Carbonyl Removal Research Articles

A novel production of aromatic hydrocarbons via dielectric barrier discharge assisted one-stage pyrolysis-catalysis of biomass: Insights into modified HZSM-5 selectivity and stability

Dielectric barrier discharge (DBD) was employed to assist to convert biomass into aromatic hydrocarbons under the vacuum pyrolysis and zeolite catalysis conditions. This study was to investigate the selectivity and stability of HZSM-5 modified by Ti, Ni, and Ni-Ti. The texture and acidity of different modified catalysts varied greatly. Ti modification strengthened the cracking removal of carbon and oxygen, while Ni-modified version improved hydrogen transfer capacity. Bimetallic modification increased the HHV to 36.93 MJ/kg, and obtained a compromised yield of 28.10%. Hydroxyl was difficult to completely remove due to hydrophilicity, carbonyl removal was better, and refined bio-oils had a high aromatic degree, of which, bimetallic modification increased the selectivity of MAHs to 76.61% and the refined bio-oil was more suitable to be used as gasoline additives. Although the aromatization performance of Ti-modified version was weaker than that of Ni-modified version, its anti-coking performance was better. The acidity adjustment of bimetallic modification cooperated with the synergistic effect of metal species and discharge, so that the difficulty of carbon deposition was increased significantly. The high-temperature catalytic coke was not distinguished and the low-temperature thermal coke mainly deposited on the outer surface was further reduced for bimetallic modified catalyst. Therefore, the Ni-Ti/HZSM-5 assisted by DBD exhibited better potential in improving the selectivity of aromatic hydrocarbons and enhancing the stability of zeolite catalyst.

Two-step continuous upgrading of sawdust pyrolysis oil to deoxygenated hydrocarbons using hydrotreating and hydrodeoxygenating catalysts

The two-step hydrodeoxygenation of pine sawdust pyrolysis oil, or bio-oil, is performed using pairs of first-step hydrotreating and second-step hydrodeoxygenating catalysts. The reaction results demonstrate that the combination of hydrotreating carbon-supported 5wt% Pd (5wt% Pd/C) and hydrodeoxygenating tungstate-zirconia-supported 3wt% Ru (3wt% Ru/WZr) catalysts produced the highest yield of oil products and the lowest yield of cokes and tars. The hydrodeoxygenated liquid products are further analyzed using FT-IR, which indicates the removal of carbonyls and hydroxyls along with an increase of methyls. The roles of hydrotreating Pd/C are further studied using GC/MS results of the hydrotreated liquid products; these results indicate that the hydrogenation of carbonyls to alcohols and the saturation of furans occur during the first step of the hydrotreating process. The removal of carbonyls and unsaturated furans can suppress their strong adsorption to noble metal surfaces and then their carbonization to cokes.

Photolytic processing of secondary organic aerosols dissolved in cloud droplets

The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ∼0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest that biogenic SOA dissolved in cloud and fog droplets will undergo significant photolytic processing on a time scale of hours to days. This type of photolytic processing may account for the discrepancy between the higher values of O/C measured in the field experiments relative to the laboratory measurements on SOA in smog chambers. In addition, the direct photolysis of oligomeric compounds may be responsible for the scarcity of their observation in the field.

Alkyne/Methylene Coupling Reactions at Adjacent Rh/Os Centers: Stepwise Transformations from C1- through C4-Bridged Species

Reaction of the methylene-bridged complex [RhOs(CO)3(μ-CH2)(dppm)2][CF3SO3] (dppm = μ-Ph2PCH2PPh2) with dimethyl acetylenedicarboxylate or hexafluorobutyne results in alkyne insertion into the Rh−CH2 bond, yielding [RhOs(CO)3(μ-η1:η1-RCC(R)CH2)(dppm)2][CF3SO3] (R = CO2Me (5), CF3 (6)). Carbonyl removal from each of these species results in a Rh-bound carbonyl being replaced by a triflate ion. Reaction of 5 with diazomethane results in CH2 insertion into the Rh−C(R) bond with accompanying C−H activation of the original osmium-bound CH2 group, yielding [RhOs(CO)3(μ-η1:η1-CH2C(R)C(R)CH)(μ-H)(dppm)2][CF3SO3] (R = CO2Me). Reaction of the alkyne-bridged species [RhOs(CO)3(μ-η1:η1-RCCR)(dppm)2][CF3SO3] (R = CO2Me) with diazomethane at −78 °C yields [RhOs(CO)3(μ-η1:η1-CH2C(R)CR)(dppm)2][CF3SO3] (12), which upon warming to ambient temperature, in the absence of diazomethane, undergoes alkyne deinsertion to yield [RhOs(CO)3(η2-RC⋮CR)(μ-CH2)(dppm)2][CF3SO3] (13). This species and the inserted product (12) appear to ...

Enhancement of diapausing flesh fly puparia with additional hydrocarbons and evidence for alkane biosynthesis by a decarbonylation mechanism

Puparia of diapausing flesh flies, Sarcophaga crassipalpis, are lined with twice as much hydrocarbon as their nondiapausing counterparts ( ca 15 vs 7 μg). The quantity of epicuticular hydrocarbon increases throughout the life of the fly, but it is only in the pupal stage that a distinction can be made between diapausing and nondiapausing cohorts. Though some of the additional hydrocarbon is deposited on the exterior surface of the puparium, the bulk of the additional hydrocarbon is on the interior surface of the puparium. The few flies that fail to diapause when reared under short day conditions also produce puparia enhanced with an abundance of hydrocarbon, thus implying that the increase in production of hydrocarbons is not invariably linked to the expression of diapause. Elevation of temperature can increase the quantity of hydrocarbon produced in puparia from nondiapausing flies, but this effect is modest in comparison to the effect of short-day (diapause) programming. In addition, we demonstrate that flesh flies convert fatty acid to alkane utilizing a mechanism that first involves reduction of fatty acid to aldehyde (with ATP, CoA and NADH as required cofactors), then carbonyl removal from aldehyde (no cofactors needed). Thus, we provide the first evidence that hydrocarbon synthesis in insects involves decarbonylation.

Carbonyl Removal from Nonoxygenated Solvents.

Carbonyl Removal from Nonoxygenated Solvents.