DE1493342C - - Google Patents

Description

The invention relates to a process for alkylating low-boiling isoparaffins in the presence a.s hydrogen fluoride catalyst, the catalyst separated off from the reaction mixture by settling as well as unconverted isoparaffin from the reaction product are recycled into the alkylation zone and recovery of the alkylate as a process product.

In known methods of this type, as they are, for. In U.S. Patents 2,691,688, 3,002,818 and 3,082,274 are described, is from the reaction mixture immediately after leaving the Separated reaction zone of the hydrogen fluoride catalyst and returned to the reaction zone while the unreacted isoparaffin elsewhere, if necessary after further processing of the reaction product is separated from this and returned to the alkylation zone.

The object of the invention is to use a process of the type mentioned at the outset to _{produce an alkylate with a higher octane number, in particular with a higher content of C 8} hydrocarbons, especially trimethylpentane, without increasing the ratio of isoparaffin, especially isobutane, to olefin at substantially Unchanged temperature and pressure conditions while reducing the consumption of hydrogen fluoride per unit weight of alkylate produced.

This object is achieved according to the invention in a very simple manner in that one that, the recirculated hydrogen fluoride-containing, emulsified reaction mixture partly in a circle to Recirculating alkylation zone, while the other part of this mixture in a vertical arranged settling zone initiates from below and for a residence time of about 60 to 1200 seconds leads upward, withdrawing the hydrogen fluoride from the central portion of the settling zone, and recycled, while the substantially hydrogen fluoride-free hydrocarbons from the The upper part of the settling zone is withdrawn and worked up in the usual way.

As comparative experiments have shown, the alkylation process, known per se, is affected by the measures improved according to the invention in various respects. A higher olefin content can be used, and under comparable operating conditions one obtains at practically the same octane number in the alkylate a higher one

ίο Percentage of trimethylpentane, based on the C ₈ hydrocarbons or a lower proportion of alkylate with 9 or more hydrocarbons with a reduced catalyst consumption. The process of the invention is particularly applicable to the alkylation of isobutane with propylene or butylene, but it also offers advantages when applied to other isoparaffins and other olefins for the production of motor fuels, aircraft alkoxides or higher boiling aliphatic products. So can

so the paraffin of the feed z. B. also from isopentane, Isohexane or mixtures thereof, branched chain heptanes and other aliphatic hydrocarbons exist with a branched chain. In a similar way, the olefin used can also be prepared from 1-butene, 2-butene, isobutylene, amylenes, hexenes or heptenes exist.

Referring to FIG. 1 is the implementation of the method of the invention in more detail below explained.

The isoparaffin-olefin mixture is mixed with hydrogen fluoride in line 1 and the reactor 2 fed. Fresh hydrogen fluoride is in controlled quantities from the storage container 12 through the Line 13 is sent by means of pump 14 to line 15 and through control valve 16 to line 11 and then through line 3, pump 4 and line 5 into line 1 prior to its entry introduced into the alkylation reactor 2.

The hydrogen fluoride catalyst is introduced into reactor 2 in an amount sufficient to provide a catalyst to hydrocarbon volume ratio in the alkylation reactor of 0.5 to 2.5. "Hydrogen fluoride catalyst" is understood to mean all those catalysts in which hydrogen fluoride is the essential active component, such as anhydrous fluoride or hydrogen fluoride with a content of various additives or accelerators or boron trifluoride. Usually anhydrous hydrogen fluoride is used. However, it is also possible to use hydrogen fluoride containing 10% water or more. Excessive dilution with water is undesirable because it reduces the alkylation activity of the catalyst and corrosion problems arise. In order to reduce the tendency of the olefinic fraction to polymerize before the alkylation in reactor 2, the molar ratio of isoparaffin to olefin in the alkylation reactor is kept at a value greater than 1 to 20: 1 and preferably from 3: 1 to 15: 1 . The alkylation takes place at temperatures from -18 ⁰ C to about +93 ⁰ C, preferably between -l ° C + 43 ⁰ C. In general, the heat of reaction from the reactor must z. 2 B. be dissipated by an internal cooler or a heat exchanger. The pressure on the alkylation system is usually just high enough to keep the hydrocarbons and catalyst essentially liquid, that is, between about atmospheric and 40 atmospheres.

3 4

The alkylation time expressed as space time, held at 24 ^° C. The heat of reaction is dissipated from the (volume of the catalyst reactor 102 to be treated in the reactor, for example by a water cooler, internal fan, divided by the volume of cooler or heat exchanger supplied per minute. The pressure lumen hydrocarbons) is expediently less than 15 Atm. held. The contact time (space time) of less than 5 minutes and preferably less than 5 in reactor 102 was maintained at 1 minute, so that 2 minutes. At least part of the emulsified reaction is the alkylation of the mixture with the Katalytionsgemisches from the reactor 2 is carried out continuously sator in intimate contact. Part of the reac is withdrawn through line 3 and, with the recirculation mixture, deposited hydrogen fluoride carried through the line is continuously withdrawn from the 103 and mixed with the withdrawn, recirculated lines 8 and 11. At least a portion of the hydrogen fluoride from lines 108 and 111 of the resulting emulsion is mixed through to the reactor. Part of the resulting emulsion is returned to lines 3, 5 and 1. The rest, ie through the lines 103, 105 and 101 to the reactor the useful amount of this emulsion, is returned through the. The useful amount of the emulsion is introduced through lines 5 and 6 into the vertical mixing-settling line 105 and 106 at the bottom into the vertical zone 7. It flows upwards and lingers 15 mixing-settling device 107 passed . The circulation in the lower mixing section of the mixing-settling zone of the emulsion serves for mixing in reactor 2 for about 60 to 1200 seconds, preferably about 100 and also for heat reduction. In addition, the up to 800 seconds, depending on the composition of the pump 104, is used to vary the mixture of hydrocarbons introduced. Acid rate occurs in the mixing section, making the process particularly economical in turbulent flow with the aid of devices not shown.

The mixing-settling device 107 has a height of called. When the desired dwell time in the 10.67 m and 2.44 m diameter and ent-mixing section is reached, which is predetermined by the geometry holding 20 trays or holes in the lower mixing section of the mixing-settling device, plates are set at intervals of 0 .3 m, so that there is a total pressure drop of 3.6 to 4.5 kg at the upper end of the mixing-settling zone to the greatest 25 total pressure drop. The part of the hydrocarbons freed from hydrogen fluoride mean residence time in this mixing section (volume withdrawn through line 17 , while the turbulent flowing hydrocarbon-hydrogen fluoride is settled from the middle of the mixing-settling zone, divided by the total useful stream of acid discharged through line 8 for recirculation plus hydrocarbon). This hydrogen fluoride flows through line 8, 30 for about 300 seconds. Through the perforated plates or the pressure control valve 10 and the line 11 to trays, a turbulent flow of high with the hydrocarbon-hydrogen fluoride emul flow rate is generated, so that the feed sion to mix in the line 3, whereupon the mixing-settling Device 107 is conveyed; Mixture through the pump 4 to the line 5 and through the pump 104 is a circulation pump with which the line 1 is sent to the reactor 2. A part 35 output of 22.7 m ³ per minute. After the desired hydrogen fluoride has settled, the line 9 separates through the th residence time in the mixing section to an acid regenerator, not shown, and hydrocarbons can be conducted from the hydrogen fluoride in the settling. section of the mixing-settling device. Hydrocarbons P 40 which have been freed from hydrogen fluoride for the most part are conveyed at the top through line 117 to stripper 118

: For the production of an isoparaffin-olefin-alkyl- deducted. Deposited hydrogen fluoride is caused by

tes of improved quality with very low catalysis- the line 108 withdrawn and with the help of the pressure

Sator consumption is in a system 3340 hl olefin control valve 110 and the line 111 that of the in

Containing material with 383 hl isoparaffin-containing Ma- line 103 containing hydrocarbon-fluorinated water-

mixed material per day and mixed in in a mixture of precursors (not shown). The emulsion then becomes

directions dried. The pretreated liquid through the pump 104 and lines 105 and 101

Stream is pumped to reactor 102 through line 101 to alkylation. Part of the deposed

reactor 102 led. The olefin-containing material containing hydrogen fluoride flows in through line 109

in mol percent: ethane 0.1%, propylene 20.1%, the acid regenerator 121.

Propane 14.8%> butylene 24.1%, isobutane 30.9%, 5 ° The amount of recirculated hydrocarbons in normal butane 9.8% and pentane 0.2%. The iso-line 145, which goes to the reactor 102 , is paraffin-containing material contains 0.8% in mole percent 26,244 hl per day. Their composition in molpro-propane, 94.8% isobutane and 4.4% normal butane. The percentage is as follows: propane 10.7%, isobutane 79.8%, an isobutane-rich paraffin recycle stream is normal butane 8.9%, pentanes 0.3% ^and alkylate 0.3% the isoparaffin-olefin stream in line 101 through 55 The total combined feed amount in the line 145 admixed. The total feed to line 101 immediately before entering the reactor in line 101 is with hydrogen fluoride of 102 is 29,964 hl per day. Total combined acid mixed to hydrocarbon of 2.0. The feed amount consists of the fresh. Fresh hydrogen fluoride from the feed plus recirculated hydrocarbon tank 112 through line 113, pump 114, 60 material from the process. The composition of the line 115, the control valve 116, the lines of the total combined feed is in 111 and 103, the pump 104 and the line 105 the mole percent: ethane traces, propylene 2.4%, propane combined feed in the line 101 before the 11.2%> butylenes 2.9%, isobutane 74.1%, normal alkylation reactor 102 mixed in. There is a tendency towards butane 9.0%, pentane 0.2% and alkylate 0.2%. The rate of the olefin fraction to be polymerized prior to the alkylation is 537,476 hl of the emulsion, to reduce the molar ratio of per day, and the rate of the useful material, isoparaffins to olefins, expediently to about 3: 1 that through line 106 Mix-settle pre-held to about 15: 1. The reactor 102 is in direction 107 , is 87,975 hl per day. from

of this amount is 29 394 hl of hydrocarbons per day and the remainder is hydrogen fluoride. The composition of the hydrocarbon portion of the mixer settler 107 entering material is in mole percent: ethane tracks, propane 12.1% ^'s ^ ° - 72.2% butane, normal butane 9.5%, 0.5% pentanes, alkylate 5.7% and traces of tar. In the mixing-settling device, the mixture receives a turbulent flow, and after the end of the residence time prescribed above, 29,553 hl per day are withdrawn from the upper section of the mixing-settling device 107 through the line 117 and arrive at the scraper 118. Of these 29 553 hl per day of loading the scraper, 29 394 hl per day are hydrocarbons and 159 hl per day are hydrogen fluoride. Accordingly, hydrocarbons freed from a larger part of the hydrogen fluoride are drawn off in this way and fed to the scraper. The line 108 attached to the side of a central section of the mixing / settling device above the mixing section serves to discharge 57,423 hl per day of deposited hydrogen fluoride. The greater part of this is returned to reactor 102 through lines 110 and 111. A smaller portion of the deposited hydrogen fluoride, namely 159 hl per day, is passed through line 109 to acid regenerator 121 and through double lines 119 and 120 in order to produce an alkylate product of increased quality.

Hydrocarbons freed from the majority of the hydrogen fluoride are introduced via line 117 into iso-stripper 118 on the uppermost tray; the Iso stripper is a fractionation column of about 2.10 m diameter with 50 plates at a distance of 61 cm, which under a pressure of 10.5 kg / cm ² , with a top temperature of 68 ° C and a bottom temperature of 177 ° C with internal reflux works. The iso stripper 118 is fed near the center of the vessel through line 128 with a saturated butane stream. The exact point where the saturated butane stream should enter is determined by the ratio of iso- to Nprmal paraffins. This stream provides isobutane to supplement the content in the olefin-containing raw material. An excess of normal butane is withdrawn further down through line 132 as a secondary cut, and leaves the plant as a separate product.

Within the isobutane stripper 118 there is a substantial separation between the lower-boiling isobutane and the higher-boiling normal butane and, in addition to the isobutane deflection, an alkylate stripping takes place. The column has no external reflux and works as a real stripper. There is no need to use very expensive reflux ratios to obtain high purity isobutane as reflux for the reaction vessel. In addition, the normal butane present in the olefin feed must leave the system together with the normal butane which is in the "outside" isobutane stream plus the small amount of normal butane formed in the alkylation process itself. For example, if this normal butane were allowed to accumulate in the spout, its vapor pressure would become extremely high and there would be no control over the vapor pressure of the alkylate product without an additional stabilization step. In known alkylation systems, vapor pressure control is achieved by taking off a secondary steam cut on the iso stripper at such a point that the secondary butane cut contains less than 5% isobutane and less than 4% pentanes, so that a certain amount of control of the vapor pressure of the alkylate product is still permissible .

In the present process, about 556 hl of saturated butanes per day are introduced into the iso stripper 118 through line 128. 611 hl of excess normal butane product per day leave the system as a separate product from line 132. The composition of this stream in mole percent is 4.3% isobutane, 90.3% normal butane, 3.6% pentanes and 1.8% alkylate. The top product is drawn off from stripper 118 in an amount of 26,920 hl per day via line 133 and passed to condenser 134 . The composition of the iso scraper top fraction in mol percent is as follows: traces of ethane, propane 13.0 ⁰ I ₀ , isobutane 77.8%. Normal butane 8.6%, pentanes 0.3% and alkylate 0.3%. The bottoms from the iso scraper 118 is circulated through the heater 127 via lines 130 and 131. There, high temperatures are maintained in order to decompose organic fluorides present in the alkylate, for example. The net bottom stream withdrawn from the iso stripper through line 129 represents finished motor fuel alkoxide of the desired vapor pressure. In the present case, 2485 hl per day are produced on this alkylate product. This is of superior quality compared to the product from known hydrogen fluoride alkylation plants which use a mixed olefin feed. Complete alkylate studies and comparisons are given below. About 26,920 hl of hydrocarbons per day and 159 hl of hydrogen fluoride per day are conducted from the iso stripper 118 via the line 133 to the condenser 134 . It is necessary to design the head system of the iso scraper correctly because, as shown above, propane is removed along with the isobutane in the overhead product. The propane stream is enriched by means of the condenser 134 , as a result of which the size of the propane stripping column is greatly reduced. The overhead product from the isobutane, consisting essentially of isobutane, is cooled and returns to the reaction vessel along with the bottoms from the propane stripping column, as described below.

The top system of the iso scraper, consisting of the condenser 134, the collecting vessel 136 and the lines 135, 138 and 137 is operated in such a way that about 23 773 hl per day of net top product with a composition in mole percent: propane 11.8%> isobutane 78, , 0.3% pentanes and alkylate 0.3% i ⁿ t ^he line 140 are obtained 8%> 8.8% normal butane, before being mixed with the bottom product of the Propanabstreifkolonne 143 in the line 144th All of this hydrocarbon return is routed via line 145 for mixing with the fresh feed supplied through line 101. A drag stream of this material in line 145 is withdrawn via line 146 to a bottom section of an acid generator 121. This has a diameter of 45 cm with five shelves or perforated plates at a distance of 45 cm. It operates under a pressure of 10.5 at at a head temperature of 88 ⁰ C and a bottom temperature of 205 ° C. As mentioned above, a minor proportion of the hydrogen fluoride deposited, viz

i 493 342

7 8

159 hl per day from mixer settler 107 via valve 154 to line 148 to collecting vessel 149, line 108 and line 109 to double line - in which the remaining hydrogen fluoride is system 119 and 120. The regenerated hydrogen fluoride settles and through line 150 to the acid circuit is in of this regeneration zone by fractionation running stream 141 goes.

purified, and it exits zone 121 through line S If one uses the 147 for mixing with fresh hydrogen fluoride process according to the invention in the manner described here, one obtains from line 113 and becomes, if necessary, a motor fuel alkoxide product with an end to the contact vessel 102 returned. Heavy tar boiling point well below 205 ° C and a leaded-like polymer and the constant boiling mixture octane number greater than 105 with a catalyst passing through line 122 to a tar settler io use of less than 90 g hydrogen fluoride per 1.6 hl 123, from where the constant boiling mixture over the generated alkylate. Line 124 to a neutralizer and the tar product of the process in an amount, usually comparative tests of less than 8 hl per day through line 125

together with heating oil from line 126 as heating 15 In a first comparison, two alkylates were sent to the heater 127 of the Iso scraper. from two different hydrogen fluoride alkylation

Of the 26,920 hl produced per day hydrocarbons and plants. Plant A delivered alkylate under 159 hl per day of hydrogen fluoride, which was obtained from the iso scraper application of the invention in the process shown in FIG. 118 shown going to capacitor 134 , the remainder of the flow diagram. Plant B delivered alkylate in a fluorine-3080 hl hydrocarbon per day from a hydrogen alkylation plant according to the stated composition in mol percent: ethane 0.1%, propane 23.1%, prior art without the measures of the invention. Isobutane 69.0%, normal butane 7.7% and pentanes The plant B used a reactor system with a 0.1% passed to the settler 139 , in which 137 hl fluorine contact zone and horizontal settlers, hydrogen per day settle and as an acid circuit In comparison, the mode of operation of the two start-up streams to the reaction vessel 102 via the line 25 were to a peak octane number FI clear + 3 cm ³ 141 go. The hydrocarbon content of the tetraethyl lead (TAB) set greater than 105.0. Settling material 139 has a small order from the system B alkylate to this octane number

Amount of hydrogen fluoride entrained by the generate were a reaction ^{temperature of 24 0} C. Line 142 goes to propane stripping column 143. and a molar ratio of isobutane to olefin of The feed to the column 143 thus comprises 3 ° 20: 1 with a hydrogen fluoride activity of 91.5% 3080 hl of hydrocarbons per day and 22 hl of fluorine required; the octane number FI clear + 3 cm ³ tetrahydrogen per day. It is a vessel of 1.20 m ethyl lead was 106.5. In addition, the propylene diameter with 15 perforated plates at a distance of 60 cm from the total olefin feed for the plant and operating under a pressure of 19.3 at was limited to only 19.4 percent by volume. The system A at a head temperature of 52 ° C and a bottom 35, however, delivered alkylate with a leaded octane temperature of 102 ° C. number (FI clear + 3 cm ³ tetraethyl lead) of 106.8

The purpose of the propane stripping is to remove excess propane from the isobutane at a reaction temperature of just over 23 ° C. with a molar ratio of isobutane to olefin from the butane recycle stream so that a bottom stream of 11: 1 with a hydrogen fluoride activity of 85.2%. 2470 hl per day is obtained. This flow in the 4 ° Furthermore, the propylene content of the total olefin line 144 has before the mixing with the 23 773 hl feed for the plant A 31.6 percent by volume, i.e. per day iso scraper head product in the line 145 more than 1.6 times as in plant B. This has a composition as follows: Propane 1.0%, it follows that the alkylate produced in plant A is superior to isobutane 89.1%, normal butane 9.8% and pentanes those from plant B, Since at about 0.1% ^{un <} i, after mixing with the isoab- 45 the same alkyl octane number, the system A is an alkylate strip head product from line 140 as a total with a much lower ratio of isobutane to hydrocarbon circuit via line 145 to the olefin and with a higher propylene content, reaction vessel 102. The overhead stream from the propane feed at about the same reaction temperature stripping column 143 in line 148 goes to the top and provided a lower activity. Moreover collecting vessel 149, wherein a portion of the entrained fluoro- 50 existed in the generated in Appendix A alkylate hydrogen settles and through the conduit 150 89.4 weight percent (is the total generated C ₈ -Kohzur acid circulation line 141st This head bons) from Trimethylpentanes compared to product still contains a small amount of hydrofluoric acid _{- 86.6 percent by weight (of the total C 8} carbon produced and is therefore transferred from the collecting vessel 149 via the hydrocarbons) in the alkylate produced in Appendix B. Line 151 to the small HF stripper 152 thus leads to fewer side reactions in system A. However, part of this stream goes back up.

flow for column 143 from line 151 via the The superior properties of the in Appendix A

Line 155. alkylate produced also result from a

The hydrogen fluoride stripper 152 has 50 cm diameter, contains 20 trays at a distance of 30 cm and 60 alkylate generated with one in a plant C is below 21 atm at a temperature at the bottom and generated alkylate. The formation of the system C operated at the peak of 62 ° C. This operation was similar to that of plant B. 39% propylene is contained per day 610 hl of a propane product from were in the total olefin feed for the other hydrogen scraper 152 through line position C, while the feed for An 156 is removed Composition in mole percent 65 layer A contained 33 percent by volume propylene. The Anfolgende is 0.6% ethane, propane were 98.3% and isophthalic worked at comparable Betriebsbedinbutan 1.1% · T ^he hydrogen fluoride, so that a useful comparison of trol cable 153 located across the conditions. He goes through the control-witnessed alkylates could be made.

The product tests are shown in the following table.

table

Specific gravity 15.6 / 15.6 ^C

RVP, kg

(Reed vapor pressure)

Engler

Start of boiling

10%

30%

50%

70%

90%

95%

99%

Final boiling point

Octane number

F-I clear

+ learn ³ TAB

+ 3 cm ³ TAB

Appendix A I C

0.694 3.7

⁰ C 38
70
93
99

113
117
157
183
183

94.0 101.1 105.6 0.690

4.5

⁰ C 35
58
89
99.5

111
163
204
208
208

91.6

99.0

102.5

Composition in percent by weight

Isobutane

Normal butane

Isopentane

Normal pentane

2,3-dimethylbutane

2-methylpentane

3-methylpentane

2,2 and 2,4-dimethylpentane

2,2,3-trimethylbutane

2-methylhexane

2,3-dimethylpentane

3-methylhexane

2,2,4-trimethylpentane

2,5-dimethylhexane

2,4-dimethylhexane

2,2,3-trimethylpentane

2,3,4-trimethylpentane

2,3,3-trimethylpentane

2,3-dimethylhexane

3,4-dimethylhexane

Cg hydrocarbons ....

(! ^ "- hydrocarbons

Cn hydrocarbons

C ₁₂ hydrocarbons

(^ -Hydrocarbons

Total 100.0

0.1

7.4 3.5

2.5 0.6 0.3 6.1

Lane 0.2

16.4 0.1

31.5 2.0 3.1 0.6

10.6 5.5 3.3 0.3 0.8 2.9 2.2

Lane 0.3 5.7

12.4 0.3 3.5 1.2 0.5 5.9 0.1 0.3

13.6 0.3

24.0 2.2 3.0 0.3 8.0 2.8 2.8 0.3 3.4 4.8 2.8 0.4 0.1

100.0

These values show that the main difference between
the alkylates to the extent of by-product formation
consists. The alkylate produced in Plant C was
richer in isopentane and richer in heavy material than C ₈ hydrocarbons. The in Appendix C
alkylate produced had a C ₉₊ fraction of 11.5 percent by weight versus 5.9 percent by weight in the
Appendix A. Further comparisons of the C ₈ fractions
show that the alkylate obtained in plant A
a more favorable distribution than the product of that
Plant C had; This is because 48.2 percent by weight (of the total alkoxide) trimethylpentanes in
Plant A produces compared to 36.1 percent by weight (des

Total alkylate) in Appendix C. The final boiling point of the alkylates also shows that the alkylate from the Plant C had more heavy ends than that from Plant A. The product composition of the alkylate from Appendix A therefore shows a relatively clean reaction system with fewer side reactions and lower catalyst consumption of about 90 g hydrogen fluoride to about 1.6 hl produced in plant A. Alkylate. The alkylate produced according to the invention in Appendix A is the same in product quality superior, which is produced in the known hydrogen fluoride alkylation plant C.

1 sheet of drawings

Claims (1)

Claim: Process for the alkylation of low-boiling isoparaffins in the presence of a hydrogen fluoride catalyst, wherein the catalyst separated off from the reaction mixture by settling and unconverted isoparaffin from the reaction product are returned to the alkylation zone and recovery of the alkylate as a process product, characterized in that that the emulsified reaction mixture containing the recirculated hydrogen fluoride is partially circulated to the alkylation zone recycled, while the other part of this mixture in a vertically arranged The settling zone is initiated from below and upwards during a residence time of about 60 to 1200 seconds leads, withdraws the hydrogen fluoride from the middle section of the settling zone and returns it, while the substantially hydrogen fluoride-free hydrocarbons from the upper part the settling zone is withdrawn and worked up in the usual way.