A study on the activation of layered double hydroxide derived Ni Catalyst for ammonia decomposition Sung Min Kim

Abstract

A Study on activation of layered double hydroxide derived Ni catalyst for ammonia decomposition Sung Min Kim Dept. of Chemical engineering The Graduate school Hanyang University NH3 has garnered significant attention as a hydrogen carrier material due to its high hydrogen capacity, ease of transport and storage, and the potential utilization of existing infrastructure. For the commercialization of ammonia as a H2 carrier, reducing the high-temperature energy costs required for the dehydrogenation process and developing a cost-effective yet low-temperature active catalyst for ammonia decomposition is essential. In this study, the Layered Double Hydroxide (LDH) structure was adopted to maximize the efficiency of ammonia decomposition based on Ni. The active metal was synthesized with a 5nm size to enhance dispersion. Additionally, Ba was applied as a promoter to improve the desorption capability of the generated hydrogen. By replacing the conventional commercial sintering process with the microwave calcination method, the growth of active particle size was suppressed, resulting in enhanced activity. Ultimately, the catalyst synthesized by simultaneously applying both strategies, Ba10/LDH-MW, exhibited a high decomposition conversion rate of 68% at 500℃ under 100% NH3 conditions. This outcome suggests the proposal of a cost-effective NH3 decomposition catalyst that is simple to synthesize and can be implemented efficiently. Chapter 1. Introduction 1.1. Necessity of NH3 decomposition reaction H2 is gaining significant attention as a clean energy source . however , challenges in transportation and storage hinder its commercialization [1]. To address this, a concept known as a H2 carrier, which involves forming a distribution network for hydrogen in a more transportable and storable compound rather than transporting H2 directly , is considered a practical alternative[2]. Among various H2 carriers, NH3 is considered the most feasible H2 storage medium due to its ease of liquefaction for transportation, high H2 contents (17.8% by weight[3]), and the existing infrastructure for NH3 storage, transportation, and distribution[4]. On the other hand, the NH3 decomposition reaction, which extracts H2 by cracking NH3, is a type of dehydrogenation involving an energy-intensive, endothermic process. For this reason, research on catalysts for NH3 decomposition has been focused on achieving high NH3 conversion rates in the low-temperature range. The element with the most efficient catalytic activity for NH3 decomposition reaction as a single active metal is ruthenium (Ru). However, due to its rarity and high cost, smooth commercialization poses challenges. As a result, research has primarily focused on low-cost catalytic materials centered around transition metals such as nickel (Ni), cobalt (Co), and iron (Fe)[3, 5]. Therefore, essential research for the establishment of a commercially viable, low-cost catalyst based on NH3 involves using transition metals with reduced precious metal content, while adjusting various catalytic active factors such as promoters, supports, and active phases.