US2018772A - Process for obtaining valuable products from hydrocarbon oils - Google Patents

Description

P. L. YOUNG Oct. 29, 1935.

Filed Nov. 19, 1931 mm ME PROCESS FOR OBTAINING VALUABLE PRODUCTS FROM HYDROCARBON OILS Patented Oct. 29, 1935 PROCESS FOR OBTAINING VALUABLE PRODUCTS FROM HYDROOARBON OILS Philip L. Young, New York, N. Y., assignor to Standard Oil Development Company Application November 19, 1931, Serial No. 576,053

1 Claim. (01. 196-53) The present invention relates to the art of producing valuable products from carbonaceous materials and more specifically to an improved method for producing valuable oil products from 5 hydrocarbon oils, by cracking or destructive hydrogenation and the like processes. The invention will be fully understood from the following description and the drawing which illustrates one form of apparatus suitable for carrying out the process.

The drawing is a semi-diagrammatic view in sectional elevation of one form of apparatus arranged according to my invention and showing the flow of oil and gas therethrough.

In previous methods of hydrogenation of mineral oils, the oil and hydrogen have either been separately heated or have been mixed at low temperatures and preheated in admixture to the reaction temperature. The latter methods have been generally preferred for several reasons, the most important of which being that under high pressures the presence of hydrogen largely avoids the formation of tarry or asphaltic material in the heating tubes which would normally occur at temperatures above about 700 F. and thereby prevents fouling of the heating tubes. But even this method is not wholly satisfactory for all types of oils, and it has been observed that in some instances small deposits of a gummy carbonaceous material tend to slowly collect, not in the hot parts of the preheating apparatus, but in the cooler portion thereof, that is, at temperatures below about 500 F. It will be readily understood that this type of deposition is essentially different from the carbonaceous deposits previously mentioned which occur at temperatures above 700 F. and which are substantially completely eliminated by the presence of hydrogen under high pressure. I have noticed that this latter form of deposition, that is at low temperatures is more often encountered with light oils, for'example, of the gas oil boiling range either cracked or uncracked, than is encountered with the heavier oils say of the lubricating type, and

I have further observed that oils which have been subjected to a prior destructive hydrogenation, particularly freshly hydrogenated oils, do not exhibit this peculiarity. It will be understood that all fresh oils do not exhibit this peculiarity and in such cases no difficulty is met, but the unstable oils may be identified by heating slowly in a small bomb to a temperature between 200 and 500 F. Oils forming a deposit in this test are classified as unstableoils for the purpose of this invention while those oils which form no deposit in this test are classified as stable oils. I have found that this peculiar deposition at low tem peratures can be eliminated by extremely rapid heating through the low temperature deposition range, for example, passing the oil directly into 5 the high temperature reaction vessel in a relatively cool state. The oil maybe unheated, or it may be preheated to a temperature below which the deposition is known to occur. In this way the oil is heated very rapidly, in fact substanl0 tially instantaneously through the range of instability where low temperature deposition would occur.

In the following description of my process and the claim I will refer to the oils which show this 15 peculiar property of causing depositions when heated with or without hydrogen to elevated tem peratures below about 500 F. as unstable oils, and in the same sense I shall refer to oils which g do not exhibit this peculiarity as stable oils, 20 and it should be kept in mind that this form of stability or instability" while it may or may not be thermic in character, is to be carefully distinguished from the ordinarily known instability of petroleum and other hydrocarbon oils at temperatures of 700 F. and above.

Referring to the drawing, reference characters I and 2 designate feed pumps which withdraw oils from different sources not shown. Oil withdrawn 30 by the feed pump l is a stable oil as defined be-' fore, and is passed through a line 3 into pipe 4. It is then picked up by a high pressure feed pump 5, and forced into line 1. Hydrogen or a gas rich in free hydrogen is added to the oil in 35 line I and. the mixture flows to a heat exchanger 8, and then by line 9 to a second heat exchanger I0, by pipe II to a heated coil l6 arranged in a furnace setting I1, and therefrom into a pipe I8.

The oil picked up by the feed pump 2 is of the 4.0 V

unstable character and is passed through an ex- (:hanger'IZ where it may be raised to a temperature not over about 200 F. It is then conducted by a pipe l3 and is mixed with the heated oil in various proportionsat difierent points, for ex- 45 ample, a small amount may be added to the stable oil in line 9 by means of the pipe M. More may be added to the stable oil by means of line l5 and it may be also added directly to the pipe !8. The oil at this point is at a temperature 50 well above the unstable range and is forced directly into the reaction drum I9. This drum is adapted to stand high pressures and temperatures in the neighborhood of to 200 atmospheres, and 900 to 1100 F., respectively. It may be packed with a suitable catalytic material designated by the character 20, the nature of which will be disclosed below, and it is protected from excessive loss of heat by an insulating layer 2!, or its equivalent. Additional heat may be added to the drum, for example, by the electric heating coil 22. The oil is withdrawn from the drum by line 23, and is passed through the exchangers 8 and I0, respectively. While the drawing shows these exchangers connected in parallel, it will be understood that they may be connected in series, if desired. The cool oil is now collected in a line 24, and passed into a separation drum 25. This will ordinarily be at a temperature sufficient to allow lighter fractions and gas to remain in a vaporous state, whereas the heavier oils will be condensed. This freshly hydrogenated, heavy oil is stable in character and may be added directly to line 4 through a pipe 26, and in this way may be re-circulated through the oven. In some instances this oil will be sufficient, and ireshstable oil need not be added by pump l as indicated above.

The vapors from separation drum 25 now pass through exchanger i2, and a cooler 28 which condenses substantially all of the normally liquefiable constituents. These may be withdrawn by a pipe 39 to any convenient storage receptacle. Permanent gases then pass through pipe 3! to a purifier 32 which is capable of removing the greater part of the gaseous hydrocarbons and hydrogen sulphide. Purified gas is then recompressed by the booster pump 33, and is re circulated into line 6 by means of pipe 34. Additional hydrogen under high pressure may also be added by pipe 35.

As stated above, I have observed that certain oils are very unstable at temperatures below 500" F. and that this instability shows itself by depositing materials when heated through the range of about 200' to 500 or 700 F. I have observed that a rapid heating of the oil through this range is effective in preventing, or largely preventing this deposition of solid material; but by rapid heating I do not mean the heating through a heat exchanger which may take from 1 to 10 minutes or' more. On: the other hand, I mean that the oil must be substantially instantaneously raised through the range of instability. While any method of heating the oil in this way would be applicable to my process, I find the-most desirable method is in selecting a stable oil, notably a highly-saturated oil or one which has been subjected to a prior hydrogenation treatment, even though it may not have been fully saturated thereby, and especially the freshly hydrogenated oils, for example, those which are obtained from the process itself and which are ordinarily re-circulated to the unit to increase the yields, and such an oil is then heated toa temperature in excess of 650 F. This temperature should be sufficiently high to raise the remainder of the oil to a temperature well above 500 F. or preferably 700 F., that is to-say, above the range of low temperature instability. It will be appreciated that this will be accomplished substantially instantaneously, and that the actual time will be in the nature of 10 to 50 seconds. The stable oil may be heated alone, but it is preferable to heat it in the presence of hydrogen and after admixturewith the unstable oil the temperature may be further increased by heating in the ordinary way through a second. heating coil, or through a further portion of a single coil. In this way temperature may be raised to the reaction range which is from about 700 to 1100 F., but in many instances, especially for vapor phase work where the unstable types of oil are most generally encountered, the reaction temperature is from 900 to 1050 F. If desired, the temperature of the stable oil may be so adjusted that no further heating of the mixture with the unstable oil is required and that reaction temperature is immediately reached on such mixing. To assist in the supply of heat the reaction vessel itself may be heated in a suitable manner, for example, by electric heating means or by the injection of oxygen containing substances which will be reduced with evolution of heat, or if preferable, both of these means may be used simultaneously. Furthermore, I have observed that the conversion of heavy oil into lighter products by destructive hydrogenation is itself an exothermic reaction, and for these reasons the stable portion of the oil with, or without the addition of hydrogen, need not be heated to so high a temperature as might be at first sight supposed in order to furnish heat suflicient to raise the temperature of the stable portion rapidly through the unstable range and to reaction temperature. It is ordinarily necessary to heat the stable oil to a temperature of 850 F. or above, but its temperature may be adjusted from say 850 to 1100 F. depending on the amount of heat which is to be added directly to the oven by the means enumerated above, by the heat of the conversion reaction which varies somewhat in different oils and other factors which may be satisfactorily adjusted after a few tests, but which cannot-be completely specified due to the fact that they vary under the various conditions as indicated. Special means may be taken to insure a rapid mixing of the hot and cooler oils but ordinarily mixing the two streams in a pipe is sufiicient. If desired, the cooler oil may be injected into the stream of hot oil, for example through a perforated pipe which is placed concentrically with a larger pipe containing the flowing stream of hot oil. If the cool unstable oil is to be forced directly into the drum the perforated pipe may project directly into the catalyst bed so that the heating through the unstable range takes place under the influence of hydrogen and the catalyst.

I have further determined that various proportions of unstable oil may be added to the stable product, and the mixture may be heated Without difiiculty. In this Way the amount of the stable oil may be increased to a considerable erally those which are known to be sulphactive, 69;

or in other words, which are not poisoned by the presence of sulphur which is almost always present in petroleum and oils derived from coal. Of these catalysts the oxides, nitrides andthe sulphides of the metals of the sixth group of the 0g periodic system are satisfactory, and these may be mixed with numerous other substances such as zinc oxide, alumina and other diflicultly reducible oxides, silica, active carbon and the like.

Materials such as ammonia, rare earths and dif- 7 ficultly reducible oxidesmay be used alone.

In an example illustrating the use of my process, an uncracked gas oil is treated in vapor phase with a relatively large excess of hydrogen over a catalyst comprising zinc oxide, tungstic and mo lybdic acids. The pressure of about 200 atmospheres is continuously maintained, and the reaction chamber is held at a temperature of about 930 F. The oil product after cooling and condensation is separated into light fractions boiling below about 400 F. and suitable for gasoline, and heavier oil boiling from 400 F. to 700 F. This heavier fraction having been hydrogenated is stable at low temperatures and is heated to a temperature of about 930 F. by passage through a fired coil in admixture with a large volume of hydrogen. The fresh gas oil which is unstable is heated without difficulty to about 200 F. At that temperature substantially no deposition occurs and it is then passed directly into the reaction chamber at this temperature. Under these conditions the load on the fired coil is great and it is found necessary to add heat to the reaction chamber either by electrical means or by addition of a small amount of carbon monoxide in the hydrogenating gas in order to maintain the temperature continuously at 900 F. It is found that about 25% or more of the unstable oil can be added to the stable recirculated product which has been heated to 750 F. without deposition on further heating, and if the temperature is then raised to about 950 F. at the coil exit the reaction chamber is continuously maintained at 900 F. without addition of heat to the reaction chamber by electrical means, or otherwise. Temperatures below 950 25. may be maintained at the coil exit without otherwise heating the reaction chamber by adding additional stable oil to the recirculated fractions from other hydrogenation units operating to produce oil from coal, lignite or from tars and the like. Hydrogenated petroleum may also be added.

While my invention has been described with particular emphasis on its application to destructive hydrogenation, it is equally applicable to cracking and especially to vapor phase cracking where lighter oils of the gas oil type are converted at temperatures above 900 F. It is also applicableto hydrogenation or dehydrogenation 5 reactions in which there may or may not be marked destructive action, for example to the preparation of good quality burning'oils from kerosene which shows a tendency to smoke, or to the purification of high sulphur naphtha either cracked or uncracked or other hydrocarbon oils such as gas oils to greatly reduce sulphur.

The present invention is not limited to any theory or specific method of operation, nor to any specific catalysts, apparatus or types of oil which may have been used to illustrate my method. My invention is to be limited only by the following claim in which I wish to claim all novelty inherent therein.

I claim:

An improved process for the destructive hydrogenation of hydrocarbon oils which are unstable in forming gummy material upon being gradually heated through the range of temperatures from about 200 F. to 500 F. under superatmospheric pressures of the order 'used in the destructive hydrogenation process, comprising preheating a heavier hydrocarbon oil, which under the same conditions of heating is stable against gum formation to a temperature above 500 F., mixing the preheated stable oil in such proportions with unstable oil having a temperature below 200 F. to substantially instantaneously raise its temperature to above 500 F., passing the mixture into a reaction zone supplying hy- 5 drogen for reaction and removing destructively hydrogenated products.

PHILIP L. YOUNG.

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