USING SUPERCRITICAL C02

DESCRIPTION

Field of the Invention

The present invention relates to a synthesis method and system of hydrocraking catalysts used in hydrocracking units wherein cracking of petroleum products is performed. Prior Art

In hydrocracker units of petroleum refineries, crude hydrocarbon is cracked in the presence of hydrogen at high temperature and under pressure so as to be converted into valuable fuels such as diesel, gasoline and jet fuel. This conversion is carried out by a catalyst used with hydrogen. Hydrocracking catalysts mainly have two functions in a hydrocracking unit. The first one is to perform cracking and the other one is to perform hydrogenation/dehydrogenation. In order to synthesize hydrocracking catalysts, a porous support material is made to adsorb metal compounds. This is called as impregnation in the prior art. After impregnation process, the support material is subjected to a calcination process so as to allow oxidation of the adsorbed metals, and the synthesis is thus completed. The support material generally comprises materials such as silica-alumina and zeolite, and due to acidic characteristics of the said materials, cracking is performed. Moreover, materials adsorbed into the support material are generally selected from Group VI B and Vill elements of the periodic table, whereby hydrogenation/dehydrogenation processes are performed.

In prior art, said adsorption of metal compounds into the support material is performed by dissolution of metals in the presence of various solvents. US4431516A describes the use of ammonia for dissolution of metals. However, in embodiments utilizing ammonia as the solvent, ammonia steam is generated in the calcination stage, which is harmful for health. Furthermore, the use of phosphoric acid, hydrochloric acid, nitric acid, sulphuric acid, citric acid, tartaric acid, oxalic acid, malonic acid and malic acid as the solvent is also known in the prior art. However, said acids also generate harmful waste in the calcination stage. Furthermore, the said document does not disclose how the waste generated in the manufacturing of the catalyst is disposed.

Brief Description of the Invention With the present invention, there is provided a synthesis system and method for synthesis of a hydrocracking catalyst by using at least one support material and at least one metal precursor to be adsorbed into the support material. The said synthesis system comprises at least one high-pressure container into which the support material and the metal precursor are placed and having at least one body resistant to high pressure; at least one carbondioxide source for supplying carbondioxide gas into the high-pressure container; at least one pump for delivering the carbondioxide supplied to the high-pressure container under a pressure allowing it to transform into the supercritical phase; at least one temperature regulation unit regulating the temperature of the high-pressure container so as to bring the carbondioxide supplied to the high-pressure container to a temperature allowing it to transform into the supercritical phase; at least one heating furnace wherein the support material is heated and subjected to calcination after the said metal precursor is dissolved in the carbondioxide in the supercritical phase and adsorbed into the support material. The said synthesis method comprises the steps of introducing the metal precursor and the support material into the high-pressure container; supplying the carbondioxide received from the carbondioxide source by means of the pump into the high-pressure container under a pressure allowing it to transform into the supercritical phase; bringing the carbondioxide in the high-pressure container to a temperature allowing it to transform into the supercritical phase by the temperature regulation unit so that the metal precursor in the high-pressure container is dissolved in carbondioxide and adsorbed by the support material; heating of the support material in the said furnace and subjecting same to calcination so as to allow the metal precursor adsorbed by the support material to oxidize. In the synthesis system according to the present invention, carbondioxide in the supercritical phase is used as the solvent. The thermo-physical properties of the supercritical carbondioxide, as in other fluids in the supercritical phase, are liquid-like density and gas-like viscosity values. These properties may vary in a wide range due to slight changes in the temperature and pressure, close to the critical point of the carbondioxide. The liquid-like density imparts the supercritical fluid the required dissolution capacity whereas gas-like viscosity values provide a higher diffusion rate than liquids. For these reasons, the fluids in the supercritical phase, with their favorable effect on the mass transfer due to the high dissolution capacity as well as their low viscosity, are advantageous, when used as solvents, in improving deposition kinetics as opposed to other conventional solvent methods. Moreover, in the synthesis system according to the present invention, carbondioxide that transforms from the supercritical phase into the gaseous phase is generated as waste. Therefore, the problem of disposal of the waste is not encountered.

Object of the Invention

An object of the present invention is to provide a method and system for synthesis of hydrocracking catalysts used in hydrocracking units.

Another object of the present invention is to provide a method and system not generating harmful waste in synthesizing of the hydrocracking catalyst.

Still another object of the present invention is to provide a method and system wherein cracking feature of the synthesized hydrocracking catalyst is enhanced.

Description of the Drawings

The exemplary embodiments of the hydrocracking catalyst synthesis according to the present invention are illustrated in the enclosed drawings, in which:

Figure 1 is a block diagram of the hydrocracking catalyst synthesis system.

Figure 2 is a side sectional view of a high-pressure container used in the hydrocracking catalyst synthesis system.

Figure 3 is a block diagram of the hydrocracking catalyst synthesis method.

All the parts illustrated in the figures are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows:

Synthesis system (S) High-pressure container (1)

Carbondioxide source (2)

Pump (3)

Inlet valve (4)

Mixer (5)

Temperature regulation unit (6)

Outlet valve (7)

Temperature sensor (8)

Pressure sensor (9)

Cover (10)

Fluid inlet (11)

Fluid outlet (12)

Body (13)

Carbondioxide inlet (14)

Carbondioxide outlet (15)

Disintegration disc (16)

Support material (17)

Metal precursor (18)

Placement of the metal precursor and support material (a)

Adsorption of the metal precursor (b)

Calcination (c)

Description of the Invention In petroleum refineries, hydrocracking units are used that crack petroleum products and convert them into different products. Hydrocracking unites comprises hydrocracking catalysts for performing cracking and hydrogenation/dehydrogenation processes. During the synthesis of the said catalysts, a metal precursor is dissolved in a solution and adsorbed into a support material and then the support material is subjected to calcination. The solvents employed in the dissolution process transform into the gaseous phase in the calcination process, thereby threatening human health. Moreover, in the traditional methods, the waste resulting from the dissolution process must be eliminated. Therefore, there is provided with the present invention a hydrocracking catalyst synthesis system and method wherein generation of harmful waste is prevented. The synthesis system (S) according to the present invention and illustrated in Figures 1 and 2 comprises at least one high-pressure container (1) into which at least one support material (17) and at least one metal precursor (18) to be adsorbed on the support material (17) are placed and having at least one body (13) resistant to high-pressure (preferably up to 350 bar); at least one carbondioxide source (2) for supplying carbondioxide gas into the high-pressure container (1); at least one pump (3) for delivering the carbondioxide supplied to the high-pressure container (1) under a pressure allowing it to transform into the supercritical phase; at least one temperature regulation unit (6) regulating the temperature of the high-pressure container (1) so as to bring the carbondioxide supplied to the high-pressure container (1) to a temperature allowing it to transform into the supercritical phase; at least one heating furnace (not shown) wherein the support material ( 7) is heated and subjected to calcination after the said metal precursor (18) is dissolved in carbondioxide in the supercritical phase and adsorbed into the support material (17). Also the said synthesis system (S) preferably comprises at least one pressure sensor (9) for measuring the internal pressure of the high-pressure container (1). With the said pressure sensor (9), internal pressure of the high-pressure container (1) is maintained at desired level. In the synthesis method using a synthesis system (S) according to the present invention and illustrated in the block diagram of Figure 3, the metal precursor (18) and the support material (17) are introduced (a) into the said high-pressure container (1). The said support material (17) is preferably in the form of a zeolite pellet (more specifically USY (ultra stable y form) zeolite pellet). The metal precursor (18) comprises at least one metal (i.e. nickel and/or tungsten) selected from Groups VIB and VIII of the periodic table. Then, the carbondioxide received from the carbondioxide source (2) by means of the said pump (3) is supplied into the high-pressure container (1) at a pressure (i.e. in the range of 180-240 bar, more specifically 208 bar) allowing it to transform into the supercritical phase. With the temperature regulation unit (6), carbondioxide is brought to a temperature in the high- pressure container (1) that allows it transform into the supercritical phase. After the carbondioxide transforms into the supercritical phase, the metal precursor (18) inside the high-pressure container (1) dissolves in the carbondioxide and adsorbed (b) by the support material (17). After the adsorption is completed, the support material (17) is heated inside the said furnace and subjected to a calcination (c) process and thus the metal precursor (18) adsorbed by the support material (17) is oxidized.

In a preferred embodiment of the invention, the synthesis system (S) comprises at least one mixer (5) mixing the carbondioxide in the supercritical form and located inside the high-pressure container (1) with the metal precursor (18). Thanks to the mixer (5), the metal precursor (18) is better dissolved in the supercritical carbondioxide and is better adsorbed by the support material (17). The said mixer (5) is preferably in the form of a magnetic mixer. In another preferred embodiment of the invention, the high-pressure container (1), as illustrated in Figure 2 in detail, comprises at least one cover (10) including at least one window preferably made of a transparent material (i.e. sapphire glass) and covering at least one opening of the pressure container (1), and at least one disintegration disc (16) covering at least another opening of the pressure container (1). With the said cover (10), the metal precursor (18) and support material (17) may be placed into the high-pressure container (1). Furthermore, since the cover (10) includes a transparent window, adsorption process may be observed externally. And with the said disintegration disc (16), the pressure container (1) is prevented from reaching undesired pressure values. In another preferred embodiment of the invention, the high-pressure container (1) comprises at least one carbondioxide inlet (14) through which carbondioxide is inputted and at least one carbondioxide outlet (15) through which carbondioxide is outputted. With the said carbondioxide inlet (14), carbondioxide coming from the carbondioxide source (2) is introduced into the high-pressure container (1). And with the carbondioxide outlet (15), following the adsorption process, carbondioxide inside the pressure container (1) is outputted so that internal pressure of the high-pressure container (1) is restored to normal values (pressure at room temperature). Thus, the support material (17) is taken from the high-pressure container (1) and sent to the said furnace. In this embodiment, the synthesis system (S) also comprises at least one inlet valve (4) connected to the carbondioxide inlet (14) and/or at least one outlet valve (7) connected to the carbondioxide outlet (15). With the said valves (4, 7), internal pressure of the high- pressure container (1) can be maintained at desired level (under a pressure allowing carbondioxide to transform into the supercritical phase) during the adsorption process. In another preferred embodiment of the invention, the said temperature regulation unit (6) is a circulation type unit. In this embodiment, the high-pressure container (1) comprises at least one fluid inlet (1 1) through which fluid coming from the temperature regulation unit (6) is received; at least one circulation line (not shown) wherein the said fluid is circulated therein so as to allow heat exchange with the high-pressure container (1), and at least one fluid outlet (12) through which the fluid exiting the high-pressure container (1) is transferred into the temperature regulation unit (6).

In another preferred embodiment of the invention, the synthesis system (S) comprises at least one temperature sensor (8) measuring the temperature of the high-pressure container (1). The temperature of the high-pressure container (1) is measured by the temperature sensor (8) preferably in the form of a metal pair. In line with the internal temperature of the high-pressure container (1), operation of the temperature regulation unit (6) is controlled so that the high-pressure container is maintained at a desired temperature level (i.e. at a temperature allowing carbondioxide to transform into the supercritical phase).

In the synthesis system (S) according to the present invention, carbondioxide in the supercritical phase is used as the solvent. The thermo-physical properties of the supercritical carbondioxide, as in other fluids in the supercritical phase, are liquid-like density and gas-like viscosity values. These properties may vary in a wide range due to slight changes in the temperature and pressure, close to the critical point of the carbondioxide. The liquid-like density imparts the supercritical fluid the required dissolution capacity whereas gas-like viscosity values provide a higher diffusion rate than liquids. For these reasons, the fluids in the supercritical phase, with their favorable effect on the mass transfer due to the high dissolution capacity as well as their low viscosity, are advantageous, when used as solvents, in improving deposition kinetics as opposed to other conventional solvent methods. Moreover, in the synthesis system (S) according to the present invention, carbondioxide that transforms from the supercritical phase into the gaseous phase is generated as waste. Therefore, the problem of disposal of the waste is not encountered.