Aqueous-phase dehydration of xylose into furfural was studied in the presence of amorphous Nb2O5 with water-compatible Brønsted and Lewis acid sites. Nb2O5 was determined as a more active and ...selective catalyst for xylose dehydration than typical homogeneous Brønsted and Lewis acid catalysts including HCl and Sc(OTf)3, and Nb2O5 converted 93% of xylose with 48% selectivity toward furfural in water at 393 K. No significant loss of the original catalytic activity was observed after Na+-exchange treatment, which indicates that the reaction proceeded only on Lewis acid sites. Isotope-labeling experiments using D2O and xylose suggested that furfural is formed through stepwise dehydration via a highly reactive dicarbonyl intermediate on Nb2O5, whereas typical Lewis acids such as CrCl3 and Sc(OTf)3 convert xylose to furfural in water through hydride transfer and subsequent dehydration via xylulose as a ketose-type intermediate. The difference in the reaction mechanism accounts for the lower activation energy (83 kJ mol–1) with Nb2O5 than those with Sc(OTf)3 and HCl (107–131 kJ mol–1). Continuous extraction of evolved furfural with toluene enabled a large increase in the selectivity toward furfural from 48% to 72% and prevented deactivation of the Lewis acid sites by covering with heavy byproducts, represented by humin.
Selective and economic conversion of lignocellulosic biomass components to bio‐based fuels and chemicals is the major goal of biorefineries, but low yields and selectivity for fuel precursors such as ...sugars, furanics, and lignin‐derived monomers pose significant disadvantages in process economics. In this Minireview we summarize the existing protection strategies used in biomass chemocatalytic conversion processes and focus the discussions on the mechanisms, challenges, and opportunities of each strategy. We introduce a concept of using analogous methods to manipulate biomass catalytic conversion pathways during the upgrading of carbohydrates to fuels and chemicals. This Minireview may provide new insights into the development of selective biorefining processes from a different perspective, expanding the options for selective conversion of biomass to fuels and chemicals.
Catalytic conversion of biomass to fuels and chemicals is fraught with low selectivity. This Minireview provides an overview of the physical and chemical protection strategies used to improve selectivity in biomass conversion and describes the potential of using protection chemistry to manipulate catalytic pathways.
Herein, we describe a one-step process for renewable aromatics from biomass-derived ketones over solid acid catalysts under liquid phase batch and flow conditions. The ion exchange resin was highly ...active for aromatics due to high acidic strength but leaching of acidic sites caused low stability. In contrary, zeolite HY showed a lower activity but higher stability in batch by regenerability and was stable in flow for 250 min-on-stream. HY is further applicable for the conversion of higher ketones (butanone and pentanone). This work contributes towards an industrially important aromatic production from biogenic ketones and thus an economical and sustainable process.
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•Stable conversion of bio-derived ketones to aromatics is achieved in liquid phase.•Large pores and higher amount of acid sites are beneficial for the aromatization.•Highly active ion exchange resin showed continuous leaching of active sites.•HY-zeolite is found as a stable catalyst in batch as well as in flow conditions.•Suitability of HY-zeolite for aromatization of higher ketones is shown.
Cardiotoxicity from chemotherapy regimens has been long reported. However, the understanding of cardiac side effects of biological therapies is rapidly evolving. With cancer patients achieving higher ...life expectancy due to the use of personalized medicine and novel targeted anticancer agents, the occurrence of cardiotoxicity is becoming more significant. Novel biological therapies include anti-HER2 antibodies, tyrosine kinase inhibitors, bruton kinase inhibitors, antivascular endothelial growth factors, proteasome inhibitors, immunomodulator drugs, and immune checkpoint inhibitors. Potential cardiovascular toxicities linked to these anticancer agents include hypertension, arrhythmias, QT prolongation, myocardial ischemia and infarction, left ventricular dysfunction, congestive heart failure, and thromboembolism. Cardiac biomarkers, electrocardiography, echocardiography and magnetic resonance imaging are common diagnostic modalities used for early detection of these complications and timely intervention. This review discusses the various types of cardiotoxicities caused by novel anticancer biologic agents, their molecular and pathophysiological mechanisms, risk factors, and diagnostic and management strategies that can be used to prevent, minimize, and treat them.
Introduction: The upper extremity is commonly involved in severe soft tissue defects that can be challenging functionally and cosmetically. Anatomical studies on skin vascularization provide ...developmental base for the flap nourished by perforating arteries. Perforator flaps reduce donor site morbidity and recovery time. Therefore, in case of cosmetic surgery of soft tissue defect of the arm, it is mandatory for reconstructive surgeons to have beforehand knowledge of vascular anatomy of cutaneous perforators of the arm. Hence, a study was done to evaluate the total number of perforators, distribution from bony landmarks, and pedicle length from source vessels on the medial, lateral, and posterior aspects of the arm. Methodology: The study was undertaken at the Department of Anatomy, King George's Medical University, Lucknow, on 15 upper limbs of fresh cadavers of both the sexes of adult age group. Methylene blue dye was injected into the arterial system of the arm. After one hour, perforators were visualized by incising the margins of the stained arm skin. Results: We observed that maximum numbers of perforators were contributed by direct branch of the brachial artery (49.7%), followed by superior ulnar collateral artery. Numbers of perforators on the medial aspect of the arm were maximum (52.0%), followed by lateral aspect and posterior aspect of the upper arm. Perforators supplying the posterior and lateral aspects of the arm had the maximum mean length. Conclusion: Thus, a detail understanding of position, length, and numbers of perforators of the arm helps surgeons to predefine the appropriate perforator flaps for reconstructive surgeries.
The need for sunlight chemical renewal and contemporary organic transformation has fostered the advancement of environmentally friendly photocatalytic techniques. For the first time, we report on the ...novel crafting of a bright future with selenium‐infused Eosin‐B (Sein‐E‐B) nanocomposite photocatalysts in this work. The Sein‐E‐B nanocomposite materials were created using a hydrothermal process for solar chemical regeneration and organic transformation under visible light. The synthesized samples were subjected to UV‐DRS‐visible spectroscopy, FT‐IR, SEM, EDX, EIS and XRD analysis. The energy band gap of the Sein‐E‐B nanocomposite photocatalyst was measured using UV‐DRS, and the result was around 2.06 eV. to investigate the generated Sein‐E‐B catalytic activity as a nanocomposite for 1,4‐NADH/NADPH re‐formation and C−N bond activation. This novel photocatalyst offers a promising alternative for the regeneration of solar chemicals and C−N bond creation between pyrrole and aryl halides.
Synthesis of high-value-added chemicals from biomass and/or biomass-derived platform molecules is considered an important strategy to mitigate the global dependency on fossil resources and include ...renewable resources in a circular economy. In recent years, the synthesis of bio-based plastics has received significant attention as a potential alternative to conventional industrial processes. Thus, a lot of effort has been put into the development of not only different classes of biomonomers but also bio-based drop-in chemicals. Amine-derived molecules, especially alcohol-amines, diamines, and N-heterocyclic amines, are the most important classes of functional monomers for the production of polyamides, polyimides, polyurethanes, and polyureas. Additionally, these amines are extensively used in pharmaceuticals. In this review, we will give a concise overview of the up-to-date methods for the production of industrially important amines from biomass-derived oxygenates. Special attention will be given to the catalytic amination of biomass aldehyde- and alcohol-based oxygenates, reaction mechanism, catalyst stability, as well as their specific challenges and opportunities. We anticipate this critical and comprehensive review to provide detailed insights into the synthesis of bio-based amines and guide the development of effective greener synthetic methodologies.
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