ES2310127B1 - SYNTHESIS GAS PRODUCTION PROCEDURE, DEVICE FOR ITS EXECUTION AND ITS APPLICATIONS. - Google Patents

Abstract

Synthesis gas production procedure, device for its execution and its applications.

The present invention describes a process for obtaining synthesis gas (gas rich in H2 and CO) from of a gas rich in CH_ {4} and CO_ {2} based on the use of a carbonaceous material that simultaneously acts as a catalyst and microwave pickup Likewise, a device or apparatus for carrying out said procedure.

Description

Synthesis gas production procedure, device for its execution and its applications.

Technical sector

The present invention describes a process for the production of synthesis gas so the sector of the technique corresponds to the energy sector, more specifically with the fuel production procedure area Respectful towards the environment.

State of the art

The present invention develops a method for the production of a gas rich in hydrogen (H2) and monoxide carbon (CO), commonly called synthesis gas. This gas is from great importance in sectors such as energy, chemical and petrochemical because it can be used directly as fuel or well it can be transformed into other products of great added value such as ammonia, methanol, ethanol, hydrogen or in fuels synthetic liquids such as diesel or gasoline. Currently and to industrial level, the production of synthesis gas is based mainly in the transformation of natural gas. The available technologies for this are: steam reforming, partial oxidation and auto-thermal reforming. The three processes are carried out at temperatures around 900ºC and under pressure. They have in common the use of an agent Oxidizing well water vapor or oxygen and metal catalysts. The steam reforming is endothermic while in the other two  processes the heat input is supplied by the system itself. As disadvantages, steam reforming presents the use of large amounts of steam to prevent deactivation of catalyst for carbon deposits from methane, while in partial oxidation and reforming Self-thermal utilization of pure oxygen the process becomes too expensive. As an example and between numerous citations present in the bibliography in which it is made reference to these technologies, you can see J.M. Ogden International Energy Agency Task 16, Hydrogen from carbon Containing-Materials 2001; N.R. Burke, D.L. Trimn. Catalysis Today 117 (2006) 248-252; S. Rabe, T.B. Truong, F. Vogel. Applied Catalysis A: General 318 (2007) 54-62.

Currently, one of the technologies that is being proposed for the production of synthesis gas is the catalytic reforming of methane with carbon dioxide (dry reforming). As an example you can see: M.C.J. Bradford and M.A. Vannice. Catal. Rev.-Sci. Eng. 41 (1) (1999) 1-42. This process would be very suitable for those gases that were constituted mainly by CH4 and CO2 as natural gas or especially biogas. Not however there is no industrial technology based on this process despite the potential economic and environmental benefits that presents. This is mainly due to the rapid deactivation of the catalysts used by carbonaceous deposits from the decomposition of methane.

This problem is attempted to be solved by using steam that gasifies the deposits formed by regenerating the catalyst. However, as with steam reforming of natural gas, the energy requirements are high due to the high H 2 O / CH 4 ratios used. As an example of the application of this tech-
Nology can be seen: A. Effendi, ZG Zhang, K. Hellgardt, K. Honda, T. Yoshida. Catalsis Today 77 (2002) 181-189.

In the present invention an alternative technology is proposed to the conventional processes of obtaining synthesis gas based on the use of microwaves. There are some articles that also describe microwave heating to obtain synthesis gas. For example, the following publication: X. Bi et al . Reaction kinetics and Catlysis Letters, 66 (2) 381-386 (1999) describes a process based on microwave heating for the partial oxidation of CH4 to synthesis gas in which various types of metal catalysts are used.

The use of microwaves in the processing of hydrocarbons to obtain hydrogen is described in the following patents: Y. Cha. Pat. . US 6783632 (2004), where a microwave-assisted method for obtaining hydrogen by steam reforming of light hydrocarbons is described; JKS Wa, et al . Pat. No. 4574038 (1986), where a microwave-assisted method for obtaining ethylene and hydrogen from methane using metal catalysts is described.

In the present invention, the CO2 present in the gas (biogas, natural gas, etc.) is reacted with the CH4 without using water vapor or metal catalysts and using microwave heating. The carbon deposits formed on the active centers of the carbonaceous catalyst are gasified " in situ " by the CO2 itself present in the gas. There are works in the literature in which a similar procedure has been used to carry out dry methane reforming, but so far all of them are based on the use of metal catalysts. As an example you can see the following publications: X. Zang, DO Hayward. Inorganica Chimica Acta 359 (2006) 3421-3433, Tanashev et al . Catalysis Today, 42 (3) 333-336 (1998).

Description of the invention brief description

An aspect of the present invention is it constitutes a procedure for obtaining synthesis gas (gas rich in H2 + CO) from a gas rich in CH4 {and} CO 2, hereinafter process of the invention, based on the use of a carbonaceous material that simultaneously acts as microwave catalyst and collector subjected to radiation and microwave heating and comprising the following stages:

i)

radiation and microwave heating of carbonaceous material with microwave until the temperature of reaction, preferably between 500 ° C and 1000 ° C, more preferably at 800 ° C,

ii)

passage of the starting gas mixture of CH4 and CO 2 through the material of i) maintaining the radiation and microwave heating, preferably between 500 ° C and 1000 ° C, more preferably at 800 ° C, and

iii)

synthesis gas recovery.

Another object of the invention is a device or apparatus necessary to carry out the procedure of the invention, hereinafter device of the invention, constituted by an oven or microwave device capable of inducing temperatures up to 1000 ° C, comprising a bed of a material carbonaceous capable of acting as a microwave sensor and catalyst in decomposition reactions, and with inputs and outputs for the starting gases and the synthesis gas produced, respectively.

Finally, another aspect of the invention is constitutes the use of the procedure and the device of the invention for the production of synthesis gas.

Detailed description

The present invention is based on the fact that inventors have observed that it is possible to convert a gas that  Contains CH4 and CO2 in synthesis gas (gas rich in H 2 + CO) used catalysts other than metal and which act at the same time as microwave sensors, which It facilitates reaching the necessary temperature in this process.

More specifically, in the present invention a new method for converting biogas, or any gas comprising CH4 and CO2, whatever the proportions, into synthesis gas (gas rich in H2 + +) is described. CO) of high purity, that is, practically free of any other gas (see Example 1 and 2). This procedure is based on passing the biogas through a bed of a carbonaceous material, preferably a granular activated carbon or a carbonized one, which in turn is irradiated by a microwave source. Under these conditions and working at the proper power, the bed reaches a temperature and conditions such that the decomposition of CH 4 to H 2 and C. occurs simultaneously carbon deposits formed on the active centers of the carbonaceous catalyst, they are gasified in situ by the CO2 present in the gas, converting them into CO and thus recovering the active centers (reactions 1 and 2).

one

So, the carbonaceous material that acts so much of microwave collector as catalyst maintains its catalytic properties for long periods of time before be affected by carbon deposits. Carbonaceous material when it captures the microwaves, it absorbs and heats them until working temperatures of the procedure.

In this way the process can be maintained with high conversions from CH4 to H2 for long periods of time before it is necessary to replace the carbonaceous material. As the gasification of carbon deposits, and part of the carbonaceous material used as catalyst / collector, gives rise to CO, the final result is to obtain a high synthesis gas purity. That is, in the gases at the outlet of the reactor the proportions of CH4 and CO2 that have not reacted are minimum

In summary, this method therefore presents the following advantages over other methods:

i)

does not require the use of water vapor or oxygen.

ii)

does not require a metal catalyst, in general much more expensive than a carbonaceous material, although these metal catalysts could be used mixed in low proportion with the carbonaceous material (sensor of microwave).

iii)

The catalysts used are low cost such as active carbons or even carbonaceous residues from biomass.

iv)

consumes two greenhouse gases to give place to synthesis gas that can be used as a source for multiple chemical processes (obtaining methanol) and obtaining other fuels (H2, synthetic diesel, etc.),

v)

allows to vary in a wide range the proportions CH 4 / CO 2 of the feed to obtain a synthesis gas with the desired proportions of H2 / CO depending on the application that wants to be given to said synthesis gas.

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Therefore, an aspect of the present invention constitutes a method of obtaining gas from synthesis (gas rich in H2 + CO) from a gas rich in CH4 and CO2, hereinafter process of the invention, based on the use of a carbonaceous material that simultaneously acts as a catalyst and microwave collector subjected to a radiation and microwave heating and comprising the following stages:

i)

radiation and microwave heating of carbonaceous material with microwave until the temperature of reaction, preferably between 500 ° C and 1000 ° C, more preferably at 800 ° C,

ii)

passage of the starting gas mixture of CH4 and CO 2 through the material of i) maintaining the radiation and microwave heating, preferably between 500 ° C and 1000 ° C, more preferably at 800 ° C, and

iii)

synthesis gas recovery.

A preferred aspect of the invention is it constitutes the process of the invention in which there is a previous inertization stage of the device used for the purpose of removing indoor air, for example, by nitrogen (see Example 1 and 2).

Another preferred aspect of the invention is constitutes the process of the invention in which the material i) catalyst is a carbonaceous material capable of absorbing microwave, belonging to illustrative title and without limiting the scope of the invention, to the following group: an active carbon, a charcoal, a charred, for example, from biomass, a coke that can be petroleum or coal, graphite materials, carbon black or smoke and other coals pyrolytic

Another preferred aspect of the invention is the process of the invention in which the catalyst material of i) contains small amounts of metal catalysts, depending on the type of carbonaceous material, such as: K, Ca, Mg, Si, Cu, Zn, Faith, Al etc. See: A. Domínguez et al . J. Anal. Appl. Pyrolysis 79 (2007) 128-135; JA Menéndez et al . J. Anal. Appl. Pyrolysis 71 (2004) 657-667. Mixtures of the carbonaceous catalyst (plus collector) with low percentages of metal catalysts could be useful to increase the conversions of the gases would increase, already very high.

Another preferred aspect of the present invention it is constituted by the process of the invention in which the gas of item may contain different proportions of CH4 and CO_ {2}, depending on the proportions of H2 / CO desired get in the synthesis gas that will depend in turn on the application that you want to give.

Another object of the invention is a device or apparatus necessary to carry out the procedure of the invention, hereinafter device of the invention, constituted by an oven or microwave device capable of inducing temperatures up to 1000 ° C, comprising a bed of a material carbonaceous capable of acting as a microwave sensor and catalyst in decomposition reactions, and with inputs and outputs for the starting gases and the synthesis gas produced, respectively.

Finally, another aspect of the invention is constitutes the use of the procedure and the device of the invention for the production of synthesis gas.

Description of the figures

Figure 1.- Decomposition of CO2 . Decomposition of CO 2 in the presence of a carbonized at 800 ° C in an electric oven (\, HE800) and in a microwave oven (\ Box, HM800).

Figure 2.- Decomposition of CH4 . Decomposition of CH4 in the presence of a carbonized at 800 ° C in an electric oven ((HE800) and in a microwave oven (circHM800)

Figure 3.- Decomposition of the CO 2 / CH 4 mixture . Decomposition of the CO2 / CH4 mixture in the presence of a carbonized at 800 ° C in the electric oven. (\ sqbullet, CO_ {2}; \ bullet, CH_ {4}).

Figure 4.- Decomposition of the mixture CO 2 / CH 4 . Decomposition of the CO 2 / CH 4 mixture in the presence of a carbonized at 800 ° C in the microwave oven. (\ Box, CO_ {2}; \ circ, CH_ {4}).

Figure 5.- Decomposition of CO2 . Decomposition of CO2 in the presence of an active carbon at 800 ° C in an electric furnace (?, HE800) and in a microwave oven (\ Box, HM800).

Figure 6.- Decomposition of CH4 . Decomposition of CH 4 in the presence of an active carbon at 800 ° C in an electric furnace (,, HE800) and in a microwave oven (circ, HM800).

Figure 7.- Decomposition of the mixture CO 2 / CH 4 . Decomposition of the CO 2 / CH 4 mixture in the presence of an active carbon at 800 ° C in the electric oven. (\ sqbullet, CO_ {2}; \ bullet, CH_ {4}).

Figure 8.- Decomposition of the mixture CO 2 / CH 4 . Decomposition of the CO 2 / CH 4 mixture in the presence of an active carbon at 800 ° C in the microwave oven. (\ Box, CO_ {2}; \ circ, CH_ {4}).

Figure 9.- Scheme of the Device of the invention .

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Examples of the invention Example 1 Production of synthesis gas from a synthetic mixture CH 4 / CO 2 in the presence of a carbonized from a vegetable waste 1.1.- Preparation of carbonized and characteristics chemical

The carbonized was obtained from a residue from the coffee industry. "Pellets" of this residue approximately 3 mm in diameter x 2 cm high, which were pyrolyzed in an electric oven at 1000ºC low nitrogen atmosphere, giving rise to carbonization. The chemical characteristics of carbonized and its ashes are shown in Table 1.

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TABLE 1 Main chemical characteristics of carbonized and its ashes

2

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1.2.- Experimental conditions

The reactions were carried out in a conventional electric oven and in a microwave oven unimode to 800 ° C. For this, a quartz reactor (45 cm high x 2.2) was used cm d.i.).

1.2.1.- Decomposition of CO2 gases and the CH_ {4} separately

The CO2 decomposition experiments were made with 3.5 g of carbonized (particle size between 1 and 3 mm) through which a 30 min was passed CO 2 flow of 60 cm 3 min -1, that is, a speed  space of 0.16 L g <-1> h <-1>. Meanwhile, the experiments of  decomposition of CH4 were performed by passing for 120 min a flow of CH 4 of 36 cm 3 min -1 at through 13 g of carbonized (particle size between (0.5 and 3 mm), thus obtaining a spatial velocity of 0.16 L g -1 h -1.

1.2.2.- Decomposition of the CO2 mixture and CH_ {4}

A CO2 / CH4 mixture (1: 1) was passed for 120 min through 13 g of the carbonized using to both gases a flow of 36 cm 3 min -1, such that the total flow was 72 cm 3 min -1, obtaining therefore both a spatial velocity of 0.33 L g <-1> h <-1>.

In all cases, before entering reactive gases, the device was inertized by passing through the reactor already charged with the carbonized a flow of 60 cm3 nitrogen min -1 for 20 min. After low this atmosphere of nitrogen, the system was heated until the reaction temperature (800 ° C). Once reached this temperature, the nitrogen was closed and the gases of reaction. At the end of the experiments the gases of the reaction and the system was cooled under nitrogen atmosphere.

The gases produced during the experiments were collected in Tediar ® bags and analyzed in a Gas chromatograph equipped with a TCD detector and two columns connected in series. The first of these columns is a Porapak Q (2 m x 1/8 'x 2 mm) and the second a 13X Molecular Screen (1.5 m x 1/8 'x 2 mm). He was used as a carrier gas with a flow of 30 cm 3 min -1. Initially, the oven temperature was 60ºC for 1.5 min and then be programmed from 60 to 90 ° C at a heating rate of 30 ° C min -1. The temperature was kept constant for 2 min and then be lowered again to 60 ° C at a rate of 50 ° C min -1 staying at this temperature 2 min. The TCD was calibrated with a mixture of standard gases periodically.

The conversions of CH_ {4} and CO_ {2} They were calculated using the following equations:

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3

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where (CH 4), (H 2), (CO 2) and (CO) are the concentrations as a percentage in volume determined by chromatography of gases

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1.3.- Results of the decomposition of CO2 and CH 4 separately and from the mixture CO 2 and CH 4

The results are shown in Figures 1 and 2 obtained from the decomposition of CO2 and CH4, respectively, both in the electric oven (HE) and in the oven microwave (HM), when the gases were passed separately to through carbonization.

The results are shown in Figures 3 and 4 obtained from the decomposition of the mixture CO 2 and CH 4, both in the electric oven (HE) and in the microwave oven (HM), respectively.

As can be seen in Figure 1, the decomposition of CO2 to CO is much greater in the microwave oven than in the electric oven, although in both cases it is maintained at values greater than 80% during the whole experiment. However, these differences are not as pronounced in the case of CH4 where the values are very high at the beginning of the experiment (100% in the case of the microwave) but then falls rapidly due to the blocking of the active centers of the catalyst ( carbonized) by the deposits generated in the decomposition of CH4. However, these results are substantially improved when the decomposition of CH4 is done in the presence of CO2 (Figures 3 and 4), especially in the case of microwave heating where the conversion of methane to hydrogen it is during the two hours of the experiment greater than 80%. This is due to the " in situ " recovery of the active centers blocked by gasification with CO2, which allows methane to continue decomposing. The results obtained in both ovens indicate that this cleaning of the active centers is more favored with microwave heating. As a result, in the microwave heating, a rich gas is obtained in the mixture H 2 and CO (synthesis gas) and low values of CH 4 and CO 2. The average composition of the gas obtained is: 56% of CO, 41% of H2, less than 3% of CH4 and less than 0.5% of CO2.

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Example 2 Production of synthesis gas from a synthetic mixture CH 4 / CO 2 in the presence of a commercial active carbon 2.1.- Chemical characteristics of active carbon commercial

It is an active carbon from coconut shell and steam activated, with a particle size between 0.5-2 mm (Filtaracarb FY5, CPL Carbonlink)

The chemical characteristics of activated carbon They are shown in Table 2.

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TABLE 2 Main chemical characteristics of coal commercial asset

4

5

2.2.- Experimental conditions

The reactions were carried out in a conventional electric oven and in a microwave oven unimode to 800 ° C. For this, a quartz reactor (45 cm high x 2.2) was used cm d.i.).

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2.2.1.- Decomposition of CO2 gases and the CH_ {4} separately

The CO2 decomposition experiments were made with 8 g of activated carbon through which passed a flow of CO 2 of 21 cm 3 for 120 min min -1, that is, a spatial velocity of 0.16 L g -1 h -1. The CH4 decomposition experiments were made by passing a flow of CH4 of 36 cm 3 min -1 through 13 g of activated carbon, resulting in a spatial velocity of 0.16 L g -1 h -1.

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2.2.2.- Decomposition of the CO2 mixture and CH_ {4}

A CO2 / CH4 mixture (1: 1) was passed for 260 min through 8 g of commercial active carbon, using for each of the gases a flow of 21 cm3 min -1, such that the total flow was 42 cm3 min -1, and thus obtaining a total spatial velocity of 0.31 L g <-1> h <-1>.

The experimental procedure in relation to the inertization and heating of the system, as well as the collection and analysis of the gases produced, is the same as described in the Example 1. On the other hand, the conversions of CH_ {4} and CO_ {2} were calculated using the equations described in the Example one.

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2.3.- Results of the decomposition of CO2 and CH 4 separately and from the mixture CO 2 and CH 4

The results are shown in Figures 5 and 6 obtained from the decomposition of CO2 and CH4, respectively, both in the electric oven (HE) and in the oven microwave (HM), when the gases were passed separately to through active carbon.

The results are shown in Figures 7 and 8 obtained from the decomposition of the mixture CO 2 and CH 4 in the electric oven (HE) and the microwave oven (HM), respectively.

As in Example 1, and as observed in Figure 5, the decomposition of CO2 to CO is much higher in the microwave (100%) than in the electric oven (40%) Again, in the case of the decomposition of CH4 (Figure 6), these differences are not as pronounced and follow the same trend described in Example 1. When the decomposition of CH4 is done in the presence of CO2 and in the electric oven, CH4 conversion (Figure 7) improves slightly, but it is in the case of microwave heating (Figure 8) where the value of methane conversion increases substantially, keeping practically 100% for more than four hours. As already occurred in the case of Example 1, in heating with In the microwave, a rich gas is obtained in the mixture H 2 and CO (gas synthesis) and practically null values of CH4 and CO2. The average composition of the gas obtained is: 58% of CO, 41% of H2, 1% of CH4 and \ approx 0% of CO2.

Claims (10)

1. Procedure for obtaining synthesis gas (rich gas H 2 and CO) from a gas rich in CH 4 and CO 2 characterized in that a carbonaceous material is used that simultaneously acts as a catalyst and Microwave sensor subjected to radiation and microwave heating and comprising the following stages:

i)

radiation and microwave heating of carbonaceous material with microwave until the temperature of reaction, preferably between 500 ° C and 1000 ° C, more preferably at 800 ° C,

ii)

passage of the starting gas mixture of CH4 and CO 2 through the material of i) maintaining the radiation and microwave heating, preferably between 500 ° C and 1000 ° C, more preferably at 800 ° C, and

iii)

synthesis gas recovery.

2. The method according to claim 1, characterized in that a previous step of inerting the device used is included in order to remove the air inside. 3. Method according to claim 2 characterized in that the inertization of the device is carried out by nitrogen. 4. Method according to claim 1 characterized in that the catalyst material of i) is a carbonaceous material capable of absorbing microwaves. 5. Method according to claim 4 characterized in that the carbonaceous material belongs to the following group: an active carbon, a charcoal, a carbonized, for example, from biomass, a coke that can be petroleum or mineral coal, graphite materials, carbon or smoke blacks and other pyrolytic coals. 6. Method according to claim 4 characterized in that the catalyst material includes small amounts of a metal catalyst. 7. Method according to claim 6 characterized in that the metal catalyst belongs to the following group: K, Ca, Mg, Si, Cu, Zn, Fe and Al. Method according to claims 1 to 7, characterized in that the starting gas may contain different proportions of CH4 and CO2. 9. Device or apparatus necessary for carrying out the process according to claims 1 to 8, characterized in that it is constituted by an oven or microwave device capable of inducing high temperatures, preferably up to 1000 ° C, comprising a bed of a carbonaceous material capable of acting as a microwave sensor and catalyst in the decomposition reactions, and with inputs and outputs for the starting gases and the synthesis gas produced, respectively. 10. Use of the procedure and the device according to claims 1 to 9 for gas production synthesis.