BRPI0900933A2 - catalyst for use in fluid catalytic cracking for the production of low aromatic hydrocarbons - Google Patents

Abstract

CATALYST FOR 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 which comprises a matrix of inorganic oxides, preferably silica-alumina having incorporated at least one dopant chemical chosen from alkaline and alkaline earth metals, and zero or reduced zeolite concentration.

Description

CATALYST FOR CATALYTIC CRACKING USE FOR THE PRODUCTION OF LOW AAROMATIC HYDROCARBONS

FIELD OF INVENTION

The present invention belongs to the field of catalytic fluid catalytic cracking (FCC) process catalysts for obtaining low aromatic hydrocarbons. More specifically, it is a catalyst based on inorganic oxides, preferably desilyl alumina, having alkaline earth alkaline metal metals as dopants.

BACKGROUND OF THE INVENTION

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

The initial objective of the FCC process was to prioritize high-octane gasoline production, but the evolution of the fuel market led to the appreciation of diesel oil production and later, environmental restrictions demanded the production of low-aromatic fuels over gasoline. which required adaptations in the FCC process, either by adjusting operating conditions, by adapting the existing or to be designed reactor, by changing the catalyst formulation or by combining these actions.

Adjustable operating conditions in FCC processes to maximize the production of middle distillates in the dodiesel range involve:

(i) reducing the reaction temperature, (ii) reducing the catalyst / oil ratio;

(iii) the reduction of catalytic activity.

Although the implementation of such measures leads to an increase in the production of medium distillates, hydrocarbon streams with a distillation range of 220 ° C to 340 ° C, which are later incorporated into the diesel pool, the high aromatic concentration of these streams, which is expected to occur. Exceeding 80% of the total hydrocarbons present, influences the quality of diesel, more specifically, decrease its detonation power, verified by its low cetane number, besides increasing its density.

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

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

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

The contamination and deactivation of the catalyst by metals in this process is much more critical and there may be a concentration of two or three times higher metals (eg nickel and vanadium) observed in FCC units that process waste.

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

The higher proportion of solvent cracked oil in the mix, in turn, causes a larger amount of heavy oil to be processed in the FCC, which leads to increased unit capacity for the same improved oil production volume, requiring higher investments.

In addition, the maximum vanadium content supported by conventional catalytic catalytic catalyst requires relatively higher catalyst replacement, which implies higher operational cost and logistical orderly complications in transporting the fresh catalyst to the oil-improving unit and the unit's discarded catalyst. final destiny.

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

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

SUMMARY OF THE INVENTION

Broadly speaking, the present invention is a catalyst based on inorganic oxides, preferably silica and alumina, having dopant chemical elements as alkali and alkaline earth metals.

Such catalyst makes it possible to produce a medium distillate of low aromaticity with aromatic concentration of less than 70% by mass and the use of conventional processing temperatures.

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

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

BRIEF DESCRIPTION OF DRAWINGS

The accompanying FIGURE 1 is a graph illustrating the relationship between the aromatic content in the average distillate fraction and the background conversion, as catalysts used: Siral 5 (A), Siral 10 (B), Siral 5/2% Na (C ) eSiral 10/2% Na (D), conventional FCC catalyst (D) and gamma-alumina base catalyst (F).

The accompanying FIGURE 2 is a graph illustrating the relationship between the aromatic content in the middle distillate fraction and the background conversion, as catalysts used: SiAI / 1% Na (G); SiAI / 2% Na (H) and SiAI / REF (I) 1 and Si02 / REF (J).

DETAILED DESCRIPTION OF THE INVENTION Broadly, the present invention is directed to a catalyst for use in FCC processes which is selective to low aromatic metal products and resistant to contaminant metals.

Such a catalyst consists of a matrix of inorganic oxides, preferably silica-alumina, in the form of microspheres, having a SiO2 / Al2 O3 ratio of 0.01 to 0.5, preferably 0.02 to 0.20, having at least one element incorporated. doping chemical, preferably an alkaline or alkaline earth metal, in a concentration between 0.1% and 6% by weight of the metal on an elemental dry basis and reduced dezeite content.

The catalyst object of the present invention has a zeolite content of less than 10 wt% and may also contain inert constituent components such as clays in a proportion of less than 40 wt%. Inert constituents are intended to impart physical properties, such as density, frictional resistance and particle size distribution, suitable for use as a catalyst.

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

The silica alumina useful as a matrix for the catalyst of the present invention may be a commercial silica alumina such as SASOL-5 and SIRAL-10, both from SASOL, or may be prepared as a co-precipitated gel of solutions. of silicate and aluminum salt or by the mixture of separate synthesized silica and alumina suspensions, preferably in the final form of colloidal dispersions (eg 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 dry basis, preferably between 1% and 3% by weight. The purpose of the addition of such elements is to selectively inhibit some catalytic sites that would tend to favor the formation of aromatic compounds. Such metals may be incorporated into the silica alumina in the preparation stage of the catalyst precursor suspension, either in the mixture or in the separate ingredients, prior to drying, or through dry matter post-impregnation steps already in the form of microspheres. undergo or not heat treatment before and / or after impregnation.

The catalyst described herein may be prepared in the form of microspheres using conventional FCC1 decatalyst fabricators in particular through the use of a Spray-Dryer system.

The selectivity to low aromatic liquid products of the catalyst proposed here, compared to the conventional (zeolitic) catalysts, is achieved through the control of acidity and / or dabasicity presented by it, which basically depends on the relative proportion of its main constituents, more specifically the concentration of doping chemical elements such as alkali metals and alkaline earths.

Some of the effects of this lower aromatic content present in cracking products obtained are increased cetane number and reduced bulk 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 to this, there is also a reduction in the gasoline fraction's octane rating. 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 herein has resistance to deactivation by contaminating metals superior to conventional FCC catalysts. This can be proven by retaining their specific area by over 70%, while in conventional FCC catalysts the retention is around 25% of their specific area, as illustrated in Table 1 of Example 3.

Although such catalysts have lower catalytic activity when compared to undoped silica-alumina catalysts, this fact can be compensated by modifying the cracking reactor so as to allow longer contact times between catalyst and oil, according to Pl 0800236-3 , fully incorporated by reference, without prejudice to the selectivity to aromatics.

The present invention will be illustrated below by Examples, which are not to be construed as limiting.

EXAMPLE 1

This example illustrates the simulation of deactivation of commercial silica-alumina-based catalysts containing Na at 2 wt.% Concentrations after their use in FCC processes, and comparing their performance against conventional catalysts.

Two silica alumina powders supplied by SASOL with the commercial name of SIRAL-5 and SIRAL-10 with Si02 / Al203 ratio of 0.05 and 0.10, respectively, were impregnated by the sodium nitrate solution pore volume method to end of 2% mass.

Siral5 (A), SiraMO (B), Siral5 / 2% Na (C) and Sirall0 / 2% Na (D) sodium doped and non-doped catalysts were subjected to 100% steam hydrothermal treatment at 788 ° C for 5h in a fixed bed to simulate catalyst adhesion caused in FCC unit. A conventional zeolitic commercial catalyst (E) and a commercial gamma alumina (F) were used as reference and also subjected to the same hydrothermal treatment.

All catalysts were tested in an FCC reactor using a fluidized fixed bed unit (ACE®) processing a vacuum gas oil charge at 540 ° C and different discharge injection times, thus simulating different catalyst / oil ratios (CTO) for each catalyst. The concentration of aromatics in the middle distillate fraction was determined by two-dimensional chromatography on the liquid product. It can be seen from Figure 1 that the two preferred catalysts of the present invention had significantly lower aromatic content when compared to references (E and F) for the same deep conversion (100% mass conversion minus the decomposed percentage that distills at higher temperatures). at 340 ° C).

EXAMPLE 2

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

An aluminum hydroxide precipitate (boehmite) was synthesized by neutralizing aluminum salts under controlled reaction and aging conditions, filtered and washed to remove contaminating ions, subjected to dilute nitric acid peptide formation 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 dry basis was Si02 / Al203 = 0.10. This suspension was processed by spray drying to obtain a silica alumina powder with physical properties (density, frictional resistance 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 wt.% Sodium, the other with 2 wt.% Sodium and the last was not impregnated, respectively generating the SiAI / 1% Na (G) samples; SiAI / 2% Na (H) and SiAI / REF (I).

These samples were hydrothermally treated with 100% steam at 788 ° C for 5h in a fixed bed to simulate the catalyst deactivation. A low specific area inert silica powder (Si02 / REF (J)) was also used as a reference and also subjected to hydrothermal treatment. The four materials after the above treatment were compared for their activity. The two sodium-doped silica-alumina catalysts, according to the teaching of the present invention, showed higher activity than silica and lower activity than undoped silica-alumina reference, but 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-allylic-alumina-based catalyst of Example 2 caused by the presence of contaminating metals such as nickel and vanadium.

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

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

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

All of these impregnated catalysts were hydrothermally treated and their specific area BET values determined before and after deactivation in order to measure metal resistance as a function of retention of textural property.

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

The catalysts of the present invention SiAI and SiAI / 2% Na with specific area around 300 m2 / g and after deactivation in any vanadium site resulted in values of the order of 200 m / g, featuring a relatively high area retention of almost 70%. %.

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

TABLE 1

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Such results demonstrate the technical advantages of the catalysts described herein as they lead to greater resistance to deactivation caused by contaminating metals.

EXAMPLE 4

This example illustrates the catalytic cracking of a 19 ° API diesel, varying the spatial velocity employed, defined herein as the charge depth divided by the catalyst weight in the reactor bed.

A sodium doped silica-alumina-based catalyst (catalyst A) prepared according to the method described in example 1 was previously hydrothermally treated with 100% steam at 788 ° C for 5h in a fluidized bed to simulate their deactivation.

Catalyst A was tested in a fluidized bed pilot unit using a 19 ° API1 diesel oil at a temperature of 530 ° C, a catalyst / oil ratio (CTO) of 3.4 and a spatial velocity of 0.3h1. An equilibrium catalyst Conventional (Catalyst B) from a refinery was taken as a reference and evaluated on a riser cracking pilot unit, employing the same load, temperature 540 ° C, catalyst / oil ratio 7.5 and spatial speed of the order of 50 h "

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

TABLE 2

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

Table 3 shows the quality-determining properties of some of these fractions. For naphtha, its octane number (motor octane number) was determined, for LCO (light recycle oil) its cetane number and relative density (d20 / 4) were determined.

TABLE 3

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The reduction in bulk density and the increase in the Cet1 cetane number relative to the reference, in addition to the strong reduction in gasoline octane, are a consequence of the reduction in the aromatic content provided by the sodium doped catalyst (catalyst A).

Claims (11)

1.- CATALYZER FOR USE IN CATALYTIC FLUID CRACKING FOR THE PRODUCTION OF LOW AROMATIC HYDROCARBONS, characterized in that it comprises an inorganic oxide matrix, preferably silica-alumina, in the form of microspheres, having a S02 / AI203 ratio between 0.01 and 0.5, having incorporated at least one doping chemical element, having a concentration of between 0.1% and 6% by weight of the doping chemical element on an elemental dry basis and a zeolite concentration of less than -10% by weight. Catalyst according to claim 1, characterized in that the zeolitate has a pore size ranging from 6 to 8 A. Catalyst according to Claim 1, characterized in that the SiO2 / Al2 O3 ratio is preferably in the range 0.02 to 0.20. Catalyst according to Claim 1, characterized in that the zeolite concentration is preferably zero. Catalyst according to Claim 1, characterized in that it has traditionally incorporated inert ingredients in a proportion of less than 40% by mass. Catalyst according to Claim 5, characterized in that the inert ingredients are preferably clays. Catalyst according to Claim 1, characterized in that the doping chemical element is preferably an alkaline or alkaline earth metal. Catalyst according to Claim 7, characterized in that the alkali metal is preferably sodium. Catalyst according to Claim 1, characterized in that the concentration of the doping chemical element in the elemental dry base is preferably between 1% and 3% by mass. Catalyst according to Claim 1, characterized in that the asylum-alumina is prepared in the form of co-precipitated gel, silicate desolutions and aluminum salt. Catalyst according to Claim 1, characterized in that the asylum-alumina is prepared by mixing separately synthesized silica and alumina suspensions, preferably in the form of colloidal dispersions.