US2876194A - Catalytic hydroforming in the presence of controlled amounts of water - Google Patents

Description

March 3, 1959 HARDY 2,876,194

CATALYTIC HYDROFORMING IN THE PRESENCE OF CONTROLLED AMOUNTS OF WATER Filed April 20, 1953 PRODUCT RECOVERY Robert L. Hardy Invmor By e f wfforney United States atent CATALYTIC HYDROFURMING IN THE PRESENCE OF CONTROLLED AMOUNTS OF WATER Robert L. Hardy, Westfield, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware 1 Application April 20, 1953, Serial No. 349,645

4 Claims. (Cl. 208-136) The present invention relates to improvements in hydroforming, and more particularly, it relates to hydroforming naphthas containing naphthenes in the presence of a fluidized bed of a supported group VI metal oxide catalyst, such as molybdenum oxide on alumina.

Hydroforming is generally defined as an operation in which a naphtha containing a substantial quantity of naphthenes is contacted at elevated temperatures and pressures, in the presence of added hydrogen with a solid catalytic material. The purpose of the hydroforming operation is to improve the octane rating of the feed naphtha. The chemical reactions involved include the following:

(1) Dehydrogenation of naphthenes to the corresponding aromatic as were methylcyclohexane is dehydogenated to form toluene.

(2) Isomerization or rearrangement of the acyclic and cyclic compounds as where straight chain paraffins are converted to branch chain parafiins and where cyclic compounds, such as methylcyclopentane isomerizes to form cyclo-hexane and (3) Hydrocracking of paraflins.

The present invention relates to improvement in the hydroforming operation involving the inclusion of a relatively small controlled amount of water in the reaction zone. The inclusion of water with the reactants in the reaction zone improves the yield of desired product when operating for a given octane number, or conversely improves the product octane number when operating for a given yield. The exact reason why the inclusion of water improves the hydroforming operation is not known. It may be that the water acts as a reduction inhibitor, thus serving to condition the molybdenum oxide by maintaining it at its most favorable state of oxidation. The atmosphere in the reaction zone is a reducing atmosphere and if the catalyst is fed to the reaction zone in the form of M it is at least conceivable that the molybdenum oxide is reduced to a lower state of oxidation than M0 0 in which case, the formation of dry gas and coke is increased. The inclusion of small controlled amounts of water may prevent reduction of the M0 0 to a lower and undesirable state of oxidation.

In the type of operation contemplated by the present invention, the process is carried out in What is essentially a two-vessel system comprising a reaction zone and a separate catalyst regeneration zone. In spite of the fact that hydrogen is fed to the reaction zone with the naphtha for the purpose of repressing the deposition of coke on the catalyst, nevertheless, such deposits occur, and periodically, it is necessary to withdraw the catalyst and subject it to treatment with an oxygen-containing gas for the purpose of removing such deposits and restoring the activity of the catalyst. In the regeneration zone the molybdenum oxide is reoxidized to the M00 state during the burning off of the carbonaceous and o her deposits. According to the present invention before this regenerated catalyst is returned to the reaction zone. it may be subjected to a pretreatment, in other "ice words, it may be treated with a reducing gas, such as hydrogen, to convert the molybdenum oxide to a state of oxidation corresponding to an average valence of about 5, in other words, to the form represented by M0 0 However, as stated, when this pretreated catalyst is fed to the reaction zone it may undergo further reduction to a valency state, which is less effective in the hydroforming operation. In any event, and whatever the explanation, the result of data obtained in a pilot unit clearly shows that the inclusion of a relatively small controlled amount of water improves the operation by increasing the yield of high octane product.

The main object of the present invention is to conduct a hydroforming operation under such conditions as to give improved yields of high octane product.

Another object of the present invention is to carry out the hydroforming operation continuously.

Other and further objects of the present invention Wlll appear in the following more detailed description and claims.

In the accompanying drawing, there is set forth, d1agrammatically, the essential elements of an apparatus layout in which the present improvements may be carried into effect.

Referring to the figure, 1 represents a reaction zone containing a body of fluidized powdered catalyst C which may comprise, for example, about 10 wt. percent of molybdenum oxide calculated as M00 on 90% of an active form of crystalline alumina. The catalyst is ground to a particle size, such that it is readily fiuidizable, namely, a particle size indicated generally by the following particle size distribution:

It will be understood, of course, that the foregoing particle size distribution is merely illustrative and any suitable particle size distribution which will fluidize satisfactorily can be used.

A naphtha, preferably, a virgin naphtha containing, say, 35-45 volume percent naphthenes is introduced into the system through line 2 and then preheated in a suitable heating means, such as a furnace 3, containing a suitable coil 4 through which the oil is passed and heated to a temperature of, say, 900f-l000" F. The heated and vaporized oil is withdrawn from the coil 4 through line 5 and charged to the reactor 1 at a lower portion thereof, but above a distributing means G, such as a grid or screen. Simultaneously, a hydrogen-containing gas in line 6 is heated in a furnace 7 containing a coil 8 through which the hydrogen-containing gas is passed, the gas being heated to a temperature of around 1200-1300 F. The thus heated hydrogen gas is withdrawn from coil 8 through line 9 and passed into the bottom of reactor 1. In other words, the vaporized oil and the hydrogen-containing gas are not contacted prior to their introduction into the reaction zone, the purpose of this precaution being to prevent degradation of the feed, particularly, the

, naphthenes therein, by contact with the highly heated The superficial yelgeity of the gasiform material in reactor lis Controlled within the limits of from about /2 to 1% feet per second, whereby, the catalyst C is maintained in the form. of a dense fluidized bed extending from G to an upper dense phase level L. From L to the top of the reactor, there is a dilute or light phase suspension of catalyst in gasiform material. The gasiform material passes from the dense phase through the light phase, and before it is withdrawn from the reactor, it is caused to flow through one or more gas-solids separating devices wherein entrained catalyst is separated and returned to the dense bed through one or more dip pipes d. The gasiform material is withdrawn from the reactor 1 through line 11 and cooled in a cooling means 12 to a temperature of about 100 F. The total cooled product is withdrawn from cooler 12 through line 13 and'charged to a separator 14 where it is separated into a two phase liquid product consisting of a lower water phase W and an upper oil phase 0. A gasiform material containing 50 to 70% hydrogen, the remainder being substantially all normally gaseous hydrocarbons except for a relatively small amount of water is withdrawn from separator 14 through line 15 and recycled to line 6 for further use in the process. A portion of this material in line 15 may be rejected from the system in line 16.

The gasiform material in line 15, as stated, contains a small amount of water, in other words, that amount of moisture or water vapor which is in equilibrium with the gasiform material. at the temperature in the cooler 12, which temperature is about 100 F. Ordinarily, this amounts to about 0.1 mol percent water and 99.9% gasiform material other than water vapor. However, additional, water is formed: in. the system by catalyst reduction.

7 Referring again to separator 14, the oil layer is separated from the water layer by withdrawal through line 17 and subjected to distillation and other treatment according to conventional methods which need not be described here to recover the desired hydrotormate or improved naphtha,-

As previously stated, the catalyst in reactor 1 requires periodic regeneration and toward this end, the catalyst is withdrawn from reactor 1 through a standpipe 18 provided with the usual gas taps t through which a fluidizing gas is charged to the said standpipe for the purpose of improving the fluidity of the said catalyst. Preferably, the gas introduced through the taps t is a stripping gas, such as steam. It will be noted that the standpipe 13 extends above the upper dense phase bed level L so that the stripping gas and the material stripped from the catalyst discharges into the upper portion of the reactor to prevent deactivation of the catalyst by steam. The catalyst in bed C enters the standpipe 18 at one or more side openings 19.

It will be noted that the standpipe 18 is provided with a valve V and this valve V is manipulated to control the downward flow of catalyst. The withdrawn catalyst is charged into a line 20 containing an oxygen-containing gas, such as air or air diluted with inert gas, and in line 20 it is formed into a suspension. This suspension is charged to a regeneration zone 21 where it passes upwardly through a grid or other gas distributing means G into a dense fluidized bed formed by controlling the gasiform superficial velocity in regenerator 21 in exactly the same manner as in reactor 1. Here also, the dense fluidized bed has an upper dense phase level at L above which there is a light phase suspension extending from L to the top of the regenerator. Under conditions more fully set forth, the catalyst is'regenerated by causing burning of the carbonaceous and other deposits thereon. The regeneration iumes pass from the dense phase through the light phase and before they are withdrawn from the regenerator, they are forced through one or more gassolids separating devices22 where entrained catalyst is separated from the said fumes and returned to the dense phase through one or more dip pipes d The regeneration fumes substantially freed of entrained catalyst are withdrawn from the regenerator 21 through line 23. The sensible heat and the chemical heat of these gases may be utilized in the system according to known means (not shown).

The regenerated catalyst is withdrawn from regenerator 21 through a standpipe 24 provided with gas taps tthrough which a fluidizing and stripping gas may be introduced to fluidize the catalyst in the standpipe and to strip it of oxygen. Such a stripping gas may be, for example, nitrogen, flue gas or any other suitable and available stripping gas. As in the case of the reactor 1, this standpipe 24 projects above the level L of the dense phase so that the gasiform material may be charged to the upper portion of the regenerator. The catalyst is admitted to the standpipe through one or more side openings 25.

As previously pointed out, the catalyst in the case of molybdenum oxide on alumina may be pretreated according to the present invention to conditionit for reuse in the reaction zone. Toward this end, therefore, the catalyst in standpipe 24 passes through valve V into a line 26 containing a stream of hydrogen-containing gas where in it is formed into a suspension, and in this form conducted into the bottom of pretreater 27. The suspension passes through a gas distributing means G in pretreater 27 and thence into the main body of the pretreater where it is formed into a dense fluidized bed by controlling the gasiform velocity in the same manner as in vessels 1 and 21. Under conditions more fully set forth hereinafter, the regenerated catalyst is pretreated or reduced so that the molybdenum oxide has an average valence corresponding to the formula M0 0 The gasiform material passing through the dense fluidized bed in pretreater 27 emerges from the upper dense phase level thereof L and thence passes through a light phase which extends from L to the top of the reactor. Before the gasiform material is withdrawn from the reactor, it is passed through one or more gas-solids separating devices 28 wherein entrained catalyst is separated and returned to the dense phase through one or more dip pipes d The pretreated catalyst is withdrawn from pretreater 27 through a standpipe 29, controlled by a valve V and charged to the reactor 1 as shown. The said standpipe 29 is provided with the usual gas taps I through which a fluidizing gas may be charged.

To those skilled in the art it will be obvious that the apparatus shown in the drawing would be provided with accessory apparatus, such as flow meters, temperature control devices, pressure control devices, etc., in a commercial installation.

It is pointed out that with most molybdenum oxide catalysts, it is preferable to omit the hydrogen pretreatment of the regenerated catalyst and to charge it directly to the reactor.

In. order further to explain the present invention, a series of runs were made employing a fluidized bed of catalyst containing about 10% M00 on an active crystalline alumina. The feed stock for these test runs was a virgin naphtha. It is pointed out that no extraneous water was added to the reactor. In other words, the water present in the reaction zone was formed in the system by reduction of the catalyst, whether it be in the reactor, the pretreater, or the catalyst transfer lines containing hydrogen, or carried into the system with the oil feed. Also, it will be noted that the runs (C and D) in group II were made under more severe conditions than those in group I (A and B) since the octane level of the C and D products is much higher than those of A and B. Also, the catalyst to oil ratio in runs C and D was higher than in runs A and B, which means that more catalyst was reduced in the reactor in runs C and D, and hence more water was formed in the reactor than in runs A and B.

The inspection of the naphtha hydroformed accord ing to the present. process was:

Gravity, API 53.3 Naphthene content --vol. percent 42.6 Distillation:

Initial boiling point, F 236 10% OH Rf 252 50% off at 282 90% off at 346 CFRR octane number 43 In order to show the beneficial effect of water in the reaction zone, the following results are set forth in two respective groups, namely, group I and group II. In making these runs in group I, for comparative purposes, conditions were so adjusted in runs A and B as to produce the same yield of C hydrocarbons in runs A and B. It will be noted that with respect to runs A and B in group I that increasing the amount of water from 0.1 to 1.0 mol percent gave an octane increase of 0.9 number. With respect to runs C and D under group II conditions were also adjusted so that the same yield of C hydrocarbons were obtained in these runs C and D. In these runs it will be noted that increasing the amount of water in the reactor from 0.1 to 4.2 mol percent resulted in an octane improvement in the product of 3.5 octane numbers.

[Catalyst-10% M; on A120 (Wgt. Percent).]

Column A B Catalyst/Oil Ratio 1 1-2 1-2 H1O in Reactor-M01 Percent based on H; fed to the reactor. 0. 1 1. 0 Octane No.CFRR Clear 98.3 99.2

1 Catalyst/oil ratio means weight units of catalyst per weight unit of oil ted to the reactor.

It will be understood that good results are obtained when the following conditions are employed in the reac tor, regenerator and the pretreater, if the latter is employed. In the reactor, the temperatures may vary from 875-925 F. The pressure may vary from 50-300, with best results attainable at pressures around 200 pounds. The oil feed rate may vary from 0.1-3.0 pounds of oil per hour fed to the reactor per pound of catalyst in the reactor, the catalyst to oil ratios, that is, the catalyst recirculation rate from the regenerator to the reactor with respect to the oil so fed, may vary from /2 to 6 pounds of catalyst per pound of oil, with best results where this catalyst to oil ratio is from 1 to 3. The cubic feet of hydrogen fed to the reactor per barrel of oil so fed may vary from 2,000-5,000 cubic feet, the concentration of hydrogen in hydrogen-containing gas fed to the reactor may vary from 50-70 volume percent, the concentration of water based on the hydrogen fed to the reaction zone may vary from to mol percent, including the water formed by reduction of the catalyst from M00 to, say M 0 The superficial vapor velocity in the reactor (i. e., the vapor velocity assuming no catalyst in the reactor) may vary from A to 1 ft. per second.

It will be understood that the use of water in connection with all alumina molybdenum catalysts is not efiective. For example, where the molybdenum oxide catalyst is one in which the molybdenum oxide is supported on a gel catalyst, such as the so-called Oronite alumina base, it has been found that the water present in the reaction zone is of no advantage. It has further been found that when the catalyst consists of molybdenum oxide on zinc spinel, it is undesirable to have water present in the reaction zone. In general, the use of water in connection with an alumina molybdenum oxide catalyst is found to be effective in improving the yield octane relationship Where the molybdenum oxide is supported on an active crystalline form of alumina.

The conditions in the regenerator may vary as follows: Temperature 1100 to 1300" F., and of course, the pressure will vary depending on these pressure conditions in the reactor.

Conditions in the pretreater if employed may vary as follows: The temperature may vary from 900 to 1200 F., the pressure will vary according to the pres sure existing in the system, the catalyst residence time in the pretreater will vary from 2 to 50 seconds, the amount of treating gas fed to the pretreater per hour per pound of catalyst in the pretreater will depend on the degree of catalyst reduction required, but in any event, the amount of treating gas should be at least 2 cubic feet per hour per pound of catalyst in the pretreater, and the concentration of the hydrogen in the treating gas may vary from 40 to 70 mol percent.

What is claimed is:

1. In the hydroforming of naphthenic naphthas carried out continuously in the system comprising a reaction zone and the catalyst regeneration zone, the improvement which comprises providing a dense fluidized bed of a catalyst comprising molybdenum oxide supported on activated crystalline alumina in the reaction zone, charging naphtha and a hydrogen-containing gas to said reaction zone wherein said naphtha and said hydrogen-containing gas contact the said bed of catalyst, maintaining elevated conditions of temperature and pressure in said reaction zone, maintaining a concentration of water in the reaction zone amounting to from about 0.5 to 5.0 mol percent based on the hydrogen fed to said reaction zone, permitting the said naphtha to remain resident in the said reaction zone for a sufficient period of time to efiect the desired conversion, withdrawing catalyst requiring regeneration from the reaction zone, treating the withdrawn catalyst in the regeneration zone in an oxygen containing gas, returning regenerated catalyst to the reaction zone and efiecting the formation of the water required in the reaction zone by reduction of the regenerated catalyst, and recovering from the reaction zone a hydroformed product of improved octane rating.

2. The method set forth in claim 1 in which no extraneous water is added to the system.

3. The method set forth in claim 1 in which the catalyst circulation rate from the regenerator to the reactor is from l-6 unit weights of catalyst per unit weight of naphtha feed.

4. The method set forth in claim 2 in which the regenerated catalyst is treated with a hydrogen-containing gas prior to recharging to the reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,131,089 Beeck et al. Sept. 27, 1938 2,366,372 Voorhies Ian. 2, 1945 2,423,163 Thomas July 1, 1947 2,433,603 Danner et al. Dec. 30, 1947 2,472,844 Munday et al June 14, 1949 2,642,383 Berger et al. June 16, 1953 2,661,383 Beckberger et al. Dec. 1, 1953

Claims (1)

1. IN THE HYDROFORMING OF NAPHTHENIC NAPHTHAS CARRIED OUT CONTINUOUSLY IN THE SYSTEM COMPRISING A REACTION ZONE AND THE CATALYST REGENERATION ZONE, THE IMPROVEMENT WHICH COMPRISES PROVIDING A DENSE FLUIDIZED BED OF A CATALYST COMPRISING MOLYBDENUM OXIDE SUPPORTED ON ACTIVATED CRYSTALLINE ALUMINA IN THE REACTION ZONE, CHARGING NAPHTHA AND A HYDROGEN-CONTAINING GAS TO SAID REACTION ZONE WHEREIN SAID NAPHTHA AND SAID HYDROGEN-CONTAINING GAS CONTACT THE SAID BED OF CATALYST, MAINTAINING ELEVATED CONDITIONS OF TEMPERATURE AND PRESSURE IN SAID REACTION ZONE, MAINTAINING A CONCENTRATION OF WATER IN THE REACTION ZONE AMOUNTING TO FROM ABOUT 0.5 TO 5.0 MOL PERCENT BASED ON THE HYDROGEN FED TO SAID REACTION ZONE, PERMITTING THE SAID NAPHTHA TO REMAIN RESIDENT IN THE SAID REACTION ZONE FOR A SUFFICIENT PERIOD OF TIME TO

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