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The catalytic supercritical water gasification (SCWG) characteristics of ethanol fermentation stillage as a model for proteinaceous biomass were examined using batch and flow reactors. Batch reactions conducted at 385 °C and 26 MPa found that certain Ni and Ru catalysts gave almost 100% carbon conversion within 60 min of reaction time, while non-catalyzed reactions gave only 10% conversion for the same duration. Ru generally showed higher catalytic activity per mass of catalyst metal than Ni. Control of the extent of reaction by changing the reaction time and catalyst amount showed that in the case of supported Ru catalysts, major gas component yields (CH 4 and CO 2 ) exhibited respective universal dependence against total carbon yield, despite the varied support materials and Ru particle sizes used. This is an indication that the present reaction system is structure-insensitive with respect to supported Ru catalysts. For repetitive batch reactions, Raney-type Ni catalysts were more stable than supported Ni or Ru catalysts. A modified Raney Ni catalyst that showed better durability than non-modified one in batch reactions did not show advantages in flow reactions, which could be explained by the differences in reaction environment with respect to the two types of reactors. The SCWG reaction pathways of ethanol stillage are discussed in relation to the steam reforming mechanism; the reason for the appearance of minor amounts of C 2 + species in the product gas stream, which is not expected from the steam reforming mechanism, is discussed.

The peak top frequency of the stretching vibration of hydroxyl (OH) groups on amorphous silica reversibly changes accompanied by the change of the sample in temperature under the constant concentration. Using this phenomenon, the estimation of the real temperatures of samples in infrared (IR) cell can be achieved. The temperatures measured from outside the cell are first calibrated to real ones. The OH frequency of silica can be correlated to the real temperature of the sample inside the cell via the calibration of the measured and the real temperatures of samples in each IR cell. Copyright © 2014 John Wiley & Sons, Ltd.

Transesterification of ethyl butyrate with methanol on the organic cation-exchanged mordenite ([bmim]M20) was studied in order to examine the reactivity of the methoxide ions that were generated on [bmim]M20 by the dissociation of methanol. Since transesterification occurred by addition of NaCl, the methoxide ions on [bmim]M20 were demonstrated to be utilizable in the reaction. The activity improved with a concentration of NaCl below 3 mmol L −1 , whereas it was constant at concentrations above 3 mmol L −1 . The adsorption of ethyl butyrate on the partially ion-exchanged [bmim]M20 samples was observed by FT-IR spectroscopy. It was found that it was difficult for ethyl butyrate to enter the micropores of [bmim]M20. From these results, a reaction mechanism was proposed in which the methoxide ions generated in the micropores of [bmim]M20 reacted with ethyl butyrate after they diffused outside of the micropores.

Dissociative alcohol adsorption was investigated on 1-butyl-3-methylimidazolium ([bmim]) exchanged mordenite ([bmim]M20) by Fourier transform infrared spectroscopy (FT-IR). Methanol, ethanol, 1-propanol and 2-propanol were adsorbed onto [bmim]M20. Although acidic OH groups were almost completely absent on [bmim]M20, bands attributed to hydrogen-bonded νOH of acidic OH groups (the so-called ABC triplet) were apparent for alcohol adsorption on [bmim]M20. This indicates the generation of acidic OH groups on [bmim]M20 by the dissociative adsorption of alcohols. Methanol and ethanol could diffuse into the [bmim]M20 micropores in the absence of observable energy barriers at room temperature, while energy barriers for diffusion into the micropores were observed for 1-propanol and 2-propanol at room temperature. The activation energy for diffusion of 2-propanol into the [bmim]M20 micropores was estimated as 25 kJ mol −1 . Shape-selective adsorption into the [bmim]M20 micropores was revealed for the alcohols examined.

The H + in the acidic OH groups on H-mordenite zeolite (HM20) was ion exchanged by using 1-butyl-3-methylimidazolium cation ([bmim] + ). No absorption band for the acidic OH groups on the zeolite could be observed in the [bmim] mordenite ([bmim]M20) by FT-IR. The CO adsorption on [bmim]M20 also showed the absence of acidic OH groups, indicating that the ion exchange reaction goes to completion. The bands attributed to the hydrogen bonded vOH of the acidic OH groups on zeolites (so-called ABC triplet) appeared due to water adsorption on [bmim]M20, for which there are no acidic OH groups. This indicates the generation of acidic OH groups, which could be attributed to dissociative adsorption of water on [bmim]M20 and water adsorption to the acidic OH groups. The vCH band for the CH on imidazolium is thought to interact with anions, which would lead to the generation of OH-.

Dehydration of adsorbed glycerol on H-MFI zeolite was investigated by FT-IR. Dehydration of glycerol was confirmed to occur at 353 K. A comparison of the adsorption of acrolein on amorphous silica and on H-MFI suggests that the product on H-MFI upon dehydration of glycerol was acrolein. Although two reaction pathways in which the OH groups on C1 and C2 of glycerol dehydrate were suggested in the acid-catalyzed dehydration of glycerol, the pathway in which the OH groups on C2 dehydrate was found to proceed selectively on H-MFI.

The reaction dynamics of trans-2-butene adsorbed to acidic hydroxyl groups on the surface of ferrierite zeolite is examined by time-resolved spectroscopy using a tunable infrared picosecond pulse laser system. The transient absorption spectra measured by a two-color pump−probe technique at 188−243 K reveal bleaching and hot bands of the OD stretching mode 2 ps after excitation. This vibrationally excited state relaxes within 20 ps at 188 K, while the bleaching band includes a long-lifetime component that lasts for more than 100 ps at 243 K. Thus, the OD (isotope-exchanged hydroxy groups) stretching band does not entirely recover in this period and is mirrored by an analogous weakening of the CH bending band of the adsorbed trans-2-butene. Simultaneously, three new bands in CH stretching region were observed at 3045, 3095, and 3130 cm-1. This result suggests the presence of a short-lived intermediate formed by reaction between the acidic hydroxyl groups and adsorbed trans-2-butene.

A joint study was organized to establish a standard set of conditions for the ion exchange of zeolite from sodium into proton-form. The sodium-form mordenite with Si/Al 2 = ca. 15 was ion exchanged into an NH 4 -form, followed by calcination according to various recipes. Then various advanced techniques for characterization (ICP, TG, XPS, SEM, XRD, N 2 adsorption, 29 Si and 27 Al NMR, benzene diffusion, IR of OH and adsorbed pyridine and CO, ammonia TPD) were applied, and some test reactions (cracking of cumene, isopropylation of biphenyl, oligomerization of propene and chichibabin condensation of acetaldehyde and ammonia into picoline) were conducted. The ion exchange (removal of sodium) proceeded as expected, but remarkable differences were observed in physicochemical and catalytic properties of the thus-prepared proton-form samples. Exceptionally high temperature (383 K) for the ion exchange resulted in the structural degradation, while most samples exchanged at 333–353 K maintained the crystallinity and pore volume. The use of NH 4 Cl slightly changed the crystal morphology. Extra-framework aluminum species was formed on most samples after calcination above 773 K. In contrast, calcination at 673 K maintained the framework aluminum. Therefore, the dealumination is considered to proceed after complete removal of ammonia from the ammonium-form zeolite. However, the proton-form zeolite was stable under dry conditions, so it is speculated that the dealumination was induced by the contact of the proton-form zeolite to atmosphere with humidity. The total and Bronsted acidity decreased with the dealumination, while Lewis acidity increased. On the other hand, rapid heating of the ammonium type zeolite caused narrowing of the micropores. These structural changes seriously affected the catalytic activities for various reactions.

The c(4×2)-CO/Ni(111) surface under pulsed near-infrared irradiation is examined by time-resolved sum-frequency generation (SFG) spectroscopy. At a surface coverage of 0.5, the surface is confirmed to consist almost exclusively of hollow CO molecules, as evidenced by a sole SFG peak at 1904 cm-1. Under pulsed irradiation, this peak weakened, followed by the emergence of a new peak attributable to atop CO. This represents a direct observation of site-hopping of adsorbed CO. The hopping phenomenon was found to be entirely transient, with the surface returning to the pre-excited state within a few hundred picoseconds without desorption. The dynamics of the process are also discussed.

Kinetics on the adsorption of n -butene onto the acidic OH groups existing in the small pores of ferrierite (FER) were studied between 233 and 253 K by IR spectroscopy. The activation energies for the adsorption of 1-butene and cis -2-butene were estimated as 23.3 and 28.4 kJ mol −1 , while that of trans -2-butene was not obtained due to its rapid adsorption. The activation energy for adsorption was considered to have resulted from the diffusion of n -butene molecules into the small micropores of FER.

Silanol groups existing on the outer surfaces of zeolites, whose OH stretching band appears at the same frequency as that of silanol groups on amorphous silica, are recognized as neutral or very weakly acidic. No significant difference in acidity between silanol groups on zeolites and those on amorphous silica has yet been found by studying the adsorption of probe molecules. However, it was found by a “reaction probe IR study” that silanol groups involved in highly crystallized structures of zeolites (ferrierite and ZSM-5) donated their protons to olefins (2-methylpropene, 2,4,4-trimethyl-1-pentene, and 2,4,4-trimethyl-2-pentene) at temperatures lower than 220 K, in contrast to those on amorphous silica. The products formed from reaction of those olefins with silanol groups were identical to 2,4,4- trimethyl-2-pentoxy groups ((CH3)3C–CH2–C(CH3)2–O–Si). These results suggest a difference in acidity between silanol groups on zeolites and those on amorphous silica.

Adsorption of n-olefins (≤C4) on a ferrierite (FER) zeolite was observed by infrared (IR) spectroscopy. Ethene and propene adsorbed selectively on the acidic OH (OD) groups in the small pores of FER, while butenes adsorbed also on the silanol groups on the external surface at ca. 200 K, a part of which transferred to the acidic sites upon increase in temperature. This indicates the existence of energy barriers for intercalation of butenes into the FER pores. The facility among butenes for migration to the FER pores was found to be in the order trans-2-butene > 1-butene > cis-2-butene.

Adsorption and reaction of 2-methylpropene (isobutene) on zeolites (ZSM-5 and faujasite (Y zeolite)), a silica−alumina, and a silica were investigated below room temperature by infrared (IR) spectroscopy. On silica, isobutene molecules that adsorbed on silanol groups simply desorbed below 230 K in vacuum, while isobutene π-bonded to the acidic OH groups (π-complex) on acid catalysts reacted to dimer alkoxy (2,4,4-trimethylpentoxy) groups. The structure of the reaction product, dimer alkoxy groups, was found to be restricted by the pore size of zeolites; 2,4,4-trimethyl-2-pentoxy species were identified on silica−alumina and Y zeolite similarly to those on mordenite, while the reaction of isobutene resulted in 2,4,4-trimethyl-1-pentoxy species on the acidic OH groups in the pores of ZSM-5. Therefore, the space restriction of the pore size of zeolites on the reaction product was directly observed by the low-temperature IR study.

Adsorption and reactions of 2-methylpropene (isobutene) on mordenite were investigated between 150 and 300 K by infrared (IR) spectroscopy. The methyl groups of isobutene interacted with the acidic...

The reaction dynamics of trans-2-butene adsorbed to acidic hydroxyl groups on the surface of ferrierite zeolite is examined by time-resolved spectroscopy using a tunable infrared picosecond pulse laser system. The transient absorption spectra measured by a two-color pump-probe technique at 188-243 K reveal bleaching and hot bands of the OD stretching mode 2 ps after excitation. This vibrationally excited state relaxes within 20 ps at 188 K, while the bleaching band includes a long-lifetime component that lasts for more than 100 ps at 243 K. Thus, the OD (isotope-exchanged hydroxy groups) stretching band does not entirely recover in this period and is mirrored by an analogous weakening of the CH bending band of the adsorbed trans-2-butene. Simultaneously, three new bands in CH stretching region were observed at 3045, 3095, and 3130 cm(-1). This result suggests the presence of a short-lived intermediate formed by reaction between the acidic hydroxyl groups and adsorbed trans-2-butene.

The double bond migration of 1-butene and cis/trans isomerization of 2-butene on deuterated acidic hydroxyl (OD) groups of ferrierite zeolite were observed by IR spectroscopy. Both reactions of irreversibly adsorbed species proceeded below 270 K under evacuation in the absence of H/D isotope exchange reaction of the acidic OD groups. This suggests the different property and catalysis of acidic OH groups on zeolites from those of H + in acidic solutions.

Using IR spectroscopy, three different surface states of HY zeolite were probed by successive adsorption of CO at 143 K followed by evacuation and pyridine adsorption at 523 K: HY zeolite [1] without strong Lewis acid sites (LAS); [2] after high temperature (873 K) evacuation to convert Brønsted acid sites (BAS) to strong LAS; and [3] after water re-adsorption on HY zeolite [2] to recover BAS from LAS. The original surface of HY zeolite [1] seemed to be recovered on HY zeolite [3] after high temperature evacuation and water treatment by CO adsorption, while a part of generated LAS on HY zeolite [2] seemed irreversible on HY zeolite [3] to HY zeolite [1] by pyridine adsorption. To clarify this discrepancy, re-examination of the IR spectra of adsorbed CO and pyridine on γ-alumina and silica-alumina after similar treatments to those on HY zeolite was conducted. Based on the results of CO adsorption on γ-alumina and silica-alumina, the presence of extra-framework aluminium sites on HY zeolite [1] was confirmed. High temperature evacuation of HY zeolite [1] formed very strong LAS, a part of which was irreversible to BAS by water re-adsorption at room temperature. The irreversible sites on HY zeolite [3] were assigned to non-acidic OH groups attributed to silica-alumina. The non-acidic OH groups on HY zeolite [3], which were BAS on HY zeolite [1], hydrogen-bonded to pyridine to show IR spectra similar to those adsorbed on LAS. Thus, LAS on HY zeolite [3] seemed irreversible by pyridine adsorption after water re-adsorption. On the other hand, CO adsorbed on non-acidic OH groups showed a band at only slightly lower frequency (2160 cm(-1)) than that of BAS (2178 cm(-1)), resulting in overlapps and ignoring their presence. Thus, CO adsorption seemed to show that complete recovery of LAS to BAS occurred.

The processes of high-temperature (473 K) resulfidation and cobalt carbonyl adsorption by chemical vapor deposition (CVD) on a cleaved basal plane of a natural molybdenite (MoS2) single crystal were examined by ultrahigh-vacuum scanning tunneling microscopy (UHV-STM) on the nanometer scale. The resulfided cleaved molybdenite basal plane showed a displacement of upper terraces, and a sinusoidal structure at step edges, both of which may be caused by the electronic effect at the surface. Cobalt carbonyl appeared to be adsorbed at both the S- and Mo-terminated edges, resulting in an agglomeration at the step edges on lower terraces with a width of a few tens of nanometers. When this surface with adsorbed carbonyl was sulfided at 513 K for 1 h, most of the adsorbed carbonyl clusters appeared to be desorbed while a small part were dispersed on the terraces in small clusters of 10–20 nm in size. The obtained results are discussed in terms of the preparation of Co-Mo hydrodesulfurization (HDS) catalysts.

The adsorption of 2-methylalkanes (propane, butane and pentane) onto ferrierite zeolite was studied by infrared (IR) spectroscopy at temperatures below room temperature. It was found that 2-methylpropane molecules penetrate into micropores only partially, and that only a small fraction of the acidic OH groups available in the micropores interact with the alkyl groups of 2-methylpropane. The interaction is therefore considered to represent interaction between the methyl groups and OH groups located close to the entrance of the micropores. Increasing the carbon number of the main alkyl chain of 2-methylalkanes resulted in a proportional increase in the fraction of acidic OH groups interacting with alkyl groups. Infiltration of n-alkane molecules into the micropores of ferrierite therefore appears to be hindered by methylation of the carbon at the second position. In general, stability was achieved when the longest alkyl chain had entered the micropores of ferrierite, allowing the pore length of ferrierite to be estimated from the extrapolated length of the main alkyl chains. The estimated length of up to 30 nm is consistent with SEM observation.