Molecular behaviour of phenol in zeolite Beta catalysts as a function of acid site presence: a quasielastic neutron scattering and molecular dynamics simulation study

Quasielastic neutron scattering (QENS) experiments complemented by classical molecular dynamics (MD) simulations at 393–443 K were employed in a study of the mobility and interactions of phenol in acidic zeolite H-Beta, to understand systems relevant to potential routes for the depolymerization and hydrodeoxygenation of lignin. QENS experiments observed isotropic phenol rotation with a fraction of static molecules, yielding rotational diffusion coefficients between 2.60 × 1010 and 3.33 × 1010 s−1 and an activation energy of rotation of 7.2 kJ mol−1. The MD simulations of phenol in the acidic and all-silica zeolite corroborate the experimental results, where molecules strongly adsorbed to the acidic sites behave as an immobile fraction with minimal contribution to the rotational diffusion, and the mobile molecules yield similar rotational diffusion coefficients to experiment. Translational diffusion is too slow to be detected in the instrumental time window of the QENS experiments, which is supported by MD-calculated activation energies of translation larger than 25 kJ mol−1. The study illustrates the effect of active sites in potential catalyst structures on the dynamical behaviour of molecules relevant to biomass conversion

A bibliometric description of lignin applicability for the removal of chemical pollutants in effluents

Several industrial sectors produce tons of effluents daily containing a high amount of hazardous chemical pollutants that pose a major threat to the environment and human health. Current wastewater treatment methods, such as flocculation and activated carbon adsorption, have drawbacks linked to high material cost and too much energy consumption. Thus, the search for renewable, biodegradable, and efficient materials has been the object of research aimed at replacing the conventional materials used to cheapen processes and reduce environmental impacts. Lignin stands out in this context as it has low cost and high availability. Therefore, several scientific researches were developed to harness the potential of lignin, especially as adsorbent, for the removal of chemical agents from effluents. This paper presents a bibliometric review performed on the Scopus database, showing the evolution of studies related to the applicability of lignin in the removal of chemical pollutants in waters over the last five years. Data regarding annual publications, languages, journals, countries, institutions, keywords, and subjects were analyzed. The realized screening selected 130 articles that met the previously defined criteria. Results indicated a strong collaboration between countries and China's substantial contribution to the documents. The analysis also has shown that lignin is mainly used as adsorbent material, sorbent, flocculant agent, and hydrogel and presents important results and information for future researchers on this topic.The authors acknowledge financial assistance from the Brazilian research funding agencies such as CAPES (Coordination for the Improvement of Higher Education Personnel) under Finance Code 001, a Brazilian foundation within the Ministry of Education (MEC), CNPq (National Council for Scientific and Technological Development), a Brazilian foundation associated to the Ministry of Science and Technology (MCT), and FAPITEC/SE (the Foundation of Support to Research and Technological Innovation of the State of Sergipe).info:eu-repo/semantics/publishedVersio

Straightforward sustainability assessment of sugar-derived molecules from first-generation biomass

© 2018 Elsevier B.V. Today, there is a general consensus in academic literature that second generation biomass is the only valuable carbohydrate resource for non-food applications. In the meantime, fermentation of sugars towards bio-ethanol, mainly from first generation biomass, is becoming widespread at an industrial level. This paper tries to investigate if there can be a valuable role for edible resources (here: sugars) in the chemical industry without affecting the food security. Moreover, a connection is proposed between a broad range of multiple technologies and sustainable resources, with main attention to the native C skeleton and functionality of biomass. Going deeper in sustainability, this paper selected four criteria, taking into account the entire valorisation route, to apply to the most promising carbohydrate-derived molecules. By doing this, the most promising chemicals and working points from a sustainable point of view are highlighted.status: publishe

Reductive splitting of hemicellulose with stable ruthenium-loaded USY zeolites

© 2016 The Royal Society of Chemistry. Reductive catalytic splitting to sugar alcohols is a promising technology to valorize (hemi)cellulosic feedstock. This contribution focuses on the conversion of arabinoxylan (AX), a common hemicellulose polymer, to pentitols like xylitol and arabitol in the presence of ruthenium-loaded H-USY zeolites. Both acid and metal sites on the catalyst play a crucial role in the bifunctional catalytic mechanism. Overall, the reaction mechanism involves hydrolysis of AX into shorter (less reactive) xylan oligomer intermediates (XOs), which are in turn hydrolysed into sugar monomers. The first step occurs fast in hot liquid water, but the second step which is rate limiting, requires acid catalysis. Literature has reported successful XO hydrolysis with soluble acids. However, USY zeolites, being non-corrosive instead of the former, are able to hydrolyse XOs more efficiently, likely due to their strong mesopore adsorption capacity. Once formed, the monomeric sugars should be hydrogenated on the metal sites as fast as possible, as otherwise undesired competitive acid catalysed side-reactions will occur. While another catalyst like Ru on carbon can also be used in the one-pot approach close proximity of the two sites, e.g. in the pores of the USY zeolite, is beneficial for the pentitol selectivity, as long as they are well harmonised. After searching for the ideal dual site balance, exceptionally high pentitol yields up to 90 mol% were achieved after only 5 h of reaction. Comparison with earlier reported cellulose reactions shows a narrowing of the ideal acid-to-metal range, besides a shift to lower ratios. Initial regeneration studies show a stable Ru/USY catalytic system able to perform multiple reaction runs with retention of activity and selectivity.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported Licence (CC BY-NC 3.0) history: Received 25 May 2016; Accepted 6 June 2016; Accepted Manuscript published 6 June 2016; Advance Article published 11 July 2016; Version of Record published 26 September 2016status: publishe

Compositional and structural feedstock requirements of a liquid phase cellulose-to-naphtha process in a carbon- and hydrogen-neutral biorefinery context

© 2016 The Royal Society of Chemistry. Processing raw (ligno)cellulosic feedstock into renewable light naphtha alkanes could lead to a gradual replacement of fossil feedstock for the production of chemicals, materials and fuels. The production of drop-in alkanes is a preferable short term strategy because of its practical implementation and integration in existing infrastructure and processes. A handful of promising cellulose-to-alkane biorefinery initiatives were recently reported, both processing in gas and liquid phase. This contribution presents a detailed study of the two-liquid phase hydrodeoxygenation of cellulose to n-hexane under relatively mild circumstances, proceeding through the recently communicated HMF route, in presence of a soluble acid and Ru/C metal catalyst. Two main points were addressed here: (i) the importance (or not) of the lignocellulose pretreatment and purification to the alkane yield, and (ii) the renewability of the consumed hydrogen in the process. A systematic study of the effect of cellulose purity, crystallinity, degree of polymerization and particle size (surface area) on the light naphtha yield was performed to tackle the first part. As fibrous cellulose with large particles was the most favourable feedstock with regard to alkane yield and as the presence of hemicellulose and lignin impurities had no effect on the cellulose-to-naphtha conversion, costly mechanical and purification steps are redundant to the process, in contrast to their notable importance in other cellulose valorisation processes (e.g. to glucose, sorbitol, isosorbide and acids). The second point regarding sustainable hydrogen supply is discussed in detail by calculating hydrogen and carbon mass and energy balances of the chemical conversions, assuming selected scenarios among others to recuperate the hydrogen by steam-reforming of waste streams (like gaseous C <6 hydrocarbons and aqueous polyol fractions) and (partial) aromatization of the C 6 fraction into benzene. The study shows potential to integrate the liquid phase cellulose-to-naptha (LPCtoN) technology into a self-sufficient biorefinery, in which the chemical processes may run without consumption of external (non-renewable) hydrogen, carbon and energy, except for solar light.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported Licence (CC BY-NC 3.0) history: Received 16 June 2016; Accepted 27 July 2016; Accepted Manuscript published 27 July 2016; Advance Article published 3 August 2016; Version of Record published 10 October 2016status: publishe