BRPI0900933B1 - CATALYST FOR USE IN FLUID CATALYTIC CRACKING FOR THE PRODUCTION OF LOW AROMATIC HYDROCARBONS - Google Patents

Abstract

catalyst for use in fluid catalytic cracking for the production of low aromatic hydrocarbons. A catalyst for use in fluid catalytic cracking for the production of low aromatic hydrocarbons is described, comprising a matrix of inorganic oxides, preferably silica-alumina, having incorporated at least one doping chemical selected from alkaline and alkaline earth metals, and zero or reduced zeolite concentration.

Description

(54) Title: CATALYST FOR USE IN FLUID CATALYTIC CRACKING FOR THE PRODUCTION OF LOW AROMATIC HYDROCARBONS (51) lnt.CI .: B01J 29/06; B01J 29/80; C10G 11/05 (73) Holder (s): PETROLEO BRASILEIRO S.A. - PETROBRAS (72) Inventor (s): EDISSON MORGADO JUNIOR; MARCO ANTÔNIO SANTOS DE ABREU; WILLIAM RICHARD GILBERT; SÉRGIO AUGUSTO SANTOS RODRIGUES

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CATALYST FOR USE IN FLUID CATALYTIC CRACKING FOR THE PRODUCTION OF LOW AROMATIC HYDROCARBONS

FIELD OF THE INVENTION

The present invention belongs to the field of catalysts for fluid catalytic cracking (FCC) processes, for obtaining hydrocarbons with a low aromatic content. More specifically, it deals with a catalyst based on inorganic oxides, preferably silica-alumina, having alkaline and alkaline earth metals as chemical elements.

BACKGROUND OF THE INVENTION

The Fluid Catalytic Cracking (FCC) process is used to convert high molecular weight liquid hydrocarbons, such as streams from oil refineries obtained from side cuts of vacuum towers, called heavy vacuum diesel, or from the bottom of atmospheric towers , these are called atmospheric residue, or mixtures of these currents, in light fractions of hydrocarbons such as gasoline and liquefied petroleum gas.

The initial objective of the FCC process was to prioritize the production of high-octane gasoline, however the evolution of the fuel market led to an increase in the production of diesel oil and, subsequently, environmental restrictions required the production of fuels with a low aromatic content at the expense gasoline, which required adaptations in the FCC process, either by adjusting the operating conditions, by adapting the existing reactor or to be designed, or by changing the formulation of the catalyst or by combining these actions.

The operational conditions subject to adjustment in FCC processes, with the objective of maximizing the production of middle distillates, in the diesel range, involve:

(i) reducing the reaction temperature;

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(ii) the reduction of the catalyst / oil ratio;

(iii) the reduction in catalytic activity.

Although the implementation of such measures leads to an increase in the production of medium distillates, hydrocarbon streams with a distillation range between 220 ° C and 340 ° C, which are later incorporated into the diesel pool, the high concentration of aromatics in these streams , which reaches more than 80% of the total hydrocarbons present, influence the quality of the diesel, more specifically, reduce its detonation power, evidenced by its low number of cetane, in addition to increasing its density.

The high concentration of aromatics in these hydrocarbon streams comes from the charge or is generated during cracking reactions, mainly due to the catalyst used, zeolites, which favor the formation of aromatics on the catalyst's protonic sites, through complex mechanisms that involve parallel or sequential reactions of oligomerization, cyclization and hydrogen transfer.

In addition to favoring the formation of aromatics, conventional catalysts for FCC processes, more specifically zeolites, still suffer from contamination by metals, a problem that has become critical due to the use of increasingly heavy loads in such processes.

An example of processing extra-heavy oils, with API <15, using FCC, is described in WO 2007/02144, which aims to produce a “cracked” oil with better flow properties, so that it acts as a solvent reducing the viscosity and density of crude oil, enabling its transportation through pipelines.

Contamination and deactivation of the catalyst by metals, in this process, is much more critical and there may be a concentration of metals

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ΛΑ '·, .ο · deleterious (eg nickel and vanadium) two to three times higher than that observed in FCC units that process waste.

Due to the reasons explained above, the use of conventional FCC catalysts in this type of process has two main disadvantages: (1) the limitation of the maximum contaminating vanadium content of the load that the zeolite catalyst Y can support and (2) the fact that conventional catalysts produce cracked oil with a high aromatic content and very low API, requiring a higher percentage of solvent cracked oil in the mixture with the heavy crude to achieve the minimum API specification of the improved oil for transportation in the pipeline.

The greater proportion of solvent cracked oil in the mixture, in turn, causes a greater amount of heavy oil to be processed at the FCC, which leads to an increase in the unit's capacity for the same improved oil production volume, requiring greater investments.

In addition, the maximum vanadium content supported by the conventional zeolitic catalyst requires a relatively higher catalyst replacement, which implies a higher operational cost and complications of a logistical nature in transporting the fresh catalyst to the oil and catalyst improvement unit. discarded from the unit to its final destination.

Similarly, the issue of tolerance to vanadium also applies to the processing of extra-heavy atmospheric waste, which often needs to be mixed with other streams to be processed in FCC units without impairing the operation or reducing the unit's flow throughput.

Therefore, it is evident the need for catalysts for use in fluid catalytic cracking units with greater specificity and robustness, translated into greater selectivity for non-aromatic compounds and

4/12 greater resistance to contaminating metals.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention deals with a catalyst based on inorganic oxides, preferably silica and alumina, with alkaline and alkaline earth metals as doping chemicals.

Such a catalyst makes it possible to produce a low-aromatic medium distillate, with a concentration of aromatics below 70% by weight, and to use conventional processing temperatures.

The catalyst has great resistance to contaminating metals, such as Nickel and Vanadium, when compared to conventional catalysts for FCC processes. This is evidenced by the retention of a higher percentage of its surface area in relation to that achieved for conventional zeolitic catalysts, when subjected to hydrothermal deactivation in the presence of vanadium, with a better preservation of its activity and selectivity when used in FCC processes.

This characteristic makes it particularly desirable for processing extra-heavy loads and optimizing the flow properties of heavy oils.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached FIGURE 1 is a graph illustrating the relationship between the aromatics content in the fraction of medium distillates and the conversion of bottoms, using as catalysts used: Siral 5 (A), Siral 10 (B), Siral 5/2% Na (C) and Siral 10/2% Na (D), conventional FCC catalyst (D) and gamma-alumina based catalyst (F).

The attached FIGURE 2 is a graph illustrating the relationship between the aromatic content in the fraction of medium distillate and the conversion of bottoms, using as catalysts used: SiAI / 1% Na (G); SiAI / 2% Na (H) and SiAI / REF (I), and SiO ₂ / REF (J).

DETAILED DESCRIPTION OF THE INVENTION

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Broadly speaking, the present invention deals with a catalyst, for use in FCC processes, selective to liquid products containing low aromatics and resistant to contaminating metals.

Such a catalyst consists of a matrix of inorganic oxides, preferably silica-alumina, in the form of microspheres, with a SiO2 / AI2O3 ratio between 0.01 and 0.5, preferably between 0.02 and 0.20, having incorporated at least a doping chemical element, preferably an alkaline or alkaline earth metal, in a concentration between 0.1% and 6% by weight of the metal on an elementary dry basis and reduced zeolite content.

The catalyst object of the present invention has a zeolite content of less than 10% by weight, and may also contain inert constituent components, such as clays, in a proportion of less than 40% by weight. The inert constituents have the objective of conferring physical properties, such as density, resistance to friction and particle size distribution, suitable for its use as a catalyst.

The zeolites useful for the present invention are zeolites with pore size ranging from 6 to 8 Â, more specifically z-type Y and ZSM-5.

The silica-alumina useful as a matrix for the catalyst of the present invention can be a commercial silica-alumina, such as, for example, SIRAL-5 and SIRAL-10, both from SASOL, or can be prepared in the form of co-gel. precipitated from silicate solutions and aluminum salt or by mixing separately synthesized silica and alumina suspensions, preferably in the final form of colloidal dispersions (for example, silica and alumina sol).

The doping chemical elements useful for the present invention are alkaline and / or alkaline earth metals, preferably sodium, in a concentration between 0.1% and 6% by weight of the metal on an elementary dry basis, preferably between 1% and 3% in pasta. The purpose of

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addition of such elements is to selectively inhibit some catalytic sites that

H j ίώ R; 2O · • s tended to favor the formation of aromatic compounds. Such% metals can be incorporated into silica-alumina in the preparation stage of the precursor suspension of the catalyst, either in the mixture or in the separate ingredients, prior to drying, or even through post-impregnation steps of the dry material already in the form of microspheres , which may or may not undergo heat treatments before and / or after impregnation.

The catalyst described here can be prepared in the form of microspheres using conventional equipment for the manufacture of FCC catalysts, in particular, through the use of an atomization drying system ("Spray-Dryer").

The selectivity of liquid products with a low aromatic content of the catalyst proposed here, in comparison with conventional (zeolitic) catalysts, is achieved by controlling the acidity and / or the basicity presented by it, which basically depends on the relative proportion of its products. main constituents, more specifically the concentration of doping chemical elements, such as alkali metals and alkaline earth metals.

Some of the effects of this lower aromatic content present in the cracking products obtained are the increase in the number of cetane and the reduction of the apparent density of the LCO fraction, which leads to an improvement in the quality of the detonating power in the diesel engine in the hydrotreating products of this fraction. In addition, there is also a reduction in the octane of the gasoline fraction. Such effects are illustrated by Table 3 of example 4.

In addition to providing a reduction in the aromatic content of cracking products in FCC processes, the catalyst presented here has greater resistance to deactivation by contaminating metals than conventional FCC catalysts. This can be proven by the retention of its specific area in more than 70%, whereas in

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> -? Conventional FCC catalyst fls retention is around 25% of your specific area, as shown in Table 1 of example 3.

Although such catalysts have less catalytic activity, when compared to non-doped silica-alumina catalysts, this fact can be compensated by modifying the cracking reactor in order to allow longer contact times between the catalyst and the oil, as taught by the patent. PI 0800236-3, fully incorporated as a reference, without prejudice to the selectivity of aromatics.

The present invention will be illustrated below by Examples, which should not be considered as limiting.

EXAMPLE 1

This example illustrates the simulation of the deactivation of catalysts based on commercial silica-alumina, containing Na in concentrations of 2% by mass, after its use in FCC processes, and the comparison of its performance in relation to conventional catalysts.

Two silica-aluminum powder supplied by SASOL with the commercial name of SIRAL-5 and SIRAL-10 with an S1O2 / AI2O3 ratio of 0.05 and 0.10, respectively, were impregnated by the pore volume method with sodium nitrate solution. for a final content of 2% by mass Na.

The catalysts with and without doping with sodium Siralõ (A), SiraHO (B), Siral5 / 2% Na (C) and Siral10 / 2% Na (D)) were subjected to hydrothermal treatment with 100% steam at 788 ° C for 5h in a fixed bed in order to simulate the catalyst deactivation caused in an FCC unit. A conventional zeolitic commercial catalyst (E) and commercial gamma-alumina (F) were used as a reference and also subjected to the same hydrothermal treatment.

All catalysts were tested in an FCC reactor using a fixed fluidized bed unit (ACE®) processing a load of vacuum diesel at 540 ° C, and different injection times of

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load, thus simulating different catalyst / oil (CTO) ratios for each catalyst. The concentration of aromatics in the fraction of ^ή middle distillates was determined by two-dimensional chromatography on the liquid product. It can be seen in Figure 1 that the two preferred catalysts of the present invention had aromatics content, significantly lower when compared to the references (E and F), for the same fund conversion (conversion of 100% in mass subtracted from the percentage of compounds distilling at temperatures above 340 ° C).

EXAMPLE 2

This example illustrates the comparison between the activity of catalysts based on silica alumina, with a concentration of 1% to 2% by mass of Na, and that of non-doped catalysts based on silica-alumina.

A precipitate of aluminum hydroxide (boehmite) was synthesized by neutralizing aluminum salts under controlled conditions of reaction and aging, filtered and washed to remove contaminating ions, and subjected to peptization with diluted nitric acid to form a colloidal alumina dispersion. . To this freshly prepared dispersion was added a commercial silica sol (Eka®) resulting in a viscous suspension, whose relative composition on a dry basis was SiO ₂ / AI ₂ O ₃ = 0.10. This suspension was processed by spray drying to obtain a silica-alumina powder with physical properties (density, resistance to friction and particle size distribution) similar to those of a conventional FCC catalyst. The product was calcined at 550 ° C for 3 hours and divided into three parts. One was impregnated with 1% by weight of sodium, the other with 2% by weight of sodium and the last was not impregnated, generating the samples respectively SiAI / 1% Na (G); SiAI / 2% Na (H) and SiAI / REF (I).

These samples were submitted to hydrothermal treatment with

100% steam at 788 ° C for 5h in a fixed bed in order to simulate the deactivation of the catalyst. An inert silica powder with a low specific area (SiO ₂ / REF (J)) was also used as a reference and also and submitted to the same

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hydrothermal treatment. The four materials, after the treatment above, were compared as to their activity. The two silica-alumina catalysts doped with sodium, according to the teaching of the present invention, showed greater activity than silica and less activity than the reference of non-doped silica-alumina, however they showed lower aromatic content for the same conversion in relation to the two. references, as shown in Figure 2.

EXAMPLE 3

This example illustrates the degree of deactivation of the 2% Na silica-alumina based catalyst of example 2 caused by the presence of contaminating metals, such as nickel and vanadium.

A sample of the SiAI / 2% Na catalyst tested in example 2 was separated into two parts and each part subjected to impregnation with nickel and vanadium following the classic Mitchell protocol resulting in the following degrees of contamination:

(i) 500 mg / kg of Ni + 500 mg / kg of V;

(ii) 1500 mg / kg of Ni + 1500 mg / kg of V. Similarly, the catalyst based on silica-alumina prepared in example 2 in its doped form was impregnated with a massive dose of metals 2500 mg / kg Ni + 7500 mg / kg V, as well as a conventional zeolitic catalyst used as a reference.

All these impregnated catalysts were subjected to hydrothermal treatment and their specific BET area values were determined before and after deactivation in order to measure the resistance against metals due to the retention of the textural property.

In Table 1 we have presented the effect of nickel and vanadium contamination, expressed in terms of the reduction of the specific area of the catalysts after the hydrothermal deactivation process.

The catalysts of the present invention SiAI and SiAI / 2% Na have a specific area around 300 m ² / g after being deactivated in any

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vanadium content, resulted in values in the order of 200 m ² / g / ^ characterizing a relatively high area retention of almost 70%.

In contrast, the conventional FCC catalyst, whose original specific area is 310 m ² / g results after deactivation in the presence of a high vanadium content in an area of only 76 m ² / g (25% retention) with drastic loss of area micropores relative to the zeolitic component.

TABLE 1 CATALYST Ni (mg / kg) V (mg / kg) BET area (m ² / g) after deactivation SiAI with 2 wt% Na 0 0 200 SiAI with 2 wt% Na 500 500 199 SiAI with 2 wt% Na 1500 1500 197 SiAI 2500 7500 200 Zeolitic Catalyst 2500 7500 76

Such results demonstrate the technical advantages of the catalysts described here, since it leads to greater resistance to deactivation caused by contaminating metals.

EXAMPLE 4

This example illustrates the catalytic cracking of a diesel with 19 ° API, varying the spatial velocity employed, here defined as the flow rate divided by the weight of catalyst in the reactor bed.

A silica-alumina-based catalyst doped with sodium 15 (catalyst A), prepared according to the method described in example 1, was previously subjected to hydrothermal treatment, with 100% steam at

788 ° C for 5h in fluidized bed, in order to simulate its deactivation.

Catalyst A was tested in a fluidized bed pilot unit, using a 19 ° API diesel fuel, temperature of 530 ° C, catalyst / oil ratio (CTO) of 3.4 and a spatial speed of 0.3h ' ¹ .

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A conventional equilibrium catalyst (Catalyst B), from a refinery, was taken as a reference and evaluated in a pilot cracking unit in riser, using the same load, temperature of 540 ° C, catalyst / oil ratio of 7.5 and spatial speed of the order of 50 h ' ¹ .

Table 2 shows the yields obtained for each fraction of interest.

TABLE 2 YIELD CATALYST B CATALYST A Fuel gas,% mass 4.1 6.0 LPG ¹ ,% by weight 19.3 10.9 Naphtha (C5-221 ° C),% by weight 42.3 30.3 LCO ² (221-343 ° C),% by weight 16.7 25.3 OD ³ (343 ° C +),% mass 13.6 21.1 Coke,% dough 4.0 6.4 1 Liquefied petroleum gas 2 Light recycling oil 3 Decanted oil

Such results show the characteristics of the catalyst object of such invention, since the yields for fuel gas, LCO and OD of the cracking process using catalyst A were higher, while the yields of gasoline and LPG were lower, when compared to the process using the reference catalyst (catalyst B).

Table 3 shows the properties that determine the quality of some of these fractions. For naphtha its octane (MON- number of motor octane) was determined, for LCO (light recycle oil) its cetane number and density 12/12 'xV

relative quality (d20 / 4).

TABLE 3 CATALYST B CATALYST A MON GC naphtha 87 73 Cetano LCO 20 29 d20 / 4 LCO 0.943 0.907

The reduction in the apparent density and the increase in the number of cetane in the LCO, in relation to the reference, in addition to the strong reduction in the octane of gasoline, are consequences of the reduction in the aromatics content provided by the sodium doped catalyst (catalyst A).

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Claims (5)

1- CATALYST FOR USE IN FLUID CATALYTIC CRACKING FOR THE PRODUCTION OF LOW HYDROCARBONS AROMATICITY, characterized by comprising an inorganic oxide matrix, preferably silica-alumina, in the form of microspheres, with a SÍO2 / AI2O3 ratio between 0.01 and 0.5, having incorporated at least one alkali metal in concentration between 1% and 3 % by weight of the alkali metal on an elementary dry basis and zeolite concentration below 10% by weight. 2- Catalyst according to claim 1, characterized in that the SiO2 / AI2O3 ratio is preferably in the range of 0.02 to 0.20. Catalyst according to claim 1, characterized in that the concentration of zeolite is preferably zero. 4- Catalyst according to claim 1, characterized in that it has additionally incorporated inert ingredients in a proportion of less than 40% by mass. Catalyst according to claim 1, characterized in that the alkali metal is preferably sodium. 1/1