385 research outputs found
Computational Investigation of Microreactor Configurations for Hydrogen Production from Formic Acid Decomposition Using a Pd/C Catalyst
Get PDFThe need to replace fossil fuels with sustainable alternatives has been a critical issue in recent years. Hydrogen fuel is a promising alternative to fossil fuels because of its wide availability and high energy density. For the very first time, novel microreactor configurations for the formic acid decomposition have been studied using computational modeling methodologies. The decomposition of formic acid using a commercial 5 wt % Pd/C catalyst, under mild conditions, has been assessed in packed bed, coated wall, and membrane microreactors. Computational fluid dynamics (CFD) was utilized to develop the comprehensive heterogeneous microreactor models. The CFD modeling study begins with the development of a packed bed microreactor to validate the experimental work, subsequently followed by the theoretical development of novel microreactor configurations to perform further studies. Previous work using CFD modeling had predicted that the deactivation of the Pd/C catalyst was due to the production of the poisoning species CO during the reaction. The novel membrane microreactor facilitates the continuous removal of CO during the reaction, therefore prolonging the lifetime of the catalyst and enhancing the formic acid conversion by approximately 40% when compared to the other microreactor configurations. For all microreactors studied, the formic acid conversion increases as the temperature increases, and the liquid flow rate decreases. Further studies revealed that all microreactor configurations had negligible internal and external pore diffusion resistances. The detailed models developed in this work have provided an interesting insight into the intensification of the formic acid decomposition reaction over a Pd/C catalyst
Breaking the temperature barrier: Unveiling the potential of ceria nanorods for low temperature thermochemical water splitting
No full textThermochemical Water-Splitting (TCWS) is a promising approach for generating clean hydrogen (H2) by employing the waste heat originating from different sources. High-temperature requirements and temperature swing approach hinder the widespread adoption of TCWS for clean hydrogen production. This study explores ceria nanorods (CeNRs) as a potential solution for overcoming these limitations. Herein, we report, the TCWS in a fixed bed reactor using CeNRs at low and constant temperature of 400 °C. We systematically explore the influence of synthesis parameters on the resulting CeNRs, including the selection of ceria precursor, effect of calcination, and their impact in TCWS. It was found that CeNRs prepared using cerium chloride as the precursor exhibited enhanced TCWS activity, resulting significantly higher total H2 yield 4.74 mL/g, at a constant temperature of 400 °C in three redox cycles. Moreover, X-ray Photoelectron Spectroscopy (XPS) analysis confirms the presence of both Ce3+ and Ce4+ states within the structure, with Ce3+ constituting approximately 30 % and Ce4+ accounting for approximately 70 % of the total cerium content. Additionally, Raman spectroscopy corroborates the presence of a higher concentration of oxygen vacancy which are beneficial for increasing the hydrogen production. We demonstrate that ceria in its nanorod structure having exposed higher proportions of (110) and (100) planes and higher concentration of oxygen vacancies is beneficial for lowering TCWS temperature as well as increasing the hydrogen yield
Hydrogenation of carbon dioxide (CO₂) to fuels in microreactors: a review of set-ups and value-added chemicals production
Get PDFClimate change, the greenhouse effect and fossil fuel extraction have gained a growing interest in research and industrial circles to provide alternative chemicals and fuel synthesis technologies. Carbon dioxide (CO2) hydrogenation to value-added chemicals using hydrogen (H2) from renewable power (solar, wind) offers a unique solution. From this aspect this review describes the various products, namely methane (C1), methanol, ethanol, dimethyl ether (DME) and hydrocarbons (HCs) originating via CO2 hydrogenation reaction. In addition, conventional reactor units for the CO2 hydrogenation process are explained, as well as different types of microreactors with key pathways to determine catalyst activity and selectivity of the value-added chemicals. Finally, limitations between conventional units and microreactors and future directions for CO2 hydrogenation are detailed and discussed. The benefits of such set-ups in providing platforms that could be utilized in the future for major scale-up and industrial operation are also emphasized
Comprehensive Review on Two-Step Thermochemical Water Splitting for Hydrogen Production in a Redox Cycle
Get PDFThe interest in and need for carbon-free fuels that do not rely on fossil fuels are constantly growing from both environmental and energetic perspectives. Green hydrogen production is at the core of the transition away from conventional fuels. Along with popularly investigated pathways for hydrogen production, thermochemical water splitting using redox materials is an interesting option for utilizing thermal energy, as this approach makes use of temperature looping over the material to produce hydrogen from water. Herein, two-step thermochemical water splitting processes are discussed and the key aspects are analyzed using the most relevant information present in the literature. Redox materials and their compositions, which have been proven to be efficient for this reaction, are reported. Attention is focused on non-volatile redox oxides, as the quenching step required for volatile redox materials is unnecessary. Reactors that could be used to conduct the reduction and oxidation reaction are discussed. The most promising materials are compared to each other using a multi-criteria analysis, providing a direction for future research. As evident, ferrite supported on yttrium-stabilized zirconia, ceria doped with zirconia or samarium and ferrite doped with nickel as the core and an yttrium (III) oxide shell are promising choices. Isothermal cycling and lowering of the reduction temperature are outlined as future directions towards increasing hydrogen yields and improving the cyclability.ChemE/Catalysis Engineerin
CO<sub>2</sub> Capture and Reduction: Placing the process in an industrial framework
No full textCapturing and utilizing the emissions of CO2 has become a method to reduce the occurring emissions from industrial flue gases. One of the methodologies to capture and use the CO2 is through the CO2 capture and reduction (CCR) process. This process uses a bi-functional catalyst to capture CO2 from diluted gas streams and subsequently reduce it to CO in the presence of H2. The obtained product (syngas) can be further used as feedstock in for example the Fischer-Tropsch process. To implement a novel technology in industry, thetechnology itself should be economical feasible.To determine the feasibility of the process a technoeconomical analysis is executed. The analysis uses process parameters obtained by evaluating the catalytic activity of the bifunctional catalysts. Two catalyticsystems have been evaluated: Cu-K/𝛾-Al2O3 and FeCrCuK/PMG20. Effect on the synthesis conditions of Cu-K/𝛾-Al2O3 were also investigated. Cu-K/𝛾-Al2O3without additional drying steps during the synthesis shows a higher CO2 capacity and a faster CO production rate compared to the other catalysts. Furthermore, toestimate the H2 requirement in an industrialized process the consumption of H2 during the process has been quantified.To ensure a continuous process operation, a two reactor process has been proposed in the techno-economical analysis. The sizing and subsequent cost of the process equipment has been determined by utilizing the obtained process parameters. Besides the capital costs, the operating costs were also estimated to determine the profitability of the process. After the monetary benefit of selling the syngas was determined, it could be stated that the process is profitable under certain conditions. The process is profitable if the used H2 source has a buying price below 2.4 to ensure a profitable process.Applied Science
QTrim : a novel tool for the quality trimming of sequence reads generated using the Roche/454 sequencing platform
Get PDFBackground
Many high throughput sequencing (HTS) approaches, such as the Roche/454 platform, produce sequences in which the quality of the sequence (as measured by a Phred-like quality scores) decreases linearly across a sequence read. Undertaking quality trimming of this data is essential to enable confidence in the results of subsequent downstream analysis. Here, we have developed a novel, highly sensitive and accurate approach (QTrim) for the quality trimming of sequence reads generated using the Roche/454 sequencing platform (or any platform with long reads that outputs Phred-like quality scores).
Results
The performance of QTrim was evaluated against all other available quality trimming approaches on both poor and high quality 454 sequence data. In all cases, QTrim appears to perform equally as well as the best other approach (PRINSEQ) with these two methods significantly outperforming all other methods. Further analysis of the trimmed data revealed that the novel trimming approach implemented in QTrim ensures that the prevalence of low quality bases in the resulting trimmed data is substantially lower than PRINSEQ or any of the other approaches tested.
Conclusions
QTrim is a novel, highly sensitive and accurate algorithm for the quality trimming of Roche/454 sequence reads. It is implemented both as an executable program that can be integrated with standalone sequence analysis pipelines and as a web-based application to enable individuals with little or no bioinformatics experience to quality trim their sequence data
Lack of social security, exploitation at work and lack of government assistance are the main problems faced by female domestic workers in the city, the report stated.
No full textOriginal Article can be viewed from http://indianexpress.com/article/cities/pune/some-good-from-unpleasant-work-they-spend-on-childrens-schooling/♦Almost 50 per cent of female domestic workers illiterate…
♦41 per cent of domestic workers send their children to private schools…
♦ Average monthly income of a family of a female domestic worker is Rs 7,772
♦13 per cent of female domestic workers spent upto Rs 5000 on their wards’ education….
These are findings of a study by Prashant Bansode and Sunil Bhosale of the Gokhale Institute of Politics and Economics, submitted last month to the Indian Council of Social Science Research
Greener and facile synthesis of Cu/ZnO catalysts for CO<sub>2</sub>hydrogenation to methanol by urea hydrolysis of acetates
No full textCu/ZnO-based catalysts for methanol synthesis by COx hydrogenation are widely prepared via co-precipitation of sodium carbonates and nitrate salts, which eventually produces a large amount of wastewater from the washing step to remove sodium (Na+) and/or nitrate (NO3-) residues. The step is inevitable since the remaining Na+ acts as a catalyst poison whereas leftover NO3- induces metal agglomeration during the calcination. In this study, sodium- and nitrate-free hydroxy-carbonate precursors were prepared via urea hydrolysis co-precipitation of acetate salt and compared with the case using nitrate salts. The Cu/ZnO catalysts derived from calcination of the washed and unwashed precursors show catalytic performance comparable to the commercial Cu/ZnO/Al2O3 catalyst in CO2 hydrogenation at 240-280 °C and 331 bar. By the combination of urea hydrolysis and the nitrate-free precipitants, the catalyst preparation is simpler with fewer steps, even without the need for a washing step and pH control, rendering the synthesis more sustainable. This journal is </p
Liquid-Liquid-Gas Triphasic Hydrogenation of Bicarbonate to Formate in a Continuous Flow Tubular Reactor
No full textMultiphasic reaction of bicarbonate hydrogenation to form formate using homogeneous Ru PNP pincer catalyst in a continuous flow tubular reactor is reported. The reaction system consists of three phases. Catalyst is dissolved in toluene while potassium bicarbonate is dissolved in water. The significance of efficient mixing among the organic phase, aqueous phase and gaseous hydrogen to improve hydrogenation reaction by using different inert packing materials is studied by operando visualization and also quantitatively discussed. The bicarbonate conversion of up to 67% is achieved after optimization of important reaction and reactor parameters. The designed reactor setup comprised of effective recycling system that recycles the catalyst with >99% activity.ChemE/Catalysis Engineerin
Characterizing the emergence and persistence of drug resistant mutations in HIV-1 subtype C infections using 454 ultra deep pyrosequencing.
Get PDFBACKGROUND: The role of HIV-1 RNA in the emergence of resistance to antiretroviral therapies (ARTs) is well documented while less is known about the role of historical viruses stored in the proviral DNA. The primary focus of this work was to characterize the genetic diversity and evolution of HIV drug resistant variants in an individual's provirus during antiretroviral therapy using next generation sequencing. METHODS: Blood samples were collected prior to antiretroviral therapy exposure and during the course of treatment from five patients in whom drug resistance mutations had previously been identified using consensus sequencing. The spectrum of viral variants present in the provirus at each sampling time-point were characterized using 454 pyrosequencing from multiple combined PCR products. The prevalence of viral variants containing drug resistant mutations (DRMs) was characterized at each time-point. RESULTS: Low abundance drug resistant viruses were identified in 14 of 15 sampling time-points from the five patients. In all individuals DRMs against current therapy were identified at one or more of the sampling time-points. In two of the five individuals studied these DRMs were present prior to treatment exposure and were present at high prevalence within the amplified and sequenced viral population. DRMs to drugs other than those being currently used were identified in four of the five individuals. CONCLUSION: The presence of DRMs in the provirus, regardless of their observed prevalence did not appear to have an effect on clinical outcomes in the short term suggesting that the drug resistant viral variants present in the proviral DNA do not appear to play a role in the short term in facilitating the emergence of drug resistance
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