The effect of H2:N2 ratio on the NH3 synthesis rate and on process economics over the Co3Mo3N catalyst

In this study, the process economics of ammonia synthesis over Co3Mo3N was investigated by searching an optimum feed stoichiometry. By ammonia synthesis rate measurements at atmospheric pressure and 400 oC over Co3Mo3N, it was found that, the rate was independent of H2:N2 stoichiometries above 0.5:1. For H2:N2 stoichiometries below 0.5:1, there was a linear dependency of ammonia synthesis rate on the H2:N2 stoichiometry. Static measurements of hydrogen adsorption isotherms measured at 25, 50, and 100 oC revealed that the adsorbed amounts of the strongly bound hydrogen over Co3Mo3N surface were saturated at around 100 Torr hydrogen pressure. This pressure corresponds to the partial pressure of hydrogen when H2:N2 stoichiometries are around 0.5:1, correlating the role of strong hydrogen in ammonia synthesis. These results were used to modify an existing kinetic expression to be used in a conceptual design, based on a lateness of mixing strategy for the hydrogen stream. This conceptual design and its economical analysis revealed that keeping low hydrogen stoichiometries can cut the investment and operating costs by a factor of 2

A High Throughput Lab-On-A-Chip System for Label Free Quantification of Breast Cancer Cells under Continuous Flow

This paper presents an LOC system combining microfluidic DEP channel with a CMOS image sensor for label and lens free detection and real-time counting of MCF-7 cells under continuous flow. Trapped and then released MCF-7 cells are accurately detected and counted under flow with a CMOS image sensor integrated underneath the DEP channel, for the first time in the literature. CMOS image sensor can capture 391 frames per second (fps) that allows detection of the released cells flowing through the channel with a flow rate up to 130 mu l/min (0.468 m/s). Therefore, the proposed system is able to detect the cells under high flow where conventional techniques for cell quantification such as fluorescent tagging become unusable. Detected cells are automatically counted with a computer program and the counting accuracy of the whole system is 95%. (C) 2016 The Authors. Published by Elsevier Ltd

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Destekli Ru esaslı amonyak sentez katalizörleri.

Ru/C type ammonia synthesis catalysts are known to be poisoned by hydrogen. In order to elucidate a mechanism for hydrogen poisoning, H2 adsorption and spillover on Ru based ammonia synthesis catalysts were investigated. Supported Ru catalysts and Na promoted Ru catalyst were prepared by incipient wetness impregnation of Ru(NO)(NO3)3 on SiO2, SBA-15, CNT and Vulcan supports. Dispersion value of the catalysts was determined via H2 chemisorption and Transmission Electron Microscopy (TEM) characterization techniques. Over SBA-15 support, the dispersion of the catalyst determined by two different characterization techniques were in agreement. On the other hand, over CNT and SiO2 supports dispersion measured by TEM characterization method was higher than H2 chemisorption method. H2 chemisorption measurements performed over extended periods of time were used to determine the spilled over hydrogen amounts over Ru/Vulcan and Na-Ru/Vulcan catalysts at 375 torr and 10 torr H2 pressure at room temperature. By using H2 uptake data measured for extended periods of 6 – 24 hours, diffusion coefficient of hydrogen species over Vulcan support was calculated assuming a point source diffusion mechanism. Coefficient of diffusion for Ru/Vulcan and Na-Ru/Vulcan was found as 1.39 x 10-14 cm2/sec and 1.23 x 10-14 cm2/sec, respectively at 375 torr. Similarly, at 10 torr, diffusion coefficients of Ru/Vulcan and Na-Ru/Vulcan catalysts were determined as 1.51 x 10-15 cm2/sec and 1.81 x 10-15 cm2/sec, respectively.M.S. - Master of Scienc

Zaman kesintili şartlar altında amonyak sentez reaksiyonu.

The objective of this thesis study is to demonstrate a solution for a sustainable ammonia production process based on the unsteady state operating conditions under milder temperatures and atmospheric pressure. In this framework, the elimination of the ammonia synthesis catalyst deactivation was investigated to improve the rates under milder operating conditions. The hydrogen adsorption /desorption characteristics over SiO2 and Vulcan supported Ru catalysts with different Ru metal loadings were investigated. It was shown that Ru metal dispersion decreased with increasing Ru metal loading. In addition, It was observed that Vulcan support Ru catalysts accommodated higher amounts of hydrogen compared to SiO2 supported Ru catalysts. It was demonstrated that dissociated hydrogen over Ru metal migrated from Ru metal surface to support surface and higher temperatures were needed to desorbed the spilled over hydrogen from the support surface. The inhibition effect of ammonia was conducted in the context of the study. Ammonia synthesis reaction experiments were performed with zeolite-Y, hydroxyapatite (HAp), and Vulcan supported Ru catalysts at 300 – 400 °C and atmospheric pressure. It was observed that ammonia synthesis catalyst was poisoned and deactivated by synthesized ammonia within 1 h., regardless of surface acidities of the supports. N2 pulses were used to diminish the poisoning effect of ammonia. It was demonstrated that under pulsed flow conditions, the inhibition effect of ammonia was eliminated. In the final part of the study, Co3Mo3N as a next generation ammonia synthesis catalyst was investigated. This catalyst operates through a different mechanism, by involving lattice nitrogen in the process. Ammonia synthesis reaction experiments were performed with different H2:N2 ratios between 0.05 and 3.0. It was observed that ammonia synthesis rate did not change between H2:N2 ratio of 3.0 and 0.5. Besides, ammonia synthesis rate decreased with decreasing H2:N2 ratio below 0.5. On the other hand, N2 pulses was also applied to the ammonia synthesis reaction over Co3Mo3N, but no improvement was obtained. As a result, it was demonstrated that ammonia synthesis reaction over Co3Mo3N catalysts can be carried out with similar rates using lower hydrogen amount (H2:N2=0.5:1) compared to stoichiometric H2:N2 ratio of 3:1 under steady flow conditions.Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Chemical Engineering

RU ESASLI KATALİZÖRLERİN DESTEK MALZEMELERİNİN YÜZEY ASİTLİK KARAKTERİSTİKLERİNİN AMONYAK SENTEZ REAKSİYONU HIZINA ETKİSİ

Bu projenin amacı, yüzey asitlik değerleri (asidik, bazik, nötr) farklı olan destek malzemeler kullanılarak sentezlenmiş rutenyum (Ru) metali esaslı katalizörlerin, amonyak sentez reaksiyonuna etkisini incelemektir. Proje kapsamında farklı destek malzemeler kullanılarak hazırlanmış olan Ru esaslı katalizörler ile amonyak sentez reaksiyon hızları, bakır-amonyak kompleksleşmesi reaksiyonunun UV-Vis spektrofotometresi ile takip edilmesi ile ölçülmesi planlanmaktadır

Using spilled over hydrogen in NH3 synthesis over supported Ru catalysts

The role of spilled over hydrogen in ammonia synthesis reaction was monitored over Ru/SiO2, Ru/SBA15 and Ru/CNF using an in-situ DRIFTS cell reactor. Strongly bound hydrogen trapped on the metal and spilled over hydrogen trapped on the support due to a diffusion barrier remained on the surface after the overnight purge followed by hydrogen exposure over a reduced catalyst. When N-2 flow was introduced at room temperature, IR characteristic signals of NH3 were observed, indicating the formation of ammonia from hydrogen trapped on the surface. Total and weak hydrogen adsorption isotherms measured at different temperatures indicated that at low coverages spilled over hydrogen is trapped on the support in a kinetically metastable state. These results indicated the possibility of ammonia synthesis with the irreversibly bound hydrogen present on the support. A new hydrogen feeding strategy was proposed after a microkinetic model was used to estimate the rates in a plug flow reactor. An incremental hydrogen feeding strategy in the earlier phases of the reaction was proposed to eliminate hydrogen poisoning. The model predictions revealed that the alternative feeding strategy increased the rates by two orders of magnitude at the early stages of the reaction

Fundamentals of hydrogen storage processes over Ru/SiO2 and Ru/Vulcan

Hydrogen adsorption and desorption over Ru/SiO2 and Ru/Vulcan are investigated in terms of hydrogen storage and release characteristics by both dynamic and static experiments. Ru particle dispersions as a function of metal loading were determined by HR-TEM and volumetric chemisorption experiments. Vulcan was more accommodating for spillover hydrogen than SiO2. High Ru dispersions, i.e., small particle sizes, favored the amount of hydrogen spillover to Vulcan, as revealed by temperature programmed desorption (TPD) of hydrogen. TPD of hydrogen under He flow experiments over Ru/SiO2 and Ru/Vulcan materials revealed a low temperature process (up to 200 degrees C) attributed to desorption of weakly bound hydrogen from Ru metal surface. A high temperature process (above 450 degrees C) was attributed to diffusion of hydrogen from the support to the Ru particle and desorption at the Ru sites. Hydrogen adsorbs strongly on Ru metal, as indicated by the initial heats of H-2 adsorption measured as 100 kJ/mol over 1 wt% Ru/Vulcan by adsorption calorimetry. At higher coverages, heat of adsorption of hydrogen was measured as 10 kJ/mol. Low heat of adsorption of hydrogen at high coverages indicate multilayer weak adsorption of hydrogen over the storage material, which can desorb at lower temperatures. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Using spilled over hydrogen in NH3 synthesis over supported Ru catalysts

The role of spilled over hydrogen in ammonia synthesis reaction was monitored over Ru/SiO2, Ru/SBA15 and Ru/CNF using an in-situ DRIFTS cell reactor. Strongly bound hydrogen trapped on the metal and spilled over hydrogen trapped on the support due to a diffusion barrier remained on the surface after the overnight purge followed by hydrogen exposure over a reduced catalyst. When N2 flow was introduced at room temperature, IR characteristic signals of NH3 were observed, indicating the formation of ammonia from hydrogen trapped on the surface. Total and weak hydrogen adsorption isotherms measured at different temperatures indicated that at low coverages spilled over hydrogen is trapped on the support in a kinetically metastable state. These results indicated the possibility of ammonia synthesis with the irreversibly bound hydrogen present on the support. A new hydrogen feeding strategy was proposed after a microkinetic model was used to estimate the rates in a plug flow reactor. An incremental hydrogen feeding strategy in the earlier phases of the reaction was proposed to eliminate hydrogen poisoning. The model predictions revealed that the alternative feeding strategy increased the rates by two orders of magnitude at the early stages of the reaction. © 2016 Elsevier B.V. All rights reserved

Soy metal amonyak sentezi katalizörlerinin hidrojenle zehirlenme mekanizmasının taşma olayları ile ilişkisinin incelenmesi

Soymetaller üzerinde H2 molekülünün parçalanarak adsorplanması ve metal üzerinden destek madde üzerine taşması ölçülebilen ve gözlemlenebilen bir fiziksel olaydır. Buna karşılık, katalizör desteği üzerine taşmış olan hidrojenin kimyasal olarak hangi formda ve/veya formlarda olduğu kesin olarak bilinememektedir. Taşmış hidrojenin endüstri ölçeğindeki tepkime üzerine olan etkisi bu güne kadar hiç dikkate alınmamıştır. Bu çalışmada, nanoyapılı destekler üzerinde hazırlanmış olan rutenyum katalizörleri üzerinde gerçekleştirilecek amonyak sentez reaksiyonunda, metal üzerinde parçalanmış ve destek madde üzerine taşmış olan hidrojen elde edildikten sonra, katalizör üzerine gönderilecek olan N2 gazı ile amonyak sentez reaksiyonunun basamaklarının in situ DRİFTS yöntemi ile gözlenmesi hedeflenmektedir. Bu şekilde amonyak sentez reaksiyonun destek üzerinde gerçekleşen mekanizması hakkında yeni bilgiler edinilmesi amaçlanmaktadır