## 1 Introduction  
The present work aims to characterize char and primary tar produced from biomasses with different contents of lignin/cellulose/hemicellulose upon heating under the following conditions:  
1. with very fast heating rates (\(10^{4}\) K/s);
2. at very high temperature (up to 2000 K);
3. in inert or CO2 rich atmospheres. It must be emphasized that, even though pyrolysis of biomass has been the object of extensive research over the past few decades, experimental studies, which combine the conditions reported in 1 to 3 points, are relatively scarce. In the present work, these conditions are achieved by means of a special heated strip reactor, which allows not only heating the solid samples with temperature (up to 2073 K) and heating rates (up to \(10^{4}\) K/s) similar to those of laminar flow reactors, but also quenching the volatiles as soon as they are emitted. The focus is posed on primary tar, i.e., on condensable volatile products collected immediately after their ejection from the particles, and before they undergo secondary reactions in the gas phase. This is indeed an important feature addressed by the present work. Several papers so far addressed the role of heating rate and temperature on the yields and composition of solid (char), liquid (tar) and gaseous products from pyrolysis of raw biomass and of single lignocellulosic fractions. A review is provided in [1]. At a low heating rate, pyrolysis of hemicellulose and cellulose occurs in the range of 470-530 K and 510-620 K [2; 3], respectively, starting with depolymerization into oligosaccharides and proceeding through bond cleavage and rearrangement of the produced molecules [4]. Lignin pyrolysis is more complex: it occurs over a broader temperature range (550-770 K) and proceeds through free radical reactions, chain propagation and termination [5; 6]. Interactions between the components are, however, possible throughout pyrolysis, as investigated in [7]. A parallel research line addressed the role of CO\({}_{2}\) in pyrolysis/gasification of biomasses [8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22] and lignocellulosic components [10]. It was shown that in a thermogravimetric apparatus, at a low heating rate (\(\approx\)1 K/s), the presence of CO\({}_{2}\) in the atmosphere does not affect thermolysis, and also, the Boudouard reaction is negligible. At a fast heating rate (100 K/s), in a fluidized bed at 800 K, [PERSON] et al. [11] observed that CO\({}_{2}\) favored the yield of acid products and instead decreased phenols in tar. At very fast heating rates (10\({}^{4}\) K/s), in a drop tube reactor at 1600 K, [PERSON] et al. [20] observed that CO\({}_{2}\) modified the degree of aromaticity of the tar and also the quality of char. A role of single lignocellulosic components was suspected, but not clarified yet. In a recent work [22], the same group carried out an experimental campaign similar to the one presented in the present paper, focusing only on single biomass components: cellulose, hemicellulose and lignin. A cellulose sample was in the form of microcrystalline cellulose supplied by JRS Pharma, the hemicellulose sample was a xylooligosaccharide extracted from Corncob supplied by Roth, while lignin was a dealkaline lignin supplied by Fisher Scientific. A very different behavior was observed during fast pyrolysis of hemicellulose and lignin (10\({}^{4}\) K/s): the former produced only light tars, almost solely anhydrous monosaccharides, and the latter produced oxo-aromatics but also polycyclic aromatic hydrocarbons (PAHs), high molecular weight species (named heavy tar), soot and char. Cellulose resembled hemicellulose, regarding the chemical composition of light tar, being largely constituted by anhydrous monosaccharides. CO\({}_{2}\) in the gaseous environment did not affect the composition of \"light tar\" from cellulose and hemicellulose, which was in fact largely dominated by chain scission and formation of anhydrous monosaccharides.