Iranian Journal of Catalysis
Volume:7 Issue: 2, Spring 2017

Microbial electrolysis cell (MEC) is a gripping bio-electrochemical device producing H2 gas from renewable biomass while at the same time treat wastewater. Through extensive global research efforts in the latest decade, the performance of MECs, including energy efficiency, hydrogen production rate (HPR), and hydrogen recovery have achieved significant breakthroughs. However, employing a low-cost, stable and high efficient cathode to replace platinum catalyzed cathode (Pt/C) is the greatest challenge for large-scale industrialization of MEC. Numerous studies have demonstrated that the performance of MEC directly depends on the kinetics of the anode and cathode reactions within the electrolysis cell, with the performance of the electrode catalyst highly affected by the materials they are made from. In a relatively short space of time, a wide range of electrode materials have been tested to amplify the performance of MECs, such as carbon-based electrode catalysts have emerged as promising electrode materials for both anode and cathode construction. Composite materials have also shown to have the potential to become materials of choice for electro-catalyst manufacture. More recently, various transition metal oxides and alloys have been extensively examined as alternatives to conventional expensive noble-metals like platinum for hydrogen evaluation reaction (HER) in MECs. Numerous studies have confirmed that stainless steel, Ni alloys, and Pd nanoparticle decorated cathode are worth mentioning and have very good efficiency. In the present article, we present a comprehensive review centered on the development of a low-cost and high efficient electrode materials and membrane to boost the performance of MECs, including anode, cathode, and membrane.

An efficient four-component synthesis of benzopyranopyridines is described by one-pot condensation of salicylaldehydes, thiols and 2 equiv of malononitrile with nano-PbWO4 as a robust and reusableheterogeneous catalyst under ultrasonic irradiation. Lead tungstate (PbWO4) nanostructures have been synthesized via a sonochemical method based on the reaction between lead (II) nitrate and sodium tungstate dihydrate in an aqueous solution. Some advantages of this protocol include use of simple and readily available starting materials, rapid assembly of medicinally privileged heterocyclic molecules, reusability of the catalyst, low amount of the catalyst and application of the sonochemical methodology as an efficient technique and innocuous means of activation in synthetic chemistry.

In this work the Origanum vulgare leaf extract was used to green synthesis of Ag nanoparticles (NPs) supported on Hazelnut shell as an environmentally benign support. The Ag NPs/Hazelnut shell as an effective catalyst was prepared through reduction of Ag ions using Origanum vulgare leaf extract as the reducing and capping agent and Ag NPs immobilization on Hazelnut shell surface in the absence of any stabilizer or surfactant. According to FT-IR analysis, the hydroxyl groups of phenolics in Origanum vulgare leaf extract as bio-reductant agents are directly responsible for the reduction of Ag ions and formation of Ag NPs. The as-prepared catalyst was characterized by Fourier transform infrared (FT-IR) and UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM) equipped with an energy dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD) and transmittance electron microscopy (TEM). The synthesized catalyst was used in the reduction of Methyl Orange (MO), and Congo Red (CR) at room temperature. The Ag/Hazelnut shell showed excellent catalytic activity in the reduction of these organic dyes. In addition, it was found that Ag/Hazelnut shell can be recovered and reused several times without significant loss of catalytic activity.

A simple and efficient procedure for the synthesis of 2-amino-3-cyanopyridines from aldehydes, ketones, malononitrile, and ammonium acetate via one-pot reaction is reported. Zinc zirconium phosphate (ZPZn) nanoparticles were used as a convenient and efficient catalyst for this multicomponent reaction (MCR) under solvent-free conditions, and fair to excellent yields were achieved. The catalyst was characterized by ICP-OES, XRD, NH3-TPD, Py-FTIR, N2 adsorption-desorption, SEM, and TEM. The steric and electronic properties of the different substrates had a significant influence on the reaction conditions. The catalyst was recovered and reused at least six times without any discernible decrease in its catalytic activity. This procedure tolerates most of the substrates and has the advantages of short reaction times, high yields, and environmentally friendly.

HMCM-22 with a Si:Al molar ratio of 15:1 has been shown to effectively catalyze the synthesis of acetals by the reaction of aldehydes with methanol under reflux conditions. Platelet HMCM-22 particles were prepared by static method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), BET techniques and N2-adsorption/desorption analysis. The catalyst was recovered by simple filtration and reused for several cycles without considerable loss of activity.

N-Methyl-Nʹ-propyltrimethoxysillylimidazolium chloride was prepared as ionic liquid (IL) containing silylating agent and then used for modification of the internal surface of SBA-15 to gain a heterogeneous ionic liquid catalyst. Subsequently, the obtained SBA-IL was characterized using various techniques, including SEM and TEM images, FT-IR, X-ray diffraction, TGA/DTA and BET analyses. It was found that the uniform SBA-15 particles, with a dimension of 400-800 nm, showed the decreasing in the pore volume, surface area, and pore diameter after modification process which is as a results of incorporating imidazole groups onto the pores of SBA-15. Afterward, catalytic activity of SBA-IL was investigated in the synthesis of 2,3-dihydroquinazolinones under solvent free condition.

An efficient route for the synthesis of dihydropyrano[2,3-g] chromenes via one-pot pseudo-five component cyclization reaction of an aldehyde, malononitrile and 2,5-dihydroxy-1,4-benzoquinone in the presence of an effective and mild catalytic system containing sodium phthalimide and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) ionic liquid (SPI/IL) was studied. The reaction products were characterized using 1H NMR, 13C NMR, FTIR, Mass spectroscopy and elemental analysis. Environmentally eco-friendly catalyst, clean reaction with easy work-up (through simple filtration) and high yield products with no more purification are the main merits of this protocol. Presented method can be used for the synthesis of mentioned products (with pharmacology and Biologic properties) in large scales.

The present study, for the first time, presents a feasible protocol for the preparation of β-cyclodextrin/ imidazolium based dicationic ionic liquid, [βCD/Im](OTs)2, and its application as an efficient and eco-friendly microvessel and host ionic liquid system for the regioselective ring opening of the epoxides in water. No evidence for the formation of diol by-products or side reactions, such as isomerization, epimerization and rearrangements was observed and 1,2-disubstituted products, β-azidoalcohols, β-cyanohydrins, and β-thiocyanohydrins, obtained in pure form. Short reaction time, easy reaction conditions, simple work-up procedure, high yield, reusability, and use of an eco-friendly catalyst are some of the striking features of the present protocol.

A novel hybrid catalyst based on grafting Cu on furfural imine-functionalized halloysite was designed, characterized and used for promoting synthesis of xanthene derivatives via three- component reaction of benzaldehyde derivatives, dimedone, and β-naphthol in aqueous media and under mild reaction condition. The results established high catalytic activity of the hybrid system, which was superior to some conventional catalysts. Moreover, the catalyst was reusable and could be easily recovered and reused for several reaction runs with slight loss of catalytic activity. Broad substrate scope, simple work up procedure and performing the process in aqueous media are other merits of this protocol.

Carbon catalyst consisting of a hybrid structure made up of amorphous carbon and nanographite was prepared from the leaves of Pinus Roxburghii. The catalyst was prepared through sodium hydroxide and hydrochloric acid treatment of the dried pine leaves; and further functionalized with sulfuric acid treatment to incorporate the acidic functionalities. The synthesized catalyst was characterized by FTIR, XRD, TEM and XPS spectroscopic techniques and used as a heterogeneous catalyst for C-N coupling reaction leading to pyrrole formation through the nucleophilic attack of nitrogen atom in amines or imines on the dicarbonyl compounds. The optimized method was explored on various 2,4- and 2,5- dicarbonyl compounds and it was found to afford the five member pyrrole nucleus is good to excellent yields. The scope of the reaction was demonstrated by synthesizing thirteen pyrrole derivatives that are well characterized by IR, NMR and mass spectrometry. The mechanism of the reaction was proposed and acidic sites present on the catalyst surface are believed to be the active sites in the conversion.