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A novel device for measuring the thermal conductivity of polymeric materials (pure polymers or nanocomposites) is presented here. Its design is based on two cylindrical tanks containing cold and hot water. Each tank wets one side of a disc-shaped polymeric sample. The proper selection of construction materials (aluminum body, Teflon fittings, etc.) and geometry (shape, size, etc.) of the two tanks and of the sample (diameter, thickness) renders the accurate measurement of the low thermal conductivity of several polymeric materials possible. The disc-shaped sample is placed in-between the two cylindrical tanks of the device, filled with cold and hot water. The water temperature in the two tanks is an adjustable operational parameter of the device. Both tank temperatures are recorded and fitted by a proper mathematical model in order to estimate the thermal conductivity of the sample. Extensive experimentation shows a very small scatter of the estimated conductivity values. The device was used to measure thermal conductivity of several polymers such as silicone rubber and epoxy resin prepared with a variety of cross-linkers and cross-linker blends. Moreover, the above polymers are used as matrices for the incorporation of various (nano)additives, like mesoporous silica foams (MCF) and organoclays (I.30E), for the preparation of the relative polymer nanocomposites whose thermal conductivity is measured.

In the current study the effect of different mesoporous silica particles like MCF and SBA-15 on the solid state polymerization (SSP) of poly(ethylene terephthalate) (PET) was investigated. PET nanocomposites containing 1 and 2.5 wt% SBA-15 silica (average pore diameter 4.7 nm) and MCF silica (average pore diameter 14.2 nm) have been prepared by in-situ polymerization. All nanocomposites have been characterized using FTIR spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). SSP was conducted at 220, 230 and 240 °C for 1, 2, 3 and 4 h under vacuum. Intrinsic viscosity (IV) measurements after solid-state polymerization of nanocomposites revealed that PET/SBA-15 nanocomposites exhibited lower IV increase compared to neat PET, while the opposite was observed for PET/MCF nanocomposites, especially for 1 wt% MCF content. A simple kinetic model was employed to predict the time evolution of IV, as well as the carboxyl and hydroxyl content during SSP at different temperatures and reaction times.

The application of heterogeneous catalysis in biomass pyrolysis is considered as one of the most promising methods to improve bio‐oil quality by minimizing its undesirable properties (high viscosity, corrosivity, instability, etc.) and producing renewable fuels and high‐value chemicals. Catalytic fast pyrolysis (CFP) of biomass refers both to the “in situ” and “ex situ or two‐stage” upgrading. A plethora of catalytic materials have been investigated in the literature for both approaches, including conventional microporous zeolites, ordered mesoporous aluminosilicates, promoted or not with several transition metals, as well as various metal (nano)oxide catalysts with Lewis acidity. Recently, hybrid micro/mesoporous and basic materials have been also suggested exhibiting most promising results due to combined micro/mesoporosity and adequate balance of acid and basic sites. Optimum catalysts are required to retain deoxygenation, enhance yields of aromatics, and other valuable compounds (such as phenolics), while limiting coke formation. Coke formation is one of the reasons of catalyst deactivation; a very challenging issue during biomass CFP, especially using zeolites. The deactivation process is affected by many factors, including the composition of the feedstock (inorganic minerals present in the feedstock may also deposit on the catalyst), reaction conditions, and the nature/properties of the catalysts used in CFP. Precoking on the surface of zeolites or MgO deposition are among the proposed effective ways to suppress coke formation and thus, catalyst deactivation. This article is categorized under: Bioenergy > Science and Materials Energy Research & Innovation > Science and Materials Energy and Transport > Science and Materials

In this work, two series of biodegradable nanocomposites of poly(ethylene succinate) (PESu) containing either graphene oxide (GO) or organomodified GO (org-GO) with 1-dodecylamine have been prepared and studied. GO was synthesized using a modified Staudenmaier method from of powdered graphite and PESu/GO and PESu/org-GO nanocomposites with GO or org-GO concentrations 0.5, 1 or 2.5 wt% were prepared with the solvent evaporation method. The nanocomposites were characterized with several techniques. Microscopic and XRD study showed intercalated dispersion of GO into PESu matrix while in the case of org-GO fully exfoliated nanocomposites were obtained. Isothermal and nonisothermal crystallization was studied from the melt or from the glass state by using DSC and it was found that nanocomposites crystallized faster than the neat PESu under both conditions. Crystallization rates increased with increasing filler content and it seems that GO have higher crystallisation effect than org-GO. This is due to the stronger interactions that are taking place between PESu and GO, as was confirmed by FTIR and DSC. In the case of the nanocomposites interesting crystalline morphologies and different to those for neat PESu were observed with PLM. Enzymatic hydrolysis studies revealed that nanocomposites have higher hydrolysis rates than neat PESu, while GO accelerates in higher extent the hydrolysis of PESu than org-GO.

In the present work, the effective use of polyethylene-grafted maleic anhydride (PE-g-MA) copolymer as a compatibilizer in high-density polyethylene composites containing 10–50 mass% hemp fibers was evaluated through mechanical and thermal properties measurements. The results revealed a significant reinforcement on the tensile strength of the composites as a consequence of the incorporation of the compatibilizer. Less pronounced effects were found on the elongation at break and impact strength of the composites. The notable enhancement of tensile strength on the compatibilized composites was related to the improved adhesion of hemp with the matrix in the presence of PE-g-MA, which was revealed through scanning electron microscopy observations. Furthermore, Fourier transform infrared spectroscopy analyses suggested that covalent bonding occurs between the fibers and the matrix in the highest PE-g-MA concentrations. Differential scanning calorimetry experiments revealed that the presence of compatibilizer increases the crystallinity of the composites. Thermogravimetry studies revealed that for low compatibilizer concentrations the thermal stability of the composites is further reduced, while for the highest concentration, when bonding occurs, it is enhanced. The biodegradation studies of all the composites revealed that the incorporation of compatibilizer enhances the stability of the composites, especially in the higher concentrations, and reduces their final residue.

In the current study the effect of different clay type, as well as clay organomodifier, on solid state polymerization (SSP) of poly(ethylene terephthalate) (PET) was investigated. PET/clay nanocomposites containing Nanomer I.30E, Cloisite 10A and Laponite have been prepared by melt mixing and their structure was studied by X-ray diffraction measurements. Solid state was conducted at 220, 230 and 240 °C for 1, 2, 3 and 4 h under vacuum application. The I.30E organo-clay exhibited the higher immobilized amorphous fraction. This is due to its better dispersion and exfoliation of the clay nanolayers into the PET matrix, compared to the other organoclays. Intrinsic viscosity (IV) measurements after solid-state polymerization of nanocomposites revealed that IV increase is time and temperature dependent. However, nanocomposites exhibited much lower IV increase compared with neat PET. A simple kinetic model was employed to predict the time evolution of IV, as well as the carboxyl and hydroxyl content during SSP. From the experimental measurements and the theoretical simulation results it was proved that the higher aspect ratio of the nano-clay added, leads to higher inactivated hydroxyls end-groups concentration, higher activation energies and lower transesterification and esterification kinetic rate constants. Increased dispersion of the clay nanolayers in the polymer matrix in addition to increased aspect ratio, leads to better gas barrier properties, reducing the diffusivity and thus the removal of the polycondensation byproducts, i.e. water and EG.

A meaningful and advanced method concerning the management of waste electrical and electronic equipment (WEEE) becomes a necessity, mainly due to their increased production, applications and their short life. Thermal methods have been an attractive option and for this reason the investigation of pyrolysis and catalytic pyrolysis as a potential method for the recycling of polycarbonate (PC) based plastics has been the aim of the current study. Nine different catalysts with variations in properties (such as porosity and acidity/basicity) were introduced in a bench scale pyrolysis system together with the polycarbonate polymeric material and the pyrolysis fractions were collected and analyzed. The liquid product consisted mainly of phenols and substituted phenols as well as the original monomer and, due to the commercial value of these products in the chemical industry, it is expected to enhance the economic viability of the process. Results showed a reduction in the degradation temperature in the presence of all catalytic materials, depending on the pore characteristics and the acidic nature of the solid. It seems that in the presence of the basic catalysts, PC degradation leads to lower molecular weight compounds and high phenolic fractions in the liquid produced. In terms of reduction in the production of the monomer, pore size rather than acidity appears to be the determining factor.

In this study, composites of high-density polyethylene (HDPE) with mesostructured cellular foam (MCF) silicas have been prepared by melt mixing and studied for the first time. Two different MCF silica analogues having different pore size were used, i.e., 12 nm (MCF-12) and 50 nm (MCF-50). The MCF content in the mesocomposites was 1, 2.5, 5, and 10 mass%. All HDPE/MCF-50 mesocomposites exhibited improved mechanical properties compared with neat HDPE, indicating that the mesocellular silica foam particles with the large mesopore size can act as efficient reinforcing agents. On the other hand, the MCF-12 silica with the smaller size mesopores induced inferior mechanical properties, mainly due to the poorer dispersion of the silica particles and the formation of large aggregates. The mesocellular silica foam particles also affected the thermal properties and the crystallization characteristics of HDPE. Crystallization of mesocomposites was faster than that of neat HDPE. Crystallization kinetics was analyzed with the Avrami equation for both isothermal and non-isothermal conditions. For isothermal crystallization, the Avrami exponent increased with increasing crystallization temperature from 2 to 3. In non-isothermal crystallization, the values of the Avrami exponent increased from 3 to 6.3 with decreasing cooling rate. Lower activation energy values of non-isothermal crystallization were calculated using the isoconversional method of Friedman, as well as using the Kissinger’s equation. Finally, the nucleation efficiency of the mesocellular silica foam particles was estimated from data associated with non-isothermal crystallization, according to the method of Dobreva.

HDPE nanocomposites containing 0.5, 1, 2.5 and 5 wt% of copper nanofibers (Cu-nanofibers) were prepared by the melt-mixing method and exhibited enhanced tensile strength, Young's modulus, and oxygen barrier as well as antibacterial properties. These improvements were attributed to the small size of Cu-nanofibers and their fine dispersion into the HDPE matrix.

Polystyrene-b-polyisoprene-b-polystyrene (PS-b-PI-b-PS), a widely used linear triblock copolymer of the glassy-rubbery-glassy type, was prepared in this study by anionic polymerization and was further used for the development of novel polymer nanocomposite materials. Hybrid nanoadditives were prepared by the catalytic chemical vapor deposition (CCVD) method through which carbon nanotubes were grown on the surface of smectite clay nanolayers. Side-wall chemical organo-functionalization of the nanotubes was performed in order to enhance the chemical compatibilization of the clay-CNT hybrid nanoadditives with the hydrophobic triblock copolymer. The hybrid clay-CNT nanoadditives were incorporated in the copolymer matrix by a simple solution-precipitation method at two nanoadditive to polymer loadings (one low, i.e., 1 wt %, and one high, i.e., 5 wt %). The resulting nanocomposites were characterized by a combination of techniques and compared with more classical nanocomposites prepared using organo-modified clays as nanoadditives. FT-IR and Raman spectroscopies verified the presence of the hybrid nanoadditives in the final nanocomposites, while X-ray diffraction and transmission electron microscopy proved the formation of fully exfoliated structures. Viscometry measurements were further used to show the successful incorporation and homogeneous dispersion of the hybrid nanoadditives in the polymer mass. The so prepared nanocomposites exhibited enhanced mechanical properties compared to the pristine polymer and the nanocomposites prepared by conventional organo-clays. Both tensile stress and strain at break were improved probably due to better interfacial adhesion of the clay-CNT hybrid of the flexible rubbery PI middle blocks of the triblock copolymer matrix.

The main objective of the present work was the study of different ZSM-5 catalytic formulations for the in situ upgrading of biomass pyrolysis vapors. An equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading (1–10 wt.%). The product yields and the composition of the produced bio-oil were significantly affected by the use of all ZSM-5 catalytic materials, compared to the non-catalytic flash pyrolysis, producing less bio-oil but of better quality. Incorporation of transition metals (Ni or Co) in the commercial equilibrium/diluted ZSM-5 catalyst had an additional effect on the performance of the parent ZSM-5 catalyst, with respect to product yields and bio-oil composition, with the NiO modified catalysts being more reactive towards decreasing the organic phase and increasing the gaseous products, compared to the Co 3 O 4 supported catalysts. However, all the metal-modified catalysts exhibited limited reactivity towards water production, while simultaneously enhancing the production of aromatics and phenols. An interesting observation was the in situ reduction of the supported metal oxides during the pyrolysis reaction that eventually led to the formation of metallic Ni and Co species on the catalysts after reaction, which was verified by detailed XRD and HRTEM analysis of the used catalysts. The Co 3 O 4 supported ZSM-5 catalysts exhibited also a promising performance in lowering the oxygen content of the organic phase of bio-oil.

Application of heterogeneous catalysis in biomass pyrolysis seems to be one of the most promising methods to improve bio-oil quality by minimizing its undesirable properties (high viscosity, corrosivity, instability, etc.) and producing renewable crude (bio-crude). This bio-crude could finally lead to transportation fuels using existing refinery processes (such as hydrotreating). A plethora of catalytic materials have been investigated in the literature as catalysts for the biomass catalytic pyrolysis process. Among them, microporous (zeolitic) or mesoporous (Al-MCM-41) acid materials have been tested, either promoted or not with several transition metals. Lately, basic materials are also suggested. For this process, a circulating fluid bed reactor seems to be the most effective technology, since it offers continuous catalyst regeneration. The research till today shows that catalysts based on ZSM- are the most promising. With these catalysts, bio-oil yield up to about 30 wt% (on dry biomass) with about 21 wt% oxygen can be produced. However, tailoring of catalyst properties such as acidity/basicity and porosity characteristics is still needed to develop an optimized catalyst.

The N2-adsorption isotherms of porous solids are received in the form V = f(P/Po). If such data are depicted in the form V(1 − P/Po) = f(P/Po) or V(1 − P/Po)/(P/Po) = f(V(1 − P/Po)), they show an identical inversion point (I-point, Inversion or Inflection point), which corresponds exactly to the monolayer volume Vm. As a result the value of specific surface area S is determined with unique precision via the trivial relationship S (m2 g−1) = 4.356Vm (cm3 g−1) without any use of the classic BET treatment. The derivates dV/d[(P/Po)] vs. (P/Po) and d(V[1 − (P/Po)])/d[(P/Po)] vs. (P/Po) exhibit maxima exactly at the same pressure (P/Po), while the second order derivative d2V/d[(P/Po)]2 vs. (P/Po) exhibits a minimum exactly at the same pressure (P/Po) with the I-point. As a consequence the specific surface area of solids can be determined just from experimental raw (P/Po), V data without any use, neither of linear BET treatment nor the Inversion or Inflection type graphs. For some MCM-41 type mesoporous materials, the I-plots show not one but two Inversion points/I-points. The first inversion/inflection point at lower (P/Po) values, “ILP-point”, corresponds to the completion of the adsorption procedure on the bare surface and the formation of monolayer and is useful for the determination of specific surface area S. The second inversion/inflection point at higher (P/Po) values, “IHP-point”, corresponds to the completion of the pore filling via condensation and may be useful for the determination of mesopore volume.

Glassy and rubbery epoxy–clay nanocomposites were synthesized by using various montmorillonite organoclays in order to investigate and compare the effect of the type of alkylammonium ion clay modifier on the structure and properties of the nanocomposites. The organoclays studied were the Nanomer I.28E and I.30E and the Cloisite C10A, C15A and C20A. The functionality (acidity), size and shape of backbone chain, hydrophobicity and polarity were the varying parameters of the organic modifiers that were correlated to the ability of the organoclays to form highly intercalated or exfoliated nanocomposites and to the changes observed in the mechanical (tensile measurements), thermo-mechanical (DMA) and thermal (TGA) properties of the epoxy nanocomposites. The primary alkylammonium ion modifiers with reactive/acidic hydrogen atoms, compared to the quaternary octadecyl, dihydrogenated tallow and benzyl-substituted hydrogenated tallow ammonium ions, were the most effective for the formation of exfoliated clay glassy and rubbery epoxy nanocomposites which exhibited improved properties compared to the pristine epoxy polymers.

Low-density polyethylene (LDPE)/silicate nanocomposites were prepared by the melt compounding and solution blend methods using unmodified LDPE polymer and layered silicates with different aspect ratio. X-ray diffraction (XRD) analysis performed on composites obtained by dispersing the organosilicates in molten LDPE evidenced an exfoliated or partially exfoliated structure for the low aspect ratio silicate (laponite) in contrast to the high aspect ratio silicate (montmorillonite), which led to the formation of intercalated nanocomposites. With regard to the preparation method, the melt compounding method was more effective in forming exfoliated/highly intercalated LDPE nanocomposites compared with the solution blend method (using CCl4 as a solvent). A gradual increase in crystallization temperatures (Tc) with increasing laponite content for LDPE-organolaponite nanocomposites was revealed by differential scanning calorimetry (DSC) measurements. Thermogravimetric analysis and tensile measurements results indicated that thermal stability and elastic modulus increment were more prevalent for nanocomposites prepared using organomontmorillonite as filler. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The use of homoionic organic clays and mixed-ion organic/inorganic clays modified by di- or triamines (Jeffamines), which are being used as epoxy resin curing agents, in the synthesis of polymer nanocomposites has been studied in this work. Our aim is to enhance polymer crosslinking and interfacial adhesion in the nanocomposite structure by utilizing the functionality of the di/triamines on the surface of clay nanolayers and by reducing the organic modifier via formation of homostructured mixed-ion organic/inorganic clays. The results show that the use of homoionic organic clays exchanged with relatively short chain di- or triamines and mixed-ion organic/inorganic clays partially exchanged (ca. 35%) with long chain diamines resulted in intercalated structures with enhanced thermo-mechanical properties (Young's Modulus, Storage Modulus). On the other hand, homoionic organic clays exchanged with long chain diamines and triamines resulted in exfoliated nanocomposites but with compromised mechanical properties due to the plasticizing effect of the long chain amine modifiers.

The effect of the textural properties and morphology of zeolite Y, used as support of iron (Fe) or cobalt (Co) oxides, on the quantity and quality of the multi-wall carbon nanotubes (MWNTs) synthesized by catalytic chemical vapour deposition (CCVD) of acetylene was studied. The parent zeolite Y was modified by various dealumination procedures, namely hydrothermal treatment (steaming), treatment with ammonium hexafluorosilicate (AHFS) and combined steaming-AHFS. The ion-exchange and wet impregnation methods were used for supporting the metals on the zeolite Y samples, with the latter method providing the most effective catalysts for carbon nanotube (CNT) formation. Severe dealumination of zeolite-Y by steaming, which induced the formation of secondary meso/macropores and of relatively large particles/aggregates, resulted in significant decrease in the formation of CNTs compared to the catalysts based on the parent zeolite-Y. Post-treatment of the steamed samples with AHFS had no beneficial effect on the catalysts' activity. Moderate dealumination of the parent zeolite Y by AHFS also inhibited the formation of CNTs, but to a lesser extent compared to the catalysts based on steamed zeolite Y. The TGA studies revealed the presence of carbon phases with different thermal stability in the zeolite-CNT composites, ranging from amorphous carbon to well-graphitized MWNTs. TEM images and micro-Raman spectra taken right after growth confirmed the formation of high quality MWNTs with a low degree of disorder irrespective of the catalysts used, the degree of dealumination of the zeolite Y and the textural and morphological characteristics of the zeolitic support. (c) 2007 Elsevier Inc. All rights reserved. Microporous and Mesoporous Materials

The present study focuses on the synthesis and characterization of vanadia catalysts supported on non-porous (SiO2), microporous (silicalite), mesoporous (MCM-41, HMS, SBA-15) and ultra-large mesoporous (MCF) silicate materials. The structure and porosity characteristics of the above mesoporous supports were verified by means of XRD, N2 porosimetry and HR-TEM studies. Vanadium was introduced in the porous materials via wet impregnation of vanadium oxalate complex in strongly acidic aqueous media. No crystalline V2O5 phases were found on the surface of all the above mesoporous supports for V loadings as high as 8 wt.%, in contrast to microporous zeolite silicalite and non-porous SiO2 on which V2O5 crystals were formed as evidenced by XRD. Increasing addition of vanadium under the strongly acidic impregnation conditions followed by typical calcination of the catalyst, resulted in partial structure breakdown and loss of surface area of the mesoporous supports which was more pronounced in the case of SBA-15 and MCF materials. The most active catalysts for the formation of propene in the oxidative dehydrogenation of propane (ODP) at reaction temperatures 500–600 °C were those supported on HMS and MCM-41 mesoporous materials showing high propene yields up to 19% at about 600 °C. The vanadia catalysts based on SBA-15 and MCF were less active in the production of propene (yields up to 13%) compared to the MCM-41 and HMS based catalysts. The SiO2 and silicalite based catalysts showed much lower yields of propene (

The ethylene epoxidation activity of Ag catalysts supported on non-porous SiO 2 , microporous silicalite zeolite and mesoporous MCM-41 and HMS silicates was investigated in the present study in comparison to conventional low surface area α-Al 2 O 3 based catalysts. The MCM-41 and HMS based catalysts exhibited similar ethylene conversion activity and ethylene oxide (EO) selectivity with the SiO 2 and α-Al 2 O 3 based catalysts at relatively lower temperatures (up to ∼230 °C), whereas their activity and selectivity decreased significantly at higher temperatures (≥300 °C). The silicalite based catalyst was highly active for a wide temperature range, similar to the SiO 2 and α-Al 2 O 3 based catalysts, but it was the less selective amongst all catalysts tested. High loadings of Ag particles (up to ca. 40 wt.%) with medium crystallites size (∼20–55 nm) could be achieved on the mesoporous materials resulting in very active epoxidation catalysts. The HMS-type silicate with the 3D network of wormhole-like framework mesopores (with average diameter of ∼3.5 nm), in combination with a high-textural (interparticle) porosity, appeared to be the most promising mesoporous support.

Aluminosilicate mesostructures (MSU-S BEA ) assembled from zeolite Beta (BEA) seeds exhibited relatively high hydrothermal stability and were significantly more active in the cracking of gas–oil compared to MCM-41 after severe steaming pretreatment. The MSU-S BEA mesoporous materials with wormhole framework structure and those having morphology of solid nanoparticles with high interparticle mesoporosity were more steam-stable and more active after severe steaming than those with hexagonal pore structure. Differences in acid sites strength between the MSU-S BEA materials and MCM-41 could not be probed by the complex reaction system of the large hydrocarbon molecules of gas–oil.

The results on the gasification of Greek lignite using two indirect heat (allothermal) pilot rotary kiln gasifiers are reported in the present work. The development of this new reactor-gasifier concept intended for solid fuels chemical conversion exploits data and experience gained from the following two pilot plants. The first unit A (about 100 kg/h raw lignite) demonstrated the production of a medium heating value gas (12-13 MJ/Nm3) with quite high DAF (dry ash free) coal conversions, in an indirect heat rotary gasifier under mild temperature and pressure conditions. The second unit B is a small pilot size unit (about 10 kg/h raw lignite) comprises an electrically heated rotary kiln, is an operation flexible and exhibits effective phase mixing and enhanced heat transfer characteristics. Greek lignite pyrolysis and gasification data were produced from experiments performed with pilot plant B and the results are compared with those of a theoretical model. The model assumes a scheme of three consecutive-partly parallel processes (i. e. drying, pyrolysis, and gasification) and predicts DAF lignite conversion and gas composition in relatively good agreement with the pertinent experimental data typical of the rotary kiln gasifier performance. Pilot plant B is currently being employed in lime-enhanced gasification studies aiming at the production of hydrogen enriched synthesis gas. Presented herein are two typical gas compositions obtain from lignite gasification runs in the presence or not of lime. .

Extrusion blown polyethylene and polyethylene/montmorillonite nanocomposite films were cold stretched to various ratios to quantify the influence of the crystal orientation and the nanofiller alignment on their dielectric breakdown performance. It was found that the crystal orientation could increase the breakdown strength (EBD) in the stretched blown films. The aligned pseudo-2D inorganic nanoclays provided additional strong improvements in EBD that can be superimposed to any EBD enhancement due to the polymer crystal orientation. At high filler loadings and high stretching ratios, the onset of percolation was observed through a substantial improvement in the dielectric breakdown strength.

Pyrolysis appears to be a promising recycling process since it could convert the disposed polymers to hydrocarbon based fuels or various useful chemicals. In the current study, two model polymers found in WEEEs, namely polycarbonate (PC) and high impact polystyrene (HIPS) and their counterparts found in waste commercial Compact Discs (CDs) were pyrolysed in a bench scale reactor. Both, thermal pyrolysis and pyrolysis in the presence of two catalytic materials (basic MgO and acidic ZSM-5 zeolite) was performed for all four types of polymers. Results have shown significant recovery of the monomers and valuable chemicals (phenols in the case of PC and aromatic hydrocarbons in the case of HIPS), while catalysts seem to decrease the selectivity towards the monomers and enhance the selectivity towards other desirable compounds.

Novel poly(butylene succinate) (PBSu) nanocomposites containing 5 and 20 wt% mesoporous strontium hydroxyapatite nanorods (SrHNRs) and silica nanotubes (SiNTs) were prepared by melt-mixing. A systematic investigation of the thermal stability and decomposition kinetics of PBSu was performed using pyrolysis-gas chromatography–mass spectroscopy (Py-GC–MS) and thermogravimetry (TG). Thorough studies of evolving decomposition compounds along with the isoconversional and model-fitting analysis of mass loss data led to the proposal of a decomposition mechanism for PBSu. Moreover, the effects of SrHNRs and SiNTs on the thermal stability and decomposition kinetics of PBSu were also examined in detail. The complementary use of these techniques revealed that the incorporation of SiNTs in PBSu does not induce significant effects neither on its thermal stability nor on its decomposition mechanism. In contrast, the addition of SrHNRs resulted in the catalysis of the initial decomposition steps of PBSu and also in modified decomposition mechanisms and activation energies. The evolving gaseous products of PBSu and their evolution pattern in the SiNT nanocomposites were the same as in neat PBSu, while they were slightly modified for the SrHNR nanocomposites, confirming the findings from thermogravimetric analysis.

In Part II of this work a flighted pilot rotating cylindrical drum, intended to be used as either a dryer or calciner ( kiln) has been used to investigate the flow, through it, of pulverized moist lignite. Tracer pulse input - response experiments have been performed. Residence Time Distribution ( RT) data have been deduced for three types of flight geometry, namely: Rectangular ( RA) Equal Angular Distribution ( E.A.D.) and Equal Horizontal Distribution ( E.H.D) For each flight shape, mean residence time t¯ has been correlated with drum operating conditions. The sequence ⩾ t¯ EAD t¯ EAD has been validated. A comparison between the residence time predictions for the flighted and the bare drum has indicated that t for the former may be higher by up to 3.5 times than that for the latter. Exceptionally high solids hold-up values ( Z= 0.13− 0.42) have been observed and compared to theoretical predictions. Particle size segregation during lignite flow through the flighted drum was not confirmed.

The enzymatic hydrolysis of cellulose toward fermentable glucose is of paramount importance for the production of ethanol or other high-value chemicals from lignocellulosic biomass via the biochemical route. A pretreatment step is usually required that alters the structure and composition of biomass, reduces its recalcitrance, and allows the efficient enzymatic conversion of carbohydrates into sugars. Biomass pretreatment aims mainly at the selective separation of hemicellulose and/or lignin, either as oligomers or as smaller sugar and phenolic molecules, which can be further converted enzymatically or via chemical catalysis to platform chemicals or fuel precursors. In this chapter, a review of the most widely applied pretreatment methods is presented, with the aim of elucidating the role of chemical or biochemical catalysis in this first step of biomass valorization.

The remarkable physical properties of carbon nanotubes and their versatile chemical reactivity leading to various types of surface organo-functionalization were the main reasons why CNTs have become one of the most important types of nano-additives for the development of novel polymer (including epoxy) nanocomposites with improved and sometimes unique properties. The present chapter deals with the organo-functionalization of carbon nanotubes and the preparation of the respective epoxy – CNT nanocomposites. The effect of functionalization on dispersion of CNTs and on the final properties of the nanocomposites is discussed, while emphasis is given on the reactivity of the functional groups and their participation in the curing process of epoxy resins.

This paper discusses settling rates, yield stresses, and shear-stress/shear-rate dependences which were determined as functions of solids concentration for suspensions in water of coal particles of narrow size fractions. Particles and suspensions are characterized by coal analyses, determination of heating value, solid heat capacity and thermal conductivity, particle size analyses, and determination of densities and maximum packing concentrations for each particle size range. Analysis of the settling data establishes that the usually strong retardation of (hindered) settling due to concentration is compounded by particle shape effects. Shear-stress/shear-rate data for concentrated suspensions of the three larger and relatively narrower sized particles over the broad range of shear rates from about 1 to 10{sup 4} s {sup {minus}1} suggest the behavior to be essentially Newtonian, albeit with a marked particle concentration augmentation. Suspensions of the smallest coal particles of broader size distribution were strongly non-Newtonian, possessing a yield stress at low shear, essentially power-law shear-thinning behavior over the intermediate range and approaching high-shear Newtonian limiting behavior above about 10{sup 3} s{sup {minus}1}.

The potential utilization of various microporous (zeolites H-Y and H-ZSM-5) and mesoporous (amorphous silica-alumina and Al-MCM-41) aluminosilicates as catalysts or active matrices in the cracking of Fischer-Tropsch waxes towards the production of liquid fuels was the subject of this study. Focus was placed on the effect of porous and acidic characteristics of the materials on products yields and properties. Both zeolitic catalysts were very active leading however to different product selectivities. The moderately steamed H-Y catalyst produced more gasoline and less LPGs compared to the H-ZSM-5 catalyst. The relatively high gasoline RON values for both catalysts were attributed to the high yield of iso-alkanes and olefins in the case of the H-Y catalyst and to the high yield of aromatics in the case of H-ZSM-5. The use of mildly acidic Al-MCM-41 type mesoporous materials resulted in relatively low wax conversion activity, while the amorphous silica-alumina catalyst was almost inactive.

The present study focuses on the effect of the metal-modification method (ion-exchange or impregnation) and of the type of dealumination procedure (steaming, AHFS) of zeolite-Y on the quantity, quality and properties of the carbon nanotubes that are formed on the supported iron or cobalt oxides. Severe dealumination of zeolite-Y by steaming, which induced secondary meso/macropores, resulted in significant decrease in the carbon nanotube formation activity of the metal-impregnated zeolite-Y catalysts, while moderate dealumination by ammonium hexafluorosilicate had a less pronounced effect. The micro-Raman spectra revealed the presence of high quality as-grown CNTs with low degree of disordered.

In this work we provide evidence of microporosity in the nanostructured mesoporous aluminosilicates MSU-S/W(BEA) synthesized from zeolite BEA seeds, based on the so called I-point plots (refs. 18–20) of the BET equation. Seventeen solids were characterized for their porous characteristics as follows: (i) one mesoporous aluminosilicate 2%Al-MSU-S/W(BEA), (ii) two typical mesoporous MCM-41 materials, one pure silica and one aluminosilicate 2%Al-MCM-41, (iii) three typical microporous zeolites, i.e., zeolites Y, ZSM-5 and beta, (iv) two typical amorphous silica–alumina (ASA) samples, (v) five mechanical mixtures of mesoporous Al-MCM-41 with zeolite beta at different addition percentages, and (vi) four amorphous or partially crystalline ZSM-5 based aluminosilicates. The P,V data from the nitrogen-adsorption isotherms of those porous solids were plotted according to the I-point modification of the BET equation in the form V[1 − (P/P0)]/(P/P0) = CVm − (C − 1)V[1 − (P/P0)]. Plots of V[1 − (P/P0)]/(P/P0) vs. V[1 − (P/P0)] provided lines which have the shape of an inclined V, i.e. >, and variable slopes corresponding to (C − 1) from which the values of the C parameter were determined for the whole range of partial pressures 0 < P/P0 < 1. The inversion point of the above plots, called the I-point, projected onto the V[1 − (P/P0)] axis corresponds exactly to the volume of the monolayer Vm = VI[1 − (PI/P0)], from which the value of the specific surface area SI (m2 g−1) was determined. The shape of the I-plots depended strongly on the type of porous solids, i.e. microporous/zeolitic and partially crystalline zeolitic materials with combined micro- and meso/macroporosity; ordered mesoporous MCM-type materials; ASA materials with random mesoporosity; and mechanical mixtures of zeolite beta with MCM-41. The I-plot for the MSU-S/W(BEA) solid exhibited the combined characteristics of the plots of ordered mesoporous MCM-41 samples and of partially crystalline zeolitic materials, thus proving the presence of microporous domains within the homogeneous mesoporous structure of the MSU-S material. The I-plot result supports the proposed presence of protozeolitic subunits in the framework walls, of MSU-S, even though XRD and electron diffraction TEM studies have shown the material to be free of any zeolitic crystalline phase. The surface areas estimated by the I-method were similar to those provided by the BET model for the zeolitic and the ASA samples, while in the case of the ordered MCM-41 and MSU-S/W(BEA) mesostructures, two surface area values can be estimated based on different interpretations of the I-method, one similar to the value from the BET model and one supported by the modified CPSM model (refs. 31–34).

A general procedure to fit optical constants, using a transfer function model with temperature-and/or-composition-dependent coefficients, is presented. The model is further inverted by a simple algorithm to retrieve temperature and composition information from optical measurements obtained by spectroscopic ellipsometry. The method was applied to fit: (1) the complex index of refraction of the system AlXGa1−xAs at 600 °C, for values of X between 0 and 1. (2) Two data bases of complex dielectric constants, for near-lattice-matched InGaAs and InAlAs, and around temperatures of 500 °C. The parameters of the model are determined with a least squares algorithm with recursive “whitening” of the error, which shows fast convergence to a near-optimal solution, even when handling a large number of parameters. The level of accuracy achieved makes this method an adequate sensor for temperature, composition, and thickness control during molecular beam epitaxy growth.

Molybdenum black has been produced in thin coating form (3 μm) on prepared aluminium surfaces by the method of electrodeposition. The microstructure of the coating has been identified as one of flat irregular platelets belonging to a material which can be described as quasi-amorphous. Its chemical composition is 90 wt% MoO2 · 2 H2O and 10 wt% Ni(OH)2 · Mo-black appears to be a good absorber of solar radiation. Absorbance values as high as 93% have been measured for the visible region of the solar energy spectrum. It has been identified that the coating is of semiconducting nature and that the dominant conduction mechanism is the Schottky emission mechanism. Photoelectrochemical measurements have finally provided evidence for photon-induced electrochemical processes at the Mo-black electrodes.