Deposition Precipitation Research Articles

Selective hydroconversion of lignin-derived compounds over a Ni/hydroxyapatite

Catalytic hydroconversion (CHC) of lignin-derived compounds (LDCs) to cyclanes and cyclohexanol (CHII) promotes the value-added utilization of LDCs. Nevertheless, designing a highly active and selective catalyst for this purpose remains a challenge. Herein, Ni/hydroxyapatite (HAP) was fabricated by a slightly modified deposition–precipitation approach and employed for the CHC of benzyloxybenzene (BOB) and phenethoxybenzene (PEOB) under different conditions. Consequently, BOB was fully converted with CHII and methylcyclohexane (MCH) as the main products (MPs) in the yield of 94.8 and 100 % under the optimum conditions of 20 mg Ni15/HAP, 140 °C, 4 MPa H2, and 4 h, while complete conversion of PEOB to CHII and ethylcyclohexane (ECH) as MPs proceeded under initial hydrogen pressure of 4 MPa at 180 °C for 4 h. In addition, other lignin-related model compounds can also be selectively hydrogenated to cyclanes and CHII, suggesting the high activity and selectivity of Ni15/HAP. Meanwhile, based on the product distribution and Ni15/HAP characterization, relevant mechanisms were proposed. Specifically, BOB conversion to CHII and MCH via the >CH–O– bond cleavage induced by H− addition, abstraction of H+ by the resulting phenoxy anion from the catalyst surface, and benzene ring hydrogenation, whereas conversion of PEOB to CHII and ECH was similar to BOB. Furthermore, Ni15/HAP displays an excellent reusability.

Chronic enhanced nitrogen deposition and elevated precipitation jointly benefit soil microbial community in a temperate forest

Global change profoundly impacts carbon and nitrogen (N) cycling processes in terrestrial ecosystems by altering soil microbial communities. However, how enhanced N deposition and elevated precipitation jointly affect soil microbes and the underlying mechanisms remain poorly understood, particularly in forest ecosystems. In a long-term field experiment conducted in a temperate forest in China, we added N and/or water above the forest canopy to investigate their effects on soil microbial communities. Our results showed that N addition led to a decrease in bacterial biomass while increasing fungal biomass, resulting in an alteration of soil microbial community structure. Conversely, water addition did not significantly impact soil microbial communities. However, when N and water were added together, both fungal and bacterial biomass notably increased, leading to alterations in the soil microbial community structure. These results suggested that the effect of N addition could be mediated by elevated precipitation. Precipitation increment amplified the positive impact of N deposition on soil fungi but shifted its impact on bacteria from negative to positive. Additionally, soil bacteria were affected by soil N availability and acidification, as well as litter quality, whereas fungi were regulated by litter quantity and soil organic carbon. This study provides crucial evidence that concurrent enhanced N deposition and elevated precipitation favor soil microbial communities in temperate forests. It highlights the potential of elevated precipitation to alleviate the negative impacts of enhanced N deposition on temperate forest ecosystems, thereby sustaining ecological stability under global change scenarios.

Geographic variation in projected US forest aboveground carbon responses to climate change and atmospheric deposition

Forest composition and ecosystem services are sensitive to anthropogenic pressures like climate change and atmospheric deposition of nitrogen (N) and sulfur (S). Here we extend recent forest projections for the current cohort of trees in the contiguous US, characterizing potential changes in aboveground tree carbon at the county level in response to varying mean annual temperature, precipitation, and N and S deposition. We found that relative to a scenario with N and S deposition reduction and no climate change, greater climate change led generally to decreasing aboveground carbon (mean −7.5% under RCP4.5, −16% under RCP8.5). Keeping climate constant, reduced N deposition tended to lessen aboveground carbon (mean −7%), whereas reduced S deposition tended to increase aboveground carbon (+3%) by 2100. Through mid-century (2050), deposition was more important for predicting carbon responses except under the extreme climate scenarios (RCP8.5); but, by 2100, climate drivers generally outweighed deposition. While more than 70% of counties showed reductions in aboveground carbon relative to the reference scenario, these were not evenly distributed across the US. Counties in the Northwest and Northern Great Plains, and the northern parts of New England and the Midwest, primarily showed positive responses, while counties in the Southeast showed negative responses. Counties with greater initial biomass showed less negative responses to climate change while those which exhibited the greatest change in composition (>15%) had a 95% chance of losing carbon relative to a no-climate change scenario. This analysis highlights that declines in forest growth and survival due to increases in mean temperature and reductions in atmospheric N deposition are likely to outweigh positive impacts of reduced S deposition and potential increases in precipitation. These effects vary at the regional and county level, however, so forest managers must consider local rather than national dynamics to maximize forest carbon sinks in the future.

Cooling Damage Characterization and Chemical-Enhanced Oil Recovery in Low-Permeable and High-Waxy Oil Reservoirs

The well productivity of high-waxy reservoirs is highly influenced by temperature changes. A decrease in temperature can cause the precipitation of wax from the crude oil, leading to a decrease in the formation’s drainage capacity and a drop in oil production. In this study, the wax precipitation of crude oil is characterized by rheological properties tests and differential scanning calorimetry (DSC) thermal analysis. The wax damage characteristics of cores and the relative permeability curves at different temperatures were investigated through coreflood experiments. Furthermore, nanoemulsion is selected as a chemical agent for injection fluid. The nuclear magnetic resonance (NMR) scanning technique is used to investigate the effects of oil recovery enhancement at different pores by increasing temperature and adding nanoemulsion. By comparing the changes in T2 spectra and the distribution pattern of residual oil before and after liquid injection, the results have shown that both increasing temperature and adding nanoemulsion have a significant effect on oil recovery. The improvement of micropores is less pronounced compared to macropores. The produced oil mainly comes from the large pores. When the temperature is lower than the crude oil dewaxing point temperature, there is a serious dewaxing plugging phenomenon in the pores. Additionally, by observing the pattern of residual oil distribution at the end of the NMR online drive, it is hereby classified into wax deposition retention type, weak water washing retention type, and immobilized type, each with its own distinct characteristics. Wettability alteration and interfacial tension reduction can help to improve the drainage capacity of high-wax oil reservoirs, which is the main mechanism of nanoemulsion for enhanced oil recovery. These findings are highly valuable for enhancing the comprehension of the impact of highly waxed crude oils on drainage capacity and the ultimate oil recovery rate, particularly in relation to wax precipitation deposition.

Quantitative modelling reservoir microalgae proliferation in response to water-soluble anions and cations influx

Atmospheric precipitation deposits acid-forming substances into surface water. However, the effects of water-soluble components on microalgae proliferation are poorly understood. This study analysed the growth characteristics of three microalgae bioindicators of water quality: Scenedesmus quadricauda, Chlorella vulgaris, and Scenedesmus obliquus, adopting on-site monitoring, culture experiments simulating 96 types of water by supplementing anions and cations, and predictive modelling. The result quantified pH > 3.0 rain with dominant Ca2+, Mg2+, and K+ cations, together with anions of NO3− and SO42−. The presence of Ca2+ of up to 0.1 mM and Mg2+ concentrations (>0.5 mM) suppressed Scenedesmus quadricauda growth. Soluble ions, luminosity, and pH had significant impacts (p ≤ 0.01) on increased microalgae proliferation. A newly proposed microalgae growth model predicted a 10.7-fold increase in cell density six days post-incubation in the case of rainfall. The modelling supports algal outbreaks and delays prediction during regional water cycles.

C–C bond coupling differences between β-O-4 and 4-O-5 ether bonds over hydrophobic mesoporous Ru/MY-O catalysts: from lignin model compounds to polycyclic alkanes

MY zeolites with mesopores were prepared by hydrothermal method using functionalized SiO2 (F-SiO2) as a silica source, and hydrophobic bifunctional Ru/MY-O catalysts were obtained by deposition precipitation method and silylation treatment. This work aims at obtaining polycyclic alkane (PCA) based high-density hydrocarbon fuels (HDHFs). We focused on the catalytic hydroconversion (CHC) of 2-phenoxy-1-phenylethanol (PP-ol) and oxydibenzene (ODB), two typical lignin-related model compounds (LRMCs), over Ru/MY-O. The effects of different reaction conditions and catalysts on the product distribution in PP-ol and ODB were investigated. The partial hydrogenation of ODB was found to be a necessary step before achieving C-O ether bond cleavage and C-C bond coupling. The balance of metal/acidic sites is critical for maximizing PCA yields. Changes in the metal/acid ratio had a greater effect on PCA yield in PP-ol than in ODB. Poor stability of cycloalkyl cations and partial hydrogenation of ODB hinder the generation of C-C coupling products. The incorporation of mesopores and hydrophobic treatment were found to weaken the negative effects of C-C bond coupling products and water on the catalyst. The conversion of Ru3/MY-O was improved by nearly 10% compared to Ru3/Y in the fifth cycle reaction. This work provided a theoretical basis for the generation of HDHFs from lignin.

Hydrogen Production from Hydrous Hydrazine Decomposition Using Ir Catalysts: Effect of the Preparation Method and the Support

Herein, Ir/CeO2 catalysts were prepared using the deposition–precipitation method with NaOH or urea as the precipitating agent or using sol immobilization with tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the protective and reducing agent. The effect of the preparation method on Ir catalyst activity was evaluated in the liquid-phase catalytic decomposition of hydrous hydrazine to hydrogen. Ir/CeO2 prepared using sol immobilization and DP NaOH showed the best activity (1740 h−1 and 1541 h−1, respectively) and yield of hydrogen (36.6 and 38.9%). Additionally, the effect of the support was considered, using TiO2 and NiO in addition to CeO2. For this purpose, the sol immobilization of preformed nanoparticles technique was considered because it allows the same morphology of the immobilized particles to be maintained, regardless of the support. Ir deposited on NiO resulted in the most selective catalyst with a H2 yield of 83.9%, showing good stability during recycling tests. The catalysts were characterized using different techniques: X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with an X-ray detector (EDX) and inductively coupled plasma–mass spectroscopy (ICP-MS).

Chemical and Ultrastructural Characterization of Dentin Treated with Remineralizing Dentifrices.

The aim of this study is to investigate dentin chemical and ultrastructural changes upon exposure to remineralizing dentifrices. Dentin disks were obtained from permanent human molars and treated for 7 days with the dentifrices: (1) C group-control (no dentifrice); (2) S group-Sensodyne Repair & Protect; (3) D group-Dentalclean Daily Regenerating Gel; and (4) DB group-D group + Dentalclean regenerating booster. Afterwards, samples were submitted to an additional 7 days of toothbrushing associated with daily acidic challenge. Samples were imaged and analyzed (days 1, 7, and 14) for Young's modulus by atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). SEM and AFM revealed precipitate deposition on dentin surfaces in groups S, D, and DB, formed as early as day 1. Surface elemental analysis showed a Si increase on all brushed surfaces. Similar surface morphology was maintained after the acidic challenge period. Bright-field TEM/SAED revealed the formation of nanocrystalline hydroxyapatite inside the dentin tubules of groups S, D, and DB after day 7. Group C presented a gradual reduction of Young's modulus from days-1-14, whereas all remaining groups had increased values. All evaluated dentifrices led to successful formation of hydroxyapatite and increased dentin stiffness.

Efficient CO Oxidation by Co/Ta2O5 Prepared by Deposition–Precipitation with Urea

Efficient CO Oxidation by Co/Ta2O5 Prepared by Deposition–Precipitation with Urea

Fabrication of gold nanoparticles supported on hollow microsphere of nanosized TS-1 for the epoxidation of propylene with H2 and O2

The TS-1 microsphere was facilely prepared via a direct spray drying of the mixture containing the nanocrystal TS-1 and mother liquor. The calcined TS-1 zeolites possess a hollow structure and numerous intercrystalline mesopores, which may facilitate the diffusion properties. Au nanoparticles were loaded on TS-1 support by utilizing a deposition–precipitation process to prepare the Au/TS-1-M catalysts for propylene epoxidation in the presence of H2 and O2 conditions. The effects of the Ti and Au loadings on the structure, porosity, morphology, and catalytic performances of the Au/TS-1 catalysts have been investigated by various techniques. Under the optimized synthesis conditions (Si/Ti molar ratio = 57, 0.49 wt% Au), a propylene conversion of 6.1 % and a PO selectivity of 91.7 % were obtained on the Au/TS-1 catalyst. A PO formation rate of 186.8 gPO·kgcat.−1·h−1 was achieved at the 20th hour.

Studies on a niobia-supported VPO catalyst for glycerol dehydration

Niobia-supported VPO catalysts were synthesized using the deposition–precipitation method with different VPO loadings to evaluate glycerol dehydration. The activity patterns are consistent with the acidity trends.

Comprehensive investigation of the mutual effect of Ce and W species in the NH3-SCR catalyst

CeO2–WO3 catalysts were synthesized using the coprecipitation method (CW-C), mixing method (CW-M) and deposition–precipitation method (CW-DP).

Clean hydrogen production from ammonia decomposition over zeolite 13X-supported Ni catalysts

Ni/zeolite 13X catalyst synthesized by deposition–precipitation exhibits improved low-temperature performance for NH3 decomposition owing to high dispersion and uniform deposition of active Ni on the surface and in the pores of the zeolite support.

Preparation of noble metal-free porous CuO–ceria and zirconia mixed oxide catalysts using the ammonia driven deposition precipitation method for toluene combustion

Non-disclosed ADP deposition of Cu onto CexZr1−xO2 supports yields noble metal-free catalysts with excellent activity and selectivity for VOCs combustion.

Ternary Fe- or Mo-Au-Ni/GDC as Candidate Fuel Electrodes for the Internal Dry Reforming of CH4: Physicochemical and Kinetic Investigation

The present study deals with the physicochemical and catalytic/kinetic investigation of Fe, Au, Fe-Au, and Mo-Au modified Ni/GDC electrocatalysts towards their performance for the DRM, RWGS, and CH4 decomposition reactions. For this purpose, Au-NiO/GDC (where Au = 1 or 3 wt.%), Fe-NiO/GDC (where Fe = 0.5 or 2 wt.%), 0.5Fe-3Au-NiO/GDC, and 0.4Mo-3Au-NiO/GDC were synthesized via deposition (co-) precipitation. There is discussion on the structural properties of the electrocatalysts on the oxidized and reduced state, as well as their use as electrolyte-supported (half) cells. A key remark after H2-reduction is the formation of binary or ternary solid solutions. Ni/GDC was the most active for the catalytic CO2 reforming of CH4 and the CH4 decomposition reactions and as a result the most prone to carbon deposition. On the other hand, the modified 3Au-Ni/GDC, 0.5Fe-3Au-Ni/GDC, and 0.4Mo-3Au-Ni/GDC exhibited the following properties: (i) the highest Ea,app for the non-desired RWGS reaction, (ii) high tolerance to carbon formation due to lower activity for the CH4 decomposition, and (iii) were also less active for H2 and CO production. Finally, 0.4Mo-3Au-Ni/GDC seems to perform the DRM reaction through a different mechanism when compared to Ni/GDC. Overall, the above three samples are proposed as potential fuel electrodes for further electrocatalytic measurements for the SOFC internal DRM process.

One-step Mo-doped praseodymium oxide construction of oxygen vacancies for efficient photothermal co-catalytic Suzuki coupling reaction

The photothermal synergistic catalytic Suzuki coupling reaction is a sustainable approach to generate biphenyl compounds using clean and renewable solar energy. The one-step Mo doping engineering resulted in more oxygen vacancies and surface free electrons on the PrxOy surface of hollow porous nanotube morphology. Subsequently, energy-efficient and environmentally friendly catalysts (PdO/PrxOy−Moz) with higher catalytic activity were successfully prepared by deposition precipitation method. The concave and convex surfaces of the carriers could better capture visible light. Mo doping greatly extends the visible absorption range of PrxOy. More OVs defects in the PrxOy−Moz carrier inhibit the complexation of photogenerated electron-hole pairs and induce the transfer of free and photogenerated electrons to Pd. The electron-rich Pd accelerated the oxidative addition step of aryl halides to aryl phenylboronic acids, which greatly improved the catalytic performance of PdO/PrxOy−Moz in the photothermal co-catalytic Suzuki coupling reaction.

Bi-doped CuCeO2−x nanorod catalysts for photothermal CO-PROX in H2-rich streams: Enhanced oxygen vacancy and light absorption capacity

The wide band gap of ceria limited the light absorption and photothermal conversion of copper-ceria catalyst for photothermal preferential oxidation of CO (CO-PROX). In the present work, doping Bi element was adopted to regulate the energy band and catalytic performance of CuCeO2−x nanorod catalysts for photothermal CO-PROX. Bi/CuCeO2−x nanorods were synthesized by co-precipitation hydrothermal and deposition precipitation method. The Bi/CuCeO2−x catalyst with the molar ratio of Bi/Ce 2.5% exhibited the best catalytic performance and the CO conversion reached 90% under 2.5 suns with a surface temperature of 120 °C. The doped Bi species were incorporated into the CeO2 lattice and promoted the formation of oxygen vacancy sites and the strong Cu-Ce interaction, as revealed by XRD, XPS, Raman and H2-TPR results. In addition, doping Bi reduced the band gap of ceria nanorod from 2.77 to 2.47 eV and remarkably enhanced the UV–vis light response and photogenerated carrier separation of Bi/CuCeO2−x-2.5.

FexNiy/ SiO2-Al2O3 catalyzed hydrodeoxygenation of biorenewable platform molecules

A series of FexNiy/SA (SA = SiO2-Al2O3) catalysts were synthesized via solvothermal assisted deposition precipitation synthesis method and explored for low-temperature hydrodeoxygenation (HDO) reaction of methyl oleate into n-alkanes and vegetable oils. A comprehensive study on the effects of increasing iron oxide loading in catalyst samples, i.e., Fe1Ni1/SA, Fe3Ni1/SA, Fe5Ni1/SA and Fe7Ni1/SA, on the crystallographic, morphological, textual and surface chemical behavioural were investigated thoroughly using various spectroscopic techniques. The study disclosed excellent surface area, high acidic strength and reducibility of Fe1Ni1/SA catalyst due to the lowest Fe2+ or FeO species. In contrast, higher iron oxide loading leads to the accumulation of Fe2+ ions on the surface with reduced metal acid centres and diminished surface area. The catalytic conversion as well as C17-C18 selectivity in catalytic HDO was also scrutinised with particular reference to Fe2+/Fe3+ ion ratio. The obtained superior catalytic activity and C18 selectivity of Fe1Ni1/SA catalyst are due to the lowest Fe2+/Fe3+ ion ratio. However, the iron oxide loading increased the Fe2+/Fe3+ ion ratio, which ultimately decreased the catalytic activity. Thus, the role of Fe2+ species in the deactivation of catalyst was discussed in detail to establish conversion and selectivity control in the catalytic HDO pathway.

On the issue of injection of CO2 into a gas-condensate deposit within the framework of the technology of extraction of oil and retrograde condensate at concentrations below the filtration threshold from gas-saturated oil and gas source deposits of oil and gas condensate fields, at the late stage of development

The study was carried out as part of the work on the hydrodynamic justification of the technology for extracting oil and retrograde condensate at concentrations below the filtration threshold from gas-saturated oil and gas source deposits of oil and gas condensate fields, at the late stages of development. On the basis of a test multicomponent model using the key parameters of the Vuktyl oil and gas condensate field, it is shown that the injection of carbon dioxide, for the early replacement of the “dry” gas injected at the previous stage, entails risks of reducing the liquid hydrocarbon recovery factor and the risks of precipitation of asphaltene-paraffin deposits.

Gold supported on Gd-doped CeO2 nanorods applied as water-gas shift catalyst under H2 rich stream

In this work, we report the synthesis of catalysts based on ceria nanorods (CeO2NRs) doped with 3% and 5% mol gadolinium. The supports were obtained from cation co-precipitation hydrothermal synthesis over which gold nanoparticles (AuNPs) were deposited by the deposition-precipitation (DP) methodology, allowing the Au nanoparticles size control at around 3 nm. The catalysts were evaluated in water gas shift reaction and showed high activity under a H2 rich stream (7%CO/7%CO2/14%N2/42%H2/30%H2O) with steam/process gas molar ratio (S/G) of 0.3 at 300 and 250 °C. The results revealed that Gd-doping increased the oxygen vacancies concentration due to the insertion of a trivalent cation in ceria lattice. In addition, the synergistic effect between AuNPs and Gd-doped CeO2 provided the increase of reducibility and oxygen storage capacity (OSC). These properties were associated with the catalytic activity in water gas shift reaction. The nanostructured materials decreased the CO concentration under conditions of H2 rich stream, indicating the catalysts potential for industrial applications after further studies. The catalyst doped with 5% mol Gd was the most active and achieved 24% of CO conversion at 300 °C.