Current Catalysis - Volume 5, Issue 2, 2016

Background: The conversion of carbon dioxide into worthwhile chemicals through photo-catalysis has been a matter of attraction for the last four decades among the scientific community. However, the conversion rate has not yet been achieved to the desired efficiency due to the inevitable barriers associated with the process making it as a Holy Grail. This presentation deals with the identification and critical evaluation of the hurdles that pulls back the photocatalytic processes on track and the recent advances in the scientific field that pertain to the photocatalytic conversion of carbon dioxide in the near future. Methods: We explored the content of more than 200 original research articles that are relevant to the desired topic and extracted the current knowledge on the so called photo-catalytic reduction of carbon dioxide. We have approached all the articles in a perspective way rather than a word to word recent advances in the field and found out the major limitations that have to be rectified. Results: The issues related to the state-of-the-art of carbon dioxide reduction are described in separate sections in detail. Mechanistic aspects should to be revisited with the help of advanced instrumentation facilities. Major problem associated is finding the appropriate material, hence efficient material should be engineered to overcome the high energy barrier associated with the reduction process. Product analysis as well as efficiency determination are highly susceptible to errors. It is very difficult to compare the work produced by any two labs between each other! Conclusion: There are so many hurdles associated invariably with the photocatalytic carbon dioxide reduction process which must be rectified in order to create an energy, sustainable society using direct sunlight as a primary energy source just as plants do. It could happen only by the collaborative research effort from various groups, irrespective of the implicit bias among the scientific community.

Background: Examples of alternate dynamics phenomenon observed in zeolites were listed. A special attention was paid to coke alternate dynamics phenomena in deactivated HZSM5 zeolite catalysts and shortcomings of its interpretation. Present investigation deals with a coke movement of different vectors observed in deactivated catalysts based on X faujasite. Methods: Two catalysts on the base of X zeolite by means of isomorphic partial substitution of aluminium atoms for silicon and ion exchange were synthesized. Catalysts were deactivated in isobutane with butenes alkylation in flow-circulating system and then were divided into three (catalyst 1) and two (catalyst 2) portions, which were aged for different time. Coke on samples obtained was subjected to investigation by the method of discrete-successive coke microoxidation. Results: Dynamics of coke microoxidation in the samples of catalysts was obtained. Differences in such dynamics for variously aged samples were treated as indicating the alternate movement of coke in zeolite structure. Conclusion: The interpretation of the nature of observed coke alternate movement was proposed. It bases on being of coke on the external surface of zeolite crystals by turn as continuous layer, which fully envelop the crystals, and as separate clusters. These states differ in chemical potential. Such difference is considered as the driving force of coke transformation from one form to another and thus a coke alternate movement in catalysts deactivated.

Background: Biodiesel is briefly defined as the monoalkyl esters of vegetable oils or animal fats. Biodiesel is the best candidate for diesel fuels in diesel engines as a "green chemistry" that has several advantages over conventional diesel. Giant polyoxometalates are nanoscale architectures with highest Euclidean symmetry, which gained signi#129;cant interest as cation carriers or nanosponges and for various other material science applications in the solid state. However, their catalytic properties in the esterification of FFAs really lag behind. In this work herein, we are reporting esterification of FFAs for biodiesel production in the presence of WPCu@ASMNP for the first time, in the presence of ethanol as a green solvent. Methods: Various free fatty acids, oleic, stearic and palmitic acid, were used for esterification. The catalyst (WPCu@ASMNP) is well characterized by various physicochemical techniques such as XRD, FT-IR, TGA¬, ICP-AES, TEM and SEM. Analyses of the reaction products were conducted using a gas chromatograph (GC). Ultrasonic irradiation enhanced the catalytic activity of this catalyst in esterification and this led to shorter reaction times and higher product yields. Results: The use of synthesized catalyst was explored for biodiesel production by esterification of free fatty acids (FFAs) with ethanol using ultrasound-assisted process was investigated. It was observed that the WPCu@ASMNP shows the highest catalytic activity on esterification of FFAs with ethanol. Influence of various reaction parameters (such as catalyst loading, acid/alcohol molar ratio, effect of ultrasonic irradiation power, reaction time and temperature) on the conversion were studied. The catalyst shows high activity in terms of conversion of oleic acid. The catalyst was recycled up to four times after simple work up without notable loss in the activity. Conclusion: Polyoxotungstate nanowheel, anchored to magnetic nanoparticles WPCu@ASMNP exhibits significant activity toward biodiesel production via esterification of free fatty acids under relatively mild condition. The catalyst was recycled up to four times after simple work up without notable loss in the activity. The FT-IR, XRD and leaching experiments after four successive cycles showed that the catalyst was most strongly anchored to the magnetite nanoparticles.It was no observed leaching in this system.

Background: Nickel-Boron amorphous alloys (catalysts) of various Ni:B ratio were synthesized and well characterized using XRD, ICP-AES, EDAX and IR spectroscopic technique. Among all the catalysts, Ni:B alloy catalyst with ratio 1:1 was found to effective for catalytic transfer hydrogenation reaction using hydrazine hydrate as a proton donor. The present work shows the effect of metalloid content and the presence of aniline over CTH of nitrobenzene. The present catalytic protocol was found effective for wide variety of substrates showing its efficacy. Methods: A typical catalytic transfer hydrogenation reaction of nitroaromatics using hydrazine hydrate was carried out in 2 necked, 25 ml round bottom flask in methanol. The progress of the reaction was monitored by the gas chromatography and products were further confirmed by GC-MS analysis. Nickel-Boron amorphous alloys (catalysts) were well characterized by XRD, SEM, EDX and ICP-AES analysis. Results: Among various compositions of Ni:B alloy catalysts, 1:1 ratio was found optimum for the CTH of nitrobenzene. It was observed that with increase in amount of nickel, catalytic activity for CTH decreases. Effect of aniline on reaction was evaluated by concentration versus time plot. Considerable induction period was observed in absence of aniline not in case of other bases like NaOH, KOH, Na2CO3, etc confirming role of aniline in CTH reaction. From the Arrhenius plot for the CTH of nitrobenzene, the Ea was found to be 23.636 KJ mol-1. The catalytic protocol was found robust and effective for various substituted nitroaromat.ics. Conclusion: Among various compositions obtained from ICP-AES analysis, the Ni:B alloy i.e. Ni62.71 B37.29 found to be the most efficient catalyst for the CTH of nitroaromatics over the other compositions. The catalyst found robust without changing its surface morphology after the reaction confirmed by SEM. Compared to reported catalytic system; this catalytic system is highly active and even worked with very low catalyst loading of 1 wt%. Apart from it we observed induction period for the said reaction and found that the presence of aniline hastens the rate of reaction. The system was widely applicable for the variety of substituted nitroaromatics which makes the system more interesting.

Background: There is considerable interest in using transition metal catalysts in place of rare and expensive precious metal catalysts in fixed bed catalysis. The use of hierarchically porous materials potentially provides a method of improving mass transport and decreasing sintering and metal particle growth that leads to decreased catalytic activity. Methods: Composites consisting of nickel nanoparticles incorporated in a hierarchically porous carbon monolith (NC/Ni), with varying Ni loading were synthesized by a one-pot, nanocasting pathway in which the carbon and nickel were produced in a single step, and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption for surface area determination, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy. Catalysis of the reduction of p-nitrophenol (p-NP) to p-aminophenol (p-AP) was carried out to evaluate the catalytic activity. Results: TEM and SEM images of the composites show well dispersed nanoparticles in the carbon matrix with small nanoparticles of about 4-12 nm located within the mesopores and larger nanoparticles (20-60 nm) located in the macropores. The nanoparticles were unevenly distributed on the mm scale within the monoliths. The surface area and the mesopore volume of the carbon decreased with increasing metal loading. XRD suggested the nanoparticles were metals at zero oxidation state but XPS showed the presence of Ni(OH)2. Raman spectra showed a significant increase in carbon ordering with increasing metal loading. The composites were found to be catalytically active for the reduction of p-NP and the intermediate p-quinoimine (p-QI) was identified by GC-MS. Conclusions: The one-pot nanocasting method is able to produce catalytically active hierarchically porous carbon monoliths incorporating nickel nanoparticles. However, the size and distribution of the nanoparticles is not yet well controlled.

Background: The development of novel synthetic methods for the preparation of structurally diverse drug-like molecules expeditiously and efficiently utilizing simple and readily available starting materials and easy experimental procedure with environmentally friendly solvent and catalyst is significant not only in the advancement of chemical research but also in the development of drug discovery research. Multicomponent reactions (MCR) are considered to be powerful and efficient synthetic methodology for building highly diverse complex organic molecules of biological relevance with high atom-economy, high selectivity, high purity and excellent yields. In the present research work, the synthetic potentialities of multicomponent reactions have been combined with the green chemistry to develop diversity oriented synthesis of structurally diverse spirooxindoles spiroannulated with benzo[a]xanthene, benzo[f]indanochromene, benzo[f]pyranochromene and benzo[f]chromenochromene with drug-like complexity and promising bioactivity. Method: Spirooxindoles spiroannulated with benzo[a]xanthene, benzo[f]indanochromene, benzo[f]pyranochromene and benzo[f]chromenochromene have been synthesized by the present synthetic protocol involving multicomponent reaction of substituted isatins, β-naphthol and 1,3-dicarbonyl compounds in aqueous ethanol [C2H5OH:H2O (v:v/1:5)] using TiO2 nanoparticles as recyclable and reusable environmentally benign catalyst. Results: We have presented an efficient and eco-compatible diversity oriented synthetic protocol for the synthesis of spirooxindoles spiroannulated with medicinally privileged heterocyclic substructures; benzo[a]xanthene, benzo[f]indanochromene, benzo[f]pyranochromene and benzo[f]chromenochromene in good to excellent yields using TiO2 nanoparticles as recyclable and reusable heterogeneous catalyst. TiO2 nanoparticles facilitate the reaction and play an important catalytic role with the involvement in the reaction mechanism. Conclusion: The potentialities of the waste-free synthetic protocol combined with recyclability and reusability of the catalyst make this method economic and environmentally benign for the synthesis of spiroheterocycles incorporating three-four medicinally privileged heterocyclic substructures. In addition, excellent yields, short reaction times, mild reaction conditions, avoiding hazardous organic solvents, and experimental simplicity with easy work-up are some interesting features of the present synthetic protocol which indicate novelty and synthetic utility of the present protocol to synthesize drug-like molecules with structural diversity and molecular complexity.