WO2014085890A1

WO2014085890A1 - Method for preparing structured catalytic systems

Info

Publication number: WO2014085890A1
Application number: PCT/BR2013/000542
Authority: WO
Inventors: Eduardo Falabella Sousa Aguiar; Alexandre De Figueiredo Costa; Luis Maria Gandia PASCUAL; Isabela Brito dos SANTOS; Maria Cruz Arzamendi MANTEROLA; Luciano Costa ALMEIDA; Mario Montes RAMÍREZ; José Antonio Odriozola GORDON
Original assignee: Petróleo Brasileiro S.A. - Petrobras
Priority date: 2012-12-07
Filing date: 2013-12-06
Publication date: 2014-06-12
Also published as: BR102012031208A2

Abstract

The present invention proposes a method for coating metallic microstructures with a catalytic suspension for producing structured catalytic systems. More specifically, suspensions containing a precursor of the active phase of a catalyst, a promoter, a carrier and additives are used for coating a metallic microstructure forming a structured catalytic system that can be used in GTL (gas to liquid) reactions (such as the methane reforming reaction and Fischer-Tropsch synthesis). This method simplifies the conventional method, which requires previous preparation of the catalyst; reduces heat treatments, which is essential for the catalysts involved in Fischer-Tropsch synthesis; and produces coatings that have good homogeneity and adherence.

Description

CATALYTIC SYSTEM PREPARATION METHOD

STRUCTURED

FIELD OF INVENTION

The present invention falls within the field of methods for preparing structured catalytic systems. More specifically, a preparation method wherein a metal microstructure is coated with a catalytic suspension, such catalysts being useful in the reactions involved in the GTL ("gas to liquid") process.

TECHNICAL STATE

Rising global energy demand and increasing pressure to control pollutant emissions, which are responsible for global climate change, have led to increased interest in the use of alternative sources for fuel production, especially natural gas.

The discovery of new reserves and exploitation of existing reserves of natural gas (NG) in the world has been growing in recent years and the conversion of this energy into synthesis gas (mixture of H ₂ and CO), and this in liquid fuels, called process GTL (gas to liquids) is a great option to reduce the world economy's dependence on the predominant use of crude oil.

Such liquid fuels are obtained via Fischer-Tropsch synthesis, where the synthesis gas is converted into hydrocarbons, water and oxygenated products such as alcohols, aldehydes and ketones.

However, in remote or space-constrained locations such as oil production platforms, installing conventional GTL units is neither technically nor economically feasible.

One of the alternatives to solve this space restriction problem is the use of microreactors combined with structured catalysts. Because of their small size by a factor of at least 100, microreactors allow fluids to pass through thousands of capillaries, giving the chemical reaction high mixing rates through diffusion between fluids, high heat transfer and better utilization. and reduce energy consumption associated with agitation and heat exchange.

As a result, microreactors bring benefits in terms of increased surface / volume ratios and reduced linear and volumetric dimensions of the plant while increasing productivity.

Such microreactors have microchannels, smaller than 1 millimeter, where chemical reactions occur. In some cases, metal structure microchannels are coated with suspensions or suns containing active compounds, the combination of the metal structure coated with the active compound called the structured catalyst.

US 6,555,725 proposes the use of a monolithic catalyst for the in-situ conversion of paraffins produced in a mud bed Fischer-Tropsch process.

US 7,067,560 and US 7,067,561 deal with chemical processes for converting natural gas (methane) to long chain hydrocarbons using microchannel technology. Both documents describe that for the reforming step, the microchannel thickness of the stabilized alumina coating on the metal substrate is less than 100 μιη and for the Fischer-Tropsch reaction, the Co / y-AI ₂ 0 ₃ catalyst coating on the surface of the metal sheets has a typical thickness of 120 μΐη - 80 μ ^η η.

US 7,087,651 and US 7,109,248 show the production of long chain hydrocarbons from synthesis gas using microreactors operating at high spatial speeds and temperatures above 230 ° C to prevent the formation of waxes that could be retained. catalyst surface and limit reagent diffusion to low CO

US 2004/0147620 A1 describes the preparation of catalysts for Fischer-Tropsch (FT) synthesis on FeCrAlloy foams. First, the FT catalyst was prepared with a solution of cobalt nitrate II hexahydrate and perrenic acid (20 wt.% Co and 4 wt.% Re) which was used to impregnate γ-ΑΙ ₂ 0 _3ι being the product. thus obtained subjected to drying at 100 ° C for at least 4 hours and calcination at 350 ° C for at least 3 hours. Then a catalyst suspension and distilled water with a water: catalyst ratio of 2.5 were prepared. The catalyst suspension was ground for 24 hours prior to foaming. The thickness of the catalyst layer (> 20 μηι) is much smaller than the particles of conventional fixed bed (> 100 μιη) or mixed or fluidized reactors (> 50 μιη). Therefore, the internal mass transfer coefficient (diffusional) is higher in monoliths.

In the same document, the catalytic activity of the catalyst and the coated foams was evaluated. In general, the powder catalyst produced greater conversion than the foam monoliths. Under the same conditions, however, the monolith showed at least three times less methane. This result may be related to the ability of the monolith to favor heat dissipation outside the reactor thus avoiding the increase of hot spots, which are typical in fixed bed reactors.

US 2005/0244304 A1 describes the construction of a methane reforming microchannel device. The microchannels were first covered by chemical vapor deposition with a layer of Ni aluminide, later oxidized to the formation of an alumina layer. Then the alumina layer was treated with a lanthanum solution and then the microchannels were coated. with an alumina sol (15 wt% alumina) and finally with a 10% platinum solution. The document concludes that the uniformity of the interior of the microchannels is influenced by the way the surface forces (capillarity and adhesion) act. And when these forces surpass the gravitational forces within the channels, the obtained coating presents greater uniformity.

US 5,208,206 describes the coating of γ-ΑΙ ₂ 0 ₃ and 15% Νϊ / γ-ΑΙ ₂ 0 ₃ on 50 mm x 0.4 mm x 0.3 mm microchannel stainless steel plates.

The plates were subjected to two different adhesion tests: the first, which is known as thermal shock, is to raise the temperature to 800 ° C (10 ° C / min.) And suddenly cool to room temperature; In the second test (previously described in US Patent 5,208,206), the plate is submerged in petroleum ether and subjected to low mechanical stress produced by ultrasonic impulses for 30 minutes. The plates showed no mass loss in the thermal shock test, while the plates submitted to ultrasound had a maximum loss of 7%.

Existing information on the preparation of structured catalysts in the literature shows the existence of two major strategies. The first is the preparation of the final catalyst in stabilized form by calcination and the subsequent preparation of a stable suspension with which to coat the metal structure and stabilize with a final calcination. This strategy therefore requires two calcinations.

The second is based on preparing the suspension only with the catalytic support, with which the structures are covered to subsequently impregnate the active phases and subject it to final calcination. This duplicate only requires calcination of the active phase, but when structures are large, complex or with very small channels, It produces important heterogeneities in active phase distribution which, moreover, is difficult to detect which leads to poor catalyst yield.

Therefore, the present invention proposes a method of preparing structured catalysts where metal microstructures are coated with catalytic suspensions, the coatings obtained being homogeneous, very adherent, and allowing the loading of the metal microstructures with the desired amount of active phase by coatings. successive.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is an alloy plate with 10 microchannels generated by tangential milling.

Figure 2 shows types of structured catalysts: (A) monoliths; micromonolite (B) and foam (C).

Figure 3 shows the sequence of preparation of a monolith or micromonolite.

Figure 4 shows coating images of microchannel plates with the suspension prepared by the method of the present invention.

Figure 5 shows the wall of the microchannel coated with the suspension useful for the method of the present invention.

Figure 6A is a graph of the bonded charge by number of coatings using different structures and prepared by the method of the present invention: "A" micromonolite 1, "B" micromonolite 2, "C" monolith 1, "D" monolith 2 Έ "foam 1," F "foam 2," G "welded microchannel plate and" H "microchannel plate with screw. Tack test: micromonolytes 97%, monoliths 82%, foams 80%, microchannel plates 88% .

Figure 6B is a graph of the bonded charge by number of deposits using different structures and prepared by the classical method, or 0542

6 is, with a suspension prepared with a previously prepared catalyst, as follows: Ί "micromonolyte 4," J "micromonolyte 5," L "monolith 3," M "monolith 4," N "foam 3," O "foam 4," P "welded microchannel plate, and" Q "microchannel plate with screws. Adhesion test: micromonolytes 92%, monoliths 73%, foam 71%, microchannel plates 63%.

Figure 7 is a graph of the bonded charge by number of coatings using different suspension substrates prepared by the method of the present invention containing catalysts for methane (Ni / La-Al ₂ 0 ₃ ), methane (Pd) combustion reactions. / La-Al ₂ 0 ₃ ) and Fischer-Tropsch Synthesis (CoRe / AI ₂ 0 ₃ ), where: "A" Co-Re micromonolyte / AI ₂ 0 ₃ (97% adherence), "B" Co-Re Monolith / AI ₂ 0 ₃ (adhesion 82%), "C" Co-Re Foam / AI ₂ 0 ₃ (adhesion 80%), "D" Co-Re / AI ₂ 0 ₃ welded microchannel plate (88%), Έ "Co-Re / AI ₂ 0 ₃ microchannel plates with screws," F "Ni / La-Al ₂ 0 ₃ micromonolyte (adhesion 98%)," G "Ni / La-Al monolith ₂ 0 ₃ (adhesion 89%) , Ή "Ni / La-Al ₂ 0 ₃ foam (adhesion 51%), Ί" Ni / La-Al ₂ 0 ₃ welded microchannel plates (93% adhesion), "J" microchannel plates with Ni / La-Bolt Al ₂ 0 ₃ , "L" Pd / La-Al micromonolyte ₂ 0 ₃ (98% adhesion), "M" Pd / La-Al ₂ 0 ₃ monolith (90% adhesion), "N" Pd / La-Al foam ₂ 0 ₃ (adhesion 77%), Ό "Pd / La-Al welded microchannel plate ₂ 0 ₃ (95% adhesion), and" P "welded microchannel plate Pd / La-Al ₂ 0 ₃

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method of preparing structured catalytic systems involving the coating of metallic microstructures with a catalytic suspension, such systems being suitable for the reactions involved in the GTL process, such as steam reforming, combustion and Fischer synthesis. -Tropsch.

The metal microstructures useful for the present invention are in the form of metal alloys. Such alloys can be chosen steel, nickel or aluminum alloys, among others, but the most commonly used are high aluminum ferric alloys (such as FeCralIoy, FeCralloy JA13, Aluchrom, Aluchrom YHf, Kant al AF and APM, Ugine Saoie12178 and 12179 , among others).

Ferric alloys undergoing treatment at high temperatures undergo a process of migration of part of aluminum to the surface, where there is the formation of an alumina shell.

This feature allows the use of these alloys in processes that employ very high temperatures between 1,100 ° C and 1,200 ° C, and since the oxidation of these alloys is carefully controlled they have a unique morphology of high roughness needles and plates allowing excellent anchoring of the catalytic cap.

Other alloys that are very suitable for structured catalytic systems are aluminum, which can be subjected to an electrochemical anodizing treatment that creates a highly adherent alumina coating which, under specific conditions, has a texture suitable for use as a catalytic support or a highly rough surface morphology, which allows excellent mechanical anchoring of a catalytic film.

As for form, the microstructures can be presented as low cell density metal monoliths (monoliths), high cell density metal monoliths (micromonoliths), meshes and foams.

When in the form of longitudinal parallel channel monoliths, they are manufactured by rolling smooth and corrugated reciprocating plates, the corrugated being obtained by passing a metal blade between two sprockets, which generates a corrugated with the shape of the teeth of the rollers. .

Thus, depending on the distance between the teeth and their depth, channels of different sizes are generated, giving rise to different cell surface densities.

In general, monoliths are prepared from FeCralIoy slides with a thickness ranging from 10 pm to 100 pm, more preferably from 25 pm to 75 pm. These monoliths also have a hydraulic diameter ranging between 100 pm and 2,000 pm, more specifically between 500 pm and .000 pm and cell density ranging between 1, 4 and 48 cells / cm ² , but densities between 4 and 20 cells are more indicated. / cm ² .

Micromonolites useful for the present invention may be prepared from FeCralIoy blades or other equivalent alloy such as Aluchrom, Aluchrom YHf, FeCrAlloy JA13, Kanthal AF, Kanthal APM, Ugine Saoie 12178 and Ugine Saoie 12179, with thicknesses ranging from 10 pm to 100 pm, preferably FeCralIoy blades with thickness ranging from 25 pm to 75 pm. Such mochromonolites generally have a hydraulic diameter ranging from 100 pm to 1,000 pm, with diameters ranging from 100 pm to 500 pm, and cell density ranging from 24 to 120 cells / cm ² , more specifically 40 to 60 cells / cm ² . cm ² .

The foams for use in accordance with the method of the present invention should be cut into aluminum blocks or sheets, such foams having porosities between 1% and 99%, preferably between 50% and 98%, and pore surface densities ranging from 0, 04 and 20 pores per linear centimeter, preferably at densities between 0.4 and 8 pores per linear centimeter.

Microchannel plates can be prepared in many ways, such as: front or tangential milling, wire or electrode erosion, chemical stripping, screen printing or deep drawing, among others.

The plates used are generally 1 mm thick aluminum alloy ferritic alloy plates 20mm x 20mm. Ten microchannels of 0.7 mm x 0.7 mm are longitudinally engraved on each plate, separated by a wall thickness of less than 1 mm, with 0.5 mm being preferable and 0.3 mm more preferable. the extremes two 5 mm bands without microchannels (figure 1).

When employing the method of the present invention for the preparation of structured catalytic systems to be employed in Fischer-Tropsch synthesis, the catalytic suspension should contain a catalyst comprising cobalt as the active metal or Fe or Ru and may also contain metallic promoters such as Re, Pd, Pt, Zr, Ti, Cr, Zn, Al, Mg, Mn, Cu or Ag, among others.

When the objective is the preparation of structured catalytic systems for methane reforming reaction, the catalytic suspension should contain a catalyst with Ni as the active phase, or Ru, Rh, Pd, Ir or Pt, using MgO, Mg ₂ as support. AI0 ₄ , Si0 ₂ , Ce0 ₂ , Zr0 ₂ , TiC½ or a mixture thereof, incorporating alkaline or alkaline earth metals, or an alumina support stabilized with La, Ce or Mg, among others.

Also, since the objective is the preparation of a catalytic system structured for combustion reactions, the catalytic suspension should contain a catalyst with Pd as active metal, or Pt, Ru, Ir, in addition to other noble metals or oxides of transition elements. , in an alumina support, stabilized with La, Ce, Mg, among others.

The deposition of the catalysts comprised in the catalytic suspension on the metal microstructures represents one of the crucial phases of the method of preparing the structured catalytic systems of the present invention. Normally, what is sought is the homogeneous distribution of the catalytic material in the metal microstructure, as well as high adhesion.

In the present invention the washcoating process is used for the catalyst deposition on the metal microstructures, all catalytic precursors being added to the metal microstructure in the form of a catalytic suspension, promoting the catalyst preparation and simultaneously coating the metal microstructure.

In order to allow adequate surface coverage of the microstructures, the microstructures must be pre-treated so that the aluminum present in the alloy migrates to the surface where the alumina is oxidized in the form of a tightly adherent and rough layer, favoring the coating process and enhancing the adhesion of the catalyst film present in the catalytic suspension after drying and calcining.

Catalytic coating is performed by immersing the metal microstructures in a catalytic suspension. Such method usually requires the control of three fundamental parameters: immersion rate, excess suspension elimination method and solid drying / calcination.

Such suspensions are prepared by dissolving the active phase precursors (eg Co for Fisher-Tropsch synthesis, Ni for methane reforming or Pd for combustion) and promoters (eg Re for Fisher-Tropsch synthesis) from soluble salt catalyst (eg Co (NO ₃ ) ₂ -6H ₂ 0, Ni (NO ₃ ) ₂ -6H ₂ 0, Pd (OH) ₂ and HRe0 ₄ ) in a solvent which may be water, ethanol acetone or a mixture thereof.

Then a desired amount of support (e.g. Al ₂ 0 ₃ ) is added and the pH adjusted to a value away from the isoelectric point of the support to potentiate repulsions that help stabilize the suspension but without reaching values. that produce the dissolution of the support.

The resulting mixture is sonicated for a time of approximately 10 minutes. The suspension is then subjected to stirring and a certain amount of colloidal suspension (additive) (e.g. 20% colloidal alumina solution) is slowly added. THE Colloid helps stabilize the suspension and increase the adhesion of the catalyst film once dried and calcined. The suspension is kept under stirring for 24 hours prior to the overcoating step.

The metal microstructures are introduced into the suspension by the washcoating technique at a constant speed of 3 cm / min. remaining in this suspension for 3 minutes. They are then lifted from the suspension at this same speed. However, the structure may be submerged in the suspension at a speed which may vary from 1 cm / m 2. and 6 cm / me. being at least 1 minute submerged in the suspension and being removed from the suspension also in the same range of input speed variation.

Excess suspension is eliminated by centrifugation, suction or blowing via compressed air. Opting for centrifugation, the speed used ranges from 10 rpm to 10,000 rpm for at least 1 minute, preferably from 100 rpm to 5,000 rpm for at least 2 minutes and most preferably from 200 rpm to 2,000 rpm for at least 2 minutes. ,5 minutes. If suction or blowing is chosen, a uniform air flow must be passed through all channels of the structure.

For drying, a warm jet stream of hot air is distributed throughout the microchannels at a temperature of 50 ° C to 120 ° C for at least 1 hour, with a preference of 60 ° C to 100 ° C. C for at least 2 hours.

Once the substrate has cooled, it is recoated to the desired load. At the end it calcines at the required temperature.

In the present invention, the substrate for STF has been calcined at a temperature between 150 ° C and 600 ° C for at least 2 hours, and preferably at a temperature of 250 ° C to 400 ° C for at least 4 hours. For reforming and combustion catalysts working at high temperatures, the calcination is done at a higher temperature, as it ensures greater adhesion of the substrate. This procedure is general for all substrates (monoliths, micromonolites, foams and microchannel plates - Figures 3A, 3B, 3C). In the case of microchannel plates, prior to coating, the plate is protected with a masking tape, leaving only the entry and exit zone of one direction of the microchannels uncovered. This prevents the catalyst from depositing on the outer surface of the block and in the microchannels in another direction. The adhesive tape is smoothly peeled off and resists drying at 50 ° C.

Several variables influence the catalytic coating, including: solids content; particle size; isoelectric point (pH), type of additive; number of coatings; type of coating; excess elimination etc.

Solids Content - The highest possible solids content is generally sought so that the amount of catalyst deposited by coating is as large as possible and therefore fewer coatings are required. By increasing the solids content, the viscosity also increases and the maximum amount will be given by the optimal value of this variable. The relationship between solids content and viscosity depends on many factors, such as particle size, the nature of the solvent or the presence of additives. Depending on the system, the maximum solids content that can be used is between 5% and 40%. For Co / AI ₂ 0 ₃ catalysts the optimal value approaches 20%.

Particle size has a double role. On the one hand it has to be small enough that the suspension is stable and does not settle. However, this sedimentation also depends on solvent viscosity, presence of additives and solids content. On the other hand, a very small particle size greatly increases the viscosity of the suspension allowing for lower maximum solids contents. Therefore, the recommended particle size is usually between 1 and 10 microns for the case of the GTL catalyst.

The isoelectric point marks the pH value at which the surface charge of the oxides is zero. For this value, there are no repulsions between the particles by which the flocculation of the particles takes place and thus the suspension destabilization. It is therefore advisable to work with pH values sufficiently different from the isoelectric point so that there is a high repulsive potential between particles that potentiates suspension stabilization. However, one must take into account that at extreme pH, the oxides dissolve and therefore it is recommended to seek pH compromise values. Usually, values of 2 to 4 pH units above or below the isoelectric point are usually adequate. The pH of the solution is adjusted with at least one acid which may be nitric, acetic or sulfuric acid.

Additives used in suspensions are usually of two types: inorganic colloids or high molecular weight soluble organic compounds.

Inorganic colloids, once calcined, remain in the coating as oxides. Its role is to increase the viscosity of the suspension, which helps its suspension stability; and enhancing the adhesion of the catalyst layer after calcination. This is achieved by greater cohesion of the catalyst film (the layer does not crumble) and greater adherence of this layer with the substrate (the layer does not peel).

Colloidal alumina is the reference colloid since the pretreated metal substrate is coated with alumina (chemical compatibility), but depending on the nature of the support colloidal silica, titania, bohemite, cerium, zinc oxide and other materials are used. etc.

The role of organic additives (surfactants) is more complex and as they are eliminated during calcination, they play an important role only in stabilizing the suspension, coating or drying. Its first role is the stabilization of the suspension by increasing the viscosity. However, it is sometimes said that they are viscosity modulators because they may also decrease it if it is too high for a very small particle size. They also reduce surface tension which improves substrate moisture facilitating homogeneous coating, and most importantly, reducing capillary forces during drying and preventing cracking of the catalyst film.

Polyvinyl alcohol, polyvinylpyrrolidone, sodium polymethacrylate or methylcellulose are typical organic additives for the formulation of catalyst suspensions. The contents of additives are very variable, but range from very low values to amounts close to catalyst. That is, they range from 0.1% to 50% by weight with respect to catalyst mass.

The number of coatings depends on the desired load and the amount deposited on each coating. In general, it is preferred to make thin, thin coatings that produce very homogeneous and sticky results even if this requires many repeated coatings. A typical coating may carry between 0.1 mg / cm ² and 0.5 mg / cm ² metal substrate. Usual loads on metallic substrates usually range from 0.5 mg / cm ² to 5 mg / cm ² , although it is preferable between 1 mg / cm ² and 2 mg / cm ² .

Calcination is a fundamental step in catalyst preparation and has a multiple role. Firstly, it allows the decomposition of precursors such as nitrates, carboxylates, oxoanions, among others in their corresponding oxides. In addition, it produces the decomposition of other additives that add to the suspensions for the coating of structured substrates. Secondly, it produces catalyst stabilization as it favors the interaction between the active phase and the support, reducing its mobility against the sintered one.

However, this interaction has to be moderate, otherwise Very stable interacting compounds can be formed which are difficult to activate by further reduction, as in the case of supported metal catalysts. In the case of Co-alumina catalysts, the problem of calcination is the formation of cobalt aluminate which is reduced to several degrees above cobalt oxides and therefore does not give rise to active catalysts under normal reduction conditions to avoid sintered active phase.

Another aspect of the invention is a catalytic microreactor containing the structured catalytic system of the present invention wherein the constituent metal microstructures of the system are distributed in the reactor in the form of metal plates with a height of 0.5 mm to 2 mm, a width of 5 mm to 50 mm. mm, and length from 5 mm to 50 mm.

Such metal plates are arranged to form microchannels with a height from 200 microns to 900 microns, width from 200 microns to 900 microns and hydraulic diameter from 0.5 mm to 1 mm.

The microchannels should be separated from each other by a wall thickness of less than 1 millimeter, preferably less than 0.5 millimeter.

Therefore, calcination treatments must be sufficient to stabilize the system, but without forming only aluminate. In the case of structured catalytic systems, calcination also aims to form the catalyst film on the metallic substrate and enhance its cohesion and adhesion.

EXAMPLES

Example: Preparation of a Co-Re catalyst by the incipient impregnation method.

200g of γ-ΑΙ ₂ Ο ₃ (Spheralite SC SCS505), with particle size of 2.5 mm, were ground in a disk mill for 5 minutes reaching a d ₉₀ = 18.7 μΐη. The pore volume of the support was determined by H ₂ O impregnation until the moisture point was detected. incipient (VpAI ₂ 0 ₃ = 0.55 cm ³ / g). 20.2 g of Οο (Ν0 ₃₎ ₂ · 6Η ₂ 0 and 0.13 g of ₄ HRe0 were dissolved in 17.5 g of deionized _H2 0. 8.75 g of the precursor salt solution (half) was slowly dripped with a pipette over 15.9 g of γ-ΑΙ ₂ 0 ₃ which was constantly homogenized to a very uniform apparently dry wet mass, in which the particles of the solids begin to agglomerate (incipient moisture). The obtained mass was dried for 6 hours at 60 ° C and the other 8.75 g of the precursor solution added. The prepared catalyst was dried at 60 ° C for 2 hours before calcination at 350 ° C for 6 hours. The calcined catalyst contains 19.8 wt% Co and 0.5 wt% Re.

Example 2: Preparation of structured supports of monoliths, micromonolites and foams.

Two types of structured supports were used, longitudinal channel metallic monoliths and foams. In turn, longitudinal channel metal monoliths are further divided into two different types: low cell density monoliths (monoliths) and high cell density monoliths (micromonoliths).

Low cell density monoliths (monoliths, Figure 2A) were prepared from 50 µm thick FeCrAlIoy (Goodfellow) slides, with a thickness ranging from 10 pm to 100 pm, with 25 pm to 75 pm being preferable. Strips 3 cm wide and 20 cm and 23 cm long were cut (Figure 3A). Once cut, the strips were cleaned with soap and water, bleached with acetone and finally air dried to remove all surface impurities.

The longer blades curled (Figure 3B) by means of a self-designed mechanical device consisting of two Nylon sprockets. The distance between the teeth and the degree of interpenetration of the wheels defines the size of the channels (hydraulic diameter) which can vary between 100 pm and 2,000 pm, more specifically between 500 pm and 1,000 pm and the density of the teeth. cells which may range from 1.4 cells / cm ^{2 to} 48 cells / cm ² , more specifically between 4 cells / cm ² and 20 cells / cm ² . Exact measurements are shown in table 1.

To form the monolith a smooth and rough plate was taken which were introduced between two steel rods joined on one side and with a locking system on the other so that the plates could not come loose (Figure 3C). Once hooked, the plates screwed together (Figure 3D) and the monolith was fastened with a wire to maintain the size and shape of the part and channels (Figures 2A and B).

For micromonoliths (Figure 2B) we used

FeCrAHoy (Goodfellow) with a thickness of 50 pm and the thickness may vary between 10 pm and 100 pm, being preferable between 25 pm and 75 pm. Strips 3 cm wide and 38 cm and 47 cm long were cut. The micromonolyte cleaning and construction steps were performed in the same way as for monoliths, but using much smaller tooth curling rollers.

The micromonoliths presented channel size (hydraulic diameter) ranging between 10 pm and 1,000 pm, more specifically between 100 pm and 500 pm and in turn the cell density which can vary between 24 cells / cm ² and 120 cells / cm ² , more specifically between 40 cells / cm ² and 60 cells / cm ² . Exact measurements are shown in table 1.

Before being coated, the monoliths and micromonolites were subjected to a heat pretreatment, which was carried out by air oxidation (calcination) for 22 hours at 900 ° C. This pretreatment aims to migrate the aluminum to the surface by creating a roughly adherent, rough-coated alumina layer.

DUOCEL commercial aluminum foams manufactured by ERG Materials and Aerospace come in the form of large blocks or sheets of 40 mm thickness. To cut the cylinder, a special hollow drill with diamond wire was used to obtain the samples. The drilling operation is delicate and it is important to control the speed of the drill introduction into the material. The obtained foams have pore surface densities ranging from 0.04 pores / cm to 20 pores / cm, more specifically between 0.4 pores / cm and 8 pores / cm and porosity ranging from 1% to 99%, more specifically between 50 % and 98%. Exact measurements are shown in table 1.

Once obtained from the 40 mm x 16 mm foams, they were subjected to a distilled water cleaning process to remove impurities and particulate debris from the material itself, followed by acetone and subsequent oven drying at 60 ° C.

The foams were pre-treated by anodizing process (1.6 M oxalic acid, 50 ° C, 40 minutes and a density of 2 A / sample) to obtain very rough alumina layers with high adhesion. .

Example 3: Fabrication of Microchannel Plates.

Initially, 20 mm x 20 mm x 1 mm FeCrAlloy ® plates were cut by wire erosion. Subsequently, 10 grooves of 0.7 mm x 0.7 mm were made, with wall separation of less than 1 mm between them, preferably less than 0.5 mm, and most preferably 0.3 mm by technique. of tangential milling with disc mills. However, microchannel plates may have a height of 0.5 mm to 2 mm; width from 5 mm to 50 mm and length from 5 mm to 50 mm, said microchannels having a height of 200 microns to 900 microns and a width of 200 microns to 900 microns and a hydraulic diameter of 0.5 millimeters to 2 millimeters. preferably between 0.5 mm and 1 mm and most preferably 0.7 mm and geometric interior area of the 56 mm ² channels / microchannel. Pairs of slotted and non-slotted plates were aligned to drill 4 holes by drilling with 3.2 mm diameter drills to subsequently insert M3 screw-nut pairs to maintain the holes. plates joined at later process stages (catalyst deposit).

Table 1 shows the main geometric characteristics of structured systems. The geometrical area is fundamental because it allows to calculate the specific catalyst load (mg / cm ² ) and thus to estimate the thickness of the catalytic coating film. Hydraulic diameter and porosity controlled the pressure drop that structures produce: the smaller the hydraulic diameter and porosity, the greater the pressure drop.

Example 4: Preparation of a conventional suspension using the catalyst of example 1.

The suspension was prepared by mixing 19 g of catalyst from Example 1 76 g of deionized H ₂ 0 at pH = 4. The mixture was subjected to ultrasound for 10 minutes. The suspension was then subjected to magnetic stirring and 5 g of 20% colloidal alumina solution (Nyacol AL-20) was slowly added. The suspension was stirred for 24 hours prior to the overcoating step. Example 5: Preparation of a suspension with the method of the present invention.

20.2 g of Co (N0 ₃₎ ₂ .6H ₂ 0 and 0.13 g of ₄ HRe0 were dissolved in 76 g of deionized H ₂ 0 and adjusted to pH = 4 with magnetic stirring. Then 14.9 g of γ-ΑΙ ₂ 0 ₃ was added slowly. The suspension was sonicated for 10 minutes. Then, under low agitation, 5 g of 20% colloidal alumina solution (Nyacol AL-20) was added. The suspension was kept under low agitation for 24 hours prior to the overcoating step. 5 g of suspension was dried for 48 hours at 60 ° C to give 1 g of catalyst. This catalyst was then milled at 400 rpm for 5 minutes in a ball mill and calcined at 350 ° C for 6 hours. The final catalyst contained 19.8 wt% Co and 0.5 wt% Re.

Example 6: Characterization of catalysts.

For the purpose of comparison between the coating methods, the catalysts were characterized by H ₂ chemorption. In the reduction step, the catalyst was reduced to 350 ° C for 600 minutes with a 2 ° C / min ramp. and 30 mL / min H ₂ flow, then the temperature was lowered to 100 ° C with 30 mL / min flow Ar. and held for 90 minutes at this temperature. Then the temperature was raised with a ramp of 10 ° C / min. to 350 ° C and was maintained for 60 minutes with the same air flow.

Table 2 shows the chemisorption results of the prepared catalysts. It is observed that the catalyst prepared by the method of the present invention, by requiring only calcination, promotes greater reducibility and larger metal area, which means dispersion and consequently smaller particle size of Co.

Table 2 shows the characterization results of the catalyst prepared by the conventional method (Vp) and the method of the present invention. In the case of the conventional catalyst, it was subjected to two calcinations, as would occur in a conventional coating procedure. Therefore, the comparison was made between the catalyst powder prepared by the traditional method (twice calcined) and the catalyst prepared by the method of the present invention (dried and calcined once). This comparison was made with the powder form, to be able to perform the characterization by hydrogen absorption (atomic absorption) that allows to determine the metallic surface, the degree of dispersion. and the particle size of the metallic Co crystals. Both methods compare both Co-only and Re-promoted catalysts. Preparation of catalysts without Re was carried out according to examples 1 and 5 without including the compound of Re.

The results show that in all cases promotion with

Re allows a larger reduced fraction (reduction promoter) accompanied by an increase in the metal surface, which supposes a decrease in the crystal size of Co. The second calcination of the catalyst prepared by the traditional method always produces a sintered metal phase and a lower reducibility. of the samples. Consequently, catalysts prepared by the method of the present invention always have better properties (metal surface, degree of reduction, dispersion and size of Co) than their counterparts prepared by the conventional method and calcined twice.

Example 7: Coating the structures prepared in examples 2 and 3 with suspensions prepared according to example 4 (conventional method).

For the coating of the metallic substrates prepared in example 2, they were submerged in the suspension prepared in example 4 at a constant rate of 3 cm / min., And were kept submerged for 1 minute and then removed at the same rate. Elimination of excess suspension was performed by centrifuging the structure at 800 rpm for 5 minutes. They were then dried at 60 ° C. This procedure was repeated until the catalyst mass reached 450 mg on each structure. Finally, they were calcined at 350 ° C for 6 hours. The results of the specific load obtained in successive coatings with each of the studied structures are shown in Figure 6B, which also indicate the results obtained in the adhesion test.

Example 8: Covering of the structures prepared in examples 2 and 3 with suspensions prepared as per example 5.

First the plates and screws were covered with an easily removable tape so that the covering of the structure could only occur in the microchannels. They were then tied with a small gag and introduced into the suspension at a speed of 3 cm / min., Holding them for 3 minutes and removing them at the same speed. Excess suspension was eliminated by suction method with the microchannels in the vertical direction. The structures were dried with a 50 ° C air dryer at a distance of 30 cm from the upright microchannel inlet. The tape was then peeled off and the plates weighed. This procedure was repeated until the plates reached between 1.5 cm / cm ² and 2.0 cm / cm ² .

The structures prepared in Example 2 were coated with the suspension of Example 5 (method of the present invention). The procedure was done in the same way as in the previous example.

The results of the specific load obtained in successive coatings with each of the studied structures are shown in Figure 6A, which also indicates the results obtained in the adhesion test.

Analysis of the results shown in Figures 6A and 6B yields several conclusions.

The coating procedure by both methods is very reproducible and additive when successive coatings are repeated in all geometries. The first cover alone seems to carry more than successive coverings in some cases, as can be deduced by extrapolating the estimate line to cut the y-axis at the intercept.

The specific load obtained by the coating is very similar in almost all studied geometries. Adhesion generally increases by decreasing the hydraulic diameter of the structure.

The adhesion obtained with the method of the present invention is always superior to that obtained with the conventional method for all tested geometries.

Example 9: Preparation of Ni / La / Al ₂ 0 ₃ suspension

Initially, the stabilized alumina used as a support (La / Al ₂ 0 ₃ ) is prepared by adding 275 g of γ-ΑΙ ₂ 0 ₃ to a solution containing 131, 14 g of La (NO ₃ ) ₃ .6H ₂ 0 in 393 ml of distilled water while stirring for 4 hours and then the solvent was evaporated at 120 ° C for 24 hours. The solid was triturated and calcined at 900 ° C for 4 hours.

26 g of La / Al ₂ 0 ₃ was mixed with 180 g of H ₂ 0 containing 5 wt% PVOH for one hour. Then 13.5 g of Ni (NO ₃ ) ₂ .6H ₂₀ , which corresponds to 7.5% by weight of Ni, was added. The mixture was stirred for 30 minutes, adjusting the pH to around 4 by adding 1 g of 2 M HN0 _3. Then 20 g of 20% colloidal alumina solution (Nyacol AL) was added. -20). This suspension was stirred for 48 hours.

Example 10: Preparation of the Pd / La / Al ₂ 0 ₃ suspension

30 g La / Al ₂ 0 ₃ (prepared in example 9) was mixed with 195 g H ₂ 0 (with 5 wt% PVOH) for 1 hour. Then 1 ml of an 8.3% palladium solution, which corresponds to 0.25 wt% Pd with respect to the support, was added. The mixture was stirred for 30 minutes, adjusting the pH to around 4 by the addition of 2 g HN0 ₃ . Then 20 g of 20% colloidal alumina solution (Nyacol AL-20) was added. This suspension was stirred for 48 hours.

Example 11: Coating of the structures prepared in Examples 2 and 3 with the Ni / La-Al ₂ 0 ₃ and Pd / La-Al ₂ 0 ₃ suspensions. For the coating of metal substrates prepared in Example 2, they were submerged in the suspension Ni / La-Al ₂ 0 ₃ and Pd / La-Al ₂ 0 _3l prepared in Examples 9 and 10, respectively.

The micromonolites, monoliths and foams were submerged at a constant rate of 3 cm / min, kept submerged for 1 minute and then removed from the mixture at the same rate. Excess elimination was performed by centrifuging the structure at 500 rpm for 2.5 minutes. It was then dried at 80 ° C. This procedure was repeated until the catalyst mass reached between 1 mg / cm ² and 2 mg / cm ² . Then the coatings made with catalyst Ni / La-Al ₂ 0 ₃ were calcined at 900 ° C for 4 hours; The coatings made with Pd / La-Al ₂ 0 ₃ were calcined at 800 ° C for 1 hour. Due to the melting point of aluminum, foams coated with Ni / La-Al ₂ 0 ₃ and Pd / La-Al ₂ 0 ₃ catalysts were calcined at 500 ° C.

The plates and screws of the microchannel plates were first covered with an adhesive tape (easily removed by the washcoating process) so that the suspension coating could only occur in the microchannels. They were then attached by means of a small gag and introduced into the suspension with the vertically oriented channels at a speed of 3 cm / min. Where they were held for 3 minutes and removed at the same speed. Excess elimination was performed by suction method and then the microchannel plates were suspended and dried at an air temperature of 50 ° C with a hot air dryer at a distance of 30 cm from the microchannel inlet in vertical position. Then the strap was removed and the plates were weighed. This procedure was repeated until the plates reached between 1 cm / cm ² and 2 cm / cm ² . Then the coatings made with catalyst Ni / Al ₂ 0 ₃ La- were calcined at 900 ° C for 4 hours; and coatings made with Pd / La-Al ₂ 0 ₃ were calcined at 800 ° C for 1 hour. Figure 7 shows the specific charge deposited on the different metallic structures with successive coatings in suspensions such as the present invention.

The analysis of the results shown in Figure 7 allows us to conclude: a) The coating procedure by the method of the present invention is very reproducible and additive when successive coatings on all geometries are repeated. The first cover alone seems to carry more than successive coverings in some cases, as can be deduced from the estimated source order. b) The specific load obtained by coating is very similar for almost all studied geometries.

c) Adhesion generally increases by decreasing the hydraulic diameter of the structure.

d) The method of the present invention adapts perfectly to all studied catalysts of the GTL process over all studied geometries, which shows its universal character for other catalytic systems.

Claims

METHOD OF PREPARING STRUCTURED CATALYTIC SYSTEMS, comprising the steps of: (a) providing a metal microstructure for the method consisting of metal alloys capable of withstanding temperatures ranging from 1,100 ° C to 1,200 ° C;

b) prepare the surface of metallic microstructures;

c) preparing a catalytic suspension comprising catalyst active phase precursors, promoters in the form of a soluble salt, a polar solvent, a catalyst support and additives;

d) promote the contact of the metal microstructure with the catalytic suspension by immersing the metal microstructure in the catalytic suspension at a speed that may vary between 1 cm / min. and 6 cm / min. remaining the metal microstructure for at least 1 minute submerged in the suspension;

e) remove excess catalytic suspension on the metal microstructure;

f) repeating items d) and e) until the catalyst concentration covering the metal microstructure exhibits adequate catalytic activity;

g) subject to calcination the coated microstructure.

METHOD OF PREPARING STRUCTURED CATALYTIC SYSTEMS according to Claim 1, characterized in that the alloy is chosen from: an aluminum alloy, FeCralIoy, or an equivalent alloy such as Aluchrom, Aluchrom YHf, FeCralIoy JA13, Kanthal AF, Kanthal APM , Ugine Saoie 12178 and Ugine Saoie 12179.

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claims 1 and 2, characterized in that the metal microstructures are chosen from: low cell density metal monoliths (monoliths), high cell density metal monoliths (micromonoliths), meshes and foams.

Method for preparing structured catalytic systems according to Claim 3, characterized in that the monoliths are prepared from FeCralIoy blades with a thickness ranging from 10 pm to 100 pm.

Method for preparing structured catalytic systems according to claim 4, characterized in that the monoliths are prepared from FeCralIoy blades with a thickness ranging from 25 pm to 75 pm.

METHOD OF PREPARING STRUCTURED CATALYTIC SYSTEMS according to claim 5, characterized in that the monoliths have a hydraulic diameter ranging from 100 pm to 2,000 pm and cell density ranging from 1,4 cells / cm ^{2 to} 48 cells / cm ²

METHOD OF PREPARING STRUCTURED CATALYTIC SYSTEMS according to claim 6, characterized in that the monoliths have a hydraulic diameter ranging from 500 pm to 1,000 pm and cell density ranging from 4 cells / cm ^{2 to} 20 cells / cm ² .

Method for preparing structured catalytic systems according to Claim 3, characterized in that the micromonolites are prepared from FeCralIoy blades or other equivalent alloy such as Aluchrom, Aluchrom YHf, FeCrAlloy JA13, Kanthal AF, Kanthal APM, Ugine. Saoie 12178 and Ugine Saoie 12179, with thicknesses ranging from 10 pm to 100 pm.

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claim 8, characterized in that the micromonolites are prepared from laminates of FeCralloy with thickness ranging between 25 pm and 75 μιη.

Method for preparing structured catalytic systems according to claim 9, characterized in that the micromonoliths have a hydraulic diameter ranging from 100 pm to 1,000 pm and cell density ranging from 24 cells / cm ^{2 to} 120 cells / cm ² .

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claim 10, characterized in that the micromonoliths have a hydraulic diameter ranging from 100 pm to 500 pm and cell density ranging from 40 cells / cm ^{2 to} 60 cells / cm ² .

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claim 3, characterized in that the foams are cut into blocks or aluminum plates.

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claim 12, characterized in that the foams have porosities ranging from 1% to 99% and surface pore densities ranging from 0.04 to 20 pores per linear centimeter.

Method for preparing structured catalytic systems according to claim 13, characterized in that the foams have porosities ranging from 50% to 98% and surface pore densities ranging from 0.4 to 8 pores per linear centimeter.

Method for preparing structured catalytic systems according to claim 1, characterized in that the catalytic suspension is prepared by dissolving the active phase precursors and promoters in a solvent followed by the addition of a support, pH adjustment and the addition of additions. Method for preparing structured catalytic systems according to claim 1, characterized in that the catalytic suspension has:

- a solids content of 5 to 40% by weight; and

- from 0.1% to 50% by weight of additives in relation to the total mass of catalyst.

Method for preparing structured catalytic systems according to claim 1, characterized in that the polar solvent is water, ethanol, acetone or a mixture thereof.

Method for preparing structured catalytic systems according to claim 1 or 15, characterized in that said additives are inorganic colloids or high molecular weight soluble organic compounds (surfactants). Method of preparing structured catalytic systems according to claim 18, characterized in that the inorganic colloids are colloidal alumina, colloidal silica, titania, bohemite, cerium zinc oxide or a mixture thereof.

Method of preparing structured catalytic systems according to Claim 18, characterized in that the surfactants are chosen from: polyvinyl alcohol, polyvinyl pyrolidone, sodium polymethacrylate or methylcellulose.

Method for preparing structured catalytic systems according to claim 15, characterized in that the pH of said suspension is adjusted with at least one acid.

Method for preparing structured catalytic systems according to claim 21, characterized in that said acids are chosen from: nitric, acetic or sulfuric acids. Method for preparing structured catalytic systems according to claim 1, characterized in that the active phase precursor is chosen from salts of Co, Fe, or Ru.

Method for the preparation of structured catalytic systems according to claims 1 and 23, characterized in that the promoter is a metal chosen from: Re, Pd, Pt, Zr, Ti, Cr, Zn, Al, Mg, Mn, Cu or Ag.

Method of preparing structured catalytic systems according to claim 1, characterized in that the active phase precursor is selected from salts of: Ni, Ru, RH, Pd, Ir, or Pt.

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claims 1 and 25, characterized in that the support is chosen from: MgO, Mg ₂ AI0 ₄ , Si0 ₂ , Ce0 ₂ , Zr0 ₂ , Ti0 ₂ or a mixture thereof having alkaline or alkaline earth metals or alumina stabilized with La, Ce or Mg.

Method for preparing structured catalytic systems according to claim 1, characterized in that the active phase procursor is chosen from salts of Pd, PT, Ru, or oxides of transition elements.

METHOD FOR PREPARING STRUCTURED CATALYTIC SYSTEMS according to claims 1 and 27, characterized in that the support is alumina, stabilized with La, CE or Mg.

Method for preparing structured catalytic systems according to claim 1, characterized in that excess suspension is eliminated by centrifugation, suction or blowing via compressed air. Method for preparing structured catalytic systems according to claim 29, characterized in that the centrifugation technique uses a speed of 10 rpm to 10,000 rpm for at least 1 minute.

Method for preparing structured catalytic systems according to claim 29, characterized in that the centrifugation technique uses a speed of 100 rpm to 5,000 rpm for at least 2 minutes.

Method for preparing structured catalytic systems according to claim 29, characterized in that the centrifugation technique uses a speed of 200 rpm to 2,000 rpm for at least 2.5 minutes.

Method of preparing structured catalytic systems according to claim 29, characterized in that the suction or blowing technique is performed at a temperature between 50 ° C and 120 ° C for at least 1 hour.

Method for preparing structured catalytic systems according to claim 33, characterized in that the drying is carried out at a temperature between 50 ° C and 120 ° C for at least 1 hour.

Method for preparing structured catalytic systems according to claim 33, characterized in that the drying is carried out at a temperature between 60 ° C and 100 ° C for at least 2 hours.

Method for the preparation of structured catalytic systems according to claim 1, characterized in that the calcination step is carried out at a temperature of from 150 ° C to 600 ° C for at least 2 hours.

Method for the preparation of structured catalytic systems according to Claim 1, characterized in because the calcination step is performed at a temperature between 250 ° C and 400 ° C for at least 4 hours.

CATALYTIC MICROREATOR, characterized in that it comprises the structured catalytic system according to claim 1, the metal microstructures being distributed in the reactor in the form of metal plates having the following dimensions:

- height from 0,5 mm to 2 mm;

- width from 5 mm to 50 mm; and

- length from 5 mm to 50 mm.

CATALYTIC MICROREATOR according to Claim 38, characterized in that the metal plates are shaped to form microchannels of the following dimensions:

- height from 200 microns to 900 microns;

- width from 200 microns to 900 microns; and

- hydraulic diameter from 0.5 mm to 1 mm.

CATALYTIC MICROREATOR according to claims 38 and 39, characterized in that said microchannels are separated from each other by a wall thickness of less than 1 mm.

CATALYTIC MICROREATOR according to claims 38 and 39, characterized in that the wall thickness between the microchannels is 0.5 mm.