Current Catalysis - Volume 7, Issue 2, 2018

Background: The role of nanocatalysts holds its wide range of applications in chemical synthesis. Application of nanocatalysts in multicomponent reactions (MCRs) increases the sustainability of processes. Reaction in which three or more reactants combine together to generate desired product without the generation and isolation of any intermediate is known as multi-component reactions. MCRs recently recognized as green, efficient and atom economic process for organic transformation. Nanocatalysts show great potential to catalyzed MCRs in recent few years. Objective: MCRs with classical catalysts violets one or more of the twelve green chemistry principle's but with nanocatalysts MCRs become green to greener processes and follows majority of green chemistry principles. Thus, nanocatalyzed MCRs follow a set of concepts of green chemistry and are able to solve the fundamental challenges of sustainable development to protect human health and environment. Copper based nanomaterials due to its eco-friendly and inexpensive nature, gain much more attention in nanocatalysis research worldwide. Thus, main objective of this article is to explore the potential of various copper based nanocatalysts in MCRs. Conclusion: Present review, reviewed the recent development in chemistry of copper based nanomaterials and their catalytic applications in multi-component reactions and found that various types of Cu-and Cu-based nanoparticles such as Cu-NPs, Cu-oxide NPs, supported Cu-NPs, etc., catalyze the various MCRs at very large extent. Copper nanocatalysts have various advantages over other metal nanocatalysts in terms of short time period, high yield, selectivity, easy and simple work-up-procedure, safe and reusability in most of cases.

Introduction: Sustainable hydrogen production via the catalytic steam reforming (SR) of acetic acid, that is one of the main constituents of the bio-oil, is attracting wide attention and much work is being devoted to the development of always more active catalysts. In the very first studies, noble metal-based catalysts were extensively employed but their cost has made Ni-based systems far more attractive, although the latter are more prone to coking and methane production. Importantly, recent theoretical works have shed light on the overall reaction network, unveiling the most crucial steps/intermediates involved in both the hydrogen generation and coke formation, which remains a major problem to overcome. Despite its importance, also reflected by the growing number of publications, there are few reports specifically dedicated to the acetic acid steam reforming, and comprehensive presentations of the reaction mechanism are still quite elusive. Conclusion: Hence, in this review, we present the latest catalysts developed on the catalytic steam reforming of acetic acid, along with detailed discussions on the strategies adopted to improve their performances, in particular as far as the active phase stabilization against sintering. The reaction mechanisms will be discussed as well, in hopes of providing helpful insight into the design of highly performing catalysts for sustainable hydrogen production from acetic acid and, possibly, from real bio-oil.

Introduction: The photocatalytic degradation of dyes has been investigated throughout the world irrespective of the level of science in that country. The normal variables considered are the concentration of oxidising species, the concentration of the dye employed, the catalyst used and intensity and source of photons applied for degradation studies. The kinetic data obtained on the decolorization have usually been treated with pseudo first order kinetic expression even there are some exceptions. Conclusion: This presentation addresses the limitations of the consideration of this topic under these experimental parameters and shows how the study can be directed in future.

Background: Oxidative desulfurization of fuel oils has attracted much attention in recent years. Ti-containing microporous zeolites exhibited good reactivity in oxidative desulfurization of thiophene with small molecular size. However, they were almost not active in oxidative desulfurization of sulfur compounds with relatively large molecular size mainly due to the inaccessibility of active sites located in micropores. To remedy this shortage, it has been of great interest to synthesize Ti-containing hierarchical zeolites by the introduction of additional mesopores or/and macropores. The aim of this work is to improve the catalytic performance of Ti-containing zeolite Y in oxidative desulfurization of sulfur compounds with relatively large molecular size by synthesizing Ti-containing hierarchical zeolite Y. Methods: The hierarchical zeolite Y was firstly synthesized by post-treatment method. Then, Ticontaining hierarchical zeolite Y with different Ti contents was prepared by wet impregnation technique. Results: The catalytic performance of catalysts was evaluated by oxidative desulfurization of dibenzothiophene. Ti-containing hierarchical zeolite Y with 30% Ti content exhibited superior catalytic activity. Conclusion: Ti-containing hierarchical zeolite Y with more active sites and relatively large mesopore volume exhibited superior catalytic performance. The removal efficiency of DBT over this catalyst with 30% Ti content reached 97% after a reaction time of 120 min at 323 K. Accordingly, the sulfur content in model fuel was reduced from 1000 ppm to 30 ppm. Such catalyst has potential applications for ODS of fuel oils due to richly accessible active sites and low preparation cost.

Background: Ruthenium catalysts supported over various carbon materials differing in the nanostructure, grade of graphitization and surface area values have been synthesized and used in the hydrogenation of levulinic acid (LA), biomass platform molecule, in aqueous media. Methods: The prepared Ru catalysts were characterized by temperature programmed reduction (TPR), transmission electron microscopy (TEM) and CO chemisorption coupled with microcalorimetry. The reduced catalysts were studied in a batch reactor and in continuous-flow reactors at 100ºC under 40-50 bar hydrogen pressure for the hydrogenation of LA. Results: A linear correlation between turnover frequency (TOF) for LA conversion and Ru particle size was found in the 1.2-2.9 nm range. TOF increasing with the decreasing Ru particle size, which suggests hydrogenation of LA is a structure-sensitive reaction on Ru nanoparticles. Reduced graphite oxide (rGO) supported Ru catalyst with the lowest metal particle size (1.2 nm) also showed high activity at ambient temperature. Remarkably, this catalyst also displayed high stability in a continuous-flow reactor at 40 bar hydrogen and 100ºC. Conclusion: The improved catalytic performance (activity, selectivity and stability) of the carbon supported Ru catalyst (Ru/rGO-700 sample) for the LA hydrogenation reaction is attributed to the low metal particle size (1.2 nm) obtained over the high surface area and non-acidic rGO-750 carbon support.

Background: In the search of new catalysts for conversion of heavy naphtha fraction (C9+) into high octane number gasoline, metal modified ZSM-5 catalysts were investigated. The result revealed that modification ZSM-5 with metals (Ni, Fe, Zn) increased the C9+ fraction conversion and reduced the gas formation. In addition, hydrogen yield has increased the presence of Ni in the catalysts, whereas the number was reduced with other metals modification. Moreover, metal modified catalysts effectively prevented coke formation. Characterization studies (BET, XRD, TPR, TPD) results elucidated the effects of metals on catalytic performance. All the prepared catalysts possessed similar specific surface areas, thus the tuning of metallic sites was decisive for good catalyst performance. The combination of metallic sites (e.g. Ni) and acidic sites, supports all necessary reactions (e.g. cracking, aromatization, cyclization, alkylation, dehydrogenation, H-transfer) and thus helps to increase both heavy fraction conversion and reduces the coke formation. The finding might provide potential strategies for naphtha cracking. Methods: Modified ZSM-5 catalysts with different metals were synthesized by hydrothermal crystallization method using TPABr (Sigma Aldrich) as a template. The prepared catalysts were evaluated for catalytic cracking of C9+ fraction of Vietnamese naphtha using a fully automated standardized Single Receiver – Short Contact Time - Microactivity Test. Then, catalysts characterization and catalytic performance were evaluated in order to verify the hypothesis and find out the useful strategies. Results: In the present study, we reported an effective catalyst for cracking of heavy fraction of Vietnamese naphtha (C9+ fraction). The combination of metallic sites and acidic sites not only increase the conversion of heavy fraction into lighter fraction but also increase olefins and aromatics fraction in the gasoline. In addition, the modification with metals, especially with Ni would reduce the acidic sites of the modified catalyst and thus strongly prevent coke formation. Conclusion: These findings might provide some valuable strategies for the development of effective catalysts for naphtha cracking and further uses reforming reaction in the simultaneous cracking and reforming. Such tests are now in progress.

Background: Various solid acid catalysts are reported in the literature for the synthesis of heterocycles. In present work, we have explored new metal free acid catalyst for the synthesis of 1, 8- dioxo-octahydroxanthenes and 1, 8-dioxo-decahydroacridines under solvent free conditions. Methods: In present manuscript, we have synthesized cellulose perchloric acid (CPA) catalyst by the addition of perchloric acid to cellulose dispersed in n-hexane by the reported procedure and explored further for the said syntheses. Results: This methodology, efficiently constructs xanthenes and acridine derivatives in moderate to excellent yields. The developed protocol features environmental friendliness, short reaction times, wider substrate compatibility with and easy operation. The catalyst was effectively recycled up to five consecutive cycles without significant loss in its catalytic activity. Conclusion: We have developed an efficient, heterogeneous and recyclable catalytic system for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines and their yields are comparable with the literature. The different aldehydes with dimedone give good to excellent yields of desired products demonstrating broad application of the methodology. The catalyst cellulose-perchloric acid (CPA) was found to be recycled for five consecutive cycles without any significant loss in catalytic activity. The catalyst CPA found best among other acid catalysts under studied parameters. The simplicity, low cost and short reaction time and solvent-free conditions make the protocol greener and interesting.

Background: To meet the rising demand for energy at the same time reducing environmental pollution, electrochemical energy synthesis through development of efficient high energetic battery is the need of the hour. The present investigation attempts to develop a new Al ion rechargeable battery by making cathode and anode more electro catalytic. Methods: The electrode Al was replaced by a modified Al-Ni electrode and graphite by Nano graphite. The base electrolyte AlCl3 was modified by adding additives such as NaCl, InCl3 and HgCl2. The electrochemical characterization of the electrodes was carried out by Cyclic Voltammetry (CV), Chronoamperometry (CA) and potentiodynamic (Pd), while the constituents and morphology of the electrodes surface were examined by XRD and Electron microscopy. Results: It was found that Nano graphite powder produced more current and energy compared to solid graphite electrode. Al coated with Ni performed better than pure Al electrode, giving higher current during electro oxidation. The effect of electrolyte additives, NaCl, InCl3, HgCl2 , made the polarization resistance lower and increased current produced from the cell. An electrolyte composition of an electrolyte composition of 0.075M AlCl3 + 2M NaCl+ 4M InCl3 +5M HgCl2 produced the highest current and energy. The effect of electrode modification by Al-Ni electrode or nano graphite electrode as well as additives in the electrolyte system had steadily increased the reversible cell current from a few μA/cm2 to over 300 mA/cm2. Conclusion: The present investigation of developing a high energetic Al – Nano graphite rechargeable battery with modified electrolyte system was successful. The current produced from the cell for a 100 cm2 electrode surface area was over 20 amps.