Search

There are several established approaches for the reductive fractionationof lignocellulose (e.g., “catalytic upstream biorefining" and “lignin-first" approaches) that lead to a lignin oil product that is composed primarily of dihydro-p-monolignols [e.g., 4-(3-hydroxypropyl)-2-methoxyphenol and 4-(3-hydroxypropyl)- 2,6-dimethoxyphenol]. Although effective catalytic methods have been developed to perform reductive or deoxygenativeprocesses on the lignin oil, the influence of the 3-hydroxypropylsubstituent on catalyst activity has previously beenoverlooked. Herein, to better understand the reactivity of thedepolymerized lignin oil obtained from catalytic upstream biorefiningprocesses, dihydro-p-coumaryl alcohol was selected asa model compound. Hydrogenation of this species in the presenceof Raney Ni with molecular hydrogen led to ring saturation(100% selectivity) in the absence of hydrodeoxygenation,whereas under hydrogen-transfer conditions with 2-propanol,hydrogenation occurred (&55% selectivity) simultaneouslywith hydrodeoxygenation (&40% selectivity). In a broadercontext, this study sheds light not only on the reactivity of dihydro-p-monolignols but also on the intricacies of the catalyticupstream biorefining reaction network in which these speciesare revealed to be key intermediates in the formation of less functionalized p-alkylphenols. [ABSTRACT FROM AUTHOR]

High speed product gas analysis during the dry reforming of CH 4 allows the observation of transient elevated H 2 and CO production rates, combined with high initial conversions of CH 4 and CO 2. The transients are observed in the first 120 s of the reaction, followed by a lower steady-state production rate after 3–5 min. The catalytic reactivity in the initial 120 s is important in understanding the catalyst performance and determining the reactions responsible for carbon deposition. Monitoring the changes in the H 2 and CH 4 partial pressures from the start, through the transient production regime, and on through the steady-state regime, shows that the transient reactivity is directly related to the decomposition of CH 4. This finding is further supported by the linear trend found between the H 2 /CO ratio and the carbon deposition in the peak region of the product gas profile. Although significant amounts of carbon are deposited on the Ni surface, it is not completely deactivated at any of the reaction temperatures in the 500–800 °C range explored herein. Characterizing the initial reactivity in terms of carbon deposition and catalyst performance in dry reforming of CH 4 may lead to changes in the sampling technique for researchers working with reforming reactions, and optimized catalysts that exhibit reduced initial carbon deposition. • We have quantified the initial carbonization of Ni catalysts during dry reforming. • Initial deactivation is due to methane decomposition. • Steady state reforming kinetics are found within 5 min of operation. • Deactivation is dominant for temperatures below ~700 °C. [ABSTRACT FROM AUTHOR]