CS221887B1 - A method for regenerating refining catalysts - Google Patents

Abstract

The invention relates to a method for the regeneration of refining catalysts containing metals of groups VI, VII or VIII or their oxides and sulfides on appropriate porous supports by oxidative removal of carbonaceous deposits formed during the processing of organic raw materials, especially crude oil, which contain predominantly carbon, hydrogen or sulfur. The regeneration takes place outside the catalytic reactor itself with the aim of reusing it in the catalytic reactor instead of fresh catalyst or of using precious or rare metals contained in the catalyst in another way. A gas containing free oxygen, preferably air, is passed through the catalyst placed on a fixed grate in a layer, while the temperature of the catalyst increases continuously or in stages or is constant and is controlled by the temperature of the supplied gas. The catalyst layer can also be placed on a conveyor belt that moves from the inlet to the regeneration device to its outlet with a graded temperature profile along the conveyor belt.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the regeneration of refining catalysts by the oxidative removal of carbonaceous and sulfur deposits formed during catalyst operation in a catalytic reactor for the treatment of organic raw materials, in particular petroleum. The proposed process, carried out outside the catalytic reactor itself, allows the use of air as a regeneration medium.

The deposition of carbonaceous deposits on the surface of the catalyst during the catalytic process is usually the most serious contribution to the decline in catalytic activity. This is also the case for the catalysts used in oil refining. Reactivation, which consists of controlled oxidation of carbonaceous deposits and hence their removal from the surface of the catalyst, allows the activity to return to a level close to its original value. Given the rising world prices of precious metals, its importance has recently increased. The removal of carbonaceous deposits is also important in the long-term recovery of raw materials - usually precious metals - contained in the catalyst.

In the traditional process, the catalyst is reactivated directly in the catalytic reactor in situ with a mixture of air and an inert medium - nitrogen or water vapor [Byrns A. C., Bradley W. E., Lee Μ. VI: Ind. Eng. Chem. 35, 1160 (1943); Cole, R. M., Davidson, D. D., Ind. Eng. Chem. 41, 2711 (1949) 3. A disadvantage of this method is the lack of temperature control and control in the reactor. Hot waves are readily produced, with the catalyst overheating above the allowable limit, which can lead to catalyst sintering and loss of activity. Other particles in the reactor may be insufficiently reacted due to the uneven temperature distribution. Other objections to the in-situ process include: insufficient sulfur removal, long reactivation times for blocking the catalytic reactor, impossibility to remove mechanical impurities and broken tablets, causing the pressure drop in the reactor to rise above the carrying limit, and the need to shut down the reactor.

Therefore, regeneration methods outside the catalytic reactor have recently been tested. A method of reactivation in a rotary furnace-like device (US Pat. 4,026,821) has been described, which makes it possible to better maintain and control the temperature than in situ. However, as the catalyst particles move relative to each other in the rotary kiln, the catalyst is rubbed off, another disadvantage of this process is the inability to effectively change the temperature during the reactive process. This disadvantage relates in particular to sulfur-containing catalysts, since its combustion requires a lower temperature than that of carbon.

It has now been found that the disadvantages of said processes in in situ regeneration or in a rotary kiln apparatus are overcome by the novel regeneration method of the present invention.

The principle of the proposed method is that the catalyst, discharged from the reactor and free of mechanical impurities and crushed tablets by sieving, is placed in a thin layer less than 30 cm, preferably 1 to 10 cm, on a support grid of dimensions larger than the layer height. wherein the grate is provided with openings allowing easy passage of gas. The regeneration medium used is air, which is preheated and supplied to the catalyst through openings in the grate. Dilution with nitrogen or water vapor necessary for in situ regeneration is not necessary here. The use of excess air and a thin catalyst layer allows efficient removal of heat generated by the combustion of deposits. Since the temperature of the catalyst does not exceed the feed gas temperature too much, the combustion gas temperature of the deposits can be controlled by adjusting the feed gas temperature, taking into account the kinetic laws of the process, the nature of the catalyst and the amount and nature of the deposits.

At low temperature, combustion of the deposits proceeds without the risk of catalyst overheating, but very slowly, which is technologically inaccessible. At high temperatures, above 500 ° C, combustion proceeds very rapidly, especially in the initial stage of the reaction, thereby generating considerable heat release, which is not sufficient to dissipate sufficiently quickly through the air stream even in the case of a thin-bed catalyst arrangement. In addition, it has been found that the sulfur contained in the catalyst or deposits ee burns at a substantially lower temperature, in the range of 200 to 350 ° C, than carbon whose combustion proceeds at an acceptable rate up to temperatures above 330 ° C. at a constant temperature, but at a gradually increasing temperature. In the case of sulfur-containing catalysts, it is advantageous to start the reactivation at a temperature of about 200 ° C and gradually increase it either continuously or in steps up to a temperature of about 500 ° C. In this combustion process, which usually lasts for 8 to 16 hours, almost complete combustion of the sulfur is achieved at temperatures of about 380 ° C, where it is not yet undesirably converted to inactive metal sulphates. Combustion of both sulfur and carbon proceeds at an acceptable rate, so that the heat provided with the reaction is simply dissipated by an air stream and there is no risk of catalyst overheating. For sulfur-free catalysts, the initial reactivation temperature can be selected to be about 330 ° C, thereby significantly reducing the reactivation time to 4 to 10 h.

If the oxidation combustion of the carbonaceous deposits is not to restore the catalyst activity but to obtain a carbon-free feedstock for further metallurgical treatment, it is preferred to carry out the combustion at a relatively high temperature of about 500 ° C, thereby substantially reducing the time required to remove carbon.

The described method of controlling the oxidation of carbon or sulfur deposits in a thin layer using a gradual increase in the combustion temperature with time, according to the present invention, can be implemented either in a batch or continuous plant. In a batch regeneration, the catalyst is placed on a fixed grate, the desired temperature regime being achieved by gradually increasing the temperature of the air supplied to the catalyst. This method is suitable for treating a smaller amount of catalyst and testing a suitable combustion temperature regime.

In continuous regeneration, the grate, on which the catalyst is placed in a thin layer, is realized by a conveyor belt, which is placed in an oven divided into several temperature zones, the temperature of which is determined by the temperature of air supplied to the belt. to the other along the conveyor belt. The belt moves slowly and continuously in the furnace and the catalyst gradually passes through the temperature zones from lower to higher temperatures. The required layer height is set by the rate of catalyst addition to the belt. This process is particularly suitable for processing large quantities of catalyst.

The invention is illustrated by the following examples.

Example 1

% Hydrodesulfurizing cobalt molybdenum catalyst containing about 3 wt. Co and 8 wt. Mo, used for 1.5 years in the hydrotreating process of petroleum distillates ranging from petrol to diesel, has been regenerated with air to restore catalytic activity. The catalyst used, which was in the form of cylindrical tablets having a diameter of 7.5 mm and a height of 6.5 mm, contained 10.2% by weight. C and 3.7% S. The regeneration was carried out in the batch apparatus for 8 h, the layer height was 1.5 cm, the space velocity - the volumetric air flow at atmospheric pressure and 20 ° C divided by the catalyst bed volume - was 20,000 h ' . The supply air temperature was increased in four steps, the average temperatures of each step being 300, 367, 434 and 500 ° C. The temperature was raised after two hours, increasing for 20 to 30 minutes. In addition to the supply air temperature, the temperature difference between the catalyst bed and the supply air was also measured. It was found that the temperature in the catalyst bed was practically the same as the supply air temperature, except for a short period of about 5 to 10 minutes when setting the first temperature step of 300 ° C, when the catalyst bed temperature temporarily exceeded the supply air temperature by up to 100 ° C. . This proves that the heat provided with the reaction is sufficient to dissipate sufficiently with a stream of air, and the catalyst overheating above 550 ° C, which is referred to as critical for the catalyst under these regeneration conditions, does not occur.

The quality of the reactivation process was assessed by chemical analysis of C and S and by testing the catalytic activity in a pilot plant reactor, using crude gasoline containing 400 ppm sulfur as the test feedstock and testing was preceded by catalyst reduction and sulfidation. These values obtained for the used - deactivated, unused and regenerated catalyst are given in Table 1.

Table

Reactivation of the hydrodeaulfurization catalyst

Catalyst Weight content Catalyst activity at temperature C,% S,% 275 C 310 ° C 346 ° C % ppm S % ppm S % ppm S 'unused 0 0 88 48 97 12 99 4 regenerated 0.26 0.70 86 56 97 12 99 . 4 deactivated 10.2 3.7 71 116 88 48 96 16

(a) Activity evaluated by desulphurisation rate,% and sulfur content, ppm, in the desulphurized product.

The results show that the regeneration carried out the activity returned to the level of unused catalyst activity, carbon was removed by · 97.5% and sulfur by 81%. Reactivation conditions indicated (reactivation time 8 h, air consumption 160 000 m ^ per 1 m ^ catalyst) are technologically acceptable.

Example 2

The deactivated catalyst of Example 1 was regenerated in a batch device in which the temperature of the air supplied to the catalyst was linearly increased with time. The regeneration was started at 180 ° C and terminated at 500 ° C, the regeneration time was 8.5 h, i.e. at a heating rate of 37.6 ° C / h. Layer heights in the range of 1.5 to 4.5 cm and air flow rates corresponding to space velocities of 10,000 and 20,000 m vzduchu / h air per m 1 of catalyst used were used. At a space velocity of 20 000 h ^- 'does not exceed the temperature difference between the catalyst and the incoming air 40 ° C, whereas at a space velocity of 10,000 h ^-1 increased air temperature around 340 ° C at a catalyst temperature above 600 ° abruptly G, thereby technologically unacceptable catalyst overheating. This demonstrates the need to ensure that the heat of reaction is dissipated at a sufficient air velocity to prevent the catalyst from overheating during ignition, i.e., a sudden and rapid rise in temperature. When an initial regeneration temperature of more than 200 ° C was selected, the catalyst ignited shortly after being poured onto the grate.

A chromatographic analysis of sulfur dioxide and carbon dioxide at the exit of the regeneration reactor was also performed at a space velocity of 20,000 h ^-1 . At a heating rate of 37.6 ° C / h, sulfur dioxide was mainly detected in the range of 200-300 ° C, carbon dioxide was present in the range of 300-480 ° C, with the highest carbon dioxide content being recorded at 370 ° C. At twice as fast heating, the temperature corresponding to the maximum carbon dioxide content increased by about 10 ° C. Measurement of the sulfur dioxide and carbon dioxide content of the flue gas shows that the regeneration of the sulfur-free catalysts can only be started later at a temperature of about 320 ° C, when the carbon contained in the deposit begins to burn more rapidly.

Example 3

The regeneration of the deactivated catalyst of Example 1 was carried out in a laboratory continuous apparatus where the fixed grate was replaced by a movable grate moving slowly in an oven with increasing temperature profile along the grate. The regeneration conditions were as follows: initial temperature 180 ° C, final temperature 500 ° C, catalyst residence time in the plant

8.5 ha space velocity of 10 000 and 20 000 h ^- ', It was found that during the regeneration, the process of characterization of the che5 catalyst temperature of supply air temperature, dependent on the use of a continuous batch type apparatus Ei.

Example 4

The deactivated hydrodesulfurization of the cobalt molybdenum catalyst described in Example 1 was subjected to oxidative removal of carbonaceous additive to obtain a carbon-free feedstock for metallurgical processing. The catalyst contains approximately 3% Co and 8% Mo.

The incineration of the deposits was carried out in a batch device, the layer height was 3 cm, the supply air temperature 520 ° C, the combustion time 3 h, the space air velocity 10 000 h ^-1 .

In this case, the temperature difference between the catalyst bed and the supply air in the initial stage of the reaction rose sharply by more than 200 ° C, the temperature equalizing only after half an hour of reaction. At the end of the combustion, the catalyst contained 0.24% and 0.6% S, the activity reaching only 80% of the original value, probably due to catalyst overheating. It is obvious that this temperature regime is not suitable for reactivation, but rather for metallurgical recovery of Co and Mo, since the oxidation time is significantly shorter than for reactivation.

Claims (2)

SUBJECT OF THE INVENTION 1. A process for the regeneration of refining catalysts containing Group VI, VII or VIII metals or their oxides and sulphides on respective porous supports, comprising the oxidative removal of carbonaceous deposits resulting from the processing of organic raw materials, in particular petroleum, containing predominantly carbon, hydrogen or hydrogen. sulfur, carried out outside the actual catalytic reactor for reuse in the catalytic reactor in place of fresh catalyst or other reuse of precious or rare metals contained in the catalysts, characterized in that the catalyst placed on the solid grate in a layer less than 30 cm high, preferably less than 10 cm, a gas containing 2 to 23 vol% of free oxygen, preferably air, is fed at a flow rate of 4 to 90 kg / h per kg of catalyst to be treated, preferably 15 to 60 kg / kg h, the catalyst temperature being raised continuously or stepwise or is constant and depends on the feed gas temperature and is in the range of 320 to 600 ° C, preferably 330 to 500 ° C for reactivated sulfur-free catalysts, in the range of 200 to 600 ° C, preferably 200 to 600 ° C for reactivated sulfur-containing catalysts 500 ° C and for catalysts where recovery of catalytic activity is not required, incl ranges from 420 to 700 ° C, preferably 480 to 600 ° C, and the period of time the catalyst is subjected to an elevated temperature in an oxidizing atmosphere is at least 1 hour for reactivated sulfur-free catalysts, preferably 3 to 8 hours; , preferably 6 to 18 hau catalysts, where recovery of the catalytic activity of at least 0.5 h, preferably 1 to 3 h, is not required. Method according to claim 1, characterized in that the catalyst is placed in a thin layer with a height of less than 30 cm, preferably less than 10 cm, on a support - a conveyor belt - which moves from the inlet to the recovery plant to its outlet, passing a regeneration medium - a gas containing free oxygen in the range of 12 to 23% by volume - preferably air, with a flow rate of 4 to 90 kg / h air per kg of catalyst, preferably 15 to 60 kg / kg h, with constant or continuous; a stepwise increasing temperature profile along the conveyor belt, the temperature profile being in the range of 320 to 600 ° C, preferably 330 to 520 ° C for reactivated sulfur-free catalysts, in the range of 180 to 600 ° C, preferably 200 to 600 ° C for reactivated sulfur-containing catalysts 520 ° C and for catalysts where recovery of catalytic activity in the range of 420 to 700 ° C, preferably 480 to 600 ° C, and up to b, the catalyst residence time in the heated regeneration zone is at least 1 h, preferably 3 to 8 h, for reactivated sulfur-free catalysts, at least 2 h, preferably 6 to 18 h, for reactivated catalysts, and for catalysts where recovery of catalytic activity is not at least 0, 5 h, preferably 1 to 3 h.