Use of Pd/activated carbon fiber catalyst to dehydrogenate cyclohexane

In this work, activated carbon fibers (ACFs) were prepared from polyacrylonitrile fibers, Pd catalyst was loaded onto the ACFs. The BET surface areas noted before activation were in the range of 120-140 m2/g. Activation of the fibers with carbon dioxide increased the surface areas of the fibers to about 150-190 m2/g. Diameters of metallic Pd particles loaded along the fibers ranged from 50 nm to 100 nm. The shape of the Pd particles was generally spherical albeit some non-spherical Pd particles were also noted. The catalytic activity of the Pd/ACF system in dehydrogenating cyclohexane at 350oC under liquid-phase conditions was investigated. Utilizing the Pd/ACF system in the micro-autoclave of a differential scanning calorimetric system was described for the liquid-phase catalytic dehydrogenation of cyclohexane. The DSC thermogram of the non-catalytic system yielded fewer endothermic events compared to the catalytic dehydrogenation of cyclohexane in the presence of Pd/ACF. The dehydrogenation of cyclohexane at 350oC was a first-order reaction with a rate constant, k = 3.5 x 10-4 s-1. GC-MS analyses of the products of catalytic dehydrogenation revealed a wide distribution of saturated and unsaturated hydrocarbons that were not present in the corresponding non-catalytic experiment. The presence of high molecular weight products could be explained by the recombination of carbon radicals during reaction

Preperation, characterization and utilization of palladium doped pan-based activated carbon fibers /

Wet-spun poly (acrylonitrile) fibers were stabilized at 200 °C for 1, 2, 3, 4, 5 hours and 300 °C for 0.5, 1, 2 hours under an air atmosphere. Carbon fibers were investigated in terms of functional groups at the surface and surface area changes at different carbonization temperatures, 500°C, 600°C, 700°C, 800°C, 900 °C, 1000 °C. After this, all carbon fibers were chemically activated with aluminium chloride (AlCl₃) and carbon dioxide (CO₂). Fourier Transformation Infrared Spectra and Scanning Electron Microscopy images of the chemically activated carbon fibers were measured to highlight possible changes on the surface. The highest surface area was obtained for the carbon fibers that was stabilized at 300°C for and carbonized at 600°C as 135.68 m²/g. Activation of fibers increased the surface area of fibers activated at 800°C under a CO₂ atmosphere for 0.5 and 1 hour. After the activation of fiber at 800°C for 0.5 and 1 hour and at 900°C for 1 hour and with AlCl₃/Et₂O, the highest surface area was obtained for the carbon fiber stabilized at 300°C, carbonized at 800°C and activated for 1hour as 189.60 m²/g. Non-activated CFs had microporous surface which was converted to macroporous surface after activation by CO₂. However, longer activation times created more ordered graphitic layers. FT-IR spectra of almost all samples showed two major peaks near ̃1200cm-1 and ̃1600cm-1 that belonged to =C-H and -C=C-, respectively. Although some fibers contains -C-N groups these groups vanished after activation. After 5%Pd (by wt) was loaded by NaBH₄ reduction method onto carbon fibers carbonized at 800°C and stabilized at 300°C for 1 hour, cyclohexane was dehydrogenated in microautoclaves at 350°C in a differential scanning calorimeter system. Two main endothermic peaks were observed in DSC thermograms until 350°C. Chemical compounds produced after dehydrogenation experiments over 5%Pd/CF were analyzed in GC-MS. Cyclohexene, 1- methyl-cyclopentene, 1,3,5-trimethylbenzene, 3-methylcyclohexene, decanal, 1-hexanol were some of the compounds observed

EVALUATION OF TENSILE PROPERTIES OF HIGH STRENGTH STEELS AT WARM TEMPERATURES AND VARIOUS STRAIN RATES

12th International Conference on Metal Forming -- SEP 21-24, 2008 -- Cracow, POLANDWOS: 000267944700043The use of advanced high strength steels in automotive industry has been increased recently. Dual-phase (DP) high-strength steel, which is an advanced high strength steel, has gained great attention due to its high strength and good formability. In this study, uniaxial tensile deformation of DP600 and DP800 advanced high strength steels were studied at temperatures between room temperature (RT) and 300 degrees C and at strain rates between 0.008 s(-1) and 0.16 s(-1). Results indicate that the formability of the materials is lower after the testing at 200 degrees C and 300 degrees C than the testing at RT. Moreover, the formability decreases with the increasing strain rate. Finally, the forming should be done at RT and low strain rates to get good formability.Akad Gorniczo Hutn, Univ Birmingham, Univ Toyohash

Low-Cost FPGA Based Antenna Pattern Measurement System

The paper entitled Low-Cost FPGA Based Antenna Pattern Measurement System describes a cost-effective antenna pattern measurement system for educational purposes. Operating the system does not require any additional computer support as it is designed to be a standalone device. The system is built upon Field Programmable Gate Array (FPGA) platform and contains 4 main blocks; namely, RF source, logarithmic RF detector, position controller and the central control unit

Treatment of Tibial and Femoral Bone Defects With Bone Transport Over an Intramedullary Nail

Objectives: To evaluate the results of the bone transport over an intramedullary nail (BTON) technique for the treatment of segmental bone defects. Design: Retrospective review of case series. Setting: Level 1 trauma center. Patients/Participants: We included 40 patients who underwent reconstruction of the lower limb with BTON technique between 2000 and 2018. The technique was performed in the tibial segments in 21 patients and in the femoral segments in 19 patients. Intervention: The surgical technique was performed in 2 stages for patients with infected nonunion. Infection was eradicated in all patients at the first stage. For the BTON at the second stage, monolateral external fixators and circular external fixators were used for femoral and tibial defects, respectively. In cases of defects without any infection, debridement with a single-stage BTON was performed. Main Outcome Measurements: Complications as well as radiological and clinical results were evaluated according to the criteria of Paley-Maar. Results: Minor complications occurred in 11 patients: pin site problems (9), cellulitis (1), and skin detachment due to Schanz screw (1). Major complications occurred in 8 patients: docking site nonunion (4), early consolidation and Schanz screw failure (1), knee flexion contracture (1), and ankle equinus contracture (2). Four patients had osteomyelitis as residual sequelae. Bone score was excellent in 27 patients. Excellent functional results were obtained in 31 patients. Conclusions: The BTON technique is associated with low cost because of the short treatment period, low complication risk, and rapid rehabilitation and is not limited by the amount of bone transport

Lyophilization-induced structural changes in solvent swollen-supercritical carbon sioxide treated- low rank Turkish coals and characterization of their extracts

In the present work lyophilization was employed to recover the readily volatile solvent fraction in previously impregnated, solvent-swollen low-rank Turkish coals as well as to potentially remove inherently volatile components of the coal matrix. Experiments were performed subsequently to assess if there existed a correlation between the conformational stability of swollen coal in certain solvents and the magnitude of lyophilization-induced structural changes. Lyophilization-induced alterations in the macroscopic and macromolecular structure of the coal and the effect of lyophilization on the structure of supercritical carbon dioxide extracts of the coal are reported in the present work. Freeze-dried samples were treated with supercritical carbon dioxide in a supercritical system at 50 bar and 80 C. Then the soluble components accessible within raw samples and supercritically treated samples were digestively extracted in tetrahydrofuran, for 24 h at 20 C. Extracts obtained were analyzed using a GC-MS system. Structural changes of the coal particles upon lyophilization were observed by SEM. Lyophilization seemed to increase the BET surface area of the coal samples. Lyophilization did not change the pore size distribution of the coal samples, but it mechanically reduced the particle size of the coal particles. In both types of coal, the amount of material that had extracted into THF after supercritical carbon dioxide treatment was greater in the case of samples that had been previously lyophilized

Diagnostic spectrum of congenital hypothyroidism in Turkish children

Background