A Comparison of the Efficiency of Catalysts Based on Ni, Ni-Co and Ni-Mo in Pressure Pyrolysis of Biomass Leading to Hythane

Pavel Straka,Olga Bičáková,Tomáš Hlinčík

doi:10.3390/catal11121480

Abstract

A thermal conversion of biomass to hythane using catalysts was studied. Low-temperature pyrolysis of two different types of biomass was performed in a pressure sealed reactor, and the resulting gas with high contents of CO2 and CO was methanized in a hydrogen atmosphere at a pressure of 30 bar. As catalysts, Ni/Al2O3, NiCo/Al2O3 and NiMo/Al2O3 were used and their catalytic activity was evaluated. The NiCo/Al2O3 catalyst showed the highest catalytic activity, Ni/Al2O3 had a lower but comparable one, and NiMo/Al2O3 showed the lowest activity. The resulting hythane contained 70 vol.% CH4 and 10 vol.% H2 (with NiCo/Al2O3 catalyst, HHV 29.20 MJ/m3, LHV 26.32 MJ/m3), or 57 vol.% CH4 and 23 vol% H2 (with Ni/Al2O3, HHV 25.92 MJ/m3, LHV 23.21 MJ/m3) or 47 vol.% CH4 and 27 vol.% H2 (with NiMo/Al2O3, HHV 23.23 MJ/m3, LHV 20.76 MJ/m3). It has been found that secondary reactions of volatile biomass products are of great importance for successful pressure pyrolysis.

Highlights

Biomass is an important source of renewable energy
Two contrasting types of biomass have been selected for the experiments: birch-wood shavings and ground apricot stones
The reason is that the efficiency of catalysts should first be tested on biomass samples with a completely different composition and only after identifying the influence of the catalysts and their compositions, it is possible to proceed to systematic experiments with a wider spectrum of biomass

Summary

Introduction

The possibilities of its conversion using non-combustion technologies into further utilizable, energy-rich products (bio-oils, solid carbonaceous residues and energy gases) are far from being explored. Bio-oil can be utilized as a clean fuel and as a source of commercially useful chemicals, whereas biochar can be used as a smokeless fuel, and alternatively as a fertilizer or sorbent. Depending on the method of thermal treatment and the type of biomass, the gas may contain predominantly CO2 and CO and can be a source of these gases in the production of synthetic methane by the Power-to-Gas technology [3], designed on the basis of the Sabatier reaction [4,5]. If the methane content in the resulting gas is higher, e.g., 20–30 vol.%, it is possible to consider its subsequent conversion to hythane, in our case in the presence of a catalyst

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Conclusion