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Abstract A mathematical model was developed based on data obtained on Fischer-Tropsch (FT) laboratory scale unit operated in steady state, belonging to BIOENERGY 2020+ GmbH, Austria to demonstrate alpha-parameter dependence on carbon number. The lab-scale unit processed the synthesis gas, obtained by the gasification of biomass (woodchips), to produce liquid fuels for transportation applications. The FT reaction took place in a slurry reactor filled with dispersed cobalt-based catalyst. The products were then separated by partial condensation depending on their boiling points. The final output of the FT laboratory scale unit comprised three product streams – wax, diesel and naphtha. The reaction and separation of products were simulated in Aspen Plus software. The mathematical model used kinetic description based on power-law rate equations. The modeled product selectivity was controlled using an alpha-parameter of the Anderson-Schulz-Flory distribution. Because of the significant deviation of products spectrum from typical Anderson-Schulz-Flory distribution, a modified description of reaction selectivity was developed. The description introduces variable alpha-parameter, dependent on number of carbon atoms in the reacting molecule. The mathematical model developed using MATLAB software considered the production of aliphatic paraffins having a number of carbon atoms from C1 to C60. The mathematical model of simulated lab-scale unit comprised an ideally mixed reactor RCSTR and three FLASH2 separators for the separation of desired products. The results from mathematical model were validated by a comparison with experimental results from FT lab-scale unit. The modified polynomial dependency of alpha-parameter on carbon number showed significantly better description of composition and amounts of FT products, especially for wax stream where the description using constant alpha led to enormous deviations. Such better prediction of composition and amounts of acquired products is important for evaluating efficiency of further upgrading the FT products to liquid fuel. [ABSTRACT FROM AUTHOR]

Despite rigorous models of the steam cracking processes being available for simulation of naphtha cracking, the simulation is often carried out using limited characterization of such a feedstock due to unavailability of detailed composition at the time when the simulation is required. A method was developed for generation of substitute naphtha composition meeting specified properties. Sets of alternative compositions were generated, matching the density, distillation curve, and optionally PIONA of real naphtha feedstocks. Its cracking product yields were calculated using a validated cracking model. Simulated product yields were evaluated in terms of result variability and deviation from the experimental data, depending on the level of available feedstock characterization. [ABSTRACT FROM AUTHOR]

Mathematical model of n-heptane pyrolysis under thermal cracking and steam cracking conditions was developed. The objective was achieving good generalization by combining two different data sources for model identification. The data sources included experimental pyrolysis data for many structurally different hydrocarbons measured at reference conditions as well as the data for n-heptane measured in different reactors at different reaction conditions. The model was developed using the automated reaction network generation. The generated network included hydrogen abstraction, β-scission, radical isomerization and recombination reactions, the kinetic parameters of which were expressed as functions of 26 group contribution factors. Molecular reactions and radical additions were substituted by 12 formal shortcut molecular reactions. The initial values of kinetic parameters and group contribution factors were adopted from previous study, where they were obtained by regression based on the experimental data involving wide range of linear, branched and/or cyclic hydrocarbons. More experimental data on n-heptane pyrolysis measured under different conditions, including the use of two different reactors, were added to the data set used for the parameter optimization. The model simulations showed good agreement with the experimental data even for the validation samples. Thus, the proposed approach proved the ability to produce models achieving good generalization. [ABSTRACT FROM AUTHOR]

Abstract: Pyrolysis experiments aimed at measuring product yields and conversion of various hydrocarbons were carried out in a micro-pyrolysis laboratory reactor. Standard pyrolysis conditions were used for all samples—810°C, 400kPa and 0.2–0.4s residence time in the reaction zone. Analysis of products was performed by on-line GC/FID/TCD. All pyrolysis products from hydrogen to pyrolysis oil were detected either individually or by fractions. Detailed compositions of the pyrolysis products of 56 hydrocarbons were obtained and are included completely in the article. The study involved hydrocarbons, which represent the wide structural variability, including linear, branched, cyclic, aromatic and unsaturated. Measured data were used to identify important relationships between structural parameters and product yields. Trends of important product yields, depending on the carbon number, molecule saturation, substitution, ring presence and substitution or a substituent size are presented. [Copyright &y& Elsevier]

Abstract: This contribution focuses on the hydrogenation and hydrodeoxygenation of aldehydes (benzaldehyde, 2-phenylpropionaldehyde, 3-phenylpropionaldehyde, cinnamaldehyde, 4-isopropylbenzaldehyde, heptanal) on supported palladium catalysts, namely zeolites and active carbon. The effects of the substrate structure, solvent, type of support and its acidity, reaction temperature and pressure on activity and selectivity of Pd catalysts were investigated in detail. Catalytic hydrodeoxygenation of aldehydes was carried out in a liquid phase in an autoclave in the temperature range from 30 to 130°C and at pressure ranging from 1 to 6MPa. Hydrogenation reactions performed in non-polar hexane proceeded with a significantly higher rate than in a polar methanol. The presence of isopropyl substituent in 4-isopropylbenzaldehyde increased both the reaction rate as well as the selectivity to hydrodeoxygenation. Hydrodeoxygenation of 2-phenylpropionaldehyde, 3-phenylpropionaldehyde, cinnamaldehyde, and heptanal did not proceed, the main products were dialkylethers, which evidences the importance of the direct attachment of Co the benzene ring. The presence of hydrogenation—hydrogenolytic mechanism as well as the direct hydrogenolysis of C the transformation of benzaldehyde was verified. [Copyright &y& Elsevier]

Abstract: Catalytic hydrogenation and hydrogenolysis of benzophenone in a liquid phase at the reaction temperature of 130°C and pressure 6MPa on supported palladium catalysts were investigated. A number of different supports including active carbon, alumina, Beta and ZSM-5 zeolites with different Si/Al ratios and MCM-41 was tested. The effects of solvent, support and its acidity on the course of benzophenone transformations were studied. Catalysts using acid zeolite or active carbon as supports were found very effective in hydrodeoxygenation reaction. Based on the kinetic model applied, possibilities of conversion of benzophenone to diphenylmethane were discussed. The model confirmed that both the possible mechanisms (the hydrogenation–hydrogenolytic and the direct hydrogenolysis of the C benzophenone) took place in a significant manner. [Copyright &y& Elsevier]

Meloxicam (MLX) is a poorly soluble drug exhibiting strong hydrophobicity. This combination of properties makes dissolution enhancement by particle size reduction ineffective; therefore, combined formulation approaches are required. Various approaches were investigated in this study, including milling, solid dispersions, and self-emulsified lipid formulations. Whereas milling studies of MLX and its co-milling with various polymers have been reported in recent literature, this study is focused on investigating the dissolution kinetics of particulate formulations obtained by co-milling MLX with sodium lauryl sulfate (SLS) in a planetary ball mill with 5–25 wt.% SLS content. The effects of milling time and milling ball size were also investigated. No significant reduction in drug crystallinity was observed under the investigated milling conditions according to XRD data. For the dissolution study, we used an open-loop USP4 dissolution apparatus, and recorded dissolution profiles were fitted according to the Weibull model. The Weibull parameters and a novel criterion—surface utilization factor—were used to evaluate and discuss the drug release from the perspective of drug particle surface changes throughout the dissolution process. The most effective co-milling results were achieved using smaller balls (2 mm), with a co-milling time of up to 15 min SLS content of up to 15 wt.% to increase the dissolution rate by approximately 100 times relative to the physical mixture reference. The results suggest that for hydrophobic drugs, particle performance during dissolution is very sensitive to surface properties and not only to particle size. Co-milling with SLS prepares the surface for faster drug release than that achieved with direct mixing. [ABSTRACT FROM AUTHOR]

• Centrifuging/image analysis was developed for particle-surface adhesion study • The effect of surface heterogeneity on particle-surface adhesion was investigated • The distribution of adhesion strength mapped particle behaviour on rugged surfaces • Adhesion strength distribution can determine critical surface coverage An interactive mixture, i.e. a blend of larger carrier particles with drug particles adhered on their surfaces, is often used in pharmaceutical formulations for promoting powder flow, improving blend uniformity, reducing the segregation risk during manipulation, and improving the solubility of poorly water-soluble drug. Obtaining uniform and stable interactive mixtures require adhesion forces between fine drug and coarse carrier particles to exceed the cohesion forces between drug particles. This work was aimed at developing the methodology measuring the particle adhesion by centrifugation combined with the optical microscopy to predict interactions between components in the mixtures. In the pilot phase, excipient particles were chosen as model substances, both for the preparation of the carrier surface and deposited particles. As expected, our developed methodology was able to map the behaviour of particles on the rugged surfaces and provide the adhesion strength distribution used for comparing different material adhesion. It can also provide a measure of interactive unit stability when the mixture undergoes process treatment characterised by certain mechanical stress. [ABSTRACT FROM AUTHOR]

Many newly developed active pharmaceutical ingredients (APIs) have very low solubility in aqueous media. The preparation of solid dispersions (SDs) is one way of avoiding this problem. However, compound wettability and thus solubility are influenced by surface energy. In this study, we used inverse gas chromatography (IGC) to evaluate the surface energies of prepared SDs, and compared them with those obtained for physical mixtures (PMs). SDs containing different weight ratios of crystalline acetaminophen and one of three polymers (Kollidon ® 12 PF, Kollidon ® VA 64 or Soluplus ® ) were prepared by the melt-quenching of corresponding PMs. In all cases, as the polymer content increased, the surface energy decreased significantly. For the SDs and PMs containing Soluplus ® , this decrease in surface energy showed the same non-linear trend. In the cases of Kollidon ® 12 PF and Kollidon ® VA 64, the trend was linear, with the SDs showing a steeper decrease in surface energy than the corresponding PMs. Typically, such decreases are ascribed to the dissolution of the crystalline structure of an API. Our results suggest that in the case of the Kollidons, the steeper decrease is caused by another mechanism, namely, strong API-Kollidon interaction leading to the less wettable surface of SDs. [ABSTRACT FROM AUTHOR]

Unsaturated C4 hydrocarbons are abundant in various petrochemical streams. They can be considered as a potential feedstock for the steam-cracking process, where they must be co-processed with C6 and higher (C6+) hydrocarbons of primary naphtha fractions. Co-pyrolysis experiments aiming at the comparison of different C4 hydrocarbon performances were carried out in a laboratory micro-pyrolysis reactor under standardized conditions: 820 °C, 400 kPa, and 0.2 s residence time in the reaction zone. C4 hydrocarbons were co-pyrolyzed with different co-pyrolysis partners containing longer hydrocarbon chain to study the influence of the co-pyrolysis partner structure on the behavior of C4 hydrocarbons. The yields of the pyrolysis products and the conversion of C4 hydrocarbons were used as the performance factors. A regression model was developed and used as a valuable tool for quantifying the inhibition or acceleration effect of co-pyrolysis on the conversion of co-pyrolyzed hydrocarbons. It was found that the performance of different C4 hydrocarbons in co-pyrolysis is substantially different from the separate pyrolysis of the individual components. [ABSTRACT FROM AUTHOR]

• Mixing/co-milling with chitosan increased dissolution rate of meloxicam greatly. • The observed effect was facilitated by meloxicam-chitosan interactive mixtures. • Specific surface area and total amount of the mixture were controlling parameters. • Work of adhesion/cohesion ratio of 0.9 indicated stability of interactive mixtures. • No marked drug amorphization or other crystalline structure changes were detected. To enhance dissolution rate of meloxicam (MX), a poorly soluble model drug, a natural polysaccharide excipient chitosan (CH) is employed in this work as a carrier to prepare binary interactive mixtures by either mixing or co-milling techniques. The MX-CH mixtures of three different drug loads were characterized for morphological, granulometric, and thermal properties as well as drug crystallinity. The relative dissolution rate of MX was determined in phosphate buffer of pH 6.8 using the USP-4 apparatus; a significant increase in MX dissolution rate was observed for both mixed and co-milled mixtures comparing to the raw drug. Higher dissolution rate of MX was evidently connected to surface activation by mixing or milling, which was pronounced by the higher specific surface energy as detected by inverse gas chromatography. In addition to the particle size reduction, the carrier effect of the CH was confirmed for co-milling by linear regression between the MX maximum relative dissolution rate and the total surface area of the mixture (R2 = 0.863). No MX amorphization or crystalline structure change were detected. The work of adhesion/cohesion ratio of 0.9 supports the existence of preferential adherence of MX to the coarse particles of CH to form stable interactive mixtures. [Display omitted] [ABSTRACT FROM AUTHOR]

In the pharmaceutical industry, silicates are commonly used excipients with different application possibilities. They are especially utilized as glidants in low concentrations, but they can be used in high concentrations as porous carriers and coating materials in oral solid drug delivery systems. The desirable formulations of such systems must exhibit good powder flow but also good compactibility, which brings opposing requirements on inter-particle interactions. Since magnesium aluminometasilicates (MAS) are known for their interesting flow behavior reported as "negative cohesivity" yet they can be used as binders for tablet compression, the objective of this experimental study was to investigate their particle interactions within a broad range of mechanical stress from several kPa to hundreds of MPa. Magnesium aluminometasilicate (Neusilin® US2 and Neusilin® S2)-microcrystalline cellulose (Avicel® PH102) physical powder mixtures with varying silicate concentrations were prepared and examined during their exposure to different pressures using powder rheology and compaction analysis. The results revealed that MAS particles retain their repulsive character and small contact surface area under normal conditions. If threshold pressure is applied, the destruction of MAS particles and formation of new surfaces leading to particle interactions are observed. The ability of MAS particles to form interactions intensifies with increasing pressure and their amount in a mixture. This "function switching" makes MAS suitable for use as multifunctional excipients since they can act as a glidant or a binder depending on the applied pressure. [ABSTRACT FROM AUTHOR]

A heavy side‐product of the Fischer‐Tropsch (FT) process called waxes are potential renewable feedstocks for the steam‐cracking process. Samples of FT wax and distillation cuts thereof were investigated using laboratory pyrolysis in order to compare their pyrolysis performance with traditional steam‐cracking feedstocks, i.e., primary naphtha and hydrocracking products. At 815 °C, waxes provided significantly higher yields of the desired products ethylene and propylene, and lower yields of oil compared to traditional feedstocks. The yields of waxes blended in traditional feedstocks and the sensitivity of cracking product yields to temperature and residence time were also examined experimentally. [ABSTRACT FROM AUTHOR]

Abstract Surface energy is extensively adopted to predict the surface properties of materials nowadays. Our study was aimed at utilizing the surface free energy measured by inverse gas chromatography to determine inter-particle interactions and to describe the overall behaviour of mixtures. The model drugs of different solubility (tadalafil, levocetirizine dihydrochloride, vardenafil hydrochloride, and amlodipine besylate) and two grades of polyvinylpyrrolidone (Kollidon® 12 PF, Kollidon® VA 64) were mixed in various ratios. Investigated components were characterized using inverse gas chromatography, particle size distribution and specific surface area. We also determined the work of adhesion and cohesion between the components in the binary mixtures. Due to the formation of levocetirizine agglomerates, the effect of mixing time on both components of the surface free energy was also studied for the binary mixture with Kollidon® VA 64. The results based on the energy analysis, especially positive or negative excess surface energies in theoretical and real binary mixtures, indicate that we can predict whether the components can form the desired ordered (interactive) mixture. For this reason, we have proposed, to the best of our knowledge, different approach to predict the interactions between components and their behaviour in the binary mixtures using inverse gas chromatography in terms of the energy balance based only on the surface parameters (surface free energy, dispersive and specific surface energy). Therefore, the approach of energy balance is an innovative and comparatively simple tool for analysis and identification of interactions between components in particulate systems, which can also predict the quality of the mixing. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The mechanism of colloidal silica action to improve flow properties of pharmaceutical powders is known to be based on inter-particle force disruption by silica particles adhered to the particle surface. In the present article, the kinetic aspects of this action are investigated, focusing on non-spherical particles of different size. Blends comprising microcrystalline cellulose or calcium hydrogen phosphate dihydrate and colloidal silica were examined using powder rheometer. The blends were formulated to represent effects of particle size, surface texture, colloidal silica loading, and mixing time. Pre-conditioning, shear testing, compressibility, and flow energy measurements were used to monitor flow properties. Components and blends were analyzed using particle size analysis and scanning electron microscopy (SEM), using energy dispersive spectroscopy (EDS) and back-scattered electron (BSE) detection to determine surface particle arrangement. All studied parameters were found to have substantial effects on flow properties of powder blends. Those effects were explained by identifying key steps of colloidal silica action, which were found to proceed at substantially different rates, causing the flow properties change over time being dependent on the blend formulation and the component properties. [ABSTRACT FROM AUTHOR]

In pharmaceutical industry, the use of lubricants is mostly based on historical experiences or trial and error methods even these days. It may be demanding in terms of the material consumption and may result in sub-optimal drug composition. Powder rheology enables more accurate monitoring of the flow properties and because the measurements need only a small sample it is perfectly suitable for the rare or expensive substances. In this work, rheological properties of four common excipients (pregelatinized maize starch, microcrystalline cellulose, croscarmellose sodium and magnesium stearate) were studied by the FT4 Powder Rheometer, which was used for measuring the compressibility index by a piston and flow properties of the powders by a rotational shear cell. After an initial set of measurements, two excipients (pregelatinized maize starch and microcrystalline cellulose) were chosen and mixed, in varying amounts, with anhydrous colloidal silicon dioxide (Aerosil 200) used as a glidant. The bulk (conditioned and compressed densities, compressibility index), dynamic (basic flowability energy) and shear (friction coefficient, flow factor) properties were determined to find an optimum ratio of the glidant. Simultaneously, the particle size data were obtained using a low-angle laser light scattering (LALLS) system and scanning electron microscopy was performed in order to examine the relationship between the rheological properties and the inner structure of the materials. The optimum of flowability for the mixture composition was found, to correspond to empirical findings known from general literature. In addition the mechanism of colloidal silicone dioxide action to improve flowability was suggested and the hypothesis was confirmed by independent test. New findings represent a progress towards future application of determining the optimum concentration of glidant from the basic characteristics of the powder in the pharmaceutical research and development. [ABSTRACT FROM AUTHOR]

[Display omitted] • The cohesion was related to the specific surface area. • The dispersive component of the surface energy (van der Waals forces) prevailed. • Surface heterogeneity results confirmed preferable drug-excipient interactions. • Alginic acid showed a better carrier effect than calcium alginate. • The W adh / W coh ratio near to unity confirmed stability of interactive mixtures. [ABSTRACT FROM AUTHOR]

[Display omitted] • The cohesion was related to the specific surface area. • The dispersive component of the surface energy (van der Waals forces) prevailed. • Surface heterogeneity results confirmed preferable drug-excipient interactions. • Alginic acid showed a better carrier effect than calcium alginate. • The W adh / W coh ratio near to unity confirmed stability of interactive mixtures. [ABSTRACT FROM AUTHOR]

[Display omitted] The aim of this study was to investigate the molecular structures of tadalafil solid dispersions prepared by different techniques and further to relate them to surface free energy information indicating the final amorphousness of the product. Thus, we tried to complement the existing knowledge of solid dispersion formation. Poorly water-soluble tadalafil was combined with different polymers, i.e. Kollidon® 12 PF, Kollidon® VA 64 and Soluplus®, to form model systems. To assess the extent of drug-polymer miscibility, we studied model solid dispersion surface energy using inverse gas chromatography and phase micro-structure using confocal Raman microscopy. The selection of the preparation method was found to play a crucial role in the molecular arrangement of the incorporated drug and the polymer in resulting solid dispersion. Our results showed that a lower surface free energy indicated the formation of a more homogeneous solid dispersion. Conversely, a higher surface free energy corresponded to the heterogeneous systems containing tadalafil amorphous clusters that were captured by Raman mapping. Thus, we successfully introduced a novel evaluation approach of the drug molecular arrangement in solid dispersions that is especially useful for examining the miscibility of the components when the conventional characterizing techniques are inconclusive or yield variable results. [ABSTRACT FROM AUTHOR]

Abstract: The search for various solid forms of an active pharmaceutical ingredient (API) is an important step in drug development. Our aim was to prepare co-crystals of trospium chloride, an anticholinergic drug used for the treatment of incontinence, and to investigate if they have advantageous properties for drug formulation. Phase identification was done by powder X-ray diffraction and single-crystal X-ray diffraction. The chemical composition was verified by solution NMR and the dissolution rate of the prepared phases was studied by IDR (intrinsic dissolution rate). For further analysis of phase stability and transitions, combined thermal analysis and temperature-resolved X-ray powder diffraction were used. Urea was selected as a co-crystallization partner. Trospium chloride urea (1:1) co-crystal was prepared by a solvent evaporation. From single-crystal data, the co-crystal structure was solved in a space group P21 /c and compared to previously published structures of trospium chloride. Intrinsic dissolution rate revealed that the co-crystal dissolves 32% faster than pure API. However, its low thermal and pressure stability makes it a challenging choice for the final drug formulation. [Copyright &y& Elsevier]

Abstract: Petroleum fractions are typical complex mixtures. For the simulation of petroleum refining processes they are characterized by substitute mixtures. In this contribution the traditional approach based on pseudocomponents is compared with the newer approach utilizing a Substitute Mixtures of Real Components (SMRCs). The main advantage of SMRC approach is the direct availability of physical property data and the knowledge of the chemical character. The most important task in many applications is to characterize the C7+ fraction. It is shown, how it can be characterized by a small number of real components. The examples used for comparison comprise separation processes and also the pyrolysis modeling, where the known chemical character of a SMRC is crucial for feeding an artificial neural network model. [Copyright &y& Elsevier]

Abstract: Processing of atmospheric gas oils (AGOs) in the petroleum industry by pyrolysis is an important task. In order to improve control of production and to predict the pyrolysis product yields, it is necessary to use novel approaches. The combination of selected analytical as well as modelling methods described in this contribution seems to be very promising and usable also for other types of pyrolysis feedstocks. Employment of an artificial neural network (ANN) model as the prediction tool is the crucial point. The main problem is the treatment of complex mixtures. While analytical methods used here give the picture of global characteristics and group composition, the method used to characterise the complex mixture by a well-defined substitute mixture of real components provides the input information for the ANN model. Unfortunately, the required measured data, typically distillation and other curves, are often incomplete and it is impossible to obtain directly the ‘phase portraits’ needed to establish the substitute mixture. Possibilities of how to solve this particular problem utilising other information about the mixture, e.g. bulk properties, are shown and applied to concrete AGO feedstocks with satisfactory results. [Copyright &y& Elsevier]

[Display omitted] • Co-milling of drugs having different glass forming ability with suitable co-formers. • Characterization of dissolution properties of physical and co-milled mixtures. • Solid state characterization of prepared mixtures. • The proper choice of excipient is the key to maximizing the dissolution rates. • The glass forming ability of the drug affects the properties of composite particles. Co-milling of a drug with a co-former is an efficient technique to improve the solubility of drugs. Besides the particle size reduction, the co-milling process induces a structural disorder and the creation of amorphous regions. The extent of drug solubility enhancement is dependent on the proper choice of co-milling co-former. The aim of this work was to compare the effects of different co-formers (meglumine and polyvinylpyrrolidone) on the dissolution rates of glass forming (indomethacin) and non-glass forming (mefenamic acid) model drugs. A positive impact of the co-milling on the dissolution behavior was observed in all co-milled mixtures, even if no substantial amorphization was observed. While meglumine exhibited pronounced effects on the dissolution rate of both drugs, the slightest enhancement was observed in mixtures with polyvinylpyrrolidone. The evaluation of specific release rate revealed the surface activation of drug particle is responsible for improving the dissolution rate of both drug types, but for the glass former, this surface activation could be persistent while maintaining a high dissolution rate even until a high fraction of drug is released. Our results, therefore, indicate that adequate co-former choice and consideration of drug glass forming ability are important for a successful co-milling approach to poorly water-soluble drugs. [ABSTRACT FROM AUTHOR]

• Dependence of products yields on the blending ratio is non-linear. • Co-pyrolysis effects are responsible for this behavior. • Light naphtha donates active radicals to improve heavy naphtha cracking. Naphtha feedstock used for the steam-cracking process is typically blended from several hydrocarbon source streams of composition varying in a broad range. This study aims at evaluation of the potential yield improvement, which could be obtained by separate steam-cracking of light and heavy sub-streams using tailored process parameters for each of the sub-streams. Laboratory pyrolysis reactor was used for both separate and blend processing of the naphtha feedstocks in the temperature range of 760–810 C, and different blending ratios. At maximum temperature, pyrolysis of light naphtha provides ethylene yield 24.1 wt. %, while only 13.6 wt. % of ethylene was obtained from heavy naphtha. Both, ethylene and propylene yield express decreasing trend with increasing content of heavy naphtha in blended feedstock. Obtained results suggest possibility of mutual effects between components resulting in non-linear dependence of products yields on the blending ratio, therefore a principle of additivity cannot be assumed. A potential for improvement of ethylene yield by 1.1 wt. % is shown on example of processing scenario. [ABSTRACT FROM AUTHOR]

The aims of this study were to investigate how the release of tadalafil is influenced by two grades of polyvinylpyrrolidone (Kollidon® 12 PF and Kollidon® VA 64) and various methods of preparing solid dispersions (solvent evaporation, spray drying and hot-melt extrusion). Tadalafil is poorly water-soluble and its high melting point makes it very sensitive to the solid dispersion preparation method. Therefore, the objectives were to make a comparative evaluation among different solid dispersions and to assess the effect of the physicochemical nature of solid dispersions on the drug release profile with respect to the erosion-diffusion mechanism. The solid dispersions were evaluated for dissolution profiles, XRD, SEM, FT-IR, DSC, and solubility or stability studies. It was found that tadalafil release was influenced by polymer molecular weight. Therefore, solid dispersions containing Kollidon® 12 PF showed a faster dissolution rate compared to Kollidon® VA 64. Tadalafil was released from solid dispersions containing Kollidon® 12 PF because of the combination of erosion and diffusion mechanisms. The diffusion mechanisms were predominant in the initial phase of the experiment and the slow erosion was dissolution-controlling at the second stage of the dissolution. On the contrary, the tadalafil release rate from solid dispersions containing Kollidon® VA 64 was controlled solely by the erosion mechanism. [ABSTRACT FROM AUTHOR]