Catalytic activities of ion-exchanged nickel and iron in low temperature hydrogasification of raw and modified birch chars
Catalytic activities of ion-exchanged nickel and iron in low temperature hydrogasification of raw and modified birch chars
复制标题
离子交换镍和铁对生桦木炭和改性桦木炭低温加氢气化的催化活性
DOI：
10.1016/0016-2361(94)90208-9
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发表时间：
1994
期刊：
影响因子：
7.4
通讯作者：
T. Homma
中科院分区：
文献类型：
--
作者：
Tsutomu Suzuki;H. Minami;Tetsuo Yamada;T. Homma
通过离子交换方法负载镍或铁的原始桦木、硝酸氧化和羧甲基桦木在500°C的氮气中碳化，生成的焦在热天平中加氢气化，以考察其在700°C以下的反应活性。生焦上的离子交换金属量太少，不能提供高的气化反应活性。然而，随着离子交换能力的增加，氧化和羧甲基化木材产生的活性焦要多得多。镍和铁在羧甲基化半焦上表现出比氧化半焦更强的催化活性，这是因为在阳离子交换性较大的羧甲基化木材上可以获得更好的金属分散性。值得注意的是，在700℃下，仅在羧甲基化半焦上负载1wt%的铁和镍就足以实现90wt%的气化。还注意到，铁对氧化和羧甲基化半焦气化的催化作用高达600℃，大于镍的催化作用。这归因于两个因素：气化过程中形成的金属铁的催化活性高于镍金属；焦炭中的灰分较低。然而，在600℃以上，在没有木灰的情况下，观察到铁的活性严重丧失。这说明木灰在低温区和高温区对铁的催化作用是不同的。
Raw, HNO3oxidized and carboxymethylated birch woods loaded with nickel or iron by the ion-exchange method were carbonized at 500 °C in a flow of nitrogen, and the resulting chars were hydrogasified in a thermobalance to examine their reactivities below 700 °C. The amounts of ion-exchanged metals on raw char were too small to give high gasification reactivity. However, oxidized and carboxymethylated woods with increased ion-exchange capacity produced much more reactive chars. Both nickel and iron exhibited larger catalytic activities on carboxymethylated chars than on oxidized chars, because better metal dispersion could be achieved on carboxymethylated wood with its larger cation exchangeability. It was noteworthy that only 1 wt% loading of iron, as well as nickel, on carboxymethylated char was sufficient to attain a gasification of 90 wt% at 700 °C. It was also noted that the catalytic effect, up to 600 °C, of iron on the gasification of oxidized and carboxymethylated chars was larger than that of nickel. This is ascribed to two factors; greater catalytic activity of metallic iron formed during the gasification than that of nickel metal, and low ash level in the chars. Above 600 °C, however, serious loss of activity of the iron was observed in the absence of wood ash. This showed the different influence of wood ash on the catalysis of iron in the low and high temperature regions.