Studies on the Thermochemical Cycle for Heat/Chemical Energy Conversion by a hybrid use of Natural Gas/Unutilized Heat

研究了甲烷转化为H_2、CO和c_2 -碳氢化合物的高热量化学燃料的热化学氧化还原循环，目的是有效地将未利用的热量（如集中的太阳能热）转化为1273 K以下的化学燃料。下面的热化学循环使用金属氧化物氧化还原系统进行了检查。甲烷重整/水分解循环ech_4 +M_xO_y→M_xO_<y-m-n-1>+(1-n)CO+nCO_2+(2-m)H_2+mH_2OM_xO_<y-m-n-1>+(m+n+1)H_2O→M_xO_y+(m+n+1) H_2O，制备了WO_3/ZrO_2和Ni_<0.39>Fe_<2.61>O_4/ZrO_2的氧化还原循环反应工作材料。特别是在1173K以下，使用Ni_<0.39>Fe_<2.61>O_4/ZrO_2的循环可以重复进行，甲烷转化率达到40 ~ 60%。第一步反应生成的合成气H_2/CO摩尔比约为2，适合生产甲醇。在单独的第二步中也获得了几乎纯的氢。甲烷偶联/水分解循环：2ch_4 +M_xO_y→M_xO_<y-2>+C_2H_4+2H_2OM_xO_<y-2>+2H_2O→M_xO_y+ 2h_2。制备了SnO_2/Fe_3O_4/SiO_2的反应工作材料。在SnO_2/Fe_3O_4/SiO_2温度为1173K的条件下，甲烷与蒸汽共进料的单步反应模式也能高度选择性地将甲烷转化为c_2 -氢和H_2。与早期以蒸汽为氧化剂的甲烷偶联反应相比，我们的实验数据显示出更高的c_2生成速率和高的c_2选择性。

Thermochemical redox Cycles for converting methane to calorie-upgraded chemical fuels of H_2, CO and C_2-hydrocarbon were investigated for the purpose of efficiently converting unutilized heat, such as concentrated solar heat, to chemical fuels below 1273 K.The following thermochemical cycles using a metal-oxide redox system were examined.1. Methane reforming/Water Decomposition CycleCH_4+M_xO_y→M_xO_<y-m-n-1>+(1-n)CO+nCO_2+(2-m)H_2+mH_2OM_xO_<y-m-n-1>+(m+n+1)H_2O→M_xO_y+(m+n+1)H_2The reactive working materials of WO_3/ZrO_2 and Ni_<0.39>Fe_<2.61>O_4/ZrO_2 were prepared for this redox cycle. Especially, the cycle using Ni_<0.39>Fe_<2.61>O_4/ZrO_2 could be repeated below 1173K, yielding 40-60% methane conversion. The syngas produced in the first reaction step has a H_2/CO molar ratio of about two, which is suitable for methanol production. Also almost pure hydrogen was obtained in a separate second step.2. Methane Coupling/Water Decomposition Cycle2CH_4+M_xO_y→M_xO_<y-2>+C_2H_4+2H_2OM_xO_<y-2>+2H_2O→M_xO_y+2H_2The reactive working material of SnO_2/Fe_3O_4/SiO_2 was prepared for this cycle. methane was also highly selectively converted to C_2-hydrocargon and H_2 by a single-step reaction mode of co-feeding methane and steam over SnO_2/Fe_3O_4/SiO_2 at 1173K.In comparison with earlier studies on methane coupling using steam as an oxidant, our experimental data gave the higher C_2-formation rate with a high C_2-selectivity.