Research and development of heterogeneous catalysts and of relevant process technologies at Mitsubishi Chemical and its collaborators since 1994 has been reviewed. The basic strategy of them was the ...catalyst design reflecting on the elucidation of reaction mechanism and its kinetics. Ring-opening polymerization catalyzed by grafted solid catalyst into mesoporous support, aerobic oxidation catalyzed by iron oxide using zeolite as an inorganic ligand, interconversion of olefin combined with specific regeneration process, water splitting catalyst showing almost 100% of quantum efficiency, reactive separation breaking through the limit of thermodynamic equilibrium and new innovative MTO catalyst having remarkable steam durability are reviewed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The drastic climate change on global scale is becoming very serious. To curb the anthropogenic CO
2
emissions will be one of the most important issues for the human society in the twenty-first ...century. The chemical industry can contribute to this issue from the viewpoint of green sustainable chemistry. We have been establishing various innovative catalyst technologies and can still continue further efforts. Considering the existence of huge infrastructure of the conventional processes based on fossil resources, it would be very difficult to turn into new technologies based on sustainable resources quickly and straightforwardly. Thus it may be good to apply more practical strategies along the realistic time line. Here we propose a strategy comprised of establishing more energy-effective chemical processes based on fossil resources in short term, utilizing biomasses as chemical feedstocks in large scale in middle term, and pursuit of the artificial photosynthesis as a final goal in long term. In this article, several topics in each category are introduced.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Curbing anthropogenic CO
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emissions is one of the most important issues in the 21st century in order to mitigate climate change. Although the installation of solar cells for energy supply is in ...progress and these are becoming popular as an efficient use of sunlight, they are mostly used by energy-related industrial sectors. In the common chemical industry, various fossil resources are used to emit a huge amount of CO
2
. We believe that the chemical industry can make an effort to curb CO
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emissions by changing its resources to more environmentally benign ones. Solar hydrogen (hydrogen obtained by catalytic water splitting under sunlight) is an ideal sustainable resource and can be utilized as a chemical resource
via
combination with CO
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. The 10 year program named "Artificial Photo Synthetic Chemical Process (ARPChem)" has been in progress under the support of the New Energy and Industrial Technology Development Organization (NEDO) in Japan since 2012. We introduce the strategy of ARPChem and the progress of the investigations including water splitting, hydrogen/oxygen separation, and olefin synthesis from solar hydrogen and CO
2
. We also argue that a realistic strategy to actualize "ARPChem" technologies in the society would be their combination with better fossil resources such as lower alkanes from a Life Cycle Assessment (LCA) point of view.
Sunlight-driven photocatalytic water splitting has been investigated as a potentially scalable and economically feasible means of producing renewable hydrogen. However, reactors suitable for ...efficient water splitting and prompt collection of gaseous products on a large scale have yet to be demonstrated. Here, we demonstrate a sunlight-powered water-splitting reactor using a fixed Al-doped SrTiO3 photocatalyst and address the key issues in the reactor design associated with the scale-up. A panel reactor filled with only a 1-mm-deep layer of water was capable of rapid release of product gas bubbles without forced convection. A flat panel reactor with 1 m2 of light-accepting area retained the intrinsic activity of the photocatalyst and achieved a solar-to-hydrogen energy conversion efficiency of 0.4% by water splitting under natural sunlight irradiation. The concept of a readily extensible water-splitting panel is a viable means for large-scale production of low-cost renewable solar hydrogen.
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•Photocatalytic water-splitting panels sustain a gas evolution rate at 10% STH•A flat panel reactor at the square-meter scale achieves an STH of 0.4% under sunlight•The system design including transport and separation of H2 and O2 gas is presented
Sunlight-driven photocatalytic water splitting is potentially a simple and inexpensive method to generate renewable hydrogen. However, large-scale photocatalytic water splitting under sunlight is yet to be demonstrated, even at bench scale. This work presents a prototype water-splitting panel and addresses the key issues in the reactor design associated with scale-up. Panel reactors filled with only a 1-mm-deep layer of water are capable of rapid release of product gas bubbles without forced convection. Moreover, panel reactors maintain the intrinsic water-splitting activity of particulate photocatalysts regardless of size and thus are readily extensible not only to the level of square meters, but to much larger scales. We propose a whole process design of photocatalytic water splitting, including exhalation of H2 and O2 mixed gas bubbles, their secure transport, and separation, presenting a vision for the future and the challenges of practical solar hydrogen production.
We demonstrate a concept of potentially inexpensive sunlight-powered water-splitting reactors using a fixed Al-doped SrTiO3 photocatalyst. A panel reactor filled with only a 1-mm-deep layer of water was capable of rapid release of product gas bubbles without forced convection. A flat panel reactor with 1 m2 of light-accepting area retained the intrinsic activity of the photocatalyst and achieved a solar-to-hydrogen energy conversion efficiency of 0.4% by water splitting under natural sunlight irradiation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In harmony: Nanoparticles of Mn3O4 and core/shell‐structured Rh/Cr2O3 as cocatalysts on the surface of a solid solution of GaN and ZnO as catalyst promote O2 and H2 evolution, respectively, under ...visible light (λ>420 nm), thereby achieving enhanced water‐splitting activity compared to analogues modified with either Mn3O4 or Rh/Cr2O3.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A multinary nitride, Eu-doped CaAlSiN3, which had previously been synthesized at 1600–1800 °C as a red-emiting phosphor material, was obtained at 500–800 °C via the reaction of a CaAlSi alloy with a ...low concentration of Eu (composition Ca0.992Eu0.008AlSi) in ammonia in the present study. In supercritical ammonia (100 MPa), CaAlSiN3 was formed at temperatures ≥ 500 °C both with and without the addition of sodium amide. The addition of sodium amide significantly facilitated the synthesis and prevented the presence of unreacted silicon, which could be due to the formation of sodium ammonometallates as intermediates in the presence of sodium amide. CaAlSiN3 was synthesized even in an atmospheric ammonia flow, but the crystallinity of the product was rather low. Evidence suggested that CaAlSiN3 was insoluble in the pressurized sodium amide−ammonia medium under the present conditions, and the prolonged reaction of the alloy in ammonia at the CaAlSiN3-forming temperatures (500–800 °C) did not result in an effective improvement of the crystallization. In contrast, well-crystallized samples with plate- and bar-like nanocrystals were synthesized by first converting the alloy at 300–400 °C into sodium ammonometallates and subsequently decomposing the ammonometallates up to 800 °C into CaAlSiN3. The products showed a red emission centered at 630–644 nm at a blue excitation of 460 nm. Instead of using sodium amide, the use of sodium azide, which was converted into sodium amide during heating, led to a product of plate-like crystals with significantly reduced oxide (oxide-free in the XRD spectrum) but did not result in an improved light emission. The size and lattice strain were calculated by refining against the XRD patterns, and the elemental composition was obtained via energy dispersive X-ray analysis on single nanocrystals with TEM observations. The synthetic conditionsstructure and compositionlight emission relationships were discussed. The deficiency in calcium was the determining factor for the decreased light emission.
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IJS, KILJ, NUK, PNG, UL, UM
Solar hydrogen production by photocatalytic water splitting is studied to solve energy and environmental problems. It is estimated that practical implementation of this technology will require a ...photocatalytic water splitting system that is not only highly efficient in solar-to-hydrogen energy conversion but also cheap and scalable. Particulate photocatalyst sheets based on immobilized particulate semiconductors are a promising approach to meet these requirements owing to their scalability without sacrificing their intrinsic water splitting activity. Nevertheless, existing sheet systems have not reached the targeted solar-to-hydrogen energy conversion efficiency yet. This is because the quality of narrow-bandgap photocatalyst materials has not been sufficiently improved, and also because methods for activating such photocatalysts in warm water under ambient pressure, which is assumed to be a practical outdoor operating condition, while suppressing reverse reactions have not been sufficiently developed. This perspective describes recent advancements in photocatalyst sheets and panel reactor systems intended for practical implementation of solar hydrogen production
via
the overall water splitting reaction, and discusses issues regarding the development of photocatalytic systems that can produce solar hydrogen with satisfactory performance.
This article presents progress and challenges in the development of photocatalyst sheets for scalable efficient production of renewable hydrogen
via
water splitting reaction.
We report the effects of synthesis pressure and sodium content in reactants on the lattice structure and photoluminescence properties of Eu‐doped CaAlSiN3, a red phosphor, synthesized by a ...low‐temperature process (up to 800°C) from ammonometallates. The lattice parameters and average and anisotropic values of crystallite size and lattice strains were calculated by refining against X‐ray diffraction data. These values are correlated with synthesis pressure and sodium content. The light emission was shown to be a result of a compromise between the effects of the lattice cell dimensions and the strains. The sample obtained at Na/Ca=2.0 under 100 MPa showed the best photoluminescence emission among all the produced samples. On the other hand, our analysis suggests the optimum pressure and Na/Ca ratio for a maximum light emission could be around 60 MPa and 2, respectively.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
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