Thermo-catalytic pyrolysis of polystyrene in batch and semi-batch reactors: A comparative study

Thermo-catalytic pyrolysis is considered as a promising process for the chemical recycling of waste polymeric materials aiming at converting them into their original monomers or other valuable chemicals. In this regard, process parameters and reactor type can play important roles for an enhanced recovery of the desired products. Polystyrene (PS) wastes are excellent feedstocks for the chemical recycling owing to the capability of PS to be fully recycled. In this respect, the present work deals with the thermo-catalytic pyrolysis of PS in batch and semi-batch reactor setups. The main goal was to perform a comprehensive study on the depolymerisation of PS, thereby investigating the effect of reactor type, catalyst arrangement, feed to catalyst ratio and residence time on the yields of oil and styrene monomer (SM). A further goal was to identify the optimum operating conditions as well as reactor type for an enhanced recovery of oil and SM. It was demonstrated that the semi-batch reactor outperformed the batch reactor in terms of oil and SM yields in both thermal (non-catalytic) and catalytic tests performed at 400 degrees C. Furthermore, it was shown that the layered arrangement of catalyst (catalyst separated from PS) produced a higher amount of oil with higher selectivity for SM as compared to the mixed arrangement (catalyst mixed with PS). Moreover, the effect of carrier gas flowrate on the product distribution was presented.Web of Scienceart. no. 0734242x2093674

Mutations in phosphodiesterase 6 identified in familial cases of retinitis pigmentosa.

To delineate the genetic determinants associated with retinitis pigmentosa (RP), a hereditary retinal disorder, we recruited four large families manifesting cardinal symptoms of RP. We localized these families to regions on the human genome harboring the α and β subunits of phosphodiesterase 6 and identified mutations that were absent in control chromosomes. Our data suggest that mutations in PDE6A and PDE6B are responsible for the retinal phenotype in these families

Loss of function mutations in RP1 are responsible for retinitis pigmentosa in consanguineous familial cases.

PurposeThis study was undertaken to identify causal mutations responsible for autosomal recessive retinitis pigmentosa (arRP) in consanguineous families.MethodsLarge consanguineous families were ascertained from the Punjab province of Pakistan. An ophthalmic examination consisting of a fundus evaluation and electroretinography (ERG) was completed, and small aliquots of blood were collected from all participating individuals. Genomic DNA was extracted from white blood cells, and a genome-wide linkage or a locus-specific exclusion analysis was completed with polymorphic short tandem repeats (STRs). Two-point logarithm of odds (LOD) scores were calculated, and all coding exons and exon-intron boundaries of RP1 were sequenced to identify the causal mutation.ResultsThe ophthalmic examination showed that affected individuals in all families manifest cardinal symptoms of RP. Genome-wide scans localized the disease phenotype to chromosome 8q, a region harboring RP1, a gene previously implicated in the pathogenesis of RP. Sanger sequencing identified a homozygous single base deletion in exon 4: c.3697delT (p.S1233Pfs22*), a single base substitution in intron 3: c.787+1G>A (p.I263Nfs8*), a 2 bp duplication in exon 2: c.551_552dupTA (p.Q185Yfs4*) and an 11,117 bp deletion that removes all three coding exons of RP1. These variations segregated with the disease phenotype within the respective families and were not present in ethnically matched control samples.ConclusionsThese results strongly suggest that these mutations in RP1 are responsible for the retinal phenotype in affected individuals of all four consanguineous families

Pathogenic mutations in TULP1 responsible for retinitis pigmentosa identified in consanguineous familial cases.

PurposeTo identify pathogenic mutations responsible for autosomal recessive retinitis pigmentosa (arRP) in consanguineous familial cases.MethodsSeven large familial cases with multiple individuals diagnosed with retinitis pigmentosa were included in the study. Affected individuals in these families underwent ophthalmic examinations to document the symptoms and confirm the initial diagnosis. Blood samples were collected from all participating members, and genomic DNA was extracted. An exclusion analysis with microsatellite markers spanning the TULP1 locus on chromosome 6p was performed, and two-point logarithm of odds (LOD) scores were calculated. All coding exons along with the exon-intron boundaries of TULP1 were sequenced bidirectionally. We constructed a single nucleotide polymorphism (SNP) haplotype for the four familial cases harboring the K489R allele and estimated the likelihood of a founder effect.ResultsThe ophthalmic examinations of the affected individuals in these familial cases were suggestive of RP. Exclusion analyses confirmed linkage to chromosome 6p harboring TULP1 with positive two-point LOD scores. Subsequent Sanger sequencing identified the single base pair substitution in exon14, c.1466A>G (p.K489R), in four families. Additionally, we identified a two-base deletion in exon 4, c.286_287delGA (p.E96Gfs77*); a homozygous splice site variant in intron 14, c.1495+4A>C; and a novel missense variation in exon 15, c.1561C>T (p.P521S). All mutations segregated with the disease phenotype in the respective families and were absent in ethnically matched control chromosomes. Haplotype analysis suggested (p<10(-6)) that affected individuals inherited the causal mutation from a common ancestor.ConclusionsPathogenic mutations in TULP1 are responsible for the RP phenotype in seven familial cases with a common ancestral mutation responsible for the disease phenotype in four of the seven families

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Offenzellige Schäume als Katalysatorträger: Beschreibung von Morphologie, Fluiddynamik und katalytischer Performance

In the chemical process industry, the use of structured reactors (e.g. monolithic honeycombs and foams) may eliminate the drawbacks (e.g. high pressure drop and hotspots) exhibited by the conventional randomly packed fixed-bed reactors. Therefore, in the last few decades, structured reactors (or structured catalysts) have been extensively investigated as alternative to the fixed-bed reactor technology. The most prominent and successful examples of structured reactors are the honeycomb-shaped monolithic catalysts, which due to their excellent properties (e.g. exceptionally low ratio of pressure drop to geometric specific surface area) have become the standard catalyst shape in most environmental applications. However, the monolithic honeycombs lack some other important properties, e.g. tortuosity of the flow and radial mixing which can be attributed to their straight channels with no interconnectivity. Open-cell foams on the other hand, due to their high porosities and three dimensional cellular structure, can combine the advantages of packed beds (radial mixing and tortuosity of the flow) and honeycombs (high geometric specific surface area and low pressure drop) on one platform. However, despite their attractive properties which can be exploited in the chemical process industry, foams have still not been applied in large-scale commercial operations to replace the conventional packed bed reactors. This can be ascribed to their high manufacturing cost, lack of sufficient knowledge of transport processes in foam like structures as well as lack of handling experience. The main aim of the present work was to address the problems related to the determination of transport properties of open-cell foams. In this regard, as a first step, a comprehensive characterization of open-cell foams with respect to their morphological parameters was performed. In addition, in order to theoretically determine the geometric specific surface area (which is relevant for heat and mass transport) of open-cell foams, a mathematical correlation was developed. For this purpose the tetrakaidecahedron geometry (an efficiently space-filling and widely accepted representative geometry of foams) was used and different shapes of strut cross-sections of foam structures were taken explicitly into account. Furthermore, periodic cellular materials of ideal tetrakaidecahedron geometry were used as model systems to describe the pressure drop in open-cell foams (replicated foams with non-ideal geometry). In this regard, as a first step, a correlation for pressure drop estimation in periodic cellular materials of ideal tetrakaidecahedron geometry was developed which was then adapted for the open-cell foams that exhibit non-ideal geometry. The applicability of the proposed correlations for geometric specific surface area and pressure drop was validated for open-cell foams of different material (ceramic and metal) with a large range of pore size and open porosity. For this purpose experimental data of specific surface area and pressure drop from the present work as well as from the open literature was used. It was demonstrated that the correlations proposed in the present work can predict the geometric specific surface area and pressure drop in foams with more precision than any other state-of-the-art correlation either theoretical or empirical. A further aim of the present work was to directly compare the catalytic performance of foam/catalyst composites (used as reactor internal) with the packed bed of catalyst pellets in a test reaction. For this purpose, open-cell foams made of sintered silicon carbide (SSiC) were coated with zeolite of the type ZSM-5. SSiC foam samples of different pore size and H-ZSM-5 zeolite of different acidity were used. In addition H-ZSM-5 was pelletized in different pellet sizes. Methanol-to-olefin conversion was performed on SSiC-foam/zeolite composite and on zeolite pellets in a lab-scale reactor setup. Methanol conversion and selectivity towards light olefins were determined at different reaction temperatures for both monolithic (foam/zeolite composite) and packed bed (zeolite pellets) reactor configurations. The SSiC-foam/zeolite composites showed higher selectivity towards light olefins and better stability towards deactivation. The superior performance of foam/zeolite composites was ascribed primarily to the macro porosity of foams and a thin layer of zeolite (instead of pellets), which can enhance the diffusion of reactant and products. Another important factor was the high thermal conductivity of silicon carbide material which can facilitate the rapid evacuation of heat in methanol-to-olefin conversion (an exothermic reaction) and accelerate the mass transfer.In der chemischen Prozessindustrie kann die Verwendung von strukturierten Reaktoren (z.B. Wabenkörper und Schäume) verschiedene Nachteile, wie z.B. hohen Druckverlust und Hotspots herkömmlicher gepackter Festbettreaktoren vermeiden. Deswegen wurden strukturierte Reaktoren (oder strukturierte Katalysatoren) in den vergangenen Jahrzehnten intensiv als Alternative zur Festbettreaktor-Technologie untersucht. Die bekanntesten und erfolgreichsten Beispiele für den technischen Einsatz strukturierter Reaktoren sind wabenförmige monolithische Katalysatoren, die aufgrund ihrer hervorragenden Eigenschaften (wie z.B. besonders geringes Verhältnis zwischen Druckverlust und geometrischer spezifischer Oberfläche) in den meisten Anwendungen im Umweltbereich die Standard-Katalysatorform geworden sind. Allerdings fehlen den Wabenkörpern aufgrund ihrer geraden Kanäle ohne Vernetzung einige andere reaktionstechnisch wichtige Eigenschaften, wie z.B. Strömungstortuosität und radiale Vermischung. Offenzellige Schäume hingegen vereinen aufgrund ihrer hohen Porosität und dreidimensionalen zellulären Struktur die Vorteile von Festbetten (z.B. radiale Vermischung und Strömungstortuosität) und Wabenkörpern (hohe geometrische spezifische Oberfläche und geringer Druckverlust). Allerdings sind Schäume trotz ihrer hervorragenden Eigenschaften noch nicht in großen kommerziellen Operationen als Ersatz für konventionelle Festbetten angewendet worden. Dies kann mit ihren hohen Herstellungskosten, dem Mangel an ausreichenden Kenntnissen über Transportprozesse in derartigen Strukturen, sowie mit mangelnden Erfahrungen im Umgang mit Schäumen begründet werden. Das Hauptziel dieser Arbeit war es, die Probleme im Zusammenhang mit der Bestimmung der Transporteigenschaften von offenzelligen Schäumen anzugehen. In dieser Hinsicht wurde zunächst eine umfassende Charakterisierung der offenzelligen Schäume hinsichtlich ihrer morphologischen Kenngrößen durchgeführt. Zudem wurde für offenzellige Schäume eine Gleichung zur theoretischen Vorhersage ihrer geometrischen spezifischen Oberfläche, die relevant für Wärme und Stofftransport ist entwickelt. Zu diesem Zweck wurde die Tetrakaidecahedron-Geometrie verwendet, bei der es sich um eine effizient raumfüllende und weithin akzeptierte repräsentative Geometrie für Schäume handelt. Die Gleichung berücksichtigt verschiedene Formen von Stegquerschnitten bei Schaumstrukturen. Darüber hinaus wurden periodisch offenzellige Schäume mit idealer Tetrakaidecahedron-Geometrie als Modellsysteme verwendet, um den Druckverlust in Schäumen (nicht-ideale Geometrie) zu beschreiben. In dieser Hinsicht wurde zuerst eine Gleichung für die Druckverlustabschätzung in periodischen offenzelligen Schäumen entwickelt, welche dann für nicht-ideale offenzellige Schäume angepasst wurde. Die Anwendbarkeit der vorgeschlagenen Gleichungen für die Vorhersage von geometrischer spezifischer Oberfläche und Druckverlust wurde an nicht-idealen offenzelligen Schäumen aus unterschiedlichem Material (Keramik und Metall) für ein großes Spektrum an Porengrößen und offenen Porositäten validiert. Zu diesem Zweck wurden experimentelle Daten für spezifische Oberfläche und Druckverlust aus der vorliegenden Arbeit sowie aus der offenen Literatur verwendet. Es wurde gezeigt, dass die Gleichungen, die in der vorliegenden Arbeit vorgeschlagen wurden, die geometrische spezifische Oberfläche und Druckverlust in Schäumen mit mehr Präzision vorhersagen können als bereits bekannten Gleichungen. Ein weiteres Ziel der vorliegenden Arbeit war es, die katalytische Leistung von Schaum/Katalysator-Kompositen mit der einer Katalysatorschüttung im Festbett zu vergleichen. Zu diesem Zweck wurden in einem ersten Schritt offenzellige Schäume aus gesintertem Siliziumcarbid (SSiC) mit Zeolith vom Typ ZSM-5 beschichtet. SSiC-Schäume mit unterschiedlicher Porengröße und H-ZSM-5-Zeolith mit verschiedener Azidität wurden eingesetzt. Außerdem wurde H-ZSM-5 in verschiedener Pellet größe hergestellt. Alle Katalysatorsysteme wurden in der Methanol-zu-Olefine Umwandlung in einer Versuchsanlage im Labormaßstab getestet. Methanol-Umsatz sowie Selektivität zu leichten Olefinen (C2-C4) wurden bei verschiedenen Reaktionstemperaturen für beide Reaktor-Konfigurationen bestimmt. Dabei zeigten SSiC-Schaum/Zeolith-Komposite eine höhere Selektivität zu leichten Olefinen und eine bessere Stabilität gegenüber Deaktivierung. Die überlegene Leistung der Schaum/Zeolith-Komposite wurde darauf zurückgeführt, dass die Makroporosität von Schäumen und die dünne Zeolithschicht an Stelle von Pellets die Diffusion von Edukten und Produkten verbessern können. Außerdem kann die gute Wärmeleitfähigkeit von Siliciumcarbid den Abtransport von Reaktionswärme in der exothermen Methanol-zu-Olefin-Reaktion verbessern

Enhancing aromatics and olefins yields in thermo-catalytic pyrolysis of LDPE over zeolites: Role of staged catalysis and acid site density of HZSM-5

The present work deals with the thermo-catalytic pyrolysis of LDPE (low-density polyethylene) in lab-scale one-and two-stage test rigs over HZSM-5 catalysts featuring different acid site densities. In the first part of this work, the influence of catalyst-to-feed ratio and temperature (in conjunction with the acid site density of HZSM-5) on the product distribution was studied with an aim to identify the optimum operating conditions for the enhanced production of aromatics and light olefins. For this purpose, one-stage thermo-catalytic pyrolysis was performed in which catalysts were mixed with LDPE pellets for in-situ catalysis. In the one-stage catalytic pyrolysis, the catalyst sample with the highest acid site density gave the highest concentration of aromatics (ca. 55%) in the pyrolysis oil with a mono-aromatics fraction of over 50% that consisted mainly of BTEX (benzene, toluene, ethylbenzene and xylenes) compounds. The highest C-2-C-4 olefins concentration (ca. 65%) in the pyrolysis gas was obtained when the sample with the lowest acid site density was used. In the two-stage catalytic pyrolysis (ex-situ catalysis), the concentration of aromatics in the pyrolysis oil reached over 77% with a mono-aromatics fraction of ca. 72% that contained mainly BTEX compounds, when the most acidic catalyst was used. When the catalyst with the lowest number of strong acid sites was employed, the high content of C-2-C-4 olefins in the pyrolysis gas remained almost independent of the reactor configuration. These findings might provide important new insights for the chemical recycling of plastic wastes.Web of Science314art. no. 12307

Chemical recycling of waste polypropylene via thermocatalytic pyrolysis over HZSM-5 catalysts

The present work deals with the chemical recycling of waste polypropylene viathermocatalytic pyrolysis over HZSM-5 zeolite catalysts. The main aim was tosystematically investigate the influence of reactor configuration, zeolite acidity,polypropylene wastes, obtained from different sources, as well as catalyst regener-ation on the product distribution. It was demonstrated that the reactor configura-tion and the acid site density of HZSM-5 catalysts strongly influence the productyields and distributions. The different types of polypropylene waste, on the otherhand, showed a comparatively small yet noticeable effect on the product distribu-tion. Moreover, it was demonstrated that the HZSM-5 catalysts exhibit goodregeneration capacity during regeneration-reaction cycles.Web of Science4661297128

Organic-free synthesis of layer-like FAU-type zeolites

The formation of layer-like FAU-type zeolites was facilitated in the absence of any organic template. Instead, the addition of simple inorganic salts turned out to be an effective and easy to handle alternative to organic additives to induce morphological and even structural changes during zeolite crystallisation