## 3 Results
### GC/MS Analysis
By contrast, the relative content of phenolics increased when 5-nitrouracil, chitin, and polyamide were added. A comparison of the structures of the six nitrogen-containing compounds shows that there is no oxygen-containing group per se in NH\({}_{4}\)Cl, polyaniline, and melamine, explaining their negligible effect on the phenolic content. By contrast, 5-nitro uracil, chitin, and polyamide have oxygen-containing groups, whereas 5-nitro uracil contains hydroxyl groups. However, these hydroxyl groups are attached to the pyrimidine ring, and their stability is much higher compared to chitin and polyamide, so the relative content of phenolics was not as high as with the latter two. Chitin not only contains hydroxyl groups, but it also has ether bonds in its structure. These oxygen-containing groups can produce free hydroxyl radicals at high temperatures, so the relative phenolic content was the highest, reaching 20.26%. In the case of polyamides, a large number of amide groups are generated during pyrolysis. Previously, [PERSON] et al. [32] found that when using cinnamic acid and its derivatives for co-pyrolysis  
Figure 5: Nitrogen-containing compounds by type as a percentage of total compounds. with NH4 Cl, the carboxyl group of cinnamic acid reacts with the amino radical produced by the decomposition of NH4 Cl to form amide at lower temperatures, while a part of the amides will be dehydrated to form cyanide as the temperature is increased further. Another part of the amide groups generated by polyamide pyrolysis produces hydroxyl radicals due to dehydration, which is also a reason for the increase in the relative content of phenolics. Corresponding to the phenolics are other compounds, the most important of which were oxygen-containing compounds, and the above three nitrogen-containing compounds generated in the pyrolysis process of the oxygen-containing groups after the reaction to generate other oxygen-containing compounds, as shown in Table 2. Chitin produced more oxygen-containing groups, so the relative content of other compounds was also higher, reaching 31.76%. The main focus of this study is on nitrogen-containing compounds. For all six nitrogen-nous compounds, the relative content of nitrogenous compounds in the co-pyrolysis tar increased to a large extent. In the case of chitin and polyamide, the nitrogen is derived from the amide structure, which is easily dehydrated to generate cyano groups, the main class of nitrogen-containing compounds in both cases. For polyaniline, the nitrogen-containing compounds in the pyrolysis product were mainly aniline and its derivatives, accounting for 85% of all nitrogen-containing compounds. For 5-nitrouracil, the nitrogen is derived from the pyrimidine ring and nitro group, both of which are relatively stable. After analyzing its tar, it was found that it contained many compounds with a pyrimidine ring as the base structure and not many new nitrogen-containing groups were generated. According to previous studies and the pyrolysis patterns of NH4 Cl and melamine, both can produce ammonia gas during pyrolysis, which in turn generates amino radicals. Many researchers have also carried out studies with coal and ammonia, which showed that many kinds of nitrogen-containing compounds can be produced by this combination. According to the GC/MS analysis, it was found that the relative content of nitrogenous compounds in both groups was relatively high, and the relative content of nitrogenous compounds in the tar after the co-pyrolysis of tar-rich coal with melamine even reached 70.48%. After analyzing the structure, pyrolysis pattern, and GC/MS data of these six nitrogenous compounds, it was found that although the highest relative content of nitrogenous compounds was produced by the addition of melamine, the product distribution of nitrogenous compounds in the tar was affected by the fact that melamine itself could react to form melam, melem, and melone during the pyrolysis process [21]. The products of NH4 Cl at high temperatures are NH3 and HCl.