Grafted zeolites for the removal of metal cations from crude oil hydrotreatment extract

Surface-modified zeolite Y has been synthesised and studied for potential application as an adsorbent for the removal of metal cations from aqueous solutions. Zeolite Y was synthesised under hydrothermal conditions at 100 °C in an autoclave and characterised by elemental analysis and thermogravimetric analysis to determine the chemical formula of the host material as Na54.91Al56Si136O384.246.5H2O. 3-Aminopropyltriethoxysilane (APTES) grafted zeolite Y was prepared by first preparing proton-exchanged zeolite Y using an 0.1 M ammonium nitrate solution followed by calcination at 350 o C. The APTES ligand was then grafted onto the protonated zeolite using three different solvent media. CHN analysis, FTIR spectroscopy, SSNMR and TG analysis indicated that the ligand was bonded covalently to zeolite Y attaching onto the inorganic surface through the available silanol groups. CHN analysis showed that hexane was the most effective solvent for carrying out ligand grafting, as indicated by the highest proportion of carbon present in the product after removal of free solvent (5.08%). APTES grafted zeolite Y was exposed to aqueous solutions containing different concentrations of divalent nickel cations (0.01 M to 0.1 M). An increase to 73.8% Ni (II) removal compared to 18.1% uptake by the parent zeolite Y without any graft was observed when the concentration of nickel was 0.01 M. The selectivity study using a solution containing five different transition metal cations; Ni (II), V (IV), Cu (II), Zn (II), and Fe (II) to mimic the species most often observed in hydrotreatment extract from crude oil, showed proportional removals of 83.7%, 91.3%, 82.8%, 70.6% and 85.7% respectively. This study indicates that APTES modified zeolite Y could be a useful material for the removal of catalytic poisons in hydroprocessing solutions during the processing of heavier crude oils

Heterogeneous and homogenous catalysts for hydrogen generation by hydrolysis of aqueous sodium borohydride (NaBH4) solutions

It is clear that in order to satisfy global energy demands whilst maintaining sustainable levels of atmospheric greenhouse gases, alternative energy sources are required. Due to its high chemical energy density and the benign by-product of its combustion reactions, hydrogen is one of the most promising of these. However, methods of hydrogen storage such as gas compression or liquefaction are not suitable for portable or automotive applications due to their low hydrogen storage densities. Accordingly, much research activity has been focused on finding higher density hydrogen storage methods. One such method is to generate hydrogen via the hydrolysis of aqueous sodium borohydride (NaBH4) solutions, and this has been heavily studied since the turn of the century due to its high theoretical hydrogen storage capacity (10.8 wt%) and relatively safe operation in comparison to other chemical hydrides. This makes it very attractive for use as a hydrogen generator, in particular for portable applications. Major factors affecting the hydrolysis reaction of aqueous NaBH4 include the performance of the catalyst, reaction temperature, NaBH4 concentration, stabilizer concentration, and the volume of the reaction solution. Catalysts based on noble metals, in particular ruthenium (Ru) and platinum (Pt), have been shown to be particularly efficient at rapid generation of hydrogen from aqueous NaBH4 solutions. However, given the scarcity and expense of such metals, a transition metal-based catalyst would be a desirable alternative, and thus much work has been conducted using cobalt (Co) and nickel (Ni)-based materials to attempt to source a practical option. “Metal free” NaBH4 hydrolysis can also be achieved by the addition of aqueous acids such as hydrochloric acid (HCl) to solid NaBH4. This review summarizes the various catalysts which have been reported in the literature for the hydrolysis of NaBH4

Mössbauer characterisation of synthetic analogues of the helvite minerals Fe4M4[BeSiO4]6X2, (M=Fe, Mn, Zn; X=S, Se)

We report on this paper on the Mossbauer characterisation of the family of synthetic helvite analogues, Fe4M4[BeSiO4]6X2 (M = Fe, Mn, Zn; X = S, Se). The data show iron to be present as high spin Fe(II) in tetrahedral coordination. The room temperature Mossbauer spectra are composed either by singlets or doublets with small quadrupole splitting values suggesting a small valence contribution at that temperature. From the dependence of the quadrupole splitting with temperature the separation Δ between the two eg orbitals has been estimated. The values of Δ range from 46.3 cm− 1 for the material Fe8[BeSiO4]6S2 to 58.2 cm1 for the material Fe4Zn4[BeSiO4]6S2. The lack of long-range magnetic order observed in the Mossbauer spectra was confirmed by neutron diffraction data which suggests that the M4X units are largely magnetically isolated within their cages leading to a frustrated magnet with no long range interaction for the sulfide species

Metal and mixed-metal (oxy)-hydroxide ceramic precursor materials prepared by cathodically-induced precipitation using a hydrogen-sorbing palladium electrode

The electrochemical reduction of several metal and mixed-metal sulfate aqueous solutions at a palladium electrode has been studied. For magnesium, lanthanum, yttrium and scandium sulfates, metal (oxy)-hydroxide films are produced by cathodicallyinduced precipitation of the metal cations, following the local generation of hydroxide ions at the hydrogen-sorbing cathode. Mixed-metal (oxy)-hydroxide films are prepared from yttrium/lanthanum and yttrium/scandium sulfate solutions. For mixed yttrium/indium sulfate solutions, the amorphous yttrium/indium (oxy)-hydroxide films initially contain indium dendrites. On calcination, a metastable yttrium/indium oxide phase is observed between 600 – 1000°C, followed by the separation of the indium and yttrium oxides above 1000°C. No films are accessible from the sulfate solutions of electropositive metals such as sodium and potassium, where the corresponding metal oxides and hydroxides are highly soluble. Metals are electrodeposited from separate sulfate solutions of zinc, nickel and indium, in preference to the cathodically-induced precipitation of the metal (oxy)-hydroxide

Solid solution formation in the metatorbernite metazeunerite (Cu(UO2)2(PO4)2-x(AsO4)x.nH2O) and their stability under conditions of variable temperature

Mineral phases which can be thought of as members of a metatorbernite–metazeunerite solid solution (Cu(UO2)2(PO4)2−x(AsO4)x.8H2O have been identified in radioactive samples from spoil heaps at the uranium mine site in South Terras, Cornwall (grid reference SW935523). A complete solid solution (0 x a unit cell parameter according to Vegard's Law, allowing the composition of the natural mineral phases found at South Terras to be determined from measurement of their unit cell parameters. High-resolution variable-temperature synchrotron powder X-ray diffraction studies were carried out at the Diamond Light Source on three members of this solid solution (x = 0, 1, 2) and showed different structural behaviour as a function of composition and temperature. Metatorbenite (x = 0) retains its tetragonal symmetry at low temperatures and dehydrates to an amorphous phase at 473 K, whereas metazeunrite (x = 2) transforms to an orthorhombic phase at low temperatures, regains its tetragonal symmetry on heating to 323 K and undergoes a further transition to an, as yet, unidentified phase at 473 K.This article is part of the theme issue ‘Fifty years of synchrotron science: achievements and opportunities’.</p

Synthesis and structural characterisation of new ettringite and thaumasite type phases: Ca6[Ga(OH)6•12H2O]2(SO4)3•2H2O and Ca6[M(OH)6•12H2O]2(SO4)2(CO3)2, M = Mn, Sn

Investigations into the formation of new ettringite-type phases with a range of trivalent and tetravalent cations were carried out to further study the potential this structure type has to incorporate cations covering a range of ionic radii (0.53–0.69 Å). We report the synthesis and structural characterisation of a new ettringite-type phase, Ca6[Ga(OH)6•12H2O]2(SO4)3•2H2O, which was indexed in space group P31c with the unit cell parameters a = 11.202(2) Å, c = 21.797(3) Å and two new thaumasite-type phases Ca6[M(OH)6•12H2O]2(SO4)2(CO3)2, M = Mn, Sn which were indexed in space group P63 with the unit cell parameters a = 11.071(5) Å, c = 21.156(8) Å and a = 11.066(1) Å, c = 22.420(1) Å respectively. These new phases show the versatility of the ettringite family of structures to tolerate a large range of cation sizes on the octahedral M site and highlights the preference of tetravalent cations to crystallise with the thaumasite structure over the ettringite structure

Supplementary information files for An iron ore-based catalyst for producing hydrogen and metallurgical carbon via catalytic methane pyrolysis for decarbonisation of the steel industry

Supplementary files for article An iron ore-based catalyst for producing hydrogen and metallurgical carbon via catalytic methane pyrolysis for decarbonisation of the steel industry Experiments to investigate the catalytic pyrolysis of methane using an iron ore-based catalyst were carried out to optimize catalytic activity and examine the purity of the carbon produced from the process for the first time. Ball milling of the iron ore at 300 rpm for varying times – from 30 to 330 minutes – was studied to determine the effect of milling time on methane conversion. Optimal milling for 270 minutes led to a five-fold increase in methane conversion from ca. 1% to 5%. Further grinding resulted in a decline of methane conversion to 4% shown by SEM to correspond to an increase in particle size caused by agglomeration. Data from Raman and Mössbauer spectroscopy and H2 temperature programmed reduction indicated a change in phase from magnetite to maghemite and hematite (at the particle surface) as the grinding time increased. Analysis of the carbon produced as a byproduct of the reaction indicated a highly pure material with the potential to be used as an additive for steel production. </p

"Copper-in-charcoal" revisited: delineating the nature of the copper species and its role in catalysis

"Copper-in-charcoal" has been shown to be a versatile catalytic source of supported copper for a variety of important synthetic transformations, as well as in other fields such as energy. We herein report the characterization of this material and the implications that its preparation has on catalysis, thus providing a greater understanding of the scope and limitations of this catalyst system. (Chemical Equation Presented)

Synthesis of activated ferrosilicon-based microcomposites by ball milling and their hydrogen generation properties

Ferrosilicon was activated toward hydrogen generation by processing using ball milling. An activation energy of 62 kJ/mol was determined for the reaction of ball-milled ferrosilicon powder with sodium hydroxide solution, which is ca. 30 kJ/mol lower than that previously reported for unmilled ferrosilicon. A series of composite powders were prepared by ball milling ferrosilicon with various additives. Three different classes of additives were employed: salts, polymers and sugars. The effects of these additives on hydrogen generation from the reaction of ferrosilicon with 2 wt.% aqueous sodium hydroxide were investigated. It was found that composites formed of ferrosilicon and sodium chloride, potassium chloride, sodium polyacrylate, sodium polystyrene sulfonate-co-maleic acid or fructose showed reduced induction times for hydrogen generation compared to that observed for ferrosilicon alone, and all but fructose also led to an increase in the maximum hydrogen generation rate. In light of its low cost and toxicity and beneficial effects, sodium chloride is considered to be the most effective of these additives for activating ferrosilicon toward hydrogen generation

A simple, low-cost, and robust system to measure the volume of hydrogen evolved by chemical reactions with aqueous solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates