Catalyst Mixture Research Articles

Influence of catalysts on hydrogen production from wastewater generated from the HTL of human feces via catalytic hydrothermal gasification

The aqueous phase from the hydrothermal liquefaction of human feces is rich in organic matter. This study explored the usage of different catalysts on the catalytic hydrothermal gasification (CHG) of wastewater resulting from the hydrothermal liquefaction of human feces. The catalyst screening study revealed that NaOH (46.9%) and Raney Ni (41.2%) resulted in the highest H2 composition, while Ru/AC resulted in the highest reduction in the liquid COD (97.7%). A catalyst mixture was then studied combining two heterogeneous catalysts, Raney Ni and Ru/AC, at different ratios to increase the H2 composition. A weight ratio of 90% Raney Ni and 10% Ru/AC yielded a H2 composition of 56.3%, a gas yield of 350.0 g/kg dry feed, and a H2 yield of 10.61 mol/kg dry feed, indicating that catalyst synergy may exist between these two catalyst which further enhances H2 production. Incorporation of a reaction coordinate diagram allowed for the direct comparison of energy recovery, CODr, and H2/COD value using a mixed Raney Ni and Ru/AC catalyst and varying temperatures and reaction times. Results showed that the optimal condition to maximize the H2/COD content (9.5 mg H2/g COD), the CODr (64.3%), and energy recovery (30.4%) occurred at a temperature of 400 °C, a retention time of 60 min, and a catalyst to feedstock ratio of 0.1.

Effect of different additives and their mixtures on thermal stability of polyethylene synthesized using iron and titanocene hybrid catalysts

ABSTRACTTraditionally, additives are introduced into a polymer matrix via extrusion process which consumes a high amount of energy. In this study, the use of different additives including antioxidants for the in‐reactor stabilization of polyethylene has been investigated in order to provide an energy saving system. Particular attention was dedicated to the efficiency of antioxidant influencing the catalysts activity and properties of polymers. The effect of the addition of Irganox 1330 and Irgafos 168 antioxidants and zinc stearate on the activities of metallocene, post‐metallocene, and their supported hybrid were studied. In addition, the effect of different additives on the thermal characteristics of the synthesized polymers and oxidative induction time (OIT) was evaluated. Our polymerization results exhibited that the factors such as chemical structure of antioxidant and its steric hindrance, type of catalysts, and their hybrid could affect the catalyst performance and OIT contents. The use of antioxidants mixture and hybrid of catalysts is a way that can increase oxidation resistance of polymers considerably. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45482.

On A-doping strategy for tuning the TWC catalytic performance of perovskite based catalysts

Several perovskites of the type La1-xAxCo0.5Cu0.5O3 (A=K, Sr, Ba; x=0, 0.25, 0.5) and a Sr-doped understoichiometric one, have been prepared by citrate method aiming at application as noble metals free catalysts for automotive application. The catalysts have been characterized by BET, X-ray diffraction (XRD), Temperature Programmed Reduction (TPR), X-Ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM) and the effect of A-doping has been investigated. The catalytic activity was studied in model reactions (CO oxidation, CO assisted NO reduction), and in a complex three way catalysts (TWC) mixture approaching automotive exhaust composition at both stoichiometric and O2-limiting conditions and the obtained results are discussed in relation with characterization results. A-doping induces the formation of highly dispersed cubic CuO particles, as observed in the understoichiometric samples. Doping also influences the surface segregation. La segregation is observed in the undoped LaCo0.5Cu0.5O3 sample whereas K is surface segregated in La0.75K0.25Co0.5Cu0.5O3; Co segregates in the Ba-doped perovskite and Sr in the understoichiometric La0.35Sr0.35Co0.5Cu0.5O3. The reducibility (TPR) is altered by A-doping. The reactivity results suggest that in simple CO+O2 and CO+NO mixtures the activation temperature is increased by any doping, but at 400°C the conversion in the CO assisted NO reduction is not significantly different with respect to the one obtained in the undoped catalyst. Activity with a more complex mixture, simulating actual engine exhaust, reveals the interesting activity of the Sr-doped catalysts, that outperform LaCo0.5Cu0.5O3 at both stoichiometric and O2-lean conditions. NO reduction can be achieved at lean O2 conditions, where it is quantitative from 400°C. The possibility to reach similar or better activity by replacing the use of La, which is a Rare Earth Element, by using Sr is particularly interesting. Stability at high temperatures and at fast fluctuations of O2 in inlet stream for 50% Sr-doped catalyst confirms these results.

Methane dry and mixed reforming on the mixture of bio-char and nickel-based catalyst with microwave assistance

This paper concerns microwave-assisted methane reforming with or without water. In this work, a heterogeneous mixture of biomass derived char (i.e., bio-char) and a commercial nickel-based catalyst is used for the reforming reaction. The obtained conversions, equivalent carbon consumption, energy efficiency and consumption are focused on. Ni/bio-char with the weight ratio of 10% imposes better activity than others. Equivalent carbon consumption on these materials initially decreases with time and tends to be stable afterward. Carbon consumption in bio-char is relieved when using Ni/bio-char with the ratio ranged from 5% to 10%. Energy efficiency is dependent of the used material and the reforming temperature. The optimized efficiency under the higher temperature is obtained on Ni/bio-char with the lower ratio. Energy consumption on Ni/bio-char with the ratio of 10% is 7.9kWh−1 of per m3 of syngas produced and this value is lower than others. From the point of the conversions, carbon consumption and energy utilization, Ni/bio-char with the ratio of 10% is favorable for the reforming reaction. The obtained conversions and the H2/CO ratio are promoted in mixed reforming on Ni/bio-char.

A new approach of probe sonication assisted ionic liquid conversion of glucose, cellulose and biomass into 5-hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) has been identified as a promising biomass-derived platform chemical. In this study, one pot production of HMF was studied in ionic liquid (IL) under probe sonication technique. Compared with the conventional heating technique, the use of probe ultrasonic irradiation reduced the reaction time from hours to minutes. Glucose, cellulose and local bamboo, treated with ultrasonic, produced HMF in the yields of 43%, 31% and 13% respectively, within less than 10min. The influence of various parameters such as acoustic power, reaction time, catalysts and glucose loading were studied. About 40% HMF yield at glucose conversion above 90% could be obtained with 2% of catalyst in 3min. Negligible amount of soluble by-product was detected, and humin formation could be controlled by adjusting the different process parameters. Upon extraction of HMF, the mixture of ionic liquid and catalyst could be reused and exhibited no significant reduction of HMF yield over five successive runs. The purity of regenerated [C4C1im]Cl and HMF was confirmed by NMR spectroscopy, indicating neither changes in the chemical structure nor presence of any major contaminants during the conversion under ultrasonic treatment. 13C NMR suggests that [C4C1im]Cl/CrCl3 catalyses mutarotation of α-glucopyranose to β-glucopyranose leading to isomerization and finally conversion to HMF. The experimental results demonstrate that the use of probe sonication technique for conversion to HMF provides a positive process benefit.

Evaluating 1,1′-Bis(phosphino)ferrocene Ancillary Ligand Variants in the Nickel-Catalyzed C–N Cross-Coupling of (Hetero)aryl Chlorides

Previous reports in the literature have established the utility of 1,1′-bis(diphenylphosphino)ferrocene (DPPF, LPh) in the nickel-catalyzed cross-coupling of (hetero)aryl electrophiles with primary or secondary amines. In an effort to evaluate the effect of varying the PR2-donor groups on catalytic performance in such transformations, a series of 10 structurally varied 1,1′-bis(bis(alkyl/aryl)phosphino)ferrocene ancillary ligands (LX) were systematically examined in selected competitive test cross-couplings of (hetero)aryl halides with furfurylamine, morpholine, and indole employing Ni(COD)2/LX catalyst mixtures. In addition to the excellent performance observed for the parent ligand LPh in a number of the test transformations explored, selected dialkylphosphino (e.g., DiPPF, LiPr) and meta-disubstituted diarylphosphino variants of LPh also proved highly effective. In particular, the electron-deficient ligand variant LCF3 featuring 3,5-bis(trifluoromethyl)phenyl groups on phosphorus was found to exhibit s...

Synthesis and physical properties of multi-layered graphene sheets by Arc-discharge method with TiO2 and ZnO catalytic

In this paper, a study to improve the structural properties of graphene synthesized by Arc discharge method with TiO2 and ZnO catalysts was studied. We have developed a method for synthesizing few layered graphene by arc- discharge in a mixture of graphite flake and different catalysts. In the presence of TiO2 and ZnO catalytic, growth mechanism is different from the mechanism of growth in the absence of catalysts. Two different growth mechanisms have been proposed. The catalytic growth mechanism that is a bottom to up approach and the exfoliation mechanism that is an up to bottom approach. Structural properties, morphology and functional groups of samples by transmission electron microscopy, scanning electron microscope, X-ray diffraction, FTIR, UV–Vis, and Raman were analyzed. The results show that graphene sheets have been produced in all methods. This study showed that Arc- graphene synthesis with TiO2 as catalytic has the best structural properties. The obtained graphene nano-sheets showed the in-plane crystallite size from 35.6 nm to 53.6 nm. The results show that the AC arc-discharge method can be used for few-layer graphene sheet synthesis with flake graphite as a carbon source and TiO2 or ZnO as a catalyst.

A systematic study on mixtures of Pt/zeolite as hydroisomerization catalysts

Mixtures of bifunctional catalysts exhibited cooperative effects in the hydroisomerization of n-hexadecane. The performance of a hybrid can be simulated based on those of individuals, as illustrated.

Electrochemical devices comprising novel catalyst mixtures

Electrochemical devices comprising novel catalyst mixtures

Study of composition of the ultrafine material produced from graphite–catalyst mixture under extreme energy action

Ultrafine materials were produced under conditions of extreme energy effects on the mixture of graphite and Ni-Mn catalysts. For the purpose to obtain various forms of carbon, including diamond-like forms, experiments were performed on a MIG high-current generator with the current amplitude of 2-2.5 MA and current rise time of 100 ns. The composition of the explosion products was studied using x-ray diffraction and x-ray phase analyses, the impedance spectroscopy, optical and scanning electron microscopy, x-ray microanalysis and energy dispersive x-ray analysis and the laser confocal Raman microscopy. It was found that the carbon in the studied materials is in the graphite, diamond-like (the faceted particles or agglomerates of faceted particles in size about or less than 250 nm) and amorphous forms.

FCC riser quick separation system: a review

The riser reactor is the key unit in the fluid catalytic cracking (FCC) process. As the FCC feedstocks become heavier, the product mixture of oil, gas and catalysts must be separated immediately at the outlet of the riser to avoid excessive coking. The quick separation system is the core equipment in the FCC unit. China University of Petroleum (Beijing) has developed many kinds of separation system including the fender-stripping cyclone and circulating-stripping cyclone systems, which can increase the separation efficiency and reduce the pressure drop remarkably. For the inner riser system, a vortex quick separation system has been developed. It contains a vortex quick separator and an isolated shell. In order to reduce the separation time, a new type of separator called the short residence time separator system was developed. It can further reduce the separation time to less than 1 s. In this paper, the corresponding design principles, structure and industrial application of these different kinds of separation systems are reviewed. A system that can simultaneously realize quick oil gas separation, quick oil gas extraction and quick pre-stripping of catalysts at the end of the riser is the trend in the future.

Organophilization of Muscovite Mica for the Synthesis of High Molar Mass/Branched‐Polyethylene Blend Nanocomposites

SummaryUltra‐high molecular weight polyethylene (UHMWPE) has excellent physical and mechanical properties. However, due to the high viscosity of UHMWPE it is difficult to process by conventional extrusion and injection since this polymer does not flow. One of the methodologies used to enable the processing of UHMWPE is by obtaining UHMWPE blends. In the present work, we have synthesized polymer blends directly in the polymerization reactor employing a mixture of catalysts, where one catalyst has a nickel center able to produce a low viscosity polyethylene, which would facilitate the processing of the material, and the other catalyst contain a titanium center responsible for the synthesis of UHMWPE. However, the incorporation of another polymer in the UHMWPE matrix can decrease its properties. Therefore, to prevent property losses, the incorporation of a nanoclay in the blend improves the properties of the final material. We used muscovite mica as nanofiller since it has higher aspect ratio than montmorillonite. Mica was modified by treatment with LiNO3/ammonium‐salt, resulting in a sharp increase of the interlayer distance. The obtained organomica was used as support for the co‐immobilization of Ti/Ni catalytic mixture to produce nanocomposites of the blend UHMWPE/branched‐PE/Mica.

In-situ incorporation of binder during sol-gel preparation of Pd-based sulfated zirconia for reduction of nitrogen oxides under lean-burn conditions: Effect on activity and wash-coating characteristics

We have developed a dual-catalyst aftertreatment system for reducing nitrogen oxides (NOx) in the exhaust stream of natural gas-fired lean-burn engines by utilizing the unburned hydrocarbons present in the engine exhaust. The dual-catalyst bed consists of a physical mixture of a reduction catalyst (Pd/SZ) and an oxidation catalyst (Co/CeO2). In order to make this dual-catalyst system viable for practical use in the real aftertreatment units, it is necessary to develop a catalytically active washcoat for loading it onto cordierite monolith cores. To be able to handle large throughputs of gases typical of aftertreatment units, irreversible loss of activity due to separation of the wash-coat from the monolith walls can be reduced by adding binders to improve the adhesive properties of the wash-coat. However, addition of such binders may affect the catalytic activity of the resulting dual-catalyst bed. In our study, we have incorporated binders such as alumina, boehmite, bentonite or silica to the Pd/SZ catalyst using a novel technique in which the binders were added in situ during the sol-gel synthesis rather than the conventional method of adding binders (ex-situ) in catalyst slurry. Surface area analysis, X-ray diffraction (XRD) and diffuse reflectance Fourier transform spectroscopy (DRIFTS) with pyridine show that in-situ addition of binder affects the textural properties, crystal phase of zirconia and the acidic properties of the resulting Pd/SZ catalyst respectively. Electron Paramagnetic Resonance (EPR) indicated the presence of Pd+, Pd3+ and Zr3+ species in the binder-free and in situ alumina-incorporated Pd/SZ catalysts. Furthermore, steady-state activity tests on the modified dual-catalyst bed with the alumina-incorporated Pd/SZ exhibit the best performance amongst the other binder-incorporated catalysts in the dual-catalyst bed. In-situ incorporation of binder during sol-gel synthesis yielded catalysts with far superior catalytic activity for NOx reduction than conventional ex-situ binder addition to the catalyst slurry for wash-coating. Time-on-stream experiments show that the alumina-incorporated Pd/SZ catalyst maintains the hydrothermal stability of the binder-free Pd/SZ in the mixed bed. Several parameters such as pH of the binder-incorporated catalyst slurry and calcination temperature of the wash-coat have also been optimized to develop a catalytically active wash-coat and its adhesivity and uniformity were tested using ultrasonication, cyclic thermal shock and SEM imaging.

Considerations on the mechanism of Ca/ethanol/Pd/C assisted hydrodechlorination of chlorinated aromatic substrates

In order to elucidate the metal-alcohol hydrodechlorination reaction mechanism, several experiments using chloroanisoles as substrates were performed. Thus, chloroanisoles were stirred at 60 °C for 2 h with a mixture of Ca, methanol and various reduction catalysts. The use of deuterated methanol and zeta potential experiments offered supplementary informations, pointing toward a probable radicalic mechanism that occurs on Ca and Pd/C surfaces.

A fluidizable Zn-offretite for selective thiophenic species adsorption. Additive performance under FCC conditions

This study evaluates a new Zn-OFF additive (3.5wt% of Zn in an offretite zeolite) to reduce sulfur in gasoline range hydrocarbons. The additive is contacted with Thiophene (Th), 2-methyl-thiophene (2MTh) and 2,5-dimethyl-thiophene (25DMTh) which are used to represent sulfur species. These species are concurrently fed with 1,3,5 trimethylbenzene (TMB) into a CREC Fluidized Reactor Simulator. Selected temperatures, partial pressures, reaction times and C/Os (catalyst/oil) are representative of operating conditions in FCC industrial units. It is proven that the Zn-OFF additive displays an excellent performance for 2MTh selective adsorption. The best sulfur removal using the Zn-OFF additive was found using the 2MTh at 530°C and 5s. It is hypothesized that the selective sulfur adsorption on the Zn-OFF additive involves dominant Lewis acid sites. On the basis of the results reported, it is anticipated that the Zn-OFF additive can provide a valuable “in situ” sulfur selective adsorption for the thiophene compounds. It is also found that the used Zn-OFF additive while blended with a FCC commercial catalyst mixture reduces coke production, in particular sulfur in coke. It is thus, demonstrated that under typical FCC unit operating conditions, the Zn-OFF additive can decrease sulfur in coke with this leading to a mitigation of SOx emissions in the FCC regenerator, where coke is combusted.

Ultra‐Long Crystalline Red Phosphorus Nanowires from Amorphous Red Phosphorus Thin Films

AbstractHeating red phosphorus in sealed ampoules in the presence of a Sn/SnI4 catalyst mixture has provided bulk black phosphorus at much lower pressures than those required for allotropic conversion by anvil cells. Herein we report the growth of ultra‐long 1D red phosphorus nanowires (>1 mm) selectively onto a wafer substrate from red phosphorus powder and a thin film of red phosphorus in the present of a Sn/SnI4 catalyst. Raman spectra and X‐ray diffraction characterization suggested the formation of crystalline red phosphorus nanowires. FET devices constructed with the red phosphorus nanowires displayed a typical I–V curve similar to that of black phosphorus and a similar mobility reaching 300 cm2 V−1 s with an Ion/Ioff ratio approaching 102. A significant response to infrared light was observed from the FET device.

Ultra-Long Crystalline Red Phosphorus Nanowires from Amorphous Red Phosphorus Thin Films.

Heating red phosphorus in sealed ampoules in the presence of a Sn/SnI4 catalyst mixture has provided bulk black phosphorus at much lower pressures than those required for allotropic conversion by anvil cells. Herein we report the growth of ultra-long 1D red phosphorus nanowires (>1 mm) selectively onto a wafer substrate from red phosphorus powder and a thin film of red phosphorus in the present of a Sn/SnI4 catalyst. Raman spectra and X-ray diffraction characterization suggested the formation of crystalline red phosphorus nanowires. FET devices constructed with the red phosphorus nanowires displayed a typical I-V curve similar to that of black phosphorus and a similar mobility reaching 300 cm(2) V(-1) s with an Ion /Ioff ratio approaching 10(2) . A significant response to infrared light was observed from the FET device.

Promotion effect between Ni and Co aerogel catalysts in CH4 reforming with CO2 and O2

Ni-MgO/Al2O3 (Ni-A) and Co-MgO/Al2O3 (Co-A) aerogel catalysts are mechanically mixed with different weight ratios and their catalytic performances in CH4 reforming with CO2 and O2 are investigated. The catalyst mixtures showed higher CH4 conversions than those theoretical values predicted from the mixture law, indicating an interesting promotion effect between them. The catalysts are characterized by XRD, BET, SEM, TG/DTG and Raman spectrum techniques. It is disclosed that the reduced Co-A can be easily oxidized during the reaction, but Ni-A can prevent its oxidation during the reaction, which enables Co-A in the mixture to maintain its catalytic reforming ability. CH4 conversion is raised dramatically for ∼50% as comparing the catalysts mixtures with Co-A. On the other hand, the amount of carbon can be decreased by ∼17wt.% with the increase of Co-A’s weight ratio in the mixture. Meanwhile, carbon species on the spent catalysts turn from inactive graphite to active carbon species. This could be attributed to the strong affinity of Co-A for oxygen species and the decreased active metal particle size in the mixtures.

Cationic polymerization of isobutylene catalyzed by iBuAlCl2 in the presence of ethers: Effect of catalyst pre-activation and mixture of two ethers

Abstract The cationic polymerization of isobutylene using pre-activated by the wet argon or salts hydrates iBuAlCl2 as catalyst in the presence of diisopropyl ether in n-hexane at 10 °C as a starting temperature and high monomer concentration ([IB] = 5.8 M) has been investigated. It was shown that pre-activated iBuAlCl2 possessed high activity (>90% of monomer conversion in 10 min) and unexpectedly high regioselectivity of β-H abstraction at rather low ether to Lewis acid ratio (iPr2O/iBuAlCl2 = 0.4). The use of pre-activated iBuAlCl2 as a co-initiator leads to formation of more uniform active species that results in narrowing of molecular weight distribution as compared to polyisobutylenes synthesized with non-pre-activated iBuAlCl2. Much better control over polydispersity can be achieved by using of mixture of two ethers of different basicity and steric structure (diethyl and diisopropyl ethers) as additive instead of one (diisopropyl ether) during IB polymerization co-initiated by pre-activated iBuAlCl2. Under optimized conditions ([iBuAlCl2 pre-act.] = 38 mM, [Et2O] = [iPr2O] = 7.6 mM, [H2O] = 0.033 M, time: 15 min), desired low molecular weight (Mn ∼ 1000 g mol−1) highly reactive polyisobutylenes in high yield (>90%) with high content of exo-olefin end groups (>80%) and relatively low polydispersity (Mw/Mn = 2.4–2.7) were readily synthesized at high reaction temperature (10 °C) and monomer concentration ([IB] = 5.8 M).

Specifics of dimethyl ether synthesis from syngas over mixed catalysts

Dimethyl ether (DME) synthesis from syngas over a mixture of a methanol synthesis catalyst (ZnO, 25.10 wt %; AuO, 64.86 wt %; Al2O3, 10.04 wt %) and a methanol dehydration catalyst (γ-A12O3) has been investigated for one-, two-, and three-layer catalyst beds. There is a common regularity for these three variants: with an increasing temperature, the total CO conversion decreases, the CO-to-methanol conversion decreases, and the CO-to-DME conversion increases. The largest values of DME selectivity and DME yield have been attained with the three-layer bed. The highest DME yield has been obtained at 250–285°C. Use of a mechanical mixture of the methanol synthesis catalyst and alumina makes it possible to efficiently obtain DME from syngas ballasted with nitrogen (20 vol %) at an H2/CO ratio of 1, which is unfavorable for methanol synthesis. The DME yield on the syngas input basis in this case with the ballast gas (nitrogen or CO2) taken into account can be about 10 wt %.