JPS611627A - Manufacture of isobutene - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for selectively producing isobutene by catalytic cracking of hydrocarbon streams.

Environmental and other political legislation adopted by some countries against the use of tetraethyl lead in motor fuels requires other additives, including oxygen-containing additives, to improve the octane rating of motor fuels. led the oil industry to explore. Among these additives, asymmetric ethers, particularly methyl tert-butyl ether (MTBE), have proven to be very effective gasoline additives. , M.T.
The most common method of producing BE consists of the reaction of isobutene with methanol.

Isobutene can be used as a compound such as t-butyl alcohol (used as a solvent), t-butyl phenol (used as a stabilizer), low molecular weight polymers (used to improve the viscosity index of lubricating oils), etc. It is also used as a starting material for the production of other valuable compounds. As a result of this increased interest in isobutenes, the current availability of isobutene does not allow the production of these derivatives in sufficient quantities to satisfy their potential Markera F.

Butenes, including 1-butene, cis- and trans-2-butene, and isobutenes, are currently used as cracked gases (cr
It can be obtained by a variety of methods including extraction of cracked gases obtained in the production of ethylene by pyrolysis of ethylene (acked gases), especially naphtha. Ethylene and propylene constitute the majority of these gases, and the butene content generally does not exceed about 8% by volume. Subjecting naphtha to catalytic cracking instead of pyrolysis produces C1 and C4 hydrocarbons, middle distillate
Preference is given to the formation of products with a high content of tes) and gasoline. For example, catalytic cracking of naphtha over moving bed catalysts provides products containing up to 12% total butenes, with isobutene representing up to 25% of that amount. As can be seen from the above, the catalytic cracking process produces only a small amount of imbutene.

It can therefore be seen that there is currently a need for a simple and economical process for producing isobutene, particularly a process that can utilize readily available starting materials.

Several methods for improving the performance of these olefin systems have been described in the literature. U.S. Pat. No. 4,404,423 to Niss, J., and Miller (S. J., M. Iller) discloses the process of treating normally gaseous olefins by oligomerization reactions in at least two stages leading to the formation of high-boiling hydrocarbons. Disclosed is a method for improving feed containing materials.

The method can be applied to propylene or a mixture of propane and propylene as starting material. normally,
Liquid olefins are formed by oligomerization in the first stage and then converted to higher oligomers in the MS2 stage. The aim of the process described in this patent is to give good yields of high boiling hydrocarbons. During the first pueq, a small amount of C,olefin (of which isobutene is only one of the three isomers) is formed starting from the propane and propylene mixture. Therefore, such a process cannot be used for the selective production of isobutene from propylene scraps or propylene-containing but sliver feeds. U.S. Pat. No. 4,407,086 to Miller and U.S. Pat. No. 4,4171,088 to Miller disclose a method for oligomerizing liquid olefins using molecular sieves of small open pore size. However, none of these currently known methods can be used to produce isobutene in significant quantities.

The aim of the present invention is to provide a new method for producing imbutene.

Another object of the present invention is that C5+ hydrocarbons (C6+hydr
The objective is to selectively leave isobutene from the ocarbon stream.

The process of the present invention essentially consists of converting a C10 hydrocarbon feed into a crystalline silica polymorph of the silica mineral type (crystalline 5ili).
In the presence of a catalyst consisting of ea polymorph),
catalytic cracking in the presence of steam at a water/feed molar ratio of about 0.5 to about 5.

The hydrocarbon feed of the present invention is typically a light distillate (light distillate).
It can consist of what are called t cristillates). The light distillate is crude oil (crud oil).
obtained in a refinery from the distillation of
boiling range from ℃ to about 196℃
ge). This is C
1 and lower hydrocarbons and includes gasoline, light naphtha, and heavy naphtha. The process of the invention can also be applied to light distillates obtained from various operations in the chemical industry, such as those produced in the oligomerization of olefins.

In a preferred embodiment of the invention, the light distillate subject to the invention is a light distillate obtained as a by-product in a process for the production of isobutene from propylene or by isomerization of n-butenes.

These processes are described in U.S. Patent Application No. 719,192, filed April 3, 1985
US Pat.

The catalyst used in the present invention is an unmodified crystalline silica polymorph of the silica mineral type.
d crystalline 5ilica p
The catalyst is therefore substantially pure silica, meaning that it contains no impurities or modifying elements or that it contains only trace amounts of them. Method and Structure of Such Silica Mineral Type Catalyst US Patent $4 by Grose
, 061,724, which is incorporated herein by reference in its entirety.

The C60 hydrocarbon feed is contacted with silica mineral in the presence of steam. Unexpectedly, the presence of water not only improves catalyst life by reducing the formation of heavier products, but more importantly, butenes,
4. It has actually been found that this results in particularly accelerated production of isobutene. The presence of steam increases isobutene selectivity, all other factors being equal. The term "isobutene selectivity" means the weight of isobutene formed, calculated on 100 parts by weight of the converted feed. This improvement in selectivity is
This is achieved even when the feed is processed in the presence of amounts of water on the order of as low as Q of water per mole of feed. Comparative experiments have also shown that it is preferable to maintain a water/feed molar ratio of no more than about 5. The reason is that higher percentages do not significantly improve the results. The water/feed molar ratio is preferably about 0.5 to 3.0;
Most preferably from about 0.75 to about 2.0.

The method of the invention is very flexible and
Or it can be applied in liquid phase.

The reaction temperature is generally from about 450°C to about 600°C. 4
Temperatures lower than 50°C give very low yields, 600°C
Higher temperatures cause some degradation of the reaction products.

Generally, temperatures of about 475°C to about 550°C are preferred.

Temperature variations within these ranges do not appreciably change the distribution of the product formed.

The hourly space velocity (WHSV) of the reaction mixture, expressed as the weight of the mixture per weight of catalyst per hour, can vary from about 5 to about 100. WH8V depends on the nature of the feed and the decomposition temperature, among other factors. The commercial space velocity allows for better isobutene selectivity, but also at the expense of feed softening rate. In particular, reduced space velocities of less than 2 can lead to product degradation. Space velocities of about 2 to about 20 are preferred, but about 5
A WH8V of from to about 15 is most preferred.

The pressure at which the reaction is carried out can be varied within a rather wide range, for example subatmospheric pressure (sul
ratmosphenie pressure) to the absolute pressure for conducting the reaction, from about 0.5 to about 20
It can be changed with a crowbar. It is advantageous to operate at low pressures in order to prioritize the production of isobutene.

One skilled in the art can determine the operating conditions within the ranges described above that will give the best yield, taking into account not only the composition of the feed but also the desired result. Thus, conditions such as WH8V favor the formation of isobutene at low conversions of the feed under such conditions, and in a preferred embodiment of the process of the invention, the light distillate subjected to catalytic cracking is Obtained as a by-product in the production of isobutene from feed stocks containing propylene or from feed stacks containing n-butenes. These light distillates are heated between 36°C and 196°C.
It has a boiling point Wk range on the order of degrees Celsius and represents a very valuable supply stock. In fact, additional amounts of isobutene are produced by processing them according to the method of the invention. Thus, by combining the above processes, particularly high yields of isobutene from propylene or n-butenes are obtained. The above processes can be combined in this method using two reactors in series,
The first reactor is used to treat a feed stock containing propylene or n-butenes with the formation of isobutene, and the second reactor is used to treat the feed stock containing propylene or n-butenes with the formation of isobutene. It is used to carry out the catalytic cracking of distillates formed as Another embodiment consists of carrying out the two stages of these combined processes in a single reactor operating under adiabatic conditions and having an appropriate temperature profile.

The following examples are meant to be illustrative and are not intended to describe limitations of the invention.

Propane 28.93 (wt%) and propylene 71.0
7% of the feed stock in the presence of silica mineral and steam at a water:feed stock molar ratio of 0.78;
79°8 W at a temperature of 303°C and an absolute pressure of 14 bar
Treated with HSV.

This gave isobutene and light distillates with selectivities of 11.3% and 64.6%, respectively. This distillate is 36℃
As 7 Rakun Yong with boiling range from 196℃ to 196℃,
That is, it was obtained as a light distillate consisting of C5+ hydrocarbons.

The process of the present invention was then carried out by combining this distillate with 55% water in the presence of silica minerals and steam at a water:distillate molar ratio of 1.26.
At a temperature of 0 °C and an absolute pressure of 2 bar, a W of 9.91
The applied garlic by treatment with HSV is 18.1
% selectivity of isobutene.

Propane 5.84% (by weight) and propylene 94.16%
% was treated in the presence of silica mineral and steam at a water:feed molar ratio of 0.92 using a WH8V of 35.6 at a temperature of 316°C and an absolute pressure of 4 bar.

This gave isobutene and light distillates with selectivities of 12.4% and 62.8%, respectively. This distillate is 36℃
As a 7 lactation with a boiling range of 196°C to 196°C,
That is, it was obtained as a light distillate consisting of C5+ hydrocarbons.

The process of the present invention is then carried out using this distillate in the presence of silica mineral and steam at a water:distillate molar ratio of 2.71.500°C.
WH8V of 8.57 at a temperature of 8.57 and an absolute pressure of 5.4 bar
It was applied by processing using.

This gave isobutene with a selectivity of 12.8%.

Although the invention has been described in terms of preferred embodiments, it should be understood that modifications and changes can be made without departing from the spirit and scope of the invention, as will be readily apparent to those skilled in the art.

Such modifications and changes are considered to be within the scope of the claims.

Claims (1)

Claims: 1. a) containing a crystalline silica polymorph of the silica mineral type in the presence of a sufficient amount of water such that the water/feed molar ratio is from about 0.5 to about 5; a) subjecting a C_5+ hydrocarbon feed to a catalytic fractionation in the presence of a catalyst comprising: b) recovering a stream containing isobutene. 2. The method of claim 1, wherein the water/feed molar ratio is from about 0.5 to about 3. 3. The method of claim 1, wherein step (a) is carried out at a temperature of about 450°C to about 600°C. 4. The method of claim 1, wherein step (a) is carried out at a temperature of about 475°C to about 550°C. 5. The method of claim 1, wherein step (a) is carried out at a weight of reaction mixture per weight of catalyst per hour (WHSV) of from about 2 to about 20. 6. The method of claim 1, wherein step (a) is carried out at a weight of reaction mixture per weight of catalyst per hour (WHSV) of from about 5 to about 15. 7. The method of claim 1, wherein step (a) is carried out at a pressure of from about atmospheric pressure to about 50 bar absolute. 8. The method of claim 1, wherein step (a) is carried out at a pressure of from about 0.5 bar to about 20 bar absolute. 9. (a) a light distillate hydrocarbon feed where the hydrocarbon has a boiling range of about 36°C to about 196°C;
from about 0.5 bar to about 20 at a temperature from 5°C to about 550°C
under an absolute pressure of bar absolute, in the presence of a catalyst consisting essentially of crystalline silica polymorphs of the silica mineral type, in sufficient quantity such that the water/feed molar ratio is from about 0.5 to about 1.5. A process for producing isobutene, comprising the steps of: catalytic cracking in the presence of steam; and b) recovering a stream containing isobutene.