Reduction In Reaction Temperature Research Articles

Synthesis of Si3N4 powder with a controllable alpha/beta ratio by sol-gel assisted carbothermal reduction and nitridation

The controllable α/β ratio of Si3N4 powder was synthesized using tetraethyl orthosilicate (TEOS), glucose, MgCl2 and YCl3·6H2O by sol-gel assisted carbothermal reduction and nitridation (CRN). This study aimed to investigate the impact of various parameters, including a H2O/TEOS mol ratio of the sol, a C/Si mol ratio, sintering aids, and the temperature of CRN on the phase transformation of α-Si3N4. The results demonstrated that the H2O/TEOS ratio significantly influenced the relative content of α and β phase in Si3N4 by changing the morphological characteristics of SiO2. When the H2O/TEOS ratio was 100, β-Si3N4 powder with an approximate β content over 88 wt% was synthesized at 1500 °C. This remarkable phase transformation was likely facilitated by the eutectic liquid phase consisting of MgSiO3/Mg2SiO4. The SEM image revealed rod-like whiskers with a length around 1.4 μm for the β-Si3N4 grains. Due to the presence of liquid phase, the synthesis of spherical-like α-Si3N4 nano-powder with an α-phase content of 91 wt% was achieved at a lower temperature of 1450 °C, with an H2O/TEOS ratio of 15 and a C/Si ratio of 4. The size of the particles was about 70 nm due to the reduced reaction temperature. Furthermore, without the addition of any sintering aids or Si3N4 seeds, high purity α-Si3N4 with an α phase content approaching 96 wt% could be synthesized at 1500 °C, using an H2O/TEOS ratio of 15 and a C/Si ratio of 4. The resulting α-Si3N4 powder exhibited an extremely regular hexagonal prism shape with a length of approximately 2 μm.

Insights of water-to-hydrogen conversion from thermodynamics

<p>Water-to-hydrogen can be achieved using a variety of driving energy sources, including thermal, electrical, or photo energy. While methods for hydrogen production in specific energy driving scenarios have been extensively studied, a comprehensive theory to explain the conversion of various energies into hydrogen is still lacking. This study provides a novel exergy-based perspective on hydrogen production methods, revealing that the thermodynamic infeasible water splitting process is derived from insufficient exergy input relative to the reaction exergy requirement. Enhancing the exergy input beyond the reaction exergy requirement can break through chemical equilibrium and enable the reaction to proceed. Providing high exergy-to-energy ratios of energy sources such as electrical, photo, and chemical energy for thermochemical water splitting reactions can reduce the thermal exergy demand for hydrogen production, thus facilitating water-to-hydrogen conversion at lower temperatures. By applying this new insight to coupled photochemical- and thermochemical water splitting reactions, equilibrium conversion rates corresponding to solar spectra with different wavelengths are obtained. The highest water-to-hydrogen conversion rate is achieved by the solar spectrum at a wavelength of about 451nm. The appropriate wavelength region for high water-to-hydrogen conversion is identified. This study also identifies the theoretical conversion limit of photochemical water splitting, providing insights into the potential improvements of current experiments. More importantly, our work offers a unified thermodynamic framework for understanding hydrogen production methods and presents a theoretical basis for reducing reaction temperature and enhancing conversion rate.</p>

Transparent and highly organosoluble aromatic polyimides with twisted backbone and bulky side substituents for flexible substrate materials

AbstractIn this study, four novel aromatic polyimides (PIs) with twisted backbone and bulky side substituents were prepared via chemical imidization reaction and two‐step condensation polymerization at reduced reaction temperature. The number‐average and weight‐average molecular weights of the resulting PIs are in the range of 1.98 × 104–4.10 × 104 and 2.66 × 104–5.32 × 104 g mol−1, respectively, while maintaining polydispersity indices consistently below 2.0. In addition, the obtained PIs showed excellent solubility in most common solvents, even in low‐boiling solvents, such as chloroform, dichloromethane, and tetrahydrofuran. The films casted from these PIs also displayed optical transparency with a cutoff wavelength in the range of 335–360 nm. Among the PIs, PAPOT‐OPDA, derived from 3,3′‐Diisopropyl‐4,4′‐diaminodiphenyl‐3″‐phenoxybenzylmethane (PAPOT) and 3,3′,4,4′‐diphenylethertetracarboxylic dianhydride (OPDA), exhibited the highest transparency of T450 = 81% and T500 = 85%, and the best solubility without compromising its thermal properties.

Simplified kinetics model for hydrogen gas generation from metallic aluminum in municipal solid waste incineration bottom ash

The reaction of metallic aluminum in the incineration bottom ash (IBA) with an alkaline medium generates hydrogen (H2) gas. The generated H2 has caused severe cracking when IBA is used as construction material. Studies have then explored applications of IBA in aerated concretes where H2 from metallic aluminum can be utilized advantageously and found that the kinetics of H2 generation influence the cellular structure and mechanical properties. However, no kinetics model is available to understand the reaction kinetics of H2 gas generation from IBA. This study presents a simplified kinetics model employing the shrinking core model for H2 generation from metallic aluminum in IBA. The uniform distribution of metallic aluminum in IBA particles and average particle size were considered to make the model simplified for practical applications. The model was calibrated by the hydrogen gas generation from IBA and a known alkaline solution (NaOH). The temperature dependency of the reaction rate was implemented using the Arrhenius equation. The study showed that the hydrogen gas generation in IBA demonstrated reaction control kinetics at higher temperatures (≥ 60 °C) and diffusion control kinetics at lower temperatures (≈ 25 °C). The yield of hydrogen gas generation also decreased with the reduction in reaction temperature. The kinetics model was successfully validated against the experimental data for the local IBA. The presented model is expected to improve the understanding of dynamic H2 gas generation from metallic aluminum in IBA and guide the development of aerated composites with target properties where IBA is used as an aerating agent.

Enhancing catalytic activity and pore structure of metal–organic framework-808 via ligand competition for biodiesel production from microalgal lipids at reduced temperatures

Catalysts with hierarchical porous structures and increased active defects play a crucial role in catalyzing the conversion of microalgae lipids. However, the template methods used for pore expansion and the acidification process employed to enhance activity are cumbersome and prone to deactivation. It is necessary to propose a simple and versatile synthetic approach to overcome these challenges. By modulating N,N-dimethylformamide basicity with formic acid, MOF-808 exhibited enhanced coordination of benzene-1,3,5-tricarboxylic acid to Zr-clusters, creating three types of functional defects. These defects increased pore size from 1.63 nm to 5.34 nm and enhanced catalyst acidity by 22.8%, while maintaining high porosity. The active catalytic sites were confirmed to be defect sites (exposed Zr4+) through density functional theory. Compared to regular MOF-808, catalyst MOF-808-3/1 shows enhanced hierarchical porosity and increased acidity, enabling efficient conversions at reduced reaction temperature (100 °C) and pressure (352 kPa) compared to 200 °C and 4036 kPa, respectively.

NiFe Nanoalloys Derived from Layered Double Hydroxides for Photothermal Synergistic Reforming of CH4 with CO2

AbstractDry reforming of methane (DRM) with carbon dioxide to produce syngas is currently attracting a lot of attention for converting greenhouse gases into valuable chemicals. However, harsh reaction conditions in thermal catalysis hinder practical applications. Herein, a series of alumina‐supported NixFey nanoalloys are synthesized from NiFeAl‐layered double hydroxide precursors, with the obtained catalysts used for photothermal synergistic DRM. The Ni3Fe1 nanoalloy catalyst shows a syngas production rate of 0.96 mol g–1 h–1 under a 350 °C photothermal condition, which is about 1100 times higher than that of the same catalyst at the same temperature in the dark. Methane activation as the rate‐determining step in DRM is greatly enhanced by the localized surface plasmon resonance of the Ni3Fe1 nanoalloy in the ultraviolet region, thus accounting for the remarkably reduced reaction temperature. Meanwhile, the nanoalloy‐based photothermal synergistic DRM exhibits sunlight‐driven feasibility and 20 h of continuous operational stability.

Protrusions induction by carbon black on surface of activated carbon to enhance its catalytic activity

Catalytic methane decomposition is considered as a promising hydrogen production technology without CO2 emission. Catalyst is generally required to reduce reaction temperature, among which, carbon-based catalysts are widely studied due to their excellent catalytic performance and low cost. Activated carbon (AC), although presents high initial activity, suffers from fast deactivation; In comparison, carbon black (CB) shows low activity but good stability, and its catalytic performance maintains ability inspires a novel method for AC optimization. According to the physical property difference of AC and CB, a novel catalyst is prepared by doping CB on the surface and in the pores of AC. And surface property modified by HNO3 is also recommended, because the increase of functional groups further improves the adsorption performance. The results illustrate that ACN + BP2000-20:3 show advantages in hydrogen yield, weight increase velocity and carbon yield. Meanwhile, not only the initial activity is improved by a large margin, but also the deactivation time is progressively prolonged. The analysis results show that CB loading significantly increased the number of micropores, which is the key factor for the high initial catalytic activity. And the protrusion, induced by CB, are characterized by unique graphene edges defect, which provides active sites and furtherly promotes the reaction.

Revealing the crystallization kinetics and phase transitions in Mg65Zn30Ca5 metallic glass by nanocalorimetry

As a potential candidate for biomedical applications, Mg65Zn30Ca5 (at%) metallic glass has attracted considerable attention. To guide the development of MgZnCa alloys with improved mechanical and biomedical properties, it is necessary to understand the phase transitions of this metallic glass. In this study, controlling phase transitions in Mg65Zn30Ca5 metallic glass is realized by nanocalorimetry. The underlying thermodynamic and kinetic features at heating rates ranging from 102 to 105 K s−1 are therefore revealed. Upon rapid heating, an intermediate amorphous phase is detected. This metastable phase facilitates the formation of the Mg7Zn3 crystalline phase with a remarkably reduced reaction temperature and activation energy. With the combination of nanocalorimetry and structural characterization, the continuous heating transformation (CHT) diagram for Mg65Zn30Ca5 metallic glass is plotted, and crystallization trajectories under various heating conditions are distinguished. Meanwhile, the crystallization kinetics covering seven orders of magnitude is estimated, giving the growth rate of the MgZn crystalline phase in the undercooled liquid with temperatures ranging from Tg to Tm. Accordingly, the maximum crystal growth rate and corresponding temperature are estimated at umax= 0.49 m s−1 and Tu,max= 563 K, respectively. With the decrease in undercooling, the transition from kinetics-controlled crystallization to thermodynamics-controlled crystallization is illustrated, causing divergence of the estimated growth rate from the experimental results.

Investigation into the crystallization of molecular sieve DNL-6

Crystallization of DNL-6, a silicoaluminophosphate (SAPO) based molecular sieve with the RHO topology, was investigated under both the hydrothermal synthesis (HTS) and dry-gel conversion (DGC) conditions. Crystallization of DNL-6 under the HTS conditions is rather fast. But a combination of crystallization under the DGC conditions and reducing reaction temperature slow down the reactions, allowing for intermediates to be captured. Under the DGC conditions, DNL-6 crystallizes through a semi-crystalline layered phase. The nature of this intermediate is aluminophosphate (AlPO) rather than SAPO with most P atoms having a local environment of P(–O–Al)3(OH). The surfactant (cetyltrimethylammonium chloride) used for synthesis appears to be part of the layered intermediate. Si is directly incorporated in the DNL-6 framework via SM II mechanism when the semi-crystalline AlPO phase is transforming to DNL-6 with the assistance of a very small amount of water. Both the structure directing agent and the surfactant play a role in the formation of DNL-6, as they were found within the final synthesized products. SEM data show that hydrothermal synthesis produces a much more crystalline product. The facts that the semi-crystalline layered phase was also observed in the powder X-ray diffraction patterns of the solid samples obtained under the HTS conditions and that the evolution of the local structure around P and Al in the intermediate phases are similar imply that under the reaction conditions employed in the present study, the formation pathways of DNL-6 under the HTS and DGC conditions appear to have some similarities.

Low-Temperature Activation of Methane with Nitric Oxide and Formation of Hydrogen Cyanide over an Alumina-Supported Platinum Catalyst

This study demonstrated methane activation with subsequent conversion to hydrogen cyanide (HCN) at low temperatures using nitric oxide (NO) as the sole oxidant together with an alumina-supported platinum catalyst (Pt/Al2O3). This process afforded HCN even at 300 °C, indicating that C–H bond cleavage, NO dissociation, and simultaneous C–N coupling all occurred at this reduced reaction temperature. The HCN yield increased with increasing temperature, resulting in a 3.2% yield with a selectivity of 49% at 425 °C. This yield was much greater than that obtained from the reaction of CH4 with NH3 and O2, which suggests a reaction mechanism different from the Andrussow process. The HCN production rate was 11.4 mmol g–1 h–1 and the corresponding turnover frequency was 253 h–1, both of which were far superior to those obtained in previous studies at similar reaction temperatures. The Pt catalyst was found to be stable and could continuously produce HCN for at least 100 h. In situ X-ray absorption fine structure analyses suggested that the high resistance of this material to deep oxidation facilitated HCN formation. The difference between X-ray absorption near-edge structure spectra before and during the reaction indicated that the specific adsorbates on the catalyst were dependent on the reaction temperature and that the extent of adsorbed Pt-CN species was correlated with the reactivity of the material.

Effect of thermal input, excess air coefficient and combustion mode on natural gas MILD combustion in industrial-scale furnace

To promote the application of MILD scheme in furnace, the present work was performed to evaluate the effect of thermal input, excess air coefficient and combustion mode on the MILD combustion at high thermal level (thermal input varies from 600 to 786 kW); meanwhile, the heat from the utilized furnace was extracted by an annular water jacket and a corundum tube was installed in the furnace tube to create the high temperature atmosphere. The results were presented on flow field using numerical simulations and on global flame signatures, temperature/species distribution and exhaust emissions using experiments. Better combustion performance of MILD mode than conventional swirling diffusion combustion mode was verified in the present work. The positive effect of increased thermal input and excess air coefficient on gas recirculation, thermal uniformity and exhaust emissions reduction was observed. In the MILD combustion regime, the switching from nonpremixed to premixed combustion resulted in lower oxygen level and reduced reaction temperature in the combustion region, also much lower NOx emissions and slightly higher CO emission were observed. At 786 kW thermal input, the reaction zone covers the entire combustion chamber; meanwhile, low NOx emission level of 32 ppm@3%O2 are achieved for premixed MILD combustion mode. The MILD regime was established for natural gas fueled furnace with colorless distributed combustion and suppressed NOx and CO emissions.

Controlled Growth of Large-Sized and Phase-Selectivity 2D GaTe Crystals.

GaTe has recently attracted significant interest due to its direct bandgap and unique phase structure, which makes it a good candidate for optoelectronics. However, the controllable growth of large-sized monolayer and few-layer GaTe with tunable phase structures remains a great challenge. Here the controlled growth of large-sized GaTe with high quality, chemical uniformity, and good reproducibility is achieved through liquid-metal-assisted chemical vapor deposition method. By using liquid Ga, the rapid growth of 2D GaTe flakes with high phase-selectivity can be obtained due to its reduced reaction temperature. In addition, the method is used to synthesize many Ga-based 2D materials and their alloys, showing good universality. Raman spectra suggest that the as-grown GaTe own a relatively weak van der Waals interaction, where monoclinic GaTe displays highly-anisotropic optical properties. Furthermore, a p-n junction photodetector is fabricated using GaTe as a p-type semiconductor and 2D MoSe2 as a typical n-type semiconductor. The GaTe/MoSe2 heterostructure photodetector exhibits large photoresponsivity of 671.52 A W-1 and high photo-detectivity of 1.48 × 1010 Jones under illumination, owing to the enhanced light absorption and good quality of as-grown GaTe. These results indicate that 2D GaTe is a promising candidate for electronic and photoelectronic devices.

Identification of extremely hard coke generation by low-temperature reaction on tungsten catalysts via Operando and in situ techniques

The coke formation in the catalytic system mainly cause to the catalyst deactivate resulting the dramatic decreasing of the catalyst performance then the catalyst regeneration was required. In this study, adding MgO physically mixed with WO3/SiO2 catalysts were prepared and compared with the ones prepared by physically mixing with SiO2. Adding MgO affected the generation of new species of coke deposited on WO3/SiO2 and MgO itself. Comparing the reaction temperature when adding MgO between at 300 and 450 °C, the different pathway of reaction and the coke formation were found. At 450 °C, the metathesis reaction was more pronounced and the lower temperature of coke deposited on WOx/SiO2 was found. Surprisingly, the extremely hard coke occurred during reaction at 300 °C that the maxima of coke formation was found over 635 °C. This due to the fact that the reduction of reaction temperature from 450 to 300 °C affected the decreasing of the metathesis activity. Conversely, the increasing of dimerization and isomerization of butenes-isomer was observed especially 1-butene and iso-butene. Thus, it could suggest that those quantity of them play the important role to generate the charged monoenyl or cyclopentenyl species by participating with ethene through the dimerization, resulting in the formation of extremely hard coke.

Conversion of Unprotected Aldose Sugars to Polyhydroxyalkyl and C-Glycosyl Furans via Zirconium Catalysis.

An efficient, zirconium-catalyzed conversion of unprotected aldose sugars with acetylacetone to polyhydroxyalkyl furans or C-glycosylfurans is reported. The furan products are formed in up to 93% yield using 5-10 mol % ZrCl4. Pentoses are readily converted at room temperature, while hexoses and their oligosaccharides require mild heating (i.e., 50 °C). Efficient conversions of glycolaldehyde, glyceraldehyde, erythrose, a heptose, and glucosamine are also demonstrated. This approach outpaces each of the previous Lewis acid-catalyzed methods in at least one the following ways: (i) lower catalyst loadings; (ii) reduced reaction temperatures; (iii) shorter reaction times; (iv) equimolar substrate stoichiometry; (v) expanded sugar scope; (vi) higher selectivities; and (vii) the use of an Earth-abundant Zr catalyst.

A brief review of CO2 utilization for alkali carbonate gasification and biomass/coal co-gasification: Reactivity, products and process

Carbon gasification in molten alkali carbonate salts over CO2 is a process to produce gaseous fuels with mitigating the greenhouse effect. Alkali carbonate salts can facilitate Boudouard reaction, which is difficult to occur even at high reaction temperature if the catalyst is absent. Alkali carbonate allows easily carbon−CO2 contact by changing the reaction interface from gas-solid to gas-liquid. This review focused on CO2 utilization for alkali carbonate gasification and biomass/coal co-gasification. CO2 gasification of biomass and coal with the alkali carbonate salts enhances the carbon conversion rate and CO yield. Furthermore, alkali carbonate salts gasification of biomass and coal could reduce reaction temperature, activation energy, and tar formation in the product gas. The factors that influence the carbon conversion rate were discussed, such as reaction temperature, CO2 concentration, alkali carbonate addition, and char feeding mode. On the other hand, blending coal with biomass is considered as potential fuel base for CO2 co-gasification and displays an advantage for improving the coal char reactivity. The alkali and alkaline earth metals (AAEMs) present in biomass ash acted as a natural catalyst to increase the coal reactivity and CO production. The catalytic effect in the co-gasification enhances by raising the percentage of biomass in the blend. In contrast, the inhibiting effect in co-gasification could be attributed to silica and alumina reactions with AAEMs to form aluminosilicates complexes.

Effect of nanostructuring on thermal stability and decomposition of aluminium titanate (Al2TiO5): A phase transformation study

As a refractory ceramic, the thermal instability of aluminium titanate (AT or Al2TiO5) has been in the crosshairs of research works in recent years. The studies have indicated that different parameters such as atmosphere, grain size, additives, oxygen pressure, and synthesis method can bilaterally affect the thermal decomposition of AT ceramic and resultant physicomechanical properties. In the present study, the AT nanostructure was synthesized by a citrate sol-gel method and influence of nanostructuring nature on its thermal instability and reaction pathway was explored in some details. It was shown that the reduction of grain size down to 30 nm can destabilize AT, so that the reaction starts from the threshold temperature of around 300 °C instead of 900 °C. This significant reduction in reaction temperature was attributed to the increase of interfaces density and crystallographic imperfections, serving as preferential sites for starting the thermal dissociation. However, the nanostructuring is not able to change the temperature spectrum in which a vast majority of AT ceramic is dissociated with a strong kinetics (i.e. 1100 °C). It was confirmed that the thermal instability of AT nanostructure bears a slow kinetics, so that a heat treatment at 1200 °C for 5 h cannot completely decompose this ceramic.

Catalytic oxidation and reaction kinetics of low concentration benzene over CuxMnyOz/SiO2

Reducing reaction temperature of catalytic combustion is the fundamental way to improve adaptability of catalysts to complex volatile organic compounds (VOCs) and off-design conditions. Using benzene which is the most difficult to be oxidized in VOCs as the catalytic target and by means of multiple characterization methods, silicon dioxide supported copper-manganese catalysts were optimized through changing the load of active material, the ratio of bimetal and calcination condition, the conclusions as following: Cu3Mn9/SiO2 with calcination temperature of 300 °C, molar ratio for Cu/Mn of 3:9 and total load mass for active substance of 11% demonstrates the best catalytic performance. And the benzene which is lower than 2000 mg/m3 in air can be completely oxidized at 265 °C. The change of activation energy and mechanism of deactivation in the process of catalyst optimization were obtained by catalytic reaction kinetic analysis. After the optimization, reaction activation energy decreased from 65.08 kJ/mol to 56.82 kJ/mol, and complete conversion temperature of the C6H6 decreased by nearly 20 °C. Additionally, the fundamental reason for deactivation of the catalyst is the structure changes at high temperature, and surface oxides agglomerate, which greatly reduces the oxygen content of the catalyst. With the increase of reaction temperature, the mass transfer capacity of O2 on the surface of catalyst increase less than that of C6H6, leading to carbon deposition, and the joint action results in the decrease of catalyst activity.

Effects of Mg contents on the microstructure evolution and Fe–bearing phase selection of Al–Mg–Si–Fe alloys under sub–rapid solidification

In this work, the effects of Mg contents on the microstructure evolution, Fe–bearing phase selection, and composition microsegregation of Al–xMg–1.0Si–0.2Fe (x = 0.2, 0.7, 1.2, and 1.7 wt.%) alloys were investigated under the sub–rapid solidification (SRS, 102–103 °C/s). The as–cast microstructure transformed from fully columnar to equiaxed grains as Mg content increases, and there was a burst of equiaxed grains in the 1.2Mg sample due to the enhanced constitutional under–cooling. Besides, Mg content altered the types of Fe–bearing intermetallic compounds. β–AlFeSi was the intermetallic compound in the 0.2Mg sample. In contrast, the Fe–bearing phase changed to α–AlFeSi in the 0.7Mg, 1.2Mg, and 1.7Mg samples, because the peritectic transformation of α–AlFeSi to β–AlFeSi was greatly suppressed due to the reduced reaction temperature with increasing Mg contents. Furthermore, 0.7Mg had the weakest composition microsegregation among the studied samples, owing to its fewer number of Mg2Si phase compared to the 1.2Mg and 1.7Mg samples. Moreover, β–AlFeSi in the 0.2Mg sample can form and exist at a high–temperature range, getting coarser and denser, and initiating a more serious composition microsegregation compared to the 0.7Mg sample. The results of this study provide guidelines for reasonably developing high–performance dilute Al–Mg–Si–Fe alloys based on the SRS.

A Comprehensive Comparison Study: The Impacts of Gasifying Agents and Parameters on Chinese Herb Medicine Residue Gasification

Traditional treatments of Chinese herb medicine residue (CHMR) inevitably cause secondary pollution and hardly remove the pesticide in it. Therefore, high-temperature treatment might be promising to achieve the reduction and resource utilization of CHMR. Based on this, the effects of essential parameters including temperature, equivalent ratio (ER), oxygen concentration and steam to biomass ratio (S/B ratio) were systematically and synthetically analyzed to explore the method and mechanism of improving gasification characteristics. Increasing temperature would promote endothermic reactions thus enhancing the gasification process. The optimal ER of air, oxygen-enriched air and oxygen-enriched air steam gasification are the same, 0.26. Higher O2 concentration would promote oxidation reaction thus increasing the temperature in gasifier and being conducive to the generation of CO and H2, while excess O2 would react with CO and H2. The optimal O2 concentration in oxygen-enriched air and oxygen-enriched air steam gasification were 40 vol% and 50 vol%, respectively. It might be caused by that more O2 was needed to offset the temperature reduction caused by steam addition. Supplying proper steam (S/B = 1.0 and 1.6 for oxygen-enriched air and oxygen-enriched air steam gasification, respectively) could promote the Primary water–gas ad Steam reforming reaction thus increasing the CO and H2 yields. However, excessive steam could reduce reaction temperature and be not conducive to gasification. Moreover, grey relational analysis was introduced to solve multi-attribute decision making issues and determine the influence levels of these parameters thus guiding CHMR gasification technology. These parameters followed the order of S/B ratio > O2 concentration > temperature > ER.

The Effects of Catalyst Support and Temperature on the Hydrotreating of Waste Cooking Oil (WCO) over CoMo Sulfided Catalysts

Waste cooking oil (WCO) hydrotreating to produce green diesel is good for both the environmental protection and energy recovery problems. The roles of catalyst support and reaction temperature on reactions during WCO hydrotreating process were evaluated over an unsupported and a commercial sulfided cobalt and molybdenum (CoMoS) catalyst supported by a mixture of Al2O3, TiO2, and SiO2. The presence of catalyst support helped to improve the dispersion and enlarge the surface area of CoMoS, and was found to be a key factor in reducing reaction temperature, in enhancing the hydrodeoxygenation (HDO) and hydrogenation capabilities, and in decreasing polymerization capability. The increase of reaction temperature strongly improved the deoxygenation, hydrogenation, and cracking reaction activities. Compared to the unsupported CoMoS, the supported one exhibited good deoxygenation and hydrogenation capabilities at 340 °C in WCO hydrotreating to produce diesel fraction; however, high temperature operation needs to be carefully controlled because it may cause overcracking and dehydrogenation.