Silica-alumina composition comprising 1-30 wt% crystalline ammonium aluminium carbonate hydroxide and process for its preparation

Abstract

A process for manufacturing a silica-alumina composition having improved properties is provided. The process comprises: (a) mixing an aqueous solution of a silicon compound with an aqueous solution of an aluminum compound and an acid while maintaining the pH of the mixed solution in a range from 1 to 3 and obtaining an acidified silica-alumina sol; (b) adding an aqueous solution of a base precipitant to the acidified silica-alumina sol to a final pH in a range from 5 to 8 and co-precipitating a silica-alumina slurry, wherein the base precipitant is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, and any combination thereof; (c) optionally, hydrothermally aging the silica-alumina slurry to form a hydrothermally aged silica-alumina slurry; and (d) recovering a precipitated solid from the silica-alumina slurry or the hydrothermally aged silica-alumina slurry, wherein the precipitated solid comprises the silica-alumina composition.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an amorphous silica-alumina composition having a high pore volume and a process for making such a composition. BACKGROUND

[0002] Compounds such as silica, alumina and their amorphous mixtures (silica-alumina) are catalysts widely used in hydrocarbon conversion reactions such as oligomerization and hydrocracking reactions. Due to their characteristic porous structure and high surface area, these compounds, particularly amorphous silica-alumina, can be used both as catalysts and as supports for metal catalysts. For example, in the case of hydrocracking reactions, one of the most widely used catalysts on an industrial scale is a bifunctional catalyst containing one or more metals uniformly distributed in a silica-alumina support. In this catalyst, the metal component catalyzes the hydrogenation reactions, while the silica-alumina catalyzes the cracking reactions due to its acidity characteristics.

[0003] Amorphous silica-alumina compositions have surface acid sites that are generally weaker than those of zeolites. This moderate acidity enables silica-alumina-based catalysts to be used generally at high temperatures and low space velocities. In order to manufacture a hydrocracking catalyst selective for diesel production, while minimizing the excessive cracking towards light naphtha, a moderate acidity is required.

[0004] Amorphous silica-alumina compositions also have a wide pore size distribution. This allows high diffusion rates of reagent molecules to be obtained (a particularly advantageous characteristic in the case of the conversion process of heavy hydrocarbon feedstocks) and provides sufficient surface area capable of receiving and effectively dispersing the possible metal components of the catalyst.

[0005] A number of processes are known for preparing amorphous silica-alumina in various forms. It is also known that the specific operating conditions applied in the preparation significantly influence the catalytic and physicochemical properties of the silica-alumina obtained, such as, for example, the pore structure, total volume, surface area and acidity characteristics.

[0006] It is desirable to have an amorphous silica-alumina composition having physical and catalytic properties that make it particularly useful as a catalyst or component of a catalyst for various catalytic applications.

[0007] It is also desirable to have a process for preparing an amorphous silica-alumina having certain desirable physical and catalytic properties. SUMMARY

[0008] In one aspect, a process for making an amorphous silica-alumina composition is provided, wherein the process comprises the steps of: (a) mixing an aqueous solution of a silicon compound with an aqueous solution of an aluminum compound and an acid while maintaining the pH of the mixed solution in the range of 1 to 3 and obtaining an acidified silica-alumina sol; (b) adding an aqueous solution of a base precipitant to the acidified silica-alumina sol to a final pH in the range of 5 to 8 and co-precipitating a silica-alumina slurry, wherein the base precipitant is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, and any combination thereof; (c) optionally, hydrothermally aging the silica-alumina slurry to form a hydrothermally aged silica-alumina slurry; and (d) recovering a precipitated solid from the silica-alumina slurry or the hydrothermally aged silica-alumina slurry, wherein the precipitated solid comprises the silica-alumina composition.

[0009] In a second aspect, a continuous process for making an amorphous silica-alumina composition is provided, wherein the process comprises the steps of: (a) continuously contacting and mixing an aqueous solution of a silicon compound with an aqueous solution of an aluminum compound and an acid in a first mixing zone while maintaining the pH of the mixed solution in the range of 1 to 3; (b) continuously removing a first mixture from the first mixing zone, wherein the first mixture comprises an acidified silica-alumina sol; (c) continuously contacting and mixing the first mixture with an aqueous solution of a base precipitant in a second mixing zone while maintaining the pH in the range of 5 to 8 to produce a silica-alumina slurry, wherein the base precipitant is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, and any combination thereof; (d) continuously removing the silica-alumina slurry from the second mixing zone; and (e) recovering a precipitated solid from the silica-alumina slurry, wherein the precipitated solid comprises the silica-alumina composition.

[0010] In a third aspect, a silica-alumina composition is provided comprising an amorphous silica-alumina having a total pore volume of at least 1.0 cm 3 / g; wherein the silica-alumina composition in its dried form contains 1 to 30 wt. % of an ammonium aluminum carbonate hydroxide in a crystalline phase based on the total weight of the silica-alumina composition. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Shown is A powder X-ray diffraction (XRD) pattern of a dried powder sample of a silica-alumina.

[0012] Figure 2 Shown is A powder XRD pattern of a dried powder sample of a silica-alumina.

[0013] Figure 3 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 3 is shown prior to calcination.

[0014] Figure 4 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 4 is shown prior to calcination.

[0015] Figure 5 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 5 is shown prior to calcination.

[0016] Figure 6 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 6 is shown prior to calcination. Figure 5 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 5 is shown prior to calcination.

[0017] Figure 7 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 7 is shown prior to calcination.

[0018] Figure 8 A powder XRD pattern of a dried powder sample of the silica-alumina prepared in Example 9 is shown prior to calcination.

[0019] Figure 9 N2adsorption pore size distributions of the silica-alumina materials prepared in Examples 3, 4, 6, and 8 are shown. DETAILED DESCRIPTION

[0020] Definitions and Abbreviations

[0021] In this patent specification, the following words and phrases, if and when used, have the meanings given below.

[0022] The term "microporous" means a solid material having pores with diameters less than 2 nanometers .

[0023] The term "mesoporous" means a solid material having pores with diameters of 2 to 50 nanometers .

[0024] The term "macroporous" means a solid material having pores with diameters greater than 50 nanometers .

[0025] Each of the above definitions of microporous, mesoporous, and macroporous is considered to be distinct, so there is no overlap and pores are not counted twice when summing percentages or values in terms of pore size distribution for any given sample.

[0026] The term "aqueous solution" herein refers to any solution in which the solvent is water. An aqueous solution can include water-soluble substances dissolved in the solution and / or water-insoluble compounds dispersed in the solution.

[0027] The term "continuous" means a system that operates without interruption or stoppage. For example, a continuous sol process to produce a silica-alumina sol is a process in which reactants (acidified alumina solution and aqueous solution of silicon compound) are continuously introduced into one or more reactors and the aqueous solution of product containing silica-alumina sol is continuously withdrawn.

[0028] The term "co-gel" refers to a product resulting from the gelation of two or more components.

[0029] The term "dried silica-alumina" refers to a silica-alumina material from which solvent, typically water, or a mixture of water and one or more water-miscible solvents, has been substantially removed.

[0030] The term "calcined silica-alumina" refers to a silica-alumina material that has been heated to at least a temperature in air, oxygen, or an inert atmosphere at which any remaining volatiles, including all organic materials and water, present in the dried substrate are removed. The temperature used in calcination is typically between 400°C and 900°C for about 0.25 to 8 hours.

[0031] The term "aluminum ammonium carbonate hydroxide" can be abbreviated as "AACH".

[0032] Silica-alumina synthesis

[0033] The process of the present invention provides co-gel precipitation of a silica-alumina composition starting from a corresponding silica-alumina co-sol.

[0034] Silica-alumina according to the present disclosure can be prepared in different combinations by a variety of methods employing both batch and continuous processes.

[0035] The acidified silica-alumina co-sol is obtained in process step (a) by mixing an aqueous solution of a silicon compound with an aqueous solution of an aluminum compound and an acid.

[0036] It is desirable to maintain the pH in the range of 1 to 3 (e.g., 1 to 2.5) and to ensure vigorous complete mixing of the aluminum and silicon solutions to minimize any undesirable gel or particle formation.

[0037] The aqueous solution of a silicon compound can include a silicon compound in an amount ranging from 2% to 15% (e.g., 5% to 10%) by weight of silicon expressed as Si02.

[0038] Suitable silicon compounds can be alkali metal silicates (e.g., sodium silicate), silicic acid, colloidal silica, precipitated silica, and fumed silica. In some aspects, the silicon compound is sodium silicate, particularly sodium silicate having a Si02 / Na20 weight ratio in the range of 2.5 to 3.5.

[0039] The aqueous solution of the aluminum compound can include the aluminum compound in an amount ranging from 2% to 25% (e.g., 5% to 10%) by weight of silicon expressed as AI2O3.

[0040] Suitable aluminum compounds include aluminum salts (e.g., aluminum nitrate, aluminum sulfate), aluminum halides (e.g., aluminum chloride, aluminum bromide, aluminum iodide), and alkali metal aluminates (e.g., sodium aluminate).

[0041] Suitable acids contained in the aqueous solution of the aluminum compound are, for example, mineral acids and / or organic acids, such as hydrochloric acid, nitric acid, sulfuric acid, formic acid, or acetic acid.

[0042] In step (b) of the process, an aqueous solution of a base precipitating agent is subsequently added to the acidified silica-alumina sol. The addition of the base precipitating agent increases the pH of the sol, resulting in the co-precipitation or co-gelation of the silica and alumina species. The base precipitating agent is selected from ammonium carbonate and / or ammonium bicarbonate.

[0043] Step (b) can be conducted via a batch process or a continuous process. In either case, the co-precipitation pH will be uniformly maintained (i.e., held constant within a pH range of 5 to 8 (such as 6 to 8 or 6.5 to 7.5)). It is desirable to thoroughly mix the silica-alumina sol solution with the basic precipitating agent and maintain a uniform pH throughout the mixture during step (b) in order to minimize the formation of separate silica and alumina domains.

[0044] The mixing or reaction vessel used for process steps (a) and (b) can be any suitable vessel and associated equipment known in the art, including a vessel equipped with means for agitating the contents of the vessel (such as a continuous stirred tank reactor or a blender) to provide for the blending and dispersion of the components and the suspension and dispersion of the precipitated solids. The vessel can also be equipped with means for heat exchange with the contents of the vessel in order to provide control over the temperature of the vessel contents.

[0045] It is desirable to minimize the time required to mix the components in process steps (a) and (b) to only that which is necessary to provide a uniform mixture within the mixing zone. While the mixing time can vary depending on the type of equipment used, the size of the equipment, and other factors, the time required to combine, blend, and disperse the components can range from 0.1 minute to 30 minutes per step.

[0046] Process steps (a) and (b) can be carried out at a temperature in the range of 10 °C to 90 °C (e.g., 20 °C to 80 °C).

[0047] The optional hydrothermal aging in process step (c) can be carried out at a temperature of 20 °C to 200 °C (e.g., 20 °C to 120 °C, or 120 °C to 180 °C) for a period of 1 to 6 hours.

[0048] In process step (d), the precipitated solids can be recovered using any suitable method known to those skilled in the art for separating precipitated solids from a hydrothermally aged silica-alumina slurry. Such methods include specific gravity separation, pressure separation, and vacuum separation and can include the use of equipment such as, for example, belt filters, plate and frame filters, and rotary vacuum filters.

[0049] The recovered precipitated solids can be further treated by washing, ion exchange, drying, and / or calcination.

[0050] The recovered precipitated solids obtained in step (d) are typically washed with water to remove impurities such as unreacted silicates and aluminate salts. The amount of water used to wash the precipitated solids can be any amount that suitably provides a washed powder having a pH in the range of 2 to 8 (e.g., 2.5 to 7). The weight ratio of water to solids used in a single step can be in the range of 01:1 to 100:1 (e.g., 0.5:1 to 50:1).

[0051] The washed precipitated solids are typically subjected to ammonium ion exchange to remove residual sodium. The weight ratio of water to solids used in a single step can be in the range of 01:1 to 100:1 (e.g., 0.5:1 to 50:1). One or more ammonium exchange and washing steps can be used to purify the recovered precipitated solids. The washing and ammonium exchange steps can be performed continuously on a belt conveyor.

[0052] The washed and ammonium exchanged precipitated solids can also be reslurried and spray dried using any of the suitable spray drying methods known in the art to provide a spray dried powder for ease of handling and storage. Alternatively, the washed and ammonium exchanged precipitated solids can be flash dried or oven dried to provide a dried powder. The silica-alumina can be dried in air or any other suitable atmosphere at an additional suitable drying condition at a drying temperature of 50 °C to 200 °C (e.g., 60 °C to 180 °C).

[0053] If desired, the dried silica-alumina material can be extruded, dried, and calcined to produce a silica-alumina catalyst or catalyst support. The extruded pellets can be dried under additional suitable drying conditions at a drying temperature of 50 °C to 200 °C (e.g., 60 °C to 180 °C) in air or any other suitable atmosphere. The extruded pellets, preferably after being further dried, can be calcined under suitable calcination conditions and in particular under an oxygen-containing atmosphere (e.g., air) at a calcination temperature of 400 °C to 900 °C (e.g., 450 °C to 650 °C) for 0.25 to 8 hours.

[0054] The silica-alumina compositions can be composited with other materials such as, for example, molecular sieves, clays, modifier clays, inorganic oxides, carbon, organic substances, and the like. Catalysts derived from the silica-alumina compositions of the present invention can have an active metal component. The active metal component can be selected from the group consisting of nickel, cobalt, molybdenum, tungsten, platinum, and palladium.

[0055] The silica-alumina compositions can be used as catalysts in industrial processes such as, for example, hydrocracking, hydroprocessing (e.g., hydrodesulfurization, hydrodenitrogenation, hydrodemetallization), hydrofining, alkylation, oligomerization, transalkylation, dechlorination, hydrocarbon oxidation, and residue upgrading processes.

[0056] Silica-alumina composition

[0057] The silica-alumina compositions prepared according to the processes of the present invention are highly amorphous. The silica-alumina contains a small amount of crystalline ammonium aluminum carbonate hydroxide in its dried form. In some aspects, the crystalline ammonium aluminum carbonate hydroxide has the formula (NH4)2Al6(C03)3(OH) 14 xH20 and is structurally related to the mineral davyne. The amount of crystalline ammonium aluminum carbonate hydroxide is indicated by its characteristic powder X-ray diffraction (XRD) pattern. The silica-alumina compositions of the present invention are significantly lacking in XRD peaks indicative of various other crystalline alumina phases such as pseudoboehmite. Generally, the amount of ammonium aluminum carbonate hydroxide in the crystalline phase is in the range of 1 wt.% to 30 wt.% (e.g., 3 wt.% to 20 wt.%, or 5 wt.% to 15 wt.%) of the total weight of the silica-alumina composition in dried form.

[0058] After calcination, the dried silica-alumina composition becomes completely amorphous and free of crystalline material. By "free of crystalline material" is meant that there are no crystalline phases present, or if there are any crystalline phases present, their total amount is not detectable by X-ray diffraction.

[0059] The amorphous silica-alumina composition can have a silica content in the range of 20 wt% to 80 wt% (e.g., 30 wt% to 70 wt%). The alumina can be present in the range of 20 wt% to 80 wt% (e.g., 30 wt% to 70 wt%). The chemical composition is determined by inductively coupled plasma-mass spectrometry (ICP-MS).

[0060] Another characteristic of the amorphous silica-alumina composition obtained by the process of the present invention is that it has a significantly high total pore volume. The total pore volume of the amorphous silica-alumina composition can be at least 1.0 cm 3 / g (e.g., 1.0 cm 3 / g to 2.0 cm 3 / g, 1.2 cm 3 / g to 1.9 cm 3 / g, or 1.3 cm 3 / g to 1.8 cm 3 / g). The total pore volume can be determined by nitrogen physisorption according to ASTM D6761.

[0061] Another characteristic of the amorphous silica-alumina composition obtained by the process of the present invention is that it has a significantly high surface area. The surface area can be in the range of 200 m 2 / g to 500 m 2 / g (e.g., 300 m 2 / g to 470 m 2 / g). The surface area can be determined by nitrogen physisorption according to ASTM D3663 using the B.E.T. method.

[0062] Another characteristic of the amorphous silica-alumina composition obtained by the process of the present invention is that it can have a high total pore volume in the mesopore region (i.e., between and , especially in the mesopore region of and . The total mesopore volume of the amorphous silica-alumina composition can be at least 0.7 cm 3 / g (e.g., 0.7 cm 3 / g to 1.8 cm 3 / g) and to The pore volume in the mesopore range of 3 / g (e.g., 0.3 cm 3 / g to 1.0 cm 3 / g).

[0063] In some respects, amorphous silica-alumina compositions possess a porosity such that the diameter is within a certain range. to The mesopore volume accounts for 30% to 80% of the total pore volume measured by nitrogen physisorption.

[0064] Example

[0065] The following illustrative examples are intended to be non-limiting.

[0066] Example 1 (Comparative Example)

[0067] Will Silica-alumina (obtained from Sasol) was used as a comparative example. The physical properties of this material are summarized in Table 1.

[0068] The powder XRD pattern of SIRAL-40 silica-alumina (original dried powder) is shown in... Figure 1 The study shows and indicates that this material contains a significant amount of crystalline boehmite. Quantitative analysis shows that SIRAL-40 silica-alumina contains approximately 48% crystalline alumina phase relative to the crystalline standard. Using pure... Alumina was used as a reference to quantify the crystalline phase.

[0069] This silica-alumina is used to prepare the hydrocracking catalyst described in Example 11.

[0070] Example 2 (Comparative Example)

[0071] Will HPV silica-alumina (purchased from Sasol) was used as another comparative example. The physical properties of this material are summarized in Table 1.

[0072] The powder XRD pattern of SIRAL-40 HPV silica-alumina (original dried powder) is shown in... Figure 2 The diagram shows and indicates that the material contains a significant amount of crystalline boehmite and trace amounts of diaspore. Quantitatively, the material contains approximately 29% crystalline alumina phase relative to the crystalline alumina standard.

[0073] This silica-alumina was used to prepare the hydrocracking catalyst described in Example 12.

[0074] Example 3 (Comparative Example)

[0075] Silica-alumina was prepared and gelled via continuous sol-gel process.

[0076] An acidic aluminum solution was prepared by dissolving 2396 g of aluminum chloride and 711 g of hydrochloric acid (37%) into 6623 g of deionized water (Solution I, containing 5.2 wt% Al203).

[0077] A dilute sodium silicate solution was prepared by diluting 2070 g of a concentrated sodium silicate solution (containing 29 wt% Si02and 9 wt% Na20) with deionized water (Solution II, containing 6 wt% Si02).

[0078] The silicate solution (Solution II) and the aluminum solution (Solution I) were separately and simultaneously pumped into the mixing chamber of an inline blender having a volume of about 100 cm3. 3 The solutions were mixed in the mixing chamber of the inline blender at 1000 rpm blade rotation for about 0.53 minutes. The final pH of the solution III was 2.1 and the mixing resulted in a clear silica-alumina sol in aqueous solution. The final solution III had a Si02 / Al203molar ratio of 2.0 and a H+ / Na+molar ratio of 1.2. + + The final silica-alumina had a Si02 / Al203molar ratio of 2.0 and a H+ / Na+molar ratio of 1.2.

[0079] A dilute ammonia solution (containing 8 wt% NH3) was prepared for gelation. The dilute ammonia solution and the solution III containing the silica-alumina sol were separately and simultaneously pumped into the mixing chamber of an inline blender. Vigorous mixing was performed in the inline blender at 1600 rpm blade rotation. The volume of the mixing chamber was less than the total volume of the solutions pumped in less than 1 minute (i.e., less than 1 minute residence time / volume). The addition rate of the ammonia solution was adjusted to maintain the pH of the gel product at 7.0 ± 0.5. The gel slurry was collected and then aged at room temperature for 2 hours while stirring. This co-gelled silica-alumina was filtered to produce a filter cake. The filter cake was washed with a hot ammonium nitrate solution (200 g of ammonium nitrate in 10 L of deionized water at 150 °F) and then rinsed with 20 L of deionized water. The washing step was repeated four more times. Finally, the slurry was spray dried using a MOBILE® spray dryer (Model H-2000, Niro Inc.) with an inlet temperature of about 550 °F and an outlet temperature of about 212 °F. A small amount of the spray dried silica-alumina was calcined at 1000 °F for 1 hour under an excess of dry air to activate.

[0080] The physical properties of the final silica-alumina are summarized in Tables 1 and 2. The powder XRD of the dried product is shown in Figure 1 and indicates that the silica-alumina is uniform throughout the particles and is completely amorphous. Figure 3

[0081] ​​​This support was used to prepare the hydrocracking catalyst described in Example 13.

[0082] Example 4 (Comparative Example)

[0083] Synthesis of silica-alumina in an open beaker at atmospheric pressure

[0084] To understand how intense mixing in a closed in-line blender affects the formation of high pore volume silica-alumina, a synthesis of silica-alumina was performed in an open beaker in which no back pressure was applied and the carbonate could freely exit the vessel via C02 evolution during gelation.

[0085] An acidic aluminum solution was prepared by dissolving 207 g of AICI3-6H20 and 59.3 g of hydrochloric acid (37%) into 648 g of deionized water (Solution I, containing 5.0 wt% Al203).

[0086] A dilute sodium silicate solution was prepared by diluting 188 g of a concentrated sodium silicate solution (containing 29 wt% Si02and 9 wt% Na20) with deionized water (Solution II, containing 5 wt% Si02).

[0087] The silicate solution (Solution II) and the aluminum solution (Solution I) were pumped separately and simultaneously into a beaker while an overhead mixer in the beaker intensely mixed the two incoming solutions to produce Solution III. Solution III was drawn from the beaker using a peristaltic pump to maintain a residence time of the mixed solution in the beaker of less than 1 minute. The final pH of Solution III was 2.2 and the mixing produced a clear silica and alumina solution. The final Solution III had a Si02 / Al203molar ratio of 2.0 and a H+ / Na+molar ratio of 1.1. + + The final pH of Solution III was 2.2 and the mixing produced a clear silica and alumina solution. The final Solution III had a Si02 / Al203molar ratio of 2.0 and a H+ / Na+molar ratio of 1.1.

[0088] A 2.0 M ammonium carbonate solution was prepared for gelation. The dilute ammonium carbonate solution and Solution III containing the silica and alumina sol were pumped separately and simultaneously into a beaker containing a mixing vessel at atmospheric pressure. The rate of addition of the ammonium carbonate solution was adjusted to maintain the pH of the gel product at 7.0 ± 0.1 and the gel slurry level was maintained by continuous withdrawal of the gel slurry. The gel slurry was collected and then aged at 160 °F for 2 hours while stirring. This co-gelled silica-alumina was filtered to produce a filter cake. The filter cake was washed with a hot ammonium nitrate solution and then rinsed with deionized water. The washing steps were repeated four more times. Finally, the slurry was filtered to produce a filter cake and dried in an oven at 120 °C for 12 hours. A small amount of the dried silica-alumina was calcined at 1000 °F for 1 hour under an excess of dry air to activate.

[0089] ​The physical properties of the final silica-alumina are summarized in Tables 1 and 2. The powder XRD of the product is shown in Figure 1 and indicates that the silica-alumina is uniform throughout the particles and is amorphous. The total pore volume of this silica-alumina is only 0.49 cm3 / g. Figure 4 3

[0090] Example 5

[0091] Synthesis of high pore volume silica-alumina by continuous gelation

[0092] An acidic aluminum solution (Solution I, containing 6 wt% Al203) was prepared by dissolving 2105 g of Al2(SO)3 x H2O and 239 g of sulfuric acid (98%) in 3023 g of deionized water.

[0093] A dilute sodium silicate solution (Solution II, containing 6.6 wt% Si02) was prepared by diluting 1317 g of a concentrated sodium silicate solution (containing 29 wt% Si02and 9 wt% Na20) with 4071 g of deionized water.

[0094] The alumina / sulfuric acid solution (Solution I) and the silicate solution (Solution II) were pumped separately and simultaneously into the mixing chamber of an in-line blender while being mixed vigorously. Vigorous mixing was performed in the in-line blender with a blender blade rotation of 1000 rpm to produce Solution III. The final pH of Solution III was 2.1 and the mixing resulted in a clear silica and alumina solution. The final Solution III had a Si02 / Al203molar ratio of 2.0 and a H + / Na + molar ratio of 1.2.

[0095] ​​A 2.0 M ammonium carbonate solution was prepared for gelling. The dilute ammonium carbonate solution and solution III containing the silica and alumina sols were pumped separately and simultaneously into the mixing chamber of an in-line blender. Vigorous mixing was performed in the in-line blender with blender blade rotation at 1000 rpm. The volume of the mixing chamber was less than the total volume of the solutions pumped in less than 1 minute (i.e., less than 1 minute residence time / volume). The rate of addition of the ammonium carbonate solution was adjusted to maintain the pH of the gel product at 7.0 ± 0.1. The gel slurry was collected and then aged at 160 °F for 2 hours while stirring. This co-gelled silica-alumina was filtered to produce a filter cake. The filter cake was washed with hot ammonium nitrate solution (200 g of ammonium nitrate in 10 L of deionized water at 150 °F) and then rinsed with 20 L of deionized water. The washing step was repeated four more times. Finally, the slurry was spray dried using a MOBILE MINOR spray dryer with an inlet temperature of about 550 °F and an outlet temperature of about 212 °F. A small amount of the spray-dried silica-alumina was calcined under excess dry air at 1000 °F for 1 hour to activate.

[0096] The physical properties of the final silica-alumina are summarized in Tables 1 and 2. The powder XRD pattern of the dry filter cake is shown in Figure 5 and indicates that the silica-alumina product prepared using ammonium carbonate as the precipitant produced a uniform gel containing a crystalline phase as well as amorphous silica-alumina. The XRD characterization confirms that the crystalline phase is an ammonium aluminum carbonate hydroxide hydrate [(NH4)2Al6(CO3)3(OH) 14 xH2O], a material that is structurally related to ammoniojacobsite. Quantification of the XRD intensities indicates that about 10% of the crystalline phase of ammonium aluminum carbonate hydroxide hydrate is present in the silica-alumina gel. The quantification of the crystalline phase was performed using pure ammonium aluminum carbonate hydroxide NH4Al(OH)2CO3 synthesized according to the procedure in X. H. Li et al. (Proc. 2012 Int. Conf. Mech. Eng. Mater. Sci. (MEMS 2012) 2013, 601-603). This silica-alumina material does not contain any of the typical alumina phases such as pseudoboehmite, boehmite, or gibbsite.

[0097] The physical properties of the final calcined silica-alumina are summarized in Table 1. After calcination at 1000 °F, the silica-alumina is completely amorphous, with no crystalline material present. The XRD pattern of the silica composition in the calcined form is shown in Figure 6 . The silica-alumina in its calcined form has a total pore volume of 1.45 cm 3 / g and a total surface area of 384 m 2 / g.

[0098] This silica-alumina was used to prepare the hydrocracking catalyst described in Example 14.

[0099] Example 6

[0100] Synthesis of high pore volume silica-alumina by continuous sol preparation and continuous gelation

[0101] The synthesis of the silica-alumina of Example 5 was repeated, except for the aging of the slurry. The silica-alumina precipitation slurry was immediately taken to the filtration step without aging. The filter cake was then ammonium exchanged using the same procedure as in Example 5. The powder XRD pattern of the dried filter cake (data not shown) contained about 10% crystalline ammonium aluminum carbonate hydroxide. After calcination, the material became completely amorphous (data not shown). The calcined material had a pore volume of 1.23 cm 3 / g and a surface area of 324 m 2 / g. The properties of this material are summarized in Table 2.

[0102] Example 7

[0103] Synthesis of silica-alumina by continuous gelation

[0104] The preparation procedure was similar to that of Example 5, except that the acidic aluminum solution was prepared by dissolving 1525 g of aluminum chloride and 453 g of hydrochloric acid (37%) in 3389 g of deionized water (solution I, containing 6 wt% Al203).

[0105] The powder XRD pattern of the silica-alumina product is shown in Figure 2, and indicates that the material contained about 10% crystalline ammonium aluminum carbonate hydroxide. Figure 7 This silica-alumina was used to prepare the hydrocracking catalyst described in Example 15.

[0106] The physical properties of the final silica-alumina are summarized in Table 1.

[0107] Example 8

[0108] Synthesis of high pore volume silica-alumina by continuous gelation

[0109] The synthesis of the silica-alumina of Example 7 was repeated. This silica-alumina had a total pore volume of 1.81 cm 3 / g after calcination. The properties of this material are summarized in Table 2.

[0110] Example 9

[0111] Synthesis of high pore volume silica-alumina by continuous gelation

[0112] Silica-alumina synthesis via continuous gelation

[0113] The preparation procedure is similar to that of Example 7, except that the SiO2 / Al2O3 molar ratio is 3.0.

[0114] The final physical properties of the silica-alumina product are summarized in Table 1. The XRD patterns of the silica-alumina powder are shown in [the table below]. Figure 8 The material is indicated to contain approximately 5% crystalline basic aluminum ammonium carbonate hydrate.

[0115] This silica-alumina was used to prepare the hydrocracking catalyst described in Example 16.

[0116] Table 1 Synthesis and characterization of silica-alumina powder

[0117]

[0118] (a) Physical properties determined by the BET method as described by S. Brunauer, P. Emmett and E. Teller (J. Am. Chem. Soc. 1939, 60, 309-319).

[0119] Further analysis was conducted on four co-gelled silica-alumina mixtures (Examples 3, 4, 6, and 8) to understand the sources of the differences in properties, and the results are summarized in Table 2. Figure 9 The N2 pore size distribution of these materials is shown.

[0120] Table 2 Synthesis and characterization of cogelled silica-alumina powder

[0121]

[0122] As shown in Table 2, the co-gelled silica-alumina (Example 3) prepared by precipitation using ammonium hydroxide solution has a density of 0.73 cm⁻¹. 3 / g of mesopore volume, and the pores are mainly in to Within the pore size range. Similar to Example 3, the high-porosity silica-alumina of Examples 6 and 8 of the present invention also contain a considerable amount of... to The mesopores are within the pore size range. Additionally, the co-gelled silica-alumina of Examples 6 and 8 contain pores larger than... substantial pore volume. The mesoporous, substantial pore volume of Examples 6 and 8 is shown in Table 1. The macroporous silica-alumina of Examples 6 and 8 has a bimodal pore size distribution with mesopores. The macropores provide high pore volumes of 1.23 cm3 / g and 1.81 cm3 / g, respectively, as shown in Table 1. 3 / g and 1.81 cm 3 / g, respectively.

[0123] When the silica-alumina synthesis method of Example 4 was applied in an open beaker, the resulting silica-alumina did not produce a high pore volume silica-alumina. This material had a total pore volume of only 0.49 cm3 / g. 3 / g.

[0124] The elemental analysis of the dry filter cake of Example 4 showed little carbon, indicating that the role of ammonium carbonate was to neutralize the acidic AlCl3solution to cause precipitation of the silica-alumina gel, rather than to incorporate carbonate into the silica-alumina gel. The elemental analysis of the dry powder samples of Examples 6 and 8 showed 2.7 wt% and 2.1 wt% carbon, respectively, indicating that carbonate was incorporated in the silica-alumina. The powder X-ray diffraction spectra of the silica-alumina materials showed the presence of crystalline aluminum ammonium hydroxycarbonate hydrate. The results show that the incorporation of ammonium carbonate in the co-gel and the presence of a crystalline aluminum ammonium hydroxycarbonate hydrate phase are needed to make the high pore volume silica-alumina of the present disclosure.

[0125] Example 10

[0126] Model Compound Testing

[0127] The silica-alumina compositions of Examples 1-3, 5, and 7 were subjected to model compound testing in which a model feed containing 50 wt% n-hexane (n-C6) and 50 wt% 3-methylpentane (MP) was used to measure the catalytic activity of the compositions. The testing was performed at 900 °F. The hydrocarbon feed, vaporized in a helium carrier gas, was flowed at 0.68 hour -1 WHSV / gram of catalytic material through 24 / 40 US mesh particulate silica-alumina, and gas chromatography was used to measure the conversion of the hydrocarbons. The results are shown in Table 3.

[0128] Table 3 Comparison of Silica-Alumina with Model Compound Testing

[0129]

[0130] Table 3 shows that the cogel silica-alumina (Example 3) has higher activity than the SIRAL silica-alumina materials (Examples 1-2) containing pseudoboehmite (a separate phase of crystalline alumina). Without being bound by theory, it is believed that the cogel silica-alumina of the present disclosure more effectively utilizes the aluminum by creating a fully amorphous silica-alumina composed of small domains of silica and alumina, thereby creating more acid sites, as evidenced by the higher activity.

[0131] Examples 5 and 7 of the present disclosure contain cogel silica-alumina and macroporosity. The conversion of 3-methylpentane is reduced somewhat due to the very large pores that the model compound adsorbs in. These silica-alumina materials are very effective in isomerization of n-hexane. These features of the silica-alumina (macroporosity and high acid site concentration) can be used to develop a second stage hydrocracking catalyst where it is desirable to minimize over-cracking of diesel components to naphtha.

[0132] Example 11 (Comparative Example)

[0133] Preparation of NiW hydrocracking catalyst Catalyst A with silica-alumina

[0134] A base-case hydrocracking catalyst containing the SIRAL-40 silica-alumina of Example 1 was prepared following the procedure below. 67 parts of SIRAL-40 silica-alumina powder, 8 parts of a low acidity ultra-stable Y (USY) zeolite, and 25 parts of a pseudoboehmite alumina powder were thoroughly mixed. Dilute nitric acid and enough deionized water were added to the mixture to form a paste that could be extruded (1 wt% HNO3 relative to total powder on a 100% solids basis). The paste was extruded in 1 / 16" cylinders and dried at 250 °F overnight. The dried extrudates were calcined at 1100 °F for 1 hour with a purge of excess dry air and then cooled to room temperature.

[0135] A solution containing nickel nitrate and ammonium metatungstate was used to impregnate the target metal loadings of nickel and tungsten into the finished catalyst. The total volume of this solution was matched to the 100% water pore volume of the base extrudate sample (initial wet method). The metal solution was gradually added to the base extrudate while tumbling the base extrudate. When the solution addition was complete, the soaked extrudates were aged for 2 hours. The extrudates were then dried at 250 °F overnight. The dried extrudates were calcined at 935 °F for 1 hour with a purge of excess dry air and then cooled to room temperature.

[0136] Example 12 (Comparative Example)

[0137] Catalyst B

[0138] A base case hydrocracking catalyst containing SIRAL-40 HPV silica-alumina of Example 2 was prepared according to the following procedure. 73 parts of SIRAL-40 HPV silica-alumina powder, 2 parts of low acidity USY zeolite, and 25 parts of pseudoboehmite alumina powder were thoroughly mixed. Dilute nitric acid and enough deionized water were added to the mixture to form a paste that could be extruded (1 wt% HNO3 relative to total powder as 100% solids). The paste was extruded in 1 / 16" cylinders and dried at 250 °F overnight. The dried extrudates were calcined at 1100 °F for 1 hour with a purge of excess dry air and then cooled to room temperature. Nickel and tungsten were impregnated as described in Example 11.

[0139] Example 13 (Comparative Example)

[0140] Catalyst C

[0141] Example 12 was repeated except that the silica-alumina of Example 3 was used in place of SIRAL-40 HPV.

[0142] Example 14

[0143] Catalyst D

[0144] Example 12 was repeated except that the silica-alumina of Example 5 was used in place of SIRAL-40 HPV.

[0145] Example 15

[0146] Catalyst E

[0147] Example 12 was repeated except that the silica-alumina of Example 7 was used in place of SIRAL-40 HPV.

[0148] Example 16

[0149] Catalyst F

[0150] Example 12 was repeated except that the silica-alumina of Example 9 was used in place of SIRAL-40 HPV.

[0151] The properties of the finished catalysts A through F are summarized in Table 4.

[0152] Table 4 Catalyst Properties and Performance

[0153]

[0154]

[0155] (a)Physical properties determined by the B.E.T. method as described by S. Brunauer, P. Emmett, and E. Teller (J. Am. Chem. Soc. 1939, 60, 309-319).

[0156] (b) Physical properties determined by mercury intrusion porosimetry according to ASTM D4284 at a mercury surface tension of 484 dynes / cm and a mercury contact angle of 140 degrees.

[0157] As shown in Table 4, the finished catalyst made with the co-gel silica-alumina (Catalyst C) has a higher bulk density and lower pore volume as measured by N2physical adsorption and Hg porosimetry, respectively, compared to the catalysts made with the reference silica-alumina (Catalysts A and B). The pore volume of the co-gel silica-alumina increased significantly with the switch of the base precipitant to ammonium carbonate. The increase in the silica-alumina pore volume allowed for the preparation of high pore volume catalysts as shown by Catalysts D, E, and F. The catalysts of the present invention (Catalysts D, E, and F) have a higher pore volume and lower bulk density than either of the reference catalysts (Catalysts A and B).

[0158] Example 17

[0159] Hydrocracking catalyst testing

[0160] The catalysts prepared above were tested under hydrocracking conditions in a single-pass downflow microreactor with a 6 cm 3 of 24 / 40 (US) mesh catalyst. The feedstock used in the testing was a typical hydrocracking hydrocarbon feedstock having the properties listed in Table 5.

[0161] Table 5 Hydrocarbon feedstock properties

[0162] API gravity 31 Sulfur [wppm] 20.2 Nitrogen [wppm] 1.28 ASTM D2887 simulated distillation ]]> ​ Initial boiling point 637℉ 10 wt% 686℉ 30 wt% 770℉ 50 wt% 825℉ 70 wt% 890℉ 90 wt% 987℉ End boiling point 1100℉

[0163] The operating conditions included: reactor pressure of 2000 psig; feed rate of 1.5 h -1LHSV; and a single pass H2flow rate of 5000 SCF H2 / bbl oil. The catalyst bed temperature was varied to cover 60 to 80 wt% conversion of the 700°F+ feed to 700°F- product. The yields of C4- gas, naphtha, and light and heavy fraction components were calculated using ASTM D2887 simulated distillation analysis results. The overall yields and reactor temperature data were interpolated to 70 wt% conversion and summarized in Table 4. Inventive catalysts D, E, and F showed about 2% higher heavy fraction selectivity than the SIRAL-40 reference catalyst (catalyst A). The increased fraction selectivity is a very unexpected benefit of the silica-alumina compositions of the present disclosure. These hydrocracking catalysts with high pore volume and containing large mesopores are expected to perform well, particularly for the conversion of heavy, high molecular weight hydrocarbons.

Claims

1. A process for preparing an amorphous silica-alumina composition, wherein the process comprises the steps of: (a) mixing an aqueous solution of a silicon compound with an aqueous solution of an aluminum compound and an acid, the aluminum compound being an aluminum salt or an alkali aluminate, while maintaining the pH of the mixed solution in the range of 1 to 3, and obtaining an acidified silica-alumina sol; (b) adding to the acidified silica-alumina sol an aqueous solution of a base precipitant and mixing the combination of the aqueous solution and the acidified silica-alumina sol, while maintaining the pH in the range of 6.5 to 7.5, and co-precipitating a silica-alumina slurry, wherein the base precipitant is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, and any combination thereof; wherein steps (a) and (b) are conducted in a closed in-line blender; (c) optionally, hydrothermally aging the silica-alumina slurry to form a hydrothermally aged silica-alumina slurry; and (d) recovering a precipitated solid from the silica-alumina slurry or the hydrothermally aged silica-alumina slurry, wherein the precipitated solid comprises the amorphous silica-alumina composition and crystalline aluminum ammonium carbonate hydroxide in an amount of 1 to 30 weight percent based on the total weight of the silica-alumina composition.

2. The process of claim 1, further comprising: subjecting the silica-alumina composition obtained in step (d) to washing, ion exchange, drying, and / or calcination.

3. The process of claim 2, comprising spray drying the silica-alumina composition obtained in step (d).

4. The process of claim 1, wherein the silicon compound is selected from the group consisting of alkali silicates, silicic acid, colloidal silica, precipitated silica, fumed silica, and any combination thereof.

5. The process of claim 1, wherein the silicon compound is sodium silicate.

6. The process of claim 5, wherein the sodium silicate has a SiO2 / Na2O weight ratio in the range of 2.5 to 3.

5.

7. The process of claim 1, wherein the aqueous solution comprising the silicon compound comprises the silicon compound in an amount ranging from 2 to 15 percent by weight of silicon, expressed as SiO2.

8. The process of claim 1, wherein the aqueous solution comprising the aluminum compound comprises the aluminum compound in an amount ranging from 2 to 25 percent by weight of aluminum, expressed as Al2O3.

9. The process of claim 1, wherein the acid is selected from the group consisting of formic acid, acetic acid, hydrochloric acid, nitric acid, sulfuric acid, and any combination thereof.

10. The process of claim 1, wherein the hydrothermal aging in step (c) is conducted at a temperature of 20 °C to 200 °C for a period of 1 to 6 hours.

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