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•Hydrothermal gasification of Cladophoraglomerata for hydrogen production.•Porous and alkaline solid product as hydrochar, favorable for using as a catalyst.•H2 and CO2 promotion in ...the presence of hydrochar as a catalyst.•Phenols enhancement and acids decrement in aqueous products.
A tubular batch micro-reactor system was used for hydrothermal gasification (HTG) of Cladophora glomerata (C. glomerata) as green macroalgae found in the southern coast of the Caspian Sea, Iran. Non-catalytic tests were performed to determine the optimum condition for hydrogen production. Hydrochar, as a solid residue of non-catalytic HTG was characterized by BET, FESEM, and ICP-OES methods to determine its physiochemical properties. Surface area and pore volume of C. glomerata increased drastically after HTG. Also, the aqueous products were identified and quantified by GC–MS and GC-FID methods. Hydrochar was loaded to the reactor to determine its catalytic effect on HTG. HTG was promoted by inorganic compounds in the hydrochar and its porosity. The maximum hydrogen yield of 9.63mmol/g was observed in the presence of algal hydrochar with the weight ratio of 0.4 to feedstock. Also, acids production was inhibited while phenol production was promoted in the presence of hydrochar.
In this work, lithium titanate oxide (Li
4
Ti
5
O
12
) (LTO) and praseodymium ion doped in lithium titanate oxide (Pr-LTO) were synthesized in a sol–gel simple method, and their catalytic effects on ...thermal decomposition of ammonium nitrate were reported using thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) techniques. The X-ray powder diffraction, Brunauer–Emmett–Teller surface area measurements, particle size analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy techniques were used to identify the structural properties and morphology of LTO and Pr-doped LTO. By doping the praseodymium ion within the LTO spinel structure, the surface area increases (from 204.2 m
2
g
−1
for LTO semiconductor to 318.9 m
2
g
−1
for Pr-doped LTO), and the catalytic activity improved. The catalytic effects of LTO and Pr-LTO on the thermal behavior of AN were studied via TG-DSC techniques. The thermal decomposition of pure AN (196–400 °C) shifted to lower temperatures, 154–280 °C, and 131–241 °C, in the presence of LTO and Pr-LTO, respectively. The results showed that the catalytic effects of LTO were improved by praseodymium doping. The Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Tang methods were used to determine activation energies of all AN samples at different conversion values (
α
). The activation energies of pure AN values were 166 ± 3, 166 ± 2, 166 ± 2, and 162 ± 2 kJ mol
−1
, while AN/LTO activation energies were 145 ± 2, 144 ± 1, 144 ± 1, and 144 ± 2 kJ mol
−1
and finally, those of AN/Pr-LTO were 112 ± 1, 109 ± 2, 110 ± 1, and 110 ± 1 kJ mol
−1
using FWO, KAS, Starink, and Tang methods, respectively.
Hydrodesulfurization (HDS) of straight run light gas oil (SRLGO) using novel highly active two-dimensional (2D) MoS
2
/graphene (G) nanohybrid catalysts is a precursor technology for the production ...of clean heavy fuel. The aim of this research is the synthesis of 2D MoS
2
/G nanohybrid catalysts by use of exfoliation method from commercial bulky MoS
2
and graphite using hydrothermal ball milling system, which is a low-cost, high-yield, and scalable method. These nanohybrid catalysts were characterized by XRD, Raman spectroscopy, XPS, SEM, TEM, STEM, ICP, BET surface, TPR, and TPD techniques. Also, catalytic activities of 2D MoS
2
/G nanohybrid catalysts were evaluated under different operating conditions such as temperature, pressure, LHSV, and H
2
/Feed (SRLGO) ratio in the HDS reaction. The conversion of the HDS of SRLGO with 14000 ppm sulfur showed a considerably higher activity of 2D MoS
2
/G nanohybrid catalyst (99.95% HDS efficiency) compared with the Co-Mo/γAl
2
O
3
as a commercial catalyst (90% HDS efficiency) in the operation condition (340 °C, 40 bars, LHSV: 1 h
−1
and H
2
/oil: 600 NL L
−1
) which is economically valuable. Using density functional theory calculations, the detailed mechanism of the HDS process over MoS
2
/G catalyst was explored. It was found that sulfur coverage on the Mo edge of MoS
2
plays an important role in the hydrogenation of sulfur components.
The rates of CO
2
absorption into fresh and regenerated aqueous solutions of N,N-diethylethanolamine (DEEA), N-methyldiethanolamine (MDEA), and their mixture with sulfolane are investigated in a ...batch stirred cell reactor. The data are obtained in the temperature range of 293.15–313.15 K, pressures up to 800 kPa, and different concentrations of alkanolamines and sulfolane. The diffusion coefficients and Henry’s law constants for all the solutions are obtained. The absorption rate of DEEA solutions increased by increasing component concentrations and pressure, but the effects of temperature on the absorption rates of hybrid and aqueous DEEA solutions are different. Comparison of absorption rates in aqueous and hybrid solutions under the same conditions can determine the role of sulfolane as the physical solvent. It has been found that sulfolane acts as an effective absorption activator in the hybrid DEEA solutions. However, in the MDEA solutions, in all experimental conditions except for high pressure (
≥
400 kPa) and certain MDEA concentration (20 wt%), sulfolane has a negative effect on the absorption rate. The absorption rates of regenerated aqueous DEEA solutions are in the range of 50.5–87.7% of fresh ones, while these values for the hybrid DEEA solution are in the range of 75–90.5%. These values for the aqueous and hybrid MDEA solutions are almost equal. Based on the values of Hatta number and enhancement factor, the CO
2
absorption regime in the DEEA solutions is determined as the fast second-order reaction. The absorption rate can be interpreted considering the tradeoff between kinetics and thermodynamics of CO
2
absorption in the aqueous and hybrid DEEA/MDEA solutions. The desorption rates in hybrid DEEA/MDEA solutions are higher than those in aqueous solutions.
Graphical abstract
An extensive study of FTS on CNTs supported Co catalysts with different loadings of Co, Ru and K is reported. Up to 30
wt.% of Co, 1
wt.% of Ru and 0.0066
wt.% of K were added to the catalyst by ...co-impregnation method. The physico-chemical properties, activity and selectivity of the catalysts were assessed. Increasing the Co loading increased the cobalt cluster sizes, the CO conversion and the C
5+ selectivity and decreased the reduction temperature and dispersion. Ru was found to enhance the reducibility of Co
3O
4 to CoO and that of CoO to Co
0, increase the dispersion and decrease the average cobalt cluster size. However, potassium was responsible in shifting the reduction temperatures to higher temperatures. Ru increased the FTS rate while addition of K decreased the FTS. Both promoters enhanced the selectivity of FTS towards the higher molecular weight hydrocarbons. Potassium increased the olefin to paraffin ratio.
▪
An extensive study of Fischer–Tropsch synthesis (FTS) on carbon nanotubes (CNTs) supported cobalt catalysts with different loadings of cobalt, ruthenium and potassium is reported. Up to 30
wt.% of Co, 1
wt.% of Ru and 0.0066
wt.% of K were added to the catalyst by co-impregnation method. The physico-chemical properties, activity and selectivity of the catalysts were assessed. For the 15
wt.%Co/CNT catalyst, most of the metal particles were homogeneously distributed inside the tubes and the rest on the outer surface of the CNTs. Increasing the Co loading to 30
wt.% increased the amount of Co on the outer surface of the CNTs, increased the cobalt cluster sizes and decreased the reduction temperature and dispersion. Increasing the Co loading from 15 to 30
wt.% increased the CO conversion from 48 to 86% and the C
5+ selectivity from 70 to 77%. Ruthenium was found to enhance the reducibility of Co
3O
4 to CoO and that of CoO to Co
0, increase the dispersion and decrease the average cobalt cluster size. However, potassium was responsible in shifting the reduction temperatures to higher temperatures. 0.5
wt.%Ru increased the FTS rate of 15
wt.%Co/CNT catalyst by a factor of 1.4 while addition of 0.0066
wt.%K decreased the FTS rate by a factor of 7.5. Both promoters enhanced the selectivity of FTS towards the higher molecular weight hydrocarbons however; the effect of Ru is less pronounced. Potassium increased the olefin to paraffin ratio from 0.73 to 3.5 and the C
5+ selectivity from 70 to 87%.
As the literature lacks any systematic study upon the sol–gel process from the process point of view, herein the current work, the influence of key operating parameters including F127/TEOS ratio, ...Aging time, and calcination rate upon final product textural and bulk properties is aimed to be screened using response surface methodology (RSM). Under user-defined criteria, central composite design tool was used to optimize the process. Following RSM results, SBA-15 synthesis under F127/TEOS ratio of 1.0, an Aging time of 9.0 h, and a calcination rate of 2.3 °C min
−1
led to an Engineering SBA-15 (E-SBA-15) with a specific surface area of 518.11 m
2
g
−1
, total pore volume of 0.68 cm
3
g
−1
, and mean pore diameter of 10.1 nm, associated with a deviation less than 5% from the predicted values. In light of textural properties acquired via employing BET, FT-IR, XRD, SEM, NH
3
-TPD, and crushing strength analyses, it was found that the adequately large mesoporous nature of the E-SBA-15 along with its unique surface chemistry is among the highest points distinguishing it from the Commercial counterparts. Such a feature might help widen its application in many industrial sectors, particularly as support material in heterogenous catalysis, especially when processing suffering from mass transfer limitation.
Along with the great efforts in producing clean and low-cost fuel and chemicals, in this work, novel nanocatalysts are reported for the fast pyrolysis of the bagasse. To this end, different catalyst ...supports were employed to load Mo oxides or sulfides through incipient wetness impregnation. The prepared nanocatalysts were characterized by X-ray diffraction to determine the formed phases, N
2
adsorption/desorption to clarify the surface properties, and SEM to observe the morphology and energy-dispersive X-ray to provide the atomic mapping. A series of nanocatalysts including the Mo sulfide loaded over graphene oxide (MoS
2
/GrO) or porous graphene (MoS
2
/graphene), Mo oxide loaded over charcoal, and Co-Mo oxide loaded over MgO were studied in the fast pyrolysis of the bagasse. The results revealed that the use of catalyst decreased the bio-oil yield of the process. Interestingly, it was found the fast pyrolysis of the bagasse is dependent on the used catalysts and the fractions of bio-oil can be determined according the catalysts types. It was found that with accordance to the demanded chemicals, the catalysts can be chosen which is highly valuable in producing chemicals and each catalysts support results in a specific set of products. In general, the acetic acid was the main product without using catalyst, and by using the MoS
2
/GrO nanocatalyst, the phenols were formed dominantly which are of great importance in different industries. This novel work successfully revealed that the metal-based catalysts can be employed instead of the zeolites which paves the way toward using low-cost metallic catalysts in producing bio-chemicals and bio-oils.
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•Ultrasonic waves can improve the synthesis of 2D porous M-GO as HDS catalysts.•2D MoS2-GO catalysts demonstrated the HDS reaction of VGO at facile condition operation.•DFT ...calculations were employed to reveal the detailed mechanism of the HDS process.
In this study, a novel, simple, high yield, and scalable method is proposed to synthesize highly porous MoS2/graphene oxide (M−GO) nanocomposites by reacting the GO and co-exfoliation of bulky MoS2 in the presence of polyvinyl pyrrolidone (PVP) under different condition of ultrasonication. Also, the effect of ultrasonic output power on the particle size distribution of metal cluster on the surface of nanocatalysts is studied. It is found that the use of the ultrasonication method can reduce the particle size and increase the specific surface area of M−GO nanocomposite catalysts which leads to HDS activity is increased. These nanocomposite catalysts are characterized by XRD, Raman spectroscopy, SEM, STEM, HR-TEM, AFM, XPS, ICP, BET surface, TPR and TPD techniques. The effects of physicochemical properties of the M−GO nanocomposites on the hydrodesulfurization (HDS) reactions of vacuum gas oil (VGO) has been also studied. Catalytic activities of MoS2-GO nanocomposite are investigated by different operating conditions. M9-GO nanocatalyst with high surface area (324 m2/g) and large pore size (110.3 Å), have the best catalytic performance (99.95%) compared with Co-Mo/γAl2O3 (97.91%). Density functional theory (DFT) calculations were also used to elucidate the HDS mechanism over the M−GO catalyst. It is found that the GO substrate can stabilize MoS2 layers through weak van der Waals interactions between carbon atoms of the GO and S atoms of MoS2. At both Mo- and S-edges, the direct desulfurization (DDS) is found as the main reaction pathway for the hydrodesulfurization of DBT molecules.
Biochar is an appropriate and value-added strategy for treating heavy metal-contaminated water in urban and industrial wastewaters. In this study, an innovative precursor based on chicken manure is ...used to produce biochar for As(III) removal. The modified biochar (MBC) was fabricated by the pyrolysis process and characterized by FT-IR, SEM, EDS, and TG-DTA analyses. Subsequently, the effect of pH, contact time, dosage of nanoadsorbent, and recycle performances have been studied for As(III) removal from wastewater. The results revealed that the optimum condition to achieve high adsorption capacity (98% As(III) removal) is at 1.5 g L
−1
adsorbent dose, pH ~ 7.8, and during 300 min, as well as MBC was capable to use and recycle at least 10 times without considerable adsorption reduction, confirming the high stability of the nanoadsorbent in the exposure of wastewaters. Finally, a possible adsorption mechanism is proposed based on ion-exchange and the participation of electrostatic attractions of hydroxyl and carbonate groups.
A bimetallic nickel–molybdenum catalyst supported on
γ
-alumina was synthesized by the two-step incipient wetness impregnation technique. The activity of the prepared Ni–Mo/
γ
-alumina catalyst was ...evaluated in a down flow fixed-bed micro-reactor. In this way, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions of the main distillate fractions of crude oil were assessed. XRD, SEM, TPR, ICP-OES, BET–BJH and nitrogen adsorption/desorption methods were used for characterizing the synthesized Ni–Mo/
γ
-alumina catalyst. The active metals with Ni/Mo mass ratio of 0.23 and total metal of 13.7 wt% were loaded on the support, similar to the commercial industrial catalyst. The performance tests were conducted at 3.0 MPa (for light naphtha and heavy naphtha) and at 4.5 MPa (for kerosene and gas oil). The results revealed that the total sulfur conversion of the light naphtha, heavy naphtha, kerosene and gas oil fractions was 98.3%, 95%, 91.7% and 90.1% (after 24 h), respectively.
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