# Microwave Pyrolysis of Biomass: The Influence of Surface Area and Structure of a Layer
## 1 Introduction
### Microwave Pyrolysis of Biomass and Waste: A Review of Modern Researches
focused on the use of different N\({}_{2}\)/CO\({}_{2}\) purge gas ratios (0/100, 25/75, 50/50, 75/25, and 100/0). They found that CO\({}_{2}\) accelerates homogeneous reactions in the gas phase between volatile organic compounds formed as a result of the rice straw pyrolysis [6]. The yield of CO started at temperatures above 480 \({}^{\circ}\)C in the presence of CO\({}_{2}\), while CO formation was not observed in the N\({}_{2}\) environment. In addition, the CO/SiO\({}_{2}\) catalyst additionally accelerated the kinetics of CO formation by a factor of 3 and H\({}_{2}\) by a factor of 6 relative to noncatalytic pyrolysis at 500 \({}^{\circ}\)C.  
The synergistic effect of the CO/SiO\({}_{2}\) and CO\({}_{2}\) catalyst led to a significant increase in the concentrations of H\({}_{2}\) and CO at temperatures above 480 \({}^{\circ}\)C. Similar conclusions were made in [37]. [PERSON] et al. [37] analyzed the effect of microwave heating, reaction temperature, and types of catalysts (Ni/Fe), and also evaluated the removal efficiency of tar and nitrogen oxides during pyrolysis of plant residues in combination with catalytic reforming. The highest gas yield (77.47 wt%) and the lowest resin yield (7.40 wt%) were obtained at a temperature of 900 \({}^{\circ}\)C in the microwave mode. An increase in the moisture content of plant residues led to a significant decrease in the yield of a solid product and a simultaneous increase in gas production (the maximum gas yield was 82.60 wt% at a moisture content of 40%). With the combined effect of microwave radiation and a nickel-based catalyst, a maximum reduction of 74% was achieved in resin yield, and gas production also increased by 143%. Different operation modes of the microwave reactor are studied to increase the yield of pyrolysis gas. In [34], the continuous microwave pyrolysis of cow manure with an initial mass of 50 g was performed using the CO\({}_{2}\) reforming technology. [PERSON] et al. [34] studied the effect of CO\({}_{2}\) on the yield and quality of the gas produced, the pyrolysis mechanism and the energy balance of the process. It was found that continuous microwave pyrolysis combined with CO\({}_{2}\) reforming technology has advantages over other pyrolysis methods (batch microwave pyrolysis and traditional electric heating). The use of CO\({}_{2}\) increases the efficiency of biomass conversion by enhancing reactions with pyrolysis products such as tar, CH\({}_{4}\) and hydrocarbons. The resulting pyrolysis gas has a reduced content of H\({}_{2}\)S, which was confirmed by many studies [44; 45; 46]. [PERSON] et al. [34] compared the operating modes of a microwave reactor of periodic and continuous modes. They found that continuous microwave pyrolysis can increase the yield and calorific value of biofuels [34]. The maximum yield of biofuel during continuous microwave pyrolysis was 72.16%, and the maximum net calorific value of biogas and biooil was 19.50 MJ/Nm\({}^{3}\) and 25.58 MJ/kg, respectively. Continuous microwave pyrolysis has low power consumption and high energy efficiency, reaching a maximum of 18.47%, which is 85% higher than for a batch microwave pyrolysis. The authors of [13; 47; 48] discussed the influence of the biomass structure on the conditions and characteristics of microwave pyrolysis and gasification. [PERSON] et al. [13] investigated the influence of the particle size and pretreatment of corn straw as well as the catalysis of Al\({}_{2}\)O\({}_{3}\) on the efficiency of microwave pyrolysis, distribution and composition of end products. It was shown that the heating efficiency and the yield of the gaseous product increase as the particle size decreases. [PERSON] et al. [13] also found that without any pretreatment, the effect of catalysis is insignificant. An increase in the microwave pyrolysis temperature was registered when the biomass was pretreated. The addition of Al\({}_{2}\)O\({}_{3}\) increased the gas yield by 4-9 wt%.