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In order to explore the effect of temperature on the cracking reaction system of 1, 1, 2-trichloro-ethane, the thermodynamic simulation calculation of the system was carried out. The reactor module RG・ ibbs in Aspen Plus VI1 was adopted and combined with the sensitivity model analysis tool to calculate the equilibrium yield of each product at 150 ~300 °C under three conditions of single component, no polymerization reaction and polymerization reaction. The thermodynamic simulation results show that under standard cond让ions, the main reaction of dehydrochlorination of 1, 1, 2・trichloroethane to produce vinylidene chloride and the side reaction of producing cis-1, 2-dichloroethylene and trans-1, 2-dichloroethylene cannot be spontaneous・ The main and side reactions are endothermic reactions・ When the temperature is 150 °C, the equilibrium conversion of the side reactions to produce trans-1, 2-dichloroethylene and cis-1, 2-dichloroethylene is the lowest and the highest, respectively・ The equilibrium conversion of 1, 1, 2-trichlo-roethane cracking reaction is directly proportional to the temperature・ When the temperature reaches 300 °C, the equilibrium conversion is close to 100%. The thermodynamic properties of related substances were verified by the DMol-3 module of Materials Stu dio. [ABSTRACT FROM AUTHOR]

Body text Keywords Body text Review policy Body text Reader comments Body text The American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications have a refined method for the calculation of time-dependent losses in prestressing force. This method estimates a gain in the prestressing force due to differential shrinkage between the precast concrete girder and the cast-in-place deck; however, it does not consider the possibility of cracking in the deck. Some state departments of transportation believe that after the deck cracks, the gain in the prestressing force is lost, and they do not include it in the prestress loss calculations. Some other state departments of transportation believe that not all of the prestress gain is lost and allow some percentage of the gain to be retained. This study focuses on the effect of deck cracking on the long-term loss of prestressing force. A finite element software model was used to simulate three different girder lengths with varying deck concrete strengths, differential shrinkage parameters, and girder ages at the time the deck was placed. When the girder age at the time of deck placement is more than 60 days, there is a high probability that the deck will crack, though a deck placed on a girder of any age may crack, depending on the properties of the deck and girder. When the deck cracks, some of the gain of prestressing force is lost, but the percentage lost depends on the extent of cracking in the deck. The older the girder is when the deck is placed, the greater the cracking. The cracked deck still provides some restraint, and even in cracked decks, nearly 50% of the prestress gain due to differential shrinkage was retained. [ABSTRACT FROM AUTHOR]

A new theoretical and practical framework has been developed through operando study of the zeolite catalytic cracking of low‐density polyethylene (as a model reaction) under reaction conditions. Results show that microporous ZSM‐5 gives rise to less cracking products. Hierarchical ZSM‐5 zeolites are more active cracking catalysts, rendering more C2‐C5 hydrocarbons, with a delayed deactivation due to the secondary porosity. This tool in combination with thermogravimetric analysis provides complementary and valuable information for the study, and design of advanced catalysts. A cracking catalyst: Operando study provides valuable information about how the ZSM‐5 catalyst works under reaction conditions for the low‐density polyethylene cracking. This study illustrates that microporous ZSM‐5 gives rise to less cracking and deactivates faster, whereas hierarchical ZSM‐5 cracking catalysts are more active with delayed deactivation due to the secondary porosity. [ABSTRACT FROM AUTHOR]

The global production of residual feedstock has reached 150 million metric tons per annum and is expected to increase in the future due to the progressively increasing heavier nature of the crudes. Petroleum coke (petcoke), one of these residues, is a solid-rich carbon typically produced during the upgrading of heavy oil and delay coking of vacuum residue in the refinery. Finding an alternative technique to treat this massive amount of petcoke is highly needed as the conventional processes like gasification and combustion have limitations in terms of efficiency and environmental friendliness. In this study, an oxy-cracking technique, which is a combination of cracking and oxidation reactions, is conducted as an alternative approach for petcoke utilization. The reaction is conducted in a Parr reactor where petcoke particles are solubilized in an aqueous alkaline medium and partially oxidized under mild operating temperature and pressure. Several operating conditions on petcoke oxy-cracking were investigated, such as temperature, oxygen pressure, reaction time, particle size and mixing rate to optimize the solubility and selectivity of oxy-cracked products. The results showed that the temperature and the residence time are the two major important parameters that affect the reaction conversion and selectivity. This enabled us to propose a reaction pathway based on the radical mechanism to describe the kinetic behavior of petcoke. Reaction kinetics indicated that petcoke oxidation undergoes a parallel-consecutive reaction in which an oxidative decomposition took place in the first step producing different oxidized intermediates. The oxy-cracked petcoke was characterized by FTIR, XPS and NMR analyses. The oxy-cracked products were found to contain carboxylic, carbonyl, phenolic, and sulfonic functions. Moreover, the elemental analysis showed that most of the metals remained in the residue, suggesting that the proposed technique could be employed for petcoke demineralization. [ABSTRACT FROM AUTHOR]

The effect of temperature on the cracking of pond acid tar and acid tar neutralized with lime has been studied. The formation of H2S or SO2 is determined by the amount of sulfuric acid in the tar. Liquid hydrocarbons obtained from neutralized acid tar are characterized by low sulfur content. [ABSTRACT FROM AUTHOR]

Purpose The cracking of a reinforced concrete lining has a significant influence on the safety and leakage of pressure tunnels. This study aims to develop, validate and apply a numerical algorithm to simulate the lining cracking process during the water-filling period of pressure tunnels.Design/methodology/approach Cracks are preset in all lining elements, and the Mohr−Coulomb criterion with a tension cutoff is used in determining whether a preset crack becomes a real crack. The effects of several important factors such as the water pressure on crack surfaces (WPCS) and the heterogeneity of the lining tensile strength are also considered simultaneously.Findings The crack number and width increase gradually with the increase in internal water pressure. However, when the pressure reaches a threshold value, the increase in crack width becomes ambiguous. After the lining cracks, the lining displacement distribution is discontinuous and steel bar stress is not uniform. The measured stress of the steel bar is greatly determined by the position of the stress gauge. The WPCS has a significant influence on the lining cracking mechanism and should not be neglected.Originality/value A reliable algorithm for simulating the lining cracking process is presented by which the crack number and width can be determined directly. The numerical results provide an insight into the development law of lining cracks and show that the WPCS significantly affects the cracking mechanism. [ABSTRACT FROM AUTHOR]

A kinetic model of the isothermal initiated cracking of tar has been developed, and parameters of the reactions have been found. A computer model of isothermal thermo-oxidative cracking of tar is implemented to determine kinetic constants, and a criterion for mismatching the calculated and experimental data is minimized. The kinetic simulation of the process has been carried out in isothermal regime so that the parameters that allow for increase in yield of target products have been determined. [ABSTRACT FROM AUTHOR]

With the aim of investigating the solutions of ethane shortage in a commercial ethylene plant, addition of propane as supplementary feedstock and increasing steam to hydrocarbon ratio were proposed as possible strategies. These strategies were proposed to compensate for the ethane shortage in the thermal cracking unit of the commercial plant. Run length, ethylene yield, and propylene yield were considered as the determining factors to appraise the strategies. The major contribution of present work would be the investigation of effect of feed shift on the run length of the steam cracker. Regarding this, five different cases were investigated in real plant condition. To include all the aspects of process, a mathematical model with reasonable assumptions was developed and then validated against the real plant data. Based on the obtained results, increasing propane concentration leads to increase in propylene yield and decrease in ethylene yield. Besides, run length of process was obtained to be longer in the cases with higher propane content in the feed stream. [ABSTRACT FROM AUTHOR]

Joint thermal treatment of heavy oil and liquid products of fast wood pyrolysis is investigated. Thermal analysis shows that the coke yield does not increase if the liquid products are added up to 20 mass%. The liquid wood-pyrolysis products decompose much earlier than heavy oil. However, the decomposition of the blends is essentially the same as pure-oil decomposition. [ABSTRACT FROM AUTHOR]

In this paper, a finite element model to analyze the cracking process of a steel fiber-reinforced concrete ( SFRC) beam on grade, loaded in two points, is presented. Already validated in the past, the numerical model used is a probabilistic explicit cracking model. The motivation of the present work is to evaluate the influence of the degree of redundancy of the mechanical system on the mechanical behavior of the beam (bearing capacity and cracking process). The main conclusion of this work is that for analyzing and properly designing SFRC structural members on grade, the only relevant tool is the finite element method using a cracking model. [ABSTRACT FROM AUTHOR]

In the paper, structural changing of resin-asphaltene molecules in cracking process of oil sand bitumen are investigated. Cracking process to natural bitumen carried out in an open-to-air reactor, which extracted from oil sand by organic solvent. Reaction temperature was 450 °С and process duration was 60 min. The reactor was heated at a rate of 10 °C/min up to the desired temperature. Di-tert-butyl peroxide was used as radical formation additive. When limiting oxygen, it can be used catalyst molecule supplies as the oxidizer. The thermal destruction processes of heavy hydrocarbons with the catalyst make it possible to increase the yield of low boiling liquid products with the formation of coke and gas as by-products. High temperature leads to increase the oil content, and decrease the total resinasphaltene components in bitumen. Monte Carlo method used for construction the molecular structure of resin-asphaltene components. The calculations data determined the most stable conformation of resins and asphaltenes molecules, that the stability of the molecules affect structural characteristics such as the number of structural blocks, their size and spatial arrangement of atoms with respect to each other. Microscopic images showed that the asphaltenes have around 40‒50 nm of particle size, which large monolithic switching, weakly focused on a major surface, provided with amorphous carbon. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the influence of Mo on the kinetics of jatropha oil cracking on HZSM-5 catalysts, in order to select catalytic materials for the production of renewable fuels and hydrocarbons as raw chemicals for the petrochemical industry. Jatropha oil was selected as a model compound of an acidic non edible vegetable oil unsuitable for biodiesel production by conventional transesterification technology. Jatropha oil was used either pure or adsorbed on Mo/HZSM-5 surfaces. A model free kinetics was developed from non-isothermal thermogravimetric experiments of vegetable oil cracking. Fast cracking experiments were performed in a micro-pyrolysis set up, at 650 °C, under helium flow, with on line products analysis (GC/MS). Results show that the increase in the Mo content of HZSM-5 induced a decrease of both specific surface area and acidity. Mo also changed the amount and distribution of hydrocarbons obtained during cracking reactions, increasing monoaromatics and decreasing polyaromatics. TG and DTG profiles during decomposition followed by thermogravimetry indicate that the jatropha oil/catalyst mixture led to a sharp decrease in the temperature at which the main mass loss events occurred. The different values obtained for the apparent activation energy of jatropha oil decomposition suggest a different route of reaction in the presence of Mo by comparison with cracking of pure oil. [ABSTRACT FROM AUTHOR]

Jet fuel is used as a coolant before it is burned in the combustor of the aircraft. Insoluble particles and surface deposits can impair engine performance. Jet fuel thermal oxidation test (JFTOT) defines the standard test method for evaluation of the deposit formed through heating fuels in tubes caused by thermal oxidation (< 400 °C). At a higher temperature, fuel in the heating process decomposes leading to surface deposits by coking. In this work, we propose a method to evaluate the security of fuel flowing in the tube at high temperatures (> 500 °C). The heat transfer and cracking performances of two hydrocarbon fuels which are laboratory modified aviation kerosene (Fuel 1 ( ρ = 0.85 g/cm 3 ) and Fuel 2 ( ρ = 0.78 g/cm 3 )) have been investigated in a heat-exchanger under supercritical conditions ( T = 700–770 °C, p = 2.5–5.5 MPa, m = 0.4–1.0 g/s). The temperature and flow rate in this work are much higher than those in JFTOT. The safe run time (SRT) is used to evaluate the heat transfer security of each fuel. As the temperature increases or the flow rate decreases or the pressure increases, the SRTs of Fuel 1 and Fuel 2 decrease clearly. In general, the heat transfer security of Fuel 1 is better than that of Fuel 2. Moreover, the volumetric heat sink of Fuel 1 is larger than that of Fuel 2. So, the overall performance of Fuel 1 is more excellent when it is used as propellant and coolant for hypersonic aircraft. In consideration of the heat transfer security, heat sink and the required driving force for aircraft, the temperature of fuel at the exit of heat transfer passage should be set as 740 °C, the flow rate of fuel should be 0.6–1.0 g/s, the pressure of heat transfer passage should be 3.5 MPa. Based on these results, we find that the modification of a high density fuel is an effective way to prepare an advanced hydrocarbon fuel. [ABSTRACT FROM AUTHOR]

A variety of materials are used in the Oil & Gas industry ranging from carbon steel, stainless steel to nickel alloys, etc. including non-metallic materials as well. Amongst these, carbon steel is the industry favorite because of many of its desirable attributes like machinability, weldability, availability, and cost. Wide use of carbon steel in the industry is also due to the presence of required properties for the specific application. In spite of carbon steel's wide uses, poor workmanship, improper heat treatment, or negligent manufacturing processes can reduce its service life and also can lead to unexpected failures. One such failure case involves carbon steel plate meant for construction of a tank that failed by cracking immediately after the welding operation. A detailed investigation was carried out by means of visual examination, metallographic and chemical analysis, SEM, and EDAX analysis. Microstructure revealed banded pearlitic structure along with a number of inclusions, a few of which were elongated. In conclusion, stresses due to weld joint restraint, elongated inclusions, and high transverse direction stresses after welding resulted in lamellar tearing which propagated in the linear direction along the weld line. [ABSTRACT FROM AUTHOR]

Uniform distribution of liquid feed on fluidzed bed increase yield on valuable of products and improves operability in the process of fluid coking, and it is of crucial improtance to optimize the contact between the injected liquid and the bed solids. The moisture in fluidized bed is divided into three groups: (a) free moisture, (b) microagglomerates, and (c) macroagglomerates. The goal of this study was to develop a rapid and reliable experimental technique to assess the liquid-solid contact efficiency resulting from the injection of gas-atomized liquid feed. Immediately after the injection of liquid through an atomization nozzle, the triboelectric charges accumulated on the particles migrated to a grounded electrode through the paths offered by the conductive liquid. The methods based on the in situ measurements of the bed conductance varies with time, therefore, use to detect the liquid distribution on different agglomerates, and the air-liquid ratio effect of nozzle is also presented. [ABSTRACT FROM AUTHOR]

HY zeolite catalysts on montmorillonite, pillared with aluminum hydroxo complexes in different concentrations, have been tested in the cracking of heavy vacuum gas oil (VGO) from the Shymkent refinery (Kazakhstan). It has been shown that the VGO cracking activity of the catalysts is directly related to the textural and acid properties of the samples. The hydrocarbon group and fractional compositions of cracked gas-oline have been determined. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the products of homogeneous cracking of rice husk tars and to investigate the conditions for production of hydrogen rich syngas. Experiments were performed in a two-stage downdraft fixed-bed gasifier as a function of temperature and residence times. Tars were generated with a medium heating rate of 25 K/min in a pyrolysis section of the gasifier. Generated tars were subsequently cracked by secondary reactions in gasification section. Tar conversion of about 91% was achieved. Tar cracking at higher temperatures resulted in the formation of hydrogen rich syngas. Secondary product yields and their kinetics were studied for tar cracking and individual gas formed by single-reaction model and distributed activation energy model. A good fit of the data was obtained with the single-reaction model; however distributed activation energy model correlated the tar cracking kinetic parameters more closely than single-reaction model. [ABSTRACT FROM AUTHOR]

Two-step hydrotreatment experiments were performed using three completely different bio-oil fractions namely: whole bio-oil, heavy bio-oil obtained after fractional condensation of pyrolysis vapours and pyrolytic lignin obtained by cold water precipitation of the bio-oil. The aim is to study the de-oxygenation and in addition SEC and UV-fluorescence analysis was used to identify the importance of cracking, polymerization and hydrogenation reactions of the three different bio-oil feedstocks. In the first step hydrotreatment, Ru/C was used at 250 or 300 °C with reaction time of 2 h. In the second step hydrotreatment, Ni-Mo/Al 2 O 3 catalyst was used at 375 or 400 °C, with reaction time of 2 or 4 h. During stabilization in the first step, pyrolytic lignin was hydrogenated to a large extent accompanied by cracking reactions. In the second step, unsulphided Ni-Mo/Al 2 O 3 catalyst was active enough to effectively crack pyrolytic lignin into smaller molecules. High molecular weight compounds including large aromatic ring structures were formed from the reactive sugar rich fraction in both first step stabilization and second step hydrotreatment. The newly formed polymerization products were difficult to crack even at extended reaction times of 4 h at 400 °C. Importantly, the presence of water (and light oxygenates) could significantly supress the polymerization reactions. [ABSTRACT FROM AUTHOR]

Cracking–Deoxygenation process is one of the important reaction pathways for the production of biofuel with desirable n- C 17 hydrocarbon chain via removal of oxygen compounds. Calcium-based catalyst has attracted much attention in deoxygenation process due its relatively high capacity in removing oxygenated compounds in the form of CO 2 and CO under decarboxylation and decarbonylation reaction, respectively. In the present study, deoxygenation of triolein was investigated using Ca(OH) 2 nanocatalyst derived from low cost natural waste shells. The Ca(OH) 2 nanocatalyst was prepared via integration techniques between surfactant treatment (anionic and non-ionic) and wet sonochemical effect. Results showed that sonochemically assisted surfactant treatment has successfully enhanced the physicochemical properties of Ca(OH) 2 nanocatalyst in terms of nano-particle sizes (∼50 nm), high surface area (∼130 m 2 g−1), large porosity (∼18.6 nm) and strong basic strength. The presence of superior properties from surfactant treated Ca(OH) 2 nanocatalysts rendered high deoxygenation degree, which are capable of producing high alkane and alkene selectivity in chain length of n-C 17 (high value of C 17 /( n -C 17 + n -C 18 ) ratio = 0.88). Furthermore, both Ca(OH) 2 –EG and Ca(OH) 2 –CTAB nanocatalysts showed high reactivity with 47.37% and 44.50%, respectively in total liquid hydrocarbon content of triolein conversion with high H/C and low O/C ratio. [ABSTRACT FROM AUTHOR]

A discrete six-lump kinetic model for the thermal cracking of vacuum residue in the visbreaking process has been developed, and the time-dependent behavior of each individual lump has been determined. A combination of the heuristic method and gradient-based method (hybrid method) has been taken into account to optimize the parameters of the model. A new concept of objective functions has been presented and applied for optimization, so more acceptable results have been obtained. Such an approach has not been presented before. A number of 60 parameters was considered primarily, which has been reduced to 36 with the aim of flash calculation information, and optimized. The obtained results are in good agreement with experimental data. The analysis of the estimated rate constants showed that the cracking of vacuum residue to lighter products was the more dominant reaction pathway during the visbreaking process over the temperature range of 400-430 °C. [ABSTRACT FROM AUTHOR]

Jatropha oil was cracked over micoporous catalysts, such as HY, HZSM-5, and HMordenite, at the optimized conditions obtained over Hβ towards cracking of jatropha oil. The synthesized catalysts were characterized by X-ray diffraction, Brunauer-Emmett-Teller surface area analyzer, inductively coupled plasma, and temperature programmed desorption techniques. Among the microporous materials, HZSM-5 catalyst was found to be the best in terms of conversion (62%), selectivity towards green gasoline (50%), and less coke formation (0.8%) in the cracking of jatropha oil. Cracking of other oils, such as castor, neem, and pongamia, under the optimized conditions resulted in 82% conversion of castor oil; however, higher selectivity towards green gasoline (49%) was obtained in the cracking of pongamia oil. [ABSTRACT FROM PUBLISHER]

The article shows the results of thermal cracking of natural bitumen of Kazakhstan's two deposits. The variation of the chemical and the fractional composition of the cracking products are determined depending on the process conditions. A comparative analysis of the influence of the catalyst is carried out to composition of natural bitumen. [ABSTRACT FROM AUTHOR]

-Highlights: [•] The concentration of BrÃnsted and Lewis sites increases upon desilication. [•] Desilication with NaOH&TBAOH preserves the crystallinity of mesoporous Beta zeolite. [•] Cracking of gasoil over mesoporous Beta results in high propylene selectivity. [ABSTRACT FROM AUTHOR]

This research involved the application of a shrinkage-compensating additive to a concrete mix, to reduce cracking due to shrinkage by drying in the construction of industrial floors. Thus, panels can be built up to ten times larger than the recommended size (3×3 m) for a thickness of 15 cm, based on the recommendations of ACI 360 and ACI 302. This can minimize the number of joints and also the problems of warping, leaking water and other liquids, chipping, and inadequate load transfer. The methodology consists in finding the optimum dose of additive, based on a mix design for a rupture modulus of 4.2 MPa, subjected to restricted expansion and contraction tests with various types of domestic cements and different percentages ofadditive dosing. Once all laboratory tests were carried out under the norm ASTM C878, it was found that the dosage of 9% of additive was adequate. Higher doses produce internal cracks in the concrete, and lower doses did not expand the concrete enough to offset the contraction of it. Following this, a 9 x 12 x 0.15 m slab without joints was built using the optimum shrinkage-compensating additivefound in the series of laboratory experiments. After implementing a curing process no cracks were generated during drying, verifying the laboratory results and leaving open the possibility to produce larger panels for industrial floors. [ABSTRACT FROM AUTHOR]

Peridynamic (PD) theory is used to investigate the dynamic responses of electronic packages subjected to impact loading arising from drop-shock. The capability of the PD theory to predict failure is demonstrated by simulating a drop test experiment of a laboratory-type package. The failure predictions and observations are exceptionally similar. For the drop test simulation of a production-type package, the finite element method (FEM) and PD theory are coupled via a submodeling approach. The global modeling is performed using the FEM while the PD theory is employed for the submodeling and failure prediction. The analysis yielded the outermost solder joint as the critical joint, with failure at the interface between the solder and copper pad on the printed circuit board side. [ABSTRACT FROM AUTHOR]

It is shown that axial, radial, and peripheral velocities of feed material in centrifugal vortex chamber pronouncedly differ in magnitude. The full velocity is high and attains 43 m/sec on the vortex surface. It is concluded that the cavitation region must be on the vortex surface itself, where indeed cracking of hydrocarbons intensifies. The parameters of the cavitaiton region are determined from the static liquid pressure at all points of the cavitation apparatus. The distribution of static pressure of the liquid in the centrifugal vortex chamber has a complicated pattern: the cavitation region represents a hollow truncated cone, inside which occurs a cylindrical steam vortex. Formation of a turbulent layer expands the cavitation region, the shape and size of which are calculated from the parameters of a real centrifugal chamber. [ABSTRACT FROM AUTHOR]

Abstract: A series of hierarchical porous zeolites (ZSM-5–ZRP-1) was synthesized by adding different contents of ZRP-1 to the procedure of hydrothermal synthesis of ZSM-5. The prepared samples were characterized by using N2 adsorption–desorption, XRD, SEM, TEM, NH3-TPD, Py-FTIR and investigated in cracking of n-heptane. The results indicate that physicochemical properties and catalytic performances of ZSM-5–ZRP-1 samples are quite different from those of HZSM-5 or ZRP-1. ZSM-5–ZRP-1 samples have a lot of mesopores and suitable amount of B+L acid sites as well as higher L/B ratio compared with HZSM-5 or ZRP-1, and also show medium acid amount and strength. These lead to a higher selectivity of olefins (ethylene plus propylene) obtained on it. [Copyright &y& Elsevier]

Here we reveal that a Cu/Cu laminated composite with an appropriate mechanical contrast between constituent layers can effectively improve the toughness and fatigue strength of cold rolled Cu. The local interface delamination-induced retardation of cracking and the secondary initiation of fatigue cracks at inner layer surfaces are the main mechanisms. Such the single material laminated with mechanical contrast provides a potential way to improve fatigue strength. [Copyright &y& Elsevier]

Abstract: Radial fretting tests on human femur cortical bone with a ball-on-flat configuration were carried out in vitro under different normal contact loads. The kinetics behaviors and damage characteristics of the cortical bone were analyzed using the load versus displacement (F–D) curves. The fretting scars were examined using laser confocal scanning microscopy (LCSM) and scanning electron microscopy (SEM). A nano-indenter was used to characterize the mechanical property of the osteon of the cortical bone. Morphologies showed that the primary damage form was due to micro-cracking. Around the osteon, three kinds of micro-crack configurations were observed; i.e. annular cracks—located at the concentric lamellae; radial cracks—initiated from the Harversion canal; and interstitial cracks—initiated and propagated between the interstitial lamellae. Plenty of interstitial cracks occurred in the wear scar, which indicated that the interstitial tissue was the weak zone in the structure of cortical bone. In addition, the contact stresses under the radial fretting condition were calculated by the finite element method analysis (FEMs) and the behaviors of cracking were explained. The results demonstrated that the stress concentration that occurred around the Harversian canal and osteon system resulted in a better resistance than that from the interstitial tissue. The concentric lamellae presented a better radial-fretting resistance and contact fatigue resistance than that from the interstitial lamellae. [Copyright &y& Elsevier]

Bio-oil has attracted considerable interest as a promising renewable energy resource because it can be utilized as a feedstock in integrated bio-refineries for the production of highly valuable chemicals and next-generation hydrocarbon fuels. However, it is necessary to improve the bio-oil quality before it can be fed to bio-refineries. Currently, catalytic vapor cracking seems a more attractive process than catalytic upgrading technologies, such as hydrotreating and esterification, in order to improve the bio-oil quality. This review presents a summary of recent research and the state of art technology for the catalytic vapor cracking of bio-oil, focusing on the catalysts applied, upgrading methods and reaction mechanisms. [ABSTRACT FROM AUTHOR]

The main process in oil refinery technologies is the cracking of the heavy fraction of oil into light and valuable hydrocarbons. Dielectric barrier discharge (DBD) reactors, working at atmospheric pressure and low temperature, is one of the newest methods for cracking hydrocarbons, which has been successfully used to crack low-carbon-containing molecules. Therefore, in this paper, the cracking of n-hexadecane as a heavy hydrocarbon fed by using the cylindrical DBD reactor (nonthermal plasma) has been investigated. We studied the effects of gas type, applied voltage, and gas flow rate quantitatively and qualitatively by using gas chromatography with flame ionization detector and mass spectrometry detector. Results showed that methane has better effects on both conversion and cracking percentage in comparison with air. Also, it has been shown that increasing the applied voltage and working gas flow rate enhances the conversion and the cracking percentages. The highest conversion percentage obtained was 9.26% when the applied voltage and methane flow rate were 12 kV and 50 sccm. In this condition, the cracking percentage obtained was 84.34% of the products. [ABSTRACT FROM PUBLISHER]

The author proposes a variant of modernization of the catalytic processes of deep hydrocarbon conversion. The main difference and advantage of the proposed approach and technology is that raw materials, basically heavy materials that contain great amount of different harmful mixtures, do not directly interact with the catalyst. The suggested method has a great perspective and can be easily used in the petroleum industry, and may be much cheaper than the known processes of deep conversion. The use of natural and accompanying gas, which is in many cases burned in flares, to generate atomic hydrogen or light radicals makes it possible to minimize costs of the process of deep conversion. The technology is easy to operate and does not require heavy investment and operating costs. [ABSTRACT FROM AUTHOR]

Abstract: An assessment of the process conditions for the isomerization–cracking of long-chain n-paraffins over commercial Pt/SO4 2––ZrO2 catalysts was made. Pretreatment and reaction conditions were optimized with a focus on the maximization of the yield of short, high octane branched paraffins for the gasoline pool. While selectivity was an important issue attention was also paid to the reduction of the yield to gases (C1–C4). Therefore cracking had to be modulated to produce the correct molecular size adjustment without scission to too much smaller fragments. Skeletal isomerization was to be maximized. The activity in both acid-catalyzed reactions had to be tuned while keeping a stable activity level. The only pretreatment condition assessed was the calcination temperature (screened in the 600–800°C range). Calcination at 600°C produced the highest activity level while 700°C was convenient from the point of view of selectivity. The optimum temperature coincided with the production of the highest concentration of Brönsted acid sites. Regarding the reaction conditions, increasing temperature values augmented the conversion but also increased the cracking. Therefore optimum values were found at a moderate temperature, 225°C, given the high reactivity of the feed. Space velocity values were analyzed with attention to the liquid C5+ yield, the selectivity to branched isomers and the stability of the catalysts. Best yields to branched naphtha products were obtained at WHSV=18h–1. The H2/hydrocarbon molar ratio was a function of the catalyst coking rate. A value of 10 was enough to attain a stable conversion value. The values of liquid yield as a function of pressure displayed a volcano pattern that was rationalized in terms of a non-classical bifunctional mechanism of reaction. High pressure values increased the concentration of Brönsted acid sites and hence the activity while high pressures enhanced hydrocracking and decreased the liquid yield. The optimal pressure value was 20atm. [Copyright &y& Elsevier]

Abstract: The article is devoted to the study of rapeseed oil cracking in the presence of zeolite catalysts in order to prepare the liquid fraction with the properties close to fossil diesel.To evaluate the cracking products, the chromatographic methods GL and GC/MS were used, together with the determination of viscosities, acid values and densities. The cracking of rapeseed oil in the presence of zeolite-type catalysts in batch arrangement at temperatures between 350 and 440°C gave a yield of liquid condensate 85 to 90wt.%. After removal of volatile components 3 to 9wt.% by distillation at the temperatures up to 190°C, the GL chromatogram of treated condensate was similar to that of fossil diesel fuel. The paper deals with the influence of the kind and amount of catalyst on composition and properties of treated products with the use of GL and GC/MS chromatography and with the tests of blends of fossil diesel fuel with cracking products at contents up to 7vol.%. The blended fuels meet all parameters specified by standard EN 590 for diesel fuel. [Copyright &y& Elsevier]

Abstract: In order to increase the yield of cymene in alkylation of toluene with isopropanol, ZSM-5 zeolite units were incorporated into a mesostructured material. The catalysts were characterized by X-ray diffraction, TGA, SEM, NH3 temperature-programmed desorption and FTIR of pyridine adsorption. XRD analysis indicated that a structurally well ordered cubic MCM-48 aluminosilicate was successfully assembled from ZSM-5 zeolite seeds. The ZSM-5/MCM-48 catalyst exhibited significantly improved toluene conversion and yield of cymene product for toluene isopropylation. Catalytic tests show that the ZSM-5/MCM-48 composite material exhibits high catalytic activity compared with the conventional Y-zeolite for catalytic cracking of 1,3,5-triisopropylbenzene (TIPB). The exceptional catalytic performance of ZSM-5/MCM-48 catalyst in cracking and alkylation reaction was attributed to the easier access of active sites provided by the mesopores for both reactant and larger product molecules. The apparent activation energies for the cracking of 1,3,5-TIPB over ZSM-5/MCM-48 catalyst were found to decrease as follows: E C/CM-3 (tertiary cracking) > E C/CM-4 (disproportionation) > E C/CM-2 (secondary cracking) > E C/CM-1 (primary cracking). [Copyright &y& Elsevier]

Abstract: We study one-dimensional flows, when air is injected into a porous medium filled with inert gas, medium or high viscosity oil and water, giving rise to a combustion wave in a process known as high-temperature oxidation (HTO). In the oil we distinguish three pseudo-components: asphaltenes, medium and light oil. At high temperatures, the heaviest components (“precoke”) are converted to coke, which undergoes combustion. Medium oil components are cracked at intermediate temperatures releasing gaseous oil. Light oil components and water are vaporized. The oxidation rate of gaseous oil components is negligible. Combustion regimes are described in the form of a sequence of waves. We develop a simple mathematical pathway based on Zeldovich’s approach to provide analytical formulae for parameters in these waves. It is shown that there is a combustion regime in which either coke or oxygen are partially consumed in the combustion as well as a regime in which both are consumed completely. Each of the regimes can be subdivided in two regimes, where the reaction is either trailing or leading with respect to the thermal wave. Explicit conditions for each combustion regime are given. The structure of the oil cracking layer is investigated. Stability of the solutions is studied. We analyse our formulae for typical in situ combustion data and compare the results with numerical simulations. [Copyright &y& Elsevier]

Abstract: Near-infrared radiation was combined with fluidized-bed drying to reduce the cracking and breakage of soybean grains because of its advantages such as a decrease in the moisture gradient and the stresses development within the grain kernel, leading to high quality of product. Physical qualities, i.e. cracking, breakage and colour, were investigated together with microstructure of soybean grains. Protein solubility and urease activity were also determined. The parameters studied were near-infrared radiation powers of 4, 6 and 8kW, air velocity of 4.5m/s, air temperature of 40°C and grain bed depth of 6cm. Results showed that the drying rate was increased with the increase of near-infrared radiation power. The moisture content was reduced from an initial moisture content of 20% d.b. to the final moisture contents of 13.5% d.b. (4kW), 12.8% d.b. (6kW) and 12.5% d.b. (8kW). The cracking and breakage of soybean grains occurred negligible, which was lower than 4.4% and 5.3% for cracking and breakage, respectively. At near-infrared radiation powers of 4 and 6kW was accepted for both soybean grains trade and animal feed industries in Thailand. The total colour difference changes (ΔE) were varied in the range of to 2.9–4.2. The protein solubility of final product was in an acceptable range (77–82%) for feed meal. The reduction of residual urease was varied in the range of to 39–70%. This study has demonstrated that the soybean grains under combined near-infrared radiation and fluidized-bed drying was properly treated. [ABSTRACT FROM AUTHOR]

The process of cracking dicyclopentadiene to produce cyclopentadiene using hydrogen as a carrier gas is investigated. This process has many advantages over using N2 or water vapor as a carrier gas for producing anhydrous polymerization level dicyclopentadiene. Factors, including cracking temperature, reaction time, and H2 to oil ratio, are studied. The conversion of dicyclopentadiene increases with the increasing of cracking temperature and reaction time; the yield of cyclopentadiene increases, and then drops a little with the increasing of reaction time. Optimal reaction conditions are as follows: suitable cracking temperature is 320°C, reaction time is 1 sec, and H2 to oil ratio is 50. Cracking temperature of the process is about 30°C lower than using N2 or water vapor as the carrier gas. At the optimal conditions, the conversion of dicyclopentadiene could reach 98%, while the yield of cyclopentadiene is 97%. The reaction kinetic model of the process is also studied, and the model could predict the conversion of dicyclopentadiene well. [ABSTRACT FROM AUTHOR]

Ni/ZSM-5 catalyst is prepared using an incipient wet impregnation method with 4 wt% of Ni on mildly framework dealuminated ZSM-5 and studied for its physicochemical properties and light alkane conversions. X-ray diffraction (XRD) and pore size distribution studies envisioned the formation of Ni crystallites smaller than 0.55 nm in the zeolite pore channels of Ni/ZSM-5. The Ni/ZSM-5 exhibited better cracking and produced more liquefied petroleum gas (LPG) in the presence of N2 (LPG mode) and better aromatization activity in the presence of H2 (aromatic mode). This has resulted in the production of gasoline blending stock with a Research Octane Number (RON) of 91. [ABSTRACT FROM AUTHOR]

Abstract: On the basis of development in the laboratory, the SiO2/S coating was prepared on the internal surface of HK40 alloy tube in a pilot plant setup. The coating sampled on the outlet of furnace tube was characterized by scanning electron microscope (SEM). The anti-coking property of the SiO2/S coating was evaluated with light naphtha according to pressure changes. The morphologies and chemical components of cokes on the outlet of the coated and blank tubes were characterized by SEM and energy dispersive spectroscopy (EDS), respectively. The main product yields of light naphtha steam cracking were analyzed by gas chromatography–mass spectrometry (GC–MS). The results show that the SiO2/S coating is compact and has a thickness of 15μm on the outlet of furnace tube. The SiO2/S coating reduces coke yield by 60% compared to that observed in the blank tube during 8h cracking run. However, the coke reductions of the SiO2/S coating are both about 40% when the cracking time is 26h and 66h, respectively. The outlet of the coated tube has the exfoliated coke with a thickness of about 30μm. The coke on the process side has many irregular particles, and the coke on the metal side is not filamentous coke but amorphous coke particles after the exfoliated coke is taken away. The yield of C2H4 has a slight increase in the coated tube, and the yield of C4H8 has a decrease. However, the SiO2/S coating has little influence on the total yield of olefin. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to investigate the Coefficient of Thermal Expansion (CTE) of anodic films on 7175 T7351 aluminium alloy and to evaluate the influence of the film characteristics on this value. In particular, effects of porosity and post-treatments, such as coloring and sealing, were studied. Beam bending analysis was used as the experimental method and a numerical finite element model was developed to verify theoretical relationships hypotheses. In particular, the errors induced by the use of theoretical relationships between the curvature of the sample and stresses in the film were not negligible. A relation based on a finite element model was then developed and used to calculate stresses. The experimental value of CTE obtained by beam bending test was then validated by comparing the experimental cracking temperature of anodic films with a theoretical value directly depending on the previously determined CTE. The CTE of anodic films was found to be 13.0±1.010−6 K−1 independent from the porosity of the films and from the post-treatment (inorganic coloring and sealing). [ABSTRACT FROM AUTHOR]

Abstract: The transformation of petroleum asphaltenes in supercritical water was studied. The experiments were performed in autoclave at temperature 380°C and pressure 226atm with stirring for 3h, medium density was about 0.33g/cm3. The reaction resulted in the formation of gas products, about 4.3%, and an insoluble residue (coke) with about 48.6% yield. The remaining products were separated into fractions by consecutive dissolution in hexane (30.0%), benzene (10.6%), and chloroform (5.7%). The properties of the obtained products were studied with FT-IR spectrometry and 1H NMR spectroscopy. The method of simulated distillation was used to demonstrate that the fractional composition of the hexane-soluble part of the products is close to the fractional composition of a mixture of the diesel fraction and vacuum gas oil of the corresponding oil in 1:1 ratio. The obtained data support the conclusion that asphaltene cracking proceeds in SCW, with most probable main processes being dealkylation of substituents in the aromatic fragments of molecules and aromatization. This leads to formation of gaseous products and hexane-soluble fraction consisting of lighter aliphatic and aromatic compounds, as well as carbonized solid residue. [ABSTRACT FROM AUTHOR]

Abstract: A mixture of hospital post-commercial polymer waste (LDPE/HDPE/PP/PS) was pyrolyzed over various catalysts using a fluidized-bed reactor operating isothermally at ambient pressure. The yield of volatile hydrocarbons with zeolitic catalysts (ZSM-5>MOR>USY) were higher than with non-zeolitic catalysts (MCM-41>ASA). MCM-41 with large mesopores and ASA with weaker acid sites resulted in a highly olefinic product mixture with a wide carbon number distribution, whereas USY yielded a saturate–rich product mixture with a wide carbon number distribution and substantial coke levels. The systematic experiments discussed in this paper show that the use of various catalysts improves the yield of hydrocarbon products and provide better selectivity in the product distributions. A novel developed model based on kinetic and mechanistic considerations which take into account chemical reactions and catalyst deactivation for the catalytic degradation of commingled polymer waste has been investigated. This model represents the benefits of product selectivity for the chemical composition such as alkanes, alkenes, aromatics and coke in relation to the performance and the particle size selection of the catalyst used as well as the effect of the fluidizing gas and reaction temperature. [Copyright &y& Elsevier]

There are two types of lead–zinc ore bodies, i.e., sandstone-hosted ores (SHO) and limestone-hosted ores (LHO), in the Jinding giant sulfide deposit, Yunnan, SW China. Structural analysis suggests that thrust faults and dome structures are the major structural elements controlling lead–zinc mineralization. The two types of ore bodies are preserved in two thrust sheets in a three-layered structural profile in the framework of the Jinding dome structure. The SHO forms the cap of the dome and LHO bodies are concentrated beneath the SHO cap in the central part of the dome. Quartz, feldspar and calcite, and sphalerite, pyrite, and galena are the dominant mineral components in the sandstone-hosted lead–zinc ores. Quartz and feldspar occur as detrital clasts and are cemented by diagenetic calcite and epigenetic sulfides. The sulfide paragenetic sequence during SHO mineralization is from early pyrite to galena and late sphalerite. Galena occurs mostly in two types of cracks, i.e., crescent-style grain boundary cracks along quartz–pyrite, or rarely along pyrite–pyrite boundaries, and intragranular radial cracks in early pyrite grains surrounding quartz clasts. The radial cracks are more or less perpendicular to the quartz–pyrite grain boundaries and do not show any overall (whole rock) orientation pattern. Their distribution, morphological characteristics, and geometrical relationships with quartz and pyrite grains suggest the predominant role of grain-scale cracking. Thermal expansion cracking is one of the most important mechanisms for the generation of open spaces during galena mineralization. Cracking due to heating or cooling by infiltrating fluids resulted from upwelling fluid phases through fluid passes connecting the SHO and LHO bodies, provided significant spaces for crystallization of galena. The differences in coefficients of thermal expansion between pyrite and quartz led to a difference in volume changes between quartz grains and pyrite grains surrounding them and contributed to cracking of the pyrite grains when temperature changed. Combined thermal expansion and elastic mismatch due to heating and subsequent cooling resulted in the radial and crescent cracking in the pyrite grains and along the quartz–pyrite grain boundaries. [ABSTRACT FROM AUTHOR]

To prevent premature failures of rehabilitated concrete pavements, transportation authorities need tools to characterize the prerehab pavement condition of its load carrying capacity, and to determine the resistance of the overlay material to underlying crack/joint movements. Two quantitative methods, the rolling dynamic deflectometer (RDD) and overlay tester (OT), along with field performance data were employed in rehabilitation studies involving reflective cracks. The RDD is able to continuously assess vertical differential movements at joints/cracks that represent the potential for reflective cracks on existing pavements. The OT has the ability to determine the resistance of the overlay material to underlying crack/joint movements. The RDD W1-W3 deflections were used to determine areas that have a high potential for reflective cracking due to poor load transfer across joints and cracks. This paper documents results from the RDD and OT on the following five rehabilitation projects: (1) SH225; (2) US96; (3) SH12; (4) SH342; and (5) IH35W. Based on the available test results from these five projects, it was observed that the W1-W3 threshold values of 5.5 mils (0.140 mm) for exposed concrete pavement and 6.5 mils (0.165 mm) for composite pavement with existing hot mix asphalt overlay and an OT threshold value of 700 cycles correlated well with the field performance. Ignoring either of these critical factors may lead to premature reflective cracking. [ABSTRACT FROM AUTHOR]

Abstract: The thermal cracking and the thermal catalytic cracking of soybean oil were evaluated for the production of biofuels as an alternative to fossil fuels. The catalyst proposed for the cracking reaction was bauxite, a high-acidity and low-cost catalyst. The chromatographic profile of the biofuels obtained by cracking showed hydrocarbon compounds such as alkanes, alkenes and aromatics, as well as some oxygenated compounds such as carboxylic acids, ketones and alcohols. The products generated by the thermal catalytic cracking process showed better results than the thermal cracking products because of the low quantity of acids present. The catalyst used was thus shown to act in the secondary cracking process, in which the fatty acids decompose and generate hydrocarbons. [Copyright &y& Elsevier]

The influence of technological parameters on the cracking performance of concretes with regards to mixture design, curing, and use of admixtures in normal-strength concretes (NSC) and high-strength concretes (HSC) was investigated. It is concluded that shrinkage and cracking sensitivity are largely independent of the water-cement ratio (w/c) and cement content in NSC. Yet, the internal shrinkage-induced stresses are higher in the lower w/c concrete, but because its strength is also higher, cracking sensitivity is not different than that of a higher w/c concrete. HSC is much more sensitive to cracking than NSC but this sensitivity can be mitigated by either sealed curing or incorporation of shrinkage-reducing admixtures (SRA). Combination of the two results in concretes with very little buildup of internal stresses upon drying. The integrated criterion for cracking sensitivity, based on combining the criteria of time to cracking and stress rate, was shown to be more reliable for the classification than the individual ones. [ABSTRACT FROM AUTHOR]

Abstract: Imperviousness of clay based barrier, which is provided in cover system of low-level radioactive waste disposal sites, is essential to mitigate the environmental hazard. The objective of this paper is to examine the influence of geogrid reinforcement on the deformation behaviour of clay based cover systems subjected to differential settlements. A series of centrifuge tests were performed on model clay barriers with and without the inclusion of geogrid reinforcement at 40 gravities. Motor-based differential settlement simulator was custom designed and developed for inducing continuous differential settlement in high gravity environment. By maintaining type and location of the geogrid within the clay barrier as constant, the thickness of clay barrier is varied. The performance of the clay barrier with and without geogrid layer having an overburden pressure equivalent to that of cover system was monitored by measuring water breakthrough at the onset of differential settlements. It was observed that both 0.6 m and 1.2 m thick clay barriers with and without overburden experienced cracks extending up to full depth. In comparison, geogrid reinforced clay barrier was found to sustain large distortions with an enhanced imperviousness. With the provision of an overburden equivalent to that of cover system, integrity of geogrid reinforced clay barrier was found to be retained even after inducing a distortion level of 0.125. This implies that provision of thickness of clay barrier equal to 0.6 m reinforced with a suitable geogrid may be adequate in sustaining higher distortion levels. [Copyright &y& Elsevier]

HMCM-22 zeolite with a high Si/Al2 ratio (158) was applied to the 1-butene cracking reaction in a fixed-bed reactor. On basis of the product distribution, the main reaction pathways of C4 alkenes catalytic transforming on HMCM-22 were proposed. Also, the preferences of the reaction pathways influenced by the temperature and conversion level were discussed, which could provide good guidance on enhancing the propene production. [ABSTRACT FROM AUTHOR]

This article is a contribution to modeling and analysis of the cohesion strength of saturated porous bodies during drying processes. The dependence of the drying-induced state of stress, the overall (reduced) stress, and the admissible stress on moisture content is discussed. The strength criterion is proposed stating that possible cracking of the material during drying takes place in regions where the reduced stress exceeds the critical admissible value for the given moisture content. Numerical calculations of the drying-induced stresses were carried out for a convectively dried kaolin cylinder, and the regions of possible material cracking within the cylinder were determined. This theoretical prediction of the possible cracking place in the material is consistent with the experimental data previously presented by the authors. [ABSTRACT FROM AUTHOR]