Effect of acidity on the performance of a Ni-based catalyst for hydrogen production through propane steam reforming: K-AlSi_<i>x</i>O_<i>y</i> support with different Si/Al ratios

Do, Jeong Yeon,Kwak, Byeong Sub,Park, No-Kuk,Lee, Tae Jin,Lee, Sang Tae,Jo, Seung Won,Cha, Moon Soon,Jeon, Min-Kyu,Kang, Misook Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.36

<P><B>Abstract</B></P> <P>Propane steam reforming (PSR) for the production of H<SUB>2</SUB> was catalyzed by a NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> catalyst synthesized with various Si/Al ratios (Si/Al = 0, 0.3, 0.5, 0.7, and 1.0). The effect of the Si/Al ratio on the acidity of the NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> catalyst for PSR was investigated. NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> gave a higher H<SUB>2</SUB> selectivity and stability during PSR than NiO/K-SiO<SUB>2</SUB> and NiO/K-Al<SUB>2</SUB>O<SUB>3</SUB>. The NH<SUB>3</SUB>-TPD results showed that the acid quantity and strength of NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> changed significantly depending on the Si/Al ratio. With an increased Si/Al ratio, the densities of both weak and strong acid sites increased. The C<SUB>3</SUB>H<SUB>8</SUB>- and CO-TPD results indicated that desorption amounts increased significantly in all NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> catalysts relative to those of NiO/K-SiO<SUB>2</SUB> and NiO/K-Al<SUB>2</SUB>O<SUB>3</SUB>, and the adsorption amount increased with the Si/Al ratio. PSR results showed that the NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> catalyst exhibited much better stability than the NiO/K-SiO<SUB>2</SUB> and NiO/K-Al<SUB>2</SUB>O<SUB>3</SUB> catalysts. This study confirms the following facts: when the acidity is appropriately adjusted for the catalyst, adsorption of the reaction gas increases, which eventually increases the reaction rate and also inhibits strong sintering between the nickel and the Al<SUB>2</SUB>O<SUB>3</SUB> support. As a result, deterioration of the catalyst can be reduced.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> catalyst was synthesized for the production of H<SUB>2</SUB> from PRS. </LI> <LI> The acid quantity and strength of NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> changed significantly depending on the Si/Al ratio. </LI> <LI> The adsorptions of C<SUB>3</SUB>H<SUB>8</SUB> and CO increased with the Si/Al ratio. </LI> <LI> The NiO/K-AlSi<SUB> <I>x</I> </SUB>O<SUB> <I>y</I> </SUB> catalyst exhibited much better stability during PSR. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The catalytic performance for LDPE destruction over aluminum-incorporated mesoporous silicates

Kyung Mi Jeong,강미숙 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.6

The aim of this study was to investigate the aluminum-incorporated mesoporous silicate (Al-MPS) as a thermal catalyst for the destruction of low density polyethylene (LDPE). Various Al-MPS (Si/Al molar ratios = 117.6, 58.8, 39.2 and 29.4) materials were successfully synthesized without any structural damage. With regard to the X-ray diffraction (XRD) pattern, the main peak of 2u = 64.0 in Al2O3 did not show until the incorporation of Si/Al = 58.8. This result implies the aluminum ions were stably substituted into the silicon site of the mesoporous framework. The hexagonal straight pore size increased to about 8.0 nm in Al (Si/Al = 58.8)-MPS, but then decreased in the range of 3.0–5.0 nm in Al (Si/ Al = 29.4)-MPS. In relation to the amount of incorporated aluminum, the Al-MPS absorbed many pyridine molecules, implying the acidities on the external surfaces up to Si/Al = 58.8, but this amount decreased somewhat above a Si/Al ratio of 39.2. The catalytic decomposition of LDPE was enhanced in Al (Si/Al = 58.8)-MPS and particularly, the selectivity to light hydrocarbons below C4 reached 43%.

The catalytic performance for LDPE destruction over aluminum-incorporated mesoporous silicates

Jeong, K.M.,Kang, M. Korean Society of Industrial and Engineering Chemi 2008 Journal of industrial and engineering chemistry Vol.14 No.6

The aim of this study was to investigate the aluminum-incorporated mesoporous silicate (Al-MPS) as a thermal catalyst for the destruction of low density polyethylene (LDPE). Various Al-MPS (Si/Al molar ratios=117.6, 58.8, 39.2 and 29.4) materials were successfully synthesized without any structural damage. With regard to the X-ray diffraction (XRD) pattern, the main peak of 2θ=64.0 in Al<SUB>2</SUB>O<SUB>3</SUB> did not show until the incorporation of Si/Al=58.8. This result implies the aluminum ions were stably substituted into the silicon site of the mesoporous framework. The hexagonal straight pore size increased to about 8.0nm in Al (Si/Al=58.8)-MPS, but then decreased in the range of 3.0-5.0nm in Al (Si/Al=29.4)-MPS. In relation to the amount of incorporated aluminum, the Al-MPS absorbed many pyridine molecules, implying the acidities on the external surfaces up to Si/Al=58.8, but this amount decreased somewhat above a Si/Al ratio of 39.2. The catalytic decomposition of LDPE was enhanced in Al (Si/Al=58.8)-MPS and particularly, the selectivity to light hydrocarbons below C<SUB>4</SUB> reached 43%.

Investigation of the active sites and optimum Pd/Al of Pd/ZSM–5 passive NO adsorbers for the cold-start application: Evidence of isolated-Pd species obtained after a high-temperature thermal treatment

Lee, Jaeha,Ryou, YoungSeok,Cho, Sung June,Lee, Hyokyoung,Kim, Chang Hwan,Kim, Do Heui Elsevier 2018 Applied Catalysis B Vol.226 No.-

<P><B>Abstract</B></P> <P>We investigated the chemisorptive NO adsorption ability at a low temperature (120 °C) of the Pd/ZSM–5 passive NO<SUB>x</SUB> adsorbers (PNA) to address the cold-start NO<SUB>x</SUB> emission. The Pd/ZSM–5 showed a much higher NO adsorption ability after the oxidative treatment at 750 °C compared with the 500 °C treatment; according to the combined EXAFS, XPS and XRD results, atomically dispersed Pd species were formed over the former, while small PdO agglomerates were observed over the latter. The Pd species on the Pd/ZSM–5 were further examined by applying a NH<SUB>4</SUB>NO<SUB>3</SUB>-titration method, where an ion exchange occurred with only the ionic Pd in the zeolite. When the Pd(2)/ZSM–5 was treated at 750 °C, it exchanged ions with an NH<SUB>4</SUB>NO<SUB>3</SUB> solution whereby most of the Pd was ion-exchanged, and this resulted in a decreased NO adsorption capability. Alternatively, a much lesser amount of ion-exchanged Pd was found on the Pd/ZSM–5 that was treated at 500 °C. The combined results indicate that the ionic-Pd species on the ZSM–5, not the bulk PdO, are the active sites for the chemisorptive NO adsorption at the low temperature. The NO adsorption capability was also investigated as a function of the Pd loading and the Si-to-Al<SUB>2</SUB> molar ratio of the ZSM–5. The results suggest that an optimum Pd-to-Al molar ratio exists for the Pd/ZSM–5 with the maximum NO adsorption capability, which was found at around 0.25, thereby suggesting that the Al in the ZSM–5 framework led to the high dispersion of the ionic-Pd species up to the optimum Pd/Al ratio. Above the optimum Pd/Al ratio, however, the bulk-PdO phase formed on the ZSM–5 resulting in a lower NO adsorption capability; that is, the ZSM–5 with the higher Al content required a higher Pd amount for the attainment of the optimum NO adsorption capability. In summary, the chemisorptive NO adsorption at the low temperature is significantly influenced by both the Si-to-Al<SUB>2</SUB> molar ratio and the Pd-to-Al molar ratio of the Pd/ZSM–5 catalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oxidative treatments at 750 °C activated the NO adsorption ability of Pd/ZSM-5. </LI> <LI> Isolated Pd species were formed in ZSM-5 after the oxidative treatment at 750 °C. </LI> <LI> Ionic Pd species turned out to be the active site for adsorbing NO. </LI> <LI> Optimum Pd to Al molar ratio for NO adsorption was found at 0.25. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis of Nanoporous Materials Al-MCM-41 from Natural Halloysite

Yaling Xie,Aidong Tang,HUAMING YANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.1

Nanoporous materials Al-MCM-41 with varying Si/Al molar ratios have been successfully synthesized from natural clay mineral halloysite nanotubes (HNTs). Hydrothermal treatment of acid-pretreated HNTs and NaOH solution resulted in the one-step synthesis of final nanoporous products by using surfactant. The effects of Si/Al molar ratios (7.7, 61.0 and 176.5) on the surface area, porosity and degree of structural order of Al-MCM-41 materials have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption measurements and Fourier transform infrared (FTIR) spectra techniques. The results indicated that Si/Al molar ratio had important effect on the characteristics of nanoporous materials, and Al-MCM-41 with an intermediate Si/Al molar ratio of 61.0 exhibited excellent characteristics with high degree of order, high surface area (SBET) of 1033 m2 /g and pore volume of 0.92 mL/g.

Investigating Various Factors Affecting the Long-Term Compressive Strength of Heat-Cured Fly Ash Geopolymer Concrete and the Use of Orthogonal Experimental Design Method

Hongen Zhang,Lang Li,Prabir Kumar Sarker,Tao Long,Xiaoshuang Shi,Qingyuan Wang,Gaochuang Cai 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.1

This work quantified the hierarchy of the influence of three common mixture design parameters on the compressive strength and the rate of strength increase over the long term of low-calcium fly ash geopolymer concrete (FAGC) through designing 16 mixtures by the orthogonal experimental design (OED) method. The parameters used in the study were liquid to fly ash (L/FA) ratio, sodium hydroxide concentration (SHC) and sodium silicate solution to sodium hydroxide solution (SS/SH) ratio. The L/FA ratio showed little effect on compressive strength when it was varied from 0.40 to 0.52. SHC showed the greatest influence on compressive strength with little impact on the rate of strength increase after the initial heat curing. Even though the SS/SH ratio showed a small effect on the initial compressive strength, it had a considerable influence on the rate of strength increase over the long term. It was found that the compressive strength at 480 days was positively related to the Na₂O/SiO₂ molar ratio when it was varied from 0.49 to 0.80 and the Si/Al molar ratio was increased up to 1.87. Analysis of the failure types of specimens demonstrated that compressive strength of FAGC was associated with the strength of the mortar–aggregate interface zone (MAIZ).

다양한 구조와 양이온을 갖는 제올라이트 분체의 수증기 흡착 거동 연구

송주섭(Ju-Sub Song),Pankaj Sharma,김범주(Beom-Ju Kim),김민지(Min-Zi Kim),한문희(Moon-Hee Han),조철희(Churl-Hee Cho) 한국에너지학회 2014 에너지공학 Vol.23 No.4