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利用热分析结合XRD、TEM、SEM、IR等对五种Fe-Cr系工业高温变换催化剂的热性能及还原活化进行了研究。结果发现,催化剂中的Cr除一般认为提高催化剂分散度、比表面和结构稳定性外,还具有提高还原温度,降低还原速度和还原度的性能,由此既可提高催化剂中Fe~(2+)/Fe~(3+)比例,又可防止其中Fe_3O_4过度还原。因而它就从一个侧面解释了助剂Cr的提高活性与耐热性的作用,还原气氛(干H_2湿H_2、CO和CO—/CO—CO_2),还原性气体浓度以及还原温度对催化剂的还原及还原后的性能有显著影响。一般宜用H_2还原,不宜直接用CO还原。催亿剂还原的难易程度及热稳定性与Fe_2O_3的晶型无明显对应关系,主要由催化剂的组成、制备工艺、结构等决定。因而不同催化剂有其各自适宜的还原活化条件。通过对催化剂的DTA及TG结果的仔细分析,得到了一些新的信息,据此可以解释并预测催化剂的活性与耐热性能。
Thermal analysis and XRD, TEM, SEM, IR and other thermal properties of the five Fe-Cr series of industrial high temperature shift catalysts were studied. The results show that the addition of Cr in the catalyst is generally considered to improve the catalyst dispersion, specific surface area and structural stability, but also has the ability to increase the reduction temperature and reduce the reduction rate and reduction degree, which can improve the catalyst Fe ~ (2+ ) / Fe ~ (3 +) ratio, but also to prevent over-reduction of Fe_3O_4. Thus, it explains from one side the effect of promoter Cr on the activity and heat resistance, the reduction of the catalyst in the reducing atmosphere (dry H 2 wet H 2, CO and CO- / CO-CO 2), the reducing gas concentration and the reducing temperature And the performance after reduction has a significant impact. H_2 generally should be reduced, not directly with CO reduction. The easiness of reduction and thermal stability of the meso-reductant did not have a clear correspondence with the crystalline form of Fe 2 O 3, which was mainly determined by the composition of the catalyst, preparation process and structure. Thus different catalysts have their own appropriate reduction activation conditions. Through careful analysis of the catalyst DTA and TG results, some new information was obtained, which can explain and predict the catalyst activity and heat resistance.