McBain Balance Research Articles

Experimental and Simulation Study on Coproduction of Hydrogen and Carbon Nanomaterials by Catalytic Decomposition of Methane-Hydrogen Mixtures

Among all hydrocarbons, the methane molecule contains the highest amount of hydrogen with respect to carbon. Therefore, the catalytic decomposition of methane is considered as an efficient approach to produce hydrogen along with nanostructured carbon product. On the other hand, the presence of hydrogen in the composition of the initial gas mixture is required for the stable operation of the catalyst. In present work, the experiments on the catalytic decomposition of methane–hydrogen mixture were performed in a flow-through quartz reactor equipped with McBain balances under atmospheric pressure. The catalyst NiO-CuO/Al2O3 was prepared by the mechanochemical activation technique. The maximum carbon yield of 34.9 g/gcat was obtained after 2 h of experiment at 610 °C. An excess of hydrogen in the reaction mixture provided the long-term activity of the nickel–copper catalyst. The durability tests ongoing for 6 h within a temperature range of 525–600 °C showed no noticeable deactivation of the catalyst. Two kinetic models, D1a and M1a, were proposed for the studied decomposition of the methane–hydrogen mixture over the nickel–copper catalyst. The kinetic constants for these models were determined by means of mathematical modelling.

Scaling up the Process of Catalytic Decomposition of Chlorinated Hydrocarbons with the Formation of Carbon Nanostructures

Catalytic processing of organochlorine wastes is considered an eco-friendly technology. Moreover, it allows us to obtain a value-added product—nanostructured carbon materials. However, the realization of this process is complicated by the aggressiveness of the reaction medium due to the presence of active chlorine species. The present research is focused on the characteristics of the carbon product obtained over the Ni-Pd catalyst containing 5 wt% of palladium in various quartz reactors: from a lab-scale reactor equipped with McBain balance to scaled-up reactors producing hundreds of grams. 1,2-dichloroethane was used as a model chlorine-substituted organic compound. The characterization of the materials was performed using scanning and transmission electron microscopies, Raman spectroscopy, and low-temperature nitrogen adsorption. Depending on the reactor type, the carbon yield varied from 14.0 to 24.2 g/g(cat). The resulting carbon nanofibers possess a segmented structure with disordered packaging of the graphene layers. It is shown that the carbon deposits are also different in density, structure, and morphology, depending on the type of reactor. Thus, the specific surface area changed from 405 to 262 and 286 m2/g for the products from reactor #1, #2, and #3, correspondingly. The main condition providing the growth of a fluffy carbon product is found to be its ability to grow in any direction. If the reactor walls limit the carbon growing process, the carbon product is represented by very dense fibers that can finally crack the reactor.

THE THERMODYNAMICS OF INTERACTIONS AND RELAXATION PROPERTIES OF THE POSS-CONTAINING NANOCOMPOSITES BASED ON POLYURETHANE-POLY(HYDROXYPROPYL METHACRYLATE) MATRIX, WHICH IS FORMED BY THE PRINCIPLE OF IPNS

A series of the nanocomposites based on a multicomponent polymer matrix consisting of polyurethane and poly(hydroxypropyl methacrylate) and 1,2-propanediolysobutyl polyhedral oligomeric silsesquioxane (1,2-propanediolysobutyl-POSS), used as a functionalized nanofiller, was synthesized. The polymer matrix was formed on the principle of interpenetrating polymer networks (IPNs). The influence of 1,2-propanediolysobutyl-POSS amount on the thermodynamics of polymer components of the matrix interactions and on the dynamic mechanical properties of the created nanocomposites was studied. With purpose of the thermodynamic parameters interactions calculations the isothermal sorption of methylene chloride vapour by samples was investigated. The methylene chloride vapour sorption by the samples was studied using a vacuum installation and a McBain balance. By calculations of the thermodynamic parameters of PU and PHPMA interactions was shown that the free energy of PU and PHPMA mixing was positive. The introduction of 1-3 wt % of POSS lead to further phase separation in semi-IPNs. This is due to concentration of POSS particles in the PU’s nanodomains. The increasing of POSS content up to 5-10 wt % lead to compatibi-lization in semi-IPNs. These is due to concentration of POSS nanoparticles not only in the PU’s nanodomains but also in the interphase region of semi-IPN. The dynamic mechanical properties of the created nanocomposites were investigated and the degree of polymer components segregation was calculated. It was shown that there are two peaks of tan δ (PU and PHPMA) in the nanocom-posites. The introduction of 1-3 wt % of POSS lead to increasing of tan δ peak of PHPMA and to deepening of the bridge between two peaks (PU and PHPMA). At the same time the degree of polymer components of the matrix segregation became higher. This means the further phase separation in semi-IPNs. Increasing of 1,2-propanediolysobutyl-POSS amount up to 5-10% leads to the concentration of the nanofiller not only in the nanodomains of PU, but also in the interfacial layers. This leads to a change in the free energy of polymer components mixing, which becomes negative. At the same time the degree of polymer components of the matrix segregation became significantly reduced. These means that the process of compatibilization took part in the semi-IPNs.

Selected Aspects of Hydrogen Production via Catalytic Decomposition of Hydrocarbons

Owing to the high hydrogen content, hydrocarbons are considered as an alternative source for hydrogen energy purposes. Complete decomposition of hydrocarbons results in the formation of gaseous hydrogen and solid carbonaceous by-product. The process is complicated by the methane formation reaction when the released hydrogen interacts with the formed carbon deposits. The present study is focused on the effects of the reaction mixture composition. Variations in the inlet hydrogen and methane concentrations were found to influence the carbon product’s morphology and the hydrogen production efficiency. The catalyst containing NiO (82 wt%), CuO (13 wt%), and Al2O3 (5 wt%) was prepared via a mechanochemical activating procedure. Kinetics of the catalytic process of hydrocarbons decomposition was studied using a reactor equipped with McBain balances. The effects of the process parameters were explored in a tubular quartz reactor with chromatographic analysis of the outlet gaseous products. In the latter case, the catalyst was loaded piecemeal. The texture and morphology of the produced carbon deposits were investigated by nitrogen adsorption and electron microscopy techniques.

Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

Dechlorination processes attract great interest since they are involved in environmental protection and waste disposal technologies. In this paper, the process of gas-phase dechlorination of 1,2-dichloroethane, chloroform, and chlorobenzene over Ni/Al2O3 catalyst (90 wt% Ni) prepared by a coprecipitation technique was investigated. The reduction behavior of the oxide precursor NiO/Al2O3 was studied by thermogravimetric analysis in a hydrogen medium. A thermodynamic assessment of the conditions under which metallic nickel undergoes deactivation due to the formation of nickel chloride was performed. The dechlorination of chlorinated substrates was studied using a gravimetric flow-through system equipped with McBain balances in a wide range of temperatures (350–650 °C) and hydrogen concentrations (0–98 vol%). The impact of these parameters on selectivity towards the products of hydrodechlorination (C2H4, C2H6, and C6H6) and catalytic pyrolysis (carbon nanomaterial and CH4) was explored. The relationship between the mechanisms of the catalytic hydrodechlorination and the carbide cycle was discussed, and the specific reaction conditions for the implementation of both scenarios were revealed. According to the electron microscopy data, the carbonaceous products deposited on nickel particles during catalytic pyrolysis are represented by nanofibers with a disordered structure formed due to the peculiarity of the process including the side carbon methanation reaction.

Synthesis of nitrogen doped segmented carbon nanofibers via metal dusting of Ni-Pd alloy

A single-phase micro-disperse Ni-Pd (5 wt.%) alloy prepared by coprecipitation technique was studied as a catalyst precursor for the synthesis of the nanostructured carbon product. Catalytic synthesis of N-doped carbon nanofibers was implemented by the joint decomposition of C2H4Cl2 and CH3CN vapors in H2 excess at 600 °C. The in situ kinetic experiments performed in a flow gravimetric setup with McBain balances showed that the carbon deposition process is characterized by an induction period (18−20 min). The intensive metal dusting of the Ni-Pd alloyed precursor in reaction conditions was found to lead to its complete disintegration. The obtained submicron-sized Ni-Pd particles were shown by XRD to have the same composition as the starting Ni-Pd (5%) precursor. The growth of carbon filaments accompanied the rapid disintegration of Ni-Pd alloy. The addition of acetonitrile vapors into the reaction mixture was found to enhance carbon yield from 24 (0%) to 40.5 (5 vol.%) and 50.9 (8 vol.%) grams per 1 g of catalyst for 2 h of reaction. Joint catalytic processing of C2H4Cl2 and CH3CN was shown to be sufficient for the production of carbon nanofibers doped with nitrogen. According to XPS and EDX data, the average amount of nitrogen within the obtained N-CNF was about 1.8 wt.%. It was revealed by microscopic studies (SEM, TEM) that the produced N-doped carbon filaments are characterized with a rather regular segmental structure similar to that observed for a reference sample of N-free CNF. The synthesized N-CNF samples are characterized by ID/IG ∼ 1.3 (Raman spectroscopy) and high textural parameters (SBET ∼ 390−450 m2/g, Vpore ∼ 0.6 cm3/g).

Effect of Mo on the catalytic activity of Ni-based self-organizing catalysts for processing of dichloroethane into segmented carbon nanomaterials

A series of micro-disperse Ni-Mo alloys with the sponge-like structure was prepared by a simultaneous precipitation method followed by sintering of the sediment in H2 atmosphere at 800 °C. According to XRD data, the formation of single-phase solid solution Ni1-xMox took place for the samples with Mo content of 0.6–8.3 wt.%. Synthesized samples were studied in a process of the catalytic CVD of C2H4Cl2 at 550–700 °C. In situ kinetic studies of carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. An interaction of Ni-Mo alloys with C2H4Cl2 is accompanied by their rapid disintegration with formation of disperse active particles catalyzing the growth of carbon nanomaterials (CNM). The strong boosting effect of Mo on the catalytic performance of Ni was revealed. The maximum yield of CNM product (8.3 wt.% Mo, 600 °C, 120 min) was as high as 45 g/gM. The study on effect of the reaction temperature on the CNM yield allowed one to define an optimal temperature regime. The impact of Mo concentration upon the morphology, structural features and textural properties of the produced carbon fibers was investigated by means of SEM, TEM, Raman spectroscopy and low-temperature nitrogen adsorption. The role of chemisorbed chlorine species in a pulse-to-pulse regime of the segmented carbon filaments formation was discussed.

Catalytic synthesis of segmented carbon filaments via decomposition of chlorinated hydrocarbons on Ni-Pt alloys

Abstract A series of micro-disperse Ni1-xPtx alloys with the sponge-like structure was prepared by a simultaneous precipitation method with subsequent sintering of the sediment in H2 atmosphere at 800 °C. The formation of single-phase solid solution Ni1-xPtx was confirmed by powder XRD analysis for entire range of Pt concentrations (1.3–75.9 wt.%). The synthesized samples were studied in a process of catalytic decomposition of C2H4Cl2 at 600 °C. In situ kinetic studies of the carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. Interaction of Ni-Pt alloys with reaction mixture is characterized by an induction period (18–32 min) followed by rapid disintegration of the bulk alloys with intensive growth of carbon fibers. The stage of the induction period was explored in detail by means of XRD and SEM techniques. According to XRD data, the interaction of Ni-Pt alloys with C2H4Cl2 vapors is accompanied by formation of Ni1-xPtxCδ interstitial solution due to entry of carbon into the crystal lattice of the alloy. The effect of Pt addition on catalytic activity of Ni in CCVD process was also studied. It was found that the yield of carbon product depends extremely on Pt concentration with a maximum at CPt =4.3 wt.% (26 g/gNi for 120 min). The impact of Pt concentration upon morphology and structural features of the produced carbon fibers was investigated by SEM and TEM techniques.

Comparative study of 1,2-dichlorethane decomposition over Ni-based catalysts with formation of filamentous carbon

Catalytic chemical vapor deposition of 1,2-dichlorethane over Ni-based catalysts into carbon nanostructured materials was studied. The catalysts were prepared by mechanochemical activation and by metal dusting of bulk nickel-containing alloy precursors. Model Ni-M alloys, where M is Co, Cu, and Fe, were obtained by coprecipitation technique. Loading of M in the samples was varied in a range of 1–5at.%. Pure nickel was used a reference. The kinetics of carbon deposition was investigated using flow reactor equipped with McBain balances. The samples of carbon product were characterized by nitrogen adsorption, scanning and transmission electron microscopies. The hydrogen addition into reaction mixture was shown to have opposite effect on both catalytic behavior and carbon yield depending on catalyst’s nature. Segmented structure of carbon filaments formed specifies its developed surface area. Both bulk chlorination of nickel particles and its blockage by dense carbon deposits in the case of mechanochemically prepared samples were suggested to be responsible for rapid deactivation of the catalyst.

Catalytic behavior of bimetallic Ni–Fe systems in the decomposition of 1,2-dichloroethane. Effect of iron doping and preparation route

Model bimetallic Ni–Fe catalysts were prepared by coprecipitation from aqueous solutions of nitrates and by mechanical alloying of metal powders. Pure nickel samples subjected to the similar procedures were used as references. The obtained samples were characterized by scanning electron microscopy and X-ray diffraction analysis. Catalytic chemical vapor deposition of 1,2-dichloroethane over the catalysts was studied in a quartz flow reactor equipped with a McBain balance. It was shown that in the case of coprecipitation followed by reduction, Ni–Fe solid solution is formed within the studied range of Fe loading (1–10 wt%). Activation times of 6 min and longer are required to obtain this solid solution by the mechanical alloying method. Despite the known catalytic activity of nickel and iron in hydrocarbon decomposition in accordance with carbide cycle mechanism, iron doping was found to worsen the behavior of nickel in the studied reaction where chlorinated alkane plays a role of substrate to be decomposed. The formation of thermodynamically more stable iron chloride in relation to nickel chloride leads to deactivation of the catalyst and deceleration of the overall process.

Catalytic conversion of 1,2-dichloroethane over Ni-Pd system into filamentous carbon material

The alloyed Ni-Pd system with Pd content of 3wt.% was prepared by coprecipitation method followed by reduction in hydrogen atmosphere at 800°C. The formation of single-phase solid solution with unit cell parameter a=3.532(1) Å (determined by (331) reflex at 2θ ≈ 145°) corresponding to NiPd alloy with weight ratio 97:3 was confirmed by XRD analysis. Kinetic studies on catalytic conversion of 1,2-dichloroethane (DCE) over NiPd alloy into carbon nanomaterial (CNM) were performed in a flow reactor equipped with McBain balances in a temperature range of 580–700°C. It was shown that interaction of DCE with NiPd system results in a fast disintegration of pristine alloy with formation of submicron (0.2-0.9μm) particles, which efficiently catalyze the growth of segmented carbon filaments. According to Raman spectroscopy and transmission electron microscopy data, hydrogen concentration in reaction mixture strongly affects the structural features and density of segmented filaments. The average values of inter-segmental distance calculated from TEM micrographs of carbon filaments were found to be 96, 46, 16nm for hydrogen concentration of 23, 36 and 47 vol.%, respectively. Strongly chemisorbed chlorine species were suggested to be responsible for the cyclic perturbations in carbon transfer and deposition. Obtained carbon nanomaterials were characterized with comparatively high specific surface area (300–400m2/g) and extremely low bulk density (<0.03g/ml).

Catalyst and technology for production of carbon nanotubes

Modifying the iron-aluminum catalyst with molybdenum oxide affords a marked increase in the yield of carbon nanotubes from 1,3-butadiene diluted with hydrogen. The optimum catalyst composition is 6.5% MoO3-52% Fe2O3-Al2O3. With this catalyst, it is possible to obtain over 100 g of carbon nanotubes per gram of catalyst in a reactor fitted with a McBain balance. Replacing expensive 1,3-butadiene with the cheaper commercial propane-butane mixture (80 mol % propane + 20 mol % butane) leads to a sharp decrease in the nanotube yield because of the lower reactivity of the latter. Based on the concept of the catalytic decomposition of hydrocarbons and the formation of nanosized carbon materials via the carbide cycle mechanism, a new, efficient, CoO-MoO3-Fe2O3-Al2O3 catalyst has been developed. The enhancement of the activity of the MoO3-Fe2O3-Al2O3 catalyst by promoting it with cobalt oxide is achieved without a change in the rate-limiting step of the process. The design of a continuous reactor for carbon nanotube synthesis is suggested. The characteristics of the resulting nanotubes are presented.

Writing in Foreign Language Contexts: Learning, Teaching, and Research, Rosa Manchón (Ed.). Multilingual Matters, Bristol, UK (2009). 296 pp.

A series of micro-disperse Ni-Mo alloys with the sponge-like structure was prepared by a simultaneous precipitation method followed by sintering of the sediment in H2 atmosphere at 800 °C. According to XRD data, the formation of single-phase solid solution Ni1-xMox took place for the samples with Mo content of 0.6–8.3 wt.%. Synthesized samples were studied in a process of the catalytic CVD of C2H4Cl2 at 550–700 °C. In situ kinetic studies of carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. An interaction of Ni-Mo alloys with C2H4Cl2 is accompanied by their rapid disintegration with formation of disperse active particles catalyzing the growth of carbon nanomaterials (CNM). The strong boosting effect of Mo on the catalytic performance of Ni was revealed. The maximum yield of CNM product (8.3 wt.% Mo, 600 °C, 120 min) was as high as 45 g/gM. The study on effect of the reaction temperature on the CNM yield allowed one to define an optimal temperature regime. The impact of Mo concentration upon the morphology, structural features and textural properties of the produced carbon fibers was investigated by means of SEM, TEM, Raman spectroscopy and low-temperature nitrogen adsorption. The role of chemisorbed chlorine species in a pulse-to-pulse regime of the segmented carbon filaments formation was discussed.

The use of the consecutive adsorption of pyridine bases and carbon monoxide in the IR spectroscopic study of the accessibility of acid sites in microporous/mesoporous materials

A new approach to the evaluation of the accessibility of acid sites in microporous/mesoporous materials is developed and tested using a series of dealuminated mordenites. This approach is based on an IR-spectroscopic study of the consecutive adsorption of substituted alkylpyridines (pyridine, 2,4,6-trimethylpyridine, and 2,4,6-triethylpyridine) and carbon monoxide. This method allowed us to determine the strength and number of acid sites with various degrees of accessibility. The adsorption of 2,4,6-triethylpyridine on various types of materials is studied. The extinction coefficients of alkylpyridines are determined using a McBain balance placed in a cell for IR-spectroscopic measurements.

Synthesis and in situ gravimetric monitoring of formation of titanium-oxide layer on silica surface

Stages of formation of a titanium oxide monolayer in a flow reactor combined with a McBain balance were studied in situ in successive treatment of porous silica with a TiCl4 vapor, dried inert gas, water vapor, and again dried inert gas. The chemical composition of the resulting products, calculated using the data obtained in gravimetric monitoring, is in agreement with the results of a chemical analysis.

Formation of a frozen-like adsorbed layer of ethyltoluenes in ZSM-5 crystals and their release upon heating

The long-term sorption kinetics of p-ethyltoluene on HZSM-5 zeolite was investigated using a McBain balance. The kinetic data suggested that the transport is coupled with immobilization. In situ isomerization of p-ethyltoluene as well as temperature-programmed desorption (TPD) of the samples containing a preloaded mixture of ethyltoluenes were followed by Fourier transform infrared spectroscopy (FTIR). TPD results indicate that no significant release of immobilized m-ethyltoluene was observed at temperatures below 543 K. TPD patterns of p-ethyltoluene were found to depend strongly on the temperature of the zeolite preloading. The removal and/or isomerization of p-ethyltoluene molecules trapped by the m-ethyltoluene species immobilized on the strong acid sites can occur only when the meta-isomer leaves the zeolite channels at temperatures above 543 K.

Studies of Benzene Adsorption Layers on Silica Gels by Thermal Analysis and McBain Balance Methods

The Q-TG mass loss and first derivative Q-DTG mass loss accompanying benzene thermodesorption from silica gel samples under quasi-isothermal conditions were studied with a Derivatograph Q-1500 D (MOM, Hungary). The isotherms of adsorption-desorption of benzene vapour on different porous silica gels were measured gravimetrically by using a McBain balance. The benzene mass loss in the adsorption region, obtained from the Q-TG curves, and the adsorption capacity, established gravimetrically, exhibited a satisfactory correlation.

A thermodesorption study of first stage graphite FeCl3 intercalation compounds

Abstract With the aim of synthesizing carbonaceous materials with specific adsorbent properties obtained from the pyrolysis of mixtures of coal tar pitch (CTP) and FeCl 3 graphite intercalation compounds (GIC), we present a study of the thermodesorption of first stage FeCl 3 GIC. These GICs were synthesized in a two temperature reactor with several kinds of graphites characterized by different granulometry and crystallinity (one a monocrystalline graphite and the others, polycrystalline). During heating under an inert atmosphere, FeCl 3 is decomposed into FeCl 2 and partially sublimed. At 500 °C, second stage FeCl 2 GIC reflections are observed on X-ray diffractograms, and at 750 °C, all iron and chlorine are desorbed out of the graphene layers in polycrystalline graphite, whereas monocrystalline graphite always contains some amount of iron and chlorine. Thermogravimetric evolution has been followed using a McBain balance. FeCl 3 desorption mainly occurs between 350 and 550 °C, and is more quantitative in the case of polycrystalline materials. The graphite granulometry significantly influences the desorption level, and the higher the heating rate, the greater the FeCl 3 desorption.

Polychloroprene ‘popcorn’ growth kinetics measured by the McBain balance

The rate at which chloroprene proliferates or polymerizes by the ‘popcorn’ mechanism from the vapour has been measured by means of a McBain balance between the temperatures of 3°C and 45°C. First-order kinetics were found for growth over 2 or 3 days once an induction period was complete. The Arrhenius activation energy for the growth was found to be 38.4 ± 0.7 kJ mol −1.

Effect of iron on the behavior of Fe2O3−MoO3/SiO2 ammoxidation catalysts

Catalytic ammoxidation of propylene was studied using Fe2O3−MoO3/SiO2 catalysts, which have been prepared following a special method. Interaction of ammonia with the catalysts was studied by means of IR spectroscopy and gravimetrically using a McBain balance. Introduction of iron into MoO3/SiO2 catalysts modifies acidic as well as redox properties.