bimetal Nickel catalysts

近年来，双金属纳米颗粒由于其有趣的催化性能而成为科学研究的焦点。在许多具有重要经济意义的过程中，二次金属的合金化提供了优化活性、选择性和长期稳定性的可能性。在这一背景下，本项目的目的是检验合金成分和粒度对Ni-Cu和Ni-Fe的催化活性和抗失活性能的双参数优化假设。一氧化碳甲烷化被选为代表性的测试反应，它在许多工艺过程中起着重要的作用，如费托合成或氨合成的上游，以保护铁催化剂不被CO失活。由于早期的研究结果令人振奋，因此选择了Fe和Cu作为合金元素。为了达到该项目的目标，有必要对高组成和高粒度的Ni-Cu和Ni-Fe催化剂的初始活性和失活行为进行研究。为了研究催化剂的性能和失活行为，需要考虑许多影响因素。它们是合金成分、颗粒大小、反应温度、反应时间和气相组成。所需反应的催化活性、结焦动力学和烧结行为这三个指标都在一定程度上取决于这些影响因素。因此，为了减少所需的实验次数，有必要减少实验矩阵。因此，在前面工作的基础上，催化反应的废气的气相组成将保持不变。催化剂的初始活性应根据镍基合金催化剂颗粒中铜和铁的浓度来表征。颗粒大小的影响将通过研究固定组成但可变颗粒大小的颗粒来单独观察。这将通过在火花放电过程中控制颗粒大小的可能性来实现，并可以通过在气载状态下产生接近单分散颗粒的分级来进一步改进。随着反应时间的增加，催化剂活性的损失将分别针对两种主要机制进行研究，即颗粒生长和结焦，这两种机制是由气溶胶过程实现的。此外，还将分别研究参数、组成和颗粒大小对机理的影响。

Bimetal nanoparticles have moved into the focus of science in recent years to a large part due to their interesting catalytic properties. For many economically important processes the alloying of a second metal offers the possibility to optimize activity, selectivity and long term stability.In this context, the aim of the proposed project is the testing of the hypothesis of a two-parameter optimum of alloy composition and particle size for the catalytic activity and deactivation resistance for Ni-Cu and Ni-Fe.Methanation of carbon monoxide was selected as representative test reaction, which plays an important role in a number of technical processes, such as Fischer-Tropsch- synthesis or upstream of ammonia-synthesis to protect the iron catalyst from deactivation by CO. As alloying elements Fe and Cu were selected, due to promising results in earlier studies. To reach the project goal the investigation of the initial activity and the deactivation behavior of Ni-Cu and Ni-Fe catalysts with highly defined composition and particle size are necessary. For the investigation of the catalytic properties and the deactivation behavior a number of factors of influence need to be taken into account. These are alloy composition, particle size, reaction temperature, reaction time, and gas phase composition. All three target figures, catalytic activity for the desired reaction, the kinetics of coke formation and sintering behavior, are expected to depend on these factors of influence to some extent. A reduction of the experimental matrix is therefore necessary to reduce the number of required experiment. Based on preceding work the gas phase composition of educt gases for the catalytic reaction will therefore be kept constant. The initial activity of the catalysts shall be characterized in dependence on the the Copper- and Iron-concentration in Nickel-based alloyed catalyst particles. The influence of particle size will be observed separately by investigating particles of a set composition but variable particle size. This will be accomplished by the possibility of manipulating the particle size in the spark discharge process and can further be improved by classification in the gasborne state yielding close to monodisperse particles. The loss of catalytic activity with increasing reaction time will be investigated separately for the two dominating mechanisms, particle growth and coking, which is enabled by aerosol processes. Again the parameters composition and particle size will be investigated separately in their influence on the mechanisms.