Ammonia Sorption Research Articles

Organo-sulfonic acids doped polyaniline – based solid acid catalysts for the formation of bio-esters in transesterification and esterification reactions

In the present work catalytic reactivity of polyaniline protonated with organo-sulfonic acids, namely methanosulfonic (MSA-Pani), camphorosulfonic (CSA-Pani) and lignosulfonic (LG-Pani) acids was evaluated for the transesterification of triglycerides (triacetin, castor oil) and esterification of fatty acid (ricinoleic) with methanol. Their reactivity was also compared with previously studied alkyl-free polyaniline-sulfate (S-Pani) catalyst. The textural and acid properties of the catalysts before and after catalytic tests were characterized by BET, FT-IR, XRD, SEM, thermogravimetric and ammonia sorption techniques. It was observed that acid characteristics, namely concentration and the strength of acid sites as well as chemical properties of the surface e.g. the type of organo-sulfonic acid played an important role in catalytic performance of studied samples. In all tested reactions, the MSA- and CSA-doped polyanilines exhibited the highest initial activity referred to the acid site capacity. However, too weak acid sites in these catalysts resulted in their partial blockage during methanolysis of triglycerides. This was not observed in the esterification reaction. Among all studied samples, the LG-Pani (commercial reagent) and MSA-Pani catalysts seem to be the most promising owing to their high activity and good stability in reaction mixture, in particular during methanolysis of triglycerides. In contrast to the MSA-Pani catalyst (thermally stable up to 260°C), lower stability of LG-Pani catalyst (up to ca. 120°C) may limit its application.

Ammonia sorption studies into thin layers of hexadecafluorinated cobalt phthalocyanine using optical techniques

In the present work, the optical response of CoPcF16 films upon exposure to ammonia vapor in the concentration range 50 to 1000 ppm was measured by total internal reflection ellipsometry. It was demonstrated that the sorption of NH3 molecules causes substantial shift of the Δ(λ) spectrum which is determined by the increase in film thickness and change of its optical parameters. It was found that the CoPcF16 films deposited at substrate temperature of 220 °C are characterized by larger grains and more developed surface demonstrating higher optical response than films deposited at substrate temperature of 60 °C. In order to gain an insight into the sorption mechanism at molecular level, we have studied the interaction of ammonia vapor with hexadecafluorinated cobalt phthalocyanine using infrared spectroscopy. It was shown that the detection of ammonia was found to be governed primarily by coordination to the metal center.

Dehydration of fructose to 5-hydroxymethyl furfural over ordered AlSBA-15 catalysts

5-Hydroxymethyl furfural is an important platform chemical. It is successfully synthesized from renewable carbohydrates using mesoporous AlSBA-15 catalysts under biphasic conditions. Fine tuning of the catalyst acidity is important to drive the reaction to give good yields of furan compound. Al-SBA-15 catalysts with different Si/Al ratios were prepared and characterized by XRD, 27Al MASNMR, SEM, TEM, N2 sorption, ICP-OES and TPD of ammonia. Results show that part of aluminium is substituted into tetrahedral positions. The catalyst with lower acid site density but medium to strong acidstrength favours selective formation of HMF. Under the optimized conditions, HMF selectivity was as high as 88% at 59 mol% conversion of fructose. Leaching of part of aluminium occurs under hydrothermal conditions, if solvent mixtures containing water are used, while activity can be retained if DMSO is used as solvent.

Ammonia Oxidation on Structured Composite Catalysts

The NH3-based selective catalytic reduction of NO x on monolithic zeolite catalysts has emerged as the technology of choice for heavy-duty diesel vehicles. A class of Cu-exchanged zeolite catalysts has been developed that have very high ammonia sorption capacity and can achieve high NO x conversion to N2 for a variety of transient conditions. In order to fully exploit the latest generation of SCR catalysts, an active, selective and robust post-SCR ammonia conversion system is needed to minimize the breakthrough of ammonia into the environment [1]. The goal of this study is to better understand the steady-state catalytic mechanism of post-SCR ammonia oxidative conversion and product selectivity on low-loading Pt-based catalysts and in so doing provide guidance in the development of a new class of ammonia slip catalysts.

Novel ammonia sorbents ‘‘porous matrix modified by active salt” for adsorptive heat transformation: 6. The ways of adsorption dynamics enhancement

The dynamics of ammonia sorption was investigated by means of a Large Temperature Jump (LTJ) method for loose grains of “BaCl2/vermiculite” and “BaCl2/BaBr2/vermiculite” composites which are promising materials for adsorption air-conditioning. The influence of the grain size, the adsorbent composition and the adsorbent load was studied. The heat transfer coefficients were calculated for adsorbents with different grain sizes. The results of LTJ experiments were used for modeling the adsorption air-conditioning cycle operating in the cyclic steady state mode. The potential of using a proper ratio of durations for the adsorption and desorption stages of the cycle along with a harmonization of the driving forces for the enhancement the dynamic performance of the adsorption chiller was discussed. Appropriate recommendations on optimization of the adsorbent composition and load were made.

Novel ammonia sorbents “porous matrix modified by active salt” for adsorptive heat transformation: 5. Designing the composite adsorbent for ice makers

The novel adsorbent of ammonia based on binary salt system BaCl 2 + BaBr 2 inside vermiculite pores was intently designed for adsorption cooling cycle specialized for ice-making. On the base of analysis of the working conditions of the cycle the requirement for the optimal adsorbent was formulated in terms of the equilibrium temperature of reaction between the salt and ammonia and the real composite adsorbent (BaCl 2 + BaBr 2 )/vermiculite with required properties was prepared. The dynamics of ammonia adsorption on the composite was studied by a Large Temperature Jump method under working conditions of the ice-making cycle. The maximum cooling power W 0 realized at t → 0 was estimated as 1.2 kW/kg. The composite allows the production of 2 kg/(kg h) of ice. Such a good performance demonstrates an advantage of the target-oriented design of the composite adsorbent with predetermined properties matching the particular conditions of the cooling cycle. ► Composite adsorbent (BaCl 2 + BaBr 2 )/vermiculite was intently prepared for ice makers. ► Dynamics of ammonia sorption was studied under conditions of adsorption cooling cycle. ► The maximum cooling power W 0 was estimated as 1.2 kW/kg. ► The composite allows production of 2 kg of ice per 1 kg of the adsorbent per hour. ► Such a good performance was a result of the target-oriented design of the adsorbent.

Biochar’s role as an alternative N-fertilizer: ammonia capture

Biochar’s role as a carbon sequestration agent, while simultaneously providing soil fertility improvements when used as an amendment, has been receiving significant attention across all sectors of society, ranging from academia, industry, government, as well as the general public. This has lead to some exaggeration and possible confusion regarding biochar’s actual effectiveness as a soil amendment. One sparsely explored area where biochar appears to have real potential for significant impact is the soil nitrogen cycle. Taghizadeh-Toosi et al. (this issue) examined ammonia sorption on biochar as a means of providing a nitrogen-enriched soil amendment. The longevity of the trapped ammonia was particularly remarkable; it was sequestered in a stable form for at least 12 days under laboratory air flow. Furthermore, the authors observed increased 15N uptake by plants grown in soil amended with the 15N-enriched biochar, indicating that the 15N was not irreversibly bound, but, was plant-available. Their observations add credence to utilizing biochar as a carrier for nitrogen fertilization, while potentially reducing the undesired environmental consequences through gas emissions, overland flow, and leaching.

Deordorization Performance of Oxidized and Succinylated Wool Fibers -Removal of Ammonia and Alkylamines-

This report describes the addition of deodorizing functionality to wool fibers by chemical modification for recycling used wool into a functional fiber material. Wool fibers were oxidized and succinylated and the effects of these treatments on ammonia sorption were evaluated. Oxidation significantly improved the ammonia sorption of wool fibers. The oxidized wool fibers also considerably sorbed methyl amine and dimethyl amine, though butyl amine and trimethyl amine were poorly sorbed. Ammonia sorbed rapidly with sulfuric acid groups but sorbed more slowly with carboxylic groups in oxidized and succinylated wool fibers. The sorbability of oxidized wool fibers after repeated sorption could be completely restored by washing with 0.5mM sulfuric acid.

Metal-catalyzed graphitic nanostructures as sorbents for vapor-phase ammonia

Activated carbons have long been used as substrates for the filtration of vapor-phase molecules, often with metal salts or oxides added to improve their sorption capacities for specific agents, but their real-world performance and applicability may be hindered by such factors as long-term stability and complex processing. En route to a new class of carbon-based sorbents, we have developed solid-state synthetic methods to produce bulk carbonaceous solids based on the pyrolysis of thermoset solids containing low concentrations (<1 wt%) of metal precursors (based on either Ni, Fe, or Co) that decompose in situ to catalyze the formation of a complex graphitic nanostructure. Selective combustion of residual amorphous carbon from the pyrolyzed solid generates a mesoporous network that facilitates diffusional transport of gas-phase molecules to the interior surfaces of the solid, and also converts the entrained metals to their respective metal oxide forms. We examine the ammonia-sorption properties of a series of these graphitic nanostructured compositions, and demonstrate that ammonia uptake is primarily determined by the type of residual metal oxide, with the Co-containing carbonaceous solid providing the best ammonia-sorption capacity (1.76 mol kg−1). Thermal reduction of the Co-containing material drastically decreases its ammonia-sorption capacity, showing that the oxide form (in this case Co3O4) of the entrained metal nanoparticles is most active for ammonia filtration. The effects of the carbon–oxygen functionalities on the nanostructured graphitic surfaces for ammonia sorption are also discussed.

Novel ammonia sorbents “porous matrix modified by active salt” for adsorptive heat transformation: 4. Dynamics of quasi-isobaric ammonia sorption and desorption on BaCl2/vermiculite

A novel composite sorbent of ammonia BaCl 2 /vermiculite has recently been proposed and tested for adsorption cooling. The aim of this paper was a detailed study of its dynamic operation under conditions of isobaric stages of an adsorption chiller cycle. Experiments were performed by a Large Temperature Jump method at the ammonia pressures 5.8, 6.9, 12.2 and 15.8 bar. The ad- and desorption temperatures were fixed, respectively, at 15, 20, 25, 30, 35 °C and 65, 70, 80, 90 °C. All kinetic curves were described by an exponential function with a single characteristic time τ . The rate constant k = 1/ τ was found to be a linear function of the temperature difference which drives the process, hence, heat transfer between the sorbent layer and the plate heat exchanger determines the process dynamics. The appropriate heat transfer coefficient does not depend on the ammonia pressure and process temperatures and equals 90 W/(m 2 ·K). The data obtained were used for analyzing the dynamic performance of adsorption chiller with this composite as a solid sorbent. Appropriate recommendations on optimization of working cycle are made. The analysis showed that the specific cooling power could reach 690–860 W/kg at the cycle duration of 100–300 s.

Adsorption of Ammonia from Aqueous Solution Using Zeolite-Attapulgite Nano-Pore Structure Ceramisite

Zeolite-attapulgite nano-pore structure ceramisite was prepared using natural zeolite and attapulgite through compounding, granulation and calcination.After elementary characterization of this ceramisite by mercury porosimeter, batch tests were carried out to examine its removal mechanism of ammonia. The influences of pH, contact time, initial ammonia concentration and temperature on the ammonia removal were investigated. The optimum pH for adsorption of ammonia was found to be less than 7. The adsorption process followed pseudo-second order rate model. Adsorption isotherm studies showed that Freundlich model fitted the experimental data. The sorption of ammonia increased with the rise of temperature because adsorption process was endothermic. The zeolite-attapulgite composite nano- pore structure ceramisite shows very good promise for practical applicability of ammonia removal from aqueous solution.

Novel ammonia sorbents “porous matrix modified by active salt” for adsorptive heat transformation: 2. Calcium chloride in ACF felt

Novel composite sorbent “31 wt.% CaCl2/ACF” was synthesised by dry impregnation of an ACF felt with a CaCl2 aqueous solution. Apparent isosters of ammonia sorption were measured at T = 20–90 °C and P = 0.1–9.0 bar by an isosteric adsorption method. The method is based on the sorbent heating in a closed volume of an adsorber with registration of the ammonia equilibrium pressure P as a function of temperature T. The uptake covered the range of 5.7–36.9 wt.%. The apparent enthalpy and entropy of the ammonia sorption as a function of ammonia uptake were obtained directly from the slop of isosteric lines lnP(1/T). Appropriate correction to obtain the true sorption enthalpy was done by taking into account the “dead” volume of the adsorber. The new adsorbent was found to be an advanced material for adsorptive chilling.

Novel ammonia sorbents “porous matrix modified by active salt” for adsorptive heat transformation

Abstract Novel composite materials BaCl 2 /vermiculite, BaCl 2 /γ-Al 2 O 3 and BaCl 2 /(carbon Sibunit) have been synthesised by impregnation of the three porous matrices with barium chloride and studied as ammonia sorbents. Isosters of ammonia sorption are measured at T = 15–80 °C and P = 0.7–9 bar. It was found that a modification of the host matrices by the salt increases the ammonia uptake due to a chemical reaction between ammonia and barium chloride. The enthalpy and entropy of ammonia sorption by the salt confined to the mesopores of alumina and Sibunit are significantly smaller with regard to those for the bulk salt. This indicates that the salt confinement to the small pores allows tuning its sorption properties. In the large vermiculite pores the properties remain unchanged. Based on the experimental isosteric charts, the feasibility of the new materials for adsorptive heat transformation has been analyzed. For composite BaCl 2 /vermiculite the coefficient of performance (COP) for ice making and air conditioning cycles calculated from the ammonia sorption data can reach 0.6 which seems quite encouraging from a practical point of view.

Spatial pattern of ammonia sorption by soil and vegetation downwind of a beef feedlot

In the recent decades NH3 emission from animal production has increased substantially worldwide and there has been indications of its adverse effect on vegetation especially near intensive livestock operations. In this study, the effect of NH3 deposition on soil and on two forage species, crested wheatgrass (CWG) (Agropyron cristatum L. Gaertn.) and timothy grass (TIM) (Phleum pratense L.), was investigated over 3 years near a large feedlot in southern Alberta, Canada. A high NH3 deposition rate of 104kgNha−1year−1 was observed at the feedlot edge, decreasing by 53% 700m downwind. Most of the NH3 deposited to soil accumulated in the 0–5cm depth resulting in increased soil NH4+, NO3− and total N (TN) concentrations at this depth. Significantly higher NO3− and TN concentrations were also observed in both vegetation and roots 0 and 20m downwind of the feedlot operation. The foliar and root biomass of CWG was higher 20, 50 and 100m downwind than at sites further away. Foliar and root biomass of CWG growing downwind of the feedlot (excluding the 0m site) was positively related to NH3 deposition, while TIM biomass was not. However, root growth of both species was significantly reduced immediately (0m) outside the feedlot operation. Foliar damage was also more severe for both species at 0m than at any other site downwind. Our study indicates that most plant damage occurred immediately outside the feedlot and that, further downwind, atmospheric NH3 deposition could be beneficial. However, N deposition near feedlot operations should be considered when making fertilizer recommendations to reduce input costs and prevent overloading of nitrogen into the environment.

Gas Sorption of Acetone, Diethyl Ether, Toluene, Acetic Acid, and Ammonia on Plasma-Polymerized Hexamethyldisiloxane Films Coated with Quartz Crystal Microbalance

Gas Sorption of Acetone, Diethyl Ether, Toluene, Acetic Acid, and Ammonia on Plasma-Polymerized Hexamethyldisiloxane Films Coated with Quartz Crystal Microbalance

The thermal equation for ammonia sorption by cellulose acetate

The thermal equation for ammonia sorption by cellulose acetate was obtained using the quasichemical model of the sorption of vapors by swelling polymeric sorbents suggested by Lindstrom and Laatikainen. The experimental data obtained by reversed gas chromatography and static methods are compared.

Chemical interaction of gaseous ammonia and water vapour with polyacrylic acid layers

The sorption of water vapour and gaseous ammonia into polyacrylic acid (PAA) induces a mass uptake and changes the electrochemical properties of the material. In order to review and confirm phenomenological models describing these processes, systematic infrared (IR) studies have been performed. The IR spectra are taken in the 400–4000 cm−1 wavenumber range and the IR spectrum of the polymer in dry air is taken as the reference for calculation of the absorbance spectra. The interpretation of increasing and decreasing bands in the IR spectra draws a consistent picture of the processes in the polymer, so that the models can be confirmed and, additionally, more detailed information is gained.

Sorption of ammonia on oxidized and succinylated wool keratin

Sorption of ammonia on oxidized and succinylated wool keratin

Influence of mass recovery on the performance of a heat pipe type ammonia sorption refrigeration system using CaCl 2/activated carbon as compound adsorbent

The performance analyses of a sorption refrigeration system with different mass recovery processes are presented, in which compound adsorbent of CaCl 2 and activated carbon is used to improve the mass and heat transfer performances of sorption bed. The heating, cooling and heat recovery processes between two sorption beds were performed by multifunction heat pipes without additional power consumption. The experimental Clapeyron diagrams showed that the cycles with mass recovery (MR), with heat and mass recoveries (HMR), and with mass and heat recoveries (MHR), have better thermodynamic performances when compared with the sorption cycle without mass recovery (MR0). The implementary order of mass recovery and heat recovery has strong influence on the efficacy of mass recovery while it has little influence on the efficacy of heat recovery. In sorption cycles with HMR and with MHR, the hot beds can be pre-cooled and cold beds can be pre-heated effectively during the switching process, and heat consumption from external heat source during desorption phase is thereby reduced. Mass recovery can enlarge cycled refrigerant mass due to the transfer of refrigerant gas between two sorption beds during mass recovery process. In comparison with sorption cycle with MR0, sorption cycles with MR, with HMR, and with MHR can generally improve the coefficient of performance (COP) and specific cooling power (SCP) by more than 20% and 16%, respectively. Especially, sorption cycle with MHR has the highest performance among different mass recovery processes due to the fact that MHR has the advantages of MR and HMR, and it can improve the COP by 46.7% when compared with the cycle with MR0.

The effect of polyoxometallate complexes of nickel and copper on the rate of their heterophase reaction with ammonia

It was established that the compounds formed by the cations in amine complexes of nickel(II) and copper(II) and the anions of polyoxometallates are capable of reacting stoichiometrically with gaseous ammonia when in the hydrated state. Some of the studied compounds are characterized by high sorption capacity (up to 40 molecules of adsorbate to a formula unit of the complex) and exhibit selectivity in the sorption of ammonia in the presence of water vapor.