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The most economic solutions of this reduction process

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Unformatted text preview: containing less water compared to the other processes. The most economic solutions of this reduction process involve a minimum content of water in the reformer effluent gas [17]. As in the steam reforming process suitable catalysts for the CO2 reforming are based on several noble metals and Ni [11, 17, 77, 80, 83, 84, 86, 87, 88, 89]. The main problem is the catalyst deactivation by coking, which is more pronounced in this process than in the STR because of the higher amount of CO produced, which leads to a shift the Boudouard reaction favouring coke formation (Eq. 8). 2 CO → C + CO2 (∆H°298 = -172 kJ/mol) (Eq. 8) As in the STR process noble metal catalysts are more resistant against coking Ni catalysts, but Ni based catalysts are preferred because of their lower costs. Some Ni catalysts supported on magnesium aluminate, MgO or mixtures of α-aluminium and calcium oxide have been reported to exhibit good stability. 1.4. Catalyst deactivation The three most common deactivation processes in heterogeneous catalysis are poisoning, thermal degradation and coking (or fouling) [17, 71, 72, 73]. Poisoning is the loss of activity due to the blocking of the catalyst’s active sites by impurities (poisons) ytrtrghrhrhhrhrhhffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff 1. Introduction 28 ytrtrghrhrhhrhrhhffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff contained in the feed. In the steam reforming process over Ni catalysts for example H2S, AsH3, chlorine and other halogen are known poisons. These compounds form inactive Ni species and must therefore be removed from the feed stream before entering the reactor. Thermal degradation is usually due to sintering or catalyst-support reactions leading to new phases for instance as a result of overheating. As many solidsolid reactions are highly activated thermal deactivation is especially important for high temperature reactions such as...
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