US2403279A - Production of high octane number fuels - Google Patents

Description

Patented July 2, 1946 PRODUCTION OF s PATENT OFFICE HIGH OCTANE NUMBER FUELS Amiot P. Hewlett, Cranford, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application March 26, 1942,

Serial No. 436,313

: 4 Claims.

The present invention is concerned with providing a method of treatment which is particularly applicable to low boiling components of naphthas formed under intensive dehydrogenation conditions which obtain in low pressure vapor phase cracking of petroleum distillates.

- It is designed to derive high anti-knock ingredients efiiciently from a low quality portion of naphthas which have a high content of low boiling olefins.

Low pressure vapor phase cracking is a development which has become important in the manufacture of highly aromatic naphthas. The high aromatic content of these naphthas is accompanied by a high content of olefins and other unsaturated hydrocarbons, particularly in the low boiling range, and it is found that these olefins, to a large extent, are detrimental to the quality of the naphtha as a motor fuel.

The low pressure vapor phase cracking is characteristicallyperfonned in the vapor phase at pressures ranging from about to 250 lbs/sq. in.

gauge, or lower, and at a temperature in the range of about 900 F. to 1400 F. It may also be conducted. with a cracking catalyst, in which event the temperature range is somewhat lowered, i. e., to about 850 F. to 1050 F.

When a naphtha product from a low pressure.

vapor phase cracking is subjected to'fractionation or stabilization, and the low boiling cuts separated are inspected for anti-knock characteristics, it is observed that debutanizer tops or C4 cuts have high octane numbers while the debutanizer bottoms composed predominantly of C5 and Cs hydrocarbons have very low Octane numbers, It is appreciated by those skilled in the art that it is commonly desirable to stabilize a gasoline, yet important to avoid completely omitting C4 to C6 hydrocarbons from the gasoline mo 'tor fuel if thefuel is to have proper volatility.

Thus, the problem created is how this low boiling part of the unsaturated gasoline should be treated to produce higher octane number fuels efficiently and economically.

A specific object of the present invention isuto provide an efficient treatment for converting C5 and Cs cuts of high olefin content into higher 00-. tane number fuel ingredients.

In accordance with the present invention, C5 and C6 olefins are effectively transformed in molecular structure without cracking and without change in molecular weight by catalytic reaction in the presence of bauxite under proper conditions, and thereafter the transformation products thus obtained are conveniently purified for blending with a gasoline fuel and in a definitely better form for alkylation to derive a high quality alkylate useful for blending, particularly when it 'is desired to manufacture aviation gasolines Bauxite is hydrated alumina which has found usefulness in avariety of petroleum refining processes and which has also been proposed to be used as a cracking catalyst, but in these operations the bauxite functions in a very different manner with respect to the types of materials treated,v the conditions of the treatment, and results. When, it is used as a cracking catalyst under cracking conditions, it acts to promote the breakdown of higher boiling hydrocarbons into gasoline and gas. When it is used in a low temperature purification treatment, it acts to adsorb colorand gum-forming unsaturated hydrocarbons from an oil and to desulfiurize an oil containing sulfur compounds without altering the hydrocarbons which remain in the oil. present instance, the bauxite is made to have a specific transformation action on olefinic C5 and C6 hydrocarbon fractions tochange the molecular structure of olefins which remain in the treated fractions without cracking.

In the operation of the present invention, it is preferred to have the low boiling hydrocarbon fraction used for the transformation reaction madeup mainly of C5 and C6 chain olefins, It may contain some amount of C4 and C7 hydrocarbons. In the preferred operation, the selected feed stock for the catalytic transformation with bauxite is carried out at a temperature between 750 F. and 850 F., and with the space velocity regulated to come within the range of about volume to 2 volumes of liquid hydrocarbonsv per volume of catalyst per hour. The contact time may be decreased within the range of about 2 minutes to A; minute with increase in temperature. I-Iot vapor products emerging from the reaction zone are then readily purified by being subsequently passed at a, temperature of about l0O F. to 500 F. through an'adsorbent, such as clay, under a superatmospheric pressure of, for example, lbs/sqQin. gauge.

In the purification treatment, clay effectively serves to eliminate diolefins. Bauxite maybe used also as an adsorbent in the purification step at temperatures below 750 F. and preferably no higher than 500 F. Following the purification treatment with a solid adsorptive material, the products separated from the polymers may be fractionated prior to blending or further processing, and at the same time be freed of any gaseous In the l gauge.

As another specific embodiment of the invention, a purified bauxite transformation product containing C-C6 hydrocarbons is recombined with the stabilized gasoline, with alkylate gasoline, or other higher boiling gasoline fuels to' example is given on the procedure and results:

EXAMPLE 1 For analytical investigation, apprOXimateIylOO gallons of cracked naphtha were prepared by cracking 333 A. P. I. East Texas virgin gas oil in a once-through coil-only cracking unit at a space velocity of 3 v./v. hr. ata temperature of 960=Fiand undera pressure of 200 lbs/sq. in. The conversion yield was to naphtha distillate per pass. Fractions of the naphtha distillatewere finished by a catalytic transformation with bauxite at 800 F., 100 lbs/sq. in. gauge pressure, and a feed rate of 1 v./v..hr. (about 53 seconds contact time) followed by a clay tower purification. Detailed analyses were made of the naphtha fractions before and after the treatment, and the results are shown in the following table:

TABLE I 4, tial increase in the proportions of the higher boiling amylenes and hexenes, and this change is accompanied by a definite octane number immovement for each of these fractions. By actual measurement, an octane improvement of 7.4 octane numbers was obtained.

Further, in order to illustrate how the transformation affects the alkylation properties of the low boiling components, olefinic components of;

the 'C5 fraction present before and after the catalytic bauxite transformation were used as =reactants with isobutaneunder typical low temperature alkylation conditions as set forth below:

The results obtained indicate that the bauxite transformation products of the C5 and Cs olefins give a much better yield of total alkylate and an alkylate of substantially higher octane number than do the original olefins of lower boiling point.

Detailed analysis of fractions from the cracking process before and after the catalytic transformation with baaztitc and-clay pmrification v v 7 Vol. Boiling range ygg gggg fif Fraction percent v Hydrocarbon and boiling point, C.

gasoline C. F. Untreated Treated i 10. 4 28-40 82-104 4 0 0t diolefin (isoprene, 34.1 0.).

- 8 C amylenes (3031 0.). 23 50 0 amylenes (3639 0.). 38 42 0 n-paraflins (pentane 36 0.).

2 3.4 40-60 104-140 s 0 05 chain and cyclic diolefins.

i 1 42 05 naphthene (cyclopentane, 49 0.); V V 42 50 0 iso-olefins (methylpentenes).

3 11.0 -70 140-158 0 r 0 0a diolefins (HO- 0.). 5 0 O diolefins (6570 0.).

60 15 06 chain olefins (60-65 0.).

8 52 05 chain olefins (GS- 0.). 6 V 6 0t isoparaflins (GO-65 0.). 21 27 n-Parafiins (hexane, 68.8 0.).

4 4. 4 70-82 158-180 19 20 Aromatics.

5 0 Ca diolefins.

'9 10 0; chain olefins. 52 54 0t cyclicolefins. 10 11 0 naphthenes. I 5 i 5 C parafiins.

chainolefins (B. pt. 303l C. and 60-6-5 C., re-

spectively) to the slightly higher boiling C5 and Cs isomers (B. pt. 36-39 C. and-65-70 C., respectively). This upward shift in boilin points indicates a shift in the double bond toward the center of the olefin molecules. The desired change becomes less pronounced as the boiling points of the; fractions are increased above1158 F. I

In the C5 and 06 fractions there is a-substani This is exemplified in the following representative data:

TABLE III Allcylatzon of isobutane under comparative conditions with difierent C's olefins Alkylate product Olefin reactants Wt. percent ASTM yield 1 O. N.

0 amylenes (B. pt. 30-3l 0.)-; 191' 89.6 C5 amylenes (B. pt. 3639 C.) 201 90. 6

1 Theoretical yield 133%.

fractions of hydrocarbons formed in low pressure vapor phase cracking, the following observations and conclusions may be made:

1. A very valuable improvement is obtained in the anti-knock quality of the olefinic C5 and Cs fractions when subjected to the transformation reaction without cracking. This reaction is catalyzed by bauxite under proper conditions of temperature. The bauxite efiectively catalyzes this reaction even when dehydrated.

2. The main observable effect of the bauxite transformation is the formation of higher boiling C5 and Cs alkenes from the lower boiling C5 and Cs alkenes, indicating the formation of more symmetrical arrangements in amylenes and hexenes.

3. The transformed C5 and Cs olefins of higher boiling point have substantially higher antiknock quality than the initial C5 and Cs olefins, and are accordingly much better blendin agents and ingredients for a motor fuel.

4. They are of enhanced value for reblending with gasoline distillates whence they originate.

They are of particular value for blending with a straight run gasoline to obtain improved road rating fuels and with parafflnic gasoline fractions requiring improved front end volatility as, for example, alkylate gasolines.

5. The transformed cs and Cs olefins are better adapted for alkylation with an isoparafiin than the relatively lower boiling initial C5 and C6 olefins. The efficiently accomplished transformation and purification by bauxite and clay places these fractions in improved condition for alkylation. The catalytic transformation with bauxite is preferably performed at a temperature between 750 F. and 850 F.

Motor fuels containing the transformed C5 and Cs olefins are further enhanced in blending value with tetraethyl lead. They may contain other useful additives, such as gum inhibitors, anticorrosion agents, dyes, etc., as needed or desired.

Although the invention has been described with reference to specific detailed examples, it is not intended to be limited thereby. Various modifications which come within the spirit of the invention are intended to be included within its scope.

I claim:

1. A process for the production of high anti-'- knock fuel ingredients which comprises segregating a C5 fraction containing predominantly amylenes boiling at about 30 C. to 31 C. from a naphtha product of low pressure vapor phase cracking, passing said segregated fraction into contact with bauxite at a temperature of about 800 F. until a substantial proportion of said amylenes are transformed to C5 olefins boiling at about 36 C. to 39 0., then passing the thus treated fraction through clay for purification, and. thereafter alkylating the transformed C5 olefins with isobutane to secure a high quality alkylate. I

A process for producing high anti-knock quality fuel which comprises segregating a fraction containing predominantly 5 i706 carbon atom olefinic hydrocarbons from a cracked distillate formed under intensive dehydrogenation conditions, contacting said fraction in vapor phase with bauxite at a sufiiciently elevated temperature and for sufficient time to transform 5 to 6 carbon atom alkenes to alkenes having the same number of carbon atoms but with higher boiling points, purifying the thus treated fraction by contact at a lower temperature with an adsorptive material, alkylating at least a portion of the purified product with an isoparaffin to form a high quality alkylate, and blending said alkylate with hydrocarbon constituents of different boiling point to obtain a fuel of suitable volatility.

3. A process for producing motor fuel of improved octane rating which comprises cracking a higher boiling oil under low pressure vapor phase conditions controlled to form a motor fuel fraction having a high aromatic content in the higher boiling portion and a high olefinic content in the lower boiling portion, separating the motor fuel so formed into a higher boiling aromatic fraction and a lower boiling olefinic fraction consisting principally of C5-C6 olefins and containing a relatively high concentration of pentene-l and hexene-l, passing the last-named fraction in vapor phase in contact with bauxite at a temperature between 750 F. and 850 F. for a period sufficient to isomerize the pentene-l and hexene-l into higher boiling isomers, thereafter alkylating the isomers so formed with a low boiling isoparaffin capable of forming an alkylate product within the motor fuel boiling range.

4. In the process defined by claim 3, the further improvement which comprises treating the isomers so formed to remove diolefins therefrom prior to the alkylation treatment.

AMIOT P. HEWLE'I'I.