The coproduction of methanol (MeOH) and dimethyl ether (DME) from biomass-derived synthesis gas on the coprecipitated Cu-ZnO-Al 2 O 3 /γ-Al 2 O 3 hybrid catalysts has been investigated to overcome the equilibrium conversion of CO on the MeOH only synthetic reaction at the H 2 -decificient condition. Two different types of γ-Al 2 O 3 were employed as the solid-acid component of hybrid catalyst: one prepared by a precipitation method and the other prepared by a sol-gel method. Several hybrid catalysts were prepared by the coprecipitation method in the slurry of γ-Al 2 O 3 with the variation in the weight ratio of MeOH synthesis catalyst (Cu-ZnO-Al 2 O 3 ) to solid-acid catalyst (γ-Al 2 O 3 ) as well as by changing aging time during synthesis. The catalytic activity results revealed that the best yield of MeOH and DME with concomitant decrease in the CO 2 formation was obtained on the hybrid catalyst containing γ-Al 2 O 3 prepared by the sol-gel method with an aging time of 6 h. The hybrid catalysts were characterized by using the BET surface area measurements, NH 3 temperature programmed desorption (NH 3 -TPD), scanning electron microscopy (SEM), temperature programmed reduction (TPR), and X-ray diffraction (XRD) methods. The observed catalytic properties were related to the surface area of Cu metal, dispersion of Cu-ZnO-Al 2 O 3 particles, and reducibility and acidity of hybrid catalysts. The enhanced catalytic activity with low selectivity to CO 2 is attributed to the facile reducibility of welldispersed copper oxides at low temperatures and also to the benign acid strength of the hybrid catalysts.

The removal efficiency of dimethyl sulfide (DMS), tert-butylmercapatan (TBM), and tetrahydo thiophene (THT) was investigated for applying to hydrogen station. The sorbents such as Cu/Al 2 O 3 , ZnO/Al 2 O 3 , Cu/ ZnO, and Cu/ZnO/Al 2 O 3 were prepared by the coprecipitation method and characterized by XRD, surface area, and pore size distribution measurements. Among the various sorbents employed for the removal sulfur compounds, the Cu/ZnO/Al 2 O 3 exhibits superior activity compared to the conventional ZnO sorbent (G-72D) as well as the others. The order of sorption capacity for the removal sulfur compounds after hydrodesulfurization (HDS) was found to be Cu/ZnO

Recently, air pollution has worsened throughout the world, and as regulations on nitrogen oxides (NOx) are gradually tightened many researchers and industrialists are seeking technologies to cope with them. In order to meet the stringent regulations, research is being actively conducted worldwide to reduce NOx-causing pollution. However, different countries tend to have different research trends because of their regional and industrial environments. In this paper, the results of recent catalyst studies on NOx removal by selective catalytic reduction are reviewed with the sources and regulations applied according to the national characteristics of South Korea. Specifically, we emphasized the three major NOx emissions sources in South Korea such as plant, automobile, and ship industries and the catalyst technologies used.

The amount of carbon formed and the H2/CO molar ratio for the carbon dioxide reforming (CDR) reaction with methane were investigated on Ni/Al2O3 catalyst using a laboratory-scale fixed-bed reactor and a bench-scale fluidized-bed reactor. A significant suppression of carbon deposition in the fluidized-bed reactor compared with the fixed-bed reactor can be mainly induced from different product gas flow patterns by the continuous circulation of catalysts in oxidizing and reducing regions. This approach also enhances the gasification rate of deposited carbon in an expanded catalyst bed by increasing the amount of water adsorbed. The higher H2/CO ratio above 1.0 in the fluidized-bed reactor is also attributed to the enhanced gasification rate of deposited carbon precursors. The differences in the conversions of CH4 and CO2 and the H2/CO ratios in the two reactors are responsible for the different competitive rates of the reverse water–gas shift (RWGS) reaction, the Boudouard reaction, and the gasification of carbon precursors.

The hydrodynamics and heat transfer characteristics were investigated in a slurry bubble column reactor whose diameter was 0.0508 m (ID) and 1.5 m in height. Effects of gas velocity (0.025-0.1 m/s), pressure (0.1-0.7 MPa), solid concentration (0-20 vol%) and liquid viscosity (1.0-38.0 mPa s) on the hydrodynamics and heat transfer characteristics were examined. The pressure difference fluctuations were analyzed by means of attractor trajectories and correlation dimension to characterize the hydrodynamic behavior in the column. The gas holdup increased with increasing gas velocity or pressure, but decreased with increasing solid concentration or liquid viscosity. It was found that the attractor trajectories and correlation dimension of pressure fluctuations were effective tools to describe the hydrodynamic behaviors in the slurry bubble column. The heat transfer coefficient increased with increasing pressure or gas velocity, but decreased with increasing solid concentration or viscosity of slurry phase in the slurry bubble column. The heat transfer coefficient value was well correlated in terms of operating variables and correlation dimension of pressure fluctuations in the slurry bubble column.

Volatile organic compounds (VOCs) are toxic and are considered the most important sources for the formation of photochemical smog, secondary organic aerosols (SOAs), and ozone. These can also greatly affect the environment and human health. For this reason, VOCs are removed by applying various technologies or reused after recovery. Catalytic oxidation for VOCs removal is widely applied in the industry and is regarded as an efficient and economical method compared to other VOCs removal technologies. Currently, a large amount of VOCs are generated in industries with solvent-based processes, and the ratio of aromatic compounds is high. This paper covers recent catalytic developments in VOC combustion over noble-metal-based catalysts. In addition, this report introduces recent trends in the development of the catalytic mechanisms of VOC combustion and the deactivation of catalysts, such as coke formation, poisoning, sintering, and catalyst regeneration. Since VOC oxidation by noble metal catalysts depends on the support of and mixing catalysts, an appropriate catalyst should be used according to reaction characteristics. Moreover, noble metal catalysts are used together with non-noble metals and play a role in the activity of other catalysts. Therefore, further elucidation of their function and catalytic mechanism in VOC removal is required.

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