Effect of Palladium and Nickel on the Temperature Programmed Reduction of Metal Oxides and Metal Oxide Layers

김종팔 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.2

A new binary oxide support was suggested as being useful in many commercial reactions. Our study wasfocused on the reduction effect of metal oxide layer on alumina during reaction. Hence temperature programmedreduction of both bulk metal oxide and metal oxide layer on alumina was studied first and the effect of palladium andnickel on the reduction of the oxide support was also investigated. Vanadium oxide was mainly studied and niobiumoxide, tantalum oxide, titanium oxide and zirconium oxide were also compared. Some metal oxides were reduced ina hydrogen stream at elevated temperature. In these cases both the bulk metal oxide and metal oxide layer werereduced. A tiny amount of palladium or nickel afected the reduction by decreasing the reduction temperature. Thedecrease of the reduction temperature was explained by means of increased adsorption of hydrogen on the transitionmetal and ability of the metal to spillover of the hydrogen to the oxides.

Effect of Palladium and Nickel on the Temperature Programmed Reduction of Metal Oxides and Metal Oxide Layers

Kim, Jong Pal 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.2

A new binary oxide support was suggested as being useful in many commercial reactions. Our study was focused on the reduction effect of metal oxide layer on alumina during reaction. Hence temperature programmed reduction of both bulk metal oxide and metal oxide layer on alumina was studied first and the effect of palladium and nickel on the reduction of the oxide support was also investigated. Vanadium oxide was mainly studied and niobium oxide, tantalum oxide, titanium oxide and zirconium oxide were also compared. Some metal oxides were reduced in a hydrogen stream at elevated temperature. In these cases both the bulk metal oxide and metal oxide layer were reduced. A tiny amount of palladium or nickel affected the reduction by decreasing the reduction temperature. The decrease of the reduction temperature was explained by means of increased adsorption of hydrogen on the transition metal and ability of the metal to spillover of the hydrogen to the oxides.

Study on the structure of reduced graphene oxide prepared by different reduction methods

Xiang Xu,Zhu Ying,Gao Changqin,Du Han,Guo Chunwen 한국탄소학회 2022 Carbon Letters Vol.32 No.2

The reduced graphene oxide (rGO) has attracted more and more attention in recent years. How to choose a suitable reduction method to prepare rGO is a critical problem in the preparation of graphene composites. In this work, the differences of rGO reduced by thermal, microwave, Ultraviolet (UV) and reducing agent were studied. The reduction degree and functional groups of rGO were compared by SEM, XPS, Raman, FTIR and TGA. Thermal can remove most of the oxygen-containing groups of graphene oxide (GO) and the thermal reduction is the most effective reduction method. UV light can directly act on the unstable oxygen-containing groups, and its reduction efficiency is second only to thermal reduction. The efficiency of chemical reduction is not as good as that of UV reduction, because the reducing agent only act on the surface of GO. Microwave reduction is a mild thermal reduction with the lowest efficiency, but the residual oxygen-containing groups increase the hydrophilicity of rGO. To sum up, this work studies that rGO prepared by different reduction methods has different characteristics, which provides a reference for selecting appropriate reduction methods to prepare graphene composites with better properties.

Hydrogen Reduction of a Black Nickel Oxide Ore in a Fluidized-Bed Reactor without Sticking

Oh, Chang Sup,Hong, Seung-Hun,Lee, Dong-Kyu,Kim, Hang Goo,Kim, Yong Ha Materials Research Society of Korea 2017 한국재료학회지 Vol.27 No.2

A black nickel oxide powder, one of the commercial nickel oxide ores, was reduced by hydrogen gas in a batch-type fluidized-bed reactor in a temperature range of 350 to $500^{\circ}C$ and in a residence time range of 5 to 120 min. The hydrogen reduction behavior of the black nickel oxide was found to be somewhat different from that of green nickel oxide ore. For the black nickel oxide, the maximum temperature (below which nickel oxide particles can be reduced without any agglomeration) was significantly lower than that observed for the green nickel oxide. In addition, the best curve fittings of the Avrami model were obtained at higher values of the overall rate constant "k" and at lower values of the exponent "m", compared to those values for the green nickel oxide. It may be inferred from these results that the hydrogen reduction rate of the black nickel oxide is faster than that of the green nickel oxide in the early stages, but the situation reverses in the later stages. For the black nickel oxide ore, in spite of the low temperature sintering, it was possible to achieve a high degree fluidized-bed reduction at lower temperatures and at lower gas consumption rates than was possible for the green nickel oxide. In this regard, the use of black nickel oxide is expected to yield a benefit if its ore price is sufficiently lower than that of the green nickel oxide.

A Kinetics of Hydrogen Reduction of Nickel Oxide at Moderate Temperature

Dong Soo Lee,Dong Joon Min 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4

Nano-metallic nickel powders are highly-valued materials applied in energy, electronic devices and aerospace, which isknown to be produced by the gaseous phase reduction method of NiCl 2 . In the case of a gaseous reduction method, sizecontrol is diffi cult due to the agglomeration of nickel powders. Therefore, a method of producing highly-valued nickel nanopowdersfrom Ni(OH) 2 has been proposed. Considering the reduction behavior of bulk nickel oxide has been reported tofollow the topo-chemical model. However, reduction behavior of nano-particle is expected to be unknown state. It is necessaryto clarify the mechanism of nickel oxide nano-particle reduction. Therefore, in this study, the temperature dependence andparticle size dependence on the reduction behavior of from micro scale to nano scale particle was confi rmed through TGAexperiment. Also, the reduction mechanism of nickel oxide powder was also investigated based on kinetic considerationsusing the grain topo-chemical model. It was confi rmed that the reduction reaction of nickel oxide powder undergoes throughthe 2nd Avrami model and reduction rate can be expressed by function of temperature and particle size of the powder. Dueto the part of the diff usion, the particle size of the powder also aff ects the rate constant of the reduction reaction. g(x) = k ⋅ f(d) ⋅ t

코발트 산화물과 지지체 표면의 코발트 산화물의 환원에 니켈과 팔라듐 첨가의 효과

김종팔,이광현 동의대학교 산업기술개발연구소 2006 産業技術硏究誌 Vol.20 No.-

A binary oxide support was suggested as being useful in many commercial reactions. This study was focused on the reduction effect of metal oxide on alumina surface. Hence temperature programmed reduction of both bulk metal oxide and metal oxide on alumina surface was studied first and effect of nickel and palladium on the reduction of the metal oxides was also investigated. Cobalt oxide was studied and it was reduced in a hydrogen stream at elevated temperature. In these cases both the bulk metal oxide and metal oxide on surface were reduced. A tiny amount of palladium or nickel affected the reduction by decreasing the reduction temperature. The decrease of the reduction temperature was explained by means of increased adsorption of hydrogen on the transition metal and ability of the metal to spillover of the hydrogen to the oxides.

산화물 사용후핵연료 전해환원 화학 반응 계산 및 동적 모사를 위한 반실험 모델

박병흥,허진목,이한수 한국방사성폐기물학회 2010 방사성폐기물학회지 Vol.8 No.1

Electrolytic reduction technology is essential for the purpose of adopting pyroprocessing into spent oxide fuel as an alternative option in a back-end fuel cycle. Spent fuel consists of various metal oxides, and each metal oxide releases an oxygen element depending on its chemical characteristic during the electrolytic reduction process. In the present work, an electrolytic reduction behavior was estimated for voloxidized spent fuel based on the assumption that each metal-oxygen system is independent and behaves as an ideal solid solution. The electrolytic reduction was considered as a combination of a Li recovery and chemical reactions between the metal oxides such as uranium oxide and the produced Li metal. The calculated result revealed that most of the metal oxides were reduced by the process. It was evaluated that a reduced fraction of lanthanide oxides increased with a decreasing Li2O concentration. However, most of the lanthanides were expected to be stable in their oxide forms. In addition,a semi-empirical model for describing U3O8 electrolytic reduction behavior was proposed by considering Li diffusion and a chemical reaction between U3O8 and Li. Experimental data was used to determine model parameters and, then, the model was applied to calculate the reduction yield with time and to estimate the required time for a 99.9% reduction. 고온 용융염 전해환원 공정은 후행핵연료 주기의 대안 공정인 파이로공정의 산화물 사용후핵연료의 확대를 위해 필수적인 공정이다. 사용후핵연료는 다성분 산화물로 이루어져 있으며 각 산화물은 전해환원 공정에서 화학적 특성에 따라 산소를 잃게 된다. 본 연구에서는 건식분말화 공정 이후 전해환원 반응기에 도입되는 사용후핵연료 조성을 기준으로 각 금속-산소 시스템을 독립적인 이상고용체로 가정하여 전해환원 반응거동을 계산하였다. 전해환원을 Li의 환원과 이어지는 Li과의 화학반응의 결합으로 산정하여 U을 비롯한 금속 환원 거동을 계산하였다. 계산결과 대부분의 산화물들은 전해환원 공정에 의해 금속으로 전환되는 것으로 예상되었다. 란타나이드 원소들의 경우 Li2O의 농도가 낮아지면 금속 전환율이 높아지나 대부분 산화물로존재하는 것으로 나타났다. 추가적으로 U3O8의 전해환원 거동에 대해 Li의 확산과 Li과의 화학반응을 고려하여 반실험적 모델이 제시되었다. 실험데이터를 활용하여 매개변수를 결정하였으며 시간에 대한 환원율 및전류에 대한 99.9% 환원 시간을 계산하였다.

산화물 환원공정에 의해 제작된 n-형 Bi2Te2.7Se0.3 화합물의 열전특성연구

임영수,박배건,이길근 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.5

We report the thermoelectric transport properties of n-type Bi2Te2.7Se0.3 compounds prepared by oxide-reduction process. The oxide-reduction process is a recently developed method that can synthesize Bi2Te3-based compounds using only oxide starting materials, which is advantageous in terms of the diversity of the starting materials and cost efficiency. In this study, starting materials of Bi2O3,TeO2 and SeO2 were ball-milled for homogenous mixing, and then oxidized to prepare mixed oxide powders. The mixed oxide powders were reduced at different reduction temperatures (573, 603, 633 and 663 K) for 7 h under hydrogen atmosphere. A single phase of Bi2Te2.7Se0.3 could be achieved when the reduction temperature was higher than 603 K, and the shape of the particles changed from granules to flakes with increasing reduction temperature. Furthermore, the formation of antisite defects of BiSe was promoted by increasing reduction temperature, which strongly affected the electrical and thermal transport properties of the Bi2Te2.7Se0.3 compounds, which were prepared by spark plasma sintering of the reduced powders. The anisotropic microstructures in the sintered bodies were significantly influenced by the shape of the reduced powders, which was also controlled by the reduction temperature. The thermoelectric transport properties were characterized at room temperature, and the detailed effects of the reduction temperature on these properties are discussed in terms of the anisotropic microstructure and antisite defects.

산화물 환원공정에 의한 n형 Bi2Te2.7Se0.3 화합물의 합성과 열전특성

임영수,박배건,이길근 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.6

We present a study on the synthesis of Bi2Te2.7Se0.3 powders through an oxide reduction process and also on the effect of the oxide reduction process on the thermoelectric transport properties of the resulting Bi2Te2.7Se0.3 compounds. Starting materials of Bi2O3, TeO2 and SeO2 were mechanical milled for homogeneous mixing, and then oxidized to prepare complex oxide powders. The complex oxide powders were reduced at different reduction temperatures under hydrogen atmosphere, and a single phase of Bi2Te2.7Se0.3 could be achieved in the reduced powder, with shorter reduction times as the reduction temperature was increased. The shape of the synthesized powder particles changed from granules to flakes with increasing reduction temperature and longer reduction time. Bi2Te2.7Se0.3 powders with different shapes were consolidated by spark plasma sintering (SPS). The SPSed Bi2Te2.7Se0.3 compounds exhibited anisotropic n-type thermoelectric transport properties along the vertical and parallel planes with respect to the pressing direction of the SPS. The degree of anisotropy in the thermoelectric properties was quite consistent with the degree of anisotropy in the microstructure, which originated from the anisotropic shapes in the Bi2Te2.7Se0.3 powders depending on the reduction conditions. Detailed thermoelectric transport properties of the n-type Bi2Te2.7Se0.3 compounds were interpreted in terms of anti-site defect formation and their structural anisotropy.

온실가스 감축 제도 및 아산화질소 감축 배출권 현황과 전망

이상구(Sang Goo Lee),하종욱(Jong-Wook Ha),박인준(In Jun Park),김정훈(Jeong-Hoon Kim),손은호(Eun-Ho Sohn),이수복(Soo-Bok Lee) 한국에너지기후변화학회 2017 에너지기후변화학회지 Vol.12 No.2

The important contents of Kyoto mechanism for greenhouse gas emission reduction, and of Korean Greenhouse Emission Trading System and certification method of offset credits were investigated and summarized. High revenue from the sale of CDM certified emission reduction of nitrous oxide from adipic acid production caused the carbon leakage which could not lead to the substantial emission reduction of nitrous oxide. Therefore, European Commission prohibited the use of the international credit for CDM project of nitrous oxide reduction in adipic acid production in EU ETS as of Jan. 1, 2013. It is prospected that the certificated emission reduction of nitrous oxide in adipic acid production will not be permitted in the future. The CDM certificated emission reduction of nitrous oxide in nitric acid production and caprolactam production will be consistently permitted in the future. Additional certificated emission reduction may not be occurred in domestic nitric acid production and caprolactam production because the certificated emission reductions in all domestic production have been issued. In the future, the technologies for emission reduction in nitrous oxide production and semiconductor and LCD production where nitrous oxide is used as an oxidizer will be expected to be developed and there certified emission reduction will be issued at home and abroad.