Effect of Exchangeable Cation in Clays on the Yield and Quality of the Bio-Oil during Microwave Pyrolysis of Cellulose

Bio-oil (pyrolysis oil) is an essential feedstock for the production of renewable fossil-free fuels and valuable chemicals. Enhancement of the pyrolysis oil yield and its quality are significant challenges for an efficient and sustainable biorefinery. Here, we report the microwave (MW)-assisted noncatalytic pyrolysis of cellulose, as a green and controllable alternative to conventional heating, in the presence of eco-friendly Li-, Na-, K-, Mg-, Ca- and Ba-bentonites. The detailed analysis of the MV heating traces demonstrates that the bentonite MW activity significantly depends on the presence of internal water. The intensity of this interaction is controlled by the cation nature reduced in the order: Li+ > Na+ > K+ and Mg2+ > Ca2+ > Ba2+. A unique experimental design for the MW-assisted pyrolysis of cellulose in the presence of Li-doped clays helps to increase the bio-oil yield to 37.8% with high selectivity towards the commercially useful levoglucosan (purity: 39.36%). The combination of an alternative green heating method and environmentally friendly bentonites can be used many times without recycling. We believe that the improved yields of bio-oil are due to: (i) high MW activity of bentonites, which conventionally increases the heating rates of cellulose; and (ii) production of water by hydrophilic clay minerals, favouring depolymerisation of cellulose.

Discovering Low Toxicity Ionic Liquids for Saccharomyces cerevisiae by Using the Agar Well Diffusion Test

Ionic liquids (ILs) are new solvents widely used in many technologies due to their unique and advantageous physicochemical properties. In biotechnological applications, ILs can be used along with microorganisms such as Saccharomyces cerevisiae. Due to the enormous number of ILs that can be synthesized through the combination of different anions and cations, it is necessary to have an easy and quick tool for the preliminary screening of their biocompatibility for being used in biotechnological applications. In this work, the agar well diffusion test was successfully applied as a rapid method to identify toxic/nontoxic ILs toward S. cerevisiae. Sixty-three ILs containing a diverse set of cations and anions were used. Through this methodology, nine fully biocompatible ILs toward S. cerevisiae were identified, including: [Bmim+] [NO3−], [HOPmim+] [NO3−], [Bmim+] [NTf2−], [N8,8,8,1+] [NTf2−], [S2,2,2+] [NTf2−], [EMPyr+] [NTf2−], [BMPi+] [NTf2−], [Moxa+] [MeSO4−] and [Chol+] [H2PO4−]. The analysis of the results also provides preliminary rules to enable the design of biocompatible ILs with S. cerevisiae. In this context, the toxicity was mainly determined by the cation nature although some anions can also display a strong influence on the IL biocompatibility as the bistriflimide anion. Besides, it was observed that an increase in the alkyl chain length of cations, such as imidazolium or pyridinium, involves an increase in the IL toxicity.

Influence of the Compensating Cation Nature on the Water Adsorption Properties of Zeolites

The influence of the compensating cation (Na+, Li+, Mg2+) nature on the water adsorption properties of LTA and FAU-type zeolites was investigated. Cation exchanges were performed at 80 °C for 2 h using 1 M aqueous solutions of lithium chloride (LiCl) or magnesium chloride (MgCl2). XRF and ICP-OES analyses indicate that the cation exchange yields reach values between 59 to 89% depending on the number of exchange cycles and the nature of the zeolite and cation, while both zeolites structures are preserved during the process, as shown by XRD and solid state NMR analyses. Nitrogen adsorption-desorption experiments indicate a higher available microporous volume when sodium cations are replaced by smaller monovalent lithium cations or by divalent magnesium cations because twice less cations are needed compared to monovalent cations. Up to 15% of gain in the available microporous volume is obtained for FAU-type zeolites exchanged with magnesium cation. This improvement facilitates the adsorption of water with an increase in the water uptake up to 30% for the LTA and FAU type zeolites exchanged with magnesium. These exchanged zeolites are promising for uses in water decontamination because a smaller amount is needed to trap the same amount of water compared to their sodium counterparts.

Synthesis of condensed cobalt (II)-zinc phosphate with the concrete anionic composition

Сondensed cobalt(II)-zinc phosphates with the concrete anionic composition (with а linear structure of anion with = 2–8 of the general formula (Co1-хZnх)(n+2)2PnO3n+1, 0<х<1.00, and a cyclic with = 4 – (Со1-xZnx)2P4O12, 0<x<1.0) were synthesized by heat treatment in the isothermal conditions of crystallohydrates of composition Со1-хZnх(H2PO4)2·2H2O (0<x<1.00). The heat treatment of Со1-хZnх(H2PO4)2·2H2O (0<x<1.00) was carried out in the air in the range of 100–350 °C (± 5 °). The sample was maintained at a predetermined temperature for 0.5, 1.5, 3.0, 5.0 and 7.0 hours. Heat treatment products were identified using a set of analytical methods: chemical, X-ray, IR spectroscopy, quantitative chromatography on paper. It has been determined that the formation of condensed phosphates in products of heat treatment Со1-хZnх(H2PO4)2·2H2O (0<x<1.00) at 100 °C for 0.5–3.0 h does not occur. The processes of anionic condensation begin under the heat treatment for 5.0–7.0 h at 100 °C and deepen for further temperature rise. With the increase in the duration of heat treatment at 150 °C to 3.0–7.0 h, the formation of condensed phosphates with a linear structure of anion with a degree of polycondensation = 2–5 of the general formula (Со1-хZnх)(n+2)2PnO3n+1. is recorded. The degree of conversion of monophosphate anion to polyphosphate is 61-73%, respectively. Similar changes in the composition of heat treatment products are realized with the destruction of the structure and complete amorphization of the solid phase. The formation of a new crystalline lattice is recorded at 225 °C. The sample, which lasts 0.5 h, is a crystalline phase identified as Со1-хZnхH2P2О7 with an admixture of Со1-хZnхP2О7. The maximum amount of diphosphate (52.9 % of the total content of P2O5) is formed during the firing of Со1-хZnх(H2PO4)2·2H2O for 1.5 h at 225 °C. The amount of diphosphate is reduced by almost 2 times during heat treatment for 7.0 hours. Similar changes in the composition of linear condensed phosphates are observed at 275 °C: with the increase in the duration of heat treatment the number of low-molecular phosphates with = 2–4 decreases, the high-molecular with = 5–8 of the general formula (Со1-хZnх)(n+2)2PnO3n+1 increases . Fosted condensed phosphate with a cyclic structure of the anion with = 4 – cyclotetraphosphate of the composition (Со1-хZnх)2Р4O12 . It increases the temperature to 350 °C and becomes the only heat treatment product. Quantitative dependences of the content of condensed phosphates with different anion structure and phosphate acids, which released as intermediate products, on the temperature regime and roasting duration were established. The influence of cation nature on the conditions of synthesis and quantitative composition of the condensed phosphates of cobalt(II)-zinc with concrete anionic composition (with а linear structure of anion with = 2–8 of the general formula (Co1-хZnх)(n+2)2PnO3n+1, 0<х<1.00, and a cyclic with = 4 – (Со1-xZnx)2P4O12, 0<x<1.0) is shown.

Solvation of alcohols in ionic liquids – understanding the effect of the anion and cation

The effect of the anion and cation nature in the solvation of alcohols in ionic liquids highlighting the R-OH anion H-bond interaction is analysed.