DD248294A1 - METHOD FOR INCREASING THE SELECTIVITY OF CATALYSTS - Google Patents

Abstract

The invention relates to a process for increasing the selectivity of catalysts for the conversion of hydrocarbons into aromatic or gasoline fuel components. Catalysts may during the activation or reactivation treatments lead to the formation of highly active catalytic centers, which in the start phase of the raw material supply lead to undesirable deactivation and in extreme cases irreversible damage due to their high hydrogenolysis activity. The aim of the invention is to eliminate this deficiency. By the process according to the invention, whereby the catalyst is treated with a gas mixture containing C2-hydrocarbons and their controlled conversion into methane as a test reaction, a procedure can be proposed by the improvements with respect to start-up time, catalyst life and quality of the target products be achieved.

Description

Explanation of the essence of the invention

The invention has for its object to find a method for the treatment of catalysts for the conversion of hydrocarbons, in which by using readily available gas media at temperatures which are comparable to those of the hydrocarbon conversion, the hydrogenolysis or hydrospaltaktiven catalyst is so influenced that Deactivation or damage thereof is suppressed, especially in the start-up phase of the conversion of hydrocarbons.

The object is achieved by a method for increasing the selectivity of catalysts for the conversion of hydrocarbons in the gasoline boiling range in fixed bed or moving bed reactors, wherein after the oxychlorination and reduction of the catalyst, the water concentration in the cycle gas keeps below 100 ppm and the inlet temperatures of Reactors to 525-725 K and the hydrogen partial pressure to a maximum of 3.0MPa sets. In the gas circulation before the reaction zones gradually a gas mixture, which in addition to hydrogen sulfur compounds such as hydrogen sulfide or those which form hydrogen sulfide under reducing conditions, such as RSH'R ₂ S, R ₂ S _2, etc., wherein R is different alkyl radicals, and as indicator material for tracking the degradation of the undesired cleavage activity, C ₂ ⁺ hydrocarbons, which are substantially gaseous under normal conditions, contains between 0.5 and 20% by volume.

In this gas mixture, the molar ratio of (^ hydrocarbons to hydrogen sulfide must be more than 1 but less than 50. The treatment of the catalyst is complete as soon as the supply of the gas mixture with the proportions of C ₂ ⁺ hydrocarbons, the absolute decrease of the C ₂ ⁺ hydrocarbons in the recycle gas is less than 0.5VoI .-%.

Subsequently, the feedstock is added at the same or higher reactor inlet temperature. It is a feature of the process of the invention that by treating catalysts for the conversion of hydrocarbons in the gasoline boiling range and a gas mixture in the presence of small amounts of light hydrocarbons, a controlled damping of the activation or reactivation caused by the formation of centers that promote the nonselectively proceeding cleavage reactions , he follows.

It is particularly advantageous that by using the controlled conversion of ^ + - hydrocarbons in methane as a test reaction, the phase between attenuation and damage as a result of the action of sulfur compounds can be accurately detected and thus made reproducible. This provides economic benefits. The required gas mixtures for the treatment of the catalysts are available in principle in every refinery and can therefore be used without problems in the plants.

With the application of the method according to the invention, the period of time from the intake of the raw material supply to the accumulation of quality-compliant products can be shortened. By suppressing the accelerated deactivation of the catalysts in the initial phase of the conversion of hydrocarbons, a longer catalyst life is achieved. In addition, by increasing the selectivity for the processing of the raw materials advantages in such a way that it can be worked at lower reaction temperature with consistent quality requirements, which also occurs an extension of the catalyst life. In addition, it is possible under otherwise unchanged process conditions to produce reformates with higher quality. The treatment also has the consequence that the hydrogen concentration is increased in the recycle gas and thus a higher quality gas is ready, which can be used in other plants of petroleum processing or petrochemicals, which use hydrogen.

embodiments

example 1

A gasoline boiling range conversion hydrocarbon using γ-alumina as a carrier material contains 0.27 mass% of platinum, 0.25 mass% of rhenium and 1.1 mass% of chlorine. This catalyst was used in the

Reaction zones of a plant converting a fraction of the boiling range 375 to 455 K from Romashkino petroleum,

used.

The plant comprises heating system, fixed bed reactor and drying device. The catalyst was subjected to an activation treatment in which oxygen treatment was carried out at 750K and dosing of an organochlorine compound in the presence of oxygen at the same temperature. The plant system was then rendered inert, followed by reduction of the catalyst at 770K, a hydrogen partial pressure of 1.0MPa and 30ppm of water in the circuit.

The conditions for adding the raw material were set to 675 Kund 2.0 MPa. Thereafter, the dosage of dimethyl disulfide was carried out in an amount to 0.025 wt .-% sulfur, based on the amount of catalyst to bring.

With the inclusion of the raw material addition occurred a pronounced exothermic cracking reaction in appearance, the content of methane in the recycle gas immediately increased from 2 vol .-% to 18 vol .-%, while the hydrogen content fell to 57 vol .-%. The conditions and results of the small-scale activity test are shown in Table 1.

Table 1

Test conditions of the activity test

Raw material: Hydrocarbon fraction of Siedelage 375-455 K

Temperatur783K

Pressure 1.8 MPa

Catalyst load 2 v / vh

Gas-to-product ratio 1 000: 1

Duration of test (h) 50 100 250 500 750 1000 2 000

aromatics 67 64.5 63.5 62.5 57.5 52.5 - yield Ma .-% hydrogen 1.56 1.62 * 1.60 1.57 1.55 1.55 - yield Ma .-% aromatics 61.5 63 65 64.5 63.5 62.5 59 ausbeuteMa .-% hydrogen 1.75 1.77 1.81 1.80 1.79 1.79 1.65 yield Ma .-%

Example 2

The process according to the invention was applied by treating the catalyst after the activation treatment according to Example 1 at 675 K and a hydrogen partial pressure of 1.8 MPa with a gas mixture which contained 86% by volume of hydrogen and 6.5% by volume of methane.

The molar ratio of C ₂ ⁺ hydrocarbons to hydrogen sulfide in this case was 4. After 65 minutes of metering time, the feed of the gas mixture was interrupted and in the recycle gas an absolute decrease of C ₂ ⁺ hydrocarbons by 1.9VoI. -% detected. Thereafter, the dosage was resumed and maintained for 30 minutes. The absolute decrease in C2 ⁺ hydrocarbons was now 0.3% by volume and no further dosing was required.

This started with the addition of raw materials. During this start-up, a course was observed during which the strong methane formation as a result of high hydrogenolysis activity did not occur. The hydrogen content in the cycle gas turned on at 86% by volume. The improvement in selectivity is evidenced by the higher aromatics and hydrogen yield during the small scale activity test under comparable conditions, which is presented in Table 1.

Claims (2)

Process for increasing the selectivity of catalysts which may be added from surface-rich and porous alumina silicates and aluminosilicates and catalytically active components of the II. And / or VII. And / or VIII. Subgroup and / or IV. Main group of the PSE and chlorine contain, for the conversion of hydrocarbons of the Benzinsiedebereiches in aromatics or gasoline fuel components in fixed bed or moving bed reactors, by treating the oxychlorinated and reduced catalysts with gas mixtures, including hydrogen and hydrogen sulfide and / or hydrogen sulfide-forming compounds such as RSH, R ₂ S, R ₂ S _2, containing, at 525 bis725K, a maximum hydrogen partial 3,0MPa and a water concentration in the recycle gas of at most 100 ppm, characterized in that the gas mixtures containing C ₂ ⁺ hydrocarbons, wherein the molar ratio between C ₂ ⁺ - hydrocarbons and hydrogen sulfide more a ls is 1 and less than 50, and the stepwise metering of these mixtures is made until the decrease of the C ₂ ⁺ hydrocarbons in the recycle gas is less than 0.5% by volume absolute when the addition of the gas mixture is discontinued. Field of application of the invention The invention relates to a process for increasing the selectivity of catalysts which contain catalytically active components, in particular platinum, in combination with chlorine on surface-rich and porous support material, for the conversion of hydrocarbons and the hydrogenolysis or hydrogenolysis processes which are marked as a result of activation or reactivation processes Hydrophilic activity. Characteristic of the known technical solutions It is known that in the use of catalysts for the conversion of hydrocarbons in the gasoline boiling range for producing hochoctaniger carburetor fuel components and starting materials for aromatic production specific methods for activating the fresh catalysts or for reactivating deactivated catalysts are applied. Such catalysts always consist of a carrier material, which is predominantly surface-rich, porous alumina, and active components. The active components used are preferably platinum or platinum in combination with other elements of the PSE. By this composition, the bifunctional mode of action of the catalyst is justified. This means that in addition to acidic centers, there are also centers where hydrogenation-dehydrogenation reactions take place. If the conversion reactions by the catalyst are to be favorably influenced, it is important to generate highly active centers by corresponding specific treatment processes, which are each tuned to a specific catalyst system, with both types of centers having to be in a corresponding ratio. The treatment methods are used both for fresh catalysts to effect the formation of the active sites, as well as for deactivated catalysts in which strong activity and selectivity losses occur due to the deposition of strongly carbonaceous substances and the recrystallization of the active components. In these treatment processes, which conclude with the reduction of the active components, disperse and thus highly active centers are to be generated. However, these centers may then have the property of promoting unselective cracking reactions already in the initial phase of catalyst use to such an extent that this results in the possibility of early catalyst deactivation and an extreme case of irreversible damage to the catalyst due to the high occurrence of exothermic fission reactions. In order to mitigate such nonselectively occurring fission reactions, generally, desulfurization technologies are proposed. About the running reactions can be found u.a. FISCHER and KELEMAN (1) and BILOEN et al. (2) Remarks. Technical solutions are shown for example in US-PS 3415737,3617520 and 4048058 and in the DD-WP 137940,138460 and 203474. These proposed methods have the disadvantage that no reproducible conditions can be achieved in their application, since it is presumably not ensured that the one hand necessary and on the other hand permissible sulfur concentration is achieved on the catalyst. The consequence is the loss of activity and selectivity of the catalysts for the conversion of the hydrocarbons. Object of the invention The object of the invention is to provide a catalyst for the conversion of hydrocarbons in the gasoline boiling range, which is present after activation and / or reactivation in reduced form and highly active catalytic centers with pronounced hydrogenolysis and hydrosoluble activity, by an in situ feasible, specific Process to suppress these nonselectively proceeding cleavage reactions, but at the same time exclude a catalyst damage.