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Large-scale production of biomass-derived fuels and chemicals requires the economical and efficient depolymerization of lignocellulosic biomass into sugars and fuels. Catalytic hydrolysis of raw wheat straw for the production of glucose was conducted using a designed porous membrane-based polymeric solid acid catalyst consisting of poly (ionic liquid) and polysulfonic acid chains. The catalyst demonstrated superior activity and selectivity with glucose yield reached over 50% from the un-pretreated raw straw. Under the optimal conditions, over 80% of cellulose and over 90% of xylan were converted to soluble sugars and furans with over 60% glucose or xylose yields reached respectively from pretreated straw biomass. Our catalyst demonstrates high glucose and total reducing sugar (TRS) yields from lignocellulosic biomass with promising application for the future lignocellulosic biorefinery. [ABSTRACT FROM AUTHOR]

Zr 1-x Ce x O x has been prepared by hydrolysis, in neutral medium, starting from rough ZrO 2 and CeO 2 materials as simple and cheaper synthesis method compared to sol-gel routes. The oxy-hydroxide precursors thus obtained were calcined under air at 450 °C, 900 °C and 1200 °C. The impact of those thermal treatments on the structure, texture and related redox properties has been investigated. Higher specific surface area than those observed on ceria were observed after calcination at low temperature, i.e., 450 °C. Above that temperature thermal sintering occurs having a detrimental effect on the specific surface area related to crystal growth more accentuated on CeO 2 . The formation of several Zr Ce mixed oxide phases formed by incorporation and substitution of Zr in the structure of ceria was characterized. A complete loss of specific surface area is noticeable after calcination at 1200 °C. XRD and SEM analysis revealed the formation of two mixed oxides structure, i.e. Ce 2 Zr 2 O 7.04 and Ce 2 Zr 2 O 7 corresponding to different redox behavior evidenced from H 2 -TPR experiments. [ABSTRACT FROM AUTHOR]

In this study, four different regeneration methods (WR, NR, AR and WNAR), regeneration conditions and regeneration mechanism of a Fe-Cu-KOH supported on WSB as a precursor catalyst (Fe-Cu-KOH/WSB) for low temperature hydrolysis of CS 2 and COS were investigated. The results showed that the WNAR method (Water washing + Nitrogen sweeping + Alkali steeping regeneration) had the best regeneration performance. Under optimal regeneration conditions (500 °C nitrogen sweeping temperature and 13% KOH steeping content), the regenerated Fe-Cu-KOH/WSB catalyst could achieve to 42.64 mg S/g sulfur capacity, and it was close to fresh catalyst (48.58 mg S/g). A small amount of sulfate and a large number of OH groups were washed away in water washing process. XPS, TG/DTA and DRIFTS results indicated that a large number of Fe 2 (SO 4 ) 3 were decomposed into Fe 2 O 3 in nitrogen sweeping process, which could recover a large number of surface area and active component. CO 2 -TPD results indicated that the supplement of OH groups in KOH steeping process recovered the alkalinity site strength, which was conducive to desulfurization. After three times regeneration, the sulfur capacity of Fe-Cu-KOH/WSB could reach 33.94 mg S/g, and it indicated that the WNAR method had good stability for the recovery of catalytic activity. From BET, CO 2 -TPD XPS and TG/DTA results, it could be seen that the decrease of adsorptive and catalytic ability was attributed to the oxidation of WSB, the block effect of KOH and decrease of CuO contents. This study provided a suitable regeneration method for industrial application of Fe-Cu-KOH/WSB on catalytic hydrolysis of organic sulfur. [ABSTRACT FROM AUTHOR]

In order to find an effective method for treating urea wastewater, the experiments on the hydrolysis of urea in wastewater were conducted in a fixed bed reactor with different aluminas (α-AlO, γ-AlO, and η-AlO) as catalysts respectively in contrast with inert ceramic particle. The results indicate that the three alumina catalysts show obvious catalytic activity for urea hydrolysis at 125 °C. The order of activity is η-AlO > γ-AlO > α-AlO, and the activity difference increases with increasing temperature. According to the characterization results, surface acidity has little impact on the activity of catalyst. However, it was found that surface basicity of alumina catalyst plays an important role in catalytic hydrolysis of urea, and the activity of catalyst may be also influenced by the basic strength. With η-AlO as catalyst, the urea concentration in wastewater is reduced to 4.96 mg/L at a temperature of 165 °C. Moreover, the η-AlO shows a good stability for urea hydrolysis. The hydrolysis of urea over η-AlO catalyst can evidently reduce the reaction temperature and is promising to replace industrial thermal hydrolysis process. [ABSTRACT FROM AUTHOR]

Lysosomal degradation of glycosphingolipids is mediated by the consecutive action of several glycosidases. Malfunctioning of one of these hydrolases can lead to a lysosomal storage disorder such as Fabry disease, which is caused by a deficiency in a-galactosidase A Herein we describe the development of potent and selective activity-based probes that target retaining α-galactosidases. The fluorescently labeled aziridine-based probes 3 and 4 inhibit the two human retaining α-galactosidases αGal A and αGal B covalently and with high affinity. Moreover, they enable the visualization of the endogenous activity of both a-galactosidases in cell extracts, thereby providing a means to study the presence and location of active enzyme levels in different cell types, such as healthy cells versus those derived from Fabry patients. [ABSTRACT FROM AUTHOR]

Theautocatalytic hydrolysis kinetics of dimethyl oxalate (DMO)was investigated in an isothermal batch reactor at 328.15–358.15K. It was observed that DMO hydrolysis involved two reactions in series,with monomethyl oxalate (MMO) as an intermediate product. The resultsshowed that water dominates the initial hydrolysis rate of DMO. Inlater stages, oxalic acid plays a major role in catalyzing DMO hydrolysisand MMO further hydrolysis. Based on these observations, a mechanisminvolving the ionization of water and oxalic acid was developed thatassumes nucleophilic substitution to be the rate-determining step.Concentration-based rate equations were further deduced includingthe contribution of water startup and the catalytic action of oxalicacid. In addition, the kinetic and equilibrium parameters were estimatedfrom the experimental data through regression analysis. [ABSTRACT FROM AUTHOR]

An efficient and cheap catalyst, montmorillonite supported Ru nanoclusters (Ru/MMT) were successfully prepared and explored for the hydrogen generation from alkaline NaBH4solution. The catalytic behavior and the kinetics of Ru/MMT catalyzed hydrolysis of alkaline NaBH4was studied detailedly by measuring the volume of generated hydrogen gas varying catalyst concentration and temperature. The relationship between the activation energy (Ea) of NaBH4hydrolysis reaction and Ru/MMT amount was constructed, and the minimum value was determined to be 49.6 kJ/mol, which was lower than the most reported Ru-based supported catalysts that have been reported in the open literatures. The higher catalytic activity of Ru/MMT was due to the more open frame of montmorillonite than the other inorganic supporters, which decreases the substrate inhibition in catalytic hydrolysis of NaBH4. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simultaneous catalytic hydrolysis activity of COS and CS2 over Fe–Cu–Ni/MCSAC was notable. [•] Low generation of K3Na(SO4)2 was in the Fe–Cu–Ni/MCSAC catalyst. [•] High specific surface areas and more micropores enhanced catalytic hydrolysis activity. [•] XPS results showed that most of COS and CS2 hydrolysis products were S/ . [ABSTRACT FROM AUTHOR]

Kinetic isotope effect (KIE) measurements are a powerful tool for studying enzyme mechanisms; they can provide insights into microscopic catalytic processes and even structural constraints for transition states. However, KIEs have not come into widespread use in enzymology, due in large part to the requirement for prohibitively cumbersome experimental procedures and daunting analytical frameworks. In this work, we introduce time-resolved electrospray ionization mass spectrometry (TRESI-MS) as a straightforward, precise, and inexpensive method for measuring KIEs. Neither radioisotopes nor large amounts of material are needed and kinetic measurements for isotopically "labeled" and "unlabeled" species are acquired simultaneously in a single "competitive" assay. The approach is demonstrated first using a relatively large isotope effect associated with yeast alcohol dehydrogenase (YADH) catalyzed oxidation of ethanol. The measured macroscopic KIE of 2.19 ± 0.05 is consistent with comparable measurements in the literature but cannot be interpreted in a way that provides insights into isotope effects in individual microscopic steps. To demonstrate the ability of TRESI-MS to directly measure intrinsic KIEs and to characterize the precision of the technique, we measure a much smaller 12C/13C KIE associated specifically with presteady state acylation of chymotrypsin during hydrolysis of an ester substrate. [ABSTRACT FROM AUTHOR]

Though unfunctionalized mesoporous carbon consisting of weakly Brønsted acidic OH-defect sites depolymerizes cellulose under mild conditions, the nature of the active site and how this affects hydrolysis kinetics—the rate-limiting step of this process—has remained a puzzle. Here, in this manuscript, we quantify the effect of surface OH-defect site density during hydrolysis catalysis on the rate of reaction. Our comparative approach relies on synthesis and characterization of grafted poly(1→4-β-glucan) (β-glu) strands on alumina. Grafted β-glu strands on alumina have a 9-fold higher hydrolysis rate per glucan relative to the highest rate measured for β-glu strands on silica. This amounts to a hydrolysis rate per grafted center on alumina that is 2.7-fold more active than on silica. These data are supported by the lower measured activation energy for hydrolysis of grafted β-glu strands on alumina being 70 kJ/mol relative to 87 kJ/mol on silica. The observed linear increase of hydrolysis rate with increasing OH-defect site density during catalysis suggests that the formation of hydrogen bonds between weakly Brønsted acidic OH-defect sites and constrained glycosidic oxygens (i.e., those juxtaposed adjacent to the surface) activates the latter for hydrolysis catalysis. Altogether, these data elucidate crucial structural requirements for glucan hydrolysis on surfaces and, when coupled with our recent demonstration of long-chain glucan binding to mesoporous carbon, present a unified picture, for the first time, of adsorbed glucan hydrolysis on OH-defect site-containing surfaces, such as unfunctionalized mesoporous carbon. [ABSTRACT FROM AUTHOR]

Abstract: The design, construction, and flight test of a fuel cell-powered small unmanned aircraft are described. A fuel cell system featuring a polymer electrolyte membrane fuel cell combined with a hydrogen generator, which serves as a new power source alternative to the existing batteries, is proposed. The hydrogen generator uses a catalytic hydrolysis reaction to extract hydrogen from an alkaline solution of sodium borohydride, and constructed with a reactor, pump, separator, and fuel cartridge. Considering the performance characteristics of the fuel cell, the hybrid power management of a fuel cell and a battery was contrived. The fuel cell stack, hydrogen generator, and power management system were evaluated at the various load conditions. A high efficiency unmanned aircraft was designed and fabricated to validate the possibility of the proposed fuel cell system, and a small flight control system was developed for a high endurance test flight. Wind-tunnel tests were conducted before the flight tests under actual flight conditions. The possibility for the utilization of a fuel cell in a small aircraft was validated through the fuel cell powered flight test. The fuel cell aircraft flew for 2 h without incidents in the fuel cell system. [Copyright &y& Elsevier]

Abstract: The paper studies the influence of temperature (50–100 °C) and alkalinity (C OH − = 2.33–9.53 M) of aqueous solutions on the hydrolysis (self-destruction) kinetics of borohydride ions . Characteristic peculiarities of the kinetic curve have been established and formulae to approximate the temperature-concentration dependence of the hydrolysis rate are proposed. An increase in temperature leads to an increase in the rate constant k of borohydride hydrolysis, and the temperature dependence of k satisfactorily obeys Arrhenius’ equation. The influence of solution alkalinity on the borohydride hydrolysis rate was explored. Within the temperature range studied, the k = f(C OH −) curve consists of two fragments, each with the prevalence of one of two different mechanisms (paths) of borohydride hydrolysis. In highly-alkaline aqueous solutions, non-catalytic hydrolysis mainly occurs, whose rate is determined by temperature, being pH-independent. At lower alkalinity, the hydrolysis rate sharply increases due to catalysis by H+ ions. A power dependence of k on the H+ concentration has been found; the point where the mechanisms are switched is determined by temperature. [Copyright &y& Elsevier]

Abstract: In this article, we report Co–Co2B and Ni–Ni3B nanocomposites as catalyst for hydrogen generation from alkaline sodium borohydride. Kinetic studies of the hydrolysis of sodium borohydride with Co–Co2B and Ni–Ni3B nanocomposites reveal that the concentration of NaBH4 has no effect on the rate of hydrogen generation. Hydrolysis was found to be first order with respect to the concentration of catalyst. The catalytic activity of Co–Co2B was found to be much higher than that of Ni–Ni3B as inferred from the activation energies 35.245 KJ/mol and 55.810 kJ/mol, respectively. Co–Co2B nanocomposites were found to be more magnetic than Ni–Ni3B. These catalysts showed superior recyclability with almost the similar catalytic activities for several hydrolytic cycles supporting the principles of sustainability. Co–Co2B catalyst showed hydrogen generation rate of about 4300 mL/min/g which is comparable to most of the reported good catalysts till date. [Copyright &y& Elsevier]

In an effort to probe the reaction of antibiotic hydrolysis catalyzed by B3 metallo-β-lactamase (MβL), the thermodynamic parameters of penicillin G hydrolysis catalyzed by MβL L1 from Stenotrophomonas maltophilia were determined by microcalorimetric method. The values of activation free energy Δ G are 88.26, 89.44, 90.49, and 91.57 kJ mol at 293.15, 298.15, 303.15, and 308.15 K, respectively, activation enthalpy Δ H is 24.02 kJ mol, activation entropy Δ S is −219.2511 J mol K, apparent activation energy E is 26.5183 kJ mol, and the reaction order is 1.0. The thermodynamic parameters reveal that the penicillin G hydrolysis catalyzed by MβL L1 is an exothermic and spontaneous reaction. [ABSTRACT FROM AUTHOR]