• Energy Research

Abstract The selective chemical conversion of biomass components to useful bioproducts may contribute to a renewable resource-based economy. The selective production of target bioproducts may be accomplished using heterogeneous catalysts operating under relatively moderate reaction conditions. In this work, carbohydrate biomass derived α-angelica lactone (AnL) and levulinic acid (LA) were converted to the versatile bioproduct γ-valerolactone (GVL), in the presence of nanohybrid catalysts (M-FDCA) and the microcrystalline metal-organic framework CAU-28, all of which were synthesized from bio-based 2,5-furandicarboxylic acid (FDCA) and a metal (M = Zr or Hf) precursor. The nanohybrids were prepared in a simple fast (FT) fashion, and, for comparison, via a conventional solvothermal (S) procedure. The M-FDCA catalysts stood on a higher footing than CAU-28 in the conversion of AnL and LA to GVL. The superior results for the M-FDCA catalysts may be partly due to their higher ratio Sext:SBET and nano-features, which may advantageously enhance active sites accessibility. In particular, the Hf-FDCA catalysts were stable and performed superiorly to the Zr-FDCA ones. Experimental mechanistic studies shed light on the multifunctional behavior of the hybrid catalysts in the one-pot conversion of AnL-to-GVL, which involved acid and reduction chemistry.

Abstract The influence of the amount of SO42−/La2O3 (2–20%) over structural and catalytic properties of HZSM-5 was evaluated. The catalysts were characterized by thermogravimetric analysis, X-ray diffraction, adsorption/desorption of N2 and infrared spectroscopy and they were tested in the esterification reaction of oleic acid and methanol. The influence of the amount of catalyst (2, 5 and 10%) and the influence of molar ratio oleic acid:methanol (1:10, 1:20 and 1:45) were evaluated. The characterization analyses indicated that the starting material had not significant structural and textural changes, but the acidity had changes. The most expressive results of conversion were obtained in the molar ratio 1:10 and 5% of catalyst. The most efficient catalyst was that modified with 10% of SO42−/La2O3 (10OLS/HZ), which presented maximum conversion (100%). In general, the catalysts were efficient. It was possible to observe that most of the modifications produced catalysts more active than the starting material.

Abstract The oligomerisation of 1-butene was studied under high-pressure continuous-flow conditions (200–250 °C, 30–40 bar), in the presence of micro/mesoporous zeotypes based on the MFI topology, which were prepared via different non-destructive bottom-up strategies: crystallization of silanized protozeolitic units; co-templating with a dual function (polymeric) template; and using a sole structure directing agent (non-surfactant and non-polymeric) to generate mesoporosity. The synthesis method influenced the material properties and consequently the catalytic performance. In targeting hydrocarbons with boiling point ranges characteristics of diesel, the zeotypes benefited from regular morphology, reduced crystallite size, mesoporosity and enhanced molar ratio of Lewis (L) to Bronsted (B) acid sites (L/B). In general, the zeotypes outperformed commercial zeolite ZSM-5. The best-performing zeotype was prepared according to the Serrano strategy based on the crystallization of silanized zeolitic seeds, and led to 97% conversion and an average space-time yield of liquid products of 1077 mg gcat−1 h−1, at 250 °C, 40 bar. The zeotypes seemed more stable than the commercial zeolite, based on molecular level characterization studies of the used/regenerated catalysts, with some differences in catalytic activity.

Abstract The present study aims at evaluating the efficiency of the HZSM-5 zeolite dealuminated with citric acid and modified with sulfated lanthanum oxide (SO42−/La2O3) as catalysts for the production of biodiesel via esterification. The effects of the treatments in the structural, textural and acid properties of produced catalysts were monitored by PXRD, adsorption/desorption of N2 and measurements of acidity by FTIR using pyridine and collidine as probe molecules. The catalysts were tested in the reaction of esterification using oleic acid and methanol as reactants. Different molar ratios (1:10, 1:20 and 1:45) and amounts of catalyst (2%, 5% and 10%) were tested and the conversion of oleic acid into methyl oleate analysed. Results show that the dealumination with citric acid and impregnation of SO42−/La2O3 over HZSM-5 produced catalysts more active for the conversion of oleic acid for the production of biodiesel, when compared to the parent HZSM-5 zeolite. The increase of external surface properties (acidity and area) was the main parameter influencing the activity of the catalysts for the considered reaction.

Abstract In this study, the efficiency of citric acid as dealumination agent was evaluated in the case of zeolite HZSM-5 by varying the experimental conditions, namely concentration (0.5, 1.0 and 2.0 mol L−1) and treatment temperature (60 and 80 °C). The effect of the CA treatment on structural, textural and acidity properties of the starting HZSM-5 material was monitored using XRD, N2 sorption and FTIR (pyridine and collidine) measurements. Heptane and methylcyclohexane cracking model reactions were used to evaluate the catalytic behavior of the modified materials, in terms of acid strength and active sites accessibility. The modified catalysts were tested in the esterification reaction, using oleic acid as reagent and different oleic acid/methanol molar ratios. All the results show the beneficial effect of the citric acid treatment on the physicochemical properties of the final materials, with an improvement of the external acidity, a crucial parameter for the reaction considered, i.e. the oleic acid esterification.

Abstract Keeping a high stability and CO2 capture capacity of CaO-based sorbents during the Ca-looping process is still a challenge. The main goal and the innovative idea addressed in this study consists of investigating if solid industrial waste resources such as a coal fly ash (CFA) and a spent Fluid Catalytic Cracking (SFCC) catalyst, can be used as particle spacers to improve the sintering resistance of two CaO-based sorbents. These two inert industrial waste materials are used in the present work for increasing the CaO particles separation and consequently, reducing their coalescence and hindering severe sintering at the high Ca-looping temperatures. There are currently no studies in the literature on the use of industrial SFCC wastes in blends with CaO based sorbents acting as CaO particles spacer with the objective of reducing the Ca-looping sorbents deactivation along the cycles of carbonation-calcination. Despite the mineralogical and textural differences between the CFA and SFCC catalyst industrial wastes, the tests carried out in a fixed bed laboratory reactor showed that the addition of a small fraction of waste to the CaO sorbent (c.a. 10%) seems to be an interesting option to improve the CO2 capture technology efficiency. During the Ca-looping, the volume and stability of sorbent mesopores is essential to achieve higher and stable carbonation conversion values, and since the CFA and SFCC increase the SBET, they contribute to enhance the sintering resistance. The innovative results presented in this study show that the industrial CFA and SFCC wastes have potential to be an economically attractive option thus contributing to reduce the cost of the Ca-looping cycle CO2 capture process, as well as to minimize the adverse environmental impacts of the high volume of industrial wastes generated.

Abstract Mesostructured zirconium-based mixed oxides (MZM) are versatile solid acid catalysts for the chemical valorisation of biomass, within sugar and fatty acid platforms of biorefineries. MZM catalysts containing tungsten and/or aluminium were prepared via a templating route that allows the texture and acid properties to be improved. Their catalytic potential was explored for synthesising different types of interesting oxygenated fuel bio-additives, specifically levulinate esters, furfuryl alkyl ethers and glycerol acetals of the type 1,3-dioxolane and 1,3-dioxane. Levulinate esters are synthesised from furfuryl alcohol (FA), which is produced industrially from lignocelluloses; the acetals are obtained from glycerol, which is a coproduct of the industrial production of biodiesel. The performances of the MZM catalysts have been compared with those of zirconium–(tungsten and/or aluminium) mixed oxides synthesised via conventional co-precipitation (without a template). Structure–activity relationships were established which reveal advantages of the templating route used for the synthesis of the MZM catalysts. The MZM catalysts were more active and led to higher total yields of bio-additives (e.g. up to 86% yield at 100% FA conversion, 140 °C, 30 min reaction) than the catalysts prepared by co-precipitation (e.g. up to 45% yield at 88% FA conversion), under similar reaction conditions. Detailed catalytic and characterisation studies were carried out for the used catalysts.