DE1215132B - Process for the catalytic isomerization of olefins which do not contain a terminal double bond to 1-olefins - Google Patents

Description

Process for the catalytic isomerization of olefins which do not contain a terminal double bond to give olefins It is known that olefins which do not contain a terminal double bond can be catalytically converted into olefins with a terminal double bond. The known methods are limited to low temperatures, since the use of higher temperatures results in undesired side reactions, such as further dehydrogenation and cracking. However, higher temperatures favor the production of 1-olefins, as can be seen from the equilibrium data in Table I below: Table I Equilibrium concentration Temperature OC in mole percent Butene- (l) J butene- (2) 27 2.9 97.1 127 7.7 42.3 227 13.7 86.3 327 19.8 80.2 427 25.6 74.4 527 30.3 69.7 627 34.9 65.1 727 38.5 61.5 While the table above shows the equilibrium data for butene- (1) and butene- (2), it is known to those skilled in the art that higher temperatures also favor the formation of other 1-olefins in the same way.

It is possible, also with the known magnesium oxide catalysts at temperatures of about 650 "C a 400% conversion of butene- (2) to butene- (1) to achieve. However, the sources of magnesium oxide are limited, and moreover can be found unwanted side reactions take place here, in particular dehydration and / or Formation of aromatics. So z. B. by this known method almost 12 mole percent Butadiene and about 25 mole percent C8 compounds and lighter gases are formed, and the amount of butenes decomposed is about 55 mole percent. In contrast, is under comparable conditions, the percentage of butene that with the invention Catalyst system is decomposed, only about 2 to 3.5 mole percent at much higher levels Yields of the desired butene- (1).

It is also known to use catalysts containing black chromium oxide contain what of the green or used by the method according to the invention real chromium (III) oxide catalysts must be distinguished. With the well-known black Chromium oxide containing catalysts is used at relatively low temperatures, viz worked below 450 "C, which lowers the yields of 1-olefins, since yes, as in Table I was shown to favor equilibrium at low temperatures the olefins which do not contain a terminal double bond is shifted.

In contrast, when carrying out the present invention, it is possible Olefins that do not contain a terminal double bond at relatively high temperatures to treat 1-olefins in increased yields and without undesired side reactions, how to achieve further dehydration and cracking.

The inventive method for the catalytic isomerization of Olefins which do not contain a terminal double bond to olefins with a terminal double bond Double bond by means of a chromium oxide catalyst consists in the fact that one is an olefin with a non-terminal double bond with a chromium trioxide-aluminum oxide catalyst, which consists of 5 to 60 percent by weight of chromium oxide and the remainder of aluminum oxide, at a throughput rate of 50 to 5000 volumes of hydrocarbon per Volume of catalyst per hour and at a temperature of 510 to 704 "C in the presence of water vapor in a molar ratio of Steam olefin from 1: 1 to 30: 1.

The method of the invention can be carried out in conventional apparatus will. The isomerization is usually done in a fixed bed reactor and the separation of the reaction product by condensation of the water vapor from the hydrocarbon and separation of the os-olefin present in the hydrocarbon is carried out. The non-terminally bound olefins that are recovered in the separation, are usually returned to the process. After prolonged use is common an oxidative regeneration of the catalyst is necessary. This will make any Removed carbon deposits on the catalyst. The length of the procedural cycle is usually 10 to 100 hours. The reaction temperature is between 510 and 704 ° C and preferably between 552 and 677 "C. As indicated above, favor the higher temperatures thermodynamically the formation of 1-olefins versus lower ones Temperatures, however, very high temperatures cause the starting material to decompose. When working in the above temperature ranges under the conditions according to the invention Sufficient conversion is obtained without excessive decomposition. When executing According to the invention, 1 to 30 moles of water vapor per mole of hydrocarbon are preferred however, 4 to 15 moles of water vapor per mole of hydrocarbon are used. While the hourly throughput speed within wide limits, d. H. from 50 to 5000 volumes Hydrocarbon per volume of catalyst per hour is a flow rate from 100 to 2000 volumes per volume of catalyst is preferable. A pressure of atmospheric pressure up to 7 atm is usually used, although higher or lower pressures are also used can be used.

The catalyst used in the invention consists of 5 to 60 Percentage by weight of chromium oxide together with aluminum oxide, which is the remainder represents. This catalyst can by common precipitation, impregnation, Mixing or by any other known means of making one Catalyst are produced.

The present process is particularly for the isomerization of non-terminally bonded olefins with 4 to 6 carbon atoms in the longest straight chain suitable. However, higher olefins, e.g. B. with up to 8 carbon atoms can be used in a straight chain. But the thermodynamic equilibrium is less favorable, so that only lower yields of 1-olefins are obtained. Examples for such non-terminally bound 1-olefins are - butene- (2), 2-methylbutene- (2), Pentene (2), 3-methylpentene (2), hexene (2), hexene (3), 3-ethylhexene (2), oetene (2), Octene (3), octene (4), 4-ethyloctene (3) and the like.

The present invention will now be made by way of the following examples. are explained in more detail, in which butene- (2) is isomerized to butene- (1).

Example A catalyst was produced by impregnating γ-aluminum oxide tablets made to a regulated depth with an aqueous solution of chromic acid, let the liquid drain off, dry net and at 532 ° C for 12 hours and calcined at 954 ° C for 28 hours. The final catalyst contains approximately 20% Cr2O3 and 80% AlsO3. This was almost entirely a solid solution of Chromium oxide and oc-aluminum oxide. For the production of an impregnated catalyst "From a regulated depth" aluminum oxide was finely ground and mixed with a binder, such as hydrogenated corn oil, after which the material was tabletted.

These tablets were partially at a temperature of 600 ° C 10 Calcined for minutes, after which the tablets were cooled and placed in the chromic acid solution were immersed. This first calcination only removes that of the catalyst surface. close binders ,. so that the solution does not get into the center of the tablet during the Immersion penetrates. The high temperature calcination that the tablets after Immersion removed the remainder of the binder, leaving the final catalyst is completely porous.

A hydrocarbon stream containing 990 /, butene- (2) was then passed over the catalyst, which had been prepared as above, at an hourly throughput rate of 400 volumes of hydrocarbon per volume of catalyst, a ratio of steam-butene- ( 2) of 12: 1 and at atmospheric pressure and 610 ° C in a rust-free stall reactor. The data obtained in this experiment are given below: Total catalyst age, hours 25 117 143 Hours since steaming * 25 23 4 Product, mole percent CO2 .............. 0.23 0.31 0.37 H2 ................ 1.04 0.46 0.80 CH4 ............... 0.29 0.28 0.37 C2H4 .............. 0.13 0.09 0.04 C4H6 .............. 1.80 1.07 1.36 Butene- (1) .......... 37.15 38.12 37.32 Butene- (2) .......... 59.36 59.67 59.74 * After about 24 hours of isomerization, the butene (2) feed was stopped and the catalyst was treated with steam for 2 hours. The butene (2) feed was then started again for a further 24 hours.

The data show the good isomerization up to.

143 hours with no loss of catalyst activity, indicating that the effectiveness of the catalyst lasts for 200 hours or more without vaporization and that with a presumed catalyst life of 6 months and even 1 Year or more can be expected.

A working time of 48 hours was observed in these tests and a sample is taken from the collected reaction product. The catalyst was then regenerated and worked again for 4 hours and then another sample taken.

In this way, drain samples were taken before and after steaming and regeneration of the catalyst obtained.

From these experiments it can be seen that the conversions are relatively high from olefins with non-terminal double bonds to 1-olefins with a chromium oxide-aluminum oxide catalyst at relative obtained high temperatures in the presence of water vapor can be.

To the importance of the presence of water vapor in the process To explain the invention, two experiments were carried out according to the example below employed except that there was no water vapor. One of those attempts was at a throughput speed of 400, as in the example, and the other performed at a throughput speed of 5200. In both cases it was the reactor clogged with carbon within 2 hours of work. After removal from the reactor the catalyst was contaminated with iron oxide, which apparently originated from the stainless steel reactor material. Such disturbances can can be essentially avoided if according to the invention in the presence of water vapor is being worked on.

As the catalyst in the two previous experiments with iron was contaminated, two additional trials were made under the conditions of the two previous attempts were made except that a glass reactor was used. Fewer as 2% of the butene- (2) became butene- (1) at each throughput rate and also isomerized before or after vapor deposition. Left during the steaming period air is passed over the catalyst to remove the coking precipitate. At both throughput rates, the carbon precipitate fell on the catalyst over 15% of the weight of the catalyst.

The 1-olefins prepared by the method according to the invention are suitable particularly suitable for the production of polymers and especially copolymers with ethylene in the presence of a chromium oxide catalyst as indicated in German Patent 1,117,309 is. These 1-olefins are also particularly suitable for the production of polymers with other catalyst systems, e.g. B. organometallic catalysts.

Claims (5)

Claims: 1. Process for the catalytic isomerization of Olefins which do not contain a terminal double bond to olefins with a terminal double bond Double bond by means of a chromium oxide catalyst, characterized in that one an olefin with a non-terminal double bond with a chromium trioxide-aluminum oxide catalyst, which consists of 5 to 60 percent by weight of chromium oxide and the remainder of aluminum oxide, at a throughput rate of 50 to 5000 volumes of hydrocarbon per Volume of catalyst per hour and at a temperature of 510 to 704 "C in the presence of steam in a molar ratio of steam-olefin of 1: 1 to 30: 1 brings into contact. 2. The method according to claim 1, characterized in that olefins with 4 to 6 carbon atoms in the longest straight chain are isomerized. 3. The method according to claim 1 and 2, characterized in that the Isomerization at a temperature of 552 to 677 "C in the presence of water vapor in a molar ratio of water vapor per mol of the olefin to be converted of 4: 1 to 15: 1 is carried out. 4. The method according to claim 1 to 3, characterized in that a Catalyst made from aluminum oxide, which is partially impregnated with chromium trioxide, is used. 5. The method according to claiml to 4, characterized in that the no terminal double bond containing olefin butene- (2) and the 1-olefin butene- (1) is. References considered: U.S. Patents No. 2,361 613, 2 387994, 2403671.