IO43 1.96

.52
8.24
0.27

1.93
373
57
10.13

0.16

1.92
418
52

.10.17
0.27

1.99

342 '

57 ■ ..

9.83

0.16

1.95

401 'x 52 9.67 0.27

-2.00 346

57 9.51 0.16

The starting material for these experiments was equivalent to 65 starting materials used. It

produced by a process gas oil having a medium boiling point (temperature at which

and a deasphalted oil to a mixture distilled over 50 percent by volume) of 463 ° C, a

usually worked for such a .Ver density of 7.9194. and a sulfur content of

1.78 percent by weight. The metal content was 0.85 parts per million (ppm) nickel, 0.88 ppm vanadium and 0.55 ppm iron. The aromatic content was 12.31 percent by weight. The one in the second stage imported hydrogen had a purity of 98 percent by volume and above and was below a pressure of 57 at in the system. The specified sulfur content was achieved in the way that a certain amount of hydrogen sulfide was added to the charge.

The catalyst was extruded in the form of

0.32 cm beads were used. It consisted of cobalt molybdate on aluminum oxide as an inert carrier and contained 12.4% MoO ₃ and 3.4% CoO. The catalyst for the test carried out in a known manner and for test series A and B came from the same batch. For test series C, however, the catalyst was used from a different batch. In Table II, unless otherwise noted, the values given for test series A, B and C represent the results of the second stage.

Table II
Sulfur content of the end product (percent by weight)

feed 1 2 3 4 ' average Dissolve
felung, ⁰ zo In a familiar way
accomplished
A. 1.78 0.25
0.135
0.14
0.15 0.30
0.12
0.12 0.25
0.12
0.16 *) 0.25 0.26
0.12
0.14
0.14 85.4
93.3 B. 92.1 C.

*) Average of the first and second level.

Coking residue according to Conradson (percent by weight)

feed 1 2 3 4th average Decrease
tion, ° / o In a familiar way
accomplished
A. 1.63 0.84
0.64
0.62
0.80 0.68
0.52
0.69 0.79
0.80
0.54 *) 0.83 0.79
0.65
0.62
0.68 51.5
60.1 B. 58.3 C.

*) Average of the first and second level.

Nitrogen content (weight percent)

feed 1 2 3 4th average Decrease
tion,% In a familiar way
accomplished
A. 0.14 0.11
0.08
0.07
0.09 0.10
0.08
0.07 0.08
0.136
0.08) 0.07 0.09
0.10
0.08 35.7
29.3 B. 42.1 C.

*) Average of the first and second level.

Nickel content (parts per million parts)

feed 1 2 3 4th average Decrease
tion, ° / o In a familiar way
accomplished
A. 0.65 0.21
0.24
0.24
0.10 0.14
0.08
0.11 0.14
0.07
0.11 *) 0.08 0.14
0.08
0.24
0.105 78.5
87.7 B. 83.8 C.

*) Average of the first and second level.

Content of aromatic compounds (percent by weight)

feed 1 2. . . 3 4 ·, average Decrease
tion, ' ⁰ /!) In a known way:
accomplished
A. 12.31 10.09
10.16
8.81
9.27 9.22
9.53
'8.94 9.21
9.84.
8.80 *) 10.04 9.64
■: 9.84.
: 9.00 21.7
20.1 B. . 26.9 C.

*) Average of the first and second level.

In experiment B, no further results were recorded after the first experiment.

From the values compiled in the table above it can be seen that the. achieved according to the invention percentage desulfurization in test series A and C is over 90%. It was also found that during the desulfurization the compounds which tend to coke in strong Dimensions are reduced and the percentage reduction is at least 58.3%. The reduction the nitrogen content is also essential; she lies between 29.3 and 42.1%>. ■

The metallic impurities consist of nickel, vanadium and iron. As is well known Vanadium and iron are reduced in an amount equal to the amount of nickel removed in one If there is a certain ratio, the nickel analysis is characteristic of the analysis of the other metals. Thus, the method of determining the reduction in metal contamination is that one determines the reduction in the nickel content. In test series A, 87.7% of the nickel was removed, in the test series C 83.8%. In comparison, the procedure was carried out in a known manner Attempt only achieved a reduction of 78,5 ° / o.

In this connection it should be noted that the value 0.24 ppm after the first attempt of the Test series A was neglected in determining the average value, since the up to Determining elapsed time likely was insufficient for the oil to spread well over the catalyst.

The table also shows that the reduction in aromatic compound content achieved is quite good. It was between 20.1 and 26.9%. It can be assumed that in this respect the The advantage resulting from test series C has two causes. On the one hand, it enables the first stage Sulfur removal allows the catalyst to develop its effectiveness better in the second stage. On the other hand, the lower temperature used in test series C shifts the equilibrium in favor of the hydrogenation of the polycyclic aromatic compounds.

If one compares the desulfurization achieved according to the invention with that achieved in a known manner, so the result is a degree of desulphurisation of more than 92% compared to a degree of desulphurisation of only 85%. The percentage reduction in the compounds forming coke products is 58 to 60% compared to about 52% in the known method. The reduction of the nitrogen content is at least comparable with the results of the previous procedure. The percentage decrease of metallic impurities is increased to: 87.7%. So far it has been 78.5%. Also the The content of aromatic compounds is reduced more than before. ...

The surprising and unforeseeable advantage of the method according to the invention is likely to be based on the application of higher temperatures, in the first hydrotreatment stage, whereby favors the removal of the sulfur compounds

will. -. Also, because of the distance. of" most of the hydrogen sulfide and light hydrocarbons after the first stage, d. H. in the separator 26 in the reactor for the second stage the partial pressure of the hydrogen is increased and the partial pressure is increased of hydrogen sulfide, so that the equilibrium for the conversion of the sulfur, Nitrogen, condensed aromatic and other harmful ones contained in the oil feed Connections is improved. In addition, by lowering the temperature in the second stage the hydrogenation and thus in particular the removal of the aromatic compounds is favored. It is also important that the addition of fresh hydrogen to the second, operated under milder conditions a higher hydrogen partial pressure at the point of the stage Process arises at which the concentration of non-hydrogenated compounds by the preceding Desulfurization with hydrogen decreased

is. The result is a more complete conversion of what has already been partially desulfurized with hydrogen Loading than was previously possible.

Preferably for the treatment according to the invention is the starting material in question

generally a hydrocarbon material having a density between 0.876 and 1.007 and one Boiling range between 205 and 705 ° C. A suitable starting material could e.g. B. a between 400 Mixture of product gas oil boiling between 205 and 565 ° C and a deasphalted mixture boiling at 705 ° C oil, the z. B. has been produced by propane extraction of crude residues. The crude residue, which is evaporated by the sudden application of a vacuum, can be removed before desulfurization Hydrogen can also be washed with a light catalytic circulating oil to reduce the metallic content Reduce impurities. The ratio of gas oil to deasphalted oil in this one Mixture can be between 1.5: 1 and 5: 1.

The degree of purity of the hydrogen introduced into the reactor for the first stage can be determined in the separator 42 can be controlled, but it can also be controlled by the degree of purity of the fresh hydrogen in the Reactor 12 is introduced for the second stage, be influenced. A suitable source of hydrogen for the second stage reactor is hydrogen from a catalytic reformer ..

As mentioned, the method according to the invention is

especially valuable for the pretreatment of feeds for catalytic cracking, it can but also for the treatment of end products used as lubricating oils or motor fuels should be applied. - -

Claims (4)

Patent claims: 1. Process for reducing the content of sulfur, nitrogen, and metal impurities aromatic compounds and the tendency to coke in high-boiling liquid hydrocarbons by two-stage treatment with hydrogen, characterized in that that the first stage at a temperature of 388 to 425 ° C and at a pressure of 45.5 to 210 at, the second stage at a temperature that is 26 to 76 ° C below the temperature of the first stage, and a pressure that is 5.9 to 9.8 at higher than the pressure in the first stage, performs, a fresh, hydrogen-rich gas with a hydrogen content of at least 65 percent by volume in the second stage, the gaseous Hydrogen-containing portions from the second stage as a hydrogen-containing gas into the introduces first stage and as a catalyst for both stages a known cobalt molybdate catalyst used. -, - 2. The method according to claim 1, characterized in that the degree of purity of the hydrogen for the second stage is 5 to 15 percent by volume higher than the degree of purity of the hydrogen for the first stage ". 3. The method according to claim 1 and 2, characterized in that "the space flow velocity in the first and second stage between 1.0 and 4.5 parts by weight hydrocarbon per part by volume of catalyst per hour. 4. The method according to claim 1 to 3, characterized in that the hydrogen in a ratio of 6.24 to "26.8 m ^{3 of} hydrogen. Per hectolitre of liquid hydrocarbon in the first stage and in a ratio of 7.14 to 26, 8 ^{ms of} hydrogen per hectolitre of liquid hydrocarbon is introduced into "the second stage. 1 sheet of drawings