US2002394A - Process for converting hydrocarbons - Google Patents

Description

May 21, 1935. F. E. FREY PROCESS FOR CONVERTING HYDROCARBONS Filed June 22, 1934 T D Y U G US M o m MN P L m 5 Wm L% O m E NR YR a R c E s OE L P K A I C G C G k0 R N T A MR 1 o l E H R RD E T D G F OY N A E l NH E R L m H F 1 g L 4 Y E k a B I! n U 6 v n: T. D r my m m E. m

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Patented May 21, 1935 UNITED STATES PATENT OFFICE .PROCESS FOR CONVERTING HYDRO- CARBONS Delaware Application June 22, 1934, Serial No. 731,920

7 Claims.

This invention relates to a process for converting hydrocarbons by thermal treatment into products of higher molecular weight and, more specifically, to reacting together parafiins and olefins into products of higher molecular weight which are substantially aliphatic in character and contain a high proportion of the paraffins.

It has been proposed to treat the lower parafiines such as butane and propane under heat and pressure to produce products of higher molecular weight at the same time forming products of lower molecular weight. It has also been proposed to heat simple olefins such as ethylene, propylene and butylene under pressure to obtain higher boiling products comprising essentially olefinic and cyclic polymers. Pressure accelerates the polymerization of olefins and under sufficiently high pressure the reaction takes place readily at temperatures too low to induce the cracking of paraifins. The conversion of lower paraffins, on the other hand, into products of higher molecular weight requires the use of a temperature sufficiently high to effect decomposition into simple parafiins and olefins, and, when the pressure likewise is suficiently high, the olefins formed then polymerize to larger molecules which undergo transformation intoalicyclic and aromatic hydrocarbons as exposure to the high cracking temperature is continued.

A mixture of olefins and parafiins heated under high pressure will ordinarily exhibit the olefin polymerization, which may go to virtual completion before substantial decomposition of the paraifin takes place, olefins of high molecular weight being chiefly formed.

I have discovered that, when the ratio of olefin to paraffin is very low, the olefin polymerization is discouraged by the low partial pressure, and the formation of parafiins of high molecular weight may be effected. This reaction, I have found, will take place under appropriate conditions, hereinafter set forth, to produce such parafiinic products in high yield and with relatively little concomitant formation of less valuable hydrocarbons of lower molecular weight than the reactants. The reaction is particularly suited to the conversion of gaseous paraffins, propane and butane together with any of the gaseous olefins into volatile normally liquid hydrocarbons.

An object of this invention is to prepare from gaseous parafiins and olefins normally liquid hydrocarbons in higher yield than is obtainable from the usual conversion by heat and under pressure.

A further object is the production of volatile normally liquid products rich in paraflinic constituents.

Still a further object is the conversion of paraffins into parafiinic products more highly branched in structure than the paraffins treated.

The process consists in subjecting a paramn'. hydrocarbon such as butane or propane to a temperature at which decomposition will take place but very slowly (400-500 C.) and under a pressure of 1000 pounds per square inch or 10 more, adding thereto a small proportion of gaseous olefins, not exceeding ten per cent of the parafiin, allowing the olefins to react and adding from time to time additional small increments of olefin, maintaining a concentration of olefin in the reaction mixture not exceeding ten per cent. Normally liquid hydrocarbons are formed containing substantial quantities of parafiins, most. fractions being saturated to the extent of 50% or more. The products are cooled and normally liquid hydrocarbons separated from the products by fractionation.

The formation of high proportions of parafins in the products and the development of high yields of products heavier than the reactants from both paraflins and olefins in a mixture are favored by higher pressures which may be of 5000 pounds per square inch or more, limited only by the strength of the apparatus. At the higher pressures the ratio of olefin to paraffin in the reacting mixture, maintained by successive additions of olefin, should be maintained at a low value; at 4000 pounds pressure, for example, the concentration of added olefin is best maintained below five per cent. The conversion of the paraffinic reactants becomes inefficient when continued heating and portionwise addition of olefin are carried to the point where the greater part of the original paraiiins are reacted.

While the exact nature of the reactions taking 40 place is obscure, it is probable that the reaction is essentially the union of a molecule of olefin with one of paraffin as follows:

The reaction will proceed without the use of catalysts, but in some cases they are beneficial.

The process may be conducted in the apparatus embodiment shown in Figure 1 of the attached drawing. Referring to this drawing, I is a pipe through which a hydrocarbon, for example, butane, is pumped at a pressure preferably in excess of 3000 pounds per square inch to the heating and reaction coil 2. Olefinic material,

for example, propylene, is simultaneously supplied through line 3 to the reaction coil 2, entering therein at a plurality of points. All of these points save the first one, at which oleflnic material is introduced, are in the hotter section of the coil, and the olefins introduced at one point will be substantially reacted by the time the hydrocarbons reach the next point of olefin introduction. The products of the reaction are passed through the line 4 into the separating zone 5, which may suitably be a fractionating column. From this separating zone, the normally liquid hydrocarbons may be removed, and'the other hydrocarbons passed to another separating zone I from which light gases will be discarded, and a recycle stock, in this case mostly butane, will be returned through line 8 for retreatment. 7

An alternative embodiment is shown in Figure 2 wherein the olefin is introduced in perforated tubes arranged coaxially within the heating tubes.

Example 1.Butane under a pressure of 3000 pounds per square inch was passed continuously 'through a stainless steel tube and maintained at 470 C. while a quantity of ethylene amounting to five per cent of the butane was introduced at each of three points spaced to provide a time lapse of about five minutes between successive additions. Normally liquid hydrocarbons were formed to the extent of 22 per cent of the hydrocarbons treated and consisting chiefly of paraflins (75 percent) in which the various isomeric hexanes predominated.

Example 2.Butane reacted as in Example 1 with propylene gave in the initial reaction stages a product consisting chiefly of the isomeric heptanes but in the later stages a product consisting chiefly of hexanes, heptanes and pentanes resulted.

While I have described my process as used to produce normally liquid hydrocarbons from normally gaseous hydrocarbons, it is evident that its utility is not limited to such use. It may be used to convert any straight chain, or moderately branched paraifinic, aromatic or nificant changes in its properties, such as antiknock value or melting point.

It is evident from the foregoing examples that in a simple aggregation of olefin polymerizing and high pressure cracking steps, but will produce new and useful'results, not heretofore recognized as obtainable.

What I claim and desire to secure by Letters Patent is:

1. A process for producing hydrocarbon mixtures containing or more of saturated hydrocarbons, which comprises heating a stream of predominantly saturated hydrocarbons to a decomposition temperature under pressures in mixture at less than 10% by weight, and separat- 2. In a process for the production of higher boiling hydrocarbons from lower boiling hydrocarbons, the step which consists in adding to a stream of predominantly saturated hydrocarbons, maintained at a conversion temperature and pressure, successive small quantities of predominantly olefinic hydrocarbons, in such amount that the content of added olefins in the mixture at no time exceeds 10% by weight of the total hydrocarbons present.

3. A process for producing hydrocarbon mixtures containing at least 50% of saturated hydrocarbons, comprising heating astream of pre-- dominantly saturated hydrocarbons to a reaction temperature under pressures in excess of 1000 pounds per square inch, adding olefin containing hydrocarbons to the said stream at a plurality of points, the said points being so spaced as to allow appreciable reaction to take place before the subsequent addition of further olefins, and maintaining the content of added olefins in the mixture at not more than 10% by weight of the hydrocarbons present therein.

4. A process for producing hydrocarbon mixtures at least 50% parafilnic and of generally branched structure, which comprises heating a stream of predominantly saturated hydrocarbons under a pressure in excess of 1000 pounds per square inch to a temperature at which decomposition will take place but very slowly, adding olefin containing hydrocarbons to the said stream at a plurality of points, the said points being so spaced as to allow appreciable reaction to take place before the subsequent addition of. further olefins, and maintaining the content of added olefins in the mixture at not more than ten percent by weight of the hydrocarbons present therein.

, 5. A process for producing hydrocarbon mixtures containing 50% Or more of saturated hydro carbons, which comprises heating a stream of predominantly saturated hydrocarbons to a temperature on the order of 400-500" C. while under maintaining the concentration of the resulting mixture at less than 10% by weight, and separating the products from the unreacted hydrocarbons.

6. A process for producing hydrocarbon mixtures containing at least 50% of saturated hydrocarbons, comprising heating a stream of predominantly saturated hydrocarbons to a reaction temperature of 400 to 500 C. under pressures in excess of 1000 pounds per square inch, adding olefin containing hydrocarbons to the said stream at a plurality of points, the said points being so spaced as to allow appreciable reaction to take place before the subsequent addition of further olefins, and maintaining the content of. added olefins in the mixture at not more than 10% by weight of the hydrocarbons present therein.

7. A process for producing hydrocarbon mixtures containing 50% or more of saturated hydrocarbons, which comprises heating a stream of predominantly saturated hydrocarbons to a demaintaining the concentration of added olefins in the resulting mixture at less than 5% by weight, and separating the products from the unreacted hydrocarbons.

FREDERICK E. FREY.

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