RU2400299C2 - Catalyst reactivation method for dehydrogenation of paraffin hydrocarbons c10-c13 - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil refining, and namely to reactivation methods of catalysts for dehydrogenation of higher paraffins (C₁₀-C₁₃) at reduction of efficiency during the operation. There described is reactivation method of catalyst for dehydrogenation of paraffin hydrocarbons C₁₀-C₁₃, which consists of platinum, metals-promoters of the group indium and/or stannum, and/or cerium, and/or molybdenum, and light metals-modifiers, e.g. magnesium, calcium, potassium, sodium, which are applied to porous heat resistant carrier - active aluminium oxide or aluminium silicate, in which the above reactivation of catalyst is performed in presence of carbon dioxide in two stages, first in nitrogen-air-CO₂ with low constant CO₂ concentration about 0.003 vol. % or with subsequently increasing concentration - 0.0001 to 0.003 vol. %, and then in steam-air mixture with additive of chlorine hydride and increased CO₂ concentration but not exceeding 0.03 vol. %.

EFFECT: increasing selectivity and stability of catalyst operation.

3 ex

Description

The invention relates to the field of oil refining, and in particular to methods of reactivation of catalysts for the process of dehydrogenation of higher n-paraffins (C ₁₀ -C ₁₃ ) to restore their effectiveness during operation.

Catalysts for the process of dehydrogenation of higher paraffins are known, which are a hydrogenating metal, mainly platinum, deposited on a carrier of active aluminum oxide or aluminosilicate, with the addition of various promoters and modifiers, and methods for their preparation and use (US 5233118; 4827072; 4048245; 4046715; 4013733; 5536694; 55677260; 5849657). There is also a method of increasing the efficiency and regenerability of a dehydrogenation catalyst by controlling the parameters of the porous structure [US 6417135].

During operation, catalysts of the platinum composition + promoters + modifiers on the carrier gradually lose their activity due to an increase in the number of coke deposits on their surface, as well as a decrease in the dispersion of platinum. When the activity decreases to a level after which the operation of the catalyst becomes ineffective, the catalyst is unloaded and replaced with a fresh one without regeneration or reactivation. This approach is used, for example, in the process of dehydrogenation of the company "Pakol" (UOP, USA), where catalysts of the Deh series are used (Thematic review. Series "Petrochemicals and shale processing. Platinum promoted catalysts in the processes of isomerization and dehydrogenation of paraffin hydrocarbons, M., 1981 ; US 5844162).

Removing coke from the catalyst does not cause any particular difficulties and is carried out by conventional heat treatment in air at elevated temperatures, as is done, for example, for reforming catalysts and the like (Maslyansky G.N., Shapiro R.N. Catalytic reforming of gasolines, L., "Chemistry", 1985 - 224 p .; R. Hughes. Deactivation of catalysts. M., Chemistry, 1989 - 180 p .; Buyanov R. A. Coking of catalysts. Novosibirsk, Nauka, 1983 - 206 p.). However, in addition to this operation, it is also necessary to redisperse platinum (to restore high dispersion). Usually this problem is solved by treating the catalyst with various chlorine compounds. The resulting platinum chlorides have mobility on the surface of the carrier, which ensures an increase in the dispersion of platinum in such a treatment. A number of methods of chlorination are known that are used for reforming catalysts and the like, which differ in the conditions and used chloragents [US 5087792].

Known methods are not very suitable for dehydrogenation catalysts, since chlorine introduced into the composition of the catalyst with platinum on the carrier increases the acidity of the latter, and this sharply reduces the selectivity and, as a rule, its stability. Attempts to subsequently lower the chlorine content to an acceptable level (less than ~ 0.2 wt.%) By treating the catalyst with water vapor are not sufficiently effective due to the fact that a significant part of the chlorine in the catalyst is present in the form of difficultly removed light metal chlorides - modifiers (magnesium and / or calcium, and / or sodium, and / or lithium). In addition, such a treatment of dehydrogenation catalysts leads to a decrease in the mechanical strength, which for very porous dehydrogenation catalysts is already at the lower acceptable limit for industrial operation (V. Skarchenko, Hydrocarbon Dehydrogenation. - Kiev, Naukova Dumka, 1981 - 328 s. ; US 4,486,547).

A known method of regeneration of a dehydrogenation catalyst containing platinum and promoter metals on a refractory support by burning coke in an atmosphere of a gas containing oxygen and a chlorine compound, wherein a high degree of coke removal is achieved by maintaining the regeneration gas feed rate within strictly defined limits (US 5672801). The disadvantage of this method is the lack of operations for dispersing platinum and removing excess chlorine, which leads to lower levels of selectivity and stability.

A known method of reconditioning (reactivation) of a dehydrogenation catalyst for paraffin hydrocarbons, comprising the steps of burning coke, drying the catalyst and redispersing platinum (US 5087792). The method involves the rapid drying of the catalyst immediately after coke burning, which improves the subsequent dispersion of platinum. The effectiveness of this procedure is determined by the details of controlling the content of chlorine compounds in the reaction zone. The disadvantage of this reactivation method is the relatively low selectivity of the processed catalyst.

Closest to the proposed method for reactivating a dehydrogenation catalyst is the method described in Brazil Patent 8906073. This method involves reconditioning (reactivating) an inactive dehydrogenation catalyst by multi-stage treatment in a mixture of gases containing, in addition to air or nitrogen, a chlorine compound and water vapor, with different In the stages, various ratios of these components are applied, and the temperature, processing time and amount of gas supplied vary. The method provides a fairly complete removal of coke deposits and a satisfactory degree of redispersion of platinum, however, it does not allow to control the content of halogen (chlorine) in the catalyst, which leads to insufficient selectivity of its work in the process of dehydrogenation of higher paraffins.

The tasks that are solved by the invention are to develop a method of reactivation of the catalyst, characterized by increased selectivity and stability.

The tasks are solved as follows. Reactivation of a catalyst for the dehydrogenation of C ₁₀ -C ₁₃ paraffin hydrocarbons, consisting of platinum, indium and / or tin promoter metals, and / or cerium and / or molybdenum, and light modifier metals (magnesium, calcium, potassium, sodium ) deposited on a porous refractory carrier - active alumina or aluminosilicate, is carried out in the presence of carbon dioxide in two stages. First, reactivation is performed in a nitrogen-air-CO ₂ mixture with a low constant concentration of CO _{2 of} about 0.003 vol.% Or with a gradually increasing concentration of from 0.0001 to 0.003 vol.% And then in an atmosphere of a steam-air mixture with the addition of hydrogen chloride and a relatively high the concentration of CO ₂ , but not exceeding 0.03 vol.%.

The increase in the selectivity and stability of the catalyst occurs by varying the carbon dioxide content in the gases used in the two-stage catalyst activation process, the main purpose of which is, firstly, to remove coke deposits and water and, secondly, to disperse platinum while minimizing the acidity of the carrier .

The invention proposes the reactivation of the spent dehydrogenation catalyst using a special operation by treating it with a gas-vapor mixture in the presence of small amounts of carbon dioxide. Moreover, in the first stage of activation, carried out in a mixture of nitrogen and air, the amount of СО ₂ in the gas mixture does not exceed 0.003 vol.%, And in the second stage, which takes place in a mixture of air with water vapor and hydrogen chloride, the CO ₂ content is increased, but it the concentration is limited to 0.03 vol.%. In the first stage, the concentration of carbon dioxide can be both constant (about 0.003 vol.%) And increasing (from 0.0001 to 0.003 vol.%), And in the second it can be constant (0.03 vol.%).

After reactivation, the catalyst is reduced in a known manner in a hydrogen atmosphere at a temperature of 500 ° C. If storage is required before use (testing), the catalyst is additionally passivated at a temperature of no higher than 100 ° C in a nitrogen atmosphere with a small addition of air (based on no more than 3 vol.% Oxygen).

The catalyst is tested in a pilot installation in the process of dehydrogenation of n-dodecane (C ₁₂ ) at temperatures of 460-490 ° C, a pressure of 2.0 atm, a volumetric feed rate of 20 hours ^-1 (in liquid) and a molar ratio of hydrogen: feed = 8: one.

The resulting catalyst ensures the conversion of n-dodecane or, what is the same, activity at the level of 13-17% with selectivity for n-monoolefins up to 95% and high stability, corresponding to a duty cycle of at least 1800 hours. The activity of the reactivated catalyst is at least 80%, and the stability exceeds 50% of the corresponding values for fresh catalyst.

The invention is illustrated by examples.

Example 1

For testing, take the catalyst spent in the process of dehydrogenation of higher paraffins C ₁₀ -C ₁₃ (the process "Pakol").

The catalyst is dried at 120 ° C for 6 hours, and then activated by calcination at 550 ° C for 5 hours in a stream of nitrogen into which air is gradually dosed, starting from a concentration of 0.5 vol.% In terms of oxygen, and at the end of the process, bring up to 10 vol.% oxygen. Accordingly, at the start of the CO ₂ is dosed at a concentration of 0.0001%, and at the end -. A concentration of 0.003 vol.%.

Upon completion of the specified first stage of processing, the catalyst is subjected to heat treatment in an air environment containing: water vapor - 0.8 g / m ³ , hydrogen chloride - 1 g / m ³ , carbon dioxide - 0.03 vol.%.

10 ml of the obtained catalyst is loaded into the reactor of the pilot plant and a standard test is carried out in the dehydrogenation reaction of n-dodecane. The following results are obtained.

The conversion of n-dodecane in the temperature range 460-490 ° C is from 7 to 16 wt.%, The selectivity for n-monoolefins is from 81 to 95%. Stability corresponds to a working cycle of 3600 hours.

Example 2

Take the catalyst in composition and physico-chemical characteristics not different from the catalyst of example 1, spent in the process of dehydrogenation and containing 7 wt.% Coke deposits.

A sample of the catalyst is subjected to activation operations in the same way as described in example 1.

When conducting a catalytic test of a reactivated and reduced sample, the following results are obtained.

The conversion of n-dodecane at 460-490 ° C is from 6 to 13%, the selectivity for n-mono-olefins is from 76 to 92%. Stability - 2600 hours of a working cycle.

Example 3

Analogously to example 2 take a deactivated dehydrogenation catalyst with a content of 5.3% coke.

A sample of the catalyst is subjected to two-stage activation, as described in examples 1 and 2, with the exception that in the first stage, the concentration of carbon dioxide is constant and is 0.003 vol.%.

When conducting a catalytic test of a reactivated and reduced sample, the following results are obtained.

The conversion of n-dodecane at 460-490 ° C is from 8 to 17%, the selectivity for n-monoolefins is from 77 to 91%. Stability - 2800 hours of a working cycle.

Claims (1)

The method of reactivation of the catalyst for the dehydrogenation of C ₁₀ -C ₁₃ paraffin hydrocarbons, consisting of platinum, indium and / or tin promoter metals, and / or cerium, and / or molybdenum, and light modifier metals, for example, magnesium, calcium , potassium, sodium, supported on a porous refractory support - active alumina or silica-alumina, characterized in that said reactivation of the catalyst is carried out in the presence of carbon dioxide in two stages, first in a mixture of nitrogen-air-CO ₂ with small constant CO ₂ concentration tat about 0.003% or about a gradually increasing concentration -. 0.0001 to about 0.003%, and then in an atmosphere of steam-air mixture with the addition of hydrogen chloride, and the high concentration of CO _2, but not exceeding 0.03%...