BR112014017691B1 - Process, catalyst and catalyst synthesis for hydrogen production - Google Patents

Abstract

PROCESS AND CATALYST FOR PRODUCTION OF HYDROGEN The present invention relates to a process for the production of hydrogen by catalytic decomposition of ammoniacal solutions. The objective is achieved by purifying an ammoniacal stream and employing this purified stream as a feedstock in a steam reforming process. The purification step removes impurities such as sulphur, halogens, metals and olefinic hydrocarbons from ammonia gas streams generated in acidic water units. The purified stream is conducted to a steam reforming process reformer furnace, for the conversion of ammonia into hydrogen, which is purified by conventional processes existing in steam reforming units. Additionally, a catalyst is synthesized, whose characteristics allow its use for the purification of the ammoniacal stream.

Description

FIELD OF THE INVENTION

The present invention finds its field of application among the processes for the production of hydrogen by catalytic decomposition of ammoniacal solutions. More specifically, the catalytic production of hydrogen from ammonia gas streams generated in the acidic water unit resulting from hydrocarbon hydrotreatment processes. FUNDAMENTALS OF THE INVENTION

Oil is composed of a complex mixture of hydrocarbons, associated with varying contents of organic compounds containing nitrogen, sulfur and oxygen and smaller amounts of metals, such as vanadium, nickel, sodium, calcium and copper.

Oil processing generates numerous derivatives, including gasoline, diesel oil and aviation kerosene.

Compounds such as sulfur, nitrogen, oxygen, halogens and metals are classified as undesirable in derivatives, as they generate atmospheric pollutants along the consumption chain and alter the integrity of equipment and the derivative itself.

To ensure quality and compliance with current legislation, it is usual to send these derivatives to a treatment called "hydrotreatment", whose characteristic is to change, or remove, the impurities present in these derivatives through the use of hydrogenation reactions.

For hydrocarbons with sulfur and nitrogen as contaminants, hydrogenation reactions generate hydrogen sulfide (H2S) and ammonia (NH3). These reactions occur in reactors filled with fixed beds and using catalysts manufactured mostly with nickel (or cobalt) and molybdenum sulfides, supported mainly on alumina.

During the hydrotreatment process, water is injected, which occurs in a step prior to the separation between the hydrogen used in excess of the stoichiometry of the hydrogenation reactions and the products of the process. The purpose of water injection is to retain hydrogen sulfide and ammonia in aqueous solution. This procedure avoids the deposition of salts, such as ammonium sulfide (NH4SH), which could clog lines and equipment, after the deposition process, if present in the hydrocarbon stream. The aqueous solution thus obtained constitutes an effluent called "acidic water".

In addition to hydrotreatment, several processes in the refining industry also generate acidic water. Examples are distillation, catalytic cracking, hydrocracking, thermal cracking and delayed coking.

The acidic water stream contains contaminants that prevent its direct release into the environment or its reuse in refining processes. For this to occur, it is usual for this effluent to undergo treatment in a specific unit called “acid water unit” for the removal of hydrogen sulfide and ammonia. Multiple configurations of acidic water units are found in the specialized technical literature. The acidic water stream is rectified, and gas streams containing ammonia and hydrogen sulfide are generated.

A method routinely used for the final treatment of these ammonia gas streams generated in the acid water unit is incineration.

In the petroleum industry, the Claus process is the standard method for removing sulfur from off-gas. It comprises a first thermal (or combustion) stage and a second catalytic (or catalytic bed) stage.

Sulfur compounds present in the ammonia stream are incinerated in the burners of a Claus process unit to recover sulfur. The reactions of the thermal step of the Claus process are:

O enxofre assim recuperado é comercializado no estado líquido ou sólido.In the catalytic step, sulfur oxide (SO2) reacts with the remaining hydrogen sulfide, represented by the following reaction.

The sulfur thus recovered is sold in the liquid or solid state.

The injection of the ammonia gas stream, recovered from the acidic water unit, into a Claus unit can be a convenient method of disposing of this effluent. However, it produces some obstacles, such as the difficulty in controlling the ratio of sulfur dioxide and hydrogen sulfide concentrations in the combustion section, particularly when the ammonia stream contains hydrocarbons. This ratio is a critical factor for the correct operation of the unit. Additionally, the carbon dioxide (CO2) formed in the combustion of hydrocarbons or previously existing in the ammoniacal stream, causes loss of sulfur recovery efficiency. Ammonia that is not incinerated has the potential to form salt deposits on equipment, such as ammonium sulfides, compromising unit efficiency or campaign time. At the same time, partial incineration can generate a high emission of nitrogen oxides (NOX), which are harmful to the environment and subject to restrictions provided for in environmental legislation.

An additional difficulty faced for the use of ammonia currents in Claus units in the state of the art is limited to a maximum value of ammonia addition in relation to the total processed load of around 30% to 35% on a wet basis.

Some oils occurring in Brazil are characterized by high levels of nitrogen compounds, for example, the one exploited in the Campos Basin. As a result, the acidic water unit produces a gas stream with high ammonia content.

A technical solution to overcome this situation is combined incineration: using the Claus unit up to the limit established by the technique, and forwarding the excess ammonia to a dedicated incinerator.

Although known in the state of the art, the incineration of the ammoniacal stream coming from the acidic water unit, either in a Claus-type unit or in a dedicated incinerator, does not generate products that can be commercialized.

Different processes for the recovery of ammonia present in acidic water streams are found in the specialized technical literature. Ammonia can be recovered directly in anhydrous form or in aqueous solution, or indirectly in the form of sodium hydrosulfide, ammonium thiosulfate, ammonium sulfate and ammonium phosphate.

It is of great importance, specifically for the oil industry, the recovery of ammonia through its transformation into hydrogen, as this is an input used on a large scale in hydrotreatment processes. Currently, for the production of hydrogen, natural gas and naphtha are used preferentially, raw materials of high cost, however, of multiple uses. The first, used in the energy matrix, the second, raw material in petrochemical plants.

The process most used to produce hydrogen on a large scale in the refining industry is steam reforming. Hydrocarbons react with water vapor at elevated temperatures and pressures. Nickel-based catalysts are used on refractory supports of alpha-alumina, magnesium aluminates and calcium aluminates.

In large capacity units, the hydrocarbons used in addition to natural gas and naphtha are refinery gases, propane and butanes. Taking methane as an example, the main reactions are represented by the equations below, which together have a highly endothermic balance.

The steam reforming process is usually carried out by introducing a previously purified feedstock into a variable number of fixed bed reactors. Such reactors are built with metallic tubes, with typical dimensions between 7 cm and 15 cm in external diameter and height in the range of 10 m to 13 m, located inside a heating furnace, which supplies the heat necessary for the reactions. The set of reactors and furnace is called a primary reformer. The typical inlet temperature of the gases to be processed in the reactors of the primary reformer is in the range of 400°C to 550°C, and the outlet temperature, in the range of 750°C to 950°C, at typical pressures in the range from 10 kgf/cm2 (980.67 kPa) to 35 kgf/cm2 (3432.33 kPa).

The ammonia decomposition reaction, thermodynamically favored by the use of high temperatures, is represented by the equation:

According to the technical literature, under reaction temperatures above 527oC and pressure of 1.9 bar (190 kPa), thermodynamic equilibrium predicts a conversion above 99.5%.

The decomposition of ammonia into hydrogen and nitrogen can be carried out over a variety of catalysts, such as those based on: platinum (Pt), rhodium (Rh), palladium (Pd), iridium (Ir) and nickel (Ni). It is known and used in industrial practice that ammonia decomposition can be carried out by nickel-based catalysts under existing conditions in the primary reformer. Such decomposition can be used for the initial reduction of the catalysts, supplied in the form of nickel oxide, according to the equations below:

Technical literature and industrial practice also teach that nickel-based catalysts used in the primary reformer are highly susceptible to deactivation by poisoning. Most common contaminants are: sulphur, arsenic, phosphorus, lead and halogens. These must be reduced to levels below 0.1 ppm, preferably below 0.01 ppm to achieve adequate catalytic activity and, consequently, a campaign time of at least 3 years.

The aqueous stream that is treated in the acidic water unit contains hydrogen sulfide and ammonia in levels ranging from 300 ppm to 20,000 ppm, with ammonia to hydrogen sulfide ratios ranging from 1 to 2.0. This stream may also contain other contaminants such as hydrocarbons, chlorides, sulfates, formates, cyanides, cations such as sodium, potassium and calcium, mineral or organic acids and dissolved gases such as carbon dioxide and oxygen in varying concentrations.

The gaseous stream that is generated in the acidic water unit, in addition to contamination by sulfur compounds, such as hydrogen sulfide and mercaptans, also presents other contaminants, sometimes below the analytical detection limits, but sufficient to cause the deactivation of the catalysts of primary reform. Potential contaminants are inorganic and organic chlorine compounds. Chlorides can significantly reduce the activity of steam reforming catalysts.

US 2007/0178034 discloses a process for removing organic and inorganic sulfur compounds from an ammonia stream. The sulfur is removed by a fixed catalytic absorbent bed composed of a catalyst with a nickel mass ranging from 10% to 30%. The catalyst support is chosen from alumina, silica, titania, magnesium, zirconia or a mixture thereof. The promoter is chosen from the oxides of the chemical elements cerium, praseodymium, neodymium, promethium, samarium or a mixture thereof. Methanation catalysts are indicated as preferred. The ammoniacal current, after

the removal of sulfur, is mixed with a stream of hydrocarbons and is used to generate hydrogen in a steam reforming process. The purification method presented in this document is specific to the removal of sulfur compounds. An ammonia stream, generated in a unit of “acidic water”, contains a plurality of other contaminants.

EP 0096970 presents a process for removing organic sulfur compounds such as hydrogen sulfide, mercaptans, sulfides and disulfides present in ammonia streams generated in the processing of hydrocarbons, oil shale and coal. Sulfur is removed in a bed of zinc oxide at a reaction temperature in the range of 260°C to 454°C. However, there is no mention of the purification of other contaminants, nor the use for the production of hydrogen.

US 7,258,848 discloses a process for treating gases containing ammonia and hydrogen sulfide. Ammonia is removed by washing the gases with a strong acid, for example concentrated sulfuric acid, in order to convert the ammonia into a salt. The aqueous solution or the crystallized ammonia salt can be used as a fertilizer.

Thus, the purification processes of ammonia streams generated in acidic water units are specific for the removal of sulfur compounds. The state of the art lacks a process that removes other contaminants, such as compounds of halogens, metals and hydrocarbons, and results in an ammoniacal stream, which, when used in a catalytic reform process for the production of hydrogen, leads to a reduced rate. deactivation of the catalysts.

SUMMARY OF THE INVENTION

The object of the present invention is a process for the production of hydrogen by catalytic decomposition of ammoniacal solutions

from acidic water units. Such a process involves purifying an ammoniacal stream and employing this purified stream as a feedstock in a steam reforming process. The purification step removes impurities such as sulfur, halogens, metals and olefinic hydrocarbons. The purified stream is conducted to a reforming furnace, which is part of the steam reforming process, for the conversion of ammonia into hydrogen.

Additionally, a catalyst is synthesized, whose characteristics allow its use for the purification of the ammoniacal stream with a reduced deactivation rate.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for producing hydrogen by catalytic decomposition of ammonia solutions from acidic water units. The objective is achieved by means of a process carried out in two main stages, namely: a first stage of purification of the ammoniacal stream, which comprises a pre-treatment of the ammoniacal stream in a plurality of catalyst beds, and, a second stage , which consists of submitting the treated stream to steam reforming.

Additionally, for the accomplishment of the process, a catalyst is synthesized, whose characteristics allow its use in the stage of purification of the ammoniacal stream.

In general terms, the invention deals with a continuous process for the production of hydrogen, carried out in two stages, where: the first stage comprises the following steps: - remove existing metals and chlorides in the gaseous ammoniacal stream coming from acidic water units, in a first bed, composed of materials chosen from alumina, silica-aluminas, silica, titanium, magnesium, zirconium and mixtures 30 thereof, maintained at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf /cm2 (98.0665 kPa) to 40 kgf/cm2 (3922.66 kPa), to obtain a first effluent stream; - transform organic compounds of chlorides and sulfur, contaminants of the first effluent stream, into hydrochloric acid and hydrogen sulfide , and, additionally, hydrogenate olefinic compounds, in a second bed, composed of hydrotreatment catalysts chosen between cobalt-molybdenum and nickel-molybdenum, supported on alumina, and alternatively, supported on oxides of zinc, at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf/cm2 (98.0665 kPa) to 40 kgf/cm2 (3922.66 kPa), to obtain a second stream of effluent;- remove hydrogen sulfide and inorganic chlorine compounds, such as hydrochloric acid, ammonium chloride, and, additionally, partially transform the ammonia into hydrogen and nitrogen, contaminants from the second effluent stream, in a third bed, composed of catalysts promoted by materials chosen from alkali metals and alkaline earth metals, supported on materials chosen from zinc oxides, alumina, silica-alumina and mixtures thereof, and having nickel oxide as the active phase, at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf/cm2 (98.0665 kPa) to 40 kgf/cm2 (3922.66 kPa), to obtain a third effluent stream; - remove existing inorganic and organic sulfur and chlorine compounds in the third effluent stream, in a fourth bed o, composed of catalysts chosen from among those containing zinc and copper oxides, at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf/cm2 (98.0665 kPa) to 40 kgf/cm2 (3922.66 kPa), to obtain a purified ammoniacal stream; the second stage comprises the following steps:- feeding the purified ammoniacal stream into a reactor, for the production of hydrogen by the steam reforming process, to obtain a rich gas stream into hydrogen;- purify the hydrogen-rich gas stream to obtain the final hydrogen product.

The present invention can be applied to existing hydrogen production units by the steam reforming process, simply by adapting the pre-treatment section of the existing unit to the plurality of beds.

In addition to the ammonia stream, a hydrocarbon stream can also be fed in the first step of the process. The hydrocarbon stream corresponds to the load that is normally used in industrial hydrogen production units by the steam reforming process. The ammonia stream corresponds to a fraction of the hydrocarbon load, and is in the range between 1% to 10% by volume. Hydrocarbons can be chosen from natural gas, liquefied petroleum gas, naphtha and a mixture of these, in any proportions.

In the purification process, hydrogen is preferably added to the charge, in order to avoid the formation of coke in the second catalytic bed.

In the third bed, the inclusion of nickel oxide in the catalyst formulation allows the partial transformation of ammonia into hydrogen and nitrogen. The catalyst is synthesized containing nickel oxide as the active phase, supported by materials chosen from zinc oxide, alumina and a mixture of these, and promoted by materials chosen from alkali and alkaline earth metals.

The catalyst is obtained by means of a dry impregnation technique, from the impregnation of a support, selected between alumina and zinc oxide, with a metal hydroxide solution, to obtain a material of the K/alumina or K/ZnO type. . The material is dried and calcined. Next, the calcined material is impregnated with nickel nitrate solution, dried and calcined again, giving rise to the catalyst whose characteristics allow its use for the purification of the ammoniacal stream with a reduced deactivation rate. The synthesis of the catalyst will be presented in detail later.

The fourth bed is composed of materials that can be chosen from zinc and copper oxides at levels above 50% by mass. For example, commercial low temperature shift (LTS) catalysts, known in the art by the English term “low temperature shift”, used in hydrogen production processes by steam reforming can be used.

The beds used in the first stage are assembled inside reactors. Each reactor contains a single type of bed, totaling four beds and four different reactors. Alternatively, the plurality of beds can be contained in a single reactor. The arrangement of beds in a single reactor, or in several, is determined by the volumetric capacity of the unit and the relative costs of the equipment. The volume of each bed must be selected according to the content of contaminants present in the ammoniacal stream, in addition to the campaign time projected for an industrial unit.

The employment of the first and second beds, in an industrial configuration of the present invention, is determined by the type of contaminants present. Thus, in a metal-free load, the use of the first bed is not necessary. In an organic sulfur-free load, the use of the second bed is not necessary. The use of the fourth bed, for the final removal of inorganic and organic compounds containing sulfur and chlorides, is determined by the content of contaminants allowed in the product, in addition to the objective campaign time of the reformer of an industrial unit.

In the second stage of the process, steam reforming, the purified ammonia stream is sent to a pre-reformer, and, alternatively, to a primary reformer, commonly used in the steam reforming process. In these equipments, residual ammonia from the third bed is converted into hydrogen and nitrogen. The stream obtained after the conversion reaction must be treated to remove impurities mixed with hydrogen.

The treatment methods employed are known in the state of the art. The reduction of carbon monoxide (CO) content occurs by the displacement reaction. Removal of carbon monoxide, carbon dioxide, methane and nitrogen occurs through the use of a pressure variation adsorption (PSA) system.

The catalyst developed according to the present invention is used in the third bed being able to decompose ammonia and simultaneously remove chloride (Cl) and sulfur (S) from the ammonia stream. The catalyst can be chosen between an alumina supported catalyst, promoted by an alkali metal or alkaline earth metal, preferably potassium, and with an active phase of nickel oxide (NiO/K/alumina) and a zinc oxide supported catalyst, promoted by an alkali metal or alkaline earth metal, preferably potassium, and with an active phase of nickel oxide (NiO/K/ZnO). In addition to alumina and zinc oxide, silica-alumina, or even mixtures thereof, can be used as a support.

The alkali metal content used in the catalyst is in the range of 1% to 7% by mass, preferably between 2% to 4% by mass. The content of nickel oxide used in the catalyst is in the range of 5% and 40% by mass, preferably between 10% and 20% by mass. Catalysts with specific area in the range of 15 m2/g to 30 m2/g are obtained.

For the synthesis of the catalyst, procedures known in the art and described in detail in the examples that illustrate the present invention are used.

EXAMPLE 1: Synthesis of NiO/K/alumina catalyst.

In this example, the catalyst supported by alumina was synthesized, promoted by potassium and nickel oxide active phase (NiO/K/alumina).

The catalyst was prepared with two hundred grams of alumina hydroxide Pural SB (Condea Chemie), impregnated with an aqueous solution of 11.5 grams of potassium hydroxide (KOH) by the dry impregnation technique (pore volume technique). The material thus obtained was dried at temperatures in the range of 100°C to 120°C for a period of time in the range of 8 hours to 12 hours and calcined at a temperature of around 600°C for a period of time in the range of 4 hours. hours. After this period of time, the calcination temperature was raised to a value of 10 around 1200°C for a period of time around 1 hour to obtain a K/alumina type material.

One hundred and thirty-three grams of K/alumina material was impregnated with an aqueous solution containing 27.2 grams of nickel nitrate hexahydrate [Ni(NO3)2.6H2O] by the dry impregnation technique (pore volume technique) , followed by drying at a temperature in the range of 100°C to 120°C for a period of time in the range of 8 hours to 12 hours and calcined at a temperature of around 450°C for a period of time in the range of 4 hours to to obtain a NiO/K/alumina catalyst. The catalyst thus obtained showed a concentration of 3% by mass of potassium (K), 15% by mass of nickel oxide (NiO) and a specific area of 27.7 m2/g, determined by the technique of nitrogen adsorption.

The catalyst is used for the conversion of ammonia and the removal of chloride and sulfur.

EXAMPLE 2: Synthesis of NiO/K/ZnO catalyst.

In this example, the catalyst supported by zinc oxide, promoted by potassium and nickel oxide active phase (NiO/K/ZnO) was synthesized.

The catalyst was prepared with one hundred and fifty grams of a commercial zinc oxide, impregnated with an aqueous solution of 3.01 grams of potassium hydroxide (KOH) by the pore volume technique.

The material thus obtained was dried at a temperature around 110°C and calcined at a temperature around 450°C for a period of time around 4 hours to obtain a material of the K/ZnO type.

Ninety grams of K/ZnO material was impregnated with an aqueous solution containing 19.5 grams of nickel nitrate hexahydrate [Ni(NO3)2.6H2O] by the pore volume technique, followed by drying at temperatures in the range of 100 °C to 120 °C for a period of time in the range of 8 hours to 12 hours and calcined at a temperature of around 450 °C for a period of time around 4 hours to obtain a material of the NiO/K/ZnO type . The catalyst thus obtained showed a concentration of 2% by mass of potassium (K) and 15% by mass of nickel oxide (NiO) and a specific area of 17.2 m2/g, determined by the technique of nitrogen adsorption. It is used for the conversion of ammonia and the removal of chloride and sulfur.

EXAMPLE 3: Performance of catalysts - retention of chlorides.

In this example, the chloride retention capacity of the catalysts of the invention, prepared according to Examples 1 and 2, was compared with commercial catalysts used in prior art processes. A first catalyst selected is a commercial nickel-based catalyst. A second catalyst selected for the low temperature shift (LTS) step in the steam reforming hydrogen production process is a commercial CuO/ZnO/Al2O catalyst.

The experiments were carried out in a laboratory-scale process unit, containing a fixed-bed catalyst reactor and using the following experimental conditions:- atmospheric pressure;- temperature of 350°C;- Catalyst mass equal to 2.0 g ; granulometry less than 0.105 mm or mesh 150.

The catalysts were initially pre-treated in hydrogen flow at a temperature of 400°C for a period of time of 60 minutes and then cooled to a temperature of 350°C.

The experiment consists of passing a flow of 40 mL/min. of hydrogen in a saturator containing concentrated hydrochloric acid PA maintained at a temperature of 10°C and fed to the reactor.

The catalysts are compared in terms of time to observe the appearance of chloride in the reactor effluent. An average concentration of the hydrogen chloride solution of 34% was assumed (corresponding to a vapor pressure of the hydrogen chloride over the solution of 26.4 mmHg, according to values tabulated in the literature). The time for the occurrence of chloride “leakage” was used to estimate the chloride holding capacity (kg Cl/kg material).

The reactor effluent was monitored by mass spectrometry, monitoring the fragment with a mass/charge ratio equal to 36.

De acordo com a Tabela 1, o material sintetizado no Exemplo 1 possui capacidade de retenção de cloreto superior em 75% em relação ao catalisador de metanação comercial (caso base). O catalisador sintetizado no Exemplo 2 possui capacidade de retenção de cloreto superior em 875% em relação ao catalisador de metanação comercial.The results are shown in Table 1 below.

According to Table 1, the material synthesized in Example 1 has a chloride retention capacity of 75% higher than the commercial methanation catalyst (base case). The catalyst synthesized in Example 2 has an 875% higher chloride retention capacity than the commercial methanation catalyst.

EXAMPLE 4: Performance of catalysts - sulfur retention.

In this example, the sulfur holding capacity of the catalysts of the invention, prepared according to Examples 1 and 2, was compared to catalysts of the state of the art. The commercial catalysts selected were the same as those used in Example 3.

The experiments were carried out in a laboratory-scale process unit, using the following experimental conditions:- atmospheric pressure;- temperature of 350°C;- catalyst mass equal to 3.0 g; granulometry less than 0.105 mm.

The catalysts were initially pre-treated in hydrogen flow at a temperature of 400°C for a period of time of 60 minutes and then cooled to a temperature of 350°C.

Sulfur was fed to the reactor by passing a flow of 18 ml per minute of a gas mixture containing 15% hydrogen sulfide in hydrogen. The presence of hydrogen sulfide was detected in the reactor effluent by using ampoules for the detection of hydrogen sulfide, known as Drager ampoule. The catalysts are compared in terms of time to observe the appearance of sulfur in the reactor effluent and this value is used to estimate the sulfur holding capacity (kg S / kg material). The results are shown in Table 2 below.

According to Table 2, the material synthesized in Example 2 has 177% higher sulfur retention capacity than the commercial methanation catalyst.

The commercial LTS catalyst, according to the process of the present invention, can be used to compose the plurality of purification beds of the acidic water stream, as it has a chloride retention capacity of 200% and a sulfur retention capacity greater than 200%. by 205% compared to the methanation catalyst.

These examples illustrate the higher chloride and sulfur holding capacity of the catalysts prepared in accordance with the present invention when compared to prior art catalysts. EXAMPLE 5: Performance of catalysts - ammonia decomposition.

In this example, the decomposition activity of ammonia by catalysts of the invention, prepared according to Examples 1 and 2, was compared to catalysts of the state of the art. The commercial catalysts selected were the same as those used in the previous examples.

The experiments were carried out in a laboratory-scale process unit, using the following experimental conditions:- atmospheric pressure;- temperature in the range of 450°C to 550°C;- catalyst mass equal to 0.5 g; granulometry less than 0.105 mm.

The catalysts were initially pre-treated in hydrogen flow at a temperature of 450°C for a time period of 60 minutes. Ammonia was fed to the reactor through flow rates in the range of 10 mL/min. at 40 ml/min. of hydrogen in a saturator containing concentrated ammonium hydroxide PA, in the concentration situated in the range of 28% to 30% of ammonia, maintained at a temperature of 10°C. The reactor effluent was monitored by mass spectrometry, monitoring the fragments with a mass/charge ratio of 17 and 28 for ammonia and nitrogen, respectively.

The catalysts are compared in relation to the ammonia conversion activity (%), varying the hourly gas space velocity (GHSV) parameter and the reaction temperature, according to the results presented in Table 3 below.

The results of Table 3 show that the catalyst synthesized in Example 1 shows activity for the decomposition of ammonia into hydrogen and nitrogen higher than that observed in the methanation catalyst. Both catalysts show significant ammonia decomposition activity only at temperatures above 450°C.

According to the present invention, it is not necessary for the ammonia decomposition reaction to occur simultaneously with the treatment of the stream to remove contaminants, such as sulfur and chloride, since such a reaction will occur downstream of the purification step, in the primary reforming stage of the hydrogen production process by steam reforming. In certain situations, however, such as limited volume of the primary reforming catalyst or high flow rate of ammonia mixed with the hydrocarbon stream, it is desirable that part of the transformation of ammonia to hydrogen occur simultaneously with the removal of contaminants, such as chlorides and sulfur. Therefore, it is possible to reconcile a high capacity to retain contaminants with a high partial conversion of ammonia by employing bed mixtures of materials synthesized according to Examples 1 and 2 and LTS catalyst.

The results confirm the great potential of the application of the process for the production of hydrogen by catalytic decomposition of ammonia solutions, as well as the potential for the purification of the ammoniacal stream by the synthesized catalyst.

The examples demonstrate that it is possible to increase chloride retention by up to 875% and increase sulfur retention by up to 177%, with the use of the catalysts synthesized in the present invention, in relation to commercial methanation catalysts. The commercial LTS catalyst, which according to the present invention, can be used to compose the plurality of acid water stream purification beds, has a chloride retention capacity of 200% and a sulfur retention capacity of 205% in compared to commercial methanation catalysts.

Therefore, the advantages of the present invention in relation to the state of the art become evident, namely:- it provides a relatively low-cost method for the purification of ammoniacal streams from acidic water units;- it provides the purification of ammoniacal streams with a high concentration of contaminants;- allows the production of hydrogen from streams with a high concentration of ammonia and other contaminants, using a steam catalytic reform process; and - can be applied to already installed large-scale hydrogen production units through the steam reforming process, without the need for additional capital costs.

Although the present invention has been described in its preferred embodiment, the main concept that guides the invention remains preserved regarding the innovative character, where those usually versed in the art will be able to envision and practice variations, modifications, alterations, adaptations and equivalents. suitable and compatible with the working environment in question, without, however, departing from the scope of the spirit and scope of the present invention, which are represented by the claims that follow.

Claims (8)

1- PROCESS FOR HYDROGEN PRODUCTION, characterized by comprising the catalytic decomposition of ammonia solutions from acidic water units, carried out in two stages, with a first stage of purification of the ammoniacal stream promoted in a plurality of catalytic beds, and a second stage steam reforming of the purified ammoniacal stream, according to which: the first stage of purification of the ammoniacal stream comprises the following steps:- removing existing metals and chlorides in the ammoniacal stream in a first bed, composed of materials chosen from alumina, silica-aluminas , silica, titanium, magnesium, zirconium and mixtures thereof, maintained at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf/cm2 (98.0665 kPa) to 40 kgf/cm2 (3922 .66 kPa), to obtain a first effluent stream;- transform organic compounds of chlorides and sulfur, contaminants of the first effluent stream, into hydrochloric acid and sulfur hydrogen, and, additionally, hydrogenate olefinic compounds, in a second bed, composed of hydrotreating catalysts chosen between cobalt-molybdenum and nickel-molybdenum, supported on alumina, and alternatively, supported on zinc oxides, at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf/cm2 (98.0665 kPa) to 40 kgf/cm2 (3922.66 kPa), to obtain a second effluent stream; - remove hydrogen sulfide and compounds chlorine, such as hydrochloric acid, ammonium chloride, contaminants from the second effluent stream and, additionally, partially transform the ammonia into hydrogen and nitrogen, in a third bed, composed of catalysts promoted by materials chosen from alkali and alkaline metals earth, supported on materials chosen from zinc oxides, alumina, silica-alumina and mixtures thereof, and having nickel oxide as the active phase, at a reaction temperature in the range of 300°C at 650°C, under pressure in the range of 1 kgf/cm2 (98.0665 kPa) to 40 kgf/cm2 (3922.66 kPa), to obtain a third effluent stream; - remove inorganic and organic compounds of sulfur and chlorine existing in the third effluent stream, in a fourth bed, composed of catalysts chosen among those containing zinc and copper oxides, at a reaction temperature in the range of 300°C to 650°C, under pressure in the range of 1 kgf/cm2 ( 98.0665 kPa) at 40 kgf/cm2 (3922.66 kPa), to obtain a purified ammoniacal stream; the second stage comprises the following steps:- feeding the purified ammoniacal stream into a reactor, for the production of hydrogen by the process of steam reforming to obtain a hydrogen-rich gas stream;- purify the hydrogen-rich gas stream to obtain the final hydrogen product. 2- PROCESS FOR PRODUCTION OF HYDROGEN, according to claim 1, characterized in that the current of ammonia solution corresponds between 1% to 10% by volume of the hydrocarbon load fed to the process. 3- PROCESS FOR PRODUCTION OF HYDROGEN, according to claim 1, characterized in that the arrangement of the beds is determined by the volumetric capacity of the unit and the volume of each bed is selected according to the content of contaminants present in the ammoniacal stream. 4- CATALYST FOR THE PRODUCTION OF HYDROGEN, by catalytic decomposition of ammonia solutions from acidic water units, such catalyst being used in at least one catalytic bed of the purification step of the ammoniacal stream for the production of hydrogen according to claim 1, characterized by having a specific area in the range of 15 m2/g to 30 m2/g and consisting of materials chosen from alkali metals and alkaline earth metals, supported on materials chosen from zinc oxides, silica-alumina and mixtures thereof, and having nickel oxide as active phase. 5- CATALYST FOR THE PRODUCTION OF HYDROGEN, according to claim 4, characterized in that the alkali metal content used in the catalyst is in the range of 1% to 7% by mass and the content of nickel oxide used in the catalyst is in the range of 5 % and 40% by mass. 6- CATALYST FOR THE PRODUCTION OF HYDROGEN, according to claim 5, characterized in that the alkali metal content is between 2% to 4% by mass. 7- CATALYST FOR THE PRODUCTION OF HYDROGEN, according to claim 5, characterized in that the content of nickel oxide is between 10% and 20% by mass. 8- SYNTHESIS OF THE CATALYST FOR THE PRODUCTION OF HYDROGEN, as defined in claim 4, characterized in that it comprises the following steps:- impregnating zinc oxide with an aqueous solution of potassium hydroxide, and drying the material at a temperature of 110°C;- calcin the material at a temperature of 450°C for a period of time of 4 hours, to obtain a K/ZnO material; - impregnate the K/ZnO material with an aqueous solution of nickel nitrate hexahydrate, and dry the material at temperatures in the range of 100°C to 120°C for a period of time in the range of 8 hours to 12 hours; - calcining the impregnated material at a temperature of 450°C for a period of time of 4 hours to obtain a NiO/K/ZnO catalyst.