Adsorption microcalorimetry characterization of K-doped MgAl mixed oxide catalysts for soybean oil transesterification synthesized by impregnation and ball milling techniques

Calorimetric measurements of the acidity of supported vanadium oxides prepared by ALE and impregnation

The effect of Mg-Al mixed oxides in the composition of the catalysts on the distribution of the target cracking products of a mixture of vacuum gas oil with sunflower oil was studied. It was established that by changing the molar ratio of magnesium to aluminum in mixed oxides, it is possible to control the process of deoxygenation of oxygen-containing compounds. For catalyst samples containing mixed oxides with high values of the molar ratio to Mg:Al, the content of carbon dioxide increased, which indicates an increased activity of the decarboxylation reaction. However, there was a significant decrease in the conversion of mixed raw materials and the yield of the gasoline fraction in comparison with a sample that does not contained mixed oxide. The solution was to introduce additional metal into the mixed oxide. So for catalysts containing Co, Mg-Al or Zn, Mg-Al mixed oxides was shown, an increase in the conversion of mixed raw materials by 5.0 wt. % relative to the sample containing mixed oxide without additional metal, as well as increasing the yield of gasoline fraction by 1.6-3.0 wt. % It was found that the modification of mixed oxides with cobalt or zinc cations does not lead to a significant change in the distribution of inorganic products, which indicates that the catalyst remains active in the decarboxylation reaction.

Ca–Mg–Al ternary mixed oxides derived from layered double hydroxide for selective etherification of glycerol to short-chain polyglycerols

The combined influence of the catalyst acidity and porosity features on the transesterification of soybean oil with methanol was investigated over micro/mesoporous hierarchical Beta (Si/Al = 18 and 30), conventional microporous Beta (Si/Al = 23 and 43) and MCM-22 (Si/Al = 40) zeolites. All the catalysts were characterized as to their structure and texture by X-ray diffraction and N2 physisorption, respectively. Their acid features were assessed by adsorption microcalorimetry, using NH3 as probe molecule. Catalytic testing was carried out in batch at 453 K and 4 MPa. The nature of the organic material adsorbed/trapped in the catalyst during reaction (“coke”) was determined by GC/MS after solvent extraction. Fatty acid methyl esters (FAMEs) yields of 22–40 mol% were attained with a reaction time of 24 h over the conventional Beta and MCM-22 samples, whereas remarkably higher values (50–70 mol%) were observed over the hierarchical Beta zeolites. For both the hierarchical and conventional zeolites, the initial FAMEs yield was found to increase with the concentration of the acid sites able to adsorb ammonia with strength higher than ca. 100 kJ mol−1. In comparison with the conventional zeolites of similar acidity, the methyl esters yield over the hierarchical zeolites was twice to three times higher, as a consequence of the enhanced reactants diffusion in their secondary mesoporous system. The presence of free fatty acids in the reaction mixture and the nature of the coke revealed that several acid-catalyzed reactions and thermal degradation processes can occur simultaneously with transesterification. A general scheme for the different reaction pathways for the oil transformation was outlined.

Nickel on alumina catalysts for the production of hydrogen rich mixtures via the biogas dry reforming reaction: Influence of the synthesis method

Effect of the preparation method on the hydrogenation activity of Ni/SBA-15 catalysts: Comparison of EDTA complexation and DPU

In this study, CeO2, La2O3, and CeO2-La2O3 mixed oxide catalysts with different Ce/La molar ratios were prepared by the soft template method and characterized by different techniques, including inductively coupled plasma atomic emission spectrometry, X-ray diffraction, N2 physisorption, thermogravimetric analysis, and Raman and Fourier transform infrared spectroscopies. NH3 and CO2 adsorption microcalorimetry was also used for assessing the acid and base surface properties, respectively. The behavior of the oxides as catalysts for the dimethyl carbonate synthesis by the transesterification of propylene carbonate with methanol, at 160 °C under autogenic pressure, was studied in a stainless-steel batch reactor. The activity of the catalysts was found to increase with an increase in the basic sites density. The formation of dimethyl carbonate was favored on medium-strength and weak basic sites, while it underwent decomposition on the strong ones. Several parasitic reactions occurred during the transformation of propylene carbonate, depending on the basic and acidic features of the catalysts. A reaction pathway has been proposed on the basis of the components identified in the reaction mixture.

The enhanced activity of Ca/MgAl mixed oxide for transesterification

Mixed oxides were obtained via calcination at 550 °C from layered double hydroxides (LDHs), which were synthesized in a previous study via co-precipitation and co-precipitation followed by hydrothermal treatment using aluminum residues as the source of this element. After characterization, these oxides (Mg-Al-LDH-CP and Mg-Al-LDH-H, named according to the synthesis methods of the precursor LDHs) were applied as heterogeneous catalysts in the methyl transesterification of ethyl acetate (EA). The formation of mixed oxides was confirmed by the absence of basal peaks associated with the layered LDH structure in the XRD analysis, due to calcination. Further characterization revealed that Mg-Al-LDH-CP exhibited the highest number of acidic sites, while Mg-Al-LDH-H had the highest number of basic sites. The transesterification activity was evaluated in the reaction between ethyl acetate (EA) and methanol (MeOH). The best result, obtained under a molar ratio of 1:5:0.005 (EA:MeOH:catalyst) at 120 °C, was a 63% conversion after 360 min of reaction for the Mg-Al-LDH-CP catalyst, which had a higher number of acidic sites and fewer basic sites. Additionally, the catalysts demonstrated robustness, maintaining catalytic activity over four cycles without a significant decrease in performance. These results indicate the feasibility of using mixed oxides derived from LDH, synthesized from aluminum residues, as heterogeneous catalysts in transesterification reactions, highlighting their potential for advancing more sustainable catalyst development.

Aldol condensation of furfural and acetone over Mg[sbnd]Al layered double hydroxides and mixed oxides

Tuning of higher alcohol selectivity and productivity in CO hydrogenation reactions over K/MoS2 domains supported on mesoporous activated carbon and mixed MgAl oxide

The influence of various anions in Mg-Al mixed oxides on presence of sodium ions in transesterification of oil

Ru/Al2O3 catalysts were prepared by conventional incipient wetness impregnation as well as colloid deposition of RuCl3 precursor via in situ reduction with ethylene glycol (polyol) method on alumina support. The samples were characterized by TEM, XRD and TPR techniques. The catalytic performance tests were carried out in a fixed-bed micro-reactor under different operating conditions. Ethylene glycol as the reducing agent in the polyol method produced well-dispersed and uniform ruthenium nanoparticles with an average diameter of 7 nm supported on Al2O3. In conventional method, however, reduction by hydrogen resulted in considerably larger particles with average size of 12 nm. The Ru/Al2O3 catalyst prepared by polyol method exhibited three-fold higher activity in ammonia synthesis compared to the catalyst prepared by conventional method. The turnover frequency ratio of ammonia synthesis of polyol to conventional catalyst was estimated to be 2.1 at 450°C implying the reaction is structure-sensitive over Ru-based catalysts.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

One-pot synthesis of biomorphic Mg-Al mixed metal oxides with enhanced methyl orange adsorption properties