Attapulgite as a Catalyst

Attapulgite (ATP, a natural clay) was used as carrier to produce a nickel-based catalyst (Ni/ATP) for the work that is presented herein. Its catalytic performance was comparatively assessed with a standard Ni/Al2O3 sample for the glycerol steam reforming (GSR) reaction. It was shown that the ATP support led to lower mean Ni crystallite size, i.e., it increased the dispersion of the active phase, to the easier reduction of NiO and also increased the basicity of the catalytic material. It was also shown that it had a significant effect on the distribution of the gaseous products. Specifically, for the Ni/ATP catalyst, the production of liquid effluents was minimal and subsequently, conversion of glycerol into gaseous products was higher. Importantly, the Ni/ATP favored the conversion into H2 and CO2 to the detriment of CO and CH4. The stability experiments, which were undertaken at a low WGFR, showed that the activity of both catalysts was affected with time as a result of carbon deposition and/or metal particle sintering. An examination of the spent catalysts revealed that the coke deposits consisted of filamentous carbon, a type that is known to encapsulate the active phase with fatal consequences.

With the rapid development of industry, the discharge of textile printing and dyeing wastewater will cause serious pollution to other pure water bodies. It is imperative to deal with textile printing and dyeing wastewater. In this paper, with titanium tetrachloride as a precursor, attapulgite (ATP) / TiO2 nanocomposites were prepared by a neutralizing hydrolysis method and their catalytic activities were investigated by the oxidative degradation of methylene blue dye using ozone as oxidant. The test results showed that there were significant interactions between TiO2 and ATP support. The effects were also studied of ozone concentration, catalyst amount, reaction temperature, and initial concentration of methylene blue on the degradation rate of methylene blue catalyzed by the prepared attapulgite / TiO2 nanocomposites, and under the optimal conditions, the methylene blue could be degraded more than 90% in 30 minutes. Compared with that of pure ATP, the catalytic activities of ATP / TiO2 nanocomposites were enhenced remarkably. The degradation mechanism of methylene blue was also discussed.

A series of Mg-modified Ni/Attapulgite (ATP) catalysts have been prepared by impregnation method for glycerol steam reforming to produce hydrogen. The physicochemical properties of catalysts were characterized using various techniques including N2 physical adsorption analysis, XRD, H2-TPR, SEM, TEM and NH3-TPD. The results of N2 physical adsorption indicated MgO modified Ni-based catalysts had unique mesostructure, resulting in the high metal dispersion and interaction between active metal and support as proven by XRD, TEM and H2-TPR. Results of glycerin reforming experiments showed that Ni/10MgO/ATP catalyst had the highest activity than that of the other catalysts. Ni/10MgO/ATP catalyst had the smallest Ni average crystal size (10.1 nm) and the highest surface area (110.31 m²/g). These excellent properties made it show the enhanced glycerol conversion (94.71%) and a higher H2 yield (88.45%) and the longest stability (30 h) during glycerol steam reforming (GSR) at 600 °C, W/G = 3, and WHSV = 1 h⁻¹. The used catalysts after 60 h of glycerin reforming experiments were also investigated by XRD, SEM, TEM, Roman and TG-DTG. The results indicated that the addition of Mg significantly inhibited the sintering of nickel grains and the formation of amorphous carbon. Therefore, Ni/10MgO/ATP catalyst increased the activity of the catalyst and extended the life of the catalyst.

Research on the catalytic conversion of lignin into value-added chemicals has grown rapidly on account of the importance of lignin in the biorefinery. There is thus a need to investigate novel technologies to depolymerize lignin in the absence of hydrogen gas and noble metal catalysts. This study developed a cheap and recyclable catalyst via a facile process involving impregnation and calcination for the conversion of lignin to value-added phenolic monomers.

​

Results

Acid sites, basic sites and magnetic components were successfully incorporated into attapulgite. The resulting catalyst displayed high catalytic activity for lignin conversion to phenolic monomers, which resulted in 10.9% total monomers yield at 250 °C for 3 h with a catalyst loading of 50% and a solvent–solid ratio of 20:1 in 50% C2H5OH. The total monomers yield decreased observably after eight successive reaction runs. After being calcined at 600 °C for 3 h, the recovered catalyst provided a total monomers yield of 6.74% in the ninth reaction run.

Conclusion

A novel catalyst was successfully prepared by incorporation of acid sites, basic sites and magnetic properties using natural attapulgite clay as a precursor via a simple and inexpensive process. The resulting catalyst could depolymerize lignin efficaciously. The reusability of the catalyst was barely satisfactory, however, the activity could be partly recovered by simple calcination. © 2018 Society of Chemical Industry

In this paper, CuO and CeO2 were screened as co-catalyst components for Fe2O3/attapulgite (ATP) catalyst, and three new catalysts (CuO–Fe2O3/ATP, CeO2–Fe2O3/ATP and CuO–CeO2–Fe2O3/ATP) were prepared for degradation of methylene blue (MB). The three catalysts' characteristics were determined by BET, XRD, FT-IR, SEM and XPS. MB degradation in different systems and at different pH values was also studied. Under the conditions of H2O2 concentration of 4.9 mmol L−1, catalyst dosage of 5 g L−1, pH of 5, reaction temperature of 60 °C and MB initial concentration of 100 mg L−1, the as-synthesized catalysts showed much greater reaction rate and degradation efficiency of MB than Fe2O3/ATP catalyst. In addition, the reusability of the as-prepared composites was evaluated. The intermediate products of MB degradation were identified by LC-MS and the possible degradation process of MB was put forward.

With an aromatic structure, lignin has great potential for the production of high value-added chemicals. In this study, Co/m-ATP catalyst was prepared by the co-impregnation method to depolymerize lignin with inexpensive attapulgite as a carrier, 1,4-dioxane as a solvent, and ethanol as an in situ hydrogen source. Meanwhile, formaldehyde stabilization facilitates lignin monomer production during biomass depolymerization. The effects of Co particle loading and reaction conditions (e.g., temperature and reaction time) on lignin conversion and product yield were investigated, resulting in a low char yield (6.6 wt %) and high bio-oil yield (63.1 wt %) when alkali lignin was depolymerized over the Co/m-ATP catalyst (cobalt loading of 15 wt %) at 220 °C for 8 h. Therefore, this catalyst with the advantage of low cost and high catalytic activity would be a potential catalyst during the depolymerization of lignin.

A series of metal oxides (MnFeOx, MnCrOx, MnTiOx, and MnFeTiOx) supported on attapulgite (ATP) were synthesized by coprecipitation for the low-temperature selective catalytic reduction (SCR) of NOx with NH3. Then, they were subjected to appropriate characterizations for their properties (XRD, TEM, BET, XPS, etc.). The catalytic activity of MnFeTiOx/ATP catalyst was over 95% NOx conversion within a wide temperature window between of 175 and 300 °C, and 88% N2 selectivity. Moreover, MnFeTiOx/ATP presented excellent potassium resistance relative to the traditional V–W–Ti catalyst, and its denitration performance was significantly improved. The NOx conversion rate could be restored to nearly 90% at 210 °C after removing potassium via washing of K–MnFeTiOx/ATP. In addition, the MnFeTiOx/ATP showed better SO2 resistance and stability than the traditional V–W–Ti catalyst. Therefore, the MnFeTiOx/ATP catalyst has been proved to have broad prospects in NH3-SCR.

Immobilized AlCl3 catalyst(AlCl3/ATP) was prepared through solvent refluxing and adsorption method with attapulgite as the support and then used in the synthesis of aspirin. The catalyst was characterized by Fourier transform infrared spectroscopy(FT-IR)， X-ray diffraction(XRD), specific surface area(BET), X-ray energy dispersive spectrometry(EDS) and Hammett indicators. Factors influencing the catalytic properties such as concentration of hydrochloric acid, heattreated temperature, AlCl3 loading and amount of catalyst were optimized according to the yield of aspirin. The catalytic properties of the catalysts and the support were compared before and after loading. The results show that the amount of AlCl3 loading on ATP reached 1.18 mmol/g after ATP acidified with 10 mol/L HCl for 12 h at room temperature and then heat-treated under 300 ℃ for 2 h. The yield of aspirin catalyzed by AlCl3/ATP reaches 92.5% when the dosage of the AlCl3/ATP is 5% mass fraction of salicylic acid, which is higher than that of unloaded AlCl3 and the support itself. The catalyst also exhibits excellent catalytic stability within 5 times reused

BACKGROUNDResearch on the catalytic conversion of lignin into value-added chemicals has grown rapidly on account of the importance of lignin in the biorefinery. There is thus a need to investigate novel technologies to depolymerize lignin in the absence of hydrogen gas and noble metal catalysts. This study developed a cheap and recyclable catalyst via a facile process involving impregnation and calcination for the conversion of lignin to value-added phenolic monomers.RESULTSAcid sites, basic sites and magnetic components were successfully incorporated into attapulgite. The resulting catalyst displayed high catalytic activity for lignin conversion to phenolic monomers, which resulted in 10.9% total monomers yield at 250 °C for 3 h with a catalyst loading of 50% and a solvent-solid ratio of 20:1 in 50% C2H5OH. The total monomers yield decreased observably after eight successive reaction runs. After being calcined at 600 °C for 3 h, the recovered catalyst provided a total monomers yield of 6.74% in the ninth reaction run.CONCLUSIONA novel catalyst was successfully prepared by incorporation of acid sites, basic sites and magnetic properties using natural attapulgite clay as a precursor via a simple and inexpensive process. The resulting catalyst could depolymerize lignin efficaciously. The reusability of the catalyst was barely satisfactory, however, the activity could be partly recovered by simple

For the first time, Fe-zeolite 5A (Fe-Z5A) efficacy in the UV-assisted ozonation process to remove ciprofloxacin (CF) in wastewater is investigated. FTIR, SEM, EDX, BET, and the mass transfer process for point of zero charge are used to characterize the catalyst. Furthermore, the synergic process (UV/O3/Fe-Z5A) is compared with O3, O3/UV, and Fe-Z5A/O3 processes. The influence of catalyst dose, hydroxyl radical scavenger, and off-gas ozone released is discussed. The removal efficiency of CF in wastewater (for the synergic process) is compared with a single ozonation process. The results indicate that the synergic process was more efficient than others, with about 73% CF being removed (in 60 minutes) in the synergic process. The results also show that synergic processes produce less off-gas ozone than other processes, suggesting more ozone consumption in the synergic process, and confirmed by the radical scavenger effect and hydrogen peroxide decomposition studies. The Fe-Z5A was found to operate through a hydroxyl mechanism in which Fe worked as an active site that promotes the formation of hydroxyl radicals. Finally, the synergic process was more efficient than the ozonation process in the wastewater matrix. Hence, Fe-Z5A/O3/UV pathway is highly efficient for the degradation of pharmaceuticals in wastewater.

On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this work, ammonia decomposition catalysts consisting of in situ-formed nano-Ru particles supported on a naturally abundant mineral fiber, attapulgite (ATP), were proposed and studied. Also, 1 wt.% Ru was uniformly dispersed and anchored onto the surface of ATP fibers via the chemical method. We found that the calcination temperatures of the ATP support before the deposition of Ru resulted in little difference in catalytic performance, while the calcination temperatures of the 1Ru/ATP precursor were found to significantly influence the catalytic performance. The prepared 1 wt.% Ru/ATP catalyst (1Ru/ATP) without calcination achieved an ammonia conversion efficiency of 51% at 500 °C and nearly 100% at 600 °C, with the flow rate of NH3 being 10 sccm (standard cubic centimeter per minute). A 150 h continuous test at 600 °C showed that the 1Ru/ATP catalyst exhibited good stability with a degradation rate of about 0.01% h−1. The 1Ru/ATP catalyst was integrated with proton ceramic fuel cells (PCFCs). We reported that PCFCs at 650 °C offered 433 mW cm−2 under H2 fuel and 398 mW cm−2 under cracked NH3 fuel. The overall results suggest low-level Ru-loaded ATP could be an attractive, low-cost, and efficient ammonia decomposition catalyst for hydrogen production.

Pollution from heavy-metal ions has become a major challenge to the global fight against environmental pollution. Given the availability of various low-cost and environmentally friendly adsorbents, adsorption has become the most efficient technology for the removal of heavy metals from water. In this study, attapulgite (ATP) was directly functionalized by coupling with an aminosilane agent. Analysis showed this maneuver provided a suitable adsorbent for the removal of lead ion (Pb2+) from an aqueous solution. The effects of several parameters including solution pH, contacting time, adsorbent dosage, and initial Pb2+ ion concentration were investigated. Batch sorption results showed that the adsorption process was rapid and over 98% of Pb2+ was removed within 30 min at the optimal pH 4.0. The maximum adsorption capacity at 25°C, calculated by the Langmuir isotherm, was 82.17, 78.80, 61.13, and 28.56 mg/g for γ-divinyltriaminepropyl-methyldimethoxylsilane-grafted attapulgite (KH-103-ATP), γ-aminopropyl-methyldiethoxysilane-grafted attapulgite (KH-912-ATP), N-(β-aminoethyl-γ-aminopropyl)-methyl-dimethoxysilane-grafted attapulgite (KH-602-ATP), and ATP, respectively. Moreover, molecular dynamics simulations of adsorption behaviors of heavy-metal ions at attapulgite surfaces (010) modified by aminosilane agents were carried out. Both the PMF value and diffusion coefficient of metal ions suggest that KH-103-ATP owns the highest rate constant and capacity compared with the other two. And the analysis of free energy and results of XPS characterization revealed that Pb2+ formed covalent bonds with the nitrogen atom of aminosilane agents.

​Heavy-metal contamination is widespread in agricultural soils worldwide, especially paddy soils contaminated by Cd. Amendment-induced immobilization of heavy metals is an attractive and effective technique, provided that cost-effective materials are used. This field experiment compared three alkaline passivators (attapulgite, processed oyster shell powder, and mixed soil conditioner) at a rate of 2.25 t ha-1 for their effectiveness in decreasing Cd bioavailability in soils and accumulation in rice plants in a paddy field contaminated by Cd (0.38 Cd mg kg-1). The utilization of attapulgite and processed oyster shell powder decreased labile fractions but increased stable fractions of Cd in soils through ion exchange, precipitation and complexation. The addition of attapulgite decreased the concentration of bioavailable Cd in both bulk and rhizosphere soils, whereas the amendment of processed oyster shell powder decreased it only in bulk soil. The Cd accumulation in rice plants correlated significantly with acid-soluble and residual Cd fractions in the rhizosphere soil but not in the bulk soil. The addition of attapulgite and processed oyster shell powder decreased Cd accumulation in rice grains from 0.26 mg kg-1 to 0.14 and 0.19 mg kg-1, respectively, meeting the National Food Safety Standard (< 0.20 mg kg-1). However, the mixed soil conditioner did not decrease the Cd accumulation in rice shoots or grains. This study demonstrated that attapulgite and processed oyster shell powder were economic agents in reducing Cd accumulation in rice grains.

As most pesticides are either insoluble or only slightly soluble in water and must be applied in relatively small amounts over large areas, they are formulated in such a way that a highly concentrated organic chemical can be put into a convenient-to-use and effective form for field use by blending it with additives and inert carriers. The formulation must be easy and economical to use, do the job it is meant for, have an adequate shelf-life, and have no undesirable side effects.....

In 1976 nearly 300,000 tons of various clays were delivered to pesticide manufacturers in the United States alone for use in pesticide formulations (U.S. Department of Agriculture 1976). Of this amount, over 65% was attapulgite. The predominance of attapulgite in the formulation of pesticides in preference to more common clay minerals such as kaolinite and montmorillonite stems from the fact that it is not easily flocculated by electrolytes and does not cake at high relative humidities but remains free-flowing (HADEN and SCHWINT1967).

Slow-release fertilizers could improve the productivity of field crops and reduce environmental pollution. So far, no slow-release fertilizers are suited for maize cultivation in semiarid areas of China. Therefore, we tested attapulgite-coated fertilizers. Attapulgite-coated fertilizers were prepared by dividing chemical fertilizers into three parts according to the nutrient demand of maize in its three main growth stages and coating each part with a layer of attapulgite. This design is novel and unique, satisfying the demands of maize throughout the whole growing season with slow release of nutrients from the coated layers. A field experiment was conducted in 2010 and 2011, using three fertilizer rates, in kg/ha: 94.22 nitrogen (N) and 22.49 phosphorus (P), 139.09 N and 38.98 P, and 254.23 N and 50.98 P. Five types of fertilizers were compared: 20 and 30 % attapulgite-coated chemical fertilizer, 20 and 30 % attapulgite-mixed chemical fertilizer, and chemical fertilizer only. The results show that the soil mineral N and available P of attapulgite-coated fertilizer has a slow-release behavior that allows a better synchronization between nutrient availability and plant needs. Attapulgite-coated fertilizer increased the grain yield by 15.1–18.4 %. The use of attapulgite-coated fertilizers also improved partial factor productivity of N fertilizer by 10.0–26.7 % and P fertilizer by 11.0–26.7 %, compared with the control fertilized without coated formulates. Given their good performance, the attapulgite-coated fertilizers could be a promising alternative slow-release fertilizer for sustainable agriculture in semiarid areas.

To improve fertilizer use efficiency and minimize its negative impact on environment, a slow-release nitrogen and boron fertilizer with water-retention was prepared. Wheat straw was used as skeletal material in copolymerization on which acrylic acid monomer can be grafted to form superabsorbent composite. Urea and borax were introduced to provide nitrogen (N) and boron (B) nutrients, respectively. The product possessed a core/shell structure. Its core was urea in attapulgite and alginate matrix, and the shell was chemically modified wheat straw-g-poly(acrylic acid)/attapulgite (CMWS-g-PAA/APT) superabsorbent composite containing urea and borax. The effects of the amount of cross-linker, initiator, chemically modified wheat straw and attapulgite on water absorbency were investigated and optimized. The water absorbency of superabsorbent synthesized under optimal conditions was 186 g g−1 in tap water. Ammonia-selective electrode and inductively coupled plasma results showed that the contents of the nitrogen and boron of the product were 23.3% and 0.65%, respectively. The water retention capacity and the slow-release behavior of N and B of the product were investigated. The results showed that the product with slow-release and water-retention capacity, being economical, nontoxic in soil and environment-friendly, could be found good application in agriculture and horticultural.

​Heavy-metal contamination is widespread in agricultural soils worldwide, especially paddy soils contaminated by Cd. Amendment-induced immobilization of heavy metals is an attractive and effective technique, provided that cost-effective materials are used. This field experiment compared three alkaline passivators (attapulgite, processed oyster shell powder, and mixed soil conditioner) at a rate of 2.25 t ha-1 for their effectiveness in decreasing Cd bioavailability in soils and accumulation in rice plants in a paddy field contaminated by Cd (0.38 Cd mg kg-1). The utilization of attapulgite and processed oyster shell powder decreased labile fractions but increased stable fractions of Cd in soils through ion exchange, precipitation and complexation. The addition of attapulgite decreased the concentration of bioavailable Cd in both bulk and rhizosphere soils, whereas the amendment of processed oyster shell powder decreased it only in bulk soil. The Cd accumulation in rice plants correlated significantly with acid-soluble and residual Cd fractions in the rhizosphere soil but not in the bulk soil. The addition of attapulgite and processed oyster shell powder decreased Cd accumulation in rice grains from 0.26 mg kg-1 to 0.14 and 0.19 mg kg-1, respectively, meeting the National Food Safety Standard (< 0.20 mg kg-1). However, the mixed soil conditioner did not decrease the Cd accumulation in rice shoots or grains. This study demonstrated that attapulgite and processed oyster shell powder were economic agents in reducing Cd accumulation in rice grains.