Stabilization of Pt at the inner wall of hollow spherical SiO₂ generated from Pt/hollow spherical SiC for sulfuric acid decomposition

Khan, Hassnain Abbas,Natarajan, Prakash,Jung, Kwang-Deog Elsevier 2018 Applied catalysis. B, Environmental Vol.231 No.-

<P><B>Abstract</B></P> <P>Catalysts for sulfuric acid (SA) decomposition, one of three reactions in Sulfur-Iodine (SI) cycle to produce hydrogen, should be active and stable up to 800–900 °C. Here, a SiC hollow sphere supported Pt catalyst (1 wt% Pt/hSiC) is prepared, and its catalytic activity and stability are monitored in SA decomposition at 850 °C. The initial SA conversion with the Pt/hSiC catalyst is ca. 80% at 850 °C and a GHSV of 76,000 mL/g<SUB>cat</SUB>/h. For comparison, a core-shell SiO<SUB>2</SUB> supported Pt catalyst (1 wt% Pt/SiO<SUB>2</SUB>@mSiO<SUB>2</SUB>) is prepared and tested for the reaction. The core-shell SiO<SUB>2</SUB> support has the structure of a dense core and a mesoporous shell. The initial SA conversion with the Pt/SiO<SUB>2</SUB>@mSiO<SUB>2</SUB> catalyst is ca. 54% at 850 °C and a GHSV of 76,000 mL/g<SUB>cat</SUB>/h. The Pt/hSiC catalyst is transformed to the SiO<SUB>2</SUB> hollow sphere supported Pt catalyst (Pt/hSiO<SUB>2</SUB>) within 6 h reaction. CO chemisorption and TEM analysis exhibit that Pt particles on the pristine and spent catalysts, pretreated at 850 °C, are encapsulated by SiC or SiO<SUB>2</SUB> on the surfaces of SiC and SiO<SUB>2</SUB> supports. When the encapsulated Pt particles are in contact with sulfuric acid vapor, the Pt particles are exposed to the reactants by the removal of SiO<SUB>2</SUB> encapsulating Pt during the reaction. Pt particles at the outer wall of the pristine hSiC are partly lost via PtOx evaporation, while Pt particles at the inner wall of the hollow sphere supports are stabilized without the severe Pt loss and Pt sintering. In contrast, the Pt particles on SiO<SUB>2</SUB>@mSiO<SUB>2</SUB> with the dense SiO<SUB>2</SUB> core are severely lost via PtOx evaporation during the reaction resulting in severe Pt sintering. The high stability of Pt particles at the inner wall of the hollow support is attributed to the Pt encapsulation and Pt anchoring of the small Pt particles at the inner walls and the diffusion barrier role of the shell for the migration of Pt at the inner wall to the outer wall.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt is encapsulated by SiO<SUB>2</SUB> and exposed to reactants with sulfuric acid at 850 °C. </LI> <LI> Pt loss and Pt sintering at inner walls of hollow sphere are prevented. </LI> <LI> Pt at outer walls of hollow sphere is severely lost and sintered. </LI> <LI> The catalyst design of Pt@hollow sphere is promising for SA decomposition. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P> <B>Hollow SiC supported Platinum catalyst:</B> Pt nano particles encapsulated into hollow sphere SiC(Pt/hSiC) have been prepared by polyol method. Facile synthesis not only confined the Pt into pores but partially embedded into the inner surface of the hSiC shell, which could effectively prevent the Pt NPs from agglomeration or leaching during the reaction, which resulted in high stability till 50 h.</P> <P>[DISPLAY OMISSION]</P>

Crop-Weed Semantic Segmentation for Plant Specific Treatment in Smart Farming

Abbas Khan,Hyongsuk Kim 제어로봇시스템학회 2020 제어로봇시스템학회 국내학술대회 논문집 Vol.2020 No.7

Synthesis of Pt/mesoporous SiC-15 and its catalytic performance for sulfuric acid decomposition

Khan, Hassnain Abbas,Natarajan, Prakash,Jung, Kwang-Deog Elsevier 2018 CATALYSIS TODAY - Vol.303 No.-

<P><B>Abstract</B></P> <P>Sulfuric acid (SA) decomposition is one of the key reactions in the sulfur-iodine (SI) cycle to produce hydrogen. Catalysts for the SA decomposition should be active and stable in a wide temperature range of 550–850°C to absorb latent heat generated from a thermal solar heat or a very high temperature nuclear reactor. Here, mesoporous mSiC-15 is prepared using the SBA-15 template. TEM analysis shows that the morphology of the mSiC-15 has the replica structure of SBA-15. Pt/SBA-15 and Pt/mSiC-15 catalysts are prepared by impregnation and the catalytic activity is examined under the reaction condition of 650–850°C and a GHSV of 76,000mL/g<SUB>cat</SUB>/h. The Pt/mSiC-15 catalyst is relatively stable for 50h at 850°C, while the Pt/SBA-15 was severely deactivated. The Pt amounts on the Pt/SBA-15 and Pt/mSiC-15 catalysts decreased from 0.73 and 0.80wt% at initial reaction time to 0.39 and 0.68wt% after 12h reaction, respectively. The Pt loss during the SA reaction is main cause of deactivation, which is caused by the evaporation of Pt oxides under O<SUB>2</SUB> environment produced during the SA decomposition. It is observed that the Pt particles are embedded in porous SiO<SUB>2</SUB> (Pt/mSiO<SUB>2</SUB>), which is transformed from Pt/mSiC-15 during the SA decomposition for 6h. The Pt/mSiC-15 was relatively active and stable for the SA decomposition and the Pt loss was minimized by the structural change from Pt/mSiC-15 to Pt/mSiO<SUB>2</SUB> after 6h.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt/mSiC-15 is prepared by Pt impregnation on SiC replica of SBA-15. </LI> <LI> Pt/mSiC-15 is relatively active and stable as compared to Pt/SBA-15. </LI> <LI> The Pt/mSiO<SUB>2</SUB> from the oxidation of Pt/mSiC-15 was thermally very stable. </LI> <LI> Pt is stabilized by the Pt embedment in mSiO<SUB>2</SUB> during the reaction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Monocular Depth Estimation Using a Modified Encoder-Decoder Network

Abbas Khan,Jeong Yong-chae(정용채),Hyongsuk Kim 제어로봇시스템학회 2021 제어로봇시스템학회 국내학술대회 논문집 Vol.2021 No.6

ON SOME GENERATING FUNCTIONS OF GENERALIZED BATEMAN'S AND PASTERNAK'S POLYNOMIALS OF TWO VARIABLES

Abbas, Sayed Mohammad,Khan, Mumtaz Ahmad,Khan, Abdul Hakim Korean Mathematical Society 2013 대한수학회논문집 Vol.28 No.1

The aim of the present paper is to study some generating functions of generalized Bateman's and Pasternak's polynomials of two variables.

Computational analysis of magnetized bio-convective partially ionized flow of second-order fluid on a bidirectional porous stretching sheet with Cattaneo–Christov theory

Khan Muhammad Naveed,Khan Aamir Abbas,Alhowaity Awatif,Masmoudi Atef,Daradkeh Yousef Ibrahim,Afikuzzaman Mohammad 한국CDE학회 2024 Journal of computational design and engineering Vol.11 No.1

After applying a magnetic field, the behavior of the partly ionized liquids is completely different from that of the ordinary fluids. In this study, we concentrated on the Cattaneo–Christov heat flux model-based three-dimensional partly ionized bio-convective flow of a second-order fluid on a bidirectional permeable stretching surface. The development of the thermal and solutal flow models takes into account the impacts of non-uniform sources and sinks, Ohmic viscous dissipation, and chemical reactions. In addition, the surface boundary effects of electron and ion collisions with convective boundary conditions are seen. The mathematical flow model is transformed appropriately to create an ordinary differential equations, which is then numerically solved with MATLAB’s BVP4C approach. To demonstrate the physical relevance of the flow field along various developing parameters, graphical and tabular results are created. It is noteworthy to note that while fluid temperature decreases with stronger values of the second-order fluid parameter, fluid velocity improves in both directions. In addition, it is shown that raising the thermal and concentration relaxation parameters, respectively, causes a drop in the fluid temperature and nanoparticle concentration.

Effects of Artificial Ageing on Viability and Leachate Exudation in Fenugreek (Trigonella foenum-grraecum L.) Seeds

Mazhar Abbas,M. Mumtaz Khan,M. Javed Iqbal,Rashid W. Khan 한국원예학회 2004 Horticulture, Environment, and Biotechnology Vol.45 No.5

The effects of environmental treatments to rapidly shorten seed viability in fenugreek (Trigonella foenumgrraecum L.) were explored. Seed germination capacity, seedling vigor (measured as radicle length), and seed leachate conductivity were measured in relation to the ageing process. Artificial ageing significantly reduced the final germination percentage and radicle length. Loss of viability and declining vigor were associated with increased solute leakage. Germination percentage was reduced up to 58% after 7 days of artificial ageing compared to the non-aged control (100%). Following artificial ageing, radicle length was reduced from 0.73 to 0.23 ㎝. The results indicated that a reduction in seed viability and vigor followed by membrane disruption might play a considerable role in deterioration of fenugreek seeds.

Survivability Analysis of MANET Routing Protocols under DOS Attacks

( Sohail Abbas ),( Muhammad Haqdad ),( Muhammad Zahid Khan ),( Haseeb Ur Rehman ),( Ajab Khan ),( Atta Ur Rehman Khan ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.9

The network capability to accomplish its functions in a timely fashion under failures and attacks is known as survivability. Ad hoc routing protocols have been studied and extended to various domains, such as Intelligent Transport Systems (ITSs), Unmanned Aerial Vehicles (UAVs), underwater acoustic networks, and Internet of Things (IoT) focusing on different aspects, such as security, QoS, energy. The existing solutions proposed in this domain incur substantial overhead and eventually become burden on the network, especially when there are fewer attacks or no attack at all. There is a need that the effectiveness of these routing protocols be analyzed in the presence of Denial of Service (DoS) attacks without any intrusion detection or prevention system. This will enable us to establish and identify the inherently stable routing protocols that are capable to survive longer in the presence of these attacks. This work presents a DoS attack case study to perform theoretical analysis of survivability on node and network level in the presence of DoS attacks. We evaluate the performance of reactive and proactive routing protocols and analyse their survivability. For experimentation, we use NS-2 simulator without detection or prevention capabilities. Results show that proactive protocols perform better in terms of throughput, overhead and packet drop.

Theoretical Investigations of Entropy Optimization in Electro-Magneto Nonlinear Mixed Convective Second Order Slip Flow

M. Ijaz Khan,Sumaira Qayyum,S. Kadry,W. A. Khan,S. Z. Abbas 한국자기학회 2020 Journal of Magnetics Vol.25 No.1

Here nonlinear mixed convective entropy based nanofluid second order slip flow of magnetic and electric field is addressed. Both electric and magnetic field is considered for the problem formulation and the flow is generated by a stretched surface. Important slip factors, i.e., Brownian and thermophoresis diffusions are accounted. Total entropy rate subject to four types of irreversibilities (i) heat transfer (ii) chemical reaction (iii) fluid friction (iv) Joule or Ohmic heating is obtained through second law of thermodynamics. Thermal radiation, heat generation/absorption, dissipation, Brownian motion, Joule or Ohmic heating and thermophoresis effects are considered in the development of the energy equation. Activation energy to undergo the physical transportation or chemical transformation of atoms or molecules is further considered in the analysis of concentration. Firstly ordinary differential system is found, then numerically solved for flow field, entropy generation, concentration, temperature, skin friction, Nusselt number, Bejan number and Sherwood number through built-in- Shooting method.

pH 감응성 NIPAM-co-MAA 고분자 마이크로젤의 제조 및 분석과 염 종류에 따른 부피상 변화

Mohammad Saleem Khan,Gul Tiaz Khan,Abbas Khan,Sabiha Sultana 한국고분자학회 2013 폴리머 Vol.37 No.6

Novel microgels of N-isopropylacrylamide (NIPAM)-co-methacrylic acid (MAA) (NIPAM-co-MAA) with different contents of N,N-methylene bis acrylamide (MBA) were prepared by emulsion polymerization technique and were studied by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and zeta potential measurement. Effect of pH, temperature and different salts concentration on the microgel particles was investigated. DLS results have shown that the hydrodynamic radius of the microgel increased upon increasing pH and decreased upon increasing temperature. The swelling/deswelling behaviors as determined by DLS showed the ionic repulsions of the carboxyl group of the methacrylic acid and hydrophobic interaction of NIPAM. The effect of various salts on volume phase transition temperature (VPTT) was also investigated. Upon increasing salt concentration, VPTT became broad and shifted to a lower temperature. Electrophoretic mobility measurements showed an increase with increasing pH and temperature at a constant ionic strength.