АЛГОРИТМ ОПРЕДЕЛЕНИЯ РАДИОМОРФОМЕТРИЧЕСКИХ ИНДЕКСОВ НИЖНЕЙ ЧЕЛЮСТИ ПО ДАННЫМ КОНУСНО-ЛУЧЕВОЙ КОМПЬЮТЕРНОЙ ТОМОГРАФИИ

Alveolar bone quality of the jaws plays a decisive role in the successful integration of dental implants. Changes in bone structure of the jaws directly depend on the age, state of the dental unit and reflect processes occurring throughout the skeleton, including systemic osteoporosis. The study is developed a method of determining radiomorphometric indices of the mandible (MI, MCI, PMI), correlated with bone mineral density of the axial skeleton, based on cone-beam computed tomography (CBCT). A comparative analysis of the efficacy of CBCT and orthopantomography for index evaluation has been done.Качество костной ткани альвеолярных отделов челюстей играет определяющую роль в успешной интеграции дентальных имплантатов. Изменения структуры костной ткани челюстей находятся в прямой зависимости от возраста, состояния зубочелюстного аппарата и отражают процессы, происходящие во всем скелете, в том числе системный остеопороз. В исследовании разработана методика определения радиоморфометрических индексов нижней челюсти (ментального MI, мандибулярно-кортикального MCI и панорамно-мандибулярного PMI), коррелирующих с минеральной костной плотностью осевого скелета, на основе данных конусно-лучевой компьютерной томографии (КЛКТ). Проведен сравнительный анализ эффективности применения КЛКТ и ортопантомографии для оценки данных индексов

Engineering Selective and Stable Methanol to Olefins Catalysts

ChemE/Catalysis Engineerin

Clinical case of endo-periodontal defeat of the first maxillary molar in peadiatric dentistry

In the practice of a dentist, a clinical situation occurs where the inflammatory processes are to varying degrees determined both in the periodontium and in the pulp of the tooth. A clinical case of endo-periodontal lesion in a 10-year-old child in the area of the upper first molar is described, which presents a difficult task, both in terms of diagnosis and treatment. The diagnostic value of CBCT was noted

Progress in Developing a Structure-Activity Relationship for the Direct Aromatization of Methane

To secure future supply of aromatics, methane is a commercially interesting alternative feedstock. Direct conversion of methane into aromatics combines the challenge of activating one of the strongest C-H bonds in all hydrocarbons with the selective aromatization over zeolites. To address these challenges, smart catalyst and process design are a must. And for that, understanding the most important factors leading to successful methane C-H bond activation and selective aromatization is needed. In this review, we summarize mechanistic insight that has been gained so far not only for this reaction, but also for other similar processes involving aromatization reactions over zeolites. With that, we highlight what can be learnt from similar processes. In addition, we provide an overview of characterization tools and strategies, which are useful to gain structural information about this particular metal-zeolite system at reaction conditions. Here we also aim to inspire future characterization work, by giving an outlook on characterization strategies that have not yet been applied for the methane dehydroaromatization catalyst, but are promising for this system.Accepted Author ManuscriptChemE/Catalysis Engineerin

The importance of heat effects in the Methanol to Hydrocarbons reaction over ZSM-5: on the role of mesoporosity on catalyst performance

Interpretation of catalytic performance during the MTH process is hampered by heat transport phenomena. We demonstrate that large temperature rises can occur during fixed bed labscale catalyst testing of ZSM-5, even when a large catalyst bed dilution is applied. Formation of mesopores in ZSM-5 leads to partial mitigation of these effects because of a lower generation of heat per unit catalyst volume and weakening of the zeolite acidity.ChemE/Catalysis Engineerin

АЛГОРИТМ ОПРЕДЕЛЕНИЯ РАДИОМОРФОМЕТРИЧЕСКИХ ИНДЕКСОВ НИЖНЕЙ ЧЕЛЮСТИ ПО ДАННЫМ КОНУСНО-ЛУЧЕВОЙ КОМПЬЮТЕРНОЙ ТОМОГРАФИИ

Alveolar bone quality of the jaws plays a decisive role in the successful integration of dental implants. Changes in bone structure of the jaws directly depend on the age, state of the dental unit and reflect processes occurring throughout the skeleton, including systemic osteoporosis. The study is developed a method of determining radiomorphometric indices of the mandible (MI, MCI, PMI), correlated with bone mineral density of the axial skeleton, based on cone-beam computed tomography (CBCT). A comparative analysis of the efficacy of CBCT and orthopantomography for index evaluation has been done.Качество костной ткани альвеолярных отделов челюстей играет определяющую роль в успешной интеграции дентальных имплантатов. Изменения структуры костной ткани челюстей находятся в прямой зависимости от возраста, состояния зубочелюстного аппарата и отражают процессы, происходящие во всем скелете, в том числе системный остеопороз. В исследовании разработана методика определения радиоморфометрических индексов нижней челюсти (ментального MI, мандибулярно-кортикального MCI и панорамно-мандибулярного PMI), коррелирующих с минеральной костной плотностью осевого скелета, на основе данных конусно-лучевой компьютерной томографии (КЛКТ). Проведен сравнительный анализ эффективности применения КЛКТ и ортопантомографии для оценки данных индексов

Quantifying the impact of dispersion, acidity and porosity of Mo/HZSM-5 on the performance in methane dehydroaromatization

The catalytic performance of the bifunctional catalyst Mo/HZSM-5 for methane dehydroaromatization (MDA) depends on the Mo dispersion and on zeolite acidity. Here we separately quantify the effect of dispersion and the effect of acidity on aromatic yields and coke selectivity. Also, the effect of porosity on the same is quantitatively assessed. For that, a suite of 17 samples with varying Mo dispersion were synthesized by means of several methods, including chemical vapor deposition with MoCl 5 , MoO 2 Cl 2 and Mo(CO) 6 as precursors and the conventional methods, incipient wetness impregnation and solid ion exchange. These catalysts were characterized with pyridine IR-spectroscopy, XPS, UV–vis spectroscopy, N 2 adsorption, XRD, TGA and 27 Al MAS NMR. The combined results yielded a measure of how much Mo is anchored to the zeolite as well-defined cationic species and how much is present as bigger clusters on the outer surface of the zeolite. Through relating these characterization results to the catalytic behavior of the catalysts, it was found that the maximum instantaneous benzene and naphthalene yields as well as the integral selectivities during methane dehydroaromatization linearly increase with the amount of Mo present as mono- or dimeric species. At the same time, the selectivity to coke increases with the amount of Mo present as bigger clusters or nanoparticles on the outer surface of the zeolite. The number of Mo cationic sites is the most important factor determining the activity of Mo/HZSM-5 for low loadings of Mo. But at higher loadings, the high rate of aromatics formation requires an easily accessible pore structure as well. </p

Consequences of secondary zeolite growth on catalytic performance in DMTO studied over DDR and CHA

Zeolites with DDR (Sigma-1 and ZSM-58) and CHA (SSZ-13) topology were synthesized by seed assisted and direct hydrothermal synthesis in order to investigate the effects of fast crystal growth on catalytic performance. Application of small amount of seeds (0.1% wt) significantly reduced synthesis time of all the studied zeolites. XRD and NH3-TPD analyses did not reveal any difference in crystallinity and acidity. On the other hand, IR spectroscopy clearly demonstrates the presence of multiple defects, internal silanols (3729 cm-1) and silanol nests (3400 cm-1), as a result of accelerated crystal growth kinetics. Comparison of catalytic properties in the dimethyl ether to olefins (DMTO) reaction at 400°C and 450°C revealed that, despite smaller crystal sizes, zeolites prepared by secondary growth display shorter lifetimes due to faster coking rates, the latter being a result of silanols promoting hydrogen transfer reactions. Fluoride treatment of CHA removed silanols and prolonged its lifetime. This work highlights the importance of zeolite quality for catalytic application and the necessity to optimize current synthetic protocols based on secondary growth.ChemE/Catalysis Engineerin

Quantifying the impact of dispersion, acidity and porosity of Mo/HZSM-5 on the performance in methane dehydroaromatization

The catalytic performance of the bifunctional catalyst Mo/HZSM-5 for methane dehydroaromatization (MDA) depends on the Mo dispersion and on zeolite acidity. Here we separately quantify the effect of dispersion and the effect of acidity on aromatic yields and coke selectivity. Also, the effect of porosity on the same is quantitatively assessed. For that, a suite of 17 samples with varying Mo dispersion were synthesized by means of several methods, including chemical vapor deposition with MoCl 5 , MoO 2 Cl 2 and Mo(CO) 6 as precursors and the conventional methods, incipient wetness impregnation and solid ion exchange. These catalysts were characterized with pyridine IR-spectroscopy, XPS, UV–vis spectroscopy, N 2 adsorption, XRD, TGA and 27 Al MAS NMR. The combined results yielded a measure of how much Mo is anchored to the zeolite as well-defined cationic species and how much is present as bigger clusters on the outer surface of the zeolite. Through relating these characterization results to the catalytic behavior of the catalysts, it was found that the maximum instantaneous benzene and naphthalene yields as well as the integral selectivities during methane dehydroaromatization linearly increase with the amount of Mo present as mono- or dimeric species. At the same time, the selectivity to coke increases with the amount of Mo present as bigger clusters or nanoparticles on the outer surface of the zeolite. The number of Mo cationic sites is the most important factor determining the activity of Mo/HZSM-5 for low loadings of Mo. But at higher loadings, the high rate of aromatics formation requires an easily accessible pore structure as well. ChemE/Catalysis EngineeringApplied Science

Revealing Lattice Expansion of Small-Pore Zeolite Catalysts during the Methanol-to-Olefins Process Using Combined Operando X-ray Diffraction and UV-vis Spectroscopy

In small-pore zeolite catalysts, where the size of the pores is limited by eight-ring windows, aromatic hydrocarbon pool molecules that are formed inside the zeolite during the Methanol-to-Olefins (MTO) process cannot exit the pores and are retained inside the catalyst. Hydrocarbon species whose size is comparable to the size of the zeolite cage can cause the zeolite lattice to expand during the MTO process. In this work, the formation of retained hydrocarbon pool species during MTO at a reaction temperature of 400 °C was followed using operando UV-vis spectroscopy. During the same experiment, using operando X-ray Diffraction (XRD), the expansion of the zeolite framework was assessed, and the activity of the catalyst was measured using online gas chromatography (GC). Three different small-pore zeolite frameworks, i.e., CHA, DDR, and LEV, were compared. It was shown using operando XRD that the formation of retained aromatic species causes the zeolite lattice of all three frameworks to expand. Because of the differences in the zeolite framework dimensions, the nature of the retained hydrocarbons as measured by operando UV-vis spectroscopy is different for each of the three zeolite frameworks. Consequently, the magnitude and direction of the zeolite lattice expansion as measured by operando XRD also depends on the specific combination of the hydrocarbon species and the zeolite framework. The catalyst with the CHA framework, i.e., H-SSZ-13, showed the biggest expansion: 0.9% in the direction along the c-axis of the zeolite lattice. For all three zeolite frameworks, based on the combination of operando XRD and operando UV-vis spectroscopy, the hydrocarbon species that are likely to cause the expansion of the zeolite cages are presented; methylated naphthalene and pyrene in CHA, 1-methylnaphthalene and phenalene in DDR, and methylated benzene and naphthalene in LEV. Filling of the zeolite cages and, as a consequence, the zeolite lattice expansion causes the deactivation of these small-pore zeolite catalysts during the MTO process.ChemE/Catalysis Engineerin