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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]

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]

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]

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]

• 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]

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]

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]

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]

The catalytic co-pyrolysis of grape seeds and waste tyres for the production of high-quality bio-oils was studied in a pilot-scale Auger reactor using different low-cost Ca-based catalysts. All the products of the process (solid, liquid, and gas) were comprehensively analysed. The results demonstrate that this upgrading strategy is suitable for the production of better-quality bio-oils with major potential for use as drop-in fuels. Although very good results were obtained regardless of the nature of the Ca-based catalyst, the best results were achieved using a high-purity CaO obtained from the calcination of natural limestone at 900 °C. Specifically, by adding 20 wt% waste tyres and using a feedstock to CaO mass ratio of 2:1, a practically deoxygenated bio-oil (0.5 wt% of oxygen content) was obtained with a significant heating value of 41.7 MJ/kg, confirming its potential for use in energy applications. The total basicity of the catalyst and the presence of a pure CaO crystalline phase with marginal impurities seem to be key parameters facilitating the prevalence of aromatisation and hydrodeoxygenation routes over the de-acidification and deoxygenation of the vapours through ketonisation and esterification reactions, leading to a highly aromatic biofuel. In addition, owing to the CO2-capture effect inherent to these catalysts, a more environmentally friendly gas product was produced, comprising H2 and CH4 as the main components. [ABSTRACT FROM AUTHOR]

The naphthenic acids (NAs) present in the crude oil can lead to the corrosion problems in oil refinery equipment apart from reduces the performances of the oil. In this study, the method to remove NA were done by means of extraction using sodium thiocyanate in ethanol with the aid of Ni/Ca/Al2O3 and Ni/Ce/Al2O3 catalysts at 27 °C reaction temperature. The catalyst was prepared by incipient wetness impregnation method (IWI) and calcined at three different temperature, 800, 900 and 1000 °C respectively. The efficiency of the extraction was affected by the catalyst calcination temperature. Both catalysts calcined at 800 and 900 °C gave total acid number (TAN) value more than 1 mg KOH/g while by using Ni/Ca(10:90)/Al2O3 and Ni/Ce(10:90)/Al2O3 calcined at 1000 °C the TAN value were reduced to 0.28 and 0.65 mg KOH/g respectively. Brunauer-Emmett Teller (BET) result shows both catalysts have large surface area that provide more reaction cites when calcined at 1000 °C. X-ray Diffraction Spectroscopy (XRD) analysis of Ni/Ca/Al2O3 catalyst revealed that the active site was dominated by the Al2O3 species while CeO2 was the active site for Ni/Ce/Al2O3 catalyst. In conclusion, both catalysts reduced the TAN value of acidic crude oil efficiently. [ABSTRACT FROM AUTHOR]

0.7 mm sheets of blends of polycarbonate (PC) with polyethylene terephthalate (PET) rich in PC in the presence and absence of three different transesterification catalysts have been obtained using reactive extrusion-calendering processing method in order to evaluate the fracture toughness of these materials applying the essential work of fracture (EWF) approach which has not been previously reported in the literature. The morphology has been characterized by scanning electron microscopy (SEM). In addition, the tensile properties of these materials were determined. There is a decrease on the essential term ( we) values of PC/PET blends without transesterification catalysts while blends with transesterification catalysts present an increment in comparison with neat PC which may related to the product of the transesterification that plays like an emulsifier/compatibilizing agent to reduce the interfacial tension between the components of the blend and reduce the interfacial tension between the two immiscible or incompatible component phases to get a better fracture behavior. This is confirmed by the tensile test results obtained which demonstrate higher values for E and σ y in the case of blends with transesterification catalysts compared with neat PC. For non-essential term of fracture (β wp), blends without catalysts exhibit an increase compared with neat PC by increasing the amount of PET which may due to the lowering of the yielding stress. In contrary, the presence of transesterification catalysts and especially Zn-based shows decrease as a consequence of the restriction that occurred on the movement of PC segments during the transesterification reactions or as a decohesion of the dispersed phase during the test. [ABSTRACT FROM AUTHOR]

Biomass thermochemical conversion with in situ CO2 capture is a promising technology in the production of high-quality gas. The adsorption competition mechanism of gas molecules (H2O, CO2, CO, CH4, and H2) on CaO-based catalyst surfaces was studied using density functional theory (DFT) and experimental methods. The adsorption characteristics of CO2 on CaO and 10 wt % Ni/CaO (100) surfaces were investigated in a temperature range of 550–700 °C. The adsorption energies were increased and then weakened, reaching their maximum at 650 °C. The simulation results were verified by CO2 temperature-programmed desorption (CO2-TPD) experiments. By the density of states and Mulliken population analysis, CaO doped with Ni caused a change in the electronic structure of the Osurf atom and decreased the C–O bond stability. The molecular competition mechanism on the CaO-based catalyst surface was identified by DFT simulation. As a result, the adsorption energies decreased in the following order: H2O > CO2 > CO > CH4 > H2. The increase of CO2 adsorption energy on the 10 wt % Ni/CaO surface, compared with the CaO surface, was the largest among those of the studied molecules, and its value increased from 1.45 eV to 1.81 eV. Therefore, the 10 wt % Ni/CaO catalyst is conducive to in situ CO2 capture in biomass pyrolysis. [ABSTRACT FROM AUTHOR]