US2031961A - Destructive hydrogenation - Google Patents

Description

Feb 25, 1936. s. A. Kiss 2,031,961

DESTRUCTIVE HYDROGENATION Filed July 24, 1951 l i' [I uw D() l lx ou N LN@ Q i `Q www N H l www l me/rito@ TUHm AA N55 E W' Clt/wwwa Patented Feb. 25, 1936 DESTRUCTIVE i rl-R() GENATION Stephen A. Kiss, Brooklyn, N. Y., assigner to Standard-I. G. Company Application July 24, 1931, Serial N0. 552,834

10 Claims.

'I'he present invention relates to an improved method for the hydrogenation of hydrocarbon oils and the production of improved products therefrom, andmore specically to an improved method for heating such oils to the reaction temperature.

'I'he drawing is a semi-diagrammatic View in sectional elevation of an apparatus which may be used to carry out the process of this invenion.

In the destructive hydrogenation of hydrocarbon oils it has been suggested that the oil Should be heated by rapid passage through red coils to the reaction temperature which is ordinarily from '700 to 950 F. with hydrogen while under a pressure of 20 atmospheres, or 50 atmospheres orV even more. This has been found high- `ly satisfactory with most oils, but at the same time I have found that if the oil has a relatively Wide boiling range and it is heated under conditions such as allow a partial vaporization within the heating coil, that undesirable reactions rapidly progress in the absence of catalytic material, and with the result that carbonaceous deposits may be formed within the heating coils. It has also been found that this may be avoided by extremely rapid passage through the coils, but at the same time I have found that there are certain vobjections even to this procedure, and that if the oils are heated as I have stated under such conditions that partial vaporization occurs within the coil, it often occurs that the undesirable reactions while not progressing to the extent of actual deposition of carbon within the heating coils, still such reactions have progressed to such an extent that there will be an appreciable carbonization in the further reaction zone, and that this cannot be wholly obviated by the use of catalytic materials. The result frequently occurs that the catalytic material is gradually coated with'a coky material and is thereby rendered unreactive. Furthermore it has been found that if such reaction in the coils is totally prohibited and the reaction in the reaction vessel is carried out under a suicient hydrogen pressure and in the presence of suitable vcatalytic agents, that the catalyst remains in an active state for a much longer time and the formation of carbon is whollyb prevented.

I have now found that these adverse effects as stated above may be prevented by a suitable operation of the heating means, which are preferably in the form of coils. In accomplishing my processthe oil is divided into two or more suitable fractions, the lighter one being capable of complete vaporization at a temperature below that at which reaction begins to progress rapidly. Under ordinary conditions this temperature may be taken to be about 700 F., although in some instances it may be somewhat higher f5' or somewhat lower, from about 650 to '750 F. The complete vaporizaticn must be accomplished in spite of an increased pressure, which should be at least 20 atmospheres, preferably considerably more, for example atmospheres or 100 10 atmospheres. A large volume of hydrogen is generally passed through the coil with this lighter fraction and under these conditions the oil is caused to fully vaporize prior to attaining a temperature within the reaction range as stated 13 above.

The heavier cut is chosen preferably to exclude fractions boiling below about 500 F. and may be even heavier. The pressure used during the heating of the heavier cut may be denoted as the critical-homogeneous-pressure It will be understood that for each fraction of oil there is a pressure at or above which the oil may be heated, so that it does not at any temperature show a separation of phases. I do not wish to be limited to a statement that this is either the liquid or the vapor state, but prefer toi use the term homogeneous state, by which I mean that at no temperature, from the lowest to the highest temperature attained by the oil, is there any separation of phase. This may 30 be readily observed in a suitable apparatus such as is used for observing the critical temperatures and pressures of pure compounds. It is a relatively simple routine test method to accurately determine the pressure suitable for the temperature and time of heating to be used commercially.

The critical-homogeneous pressure is governed largely by the boiling range of the hydrocarbon cut. In general, the wider the cut the greater will be the pressure required to maintain the oil in the homogeneous state, and also in general the higher the boiling temperature of the oil the lower will be the pressure, to keep the cil homogeneous. For example, a gas oil fraction having 45 a gravity of 31.2 A. P. I. and boiling substantially between 500 to 700 F. may be maintained in a homogeneous condition at a pressure of 350 pounds while heated rapidly to 850 F., where the heating is accomplished in less than about 30 50 seconds. In such case the oil at the high temperature is substantially of the same boiling range as the initial oil. If, however, a time of 16 minutes is taken for the heating, there has been a considerable decomposition and a pressure of 750 pounds per square inch is required to maintain the homogeneous state. Furthermore, if the heating is accomplished slowing during an hours time a pressure of 2,000 pounds per square inch will be required. If a lighter oil such as a 45 A. P. I. cut, and corresponding to an ordinary kerosene, is heated rapidly so as to avoid decomposition, a pressure of 380 pounds was found sufficient to maintain a homogeneous state. A mixture o'f 10 percent of kerosene in gasoline required a pressure of 500 pounds per square inch to maintain the same homogeneous condition.

It will thus be seen that, as stated above, the wider the cut the greater will be the pressure to maintain homogeneity, and in the same manner the higher boiling the cut the lower will be the pressure to maintain the same state. However, in the case of a high boiling o'il it is also requisite to heat at a relatively rapid rate or to maintain a pressure somewhat higher than is obtained when vthe heating is very rapid because of the formation of lower boiling oils during such heating period. In general, however, with oils boiling in the gas oil range, homogeneity may be maintained at 20 atmospheres if the heating is rapid, say within 10-20 minutes, 50 atmospheres is preferably used under commercial conditions where coil heating is utilized since in this case it is preferred to heat somewhat more slowly than stated above. Under many conditions, however, I prefer to maintain a pressure of or 200 atmospheres. It will be understood that the excessive pressure does not harm, although it may not be entirely necessary.

In my process the separate oil cuts are thus heated to temperatures in excess of 700 and preferably to 800 or 850. They are then discharged together into a reaction vessel which is maintained at a pressure above 20 atmospheres. If the separate cuts are heated at diiferent pressures, it will be understood that the reaction chamber should be maintained at substantially the lower of these two pressures. It is preferable to heat both cuts under the same pressure and to maintain the drum at that pressure, except, of course, deducting frictional losses.

On the other hand it is sometimes desirable to heat the heavier cut at considerably higher pressure and to reduce this pressure by passage through a reduction valve on discharge into the reaction Vessel. The reaction vessel is preferably unheated and is protected against loss of heat by suitable insulation. It is preferably packed with strongly hydrogenating catalysts, of which the metals and the metal compounds of the sixth group elements are preferably used, such as molybdic acid, tungsten and chromium oxides or sulphides as well as other compounds. These may be used alone or in admixtures either with each other or with other substances, preferably the oxides of the metals of the third and fourth groups o'f the periodic system. These catalysts are characterized by strong hydrogenating properties and by indifference to ordinary catalytic poisons, notably sulfur.

The entire requirements of hydrogen may be forced with the lighter oil through the heating coil or a portion of the hydrogen may be added directly to the reaction Vessel. Feed rate and the size of the drum are adjusted so as to allow a suitable decomposition in the reaction vessel. For example 10 to 20, 30 or even 50 percent of the oil may be converted to lighter products falling within the ordinary range of commercial gasoline.

The exit products are cooled and separated into the naphtha fraction and a heavier oil which may be recirculated through the system, for increased yields. Hydrogen may also be purified and returned to the system.

Referring to the drawing pipe I conducts oil from any convenient source through a reflux coil 2 in the top of a rectifying column 3. Preheated oil is then passed through a fired coil 4 and is discharged into the rectifying tower 3 mentioned above. This tower is fitted with rectifying plates 4. Light vapor is removed by line 5, is condensed in the cooler 6 and discharged into a collecting drum 1. The rectifying plates 4 are arranged in two series an upper and a lower which are separated by a plate da. This plate is arranged for the withdrawal of a side stream or cut by means of pipe 8 which cut comprises a condensate produced by the coil 2 in the upper part of the column. The heaviest or unvaporized oil is removed frorn the lower part of the column by a pipe 9. Steam may be introduced by a pipe I0 and by branch lines on plate 4a and also in the bottom of the column so as to assist in the vaporization of the oil at these points. Pumps II, I2, and I3 are connected so as to withdraw the oil from collection drum 1, lines 8 and 9 respectively and to force the oil through the separate pipes I4, I 5, and IS into and through the separate fired coils I'I, I8, and i9. Hydrogen may be admitted to the inlet of coils I1 and IB from a hydrogen line 2U and branch pipes 2| and 22 respectively. These coils are arranged with suitable valves indicated on the drawing so that either one or the other or all may be used at the same time. T'he heated oil is collected in a manifold 23 and is then discharged therefrom into a reaction chamber 24 which is packed with a suitable catalyst indicated at 25 the nature of which has been indicated above. Additional hydrogen may be ad-l mitted directly into drum 24 by means of a branch pipe 26 which is connected with the hydrogen feed line 20. Oil and gas are Withdrawn from the reaction drum by a line 2l, are cooled in condenser 28 and discharged into a separation drum 29 from which the oil is withdrawn by line 3l). The permanent gas is drawn by a pipe 3I through a purification chamber Sla and the purified gas is mixed with makeup hydrogen furnished by line 32. The gas is then compressed by a compressor 33 and is fed into the hydrogen line 20.

As examples of the manner in which I prefer to carry out my process, the following may be considered- Eample 1.-An oil having an initial boiling point of about 100 F. and a final boiling point of '720 F. is fractionated into three cuts, the rst boiling below about 450 F. This cut may be completely vaporized at a temperature below 700 even under 20 or 50 or more atmospheres.

'Ihe second cut boiled between about 400 and 500 F. The third cut boiled from 500 to 720 F.

'Ihe first cut was passed rapidly through a heating coil with a large volume of hydrogen amounting to about 6,000 cubic feet per barrel of the total oil. A temperature of 850 was attained within a short time. The third cut was heated under a pressure of 100 atmospheres through a coil in the absence of hydrogen. A temperature of 850 was attained without separation of phases. The first and third cuts were thus discharged together into a reaction vessel which was held at 20 atmospheres. The second cut was preheated to about 700 at which substantially no vaporization occurred, and was disrecovered. 'Itwas substantially Ifr'ee from sulfur,

Y gum andwas color stable. Therewasno'evidence of tar formation or of coke' depositionleither-in the coilor onthe catalyst,"which was -in'afcondi- `tion to" remain active for a long period of time.

It Awillbe -understood that the cillin each case is heated under coil pressures vabove that of the reaction vessel.

Example 2.-In anothercase, aln oil comprising a gas o-il boiling from500 to"800F. is separated into two cuts, the rst boiling to about 600 F. This oil waslpassed lat a pressure of 50 atmospheres with hydrogen through a heating coil and raised to a temperature of 875 F. The oil was completely vaporized prior to 700 F. The second cut was heated rapidly at a pressure of 50 atmospheres and was maintained completely in a homogeneous state throughout. 'I'he oils were discharged into a reaction vessel as in the first example. A large portion of the oil was recovered and above 50 percent thereof boils within the range of commercial gasoline.

My invention is not to be limited by any theory in the operation of the heating coils nor by any particular example which may have been given for illustrative purposes, but only by the following claims in which I wish to protect all novelty inherent in my invention.

I claim:

1. In a process for destructive hydrogenation of petroleum the steps of preheating with hydrogen a rapidly flowing stream of an oil fraction capable of complete vaporization below 700 F. at a selected pressure in excess of 20 atmospheres by passing the same through an elongated heating Zone of narrow cross section, separately preheating a heavier oil fraction in the absence of hydrogen by passage of a stream thereof through an elongated heating zone of narrow cross section to a temperature above 700 F. while at a pressure above its critical homogeneous pressure, the rapidity of heating and pressure applied to said heavier fraction being adapted to prevent separation of phase, and discharging both streams into a reaction zone, maintained under conditions adapted for destructive hydrogenation.

2. Process according to claim l in which the rapidity of heating of the last m-entioned stream is adapted with relation to pressure to obtain no substantial conversion to light oil during the heating period.

3. Process according to claim 1 in which the heating takes place in absence of catalytic substances at pressure above 20 atmospheres and the time of heating of the heavy oil is of the order of to 20 minutes in order to prevent substantial conversion to light oil during the preheating period.

4. In the destructive hydrogenation of petroleum distillates, the step of passing with hydrogen a continuous stream of an oil capable of complete vaporization below reaction temperature while at pressure in excess of 50 atmospheres through an elongated heating zone of narrow cross section, separately passing a continuous stream of heavier oil fraction in the absence of hydrogen through another elongated heating zone of narrow cross section and rapidly heating the` same to a temperature in excess of 900 F. while under pressure of at least 50 atmospheres, the rapidity of heating and the pressure being adapted to prevent substantial separation of phase during the heating of theheavier fraction and Ydlsc'iharging theg heated jfractions into a common enlarged'reac'tion /:on'e

maintained under conditions yfor destructive hydrogenaton.

5. In the destructive hydrogenation 'of Vhydrocarbon oil distillates the steps of passing acontinuous stream of a lighter oil cut free from fractions boiling above 500 F. through anY elongated Vheating zone of narrow cross section and heating the cut to a temperature in excess of 850 F. while under pressure in excess of 50 atmospheres in the presence 0f hydrogen, separately Apassing a continuous stream of heavy oil cut free from fractions boiling below 550 F. in the absence of hydrogen through another elongated heating zone of narrow cross section and rapidly heating the same to a temperature in excess of 850 F. while at pressure in excess of 50 atmospheres and above the critical homogeneous pressure, rapidity of heating and pressure being adjusted to prevent separation of phase, discharging both cuts into an enlarged reaction zone maintained at pressure not substantially below the lower pressure at which the heating is accomplished.

6. In the destructive hydrogenation of petroleum oil fractions the steps of separating the petroleum oil into a plurality of cuts, the lightest being capable of complete vaporization below reaction temperature while at pressure in excess of atmospheres, the heaviest being of sufciently high boiling rangeto be capable of being maintained in a state of homogeneity at reaction temperature while at pressure of 20 atmospheres, separately heating continuous streams of these oil cuts rapidly to temperature in excess of 850 F. by passing each stream through a separate elongated heating zone of narrow cross section while under pressure in excess of 20 atmospheres, the lightest in the presence of hydrogen and the heaviest in the absence thereof, the time being insufficient to bring about a substantial conversion to low boiling products during the heating steps, and discharging the heated cuts into a common reaction zone maintained at a lower pressure but in excess of 20 atmospheres for destructive hydrogenation.

7. Process according to claim 6 in which the lighter fraction comprises an oil boiling below about 600 F. and the heavier fraction boiling above about 600 F.

8. Process according to claim 6 in which the lower boiling oil boils below 500 F. and the higher boiling fraction boils above 650 F. and an intel'- mediate cut is forced directly into the reaction zone preheated to a temperature below its initial vaporization point under pressure imposed.

9. In the destructive hydrogenation of petroleum, the steps of preheating with hydrogen a rapidly flowing stream of an oil fraction capable of complete vaporization below '700 F. at a selected pressure in excess of 20 atmospheres by passing the same through an elongated heating zone of narrow cross section maintained at a temperature in excess of 700 F. and under a pressure of the order mentioned such that complete vaporization of said fraction is effected, separately preheating a heavy oil fraction in the absence of hydrogen by passage of a stream thereof through an elongated heating zone of narrow cross section to a temperature above 7 00 F. while applying a pressure above its critical homogeneous pressure, the rapidity of heating and pressure applied to said heavier fraction being adapted to prevent separation of phase, discharging both streams into a reaction zone maintained under conditions adapted for destructive hydrogenation and subjecting such material in said zone to the action of a destructive hydrogenation catalyst.

10. 1n the destructive hydrogenation of a petroleum having a wide boiling point range, the steps of fractionating said petroleum into at least two fractions, the lighter of which contains only vconstituents capable of complete vaporization below 700 F. at a selected pressure in excess of 20 atmospheres, preheating the light fraction together with hydrogen by passing it through an elongated heating zone of narrow cross section maintained at a temperature above 700 F. and under a pressure of the order mentioned, such that complete vaporization of said fraction is effected, separately preheating a heavier frac- Vtion in the absence of hydrogen by passagey of a stream thereof through an elongated heating zone of narrow cross section to a temperature above 700 F. while applying a pressure above the critical homogeneous pressure of said fraction, the rapidity of heating and pressure applied to said heavier fraction being adapted to prevent separation of phase, discharging both streams into a reaction Zone maintained under conditions adapted for destructive hydrogenation and subjecting said material in said zone to the action of a destructive hydrogenation catalyst.

STEPHEN A. KISS.

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