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Production of γ-butyrolactone (GBL) from vapour-phase dehydrocyclization of biomass derived 1,4-butanediol is considered as more sustainable and significantly commercial industrial process. In this regards, Cu-based catalyst was designed with ZnAl2O4 spinel support and CeO2 as a promoter to obtain Cu/ZnAl2O4-CeO2 catalyst with different Cu:Ce mass ratio. The catalysts were characterized by XRD, H2-TPR, FT-IR, CO2-TPD, FE-SEM and BET analysis and then tested for the production of γ-butyrolactone (GBL) by dehydrocyclization of 1,4-butanediol (BDO). Further, various reaction parameters were optimized and their effects on the catalytic activity were studied to obtain maximum yield towards desired product at ambient reaction conditions. The results revealed that metallic Cu species and CeO2 as a promoter were highly dispersed on ZnAl2O4 support with appreciable surface area. Additionally, CeO2 as a promoter prevented agglomeration, increased the basic character of catalyst to selectively obtain GBL as a major product. 10 wt% Cu/ZnAl2O4-10 wt% CeO2 catalyst exhibited excellent yield (94%) towards GBL product with tetrahydrofuran (THF) as the only by-product and demonstrated consistent activity and selectivity during 26 h time on stream. Further, the optimized catalyst displayed appreciable recyclability performance up to seven recycles without much loss in its catalytic performance making the catalyst feasible at industrial scale.

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules.

In this work, a uniquely designed imidazolium-based dicationic ionic liquid (IL) was synthesized as a greener template and applied for the synthesis of ZSM-5 zeolite as a heterogeneous catalyst for...

Heterocyclic chemistry has fascinated the researchers owing to its wide range of applications in various chemical fields. With this perspective, herein we present an environmentally benign procedure for the synthesis of pyrazole and its derivatives through multicomponent reaction by using SPVA as a heterogeneous acid catalyst. The synthesis protocol of SPVA catalyst includes functionalization of polyvinyl alcohol by sulfonic acid groups. The synthesized SPVA catalyst was then subjected to several characterization techniques to confirm its formation and study its physicochemical properties. The SPVA catalyst was then tested for its activity toward a multicomponent reaction of aromatic aldehyde, malononitrile and phenyl hydrazine. The SPVA catalyst with sufficient acidic sites displayed appreciable catalytic performance yielding 89% of the desired pyrazole product under ambient reaction conditions. The SPVA catalyst showed recyclability up to the sixth cycle without considerable loss in its activity. Furthermore, we made an effort to demonstrate the plausible mechanistic pathway for the SPVA-catalyzed pyrazole synthesis reaction. Interestingly, the present synthetic approach could effectively produce pyrazole products with high yields in the absence of base and solvent and in short reaction time making it a green and sustainable process.

The present work describes synthesis of a series of benzimidazoles, benzoxazoles and benzothiazoles through the cyclization of 1, 2-phenylenediamine, 2-aminothiophenol, or 2-aminophenol with aryl, ...

Selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde is captivating due to its industrial relevance. Herein, a two-step synthesis method was adopted to develop oxygen vacancies in Pd@ZrO2 catalysts. The oxygen vacancies were developed in Pd@ZrO2 catalysts during impregnation of Pd which was confirmed by XPS and HR-TEM analyses. The characterization results revealed that there was a synergistic role of oxygen vacancies and nano-sized active Pd metals in Pd@ZrO2 catalysts that assisted in achieving selectivity for hydrocinnamaldehyde which has been discussed in this study. We also studied the effects of different reaction parameters which revealed that 4 wt% Pd loading in a Pd@ZrO2 catalyst provided enough active sites for complete conversion of CAL. Additionally, 100 °C temperature and 10 bar H2 pressure provided enough energy for effective collisions and activation of reactants and catalysts to form the desired product in a reaction time of 9 h. Therefore, a defect-rich 4-Pd@ZrO2 catalyst demonstrated complete CAL conversion with 86% yield towards HCAL which is the best result amongst various Pd@ZrO2 catalysts with different Pd loading investigated for the hydrogenation of cinnamaldehyde. Moreover, a plausible mechanism was proposed to support the chemoselective hydrogenation of cinnamaldehyde over a 4-Pd@ZrO2 catalyst. Along with high catalytic performance, the 4-Pd@ZrO2 catalyst also showed impressive recyclability performance for up to six recycles. Thus, the oxygen-vacancy-rich Pd@ZrO2 can be considered as an efficient catalyst for the chemoselective hydrogenation of cinnamaldehyde.

The involvement of CO2 as a renewable and abundant feedstock toward a carbon balanced future has led to production of several value-added products. The primary focus in the current effort is to ass...

Hydrogen being a dynamically impending energy transporter is widely used in hydrogenation reactions for the synthesis of various value added chemicals. It can be obtained from dehydrogenation reactions and the acquired hydrogen molecule can directly be utilized in hydrogenation reactions. This correspondingly avoids external pumping of hydrogen making it an economical process. We have for the first time tried to carryout 1,4-butanediol dehydrogenation and benzaldehyde hydrogenation simultaneously over ceria-alumina supported copper (Cu/CeO2–Al2O3) catalyst. In this concern, 10 wt% of Cu supported on CeO2–Al2O3 (3:1 ratio) was synthesized using wet impregnation method. The synthesized catalyst was then characterized by various analytical methods such as BET, powder XRD, FE-SEM, H2-TPR, NH3 and CO2-TPD, FT-IR and TGA. The catalytic activity towards simultaneous 1,4-butanediol dehydrogenation and benzaldehyde hydrogenation along with their individual reactions was tested for temperature range of 240 °C–300 °C. The physicochemical properties enhanced the catalytic activity as clearly interpreted from the results obtained from the respective characterization data. The best results were obtained with 10 wt% of Cu supported on CeO2–Al2O3 (3:1 ratio) catalyst with benzaldehyde conversion of 34% and 84% selectivity of benzyl alcohol. The conversion of 1,4-butanediol was seen to be 90% with around 95% selectivity of γ-butyrolactone. The catalyst also featured physicochemical properties namely increased surface area, higher dispersion and its highly basic nature, for the simultaneous reaction towards a positive direction. In terms of permanence, the Cu/CeO2–Al2O3 (10CCA) catalyst was quite steady and showed stable activity up to 24 h in time on stream profile.

The present study describes the hydrogen production as a future energy source via hydrolysis of NaBH4 catalyzed by urchin-like CuCo2O4 spinel catalyst prepared by urea-assisted hydrothermal synthesis method. The as-synthesized copper–cobalt double hydroxide precursor and the resultant CuCo2O4 spinel were characterized by using various analytical, spectroscopic and microscopic techniques in order to understand their physiochemical and morphological aspects. The detail characterization results confirmed the successful formation of CuCo2O4 spinel phase with urchin-like morphology. The CuCo2O4 spinel catalyst was then tested for its application in hydrogen generation from NaBH4 hydrolysis by performing the reaction using 10 wt% of CuCo2O4 spinel catalyst and 0.5 g NaBH4 at room temperature. The CuCo2O4 spinel catalyst with tailored architecture displayed high catalytic activity with H2 generation rate of 1370 mL min−1 g−1 (1438 mL in 21 min). Major factors affecting the hydrolysis of NaBH4 reaction such as catalyst loading, NaOH concentration and temperature variation was also studied and discussed in detail. Correspondingly, the low activation energy of 22 kJ mol−1 was obtained from the Arrhenius plot and kinetic studies revealed that the hydrolysis of NaBH4 followed first order kinetics. Further, recyclability study of CuCo2O4 spinel catalyst was also performed which displayed good catalytic activity and stability even after five successive recycles. Characterization data of reused catalyst revealed that physiochemical properties of fresh CuCo2O4 spinel catalyst were well-preserved in the reused catalyst as well. Therefore, nanostructured CuCo2O4 spinel can be demonstrated as one of the most efficient, cost effective bimetallic spinel catalyst so far for application in the hydrogen generation.

The world's growth mainly depends on energy consumption. Fossil fuel is the major contributor for primary energy consumption and is raising severe environmental concerns. Hydrogen energy can prove to be a greener replacement for future energy requirements. In the present work, we present eminently competent recyclable magnetically active iron oxide nanoparticles supported on functionalized carbon nanotubes hybrid nano structures which are used for the hydrolysis of sodium borohydride for hydrogen generation. A very simple reaction process is used to synthesize the catalyst. Especially, oxidized carbon nanotubes are used for uniform anchoring of iron oxide nanoparticles on the surface of oxidized carbon nanotubes and achieved successfully using modified technique under nitrogen condition. Instead of neat carbon nanotubes, the oxidized carbon nano tubes containing oxidized functional groups help to produce additional interaction with the iron precursor, which eventually leads to uniform distribution of iron oxide nanoparticles on oxidized carbon nanotubes. The prepared catalysts are then characterized by using modern analytical and spectroscopic techniques. Subsequently, the catalytic activity of prepared catalysts is determined in hydrogen generation via hydrolysis of sodium borohydride. The catalyst (0.037 g) demonstrated high catalytic activity towards hydrogen generation reaction and produced 1368 mL of hydrogen in just 140 min reaction time at room temperature. The catalyst not only shows high efficiency but also reveals lower activation energy of 15.92 kJ mol−1 compared to literature reported values. Meanwhile, the effect of various parameters such as temperature, catalyst loading, effect of base and the effect of reducing agent concentration are also determined. After the reaction, magnetically separated catalyst is tested for its recyclability. The catalyst can be recycled up to five successive cycles without significant loss in yield, morphology and physiochemical property.

Hydrolysis of NaBH4 is a promising solution for on-site hydrogen energy generation. In the present paper, we report the preparation of hollow composite microcapsules made from sulfonic acid functionalized polyvinyl alcohol (SPVA) using simple chemical reaction followed by the addition of PVDF and applied for the hydrogen generation by means of hydrolysis of NaBH4. To develop series of microcapsules different ratios of water and isopropanol solvent systems such as 90: 10, 80:20, 70:30, 60:40 and 50:50 were used and five types of composite microcapsules were prepared. The structure, morphology and properties of the prepared microcapsules were characterized with the assistance of various spectroscopic and analytical techniques. By employing prepared SPVA/PVDF hollow composite microcapsules as catalyst, hydrogen generation was studied by hydrolysis of NaBH4. Interestingly, SPVA/PVDF-Mcs-3 hollow composite microcapsules prepared using 70:30 ratio of water and isopropanol generated the highest amount of 570 mL hydrogen in 180 min at room temperature which can be attributed to the high porosity and less wall thickness. Additionally, various microcapsules and effect of different reaction parameters were also studied and discussed. The synthesized composite microcapsules have an imperative advantage of easy recovery and consecutive reusability for 10 cycles without destruction of activity and morphology. The fast kinetics, hydrogen generation efficiency and comparatively low activation energy (10.91 kJ mol−1) makes SPVA/PVDF composite microcapsules a promising candidate as catalyst for hydrogen generation by hydrolysis of NaBH4.

The growing pursuit of the viable application of γ-butyrolactone (GBL) as an industrially important product offers the possibility to use 1,4-butanediol (1,4-BDO) as a potential reactant. In this regard, different proportions of copper-based ceria catalysts (5, 10, 15, and 20CC) were synthesized using a wet impregnation method and their catalytic activities were tested for the vapour phase dehydrogenation of 1,4-BDO to GBL at temperatures from 240–300 °C. The synthesized copper-based ceria catalysts (5CC, 10CC, 15CC, and 20CC) were characterized using various analytical tools and the consequent results revealed that the activities of the CC catalysts were influenced by the physicochemical properties of the materials. In order to determine the influence of various supports on the catalytic activity, the addition of 10 wt% copper (Cu) to TiO2, Al2O3, ZnO, ZSM-5, and SBA-15 supports was carried out, and the respective influence on the catalytic activity was also experimentally established. The most outstanding catalytic activity was seen for the 10 wt% copper-based ceria catalyst, with a high conversion of 93% and selectivity of 98% at 240 °C. Factors like a high surface area, and better dispersion and basicity of active sites had a marked impact on the catalytic activity. Mechanistic analysis suggested that 1,4-BDO undergoes dehydrogenation over the copper surface to give 4-hydroxybutanal, followed by hemiacetylation and subsequent dehydrogenation to give GBL as the selective product. In terms of the stability of the catalysts, the 10 wt% copper-based ceria catalyst maintained a stable GBL selectivity of 98% for up to 7 h on-stream.

The present work demonstrates the chemical fixation of CO2 for the synthesis of organic carbonates using mesoporous hollow marigold CuCo2O4 spinel microspheres as a catalyst prepared using the solvothermal method. The synthesized microspheres were characterized using contemporary analytical and spectroscopic tools. The CuCo2O4 spinel microspheres with the best morphological behaviour obtained after solvothermal treatment for 3 h were employed as a heterogeneous catalyst for the solvent-free conversion of epoxides and CO2 to generate cyclic carbonates. As a result, the model reaction of styrene oxide and CO2 revealed 94% conversion, 88% yield and 94% selectivity towards styrene carbonate in the presence of TBAI as a base under mild reaction conditions (80 °C, 20 bar, 3 h). Notably, the enhanced catalytic activity was attributed to the cooperative effect of the exposed Lewis acidic sites of CuCo2O4 and the efficient basic nature of TBAI. The effects of different reaction variables such as catalyst loading, temperature, pressure and time were investigated and discussed. Additionally, the effect of different bases was also experimentally determined. Further, the substrate scope using the CuCo2O4 and TBAI catalytic system revealed good performance towards CO2 fixation with a variety of terminal and internal epoxides. The catalyst was easily separated out after the reaction and tested for its recyclability. Results showed good recyclability up to five cycles without a substantial loss of catalytic activity. Based on the results obtained from XPS, XRD, and TPD and the available literature, an effort to predict a plausible mechanism was made in order to support the cycloaddition reaction. The present protocol is the first report of hollow marigold CuCo2O4 spinel microspheres as an outstanding and efficient catalyst with high selectivity towards fixation of CO2 into epoxides for cyclic carbonate formation.

Catalytic hydrolysis of sodium borohydride can potentially be considered as a convenient and safe method to generate hydrogen, an environmentally clean and sustainable fuel for the future. The present effort establishes the development of FeCuCo tri-metallic oxide catalyst by a simple, single-step solution combustion synthesis (SCS) method for hydrogen generation from NaBH

Catalytic hydrolysis of sodium borohydride can potentially be considered as a convenient and safe method to generate hydrogen, an environmentally clean and sustainable fuel for the future. The present effort establishes the development of FeCuCo tri-metallic oxide catalyst by a simple, single-step solution combustion synthesis (SCS) method for hydrogen generation from NaBH4 hydrolysis. Amongst series of FeCuCo tri-metallic oxide catalyst synthesized, FeCuCo with 50:37.5:12.5 wt% respective precursor loading displayed remarkable activity by generating hydrogen at the rate of 1380 mL min−1 g−1 (1242 mL in 18 min) with turnover frequency (TOF) of 62.02 mol g−1 min−1. The catalyst was characterized by using various techniques to understand their physiochemical and morphological properties. The results revealed that the catalyst synthesized by combustion method led to the formation of FeCuCo with appreciable surface area, porous foam-like morphology and high surface acidity. Major factors affecting the hydrolysis of NaBH4 such as catalyst loading, NaOH concentration and temperature variation were studied in detail. Additionally, the FeCuCo catalyst also displayed substantial recyclability performance up to eight cycles without considerable loss in its catalytic activity. Therefore, FeCuCo oxide can be demonstrated as one of the most efficient, cost effective tri-metallic catalyst so far for application in the hydrogen generation.

The present work demonstrates basicity controlled MgCo2O4 spinel oxides as promising catalysts for fixation of CO2 into epoxides at atmospheric pressure. Four different MgCo2O4 nanostructures were synthesized using different interlayer anions (chloride, nitrate, acetate, sulphate) present in the metal salt precursors which strongly altered their basicity and played a stimulating role in their catalytic efficiency. The characterization results of all four MgCo2O4 nanostructures revealed effect on morphology, surface area and developed diversely exposed Lewis basic (O2−) sites on the catalyst surface. Particularly, [MgCo2O4]-[Cl−] nanostructures prepared using chloride (Cl−) anion showed porous 3D-flower morphology with high pore diameter and highly exposed basic sites. Catalytic activity studies revealed that [MgCo2O4]-[Cl−] catalyst in presence of base, exhibited 95% conversion of styrene oxide and 96% selectivity towards styrene carbonate at atmospheric pressure. The enhanced activity of [MgCo2O4]-[Cl−] was due to the relatively smaller size of Cl− anion which replaced the hydroxyl groups in the Brucite-like structure and exposed maximum number of basic (O2−) sites during the thermal decomposition of the Mg-Co DH-[Cl−] precursor. Additionally, various reaction parameters were investigated to optimize reaction conditions. The obtained results with [MgCo2O4]-[Cl−] and base suggested that this catalytic system showed good tolerance for a broad substrate scope in good yields and demonstrated good reusability with retention in activity and physicochemical properties for eight recycles. A plausible mechanism was proposed to support the activation of epoxide and CO2 by the unique cooperation of active Lewis acidic and basic sites present in [MgCo2O4]-[Cl−] for formation of cyclic carbonates at atmospheric pressure.

Mesoporous copper based ceria-alumina catalysts prepared by wet impregnation method were used for dehydrogenation of 1,4-butanediol to γ-butyrolactone. The reaction was carried out under vapour phase conditions in the temperature range of 240–300 °C. The better activity results observed using 10 wt% copper supported over ceria-alumina (75:25) catalyst wherein 1,4-butanediol showed a conversion of 100% and selectivity towards γ-butyrolactone was 99% at 240 °C. The activity was due to synergistic effect of alumina and ceria support along with the presence of highly basic sites and other physico-chemical properties. In terms of stability, the catalyst is stable activity upto 24 h.