Abstract
The present study deals with the development, characterization, and performance evaluation of an eco-friendly catalyst, using 2-methoxy-4-methylphenol (2M4MP) as a surrogate tar. The 2M4MP was selected due to its chemical functionalities and the fact that it is a good model compound to represent the tar formed during biomass low temperature gasification. The eco-friendly catalyst was prepared using the typical Fe and Ca minerals which are present in ash. These ash components were added to a fluidizable γ-Al2O3 support using a multistep incipient impregnation, yielding Fe oxides as an active phase and CaO as the promoter. The prepared catalyst displayed a 120 m2/g BET specific surface area, with few γ-Al2O3 bulk phase changes, as observed with XRD. TPD-NH3 and pyridine FTIR allowed us to show the significant influence of CaO reduced support acidity. A TPR analysis provided evidence of catalyst stability during consecutive reduction–oxidation cycles. Furthermore, catalyst evaluation vis-à-vis catalytic steam 2M4MP gasification was performed using the fluidized CREC riser simulator. The obtained results confirm the high performance of the developed catalyst, with 2M4MP conversion being close to 100% and with selectivities of up to 98.6% for C1-C2 carbon-containing species, at 500 °C, with a 7.5 s reaction time and 1.5 g steam/g 2M4MP. These high tar conversions are promising efficiency indicators for alumina catalysts doped with Fe and Ca. In addition, the used catalyst particles could be blended with biochar to provide an integrated solid supplement that could return valuable mineral supplements to the soil.
Highlights
Biomass steam gasification is a key process for renewable waste resource conversion, as is the case for Costa Rican coffee pulp [1]
Important considerations are required for the design and the development of an eco-friendly catalyst emulating ash in biomass gasification [44]
This respect, it is important to note that some identified ash components, such as potassium, In this respect, it the is important to catalyst note that some identified ash components, such aswas potassium, should be avoided in eco-friendly formulation
Summary
Biomass steam gasification is a key process for renewable waste resource conversion, as is the case for Costa Rican coffee pulp [1]. Coffee pulp gasification can be negatively affected by tar formation [2]. Tar is a by-product of biomass gasification, consisting of a range of hydrocarbon species, mainly aromatics, and complex aromatic polycyclic hydrocarbons. Tar constituents can be classified either by their number of rings [8,9] or as primary, secondary, and tertiary [10]. These chemical species usually contain oxygenates (phenolic ethers), alkylphenols, heterocyclic ethers, and other polyaromatic hydrocarbons (PAHs). One of the simplest definitions of tar includes all the organic compounds that result from biomass steam gasification, with a molecular
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