US3272888A - Reducing propane production in an alkylation process - Google Patents

Description

United States Patent 3,272,888 REDlJCllNG PROPANE PRODUCTION IN AN ALKYLATION PRO CESS Richard S. Logan and Thomas Hutson, Jr., Bartlesville,

01:121., assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Nov. 16, 1964, Ser. No. 411,572 4 Claims. (Cl. Zed-683.43)

This invention relates to an improved alkylation process. In another aspect, this invention relates to an improved alkylation process wherein the production of propane in the alkylation zone is reduced to a minimum.

The catalytic alkylation of an olefin with an isoparafiin to form high-octane gasoline boiling range products is well known in the art. In a conventional alkylation process, an olefin feed comprising propylene and butylenes is passed with isobutane to an alkylation zone wherein the olefin and isobutane feeds are contacted with liquid hydrofluoric acid, said hydrofluoric acid acting as an alkylation catalyst. The alkylation zone hydrocarbon eifiuent is separated from the acid catalyst and fractionally separated with the isobutanes and lighter hydrocarbon fractions recycled to the alkylation zone.

The production of propane in the alkylation zone substantially decreases the efficiency of the alkylation process, representing a net consumption of isoparaifin in an undesirable side reaction. As the isoparafiin is more valuable than propane, it is economically desirable to minimize propane production in the alkylation zone.

Accordingly, an object of our invention is to provide an improved alkylation process. Another object of our invention is to provide an improved process wherein the production of propane in an alkylation zone is reduced to a minimum. Other objects, advantages and features of our invention will be readily apparent to those skilled in the art from the following description and the appended claims.

We have discovered that the production of propane in the alkylation zone can be reduced to a minimum by introducing propane into the alkylation zone so as to maintain a concentration of propane in the hydrocarbon feed to the alkylation zone in the range of 7-22 weight percent, preferably 11-18 weight percent.

The invention is applicable to an alkylation process wherein an olefin is contacted with an isoparaffin in the presence of an alkylating catalyst such as hydrofluoric acid, sulfuric acid, phosphoric acid, or a metal halide with a hydrogen halide promoter. The olefin employed in the alkylation process is selected from the group of olefins having 3-5 carbon atoms per molecule or mixtures thereof, and the isoparaffin is selected from the group consisting of isobutane, isopentane, or mixtures thereof.

Conventional alkylation conditions are employed in the alkylation of the olefins with isoparaffins. For example, assuming that the olefin feed comprises propylene and butylenes, the alkylating agent comprises isobutane and the catalyst comprises hydrofluoric acid, the temperature of the alkylation zone is preferably maintained in the range of between about 85-105 F. with the pressure maintained within the alkylation zone sufiicient to maintain a liquid phase reaction. The volume ratio of acid to hydrocarbon maintained in the alkylation zone is preferably in the range from about 8:1 to 0.8: 1. Normally, the residence time in the alkylation zone is within the range of 0.25 to minutes.

The alkylation zone effluent mixture can be subjected to conventional separation steps to separate catalyst, product alkylate, propane, other normal paraffins and isoparafiins thereof. Wherein acid catalyst is employed in the alkylation zone, the alkylation zone efiluent mixture is conventionally passed to a separation zone wherein the acid phase is separated from the hydrocarbon effluent mixture. A portion of the separated hydrocarbon effluent can be passed to a depropanizing fractionation zone wherein the propane is separated therefrom. The residual hydrocarbon fraction from the depropanizing zone in combination with the remainder of the hydrocarbon efi'luent from the alkylation zone can be passed to a second fractionation zone wherein a product alkylate fraction is separated from the hydrocarbon feed. An isoparaffin fraction can be recycled from the second fractionation zone to the alkylation zone.

By maintaining the concentration of the propane in the hydrocarbon feed to the alkylation zone in the range of 7-22 weight percent, the production of synthetic propane during the alkylation reaction is reduced to a minimum. It is recognized that the introduction of propane as feed into the alkylation zone reduces the quantity of olefin and isoparaifin feed to the alkylation zone. Accordingly, preferably the propane concentration in the feed is maintained at or near the optimum value so as to permit the maximum isoparaffin and olefin feed to the alkylation zone while holding the production of propane in the alkylation zone to a minimum. We have discovered that the optimum economic concentration of propane in the hydrocarbon feed to the isomerization zone is about 14 weight percent with the economic optimum concentration based on an evaluation of the hydrocarbon alkylation Zone efiluent to determine the increased value of the olefin feed due to the alkylation reaction.

The following examples are presented to illustrate the objects and advantages of the invention.

Example I In this example, propylene is alkylated with isobutane at an alkylation reaction temperature of 60 F. employing variant amounts of propane in the hydrocarbon feed to the alkylation zone as illustrated below in Runs 1, 2 and 3 of Table I. Hydrofluoric acid was employed as the alkylation catalyst. The operating conditions and yield data are presented below m Table I.

TABLE I Run 1 Run 2 Run 3 Operating Conditions:

Reactor temperature, F 60 60 60 Reactor Pressure, p.s.i.g 200 205 200 IC /01efin, Vol. Ratio 11.3 10. 8 12.2 HF/HG, Vol. Ratio 3. 2 2.9 2. 9 Propane in Hydrocarbon Reactor Feed,

Wt. Percent. 0. 28 1. 53 15.64 Duration of Test, Hours 0.67 0.75 0.75 HF Acid Data, Wt. Percent Total Acidity 92. 42 92. 95 91. 42 Water 0. 76 0.99 0. 64 Acid soluble oils O. 26 1. 68 2. 14 Inorganic Fluorides 0. 19 0.28 0.30 Yield Data:

Alkylate/Olefin, Vol. Ratio 1. 57 1. 54 1. 64 Isobutane Consumed/Olefin, Vol. Ratio 1. 25 1.18 1. 22 Synthetic Propane, Wt. Percent of Propylene 22. 0 19. 9 10. 2 Alkylate Data:

Reid Vapor Pressure, p.s.i 5. 00 4.70 5. 80 API Gravity 67.6 69.5 70.1 ASTM Dist, F 760 mm IBP 118 120 110 5%. 153 155 141 10%. 168 169 162 50% 215 205 207 430 348 351 428 443 EP 455 495 502 Motor Octane No. (+3 ml. TEL) 100. 9 Research Octane N 0. (+3 ml. TEL 100.0 10D. 0

1 Debutanized alkylate.

Comparison of Runs 1, 2 and 3 of Table I clearly establishes that the production of synthetic propane in the alkylation zone was significantly reduced when the concentration of propane in the hydrocarbon feed to the 3 alkylation zone was increased to 15.64 weight percent (Run 3).

Example II In this example, a mixed olefin feed was alkylated with isobutane at an alkylation temperature of 80 F., employing variant amounts of propane in the hydrocarbon feed to the alkylation zone as illustrated below in Runs 4, 5 and 6 of Table III. Hydrofluoric acid was employed as the alkylation catalyst. The composition of the mixed olefin feed, as determined by chromatographic analysis, employed in Runs 4, 5 and 6, is illustrated below in Table II.

TABLE II Run 4 Run 5 Run 6 Ethane 0. 1 0. 1 0. 1 Propane. 14.1 14.4 14. G Propylene 15. 5 16. 16. 4 Isobutano 24. 9 24. 3 24. 3 n-Butane 16. 4 16. 3 l6. 1 Isolontylene and Enter 14.0 14. 0 13.9 Trans-butene-2 7. 8 7. 7 7. 6 Cis-butene-2 5. 8 5. 8 5. 7 Isopcntane 1. 0 1. O O. 9 3methy1butene-1 0.2 0. 2 0. 2 n-Pcntanc 0. 1 0. 1 0. 1 2-methylbntene-1 0. 1 0. 1 0. 1

Total 100. 0 100. 0 100. 0

The operating conditions and yield data for Runs 4, and 6 are presented below in Table III.

TABLE III Run 4 Run 5 Run 6 Operating Conditions:

Time in Reactor, seconds. 35. 2 33. 9 34.0 Reactor Temperature, F 80 80 80 IC4/Olefin, Vol. Ratio-.- 171 176 175 IIF/HC, Vol. Ratio 12. 5 12.6 12. 7 Propane in Hydrocarbon Reactor Feed,

Wt. Percent 2. 20 7.61 14. 56 Duration of Test, I-Iours 4.0 4. 4.0 HF Acid Data, Wt. P61191117! Total Aeidit 86. 91 90. 51 01. 45 Water 2. 66 2. 67 2. 48 Acid soluble 2. 29 0. 80 0. 43 Inorganic Fluorides..- 0. 65 0. 69 0. 48 Yield Data Alkylate/Olefin, Vol. Ratio 1. 74 1. 71 1. 69 Isobutane Consumed/Olefin, Vol. Ratio. 1. 22 1. 21 1. 27 Synthetic Propane, Wt. Percent of Propylene 30. 8 15. 6 7. 9 Alkylate Data: 1

Reid Vapor Pressure, p.s.i 6.40 5. 05 5. 90 API Gravity 72.0 70. 9 71.0 ASTM Dist. F, 760 mm.:

IBP 101 110 107 146 172 162 157 213 214 280 278 334 330 P 397 400 Motor Octane No. (+3 ml. TEL) 104. 4 103.8 Research Octane No. (+3 m1. TEL) 103. 8 103. 4 103. 2

1 Dcbutanized alkylate.

Comparison of Runs 4, 5 and 6 of Table III clear-1y establishes that the production of synthetic propane in the alkylation zone was significantly reduced when the concentration of propane in the hydrocarbon feed to the alkylation zone was increased to 14.56 weight percent (Run 6).

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, in the light of the foregoing disclosure, without departing from the spirit or scope thereof.

We claim:

1. A process which comprises passing propylene to an alkylation zone containing an alkylation catalyst, passing isobutane to said alkylation zone, maintaining liquid phase alkylation conditions within said alkylation zone, maintaining a concentration of propane in the range of about 14 to about 16 weight percent in the total hydrocarbon feed to said alkylation zone, and maintaining said propane in the liquid phase throughout the alkylation reaction.

2. A process which comprises passing a mixed olefin feed to an alkylation zone containing an alkylation catalyst, each of said olefins in said mixed olefin feed having 3-5 carbon atoms per molecule, passing isobutane to said alkylation zone, maintaining alkylation conditions within said alkylation zone, introducing propane into said alkylation zone so as to maintain a concentration of propane in the total hydrocarbon feed to said alkylation zone in the range of about 14 to about 16 weight percent and maintaining said propane in said alkylation zone in the liquid phase throughout the alkylation reaction.

3. In an alkylation process which comprises passing an olefin having 3-5 carbon atoms per molecule to an alkylation zone containing an alkylation catalyst, passing an isopar-aflin selected from the group consisting of isobutane and isopentane to said alkylation zone, and maintaining liquid phase alkylation conditions within said alkylation zone; the improvement which comprises introducing propane into said alkylation zone in the range of about 14 to about 16 weight percent of the hydrocarbon feed to said alkylation zone, and maintaining said propane in the liquid phase throughout the alkylation reaction.

4. The process of claim 3 wherein the temperature of said alkylation zone is maintained in the range between about -105 F.

References Cited by the Examiner UNITED STATES PATENTS 2,881,235 4/1959 VanPool 260683.48 2,967,208 1/1961 Clauson et al 260683.61 3,007,983 11/1961 Clauson 260683.61 3,200,883 8/1965 Phillips 260683.48 3,204,010 8/1965 VanPoOl 260683.48

DELBERT E. GANTZ, Primary Examiner.

R. H. SHUBERT, Assistant Examiner.

Claims (1)

1. A PROCESS WHICH COMPRISES PASSING PROPYLENE TO AN ALKYLATION ZONE CONTAINING AN ALKYLATION CATALYST, PASSING ISOBUTANE TO SAID ALKYLATION ZONE, MAINTAINING LIQUID PHASE ALKYLATION CONDITIONS WITHIN SAID ALKYLATION ZONE, MAINTAINING A CONCENTRATION OF PROPANE IN THE RANGE OF ABOUT 14 TO ABOUT 16 WEIGHT PERCENT IN THE TOTAL HYDROCARBON FEED TO SAID ALKYLATION ZONE, AND MAINTAINING SAID PROPANE IN THE LIQUID PHASE THROUGHOUT THE ALKYLATION REACTION.