Preparation of Mn substituted La-hexaaluminate catalysts by using supercritical drying

LaMnxAl12-xO19 catalysts were prepared from NH4OH and metal nitrates solutions. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods on properties of the catalysts were investigated by means of TEM, N-2-adsorption, thermogravimetry (TG)-differential thermal analysis (DTA) and X-ray diffraction. SCD method is beneficial to maintain high surface area and improving catalytic activity for methane combustion of the catalyst. The specific surface area and pore volume of LaMn1Al11O19 catalyst prepared by SCD method are 28 m(2)/g and 0.23 cm(3)/g, respectively, and the ignition of methane could be carried out at 450degreesC. However, those of the CD catalyst prepared from the same precursor are 15 m(2)/g, 0.11 cm(3)/g and 530 degreesC, respectively. Suitable Mn content (0 less than or equal to x less than or equal to 2) could promote the formation of LaMnAl11O19 hexaaluminate, while further addition of Mn (2 less than or equal to x less than or equal to 6) cause the formation of LaMnO3. (C) 2003 Elsevier B.V All rights reserved.

Mn-containing AlPO-11 and SAPO-11 catalysts for simultaneous isomerization and dehydrogenation of n-butane

MnAPO-11 and MnAPSO-11 were synthesized hydrothermally, and supported Mn-AlPO-11 and Mn-SAPO-11 were also prepared for comparison. Characterization results showed that there were differences in acidity and reducibility caused by the different incorporation methods of manganese. The manganese species in the samples also weakened the metallic properties of the palladium particles when the latter was added into the catalysts. Catalytic testing results for dehydroisomerization of n-butane indicated that incorporation of manganese increased the selectivity toward isomerization products. The highest isobutene selectivity (34.86%) could be obtained over a Pd/MnAPO-11 catalyst. When a combined catalyst system containing Pd/SAPO-11 and MnAPSO-11 was used in a single bed of two layers, the isobutene selectivity could be greatly improved, as compared to the single catalyst alone.

腐殖质对白浆土中Fe、Mn、Al形态转化及磷生物有效性的影响

在三江平原布置长期试验，研究连年施用有机肥后土壤腐殖质变化及其对白浆±Fe、Mn、Al形态转化及磷生物有效性的影响。结果表明，施用牛粪后土壤腐殖质含量升高，且以松结态腐殖质的增长为主；土壤的DTPA提取态和有机络合态Fe、Mn、Al含量上升，使土壤有效态磷含量上升。因此，生物措施是治理白浆土，促进土壤磷素养分有效性上升，增大土壤缓冲容量和抗逆性的有效措施。

Influence of iron promoter on catalytic properties of Rh-Mn-Li/SiO2 for CO hydrogenation

The effect of iron promoter on the catalytic properties of Rh-Mn-Li/SiO2 catalyst in the synthesis Of C-2 oxygenates from syngas was investigated by means of the following techniques: CO hydrogenation reaction, temperature-programmed reduction (TPR), temperature-programmed desorption and reaction of adsorbed CO (CO-TPD and TPSR) and pulse adsorption of CO. The results showed that the addition of iron promoter could improve the activity of the catalysts. Unexpectedly, the yield of C-2 oxygenates increased greatly from 331.6 up to 457.5 g/(kg h) when 0.05% Fe was added into Rh-Mn-Li/SiO2 catalyst, while no change in the selectivity to C-2 oxygenates was observed. However, the activity and selectivity Of C-2 oxygenates were greatly decreased if the Fe amount exceeded 1.0%. The existence of a little iron decreased the reducibility of Rh precursor, while the reduction of Fe component itself became easier. CO uptake decreased with increasing the quantity of Fe addition. This phenomenon was further confirmed by CO-TPD results. The CO-TPD and TPSR results showed that only the strongly adsorbed CO could be hydrogenated, while the weakly adsorbed CO was desorbed. We propose that Fe is highly dispersed and in close contact with Rh and Mn; such arrangements were responsible for the high yield Of C-2 oxygenates. (C) 2002 Elsevier Science B.V. All rights reserved.