QENS shows that methanol is immobile in a fresh ZSM-5 catalyst and one used for methanol conversion at 623 K, but undergoes isotropic rotation within the mesopores generated in a catalyst used for methanol conversion at 673 K.

A ZSM-5 catalyst is examined in relation to the methanol-to-hydrocarbon (MTH) reaction as a function of reaction temperature and time-on-stream. The reaction profile is characterised using in-line mass spectrometry. Furthermore, the material contained within a catch-pot downstream from the reactor is analysed using gas chromatography-mass spectrometry. For a fixed methanol feed, reaction conditions are selected to define various stages of the reaction coordinate: (i) initial methanol adsorption at a sub-optimum reaction temperature (1 h at 200 °C); (ii) initial stages of reaction at an optimised reaction temperature (1 h at 350 °C); (iii) steady-state operation at an optimised reaction temperature (3 days at 350 °C); and (iv) accelerated ageing (3 days at 400 °C). Post-reaction, the catalyst samples are analysed ex situ by a combination of temperature-programmed oxidation (TPO) and spectroscopically by electron paramagnetic resonance (EPR), diffuse-reflectance infrared and inelastic neutron scattering (INS) spectroscopies. The TPO measurements provide an indication of the degree of 'coking' experienced by each sample. The EPR measurements detect aromatic radical cations. The IR and INS measurements reveal the presence of retained hydrocarbonaceous species, the nature of which are discussed in terms of the well-developed 'hydrocarbon pool' mechanism. This combination of experimental evidence, uniquely applied to this reaction system, establishes the importance of retained hydrocarbonaceous species in effecting the product distribution of this economically relevant reaction system.

No abstract

The nature of the hydrocarbon pool at different stages of the methanol‐to‐hydrocarbons reaction over ZSM‐5 is examined. A combination of reaction testing, analytical and spectroscopic techniques is employed to investigate changes in the nature and form of the hydrocarbon pool as a function of reaction conditions and reaction time. It is shown that inelastic neutron scattering spectroscopy (INS) complements other spectroscopic methods for observing molecular components in the hydrocarbon pool of working catalysts. INS is uniquely able to spectroscopically identify the form of coke species present in deactivated catalysts.

<p>Coffee is the second most common trade commodity in the world after petroleum. The coffee industry generates large amounts of waste in the form of coffee peels. Coffee peel waste consist of lignocellulose containing hemicellulose and other chemical compounds. The objective of this research was to extract xylan, the main component of hemicellulose from coffee waste, and to utilize the xylan in the production of xylooligosaccharide (XOS). Xylan was extracted from coffee waste using NaOH solution and neutralized by HCl 6 M. Afterward, xylan was precipitated using ethanol. Various NaOH concentrations (4, 8, 12 and 16 % w/v) were used to obtain the xylan. NaOH solution with a concentration of 12 % results 43 % extraction of xylan from coffee waste. Xylan obtained from the extraction was hydrolyzed using endo-β-1,4-xylanase from Bacillus sp. to produce XOS. The incubation time of enzyme-substrate was observed at 40 oC, pH 5 and enzyme dose of 23.6 U. Thin layer chromatography results showed that the hydrolyzed products of xylan are XOS with composition xylobiose (X2), xylotriose (X3), xylotetraose (X4) and xylopentaose (X5). LC-MS studies revealed that X2 is the dominant product with the concentration of 6.00 ppm. This research demonstrates the potential to utilizate coffee peel waste as a source of xylan for the production of XOS.</p>