Ni Catalysts Based on Attapulgite for Hydrogen Production through the Glycerol Steam Reforming Reaction

Nikolaos D Charisiou,Mark A Baker,Kyriaki Polychronopoulou,Maria A Goula,Victor Sebastian,Steven J Hinder

doi:10.3390/catal9080650

Abstract

Attapulgite (ATP, a natural clay) was used as carrier to produce a nickel-based catalyst (Ni/ATP) for the work that is presented herein. Its catalytic performance was comparatively assessed with a standard Ni/Al2O3 sample for the glycerol steam reforming (GSR) reaction. It was shown that the ATP support led to lower mean Ni crystallite size, i.e., it increased the dispersion of the active phase, to the easier reduction of NiO and also increased the basicity of the catalytic material. It was also shown that it had a significant effect on the distribution of the gaseous products. Specifically, for the Ni/ATP catalyst, the production of liquid effluents was minimal and subsequently, conversion of glycerol into gaseous products was higher. Importantly, the Ni/ATP favored the conversion into H2 and CO2 to the detriment of CO and CH4. The stability experiments, which were undertaken at a low WGFR, showed that the activity of both catalysts was affected with time as a result of carbon deposition and/or metal particle sintering. An examination of the spent catalysts revealed that the coke deposits consisted of filamentous carbon, a type that is known to encapsulate the active phase with fatal consequences.

Highlights

The need to find an alternative to petro-based sources in the transport sector has provided the impetus for the development of the biodiesel industry, with its production increasing from 774,000 tons in 2000 to 30 million tons in 2016, i.e., in a decade and a half the sector experienced an increase of almost40-fold [1]
In previously published work by our group [27], we showed that the presence of alkaline earth metals, CaO and MgO, as promoters of γ-Al2 O3, facilitate the dispersion of the active species, strengthens the interaction between the active phase and the support, and increases the population of basic sites
The results presented above indicate that the use of lower water to glycerol feed ratio (WGFR) led to significant carbon deposition, and subsequently to catalyst deactivation

Summary

Introduction

The need to find an alternative to petro-based sources in the transport sector has provided the impetus for the development of the biodiesel industry, with its production increasing from 774,000 tons in 2000 to 30 million tons in 2016, i.e., in a decade and a half the sector experienced an increase of almost40-fold [1]. Amongst the different options that have been proposed (Bagheri et al [4] has provided an excellent review on the topic), the steam reforming of glycerol (GSR) for the production of hydrogen—a clean and renewable energy source—is increasingly drawing the attention of the scientific community (e.g., [5,6,7]). This is because SR is a mature industrial technology, and because, as the overall reaction (Equation (1)) shows, every 1 mol of converted C3 H8 O3 can produce 7 mol of H2. The steam reforming of methane leads to the production of only 4 mol of H2 per mol of converted

Methods

Results

Conclusion