等离子体强化制备镍基催化剂过程机理研究

Nickel based catalysts have been extensively applied for syngas production from natural gas and methanation of syngas (from coal and other resources). They are also promising for the potential application of shale gas, biogas, coal mine methane and coal oven gas. All the related reactions are carried out at high temperature. The nickle catalysts suffer from deactivation due to sintering, coking and sulfur poison. It has been confirmed that the catalyst size and structure show significant influence on the catalyst performance. However, the size and structure control of the nickel catalysts is a big challenge. We previously demonstrated that the nucleation and crystal growth under the influence of plasmas during the decomposition of the nickel precursor lead to a control for the catalyst size and structure and catalyst-support interface.By this way, the anti-sintering property, coke resistence and surfur tolerence of the Ni catalysts are significantly improved. Because of the nolvety and complex issue of the plasma preparation, the process mechanism is still not clear and needs to be investigated immediately. In this proposed work, we aim to study the process mechanism of the plasma catalyst preparation. The effect of various active species in the plasma (including electrons, excited species and ions) on the energy and mass transportation of the decomposition of the catalyst precursors will be investigated. The thermodynamic and kinetic of the nucleation and crystal growth under the influence of the plasma will be studied too. Steam reforming, CO reforming and CO methanation will be employed for the evaluation of the catalysts obtained. The theoretical and experimental system of the plasma catalyst preparation will be established. The results of the proposed study will be very helpful for the further improvement in the industrialized Ni catalysts.

镍基催化剂已被广泛用于合成气生产、煤制天然气等工业过程，并在页岩气、沼气、煤层气、焦炉气等利用方面将有重要应用。镍基催化剂上述应用涉及高温反应，均存在高温烧结、积炭严重和耐硫性差等问题，而催化剂尺度和结构对催化剂性能影响很大，但相关尺度和结构控制存在很大困难。本项目组在前期研究中已发现采用非氢等离子体法影响镍催化剂前驱体分解，可实现催化剂尺度、结构、表界面控制制备，并由此获得抗烧结、抗积炭和耐硫性能的改进。由于方法的新颖性和复杂性，等离子体强化催化剂制备过程控制机理还有待于研究。本项目围绕上述过程控制机理问题，研究等离子体活性物质（包括电子、激发态物质、离子等）影响催化剂前驱体分解相关能量、质量传递控制机理，研究等离子体影响下晶体成核与生长相关热力学和动力学特性，并通过甲烷水汽重整、CO2重整和CO甲烷化评价催化剂，建立相关非平衡传递过程理论与实验体系，为工业镍基催化剂改进制备打下基础。

本项目针对合成气生产、甲烷化等相关工业镍基催化剂存在的抗积碳性能差、低温活性不高的问题，采用辉光放电和介质阻挡放电冷等离子体制备镍催化剂，发挥等离子体快成核、慢生长的晶体生长优势，由此在镍催化剂尺度和结构可控制备方面取得重要进展，制备出的镍催化剂尺度小、分散性好、111面为主要暴露面、镍与载体相互作用强，用于甲烷水汽重整、甲烷CO2重整、CO和CO2甲烷化反应，低温活性和抗积碳性等方面获得很大改进。特别是在甲烷水汽重整降低进料水碳比方面，取得很大改进，由此可以降低发生水汽所造成的能耗。我们还在辉光放电、介质阻挡放电催化剂制备机理和放大规律取得研究进展，研究发现，电子在辉光放电等离子体催化剂制备起了关键决定作用，热效应可控，这类等离子体装置可以很容易放大。而介质阻挡放电等离子体主要通过大量随机的微放电通道作用，影响机制复杂，热效应显著，装置放大需要特别考虑电场参数影响。本项目研究成果丰富发展了催化剂制备基础理论体系内涵，为工业镍基催化剂改进制备打下基础。