This study reports a two-step hydrolysis
process for achieving
near-complete recovery of sugar monomers from crystalline cellulose
or lignocellulosic biomass. The first step is mechanochemical hydrolysis
of the acid-impregnated sample in the solid state via ball milling
at room temperature. It was found that mechanochemical hydrolysis
not only effectively breaks the hydrogen-bonding network within the
crystalline cellulose but also drives the acid-catalyzed hydrolysis
reactions to form water-soluble products, mainly consisting of glucose
and its oligomers, with a degree of polymerization up to 15. However,
mechanochemical hydrolysis appears to be incapable of further hydrolyzing
these oligomers into monomers and, hence, is not suitable for producing
sugar monomers directly. Therefore, the second step is dilute acid
hydrolysis of the mechanochemically hydrolyzed sample in the aqueous
phase under low-severity conditions, i.e., at a low acid concentration
of 0.25 wt % and a low temperature of 150 °C. The second dilute
acid hydrolysis step can be completed rapidly (within 30 min) and
achieves remarkable glucose recovery, up to ∼91% from cellulose.
A key innovation of the two-step hydrolysis process is that deep depolymerization
in the first step (mechanochemical hydrolysis) is not required for
completely converting crystalline cellulose into water-soluble products
because all sugar oligomers can be effectively hydrolyzed into monomers
in the second step (dilute acid hydrolysis). Our results also show
that near-complete recovery of sugar monomers (∼94%) can be
achieved from wood biomass via the two-step hydrolysis process, suggesting
that this technology has the potential to replace the conventional
enzymatic hydrolysis to recover sugar monomers from lignocellulosic
biomass.
The efficiency of hydrogen sulfide scavengers directly injected into gas streams is often compromised by short contact times due to space limitations on offshore assets. The use of static mixers is often employed to increase the efficiency of gas-liquid mixing. The performance of two commercially available hydrogen scavenger products were assessed in the laboratory utilising a specially fabricated test chamber designed to mimic a static mixer. A continuous feed of both gas and a liquid scavenger solution were mixed through a glass bead static mixer. The liquid scavenger was atomized into the gas prior to traveling through the bed. The impact of dose rate, water content, carbon dioxide and contact time were assessed on the scavenging efficiency and kinetics of two triazine chemicals used to sequester H2S from a gas stream containing 180 ppmv H2S in nitrogen, to achieve a target H2S concentrations of <10 ppmv. Efficiencies derived from the test apparatus revealed that the formulation based on the ethanolamine triazine chemistry performed significantly better than the methylamine triazine product at the two contact times of 3 and 25 seconds. The equilibration time required to reach the target concentration were significantly longer at the shorter contact time, and unachievable without the static mixer. The dosages of scavenger required to reduce the H2S concentrations from 180 ppmv to 10 ppmv were much higher than theoretical dosages. The addition of water to the scavenger mixtures was found to increase the efficiency of the ethanolamine scavenger but decrease the performance of the methylamine based triazine. The importance of atomisation of the scavenger onto the fixed bed was reinforced by the dramatic reductions in performance associated with a lack of atomisation. The presence of CO2 had no significant impact on the scavenging efficiency but had a kinetic impact and reduced the time to achieve the target concentration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.