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本文由三部分内容组成。第一部分为气化动力学的研究;第二部分为细粒石墨的润湿现象和催化剂母体的反应;第三部分为催化剂原位活性化化学。后两部分可以认为是硫酸钾和硫酸铁混合物作为催化剂的碳的水蒸汽气化机理研究。在第一部分内容中作者给出了K_2SO_4,FeSO_4·5H_2O及这两种盐的混合物在PVC型焦炭水蒸汽气化中催化活性的研究结果。实验所使用的H_2和H_2O混合气压力为0.2,1和2MPa,加热速率为4Kmin(-1),温度为800—910℃(1h)。近似重量组成为20%Fe和80%K(总金属量为碳重量的7%)的催化剂混合物在等克分子的H_2/H_2O混合气中表现出最佳活性。提高压力将加快总的气化速率并将显著地增加CH_4的收率。在第二部分内容中,作者通过测定一种细粒石墨的润湿性,进入这种材料的浸透性和在各种温度下经H_2/H_2O混合气处理后的金属分布,研究了第一部分内容中在碳的水蒸汽气化中显示出很好催化活性的混合催化剂(FeSO_4和K_2SO_4,Fe/K的重量比为1:5)与碳之间的相互作用。通过测定相对重量损失分析研究了分解和转化反应。结果发现,催化剂混合物在650℃形成熔融相而纯硫酸盐却仍然是粉末态。在700℃处理2小时后浸透是完全的,EMPA研究表明Fe和K在石墨基质上的分布是均匀的。然而用纯的硫酸盐进行相同的处理并不引起明显的变化。相对质量损失的测定使作者假定熔融物可能由FeS,FeO,K_2和KOH组成。作者进一步假定,K_2SO_4转化成K_2S以至KOH可能受到FeS,FeO或Fe的催化作用影响。作者通过第二部分的研究指出,为分析催化剂的活性状态,尤其是Fe和K的相互催化活性,进一步的研究是必要的。所以在第三部分中,作者采用TGA,DTA,ESCA,EPMA和目测等测试手段研究了各种K_2SO_4/FeSO_4混合物在H_2和H_2/H_2O气氛下处理过程之中或之后的熔融情况。结果发现,元素态铁在加热的早期阶段生成,然后催化还原K_2SO_4成K_2S,而后者很容易被水蒸汽水解成液体KOH。K_2SO_4和K_2S形成一种中间态低共熔点(mp=610℃)混合物,这种混合物有利于碳表面的润湿和K_2S的水解。不仅是FeSO_4,任何在气化气氛中容易还原成元素态铁的铁盐都可以使用。作者最后提出了包括活化和催化气化在内的总反应模式。K_2SO_4活化成具有催化活性的KOH的过程如下: Fe盐+? Fe 3K_2SO_4+8Fe?3K_2S+4Fe_2O_3 Fe_2O_3+3H_2?2Fe+3H_20 K_2S+H_2O?KHS+KOH KHS+H_2O?KOH+H_2S
This article consists of three parts. The first part is the study of gasification kinetics. The second part is the wetting phenomenon of fine graphite and the reaction of catalyst precursor. The third part is the in situ activation chemistry of catalyst. The latter two parts can be considered as the mechanism of steam gasification of carbon by the mixture of potassium sulfate and ferric sulfate. In the first part, the authors present the results of K_2SO_4, FeSO_4 · 5H_2O and their catalytic activity in the steam gasification of PVC coke. The pressures of H 2 and H 2 O used in the experiment were 0.2, 1 and 2 MPa, the heating rate was 4Kmin (-1) and the temperature was 800-910 ℃ (1h). Approximately by weight, the catalyst mixture having a composition of 20% Fe and 80% K (7% of the total metal amount of carbon) showed the best activity in an equimolar H 2 / H 2 O mixture. Increasing the pressure will speed up the overall gasification rate and will significantly increase CH4 yield. In the second part, the author studied the wettability of a fine graphite, the penetration into the material and the metal distribution after H_2 / H_2O mixture treatment at various temperatures. The first part Shows a good catalytic activity in the steam gasification of carbon (FeSO 4 and K 2 SO 4, the weight ratio of Fe to K is 1: 5) and the interaction between carbon. Decomposition and conversion reactions were investigated by measuring the relative weight loss analysis. As a result, it was found that the catalyst mixture formed a molten phase at 650 ° C while the pure sulfate was still in the powdered state. The soaking was complete after treatment at 700 ° C for 2 hours and the EMPA study showed that the distribution of Fe and K on the graphite substrate was uniform. However, the same treatment with pure sulphate does not cause significant changes. The determination of relative mass loss led the authors to assume that the melt might consist of FeS, FeO, K 2 and KOH. The authors further hypothesize that the conversion of K 2 SO 4 to K 2 S may result from the catalysis of FeS, FeO or Fe. The second part of the study by the author pointed out that for the analysis of the catalyst activity status, especially the mutual catalytic activity of Fe and K, further research is necessary. Therefore, in the third part, the authors used the TGA, DTA, ESCA, EPMA and visual test methods to study the melting process of K_2SO_4 / FeSO_4 mixture in the H_2 and H_2 / H_2O atmosphere during or after the treatment. It was found that elemental iron was formed in the early stages of heating and then catalytically reduced K 2 SO 4 to K 2 S, which was easily hydrolyzed by water vapor into liquid KOH. K_2SO_4 and K_2S formed a mixture of intermediate eutectic point (mp = 610 ℃), which is conducive to the carbon surface wetting and K_2S hydrolysis. Not only FeSO 4, but also any iron salts that are easily reduced to elemental iron in a gasified atmosphere. The authors finally proposed an overall reaction model including activation and catalytic gasification. The process of K_2SO_4 activation into a catalytically active KOH is as follows: Fe salt +? Fe 3K_2SO_4 + 8Fe? 3K_2S + 4Fe_2O_3 Fe_2O_3 + 3H_2? 2Fe + 3H_20 K_2S + H_2O? KHS + KOH KHS + H_2O? KOH + H_2S