32 research outputs found
Catalytic pyrolysis of crude glycerol over shaped ZSM-5/bentonite catalysts for bio-BTX synthesis
Ex-situ catalytic pyrolysis of crude glycerol for the synthesis of bio-based benzene, toluene and xylenes (bio-BTX) was performed in a tandem micro-reactor (TMR), a batch gram scale reactor and a continuous integrated bench scale unit using ZSM-5/bentonite extrudates. A bio-BTX yield of 8.1 wt.% (14.6% carbon yield) based on crude glycerol was obtained over the fresh catalysts (Cat-F) in the bench scale unit (crude glycerol feed rate of 200 g hâ1, pyrolysis temperature of 520 °C and catalytic upgrading temperature of 536 °C). Catalyst activity was shown to be a function of the time on stream (TOS) and after 4.7 h the activity dropped with about 8%. After an oxidative regeneration step to remove coke, the activity of the regenerated catalysts (Cat-R1) was recovered to 95% of the original catalyst activity. After 11 reaction-regeneration cycles, the bio-BTX yield decreased to 5.4 wt.% (9.7% carbon yield) over Cat-R11. The fresh, deactivated and regenerated ZSM-5/bentonite catalysts were characterized in detail using nitrogen physisorption, XRD, ICP-AES, EA, TEM-EDX, TGA, NH3-TPD, pyridine-IR and solid MAS NMR. Coke (10.5 wt.% over Cat-D) was mostly deposited on ZSM-5 planes, and not only decreased the number of Lewis and Brönsted acid sites, but also blocked the pores, resulting in catalyst deactivation. Coke removal was effectively performed using an oxidative treatment. However, exchange of cations (e.g., Na) of the bentonite and possibly also from the crude glycerol feed with protons of ZSM-5 was observed, leading to irreversible deactivation. Furthermore, the layered structure of bentonite collapsed due to the removal of interlamellar water and dehydroxylation
Uma investigação sobre a relação entre o projeto do produto e produção em uma montadora automotiva e fornecedores de motores que adotam a modularidade
Toxic effects of lab-grade butyl rubber stoppers on aerobicmethane oxidation
Methods for measuring aerobic methane oxidation (MOx) rates in aquatic environments are often based
on the incubation of water samples, during which the consumption of methane (CH4) is monitored. Typically,
incubation vessels are sealed with butyl rubber because these elastomers are essentially impermeable for
gases. We report on the potential toxicity of five different commercially available, lab-grade butyl stoppers
on MOx activity in samples from marine and lacustrine environments. MOx rates in incubations sealed with
non-halogenated butyl were > 50% lower compared to parallel incubations with halogenated butyl rubber
stoppers, suggesting toxic effects associated with the use of the non-halogenated butyl type. Aqueous extracts
of non-halogenated butyl rubber were contaminated with high amounts of various organic compounds
including potential bactericides such as benzyltoluenes and phenylalkanes. Comparably small amounts of
organic contaminants were liberated from the halogenated butyl rubber stoppers but only two halogenated
stopper types were found that did not seem to leach any organics into the incubation medium. Furthermore,
the non-halogenated and two types of the halogenated butyl elastomers additionally leached comparably
high amounts of zinc. While the source of the apparent toxicity with the use of the non-halogenated rubber
stoppers remains elusive, our results indicate that leaching of contaminants from some butyl rubber stoppers
can severely interfere with the activity of MOx communities, highlighting the importance of testing rubber
stoppers for their respective contamination potential. The impact of leachates from butyl rubber on the
assessment of biogeochemical reaction rates other than MOx seems likely but needs to be verified
Fossil and non-fossil source contributions to atmospheric carbonaceous aerosols during extreme spring grassland fires in Eastern Europe
In early spring the Baltic region is frequently affected by
high-pollution events due to biomass burning in that area. Here we present a
comprehensive study to investigate the impact of biomass/grass burning (BB)
on the evolution and composition of aerosol in Preila, Lithuania, during
springtime open fires. Non-refractory submicron particulate matter
(NR-PM<sub>1</sub>) was measured by an Aerodyne aerosol chemical speciation
monitor (ACSM) and a source apportionment with the multilinear engine (ME-2)
running the positive matrix factorization (PMF) model was applied to the
organic aerosol fraction to investigate the impact of biomass/grass burning.
Satellite observations over regions of biomass burning activity supported
the results and identification of air mass transport to the area of
investigation. Sharp increases in biomass burning tracers, such as
levoglucosan up to 683âŻngâŻm<sup>â3</sup> and black carbon (BC) up to 17âŻÂ”gâŻm<sup>â3</sup>
were observed during this period. A further separation between
fossil and non-fossil primary and secondary contributions was obtained by
coupling ACSM PMF results and radiocarbon (<sup>14</sup>C) measurements of the
elemental (EC) and organic (OC) carbon fractions. Non-fossil organic carbon
(OC<sub>nf</sub>) was the dominant fraction of PM<sub>1</sub>, with the primary
(POC<sub>nf</sub>) and secondary (SOC<sub>nf</sub>) fractions contributing 26â44âŻ% and
13â23âŻ% to the total carbon (TC), respectively. 5â8âŻ% of the TC had a
primary fossil origin (POC<sub>f</sub>), whereas the contribution of fossil
secondary organic carbon (SOC<sub>f</sub>) was 4â13âŻ%. Non-fossil EC
(EC<sub>nf</sub>) and fossil EC (EC<sub>f</sub>) ranged from 13â24 and 7â13âŻ%,
respectively. Isotope ratios of stable carbon and nitrogen isotopes were
used to distinguish aerosol particles associated with solid and liquid
fossil fuel burning