US3283024A - Hydrocarbon conversion - Google Patents

Description

United States Patent i O HYDROCARBON CONVERSION Clarence L. Dulaney, Robert J. Evans, and Marvin Lee Owens, In, Texas City, Tex., assignors to Monsanto Company, a corporation of Delaware No Drawing. Filed Feb. 28, 1963, Ser. No. 261,839

8 Claims. (Cl. 260-673.5)

The present invention relates to a process for the thermal cracking of hydrocarbons. Further, the present invention relates to a process for the production or aromatic hydrocarbons. More particularly, the present invention relates to a process for the thermal cracking of parafiinic hydrocarbons to obtain a cracked product having a significantly increased aromatic hydrocarbon content.

Because of the relatively low economic value of parafiin hydrocarbons, there is a continuous search for methods whereby these hydrocarbons may be converted into more valuable materials. Among the more valuable materials which may be produced from paraffins are olefin and aromatic hydrocarbons. Thermal cracking of the parafiin hydrocarbon is one of the well known and widely used processes whereby the parafiins are converted to more valuable olefinic hydrocarbons. In addition to the olefinic hydrocarbons, -a very small amount of aromatic hydrocarbons generally are produced by the thermal cracking of paraflins. However, the amount of aromatic hydrocarbons produced is generally so small that the value of the cracked products is not enhanced despite the inherent higher value of the aromatic hydrocarbons. Because of the high value of the aromatic hydrocarbons, the greater the amount of such hydrocarbons which can be produced from the thermal cracking of paraflins the greater the value of the cracked product.

It is an object of the present invention to provide a new and improved process for the thermal cracking of p'arafiin hydrocarbons. Another object of the present invention is to provide a process for the thermal cracking of parafiin hydrocarbons whereby the quantity of aromatic hydrocarbons produced is significantly increased. Still another object of the present invention is to provide a process for the production of aromatic hydrocarbons from paraflin hydrocarbons. Additional objects will become apparent from the following description of the invention herein disclosed.

In fulfillment of these and other objects, it has been found that when paraflin hydrocarbons are subjected to thermal cracking in the presence of an aldehyde or ketone there is a substantial increase in the yield of aromatic hydrocarbons. The thermal cracking may be carried out under any conditions of temperature and pressure conventional to such processes. Most often the temperature will be within the range of 400 to 900 C. with temperatures of from 500 to 800 C. being preferred. The pressure, generally, will be within the range of from atmospheric to 1000 p.s.i.g., but preferably within the range of to 300 p.s.i.g. Generally, the thermal cracking of paraffin hydrocarbons is carried out in the presence of an inert diluent, preferably steam. When an inert diluent is used it generally will be used in an amount of 0.1 to 2.0 parts by weight of diluent per part by weight of hydrocarbon feed. Preferably, a diluent to hydrocarbon weight ratio of 0.2:1 to 08:1 will be used in the present invention.

Virtually, any aldehyde or ketone may be used in promoting the formation of aromatic hydrocarbons in accordance with the present invention. Generally, the aldehyde and ketones operable in the present invention will be within the general formula y liquids or high molecular weight waxy solids.

wherein R is a hydrocarbon radical of l to 20 carbon atoms and wherein R is hydrogen or a hydrocarbon radical of 1 to 20 carbon atoms. The hydrocarbon radicals in this formula may 'be saturated or unsaturated, cyclic or non-cyclic, straight-chain or branched-chain, and includes aromatic, naphthenic, paraflinicand/ or olefinic hydrocarbon radicals. Several non-limiting examples of such compounds are acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, caproaldehyde, heptaldehyde, citral, citronellal, acetone, ethylmethyl ketone, diethyl ketone, methyl propyl ketone, methyl isopropyl ketone,

nbutyl methyl ketone, ethyl propyl ketone, dipropyl ketone and dibutyl ketone. The most useful compounds within the above general formula are those in which R is an alkyl hydrocarbon radical of 1 to 8 carbon atoms, either straight or branched chain, and R is hydrogen or an alkyl radical of 1 to 8 carbon atoms. The preferred compounds within the above general formula are those in which R, is an alkyl radical of l to 4 carbon atoms in a straight chain and R is hydrogen or an alkyl radical of 1 to 4 carbon atoms in a straight chain.

The amount of aldehyde or ketone useful in the present invention, inmost instances, will be within the range of approximately 0.1 to 10 mol percent of the parafiin hydrocarbons in the feed. However, it. is preferred that the amount of aldehyde or ketone be within the range of from approximately 0.5 to 5 mol percent of the parafiin hydrocarbons in the feed.

The feedstocks which may be processed in accordance with the present invention are par-aflinic fractions containing 20 to 100% by Weight of paraifin hydrocarbons. Preferably, the feedstock will be a paraffin fraction of to by weight parafiin hydrocarbons. The parafiin hydrocarbons may be relatively low molecular weight Generally, the paraffinic hydrocarbons will have at least 6 carbon atoms and may be straight-chain or branched-chain. Several non-limiting examples of paraffinic hydrocarbons within the scope of the present invention are n-hexane, 2- methylpentane, 3-methylpentane, n-heptane, Z-methylhexane, 3-methylhexane, Z-ethylpentane, n-octane, 2- methylheptane, Z-ethylhexane, 3-rnethylheptane, 3-ethylhexane, n-nonane, 2,2-dimethylheptane, 2-methyl-4-ethylhexane, 3,3-diethylpentane, n-decane, and the like on up to and including nand iso-parafiins of 70 carbon atoms and higher. The preferred parafiin hydrocarbons are those containing 6 to 40 carbon atoms and are either straight-chain or branched-chain. In feed-stocks containing less than 100% paraffin hydrocarbons of at least 6 carbon atoms, the impurities may include any hydrocarbon such as paraifins having less than 6 carbon atoms, olefins, aromatics, naphthenes and the like as well as various diluents or inert materials.

In carrying out the practice of the present invention, space velocities of 0.5 to 10 parts by volume of feed per volume of internal reaction space generally are used. However, it is preferred that the space velocity be Within the range of 2 to 6 parts by volume of parafiinic feed per volume of internal reaction space.

In order to demonstrate the efiicacy of the present invention the following examples are presented.

Example I The paraflinic feedstock used in this demonstration was 100% paratlinic hydrocarbons having a molecular weight range of 50 to 700. This paraifinic feed was passed through 35 feet of inch stainless steel pipe at a rate of 4.23 pounds of feed per hour. The paraffinic feed was passed into the reaction tube concurrently with steam in a ratio of 0.4 pound of steam per pound of feed. Five mol percent of acetone was introduced concurrently with the parafiinic feed and steam. The inlet temperature of r; it)

the 35 foot reaction tube was approximately 450 C. and the exit temperature 602 C. The pressure within the reaction tube was maintained at approximately 11.3 p.s.i.g. A conversion of 82.4% was obtained. A C C fnaction Was obtained from the cracked oil product by distillation. This cut represented 12.0% of the total product and was found to contain 8.0% by weight of aromatic hydrocarbons.

Example [I Example I Was substantially repeated with the exception that mol percent of methyl isobutyl ketone was used. Conversion was approximately 76.9%. A C -C fraction was obtained from the cracked oil product by distillation. This fraction represented 13.2% by weight of the total cracked oil product and was found to contain 4.7% by weight of aromatic hydrocarbons.

Example III Example I was substantiallyrepeated with the exception that no additive was used. Conversion was approximately 74.5% The cracked oil product was fractionated to obtain a C -C fraction. This fraction represented 9.0% by weight of the total cracked oil product and was found to contain 1.2% by weight of aromatic hydrocarbons.

From the above examples, it is quite apparent that the present invention produces substantially increased yields of aromatic hydrocarbons. Further, it should be noted that in both instances in which a ketone was added that significantly improved conversions of parafiinic hydrocarbons to cracked products were obtained.

The equipment which may be used in carrying out the present invention is not critical. Any conventional thermal cracking equipment may be used. It is only necessary that the equipment be such as to withstand the pressures and temperatures of the reactions and that the equipment follow good engineering principles.

What is claimed is:

1.. A process for increasing the production of aromatic hydrocarbons from the non-catalytic thermal cracking of paraflin hydrocarbons which comprises subjecting a paraffin hydrocarbon feed containing 20 to 100 percent by weight of parafiin hydrocarbons of 6 to 40 carbon atoms to a temperature of 400 to 900 C. and a pressure of from atmospheric to 1000 p.s.i.g. in a thermal reaction zone in the absence of a catalyst and in the presence of an organic compound having the formula wherein R is a hydrocarbon radical of 1 to 20 carbon atoms and wherein R is a radical selected from the group consisting of hydrogen and hydrocarbon radicals of l to 20 carbon atoms, said organic compound being present in an amount of from 0.1 to 10 mole percent of the parafiin hydrocarbons in the feed.

2. The process of claim 1 wherein the process is carried out in the presence of an inert diluent.

3. The process of claim 2 wherein the inert diluent is present in an amount of from 0.1 to 2.0 parts by weight of diluent per part by weight of hydrocarbon feed.

4. The process of claim 2 wherein the diluent is steam,

5. The process of claim 1 wherein R is an alkyl hydro carbon of 1 to 8 carbon atoms and wherein R is a radical selected from the group consisting of hydrogen and alkyl hydrocarbon radicals of 1 to 8 carbon atoms.

6. The process of claim 1 wherein the thermal reaction zone is maintained within the temperature range of 500 References Cited by the Examiner UNITED STATES PATENTS 2,242,836 5/1941 R'amage 260-673.5 2,404,914 7/1946 Mattox 260673.5 3,149,138 9/1964 Hubelet a1. 260673.5

ALPHONSO D. SULLIVAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,283,024 November 1, 1966 Clarence L. Dulaney et 211.

r appears in the above numbered pat- It is hereby certified that erro e said Letters Patent should read as ent requiring correction and that th corrected below.

Column 4, line 28, for the claim reference numeral "1" read 2 Signed and sealed this 24th day of October 1967.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Commissioner of Patents Attesting Officer

Claims (1)

1. A PROCESS FOR INCREASING THE PRODUCTION OF ARMOATIC HYDROCARBONS FROM THE NON-CATALYTIC THERMAL CRACKING OF PARAFFIN HYDRO-CARBONS WHICH COMPRISES SUBJECTING A PARAFFIN HYDROCARBON FEED CONTAINING 20 TO 100 PERCENT BY WEIGHT OF PARAFFIN HYDROCARBONS OF 6 TO 40 CARBON ATOMS TO A TEMPERATURE OF 400 TO 900*C. AND A PRESSURE OF FROM ATMOSPHERIC TO 1000 P.S.I.G. IN A THERMAL REACTION ZONE IN THE ABSENCE OF A CATALYST AND IN THE PRESENCE OF AN ORGANIC COMPOUND HAVING THE FORMULA R1-CO-R2 WHEREIN R1 IS A HYDROCARBON RADICAL OF 1 TO 20 CARBON ATOMS AND WHEREIN R2 IS A RADICAL SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND HYDROCARBON RADICALS OF 1 TO 20 CARBON ATOMS, SAID ORGANIC COMPOUND BEING PRESENT IN A AMOUNT OF FROM 0.1 TO 10 MOLE PERCENT OF THE PARAFFIN HYDROCARBONS IN THE FEED.