US2935464A - Hydroforming process with the addition of a nitrogenous base - Google Patents

Description

HYDROFORMING PROCESS WITH THE ADDITION OF A NITROGENOUS BASE Richard H. Dudley, Cranford, Robert B. Long, Wanamassa, James C. Rohrer, Plainlield, and Barney R. Strickland, Westfield, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application December 31, 1954 Serial No. 479,228

4 Claims. Cl. 208-134) This invention pertains to'the catalytic conversion of hydrocarbons and more particularly to the catalytic reforming or hydroforming of hydrocarbon fractions boiling within the motor fuel or naphtha range of low octane number into high octane number motor fuels rich in aromatics.

It is known that petroleum naphthas can be subjected to a reforming treatment to yield liquid products boiling within the naphtha or motor gasoline boiling range and possessing improved octane numbers and better engine cleanliness characteristics. A well known and widely used method for upgrading petroleum naphthas is called hydroforming. In hydroforming, the naphtha feed stock is treated at elevated pressures of from 15 to 1000 pounds per square inch and at temperatures of 7501050 F. in the presence of solid catalyst particles and hydrogen or recycle gas rich in hydrogen. A variety of reactions including dehydrogenation, paraflin and naphthene isomerization, cyclization or aromatization, hydrogenation and hydrocracking, occur during hydroforming. All these reactions contribute to the production of a motor fuel product of increased value not only because of its higher octane number but also because'of its improved cleanliness characteristics due to the elimination of gum-forming unsaturated constituents and the removal of sulfur.

Catalysts that have been used for hydroforming include metals such as platinum and palladium as well as oxides and sulfides of group VI metals, particularly molybdenum, chromium, vanadium, and tungsten. These catalytic components are usually supported upon a base or spacing agent, preferably on an adsorptive or high surface area alumina-containing composition such as various activated aluminas, alumina gel, zinc aluminate spinel, and the like.

ln view of the ever-increasing demands for more and higher octane number premium motor fuels, a'great deal of research has been directed toward the development of new catalysts having increased activity, permitting the charging of greater quantities of feed stock and/or havnaphtha feed stocks. Sulfur or organic sulfur compounds. in naphthas has been particularly troublesome in hydroforming. It has been found, for example, that when a high sulfur feed is introduced into a hydroforming reaction zone containing a catalyst comprising platinum dis I persed upon alumina obtained by hydrolysis of aluminum alcoholate after a considerable period on low sulfur feed with h gh gasoline yield, there is a considerable drop in activity amounting to as much as 8 to 10 octane numbers.

It is the object of this invention to provide the art with a novel hydroforming process. p

it is also the object of this invention to provide the art with a method of carrying out a hydroforming process whereby excessive hydrocracking may be inhibited or prevented.

It is a further object of this invention to provide an. improved process of hydroforming naphtha feed stocks of I high sulfur content whereby high yields of high octane number products are obtained.

These and other objects will apear more clearly from f the detailed specification and claims which follow.

It has now been found that excessive cracking or hydrocracking that occurs in aromatization and hydroforming processes, especially at pressures of 200 pounds per square inch and over, when charging certain sulfur-containing pounds which may be reduced to amino compounds under tion without simultaneously suppressing the other reactions such as dehydrogenation and cyclization which lead to the formation of aromatics from naphthenes and paraffins. In other words, the addition of a nitrogenous base, preferably ammonia, to a reforming reaction zone serves to minimize dry gas formation while simultaneously maximizing the production of aromatics.

v per square inch, while molybdic oxide upon anadsorptive The'reforming reaction in accordance with the present invention can be carried out in a fixed-bed, moving bed, or fluidized solids type of operation. The reaction zone is maintained at a temperature of from 8001100 F.,

preferably at about 950 F., and at' pressures from atmos pheric up to about 1000 pounds per square inch. Difierent catalyst compositons have different optimum operating pressures. Molybdic oxide or chromic oxide on zinc aluminate spinel are most effective at about 50 pounds alumina support is generally most effective at about 200 pounds per square inch. Platinum on alumina, on the other hand, is effective over a wide pressure range, at about 200-350 pounds per square inchto produce high octane number (90+) products in av regenerative type operation and at pressures above about 400 pounds per square inch in a non-regenerative operation to produce lower octane number products. Hydrogen is circulated through the reaction zone at a rate of from about 2000 to 8000 cubic feet per barrel of liquid naphtha feed. The weight ratio of catalyst to oil introduced into the reactor should be about 0.5 to 3.5, preferably about 1.0. The space velocity or weight in pounds of feed charged per hour depends upon the age or activity level of the catalyst,

i the character of the feed stock, and the desired octane number of the product. about 0.5 w./hr./w. to 15 w./hr./w.

num or 0.05 to 5.0 weight percent palladium upon acti- Patented May 3, 1966 0 c Ordinarily, it may vary froma or one containing a group VI vatedgor adsorptive alumin metal oxide upon a support such as activated alumina,

alumina gel, or zinc aluminate spinel. A particularly effective catalyst of this type is one containing from about 4.0 to 15.0 weight percent molybdic oxide, preferably about 10.0 weight percent, dispersed upon activated or adsorptive alumina.

The nitrogenous bases that.can be supplied to the hydroforming reaction zone,,may. be ammoniaor amines including arylamines suchasanilineor allcyhandalkanol:

amines such as methyl, ethyl, propyl, ethanolaminqand the like. Ammonia is preferred because it is, economical,

continuously or intermittently. When applied with therecyclegas or the feed, the amount added may vary from about 1 to about 20, preferably 25, parts per million based upon the naphtha fed to the unit.

The naphthas that may be treated in accordance with the present invention are virgin naphthas, cracked naphthas, FischeraTropsch.naphthas, or-mixtures of two or more .naphthashaving. a boiling range of from about 125 F. to about450 F., or it may be a narrow boiling cut within this. broad range. The naphthas treated in accordancewith this invention may be termed highsulfur naphthas, and arecharacterized ,bycontainingmore than about 0.10, weight percent sulfur.

The. following examples, are. illustrative of the present invention.

EXAMPLE I A, virgin naphtha containing 0.21 weight percent of added sulfur (as n-dipropylsulfide) was hydroformed in contact with-aplatinum (0.6 weight percent) on alumina catalyst at915 F., 200 p.s.i.g., and 5000 s.c.f./b. hydrogen rate. At the start of the process the correlated C gasoline yield at 95 O.N. was 85 volume percent. After about 440 hours on this feed, the correlated C yield at 95 ON. had declined to about 80.5 volume percent.

At this stage addition of 7 p.p.m. of ammonia to the feed'served to restore the yield to 85 volume percent. Thiswas accompanied by adecline in activity and product octane. Raising the temperature essentially restored theproduct octane while the higher selectivity was retained. Data from these runs areshown in Table I.

Table 1 Hour; 500-540 Ammonia, p.p.m. in Feed 7 7 Mid-Sand Temperature, T. CFR-R Octane No., Clear. 0 Yield at 95 0 .N., Vol. percent EXAMPLE 1r Inanother experiment, an overdose of ammonia was added. In a liferun with a platinum (0.6 weight percent) on alcoholate alumina catalyst the selectivity had dropped from 85 to 79.5 volume percent at 95 octane after 340 hours operation with a. virgin naphthato ammoniahaddestroyedtheactivity of theqcatalyst. The:

results; are=.shqwn-.in Table II:

- a Table II- Hour 340-380 392 413 Ammonia, p.p.m. in Feed 0 200 200 Mid-Sandlemperature, F 915 915 950 OFR-R Octane No., Clear 95 78 82 0 Yield at 95 O.N., Vol. percent 79. 5 88 87 Based on these experiments, it appears that the optimum amount of ammonia may be below 7 p.p.m. In these examples, the ammonia was added after thecatalyst had been on high sulfur feed for several hundred hours. The addition of as little as 2 p.p.m. of ammonia from the very beginning of the run would be effective" for improving selectivity, without decreasing activity appreciably.

EXAMPLE III A virgin naphtha containing 0.15 weight percent sulfur was hydroformed in contact with a platinum (0.6 weight percent) on alcoholate alumina catalyst at 965 F., 500 p.s.i.g., and 6000 s.c.f./b. hydrogen rate and at 12 w./hr./w. space velocity. After the catalyst had lost 7 volume percent correlated C yield at octane, a small amount of nitrobenzene, which is readily reduced to aniline under reactor conditions, was added to the feed. As with ammonia addition, activity declined and correlated gasoline yield improved. The data obtained are summarized in Table III below.

Table III.

Run Hours 955-7 961-6 973-5 Sand Bath Temperature 966 963 965 Nitrobenzene Added, Wt. percent None 0.012 None Product Yields and Quality-Total C Gasoline:

Yield, Vol. percent on Fresh Feed 86. 4 92. 2 88. 6 CFR Research Octane, Clear 81.4 76.0 79. 6 0 Vol. percent on Fresh Feed 5.5 3.0 4. 6 Dry gas, Wt. percent on Fresh Feed 8. 8 4. 4 7. 2 Yields Correlated to 78 Octane:

(DH-Gasoline, Vol. percent on Fresh Feed- 88. 9 91. 2 89. 2 0 Vol. percent on Fresh Feed 4. 2 2. 0 3.6 Dry Gas, Wt. percent on Fresh Feed 7. 2 5.0 6. 8

The foregoing description contains a limited number of embodiments of this invention. It will be understood that numerous variations are possible without departing from the scope of this invention.

What is claimed is:

1. In the hydroforming of. an initial naphtha feed fraction containing over 0.1 weight percent of sulfur in admixture with hydrogen at conversion conditions of temperature and pressure and in the presence of an active hydroforming catalyst, the improvement which comprises minimizing cracking reactions by adding a nitrogenous base in an amount below 20 parts per million based on naphtha feed to the reaction zone during the hydroforming process, said nitrogenous basebeing in addition to the nitrogen present in the initial naphtha feedfraction to be reformed.

2. The process as defined in claim 1 in which the catalyst comprises platinum upon an alumina support.

3. The process as defined in claim 1 in-which the catalyst is a group VI metal oxide uponan alumina support.

4.: In the hydroforming of naphtha fractions containing. over 0.1wt. percent sulfur, in admixture with by.-

drogenat a conversiontemperature and in the-presencev ofan active hydroforming catalyst, the improvement which comprises continuing the conversion of said naphtha until'the. yield drops below a desired value, then adding a nitrogenous base in an amount below 20' parts permillion based on-naphtha feed to restore the. yield,

5 I and increasing the conversion temperature to restore 2,744,053 catalyst activity and product octane. 2,752,289 2,766,179 References Cited in the file of this patent 2,849,377

UNITED STATES PATENTS 5 2,321,604 Kalichevsky et a1. June 15, 1943 2,642,383 Berger June 16, 1953 2,717,230 Murray et al. Sept. 6, 1955 6 1 Kay et a1. May 1, 1956 Haensel June 26, 1956 Fenske et al. Oct. 9, 1956 Ogburn et al. Aug. 26, 1958 OTHER REFERENCES Oblad et al.: Advance in Catalysis, vol. III (1951), Chemical Properties of Cracking Catalysts; pages 211- 219, Academic Press, publishers, New York.

Claims (1)

1. IN THE HYDROFORMING OF AN INITIAL NAPHTHA FEED FRACTION CONTAINING OVER 0.1 WEIGHT PERCENT OF SULFUR IN ADMIXTURE WITH HYDROGEN AT CONVERSION CONDITIONS OF TEMPERATURE AND PRESSURE AND IN THE PRESENCE OF A ACTIVE HYDROFORMING CATALYST, THE IMPROVEMENT WHICH COMPRISES MINIMIZING CRACKING REACTIONS BY ADDING A NITROGENOUS BASE IN AN AMOUNT BELOW 20 PARTS PER MILLION BASED ON NAPHTHA FEED TO THE REACTION ZONE DURING THE HYDROFORMING PROCESS, SAID NITROGENOUS BASE BEING IN ADDITION TO THE NITROGEN PRESENT IN THE INITIAL NAPHTHA FEED FRACTION TO BE REFORMED.