Alexey Kirilin

Ultrasound enhancement of cellulose processing in ionic liquids: from dissolution towards functionalization

The ionic liquids 1-allyl-3-methylimidazoliumchloride[Amim][Cl] and 1-butyl-3-methylimidazoliumchloride[Bmim][Cl] were utilized in the dissolution of different natural cellulose biopolymers. The biopolymers subject to this investigation were microcrystalline cellulose, cotton linters as well as Kraft cellulose cut to 0.35 mm fibres. High-intensity acoustic irradiation by means of an ultrasonic horn was applied to enhance the dissolution process. The ionic liquids investigated were able to dissolve cellulose at elevated temperatures, in high concentrations, although significant differences were observed, depending on the type of cellulose and ionic liquid. Moreover, the dissolution process under conventional heating was rather slow, typically extending for a period of several hours. Upon use of high-power ultrasound, the dissolution process was dramatically intensified and complete dissolution was achieved in a matter of few minutes only. Various approaches to cellulose functionalization were proposed and investigated. The effect of external parameters, such as the reaction temperature, the cellulose–derivatising agent molar ratio and the batch time of experiment were studied. Various physico-chemical methods, such as acid methanolysis, TGA, DSC, SEM as well as NMR on 1H and 13C nuclei were applied to investigate the structure and morphology of both the cellulose samples and ionic liquids before and after processing.

Reaction Products and Transformations of Intermediates in the Aqueous‐Phase Reforming of Sorbitol

Aqueous phase reforming of sorbitol over Pt supported on an alumina catalyst is investigated, in order to identify the intermediates involved in the transformation of the initial feed. Parameters such as the sorbitol feed rate and temperature are studied. To identify the intermediates, an approach based on analysis of the gas and liquid phases as well as the total carbon content was developed. According to analysis by gas chromatography combined with mass spectrometry of volatile substances collected with solid-phase microextraction, over 260 compounds are involved in the transformation of sorbitol. Of these, 50 of the major products are identified with high reliability. It is shown that a great variety of compounds, bearing different functionalities, form part of the reaction network. The formation of the majority of identified compounds is explained and a reaction network for the formation of sorbitol and intermediate molecules transformation is proposed.

Aqueous-phase reforming of xylitol over Pt/C and Pt/TiC-CDC catalysts: catalyst characterization and catalytic performance

The aqueous phase reforming (APR) of xylitol was studied over five Pt/C catalysts. The correlation between physico-chemical properties of the catalysts and catalytic performance was established. The Pt/C catalysts have different textural properties as well as different mean Pt cluster sizes and surface acidity. The average Pt cluster size was investigated by means of CO chemisorption as well as by TEM. The reaction was found to be structure sensitive and TOF linearly increases with increasing average Pt cluster size in the studied domain. The catalysts which possess higher surface acidity favoured higher rates of hydrocarbon production. On the contrary the Pt/C materials with lower acidities generated hydrogen with high selectivity and TOF.

Dynamic Kinetic Resolution of rac-2-Hydroxy-1-indanone by using a Heterogeneous Ru(OH)3/Al2O3 Racemization Catalyst and Lipase

Kinetic resolution and dynamic kinetic resolution, in particular, provide practical tools for synthesis of enantiomerically pure compounds. In the present work, the resolution of rac‐2‐hydroxy‐1‐indanone and racemization of (S)‐2‐hydroxy‐1‐indanone were investigated. Immobilized lipase AK (Pseudomonas fluorescens) was found as the best enzyme catalyst for kinetic resolution and ruthenium supported on Al2O3 as a potential heterogeneous catalyst for racemization of the starting material. By combining the two reactions, a simple dynamic kinetic resolution of rac‐2‐hydroxy‐1‐indanone producing (R)‐1‐oxo‐indan‐2‐yl butanoate was developed. Under optimal conditions, the product was obtained in 92 % ee at approximately 90 % conversion.

Chemo-bio catalyzed synthesis of R-1-phenylethyl acetate over bimetallic PdZn catalysts, lipase, and Ru/Al2O3. Part II

The effect of calcination and reduction temperature on the physical properties of PdZn/Al2O3 catalysts, prepared by co-precipitation deposition technique and characterized by XPS, XRD, and TEM methods are reported. The temperatures were varied in a range of 300–500°C. The catalyst calcined at 300°C and reduced at 400°C exhibited the metal particle size of 2–6 nm and contained the highest surface concentrations of Pd and Zn according to XPS measurements. The size and the fraction of large particles (above 10 nm) increased with increasing the calcinations and reduction temperatures.

Ionic Liquid-Aided Carboxymethylation of Kraft Pulp

Different ionic liquids containing the cation such as 1-N-butyl-3-methylimida-zolium (Bmim+) are able to efficiently dissolve cellulose. The ability of ionic liquids to truly dissolve cellulose is significant when cellulose derivatization is attempted. A series of experiments on etherification (carboxymethylation) of cellulose was performed, using both the conventional suspension approach (slurry) with 2-propanol as the principal reaction media and a totally homogenous reaction approach utilizing ionic liquids as a reaction media capable of dissolving cellulose. It was observed that a pre-treatment with the ionic liquid 1-N-butyl-3-methylimidazolium iodide ([Bmim][I]) seems to promote substitution in line with the conventional, heterogeneous suspension process. Under carefully chosen reaction conditions, a higher degree of substitution was obtained when wetting the cellulose with [Bmim][I] prior to classical derivatization than without this pre-treatment. It was also observed that the substitution pattern was changing upon use of the ionic liquid [Bmim][I]. Upon a totally homogenous etherification, it was found that the ionic liquid 1-N-butyl-3-methylimidazolium acetate ([Bmim][oAc]) gave the highest degree of substitution. The product obtained was water-soluble and had a DS (degree of substitution) of 0.59. The substitution pattern of the products obtained from the homogenous reactions follow the same substitution pattern as the products obtained from the conventional suspension process. This indicates that the properties of the products are in line with products prepared via the conventional reaction route.

Sibunit-Supported Mono- and Bimetallic Catalysts Used in Aqueous-Phase Reforming of Xylitol

Carbon-supported mono- and bimetallic catalysts prepared via incipient wetness impregnation were systematically studied in aqueous-phase reforming (APR) of xylitol aiming at hydrogen production from biomass. The catalytic performance of several VIII group metals and their combinations, such as Pt, Ni, Pt–Ni, Re, Pt–Re, Ru, Pt–Ru, and Pt–Co, was compared for xylitol APR in a fixed-bed reactor at 225 °C and 29.7 bar (N2). Ni/C, Ru/C, and Re/C catalysts displayed significantly lower activity compared to others. Activity and selectivity to H2 of bimetallic Pt–Ni/C, Pt–Co/C, and Pt–Ru/C catalysts were close to that of Pt/C. Pt–Re/C catalyst showed an outstanding performance which was accompanied by a shift of the reaction pathways to the alkane formation and thereby lower hydrogen selectivity. Addition of the second metal to Pt was not found to be beneficial for hydrogen production, thus leaving Pt/C as the optimum carbon-supported catalyst.

Mechanistic investigations of the reaction network in chemo-bio catalyzed synthesis of R-1-phenylethyl acetate

The kinetics and reaction network of the one-pot synthesis of R-1-phenylethyl acetate was investigated at 70°C in toluene over a combination of three different catalysts: PdZn/Al2O3 as a catalyst for acetophenone hydrogenation, lipase as an enzymatic catalyst for R-1-phenylethanol acylation with ethyl acetate and Ru/Al2O3 as a racemization catalyst for S-1-phenylethanol. In addition to the desired reactions, other reactions, namely hydrogenolysis and dehydration of (R, S)-1-phenylethanol and debenzylation of (R, S)-1-phenylethyl acetate also occurred. The kinetic results revealed that ethylbenzene formation was enhanced with higher amounts of PdZn/Al2O3, whereas lipase did not catalyze ethylbenzene formation. Furthermore, ethylbenzene was formed in the hydrogenolysis of (R, S)-phenylethanol and in the debenzylation of (R, S)-1-phenyl-ethylacetate over Pd/Al2O3 catalyst. The presence of Ru/Al2O3 catalyst, in which Ru was in the oxidation state of 3+, enhanced the formation of R-1-phenylethyl acetate, although no clear racemization of S-1-phenylethanol during the one-pot synthesis of R-1-phenylethyl acetate was observed. Dynamic kinetic resolution of (R, S)-1-phenylethanol in toluene, was, however, demonstrated over Ru/Al2O3 and lipase.