Presence Of High Pressure Hydrogen Research Articles

Comparison of Mg-ethoxide based Ziegler Natta catalysts using different internal donors employed for ethylene polymerization

The effect of two types internal electron donors (IDs) on Mg-ethoxide based ZN catalysts employed for ethylene polymerization, was investigated using three similar catalysts with different IDs. P-cat (containing di isobutyl phthalate), S-cat (containing tetra ethoxy silane) at a constant molar ratio ID/Mg = 0.1, and N-cat (with no electron donor) were analyzed by FTIR, XRD, SEM, PSD, and BET. Some of available data of an Industrial catalyst (I-cat) were added to compare. FT-IR spectroscopy in transmission mode confirmed the presence of each electron donor in the catalyst. X-ray patterns of the catalysts showed that the disordered structure of δ-MgCl2 was formed in each catalyst and IDs in this manner do not influence the crystallinity of the support. This study showed that the use of IDs has a great influence on the resulting catalyst morphology (particle size and porosity) so that S-cat has the lower particle size and higher porosity but P-cat has the highest particle size and the lowest porosity. Ethylene polymerization was performed using catalysts under the same set of conditions (time, temperature, and Al/Ti) and in the presence of high pressure hydrogen. Then to better compare, an industrial catalyst (I-cat) was also used in this condition and the result were compared by the synthesized catalysts. The activity of catalysts with various kinds of IDs is in the following order: S-cat > N-cat > I-cat > P-cat. To better comparison, the kinetic polymerization rate of catalysts was fitted by a simple model and showed that the P-cat activated more slowly than others, I-cat has the fasten activation and deactivation rate, and S-cat has the highest propagation rate constant. IDs can change the active site behavior against hydrogen by affecting on the chain lengths measured by MFR value and molecular weight distribution. DSC analysis of the polymers showed the IDs can change the crystalline content of homo polyethylene. So that polymer obtained from P-cat and N-cat have more crystalline ( $$\approx$$ 80%) but polymer from S-cat has lower crystalline content ( $$\approx$$ 65%). Polymers with higher crystallinity also have lower molecular weight value. The polymer Bulk density as an important industrial parameter are presented for the catalysts.

Synthesis of hierarchical SAPO-34 to improve the catalytic performance of bifunctional catalysts for syngas-to-olefins reactions

Bifunctional process integrating methanol synthesis and methanol-to-olefins conversion provides a new synthetic strategy for lower olefins (C2C4=), whereas designing matchable zeolite components is still challenging due to the harsh reaction conditions. Here, a hierarchical SAPO-34 zeolite with a sandglass-like hollow structure is synthesized from an aluminum-rich precursor gel, which provides an abundance of crystal defects during zeolite crystallization. The bifunctional catalyst obtained by integrating the hierarchical SAPO-34 and ZnOZrO2 oxide offers a C2C4= selectivity of 80% at 25% CO conversion with excellent stability in syngas conversion. We demonstrate that in the presence of high-pressure hydrogen, a moderate density of acid sites is the prerequisite for obtaining high C2C4= selectivity in syngas/methanol conversion, because the olefins are easily hydrogenated into alkanes by excessive Brønsted acid sites. The hierarchical architecture significantly prolongs the lifetime of bifunctional catalysts, by facilitating C2C4= desorption and slowing down the coking rate.

Upgrading of hydrothermal liquefaction biocrude from algae grown in municipal wastewater

Algae biocrude was treated with hydrogen using metal catalysts supported on activated carbon for the production of biofuel. The biocrude was produced using hydrothermal liquefaction of microalgae (Scenedesmus-dominated polyculture) grown in municipal wastewater. Four metal catalysts (platinum, ruthenium, nickel and cobalt) were tested at 350°C under the presence of high pressure hydrogen, and all the experiments were conducted at a weight hourly space velocity of 0.51g/gcat·h. Hydrotreating with all the catalysts increased higher heating value, while reducing viscosity and total acid number (TAN) of the biocrude. For example, biocrude upgraded using platinum catalyst increased the heating value from 45.9 to 47.0MJ/kg and reduced the TAN from 11.56 to 0.1mgKOH/g. In addition, the liquid produced was colorless. Furthermore, the use of ruthenium and platinum catalysts greatly enhanced the yield of hexadecane and octadecane in the hydrogen-treated liquids whereas heptadecane was less favored. Overall, hydrogen treatment of biocrude was effective in improving the quality of biocrude produced from algae grown in wastewater. The BET surface area was reduced for all the spent catalysts. An SEM-EDS analysis revealed that some liquid products and sulfur were deposited in the spent catalysts.

The Role of Nonstoichiometry on the Electrocatalytic Properties of TiO2-δ towards the Conversion of Carbon Dioxide to Fuels

Crystalline titanium oxide (TiO2), which exists in the three ubiquitous phases: rutile, anatase and brookite, possesses a direct wide band gap (Eg ~ 3.3 eV at 300 K) similar to that of GaN (Eg ~ 3.4 eV at 300 K), is under consideration as an alternative material to replace GaN for optoelectronic applications. It's known that reduced titanium dioxides (TiO2-x and TiO) exhibit some unique chemical activities towards water oxidation. In this presentation, we will report our recent studies of using TiO2-x and TiO as the electrocatalysts to convert carbon dioxide to fuels by incorporating the electrocatalysts into a polymer exchange membrane fuel cell (PEMFC) based full electrochemical cell. Nonstoichiometric Ti3O5 was prepared by reducing TiO2 at high temperature in the presence of high pressure hydrogen. X-ray diffraction and thermogravimetric analysis were used to analyze the phase and nonstoichiometry of TiO and Ti3O5. Ti3O5 exhibits the highest Faradaic efficiency (~ 12%) towards the formation of formate, comparing to < 2% for both TiO and TiO2 P25. X-ray photoelectron spectroscopy (XPS) measurements of the Ti3O5 gas diffusion electrodes (GDEs) before and after electrolysis also suggest the presence of surface defects such as Ti3+ and oxygen vacancies which significantly influence the electrocatalytic activity for CO2 reduction.

Hydrogen embrittlement resistance of GRCop-84

GRCop-84 contains approximately 5.5 wt% Nb. Nb can react with hydrogen and embrittle easily. Previous work had indicated the thermodynamic possibility that Cr 2Nb could react with hydrogen and form niobium hydrides in the presence of high pressure hydrogen. In this study, samples were charged with hydrogen and tested in both high pressure gaseous H 2 and He environments to determine if measurable differences existed which indicate that hydrogen embrittlement occurs in GRCop-84. Tensile, notched tensile, stress rupture and low cycle fatigue properties were surveyed. High pressure H 2 environment stress rupture testing resulted in a lower reduction in area than a high pressure He environment, and the LCF lives at high strain ranges fall below the lower 95% confidence interval for the baseline data, but in general no significant differences were noted either between H 2 and He environment tests or between H charged materials and the baseline, uncharged extruded GRCop-84 data sets. There was also no discernable evidence of the formation of hydrides or changes in fracture morphology indicating hydrogen embrittlement occurred.

Study of the reaction of Rh(acac)(CO) 2 with alkenes in polyethylene films under high-pressure hydrogen and the Rh-catalysed hydrogenation of alkenes

The thermal reaction of Rh(acac)(CO) 2 with alkenes has been studied both in the absence and in the presence of high-pressure hydrogen using in situ FTIR and polymer matrix techniques. A series of rhodium alkenes complexes, Rh(acac)(CO)(alkene) (alkene=ethene, propene, 1-butene, 1-octene and trans-3-octene), have been characterized using IR spectroscopy. In the presence of a high-pressure hydrogen, catalytic hydrogenation of alkenes was achieved using Rh(acac)(CO) 2 within the polyethylene matrix. These results suggest that this hydrogenation process follows the so-called “olefin route” operating via a sequence of ligand loss, binding of an alkene, oxidative addition of hydrogen to the rhodium metal centre, insertion of the coordinated alkene into the MH bond and finally reductive elimination of the alkane. Rh(acac)(CO) appears to be the active catalytic species in this process. High-pressure polymer matrix techniques have allowed us to unravel some of the interconversions of the catalytic species involved in this catalytic process.

高圧水素下におけるクレゾールの脱アルキル反応

高圧水素下におけるクレゾールの脱アルキル反応

Dealkylation Rates of Xylene Isomers in the Presence of High Pressure Hydrogen

Dealkylation Rates of Xylene Isomers in the Presence of High Pressure Hydrogen

Method of Calculation of Equilibrium Flash Vaporization of Petroleum Oils in the Presence of High Pressure Hydrogen

Method of Calculation of Equilibrium Flash Vaporization of Petroleum Oils in the Presence of High Pressure Hydrogen

The catalytic destructive hydrogenation of paraffin wax

1. When heating paraffin wax in an autoclave in the presence of high pressure hydrogen at 450°C during one hour as described below, approx. 30% by weight of this wax is converted into hydrocarbons boiling below 100°C. 2. Under identical conditions but in the presence of hydrogenation catalysts the conversion into lower hydrocarbons was far more pronounced. For instance, by the use of tungsten disulphide as hydrogenation catalyst even 75% by weight of the wax was converted into hydrocarbons boiling below 100°C. Moreover the quality of the reaction products was different. In the experiments in the presence of hydrogenation catalysts these products were far more or completely saturated and the formation of cyclic compounds was very low in comparison with the products of hydrogenation without a catalyst. The catalysts used were : nickel on guhr (i.e. kieselguhr), tungsten disulphide, colloidal molybedunum on active carbon and molybdenum trioxde. 3. By the use of SiO 2-Al 2O 3 cracking catalyst under otherwise identical conditions conversion into lower hydrocarbons was also increased as compared with the experiments mentioned under 1. The products, however, were more unsaturated but they contained about the same amount of rings per molecule, that is approx. 0·3. 4. By the use of mixed type catalyst the conversion as well as the quality of the products were between those of the experiments mentioned under 2 and 3.