Design and Applications of Hydroxyapatite‐Based Catalysts by Doan Pham Minh

Author:Doan Pham Minh [Minh, Doan Pham]
Language: eng
Format: epub
ISBN: 9783527830206
Published: 2022-09-06T00:00:00+00:00

8

Reforming Processes Using Hydroxyapatite‐Based Catalysts

Zouhair Boukha Rubén López‐Fonseca, and Juan R. González‐Velasco

Chemical Technologies for Environmental Sustainability Group, Department of Chemical Engineering, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, E‐48080 Bilbao, Spain

8.1 Introduction

The development of clean and efficient solutions for fuels and chemicals production from fossil resources is considered one of the most important challenges facing scientific and technological research since the turn of the century. In this sense, the proven large reserves of natural gas (NG) and the development of biogas production technologies allow implementing relatively long‐term strategies for their efficient utilization. For instance, the transformation of the available natural resources into products of high added‐value, such as ammonia, alcohols, olefins, and higher hydrocarbons, among others, via synthesis gas (H2 + CO), is a major challenge of the chemical industry. Moreover, owing to its clean combustion, emitting only water, and its high calorific value (120.7 kJ g−1), hydrogen is considered as the most promising fuel to be integrated in the future energy strategies [1]. Currently, over 50 million tons of hydrogen are produced by global chemical industry for many applications [2].

The synthesis gas is mainly produced from fossil fuels by different reforming processes [1–8]. Among them, the endothermic steam reforming of methane (SRM) (8.1) is the most used one [8]. This technology has largely been applied for the production of large amounts of H2, providing a high H2/CO ratio (≥3). However, in many cases, the exothermic methane partial oxidation (POM) (8.2) is considered a good alternative, since it offers some interesting advantages, especially when the posterior use requires an H2/CO ratio close to 2, as in the case of Fischer–Tropsch synthesis [8]. In the last decades, an increasing interest has also been devoted to the DRM (8.3), which appears to be a suitable strategy for long chain hydrocarbon production, which requires an H2/CO ratio close to unity [9]. For environmental concerns, this is an attractive strategy fulfilling one of the constant challenges, because it allows the use of greenhouse gases (CH4 and CO2) as reactants [4–9].

(8.1)

(8.2)

(8.3)

Due to its high symmetry, the activation of the tetravalent methane molecule through the dissociation of CH3—H bond requires a relatively high energy (439.3 kJ mol−1) [3]. Therefore, the use of active catalysts is essential for all strategies aiming its efficient conversion by reforming processes. Noble metal catalysts, such as Rh, Pt, Pd, and Ru, exhibit a high reforming activity and good resistance to coke formation. Regarding economic considerations, current research is focused on other promising alternatives based on cheaper transition metals. Among them, judging from their high activity, Co‐ and Ni‐based catalysts are the most investigated ones. However, the major drawback that limits their use is their sensitivity to the structural changes under the severe conditions of the reductive pretreatment and/or during the reforming process that can in turn affect the efficiency of their active species. According to previous reports, these changes result in sintering and coking, leading to a severe drop in the activity and the resistance during a long‐term operation [4,7,8].

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