Alkaline Earth Metal Oxide Catalysts Research Articles

Developments in Titanium-Based Alkali and Alkaline Earth Metal Oxide Catalysts for Sustainable Biodiesel Production: A Review.

Biodiesel represents a biodegradable, environmentally friendly, and renewable alternative to fossil fuels. Despite more than three decades of research, significant obstacles still hinder the widespread production of biodiesel. This current review elucidates both the potential and the existing challenges associated with homogeneous and heterogeneous catalysts in catalyzing biodiesel production, with a particular focus on alkali analogues, alkaline earth metal oxides, and titania-based catalysts. In particular, a comprehensive analysis is presented concerning alkali and alkaline earth-based titania (TiO2 ) catalysts. Among these, the alkaline earth metal oxides, including lithium, calcium, and strontium when combined with titanium-based catalysts, exhibit superior catalytic activity compared to other metal oxides, owing to their heightened basicity. Consequently, this review offers a thorough and up-to-date insight into the potential of titania-based heterogeneous catalysts for advancing biodiesel production.

Mechanistic insights into the catalytic transfer hydrogenation of furfural with methanol and alkaline earth oxides

DRIFT characterization and DFT calculation were carried out to clarify the previously unexplored use of methanol as a H-transfer agent for the liquid-phase Meerwein-Ponndorf-Verley reduction of biomass-derived furfural using alkaline earth oxide catalysts (MgO, CaO, SrO). Methanol adsorption mechanism has been studied in detail and the energy correlated to the process has been theoretically calculated for each of the prepared catalyst to investigate the relative performances of the three basic oxides. Although, the higher-surface-area MgO displayed an exceptionally high activity for the H-transfer process at low temperatures, CaO and SrO were found to be the catalysts with the highest specific productivity per unit surface area and unit basic site. The different specific productivities of the three catalysts was explained by DRIFT with different adsorption mode selectivities (3 different modes for MgO versus only 1 for CaO and SrO, with the production of only the active methoxide), which may indicate a different methanol activation with regard to the H-transfer toward the carbonyl moiety of FAL. Furthermore, higher SrO than CaO productivity can be explained by the different basicity, which in turn leads to differences in the main methanol activation pathways. DFT calculations make it possible to gain further insight into the role of the basic strength on methanol activation and H-transfer reaction suggesting the increased ability of activating the alcohol via formation of the methoxide ion being the key factor in modulating the catalyst activity rather than the polarization of the aldehydic carbonyl group due to the coordination onto the M3C site.

The catalytic deacidification of acidic crude oil using Cu-doped alkaline earth metal oxide catalysts

ABSTRACTNaphthenic acids (NAs) tend to cause operational problems that can lead to the deactivation of catalysts. To overcome the problem, catalytic deacidification was introduced utilizing an ammonia solution in ethylene glycol with the aids of alkaline earth metal catalyst with alumina as a support. The initial total acid number observed for NAs in n-dodecane was 4.21 mg KOH/g. In total, 1,000 mg/L of 0.4% NH3-EG were used as the acid removal agent. Calcium, barium, and magnesium catalysts were tested in this study. The results showed Cu/Ca/Al2O3 was found to be the best catalyst that could be used to enhance the reaction.

Catalytic performances of potassium and sodium hydroxides/carbonates and calcium and magnesium oxides on hydrolysis of α-chloropropionic acid to lactic acid

Catalytic hydrolysis of α-chloropropionic acid to lactic acid in liquid phase over different alkaline catalysts, such as alkali metal hydroxides, alkali metal carbonates, and alkaline-earth metal oxides, was investigated. Lactic acid was mainly produced by the hydrolysis of α-chloropropionic acid over the alkaline catalysts. The catalytic activities of the alkaline catalysts were in an order of KOH > NaOH > K2CO3 > Na2CO3 > CaO > MgO. The catalytic activities of the alkali metal hydroxides and carbonates were related to both concentrations of their hydroxide anions and hydrated ionic radiuses of K+ and Na+. For the alkaline-earth metal oxide catalysts, their catalytic activities in the hydrolysis of α-chloropropionic acid were mainly related to the solubilities of the resultant hydroxides. A power-function type kinetic equation was used for the evaluation of the effect of catalyst loading and reaction temperature on the hydrolysis of α-chloropropionic acid to lactic acid. The activation energies over the alkaline catalysts were in an order of E a,KOH < E a,NaOH < $$ E_{{\rm a},{\rm K}_{2}{\rm CO}_{3}} $$ < $$ E_{{\rm a},{\rm Na}_{2}{\rm CO}_{3}} $$ < E a,CaO < E a,MgO. The alkaline catalyst with low activation energy had high catalytic activity for the hydrolysis of α-chloropropionic acid to lactic acid.

Catalytic neutralization of acidic crude oil utilizing ammonia in ethylene glycol basic solution

Naphthenic acids in crude oil is a main contributor to the corrosion problem in the petroleum industry and removal of these acids from the crude oil fraction become a great concern nowadays. Catalytic neutralization is an alternative technique to be investigated in this study. A basic chemical with a dosing of 0.4% and 4% of ammonia solution in ethylene glycol (NH3-EG) were used as the acid removal agent with a concentration of 100mg/L, 500mg/L, and 1000mg/L for three different crude oils which are Petronas Penapisan Melaka heavy (crude A) and light crude (crude B) and Korean crude (crude C). A series of alkaline earth metal oxide catalysts; calcium, barium and magnesium supported onto alumina with different calcination temperatures were used to enhance the reaction. The results showed 67.4% (3000mg/L of 4% NH3-EG) reduction in TAN for crude A and 78.7% (10,000mg/L of 4% NH3-EG) reduction for crude C by using the best studied catalyst which was Ca/Al2O3 with a calcination temperature of 1100°C. For crude B, there was 71.2% reduction of TAN with 1000mg/L of 0.4% of NH3-EG. Additionally, based on the results obtained, a mechanistic naphthenic acid reduction reaction pathway was postulated.

Alkaline Earth Metal Oxide Catalysts for Biodiesel Production from Palm Oil: Elucidation of Process Behaviors and Modeling Using Response Surface Methodology

Four different alkaline earth metal oxides i.e. MgO, CaO, SrO and BaO were used as heterogeneous catalysts for biodiesel production from palm oil. Effects of critical process variables i.e. reaction time, methanol to oil ratio and temperature were investigated. The results were then fitted to a historical design to study the Analysis of Variance (ANOVA), to characterize interactions between variables and to simulate the process. MgO did not show good catalytic activity while CaO produced undesired products at longer reaction time. BaO showed the best biodiesel result with a yield of up to 95 %, followed by SrO with a yield of 91 %. A methanol to oil ratio of 9:1 and 60 oC were found to be the optimum conditions. The experimental data were satisfactorily predicted at 99 % confidence level under various conditions with R2 values higher than 0.92. Characterizations of the catalysts before and after the transesterification process were also performed using a surface analyzer, scanning electron microscopy, Hammett indicator and Atomic Absorption Spectrophotometeric (AAS) methods. The catalytic activity was in the order of BaO > SrO > CaO. However, due to lixiviation of BaO in the product, SrO was found to be the most potential catalyst.

The Nature of Surface Deposits Following Valeric Acid Interactions with Al2O3-Supported Alkaline Earth Oxide Catalysts: Towards Cellulosic Biofuels

Two Al2O3-supported alkaline earth metal oxide catalysts (MgO and BaO) were contacted with valeric acid at 250 °C. Each formed amounts of 5-nonanone (BaO more than MgO). A significant deposition of hydrocarbonaceous material onto the catalyst surface is noted. This adsorbed material is characterised using TGA and FTIR and relates to a carboxylate species.

Decarboxylation of naphthenic acid using alkaline earth metal oxide

Removal of naphthenic acid in model acid solution by the catalytic decarboxylation using alkaline earth metal oxide catalysts such as MgO, CaO, BaO and SrO was investigated. Among the alkaline earth metal oxides, MgO and CaO showed better activity than BaO and SrO. The surface properties of MgO have been modified by calcination or hydration followed by dehydration under vacuum and the effects of those treatments on the catalytic activities were investigated. Although the calcination at higher temperature reduced the BET surface area and number of basic sites, it gave the highest decarboxylation activity. The CP–MgO which was made by hydration–dehydration under vacuum gave the highest BET surface area and number of basic sites. But, the catalytic activity of CP–MgO was inferior to the catalyst calcined at 800 °C. This fact implies that both pyrolytic and catalytic reactions play important roles in decarboxylation of naphthenic acid. FT-IR spectra of the catalysts before and after reaction gave the evidence for the formation of bulk magnesium naphthenate, which is the reaction intermediate of the pyrolytic decarboxylation.

Ultrasonic-assisted biodiesel production process from palm oil using alkaline earth metal oxides as the heterogeneous catalysts

The ultrasonic-assisted transesterification of palm oil in the presence of alkaline earth metal oxide catalysts (CaO, SrO and BaO) was investigated. Batch process assisted by 20 kHz ultrasonic cavitation was carried out to study the effect of reaction time (10–60 min), alcohol to palm oil molar ratio (3:1–15:1), catalysts loading (0.5–3%) and varying of ultrasonic amplitudes (25–100%). The activities of the catalysts were mainly related to their basic strength. The catalytic activity was in the sequence of CaO < SrO < BaO. At optimum conditions, 60 min was required to achieve 95% yield compared to 2–4 h with conventional stirring. Also, the yields achieved in 60 min increased from 5.5% to 77.3% (CaO), 48.2% to 95.2% (SrO), and 67.3% to 95.2 (BaO). Fifty percentage amplitude of ultrasonic irradiation was deemed the most suitable value and physical changes on the catalysts after the ultrasonic-assisted reaction were successfully elucidated. BaO catalyst underwent relatively more severe activity drop in the catalyst reusability test. Catalysts dissolution was found to be mainly responsible for activity drop of the reused catalysts, especially with BaO catalyst.

Optimization of ultrasonic-assisted heterogeneous biodiesel production from palm oil: A response surface methodology approach

The use of ultrasonic processor in the heterogeneous transesterification of palm oil for biodiesel production has been investigated. Response surface methodology was employed to statistically evaluate and optimize the biodiesel production process catalyzed by two alkaline earth metal oxide catalysts i.e. BaO and SrO. SEM, surface analysis, AAS analysis and the Hammett indicator methods were used for characterization of the catalysts. Four different variables including reaction time (10–60 min), alcohol to oil molar ratio (3:1–15:1), catalyst loading (0.5–3.0 wt.%) and ultrasonic amplitude (25–100%) were optimized. Mathematical models were developed and used to predict the behavior of the process. The models were able to accurately predict the biodiesel yield with less than 5% error for both catalysts. The basic strength of the catalysts was the main reason of their high activities. This study confirmed that the ultrasonic significantly improved the process by reducing the reaction time to less than 50 min and the catalyst loading to 2.8 wt.% to achieve biodiesel yields of above 95%. The optimum alcohol to oil ratio was found to be at 9:1 while the best amplitudes were ∼ 70 and ∼ 80% for the BaO and SrO catalysts, respectively.

Reduction of benzaldehyde on alkaline earth metal oxides

Benzaldehyde reduction was studied over alkaline earth metal oxide catalysts and carried out in a nitrogen or a dihydrogen atmosphere at the 100–350 °C of the range reaction temperature. The results show that benzyl alcohol is produced by the Cannizzaro reaction under nitrogen flow on MgO oxide and by direct hydrogenation under dihydrogen on irreducible oxides such as CaO, BaO and SrO. The Cannizzaro reaction involves the basic hydroxyl groups and is followed by the reduction of benzoate species by H 2 to benzaldehyde. Toluene and benzene were produced at high reaction temperature under N 2 flow over alkaline earth oxides from a reaction involving benzylate species. Under H 2 flow, toluene and benzene were also formed by means of consecutive reduction reactions. The present work deals with the acid–base properties of alkaline earth metal oxide catalysts (MgO, CaO, BaO, SrO) and benzaldehyde reduction was used as probe reaction for characterizing the surface properties.

Direct Decomposition of NO over Supported-alkaline Earth Metal Oxide Catalysts

NO decomposition over supported alkaline earth metal oxide catalysts was strongly dependent on the type of metal oxide support. Y 2 O 3 was the most effective support. Ba/Y 2 O 3 showed the highest NO decomposition activity, which decreased in the order of Ba/Y 2 O 3 > Sr/Y 2 O 3 > Ca/Y 2 O 3 > Mg/Y 2 O 3 ∼Y 2 O 3 . The catalytic activity of Ba/Y 2 O 3 for NO decomposition at 900°C gradually increased with reaction time. The activity enhancement was due to the decomposition of barium carbonate into barium oxide during the reaction. Barium carbonate was completely decomposed by reduction with H 2 at 900°C, resulting in significant enhancement of NO decomposition activity. The activity of Ba/Y 2 O 3 increased with higher barium loading up to 5 wt%, and then became constant. There was a strong relationship between NO conversion and the amount of NO adsorption on Ba/Y 2 O 3 , suggesting that NO adsorption sites are the reaction sites for NO decomposition. The relationship between the activity for 1-butene isomerization, which is an indicator for the basicity of Ba/Y 2 O 3 catalysts, and the activity for NO decomposition suggests direct participation of basic sites in the NO decomposition reaction over supported alkaline earth metal oxide catalysts.

Direct Decomposition of NO Over Alkaline Earth Metal Oxide Catalysts Supported on Cobalt Oxide

The direct decomposition of NO proceeds catalytically on alkaline earth metal oxides supported on Co3O4. Activity decreased in the order of Ba/Co3O4> Sr/Co3O4> Ca/Co3O4≫ Mg/Co3O4≈ Co3O4. The catalytic activity of supported alkaline earth metal oxides was found to be directly related to not only the number of surface basic sites, which corresponds to the surface density of alkaline earth elements, but also to the strength of basicity, suggesting that NO decomposition proceeds on alkaline earth metal oxides.

Basicities of alumina-supported alkaline earth metal oxides

A series of alumina-supported alkaline earth metal oxide catalysts were prepared by incipient-wetness impregnation. These catalysts were characterized by nitrogen-sorption to determine their surface areas and pore size distributions. The basicities of these catalysts were characterized by temperature-programmed desorption of carbon dioxide. The TPD results demonstrate that all of the catalysts have one-peak profiles. The basicity increases with increasing atomic number of the alkaline earth metal. The alumina-supported alkaline earth oxides exhibit the same basic properties as bulk metal oxides. However, the presence of alumina can increase the mechanical strength of the catalyst, since the alkaline earth oxides have a weak mechanical strength. The basic properties of the catalysts are strongly influenced by the calcination temperature.

Self-Condensation of n-Butyraldehyde over Solid Base Catalysts

The catalytic properties of various solid bases for self-condensation of n-butyraldehyde in liquid phase were studied to elucidate the factors governing the activity and selectivity. For alkaline earth oxide catalysts and γ-alumina catalyst, aldol condensation occurred, followed by Tishchenko-type cross-esterification of n-butyraldehyde with the dimer produced by the aldol condensation to form trimeric glycol ester. Alkali ion-modified alumina catalysts exhibited a high selectivity for the aldol condensation dimer, the trimeric glycol ester being formed tittle. Both basic and acidic sites on the surfaces of the alkaline earth oxides and γ-alumina were assumed to contribute to Tishchenko-type cross-esterification. The suppression of Tishchenko-type cross-esterification for alkali ion-modified alumina catalysts is due to the absence of acidic sites on the surfaces. The catalytic performances of alumina-supported magnesium oxide and alkali zeolite X were also examined. Alumina-supported magnesium oxide exhibited lower activity but higher selectivity to trimeric glycol ester than MgO. This catalytic feature was caused by the lower basicity and higher acidity on the surface of alumina-supported magnesium oxide as compared with MgO. The activity of alkali ion-exchanged zeolites was lowest among the catalysts examined in this study. The modification of zeolites with excess alkali ions improved the activity.

Influence of basicity on the catalytic activity for oxidative coupling of methane

Basicity is shown to be a fundamental catalytic property of the alkaline earths and the rare-earths oxide (REO) catalysts to promote the oxidative coupling reaction of methane (OXCO). The basicity was measured by thermogravimetry from the decomposition temperatures of the carbonates. At an OXCO reaction temperature that allows at least part of the catalyst to be in the oxide form, the C 2+ selectivity is directly proportional to the basicity of the alkaline earth oxide catalysts. A similar basicity-C 2+ selectivity relationship can also be seen among the REO's. The difference in basicity between two REO's is not as great as the alkaline earth oxides, nor does basicity change uniformly across the periodic table. Moreover, the REO's contain sites of various basic strengths. Some of these sites are active for OXCO reaction through the rupture of C-H bond whereas others promote deep oxidation of the product hydrocarbons, giving rise to a low apparent selectivity.

Structure and performance of La 2O 3 promoted alkaline earth oxide catalysts for the oxidative coupling of methane

Structure and performance of La 2O 3 promoted alkaline earth oxide catalysts for the oxidative coupling of methane

Benzene-oxygen reaction over alkaline earth metal oxide catalysts.

Benzene-oxygen reaction over alkaline earth metal oxide catalysts.

Effects of carbon dioxide and catalyst preparation on the oxidative dimerization of methane

The use of carbon dioxide as a reactive diluent for the oxidative coupling of methane increased the yields of ethane and ethene (C 2 compounds) from 13.4 to 18.3% with an increase in C 2 selectivity from 42.3 to 49.4% over MgO catalyst at 1073 K, CH4-to-O2 ratio = 2 and W/F = 6.07 g/h.mol. Alkaline earth metal oxide catalysts prepared by thermal decomposition of their oxalates at 1023 K gave high C 2 space—time yield (e.g., 8.6 mmol/g·h). Sm 2O 3 (15 wt.-% )/porous MgO catalyst prepared at 1173 K showed high C 2 selectivity (47.9% with a C 2 yield of 13.3%). The selectivity for C 2 compounds was further improved to 57.4% in a stream of CH 4 O 2 CO 2 without reducing the C 2 yield (13.6%). Addition of carbon dioxide suppressed the deactivation of the catalyst and decreased the amount of coke deposited on the catalyst surface in a prolonged run. Partial adsorption of carbon dioxide on the catalyst surface inhibits the deep oxidation of methane or C 2 products, resulting in increased C 2 selectivities on dilution of the feed stream with carbon dioxide.

Role of carbon tetrachloride in the conversion of methane on silica-supported alkali metal added alkaline earth oxide catalysts

The effect of the reactant stream addition of small quantities of carbon tetrachloride (TCM) on the conversion of methane has been studied on silica-supported Mg, Ca, Sr and Ba catalysts with and without the addition of lithium. In general both the conversions and selectivities were enhanced by the addition of TCM particularly with lithium added Ba/SiO 2. Consequently further experiments focussed on Ba/SiO 2 to which various alkali metals were added. For the LiBa/SiO 2 catalysts the effect of lithium content, time-on-stream, residence time, pressures of methane and oxygen and reaction temperature were studied. A qualitative mechanism for the TCM modified methane conversion process is discussed.