RU2719176C1 - Synthetic gas production method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to high-temperature catalytic oxidative methods of converting methane to synthesis gas and can be used in chemical engineering. Method is implemented by feeding into reactor, in which catalytic system is placed, of initial gas mixture containing mixture of methane and carbon dioxide with volume ratio of methane:carbon dioxide equal to 0.97–1.1:1, and carrying out the process at temperature of 700–950 °C and atmospheric pressure, wherein the catalytic system used is a macrocyclic ruthenium complex Ru(CwGm)₃ (Bn-C₄H₉)₂, where CwGm is a chelating bis-2-oxyphenoxyl gliocimate group and Bn-C₄H₉ is a cross-linking n-butyl-borate group supported on a heat-resistant, highly porous ceramic support in amount of 5.0 % of the weight of the carrier.

EFFECT: technical result consists in provision of effective immobilisation of monolayers of used catalytic system on common surface of highly porous carrier, as well as in process of carbon dioxide conversion of methane without additional supply of inert gases and at atmospheric pressure.

1 cl, 1 tbl, 10 ex

Description

The invention relates to the field of chemistry, petrochemistry and oil refining, in particular, to high-temperature catalytic oxidative processes for the conversion of methane to produce synthesis gas (a mixture of H ₂ and CO), which is the feedstock for producing motor fuels, methanol, dimethyl ether, aldehydes, alcohols and other valuable products.

The carbon dioxide conversion of natural gas and its main component, methane, is advantageous in producing synthesis gas with a H ₂ / CO ratio of ~ 1, which allows it to be used in a number of industrial syntheses of fuels and valuable chemical products (in particular, alcohols, aldehydes, esters, acids and hydrocarbons using the Fischer-Tropsch reaction). In addition, methane and carbon dioxide are greenhouse gases, and their disposal leads to the solution of environmental problems. However, the problem of creating highly active and resistant to carbonization catalysts for carbon dioxide conversion of methane remains very relevant.

Various methods are known for producing synthesis gas by carbon dioxide methane conversion, in which catalysts containing active components on a support are used.

As the active component, nickel and nickel-containing components, foam nickel are most common (US 6271170, 2001, US 7824656, 2006, 2594161, 2016, CN 108554411, 2018, RU 2350386, 2009, RU 2349380, 2009, WO 2019009754, 2019), also widely the use of platinum group metals is known: platinum, palladium, rhodium, iridium, ruthenium (RU 2453366, 2012). A significant disadvantage of using nickel-containing active components is the rapid deactivation of the catalyst due to the occurrence of carbonization of its surface.

At the same time, much attention is paid to the supports of these catalysts, which, in particular, use such as alumina, complex oxide supports, in particular, complex supports based on cerium-zirconium, aluminosilicates, alloys, porous catalytic modules, single-crystal nanofibres of aluminum oxide having a diameter of more than 3 nm and a length of more than 100 nm. (RU 2115617, 1998, RU 2350386, 2009, RU 22922237, 2007, CN 101352687, 2009, RU 2453366, 2012, RU 2325219, 2008, RU 2349380, 2009, RU 2351392, 2009, 2690496, 2019, 2659078, 2018, WO 2019009754, 2019), as well as the properties of dispersion carriers, the degree of distribution of the active component, thermal stability, and others (CN 102942225, 2013, RU 2629667, 2017).

Catalysts for carbon dioxide conversion of methane also contain promoters, which are used as oxides of alkaline or alkaline earth elements. (RU 2453366, 2012, RU 2418632, 2011), rare earth oxides in an amount of 0.5-10 wt. Are more effective, but also more expensive. %, with high oxygen mobility and contributing to the oxidation of carbon formed on the surface of the catalyst (CN 101352687, 2009). It should be noted that the used promoters reduce the coking of the catalyst, while at the same time, however, reducing its overall activity.

Known methods using catalysts containing as the active component of ruthenium or its compounds.

Thus, a known method for producing synthesis gas by carbon dioxide conversion of methane in the presence of a catalyst containing a carrier containing a carbonate of at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba, and a catalytic metal promoting a decomposition reaction of gaseous hydrocarbon feedstock. At least one metal selected from the group consisting of Ni, Rh, Ru, Ir, Pd, Pt, Re, Co, Fe and Mo is used as a catalytic metal. As a result of the implementation of this method, the degree of formation of carbon deposits is reduced, however, the yields of hydrogen and carbon monoxide are insufficient (RU 2418632, 2011).

A known method of carbon dioxide reforming of hydrocarbons, preferably methane, in order to obtain synthesis gas by contacting the gas with a catalyst, the active mass of which contains iridium as an active component and zirconium dioxide as a substrate. The content of iridium in terms of the content of the active mass is from 0.01 to 10 wt. %, preferably from 0.05 to 5 wt. %, more preferably from 0.1 to 1 wt. %, and the predominant part of zirconia has a cubic and / or tetragonal structure, and the proportion of cubic and / or tetragonal phase is> 50 wt. %, preferably> 70 wt. %, more preferably> 90 wt. % The active mass can be doped with one or more elements selected from the group consisting of rare earth elements (scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium) , elements of group IIa (magnesium, calcium, strontium, barium), elements of group IVb (titanium, hafnium), elements of group Vb (vanadium, niobium, tantalum) and silicon, and the proportion of alloying elements in terms of the amount of active mass is from 0, 01 to 80 wt. %, preferably from 0.1 to 50 wt. %, more preferably from 1.0 to 30 wt. %

Preferably, the catalyst contains at least one promoter - a noble metal selected from the group comprising platinum, rhodium, palladium, ruthenium and gold, the proportion of which is from 0.01 to 5 wt. %, more preferably from 0.1 to 3 wt. %

The active mass of the catalyst may contain at least one promoter selected from the group comprising nickel, cobalt, iron, manganese, molybdenum and tungsten, the proportion of which is from 0.1 to 50 wt. %, more preferably from 0.5 to 30 wt. %, even more preferably from 1 to 20 wt. %

Preferably, the active mass of the catalyst also contains cations of other metals, preferably selected from the group comprising magnesium, calcium, strontium, gallium, beryllium, chromium and manganese, more preferably from the group comprising calcium and / or magnesium.

When carrying out the method, the total content of hydrocarbons, preferably methane, and carbon dioxide in the feedstock is more than 80 vol. %, preferably more than 85 vol. %, particularly preferably more than 90 vol. %, The specified method is carried out at a pressure of from 5 to 500 bar, preferably from 10 to 250 bar, more preferably from 20 to 100 bar, at a temperature in the range from 600 to 1200 ° C, preferably from 850 to 1100 ° C, particularly preferably from 850 to 950 ° C., a gas flow rate of from 500 to 100,000 h ⁻¹ , preferably from 500 to 50,000 h ⁻¹ . The ratio of hydrogen to carbon monoxide in the resulting synthesis gas is from 0.5 to 1.4, particularly preferably from 0.6 to 1.2.

The feed used may not contain water or contain a small amount of water, the ratio of the proportion of water vapor and carbon in the gas to be reformed is less than 0.2, more preferably less than 0.1, even more preferably 0.05 (WO 2014/001423, 2014) .

The disadvantages of this method are the complex technology of its implementation, due to the need to use high pressure, as well as in a multi-stage procedure for producing the catalyst used in the method.

Closer to the proposed invention is a method for producing synthesis gas by carbon dioxide methane conversion in the presence of a catalyst, which is a complex cerium-zirconium-based carrier containing one or two metals selected from the group of rare-earth elements, such as Pr, Sm, La, or any combination and active component is a platinum group metal selected from Pt or Ru; Pt or Ru with Ni additives; La with Ni additives; La with additives of Ni, Pt or Ru. Moreover, the catalyst used has the general formula M ₁ M ₂ M ₃ [A _x B _y Ce _0.35 Zr _0.35 ] O ₂ , where: x is 0-0.3, y = 0-0.3, A and / or B are selected from rare-earth metals Pr, La, Sm, M ₁ - selected from platinum group metals - Pt or Ru; M ₂ is Ni; M ₃ - La, provided that the metal content is M ₁ = 0, then the content of M ₂ ≠ 0, and if the content of M ₂ = 0, then the content of M ₁ ≠ 0 (RU 2453366, 2012).

To prepare the complex oxide support AxByC _0.35 Zr _0.35 O ₂ , 8-zirconium zirconium oxychloride (chda), 6-cerium nitrate (chda), 6-praseodymium nitrate (os) and / or 6-water samarium nitrate (os) are used and / or 6-aqueous lanthanum nitrate (chda), citric acid (LA, chda), ethylene glycol (EG, h), ethylenediamine (ED). Reagents are taken in molar ratios of LC: EG: ED: Me ((Pr and / or Sm and / or La) + Ce + Zr) equal to 3.75: 11.25: 3.75: 1. Citric acid is dissolved in ethylene glycol in a ratio of LC: EG equal to 1: 3 with stirring in a water bath (60-80 ° C). In parallel, cerium nitrate crystalline hydrate was dissolved in 30 ml of distilled water with stirring in a water bath, while the solution was clear. Then, praseodymium and / or samarium nitrate crystalline hydrate and / or lanthanum are added to it and mixed until completely dissolved, the resulting solution was colorless (light green for praseodymium). A solution of citric acid in ethylene glycol obtained earlier is added to the mixed solution. With constant stirring without a water bath, ethylene diamine is added, the solution heats up, and it becomes dark yellow (sometimes dark brown) and thick, while the pH of the solution rises to ~ 5. The resulting solution is kept at 80 ° C for 3 days to remove excess solvent, then the resulting substance is calcined in the temperature range up to 900 ° C. On the obtained doped oxides of cerium-zirconium, platinum or ruthenium is applied in an amount of 1-1.5 wt. % by impregnation with a solution of H ₂ PtCl ₆ or RuCl ₃ for moisture capacity. The resulting substances are dried in air and calcined at 900 ° C (for platinum) or at 800 ° C (for ruthenium) for 1 hour. A catalyst containing a mixed ceria-zirconium oxide in a ratio of 1: 1 and containing praseodymium and / or samarium, praseodymium and / or lanthanum coated with the active component — platinum or ruthenium — are pressed into tablets with a diameter of 15 mm under a pressure of 2 MPa. Then, a fraction with a particle size of 0.25-0.5 mm is extracted from a tablet previously ground in an agate mortar using sieves with a fixed hole size.

A method of producing synthesis gas from methane is carried out using the above-described catalyst at a temperature of 650-850 ° C. The reaction mixture enters a flow reactor of ideal displacement in the ratio of 7% methane, 7% carbon dioxide and 86% nitrogen. The best results are obtained with RuNi / Pr _0.3 Ce _0.35 Zr ₀ , ₃₅ O ₂ and RuNi / Sm _0.15 Pr _0.15 Ce _0.35 Zr _0.35 O ₂ catalysts. At 850 ° C, the CH ₄ conversion is 97.1-99.6%, and the CO ₂ conversion is 95.6-97.7%.

Despite the achieved high yields of synthesis gas, the method has such disadvantages as: a high degree of dilution of the product with an inert gas - nitrogen and, as a consequence, the need for a separation unit for the specified gas, the use of a catalyst characterized by a complex, multi-stage procedure for its production, leading to increased the complexity of carrying out the method as a whole and reducing the economic efficiency of the method.

Thus, the known method for producing synthesis gas is not effective enough.

The technical problem of the invention is to increase the efficiency of the method of producing synthesis gas, namely, to simplify the technology of the method while ensuring high conversion of methane and carbon dioxide, high yields of H ₂ and CO, as well as high performance of the used catalyst system.

This technical problem is solved by creating a method for producing synthesis gas by high-temperature catalytic oxidative conversion of methane, which consists in supplying to the reactor in which the catalyst system is placed an initial gas mixture containing a mixture of methane and carbon dioxide with a volume ratio of methane: carbon dioxide equal to 0.97 -1.1: 1, and carrying out the process at a temperature of 700-950 ° C, atmospheric pressure, while the macrobicyclic ruthenium complex Ru (CwGm) ₃ (Bn-C ₄ H ₉ ) _{2 is} used as a catalytic system, where CwGm is It is a chelating bis-2-hydroxyphenoxyl glyoximate group and Bn-C ₄ H ₉ is a crosslinking n-butyl borate group deposited on a carrier - heat-resistant, highly porous ceramic material, in an amount of 5.0% by weight of the carrier.

Preferably, the process is carried out at a temperature of 900 ° C.

The invention consists in the following.

The catalyst used in the method, which is a macrobicyclic complex with an encapsulated metal ion - ruthenium, is a representative of a new promising class of coordination compounds (clathrochelate macrobicyclic complexes) with unusual chemical, physical, and physicochemical properties due to the unique properties of a metal ion encapsulated by a three-dimensional macroligand cavity and, to a large extent, isolated from the influence of external factors. These properties include, but are not limited to, the availability of such compounds, their chemical and photochemical stability, intense color, low toxicity, and the ability to reverse redox processes (which implies, in particular, their use as catalysts for photochemical and redox processes), as well as a tendency to form ordered molecular structures.

According to the invention, the process is carried out in a heated flow-through quartz reactor with a pocket for a thermocouple. The end of the thermocouple is located in the center of the catalyst system layer and does not contact the latter. The particle size of the catalyst system is 1-2 mm, the content of the macrobicyclic complex Ru (CwGm) ₃ (Bn-C ₄ H ₉ ) ₂ is 5.0% by weight of the carrier.

A mixture of CH ₄ with CO ₂ (pure 99.9%) is fed into the reactor with an inert gas undiluted. The feed rate of the gas mixture is 14.8-15.4 l / g per hour. The catalyst is heated to a predetermined temperature in a stream of a mixture of CH ₄ with CO ₂ . The analysis of the composition of the products is carried out by gas-liquid chromatography (GLC).

The feedstock is a mixture of methane and carbon dioxide, preferably in a volume ratio of 0.97-1.1: 1. Moreover, it is possible to use as a feedstock a mixture of main natural gas and carbon dioxide.

The feed gas mixture is fed to a reactor in which it reaches the catalyst system, and the catalyst system is heated to a temperature of 700-950 ° C., preferably 900 ° C., which is maintained during the entire process of oxidative conversion of methane.

In the described method for producing synthesis gas, a catalytic system is used prepared by applying to the heat-resistant, highly porous ceramic support the above macrocyclic complex Ru (CwGm) ₃ (Bn-C ₄ H ₉ ) ₂ .

The specified complex is obtained as follows.

First, the Ru (Cl ₂ Gm) ₃ (Bn-C ₄ H ₉ ) ₂ complex is prepared, where CbGm is the dichloroglyoxime group and Bn-C ₄ H ₉ is a crosslinking n-butyl borate group.

(15 г)]. Реакционную смесь нагревают с обратным холодильником в течение 3 часов при температуре бани 110°С, затем отгоняют нитрометан (приблизительно 50 мл) и оставляют реакционную смесь на ночь при комнатной температуре. Затем реакционную смесь упаривают до небольшого объема и осаждают трехкратным объемом метанола. Осадок отфильтровывают, промывают 5% соляной кислотой и затем небольшим объемом метанола и экстрагируют комплекс хлороформом. Хлороформный раствор фильтруют через слой силикагеля Silasorb SPH-300 (10 мм), упаривают до небольшого объема и осаждают гексаном. Желтый осадок промывают небольшим объемом метанола, затем гексаном и удаляют растворитель в вакууме. Выход Ru(Cl₂Gm)₃(Bn-C₄H₉)₂. составляет 2.2 г (31 масс. %).Ru (OH) Cl ₃ (2.25 g, 10 mmol), freshly distilled SbCl ₃ (11.5 g, 50 mmol), H ₂ Cl ₂ Gm (5.2 g, 33 mmol), and sponge lead (4.0 g, 2 mmol) are dissolved / suspended in nitromethane (50 ml) with stirring under argon. A solution of (n-C ₄ H ₉ BO) ₃ in chloroform is added dropwise to a solution heated to boiling with stirring [this solution was obtained by heating a solution / suspension of n-butylboric acid (2.6 g, 25 mmol) in chloroform (50 ml) in for 6 hours under argon in a flask equipped with a Soxhlet extractor with molecular sieves 4

(15 g)]. The reaction mixture was heated under reflux for 3 hours at a bath temperature of 110 ° C., then nitromethane (approximately 50 ml) was distilled off and the reaction mixture was left overnight at room temperature. Then the reaction mixture was evaporated to a small volume and precipitated with a three-fold volume of methanol. The precipitate was filtered off, washed with 5% hydrochloric acid and then with a small volume of methanol, and the complex was extracted with chloroform. The chloroform solution was filtered through a Silasorb SPH-300 silica gel layer (10 mm), evaporated to a small volume and precipitated with hexane. The yellow precipitate was washed with a small volume of methanol, then with hexane, and the solvent was removed in vacuo. Yield Ru (Cl ₂ Gm) ₃ (Bn-C ₄ H ₉ ) ₂ . is 2.2 g (31 wt.%).

The compound Ru (CwGm) ₃ (BH-C ₄ H ₉ ) _{2 is} then prepared, where CwGm is a chelating bis-2-hydroxyphenoxy glyoxime group and BH-C ₄ H ₉ is a crosslinking n-butyl borate group.

Excess disodium salt of bis- (2- (o-hydroxyphenoxy)) diethyl ether obtained by reacting sodium metal (0.28 g, 12.3 mmol) and bis (2- (o-hydroxyphenoxy)) diethyl ether (2.2 g , 7.7 mmol), and the interphase carrier ((n-C ₄ H ₉ ) ₄ N) Br (0.77 g, 5.1 mmol) is dissolved / suspended in dry tetrahydrofuran (THF) (50 ml) and the solution is added complex Ru (Cl ₂ Gm) ₃ (BH-C ₄ H ₉ ) ₂ (1.2 g, 1.7 mmol) in THF (30 ml) dropwise with stirring for 2 hours at 50 ° C. The reaction mixture was stirred for 30 hours at 50 ° C and cooled to room temperature. Then filtered off. The resulting filtrate is precipitated with a three-fold volume of hexane. The precipitate formed is filtered off, washed with water and methanol and dissolved in chloroform. The resulting solution was filtered through a pad of Silasorb SPH-300 silica gel (20 mm), evaporated to dryness and extracted with a small amount of diethyl ether. The extract was evaporated to dryness, the orange precipitate was washed with hexane and dried in vacuo. The yield of Ru (CwGm) ₃ (BH-C ₄ H ₉ ) ₂ is 0.32 g (14 wt.%). (Voloshin YZ, Varzatskii O.A., Kron T.E., Belsky VK, Zavodnik VE, Strizhakova, NG, Nadtochenko VA, Smimov VA Encapsulation of ruthenium (II) with macrobicyclic dioxime-functionalized ligands: on the way to new types of DNA-cleaving agents and probes. Dalton Transactions, 2002, 1203).

Then, the Ru (CwGm) ₃ (Bn-C ₄ H ₉ ) ₂ complex is applied, where CwGm is a chelating bis-2-hydroxyphenoxyl glyoxime group and BH-C ₄ H ₉ is a crosslinking n-butyl borate group on a carrier - a heat-resistant, highly porous ceramic material.

As the specified carrier, it is possible to use, in particular, materials such as TZMK, for example, TZMK-10, TZMK-25 (manufacturer of FSUE VIAM).

The application is carried out by dissolving the above high-intensity visible in the visible region (450-500 nm) complex with terminal polar groups in methylene chloride and contacting the resulting solution with the carrier described above. In this case, the complex penetrates into the pores of the carrier. The resulting system is kept in air until the solvent evaporates. This allows you to achieve a high level of immobilization on the media of the specified clathrochelate with terminal polar groups due to physical sorption on the common (internal and external) surface of the carrier. Then, the obtained sample was washed with a small amount of methylene chloride, visually monitoring the removal of the complex, which was not immobilized on the surface of the carrier.

The following are examples illustrating the invention, but not limiting it.

Examples 1-10

Particles of a catalytic system containing the above-described Ru (CwGm) ₃ (Bn-C ₄ H ₉ ) ₂ complex on a TZMK-10 heat-resistant, highly porous ceramic material (particle diameter 2-3 μm, are placed in a heated flow-through quartz reactor with a thermocouple pocket) density 0.25 g cm ^-3 , porosity 88%). The particle size of the catalyst system is 1-2 mm, the mass is 0.2 g, the content of the macrobicyclic complex is 5.0% by weight of the carrier. The end of the thermocouple is located in the center of the catalytic system layer without contacting it. A mixture of CH ₄ with CO ₂ in a volume ratio of 1.1: 1 (purity 99.9%) is fed into the reactor, which is undiluted with inert gas. The feed rate of the gas mixture is 15.0 l / g per hour.

Methane and carbon dioxide are fed through flowmeters to the reactor, where they form a homogeneous mixture. After the stream of the homogeneous methane-carbon dioxide mixture in the reactor reaches the bed of the catalytic system, the specified system in the stream of this mixture is heated for one hour to the required temperature.

The gas mixture formed as a result of the reaction on the catalytic system is cooled in a condenser to separate water vapor and part of the resulting mixture is sent to a gas chromatograph to determine the composition of the reaction products by GLC.

Analysis of the reaction gas mixture leaving the reactor shows that in addition to the target products, a mixture of H ₂ and CO, it can include unreacted methane, carbon dioxide and water.

The table shows the conditions for the method of producing synthesis gas by varying the temperature in the layer of the catalytic system (T ° C), the molar ratio methane - carbon dioxide (CH ₄ / CO ₂ ), the feed rate of methane - carbon dioxide mixture (W l / g / h ) As indicators of the effectiveness of the method, the table shows data on the conversion of CH ₄ and CO ₂ , the yield of target products and the productivity of the catalyst in moles of CO per gram-atom of ruthenium per hour. The yield of carbon monoxide is calculated by dividing the total number of moles of the obtained CO by the sum of the number of moles fed to the reactor methane and carbon dioxide. The hydrogen yield is calculated by the formula wH ₂ × 100 / wCH ₄ × 2, where wH ₂ is the amount of hydrogen at the outlet of the reactor, mol, wCH ₄ is the feed rate of methane at the entrance to the reactor, mol.

According to the experimental data given in the table, the method according to the invention provides methane conversion up to 95% by mass, CO ₂ conversion up to 98% mass, Н ₂ yield and СО output up to 95% mass, catalytic system productivity up to 62604 mole СО per gram ruthenium atom at one o'clock.

The data in the table show that an increase in temperature in the catalyst bed contributes to an increase in the conversion of methane and carbon dioxide, an increase in the yield of target products and the productivity of the catalytic system in moles of CO per gram-atom of ruthenium per hour. Moreover, the process is preferably carried out at a temperature in the catalyst bed of at least 900 ° C, more preferably at 900 ° C.

Thus, the method according to the invention provides high conversion of methane and CO ₂ , yields of H ₂ and CO, as well as high productivity of the catalytic system. At the same time, a significant advantage of the proposed technology is the possibility of carrying out the process without the use of inert gases, the presence of which, as is known, significantly complicates the process technology, as well as the implementation of the latter at atmospheric pressure, which greatly simplifies the process technology as a whole.

Claims (1)

A method of producing synthesis gas by high-temperature catalytic oxidative conversion of methane, which consists in supplying to the reactor in which the catalytic system is placed an initial gas mixture containing a mixture of methane and carbon dioxide with a volume ratio of methane: carbon dioxide equal to 0.97-1.1: 1, and carrying out the process at a temperature of 700-950 ° C and atmospheric pressure, while the macrobicyclic ruthenium complex Ru (CwGm) ₃ (Bn-C ₄ H ₉ ) ₂ , where CwGm is a chelating bis-2-hydroxyphenoxyl, is used as a catalytic system glyoxy atnoy group and BH-C ₄ H ₉ n-crosslinking is butilboratnoy group, supported on a heat resistant, highly porous ceramic carrier in an amount of 5.0% by weight of the carrier.