RU2036718C1 - Porous carbonic material - Google Patents

Abstract

FIELD: production of catalysts. SUBSTANCE: porous carbonic material is three-dimensional matrix formed by bent layer of carbon in form of fibers 10-150 nm in diameter with length-to-diameter ratio of 160-2500 and randomly bound into granules. Fibers consists of packed into one another packages of graphitic carbon of conical shape with cone opening of 60-180 deg., interplane distance d 002 of 0.340-0.350 nm, X-ray density of 2.17-2.24 g/cu. cm, and real density of 2.05-2.17 g/cu.cm. EFFECT: higher efficiency. 4 dwg, 1 tbl

Description

 The invention relates to porous carbon materials, more specifically to carbon carriers for catalysts and adsorbents.

The closest technical solution for the achieved effect is a porous carbon material (prototype). According to the prototype, the porous carbon material is a matrix formed by curved carbon layers with a thickness of 10-1000 nm, a radius of curvature of 10-1000 nm, a true density of 1.8-2.1 g / cm ³ and a pore size distribution with a maximum in the region of 20 200 nm and an additional maximum of 4-20 nm. The porous carbon material according to the prototype is prepared by the deposition of pyrocarbon on the soot surface, which is formed by the decomposition of gaseous hydrocarbons at a temperature of 750-1200 ^о С, followed by activation of the obtained carbon material with a steam-air mixture. The adsorption surface of this material is mainly formed by layers of sp ² -hybridized carbon, i.e. basal faces of graphite microcrystallites (Fig. 1).

 The disadvantages of the considered technical solution are low operational characteristics due to the surface relief of the carbon material. In particular, the low resistance of the catalysts prepared on this support to deactivation under the conditions of a liquid phase reduction process and sintering of the deposited metal at elevated temperature.

 The purpose of the invention is the creation of a porous carbon material with high performance.

The goal is achieved in that the porous carbon material is a three-dimensional matrix formed by curved carbon layers in the form of fibers having a thickness of 10-150 nm, a length to thickness ratio of 160-2500 and randomly bound into granules. The fibers consist of packed into each other packets carbon graphite conical shape with an angle of ^about 60-180 solution, interplanar spacing d ₀₀₂ 0,340-0,350 nm, x-ray density of 2.17-2.24 g / cm ³ and a true density of 2,05-2 , 17 g / cm ³ .

 The invention is illustrated in FIG. 1-4.

 According to scanning electron microscopy, the porous carbon material is a three-dimensional matrix formed by curved carbon layers in the form of fibers, randomly bound into granules (Fig. 2). The size of these granules is determined by the particle size of the catalyst, on the surface of which decomposition of the hydrocarbon feedstock is carried out, as well as by the degree of grinding of the resulting carbon material and may be 0.01-10 mm (preferably 2-3 mm). According to transmission electron microscopy, the fibers have a thickness of 10-150 nm and a length to thickness ratio of 160-2500 (Fig. 3). Carbon fibers grow at the active sites of the catalyst and randomly intertwine during the decomposition of hydrocarbon materials, creating a product framework (carrier granule) in a porous carbon matrix.

Fibers with a diameter of 10-150 nm with a length to diameter ratio of 160-2500 create an optimal mesoporous structure for the catalyst with a pore size of 12-20 nm and a specific transition pore surface of 85-135 m ² / g.

According HREM fibers consist of packed into each other packets carbon graphite conical shape with an angle of 60-180 ^{of the} solution (FIG. 4). These packets are curved basal layers of graphite-like carbon. The ends of the basal layers of carbon extend onto the surface of the carbon fibers.

According to x-ray phase analysis and adsorption methods, the porous carbon material has an x-ray density of 2.17-2.24 g / cm ³ , a true density of 2.05-2.17 g / cm ³ , an average pore size of 12-20 nm, pore volume 0 , 27-0.32 cm ³ / g and the specific surface of the transition pores 85-135 m ² / g.

Fibers formed packed into each other packets carbon graphite conical shape with an angle of ^about 60-180, X-ray density of 2.17-2.24 g / cm ^3, an interplanar distance d ₀₀₂ 0,340-0,350 nm, and the true density of 2,05-2 , 17 g / cm ³ have a unique surface relief, which provides increased stability of the deposited palladium particles to deactivation under the conditions of a liquid-phase reduction and to sintering at elevated temperature.

PRI me R 1 (prototype). 100 g of carbon black with a predominant particle size of 20 nm is loaded into a quartz reactor with an internal diameter of 90 mm, the reactor is rotated at an angular velocity of 2 π rad / min. With an external electric heater, the soot reactor is heated to 900 ^° C and 176 l / h of a propane-butane mixture with a butane content of 50% are fed into the continuously mixed soot layer. After soot has been treated for 5 hours, instead of propane-butane, water vapor with a specific flow rate of 1 kg / kg of carbon for 6 hours. The resulting porous carbon material is formed by curved carbon layers with a radius of curvature of 10-1000 nm and has the following physicochemical characteristics:
The total pore volume, cm ³ / g 0,81
Maximum pore size distribution, nm 5-48 Carbon layer thickness, nm 20-100 True density, g / cm ³ 1.97
X-ray density, g / cm ³ 2.21
Catalyst Preparation: To a suspension of 1 g of carbon carrier in 20 ml of distilled water at ²⁰ ° C was added 10 ml of a solution prepared by neutralization of H ₂ PdCl ₄ with sodium carbonate (pH 7.0) and containing 0.01 g of Pd (calculated as palladium metal ) After complete deposition of palladium on a carrier sample was washed with water, air dried and reduced in a stream of hydrogen at 90 ^° C to give a catalyst with Pd content 1 wt.

Catalyst test. A catalyst sample (0.1 g) was charged into a flow reactor, purged with nitrogen, heated to 120 ^° C, and a stream of a gas mixture with a molar ratio of hydrogen: benzene of 10: 1 was passed through the catalyst bed at a volumetric rate of 0.27 ml / s. The reaction products are analyzed chromatographically. The activity of the fresh catalyst (A _o ) is characterized by the degree of conversion of benzene.

Testing the stability of the catalyst to deactivation under the conditions of a liquid phase reduction process: 0.5 g of catalyst is loaded into a glass reactor, 20 ml of a 1 M NaCl solution are added, purged with nitrogen and hydrogen, heated to 90 ^° C in a hydrogen atmosphere for 1 hour. Then, the catalyst is washed on the filter with distilled water and air dried. After this operation, which simulates the operating conditions of the catalyst in the liquid phase reduction process, the activity of the catalyst in the hydrogenation of benzene is re-determined. The activity of the thus treated catalyst is characterized by A ₁ . The resistance of the catalyst to deactivation in the process of liquid phase recovery (Y _W ) is determined by the formula
Y _W 100% (A _about A ₁ ) / A _about . For the carbon carrier of the prototype, the value of Y _W is 48.8%
Testing the stability of the catalyst against sintering at elevated temperature: flow reactor was charged with 0.1 g of fresh catalyst was purged with nitrogen and a hydrogen stream (0.3 ml / s) is kept at a temperature of 500 ^{° C} for 1 hour and then cooled reactor is conducted. testing this catalyst in the hydrogenation of benzene. The activity of the catalyst thus treated is characterized by (A _t ). The resistance of the catalyst to sintering at elevated temperature is characterized by the value of Y _t : Y _t A _t / A _about . For the carbon carrier of the prototype, the value of Y _t is 0.30.

EXAMPLE Example 2 In a quartz reactor was charged 0.1 g of catalyst containing 57% Ni and 43% Al ₂ O _3, is heated to the gaseous hydrocarbons (methane), temperature 550 ^C and stirred over the catalyst bed is passed at a speed of 12 l / h for 4 hours. As a result of the catalytic decomposition of hydrocarbons, a granular porous carbon material is formed having the following characteristics: Carbon content, 96.5
Specific surface of transition pores, m ² / g 120 Pore volume, cm ³ / g 0.32 Pore diameter, nm 20
The size of carbon crystallites (O.K.R.), nm 6.0
Diameter of carbon fibers, nm 40-60
The ratio of fiber length to diameter 160-250
The angle of the solution of the conical layers of carbon, ^about 60-90
Interplanar distance d 002, nm 3.45
X-ray density, g / cm ³ 2.20
True density, g / cm ³ 2.15.

The preparation and testing of the Pd / C catalyst is carried out according to the procedure described in example 1
Catalyst stability
Pd / C in process conditions
liquid phase recovery, Y _w 32.9
Catalyst stability
Pd / C for sintering at elevated temperature, Y _t 0.38
The characteristics of the carbon materials obtained in examples 3-5 are presented in the table.

 The above results show that the inventive carbon carrier is fundamentally different in structure from known carbon materials. The positive effect of the proposed carbon carrier is to significantly increase the resistance of supported palladium catalysts to sintering at elevated temperature and in the conditions of the liquid phase reduction, due to the special nature of the location of carbon atoms on the surface of the carrier. So the catalysts prepared on carbon supports according to examples 2-5 under liquid-phase reduction conditions lose only 1.5-32.9% of activity, while known carbon supports under these conditions lose 48.8% of activity. Resistance to sintering of Pd / C catalysts on a carbon support in examples 2-5 is 1.3-2 times higher compared to the prototype.

Claims (1)

POROUS CARBON MATERIAL in the form of a three-dimensional carbon matrix formed by curved carbon layers, characterized in that the curved layers are in the form of fibers with a diameter of 10 to 150 nm and a ratio of length to diameter of 160 - 2500, consisting of conical carbon packets packed into each other with an angle of 60 180 ^o , interplanar distance d _{0 0 2} 0.34 0.35 nm, x-ray density of 2.17 2.24 g / cm ³ and a true density of 2.05 to 2.17 g / cm ³ , randomly bound into granules.

Images