Voltage cycling process for the electroconversion of biomass-derived polyols

2021 ◽  
Vol 118 (41) ◽  
pp. e2113382118
Author(s):  
Dohyung Kim ◽  
Chengshuang Zhou ◽  
Miao Zhang ◽  
Matteo Cargnello

Electrification of chemical reactions is crucial to fundamentally transform our society that is still heavily dependent on fossil resources and unsustainable practices. In addition, electrochemistry-based approaches offer a unique way of catalyzing reactions by the fast and continuous alteration of applied potentials, unlike traditional thermal processes. Here, we show how the continuous cyclic application of electrode potential allows Pt nanoparticles to electrooxidize biomass-derived polyols with turnover frequency improved by orders of magnitude compared with the usual rates at fixed potential conditions. Moreover, secondary alcohol oxidation is enhanced, with a ketoses-to-aldoses ratio increased up to sixfold. The idea has been translated into the construction of a symmetric single-compartment system in a two-electrode configuration. Its operation via voltage cycling demonstrates high-rate sorbitol electrolysis with the formation of H2 as a desired coproduct at operating voltages below 1.4 V. The devised method presents a potential approach to using renewable electricity to drive chemical processes.

2021 ◽  
Vol 50 (14) ◽  
pp. 4783-4788
Author(s):  
Jie Yang ◽  
Shuanglin He ◽  
Qianqian Wu ◽  
Ping Zhang ◽  
Lin Chen ◽  
...  

A bio-inspired manganese molecular catalyst featuring an intramolecular aniline as a proton relay was synthesized and used for hydrogen production. Electrochemical measurements with this complex show excellent activity (turnover frequency over 104 s−1).


1981 ◽  
Vol 103 (4) ◽  
pp. 307-317
Author(s):  
K. S. Udell ◽  
H. R. Jacobs

The heat transfer to a single cylindrical sample of oil shale in a staggered tube bundle was studied both numerically and experimentally in order to evaluate the thermal and chemical processes associated with the retorting of oil shale in packed beds particular to in-situ processing. The cylinders were subjected to constant gas temperatures and to gas temperature histories experienced in an actual combustion retort. The results of the numerical modeling were compared with the experimental data in order to evaluate the model’s performance. It was found that the model satisfactorily described the thermal processes experienced during the combustion retorting of oil shale within the limits of the accuracy of published data on oil shale thermal properties and chemical kinetics. Net heat transfer to cylindrical oil shale samples in a staggered bundle configuration was also calculated and was shown to nearly duplicate published data related to gas-solid heat transfer in a packed bed combustion retort.


1960 ◽  
Vol 37 (1) ◽  
pp. 83-99 ◽  
Author(s):  
G. W. BRYAN

1. In Bristol tap water containing 0.4 mM./l. sodium and artificial tap water containing 2 mM./l. sodium, Astacus maintains a blood sodium concentration of about 203 mM./l. This value was not markedly affected by starvation periods of up to a month. 2. Methods of taking small blood and urine samples from individual crayfish at intervals over several hundred hours have been described. 3. Under steady state conditions, curves for the uptake and loss of 22Na by the blood are described by equations derived for a one-compartment system. 4. The volume of this single compartment, which exchanges sodium with the medium, is larger than the actual blood volume by an amount roughly equivalent to the sodium in the tissues. Exchange of sodium between the blood and tissues is probably very rapid. 5. Sodium losses in the urine account for about 6% of the total sodium outflux found using 22Na. The urine sodium concentration of about 6 mM./l. was temporarily increased by conditions such as heavy feeding when the blood may have gained additional sodium. 6. Potential difference measurements across the body surface indicate that the high blood sodium concentration is maintained by active uptake of sodium.


1981 ◽  
Vol 8 (1) ◽  
pp. 5-18 ◽  
Author(s):  
Douglas Argyle Campbell

This survey has described the foreseeable environmental and economic impacts of enhanced oil-recovery (EOR) on U.S. oil production between 1980 and 2000. It has indicated that EOR production may be expected to rise from the approximately 4% of total U.S. oil production in 1980, to the projected approximations of 10.5% in 1985, 18.5% in 1990, 23% in 1995, and perhaps 30% in 2000. These percentages are substantial, particularly as this form of oil production has been, up until recently, quite limited. Many of the processes are still in the laboratory stage of development—particularly chemical and microbiological processes. With continued laboratory experimentation and field research, it is possible that the percentages could be even greater than the above suggestions as we reach into the 21st Century.The potential for EOR is very considerable and probably great, as it could involve some two-thirds of all the oil already identified in the United States and assumed to be unrecoverable by primary or secondary means. The U.S. Department of Energy (DOE) has given important incentives to the EOR industry to make such increased production worth while through raising prices to compensate for the cost of equipment, and deducting expenditure on such equipment from a new ‘Windfall Profit Tax’.Along with EOR's economic potential, there are two major ecological dangers: air pollution through thermal processes, and ground-water pollution through chemical processes. It is essential to the well-being of the United States that clean air standards be adhered to, and that the equipment necessary to purify the air (particularly in California) be available and operate to reduce emissions.A great deal more research needs to be undertaken towards developing safeguards to ensure that drinkingwater is not contaminated by dangerous chemicals which may be used in ‘chemical flooding’ of depleted oil-wells. Many of these chemicals have merely ‘come out of the laboratory’ and are sold by chemical companies without sufficient field-testing. How far these chemicals could travel underground must still be determined. It is also important to ensure that carbon dioxide, fed into a geological formation, can be recaptured and re-injected without escaping into the atmosphere, where there is the potential danger of a global ‘greenhouse effect’ upon the world's temperature. Finally, it is important to safeguard the Earth against microbes which could be injected into its geological strata without sufficient knowledge of their impact on the ecology of the Earth. Thus, much environmental research will be called for with these new methods of producing oil for Man's use.This study has reviewed the four major methods of EOR that are currently being utilized or proposed— thermal processes, miscible and semi-miscible processes, chemical processes, and microbiological processes, and found that they could all have ongoing possibilities.Given appropriate environmental safeguards, EOR should become a major force in the production of energy for the United States over the next 20 years, and it seems reasonable to expect that much the same could apply to other parts of the world. However, it is important that safeguarding the environment should guide the DOE in terms of its incentive programmes for specific processes.


Author(s):  
Thomas E. Martin ◽  
Robert W. Mitchell ◽  
Edward D. Boyes ◽  
Pratibha L. Gai

Supported Pt nanoparticles are used extensively in chemical processes, including for fuel cells, fuels, pollution control and hydrogenation reactions. Atomic-level deactivation mechanisms play a critical role in the loss of performance. In this original research paper, we introduce real-time in-situ visualization and quantitative analysis of dynamic atom-by-atom sintering and stability of model Pt nanoparticles on a carbon support, under controlled chemical reaction conditions of temperature and continuously flowing gas. We use a novel environmental scanning transmission electron microscope with single-atom resolution, to understand the mechanisms. Our results track the areal density of dynamic single atoms on the support between nanoparticles and attached to them; both as migrating species in performance degradation and as potential new independent active species. We demonstrate that the decay of smaller nanoparticles is initiated by a local lack of single atoms; while a post decay increase in single-atom density suggests anchoring sites on the substrate before aggregation to larger particles. The analyses reveal a relationship between the density and mobility of single atoms, particle sizes and their nature in the immediate neighbourhood. The results are combined with practical catalysts important in technological processes. The findings illustrate the complex nature of sintering and deactivation. They are used to generate new fundamental insights into nanoparticle sintering dynamics at the single-atom level, important in the development of efficient supported nanoparticle systems for improved chemical processes and novel single-atom catalysis. This article is part of a discussion meeting issue ‘Dynamic in situ microscopy relating structure and function’.


2021 ◽  
Author(s):  
Laxman Gouda ◽  
Laurent Sévery ◽  
Thomas Moehl ◽  
Elena Mas Marzá ◽  
Pardis Adams ◽  
...  

Electrochemical reactions powered by renewable electricity are an important means of reducing the carbon footprint of large-scale chemical processes. Here, we investigate the efficient conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to...


1972 ◽  
Vol 34 (1) ◽  
pp. 53-63 ◽  
Author(s):  
A. K. Thakur ◽  
A. Rescigno ◽  
D. E. Schafer

Author(s):  
Oludare Adedire ◽  
J. N. Ndam

In this research work, we investigate the concentration profiles in the single and the interconnected multiple-compartment systems with sieve partitions for the transport of chemical species with second order chemical reaction kinetics. With assumption of unidirectional transport of chemical species and constant physical properties with same equilibrium contant, the developed partial differential equations representing the two systems are spatially discretized using the Method of Lines (MOL) technique and the resulting semi-discrete system of ODEs are solved using MATLAB ode15s solver. The results show that the interconnected multiple-compartment system has lower concentration profile than the single-compartment system for different values of diffusivities.


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