RU2424974C2 - Method of processing light hydrocarbons to synthetic gas - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemistry and can be used to produce synthetic gas from light hydrocarbons. Light hydrocarbons are converted to synthetic gas via conversion thereof with carbon dioxide gas at high temperature and pressure in filtration conditions on a catalytic porous membrane containing a porous module obtained via vibration moulding of an exothermal mixture of nickel and aluminium, with a catalytic coating in form of palladium or palladium-cobalt, or manganese, or gold-nickel in amount of 0.004-0.025 wt % with respect to mass of the module. The light hydrocarbons used are products of incomplete oxidation of kerosene or Fischer-Tropsch process exhaust gases, while feeding products of incomplete oxidation of kerosene into the mixture with carbon dioxide through the catalytic membrane at a rate of 15000-25000 h^-1 and feeding Fischer-Tropsch process exhaust gases into the mixture with carbon dioxide at a rate of 7500-8500 h^-1. The products of incomplete oxidation of kerosene are C₂-C₅ olefins and the Fischer-Tropsch process exhaust gases used are C₁-C₅ alkanes. Conversion of the light hydrocarbons is carried out at temperature 600-800°C.

EFFECT: obtaining synthetic gas from light hydrocarbons.

5 cl, 6 dwg, 6 tbl, 21 ex

Description

The present invention relates to a method for producing synthesis gas from light hydrocarbons, more particularly C ₁ -C ₅ alkanes and olefins, formed in the processes of incomplete oxidation of kerosene and exhaust gases of the Fischer-Tropsch process.

At present, natural gas is the main source of hydrogen production and gas synthesis, which are obtained in industry in various modifications of energy-intensive methane steam reforming processes.

An important issue today is the need to include carbon dioxide in the cycle of important processes. This problem is caused by gigantic CO ₂ emissions as a result of technogenic activities leading to the irreversible loss of the planet’s organic deposits.

One of these processes is the production of a hydrogen-containing gas, in particular synthesis gas, by carbon dioxide conversion of methane, which proceeds according to the following mechanism

CH ₄ + CO ₂ = 2CO + 2H ₂ ΔН = - + 247 kJ / mol

and requiring significant amounts of carbon dioxide to carry out this reaction.

Methods for producing hydrogen-containing gases, in particular synthesis gas, by carbon dioxide methane conversion have been the subject of many works, mainly describing processes in traditional flow reactors with a bulk catalyst, in which high conversions by reactants are achieved due to high temperatures (800-1100 ° C), which causes a very high formation of carbon deposits and, as a consequence, poisoning of most catalysts, and therefore there is a need for their regular regeneration.

Carrying out the carbon dioxide conversion of methane in the presence of noble metal catalysts (Pt, Pd) can reduce the process temperature by an average of 200 degrees and reduce coke formation, but their high cost makes the process economically disadvantageous.

At the same time, with the prospect of developing this particular approach, the possibility of a significant expansion of raw materials and a significant return of CO ₂ to organic products, including fuel, is associated, and the task of many developers is to search for new catalytic systems that allow hydrocarbon processing by carbon dioxide conversion to synthesis -gas.

Known membrane methods for carbon dioxide methane conversion, which use dense membranes with the so-called oxygen conductivity and made on the basis of complex oxides, mainly of perovskite structure.

So, in patents CA 2420337 A1 and US 6492290 B1 processing of associated gas is carried out by oxidation of methane on ion-conducting membranes.

There is also a method of producing synthesis gas using ion-conducting membranes, described in patent RU 2144494.

However, the performance of the described processes is very low. In addition, due to the solid-phase diffusion of lattice oxygen, the membrane material undergoes mechanical destruction.

In this regard, one of the promising and new approaches to solving the processing of natural and associated gases can be considered processes based on porous catalytic membranes, which are an ensemble of microreactors.

The patent RU 2208475 is known in which a radial type catalytic reactor is used to produce synthesis gas, in which the catalyst is a reinforced porous material made in the form of corrugated tapes.

According to this method, methane conversion up to 99.9% is obtained with selectivity for CO - 77%, for Н ₂ - 90%.

The disadvantage of this method is the use of high temperatures.

RU 2325219 proposes a method for producing synthesis gas by converting a mixture of methane and carbon dioxide, in which the conversion is carried out at a temperature of 450-700 ° C and a pressure of 1-10 atm in the filtration mode on a porous ceramic catalytic module, which is a compacted thermal synthesis product by vibropressing a finely divided exothermic mixture of nickel and aluminum, containing in wt.%: nickel 55.93-96.31, aluminum 3.69-44.07, which may contain titanium carbide in an amount of 20 wt.% with respect to the weight of the module, at speed giving a mixture of methane and carbon dioxide through a module equal to 500-5000 l / dm ³ · h, and the ratio of methane to carbon dioxide in the initial mixture is from 0.5 to 1.5.

To increase the activity of the catalyst system in the process of producing synthesis gas, the porous ceramic catalyst module may comprise a catalyst coating comprising La and MgO or Ce and MgO or La, Ce and MgO, or ZrO ₂ , Y ₂ O ₃ and MgO or Pt and MgO or W ₂ O ₅ and MgO in an amount of 0.002-6 wt.% In relation to the weight of the module.

However, the disadvantage of the described method is the high content of active components in the catalytic module - up to 6%, high coke formation from 6 to 48% and, as a result, the low productivity of the catalyst for synthesis gas, not exceeding 560 l / g of _catalyst · dm ³ _membranes · h .

This technical solution is the closest in technical essence and the achieved result and we have chosen for the prototype.

This situation is explained by the high thermodynamic stability of the hydrocarbon feedstock - methane used in carbon dioxide conversion, therefore, the most important problem at the moment is the search for alternative feedstocks with lower thermodynamic stability than methane for carbon dioxide conversion in order to produce synthesis gas.

The objective of the invention is to develop a method of processing light hydrocarbons into synthesis gas by carbon dioxide conversion of hydrocarbon raw materials, which eliminates these disadvantages of the prototype, as well as in the search for hydrocarbon raw materials, alternative to methane.

The problem is solved in that a method for processing light hydrocarbons into synthesis gas by converting them with carbon dioxide at an elevated temperature and pressure in a filtration mode on a catalytic porous membrane containing a porous module obtained by vibrocompressing an exothermic mixture of nickel and aluminum, and a catalytic coating, is proposed. in which palladium or palladium-cobalt, or manganese, or gold-nickel in the amount of 0.004-0.025 wt.% in relation to the weight of the module is used as a catalytic coating, and onversii subjected to partial oxidation products or waste gases kerosene Fischer-Tropsch process with feed rate of kerosene incomplete oxidation products in the mixture with carbon dioxide through catalytic membrane equal 15,000-25,000 h ^-1, feed rate and offgas Fischer-Tropsch process in a mixture with carbon gas through a catalytic membrane equal to 7500-8500 h ^-1 . Moreover, C ₂ -C ₅ olefins are used as products of incomplete oxidation of kerosene, and C ₁ -C ₅ alkanes are used as exhaust gases from the Fischer-Tropsch process. The Fischer-Tropsch process off-gas conversion is preferably carried out in two stages. The conversion of the feedstock is carried out at a temperature of 600-800 ° C.

Technical results that can be obtained using the invention:

1) a decrease in the amount of the contained catalyst component in the composition of the porous catalytic membrane to 0.004-0.034 wt.%;

2) an increase in the supply of the initial carbon mixture through the membrane to 15000-25000 h ^-1 and, as a result, taking into account both first parameters, an increase in the productivity of the catalyst for synthesis gas up to 220,000 l / g of _catalyst · dm ³ _membranes · h, which is several orders of magnitude higher productivity of the catalyst according to the prototype (560 l / g of _catalyst · dm ³ _membranes · h);

3) the use of alternative hydrocarbon feedstocks - products of incomplete oxidation of kerosene or waste gases from the Fischer-Tropsch process, where light olefins or alkanes predominate, respectively, which are not so thermodynamically stable compared to methane, which allows the process to be carried out during the conversion of hydrocarbon feeds close to the prototype method with significantly greater selectivity for synthesis gas due to a sharp decrease in coke formation to almost zero.

It should be noted that in the patent technical literature there are no known methods for processing the exhaust gases of the Fischer-Tropsch process and products of incomplete combustion of kerosene by carbon dioxide conversion using membrane-catalytic systems.

Figure 1 presents a diagram of a membrane-catalytic installation. 1 - cylinder with the test gas mixture; 2 - gear; 3 - gas flow regulator; 3a - a liquid dispenser for supplying a liquid substrate to the mixing tee; 4 - a furnace for preheating a gas stream; 5 - pressure gauge on the inside of the membrane; 6, 7 - thermocouples; 8 - membrane-catalytic reactor; 8a - a second membrane-catalytic reactor connected in series with the first for the preferred carbon dioxide conversion of the exhaust gases of the Fischer-Tropsch process; 9 - a fluid collection; 10 - shutoff valve; 11 - CO analyzer; 12 - chromatograph; 13 - ADC; 14 is a computer.

The following examples illustrate the invention, but in no way limit its scope.

Obtaining membrane-catalytic systems

A porous catalytic membrane is prepared as follows.

First, a porous ceramic catalytic module is prepared from a highly dispersed exothermic mixture of nickel and aluminum sealed by vibrocompressing, according to the procedure described in the prototype patent.

The prepared mixture is placed in a vacuum oven, vacuum to a residual pressure of 1.5 · 10 ^-3 Pa, raise the temperature until the mixture begins to ignite, maintain at this temperature, and then the sample is cooled.

Then, the catalytic components are applied to the inner surface of the channels of the porous module: palladium, or a mixture of palladium-cobalt, or a mixture of palladium-zinc, taken in amounts that ensure the content of active components Pd (I), Pd-Co (2), Mn (3) and Au-Ni (4), with respect to the mass of the module, equal to 0.023 wt.% (Pd), 0.021 wt.% (Pd-Co), 0.008 wt.% (Mn) and 0.0038 wt.% (Au- Ni), which corresponds to the catalytic systems 1-4 listed in table 1.

The catalytic components are applied from solutions of their organic complexes, followed by calcining at 800 ° C for 4-6 hours.

Table 1 Catalytic Membrane No. The composition of the active components The content of active components, wt.% one Pd 0.023 2 Pd-co 0.014-0.007 3 Mn 0.008 four Au-ni 0.0029-0.0009

Method for carbon dioxide gas processing of incomplete oxidation of kerosene into synthesis gas

Below are examples of the application of the method for processing light hydrocarbons C ₁ -C ₄ , which are products of incomplete combustion of aviation kerosene, which illustrate the proposed technical solution, but in no way limit the scope of its application.

Examples 1-4.

As a light hydrocarbon feed, the gas of incomplete oxidation of kerosene is used, the composition of the model mixture of which is given in Table 2.

table 2 The composition of the model gas mixture of incomplete oxidation of kerosene With CO ₂ CH ₄ C ₂ H ₄ C ₃ H ₆ C ₄ H ₁₀ N ₂ The quantitative composition, vol.% 6.63 9,416 2,123 4,166 0.724 0.564 76,377

The gas mixture of this composition is mixed with water vapor and fed to the catalytic membrane at a temperature of 800 ° C at a speed of 17200 h ^-1 . The experimental results are shown in table.3.

Table 3 The conversion of the feedstock and the composition of the products of carbon dioxide gas conversion of incomplete oxidation of kerosene. Example No. Catalytic membrane Temperature, T _react ., ° С The conversion of feedstock, vol.% C _H2 With _CO X _methane one Pd 800 38.84 8.19 89.6 2 Mn 800 36.23 6.46 76.0 3 Pd-co 800 35.85 6.37 70.5 four Au-ni 800 38,99 25.70 75.54

The productivity of the catalyst for synthesis gas, depending on the selected catalytic membrane, varies between 1344-69440 l / g of _catalyst · dm ^{3 of the} _membrane · h.

Examples 5-8.

The gas mixture of the composition described in example 1 is mixed with water vapor and fed to a heater in which the hydrocarbon feed is preheated to a temperature of 650 ° C and then at various temperatures (650 ° C-800 ° C in increments of 50 ° C) and speed feedstock 17,200 h ^-1 on an Au-Ni catalyst determines the optimal process mode.

In figure 2. The content of various components in the product mixture at different temperatures and a feed rate of 17,200 h ^-1 on an Au-Ni catalyst presents the results of an experiment at different temperatures, from which it can be seen that an increase in temperature to 750-800 ° C contributes to a deeper processing of the feedstock with an increase in the content of synthesis gas. In this case, light C ₂ -C ₄ olefins are almost completely converted to synthesis gas already at 650 ° C.

The productivity of the catalyst for synthesis gas with temperature changes from 672 l / g of _catalyst · dm ³ _membranes · h to 1366 l / g of _catalyst · dm ³ _membranes · h.

Examples 9-12

The gas is incompletely oxidized with kerosene with steam at a temperature of 800 ° C and various feed rates (17000 h ^-1 - 26500 h ^-1 ) are processed on an Au-Ni catalyst.

In figure 3. The conversion of alkanes and olefins on a membrane containing Au-Ni at various feed rates of the feedstock presents the results of the conversion of a gas of incomplete oxidation of kerosene, which shows that the optimal conditions for this experiment are as follows: temperature above 750 ° C, feed rate above 20,000 h ^{- 1} (methane conversion reaches 75%, (negative methane conversion means that it is formed from other hydrocarbons) the conversion of other hydrocarbons is 100%).

Further experiments were carried out under optimal conditions or as close to optimal as possible.

The productivity of the catalyst for synthesis gas depending on the selected catalytic membrane varies in the range 1366-2128 l / g of _catalyst · dm ³ _membranes · h.

Examples 13-14.

At optimal temperatures of 750 and 800 ° C and a gas mixture feed rate of 23,200 h ^-1 , the gas is incompletely oxidized with kerosene on a palladium catalytic membrane.

The results of the conversion of a model mixture of gases of partial oxidation depending on the temperature are presented in Figure 4. Methane conversion on a palladium catalyst, on which the experimental results are presented on the example of methane conversion because it is the only hydrocarbon from the mixture whose conversion is less than 100%, the remaining hydrocarbons in the mixture are converted 100%. The figure shows that at a temperature of 800 ° C the methane conversion is 90%.

The productivity of the catalyst for synthesis gas reaches 38080 and 47040 l / g of _catalyst · dm ³ _membranes · h, respectively.

Examples 15-16

The products of incomplete oxidation of kerosene are processed as described in Example 2 at temperatures of 750 and 800 ° C on a manganese catalyst. The results are shown in Fig.5. Conversion of methane on a manganese catalyst.

From the graph shown in the indicated Figure 5, it is seen that the Mn-containing membrane is less active than the Pd-containing (methane conversion does not reach 80%).

The productivity of the catalyst for synthesis gas is 51520 and 69440 l / g of _catalyst · dm ³ _membranes · h, respectively.

Examples 17-18

The products of incomplete oxidation of kerosene are processed as described in Example 3 on a Pd-Co-containing catalytic membrane at optimal temperatures of 750-800 ° C.

The results of the conversion of gas incomplete oxidation of kerosene are presented in Fig.6. Methane conversion on a palladium-cobalt catalyst.

It can be seen from the figure that the palladium-cobalt membrane is also less active than the palladium membrane (methane conversion 70.5%). The feed rate is determined by the permeability of the membrane.

The productivity of the catalyst for synthesis gas reaches 12320 and 29680 l / g of _catalyst · dm ³ _membranes · h, respectively.

Thus, the best process indicators were obtained in the presence of a palladium system.

The amount of supported active catalyst components is more than an order of magnitude lower than in conventional catalytic systems, and the productivity of catalytic membranes is 1-2 orders of magnitude higher than in the prototype.

The method of carbon dioxide conversion of hydrocarbons contained in the exhaust gases of the Fischer-Tropsch process.

Carbon dioxide conversion is carried out on real raw materials - exhaust gases of the Fischer-Tropsch process, the composition of which is presented in table 4-6 on the membrane-catalytic installation described on page 5-6 and shown in figure 1. Diagram of a membrane-catalytic installation.

Example 19

The Fischer-Tropsch process off-gas is processed in the presence of a Pd-Co-containing catalytic membrane at a Fischer-Tropsch process off-gas feed rate mixed with carbon dioxide to the membrane equal to 7500 h ^-1 .

The composition of the product gas after two stages of processing is also presented in table 4.

The productivity of the catalyst for synthesis gas in the first stage of the process is 986 l / g of _catalyst · dm ³ _membranes · h.

The productivity of the catalyst for synthesis gas in both stages is 1725 l / g of _catalyst · dm ³ _membranes · h.

Table 4 The composition of the initial gaseous products of the Fischer-Tropsch process and the products of carbon dioxide conversion on a palladium-cobalt catalyst Components The initial mixture, vol.% Food mix, vol.%, 1st stage Food mix, vol%, 2nd stage H ₂ 40.00 46.63 fifty With 15.69 27.62 34 CH ₄ 8.06 14.88 10 CO ₂ 17.23 10.27 6 C ₂ 2.08 0.56 0 C ₂ = 0.50 0 0 C ₃ 0.79 0.05 0 C ₃ = 1.14 0.01 0 iC ₄ 0.20 0 0 C ₄ 0.38 0.01 0 C ₄ = 0.10 0 0 iC ₄ = 0,03 0 0 tC ₄ = 0.09 0 0 iC ₅ 0.21 0 0 C ₅ 0,03 0 0 Unidentified gaseous products 13.5 0 TOTAL: one hundred one hundred one hundred

Example 20

The exhaust gases of the Fischer-Tropsch process, the composition of which is presented in Table 5, are processed in the presence of a Pd-containing catalytic membrane at a feed rate of the exhaust gases of the Fischer-Tropsch process in a mixture with carbon dioxide to the membrane equal to 8000 h ^-1 .

The composition of the product gas after two stages of processing is also presented in table 5.

The productivity of the catalyst for synthesis gas in the first stage of the process is 784 l / g of _catalyst · dm ³ _membranes · h.

The performance of the catalyst in both steps is 1366 l / g of _catalyst · dm ³ _membranes · h.

Table 5 The composition of the initial gaseous products of the Fischer-Tropsch process and the products of carbon dioxide conversion on a palladium catalyst Components The initial mixture, vol.% Food mix, vol.%, 1st stage Food mix, vol%, 2nd stage H ₂ 40.00 44.35 49.37 With 15.69 29.32 35.18 CH ₄ 8.06 13.47 8.01 CO ₂ 17.23 11.71 7.44 C ₂ 2.08 1.05 0 C ₂ = 0.50 0 0 C ₃ 0.79 0.09 0 C ₃ = 1.14 0.01 0 iC ₄ 0.20 0 0 C ₄ 0.38 0 0 C ₄ = 0.10 0 0 iC ₄ = 0,03 0 0 tC ₄ = 0.09 0 0 iC ₅ 0.21 0 0 C ₅ 0,03 0 0 Unidentified gaseous products 13.5 0 TOTAL: one hundred one hundred one hundred

Example 21

The exhaust gases of the Fischer-Tropsch process, the composition of which is shown in Table 6, are processed in the presence of an Mn-containing catalytic membrane at a feed rate of the exhaust gases of the Fischer-Tropsch process in a mixture with carbon dioxide to the membrane equal to 8500 h ^-1 .

The composition of the product gas after two stages of processing is also presented in table.6.

The productivity of the catalyst for synthesis gas in the first stage of the process is 1792 l / g of _catalyst · dm ³ _membranes · h.

The performance of the catalyst in both steps is 2934 l / g of _catalyst · dm ³ _membranes ^· h.

Table 6 The composition of the initial gaseous products of the Fischer-Tropsch process and products of carbon dioxide conversion on a manganese catalyst Components The initial mixture,% vol. Food mix, vol.%, 1st stage Food mix, vol.%, 2nd stage H ₂ 40.00 48.03 52.13 With 15.69 24.60 31.32 CH ₄ 8.06 12.31 7.10 CO ₂ 17.23 14.71 9.45 C ₂ 2.08 0.30 0 C ₂ = 0.50 0.04 0 C ₃ 0.79 0 0 C _{3 =} 1.14 0.01 0 iC ₄ 0.20 0 0 C ₄ 0.38 0 0 C ₄ = 0.10 0 0 iC ₄ = 0,03 0 0 tC ₄ = 0.09 0 0 iC ₅ 0.21 0 0 C ₅ 0,03 0 0 Unidentified gaseous products 13.5 0 TOTAL: one hundred one hundred one hundred

As can be seen from the tables, in the first step, mainly higher molecular weight homologues of methane C ₂ -C ₅ undergo conversion. Moreover, an increase in methane concentration after the first stage indicates the cracking of gaseous methane homologs. The concentration of carbon dioxide is reduced from 17.2 to 10-14%; the degree of conversion of CO ₂ is ~ 40%.

The resulting gas is preferably sent to the 2nd stage of processing, after which the concentration of carbon dioxide is reduced even to 6% -10%.

Thus, the total conversion of CO ₂ during two-stage processing is 55-65%.

The increment of the total productivity in two stages of processing is 582-1142 l / g of _catalyst · dm ³ _membranes · h.

Thus, the proposed method allows you to process light hydrocarbons with high selectivity and productivity of the catalytic membrane for synthesis gas, equal to from 784 to 69440 l / g of _catalyst · dm ³ _membranes · h depending on the composition of the initial hydrocarbon mixture.

It should be noted that the proposed method for producing the target product - synthesis gas, which uses hydrocarbon raw materials, which is a gas industrial waste, which simultaneously solves the problem of utilization of gas industrial emissions.

Claims (5)

1. A method of processing light hydrocarbons into synthesis gas by converting them with carbon dioxide at elevated temperature and pressure in a filtration mode on a catalytic porous membrane containing a porous module obtained by vibropressing an exothermic mixture of nickel and aluminum, and a catalytic coating, characterized in that As a catalytic coating, palladium, or palladium-cobalt, or manganese, or gold-nickel in the amount of 0.004-0.025 wt.% in relation to the mass of the module is used, and the products are subjected to conversion lnogo oxidation kerosene or offgases Fischer-Tropsch process with feed rate of kerosene incomplete oxidation products in the mixture with carbon dioxide through catalytic membrane equal 15,000-25,000 h ^-1, and the feed rate of exhaust gases Fischer-Tropsch process in a mixture with carbon dioxide, equal to 7500-8500 h ^-1 . 2. A method of processing light hydrocarbons into synthesis gas according to claim 1, characterized in that C ₂ -C ₅ olefins are used as products of incomplete oxidation of kerosene. 3. The method of processing light hydrocarbons into synthesis gas according to claim 1, characterized in that C ₁ -C ₅ alkanes are used as the exhaust gases of the Fischer-Tropsch process. 4. The method according to claim 1, characterized in that the conversion of the exhaust gases of the Fischer-Tropsch process is preferably carried out in two stages. 5. The method of processing light hydrocarbons into synthesis gas according to claim 1, characterized in that the conversion is carried out at a temperature of 600-800 ° C.

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