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In order for catalytic biomass pyrolysis to be economically sustainable, low cost and highly efficient catalysts are needed. In a previous work, Magnesium oxide (MgO) basic catalysts produced from natural magnesite (MgCO3) were found to be highly efficient alternatives to zeolitic catalysts which apart from their relatively high cost, they are easily deactivated due to biomass alkali deposition. In order to validate these findings in pilot scale, these natural MgO catalysts were investigated in a circulating fluidized bed pilot scale unit and were compared to a commercially available ZSM-5 catalyst. This is to the best of our knowledge the first attempt to evaluate a basic catalyst in biomass fast pyrolysis in a pilot unit employing commercially relevant process technology. The basic sites of the MgO catalysts enhanced ketonization and aldol condensation reactions, as it was verified by 2DGC-TOFMS analyses of the produced bio-oils. Deoxygenation was achieved mainly via formation of CO2, while H2O yield was substantially reduced in comparison to the ZSM-5 catalyst. As a result, bio-oils richer in hydrogen were obtained by the use of MgOs. However, the MgO catalysts led to a significant increase of the catalytically produced coke compared to ZSM-5. The effect of MgO properties, such as surface area and basicity on product yields and bio-oil composition was elaborated. In contrast to the acidic ZSM-5, no alkali metals were found to deposit on MgO, indicating different deactivation mechanisms between acidic and basic catalysts in biomass fast pyrolysis.

Among the different metal-promoted catalysts for the conversion of C6 sugars to platform chemicals, Sn-based catalysts have demonstrated high activity for different types of reactions, such as isomerization, retro-aldol conversion and dehydration of glucose or its isomers. The form of Sn species, as oxides or ions, along with the properties of the support are important factors determining the prevalent reaction pathway and product distribution. In this framework, we have studied the conversion of glucose mainly in biphasic (H2O/DMSO) media, using four types of Sn-based catalysts, i.e. Sn(II) and Sn(IV) as homogeneous catalysts (Cl- salts) or as the respective oxides in heterogeneous systems, Sn(IV) as SnO2 supported on γ-Al2O3, zeolites (ZSM-5 and Beta) or mesoporous aluminosilicates (Al-MCM-41), and Snδ+ as ion-exchange cations on the above zeolites. The solid catalysts were characterized by XRD, FT-IR/pyridine, ICP-OES, XRF and N2 porosimetry. Under the studied conditions, the main products obtained were 5-HMF and lactic acid in both the homogeneous and heterogeneous systems. Based on the results obtained, it was concluded that the Lewis acidity offered by Sn oxides promotes the retro-aldol reaction pathway towards lactic acid, while the Lewis acidity offered by γ-Al2O3 enhances the synthesis of both 5-HMF and lactic acid. By combining these two functions, the Sn impregnated γ-Al2O3 catalysts induce further increase of both 5-HMF and lactic acid yields. In case of catalysts that possess Bronsted acidity as well (i.e. Sn ion-exchanged or impregnated zeolites and Al-MCM-41), dehydration reactions are promoted and the product selectivity is shifted towards 5-HMF synthesis. The highest 5-HMF molar yield of 27.5% (at complete glucose conversion) was achieved by Sn20/γ-Al2O3 accompanied by lactic acid at 16.5% molar yield. For this catalyst the effect of the solvent, catalyst concentration and reaction temperature and time, were further evaluated.

5-Hydroxymethylfurfural (5-HMF) is one of the most promising biomass derived platform chemicals. It can be synthesized from biomass carbohydrates, mainly glucose and fructose, via dehydration under acidic conditions. The reaction may be performed either in water, ionic liquids or organic solvents, in particular polar aprotic solvents. In this work, the process modelling of a two-step synthesis of 5-HMF from biomass is presented. Starting from hemicellulose-free biomass, the first step includes the hydrolysis of cellulose towards glucose in the presence of H2SO4 as catalyst, while in a second step glucose is dehydrated to 5-HMF with the aid of Sn20/γ-Αl2O3 catalyst. Hydrolysis is performed in aqueous medium, while dehydration of glucose is taking place in a DMSO/H2O mixture. The overall production of 5-HMF is modelled via the chemical process optimization software ASPEN PLUS™. The optimized process is scaled up at an industrial scale where the heat integration, mass and energy balance calculations are performed.

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.

The “ one-pot ” hydrolyltic hydrogenation of cellulose towards C2-C6 sugar alcohols has been recognized as one of the most promising biomass valorization routes for the production of high added-value chemicals. In this work, we studied the performance of Ru and Pt catalysts supported on micro/mesoporous activated carbon, in the hydrolytic hydrogenation of microcrystalline and ball-milled cellulose, in neat water, at 180 °C and at relatively low hydrogen pressure of 2 MPa. The impact of metal loading (1–5 wt.%), metal reduction method (H 2 at 350 °C or NaBH 4 ) and acidification (sulfonation) of the AC support on cellulose conversion and selectivity to the various products were systematically addressed. It was shown that Pt is significantly more selective towards hexitols (sorbitol and mannitol) compared to Ru, in glucose-rich reaction media, such as those offered by the easily hydrolyzed ball-milled cellulose. For example, the 5wt%Pt/AC-SO 3 H catalyst afforded hexitols yield of 69.5 wt.% (at 96.1% conversion) compared to 10.9 wt.% (at 95.2% wt.% conversion) obtained by the corresponding Ru catalyst, the latter being also selective towards glycerol and propane-1,2-diol (propylene glycol). A relatively moderate metal loading, such as in 3 wt.%Ru/AC-SO 3 H, was more favorable for hexitols production (44.5 wt.% yield, at 94.8 wt.% conversion) with Ru catalysts. These results were also verified by glucose hydrogenation experiments that were conducted at the same experimental conditions. Both Pt and Ru exhibited relatively high glucose hydrogenation activity towards hexitols, versus retro-aldol reactions that lead directly to smaller C2–C4 compounds, while the difference in the final product yields between the two metals was attributed to the higher hexitols hydrogenolysis (C C cleavage) reactivity of Ru. HRTEM data showed the formation of metallic crystalline Pt and Ru nanoparticles (≤4 nm, depending on loading) as well as of amorphous oxygen-rich M(O) x δ+ phases, which were also confirmed by the XPS data. The presence of these phases which may be a source of acidity, as well as the bacisity of the parent AC used in this study, were mainly responsible for inducing isomerization, retro-aldol and dehydration reactions leading eventually to increased glycerol and propylene glycol selectivity, as was observed for both low-metal catalysts, i.e. 1 wt.% Pt or Ru/AC.

The catalytic activity of supported silver nanoparticles on mesoporous silica was studied, for the selective reduction of azines into benzyl hydrazones using sodium borohydride as mild reducing agent. Different sizes of silver nanoparticles supported on mesoporous silica (Ag/HMS) were successfully prepared by two methods, i.e. wet impregnation followed by reduction with hydrogen at 350oC and in situ deposition/reduction with a mixture of amines (ethanolamine and ethylenediamine). The Ag/HMS (amines) catalyst was found to promote the selective 1,2-reduction of aryl-substituted azines, compared to the corresponding 1,4-reduction that occurs in general reduction processes. This catalytic transfer hydrogenation process found to be clear, fast and quantitative (>99% yields and selectivity) towards benzyl hydrazones synthesis under mild conditions. Of great importance is that under the present catalytic conditions reducible functional groups remain intact. Formal kinetics, support the in situ formation of silver-hydride species being responsible for the reduction process. The presence of protic polar methanol enhanced the catalytic activity of Ag/HMS. Based on the recycling studies the catalytic system Ag/HMS-NaBH4 was found to catalyze the selective reduction of azines nine times without significant loss of its activity. Finally, one-pot reaction between the in situ produced benzyl hydrazones and a series of nitrostyrenes readily provided the regioselective synthesis of 1,3,5,-subtituted pyrazoles, highlighting a useful synthetic application of the catalytic protocol.

The thermal and catalytic fast pyrolysis of biomass aims at the production of pyrolysis oil (bio-oil), which can be utilized as a source of chemicals or as a bio-crude for the production of hydrocarbon fuels. We investigated low-cost, naturally derived basic MgO materials as catalysts for the catalytic fast pyrolysis of lignocellulosic biomass as alternatives to classical acidic zeolite catalysts. The MgO catalysts were produced from natural magnesite mineral without any significant treatment besides calcination, crushing and sieving. Their structure, composition, porosity, morphology and surface properties were thoroughly examined by XRD, XRF, N 2 porosimetry, SEM, TEM, TPD-CO 2 and TPD-NH 3 . The physicochemical characteristics of the MgO catalysts depended mainly on the different production conditions (duration and temperature of calcination). Despite their negligible acidity, the MgO catalysts effectively reduced the oxygen content of the produced bio-oil and exhibited similar or even better performance compared to that of an industrial ZSM-5 catalyst formulation ( i.e. non-catalytic pyrolysis: 38.9 wt.% organic bio-oil with 38.7 wt.% O 2 ; ZSM-5 based catalyst: 20.7 wt.% organic bio-oil with 30.9 wt.% O 2 ; selected natural MgO catalysts: 25.7 wt.% organic bio-oil with 31.0 wt.% O 2 or 21.1 wt.% organic bio-oil with 28.4 wt.% O 2 ). The basic sites of the MgO catalysts favored reduction of acids and deoxygenation via ketonization and aldol condensation reactions, as indicated by the product distribution and the composition of the bio-oil. Oxygen was removed mainly via the preferred pathway of CO 2 formation, compared to CO and water as in the case of ZSM-5 zeolite. On the other hand, reaction coke slightly increased over the MgO catalysts as compared to ZSM-5; however, the MgO formed coke was oxidized/burnt at significantly lower temperatures compared to that of ZSM-5, thus enabling MgO regeneration by relatively mild calcination in air. A systematic correlation of product yields and oxygen content of bio-oil with the physicochemical properties of the MgO catalysts has been established.

The sustainable utilization of lignocellulosic biomass as a renewable and abundant source lies at the core of the emerging biobased economy for the production of fuels, materials, and platform chemicals. The first step in the implementation of many biomass valorization technologies is the “pretreatment” that aims at biomass fractionation and recovery of its main structural components, i.e., cellulose, hemicellulose, and lignin, which can be then converted by downstream (bio)catalytic processes to targeted high added value intermediate chemicals or final products. In this respect, hydrothermal pretreatment in pure water (also called liquid hot water or autohydrolysis) offers a method with low operational costs, free of organic solvents and corrosive acids or bases, and with no use of “external” liquid or solid catalysts. In the present work, the hydrothermal pretreatment of three types of lignocellulosic forestry and agricultural residues/byproducts was studied. They are representative of hardwood (residua...

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.

Catalytic fast pyrolysis (CFP) of lignin with amorphous mesoporous aluminosilicates catalysts yields a high fraction of aromatics and a relatively low amount of char/coke. The relationship between the acidity and porosity of Al-MCM-41, Al-SBA-15, and Al-MSU-J with product selectivity during lignin CFP is determined. The acid sites (mild Brønsted and stronger Lewis) are able to catalyze pyrolysis intermediates towards fewer oxygenated phenols and aromatic hydrocarbons. A generalized correlation of the product selectivity and yield with the aluminum content and acidity of the mesoporous aluminosilicates is hard to establish. Zeolitic strong acid sites are not required to achieve high conversion and selectivity to aromatic hydrocarbon because nanosized MCM-41 produces a high liquid yield and selectivity. The two most essential parameters are diffusion, which is influenced by pore and grain size, and the active site, which may be mildly acidic, but is dominated by Lewis acid sites. Nanosized grains and mild acidity are essential ingredients for a good lignin CFP catalyst.

Isomerization of glucose to fructose is an important reaction with numerous applications in terms of biomass valorization. The reaction is catalyzed enzymatically but may also proceed under alkaline conditions, in which case it is accompanied by low selectivity and formation of byproducts. Solid Lewis acid and basic catalytic materials are being studied as alternative catalysts. In this work, the isomerization of glucose to fructose in aqueous media over homogeneous and heterogeneous catalysts has been investigated. The effect of polar aprotic solvents and their mixtures with water on glucose conversion and fructose selectivity was also studied. Sodium aluminate (NaAlO2) has been proven to be very effective, resulting in high fructose yield (52.1 %) and high selectivity (84.8 %). Among the various solid catalysts tested, MgO afforded glucose conversion of 44 %, with 75.8 % and 33.4 % fructose selectivity and yield, respectively, when the isomerization reaction was conducted in neat H2O.

In the present work we studied the hydrogenation/hydrogenolysis of d -glucose over Pt and Ru catalysts supported on activated micro/mesoporous carbon (AC), under low hydrogen pressure (1.6 MPa) and relatively high reaction temperature, i.e. 180 °C. We also studied the effect of metal content (1–5 wt.%), method of metal pre-treatment/reduction (H 2 at 350 °C or NaBH 4 ) and reaction time (1–12 h). All the Ru and Pt/AC catalysts were very active (conversion ≥97%) with the Pt/AC catalysts being also very selective toward sorbitol (sel. ≥90%) irrespective of metal content, method of reduction and reaction time (up to 12 h). On the other hand, the Ru/AC catalysts exhibited a wide range of sorbitol selectivity values (55–93%) having various C 3 –C 6 sugar alcohols (1,2,5,6-hexanetetrol, arabinitol, threitol, glycerol and 1,2-propanediol) as main by-products. The formation of by-products was dependent on the crystalline/amorphous nature of Ru and Ru(O) x δ + nanoparticles which were in turn affected by the Ru content and the method of reduction.

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.

This study investigates the effect of active metal and the nature and pre-treatment of the support in a series of K-promoted NiMo catalysts supported on activated carbon (AC) for the hydrogenation reaction of CO. The Ni Mo synergistic effect was found to be essential for the activation of CO. The use of activated carbon as support led to a three-fold increase in the selectivity toward higher alcohols, compared to the unsupported material, probably due to a reduction in the crystallinity of the active NiMoO4 phase and its partial transformation from alpha to beta form. Pre-treatment of the activated carbon prior to its use as support with HNO3 aqueous solution led to significant increase in CO conversion, related to the lower amount of ash and the much higher acidity of the acid treated sample. The use of a higher surface area acid-treated support also increases activity, with the K NiMo/AC2a catalyst exhibiting a 45% higher conversion at 280 °C compared to K NiMo/AC1a. The improvement in activity can be ascribed to better dispersion of the active phase on the higher surface area AC support and therefore higher exposure of active Ni O Mo sites. Overall, the K NiMo/AC2a catalyst exhibited the optimum performance, with high CO conversion (25% at 280 °C) and high production of oxygenates, with a space time yield to oxygenates of 141.5 mg/gcatalyst/h at 280 °C. A clear tendency of increasing higher alcohol production with decreasing acidity was evidenced for all K-promoted bimetallic NiMo catalysts.

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.

The valorization of various types of low-quality vegetable oils with relatively high content of free fatty acids (FFA) is a research field of increased interest. The esterification of oleic acid, a highly abundant FFA in waste oils, with trimethylolpropane (TMP) towards the production of the corresponding triesters, which can be used in lubricants or hydraulic fluids, was studied in this work. The catalysts tested were various meso/macroporous oxides, such as ZrO2, 3.5%SiO2-ZrO2, SiO2-Al2O3, SBA-15 and Al-SBA-15 with varying textural and acidic properties and the corresponding supported heteropoly acid catalysts, prepared by the use of phosphotungstic (H3PW12O40) and tungstosilicic (H4SiW12O40) acids. The catalysts were characterized by ICP-AES, XRD, FT-IR, N-2 porosimetry and FT-IR coupled with pyridine adsorption. The main product at 200 degrees C and after 6 h of reaction was the triester (TE) of oleic acid with selectivity values ranging from 85% to 99% at conversion degrees of 82% to 96%. The two aluminosilicate catalysts that combine Bronsted and Lewis acidity (i.e. SiO2-Al2O3 and Al-SBA-15) showed slightly higher yields of triester (similar to 83%) compared to the rest oxides (similar to 78%), while the Bronsted acidity induced by the two heteropoly acids, especially by PW, provided very high reactivity and selectivity towards triesters, irrespective of the type of support used, reaching triester yield values of 95% (96.2% conversion, 98.7% selectivity) with the 20%PW/ZrO2 catalyst, The most stable catalysts against leaching of heteropoly acids were those supported on 3.5%SiO2-ZrO2 and SiO2-Al2O3. (C) 2017 Elsevier B.V. All rights reserved.

The transformation of α-limonene into p -cymene over oxide catalysts (γ-Al 2 O 3 , TiO 2 , SiO 2 , MCM-41) has been studied under H 2 and He atmosphere in the temperature range 200–300 °C using a fixed bed micro-reactor working under atmospheric pressure. The catalysts were characterized using various physicochemical techniques (N 2 adsorption–desorption, NH 3 -TPD, XRD, TPR, HR-TEM). We demonstrated that an almost complete transformation of α-limonene into p -cymene can be obtained at 300 °C over a high surface area anatase (Alfa Aesar) in helium atmosphere. The high surface area titania was also proved a very stable catalyst. The high catalytic performance of this oxide could be attributed to a good balance between the acidity and surface reducibility exhibited by this material. The aforementioned properties are, respectively, relevant to the isomerization and disproportionation/dehydrogenation steps involved in the mechanism of title reaction. Based on the yields obtained for p -cymene and by-products we proposed a mechanistic scheme for the title reaction over the high surface area titania.

Supported Ir, Pd, Rh and Ru catalysts were examined for the conversion of glucose and cellulose in water in the presence of hydrogen. The catalysts were prepared by incipient wetness impregnation of a BEA zeolite (SiO2/Al2O3 = 21.6, Ssp = 739 m2/g) with acetylacetonate metal precursors. Among these catalysts, Ru-BEA was found to be the most active for the conversion of cellulose, while Ir-BEA was found to be the most selective for the formation of sorbitol. Thus, the highest yield to sorbitol was found in the presence of 3 wt%Ru/BEA catalyst irrespective of the raw material nature (glucose or cellulose). It corresponded to a value of 22% for the conversion of the commercial cellulose, and of 72.8% for the conversion of glucose. The Ru-BEA catalyst was followed by the 3 wt%Ir-BEA that led to a yield of 55.3% for glucose and 22% for cellulose but to a much higher selectivity, i.e. over 99.9% for glucose and 89.2% for cellulose. While the high selectivity of Ir to sorbitol was correlated with the d-band width of the metal, the high activity of Ru for the cellulose conversion was assigned to the generation of H+ and [Ru(H2O)5OH]2+ as Bronsted acids by Ru species in water. Finally, the addition of pure nanoscopic hydroxylated SnF4 to the 3 wt%Ir-BEA catalyst led to a conversion of cellulose of almost 99% after only 3 h with a selectivity to sorbitol of 72.5%.

Adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from solutions in hexadecane was investigated on three commercial nanoporous activated carbons of different origin and nature, which possessed either microporous or combined micro/mesoporous structures, and their oxidized counterparts. The initial and exhausted carbons were characterized using the nitrogen porosimetry at 77 K, thermal analysis, Boehm titration, and FTIR. The capacity for 4,6-DMDBT removal increases with an increase in the volume of pores with size similar to that of 4,6-DMDBT molecules, which is about 6 A. Functional groups present on the surface of larger pores contribute to adsorption via polar interactions.

A series of C 60 catalysts supported on MCM-41 was prepared for the singlet oxygen-mediated oxidation of alkenes to the corresponding hydroperoxides (ene or Schenck reaction). The one-step wet impregnation method, followed by heating at 180 °C, was used for dispersing effectively 6, 9 and 12 wt% C 60 onto the MCM-41 surface. N 2 adsorption–desorption measurements, FT-IR, XRD, DRS and TGA were used to characterize the prepared photocatalysts. The photocatalytic activity of the C 60 /MCM-41 series was determined by using the photooxygenation of 2-methyl-2-heptene as a probe reaction. The results of the present study were compared with those obtained in our previous studies where the same photocatalysts had been prepared by using the successive wetness impregnation method. It was found that very effective C 60 /MCM-41 photocatalysts can be synthesized by applying the one-step wet impregnation method. All three photocatalysts exhibited similar activity in terms of substrate conversion, whereas their intrinsic activity which is expressed by the TON or TOF values, decreased with increasing C 60 content. The replacement of the successive incipient wetness impregnation by the simpler wet impregnation method provokes an increase in the photocatalytic activity of the samples with C 60 content equal to 9 and 12 wt% but it does not affect the photocatalytic activity of the sample with C 60 content equal to 6 wt%, which exhibits the maximum intrinsic activity. The influence of the deposition method and the C 60 loading on the photocatalytic performance of the C 60 /MCM-41 catalysts was rationalized on the basis of the different size of the supported C 60 crystallites.

The main objective of the present work was the evaluation of commercial ZSM-5 catalysts (diluted with a silica–alumina matrix) in the in situ upgrading of lignocellulosic biomass pyrolysis vapours and the validation of their bench-scale reactor performance in a pilot scale circulating fluidized bed (CFB) pyrolysis reactor. The ZSM-5 based catalysts were tested both fresh and at the equilibrium state, and were further promoted with cobalt (Co, 5% wt%) using conventional wet impregnation techniques. All the tested catalysts had a significant effect on product yields and bio-oil composition, both at bench-scale and pilot scale experiments, producing less bio-oil but of better quality. Incorporation of Co exhibited no additional effect on water or coke production induced by ZSM-5, compared to non-catalytic fast pyrolysis. On the other hand, Co addition significantly increased the formation of CO2 compared to the CO increase which was favored by the use of ZSM-5 alone. These changes in CO2/CO yields are indicative of the different decarbonylation/decarboxylation mechanism that applies for Co3O4 compared to ZSM-5 zeolite, due to the differences in their acidic properties (mainly type of acid sites). Co-promoted ZSM-5 catalysts simultaneously enhanced the production of aromatics and phenols with a more pronounced performance in the pilot-scale experiments resulting in the formation of a three phase bio-oil, rather than the usual two phase catalytic pyrolysis oil (aqueous and organic phases). The third phase produced is even lighter than the aqueous phase and consists mainly of aromatic hydrocarbons and phenolic compounds. Addition of Co in ZSM-5 is thus suggested to strongly enhance aromatization reactions that result in selectivity increase towards aromatics in the bio-oil produced. Possible routes of catalyst deactivation in the pilot plant's continuous operation process have been suggested and are related to pore blocking and masking of acid sites by formed coke (reversible deactivation), partial framework dealumination of the fresh zeolitic catalyst, and accumulative ash deposition on the catalyst that depends on the nature of biomass (content of ash).

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 natural resistance to enzymatic deconstruction exhibited by lignocellulosic materials has designated pretreatment as a key step in the biological conversion of biomass to ethanol. Hydrothermal pretreatment in pure water represents a challenging approach because it is a method with low operational costs and does not involve the use of organic solvents, difficult to handle chemicals, and "external" liquid or solid catalysts. In the present work, a systematic study has been performed to optimize the hydrothermal treatment of lignocellulosic biomass (beech wood) with the aim of maximizing the enzymatic digestibility of cellulose in the treated solids and obtaining a liquid side product that could also be utilized for the production of ethanol or valuable chemicals. Hydrothermal treatment experiments were conducted in a batch-mode, high-pressure reactor under autogeneous pressure at varying temperature (130-220 °C) and time (15-180 min) regimes, and at a liquid-to-solid ratio (LSR) of 15. The intensification of the process was expressed by the severity factor, log R(o). The major changes induced in the solid biomass were the dissolution/removal of hemicellulose to the process liquid and the partial removal and relocation of lignin on the external surface of biomass particles in the form of recondensed droplets. The above structural changes led to a 2.5-fold increase in surface area and total pore volume of the pretreated biomass solids. The enzymatic hydrolysis of cellulose to glucose increased from less than 7 wt% for the parent biomass to as high as 70 wt% for the treated solids. Maximum xylan recovery (60 wt%) in the hydrothermal process liquid was observed at about 80 wt% hemicellulose removal; this was accomplished by moderate treatment severities (log R(o)=3.8-4.1). At higher severities (log R(o)=4.7), xylose degradation products, mainly furfural and formic acid, were the predominant chemicals formed.

The development of novel catalytic processes for the upgrading of F–T waxes towards the production of clean transportation fuels as well as other valuable gaseous alkenes in the overall Biomass-to-Liquid (BTL) process would increase the sustainability of this growing technology significantly. Recent studies have shown that an alternative to the classical hydrocracking process for the upgrading of heavy waxy hydrocarbons could be the Fluid Catalytic Cracking (FCC) process, which aims mainly to the production of gasoline and gaseous (C3, C4) alkenes. In the present work, we have used “model” zeolitic and mesoporous aluminosilicate catalytic materials that exhibit different acidic and porosity characteristics, in order to elucidate the reaction mechanism of F–T wax cracking and to identify the effects of these catalyst properties on conversion and product yields. In addition, the effect of moderating the acidity of zeolites via steaming (in analogy to commercial FCC equilibrated catalysts) or by using alkaline metals that block the acid sites and the effect of using specific metals with dehydrogenation activity, have also been studied. It was shown that the Bronsted zeolitic acid sites, mainly the ones of higher strength, are responsible for the high cracking activity of the heavy paraffinic feed, while the Lewis acid sites contributed to a lesser extent. Furthermore, the different micropore structure/size of zeolites Y, ZSM-5 and Beta had a significant effect on conversion and product yields (C2–C4 gases, gasoline, LCO, coke), as well as on gasoline composition (PIONA) and octane number (RON/MON). The mildly acidic amorphous mesoporous aluminosilicates exhibited moderate conversion and different product yields and gasoline composition, compared to zeolites. The catalytic results of the present study were rationalized on the basis of well-established reaction mechanisms for n-paraffins cracking on zeolites, and can be utilized for the design of new cracking catalysts with tailored catalytic properties in F–T wax upgrading.

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.

A series of C 60 catalysts supported on MCM-41 was prepared in the context of developing a highly active heterogeneous catalytic system for the singlet oxygen-mediated oxidation of organic substrates. Successive incipient wetness impregnation was used for preparing 3, 6, 9 and 12 wt.% C 60 onto MCM-41 surface. N 2 adsorption, FT-IR, XRD, HR-TEM, DRS and TGA, have been used to characterize the photocatalysts. It was found that C 60 is highly dispersed (especially in the 3 and 6 wt.% C 60 catalysts) within the mesopores or on the external surface of MCM-41, as clusters or crystallites/aggregates of very small size and presumably in the form of atomic layers. The mesoporous structure and characteristics (surface area, mesopore size and volume) of MCM-41 remain almost intact upon deposition of C 60 on its surface. The photocatalytic activity was assessed in the photocatalytic oxidation of olefins via the singlet oxygen ene reaction by studying the photooxygenation of 2-methyl-2-heptene as a probe reaction. The catalytic tests were carried out at 0–5 °C in CH 3 CN under oxygen atmosphere and using a 300 W xenon lamp as the light source. To investigate further the potential applications of our catalysts we examined various types of photooxidations including the [4 + 2] or [2 + 2] cycloaddition, the heteroatom oxidation with sulfur or phosphorus containing compounds and the oxidation of phenols. The heterogeneous photocatalysts obtained were proved to be very active exhibiting higher substrate conversion, TON and TOF values, compared to those of the unsupported (solid) C 60 and the corresponding photocatalysts supported on silica or γ-alumina. This was mainly attributed to the better dispersion of C 60 on the MCM-41. The conversion achieved over the catalysts increases with the amount of the supported C 60 up to a value of 6 wt.% and then it decreases whereas the TON and TOF values decrease monotonically as the amount of the supported C 60 increases following the increase in the size of the supported C 60 crystallites/aggregates. Shadow effects were not observed under our experimental conditions.

BACKGROUND: Water-soluble reactive azo dyes are the most problematic dye house effluents, as they tend to pass through conventional treatment systems unaffected. The release of these compounds into the environment is undesirable and their removal becomes environmentally important. In this work, synthesis, characterization and sorption properties of hydotalcite-like compounds (Mg/Al and Mg/Fe), calcined and uncalcined, were investigated for the removal of the reactive azo dye Remazol Red 3BS. RESULTS: The calcined compounds present higher surface area than the uncalcined. The optimum pH for sorption was found to be 6. Thermodynamic analysis reveals that the sorption is spontaneous and endothermic. Equilibrium data were fitted by a Langmuir model, and kinetic data by a second-order model. The calcined Mg/Al compound showed the highest sorption capacity, at 0.125 mmol g−1. Regeneration of dye loaded derivative is achieved using the surfactant SDS. CONCLUSIONS: The prepared hydotalcite-like compounds and especially calcined Mg-Al exhibited significant adsorption capacity, kinetics, and regenerative ability. Its potential applicability as sorbent should be tested in a large-scale implementation. Copyright © 2011 Society of Chemical Industry

The main objective of the present work was the study of the effect of hydrothermal pretreatment of lignocellulosic biomass (beech wood) on the product yields and bio-oil composition produced from biomass flash pyrolysis as well as from the catalytic upgrading of the biomass pyrolysis vapours. The hydrothermal pretreatment of lignocellulosic biomass was performed at a severity factor (Ro) of 3.55 leading to ∼35 wt.% loss of solids, mainly due to solubilization and removal of hemicellulose. The production of sugars (mainly levoglucosan) was significantly increased by the use of the hydrothermally pretreated biomass instead of the untreated biomass in the non-catalytic flash pyrolysis experiments. On the other hand, the concentration of carboxylic acids, ketones and phenols was decreased in the bio-oil derived from the pretreated biomass. The catalysts tested in the upgrading of the biomass pyrolysis vapours were the strongly acidic zeolites H-ZSM-5 and silicalite (with very low number of acid sites) and the mildly acidic mesoporous aluminosilicate Al-MCM-41. The effect of catalysts on product yields and composition of bio-oil in the upgrading of pyrolysis vapours, was similar for both the pretreated and untreated biomass. The use of zeolite H-ZSM-5 decreased the total liquid yield (bio-oil) via decreasing the organic phase of bio-oil and increasing its water content, accompanied by increase of gases and moderate formation of coke on the catalyst. The zeolite silicalite and the Al-MCM-41 induced similar effects with those of H-ZSM-5 but to a less extent, except of the significantly higher coke that was deposited on Al-MCM-41. With regard to the composition of the bio-oil, all the catalysts and mostly the strongly acidic H-ZSM-5 zeolite reduced the oxygen content of the organic fraction, mainly by decreasing the concentration of acids, ketones and phenols in the untreated biomass pyrolysis oil or the concentration of sugars in the pretreated biomass pyrolysis oil. Aromatics and polycyclic aromatic hydrocarbons (PAHs) were significantly increased by the use of all catalysts, for both types of biomass feed. A substantial increase in the concentration of phenols was observed in the upgraded bio-oil derived by the hydrothermally pretreated biomass, using the less acidic silicalite and Al-MCM-41 catalysts.

In the present work we studied the N2O decomposition activity of nano-Ru/-Al2O3 catalysts prepared by in situ reduction with ethylene glycol (EG), in comparison to catalysts prepared via typical incipient wetness procedure. The metal content, particle size, dispersion and reduction characteristics of the supported Ru catalysts were studied by means of ICP-AES, XRD, HRTEM, TPR-H2 and TPD-H2. The EG reduction method favored the formation of almost spherical metallic Ru nanoparticles with the size of 1–3 nm (HRTEM) and dispersion of 70–35% (TPD-H2), at Ru loading levels of 0.4–1 wt.%. The impregnatedcalcined catalysts exhibited larger Ru nanoparticles (10–80 nm, TEM) with very low degree of dispersion (∼10%). The activity of the EG-prepared catalysts for the decomposition of N2O in oxygen rich feeds and in the absence or presence of NO, H2O, SO2, CO and CO2, was significantly higher compared to that of the impregnated-calcined samples and comparable with that of the most active catalytic systems reported in the literature for the treatment of combustion processes off-gases. The superior activity of the former catalysts, especially of the sample with low Ru content (0.4 wt.% Ru, 1–2 nm particle size), was attributed both to the high dispersion of Ru (70% dispersion), i.e., the high surface area of Ru metal available for reaction, and to the higher intrinsic activity and lower apparent activation energy of the very small supported Ru nanoparticles prepared by the EG reduction method. The EG-prepared nano-Ru/-Al2O3 catalysts could retain their high N2O decomposition activity (higher than 90%) for long time-on-stream by applying intermediate, short term regenerations in reducing atmosphere at moderate temperatures (i.e., 500

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 removal of Remazol Red 3BS (C.I. 239) dye by HMS ordered mesoporous silica, aminopropyl-modified HMS (HMS-NH2) and β-cyclodextrin-modified HMS (HMS-CD) materials was studied in the present work. The modified materials were functionalized in situ by adding the organic modifiers (3-aminopropyltriethoxysilane and a silylated derivative of MCT-β-CD) in the synthesis mixture and using dodecylamine as the mesopore structure directing agent. The successful incorporation of aminopropyl groups in HMS-NH2 and of cyclodextrin moieties in HMS-CD was verified by means of FT-IR spectroscopy, elemental analysis and N2 porosimetry. The HMS-CD material exhibited significantly higher adsorption capacity compared to that of the HMS-NH2 material, while the parent HMS mesoporous silica showed negligible adsorption capability. The maximum adsorption capacities obtained (at the optimum pH 2) on the basis of the Langmuir analysis were 0.28 mmol/g for HMS-CD and 0.14 mmol/g for HMS-NH2. It was shown that the HMS-CD sorbent can be effectively regenerated by the surfactant-enhanced regeneration method using SDS and that can be reused without significant loss of its adsorption capabilities.

The effect of the pretreatment (inert, oxidative, and reducing) of Ru/γ-Al 2 O 3 catalyst on its activity and stability in the decomposition of N 2 O in the absence or presence of O 2 , SO 2 , H 2 O and NO X was studied in the present work. Decomposition of pure N 2 O was slightly enhanced by the H 2 -pretreated catalyst (metallic Ru) compared to the O 2 - or He-pretreated ones, owing to a cyclic oxidation–reduction pathway of metallic Ru. The observed decrease of activity by O 2 or H 2 O addition was reversible compared to SO 2 which caused a strong, irreversible deactivation of the catalyst, irrespective of the type of pretreatment. This was attributed to the formation of stable sulphates, mainly those on RuO 2 surface, which could only be removed by regeneration under reducing (H 2 in He) atmosphere at temperatures of ca. 500 °C. Oxidative or inert regeneration required very high temperatures (i.e. >700 °C) in order to decompose these sulphates. A method of retaining N 2 O conversion activity very high (≥98%) for long reaction times is suggested and is based on frequent and short-time (ca. 10 min) regenerations of the catalyst under reducing atmosphere (ca. 5% H 2 in He). The effect of co-feeding various reducing agents, such as CO or C 3 H 6 , on the N 2 O conversion activity in the presence of O 2 , SO 2 , H 2 O and NO X is negligible, mainly because they are oxidized at relatively low temperatures in the O 2 -rich feeds used in this study.

The structural characteristics and the performance of vanadia catalysts (0.7–8 wt.% V) supported on mesoporous (MCM-41, HMS, MCF, SBA-15), microporous (silicalite) and non-porous (SiO 2 ) silicas in oxidative dehydrogenation of propane were investigated. The structure of vanadia species, the redox and the acidic properties of the catalysts were studied using in situ Raman spectroscopy, TPD- NH 3 and H 2 -TPR. The only vanadia species detected on the surface of HMS and MCM-41 for V loadings up to 8 wt.% were isolated monovanadates indicating high vanadia dispersion. Additional bands ascribed to V 2 O 5 nanoparticles were evidenced in the case of SBA-15 and MCF supported catalysts while these bands were the only ones identified on the surface of the catalysts supported on silicalite and non-porous silica. The catalysts supported on mesoporous HMS and MCM-41 materials showed the best performance achieving high propane conversions (35–40%) with relatively high propene selectivities (35–47%). Lower activity due to the lower degree of vanadia dispersion, caused by the partial destruction of the pore structure was observed for the SBA-15 and MCF supported catalysts. The degree of dispersion of the V species on the catalyst surface and not the pore size and structure of the mesoporous support or the acidity/reducibility characteristics mainly determine the catalytic activity towards propene production. In addition, it was shown that the pore structure and size of the mesoporous supports did not have any significant effect in the turnover rates (TOF values) of propane conversion (and propene formation at low propane conversion, below ca. 10%). However, the highest propene yield (up to 19%) and stable catalytic behavior was attained for catalysts supported on HMS mesoporous silica, and especially for those combining framework mesoporosity and textural porosity (voids between primary nanoparticles).

In the present study two synthetic mesoporous carbons, a highly ordered CMK-3 sample with hexagonal structure and a disordered mesoporous carbon (denoted DMC) were investigated for the sorption of Remazol Red 3BS (C.I. 239) dye in comparison to three commercial activated carbons and a HMS mesoporous silica with a wormhole pore structure. The structural, porosity and surface characteristics of the materials were evaluated using XRD, TEM, N 2 porosimetry, FT-IR spectroscopy and zeta-potential measurements. Optimal dye sorption occurred at pH ∼2. Equilibrium sorption data followed the Langmuir model and showed that the two synthetic mesoporous carbons exhibit higher sorption capacities ( q max ∼ 500–580 mg/g at 25 °C) in comparison to the commercial activated carbons which possessed either microporous (Takeda 5A and Calgon carbon) or combined micro-/mesoporous (Norit SAE-2) structures and to the HMS mesoporous silica. Thermodynamic parameters as the change in free energy, enthalpy, and entropy of sorption were also estimated. Kinetic studies were carried out and showed a rapid sorption of dye in the first ca. 30 min while equilibrium was reached after ca. 3 h. The sorption kinetics of dye was best described by a second-order kinetic model. A surfactant enhanced carbon regeneration (SECR) technique was used to regenerate the dye-loaded carbon sorbents.

Well defined layered-double hydroxides (LDH: Mg3Al–NO3/CO3, Mg3Ga–NO3/CO3, Zn2Al–NO3/CO3 and Zn2Ga–NO3/CO3) were prepared using typical procedures starting from Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, Al(NO3)3·9H2O and Ga(NO3)3·H2O. Rh-TPPTS complex was prepared by simple complexation of a Rh precursor [Rh(cod)Cl]2 and TPPTS (3,3′,3″-phosphanetriyl benzenesulfonic acid) in water. The heterogeneization of the Rh-TPPTS complex was performed by anionic exchange between Rh-complex and LDH supports. The catalysts’ structures and the chemical composition were confirmed by chemical analysis, XRD patterns, XP, FTIR and DRIFT spectroscopy. LDH-substituted Rh-TPPTS heterogeneous catalysts showed good catalytic activity in the 1,4-addition of arylboronic acid to 2-cyclohexen-1-one.

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 (

In the present study, two mesoporous aluminosilicate Al-MCM-41 materials (Si/Al = 30 or 50) were tested as catalysts for the in situ upgrading of biomass pyrolysis vapours in comparison to a siliceous MCM-41 sample and to non-catalytic biomass pyrolysis. The product yields and the quality of the produced bio-oil were significantly affected by the use of all MCM-41 catalytic materials. This behavior was mainly attributed to the combination of the large surface area and tubular mesopores (pore diameter ∼2–3 nm) of MCM-41 materials, with their mild acidity that leads to the desired environment for controlled conversion of the high molecular weight lignocellulosic molecules. The major improvement in the quality of bio-oil with the use of Al-MCM-41 catalytic materials was the increase of phenols concentration (useful chemicals) and the reduction of corrosive acids (undesirable in fuel bio-oils). Higher Si/Al ratios (i.e. lower Al content and lower number of acid sites) of the Al-MCM-41 samples enhanced the production of the organic phase of the bio-oil, while lower Si/Al ratios favoured the conversion of the hydrocarbons of the organic phase towards gases and coke. Moderate steaming of the Al-MCM-41 samples (at 550 and 750 ◦ C, 20% steam partial pressure) decreased their surface area and number of acid sites by 40–60% depending on the Si/Al ratio of the samples and the steaming temperature. However, the steamed samples were still active in the in situ upgrading of biomass pyrolysis vapours, resulting in different product yields and bio-oil composition compared to the parent calcined samples, mainly after higher-temperature steaming. © 2007 Elsevier B.V. All rights reserved.

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.

Cu-exchanged ZSM-5 zeolites finely coated with CeO2 nanoparticles were tested in this work as catalysts for the selective catalytic reduction (SCR) of NO with C3H6. The CeO2 coated Cu/ZSM-5 shows lower maximum NO conversion activity compared to the non-coated Cu/ZSM-5 catalyst at relatively high temperatures (ca. 450 8C) but the former catalyst is significantly more active at lower temperatures (ca. 350 8C), especially at lower space velocities, both under dry and wet feed conditions. Under simultaneous addition of both SO2 and water in the feed, the beneficial effect of the CeO2 coating at lower reaction temperatures was retained only at low space velocities. The same Cu/ZSM-5 based samples were evaluated as fluid catalytic cracking (FCC) catalytic additives for the in situ reduction of NOx formed during regeneration of the coked FCC catalyst. The amounts of NO and CO emitted during regeneration of the spent FCC catalyst at 700 8C in the presence of Cu/ZSM-5 based additives were compared with those obtained when a commercial CO promoter was used in the FCC catalyst inventory. All Cu/ZSM-5 additives exhibited significant NO reduction ability, which was further enhanced by increasing the Cu loading or the amount of additive in the FCC catalyst. The CeO2coated sample reached the highest deNOx performance (up to 78% NO reduction); however, all additives presented insufficient activity for CO oxidation. Simultaneous NO reduction and CO oxidation was achieved only when the CeO2-Cu/ZSM-5 additive was promoted with Rh or when the non-promoted additives were combined with a commercial CO promoter. Preliminary studies suggested that the Rh-promoted CeO2-Cu/ZSM-5 additives can be very effective for both NO reduction by CO and CO oxidation at certain O2 concentrations, such as in the O2-deficient zones of the FCC regenerator. Further studies are in progress in order to elucidate the reaction mechanism and optimize the additive’s formulation. # 2007 Elsevier B.V. All rights reserved.

The thermal degradation mechanism of the aliphatic biodegradable polyester poly(propylene succinate) (PPSu) and the effect of the polymerisation catalyst (tetrabutyl titanate, TBT) were studied using pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) and TGA analysis. It is found from mass ions detection, that the decomposition takes place, mainly, through β-hydrogen bond scission and secondarily by α-hydrogen bond scission. At low pyrolysis temperatures (360 and 385 °C) gases as well as succinic anhydride, succinic acid and propanoic acid are mainly produced while allyl and diallyl succinates are formed in smaller quantities. At high temperatures (450 °C) the behaviour is inverted. Using the isoconversional methods of Ozawa and Friedman it is founded that PPSu degrades by two consecutive mechanisms. According to this analysis the first mechanism that takes place at low temperatures is autocatalysis with an activation energy of about E = 110–120 kJ/mol. The second mechanism is a first-order reaction with E of 220 kJ/mol, and corresponds to the extended β- and α-hydrogen bond scissions. These activation energies are slightly dependent on the catalyst amount and are shifted towards lower values with an increase of TBT content from 3 × 10 −4 to 3 × 10 −1 mol TBT/mol succinic acid (SA).

The in situ upgrading of biomass pyrolysis vapors with two mesoporous aluminosilicate materials (MSU-S BEA ) assembled from zeolite Beta (BEA) seeds was tested in the present study, in comparison to conventional Al-MCM-41 and to non-catalytic biomass pyrolysis. The first sample (MSU-S/H BEA ) exhibited an hexagonal mesopore structure while the second one (MSU-S/W BEA ) possessed a wormhole-like mesopore structure with high textural porosity. The catalytic tests were performed on a fixed-bed reactor, the reaction temperature was 500 °C and the feed was a lignocellulosic biomass based on beech wood. The use of the MSU-S catalytic materials led to significantly lower organic phase in the produced bio-oil and also to higher coke and char yields, compared to non-catalytic pyrolysis and to the use of Al-MCM-41 which induced a small increase in the yields of liquid oil and coke. Pyrolysis gases were also affected by all mesoporous catalysts. The MSU-S catalytic materials were very selective towards polycyclic aromatic hydrocarbons (PAHs) and heavy fractions, while they produced negligible amounts of acids, alcohols and carbonyls, and very few phenols. The MSU-S materials appeared to possess stronger acid sites than Al-MCM-41, resulting in enhanced yields of aromatics, PAHs and coke, as well as propylene in the pyrolysis gases.