Hydrogen generation from methanolysis of sodium borohydride over Co/Al_2O_3 catalyst

Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride （NaBH 4） for hydrogen generation.At solution temperature of 0 C,the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate,which makes it suitable for applications under the circumstance of low environmental temperature.The byproduct of methanolysis reaction is analyzed by X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FTIR）.The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct,NaB（OCH 3） 4.The catalytic activity of Co/Al2O3 towards NaBH 4 methanolysis can be further improved by appropriate calcination treatment.The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.

Reductive amination of aldehydes and ketones using sodium borohydride in the presence of silica chloride under solvent-free conditions

A simple and convenient procedure for the preparation of amines from aldehydes and ketones with sodium borohydride activated by silica chloride as a catalyst under solvent-free conditions is described.A variety of aliphatic and aromatic aldehydes,ketones and amines when mixed with NaBH;/silica chloride at room temperature,afforded excellent yield of the corresponding amines.

Oxalic Acid Promoted Hydrolysis of Sodium Borohydride for Transition Metal Free Hydrogen Generation

We reported an inexpensive and high-efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt%based on all the reactants can be achieved with excellent hydrogen generation kinetics.

Oxalic Acid Promoted Hydrolysis of Sodium Borohydride for Transition Metal Free Hydrogen Generation

We reported a low cost,high efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt% based on all the reactants can be achieved with excellent hydrogen generation kinetics.

The Unexpected Reductive Products of δ-Alkoxyenal by Sodium Borohydride in Methanol with A Trace of Magnesium Methoxide

Reduction of d-alkoxy enal 1 and 4 by sodium borohydride in methanol with a catalytic amount of magnesium methoxide gave unexpected methoxylated poducts 3 and 6 respectively.

THE UNUSUAL REDUCTION OF SOME AROMATIC ALDEHYDES BY SODIUM BOROHYDRIDE

Two aromatic aldehydes are found to be reduced by an unusual way by sodium borohydride in the presence of water to yield the corresponding methyl substituted aryl compounds.

Chemoselective Reduction of Fenofibric Acid to Alcohol in the Presence of Ketone by Mixed Anhydride and Sodium Borohydride

A highly efficient and facile protocol for the selective reduction of carboxylic acid of Fenofibric acid to corresponding alcohol was developed. The selective reduction was carried out by activation of carboxylic acid by mixed anhydride followed by the reaction of sodium borohydride in presence of methanol. This is the first example of chemoselective reduction of carboxylic acid to alcohol in presence of a ketone without any external catalyst or ligand in a single step. The reaction offers wide applicability for the selective carboxylic group reduction methodology. The chemoselective reduction was demonstrated by the reduction of Fenofibric acid, an active metabolite of the drug Fenofibrate, to corresponding alcohol in excellent selectivity, yield, and purity.

TELLURIUM-CATALYZED DEPROTECTI ON OF ARYL CHLOROACTATES BY SODIUM BOROHYDRIDE

In the presence of catalytic amounts of tellurium,aryl chloro- acetates can be cleaved by sodium borohydride and regenerate parent phen- ols in good yields.

Cotton stalk activated carbon-supported Co-Ce-B nanoparticles as efficient catalysts for hydrogen generation through hydrolysis of sodium borohydride

Porous cotton stalk activated carbons(CSAC)were prepared by phosphoric acid activation of cotton stalks in a fluidized bed.The CSAC-supported Co-B and Co-Ce-B catalysts were prepared by the impregnation-chemical reduction method.The samples were characterized by the nitrogen adsorption,XRD,FTIR and TEM measurements.The effects of the sodium borohydride(NaBH_(4))and sodium hydroxide(NaOH)concentrations,reaction temperature and recyclability on the rate of NaBH_(4)hydrolysis over the CSAC-supported Co-Ce-B catalysts were systematically investigated.The results showed that the agglomeration of the Co-Ce-B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium.The CSAC-supported Co-Ce-B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min^(−1)g^(−1)Co at 25℃,which is higher than the most reported cobalt-based catalysts.The catalytic hydrolysis of NaBH_(4)was zero order with respect to the NaBH_(4)concentration,and the hydrogen generation rate decreased with the increase in the NaOH concentration.The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol^(−1).A kinetic rate equation was also proposed.

Ultrafast room-temperature reduction of graphene oxide by sodium borohydride,sodium molybdate and hydrochloric acid

Since graphene-based materials have shown great potential in many fields,it is important to explore ultrafast and high-efficient methods to synthesize reduced graphene oxide(rGO) using inexpensive reducing agents under mild conditions.Here,we reported a novel method for the ultrafast chemical reduction of graphene oxide(GO) at room temperature using sodium borohydride(NaBH_(4)),sodium molybdate(Na_(2)MoO_(4)) and hydrochloric acid(HCl).The reduction was carried out within 2 min.A series of characterization results revealed that the obtained reduced graphene oxide has higher reduction degree than that synthesized by NaBH_(4) alone at high temperature.Moreover,rGO electrode based on the present reducing method exhibited a superior specific capacitance of 139.8 F/g at a current density of1 A/g,indicating that it can be used as electrode materials for supercapacitors.

The mechanism of unexpected reduction of dimethyl pyridine-2,3-dicarboxylate to l,2,3,4-tetrahydrofuro[3,4-b]-pyridin-5(7H)-one with sodium borohydride

An unexpected reduction of dimethyl pyridine-2,3-dicarboxylate to 1,2,3,4-tetrahydrofuro[3,4-b]pyridin-5（7H）-one with sodium borohydride in ethanol and tetrahydrofuran, respectively, is described, a hypothetic mechanism for the unusual reductive product is proposed.

A Facile Route to Phosphanylborohydrides:Synthesis, Crystal Structure and Spectroscopic Properties of 1,2-Bis(Diphenylphosphinoborane)Ethane

A novel and simple synthetic way using NaBH4 in the mixure of H2O-THF was applied to prepare 1,2-bis(diphenylphosphinoborane)ethane, dppe(BH3)2, in high yield and purity. The phosphanylborohydride compound dppe(BH3)2 was isolated in the form of colorless crystals and characterized by single crystal X-ray diffraction, 1H, 13C, 31P and 11B NMR spectroscopy. Prismatic colorless crystals of dppe(BH3)2 were obtained in monoclinic crystal system and space group P21 with two asymmetric units in the unit cell. Lattice parameters were: a = 11.657(2), b = 17.237(2), c = 12.764(2) ?, β = 98.735(14)°, 2535.0(7) ?

Ambient Ionic Liquids Used in the Reduction of Aldehydes and Ketones

The sodium borohydride reduction of aldehydes and ketones to corresponding alcohols has been accomplished via the use of ionic liquids. The alcohols are easily obtained with excellent yields and the ionic liquid BMImBF4 could be reused.

Immobilized silver nanoparticles on silica gel as an efficient catalyst in nitroarene reduction

Nanoparticles have properties that can be fine-tuned by their size as well as shape.Hence,there is significant current interest in preparing nano-materials of small size dispersity and to arrange them in close-packed aggregates.This letter describes a way of synthesising silver nanoparticles and their protection to aggregate by silica gel.The combination of catalytic quantities of immobilized silver nanoparticles with reductive ability of NaBH_4 efficiently reduces aromatic nitroarenes to the corresponding amines in aqueous medium.Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogen and carboxylic acid groups.The silver particles immobilized on silica gel are stable in the presence of oxygen for several months.

Practical reduction of imines by NaBH_4/alumina under solvent-free conditions:An efficient route to secondary amine

Sodium borohydride supported on alumina reduces imines to the corresponding secondary amines in high to excellent isolated yields under solvent-free conditions. Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogen, nitro, and cyano groups.

Direct reduction of some benzoic acids to alcohols via NaBH_4-Br_2

Direct reduction of seven benzoic acids to alcohols via sodium borohydride-bromine （NaBH4-Br2） reagent was developed. The isolated yields for the seven acids to reduce reached 60.6-90.1%. This new synthesis route has the advantages of simple of application, low cost, mild nature, and satisfactory yields.

Reduction of Aromatic Aldehydes and Ketones with Acyloxy Substituent at the Ortho-position by NaBH_4 in the Presence of Waters

An unusual reduction of some aromatic aldehydes and ketones by sodium borohydride was discovered.In a THF/H2O or DMSO/H2O solvent system the aromatic aldehydes and ketones with acyloxy substituent on the orthoposition to the carbonyl group can be reduced to the corresponding alkyl phenols.This unusual reduction is applicable also to the corresponding alcohols of all the above aldehydes and ketones.A putative mechanism was suggested.In addition to the above aldehydes,ketones and benzyl alcohols,certain 4acyloxybenzyl esters(probably also the 2substituted analogues)such as 4benzoyloxybenzyl benzoate was also found to be reduced to methylphenol by this unusual reduction.

Application of Liquid Nitrogen Cold Trap for Purification of Hydrogen Gas Stream Generated from NaBH4

The feasibility of using liquid nitrogen cold trap （LNCT） for the removal of water vapour and alkaline mist from the hydrogen gas stream which is generated from the catalytic and acidic decomposition of sodium borohydride is investigated. Practically, the target application is mobile fuel cells based on hydrogen production from storage in chemical hydrides. The LNCT would be used as a one step purification method with less cost and space requirements instead of applying the conventional purification techniques. Two catalysts were investigated for the production of hydrogen from the aqueous solution of NaBH4 in a small scale packed bed reaction column. The hydrogen generated from the catalytic decomposition of NaBH4 was accompanied by limited quantity of water vapour and alkaline mist. Nonetheless, higher quantities were generated when applying the acidic decomposition of NaBH4 and consequently the utilization of LNCT for H2 purification has proved useful and lead to a reduction in the content of these impurities; thereby the concentration of hydrogen in the outlet stream has increased.

Hydrogen production from hydrolysis of NaBH_(4) solution over Co-Fe-B@g-C_(3)N_(4)/NF thin film catalyst

In this study,the double loaded Co-Fe-B@g-C_(3)N_(4)/NF(NF:Ni foam)thin film catalysts were prepared for the first time via chemical deposition method at room temperature.By optimizing the reducing agent concentration to 0.9 mol·L^(-1),the as-obtained Co-Fe-B@g-C_(3)N_(4)/NF exhibited the twisted ribbon structure with more distinct three-dimensional hierarchy and the smaller particle size,showing the good catalytic property for the hydrolysis of NaBH_(4)solution.The H_(2)generation rate of Co-Fe-B@g-C_(3)N_(4)/NF and binary Co-B@g-C_(3)N_(4)/NF under visible light irradiation surpassed the value under natural condition.The apparent activation energy of Co-Fe-B@g-C_(3)N_(4)/NF(45.0 kJ·mol^(-1))under visible light irradiation was obviously reduced when compared with the natural condition(48.4 kJ·mol^(-1))and binary Co-B@g-C_(3)N_(4)/NF(60.6 kJ·mol^(-1))under visible light irradiation.Furthermore,the catalytic performance of the optimized Co-Fe-B@g-C_(3)N_(4)/NF thin film catalyst was superior to most of the reported non-noble metal and even noble metal catalysts.Hence,it illustrated that the catalytic H_(2)production performance of Co-Fe-B@g-C_(3)N_(4)/NF thin film was distinctly improved after the introduction of light and multicomponent recombination.

The formation and catalytic activity of silver nanoparticles in aqueous polyacrylate solutions

Silver nanoparticles （AgNPs） have been synthesized in the presence of polyacrylate through the reduction of silver nitrate by sodium borohydride in aqueous solution. The AgNO3 and polyacrylate carbox- ylate group concentrations were kept constant at 2.0× 10^-4 and 1.0 × 10^-2 mol·L^-1, respectively, while the ratio of [NaBH4]/[AgNO3] was varied from 1 to 100. The ultra- violet-visible plasmon resonance spectra of these solutions were found to vary with time prior to stabilizing after 27 d, consistent with changes of AgNP size and distribution within the polyacrylate ensemble occurring. These obser- vations, together with transmission electron microscopic results, show this rearrangement to be greatest among the samples at the lower ratios of [NaBH4]/[AgNO3] used in the preparation, whereas those at the higher ratios showed a more even distribution of smaller AgNP. All ten of the AgNP samples, upon a one thousand-fold dilution, catalyze the reduction of 4-nitrophenol to 4-aminophenol in the temperature range 283.2-303.2 K with a substantial induction time being observed at the lower temperatures.