Infrared study of salt free and salt treated cellulose pyrolysis under nitrogen atmosphere

The pyrolysis under nitrogen of salt free and salt treated cellulose was studied by infrared spectroscopy. The results confirm the unzipping mechanism suggested by DTA and TGA studies, and show this mechanism to apply to the untreated and salt treated samples. The results also show the unzipping to stop at the stage of char formation. The onset of this stage was found to occur after the volatilization of only 45–50% of the initial sample of the borax treated cellulose, compared with 65–70% of the KCl treated cellulose and 80–85% of the untreated cellulose.     

煤中吡啶型氮热解机理的量子化学研究

用密度泛函 ( DFT)方法 ,在 UB3LYP/6- 31 G( d)水平上研究了煤中吡啶型氮的热解机理 ,对热解过程中由于官能团周围环境的不同而形成的三类吡啶自由基进行了量子化学计算 ,通过对键的 Mulliken布居数等计算结果的分析 ,分别得到了这三类自由基的热解途径 .并优化得到了反应物、中间体和产物的几何构型 .计算结果表明 ,吡啶型氮主要是以 HCN的形式释放出来的 .NH3 是 HCN二次反应的产物 .     

Fate of the chlorine and fluorine in a sub-bituminous coal during pyrolysis and gasification

The fate of the chlorine and fluorine present in a sub-bituminous coal from Indonesia during pyrolysis and gasification has been studied with fixed and entrained bed reactors. The rate profile for HCl evolved in the temperature programmed pyrolysis exhibits the main and shoulder peaks at 480 and 600 °C, respectively. Model experiments and subsequent Cl 2p XPS measurements show that HCl reacts with metal impurities and carbon active sites at 500 °C to be retained as inorganic and organic chlorine forms, from which HCl evolves again at elevated temperatures. It is suggested that the HCl observed in the coal pyrolysis may originate from the above-mentioned chlorine functionalities formed by secondary reactions involving the nascent char. In the CO₂ gasification of the 900 °C char at 1000 °C and 2.5 MPa, any measurable amounts of HCl and HF could not be detected even at a high conversion of 75 wt% (daf), suggesting the accumulation of these halogens in the residual char. When the coal is injected into an O₂-blown, entrained bed gasifier at 1200-1400 °C under 2.6 MPa, the partial oxidation proceeds to a larger extent at a higher O₂/coal ratio, whereas the chlorine and fluorine are enriched in the remaining char, and the extent of the enrichment at the latter stage of gasification is larger with the fluorine. The XPS measurements of the chars reveal the presence of the broad F 1 s peak, which can cover a wide range of binding energies attributable to inorganic and organic fluorine. The halogen enrichment during gasification is discussed in terms of secondary reactions of HCl and HF with char.     

Effect of alkali and alkaline earth metals on nitrogen release during temperature programmed pyrolysis of coal

Formation of HCN, NH₃, and N₂ during fixed-bed pyrolysis at 10K min⁻¹ has been studied using coal samples after partial demineralization followed by addition of metal hydroxides from aqueous systems. Without additives, NH₃ is the predominant product at ≤ 700°C, showing the two peaks in the formation rate profile, whereas N₂ is the only product at ≥ 800°C. The presence of NaOH, KOH and Ca(OH)₂ promotes considerable NH₃ formation between 450 and 600°C, but in contrast suppresses HCN formation in this region. The Ca shows the largest effect on both the promotion and suppression. It is likely that the NH₃ increased by Ca addition arises partly from HCN, but mainly from secondary reactions of tar-N. These hydroxides affect N₂ formation in quite different manners: the Na decreases the rate between 700 and 950°C, and the K changes it less significantly than the Na, but the Ca remarkably increases the rate in a low temperature region of 550–700°C. These different features are discussed in terms of solid-phase reactions of alkali metal carbonates with char-N and secondary decomposition reactions of tar-N on CaO particles. As a result, total conversion of coal-N to HCN, NH₃ and N₂ up to 1000°C increases in the sequence of Na < none < K < Ca.     

大庆常压渣油催化裂解反应规律研究

采用小型固定流化床实验装置,以大庆常压渣油为原料,针对Ca-Al裂解催化剂,详细分析了催化裂解气体产品和液体产品的组成,考察了反应温度、剂油比、水油比和停留时间对裂解产物分布的影响。发现各操作条件对大庆常渣催化裂解产物分布具有不同程度的影响,其中反应温度的影响最大;随反应温度的升高,乙烯产率单调增加,而丙烯、丁烯和总低碳烯烃产率均存在一个最大值。在优化的操作条件下,乙烯质量产率可达25%,总低碳烯烃质量产率超过50%。     

重金属元素在煤热解过程中的分布迁移规律

针对大同煤、神府煤和新汶煤 ,进行热解实验 ,计算了煤中五种重金属元素砷( As)、镉 ( Cd)、铬 ( Cr)、汞 ( Hg)和铅 ( Pb)在热解三相产物中的分配比例 .进行正交设计实验 ,研究了热解终温、热解升温速率及煤中的灰分含量对重金属元素在热解反应中的分布、迁移的影响 ,发现热解工况和灰分含量对重金属元素在热解产物中的含量有相关性 .采用三变量相关分析法 ,建立了重金属元素在热解产物中的回归模型 ,用该模型对不同热解产物中的重金属含量的实测值进行预报 ,结果表明实测值与预报值有较好的符合     

Kinetic studies of the pyrolysis of sewage sludge by tga and comparison with fluidized beds

The pyrolysis of sewage sludge was examined by thermogravimetric analysis using different heating rates, particle sizes and final temperatures. A semi-empirical model was developed with four global consecutive/competitive reactions to volatile and solid products including also a heat balance. This model was extrapolated to isothermal reactor conditions and compared to experimental data on fluidized bed pyrolysis. Depending on the particle size and reactor temperature, about 90% of the maximum conversion in a fluidized bed takes place under external heat transfer control, the rest under kinetic control. Incomplete conversion occurs at short particle residence times, which were calculated approximately by the model.     

裂解色谱法对共聚物与共混物的鉴定

李文应用裂解色谱法对丙烯酸酯等物质的共聚物与共混物进行了鉴定。     

Rapid pyrolysis of brown coal and oil shale

A brown coal, peat and oil shale were subjected to a rapid pyrolysis process and medium-heat-value gases together with tar were collected. The char residue was of high activity and suitable for gasification to create a two-stage gasification system. The coal-tar is used for manufacturing liquid fuels and chemicals.     

Synthesis of Cubic Boron Nitride from Boron Nitride Synthesized by Pressure Pyrolysis of Borazine

Cubic BN was synthesized under high-temperature and -pressure conditions from BN powder formed by pressure pyrolysis of borazine below 700°C and 100 MPa. The conversion of BN powder to cubic BN was strongly influenced by the residual hydrogen identified by the BH/BN ratio of IR absorption band. The activation energy for cubic BN synthesis from BN powder-20 mol% AIN was 46 kJ/mol, when the starting BN was synthesized at 250°C. A mixture of BN powder and cubic BN particles was converted to cubic BN in a 100% yield by heat treatment at 1800°C and 6.5 GPa without any catalyst. The presence of cubic BN particles does enhance the conversion to cubic BN from BN powder. The energy required for the transformation of starting BN to cubic BN in the presence of cubic BN seed was 355 kJ/mol.