A new method based on addition of polyethyleneimine (PEI) functionalized HKUST-1 into an aqueous methyldiethanolamine (MDEA) solution for absorption of carbon dioxide is developed. HKUST-1 was ...synthesized via solvothermal method and functionalized with polyethyleneimine after activating by heating at 120 °C for 12 h. Addition of 0.2 wt% of PEI-HKUST-1 to aqueous solution of 40 wt% MDEA at different temperatures (303.15, 313.15, 323.15, 333.15 K) and carbon dioxide pressures up to 2200 kPa, increased the CO2 absorption capacity up to 16%. Absorption capacity was increased with increasing partial pressure of carbon dioxide and decreased with increasing temperature for both solutions.
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•CO2 absorption enhancement by addition of 0.2 wt% PEI-KUST-1 into MDEA solution was evaluated in this study.•Experiments were carried out using pressure swing experiments (PSE) to measure the CO2 solubility.•CO2 absorption was enhanced up to 16% in the presence of PEI-HKIST-1.•The effect of temperature and partial pressure on the absorption capacities was investigated.•Solubility increased with increasing the pressure and decreased with increasing the temperature.
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•2D-TiO2@MWCNT nanocomposites via grafting TiO2 nanoparticles onto functionalized multi-walled carbon nanotubes.•2D-0.6TiO2@MWCNT nanocomposite catalyst had the lowest activation ...energy with the highest turnover frequency.•Catalytic oxidative desulfurization of straight run gas oil (SRGO) using of 2D-TiO2@MWCNT nanocomposites catalyst was done.•2D-0.6TiO2 @MWCNT nanocomposite catalyst has an excellent recyclability.
The novel heterogeneous catalysts of 2D-TiO2@MWCNT nanocomposites are designed and synthesized via grafting TiO2 nanoparticles onto functionalized multi-walled carbon nanotubes and used for oxidative desulfurization of dibenzothiophene and real straight run light gas oil. The 2D-TiO2@MWCNT nanocomposite catalysts are completely characterized by FT-IR, Raman spectroscopy, XRD, TEM, NH3-TPD, ICP, and N2 adsorption–desorption isotherms. At first, the effect of various loading Ti on the MWCNT for ODS efficiency was investigated. The results revealed that 2D-0.6TiO2@MWCNT had the highest sulfur removal for the model, and SRLGO fuel compared to the other catalyst. Then, the optimal design of experiments using Box–Behnken experimental design was used to evaluate the effects of individual process variables such as temperature, O/S molar ratio, time, catalyst dosage, and their optimum values were found to be 69 °C, 46 min−1, O/S molar ratio: 9, and 0.03 g cat (25 ml DBT model fuel with 500 ppm S or 25 ml SRLGO with 12500 ppm S, 25 ml of acetonitrile), to achieve a high removal sulfur efficiency for DBT model oil (100%) and SRLGO (97.5 %), respectively. Based on optimal conditions, the 2D-0.6TiO2@MWCNT catalyst possesses superior catalytic activity and excellent reusability. The desulfurization reaction could be recycled for at least nine cycles without considerable reduction of catalytic performance, showing the good stability of the nanocomposite catalysts. An empirical kinetic model was applied to explain the rate data. Also, 2D-0.6TiO2@MWCNT nanocomposite catalyst had the lowest activation energy (27.65 Kj.mol−1) with the highest turnover frequency (16.15 h−1, around 2–3 times of the best catalyst so far) in desulfurization reactions compared to any TiO2-based catalysts. Furthermore, the catalytic reaction mechanism is investigated.
The effects of nitrogen functional groups on graphene surface and also the effects of cobalt loading and ruthenium promoter on the performance of nitrogen functionalized graphene nanosheets (N-GNS) ...supported cobalt catalysts in Fischer–Tropsch synthesis (FTS) are investigated. A 15 wt% Co/PGNS catalyst, a series of Co/N-GNS (15–30 wt% loading) and ruthenium promoted catalysts (25 wt% Co,0.5 wt% Ru/N-GNS and 25 wt% Co,0.5 wt% Ru/PGNS) were prepared by impregnation method. The purified GNS and functionalized GNS and all catalysts were characterized by Raman spectroscopy, FTIR, SEM, EDS, ICP, BET, TEM, XRD and TPR. The catalysts assessed in FTS in a fixed bed micro-reactor at 220 °C, 1.8 Mpa and H2/CO ratio of 2. Functionalization of GNS shifted the TPR reduction peaks to lower temperature, increased the dispersion of cobalt particles and increased the percentage CO conversion from 70.6% to 74.5%. Increasing the cobalt loading resulted in increasing the average cobalt cluster size, improvements in the reducibility of Co3O4. The maximum FTS activity for N-GNS supported catalyst is achieved at 30 wt % cobalt loading. The C5+ selectivity for the 30 wt % cobalt catalyst was higher than that of the 15 wt % Cobalt catalyst. Addition of 0.5 wt%Ru increased the FTS rate (gCH/(gcat·h)) from 0.377 to 0.412 and the liquid products selectivity from 86.5% to 91.2%.
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•Nitrogen functionalized graphene nanosheets as cobalt catalyst support in FTS.•The effect of Co loading and Ru promoter for producing liquid products.•Increasing the activity of catalyst by increasing the Co loading.•Improving the FTS rate by addition of Ru promoter.
Pyrolysis of bagasse followed by thermal cracking of tar was carded out at atmospheric pressure using a dual bed reactor. The first bed was used for the pyrolysis and the second bed was used for ...thermal cracking of tar. Iron fillings were used as the packed bed material in the second bed. The effects of reaction time （20 to 40 rain）, reactor temperature （600 to 900 ℃） and packed bed height （40-100 mm） on the product （char, tar and gas） yield and gas （H2, CO, CO2, CH4, CnHm） composition were studied. Over the ranges of the experimental conditions used, the operating conditions were optimized for pyrolysis temperature around 850 ℃, a reaction time of 30 min and packed bed height of 100 mm, thus we could obtain a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. It was observed that compared with single bed process, dual bed process increased the gas yield from 0.397 to 0.750 m3/kg and decreased the tar yield from 0.445 to 0.268 g/g while the heating value of the product gas remained almost constant （10-11 M J/m3）.
•Functionalized CNTs and graphene were used as Cobalt Fisher–Tropsch synthesis catalyst support.•Graphene increased the reduction degree, and dispersion of cobalt particles.•Graphene increased the ...FTS rate and %CO conversion significantly.•Catalysts supported on graphene showed better stability.
Graphene and CNTs-supported cobalt catalyst, is introduced for Fischer–Tropsch synthesis (FTS). The catalysts were prepared using wet impregnation method with cobalt loading of 15.0wt%. The catalysts were characterized by TGA, BET, XRD, XPS, H2 chemisorption, TPR, and TEM techniques. The activity, selectivity and stability of the catalysts in FTS were assessed in a fixed-bed micro-reactor, and the results were compared with each other. Comparing TEM images showed dispersion of cobalt clusters in graphene-supported catalyst is higher and the average clusters size decreased from 7.5 to about 6.0nm. Graphene as the support shifted the reduction temperature of cobalt oxide species to lower temperatures. Degree of CO conversion increased from 61 to 74%, FT synthesis rate increased by about 22%; the product distribution shifted to the higher molecular weight hydrocarbons, compared to CNTs-supported catalyst. On the graphene-supported cobalt catalyst, 480h continuous FT synthesis decreased 22% of the initial CO conversion. However, at the same time for CNTs-supported catalyst the CO conversion decreased 34%.
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•HZSM-5/HMS composite is acted as a promising novel micro/mesoporous catalyst.•HZSM-5/HMS composite indicates the excellent performance toward bulky molecules.•Gracilaria gracilis ...originates from free renewable marine biomass waste.•Gracilaria gracilis has great potential as a feedstock for biofuel production.
Conversion of Gracilaria gracilis (G. gracilis) into bio-products was carried out via pyrolysis at different temperatures to determine its potential for phenol-rich bio-oil. Co-Mo supported on zeolites (HZSM-5), mesoporous (HMS) catalysts and their composites (ZH) were investigated and compared to each other on catalytic pyrolysis processes. In non-catalytic tests, the maximum weight percentage of bio-oil was 42wt% at 500°C and had the maximum amount of phenol (6.28wt%). in the catalytic tests by ZH composites; the addition of zeolite content in the structure of composites significantly decreased total concentrations of acetic acid and formic acid from 9.56 to 8.12wt% and slightly decreased phenol and furfural concentrations from 6.65 and 6.98 to 5.88 and 5.49wt%, respectively. Furthermore, the best selectivity for hydrogen yield (6.08mmol/g macroalgae) and lowest amount of acetic acid (5.4wt%) was observed for CoMo/ZH-20 catalyst, that is synthesized by 20wt% of zeolite.
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•Solubility of carbon dioxide was investigated in the MDEA solution by addition of GO.•Results showed 9.1% enhancement for addition of 0.1 mass % GO to the 40 mass % MDEA.•Addition of ...0.2 mass % GO presented a capacity absorption promotion up to 10.4% at different temperatures.•Further concentration of graphene oxide showed no significant enhancement in absorption capacity.
Graphene-Oxide (GO)/MDEA nanofluid was prepared for CO2 absorption enhancement in gas sweetening process. GO was synthesized using a modified Hammer method and characterized by XRD, BET, SEM and IR spectroscopy to determine the structure. The XRD analysis showed a strong peak at 2θ = 10.3°. GO was dispersed in MDEA by ultrasonic treatment and zeta potential analysis was employed to examine the stability of the nanofluid. The measured zeta potential (35 mv) confirmed the excellent stability in the solution. GO/MDEA nanofluid showed high absorption capacities toward CO2 due to the high surface area and existence of OH groups on the GO surface and enhancement in mass transfer coefficient. When 0.1 wt.% GO was introduced to the 40 wt.% MDEA, the absorption capacity of the solution was promoted up to 9.1%. This enhancement for 0.2 wt. % slightly more while the solutions with higher GO content showed no significant enhancement in absorption capacity. This enhancement has a reverse and direct relationship with increasing temperature and pressure, respectively.
Hydrothermal liquefaction of granular bacteria, a surplus byproduct in wastewater treatment units, was performed with and without catalyst. Process operating conditions including temperature, feed ...concentration and reaction time were optimized through the central composite method in Design-Expert Software to reach maximum bio-oil yield and energy recovery. The data obtained were 38.5% and 61.0% of bio-oil yield and energy recovery respectively, in optimum conditions of 332 °C, 14.22 wt% feed concentration and the reaction time of 44 min. To improve the quantity and quality of bio-oil, catalytic hydrothermal tests were investigated using Ni and Ce impregnated on activated carbon and functionalized activated carbon by HNO3 and H2SO4. The results showed that the functionalization of activated carbon and adding Ce promoter to the catalyst had a significant effect on improving the Ni catalyst activity. The highest bio-oil yield and energy recovery of 48.1 and 86.84% were achieved by using Ni–Ce/ACHNO3 Catalyst.
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•Conversion of granular bacteria as a novel and ideal biomass was performed into the bio-oil and activated carbon.•Ni and Ni–Ce catalysts supported on activated carbon were applied to improve the quality and quantity of bio-oil.•Functionalization of activated carbon carried out by HNO3 and H2SO4 to enhance Ni activity.•Ni–Ce/ACHNO3 as the best catalyst led to increase bio-oil yield and energy recovery, and reduce O, N and S contents.
Bagasse conversion to H2, CO and light gaseous hydrocarbons as gaseous fuels, and higher alcohols and ethers as liquid fuels and fuel additives were performed in a basic water medium with ...near-critical condition in presence of potassium promoted Cu/γ-Al2O3–MgO catalysts. The catalysts were extensively characterized using ICP, XRD, TPR, BET, CO chemisorption and TEM techniques. In order to investigate support stability at reaction condition, XRD test also was carried out for used catalysts. Maximum dispersion of 48% and minimum average particles sizes of 8.4 nm were obtained for Cu20–K7.5/γ-Al2O3–MgO catalyst. Copper and potassium effects on quality and quantity of gaseous and liquid products were investigated. The maximum amounts of H2 (10 mmol g−1 of bagasse) and total produced gases (41 mmol g−1 of bagasse) were obtained with unpromoted Cu20/γ-Al2O3–MgO catalyst. Addition of K increased the bagasse conversion to liquid fuels. Potassium made the process more selective for alcohols and ethers production. Maximum amount of alcohols and ethers (83.3 mmol g−1 of bagasse) was obtained for Cu20–K7.5/γ-Al2O3–MgO catalyst.
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•Production of higher alcohols and ethers as fuels and fuel additives from a bagasse hydrothermal process in near-critical water medium.•Production of hydrogen rich gas from a bagasse hydrothermal process in near-critical water medium.•Using potassium promoted Cu based catalyst on γ-Al2O3–MgO support for liquefaction and gasification of bagasse.•Maximum amount of alcohols and ethers was obtained for Cu 20% and K 7.5 on γ-Al2O3–MgO.•The maximum amount of H2 was obtained with Cu 20% on γ-Al2O3–MgO.
This study investigated the catalytic behavior of two different types of materials: (i) algal biochar and (ii) 15 wt% Ni impregnated on SBA-15 support (Ni/SBA-15), in the thermochemical decomposition ...of Venice lagoon brown marine algae (Sargassum). First, non-catalytic pyrolysis tests were conducted in a temperature range of 400–800 °C in a dual-bed slow pyrolysis reactor. The optimum temperature for maximized liquid yield was at the temperature of 700 °C. Biochar catalyst exhibited excellent catalytic activity toward producing aromatic compounds via Diels-Alder-type reactions. However, Ni/SBA-15, because of interconnected pores provided easy passage for reactant and product during the catalytic pyrolysis process and resulted in an improvement in total gas yield (25.87 mmol/g Sargassum) and hydrogen-rich gas production (8.54 mmol/g Sargassum). The catalytic performances of both biochar and Ni/SBA-15 catalysts were compared to biochar-based catalysts derived from red and green macroalgae. High specific surface area, large pore volume, highly ordered pore structure, and narrow pore size distribution make SBA-15 a promising catalyst support in pyrolysis of biomass.
•Algal biochar as a catalyst/catalyst support in the renewable fuel production.•The effect of Ni/SBA-15 for producing biofuel and valuable chemicals.•Hydrogen-rich gas in the presence of Ni/SBA-15.•Phenol production in catalytic pyrolysis process using algal biochar.
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