Hydrogenolysis of ethylene glycol to methanol over modified RANEY® catalysts.

There is tremendous growing interest in utilizing biomass molecules for energy provision due to their carbon neutrality. Here, we employ ethylene glycol as a model compound for catalytic activation, which represents a basic unit for complex carbohydrate molecules (polyols). In this paper, hydrogenolysis of ethylene glycol to produce methanol in hydrogen over modified RANEY® Ni and Cu catalysts has been studied. This work provides essential information that may leads to the development of new catalysts for carbohydrate activation to methanol, a novel but important reaction concerning biomass conversion to transportable form of energy. Particularly, in this study, modification of electronic structure hence adsorption properties of RANEY® catalysts has mainly been achieved by blending with second metal(s). It is found that the activity and selectivity of this reaction can be significantly affected by this approach. In contrast, there is no subtle effect on methanol selectivity despite a great variation in the d-band centre position which shows a distinctive effect on other products. This result suggests that methanol is produced on specific surface sites independent from the other sites at an intrinsic rate and will not be converted to other products by the d-band alteration.

Continuous hot pressurized solvent extraction of 1,1-diphenyl-2-picrylhydrazyl free radical scavenging compounds from Taiwan yams (Dioscorea alata).

This study investigates a semicontinuous hot pressurized fluid extraction process and the scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical of the extract from Taiwan yams (Dioscorea alata). Liquid-liquid extractions were preliminarily employed to generate six fractions, initially extracted by ethanol. Then, the aqueous solution of dried crude ethanol extract was sequentially fractionated by hexane, chloroform, ethyl acetate, and n-butanol. The EC50 value was defined as the UV absorption of DPPH concentrations sufficiently decreased to 50% of the original value. It was found that all peel portions have a better effect on scavenging of the DPPH free radical than meat portions, especially for the ethyl acetate partition of the peel portion of Tainung #2 yam. Its EC50 value (14.5 microg mL(-1)) was even lower than that of ascorbic acid (21.4 microg mL(-1)). Furthermore, semicontinuous hot pressurized ethanol was superior to hot pressurized water in extracting the compound scavenging the DPPH radical from the Purpurea-Roxb peel. The recovery of four unknown compounds corresponded to the scavenging ratio of DPPH free radical in the hot pressurized ethanol extract. Finally, three-level and four-factor experimental design revealed that ethanol ratio and temperature were the most effective factors in order. Conditions of 80% of aqueous ethanol, 20.0 kg/kg solid ratio, 180 psig (1.342 MPa), and 100 degrees C were preferred to extract those antioxidants from the yam peel.

A non-syn-gas catalytic route to methanol production.

Methanol is an important platform molecule for chemical synthesis and its high energy density also renders it a good candidate as a cleaner transportation fuel. At present, methanol is manufactured from natural gas via the indirect syn-gas route. Here we show that ethylene glycol, a versatile chemical derived from biomass or fossil fuels, can be directly converted to methanol in hydrogen with high selectivity over a Pd/Fe(2)O(3) co-precipitated catalyst. This opens up a possibility for diversification in natural resources for energy-starved countries. The working catalyst contains extremely small 'PdFe' clusters and metal adatoms on defective iron oxide to give the required metal-support interaction for the novel synthesis.

Detection of nicotine based on molecularly imprinted TiO2-modified electrodes.

Amperometric detection of nicotine (NIC) was carried out on a titanium dioxide (TiO(2))/poly(3,4-ethylenedioxythiophene) (PEDOT)-modified electrode by a molecular imprinting technique. In order to improve the conductivity of the substrate, PEDOT was coated onto the sintered electrode by in situ electrochemical polymerization of the monomer. The sensing potential of the NIC-imprinted TiO(2) electrode (ITO/TiO(2)[NIC]/PEDOT) in a phosphate-buffered saline (PBS) solution (pH 7.4) containing 0.1M KCl was determined to be 0.88 V (vs. Ag/AgCl/saturated KCl). The linear detection range for NIC oxidation on the so-called ITO/TiO(2)[NIC]/PEDOT electrode was 0-5mM, with a sensitivity and limit of detection of 31.35 microA mM(-1)cm(-2) and 4.9 microM, respectively. When comparing with the performance of the non-imprinted one, the sensitivity ratio was about 1.24. The sensitivity enhancement was attributed to the increase in the electroactive area of the imprinted electrode. The at-rest stability of the ITO/TiO(2)[NIC]/PEDOT electrode was tested over a period of 3 days. The current response remained about 85% of its initial value at the end of 2 days. The ITO/TiO(2)[NIC]/PEDOT electrode showed reasonably good selectivity in distinguishing NIC from its major interferent, (-)-cotinine (COT). Moreover, scanning electrochemical microscopy (SECM) was employed to elucidate the surface morphology of the imprinted and non-imprinted electrodes using Fe(CN)(6)(3-)/Fe(CN)(6)(4-) as a redox probe on a platinum tip. The imprinted electrode was further characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).

Fabrication of a molecularly imprinted polymer sensor by self-assembling monolayer/mediator system.

Detection of dopamine (DA) by using a molecularly imprinted polymer (MIP) which fabricated by the self-assembling monolayer (SAM)/mediator system was studied. The SAM was made by attaching thioglycolic acid (TGA) on a gold electrode and quercetin (Q) was selected as an electron transfer mediator in this system. Methyl methacrylate (MMA) was polymerized by photopolymerization with the addition of dopamine to form a MIP electrode. The MIP and non-MIP (NMIP) modified electrodes were identified by FTIR and scanning electrochemical microscopy (SECM) approach curves. DA was detected by an amperometric method at a constant potential of 0.45 V and obtained a sensitivity of 0.445 mA cm(-2) M(-1). The imprinting efficiency approaches infinity due to a non-reactive surface of NMIP. In the interference test, ascorbic acid contributed less than 12% of current response in the coexistence solution with DA and the performance is highly related to the concentration of template added during the fabrication process.