JPS6345757B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a process for fluid catalytic cracking of hydrocarbons. According to the method, it is possible to operate using hydrocarbons as raw materials contaminated with large amounts of metals. This cracking method involves preparing a suspension consisting of a hydrocarbon, a cracking additive, and a cracking catalyst, permanently mixing this suspension with a fresh hydrocarbon stream, and subjecting the mixture to a cracking operation. It consists of doing. The conventional conventional fluid catalytic cracking process (hereinafter referred to as "FCC" for "fluid catalytic cracking") involves contacting the catalyst and the reactants and passing the mixture through a riser and into a reactor. In this reactor, the catalyst is separated from the reaction products, usually by a cyclone, the reaction products are sent to a distillation step, the catalyst is subjected to a stripping treatment and then sent to a regenerator. Relatively weak compounds adsorbed on the surface of the catalyst are removed by the steam stripping process described above, while coke present on the surface of the catalyst is burnt off by the process in the regenerator described above. However, at this time, the central part of the catalyst that retains activity is damaged, resulting in a decrease in catalytic activity. Catalyst particles drawn into the combustion gas can be recovered by a cyclone provided in the regenerator. After the regeneration process, the catalyst is returned to the cracking step and contacted with fresh reaction feed. The reaction product to be distilled is sent to a fractionation column where it is separated into gas, naphtha, light gas oil, heavy gas oil, clarified oil and slurry oil. This slurry oil also contains catalyst particles that have been drawn into the reaction product during the separation of the catalyst from the reaction product at the reactor outlet. Although modern FCC units are equipped with one or more sets of single-stage or multi-stage cyclones, the amount of catalyst loss in said units is considerable. In the fluidized catalytic cracking method of the present invention, a catalyst feeding operation is performed that can significantly reduce the amount of catalyst loss as described above, and this will be explained in detail later. As is well known, due to the oil crisis, various studies are being carried out around the world to develop processing methods with even higher efficiency in oil utilization. The cracking method is a processing method in which relatively heavy fractions in crude oil can be used as raw materials. New catalysts are now being developed that are more active and less toxic than previously used catalysts. When carrying out the cracking process using conventional conventional catalysts, the presence of metals such as Ni and V in the reaction raw materials significantly inhibits the reaction operation. This is because the metal quickly poisons the catalyst. Furthermore, the heavy fraction (heavy cut) of crude oil contains a considerably large amount of these metals. In order to overcome this technical difficulty, research was carried out to develop a method of reducing the effect of said catalyst poisons on the catalyst, and the method was found and is now known. This known method thus consists of using substances currently known as cracking additives or passivators. The presence of this substance in the reaction medium makes it possible to process hydrocarbon feedstocks with high Ni- and V contents. B, Sn, Te, Sb, Mn, Bi, W, Tl, In, Ge
It has been found that compounds containing the above have the above-mentioned effects. A variety of products are currently commercially available that can be used for this purpose. Several other catalyst poison reduction methods are also known and are described in various publications in the art. Various methods for more effectively processing crude oil using such techniques have also been developed in recent years. One of the objects of the present invention is to provide a method for fluid catalytic cracking of hydrocarbons in which a cracking reaction can be carried out using metal-contaminated hydrocarbons as a raw material. Another object of the present invention is to reduce the amount of catalyst loss by about 50%.
- To provide a method for fluid catalytic cracking of hydrocarbons that can be reduced by as much as 80%. Yet another object of the present invention is to provide a cracking process in which finely divided catalysts (particle size 0-40 microns) can also be utilized for the cracking reaction. Such objectives can be achieved by using the feedstock made by the above method for feeding catalyst to the reaction process. Instead of carrying out the conventional method of compensating for catalyst losses, i.e. consisting of using a pressurized silo leading to a regenerator, according to the method of the invention the catalyst is fed directly into the reaction medium in a wet state. By doing so, the above purpose can be achieved. There is also the advantage that pulverulent catalyst can also be used for the cracking reaction by supplying fresh catalyst in a wet state to the reaction process, i.e. by supplying a suspension of the catalyst in a hydrocarbon. can get. Additionally, the method of the present invention provides tighter control over the amount of catalyst and cracking additive (which are optional) added to the reactant stream. Catalysts, such as heavy vacuum distilled gas oils, heavy recycled gas oils, LCO or FCC diesel oils,
Suspended in a hydrocarbon stream such as naphtha, FCC fuel oil, etc. This suspension is injected directly into the riser with or without mixing with the reaction raw materials, after which a cracking reaction occurs. If the reaction raw material is contaminated with metal, it is advisable to add a cracking additive to prevent poisoning of the catalyst. This additive is generally antimony-based,
Several types are available on the market. The present invention comprises: (a) creating a suspension comprised of a hydrocarbon, a virgin cracking catalyst, and an optional cracking additive; and (b) using the suspension as a fresh reactor feed. A method for fluid catalytic cracking of hydrocarbons, characterized in that: (b) a mixture of this suspension and fresh reaction materials is subjected to a cracking operation; It is something. Alternatively, it is also possible to inject the catalyst suspension directly into the riser to carry out the cracking reaction. By feeding the reactor with fresh catalyst in a wet state, i.e. by feeding a suspension of the type mentioned above, finely divided catalyst can also be made available for the cracking reaction, and Therefore, the amount of catalyst and cracking additive to be added to the flow of reaction raw materials and the reaction can be controlled more precisely. In order to be able to determine the respective addition amount of the suspension to the reactor, it is necessary to take into account the appropriate mode of operation. The degree of metal contamination of the catalyst can be determined by measuring the amount of hydrogen and methane produced during the implementation of the process of the invention, and this method for measuring is already well known. If the catalyst is poisoned by Ni and V,
Dehydrogenation and coke-forming reactions occur simultaneously through the catalysis of these metals. Therefore, an increase in the amount of hydrogen in the combustion gas is a "signal" that the catalyst has been poisoned. Generally, by replacing the spent catalyst with regenerated catalyst (regenerated catalyst) or fresh catalyst in small increments, and also keeping the quantitative proportion of hydrogen and methane present in the combustion gases within an acceptable range. By making these efforts, the catalyst activity can be controlled. It is therefore worthwhile to keep the limits of the above tolerance ranges as low as possible. Experiments were conducted to compare the effects of the method of the present invention and known methods described in literature. A suspension containing the catalyst was prepared on a laboratory scale and the process of the invention was carried out according to the method of implementation described below. Thereafter, a known cracking method was carried out simply as a comparative experiment. When carrying out the process of the invention, the amount of catalyst loss is substantially greater than in the conventional process, both with and without cracking additives added to the catalyst suspension. It was found that there were even fewer Furthermore, when carrying out the method of the present invention,
In order to always keep the hydrogen/methane ratio in the combustion gases at the same value (other operating conditions being the same),
It has also been found that it is generally necessary to add some amount of cracking additive. However, the amount of cracking additive required is only about half that of the conventional method. Furthermore, it has been found that, following the process of the invention, the hydrogen/methane ratio in the combustion gas is always lower than in the conventional process, regardless of the amount of cracking additive used in the conventional process. . With conventional methods, it is not possible to reduce the hydrogen/methane ratio in the combustion gas below a certain value using any amount of cracking additive. As explained above, the fluid catalytic cracking method according to the invention has proven to be a more effective method than previously known methods described in the literature. Next, some specific examples of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the scope of the method of the present invention is in no way limited within the scope of these specific examples. FIG. 1 is a schematic diagram of the apparatus used in one embodiment of the method of the invention. The cracking reactor is designated by number 1, the catalyst regenerator is designated by number 2, and the mixing tank for suspension preparation is designated by number 3. Hydrocarbon 5, cracking additive 6 and fresh catalyst 7 are added in appropriate proportions to a mixing tank 3 equipped with a mechanical stirrer 4. The hydrocarbon 5 also acts as a dispersion medium for the catalyst. Stream 8 of "the said suspension containing catalyst 7" is continuously mixed with fresh reaction feed 9 and introduced as mixed feed stream 10 into the cracking reactor 1. Reaction product stream 11 is separated into a fractionation column (not shown), while spent catalyst stream 12 enters regenerator 2 where the catalyst is regenerated. Combust gas is used in the regenerator 2.
13 is supplied to burn off the coke attached to the spent catalyst, and the resulting combustion gas flow 1
4 is discharged from the regenerator 2. Also, a stream 15 of regenerated catalyst is discharged from the regenerator 2 and mixed with the mixed feed stream 10 into the cracking reactor 1. In carrying out the process of the present invention, heavy gas oil was used as a reactant and as a dispersant, and air was used as a combustion agent gas. Another specific example of the method of the present invention will be shown. In this case, a suspension 8 of the catalyst in a hydrocarbon is prepared in the presence or absence of a cracking additive, and this suspension is continuously injected into the riser. The example lacks the step of mixing the suspension into fresh reactant stream 9. For comparison, a conventional method experiment was conducted as follows. The catalyst stored in a silo was transferred to the regenerator by pressurizing the silo and the catalyst was continuously added to the cracking reaction process. The cracking additive was diluted with gas oil in a drum and continuously injected into the reactant stream.
The amount of additive used was large enough to achieve the desired results. A cracking reaction was carried out using the thus protected mixture. In order to follow up on the results of experiments conducted on a small scale on a laboratory bench, standard units were assembled and conducted actual tests. This test provides more reliable data than small-scale benchtop experiments, especially regarding the amount of catalyst loss, ideal operating conditions, and the effectiveness of the inventive method versus the conventional method. Detailed data was obtained regarding the differences between The description of Examples below describes the results of the above tests. However, the scope of the present invention is in no way limited to the scope described in these Examples. Examples of catalysts that can be used in the process of the invention include conventional catalysts such as low alumina, high alumina, zeolites, and the like. The operating conditions in the above tests were generally the same as those commonly used. The quality of the reactants was kept constant throughout the duration of these tests. EXAMPLE The purpose of the experiment described in this example was to investigate the difference in efficiency between the feed system in the process of the present invention and the feed system in the conventional process. In Tests 1 and 2, the conventional method was used to continuously exchange the catalyst, ie, transport the catalyst from the silo to the regenerator. Tests 3 and 4 were operated according to the method of the invention. A suspension of catalyst in gas oil was prepared in a mixing tank equipped with a mechanical stirrer. This suspension was continuously fed to the reactor together with the reaction raw materials. The reaction feedstock used in these tests was heavy gas oil obtained from Leona crude oil. On the other hand, the catalyst used was high alumina. In all tests the amount of catalyst exchange (replenishment) was exactly equal to the amount of catalyst lost.

[Table] As is clear from the comparison between Test 2 and Test 3,
In test 3, the amount of catalyst exchanged was lower than in test 2.
It was 80.3% less. Example The purpose of the tests conducted here was to find the optimal operating conditions for the cracking reaction operation. Test 5 was conducted according to the conventional method, and Test 6 was conducted according to the method of the present invention, and these results were compared. The reaction temperature, catalyst/oil ratio, and raw material mixing ratio were kept as constant as possible. A "raw material mixing ratio of 1.0" means that no recirculation took place. The results (average values) of these tests are shown in Table 1.

[Table] Atsuta.
As is clear from the above results, in the case of the method of the present invention, the amount of catalyst loss was only about half of that in the case of the conventional method. And it should be noted that even when the amount of additive was reduced by 1/3, the value of the hydrogen/methane ratio was lower than in the case of the conventional method. This means that the cracking additive was used very effectively. EXAMPLE The purpose of the tests described in this example was to increase the above hydrogen/carbon (H ₂ /C) ratio by increasing the amount of cracking additive used in conventional catalyst exchange methods. The purpose was to investigate whether the ratio could be lower than that in the invention method. In the case of the method of the present invention, the amount of Sb used is 2.7Kg/
The H ₂ /C ₁ ratio was 2.7. In addition, commercially available cracking additives (Sb-based)
Experiments were carried out using the conventional method using various amounts of . The results obtained are shown in Table 1. Table Kg(Sb)/day H ₂ /C ₁ 1.80 3.8 2.76 3.17 3.50 3.3 4.00 3.5 When the conventional conventional method is used, H ₂ /C ratio could not be lowered below 3.17.

[Brief explanation of the drawing]

FIG. 1 is a piping diagram of an apparatus used in one embodiment of the method of the present invention. 1... Cracking reactor, 2... Catalyst regenerator, 3
...mixing tank, 4.mechanical stirrer, 5.hydrocarbon, 6.cracking additive, 7.cracking catalyst, 8.catalyst-containing suspension stream, 9.fresh reactant stream, 10.raw material mixing Flow, 11... Reaction product stream, 12... Flow of used catalyst, 13... Flow of combustion agent gas, 14... Flow of combustion gas, 15... Flow of regenerated catalyst.

Claims (1)

[Scope of Claims] 1 (a) In a mechanically stirred vessel into which a cracking catalyst additive can be introduced,
preparing a suspension of fresh catalyst in a liquid hydrocarbon; (b) with a fresh hydrocarbon feed to be treated;
(c) continuously introducing a suspension of said catalyst with an optional catalyst additive at the feed point of the riser of the catalytic cracking device; A method for fluid catalytic cracking of hydrocarbons, comprising the steps of subjecting a mixture of turbid liquids to catalytic cracking conditions. 2. The method for fluid catalytic cracking of hydrocarbons according to claim 1, wherein the amount of catalyst loss is reduced by about 50 to 80% by weight compared to a conventional known fluid catalytic cracking method. 3. A process for fluid catalytic cracking of hydrocarbons as claimed in claim 1 or claim 2, wherein catalyst particles having a particle size of less than 40 microns are available for the fluid cracking reaction.