Use of aluminas as a capture mass for organometallic silicon complexes
Patent Information
- Application Number
- BRPI0704030
- Authority / Receiving Office
- BR · BR
- Patent Type
- Applications
- Current Assignee / Owner
- Publication Date
- 2008-06-03
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Catalysts in catalytic processes are prone to premature contamination and performance degradation due to organosilicon complexes, particularly organic silicon derived from organometallic complexes, which react irreversibly with downstream catalysts, leading to issues like gum formation and reduced activity/selectivity.
Employing aluminas with specific properties, such as high pore volume and surface area, to capture and adsorb organosilicon complexes on their surface through reactive adsorption, thereby preventing contamination.
Aluminas effectively retain organosilicon complexes, maintaining catalyst performance by preventing irreversible contamination and reducing gum formation, thus enhancing catalyst longevity and efficiency.
Abstract
Description
PI0704030Descriptive Report of the Invention Patent for the USE OF ALUMINAS AS A CAPTURE MASS FOR ORGANOMETALLIC SILICON COMPLEXES. The present invention relates to a process employing capture masses for organometallic silicon complexes. Such complexes can be found in liquid or gaseous streams that typically carry a catalyst. If the catalyst is not protected, it can become contaminated and its performance (activity and / or selectivity) will decline prematurely. The feedstock for the invention process can be a portion of gasoline, preferably a portion of gasoline from a cracking unit, and more preferably gasoline derived primarily from a catalytic cracking unit. The treated gasoline can also be a mixture of gasolines from different conversion processes such as cracking, coking or thermal cracking processes, or even gasolines that are directly derived from the distillation of petroleum products. Silicon generally acts as a primary contaminant in a number of catalytic applications (hydrogenation, Prime G+, etc.). Experiments have shown that instead of referring to silicon in general, a distinction should be made between different types of silicon: • Silicon, which is called mineral silicon, is generally the result of the presence of fragments of refractory beads. It is physically present, but does not appear to affect the activity or selectivity of the catalyst of interest. • Silicon, which is commonly called organic silicon, derived from organometallic complexes, can react with a downstream catalyst and irreversibly contaminate it. The upstream addition of antifoaming agents, frequently based on polysiloxanes, appears to play a major role in this phenomenon. We have shown that the use of alumina can efficiently retain organosilicon complexes on its surface by reactive adsorption. We then show that particular aluminas can be used advantageously, namely those demonstrating a superior capture potential for such complexes. Throughout the text, quantities are expressed as a % by weight and ppm by weight. Therefore, the invention relates to a process for capturing organosilicon complexes in the gaseous or liquid phase of a solid containing at least 80% by weight of alumina after calcination at 100°C. The total pore volume (TPV) of alumina is greater than 30 mL / 100 g, preferably greater than 45 mL / 100 g, more preferably greater than 50 mL / 100 g, and even more preferably greater than 55 mL / 100 g. The pore volume fraction found in pores with a diameter of 70 Å or more (hereinafter referred to as V7oa) is greater than 10 mL / 100 g, preferably greater than 15 mL / 100 g, more preferably 25 mL / 100 g, even more preferably greater than 35 mL / 100 g, much more preferably greater than 45 mL / 100 g, or even greater than 55 mL / 100 g. Alumina has a specific surface area greater than 10 m² / g, preferably greater than 20 m² / g, more preferably greater than 30 m² / g up to greater than 50 m² / g or even greater than 70 m² / g. Problems with gum formation resulting from unwanted polymerization can occasionally be observed under certain operating conditions of certain catalysts, and therefore also in their protective trapping mass. For this reason, in a particular implementation of the invention, the specific surface area may be less than 300 m² / g, preferably less than 200 m² / g, and more preferably less than 150 m² / g. The powder used as starting material for the preparation of alumina can be obtained by conventional processes such as gel precipitation processes or by rapid dehydration of an alumina hydroxide such as hydrargillite. The alumina can then undergo optional drying and calcination operations; the latter operation can, for example, be carried out at a temperature between 200°C and 1200°C, preferably between 300°C and 1000°C. Alumina can be in any of its normal forms known to a skilled person: powders, beads, extrudates, compressed material, monolith, etc. Beads and extrudates are preferred. The size of the beads (corresponding to the diameter of the beads) is therefore in the range of 0.5 to 10 mm, preferably in the range of 0.7 to 8 mm, more preferably in the range of 0.8 to 5 mm. Extrudates can be cylindrical or polylobed, solid or hollow in shape. Their size (corresponding to their length) is in the range of 0.5 to 5 mm, preferably in the range of 0.7 to 3 mm. It should be noted that the term size means diameter for beads and length for extrudates. More generally, the term size is applied to the largest dimension of the shape under consideration. When using alumina beads, they can be obtained by molding, by drop freeze-drying, from an aqueous suspension or dispersion of alumina or from a basic aluminum salt solution in the form of an emulsion consisting of an organic phase, an aqueous phase and a surface agent or an emulsifier. Alumina beads can also be obtained by agglomerating alumina powder using rotary techniques such as a rotary pelletizer or a rotary drum. Beads can be obtained with controlled dimensions and pore size distribution, the entirety of which is generally generated during the agglomeration step. Alumina extrudates can be obtained by grinding and then extruding an alumina-based material, such material possibly being obtained by the rapid dehydration of hydrargillite and / or the precipitation of one or more alumina gels. Following formation, alumina can undergo various operations to improve its mechanical properties, such as maturation by maintaining it in an atmosphere with controlled humidity followed by calcination, and then optionally by impregnation of alumina using a solution of one or more organic and / or mineral acids, and hydrothermal treatment in a confined atmosphere. Generally, after these treatments, the alumina is dried and calcined. In a particular embodiment of the invention, alumina can be dulled with one or more elements selected from the group consisting of alkali metals, alkaline earth metals and rare alkaline earth metals. The total weight content of such dulling elements is less than 20% by weight, preferably less than 10% by weight and more preferably in the range of 500 ppm by weight to 5% by weight. The dulling elements can be added before, during and / or after the molding operation. In the case of numbing with a cumulative amount of promoting elements exceeding 5000 ppm by weight, the total pore volume of the adsorbent is greater than 30 mL / 100 g, more preferably greater than 35 mL / 100 g, for a specific surface area greater than 20 m² / g, preferably in the range of 30 to 300 m² / g, more preferably in the range of 30 to 200 m² / g. V70A is greater than 10 mL / 100 g, preferably greater than 15 mL / 100 g, more preferably greater than 25 mL / 100 g, even more preferably greater than 35 mL / 100 g, even more preferably greater than 45 mL / 100 g, or even greater than 55 mL / 100 g. Preferred narcotics are sodium, potassium, calcium, magnesium, and lanthanum. Most preferably, sodium and lanthanum are selected. Most preferably, lanthanum is selected. The following examples illustrate the invention, without, however, limiting its scope. EXAMPLE 1 The reaction was carried out in a 600 mL beaker containing the working solution and protected from the ambient atmosphere by a watch glass encased in paraffin. The solids were studied in their normal state (i.e., without compression) and rested in the beaker on a tripod to prevent any wear from the magnetic stirrer. All experiments were performed at room temperature under atmospheric pressure. The organometallic complex was polymethylhydrosiloxane ((CH3)3SiO[(CH3)HSiO]nSi(CH3)3); it was dissolved in cyclohexane. The reactions were carried out on 6.3 g of solid at ambient temperature and pressure, with a 200 mL solution of cyclohexane containing 5000 ppm by weight of polymethylhydrosiloxane. '25 Each point corresponded to an experiment, with the analysis being performed on the solid by inductively coupled plasma (ICP) using the addition method. ICP was performed as follows: the sample was dissolved by rapid acid attack using a mixture of H2SO4-H3PO4 on a heated plate. The peak selected for ICP measurement was at λ = 288.158 nm. The addition method consisted of making identical samples of the sample to be analyzed, adding to each one increasingly higher concentrations of the element to be examined. An increasingly larger calibration scale was obtained with the same matrix and constant final volume. The sample analysis produced a calibration curve. The intersection of this curve with the abscissa determined the origin of that axis and, as a result, the concentration of the element in the sample. The solution titration was also monitored by gravimetric analysis: the material balances obtained were in agreement. Attack of a solid sample tested in a sealed tube and then gravimetrically analyzed produced a result very close to that given by ICP. Gravimetric analysis of silicon was performed following attack with hydrofluoric acid. By evaporating the solution containing an excess of hydrofluoric acid, all the silicon can be eliminated and the amount of silicon can be determined by difference. The aluminas used in this study are shown in Table I, and the results obtained are given in Figures 1 and 2. TABLE I: Characteristics of the aluminas studied Alumina ABCDEF Shape Beads Beads Beads Extruded Beads Beads Diameter (mm) 2-5 2-4 1.8-3.15 12 2-5 2-5 Specific surface area (m2 / g) 332 73 189 275 321 341 Alumina ABCDEF Total pore volume (mL / 100 g) 39.7 63.9 66.7 64.2 43.2 42.7 V70a (mL / 100 g) 23.4 60.9 62.5 53.5 6.1 30.9 Figure 1 corresponds to the amount of silicon (as a % by weight) analyzed in the solids as a function of the time of exposure to the solution. Figure 2 corresponds to the amount of silicon (as a 5% by weight) analyzed in the solids after 3 hours of reaction. It can be seen from Figure 2 that capture mass E (which does not conform to the invention) had a V70a of 6.1 mL / 100 g, and was less efficient at capturing silicon than capture masses A to D and F (which conform to the invention). EXAMPLE 2: Alumina dulling Aluminas G and H resulted from dry impregnation, after formation, of alumina A with sodium hydroxide and lanthanum nitrate, respectively. After calcination at 450°C, G and H had respective contents of Na2O and La2Ü3 of 2.1% by weight and 0.9% by weight. When tested under the same conditions as the other aluminas (Example 1), after 3 hours of reaction, G and H showed 0.75% by weight and 0.82% by weight of captured silicon, respectively. Alumina I resulted from dry impregnation, after formation, of alumina F with sodium hydroxide. After calcination at 450°C, I had a Na2O content of 1.7% by weight. When tested under the same conditions as the other aluminas discussed above (Example 1), after 3 hours of reaction, I showed 0.91% by weight of captured silicon.
Claims
CLAIMS 1. Process for capturing, in the gaseous or liquid phase, organosilicon complexes in a portion of gasoline by contacting a solid with said portion of gasoline, said solid containing at least 80% by weight of alumina after calcination at 1000°C, said alumina having a total pore volume of more than 30 mL / 100 g, a fraction of the pore volume found in pores with a diameter of 70 Å or more or greater than 10 mL / 100 g and a specific surface area greater than 10 m² / g.
2. Process according to claim 1, wherein the alumina has a total pore volume greater than 45 mL / 100 g.
3. Process according to claim 1 or 2, wherein the alumina has a volume represented by pores with a diameter of 70 Å or more, or greater than 25 mL / 100 g.
4. Process according to one of claims 1 to 3, wherein the alumina has a specific surface area greater than 20 m2 / g.
5. Process according to one of claims 1 to 4, wherein the alumina has a specific surface area in the range of 70 m2 / g to 200 m2 / g.
6. Process according to one of claims 1 to 5, wherein the alumina has a volume represented by pores with a diameter of 70 Å or more or greater than 45 mL / 100 g.
7. Process according to claims 1 to 6, wherein alumina is dulled with one or more elements selected from the group consisting of alkali metals, alkaline earth metals and rare alkaline earth metals, the total amount of said dulling elements being less than 20% by weight.
8. Process according to claim 7, wherein alumina is dulled with one or more elements selected from the group consisting of sodium, potassium, calcium, magnesium and lanthanum.
9. Process according to claim 8, wherein the narcotic is lanthanum.
10. Process according to one of claims 1 to 9, wherein the alumina is in the form of beads or extruded.
11. Process according to claim 10, wherein the alumina is in the form of beads with a size in the range of 0.5 to 10 mm.
12. Process according to claim 10, wherein the aluminum is in the form of extrudates with a size in the range of 0.5 to 5 mm. 1 / 1 Amount of Si in the solid after 3h (%) Amount of Si in the solid (%)