Madona Labaki

Thermochemical conversion of waste tyres—a review

A review of the energy recovery from waste tyres is presented and focuses on the three thermochemical processes used to valorise waste tyres: pyrolysis, gasification, and combustion/incineration. After recalling the chemical composition of tyres, the thermogravimetric behaviours of tyres or their components under different atmospheres are described. Different kinetic studies on the thermochemical processes are treated. Then, the three processes were investigated, with a particular attention given to the gasification, due to the information unavailability on this process. Pyrolysis is a thermochemical conversion to produce a hydrocarbon rich gas mixture, condensable liquids or tars, and a carbon-rich solid residue. Gasification is a form of pyrolysis, carried out at higher temperatures and under given atmosphere (air, steam, oxygen, carbon dioxide, etc.) in order to yield mainly low molecular weight gaseous products. Combustion is a process that needs a fuel and an oxidizer with an ignition system to produce heat and/or steam. The effects of various process parameters such as temperature, heating rate, residence time, catalyst addition, etc. on the energy efficiency and the products yields and characteristics are mainly reviewed. These thermochemical processes are considered to be the more attractive and practicable methods for recovering energy and material from waste tyres. For the future, they are the main promising issue to treat and valorise used tyres. However, efforts should be done in developing more efficient technical systems.

Detection of adsorbed O2− species on CeO2 solid impregnated with Ag2+ ions during its thermal treatment under a H2 atmosphere, an EPR study

10% Ag/CeO2 solid was prepared by the impregnation method. When the solid is calcined at 400 °C, three types of Ag2+ species are formed. One of them is more thermally stable compared to the others. The adsorption on the solid of O2 or H2 molecules gives an adsorbed O2- species on the surface, detected by electron paramagnetic resonance (EPR). The mobility of oxygen in CeO2 and the nature of cations loaded on this support can be the origin of the adsorbed O2- species particularly when the solid is treated under H2 molecules.

Highly active noble metal-free copper-hydroxyapatite catalysts for toluene total oxidation

Hydroxyapatite (Hap) supported Cu materials prepared by the wet impregnation method were designed as noble‐metal‐free catalysts for the total oxidation of toluene. Cu/Hap materials with different Cu loadings (2.5–20 wt %) calcined at 400 °C were characterized by using inductively coupled plasma optical emission spectroscopy, N2 physisorption, XRD, Raman spectroscopy, IR spectroscopy, X‐ray photoelectron spectroscopy, and time‐of‐flight secondary ion MS. The tenorite CuO phase was detected in all materials, and the libethenite Cu2(PO4)OH phase was observed for the sample with 20 wt % Cu. The presence of libethenite was accompanied by the formation of Ca2CO3H+ ions at the Hap surface. Residual NO3− species that interact with Cu and Ca were also found, and their amount increased with the increase of the Cu content in the sample. Interestingly, the specific activity in the total oxidation of toluene increased with the decrease of the Cu content in the catalyst. The rate per mole of Cu was increased by 10 times if the Cu content was decreased by four times. This noticeable result could be related to the presence of acid sites with a moderate strength as well as finely dispersed CuO species on the Hap, which allow the activation of toluene molecules and their oxidation through a redox mechanism. Moreover, Cu2.5 wt %/Hap showed a remarkably stable catalytic performance for 45 h time‐on‐stream, which evidences that this material has a high potential for applications in the removal of volatile organic compounds.

Energy applications of coffee processing by-products

Abstract This chapter explores the possibilities of using coffee processing by-products (e.g., coffee husks and spent coffee grounds [SCG]) for energy applications (e.g., biofuels, biodiesel, bioethanol). In particular, the recovery of energy from biomass through thermochemical processes (pyrolysis, gasification, combustion, hydrothermal treatment, etc.) and biochemical processes is presented. The energy recovery from biomass is an ecological route to produce energy from renewable sources, reduce waste, produce cleaner-burning fuels, protect the environment, reduce fossil fuels consumption and dependence, decrease fuel costs, lower greenhouse gas (GHG) emissions, and find a solution for the limited availability of fossil fuels. Moreover, it has a good impact on economic, social, and agricultural development and ensures a regular supply of energy.

Catalytic Oxidation of Propylene, Toluene, Carbon Monoxide, and Carbon Black over Au/CeO2 Solids: Comparing the Impregnation and the Deposition-Precipitation Methods

Au/CeO2 solids were prepared by two methods: deposition-precipitation (DP) and impregnation (Imp). The prepared solids were calcined under air at 400°C. Both types of catalysts have been tested in the total oxidation of propylene, toluene, carbon monoxide, and carbon black. Au/CeO2-DP solids were the most reactive owing to the high number of gold nanoparticles and Au+ species and the low concentration of Cl− ions present on its surface compared to those observed in Au/CeO2-Imp solids.

H2 production by dry reforming of biogas over Ni-Co-Mg-Al mixed oxides prepared via hydrotalcite route

Ni, Co, Mg and Al mixed-oxide catalysts derived from hydrotalcite were synthesized by coprecipitation for the dry reforming of biogas. The catalysts were characterized using X-ray diffraction, Differential Scanning Calorimetry and Thermogravimetric analysis. The specific surfaces were determined by the BET method. After calcination under an air flow, hydrotalcite-like precursors were completely decomposed. The dry reforming of biogas was carried out using a mixture of CH4:CO2 (1:1) after 2 hours of reduction under an H2 flow at 800 °C. Ni-Co containing catalyst revealed better catalytic activity than the monometallic Co catalyst.

Preparation and characterization of Ni-Co-Mg-Al mixed oxides derived from layered double hydroxides and their performance in the dry reforming of methane

The hydrotalcite route was used to prepare Ni and Co oxides catalysts, with different Ni/Co contents. The catalytic performance of these oxides was investigated with the dry reforming of methane in order to produce energy vector from renewable energy. The samples were characterized, before and after calcination, by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), Fourier Transform Infrared spectroscopy (IR), and determination of the specific surfaces by the BET method. After calcination at 800 °C under an air flow, the hydrotalcite structure was completely decomposed. The dry reforming of methane was carried out using a mixture of CH4:CO2 (1:1) after 2 hours of reduction under an H2 flow at 800 °C. Ni-Co based catalysts revealed better catalytic activity than the Co based one.

Environmental applications of coffee processing by-products

Abstract This chapter explores the possibilities of using coffee processing by-products (e.g., coffee husks, coffee grounds and coffee beans) for environmental applications (e.g., adsorption of heavy metals, dye removal etc.). The elaboration of char from coffee processing by-products is presented and some applications devoted to the removal of cations and dyes from wastewater. The preparation of activated carbon (AC) is detailed. Chemical and physical activation methods are described as well as the characteristics of the AC obtained (textural, structural properties and surface chemistry). The role of the activation process on the adsorption of cations, anions, and organic molecules (pharmaceutical products, pesticides, micropollutants) contained in water is discussed. The use of AC for gas treatment is detailed, especially for acid pollutants (H2S, NO2) and CO2 coming from postcombustion. The last part of this chapter is devoted to the preparation of AC for catalytic application (decomposition of organic molecules). For this specific application, AC has to be functionalized (sulfonation of the surface, or impregnation of K and Fe) in order to obtain catalytic properties.

Catalytic performance of nickel-based solid materials in the steam reforming of methane

Ni_xMg_6-xAl₂ (with 0 ≤ x ≤ 6) mixed oxides catalysts were synthesized via hydrotalcite route followed by calcination under air at 800 °C. Their catalytic performances were studied towards steam reforming of methane. A performant catalyst should show simultaneously good activity, stability of crystallite size of metal particles during the test and resistance to carbon deposit.