Hasil untuk "Chemical industries"

B. Cuenya

W. Kern

R. Noyori

Zhen Guo, B. Liu, Qinghong Zhang et al.

J. Rubio, M. L. Souza, R.W Smith

G. Dodekatos, Stefan Schünemann, H. Tüysüz

Glycerol is a highly versatile molecule because of its three hydroxyl groups and can be transformed to a plethora of different value-added fine chemicals and products. It is an important byproduct in biodiesel production and, hence, produced in high amounts, which resulted in a high surplus flooding the market over the last decades. Thus, glycerol is regarded as a potential platform chemical, and many research efforts were devoted to find active catalysts to transform glycerol to various products via different catalytic processes. The selective oxidation reaction is one of the most promising reaction pathways to produce valuable fine chemicals used in the chemical and pharmaceutical industry. This Review describes the recent developments in selective glycerol oxidation to value-added products over heterogeneous catalysts. Particular emphasis is placed not only on newly developed catalysts based on supported noble-metal nanoparticles but also on catalysts containing nonprecious metals. The idea of using co...

Le-Yong Yu, C. Shearer, J. Shapter

Agneev Mukherjee, M. Dumont, V. Raghavan

Romaric Gérardy, D. Debecker, J. Estager et al.

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C2 to C6 bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.

G. Puts, P. Crouse, B. Améduri

This Review aims to be a comprehensive, authoritative, and critical review of general interest to the chemistry community (both academia and industry) as it contains an extensive overview of all published data on the homopolymerization of tetrafluoroethylene (TFE), detailing the TFE homopolymerization process and the resulting chemical and physical properties. Several reviews and encyclopedia chapters on the properties and applications of fluoropolymers in general have been published, including various reviews that extensively report copolymers of TFE (listed below). Despite this, a thorough review of the specific methods of synthesis of the homopolymer, and the relationships between synthesis conditions and the physicochemical properties of the material prepared, has not been available. This Review intends to fill that gap. As known, PTFE and its marginally modified derivatives comprise some 60-65% of the total international fluoropolymer market with a global increase of ca. 7% per annum of its production. Numerous companies, such as Asahi Glass, Solvay Specialty Polymers, Daikin, DuPont/Chemours, Juhua, 3F, 3M/Dyneon, etc., produce TFE homopolymers. Such polymers, both high-molecular-mass materials and waxes, are chemically inert and hydrophobic and exhibit an excellent thermal stability as well as an exceptionally low coefficient of friction. These polymers find use in applications ranging from coatings and lubrication to pyrotechnics, and an extensive industry (electronic, aerospace, wires and cables, and textiles) has been built around them. South Africa, being the third largest producer of fluorspar (CaF2), the precursor to hydrogen fluoride and fluorine, has embarked on an industrial initiative to locally beneficiate its fluorspar reserves, with the local production of fluoropolymers being one projected outcome. As our manuscript focuses specifically on the homopolymerization of TFE (the starting point for all fluoropolymer industries), it will be of considerable use to start-up companies and other commercial entities looking to enter the fluoropolymer market, as well as to end-user companies. The manuscript commences with a short discussion on the synthesis and production of TFE (both at industrial and laboratory scales), including the safety aspects surrounding handling (because that monomer is regarded as explosive if brought into contact with oxygen due to the formation of peroxides), transport, and storage, and then expands into detailed discussions dealing with aspects such as the various additives used (buffers, chain transfer agents, surfactants, etc.), the solvent environment, and the reaction conditions. A further section reports the properties of PTFE with respect to the polymerization conditions as well as an overview on the specialized techniques used to characterize PTFE. Finally, the applications of PTFE in various fields, ranging from electrical insulation to tribological to medical applications, as well as chemically resistant coatings and pyrotechnics, are discussed.

A. Varela, W. Ju, A. Bagger et al.

The electrochemical CO2 reduction reaction (CO2RR) is a promising technology for converting waste CO2 into chemicals which could be used as feedstock for the chemical industry or as synthetic fuels...

I. Aranaz, N. Acosta, C. Civera et al.

Marine resources are well recognized for their biologically active substances with great potential applications in the cosmeceutical industry. Among the different compounds with a marine origin, chitin and its deacetylated derivative—chitosan—are of great interest to the cosmeceutical industry due to their unique biological and technological properties. In this review, we explore the different functional roles of chitosan as a skin care and hair care ingredient, as an oral hygiene agent and as a carrier for active compounds, among others. The importance of the physico-chemical properties of the polymer in its use in cosmetics are particularly highlighted. Moreover, we analyse the market perspectives of this polymer and the presence in the market of chitosan-based products.

Mevan Mustafa, Samir Hasan, Lokman Abdulkareem

This study aims to enhance the performance of asphalt mixes by improving the physical characteristics of bitumen across various temperatures. The focus is on the use of innovative modified bitumen to optimize both fundamental and rheological properties. Bituminous binders are tested with varying additive contents (0%, 0.5%, 1%, and 1.5% by binder weight), incorporating iron oxide and zinc oxide nanoparticles (NPs) into Grade (40/60) bitumen. A comprehensive range of testing methods is employed to evaluate the binders, including penetration, ductility, softening point, aging resistance under heat and air exposure, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and direct tension test. The results demonstrate that the addition of iron oxide and zinc oxide NPs significantly alters the physical behavior of the binders, leading to increased viscosity and improved aging resistance. Notably, the modified bitumen shows an increased softening point and decreased penetration and ductility, indicating a hardening effect, while elastic recovery improves with higher additive percentages, enhancing flexibility. These findings provide valuable insights into the modification of asphalt binder and its impact on the performance of asphalt concrete mixtures, particularly in Hot Mix Asphalt (HMA) applications at elevated temperatures, highlighting the novelty of this approach.

Safeer Arbab, Naveed Alam, Noor Khan Khattak et al.

This research aims to improve the production of geopolymer composites with high tensile strength by utilising local waste resources in Pakistan. Pakistan produces over 49.6 million tonnes of solid waste annually. In this study, we look into the possibility of using local waste streams as raw materials for synthesising geopolymer composites. The investigation thoroughly addresses the formulation of geopolymer matrices, including the precise selection of precursors, activators, and curing conditions according to the region's distinct waste sources. The study's findings encourage a circular economy and sustainable development by demonstrating how locally generated waste resources may be converted into useful building materials. After increasing polyvinyl alcohol content from 0% to 1% in 17 mol/dm3 concentration of NaOH, the material's flexural strength was 4 to 6 MPa. In 17 mol/dm3 concentration of NaOH, the material's compressive strength rises from 30 to 45 MPa upon increasing the PVA fiber content from 0% to 1%. Maximum mechanical strength is achieved at a concentration of 17 mol/dm3 of NaOH. The mechanical strength decreases as the concentration of NaOH rises. Although, geopolymer matrix is mostly amorphous, some crystalline phases may be present, including calcite, quartz, and gehlenite. The findings of these experiments indicate that PVA fibres have little effect on the phase composition of the geopolymer matrix. They improve the composites' mechanical properties by bridging the cracks and preventing their spread. As the SEM data shows, by bridging cracks and stopping their propagation, PVA fibres helped the composite's enhanced toughness. The flexural strength of 4.5 MPa (15% reduction) was found after performing a freeze-thaw cycle. The compressive strength reduces from 35 to 32 MPa with an average mass loss of 3% after performing a salt spray test. The blocks were immersed in water for 24 hours. The water absorption of 8% was measured, indicating effective moisture resistance.

Kai Wu, Zilin Zhang, Xiuhan He et al.

Abstract Nondestructive, rapid, and accurate detection of nutritional compositions in sorghum is crucial for agricultural and food industries. In our study, the crude protein, tannin, and crude fat contents of sorghum variety samples were taken as the research object. The visible near-infrared (VIS-NIR) hyperspectral of sorghum were measured by the indoor mobile scanning platform. The nutritional components were determined using chemical methods to analyze the differences in nutritional composition among different varieties. After preprocessing the original spectral, the competitive adaptive reweighted sampling (CARS) and bootstrapping soft shrinkage (BOSS) algorithms were used to coarsely extract the key variables. Subsequently, the iteratively retains informative variables (IRIV) was employed to assess the importance of these key variables, resulting in explanatory wavelength sets for crude protein, tannin, and crude fat. Finally, the partial least squares (PLS), back propagation (BP) and extreme learning machine (ELM) were utilized to establish detection models. The results indicated that the optimal wavelength variable sets for crude protein, tannin, and crude fat contained 41, 38, and 22 wavelength variables, respectively. The CARS-IRIV-PLS, BOSS-IRIV-PLS and BOSS-IRIV-ELM were suitable for detecting crude protein, tannin and crude fat, respectively. Meanwhile, the Rp 2, RMSEp and RPDp values of the model were 0.69, 0.80% and 1.80, 0.88, 0.22% and 2.84, 0.61, 0.32% and 1.61, respectively. These detection models can be used for the effective estimation of the nutritional compositions in sorghum with VIS-NIR spectral data, and can provide an important basis for the application of food nutrition assessment.

Shunsuke Ichii, Tetsuhiro S. Hatakeyama, Kunihiko Kaneko

Enhanced enzyme diffusion (EED), in which the diffusion coefficient of an enzyme transiently increases during catalysis, has been extensively reported experimentally. We numerically and analytically demonstrate that such enzymes can act as Maxwell's demons. They use their enhanced diffusion as a memory of the previous catalytic reaction, to gain information and drive steady-state chemical concentrations away from chemical equilibrium. Our theoretical analysis identifies the conditions for this process, highlighting the functional role of EED and its relevance to cellular systems.

Tarequl Islam

The printing and labeling industries are struggling to meet the need for more complex and dynamic design requirements coming from the customers. It is now crucial to implement technological advancements to manage workflow, productivity, process optimization, and continual improvement. There has never been a time when the imagery and embellishments of apparel has been more commercially viable as it is now. Images and text are fused directly to fabric by heat transfer printing and labeling. For screen development which is required for heat transfer label mass production, many industries are still using the conventional method of screen development process. A CTS (computer-to-screen) innovates the printing and labeling industries by enhancing workflow, lowering consumable consumptions and chemical usage, speeding up setup, guaranteeing flawless design, and raising the print quality of the producing screens. The study's objective is to assess how CTS machines are used and how they affect existing heat transfer screen development processes in one of Bangladesh's leading printing and labeling companies. The study's primary goal is to highlight and analyze how the use of CTS machines reduces material and operational costs by optimizing the process. Costs for CapEx and OpEx are computed and compared for using CTS technology before and after adoption. Savings data such as material, consumable, and operating cost savings versus depreciation and machine payback period analysis were taken into consideration. It is clear from this study that CTS machines in the printing and labeling industries can guarantee profitability on top of Capital Expenditures.

Tomoya Shiota, Kenji Ishihara, Wataru Mizukami

Accurate prediction of diverse chemical properties is crucial for advancing molecular design and materials discovery. Here we present a versatile approach that uses the intermediate information of a universal neural network potential as a general-purpose descriptor for chemical property prediction. Our method is based on the insight that by training a sophisticated neural network architecture for universal force fields, it learns transferable representations of atomic environments. We show that transfer learning with graph neural network potentials such as M3GNet and MACE achieves accuracy comparable to state-of-the-art methods for predicting the NMR chemical shifts of using quantum machine learning as well as a standard classical regression model, despite the compactness of its descriptors. In particular, the MACE descriptor demonstrates the highest accuracy to date on the ${^{13}}$C NMR chemical shift benchmarks for drug molecules. This work provides an efficient way to accurately predict properties, potentially accelerating the discovery of new molecules and materials.

Wenhao Gao, Priyanka Raghavan, Ron Shprints et al.

A synthetic method's substrate tolerance and generality are often showcased in a "substrate scope" table. However, substrate selection exhibits a frequently discussed publication bias: unsuccessful experiments or low-yielding results are rarely reported. In this work, we explore more deeply the relationship between such publication bias and chemical reactivity beyond the simple analysis of yield distributions using a novel neural network training strategy, substrate scope contrastive learning. By treating reported substrates as positive samples and non-reported substrates as negative samples, our contrastive learning strategy teaches a model to group molecules within a numerical embedding space, based on historical trends in published substrate scope tables. Training on 20,798 aryl halides in the CAS Content Collection$^{\text{TM}}$, spanning thousands of publications from 2010-2015, we demonstrate that the learned embeddings exhibit a correlation with physical organic reactivity descriptors through both intuitive visualizations and quantitative regression analyses. Additionally, these embeddings are applicable to various reaction modeling tasks like yield prediction and regioselectivity prediction, underscoring the potential to use historical reaction data as a pre-training task. This work not only presents a chemistry-specific machine learning training strategy to learn from literature data in a new way, but also represents a unique approach to uncover trends in chemical reactivity reflected by trends in substrate selection in publications.

Takao Tsuneda, Tetsuya Taketsugu

This study offers a physics-based framework for understanding chemical reactions, unveiling the pivotal role of the occupied reactive orbital (ORO), the most stabilized occupied molecular orbital during a reaction, in driving atomic nuclei along the reaction pathway via electrostatic forces. We show that these electrostatic forces are governed by the negative gradient of orbital energy, establishing a direct link between molecular orbital energy variations and nuclear motion. The forces generated by OROs, termed reactive-orbital-based electrostatic forces (ROEFs), were systematically analyzed across 48 representative reactions. Our findings reveal that reactions can be classified into four distinct types, with two dominant types emerging: those that maintain reaction-direction ROEFs either from the early stages or immediately preceding the transition state. These ROEFs carve distinct grooves along the intrinsic reaction coordinates on the potential energy surface, shaping the reaction pathway. Notably, ORO variations align directly with the curly arrow diagrams widely employed in organic chemistry, bridging the curly arrow-like representation of electron transfer with the rigorous potential energy surface framework. This connection highlights the integration of electronic and nuclear motion theories, offering a unified perspective on the forces that drive chemical transformations. By linking orbital energy variations to nuclear motions, this study establishes a robust framework for understanding the interplay between electronic structure and reaction mechanisms.