J.M. Bermúdez

Microwave pyrolysis of microalgae for high syngas production

The microwave induced pyrolysis of the microalgae Scenedesmus almeriensis and its extraction residue was carried out at 400 and 800°C. The results show that it is possible to obtain a gas fraction with a high content (c.a. 50vol.%) in H2 from both materials, regardless of the pyrolysis temperature. Furthermore, an outstanding syngas production and high gas yields were achieved. The maximum syngas concentration obtained was c.a. 94 vol.%, in the case of the pyrolysis of the residue at 800°C, indicating that the production of CO2 and light hydrocarbons was minimized. The same experiments were carried out in a conventional electric furnace in order to compare the products and yields obtained. It was found that microwave induced pyrolysis gives rise not only to higher gas yields but also to greater syngas and H2 production.

Continuous flow nanocatalysis: reaction pathways in the conversion of levulinic acid to valuable chemicals

The selective production of 2-methyltetrahydrofuran from levulinic acid has been effectively conducted using designed Cu based catalysts and compared with a commercial Pd/C system under microwave irradiation. Optimised conditions for the most active catalysts Cu-MINT (>90% conversion, 75% selectivity to MTHF) and Pd/C (78% conversion, 92% selectivity to MTHF) were further translated into a continuous flow process using the proposed catalysts to find out the deactivation of Cu-MINT under flow conditions (79 vs. 13% conversion with a switch in selectivity to products after 30 min in flow), the high stability of Pd/C (73 vs. 70% conversion at stable selectivity under analogous conditions to those of Cu-MINT) but, most importantly, different relevant pathways to valuable products from levulinic acid depending on the type of catalyst employed.

Conventional and microwave pyrolysis of a macroalgae waste from the Agar–Agar industry. Prospects for bio-fuel production

A comparative study of the pyrolysis of a macroalgae industrial solid waste (algae meal) in an electrical conventional furnace and in a microwave furnace has been carried out. It was found that the chars obtained from both pyrolyses are similar and show good properties for performing as a solid bio-fuel and as a precursor of activated carbon. Bio-oils from conventional pyrolysis have a greater number of phenolic, pyrrole and alkane compounds whereas benzene and pyridine compounds are more predominant in microwave pyrolysis with a major presence of light compounds. The bio-gas fraction from microwave pyrolysis presents a much higher syngas content (H2+CO), and a lower CO2 and CH4 proportion than that obtained by conventional pyrolysis. Yields are similar for both treatments with a slightly higher gas yield in the case of microwave pyrolysis due to the fact that microwave heating favors heterogeneous reactions between the gases and the char.

CO2 Separation and Capture Properties of Porous Carbonaceous Materials from Leather Residues

Carbonaceous porous materials derived from leather skin residues have been found to have excellent CO2 adsorption properties, with interestingly high gas selectivities for CO2 (α > 200 at a gas composition of 15% CO2/85% N2, 273K, 1 bar) and capacities (>2 mmol·g−1 at 273 K). Both CO2 isotherms and the high heat of adsorption pointed to the presence of strong binding sites for CO2 which may be correlated with both: N content in the leather residues and ultrasmall pore sizes.

Microwave-induced low temperature pyrolysis of macroalgae for unprecedented hydrogen-enriched syngas production

An efficient methodology based on low temperature microwave-induced pyrolysis has been developed for syngas production from macroalgae. The protocol provided unprecedented hydrogen production, with switchable H2/CO ratios depending on pyrolysis conditions which were found to remarkably improve conventional pyrolysis experiments even at significantly higher temperatures (400 vs. 800 °C). Arcing effects under microwave irradiation, which result in an interesting observed pseudo-catalytic effect promoted by the metal oxides contained in macroalgae, seem to account for the improved results.

Microwave Pyrolysis of Organic Wastes for Syngas-Derived Biopolymers Production

Bioplastics production is a growing industry that offers an alternative to that of conventional fossil-derived plastics. Polyhydroxyalkanoates are biopolymers whose thermo-mechanical properties can be comparable to those of conventional plastics. Polyhydroxyalkanoates can be produced through the bacterial fermentation of carbon substrates, although to be commercially viable cheap renewable resources such as syngas (CO + H2 + CO2) from waste pyrolysis are required. Microwave pyrolysis has been demonstrated to have the potential of maximising both the gas production and syngas concentration. Hence it is an appropriate thermochemical route for further syngas fermentation. A combination of different factors, such as the type of waste, the moisture content, the pyrolysis temperature or the use of a microwave receptor makes microwave pyrolysis highly versatile, so that the syngas produced can be virtually tailored to the specific requirements of the bacteria.

Mixtures of Steel-Making Slag and Carbons as Catalyst for Microwave-Assisted Dry Reforming of CH4

The use of steel-making slag as catalysts for microwave-assisted dry reforming of CH4 was studied. Two carbon materials (an activated carbon and a metallurgical coke), mixtures of the carbon materials and Fe-rich slag, and mixtures of the carbon materials and Ni/Al2O3 were tested as catalysts. The mixtures of slag with carbons gave rise to higher and steadier conversions than those achieved over the carbon materials alone. In addition, the use of the metallurgical coke mixed with metal-rich catalysts gave rise to remarkable results. Thus, no CH4 and CO2 conversions were achieved when coke was used alone, whereas high conversions were obtained when it was mixed with the metal-rich catalysts.

Microwave-induced cracking of pyrolytic tars coupled to microwave pyrolysis for syngas production

Herein a new process is proposed to produce a syngas-rich gas fraction (>80vol% H2+CO) from biowaste based on microwave heating within two differentiated steps in order to avoid tars production. The first step consists of the microwave pyrolysis of biowaste induced by a char-based susceptor at 400-800°C; tars, char and syngas-rich gas fractions being produced. The tars are then fed into the second step where a portion of the char from the first step is used as a bed material in a 0.3:1wt% ratio. This bed is heated up by microwaves up to 800°C, allowing thermal cracking of tars and additional syngas (>90vol% H2+CO) being then produced. This new concept arises as an alternative technology to the gasification of biowastes for producing syngas with no need for catalysts or gasifying reagents to minimise tars production.