Synergistic Effects of Catalyst Mixtures on Biomass Catalytic Pyrolysis.

Badr A Mohamed,Chang Soo Kim,Naoko Ellis,Xiaotao Bi

doi:10.3389/fbioe.2020.615134

Abstract

This paper studied the synergistic effects of catalyst mixtures on biomass catalytic pyrolysis in comparison with the single catalyst in a microwave reactor and a TGA. In general, positive synergistic effects were identified based on increased mass loss rate, reduced activation energy, and improved bio-oil quality compared to the case with a single catalyst at higher catalyst loads. 10KP/10Bento (a mixture of 10% K3PO4 and 10% bentonite) increased the mass loss rate by 85 and 45% at heating rates of 100 and 25°C/min, respectively, compared to switchgrass without catalyst. The activation energy for 10KP/10Bento and 10KP/10Clino (a mixture of 10% K3PO4 and 10% clinoptilolite) was slightly lower or similar to other catalysts at 30 wt.% load. The reduction in the activation energy by the catalyst mixture was higher at 100°C/min than 25°C/min due to the improved catalytic activity at higher heating rates. Synergistic effects are also reflected in the improved properties of bio-oil, as acids, aldehydes, and anhydrosugars were significantly decreased, whereas phenol and aromatic compounds were substantially increased. 30KP (30% K3PO4) and 10KP/10Bento increased the content of alkylated phenols by 341 and 207%, respectively, in comparison with switchgrass without catalyst. Finally, the use of catalyst mixtures improved the catalytic performance markedly, which shows the potential to reduce the production cost of bio-oil and biochar from microwave catalytic pyrolysis.

Highlights

The global energy demand is heavily relied on fossil fuels, with more than 80% of the world’s supply of primary energy from fossil fuel in 2019
We studied the effects of catalyst mixtures on the microwave heating behavior and found that the type of coke deposited on catalyst surfaces plays a key role in microwave absorption and microwave heating in microwave catalytic pyrolysis (Mohamed et al, 2019a)
The synergistic effects of the catalyst mixtures were observed in the mass loss rate when compared to the case with single catalyst at different heating rates. 10KP/10Bento showed the highest mass loss rate at 100◦C/min, and the mass loss rate increased by 85 and 45% at 100◦C/min and 25◦C/min, respectively, compared to SG without the catalyst

Summary

Introduction

The global energy demand is heavily relied on fossil fuels, with more than 80% of the world’s supply of primary energy from fossil fuel in 2019. The concerns on the rising environmental impacts call for clean and renewable energy sources, including biomass energy (Chandrasekaran and Hopke, 2012; Rezaei et al, 2014; Bundhoo, 2018; Yang et al, 2019). Biomass is decomposed under oxygen-free environment into multiple products, including biochar, bio-oil, and non-condensable gases, over a very short reaction time (Chandrasekaran and Hopke, 2012; Rezaei et al, 2014; Wang et al, 2019; Sun et al, 2020; Yu et al, 2020). The challenge remains on how to upgrade pyrolysis bio-oil to drop-in liquid fuels due to their high oxygen content, high viscosity, and acidity. Several techniques have been investigated, including the use of catalytic

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Conclusion