Experimental studies on a two-step fast pyrolysis-catalytic hydrotreatment process for hydrocarbons from microalgae (Nannochloropsis gaditana and Scenedesmus almeriensis)

Neil Priharto,Frederik Ronsse,Wolter Prins,Robert Carleer,Hero Jan Heeres

doi:10.1016/j.fuproc.2020.106466

Neil Priharto, Frederik Ronsse + Show 3 more

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https://doi.org/10.1016/j.fuproc.2020.106466

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Abstract

Two microalgae species (marine Nannochloropsis gaditana, and freshwater Scenedesmus almeriensis) were subjected to pyrolysis followed by a catalytic hydrotreatment of the liquid products with the objective to obtain liquid products enriched in hydrocarbons. Pre-dried microalgae were pyrolyzed in a mechanically stirred fluidized bed reactor (380 and 480 °C) with fractional condensation. The heavy phase pyrolysis oils were hydrotreated (350 °C and 15 MPa of H2 pressure for 4 h) using a NiMo on alumina catalyst. The pyrolysis liquids after pyrolysis and those after catalytic hydrotreatment were analyzed in detail using GC–MS, GC × GC–MS, and 2D HSQC NMR. The liquid products are enriched in aromatics and aliphatic hydrocarbons and, as such have a considerably lower oxygen content (1.6–4.2% w/w) compared to the microalgae feeds (25–30% w/w). The overall carbon yield for the liquid products was between 15.6 and 19.1% w/w based on the initial carbon content of the algae feedstock.

Highlights

The use of unconventional biomass for thermochemical conversion processes is gaining more and more interest in the last decade
Two microalgae species were subjected to pyrolysis followed by a catalytic hydrotreatment of the liquid products with the objective to obtain liquid products enriched in hydrocarbons
This study shows that both marine microalga Nannochloropsis gaditana and freshwater microalga Scenedesmus almeriensis in dried form can be used as feedstock for fast pyrolysis processes

Summary

Introduction

The use of unconventional biomass for thermochemical conversion processes is gaining more and more interest in the last decade. A wellknown example is the use of microalgae as the feed. Higher photosynthetic efficiency compared to lignocellulosic biomass, high biomass yields, and the non-competitiveness with food production are advantages of the use of microalgae as biomass feed [1,2,3]. Microalgae contain considerable amounts of lipids (7–26% w/w), carbohydrates (9–40% w/w), and proteins (27–61% w/w) [4,5,6]. The exact amount depends on the microalgae species and the cultivation techniques applied during production. A major advantage of the use of microalgae for thermochemical conversions is the low amount of recalcitrant lignin and lignin-derived compounds [7]

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