BR102019003417A2 - PROCESS FOR REDUCING NOX EMISSION IN OIL REFINERIES - Google Patents

Abstract

Process for reducing the emission of nox in oil refineries The present invention describes a process for reducing the emission of nox in oil refineries, in which the fcc unit regenerator operates in a partial combustion mode. said process comprises contacting a mixture of gases comprising nitrogen compounds and carbon monoxide with oxygen and a catalyst in the temperature range of 100 to 700 ° c. the gas mixture comprises gases present in the regenerator or its effluents. the catalyst consists of a zeolite component modified with copper.

Description

PROCESS FOR REDUCING NOX EMISSION IN OIL REFINERIES FIELD OF THE INVENTION

[0001] The present invention relates to a process for reducing NOx emissions in oil refineries, in which the FCC unit's regenerator operates in partial combustion mode, employing a copper-modified zeolite catalyst.

BACKGROUND OF THE INVENTION

[0002] During fluid bed catalytic cracking (FCC) reactions in an oil refinery, non-volatile carbonaceous material or coke is formed and deposited on the catalyst. This deposited coke temporarily deactivates the active sites of the catalyst, thus causing a considerable loss of catalytic activity.

[0003] To recover activity, the FCC process catalysts are continuously recirculated between the reactor and the regenerator. In the regeneration stage, total or partial combustion of coke occurs.

[0004] In total combustion, all carbon in the coke is transformed into CO2, which is directly eliminated into the atmosphere. However, to achieve complete combustion within the regenerator, a considerable excess of oxygen is required.

[0005] This excess reduces the combustion capacity of the coke and increases the emissions of nitrogen oxides (NOx) due to the oxidation of nitrogenous organic compounds present there.

[0006] In partial combustion, in turn, a mixture of carbon monoxide and dioxide is formed. NOx compounds, if formed, are reduced by the large amount of CO in the regenerator.

[0007] The output current from the regenerator passes through a boiler to complete the burning of CO with the use of energy to generate steam. However, since this current is rich in CO, high levels of NOx can be generated in the boiler, from precursors present in the current, and emitted into the atmosphere.

[0008] Thus, there is a need to reduce or eliminate NOx precursors, such as HCN and NH3, before redirecting the output current from the regenerator to the steam boiler.

[0009] US 7,497,942 reduces the presence of these precursors through the addition of an additive in the regenerator that comprises noble metals selected from ruthenium, rhodium, iridium or mixture thereof.

[00010] This document demonstrated that, in the absence of O2, these noble metals are capable of decomposing 450 ppm of NH3 in the presence of 2 to 6% CO, forming N2.

[00011] However, it was observed that in the presence of O2, the active sites on the surface of these metals can be deactivated with adsorbed oxygen, which changes the profile of the products, generating NOx and decreasing the formation of N2.

[00012] Thus, the effectiveness of using these noble metals in the treatment to reduce or eliminate NOx precursors has not yet been clearly verified.

[00013] WO 2006/118700 describes the use of NOx reducing compositions in FCC plants to reduce emissions of NOx and its precursors released in the regeneration zone operating in partial combustion mode.

[00014] The reducing compositions comprise a zeolite and at least one noble metal selected from platinum, palladium, iridium, rhodium, osmium, ruthenium, rhenium, or a mixture thereof.

[00015] However, catalysts containing noble metals have the disadvantage of having a high cost.

[00016] Therefore, there is a need in the state of the art for lower cost catalysts for the treatment of typical gas effluents from the FCC unit regenerator operating in partial combustion mode.
Catalysts that have high activity and selectivity are needed for oxidation of these NOx precursors in relation to CO oxidation, transforming this NOx precursor into N2.

[00017] However, in the oxidation reaction of NH3 with O2 as the oxidizing gas, NOx can still be formed, which cannot be released directly into the atmosphere.

[00018] Therefore, it is necessary to use a catalyst that has a high capacity to catalyze the reaction between NOx and CO in order to release N2 and CO2.

[00019] Therefore, it is an objective of the present invention to provide a process for the reduction of NOx emissions in oil refineries, in which the FCC unit regenerator operates in partial combustion mode.

[00020] The process employs a catalyst with high selectivity for the NH3 oxidation reaction in the presence of CO, in addition to having high activity in promoting the reaction of NOx with CO.

SUMMARY OF THE INVENTION

[00021] The present invention relates to a process for the reduction of NOx emission in oil refineries, in which the FCC unit regenerator operates in a partial combustion mode.

[00022] The disclosed process comprises contacting a mixture of gases comprising nitrogen compounds and carbon monoxide with oxygen and a catalyst in the temperature range of 100 to 700 ° C. The gas mixture comprises gases present in the regenerator or its effluents.

[00023] The catalyst consists of a zeolite component modified with copper, said zeolite component having pore size less than or equal to 5 Å, a molar ratio of silica to alumina in the range of 1 to 100 and a BET surface area in the range of 100 at 500 m2 / g.

[00024] The copper content of the catalyst is in the range of 0.1 to 10 mmoles per gram of zeolite.

DETAILED DESCRIPTION OF THE INVENTION

[00025] The present invention relates to a process for reducing NOx emission in oil refineries, in which the FCC unit regenerator operates in a partial combustion mode.

[00026] The said process comprises contacting a mixture of gases comprising nitrogen compounds and carbon monoxide with oxygen and a catalyst in the temperature range of 100 to 700 ° C. The gas mixture comprises gases present in the regenerator or its effluents.

[00027] The catalyst used consists of a zeolite component modified with copper. In a preferred modality, the zeolite component is selected from Ferrierite, Beta and ZSM-5. Most preferably, Ferrierite is the zeolite component employed.

[00028] The zeolite component contains small pores, which are less than or equal to 5 Å in size. Preferably, the pore size is in the range of 3 to 5 Å.

[00029] The use of a small pore zeolite increases the affinity of the precursors of NOx formation, such as NH3 and HCN, for the acid catalyst, as well as ensures the active state of the deposited active phase.

[00030] In addition, the zeolite component has a molar ratio of silica to alumina in the range of 1 to 100 and a BET surface area in the range of 100 to 500 m2 / g.

[00031] In a preferred embodiment, the zeolite component employed in the present process has a molar ratio of silica to alumina in the range of 5 to 50 and a BET surface area in the range of 250 to 450

[00032] The content in which copper is present in the catalyst is in the range of 0.1 to 10 mmoles per gram of zeolite. Preferably, copper is present in a content of 0.3 to 5 mmoles per gram of zeolite.

[00033] According to the invention, the present process is employed when the regenerator of the FCC unit operates in a partial combustion mode. Thus, the amount of oxygen in the reaction medium is not sufficient to oxidize all the carbon present in the coke deposited on the CO2 catalyst and, consequently, there is the presence of CO and CO2 in the medium.

[00034] Preferably, the nitrogen compounds found in the gas mixture are one or more among nitrogen oxides, such as, but not limited to, NO and NO2, ammonia and hydrogen cyanide.

[00035] In a preferred embodiment, the catalyst used in the described process has catalytic activity in a zone between the FCC process regenerator and the CO boiler.

[00036] According to the present invention, the catalyst used has a high preference in the oxidation of NOx formation precursors over the oxidation of CO, in addition to having high activity in promoting the reaction of NOx with CO.

[00037] Additionally, the catalyst of the present invention is compatible with the FCC process, and can act as an additive to catalysts usually used in this cracking process. This additive is preferably in the form of microspheres.

[00038] The following description will start from preferred embodiments of the invention. As will be apparent to any person skilled in the art, the invention is not limited to these particular embodiments.

EXAMPLES Example 1 - Preparation of a series of Cu / Z catalysts, where Z represents various types of zeolites

[00039] The method used for the preparation of the catalyst was impregnation in the wet spot, in which a copper salt was deposited on the FER zeolite and on other zeolites for comparison. The salt used was copper nitrate (Cu (NO3) 2.3H2O), which was dissolved in deionized water.

[00040] Table 1 shows some properties of the zeolites used. For comparison purposes, alumina in the form of a microsphere containing silica binder and kaolin was also used as a copper support. This support was called Alu-Cat.

[00041] The volume of solution used to impregnate one gram of zeolite was calculated in order to fill the entire pore volume of the zeolite and the deposition of the desired copper content was guaranteed by the quantity and concentration of the salt solution employed.

[00042] Once the solution of predetermined concentration was prepared, it was slowly dosed to zeolite, the resulting mixture being mechanically homogenized.

[00043] During the impregnation process, the zeolite particles have a dry external surface and, when they reach the wet point, they agglutinate. At that moment, the solution addition was finished, that is, the impregnation was finished.

[00044] Then, the sample was dried in air at 120 ° C for about 15 hours and calcined at 500 ° C for 3 hours. The prepared samples were designated in examples [2] - [5] as xM / Z, where x indicates the number of mmoles of metal M that was impregnated per gram of zeolite (Z).

[00045] The amount of salt that can be dissolved in water to fill the pores of the zeolites during the impregnation process limits the metal content that can be deposited by the procedure described above. Thus, if it is desirable to impregnate a greater amount of metals in the zeolites, successive impregnations can be used.

[00046] The above procedure can be repeated again, if desired. In this case, the calcination step can be omitted between the impregnations and can be carried out after reaching the desired content of the metal being deposited.

[00047] Optionally, to ensure stable property during catalytic tests at high temperature, the sample was calcined in air at 750 ° C for 5 h.

Example 2 - Demonstration of the high activity and selectivity of the Cu / FER system in the oxidation of NH3 in the presence of CO

[00048] Cu / FER (copper supported on Ferrierite) catalysts prepared according to example [1] were tested and compared with others in the competitive oxidation between NH3 and CO using a continuous flow reactor.

[00049] In each test 100 mg of catalyst was used together with 100 mg of inert material (silicon carbide).

[00050] A flow of 80 ml / min containing 0.625% CO, 0.3125% NH3 and 0.3125% O2 with He balance, was fed continuously to the reactor containing the tested catalysts.

[00051] In this condition, the molar ratios CO / NH3 and CO / O2 were equal to 2. That is, if all the oxygen was consumed to oxidize CO to CO2, as occurs in usual processes of the prior art, there would be no oxygen for oxidize NH3.

[00052] The reactor temperature was increased from 100 to 700 ° C in increments of 50 ° C and the generation of N2 and NO due to the oxidation of NH3, as well as the consumption of CO, was calculated from gas chromatography data coupled in line to the reactor.

[00053] Table 2 shows the conversions of NH3 and CO. At 400 ° C, it can be seen that Cu / FER catalysts are the most active and the most selective for the oxidation of NH3. The catalysts typically promoting CO combustion (containing Pt and / or Ce), in turn, showed no detectable activities.

[00054] At 600 ° C, Cu / FER type samples maintained their high activity in the conversion of NH3 and their selectivity in relation to the conversion of CO.

[00055] Results similar to the Cu / FER system were obtained using the Cu / Beta system at a temperature of 600 ° C. At a temperature of 400 ° C, the Cu / Beta system showed selectivity for the conversion of NH3 in relation to the conversion of CO, despite having demonstrated a lower conversion value.

[00056] In table 2, the most active catalysts for oxidation of NH3 can be clearly identified because they present conversion of the desired reagents at a lower temperature. In higher temperature applications, a lower amount of catalyst can be used.

[00057] Therefore, it is observed that Cu / FER catalysts can act in a process of treatment of effluent gases to selectively remove precursors of NOx over a wide temperature range.

[00058] More specifically, from the regenerator of an FCC unit to the entrance of the CO boiler the gas temperature can vary from 700 ° C to 400 ° C. In this way, these catalysts are able to act in a catalytic zone inserted between these units.

Example 3 - Demonstration of the high activity and selectivity of the Cu / FER system in the oxidation of NH3 in the presence of excess CO

[00059] To demonstrate the effectiveness of Cu / FER type catalysts, the concentration of the fed reagents was modified as shown in Table 3.

[00060] In summary, there was a change in the CO / O2 ratio to 2.5, leaving the O2 system more deficient. At the same time, the CO / NH3 ratio was increased from 5 in condition (1) to 10 in condition (2). Thus, the system became much more demanding for the action of the catalyst in the NH3 oxidation reaction.

[00061] It is possible to observe that in condition (2) the conversion of CO increased because of the increase in its partial pressure, becoming more competitive in relation to oxygen to be adsorbed on the surface of the catalysts.

[00062] However, despite the high concentration of CO and the lower availability of O2 in condition (2), the conversion of NH3 does not decrease. Thus, the low NH3 content present in condition (2) is still being effectively eliminated.

Example 4 - Demonstration of the high activity of the Cu / FER system in promoting the NO reaction with CO

[00063] The M / Z catalysts prepared in example [1] were tested using a continuous flow reactor similar to the system employed in the examples [2] to [3] above.

[00064] This test used 100 mg of catalyst diluted in 100 mg of inert material (silicon carbide). A flow of 50 ml / min containing 0.50% CO and 0.50% NO, with He balance, was fed to the reactor, which passed through the catalytic bed.

[00065] The reactor temperature was increased from 150 to 700 ° C in increments of 50 ° C and the consumption of NO and CO was recorded. The conversion of CO was, in general, similar to the conversion of NO, consistent with the reaction of NO + CO resulting in N2 and CO2 as products.

[00066] Table 4 shows the degree of conversion from NO to N2 at a temperature of 500 ° C.

[00067] It can be seen in Table 4 that, with the same copper content deposited on the zeolitic support, the most active system is that using Ferrierite zeolite as a support.

[00068] In addition, it is observed that the increase in copper content in zeolite Ferrierite caused the increase in conversion, indicating the important role of copper in the catalytic system.

[00069] Thus, it was demonstrated that the Cu / FER catalyst is very active in promoting the reaction of NO with CO, in which, even at 500 ° C, there was a high conversion of NO.

[00070] Thus, the Cu / FER catalyst showed its ability to remove NO, if it is produced in the oxidation of its precursors NH3 and HCN, converting to N2 when reacting with CO present in the gaseous effluent from the regenerator operating in the partial combustion.

[00071] Additionally, it can also be seen that the Cu / Beta and Cu / ZSM-5 systems, when copper is present in a content of 2 mmoles per gram of zeolite, also present a high NO conversion rate.

Example 5 - Demonstration of the high activity and selectivity of the Cu / FER system in the oxidation of NH3 in the presence of excess CO

[00072] The Cu / FER catalyst prepared according to example [1] was used in a simple process, in which a gas containing NH3 mixed with a high CO content was passed in a fixed bed reactor maintained at a constant temperature 500 ° C.

[00073] The content of O2 fed into the reactor was adjusted and the levels of CO and NH3 were kept constant, with the NH3 content of the gas being kept to a minimum, while the CO content remained in excess.

[00074] Specifically, 100 mg of 0.3Cu / FER catalyst (0.3 mmoles of Cu per gram of FER) was mixed with 100 mg of inert material (silicon carbide) in a continuous flow reactor. A flow of gas of 84 ml / min containing CO, NH3 and O2 with He balance, with the composition selected according to table 5, was fed continuously to the reactor.

[00075] It is possible to see in table 5 that the selective conversion of NH3 in relation to the conversion of CO continued to occur, even with the use of highly excess CO and with a lower copper content supported in Ferrierite.

Example 6 - Demonstration of the high activity and selectivity of the Cu / FER system incorporated as an additive in the FCC catalyst in the oxidation of NH3 in the presence of CO

[00076] An additive containing 50% Cu / FER, prepared according to the procedure described in example [1], and 50% of a fluidizable particle of silica-alumina-kaolin, was tested in a FST ACE type reactor.

[00077] The additive was mixed with equilibrium catalyst from a Petrobras refinery at a concentration of 1.5%, based on the weight of the chosen catalyst, and put in contact with vacuum oil diesel from the Campos basin at a temperature of 535 ° C , with the catalyst / oil ratio varying from 4 to 8.

[00078] The catalytic tests produced yield versus conversion curves that allowed the comparison of yields to the constant conversion of the base catalyst with and without additive, illustrated in table 6.

[00079] The test results showed that the additive containing copper, a notoriously dehydrogenating metal, did not impair the performance of the base catalyst. Thus, the use of the additive proved to be perfectly viable in a commercial unit.

[00080] Even after the addition of the Cu / FER additive, the selective conversion activity of NH3 was maintained, as can be observed the high conversion of NH3 and low conversion of CO in the FCC partial combustion simulation laboratory test, as table 7.

Example 7 - Comparative test of the Cu / FER system with the Pt / FER system

[00081] Ferrierite based catalysts are prepared by impregnating copper and platinum.

[00082] The Cu content obtained was 0.425 mmoles per gram of FER and that of Pt was 0.03 mmoles per gram of FER. Both were tested for competitive oxidation using a continuous flow reactor.

[00083] In each test 100 mg of catalyst mixed with 100 mg of inert material (silicon carbide) was used. A flow of 85 ml / min containing 2.95% CO, 0.29% NH3 and 1.18% O2 with He balance was fed continuously to the reactor containing the catalysts.

[00084] In this condition, the molar ratios CO / NH3 and CO / O2 were 10 and 2.5, respectively. The reactor temperature was increased from 100 to 700 ° C in increments of 50 ° C and the generation of N2 and NO due to the oxidation of NH3, as well as the consumption of CO, was calculated from gas chromatography data coupled in line to the reactor.

[00085] Table 8 shows the conversions of NH3 and CO. It can be seen that, at any of the temperatures tested, the Cu / FER catalyst is more active and selective for the oxidation of NH3 compared to CO. The Pt-containing catalyst is more active and selective for CO oxidation.

[00086] In this way, the most active catalyst for oxidation of NH3 can be clearly identified in table 8 because it presents conversion of the desired reagent at a lower temperature. In higher temperature applications, a lower amount of catalyst can be used.

[00087] In addition, it is observed that active Cu / FER catalysts can act in a process of treating effluent gases to selectively remove NOx precursors over a wide temperature range.

[00088] More specifically, from the FCC unit regenerator to the CO boiler inlet, the gas temperature can vary from 700 ° C to 400 ° C. Therefore, these catalysts are able to act in a catalytic zone inserted between these units.

[00089] The description that has been made so far of the object of the present invention should be considered only as a possible or possible embodiments, and any particular characteristics introduced therein should be understood only as something that has been written to facilitate understanding. Therefore, they cannot in any way be considered as limiting the invention, which is limited to the scope of the following claims.

Claims (8)

Process for the reduction of NOx emission in oil refineries, in which the regenerator of the FCC unit operates in a partial combustion mode, said process characterized by understanding the contact of a mixture of gases comprising nitrogen compounds and carbon monoxide with oxygen and a catalyst in the temperature range of 100 to 700 ° C, said mixture of gases comprising gases present in the regenerator or effluents thereof, in which:
said catalyst consists of a zeolite component modified with copper, said zeolite component having pore size less than or equal to 5 Å, a molar ratio of silica to alumina in the range of 1 to 100 and a BET surface area in the range of 100 to 500 m2 / g; and
the copper content of the catalyst is in the range of 0.1 to 10 mmoles per gram of zeolite. Process according to claim 1, characterized in that said zeolite component is selected from Ferrierite, Beta and ZSM-5. Process according to claim 2, characterized in that said zeolite component is Ferrierite. Process according to claim 1, characterized in that said zeolite component has pore size in the range of 3 to 5 Å, a molar ratio of silica to alumina in the range of 5 to 50 and a BET surface area in the range of 250 to 450 m2 / g. Process according to claim 1, characterized in that said nitrogenous compounds are selected from oxides of nitrogen, ammonia, hydrogen cyanide and mixture thereof. Process according to claim 1, characterized in that said catalyst has catalytic activity in a zone between the regenerator of the FCC unit and the CO boiler. Process according to claim 1, characterized in that said catalyst acts as an additive to an FCC catalyst. Process according to claim 7, characterized in that said additive is in the form of microspheres.