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Abstract: The technologies conventionally used for biodiesel purification imply high consumptions of both energy and water. In the present work, biodiesel was produced by transesterification using a very active calcium glyceroxide catalyst and purified using water-free processes. The study focused on soaps removal that was the main product impurity. The best results were obtained when the crude biodiesel (methyl ester content of 90.2–91.2wt.% and calcium content of 372–393ppm) was pretreated with Na2CO3 and afterward treated by an ion-exchange resin (6wt.%) or a ceramic membrane (0.1μm). The purification was effective using biodiesel produced from both soybean oil and waste frying oil and the quality of the product agreed with the one obtained using the conventional water washing process. The effectiveness of the treatment could be explained by calcium elimination through precipitation as CaCO3 during pretreatment and sodium soaps removal by absorption into the resin or filtration by the ceramic membrane, according to the micelle formation mechanism. The studied process presents a high potential to remove calcium soaps from biodiesel. [Copyright &y& Elsevier]

Fires originating from coal spontaneous combustion within coalfields result not only in substantial coal resource depletion but also producing residual low-activity pyrolysis coal chars exhibiting varying degrees of oxidation. These chars develop progressively through successive heat penetration at the fire front and post-fire extinguishment phases. This paper focuses on the alkaline earth metal-activated catalytic gasification of residual oxidized coal in fire zones, constructs a carbon-based model of oxidized coal in fire zones. The results show that the reaction active sites of the oxidized coal carbon matrix model are mainly concentrated on the carbon atoms at the end of the aromatic ring. During catalytic gasification, the calcium-based catalyst engages with these active sites, forming a preliminary catalyst. The transformation of oxidized coal into CO primarily occurs through two distinct routes. Calcium attaches to the surface of the oxidized coal's carbon-based structure, establishing active sites. Acting as a facilitator, it aids the movement of CO2 to the carbon-based surface, leading to its further breakdown into CO. The catalytic species containing calcium persistently amalgamates with active sites on coal coke surface, fostering the release of additional CO. Moreover, these catalytic species with calcium also bind CO2 and unite with active coal coke sites, generating carbon–oxygen complexes on the surface. These complexes are thermally unstable and decompose, yielding CO and initiating the formation of fresh active sites on the coal coke surface. Consequently, they interact further with calcium-based catalytic species, culminating in the creation of catalyst precursors, which drive a recurrent catalytic reaction process. [ABSTRACT FROM AUTHOR]

Physicochemical treatment was applied with 20 mg/L alum to the marble processing effluents as 5 minutes 200 rpm mixing, 25 minutes 15 rpm mixing and 60 minutes settling and marble sludge (MS) was produced. Catalytic performance of MS in olive pomace (OP) pyrolysis process was evaluated and compared to commercial Ca(OH)2 since it mainly comprises of different AAEMs (especially Ca and its forms such as CaCO3, CaO) functioned as catalyst. Catalytic pyrolysis was conducted at 600°C and 5°C/min heating rate with 5% and 10% catalyst (MS or Ca(OH)2) dosages. Although both catalysts had important effect on pyrolysis product yields, Ca(OH)2 was found as good alternative for higher gas production and MS was introduced as better option for the higher char production comparing to the conventional OP pyrolysis. Pyrolysis biochars produced with MS were in higher thermal strength than the biochars generated with Ca(OH)2. Moreover, biooils of OP+MS include different organic compounds, such as 9 heptadecanol, 1-eicosanol, ethyl linoleate, ethyl oleate, addition to the compounds observed in pyrolysis liquids of OP and OP+ Ca(OH)2. All detected organic components have diverse usage areas. Ca(OH)2 provided more decrement in the percentages of oxygenated compounds as compared to the MS. Consequently, it can be stated that MS can be used successfully as an alternative to Ca-based commercial catalyst in OP pyrolysis. [ABSTRACT FROM AUTHOR]

• One-step synthesis of sub-micrometric Calcium Hydroxide/Chitosan hybrid catalyst • Biodiesel production with yield up to 98 % and recyclability up to 10 cycles • No calcination step was required for catalyst preparation. • Kinetics and mechanistic insights were provided for heterogeneous catalysis. • Full characterization demonstrated high Ca loading onto the biopolymer. In this work, a novel supported catalyst was prepared starting from calcium chloride and chitosan flakes using a very mild approach in an aqueous medium without final calcination at high temperatures. The as-prepared catalyst was fully characterized by thermogravimetric analysis (TGA), attenuated total reflectance Fourier transform infrared (ATR-FTIR), and X-ray photoelectron (XPS) spectroscopies, transmission and scanning electron microscopies (TEM, SEM), Energy Dispersive X-ray Spectroscopy (EDS), demonstrating that it consists of calcium hydroxide particles of about 200 nm supported on chitosan micrometric structures. The most crucial parameters in the transesterification process were investigated. A methanol/oil ratio of 6:1, a reaction time of 6 h, and a temperature of 60 °C were found to lead to complete conversion. A reaction on a gram scale using waste oil as a starting material was also tested, and excellent results were achieved. Moreover, the catalyst proved to be very robust, since even after the 10th recycle, the conversion rate remained at around 90 %. Spectroscopic analyses showed minimal leaching of material without modification of chemical composition. The kinetic behavior (activation energy, E a) of the catalyst was also studied, which resulted in similar outcomes to Ca-based systems present in the literature, but without the need for costly preparations and with superior recycling resistance. An E a value of 63.25 kJ·mol−1 was found, which agrees with data reported in the literature. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper reports an ozone oxidation catalyst for the advanced treatment of salty wastewater. The green Al 2 O 3 -polydopamine (PDA)-Ca x O y catalyst was synthesized using Ca2+ as the main active site, Al 2 O 3 as carrier, and PDA as a coating agent. The efficiency of Al 2 O 3 -PDA-Ca x O y to treat petrochemical wastewater was investigated by studying the effects of preparation and reaction conditions, such as Ca2+ concentration, calcination temperature and time, catalyst dosage, and pH on the chemical oxygen demand (COD) removal. Al 2 O 3 -PDA-Ca x O y displayed good degradation effects, with a COD removal of 62%, which is higher than that of commercial catalysts. Structure and morphology characterization analyses of Al 2 O 3 -PDA-Ca x O y revealed that Ca2+ was uniformly dispersed through the traction and anchoring effect of PDA. Compared with traditional acidification treatment, the surface modification method used herein was not detrimental to the morphology of the carrier. A reaction mechanism based on the Al 2 O 3 -PDA-Ca x O y catalyst was proposed using electronic spin resonance spectroscopy. [Display omitted] • A novel green Ca-based catalyst was designed and synthesized for ozone oxidation. • The prepared catalyst was used for treatment of real petrochemical wastewater. • The COD removal of 62% was much higher than that of commercial catalysts. • Ca2+ was uniformly dispersed through the traction and anchoring effect of PDA. • A reaction mechanism based on the Al 2 O 3 -PDA-Ca x O y catalyst was proposed. [ABSTRACT FROM AUTHOR]

While catalytic pyrolysis with catalyst addition has been widely studied with a primary focus on optimising gas, tar and char yields, studies exploring the evolution of char structure during coal pyrolysis remain scarce. This knowledge gap potentially affects subsequent char gasification processes during coal conversion within gasifiers. This study presents demineralised anthracite (TM) prepared by HCl–HF acid washing. The pyrolysis performance of TM while adding Ca, Fe and Ca–Fe composite catalysts was investigated through thermogravimetric analysis. The char structure, morphology and functional groups in the obtained char samples were clarified through X‐ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The results indicated that de‐ashing by acid washing promoted the formation of C–O functional groups in coal due to the decomposition of C=O or a combination of oxygen with unsaturated carbon, or both. The TM sample exhibited improved thermal decomposition upon adding either Ca or Fe catalysts, which became more pronounced after adding the Ca–Fe composite catalyst under the same conditions. While the addition of Ca–Fe composite catalysts inhibited the crystalline carbon formation and char graphitisation degree compared to their individual additions, it led to enhanced decomposition of phenol C–O, thereby facilitating the thermal decomposition of TM. [ABSTRACT FROM AUTHOR]

Catalytic gasification of a pig compost (PC) was investigated over transition metal catalysts (TMCs, including limonite, CoMo/Al 2 O 3 , Ni/Al 2 O 3 , and nickel loaded on lignite char) and Ca-based catalysts (dolomite and CaO) in a two-stage fixed-bed reactor to understand the effects of catalyst, temperature, and steam on nitrogen distributions. Non-catalytic thermal decomposition (TD) of PC volatiles below 750 °C is not effective for decomposing the entire volatile nitrogen species (VNSs) to N 2 . NH 3 was found to be the predominant nitrogenous gas under inert conditions used in this investigation, and its yield increased with raising TD temperature. The N yield in HCN is lower than 5% below 550 °C, and sharply increased to 13.9% at 750 °C due to TD of volatiles. Most of VNSs were converted to N 2 over TMCs, especially over Ni-based ones. The TMCs proved to be quite active not only for tar reduction, but also for VNSs decomposition at 450–650 °C. On the contrary, CaO-based catalysts, especially dolomite, significantly promoted the conversion of VNSs to NH 3 . Ni/Al 2 O 3 effectively promoted the conversion of NH 3 and HCN to N 2 at 550 °C. Steam introduced mainly prevented HCN decomposition over dolomite and coke deposition over Ni/Al 2 O 3 . This study provides a basic insight into the nitrogen transformations during catalytic gasification of PC, which would benefit the clean utilization of PC as an energy source. [ABSTRACT FROM AUTHOR]

Modelling the effect of reaction time, catalyst concentration, and oil-to-methanol ratio on the waste cooking oil biodiesel was studied using response surface methodology. Biodiesel was made using three different heterogeneous catalysts. Analysis showed catalysts 2 and 3 to be significant in transesterification. However, all catalysts had second-degree significance for esterification yield. For catalysts 1 and 2 there was a clear interaction between catalyst concentration and oil-to-methanol ratio. Clear interaction was also noticed between reaction time and oil-to-methanol ratio for all catalysts. There was moderate to no interaction between the effects of time and catalyst concentrations for all catalysts. The best yield was found at lower oil-to-methanol ratios (nearly 0.02) and higher catalyst concentrations (at 10%). Reaction times close to 7 hours for catalyst 1 and close to 5 for the other catalysts were the optimum values for best yield and lowest acid value. [ABSTRACT FROM AUTHOR]

Synthetic textiles such as polyesters are essential for daily life. However, large‐scale production generates large amounts of waste. This study introduces a new approach for valorising polyester textile waste (PTW) by transforming it into a catalyst for biodiesel production via pyrolysis. Specifically, a metal/carbon composite (PTW + steel slag [SS] composite—PSC) with enhanced catalytic properties was prepared by pyrolysing PTW with SS. The alkaline metals in SS facilitate the carbonisation of PTW via decarboxylation, resulting in a PSC rich in carbon, iron, and alkaline compounds. This composite featured mesopores that were larger than the micropores (MPs) typically found in PTW char. The use of porous material (silica) in thermally induced transesterification has been proven to be an efficient method for biodiesel production, achieving a yield of 97.20 wt.% in 1 min (faster than the 93.82 wt.% yields in 60 min observed from conventional alkali‐catalysed transesterification). However, the high reaction temperature (≥ 360°C) poses economic/technical challenges. To overcome this, PSC has been employed as a catalyst in thermally induced transesterification, leveraging its mesoporous structure and high alkaline content, particularly calcium oxide. The PSC achieved a biodiesel yield of 98.10 wt.% at a markedly lower reaction temperature of 120°C within 1 min. This performance was not attainable using silica or PTW char under similar conversion conditions. These findings highlight the potential of PSC produced through the pyrolysis of PTW and SS as effective catalysts for biodiesel production. This process is a promising strategy for converting waste into valuable resources and mitigating the environmental impacts associated with polyester waste. [ABSTRACT FROM AUTHOR]

Calcium-based catalysts are of high interest for glycerol polymerization due to their high catalytic activity and large availability. However, their poor stability under reaction conditions is an issue. In the present study, we investigated the stability and catalytic activity of Ca-hydroxyapatites (HAps) as one of the most abundant Ca-source in nature. A stochiometric, Ca-deficient and Ca-rich HAps were synthesized and tested as catalysts in the glycerol polymerization reaction. Deficient and stochiometric HAps exhibited a remarkable 100% selectivity to triglycerol at 15% of glycerol conversion at 245 °C after 8 h of reaction in the presence of 0.5 mol.% of catalyst. Moreover, under the same reaction conditions, Ca-rich HAp showed a high selectivity (88%) to di- and triglycerol at a glycerol conversion of 27%. Most importantly, these catalysts were unexpectedly stable towards leaching under the reaction conditions based on the ICP-OES results. However, based on the catalytic tests and characterization analysis performed by XRD, XPS, IR, TGA-DSC and ICP-OES, we found that HAps can be deactivated by the presence of the reaction products themselves, i.e., water and polymers. [ABSTRACT FROM AUTHOR]

• Biodiesel was produced from soybean oil and WFO over Ca catalyst. • Crude biodiesel was purified by dry washing using fumed silica. • Silica behaves as a non-selective sorbent. • Silica its able to remove calcium from produced biodiesel. • Used sorbents are easily regenerated by solvent wash. Aiming the decarbonization of the transport sector, biodiesel, obtained by alcoholysis of oils or animal fats, is currently mixed with conventional fossil diesel. For this purpose, biodiesel has to comply with the established quality standards and, therefore, the production process comprises purification steps, which need huge volumes of water. Thus, the biodiesel purification procedure must be improved in order to provide a greener and low-cost renewable fuel. Biodiesel (FAME) produced by methanolysis of soybean and waste frying oils over a heterogeneous calcium-based catalyst was purified by dry washing, using commercial silica sorbent (Sipernat 22 from Evonik). ATR-FTIR spectra of post-purification sorbents showed that silica was effective to remove unreacted oil species, glycerin and Ca soap from biodiesel and, contrary to the previously reported in the literature, it was also able to remove leached calcium from the biodiesel. For both feedsotcks, the highest purity was reached for the sorption test carried out at 45 ℃ during 60 min. Sorbent regeneration was evaluated using acetone, methanol, and isopropanol alcohols at room temperature during short contact time (5 min for 1 g of sorbent and 20 mL of solvent). All the tested solvents were effective to remove the adsorbed species from silica surface. [ABSTRACT FROM AUTHOR]

In the present study, an acid catalyst (UiO-66-SO3H) with Brønsted and Lewis acid sites was synthesised for the preparation of highly efficient biodiesel from oleic acid and methanol using chlorosulphonic acid sulfonated metal–organic frameworks (UiO-66) prepared with acetic acid as a moderator. The prepared catalysts were characterised using XRD, SEM, FT-IR and BET. The catalytic efficiency of the sulfonated catalysts was significantly improved and successful sulfonation was demonstrated by characterisation techniques. Biodiesel was synthesised by the one-pot method and an 85.0% biodiesel yield was achieved under optimum conditions of the reaction. The esterification reaction was determined to be consistent with a proposed primary reaction and the kinetics of the reaction was investigated. A reusability study of the catalyst (UiO-66-SO3H) was also carried out with good reproducibility. In conclusion, the present study provides some ideas for the synthesis of catalysts with high catalytic activity for the application in the catalytic preparation of biodiesel. [ABSTRACT FROM AUTHOR]

To increase the carbon conversion of char in gasification, this paper aimed to reveal the gasification behaviours of char residues. Char residues with different ash contents in this work were prepared from Shenmu char and Tejing char. Those char residues were gasified by different CO2 gas mixtures at different temperatures. The gasification process of char residue was different from the end stage of the gasification process of the corresponding raw char: the gasification rate of the char residue increased at first and then decreased, whereas the gasification rate of the corresponding raw char kept decreasing during the end stage of gasification. The highest gasification rate was achieved at a lower conversion in the gasification of char residue than in the gasification of the corresponding raw char. Catalytic minerals, high temperature, and high CO2 partial pressure benefited the gasification of gasified char residues. The char residues that contained more catalytic minerals were more reactive in gasification and were less sensitive to changes in temperature and CO2 partial pressure. The Modified Random Pore Model (MRPM) and Random Pore Model (RPM) were used to predict the gasification kinetics of the chars, and the MRPM describes the gasification processes of gasified char residues well. [ABSTRACT FROM AUTHOR]

This study investigated biodiesel production via the transesterification of grapeseed oil with plasma-modified biomass-based catalysts originating from starfish. Dried starfish was first converted into magnesium and calcium oxide through heat treatment and then further modified by plasma engineering to improve the catalyst's surface area and active sites via zinc addition. The Zn content was added via plasma engineering in the ratios of starfish (Mg0.1Ca0.9CO3): ZnO varying from 5:1, 10:1, to 20:1. The structure and morphology of the catalyst were confirmed through XRD, SEM, and XPS analysis. After the Zn addition and activation process, the surface area and the basicity of the synthesized catalysts were increased. The plasma-modified catalyst showed the highest basicity at the ratio of 10:1. Based on HPLC analyses, the optimized biodiesel yield in transesterification demonstrated 97.7% in fatty acid conversion, and its catalytic performance maintained 93.2% even after three repeated runs. [ABSTRACT FROM AUTHOR]

The electrocatalysis of the oxygen reduction reaction (ORR) on cobalt-containing nitrogen-doped carbon aerogels (CAs) was studied in alkaline solution. CA-based catalyst materials with varied compositions were prepared through the sol-gel polymerisation of organic precursors (resorcinol derivatives and melamine), followed by insertion of Co by using an ion-exchange process and pyrolysis. The concentrations of the precursors had a large effect on the structure and physicochemical properties of the materials, as characterised by using SEM, XRD, XPS, atomic adsorption spectroscopy, and N2-adsorption analysis. The electrocatalytic activity of Co-containing N-doped CAs for the ORR was higher than that of nitrogen-free CA, and this activity increased with increasing Co content. The most active catalyst materials supported the four-electron reduction of O2 and short-term stability tests indicated their high durability. Co-containing N-doped CAs can be regarded as a promising class of material for the cathode catalysts of alkaline membrane fuel cells. [ABSTRACT FROM AUTHOR]

Optical and rheological properties of polycarbonate (PC)/poly(ethylene terephthalate) (PET) blends rich in PC with the presence or absence of different types of transesterification catalysts were investigated in this study. PC/PET blends maintain a high level of transparency (transmittance between 86 and 93%) in all cases, regardless of the blending ratio or the presence or absence of transesterification catalysts. These variations in transmittance are due to the size, distribution and number of dispersed particles. The linear viscoelastic properties confirmed the partial miscibility of blends containing transesterification catalysts in the polymer melt. Additionally, the Palierne emulsion model, with a few changes, gave accurate predictions of the linear viscoelastic data for all PC/PET blends. However, as predicted, the low-frequency data demonstrated the distinct impact of interfacial tension on the elastic modulus of the blends, particularly, as the PET content is increased. [ABSTRACT FROM AUTHOR]

In order to achieve power-generation efficiency higher than those of integrated coal gasification combined cycle plants, advanced integrated coal gasification combined cycle systems have been developed. Here, we developed a triple-bed combined circulating fluidized bed gasifier model using the commercial process simulator Aspen Plus® (version 8.6) and Excel®. The heat balance and reaction kinetics, including the inhibition of steam gasification by H 2 , were simulated for a combustor temperature of 950 °C using porous alumina particles as heat-carrying particles. The theoretical maximum cold gas efficiency of the triple-bed combined circulating fluidized bed gasifier model was 85.0% for a gasification temperature of 800 °C. However, when the temperature was increased to 900 °C, the efficiency decreased to 80.9%. This indicates that, for triple-bed combined circulating fluidized bed gasifiers, a relatively low gasification temperature is suitable for ensuring higher cold gas efficiency and reducing the amount of circulating heat-carrying particles needed. On the other hand, gasification temperatures lower than 850 °C resulted in significantly higher bubbling fluidized bed gasifier volumes even when an effective Ca-based catalyst was used. The cold gas efficiency can be increased further by 8.6% by converting and recovering the missing hydrogen as H 2 gas. Hence, there is a trade-off between the cold gas efficiency, gasifier size, and heat-carrying particle/coal ratio. The optimal gasification temperature for triple-bed combined circulating fluidized bed gasifier is 850 °C. • We develop TBCFB gasifier model based on Aspen Plus® and Excel® models. • Heat balance and gasification reaction rates with inhibition by H 2 were simulated. • Maximum cold gas efficiency of the TBCFB gasifier is 85.0%–80.9% at 800–900 °C. • Required gasification time and BFB gasifier volume greatly increase below 850 °C. • Optimal gasification temperature for these gasifiers is 850 °C. [ABSTRACT FROM AUTHOR]

• Ca-based catalysts are promising in both conventional DRM and CaLDRM processes. • Roles and mechanisms of Ca in various DRM catalyst formulas are summarized. • CaO enhances the metal-support interaction and promotes the dispersion of metals. • The increased basicity by CaO accelerates the CO 2 adsorption and coke gasification. • The presence of Ca in mineral catalysts promotes the creation of lattice defects. Dry reforming of methane (DRM) is a promising and well-studied process that could simultaneously convert the two most abundant greenhouse gases (CH 4 and CO 2) to syngas (CO and H 2). The main obstacle for this reaction, however, is the easy catalyst deactivation caused by coke deposition. Various catalysts have been developed and employed, among which calcium (Ca)-based catalyst is one of the most economically feasible options for industrial scaling-up due to its low cost, easy availability, non-corrosiveness and environmental friendliness. In this paper, therefore, a comprehensive summary of the role and mechanism of Ca-based catalysts in DRM reaction was presented. Specifically, the deactivation behaviors and mechanism of conventional catalysts in DRM reaction were introduced. Subsequently, the role of Ca in various catalyst formulas as a support, a promoter, or a constituent element in specific mineral phases such as perovskites were summarized, and meanwhile the effect of different preparation methods on the performance of Ca-based catalysts was described. As the most widely used agent for CO 2 capture, the employment of Ca-based materials in chemical looping dry reforming of methane was also reviewed. Furthermore, the integration of Ca-based catalysts in some novel catalysis systems such as the membrane catalysis and plasma catalysis systems were briefly surveyed. Finally, the future prospects were proposed, in order to provide a guidance for the development and application of Ca-based catalysts in DRM reaction. [ABSTRACT FROM AUTHOR]

The current research proposed the work on the consumption of waste cooking oil (WCO) as a valuable resource for the production of biodiesel. This study focuses on maximizing output yield by employing composite heterogeneous catalysts, namely calcinated calcium oxide with aluminum oxide (CaO/Al2O3) and calcium oxide with titanium oxide (CaO/TiO2). The calcination process was adopted for the catalysts at 600°C for 5 h to improve catalytic activities and to increase surface area. XRD and TGA were implemented to analyze the crystal structure and thermal stability of these heterogeneous catalysts. Experimentation was planned by implementing the response surface methodology (RSM) approach in combination with the BoxBehnken design. The optimum yield of fatty acid methyl esters (FAMEs) was experimentally observed at 96.56%, using CaO/Al2O3 at methanol to oil (m/o) molar ratio of 11.9:1, 3.19% catalyst loading, 53.79°C and 76.86 minutes (min). The maximum experimental yield with CaO/TiO2 was observed at 98.15% with the optimized operating conditions of independent process variables viz. m/o molar ratio 11:99, 2.53 wt.% catalyst loading and 68.14 min at 59.79°C. The research recommends the potential use of WCO and both the heterogeneous catalysts for optimal biodiesel yield; however, CaO/TiO2 exhibits superior performance over CaO/Al2O3, which is also confirmed by the XRD and TGA results. [ABSTRACT FROM AUTHOR]

This investigation explores the synthesis of advanced catalysts for epoxidizing long-chain linear α-olefins, a pivotal process in the chemical industry for generating critical intermediates. Employing a hydrothermal technique, we developed four distinct catalysts (CS-1–4), methodically modulating the Ca/Sn ratio to elucidate its impact on the catalysts' physicochemical properties. Our research uncovered that an escalated Ca/Sn ratio induces a morphological shift from octagonal to cubic structures, concomitant with a diminution in particle size and an enhancement in specific surface area. Significantly, the CS-3 catalyst outperformed others in 1-octene epoxidation, an efficacy attributed to its augmented surface alkalinity and proliferation of medium-strength alkaline sites, likely emanating from increased surface oxygen defects. Subsequent hydrogen reduction of CS-3 further amplified these oxygen defects, yielding a 10% uptick in catalytic activity. This correlation underscores the potential of oxygen defect manipulation in optimizing catalytic efficiency. Our findings contribute a novel perspective to the development of robust, high-performance catalysts for α-olefin epoxidation, seamlessly aligning with the principles of sustainable chemistry. [ABSTRACT FROM AUTHOR]

The catalytic transesterification of vegetable oil over heterogeneous catalysts is an effective approach for biodiesel production. To elucidate the role of MgO in catalyzing this reaction, several CaO-MgO catalysts with various Mg/Ca ratios were synthesized by co-precipitation. The catalysts were characterized by BET, XRD, SEM, HRTEM, FTIR, TGA, CO2-TPD, O2-TPO, and in situ DRIFTS. The catalytic performance in the transesterification of soybean oil with methanol was evaluated in a stirred batch reactor. The results indicated that the synthesized pure MgO had weak basic sites and poor pore structure, showing the lowest activity. The added Mg in the CaO-MgO composites was present in both doped and supported forms. The doped Mg reduced the lattice spacing of CaO, improved the intensity and number of basic sites, and enhanced the activity of catalysts, while the supported Mg hindered the diffusion of reactants to the basic sites. The amount of the doped Mg showed a maximum value due to the solubility nature of CaCO3 and MgCO3. 1Mg3Ca (Mg/Ca=1/3) exhibited the highest activity with a biodiesel yield of 92.28% at 60 °C for 2 h. CaO is sensitive to water and CO2, forming hydroxides and carbonates. The supported MgO with a low porous structure well protected the basic sites from contamination. High-temperature treatment is an effective method to remove the contaminates and the removal temperature increases in the order of H2O < Mg(OH)2 < Ca(OH)2 < CaCO3. [ABSTRACT FROM AUTHOR]

Reactive melt mixing of recycled polyethylene terephthalate (r-PET) and recycled polycarbonate (r-PC) blends in presence of various concentration of Cobalt(II) acetylacetonate catalyst was studied to obtain optimum of catalyst content. r-PET/r-PC blends in presence of catalyst exhibit enhanced mechanical properties in comparison to without catalyst. XRD patterns reveals decreasing crystallite of samples also miscibility of blend will increase in presence of 0.1 wt.% of catalyst. Melt flow index (MFI) analysis demonstrated a decreasing in molecular weight with increasing catalyst concentration. Mechanical properties in samples contain 0.1 wt.% of transesterification catalyst are improved, in which Tensile analysis test showed an improvement in elongation at break, modulus and tensile strength of samples in comparison with r-PET/r-PC. Izod impact test showed that catalyst in blends caused higher impact strength in samples. [ABSTRACT FROM AUTHOR]

Producing hydrogen from catalytic gasification of biomass represents an interesting process to facilitate the development of hydrogen economy. However, the design of catalyst is a key challenge for this technology. In this work, cost-effective Ca added Ni-based catalysts were developed and studied for producing hydrogen with a fixed-bed reactor. The relationship between Ca addition and the performance of catalyst in terms of the yield of hydrogen and catalyst deactivation (metal sintering and coke formation) was studied. The results showed that hydrogen production was largely enhanced when Ca was added, as the yield of hydrogen was enhanced from 10.4 to 18.2 mmol g −1 sample in the presence of Ca-based catalyst. However, the yield and concentration of hydrogen were kept at similar levels with the increase of Ca. By normalizing the yield of hydrogen in relation to the amount of Ni presented inside the catalyst, the hydrogen yield per mole of nickel was increased from 50 g Ni −1 (0.1Ca catalyst) to 80 g Ni −1 (0.8Ca catalyst) when the Ca addition was increased from 10 mol% to 80 mol%. TPO-FTIR analysis of the experimented catalysts showed that 0.5 Ca catalyst had the highest amount of coke formation, in particular, most of the deposited carbons were amorphous which could deactivate the catalyst seriously. It is therefore concluded that the addition of cost-effective Ca could enhance the yield of hydrogen from biomass gasification. However, the concentration of Ca in the catalyst needs to be controlled to mitigate the generation of coke on the used catalyst. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to examine the catalytic behaviors exhibited by diverse metal catalysts such as CaO, NiO, and K2CO3 for pyrolysis and gasification application with waste biomass. The investigation involved fine tuning the conditions of pyrolysis/gasification by optimizing the pyrolysis atmosphere, catalyst addition methods, and catalyst quantities. The behaviors were investigated using thermal analysis (TG-DTA), and the production gaseous contents were analyzed via GC-FID. The results showed that Ar gas proved to be well suited for the pyrolysis reaction. The incorporation of catalysts through mixing and impregnation techniques ensured the homogeneous dispersion of catalyst particles within the sample, offering a clear advantage over the two-stage approach. Among the various catalysts explored, K2CO3 demonstrated the most favorable catalytic impact, resulting in an enhancement of char yield from 20.2 to 26.8%, while the tar yield was reduced from 44.3 to 38.6%. Furthermore, the presence of K during gasification reactions was found to foster accelerated reaction rates and an increase in syngas production yield. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial electrochemical reactions that play vital roles in energy conversion and storage technologies, such as fuel cells and metal–air batteries. Typically, noble-metal-based catalysts are required to enhance the sluggish kinetics of the ORR and OER, but their high costs restrict their practical commercial applications. Thus, highly active and strong non-noble metal catalysts are essential to address the cost and durability challenge. Based on previous research, carbon-based catalysts may present the best alternatives to these precious metals in the future owing to their affordability, very large surface areas, and superior mechanical and electrical qualities. In particular, carbon aerogels prepared using biomass as the precursors are referred to as biomass-derived carbon aerogels. They have sparked broad attention and demonstrated remarkable performance in the energy conversion and storage sectors as they are ecologically beneficial, affordable, and have an abundance of precursors. Therefore, this review focuses on various nanostructured materials based on biomass-derived carbon aerogels as ORR/OER catalysts, including metal atoms, metal compounds, and alloys. [ABSTRACT FROM AUTHOR]

A series of stable natural diatomite-supported CaO catalysts were synthesized for biodiesel production. All materials have been thoroughly characterized by Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Energy dispersive spectrometer (EDS), Fourier transform-infrared spectroscopy (FTIR), IR-Raman, X-ray diffraction (XRD), N 2 adsorption/desorption, and Hammett indicator. The results indicated that 30Ca/Di_800 catalyst exhibited the highest catalytic activity (a biodiesel yield of 92.4% was acquired) owing to its highest total basicity. Meanwhile, the superior stability of the catalyst during reaction was also demonstrated. The catalyst can be recycled 10 times without significant loss of catalytic efficiency. Therefore, natural diatomite not only can be successfully used as the support for the synthesis of catalyst but also can strongly interact with CaO to form the stable Ca O Si bond. Furthermore, the as-synthesized catalyst also exhibited good better water-tolerant ability. The Ca O Si bond existed on the catalyst surface considered to be a main factor for its high stability and water-tolerance. [ABSTRACT FROM AUTHOR]

Calcium-catalyzed coal pyrolysis to light tar is an attractive technology in coal clean conversion. The pyrolysis behavior and product distribution of low-rank coal over carbide slag (CS) were investigated by a thermogravimetric analyzer, fixed-bed reactor, and in-situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry (in-situ Py-VUVPI-MS). The results indicated that CS impregnation has a more significant effect on coal pyrolysis products than mechanical mixing and layered packing. The addition of CS makes coal pyrolysis tar significantly lighter, and the pitch content decreases from 33.5 wt. % without CS to 8.0 wt. % with CS impregnation but also makes benzenes and phenols content reduced by 16.4% and 55.5%, respectively. In-situ Py-VUVPI-MS analysis revealed that the decrease of benzenes content is mainly due to the secondary reaction of primary products catalyzed by calcium in CS, while the decrease of phenols content is mainly from the changed reaction path of oxygen-containing structure in coal caused by calcium catalysis. This work provides a theoretical basis for experimental research and practical application of coal pyrolysis catalyzed by CS, and the high catalytic activity, low cost, and abundant storage make the waste CS a promising Ca-based catalyst in coal pyrolysis. [Display omitted] • Catalytic pyrolysis of low-rank coal using carbide slag (CS) as catalyst was studied. • Addition of CS performed an excellent effect on obtaining high-quality oil. • CS is an efficient catalyst for pitch and phenols oil conversion. • CS is expected to develop as the novel Ca-based low-cost catalyst for coal pyrolysis. [ABSTRACT FROM AUTHOR]

Hydrogen is a type of clean energy which has the potential to replace the fossil energy for transportation, domestic and industrial applications. To expand the hydrogen production method and reduce the consumption of fossil energy, technologies of using renewable energy to generate hydrogen have been developed widely. Due to the advantages of widespread distribution and various hydrogen production methods, most of the research or review works focus on the solar and biomass energy hydrogen production systems. To achieve a comprehensive acknowledge on the development state of current renewable energy hydrogen production technology, a review on hydrogen production systems driven by solar, wind, biomass, geothermal, ocean and hydropower energy has been presented. The reaction process, energy efficiency, exergy efficiency, hydrogen production rate, economic and environmental performance of these systems have been evaluated. Based on the analysis of these different systems, the challenge and prospects of them are also analyzed. [ABSTRACT FROM AUTHOR]

The leaching and reusability problem of the catalyst in the catalytic transesterification for biodiesel production led to the poor sustainability and high posttreatment cost. Herein, a reusable magnetic Ca2Fe2O5/CaO@MgFe2O4-Fe2O3 catalyst with high textural stability and good catalytic activity was prepared in this study, and its catalytic performance toward transesterification of five different oil feedstocks was evaluated. Catalyst preparation conditions were optimized and characterizations including scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and so on, were also conducted to investigate the catalytic behaviors. The results demonstrated that the catalyst has good ferromagnetism for magnetic separation, and the presence of synergistic interaction enhanced catalytic activity with all of > 90% biodiesel yield and improved the reusability with > 75% biodiesel yields at the 10th cycle. In addition, the biodiesel yield reached the maximum under the transesterification reaction parameters were optimized, and at the 15/1 methanol/oil molar ratio, 2.5 wt% catalyst dosage, 70°C for 120 min. Further, for biodiesel from five different oil feedstocks, the same composition, all of > 90% yield and the quality that met the American Society of Testing Materials (ASTM) standards demonstrated the strong oil feedstocks applicability and application potential of catalysts. [ABSTRACT FROM AUTHOR]

Despite the increasing need for chemicals and energy, the scenario in which fossil feedstocks can be completely replaced by renewables is currently unrealistic. Thus, the combination of biomass and non-renewable matrix-based (i.e., coal) technologies could provide a greener way toward the partial substitution of traditional fuels. The hydrogasification of carbonaceous feedstocks (coal and biomass) for the main production of CH4 offers a promising alternative to this end. However, hydrogasification has received very little attention, and the present review seeks to shed light on the process, reactor, and catalytic advances in the field. Independent of the selected matrices, various efforts have been devoted to the identification of efficient methods for the production of hydrogen feed to the gasifier and energy as well as the reduction in pollutant emissions from the plants. Moreover, the reactor configurations proposed are focused on the intensification of gas-solid contact to reduce by-product formation. The co-hydrogasification of both renewable and non-renewable feedstock is also reviewed, paying attention to the synergistic effect between the two matrices. In addition, due to the slow rates of hydrogasification reaction, the key role of catalysts and feedstock impurities on the reaction kinetics is discussed. [ABSTRACT FROM AUTHOR]

Cracking-Deoxygenation process is one of the important reaction pathways to produce renewable diesel with desired range of C 8 -C 17 from oxygenated biomass liquid via removal of oxygen molecule. Utilization of Ca-based catalyst has attracted much attention in deoxygenation reaction due to its superior physicochemical properties. These type of catalysts capable to remove oxygen from carboxyl group of fatty acid or oil in the form of CO 2 and CO via decarboxylation or decarbonylation reaction, respectively. In this study, triolein was used as a model compound for the production of renewable fuels. Furthermore, waste clamshell-derived CaO-based catalysts (Co-CaO and W-CaO) were used as catalysts for the deoxygenation reaction. The liquid product over Co-CaO and W-CaO yielded 32% and 22% of C 8 -C 17 hydrocarbon fractions with gasoline selectivity of 75% and 65%, respectively. Co-CaO catalyst with positive effect on cracking-deoxygenation process was further investigated by study the effect of Co content from 10 to 40 wt.%. Results showed that paraffinic hydrocarbon yield was increased from 25% to 65%, while gasoline selectivity increased from 56% to 84% at reaction conditions; 350 °C reaction temperature, 45 min reaction time, 5 wt.% catalyst loading, 10 mbar pressure under 40 wt.% of active Co metal. [ABSTRACT FROM AUTHOR]