Aqueous-Phase Cellulose Hydrolysis over Zeolite HY Nanocrystals Grafted on Anatase Titania Nanofibers
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Aqueous‑Phase Cellulose Hydrolysis over Zeolite HY Nanocrystals Grafted on Anatase Titania Nanofibers Longlong Shan1 · Jun Yan1 · Yang Wang1 · Xuebin Ke2 · Junmeng Cai3 · Shirui Yu4 · Adam F. Lee5 · Xiaoli Gu1 · Xingguang Zhang1,6 Received: 7 July 2020 / Accepted: 21 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Acid-catalyzed aqueous-phase hydrolysis of cellulose was investigated over zeolite HY nanocrystals grafted on anantase titania nanofibres (HY-TiO2). H-exchanged NaY zeolite nanocrystals of controlled size (40–60 nm) were synthesized and deposited over T iO2 nanofibres prepared by hydrothermal treatment of anatase nanoparticles. The resulting materials were characterized by XRD, SEM, TEM, N H3-TPD and FT-IR, and evidenced a homogeneous distribution of HY nanocrystals across the TiO2 nanofibres. HY-TiO2 catalysts exhibited higher turnover numbers and selectivity to glucose than large (500 nm to 2 μm) unsupported HY nanoparticles; this performance enhancement is attributed to the greater accessibility of Brønsted acid sites in HY nanocrystals to cellulose particles. The importance of active site accessibility to β-1,4-glycosidic bond cleavage was highlighted by a significant increase in the rates of glucose and cellobiose hydrolysis (versus cellulose) over HY-TiO2-100. Engineering of zeolite particle size is a critical design parameter for the valorization of sterically-challenging cellulosic feedstocks. Graphic Abstract
Keywords Cellulose · Glucose · Hydrolysis · Diffusion · Zeolite nanocrystals
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10562-020-03402-w) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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1 Introduction Biomass valorization is an attractive route to sustainable energy and material resources as an alternative to current fossil derived feedstocks. Among biomass resources, nonfood cellulose accounts for 45–50 wt% of lignocellulose, however its transformation to platform chemicals and/or liquid transport fuels and fuel additives necessitates active, selective, scalable and recyclable catalysts [1–4]. Early research in this field focused on the use of homogeneous mineral acid catalysts, however these are problematic due to their hazardous and corrosive nature and difficulties in product separation and catalyst re-use. Increasing pressure to meet UN Sustainable Development Goals (notably 6, 7, 12 and 13) has shifted the research focus to the development and application of heterogeneous catalysts prepared from Earth abundant elements, able to effect the selective transformation of cellulose and carbohydrate derivatives under mild conditions in water [5–8]. Heterogeneous catalysts such as zeolites [9–11], metal oxides [12, 13], and functional polymers [14, 15], magnetic nanoparticles [16, 17] and carbons [18, 19] can offer improved atom economy, safety, process and economi
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