IMPROVEMENT OF THE CATALYST CARRIER FOR PRIMARY REFORMING OF NATURAL GAS IN A LABORATORY SETUP

ABSTRACT

The article describes the process of extracting nickel from the composition of the used GIAP-8 catalyst waste in the form of nickel nitrate, in which it not only does not affect the environment, but is also a cost-effective solution for the production of nickel catalysts. To prepare the carrier, 150 g of water at a temperature of 70-90℃ was added to 50 g of sawdust and the sawdust was impregnated for 1 hour. Then 170 g of Ca(NO₃)₂•4H₂O was added and mixed well for 5 minutes. 400 g of alumina was added to the mixture and mixed. Then 40/30/20 g of MgO, 20 g of 20% HNO₃ were added and mixed. The prepared dough-like mass was formed using an extruder and dried, increasing the temperature.

АННОТАЦИЯ

В статье описан процесс извлечения никеля из состава используемых отходов катализатора ГИАП-8 в виде нитрата никеля, в котором он не только не влияет экологическую среду, но и является экономически эффективным решением для производства никелевых катализаторов. Для приготовления носителя к 50 г опилок, добавляли 150 г воды с температурой 70-90℃ и пропитывали опилки 1 час. Затем добавляли 170 г Ca(NO₃)₂•4H₂O и хорошо перемешайте в течение 5 минут. В смесь добавляли 400 г глинозёма и перемешивали. Затем добавляли 40/30/20 г MgO, 20 г 20% HNO₃ и перемешивали. Приготовленную тестообразную массу формировали с использованием экструдера и сушили, увеличивая температуру.

Keywords: GIAP-8 catalyst waste, nickel oxide, catalyst, nickel nitrate, carrier, alumina.

Ключевые слова: отходов катализатора ГИАП-8, оксид никеля, катализатор, нитрат никеля, носитель, глинозём.

Currently, scientific research is being conducted in the world on the synthesis of catalysts with high strength, low hydraulic resistance and specific surface area. In this regard, special attention is paid to the creation of technology for the production of our own highly effective and durable catalysts based on the processing of spent industrial catalysts; development of technology for extracting nickel from spent industrial catalysts; technology for obtaining high-strength reforming catalyst carriers and the scientific basis for obtaining a nickel-containing catalyst on a high-strength carrier.

To prepare the carrier, 150 g of water at 70÷90℃ was added to 50 g of sawdust and soaked for 1 hour. Then 170 g of Cа(NO₃)₂•4H₂O was added and mixed well for 5 minutes. 400 g of alumina was added to the mixture and mixed. Then 40/30/20 g of MgO and 20 g of 20% HNO₃ were added and mixed.

The prepared dough-like mass was formed using an extruder and dried by increasing the temperature. After reaching a temperature of 120÷140℃, it was held for 3 hours. Then the prepared carrier was cooled to room temperature and placed in a muffle furnace, increasing the temperature to 1380℃ and held for 5 hours. After cooling to room temperature, the properties of the carrier were studied. Three catalyst samples with different MgO contents were prepared (Table 1).

Table 1

Composition of the prepared catalysts

Properties such as moisture absorption, bulk density of the carrier, and mechanical strength were determined (Table 2).

To prepare a solution of nickel nitrate and to impregnate the carrier, 75 g of Ni(NO₃)₂•6H₂O were placed in a conical flask and mixed with 100 cm³ of distilled water, 25 g of Al(NO₃)₃•9H₂O were added, stirring at 60℃ for 1.5 hours [4].

Table 2

Characteristics of the media samples

The density and viscosity of the liquid phase prepared for soaking were studied (Table 3).

Table 3

Density and viscosity of nickel nitrate solutions

After soaking, the carrier was dried for 4 hours at 300℃.

The amount of Ni(NO₃)₂ solution impregnated once in the liquid phase was 566 g/dm³. After the liquid phase passed through the impregnated filter, a solution was prepared for the second impregnation in 566 g/dm³ Ni(NO₃)₂ solution. The liquid phase should again be reduced to Ni(NO₃)₂ = 490 g/dm³. For this, distilled water was added, stirred and heated to 60℃[5].

The bulk density, mechanical strength and amount of adsorbed nickel were determined (Table 4).

To develop the catalyst carrier technology for primary reforming of steam conversion of natural gas, mixtures of alumina, calcium hydroxide with the addition of wood flour or graphite were prepared. Calcium hydroxide was dissolved in nitric acid with a concentration of 56% and mixed with alumina with the addition of wood flour [6].

Table 4

Characteristics of catalyst samples after single impregnation

Table 5

Characteristics of catalyst samples after double impregnation

The carriers were prepared by pressing in a screw extruder. The extruder was equipped with dies with one hole, with five and seven holes with a smooth surface and with one hole with external grooves. The outer diameter of the carriers was 19 mm, the diameter of the holes of the multi-hole carriers was 3 mm, and the diameter of the single-hole carriers was 6 and 7±1 mm.

The first 6 batches of the mixture, molded in a screw press, were dried and calcined in a shaft piercing furnace at a temperature of 1280÷1300℃ for 14 hours. The same molded granules were additionally calcined at 1400℃ [7].

The calcined carrier samples were tested for mechanical strength and moisture capacity.

The obtained carrier samples were used to obtain supported catalysts using nickel nitrate solutions obtained from spent GIAP-8 catalysts.

The activity was determined at a temperature of 500 and 700℃ for 7 hours, taking a sample of the converted gas for analysis every hour. Before determining the activity, the catalyst was reduced in a hydrogen stream at a temperature of 500℃ for 2 hours. All the prepared catalysts provide natural gas conversion. The conversion degree is on average 63% at 500℃, 93% at 700℃ and 99.4/99.5% at 800℃ [8].

The results of testing the activity of the developed catalysts were compared with the data of the operating AM-76 unit of JSC Maxam Chirchik, which confirmed that the developed catalysts meet the activity requirements for a primary endothermic reforming catalyst.

Conclusion. Summarizing the results of the development of the primary reforming catalyst on an aluminum-calcium carrier and pilot tests, it is shown that the catalyst meets the requirements of the chemical industry in terms of methane concentration at the outlet of the tubular furnace (in terms of activity). However, with prolonged use of the catalyst, hydraulic resistance in the pipes increases. Furnaces, leading to cracking of individual pipes. When unloading the catalyst from the tubular furnace, 25-30% of destroyed granules were found. One of the reasons for this is insufficient mechanical strength.

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