摘要
研究了钠、钾助剂对FeMn合成低碳烯烃催化剂结构及性能的影响.低温N2吸附、X射线光电子能谱(XPS)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)、CO/CO2程序升温脱附(CO/CO2-TPD)、M?ssbauer谱和CO+H2反应的研究结果表明,增加Mn助剂含量促进了活性相的分散和低碳烯烃的生成,而过多锰助剂在催化剂表面的富集则降低了费托合成反应的CO转化率;钾助剂和钠助剂的加入均抑制了催化剂的还原并且促进了CO2和CO的吸附.比较还原后(H2/CO摩尔比为20)和反应后(H2/CO摩尔比为3.5)催化剂的体相结构可以发现,在FeMn、FeMnNa和FeMnK催化剂中,由于钾助剂的碱性和CO吸附能力较强,因此体相中FeCx的含量相对较高;而活性测试结果表明,FeMnNa催化剂拥有最好的CO转化率(96.2%)和低碳烯烃选择性(30.5%,摩尔分数).
The influence of sodium and potassium promoters on the structure and reaction behavior of an FeMn catalyst toward light olefin synthesis from syngas was investigated by N2 adsorption, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, H2 temperature-programmed reduction （H2-TPR）, CO/CO2 temperature-programmed desorption （CO/CO2-TPD）, M6ssbauer spectroscopy （MES） and CO＋H2 reaction. We found that an increase in manganese improves the dispersion of the active Fe component and light olefin selectivity; however, excessive enrichment with the Mn promoter on the catalyst surface suppresses CO conversion. Potassium and sodium inhibit the reduction of the catalyst in H2 and improve the adsorption of CO2 and CO because of the enhanced surface basicity of the catalysts. After reduction with syngas （nH2/nco=20） and reaction with syngas （nH2/nco=3.5）, the analysis of the bulk structure was compared with those of the FeMn, FeMnNa, and FeMnK catalysts. The results show that FeCx is found in relatively high levels in the FeMnK catalysts because of the stronger alkalinity and adsorbability of CO. However, Fischer-Tropsch synthesis （FTS） results indicate that sodium and potassium improved the selectivity toward light olefins. The best catalytic performance was achieved by the FeMnNa catalyst. Its CO conversion and ~ight olefins selectivity were 96.2% and 30.5% （molar fraction）, respectively.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2014年第10期1932-1940,共9页
Acta Physico-Chimica Sinica
基金
supported by the Major State Basic Research Program of China(2010CB736203)
National High-Tech R & D Program of China(2011AA05A204)~~
关键词
低碳烯烃
费托合成
铁锰催化剂
钠助剂
钾助剂
Light olefin
Fischer-Tropsch synthesis
FeMn catalyst
Sodium promoter
Potassium promoter
