# Study of Soot Deposits during Continuous Methane Pyrolysis in a Corundum Tube
## 1 Introduction  
One of the promising methods of hydrogen and carbon black production with reduced CO\({}_{2}\) emissions is the thermal decomposition of methane (so called methane pyrolysis) [1], the reaction of which is:  
\[\mathrm{CH_{4}}\rightarrow\mathrm{C_{J}}+2\mathrm{H_{2}}\upuparrow\]  
The development of methane pyrolysis technology is an urgent task, the solution of which can significantly reduce carbon dioxide emissions into the atmosphere in the industrial production of hydrogen and carbon black, providing economic efficiency [2, 3]. Hydrogen is one of the most in-demand technical gases. Annual consumption of hydrogen is about 94 million [4]. It is used in chemical industry for the synthesis of many substances, and it is a raw material for ammonia production [5]; methanol and hydrochloric acids are also produced using hydrogen [6]. Also, hydrogen is used in metallurgy for the direct reduction of iron [7]. Hydrogen is required for hydrotreatment of petroleum products, which increases the level of refinement of raw materials and the quality of products [8]. Hydrogen is also used in medicine [9], the food industry [10] and the glass industry [11]. In addition, hydrogen is considered a promising energy carrier inthe stationery and transport energy sectors [12]. Currently, hydrogen is produced mainly by steam conversion of methane:  
\[\mathrm{CH_{4}+2H_{2}O\to CO_{2}+4H_{2}},\]  
However, it leads to significant emissions of CO\({}_{2}\). Due to the necessity of carbon dioxide emission reduction in hydrogen production, oxygen-free methane decomposition may become a sustainable alternative in hydrogen production on the industrial scale [13]. Carbon black is another important substance, which is used in many applications. Technical carbon is a specially produced industrial carbon black. It strengthens car tires, improves the mechanical properties of plastics, and determines the distinctive properties of many other chemical products. The annual production of carbon black is about 13-14 million tons [14]. Carbon black is used in the production of tires [15], rubbers and plastics, and it is used as a reinforcing component in composite materials [16]. Carbon can be used in the production of structural materials formed from carbon plastics [17]. Also, carbon black is used in the manufacture of technical products, plaster and construction mixtures, as well as in the paint and varnish industry [18]. High-quality carbon black with the minimum content of impurities and low emissions of carbon dioxide during its production is also in high demand. Today, carbon black is mainly produced from raw petroleum [19]. This process intensifies the greenhouse effect by emitting greenhouse gases. In methane pyrolysis, the formation of CO\({}_{2}\) is negligible. The development of this method will help to normalize the level of greenhouse gas emissions and replace the existing production process, along with its high emission of carbon dioxide. Methane pyrolysis can be carried out in several ways. One of these methods is plasma pyrolysis [20]. The advantage of this method is its low metal consumption due to the compact plasma-based equipment. Modern plants for plasma methane pyrolysis can be created without additional transformers or frequency converters; power can be supplied from an industrial three-phase network. Another basic method is catalytic methane pyrolysis [21; 22; 23]. The main drawback of this method is the neutralization of the catalyst by carbon deposits, which reduces the catalyst efficiency, and its subsequent destruction is possible [21]. Another method of methane pyrolysis is the decomposition in a melt of metals or salts [24; 25; 26]. A common method to produce hydrogen and carbon black is the thermal decomposition of methane in an oxygen-free environment. One of the main problems of thermal methane pyrolysis is a problem of solid soot deposition in the reactor space.