Conversion of wastewater containing organic compoundes to hydrogen and methane by the hydrothermal gasification using novel Ni/Carbon catalyst

将甲基丙烯酸离子交换树脂在硫酸镍水溶液中用NH3处理，保持pH接近中性，通过碳化法制备了一种新型的Ni/碳催化剂。该催化剂的性能如下：Ni含量47wt %， Ni粒度2 ~ 4nm， BET表面积180m2 /g。该催化剂用于200 ~ 350℃水热条件下水溶性有机化合物的气化。醋酸和蔗糖在300℃下完全气化，产生甲烷、氢气和二氧化碳。芳香族化合物如苯也在350℃下气化，产生大量的氢。甲苯的氢产率惊人地达到2.8 mol/mol- c。本研究采用了两种实际废水。一种是褐煤水热脱水废水。另一种是电子厂的工业废水。两种废水中所含的有机化合物在300℃下完全转化为气态产物。结果表明，该催化剂可用于实际废水的处理。产品气中含有相当多的可燃气体（CH4和H2），特别是工业废水。并利用该工业废水进行了催化剂寿命的长期试验。该催化剂在废水中不含促进Ni颗粒烧结的物质的情况下，保持了2000小时的完全气化。这一结果表明，该催化剂具有足够的耐久性，可供实际应用。研究了该工艺的能量平衡。结果表明，反应器出口流的热量通过与进料蒸汽的热交换回收，废水中有机化合物的能量可回收52%作为燃料气。这一结果清楚地表明，该工艺不仅可以用于废水处理，而且可以用于废水的能量回收。

A novel Ni/carbon catalyst could be prepared through the carbonization of methacrylic ion exchange resin, which was treated in an aqueous solution of nickel sulfate using NH3 to keep pH at near neutral. The properties of this catalyst are as follows ; Ni content 47 wt%, Particle size of Ni 2〜4 nm, BET surface area 180 m2/g. This catalyst was used for the gasification of water-soluble organic compounds under hydrothermal conditions at 200〜350℃. Acetic acid and sucrose were completely gasified at 300℃, producing methane, hydrogen and carbon dioxide. Aromatic compounds such as benzene are also gasified at 350℃, yielding large amount of hydrogen. The yield of hydrogen surprisingly reached 2.8 mol/mol-C for toluene.Two real wastewaters were used in this study. One is a wastewater from dewatering process of brown coal through hydrothermal treatment. The other is an industrial wastewater from electronic factory. Organic compounds containing in the both wastewaters were completely converted to gaseous product at 300℃. It was found that this catalyst can be used for treating real wastewaters. The product gas contained fairly large amount of combustible gas (CH4 and H2) especially for industrial wastewater. This industrial wastewater was also used for the long-run experiment to examine the life of the catalyst. This catalyst kept complete gasification for 2000 hours when no substances promoting the sintering of Ni particles contained in the wastewater. This result indicates that this catalyst has enough durability for practical use. The energy balance of this proposed process was examined. It was found that 52 % of energy can be recovered as fuel gas from the organic compounds in the wastewater when the heat of exit stream of the reactor was recovered by the heat exchange with the feed steam. This result clearly indicates that this proposed process is promising not only for the wastewater treatment but also for the recovery of energy from wastewater.