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.

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.

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

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.

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 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.

Urtica dioica extract as a facile green reductant of graphene oxide for UV resistant and corrosion protective polyurethane coating fabrication

M. Mahmudzadeh,H. Yari,B. Ramezanzadeh,M. Mahdavian 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.78 No.-

Reduction of graphene oxide still is one of discussion subjects in scientific communities. The use of toxicchemicals like hydrazine is a well-known procedure for graphene oxide reduction. In this paper, a newecofriendly, fully scalable, and cheap approach with easy procedure on industrial scale for producingreduced graphene oxide is introduced. The studied method was based on successful reduction ofgraphene oxide by urtica dioica leaves’ extract in 1 h at 90 C. Raman spectroscopy evidenced thesignificant removal of considerable oxygen functional groups in graphene oxide after reduction. Improving corrosion properties by helping the functionalization ability of u. dioica leaves’ extract forsuperior dispersion in polyurethane coatings was studied as well. Electrochemical impedancespectroscopy measurements along with salt spray exposure test revealed the remarkable role ofresultant reduced graphene oxide in protective function of polyurethane coatings before and afteraccelerated weathering condition. Impedance value in low frequency diagrams reveals more than 99%protection efficiency indicating the great role of u. dioica in barrier property of PU coatings afteraccelerated weathering condition.