Search

The effects of cloudiness on solar ultraviolet irradiance recorded between May and October 2012 at Marsaxlokk, Malta, are analysed. A statistical analysis of cloudiness is carried out, with clear skies (0–2 oktas) proving to be the most frequent conditions under total and low cloud cover. Hence, the dependence of erythemal UV solar irradiance (UVER) on total and low cloud cover is evaluated. In all cases, low clouds show higher attenuation. The effects of total cloud cover and low clouds on UVER are evaluated by means of the cloud modification factor (CMF) that is defined as the ratio between the measured irradiance and the estimated irradiance under cloud-free conditions. The results show that the effect on UVER is less than on global solar irradiance and that UVER transmissivity under overcast conditions can reach 50%. The effect of cloud optical thickness (COT) on UVER under all conditions shows a clear exponential dependence. The analysis shows that for fairly thick clouds with a COT of 10, the UVER reaching the Earth’s surface is about 50% of its cloud-free value. The CMF UVER is found to decrease from 0.7 for COT = 0.5 to 0.25 for COT = 30. 10-min estimated COT from global solar irradiance are then compared with the GOME2 instrument. The correlation is found to be low. The influence of COT is studied by observing the evolution of irradiance on two cloudy days. When comparing the 10-min CMF under high COT for UVER and global irradiance, the first variable is found to be slightly higher than the second. As a consequence, changes in the ultraviolet index (UVI) due to COT effects are then described. Finally, the results obtained are compared with those from previous studies performed by different authors. [ABSTRACT FROM AUTHOR]

This paper analyzes Harsanyi power solutions for cooperative games in which partial cooperation is based on union stable systems. These structures contain as particular cases the widely studied communication graph games and permission structures, among others. In this context, we provide axiomatic characterizations of the Harsanyi power solutions which distribute the Harsanyi dividends proportional to weights determined by a power measure for union stable systems. Moreover, the well-known Myerson value is exactly the Harsanyi power solution for the equal power measure, and on a special subclass of union stable systems the position value coincides with the Harsanyi power solution obtained for the influence power measure. [ABSTRACT FROM AUTHOR]

Atmospheric turbidity causes attenuation of solar radiation reaching the earth's surface under a cloudless sky. The Ångström turbidity coefficient and the aerosol optical thickness, AOD550, were obtained from 10-minute direct normal solar irradiance measurements recorded in a rural area of Castilla y León region, Spain, from July 2010 to December 2012. During the study period, the diurnal variation of the mean monthly 10-minute turbidity coefficient increased in early morning, remained with fluctuations around noon, and increased or diminished in the evening, near sunset. The monthly turbidity coefficient shows an annual cycle with minimum values in winter and maximum values in summer, varying between 0.04 in winter and 0.16 in summer. The frequency distribution of 10-min Ångström turbidity coefficient on cloudless days shows that 0.65% of values are below 0.02, 84.50% between 0.02 and 0.15, and 14.85% above 0.15. Comparing at solar noon AOD550nm retrieved from MODIS (MODerate resolution Imaging Spectroradiometer on-board the Terra satellite) with those estimated from direct normal solar radiation measurements shows a good correlation coefficient of 0.78, although MODIS values are lower than estimated ones. High turbidity situations were investigated depending on the season and air-mass origin; the results show that they might be attributed to aerosol dust from the Sahara desert.The most significant high turbidity situations were investigated on base of wind at 700mb and air-mass origin; the result shows that this might be attributed to aerosol dust from the Sahara desert. [ABSTRACT FROM AUTHOR]

Abstract: A series of Ultraviolet-B broadband solar irradiance, 280–315 nm, measured during the period 2002–2011 in Valladolid (Spain) is analysed. UV-B daily values follow the pattern of the solar elevation angle. Daily maximum value occurred in June, 50.29 kJ m−2, and minimum, 0.88 kJ m−2, in December. The total accumulated UV-B irradiation along a mean year reached 7.1 MJ m−2. The elemental statistical characteristics of hourly and daily irradiation show that the inter-quartile range is small in winter and increases in spring; maximum stability in UV-B takes place at solar noon and around summer; it can be concluded that this maximum may be considered representative of the UV-B irradiance values. The monthly-integrated UV-B irradiation values show a large annual cycle with a maximum in July, when the influence of the annual ozone column diminishes and summer solstice occurs. The results show that the harmonic analysis permits constructing long-term monthly UV-B values under clear and all sky conditions and from low number of parameters. The UV-B percentage attenuated by the atmosphere increases from winter to summer, a maximum value of 8% is obtained in summer and a minimum of 2% in winter. The cloudiness effects on the surface solar UV-B radiation are strong during the winter months, being the cloud transmittance 0.7 in December and 0.94 in July. [Copyright &y& Elsevier]

Abstract: The satellite Ozone Monitoring Instrument (OMI) erythemal daily dose (EDD) product is validated through an inter-comparison with ground-based measurements at 14 ground-based stations distributed worldwide between 43°N and 64°S in 5 different countries of both hemispheres: Argentina, Australia, Italy, Israel, and Spain. The results show that OMI data overestimate ground-based EDD measurements except in stations with high surface albedo (e.g., covered by snow), in agreement with the results reported by previous studies. The average differences between satellite and ground-based data reached a maximum of ~25% for all-sky cases. When cloudless conditions are selected, removing intra-daily changes in cloudiness, the agreement improves; although average differences between 10 and 20% still appear for seven low-albedo stations. The influences of ozone and aerosol on the observed differences show opposite trends: viz., high ozone column values result in a decrease whereas high turbidity conditions produce an increase in the differences. A correction factor based on the aerosol absorbing optical thickness was applied to correct for this effect, which is not considered in the OMI algorithm. After applying this correction, the agreement between OMI and ground-based EDD measurements improves and the difference between them falls below 20% for more than 90% of the cases at 8 stations. A dependence on station altitude is also noted for both all-sky and clear-sky cases. [Copyright &y& Elsevier]

Biologically active ultraviolet (UVER, 280-400 nm) and global (300-3000 nm) solar irradiances have been recorded and analysed in a rural area in Valladolid (Spain) for a period of 49 months between June 2002 and December 2008. UVER daily measurements follow the pattern of the solar elevation angle and maximum hourly average irradiances occur in July, 0.20 Wm−2 and minimum, 0.03 Wm−2, in December at noon; the total accumulated UVER along a year reaches 1470 kJm−2. The temporal evolution of the erythemal ultraviolet radiation and its distribution under different sky conditions have been studied, being 25% clear, 57% partly cloudy and 18% overcast days. The most representative statistical characteristics of the hourly and daily UVER data have been evaluated for different sky conditions and the fundamental indices show symmetry with respect to solar noon. Maximum values may be considered as representative of the UVER characteristics in the area, whereas the minimum values are not significant, mainly during summertime. The UVER records show quite stable values in the analysed period, particularly along the months of July. The isoline-set of the first four moment distribution of the hourly UVER values has been plotted and the relative gradients are shown. The results are compared with the values obtained in other stations. The UVER cloud attenuation through the atmosphere shows that the transmitted percentage increases from winter to summer and a maximum value of 10% was achieved in July and a minimum of 30% in winter and spring. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

This paper deals with cooperative games in which only certain coalitions are allowed to form. There have been previous models developed to confront the problem of nonfeasible coalitions. Games restricted by a communication graph are games in which the feasible coalitions are those that induce connected subgraphs. Another type of model is determined by the positions of the players in a so-called permission structure. In this paper, the restrictions to the cooperation are given by a combinatorial structure called an augmenting system which generalizes antimatroid structure and the system of Connected subgraphs of a graph. Furthermore, the class of augmenting systems includes the conjunctive and disjunctive systems derived from a permission structure. The value is a generalization of the Myerson value for games restricted by graphs and the Shapley value for gaines restricted by permission structures. The main results of the paper are the characterization of the value a for augmenting structures by using component efficiency, loop-null and balanced contributions, and another characterization by consistency of this value. Furthermore, we implement a direct algorithm to compute this value by using the outputs of the original game. [ABSTRACT FROM AUTHOR]

Abstract: UV-B solar irradiance and meteorological variables were measured at the C.I.B.A. site (Low Atmosphere Research Laboratory), University of Valladolid, Spain, between January 2003 and March 2006. Calculated Ångström turbidity and aerosol optical thickness values were evaluated from the direct downward irradiance, surface pressure, air temperature and relative humidity values. Monthly turbidity β values for an average year showed minimum values in winter and maximum values in summer. The obtained values are according to an aerosol standard atmosphere between mean and clean continental model. UV-B model calculations were performed using a radiative transfer tropospheric model, TUV 4.1a; measured and calculated UV-B irradiance values were compared in order to establish possible values of single scattering albedo. The results show that calculated single scattering albedo values are according to an aerosol standard atmosphere between mean and polluted continental model. [Copyright &y& Elsevier]

The aim of the present paper is to study a one-point solution concept for bicooperative games. For these games introduced by Bilbao (Cooperative Games on Combinatorial Structures, ) , we define a one-point solution called the Shapley value, since this value can be interpreted in a similar way to the classical Shapley value for cooperative games. The main result of the paper is an axiomatic characterization of this value. [ABSTRACT FROM AUTHOR]

Interior operator games arose by abstracting some properties of several types of cooperative games (for instance: peer group games, big boss games, clan games and information market games). This reason allow us to focus on different problems in the same way. We introduced these games in Bilbao et al. (Ann. Oper. Res. 137:141–160, ) by a set system with structure of antimatroid, that determines the feasible coalitions, and a non-negative vector, that represents a payoff distribution over the players. These games, in general, are not convex games. The main goal of this paper is to study under which conditions an interior operator game verifies other convexity properties: 1-convexity, k-convexity ( k≥2 ) or semiconvexity. But, we will study these properties over structures more general than antimatroids: the interior operator structures. In every case, several characterizations in terms of the gap function and the initial vector are obtained. We also find the family of interior operator structures (particularly antimatroids) where every interior operator game satisfies one of these properties. [ABSTRACT FROM AUTHOR]

This paper studies two classical solution concepts for the structure of bicooperative games. First, we define the core and the Weber set of a bicooperative game and prove that the core is always contained in the Weber set. Next, we introduce a special class of bicooperative games, the so-called bisupermodular games, and show that these games are the only ones in which the core and the Weber set coincide. [ABSTRACT FROM AUTHOR]

The major susceptibility locus for type 1 diabetes mellitus (T1D) maps to the human lymphocyte antigen (HLA) class II region in the major histocompatibility complex on chromosome 6p21. In southern European populations, like the Basques, the greatest risk to T1D is associated with DR3 homo- and heterozygosity and is comparable to that of DR3/DR4, the highest risk genotype in northern European populations. Celiac disease (CD) is another DR3-associated autoimmune disorder showing certain overlap with T1D that has been explained by the involvement of common genetic determinants, a situation more frequent in DR3-rich populations, like the Basques. As both T1D- and CD-associated HLA alleles are part of conserved extended haplotypes (CEH), we compared DR3-homozygous T1D and CD patients to determine whether CEHs were equally distributed between both disorders or there was a differential contribution of different haplotypes. We observed a very pronounced distribution bias (P<10−5) of the two major DR3 CEHs, with DR3-B18 predominating in T1D and DR3-B8 in CD. Additionally, high-density single nucleotide polymorphism (SNP) analysis of the complete CEH [A*30-B*18-MICA*4-F1C30-DRB1*0301-DQB1*0201-DPB1*0202] revealed extraordinary conservation throughout the 4.9 Mbp analyzed supporting the existence of additional diabetogenic variants (other than HLA-DRB1*0301-DQB1*0201), conserved within the DR3-B18 CEH (but not in other DR3 haplotypes) that could explain its enhanced diabetogenicity.Genes and Immunity (2006) 7, 550–554. doi:10.1038/sj.gene.6364328; published online 24 August 2006 [ABSTRACT FROM AUTHOR]

The aim of this paper is to study a new class of cooperative games called interior operator games. These games are additive games restricted by antimatroids. We consider several types of cooperative games as peer group games, big boss games, clan games and information market games and show that all of them are interior operator games. Next, we analyze the properties of these games and compute the Shapley, Banzhaf and Tijs values. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a new method for generating test reference year (TRY) from the measured meteorological variables is proposed. Hourly recorded data of air temperature, relative humidity and wind velocity for two stations, Valladolid and Madrid (Spain) were selected to develop the method and a TRY was obtained. Monthly average solar radiation values were calculated taking into account the temperature and solar radiation correlations. Four different methodologies were used to evaluate hourly global solar radiation from hourly weather data of temperature and, as a consequence, four different TRYs with common data sets of temperature, relative humidity and wind velocity were generated for Valladolid and Madrid (Spain) stations. In order to evaluate the four different methodologies, TRYs data were compared with long-term measured data series using statistical estimators such as average, standard deviation, root mean square error (rmse) and mean bias error (mbe). Festa and Ratto and the TAG model, from Aguiar and Collares-Pereira, respectively, turned out to be the best methods for generating hourly solar irradiation data. The best performance was shown by the TRY0 year which was based on the solar radiation models mentioned above. The results show that the best reference year for each site varies with the season and the characteristics of the station. [Copyright &y& Elsevier]

The role of transjugular intrahepatic portosystemic shunt (TIPS) in the management of complications of portal hypertension such as variceal hemorrhage and ascites is well established. However, TIPS has a limited patency due to dysfunction consisting in occlusion or stenosis of the intrahepatic tract or stenosis of the outflow hepatic vein. Timing of dysfunction cannot be predicted, so routine surveillance and percutaneous intervention are continuously required to maintain TIPS patency. Trans-shunt venography is the gold standard technique in TIPS evaluation, but it is expensive and invasive. Doppler ultrasound (DU) has been the most commonly used noninvasive tool in TIPS patency. Despite many reported series, its role remains controversial. After more than 10 years of experience with TIPS, we followed our patients with DU and trans-shunt venography to establish Doppler criteria of dysfunction and its accuracy in assessing shunt dysfunction. [ABSTRACT FROM AUTHOR]

The performance of five different diffuse hourly irradiation models on tilted surfaces is examined using an assembled data set of measured hourly global and diffuse solar irradiation on horizontal and tilted surfaces in the Castile and Leon region and from surrounding stations. Estimated and measured diffuse solar irradiation values on a tilted surface have been compared using statistical tests based on root mean square error and mean bias error. From the results, it has been found that the Perez’ 25° model presents the best overall calculated performance.The global solar irradiation on a tilted surface has been calculated using Perez’ 25° model, and the results have been compared and plotted against the tilt angle for all year.The yearly mean solar irradiation isoline maps over tilted surfaces and over vertical surfaces with different orientations have been plotted, and the optimum tilt angle has been shown. The results show that the highest irradiation values of 5.0 kW h m−2 are obtained in the centre of the region (Valladolid) with 30° or 45° tilt. There is a strong gradient from the centre to the north region. [Copyright &y& Elsevier]

The aim of this paper is to compute Shapley's and Banzhaf's values of cooperative games restricted by a combinatorial structure. There have been previous models developed to study the problem of games with partial cooperation. Games restricted by a communication graph were introduced by Myerson and Owen. Another type of combinatorial structure introduced by Gilles, Owen and van den Brink is equivalent to a subclass of antimatroids. Cooperative games in which the set of players is a partially ordered set, that is, games on distributive lattices was investigated by Faigle and Kern. We introduce a new combinatorial structure called augmenting system which is a generalization of the antimatroid structure and the system of connected subgraphs of a graph. We present new algorithmic procedures for computing values of games under augmenting systems restrictions and we show that there exist problems with polynomial algorithm complexity. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the performance of daily and hourly diffuse horizontal solar irradiation models and correlations among countries in the North Mediterranean Belt area. Methodology of the study; Results and discussion on the study; Conclusions.

Presents information on several research related to peripheral nerve. Pathology of peripheral nerve; Information on dysproteinemic polyneuropathies; Molecular genetic identification of mutations in paraffin embedded, archival sural nerve biopsies.

Abstract: It has been shown that mutations in the Fused in Sarcoma gene (FUS) could explain up to 5% of cases with familial amyotrophic lateral sclerosis (ALS). Our mutation analysis of FUS in a Canadian ALS patient of Chinese origin revealed an unusual novel heterozygous double point mutation (R514S/E516V) confirming that exon 15 is a mutation hot-spot. The substitutions are in cis position to each other and affect highly conserved codons in the RGG-rich region of the FUS protein. The absence of clinical signs of ALS in the relatives of the affected carrier could indicate that this mutation is incompletely penetrant or de novo. The pathologic significance of the R514S/E516V mutation was confirmed by immunohistochemistry. FUS-positive cytoplamsic inclusions were noted in a moderate number in neurons and abundantly in glial cells in the motor cortex and the brainstem. Of interest, a significant number of neuronal and glial FUS-positive inclusions were found in the tegmentum of the brainstem. Importantly, some neurons with inclusions showed retention of the normal nuclear FUS immunostaining. [Copyright &y& Elsevier]

Measurements of ozone concentrations, and meteorological and surfaceparameters were carried out over a flat green grassland in northwestSpain, in July 1995. Turbulent parameters and sensible and latent heat fluxes were calculated using the gradient technique. Fluxes and deposition velocity and resistances were evaluated assuming that the diffusivity for heat fluxes was equal to pollutant diffusivity. The daily average value of dry deposition velocity was 6 mm s-1 but it was influenced by wind velocity and atmospheric stability. Resistances have been calculated according to a simple resistance model and a comparison between theoretical and measured values has been made. [ABSTRACT FROM AUTHOR]

Sometimes, the severity of the trauma or the existence of a cancer force to amputate a limb. The prosthetic rehabilitation process and residual function will be influenced by the remaining length of the limb, the presence or absence of functional joints and the quality of the coverage of the stump. Two cases of amputations are shown. The former is an acute traumatic upper limb amputation at the level of the proximal third of forearm with skin avulsion from the middle third of the arm and the elbow joint preserved. The second case is the sequelae of an amputation below the knee due to lower extremity osteosarcoma, which was referred with suppurative draining cutaneous fistulas as a consequence of an osteomyelitis of the femur in the stump. In both patients the stumps were covered with anterolateral thigh flap anastomosed over the radial artery in the case of the upper extremity, and over the descending genicular artery in the lower extremity. In both cases the postoperative course was uneventful, preserving the elbow and knee respectively and allowing the subsequent prosthetic rehabilitation. We consider that anterolateral thigh flap is a suitable option for the treatment of the amputation stump. Given the characteristics of the tissue and volume provided by this flap, it is appropriate for coverage of acute defects and for padding deficits in chronic cases. [ABSTRACT FROM AUTHOR]

Measurements of spectral global and diffuse ultraviolet (UV) irradiance, and of spectral actinic flux were made jointly with determinations of cloud properties during a two- month experimental campaign that took place in southern Italy in May-June 2010. The cloud modification factor (CMF) which is the ratio between the incoming radiation under cloudy and in cloud-free conditions, was obtained for the global (direct plus diffuse) and diffuse components of the irradiance, and for the actinic flux in the UV spectral range for overcast conditions. Measurements of the diffuse irradiance and actinic flux CMFs are very scarce, and are particularly important to characterize the radiation field and verify the behaviour of radiative transfer models in cloudy conditions. In addition to measurements, one-dimensional radiative transfer simulations are used to investigate the cloud influence on the spectral solar UV radiation. The analysis shows that the wavelength dependence of CMF for the global irradiance is mainly due to the normalization for cloud-free conditions. The CMF for the diffuse irradiance and for the actinic flux displays a strong dependence on the solar zenith angle. This dependence appears to be mainly driven by the large role played by the zenith radiation in overcast conditions. Radiative transfer model determinations of CMF satisfactorily reproduce observations. [ABSTRACT FROM AUTHOR]

Abstract: Erythemal ultraviolet (UVER; 280–400nm) and total shortwave (SW; 305–2800nm) solar irradiances were recorded from 2000 to 2009 in Valladolid, Spain. UVER and SW values under cloudless conditions are simulated by radiative transfer (TUV 4.6) and empirical models. These model estimations are tested with experimental measurements showing a great agreement (root mean square error around 7%). The aerosol effect on UVER irradiance is determined through a model study. UVER radiation and total ozone column (TOC) temporal evolutions show a negative relationship. TOC accounts for 80% of UVER variance and its radiation amplification factor is 1.1 at zenith of 65°. Cloud effects on solar radiation are shown and quantified by the cloud modification factor. Moreover the enhancement effect cases are analysed. SW radiation proves more sensitive to clouds than UVER. Clouds are seen to attenuate and enhance solar radiation by up to 93% and 22% in the UVER range, respectively. [Copyright &y& Elsevier]

Abstract: This paper presents the performance of 10 arithmetic models used to estimate diffuse solar irradiance on inclined surfaces in a comparative study with actual data readings made available on an hourly and a daily basis. The data readings have been taken from a south facing surface inclined at 42° in an area at some distance from the provincial capital in the Spanish province of Valladolid. In order to confirm the results, three statistical parameters have been used in the study; root mean square error (RMSE), mean bias error (MBE) and Stone’s t-statistic. The results obtained favour the Muneer model, followed by the Reindl model, for hourly as well as for daily values. The Temps–Coulson model gives rise to great discrepancies with respect to the values measured. The results for the Perez model are not good due to the use of parameters that are not specifically calculated for the area in this study, which underlines the need to take an area’s features into account so that predictions for diffuse irradiance measured on inclined surfaces may be as accurate as possible. [Copyright &y& Elsevier]

Background : Addison's disease (AD) is an autoimmune disorder caused by the destruction of the adrenal gland by the lymphocytes in genetically susceptible individuals. The contribution of HLA genes to the genetic risk to AD has been known for a long time; however, non-HLA genetic factors are likely to be required for the development of the disease. Several studies have associated the CD28/CTLA4 region on chromosome 2q33 with the disease in different populations. The cytotoxic T lymphocyte-associated antigen 4 ( CTLA4 ) gene encodes a receptor involved in the control of T cell proliferation and mediates T cell apoptosis. Aim : To determine the contribution of two polymorphisms of the CTLA4 to the disease; the A/G dimorphism at position +49 in exon 1 and the (AT) n microsatellite in the 3′ untranslated region of exon 3. Patients : Fifty seven patients with autoimmune AD (autoimmunity for anti 21-hydroxylase was confirmed) and 111 unrelated healthy subjects from the general populations were analyzed as controls. Methods : Restriction enzyme digestion of polymerase chain reaction (PCR) amplified genomic DNA for the A/G dimorphism and PCR followed by high-resolution electrophoresis for the (AT) n microsatellite. For disease association studies, the case-control approach was used. Results : The frequency of the A allele of 49 A/G polymorphism was 65.79% in the patients compared with 72.07% in the control group. These differences were not significant. Analysis of the (AT) n polymorphism identified 19 different alleles, ranging from 262 to 308 bp in length, but no allele was significantly associated with the disease. Conclusions : Our results did not show any evidence of association of any of the CTLA4 gene polymorphisms with the disease. This might result from population-specific differences in genetic and environmental susceptibility to AD. [ABSTRACT FROM AUTHOR]

• The fountain confined conical spouted bed enhances the performance of primary catalysts. • Dolomite and γ-alumina improved syngas composition and reduced tar content. • Olivine and FCC catalysts reduced tar content, but hardly affect syngas composition. • The lowest tar content (5.0 g Nm−3) was obtained using dolomite as catalyst. • Light PAHs were the prevailing tar compounds on all the catalysts studied. The performances of the primary catalysts olivine, dolomite, γ-alumina and FCC spent catalyst were evaluated in the continuous steam gasification of sawdust in a bench-scale plant equipped with a fountain confined conical spouted bed reactor. The experiments were carried out at 850 °C, and the efficiency of the gasification process was defined by gas yield, H 2 production, tar concentration and composition, and carbon conversion efficiency. The benefits of the fountain confiner not only helped to improve the gas-solid contact, and therefore favoured the primary catalysts' reforming and cracking activity, but also enhanced H 2 production and reduce tar formation. Thus, dolomite and γ-alumina recorded the lowest values of tar, 5.0 and 6.7 g Nm−3, respectively, which corresponded to 79% and 72% tar reduction compared to the inert sand, whereas olivine and the FCC spent catalyst recorded higher tar contents, 20.6 and 16.2 g Nm−3, respectively. It is noteworthy that light PAHs were the most abundant species in the tar (60 wt% of the whole tar content). [ABSTRACT FROM AUTHOR]

Abstract The behavior of the CuO-ZnO-ZrO 2 @SAPO-11 core-shell catalyst in the direct synthesis of DME from H 2 + CO + CO 2 mixtures has been assessed. The effect of the reaction conditions (temperature, pressure, space-time) and feed composition (CO 2 and H 2 concentration) on the DME yield and selectivity, CO 2 and CO x (CO 2 +CO) conversions and stability of the catalyst have been studied. The experiments have been carried out in a fixed-bed reactor in the following condition ranges: 250–325 °C; 10–50 bar; space-time, 1.25–15 g h mol C −1; CO 2 /CO x molar ratio in the feed, 0–1; and H 2 /CO x molar ratio in the feed, 2.5–4; time on stream, up to 48 h. Under mild conditions (275–300 °C range, 20–30 bar, space-time over 5 g h mol C −1, CO 2 /CO x molar ratio in the 0.5–0.75 range, and H 2 /CO x molar ratio around 3) a good compromise is reached between the yield of DME and the conversion of CO 2 , with high catalyst stability. Coke deposition is the main cause of catalyst deactivation, formed by condensation of the hydrocarbon byproducts, blocking the metallic sites in the core. The formation rate of this fraction of coke is greater than that of the coke deposited in the SAPO-11 of the shell. Increasing reaction temperature favors the formation of coke, while co-feeding CO 2 attenuates this formation, due to the increase of H 2 O concentration. Highlights • CuO ZnO ZrO 2 @SAPO-11 core-shell catalyst is active and stable in the STD process. • Good compromise between DME yield and CO 2 conversion is attained at mild conditions. • Blockage of CuO ZnO ZrO 2 sites in the core by coke causes reversible deactivation. • Increasing temperature favors coke formation while co-feeding CO 2 attenuates it. • In the SAPO-11 shell coke development is slow and does not influence deactivation. [ABSTRACT FROM AUTHOR]

Highlights • The residence time distribution of the gas in the pyrolysis plant was studied. • The E curves have been determined for the pyrolysis plant. • Two models have been proposed to simulate the gas flow pattern. • The flow model has been coupled with the kinetic one to study pyrolysis kinetics. Abstract A novel strategy has been proposed for the rigorous kinetic modeling of tyre pyrolysis in a conical spouted bed reactor. A kinetic model coupled with a gas flow model was used in the fitting of experimental results obtained in a bench scale unit in the 425–610 °C range. A gas flow model should be incorporated to account for the delay and mixing phenomena observed in tracer experiments, as these phenomena cause remarkable deviations in the assessment of the kinetic parameters. The gas flow pattern from the reactor to the measuring device was modeled using two different approaches based on ideal flow reactors. Furthermore, two kinetic schemes considering lumped products have been proposed; the first one is based on four parallel independent reactions accounting for the volatile products (gas, liquid, aromatics and tar). The second one considers an additional secondary reaction of aromatic formation from the liquid. The strategy proposed for coupling the kinetics and the flow model led to a suitable fitting of the experimental results, with the performance of the model considering a secondary reaction being slightly better than the simple one. [ABSTRACT FROM AUTHOR]

[Display omitted] • CFD -DEM simulations were run with a variety of internal devices. • The effect of draft tubes in solids cycle times is very significant. • Use of draft tubes or high air flow rates leads to gas pockets. • A fountain confiner located at a reasonable height removes gas pockets and improves gas mixing. • The fountain confiner allows controling the particle cycle time distribution. The effect of draft tubes and fountain confiner on the gas and solids mixing behavior is studied in conical spouted beds. Accordingly, the bed porosity has been determined in different hydrodynamic regimes of 1.1 , 1.25 and 1.5 u / u ms , with beds equipped with draft tubes of 0 % , 56 % and 100 % opening ratio. These devices significantly affect the gas residence time and particle cycle time distributions, which are further improved by using a fountain confiner, specially when high inlet gas flow rates are desired. The addition of this device was found to remove stagnant gas pockets over the annular zone, while reducing the particle cycle time by 15 % with the OSDT configuration at 1.5 u / u ms . This reduction heavily depends on the distance between the bed surface and the fountain confiner. By including draft tubes, the expected particle cycle time can be more than doubled due to the reduced annular-spot solids circulation. Therefore, it was found that a combination of internal devices and operating flow rate present a promising strategy to control the gas flow pattern, while keeping the distribution of particles cycle times required for each application. [ABSTRACT FROM AUTHOR]

Highlights • Continuous pyrolysis reforming strategy allows for the H 2 production from biomass. • ZrO 2 is a suitable Ni support for the reforming of pyrolysis volatiles. • Ni/ZrO 2 showed limited coke deposition and low coke combustion temperatures. • A maximum H 2 production of 10.73 wt.% was obtained. Abstract The activity and stability of a Ni/ZrO 2 catalyst have been studied in a continuous bench scale plant, in which biomass has been pyrolysed at 500 °C in a conical spouted bed reactor and the outlet volatile stream has been subjected to catalytic steam reforming at 600 °C in a fluidized bed reactor. The influence of space time has been analyzed, and both the fresh and the deactivated catalysts have been characterized by means of different techniques: N 2 adsorption-desorption, X-ray fluorescence (XRF), X-ray powder diffraction (XRD), temperature programmed oxidation (TPO), and transmission electron microscopy (TEM). The aim of this characterization is to relate catalyst performance to the evolution of the properties from the fresh to the deactivated catalysts. Thus, an increase in space time leads to an improvement in the stability of the catalyst extending its operation period from 20 to 100 min on stream, with a maximum H 2 yield of 92.4% (referred to the maximum allowed by stoichiometry) when a space time of 20 g cat min g volatiles −1 has been used. Although the ZrO 2 support has suitable properties, coke deposition is the main cause of catalyst deactivation. [ABSTRACT FROM AUTHOR]

Self-excited combustion instabilities in a high pressure, single-element, lean, premixed, natural gas (NG) dump-combustor are investigated. The combustor is designed for optical access and instrumented with high frequency pressure transducers at multiple axial locations. A parametric survey of operating conditions including inlet air temperature and equivalence ratio has been performed, resulting in a wide range of pressure fluctuation amplitudes (p') of the mean chamber pressure (pCH). Two representative cases, flames A and B with p'/pCH=23% and p'/pCH=12%, respectively, both presenting self-excited instabilities at the fundamental longitudinal (1L) mode of the combustion chamber, are discussed to study the coupling mechanism between flame-vortex interactions and the acoustic field in the chamber. 10 kHz OH*-chemiluminescence imaging was performed to obtain a map of the global heat release distribution. Phase conditioned and Rayleigh index analysis as well as dynamic mode decomposition (DMD) is performed to highlight the contrasting mechanisms that lead to the two distinct instability regimes. Flame interactions with shear layer vortex structures downstream of the backward-facing step of the combustion chamber are found to augment the instability magnitude. Flame A engages strongly in this coupling, whereas flame B is less affected and establishes a lower amplitude limit cycle. [ABSTRACT FROM AUTHOR]

The preparation by physical coating of a bifunctional core-shell-structured catalyst (CZZr@S-11), using CuO-ZnO-ZrO 2 (CZZr) as metallic function and SAPO-11 (S-11) as acid function, has been studied. The effects of calcination temperature and mass ratio between the metallic and acid functions (M/A) on their kinetic behavior for the synthesis of DME from syngas and CO 2 feeds has been assessed. The reaction indices considered have been: the conversion of CO x (CO + CO 2 ) and CO 2 ; yields and selectivities of dimethyl ether (DME), methanol and hydrocarbons; and stability. The experiments have been carried out in a fixed-bed reactor (275 °C, 30 bar). The CZZr@S-11 catalyst prepared under suitable conditions (calcination at 400 °C and M/A of 1/2), shows better reaction indices than the hybrid catalyst (CZZr/S-11), prepared by physical mixture of the individual functions, which is explained by the advantages of the core-shell structure, especially interesting for the valorization of CO 2 . [ABSTRACT FROM AUTHOR]

Self-excited combustion instabilities in a high pressure, single-element, lean, premixed, natural gas (NG) dump-combustor are investigated. The combustor is designed for optical access and instrumented with high frequency pressure transducers at multiple axial locations. A parametric survey of operating conditions including inlet air temperature and equivalence ratio has been performed, resulting in a wide range of pressure fluctuation amplitudes (p') of the mean chamber pressure (pCH). Two representative cases, flames A and B with p'/pCH=23% and p'/pCH=12%, respectively, both presenting self-excited instabilities at the fundamental longitudinal (1L) mode of the combustion chamber, are discussed to study the coupling mechanism between flame-vortex interactions and the acoustic field in the chamber. 10 kHz OH*-chemiluminescence imaging was performed to obtain a map of the global heat release distribution. Phase conditioned and Rayleigh index analysis as well as dynamic mode decomposition (DMD) is performed to highlight the contrasting mechanisms that lead to the two distinct instability regimes. Flame interactions with shear layer vortex structures downstream of the backward-facing step of the combustion chamber are found to augment the instability magnitude. Flame A engages strongly in this coupling, whereas flame B is less affected and establishes a lower amplitude limit cycle. [ABSTRACT FROM AUTHOR]

A study was carried out on the advantages of inserting a fountain confiner in conical spouted beds for biomass steam gasification and the results (gas yield and composition, tar content, carbon conversion efficiency and H 2 production) are compared with those obtained under conventional spouting regime. The experiments were carried out in a bench scale unit operating in continuous regime under the same gasification conditions in all the configurations (850 °C, S/B ratio of 2 and olivine as primary catalyst). The gaseous product was analyzed by on-line gas chromatography and micro-gas chromatography, and the tars by gas chromatography-mass spectrometry. The use of a fountain confiner allows enhancing process versatility, increasing gas velocity over the minimum spouting one, increasing the fountain height and reducing olivine particle size (enhanced fountain regime). Thus, as a result of a better gas-solid contact, tar content was reduced from 49.2 g Nm −3 without fountain confiner to 20.6 g Nm −3 under enhanced fountain regime, with the reduction of heavy PAHs being especially remarkable. In the same line, a great improvement in process conversion efficiency was attained under the enhanced fountain regime, with gas production reaching a value of 1.3 m 3  kg −1 and that of H 2 production 5.0 wt%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coke deposition in SAPO-34 is responsible for the deactivation of In 2 O 3 -ZrO 2 /SAPO-34. • Coke forms from methanol/DME in the reaction medium. • H 2 O concentration in the medium is key for attenuating deactivation. On account of the superior performance of In 2 O 3 -ZrO 2 /SAPO-34 tandem catalyst in the direct synthesis of olefins from CO, CO 2 and CO/CO 2 mixture by hydrogenation, it is interesting to establish the conditions to avoid its deactivation due to the rapid coke deposition on SAPO-34. The co-feeding of H 2 O and/or methanol together with H 2 + CO 2 /CO was studied in a packed bed reactor at: 400 °C, 30 bar; CO 2 /CO x in the feed, 0–1; H 2 /CO x in the feed, 1–3; and space time of 5 g cat h mol C −1, quantifying the evolution with time on stream (up to 16 h) of CO 2 and CO x conversions and olefin, paraffin and CH 4 yields. The effects of the co-feeding on coke content and its nature were determined by temperature programmed oxidation (TPO) analyses of the spent catalyst. The results highlighted the complex effect of the concentration of H 2 O and oxygenates (methanol/dimethyl ether (DME)) on the deactivation of SAPO-34 and on the products yields in the pseudo-steady state of the catalyst. Co-feeding H 2 O lessens coke deactivation, however, high H 2 O concentration leads to attenuate the acidity of SAPO-34, limiting the performance of the tandem catalyst (mainly in the CO 2 conversion). Oxygenates co-feeding concentration limit value lies on its favoring effect for coke formation. In addition to this effect, the favorable attenuation of coke deactivation by the high H 2 concentration (studied in runs with H 2 /CO x ratio in the feed in the 1–3 range) plays a key role in the viability of the process, leading to a pseudo-steady catalyst state in which the activity is constant. The proven effect of H 2 O and methanol concentrations will be useful for establishing new catalysts and reaction conditions at which their presence in the reactor will attenuate deactivation. [ABSTRACT FROM AUTHOR]

The composition of the carbonaceous deactivating species (coke) deposited on a Pt and Pd supported P-containing activated carbon catalyst has been studied. These deactivating species were deposited on the catalyst during the hydrocracking of scrap tire pyrolysis oil at 400–500 °C, and it has been selectively characterized by means of temperature-programmed oxidation (TPO), temperature-programmed desorption/gas chromatography (TPD/GC) and laser desorption-ionization/mass spectroscopy (LDI/MS). In addition, the evolution of the textural properties and the acidity of the deactivated catalysts have been evaluated. The high thermal and oxidation resistance of the catalytic support has allowed to combust the coke in the TPO and calculate its intrinsic activation energy as a function of the extent of the combustion. Combined TPO and LDI/MS results have shown that an increase in the hydrocracking temperature attenuates the catalyst deactivation due to the hydrocracking of coke precursors. Coke aging, by evolving towards a more condensed structure, is also favored at higher hydrocracking temperatures. The combustion of the most condensed coke requires of higher temperatures than 375 °C, which hinders the complete regeneration of the activated carbon-based catalyst. [ABSTRACT FROM AUTHOR]

This study pursues the development and characterization of a fountain enhanced spouting regime. This novel gas solid-contact method combines the advantages of fountain confined conical spouted beds with those of draft tube conical spouted beds. The aim of confining the fountain, and therefore attaining a clearly differentiated regime, is to progress towards a highly efficient conical spouted bed reactor for biomass gasification. Accordingly, and in order to delve into the knowledge of the regimes attained in this contact method, a study has been conducted by analyzing the influence operating parameters (temperature, gas flow rate, particle size and bed mass) and draft tube geometry (tube diameter and entrainment zone height) have on hydrodynamics. Fountain confinement allows greatly enlarging the fountain region, especially the height, which improves the contact between reacting gases and the catalyst. Moreover, the residence time distribution, and therefore the average residence time, may be optimized by confining and enlarging the fountain zone. These features promote tar cracking and so increase biomass conversion efficiency, which are highly relevant facts for use of conical spouted bed reactors in gasification. [ABSTRACT FROM AUTHOR]

The flash pyrolysis of waste truck-tyres was studied in a conical spouted bed reactor (CSBR) operating in continuous regime. The influence of temperature on product distribution was analysed in the 425–575 °C range. A detailed characterization of the pyrolysis products was carried out in order to assess their most feasible application. Moreover, special attention was paid to the sulphur distribution among the products. The analysis of gaseous products was carried out using a micro-GC and the tyre pyrolysis oil (TPO) by means of GC-FID using peak areas for quantification, with GC/MS for identification and elemental analysis. Finally, the char was subjected to elemental analysis and surface characterization. According to the results, 475 °C is an appropriate temperature for the pyrolysis of waste tyres, given that it ensures total devolatilisation of tyre rubber and a high TPO yield, 58.2 wt.%. Moreover, the quality of the oil is optimum at this temperature, especially in terms of high concentrations of valuable chemicals, such as limonene. An increase in temperature to 575 °C reduced the TPO yield to 53.9 wt.% and substantially changed its chemical composition by increasing the aromatic content. However, the quality of the recovered char was improved at high temperatures. [ABSTRACT FROM AUTHOR]

Waste truck tyre valorization by fast pyrolysis has been performed in a conical spouted bed reactor in the 425–575 °C range. The tyre pyrolysis oil (TPO) yield was found to decrease with increasing temperature whilst the yield of gas increased. The effect of temperature on TPO properties has been studied in order to establish the best possible valorization route. FTIR and chromatographic analysis revealed the presence of some undesired compounds with sulphur, nitrogen or oxygen functionalities (benzotiatholes, nitriles and carboxylic acids amongst others) and an increase of TPO aromaticity with increasing temperature. The carbon and sulphur content and the heating value of the TPO increased with temperature. The simulated distillation showed that approximately 70% of the TPOs produced at 425 and 475 °C correspond to diesel range, whereas that TPO obtained at 575 °C is between diesel and gasoline range. The properties of the TPOs evidenced their potential to substitute conventional fuels. However, some of them need to be improved, i.e., by reduction of the sulphur, nitrogen and aromatic content. Additionally, the TPO obtained at 425 and 475 °C could be an important source of limonene and that at 575 °C of xylenes, although current removal methods present some limitations. [ABSTRACT FROM AUTHOR]

Different acid catalysts (silicoaluminophosphates (SAPOs) -34, −18, and − 11, and HZSM-5 zeolite) were tested as components of In 2 O 3 -ZrO 2 /acid tandem catalysts in the direct synthesis of light olefins by hydrogenation of CO 2 , CO and their mixture. The conversion and olefins yield and selectivity evidence that the presence of the large amount of strongly acidic sites in SAPO-34 favors the extent of the reaction mechanism with methanol as intermediate, minimizing secondary methanation reactions. In addition, the shape selectivity of SAPO-34 boosts olefins selectivity (mainly of propylene), limiting the extent of the secondary reactions for the formation of other hydrocarbons. Using SAPOs as acid catalysts enhances olefins selectivity when co-feeding CO 2 with CO. Despite all tandem catalysts undergo deactivation by coke deposition (mostly in the acid catalyst), a pseudo-steady state of stable remaining activity is acquired. From the study of the coke nature, soft and hard coke were discerned. For the complete regeneration of the SAPO-34 in the tandem catalyst, the stripping of the soft coke is not sufficient and the combustion at 500 °C of the hard coke (little developed) deposited on the micropores is required. [Display omitted] • Shape-selectivity and acid properties of IZ/acid are key for selectivity &stability. • The high density of strong acid sites of SAPO-34 is the most suitable • The strong acid sites in tandem catalyst shift thermodynamics to olefins formation • The co-feeding of CO 2 with syngas boosts olefins selectivity • In SAPO-34 coke is mainly of hard nature, only removable by combustion [ABSTRACT FROM AUTHOR]

Sewage sludge fast pyrolysis bio-oil, produced in a conical spouted bed reactor (CSBR) in the 450–600 °C range, has been characterized. On the one hand, the effect of temperature on bio-oil composition has been analyzed by means of online chromatography and, furthermore, the ultimate analysis and the higher heating value of each liquid have been determined. On the other hand, the bio-oil collected at 500 °C, at which the liquid yield is maximized (77 wt.% on dry ash free), has been characterized in detail by determining its density, viscosity, water content and pH. The major organic compounds in the bio-oil were oxygenated and nitrogenated ones (phenols, ketones, alcohols, amides and nitriles among others). It is noteworthy that the bio-oil obtained in this work contains a lower amount of O than those derived from lignocellulosic materials; therefore, the concentrations of C and H in this bio-oil, as well as the lower heating value (LHV), are higher. In addition, the simulated distillation reveals that > 70% of the sewage sludge pyrolysis oil corresponds to the gasoil range. The fuel properties of sewage sludge bio-oil evidence that it has the potential to substitute conventional fuels; however, some properties need to be improved, i.e., the heating value should be increased and the nitrogen content reduced by subjecting this bio-oil to further treatments. [ABSTRACT FROM AUTHOR]

[Display omitted] • DME is interesting as green fuel, hydrocarbon source and H 2 vector. • Valorizing CO 2 and syngas is thermodynamically favored in the direct DME synthesis. • Kinetic models based on individual reactions and ad hoc models have been studied. • Removing H 2 O in the reactor is a key feature for the extent of the reactions. • A hydrophilic membrane reactor is effective for reducing thermodynamic limitations. The direct synthesis of dimethyl ether (DME) is considered one of the most attractive routes for valorizing CO 2 and syngas on a large scale. DME has a high cetane number and its properties are similar to those of liquefied petroleum gases (LPG). It can be used directly as fuel, selectively converted into hydrocarbons (olefins, aromatics) or used as H 2 vector. This review explains briefly the advances in the study of the thermodynamics of DME synthesis and in the preparation of suitable catalysts. Subsequently, analyzes in detail the studies regarding the kinetic modeling, reactors design and reaction strategies. Extensive information is given on the kinetic models described in the literature, indicating the catalysts and reaction condition ranges for which the models were proposed. These kinetic models were whether based on those previously proposed separately for methanol synthesis and methanol dehydration stages on monofunctional catalysts, or models specifically proposed for bifunctional catalysts and conditions of the integrated process. Coke deposition is considered the main cause for catalyst deactivation and is quantified with different kinetic models. The presence of H 2 O in the reaction medium is a limiting factor for the thermodynamics and for the extent of the reactions. This problem is overcome using hydrophilic membrane reactors, whose behavior has been studied by simulation and recently with an experimental system (with an LTA zeolite membrane). Finally, an analysis of the advantages and limitations of the different reactors and the challenges to progress towards the implementation of the direct CO 2 to DME synthesis process have been addressed. [ABSTRACT FROM AUTHOR]

ISHP (Ion Source Hydrogen Positive) project consists of a highly versatile ECR type ion source. It has been built for several purposes, on the one hand, to serve as a workbench to test accelerator related technologies and validate in-house made developments, at the first stages. On the other hand, to design an ion source valid as the first step in an actual LINAC. Since this paper is focused on the control system of ISHP, besides the ion source, all the hardware and its control architecture is presented. Nowadays the ion source is able to generate a pulse of positive ions of Hydrogen from 2~\mu\s to a few ms range with a repetition rate ranging from 1~Hz to 50~Hz with a maximum of 45~mA of current. Furthermore, the first experiments with White Rabbit (WR) synchronization system are presented. [ABSTRACT FROM PUBLISHER]

The effect of the ZrO 2 content on the performance (activity, selectivity, stability) of In 2 O 3 –ZrO 2 catalyst has been studied on the hydrogenation of CO 2 /CO mixtures. This effect is a key feature for the viability of using In 2 O 3 –ZrO 2 /SAPO-34 tandem catalysts for the direct conversion of CO 2 and syngas into olefins via oxygenates as intermediates. The interest of co-feeding syngas together with CO 2 resides in jointly valorizing syngas derived from biomass or wastes (via gasification) and supplying the required H 2. The experiments of methanol synthesis and direct synthesis of olefins, with In 2 O 3 –ZrO 2 and In 2 O 3 –ZrO 2 /SAPO-34 catalysts, respectively, have been carried out under the appropriate conditions for the direct olefins synthesis (400 °C, 30 bar, H 2 /CO X ratio = 3) in an isothermal fixed bed reactor at low space time values (kinetic conditions) to evaluate the behavior and deactivation of the catalysts. The Zr/In ratio of 1/2 favors the conversion of CO 2 and CO X , attaining good oxygenates selectivity, and prevents the sintering attributable to the over-reduction of the In 2 O 3 (more significant for syngas feeds). The improvement is more remarkable in the direct olefins synthesis, where the thermodynamic equilibrium of methanol formation is displaced, and methanation suppressed (in a greater extent for feeds with high CO content). With the In 2 O 3 –ZrO 2 /SAPO-34 tandem catalysts, the conversion of CO x almost 5 folds respect oxygenates synthesis with In 2 O 3 –ZrO 2 catalyst, meaning the yield of the target products boosts from ∼0.5% of oxygenates to >3% of olefins (selectivity >70%) for mixtures of CO 2 /CO X of 0.5, where an optimum performance has been obtained. • Loading Zr into In 2 O 3 catalysts improves the stability for CO 2 hydrogenation. • The direct CO 2 to olefins synthesis displaces the equilibrium of methanol synthesis. • In 2 O 3 –ZrO 2 /SAPO-34 tandem catalyst with Zr/In of 1/2 offer the best performance. [ABSTRACT FROM AUTHOR]

The direct synthesis of dimethyl ether (DME) on bifunctional catalysts is highly attractive for valorizing CO 2 and syngas derived from biomass gasification and is a key process to reduce greenhouse gas emissions. DME economy (conventionally based on its use as fuel) arouses growing interest, in parallel with the development of different routes for its conversion into hydrocarbons (fuels and chemicals) and H 2 production. This review, after analyzing different routes and catalytic processes for the valorization of CO 2 , focuses on studies regarding the thermodynamics of the direct synthesis of DME and the advances in the development of new catalysts. Compared to the synthesis of methanol and the synthesis of DME in two stages, carrying out the reactions of methanol synthesis and its dehydration to DME in the same reactor favors the formation of DME from CO 2 and from CO 2 co-fed with syngas. Starting from the experience for syngas feedstocks, numerous catalysts have been studied. The first catalysts were physical mixtures or composites prepared by extrusion of methanol synthesis catalysts (CuO-ZnO with different carriers and promoters) and dehydration catalysts (mainly γ-Al 2 O 3 and HZSM-5 zeolite). The performance of the catalysts has been progressively improved with different modifications of the composition and properties of the components to upturn the activity (lower for the hydrogenation of CO 2 than for CO) and selectivity, and to minimize the deactivation by coke and by sintering of the metallic function. The core-shell configuration of the bifunctional catalyst allows physically separating the environments of the reactions of methanol synthesis and its conversion into DME. The confinement facilitates the extent of both reactions and improves the stability of the catalyst, since the synergies of the deactivation mechanisms are eliminated. [Display omitted] • DME offers good prospects as fuel, H 2 vector and raw material. • The direct synthesis of DME is attractive for valorizing CO 2 and syngas. • CO 2 conversion is greater than for methanol synthesis or two-stage DME synthesis. • In the core-shell catalyst hydrogenation and dehydration reactions are separated. • Reactions separation prevents the synergy of both coke & sintering in deactivation [ABSTRACT FROM AUTHOR]

Continuous catalytic pyrolysis of high density polyethylene has been carried out for obtaining light olefins in a two step reaction system: (i) thermal pyrolysis in a conical spouted bed at 500°C; (ii) cracking of the volatiles (mainly waxes, C21+) formed in the first step, in a fixed bed reactor using a catalyst based on HZSM-5 zeolite. A kinetic model based on lumps including catalyst deactivation by coke deposition has been established to quantify the product distribution obtained in the second step and its evolution with time on stream. Experimental data have been obtained at 400, 450 and 500°C, with space-times of 0, 1, 2, 4, 6 and 8gcatmingHDPE−1 and for 5h time on stream. The discrimination of kinetic models has been carried out based on statistics calculated for Fischer distribution (stepwise procedure), and the best fits have been obtained for a model considering six steps: cracking of waxes to produce non-aromatic C5-C11 compounds, single-ring aromatics, light alkanes and light olefins; cracking of non-aromatic C5-C11 compounds to yield light olefins and light olefin condensation reactions to produce single-ring aromatic compounds. The deactivation kinetic equation considers waxes as main coke precursors, whose deposition rate decreases with time on stream. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sequenced pyrolysis–cracking of HDPE using HZSM-5 zeolite yields 60wt% of olefins. [•] Catalyst is deactivated by coke; we report on pathways, equations and precursors. [•] Waxes deposit on the mesopores of the catalyst and evolve towards condensed coke. [•] Olefins form coke on the acid sites of the catalyst that plug the micropores. [ABSTRACT FROM AUTHOR]

Particle cycle times(average, maximum, and minimum) have beenmeasured in draft tube conical spouted beds for different geometricfactors of the contactor (angle and gas inlet diameter), draft tubes(diameter, height of the entrainment zone, and width of the faces)and under different operating conditions (particle density). On thebasis of the results, the effects of the type of draft tube and differentfactors of the contactor/draft tube/particle system have been studied,and those of greater influence have been determined. The results showthat particle cycle times and solid circulation rates are highly dependenton the type of draft tube, solid density, and contactor angle. Open-sideddraft tubes are the ones with the highest solid circulation rate withstable spouting performance. Therefore, this internal device is asuitable option for scaling up spouted beds with a hydrodynamic performancesimilar to those without tubes. [ABSTRACT FROM AUTHOR]