Lanthanum Catalysts Research Articles

Mitigating deactivation in dry methane reforming by lanthanum catalysts for enhanced hydrogen production: A review

Catalyst deactivation in dry methane reforming, resulting from coke accumulation and sintering, has long captivated academic interest due to its negative impact on catalytic performance and hindrance to industrial scalability. Thus, developing efficient catalysts capable of sustaining high reforming activity and stability is crucial. Lately, lanthanum (La) has gained popularity in catalysis for its ability to enhance performance and resist coking, owing to its great basicity, redox capabilities, and high oxygen storage capacity. As a result, diverse strategies for incorporating La into catalysts, including support, promoter, bimetallic combinations, and perovskite formation, have been extensively explored. Herein, this review delves into various advancements in lanthanum-based catalysts and their effectiveness in dry methane reforming while addressing catalyst deactivation and regeneration. Finally, the prospect of La-based catalysts in dry methane reforming is also emphasized in this review.

Visible-Light-Enabled Lanthanum-Mediated Intramolecular Epoxy-Ring Opening/Dehydrogenative Lactonization.

Catalytic C(sp3)-H functionalization has afforded great opportunities to prepare organic substances, facilitating the derivatization of complex drugs and natural molecules. This letter describes an efficient and practical protocol for lanthanum-catalyzed continuous epoxy-ring opening and oxidative dehydrogenative lactonization under visible-light irradiation. Notably, the lanthanum catalyst also acts as a photocatalyst while acting as a Lewis acid in this reaction; therefore, no additional photocatalyst is required. We can conveniently prepare a series of diverse isochromanones with oxygen-containing spirocyclic structural units under a balloon-oxygen atmosphere at room temperature. Mechanistic studies and control experiments reveal that the in situ-generated lanthanum bromide should be crucial in the reaction.

Lanthanum-Catalyzed Stereospecific Cross-Coupling of Propargylic Substrates with Grignard Reagents.

Transition-metal-catalyzed cross-coupling of propargylic electrophiles and Grignard reagents provides densely functionalized products that are extremely useful synthetic intermediates. However, examples of conversion of propargylic derivatives to form propargyl compounds remain limited due to the challenging regioselectivity. We use LaCl3·2LiCl to catalyze propargylation of Grignard reagents in the absence of ligand in high regioselectivity and stereospecificity. The approach shows a wide substrate scope using alkyl or (hetero)aryl Grignard reagents and alkynyl electrophiles with different leaving groups. Our protocol was further applied for the formal synthesis of frondosin B. It is worth exploring methodologies utilizing the naturally abundant and relatively nontoxic lanthanum catalysts.

An efficient, reusable heterogeneous Ceria pramoted lanthanum catalyst developed for the synthesis of (e)-1-(Arylmethylene)-2-phenylhydrazines

An efficient, reusable heterogeneous ceria promoted Lanthanum catalyst was developed for the synthesis of (E)-1-(Arylmethylene)-2-phenylhydrazine derivatives by condensation of aromatic aldehydes and phenyl hydrazine under solvent-free condition. The catalyst was characterized by using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface Area, Energy Dispersive X-ray Spectrometry (EDS) and UV-Visible DRS.

Lanthanum Ate Amide-Catalyzed Regio- and Stereoselective Hydrosilylation of Internal Alkynes

Silylalkenes are important synthetic intermediates to substituted alkenes and silicon materials and can be directly obtained by the catalytic selective hydrosilylation of alkynes. In this Letter, the catalytic selective α-syn-hydrosilylation of both aryl- and silyl-substituted internal alkynes is described with an ene-diamido rare-earth ate complex as a catalyst. The reaction resulted in the selective formation of trisubstituted silylalkenes, including geminal disilylalkenes. The kinetic study and DFT calculations disclosed crucial roles of ate structure of the lanthanum catalyst for high reactivity.

Heterogeneous Catalytic Method for the One-pot Three-component Synthesis of Isoquinolonic Acid Derivatives Catalyzed by a 4Å Molecular Sieves Supported Lanthanum Catalyst

Lanthanum supported on 4Å molecular sieves proved to be an efficient heterogeneous catalyst for the one-pot three-component synthesis of 1,2,3,4-tetrahydroisoquinolinone-4-carboxylic acid derivatives from homophthalic anhydride, aromatic aldehydes and an amine component, ammonium acetate or aralkyl amines, with good to excellent yields. The catalyst could be recovered easily and reused without significant loss of its initial activity.

The study of amorphous La@Mg catalyst for high efficiency hydrogen storage

Amorphous catalysts have a large number of catalytic active sites. Here, we report a magnesium composite trace lanthanum catalyst (La@Mg), in which La and Mg layers form amorphous Mg–La compound on the surface of layered Mg. The test shows this La@Mg has hydrogen storage capacity of about 7.6 wt% and hydrogen desorption of 7.2 wt%, higher than that of crystalline La@Mg and sole Mg, rapid absorption/desorption kinetic and stable reversible absorption/desorption cycles. La@Mg exhibits an optimistic hydrogen storage performance than Mg-based materials previously reported in the literature. Combined with theoretical calculations, it is shown that the amorphous Mg–La has an catalysis on hydrogen storage performance of La@Mg system, which contributing to the dispersion of Mg and providing channels for hydrogen diffusion, facilitating hydrogenation by accelerating H atoms diffuse between the subsurface and the surface. This work provides experiment and mechanism guidance for the development of efficient hydrogen storage materials.

Application of supported lanthanum catalysts in the hydrogenation of nitriles

Nickel and lanthanum on MgO or MgO–Al2O3 catalysts were prepared and characterized. The applicability of the catalysts was studied in the liquid-phase hydrogenation of benzonitrile. A La/MgO catalyst showed surprisingly high activity and selectivity. The scope of the reaction was extended to other nitriles (benzyl cyanide, cinnamonitrile, adiponitrile) over this La/MgO catalyst.

Copper‐Lanthanum Catalysts for NOx and Soot Removal

AbstractThe individual and simultaneous removal of NOx by Storage and Reduction with H2 (H2‐NSR) and combustion of soot have been studied for La and CuLa catalysts. The NOx storage capacity of pure lanthanum oxide is improved either by copper addition or by using a colloidal crystal hard template for the synthesis of a macroporous structure. Although the NOx storage capacity of the CuLa macroporous material is around ten times lower regarding conventional PtBa catalysts, the kinetics of the H2‐NSR cycles are fast enough to allow high NOx removal (until 90 % removal). Lanthanum oxide catalyst prepared with uncontrolled structure has no activity for soot combustion, but the activity increases for a macroporous counterpart prepared using the colloidal crystal template because the macroporous structure improves the soot‐catalyst contact and allows the nitrogen‐oxygen surface groups yielded upon NOx chemisorption to oxidize soot. The soot combustion activity of lanthanum catalysts is also enhanced upon copper loading, because copper improves the NO2‐assisted soot combustion mechanism and favors the chemisorption of NOx, enhancing soot oxidation by nitrogen‐oxygen surface species. Finally, it is demonstrated that the simultaneous removal of NOx by H2‐NSR and soot combustion can be carried out with a CuLa catalyst at 450 °C. The simultaneous removal does not affect the combustion of soot and only has a small effect in NOx removal.

Deep Control of Linear Oligomerization of Glycerol Using Lanthanum Catalyst on Mesoporous Silica Gel

The valorization of glycerol (1), a waste of biodiesel production of Fatty Acid Methyl Esters (FAMEs), adopting a “green” approach, represents an important goal of sustainable chemistry. While the polymerization of 1 to hyperbranched oligomers is a well-established process, the linear analogues are difficult to obtain. In this context, we explore the reaction without the solvent of heterogeneous hybrid La(III)O-KIT-6 catalyst (2), which is based on lanthanum oxide on mesoporous silica gel, showing a superior linear selectivity compared to most of the analogous catalysts recently reported.

Pyrolysis-gasification of wastes plastics for syngas production using metal modified zeolite catalysts under different ratio of nitrogen/oxygen

The aim of this study was the syngas production by the gasification of plastic waste (polyethylene, polypropylene and terephthalate polyethylene). Ca, Ce, La, Mg and Mn were used to promote the Ni/ZSM-5 catalyst in order to enhance the production of higher syngas yield. The modified catalysts can enhanced the reaction rate of the pyrolysis process and resulting in high syngas in the product yields. Especially cerium, lanthanum promoted catalysts can enhance the yield of syngas. The effect of the reaction temperature and nitrogen/oxygen ratio of the carrier gas was also investigated. The maximum syngas production was obtained with lanthanum catalyst (112.2 mmol/g (95%N2 and 5%O2), and 130.7 mmol/g (90%N2 and 10%O2) at 850 °C. Less carbon depositions was found at 850 °C or even by the using of catalyst and more oxygen in the carrier gas. The oxygen content of the pyrolysis-gasification atmosphere had a key role to the syngas yield and affects significantly the carbon-monoxide/carbon-dioxide ratio. Catalysts can also accelerate the methanization reactions and isomerize the main carbon frame. Increasing in both temperature and oxygen in the atmosphere led to higher n-paraffin/n-olefin ratio and more multi-ring aromatic hydrocarbons in pyrolysis oils. The concentration of hydrocarbons containing oxygen and branched compounds was also significantly affected by catalysts.

Polynuclear lanthanide–diketonato clusters for the catalytic hydroboration of carboxamides and esters

Catalytic reduction of carboxamides into their corresponding amines is an attractive but extremely challenging transformation, which often meets with limited success; the valuable amine products drive ongoing research in this area. Here we show the direct deoxygenation of carboxamides using earth-abundant lanthanum catalysts in the presence of HBpin, presenting good to excellent yields with broad substrate scope and functional group/heteroatom tolerance. Moreover, this method is also effective in catalysing the hydroboration of esters. Finally, selective cleavage of the amide group bonds (C–N versus C–O) could be achieved based on the nature of the nitrogen substituents. Amide reduction via hydroboration is challenging, and catalysts often exhibit limited substrate scope. Here the authors report synthesis of a lanthanum cluster as a catalyst for the hydroboration of esters and amides, capable of reducing a wide range of primary, secondary and tertiary amides to amines.

Catalytic coupling of CH4 with CHF3 for the synthesis of VDF over LaOF catalyst

AbstractThe oxidative coupling of methane (OCM) with CHF3 facilitates the synthesis of vinylidene fluoride (VDF). The aim is to utilize CHF3, which is otherwise considered a waste with a very high global warming potential. This study focuses on the effect of a LaOF catalyst on OCM occurring in the presence of CHF3, which engenders a promoting effect of O2 on CH4 activation. It examines the structural and phase changes of the lanthanum catalyst during the reaction and then speculates on the reaction mechanism. In combining OCM with CHF3, both the conversion of CH4 and the formation rate of VDF are almost tripled at 700°C. However, at higher temperatures, gas‐phase reactions play a dominating role in the conversion of CH4 and LaOF catalyst plays a very minor role in the reaction system at elevated temperatures. Irrespective of the reaction temperature, VDF is produced via the gas‐phase coupling of CH3 radicals with CF2. During pretreatment or during the reaction itself, La2O3 is fluorinated by CHF3 and HF, yielding the formation of surface LaOF and LaF3 species. LaF3 is a relatively inactive catalyst for CH4 conversion, whereas, in comparison LaOF appears to play a very important role in the activation of CH4 at low temperatures. The activation mechanism of CH4 at relatively low temperatures is similar with that postulated to occur during the OCM. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

Investigation of lanthanum and Si/Al ratio effect on the HZSM-5 catalyst efficiency for production of Olefin from Methanol

ABSTRACTThe effect of lanthanum and Si/Al ratio on catalytic performance of HZSM-5 in methanol to olefin process is investigated in this paper. The catalyst with bases of HZSM-5 is modified using the lanthanum by a wet impregnation producer. The Box-Behnken method, experimental design is used to evaluate effects of lanthanum parameters, Si/Al ratio, temperature and the effect of the interaction between them in methanol to olefin process for production of ethylene and propylene. Finally, the obtained results show the highest yield of ethylene is achieved for high load lanthanum catalyst, low Si/Al ratio and high temperature.

Diastereodivergent Asymmetric Carboamination/Annulation of Cyclopropenes with Aminoalkenes by Chiral Lanthanum Catalysts.

Stereodivergent asymmetric catalysis is an important technology that can allow efficient access to various stereoisomers of a given product with multiple stereocenters from the same set of starting materials, but its application to the synthesis of a highly strained cyclopropane compound has remained unexplored to date. We report here the first diastereodivergent enantioselective synthesis of bicyclic aminocyclopropanes by lanthanum-catalyzed asymmetric carboamination/annulation of cyclopropenes with aminoalkenes. This protocol features 100% atom efficiency, good yield (up to 90%), and high chemo- (up to >20:1) and stereoselectivity (up to >20:1 dr and 99% ee), constituting a unique route for the efficient synthesis of two different diastereoisomers of a given chiral bicyclic aminocyclopropane compound.

Molecular Sieve Supported Lanthanum Catalyst for the Efficient Synthesis of Polyhydroquinolines via Hantzsch Synthesis

Molecular sieve supported lanthanum catalyst proved to be an efficient heterogeneous catalyst for the one-pot, four-component synthesis of polyhydroquinoline derivatives from aromatic aldehydes, dimedone, ethyl acetoacetate and ammonium acetate in ethanol via Hantzsch reaction. The method has several advantages such as simple reaction conditions, short reaction time, high yields and simple workup procedure, which make it an attractive route for the synthesis of polyhydroquinolines. The catalyst could be reused several times without the loss of its initial activity.

Lanthanum-Catalyzed Double Hydrophosphinylation of Nitriles

A new lanthanum-based catalyst was shown to be effective for the double hydrophosphinylation of unactivated nitriles under very mild conditions. Surprisingly, the lanthanum catalyst gave two regioisomeric products depending on the nature of the starting nitrile. Primary alkyl nitriles undergo 1,1-addition to give products with a new P–C–P linkage and concomitant formation of a primary amine. Under the same conditions, secondary alkyl and aryl nitriles instead produced 1,2-addition products, where 1 equiv of the phosphine oxide was added to the carbon, while a second equivalent added to the nitrogen of the nitrile, resulting in a P–C–N–P framework. Further investigation of the catalytic cycle yielded evidence that all nitriles first undergo 1,1-addition (deemed the kinetic product) that then undergoes isomerization to the final unsymmetric addition product (the thermodynamic product). All catalytic reactions were run neat or with very little solvent, required little workup, and had high to moderate yields.

Vapor phase aldol condensation of methyl acetate with formaldehyde over a Ba–La/Al2O3 catalyst: the stabilizing role of La and effect of acid–base properties

Vapor phase aldol condensation of methyl acetate with formaldehyde was studied over Ba–La/Al2O3 with different amounts of lanthanum catalysts.

Quantitative screening of an extended oxidative coupling of methane catalyst library

A comprehensive microkinetic model, including catalyst descriptors, that accounts for the homogeneous as well as heterogeneously catalyzed reaction steps in Oxidative Coupling of Methane (OCM) was used in the assessment of large kinetic datasets acquired on five different catalytic materials. The applicability of the model was extended from alkali magnesia catalysts represented by Li/MgO and Sn-Li/MgO and alkaline earth lanthana catalysts represented by Sr/La2O3 to rare earth-promoted alkaline earth calcium oxide catalysts, represented by LaSr/CaO, and to a Na-Mn-W/SiO2 catalyst. The model succeeded in adequately simulating the performance of all five investigated catalysts in terms of reactant conversion and product selectivities in the entire range of experimental conditions. It was found that the activity of Sr/La2O3, in terms of methane conversion, is approximately 2, 5, 30 and 33 times higher than over the La-Sr/CaO, Sn-Li/MgO, Na-Mn-W/SiO2 and Li/MgO catalysts, respectively, under identical operating conditions. This was attributed mainly to the high stability of adsorbed hydroxyls, the high stability of adsorbed oxygen and the high concentration of active sites of Sr/La2O3. The selectivity towards C2 products was found to depend on the methyl radical sticking coefficient and the stability of the adsorbed oxygen and was the highest on the Na-W-Mn/SiO2 catalyst, that is 75% at about 1% methane conversion and 1023K, 190kPa and inlet molar CH4/O2 ratio of 4.

One-Pot Three-Component Synthesis of 2,3-Dihydroquinazolin-4(1H)-Ones in the Presence of a Molecular Sieve Supported Lanthanum Catalyst

A series of 2,3-dihydroquinazolin-4(1H)-ones have been synthesized with good to excellent yields by one-pot reaction using isatoic anhydride, aldehydes, and ammonium acetate or amines in acetonitrile in the presence of 4 A molecular sieve modified with lanthanum(III) as an efficient heterogeneous catalyst. The catalyst could be reused without evident loss of activity.