The inhibition effect of three amphiphilic monoalkyl phosphate esters with different chain lengths, mono-n-butyl phosphate ester (BP), mono-n-hexyl phosphate ester (HP) and mono-n-octyl phosphate ester (OP), on the corrosion of iron in 0.5 M H 2 SO 4 solutions was investigated by using electrochemical impedance spectroscopy (EIS) and polarization curve methods. The electrochemical results indicate that, BP, HP and OP all acted as mixed type corrosion inhibitors with dominant cathodic effect. BP shows the lowest inhibition efficiency as compared to HP or OP. However, the inhibition efficiency of HP is almost the same with that of OP under similar conditions since the molecular aggregation state at the iron / solution interface plays a more important role. X-ray photoelectron spectroscopic (XPS) characterization demonstrates that three alkyl phosphate esters adsorbed on the iron surface through the unionized P-OH groups. The adsorption of BP, HP and OP fitted well with the Langmuir model.
We report herein on a new method to achieve a high yield of hydrocarbons from hydrothermal catalytic hydrodenitrogenation (HDN) of indole, which is higher than that from conventional pyrolysis methods. The main hydrocarbon products were aromatic hydrocarbons and alkanes, which are similar to fossil oils to be used as liquid fuels in the future. Catalyst screening experiments show that noble metal catalysts (e.g., 5 wt % Pt, Pd, or Ru) supported on porous solids (e.g., carbon, Al 2 O 3 ) enhanced the conversion of indole to hydrocarbons under hydrothermal condition. Of those different catalysts, Pd/γ-Al 2 O 3 shows the greatest influence on the yield of hydrocarbons, which we focus on the catalyst Pd/γ-Al 2 O 3 in more details. On the basis of the Pd/γ-Al 2 O 3 catalyst, the effects of time, temperature, and H 2 pressure on the hydrocarbons were discussed. HDN of the indole reaction at 450 °C, 0.015 g/cm 3 water density, 5 MPa H 2 , and 50 wt % Pd/γ-Al 2 O 3 loading led to a maximum yield (51 mol %) of hydrocarbons at 120 min. It proposes the mechanism to acquire hydrocarbons from hydrogenational indole denitrogenation, which experiences two different pathways, as (1) indole is directly hydrodenitrogenated into hydrocarbons, and (2) intermediate oxygenated products from hydrolysis of partly hydrodenitrogenated indole were hydrodeoxygenated to removal of O to acquire hydrocarbons. The factors for deactivation of catalyst under hydrothermal condition are also discussed by the results from characterizing the surface, bulk structure, and microscopy experiments.
Despite the vast potential for the depolymerization of kraft lignin in supercritical systems, selective access to desired renewable products remains a very challenging target. Catalytic depolymerization of kraft lignin was carried out in an isopropanol‐water mixture system over a Rh/La2O3/CeO2‐ZrO2 catalyst. The H2 selectivity was adjusted by changing the proportions of isopropanol and water. The introduction of formic acid was more helpful to extend the selectivity range. A correlation was established between liquid product distribution and H2 selectivity. It was used for predicting the composition of the liquid oil by H2 selectivity or, optionally, for converting kraft lignin to the desired liquid products. This correlation was applicable to different solvents, temperatures, and catalysts.
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