WO2016054702A1

WO2016054702A1 - Additive for reducing sox gas emission in hydrocarbon fluid catalytic cracking units

Info

Publication number: WO2016054702A1
Application number: PCT/BR2014/000364
Authority: WO
Inventors: Eliana CARMO DE SOUZA; Lam Yiu Lau; William Richard Gilbert; Rodolfo Eugênio RONCOLATTO; Eliana Bernadete CASTRO MATTOS; Maria Luisa Aleixo GONÇALVES; Marcelo Maciel Pereira; Bianca Guatiguaba DE OLIVEIRA
Original assignee: Petróleo Brasileiro S.A. - Petrobras; Universidade Federal Do Rio De Janeiro - Ufrj
Priority date: 2014-10-08
Filing date: 2014-10-08
Publication date: 2016-04-14
Also published as: BR112015010500A2; BR112015010500B1

Abstract

The present invention provides additives for reducing SO_x emission in hydrocarbon fluid catalytic cracking units, prepared on the basis of an alumina substrate, with a large surface area of at least 150 m²/g and a large pore volume of at least 0.25 cm³/g, and containing calcium in a concentration of at least 5% in the form of calcium oxide and an oxyreduction promoter in a concentration range from 1 to 5% m/m in the form of the oxide thereof.

Description

ADDITIVES FOR REDUCING SOx GAS EMISSIONS IN FLUID CATALYTIC CRACKING UNITS

HYDROCARBONS

FIELD OF INVENTION

The present invention relates to additives for reducing SOx-type pollutant gas emissions in hydrocarbon fluid catalytic cracking units (FCC), more specifically to additives prepared from calcium oxides and a redox promoter dispersed on a carbon support. high pore volume.

BACKGROUND OF THE INVENTION

The fluidized catalytic cracking (FCC) process stands out in a refinery for turning heavy fractions of petroleum into high value-added products, notably gasoline. The FCC catalyst, consisting of zeolite Y, active alumina matrix, synthetic silica matrix and inert kaolin matrix, is the compound responsible for load cracking and product yield.

The main components of the FCC industrial unit are the riser, reactor where the cracking reactions occur, generating the products, and the regenerating vessel, where the spent catalyst is burned to eliminate coke and metallic contaminants deposited on its surface. After regeneration, the catalyst is reinjected in the riser for a new reaction cycle.

During the burning of coke, contaminant sulfur from the cargo is also oxidized, releasing gases S0 ₂ and S0 ₃ , hereafter referred to as SOx gases. The emission of SOx is potentially harmful to the environment and human health by causing acid rain and the formation of particulate matter in the atmosphere. In Brazil and worldwide, environmental regulators impose restrictive standards on industrial and vehicular SOx emissions.

With this, it becomes critical to control emissions from a FCC, as this unit is the largest single S0 ₂ emitter of a refinery, contributing approximately 17% of total pollutant emissions.

One technique adopted for controlling SOx emissions is the physical mixing of additives to the FCC base catalyst in a ratio of 0.5% to 3% by weight. Additives are specific catalytic systems for capturing SOx gases during spent catalyst firing, reducing the atmospheric emission of the contaminant.

Commercial SOx emission abatement additives consist of magnesium oxide in the form of spinel or hydrotalcite. Spinel contains mixed oxides of MgO and Al ₂ 0 ₃ with the structure MgAI ₂ 0 ₄ , while hydrotalcites are magnesium and aluminum hydroxycarbonates belonging to the class of compounds called anionic clays of lamellar structure and formula [Mg ₆ Al ₂ (OH ) ₁₆ ] (C0 ₃ ) .4H ₂ 0. Oxidation reduction promoter, preferably cerium oxide - Ce0 ₂ , which is an active metal phase impregnated to the support with the function of favoring the reactions involved in the process, is also necessary. , such as the oxidation of S0 ₂ to S0 ₃ .

The mechanism of action of the additive involves two steps. Firstly, in the regenerator at approximately 710 ° C and with the presence of oxygen, the additive promotes the oxidation of S0 ₂ to S0 ₃ and the formation of magnesium sulfate, MgS0 ₄ , according to reactions 1.1 to 1.3:

Regenerator reactions:

S (coke) + 0 ₂ → S0 ₂ (1.1)

50 ₂ + 0 ₂ → S0 ₃ (1.2)

50 ₃ + MgO → MgSO ₄ (1.3)

Then, the formed sulfate proceeds to or together with the regenerated catalyst. The riser presents a reductive environment due to the H ₂ molecules and light hydrocarbons from the cracking of the charge. In this condition, sulfate must be reduced to H ₂ S and MgO (reaction 1.4) in order for H ₂ S to be released and, in the presence of the other FCC products, lead to appropriate treatment. The additive in turn becomes recovered to return to the regenerator and start a new sulfur capture and desorption cycle. There may also be MgO regeneration with release of S0 ₂ (reaction 1.5). Another possible mechanism is the formation of the riser MgS sulfide (reaction 1.6) and its subsequent conversion to MgO in the rectification step (reaction 1.7):

Reactions in the riser.

MgSO ₄ + 4H ₂ → MgO + H ₂ S + 3H ₂ 0 (1.4)

MgSO ₄ + H ₂ → MgO + S0 ₂ + H ₂ 0 (1.5)

MgSO ₄ + 4H ₂ → MgSO + 4H ₂ 0 (1.6)

Rectifier Reaction:

MgS + H ₂ 0 → MgO + H ₂ S (1.7)

To comply with these assumptions, the additive must form a sulfate that is stable under the oxidizing conditions of the regenerator but is unstable under the reducing conditions of the riser. Calcium oxide binds more strongly to S0 ₃ which MgO so that the substitution of MgO for CaO increase additive efficiency for storing SOx. Moreover, the magnesium replacement by calcium can reduce the final cost of the additive, as Calcium oxide is found in the market with lower cost as compared to magnesium oxide.

However, the use of CaO is strongly contraindicated in the literature, on the grounds that the resulting calcium sulfate, precisely because it is very stable, does not break down in the riser, drastically limiting the useful life of the additive. Commercial additives for use in FCC units do not contain calcium in their composition.

The use of calcium oxide for SOx treatment reported in the literature concerns dolomite (CaC0 ₃ .MgC0 ₃ ) and limestone (CaC0 ₃ ) minerals, used as sulfur absorbers in burning plants. coal for energy production. In the past decades, precisely because of the stability of reaction products and the low cost of raw materials, spent pads could simply be discarded. However, due to stricter environmental standards, the step of regeneration of the additive has become necessary where waste material treated with a reducing gas such as hydrogen, methane or carbon monoxide at temperatures above 1000 ° C is required. nonexistent in the FCC unit.

US 4,529,502 explores the use of alumina supported CaO as an additive for UFCC. In order to circumvent the problem of deactivation of the additive, the patent describes the need to install an additional reactor between the regenerator and the riser precisely to decompose CaS0 ₄ at elevated temperatures and presence of reducing gas. This would make the SOx removal process very expensive.

MX patent application 2009004594A claims alkaline earth metal additives including magnesium and calcium and alumina-supported transition series metals. However, calcium is not the main component of the additive. Oxides such as calcium and vanadium are impregnated on alumina together with magnesium oxide, and there is no further advantage of such compositions compared to that using mainly magnesium.

US 2008/0227625 discloses NOx reduction additives comprising an alkaline or alkaline earth metal (preferably calcium and / or manganese), phosphorus, and transition metals in a support. The preferred composition of the additive comprises: CaO (3 to 6 wt%), P ₂ 0 ₅ (3 to 5 wt%), MOx (1 to 4 wt%), where M is a transition metal and x varies with the oxidation state of the metal, supported by alumina (85% to 93% by mass).

In this case, the presence of phosphorus, more specifically phosphates, would facilitate the formation and reduction of alkali metal sulfates or alkaline earth by the formation of highly dispersed alkaline / earth alkaline metal phosphate surface or monolayer coatings on the alumina support, preventing the formation of alkaline earth metal spinel. Although it promotes the stabilization of alkaline / alkaline earth metal sulphates, the presence of phosphorus in the additive formulation leads to the inhibition of the capture of SO ₃ by calcium oxide, as can be seen from the analysis of the examples presented.

Thus, a catalytic system containing calcium as a main component is still unheard of, where there is no need to incorporate other elements, such as magnesium, or specific crystalline structures (spinel), capable of reducing SOx-type pollutant gas emissions. in hydrocarbon fluid catalytic cracking units.

SUMMARY OF THE INVENTION

In oil refining, the control of SOx-type gas emissions in fluid catalytic cracking process units - FCC can be advantageously performed by mixing additives into the circulation catalyst inventory.

Such additives comprise calcium oxide particles and an oxirreduction promoting agent, where calcium oxide acts as a sulfur storage agent, such particles being highly dispersed, in the form of small crystallites, on the high pore volume support.

The product obtained has high sulfur capture efficiency during the regeneration step of FCC spent catalysts and is susceptible to reduction of sulfate particles absorbed on its surface under r / ser conditions, ensuring additive regeneration and a longer time. campaign

Thus, the present invention provides additives prepared from of an alumina-type support having a high surface area of at least 150 m ² / g and a high pore volume of at least 0,25 cm ³ / g incorporating:

(a) calcium in the form of calcium oxide at a concentration of at least 5%.

(b) an oxide reduction promoter, in the form of its oxide, in the concentration range between 1 and 5% w / w.

Mixing such an additive to the circulation catalyst inventory in an FCC unit provides control of SOx pollutant emissions while maintaining the unit's product conversion and yield levels under fluid catalytic cracking conditions.

Therefore, the invention addresses the use of additives in admixture with the circulation catalyst inventory in an FCC process, being applicable to hydrocarbon-containing fillers; Advantageously, the SOx emission concentrations in the regenerator effluent gas are controlled, providing the reduction of atmospheric pollutants in the oil refining.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 illustrates diffractograms of two samples: (1a) Gamma-alumina support; (1b) CA1V additive: 10% w / w CaO and 3% vanadium incorporated into gamma alumina.

Figure 2 illustrates the Raman spectra of two samples: (3a) Analytical grade anhydrous calcium sulfate reagent - CaS0 ₄ PA, for comparison; (3b) CA1S: 10% w / w CaO incorporated in gamma-alumina and sulfated; (3c) CAV1S: 10% w / w CaO and 3% w / w vanadium incorporated into gamma-alumina and sulfated.

Figure 3 illustrates the programmed temperature thermal reduction curves of three samples: (4a) CAV1S: 10% w / w CaO and 3% w / w vanadium incorporated in gamma-alumina sulfated; (4b) CA1S: 10% w / w CaO incorporated in gamma-alumina and sulfated; (4c) MF1S: Physical Mix 10% w / w CaO PA and 90% sulfated gamma-alumina.

DETAILED DESCRIPTION OF THE INVENTION

Broadly, the invention deals with additives applicable to the control of SOx emissions in the effluent flue gas of the fluid catalytic cracking process regenerator - FCC.

Such additives consist of a high surface area support of at least 150 m ² / g and a high pore volume of at least 0.25 cm ³ / g, incorporating: calcium as calcium oxide, with a concentration of at least 5% and preferably 10%; and an oxide reduction promoter, in the form of its oxide, in the concentration range between 1 and 5% w / w.

The high pore volume of the support is necessary to enable the high dispersion of calcium oxide particles and the oxireduction promoter in it. The high dispersion of calcium and the redox promoter on the support enables the S0 ₃ present in the regenerating vessel and the reducing gases present in the FCC unit riser to have greater accessibility to the sites containing the metals, which favors the extension of the reactions involved. in the process. Consequently, the high pick-up factor (PUF) is achieved, ie the molar ratio between captured S0 ₃ and existing CaO and the required reduction of CaS0 ₄ under existing conditions in a fluid catalytic cracking unit riser.

Among the high porous volume supports useful for the present invention we can mention:

(i) gamma alumina;

(ii) high pore alumina type catalysts containing an inert matrix. An example is the catalyst comprising 90% low crystallinity alumina and 10% kaolin, also tested in the art. present invention, named VCLA-kaolin 90:10 .. The crystallinity of alumina is defined in terms of crystal size. Alumines containing 4.5nm crystal size are considered to have low crystallinity. Crystal sizes of 7.5 nm and 15 nm, for example, refer to medium and high crystallinity aluminas, respectively.

In the case of gamma alumina, it is prepared by calcining hydrated aluminum hydroxide (Boehmita) at 500-650 ° C, preferably at 600 ° C, for up to 5 hours, preferably one hour, in the presence of air. Alumina is obtained with high surface area, approximately 200 m ² / g and high pore volume, approximately 0.35 cm ³ / g.

The VCLA-90:10 kaolin support is prepared from alumina peptization and subsequent addition of kaolin. The matrix thus obtained has a surface area of approximately 290 m ² / g and a pore volume of approximately 0.35 cm ³ / g.

For the preparation of the additives, an active phase comprising calcium, preferably by the pore volume impregnation method, in the form of their respective salts, such as sulfate, chloride or nitrate, preferably nitrate, is incorporated into the support first. drying at 100 ° C for 1 to 3 hours, preferably one hour.

Next, an oxireduction promoting metal such as iron, copper, zinc, chromium, manganese, and especially vanadium, preferably 3% w / w vanadium is incorporated.

The incorporation of the transition metal is preferably carried out by the pore volume impregnation method in the form of their respective salts, such as sulfate, chloride or nitrate, preferably nitrate.

For the vanadium impregnation _^ metavanadato.de.amônio.e vanadila oxalate salts are preferably employed. With these reagents, vanadium incorporation can be performed in two ways: (i) pore volume impregnation with aqueous vanadyl oxalate solution, followed by drying at 100 ° C for 1 to 3 hours, preferably one hour; (ii) wet spot impregnation with aqueous ammonium metavanadate solution conducted at 80 - 100 ° C for 1 to 5 hours, preferably 4 hours, followed by evaporation of excess solvent and drying at 100 ° C for 1 to 3 hours; preferably one hour.

Thereafter, a calcination step between 500 and 650 ° C, preferably at 500 ° C, for up to 5 hours, preferably 3 hours, in the presence of air, allows the embedded metals to be fixed, which are homogeneously dispersed throughout the particle. Support.

The presence of the oxeduction promoter, notably vanadium, is justified for two reasons. First, in the regenerating vessel, the oxidoreduction promoter catalyzes the oxidation of S0 ₂ to S0 ₃ so that S0 ₃ is captured by CaO for CaS0 ₄ formation. The presence of the promoter becomes indispensable because CaS0 ₄ generation necessarily passes through the reaction intermediate S0 ₃ and, however, the thermodynamic conditions of the regenerating vessel shift the reaction equilibrium to the predominance of S0 ₂ .

Secondly, in the riser, the oxidoreduction promoter acts on the CaS0 reduction step, leading to an alternative reaction mechanism that results in a decrease in sulfate reduction temperature and, consequently, a higher percentage of reduced particles at lower temperatures. .

The mechanism of action of the promoter in reducing CaS0 ₄ is not well known. It is speculated that the promoter acts either by effectively participating in the reduction step by forming an unstable intermediate under riser conditions, or by inducing the formation of an alternative structure for Ca_S_4 ₄ _supported.which is easier. reduced.

Thus, the results show that the presence of vanadium enables the reduction of sulfated CaO layers at a temperature of 530 ° C.

EXAMPLES

The following examples were developed based on the following considerations:

(a) Examples 1 and 2 illustrate the chemical and textural properties of the additive objects of the present invention, indicating their properties; (b) Examples 3 and 4 are the results of laboratory scale tests showing the performance of sulfur capture and desorption additives as a function of their composition;

c) Example 5 is the result of pilot scale testing that proves the performance of sulfur capture and desorption additives under application conditions in an FCC process;

d) Example 6 illustrates that the presence of the additives developed in this invention does not interfere with the performance of the final catalytic system. e) Example 7 illustrates that the additives of the present invention meet the requirements of physical properties.

EXAMPLE 1

This example illustrates the characterization of additives comprising calcium and vanadium supported on γ-ΑΙ ₂ 0 ₃ . Two diffractograms are illustrated: (1a): diffractogram of the gamma-alumina support; (1b): Diffractogram of the additive called CA1V containing 10% w / w calcium oxide (CaO) and 3% w / w vanadium incorporated in gamma-alumina by the procedure described above.

The X-ray diffractogram of the CA1V additive overlaps with the γ-ΑΙ ₂ 0 ₃ support diffractogram (Fig. 1), revealing the non-occurrence of XRD-related crystalline CaO phases. At this concentration, vanadium forms vanadate (VOx) n polymer layers, which are amorphous against XRD.

Thus, the data obtained by X-ray diffraction confirm that the samples have a high degree of scattering of the particles of calcium and vanadium on the support.

Example 1 also illustrates the RAMAN spectra of the samples so named: (3a) Analytical grade anhydrous calcium sulfate reagent (CaS0 ₄ PA) for comparison; (3b) CA1S: precursor containing 10% w / w calcium oxide incorporated in gamma alumina and sulfated; (3c) CA1VS: additive containing 10% w / w calcium oxide and 3% w / w vanadium incorporated in gamma-alumina and sulfated. The sulfation reaction of fixed bed additives and precursors is described in detail in Example 2.

The analysis by Raman spectroscopy (Fig. 2) shows that the peaks of sulfated precursor CA1S perfectly overlap the spectrum of analytical reagent grade anhydrous CaS0 _4, confirming the obtaining of particles supported CaS0 _4. The spectrum of the CAV1S sulphated additive also confirms the formation of these particles and, in addition to these peaks, the 890 cm- ¹ centered band envelope for vanadium, which is not sulphated, is observed.

EXAMPLE 2

This example illustrates the ease of reduction of sulfated compounds formed in the additive object of the present invention.

The following samples were subjected to the sulfation reaction described below: CA1 (10% w / w calcium oxide incorporated in gamma-alumina); CA1V (10% w / w calcium oxide and 3% w / w vanadium incorporated in gamma alumina); MF1 (physical mixture containing 10% w / w calcium oxide PA reagent and 90% w / w gamma-alumina).

These were sulfated in a simulated laboratory process. The sulfation process of the samples was conducted in a fixed bed quartz reactor having a quadrupolar mass spectrometer coupled to the reactor output.

Initially the temperature was raised to 725 ° C at a rate of 10 ° C / min under helium flow, at a flow rate of 60_mL / min and thus maintained for 30 minutes. In the second step, the samples also at 725 ° C was subjected to the gas mixture of S0 _2/0 ₂ in helium containing 0.5% v / v and 2% S0 ₂ v / v 0 _2. The reaction continued until gas saturation was reached, which was observed by stabilizing the S0 ₂ signal on the mass spectrometer. The CA1, CA1V and MF1 samples after the sulfation step were named, respectively: CA1S, CA1VS and MF1S. The physical mixture was analyzed for comparison.

The programmed temperature reduction assays (Fig. 3) of samples CA1S, CA1VS and MF1S show that obtaining CaS0 ₄ particles anchored to a high surface area support already results in a significant decrease in their reduction temperature compared to the temperature. of the CaS0 ₄ in the physical mixture, being the drastic temperature reduction when vanadium is present, as observed in CA1VS. The peak observed in MF1 at approximately 650 ° C refers to gamma-alumina sulfation.

From the characterization tests and reduction test, it is concluded that, in fact, the supported particles of calcium compound are in the form of highly dispersed CaO. It is also concluded that CaS0 ₄ formed by sulfation can be reduced at temperatures significantly lower than mass CaS0 ₄ .

EXAMPLE 3

This example illustrates the performance of the object additives of the present invention as a function of thermogravimetry analysis (TGA).

The operation of the additives will be illustrated for both SOx capture and release of absorbed SOx.

In addition to samples CA1 and CA1V, data from the following samples are illustrated: CA2 (20% w / w CaO incorporated in gamma-alumina); CA2V (20% w / w CaO and 3% w / w V incorporated in gamma-alumina); CA1c (10% m / m CaO incorporated into VCl_A-kaolin) CA2c (20% m / m CaO incorporated into VCLA-kaolin); CA1Vc (10% w / w CaO and 3% w / w V incorporated into VCLA-kaolin); CA2Vc (20% w / w CaO and 3% w / w V incorporated in VCLA-kaolin).

In the S0 ₃ capture and desorption test, the sample is initially pretreated in situ when the temperature is raised to 725 ° C in an inert atmosphere, a condition maintained for 30 minutes. Then, still at 725 ° C, the inert gas flow is exchanged for the helium oxidant mixture containing 0.5% v / v S0 ₂ and 2% v / v C½, which is maintained for 45 minutes when gain of mass due to the capture of S0 ₃ and supported the formation of particles of CaS0 _4. Then the sulfated sample is subjected to the reduction process when the temperature is reduced from 725 ° C to 530 ° C and the oxidizing mixture is exchanged for the 5% v / v H ₂ mixture in helium. This condition would simulate the riser reduction step of an FCC unit. The H ₂ / He flow is maintained for 45 minutes. Mass loss in this condition occurs due to the desorption of SO ₃₎ provided by the reduction of part of the absorbed sulfate.

The percentage of desorbed SO ₃ in relation to the absorbed SO ₃ mass, which is related to the reducibility of the additive, is then calculated.

Vanadium oxidation can also cause mass gain and / or loss. The contribution of vanadium was evaluated by subjecting the additives to oxidation with the 5% v / v 0 ₂ mixture in He and then to the reduction step. Gain and / or mass loss of 0.1% or 0.2% was observed in some additives and these numbers were discounted from their respective S0 ₃ capture and desorption values of the additives.

Corrected data for S0 ₃ captured and desorbed by the samples are found in Table 1. TABLE 1

In terms of capture, we can clearly see from Table 1 that CA1 and CA2 supported calcium samples have approximate pick-up factor values for the physical mixture MF1, whereas samples according to the present invention, CA1V and CA2V, are better to absorb S0 ₃ , resulting in pick-up factor of approximately 0.80. Similar conclusion is obtained by observing the samples prepared with the VCLA-kaolin support: the CA1c and CA2c sample pairs have lower pick-up factors than the respective vanadium, CA1Vc and CA2Vc samples. The data show the highest susceptibility to capture and ultimately the highest production of SO ₃ when vanadium is present. The promoter also contributes to S0 ₃ higher capture rate by the additive.

Table 1 also compares the additives for ease of reduction, ie ease of desorbing S0 ₃ at 530 ° C. The ease of reduction of samples at 530 ° C is not observed for vanadium-free precursors and physical mixing. The vanadium samples, however, show mass losses of 7.6% to 29% over the initially absorbed mass. Thus, the results show that the presence of vanadium makes it possible to reduce sulfated CaO layers to a temperature of 530 ° C.

EXAMPLE 4

In order to demonstrate the influence of the pore volume of the support employed on the additives object of the present invention, additives were prepared with nominal CaO and V concentrations of 20% and 3%, respectively, but used as a support. , different equilibrium catalysts (e-cat). Equilibrium catalyst is a representative sample of the catalyst circulating in the FCC unit composed of particles of different ages due to the frequent removal of a spent catalyst fraction and replacement of virgin catalyst fraction. The older the particle in the FCC unit, the higher the contaminant metal content deposited on it and the lower its remaining catalytic activity. That is, for Example 4 a support containing low crystallinity alumina and kaolin was used in its composition, but with low pore volume.

Table 2 shows the values of the PUF and the percentage reduction of CaS0 _4-530 ° C, determined by thermogravimetric analysis, the equilibrium catalyst samples containing calcium and supported on their cats e. Comparing these data with Table 1, it is clearly noted that the pick-up factor values are significantly lower than those obtained with the high porous volume supports. The low pore volume of the e-cats also provided very small reduction values for CaS0 ₄ at 530 ° C.

Although e-cats have relatively high surface areas for this preparation, the low pore volume causes the deposition of larger CaO and CaS0 particles, which reduces the accessibility of gases to their sites and, consequently, reduces the extent of reactions. involved. TABLE 2

EXAMPLE 5

This example illustrates the performance of the object additives of the present invention in a DCR - Davison Circulating Riser pilot unit licensed from WR GRACE & Co. In the pilot scale test, CA1V and CA1Vc additives were evaluated with actual load typical of the oil fields. Brazilians, containing 2.9% sulfur. The commercial additive used as reference was KDSOx, marketed by ALBEMARLE, containing transition metals and approximately 50% magnesium oxide.

The other test conditions are described below:

Riser reaction temperature. 530 ° C

Charge temperature: 120 ° C

Regenerator temperature: 720 ° C

Excess 0 ₂ : 2%

Approximate running time per additive: 2.5 hours

At the start of the test, 1800g of equilibrium catalyst circulated throughout the unit until the S0 ₂ level emitted by the load stabilized. Then a mixture containing a small amount of additive and the required mass of the equilibrium catalyst was prepared to give a total of 200 grams. This mixture was then injected, totaling 2000 grams of catalyst circulating in the unit. The amount of SO ₂ absorbed from the area of the figure formed by the time elapsed between the moment of additive injection and the restoration of SC½ level after injection was calculated. The additive shelf life, which corresponds to the time taken for the S0 ₂ level to return to the initial value and the pick-up factor, calculated in this test by the relationship between the amount of SC½ absorbed and the dose of the additive, was also determined. additive used in the test. In addition, due to the different active metal contents (Mg and Ca) in the additives, the pick-up factor metal (PUF / m) was used, and the absorbed S0 ₂ value based on the active metal mass (Mg or Ca) present in the dose of the additive.

Data on pilot unit assessments are shown in Table 3.

TABLE 3

The advantages of using additives are quite evident:

_ CA1V and CA1Vc additives have significantly longer shelf life than KDSOx, due to the reducibility of the supported CaS0 ₄ particles. Primarily, the present invention has residual activity for SOx capture, which reduces the percentage of additive to be replenished by the refiner.

Considering the metallic pick-up factor, CA1V and CA1Vc have performances approximately three times higher than the additive commercial. This means that even though they have a metal content (calcium) three times lower than KDSOx (magnesium), these additives should perform similarly in one FCC unit.

Thus, the pilot scale test proves the reducibility of CaS0 ₄ particles when well dispersed on a high specific area support, such as the alumina range and the VCLA-kaolin catalyst. 90:10. The feasibility of using the additive obtained by the present invention to capture SOx in FCC units is proven. Its excellent performance against the commercial additive is demonstrated.

EXAMPLE 6

This example illustrates the performance of the object additives of the present invention in relation to their catalytic activity.

In order to verify the possible impact of the additive of the present invention on conversion and load selectivity, catalytic evaluation tests were performed on the ACE unit. CA1V and KDSOx additives were tested in the virgin state, ie without any contamination or deactivation and also previously deactivated. The deactivation was performed in a tubular oven, with fixed bed reactor, at 788 ° C for 5 hours and with 100% water vapor.

Each additive was mixed with the reference equilibrium catalyst to yield 2% w / w of the former. All samples were evaluated in duplicate keeping the catalyst / oil ratio equal to five. Diesel oil typical of the Brazilian oil fields was employed and the reaction temperature was 535 ° C. Data were compared to the equilibrium catalyst without additive.

It can be concluded from the data in Table 4 that CA1V additive does not significantly impact the conversion or load selectivity under the test conditions.

Additionally, similar performance was observed _. , with. .The. catalytic system containing the commercial additive KDSOx. TABLE 4

EXAMPLE 7

The CA1 V and CA1 Vc additives were subjected to FCC catalyst frictional resistance testing by air injection in a home-made unit.

Controlling the friction index is important to maintain proper catalyst fluidization in the riser and reduce particulate emissions. The values obtained for the additives of this invention, in addition to meeting the specification, are better for certain commercial additives. Table 5 shows the friction index values of the additives of this invention and the commercial additives, KDSOx, LoSOx-PB and SuperSOxgetter, the latter marketed by INTERCAT. TABLE 5

Additive Friction Index Manufacturer

CA1V PETROBRAS 7.5

CA1Vc PETROBRAS 4.6

KDSOx ALBEMARLE 10.5

LoSOx-PB INTERCAT 16.0

SuperSOxgetter INTERCAT 7.6

Claims

1. ADDITIVES FOR REDUCING SOx GAS EMISSIONS IN HYDROCARBID CATALYTIC CRACKING UNITS, characterized by having a high surface area support of at least 150 m ² / g and a high pore volume of at least 0.25 cm ³ / g, having incorporated: calcium, in the form of calcium oxide, with a concentration of at least 5 mass% and preferably 10 mass%; and an oxide reduction promoter, in the form of its oxide, in the concentration range between 1 and 5% w / w.

Additives according to Claim 1, characterized in that the concentration of calcium oxide in the additive is preferably 10% by weight.

Additives according to Claim 1, characterized in that the high porous volume support is chosen from:

(i) gamma alumina;

(ii) high pore alumina type catalysts containing an inert matrix.

Additives according to Claim 1, characterized in that calcium is incorporated into the support by the pore volume impregnation method in the form of a salt, chosen from a salt of: sulphate, chloride or nitrate, followed by drying. 100 ° C for 1 to 3 hours.

Additives according to claims 1 and 4, characterized in that the drying period is preferably 1 hour.

Additives according to Claim 1, characterized in that the redox promoter is chosen from: iron, copper, zinc, chromium, manganese and vanadium.

Additives according to Claims 1 and 6, characterized in that the vanadium oxidoreduction promoter is at a concentration of 3% w / w.

Additives according to claims 1 and 6, characterized in that incorporation of the oxeduction promoter obtained by the pore volume impregnation method in the form of a salt, chosen from a salt of: sulphate, chloride or nitrate.

Additives according to Claims 1 and 6, characterized in that the incorporation of the vanadium oxirreduction promoter is obtained by the pore volume impregnation method with aqueous vanadyl oxalate solution or wet spot impregnation with aqueous vanadium metavadate solution. ammonium.

Additives according to claims 1 to 9, characterized in that after the steps involving the incorporation of calcium and an oxireduction promoter, a calcination step at temperatures between 500 and 650 ° C for up to 5 ° C is followed. hours in the presence of air.

Additives according to Claim 1 to 10, characterized in that the calcination step is preferably at 500 ° C.

Additives according to Claim 1 to 10, characterized in that the calcination step lasts for 3 hours.