Adsorption and solvent desorption behavior of ion-exchanged modified Y zeolites for sulfur removal and for fuel cell applications

Metal Modified NaY Zeolite as Sorbent for the Ultra-Deep Removal of Thiophene in Simulated Coke Oven Gas

The ultra-deep removal of thiophene is essential for the conversion of coke oven gas to methane and metal modified Y zeolite has excellent thiophene adsorption capacity. The effects of temperature on chemisorption between metal modified Y zeolite and thiophene and the reductive gases in coke oven gas on the thiophene adsorption performance still remains ambiguous. To address the aforementioned aims, series of NaMY (M = Ce, Ni, Zn and Ag) were prepared via ion-exchanged with Na+ of NaY, and two comparable sets of thiophene adsorption evaluation were conducted in a fixed bed reactor: (1) NaY and NaMY were evaluated at different temperatures in simulated coke oven gas, and (2) NaCeY was evaluated in N2 and different reductive atmospheres. The results show that NaNiY, NaZnY and NaAgY could adsorb thiophene via π-complexation, however, NaCeY mainly through S-Ce bond. Π complexation becomes weak above 150 °C, and the strength of S-Ce bond varies little when the temperature rises to 250 °C. Compared with that of other sorbents, the breakthrough adsorption capacity for thiophene (Qb-thiophene) of NaAgY reaches the highest 144 mg/g at 100 °C, but decreases sharply when temperature rises to 200 °C. NaCeY has relatively low variation in Qb-thiophene from 100 °C to 200 °C. Moreover, Ce(IV) in NaCeY is more favorable for thiophene adsorption than Ce(III) in coke oven gas and the presence of H2 and CO would reduce the desulfurization activity of NaCeY. For the industrial utilization of thiophene ultra-deep removal, NaAgY has an excellent potential below 150 °C, while NaCeY with more Ce(IV) has a good prospect at 150–250 °C.

Hierarchical-pore UiO-66 modified with Ag+ for π-complexation adsorption desulfurization

Adsorption desulfurization represents an alternative technology for the effective removal of thiophenic compounds from fuels. Metal-organic frameworks have been the ideal candidates for the adsorptive desulfurization of fuel due to the high surface areas. Pristine UiO-66 is thought to be appropriate for the removal of small thiophenic compounds. This work developed a new type of hierarchical-pore (micro and mesopores) UiO-66 with a higher specific surface area and porosity for the removal of larger adsorbates using MOF-5 as the template. To enhance adsorption desulfurization performance, the Ag⁺-exchanged hierarchical-pore UiO-66 (HP-UiO-66-SO₃Ag) with π-complexation was synthesized by the ion-exchange method. The HP-UiO-66-SO₃Ag samples were characterized by FTIR, XRD, SEM, TEM, and N₂ adsorption-desorption isotherms. Compared with the original UiO-66, the HP-UiO-66-SO₃Ag has a higher specific surface area, pore volume, and pore size. The static adsorption experiments showed that HP-UiO-66-SO₃Ag had a high adsorption capacity for thiophene and benzothiophene. Moreover, the HP-UiO-66-SO₃Ag sample still exhibits high adsorptive performance in the presence of toluene. The regeneration results show that about 90% of the initial adsorption capacity of HP-UiO-66-SO₃Ag can be regenerated after four cycles.

Adsorptive desulfurization of liquid hydrocarbons using zeolite-based sorbents: a comprehensive review

Adsorptive desulfurization using modified Y zeolite is an efficient process for the removal of sulfur from transportation fuels.

High removal of thiophene from model gasoline by porous MIL-101(Cr)/SA hybrid membrane

Membrane separation technologies have great promising potential for applications in several industries. Metal-organic frameworks (MOFs), for their large surface areas, low framework densities, transition-metal ions in the skeleton and high pore volumes relative to other porous matrices, have great potential for the removal of sulfur from gasoline with high efficiency. In the present study, a novel porous membrane adsorbent MIL-101(Cr)/SA was prepared by immobilizing MIL-101(Cr) onto sodium alginate (SA) matrix, which can combine the size/shape selectivity of MIL-101(Cr) with the processability and mechanical stability of SA polymer. The physico-chemical properties of MIL-101(Cr)/SA were investigated by FT-IR, SEM, BET, XRD and EDX methods. To investigate the effects of some important factors on the adsorption behavior for thiophene, a batch of experiments were performed by changing the concentration of porogen polyethylene glycol in the MIL-101(Cr)/SA, solution temperature, initial thiophene concentration and contact time. Meanwhile, benzothiophene, thiophene and 3-methyl thiophene were used to test the selectivity of MIL-101(Cr)/SA. The MIL-101(Cr)/SA showed an excellent uptake capacity of 671 mg g-1 under the optimal adsorption conditions. Selectivity testing indicated that the uptake capacity of MIL-101(Cr)/SA follows the order of benzothiophene > thiophene > 3-methyl thiophene. Kinetics experiments indicated the pseudo-second-order model displayed good correlation with adsorption kinetics data. The Crank model showed that the intraparticle solute diffusion is the rate-controlling adsorption step. Regeneration experiment result shows that the prepared MIL-101(Cr)/SA has excellent adsorption and desorption efficiencies.

The Removal of Benzothiophene from Model Diesel on NaY and NiY Zeolites: Equilibrium and Kinetic Studies

This work investigates the adsorption of sulfur compounds in model fuel (benzothiophene dissolved in n-octane) on NaY and NiY zeolites from the points of adsorption equilibrium and kinetics. The crystal structures, textural properties and chemical compositions of zeolites were characterized by XRD, N2 physisorption and ICP-AES, respectively. The adsorption of sulfur from model diesel was processed in a batch experiment on NaY and NiY zeolites, and the effects of adsorption temperature and adsorption time on adsorption capacity were investigated. The experimental isotherm data were fitted using Langmuir, Freundlich and Toth models. The pseudo-first order, pseudo-second order, pseudo-n order and intra-particle diffusion models were applied to fit the kinetic data and determine the adsorption mechanism. It is observed from the correlation coefficient (R2) that Toth model is more appropriate to depict the isotherm equilibrium adsorption process and the sulfur uptake process follows the pseudo-n order rate expression on NaY and NiY zeolites. The diffusion study indicated that the adsorption of benzothiophene is controlled by two steps. Moreover, the results of the relative error (RE) analysis further confirm the conclusion of the kinetic study. Thermodynamic studies demonstrated that the adsorption process is exothermal and spontaneous. The equilibrium adsorption sulfur capacities are 20.66 and 28.21 mgS˙g−1 on NaY and NiY zeolites at 50 °C, respectively.

An aluminum selective electrode via modification of PVC membrane by modified clinoptilolite nanoparticles with hexadecyltrimethyl ammonium bromide (HDTMA-Br) surfactant containing Arsenazo III

A modified PVC (polyvinyl chloride) membrane with clinoptilolite nanoparticles/hexadecyltrimethyl ammonium bromide surfactant (HDTMABr)/Arsenazo III: (NSMZ-ARS), was used for construction of Al(III) -selective electrode. The raw and modified samples were characterized by XRD, FTIR, SEM and TEM methods. Among the different tested membranes constructed by raw and modified samples, only, the membrane electrode containing NSMZ-ARS showed a suitable Nernstian response to aluminum in the concentration range of 2.04×10^-5 to 1.99×10^-1M (r=0.9987), with a detection limit of 1.0×10^-5molL^-1 and a Nernstian slope of 19.6±0.5mV per decade of aluminum concentration. The electrode response to aluminum remained constant in the pH range of 2-4. The sensor was selective for aluminum over a wide variety of other ions and exhibited. The electrode had a rapid response time and its response reached to steady potential at 5s. The electrode had also satisfactory long term stability and held its activity at least 3months.

Equilibrium and kinetic studies on the adsorption of thiophene and benzothiophene onto NiCeY zeolites

NiCeY zeolites were prepared by ion-exchanging NaY with 0.1 M Ni(NO₃)₂ and 0.1 M Ce(NO₃)₃ solution.

Copper-containing porous carbon derived from MOF-199 for dibenzothiophene adsorption

A novel type of copper-containing porous carbon derived from MOF-199 has a good performance in adsorption desulfurization.

Desenvolvimento e caracterização de filmes compósitos de quitosana e zeólitas com prata

Resumo Zeólitas foram submetidas à troca iônica ou impregnação com prata e posteriormente adicionadas em filmes de quitosana para a confecção de curativos para queimaduras. As zeólitas foram avaliadas por Ressonância magnética nuclear (RMN), Fluorescência de raios X por reflexão total (TXRF), Microscopia eletrônica de varredura (MEV). Os filmes poliméricos foram analisados com relação às suas propriedades mecânicas, permeabilidade ao vapor d’água (PVA) e liberação de prata. Observou-se que o procedimento de troca iônica não alterou a morfologia das zeólitas de partida. Grumos de zeólita foram observados nas micrografias dos filmes e estes influenciaram nas propriedades mecânicas devido à desorganizaçao local no empacotamento das cadeiras poliméricas da quitosana. A metodologia de troca iônica ou impregnação influenciou diretamente na quantidade de prata presente superficialmente na zeólita e consequentemente alterou o perfil de liberação de prata em uma solução simulada de exudato de ferida. Os modelos cinéticos sugeriram que a liberação da prata não foi essencialmente regulada pela lei de difusão de Fick.

Preparation and characterization of poly(3-methylthiophene)/CeY zeolite composites

Poly(3-methylthiophene)/CeY zeolite nanocomposites are prepared by chemical oxidative polymerization using anhydrous FeCl₃ as the oxidizing agent.

Sulfur removal from fuel using zeolites/polyimide mixed matrix membrane adsorbents

A novel membrane adsorption process was proposed for the sulfur removal from fuels. The mixed matrix membranes (MMMs) adsorbents composed of polyimide (PI) and various Y zeolites were prepared. By the detailed characterization of FT-IR, morphology, thermal and mechanical properties of MMMs adsorbents, combining the adsorption and desorption behavior research, the process-structure-function relationship was discussed. Field-emission scanning electron microscope (FESEM) images show that the functional particles are incorporated into the three-dimensional network structure. MMMs adsorbents with 40% of zeolites content possess better physical properties, which was confirmed by mechanical strength and thermo stability analysis. Influence factors including post-treatment, content of incorporated zeolites, adsorption time, temperature, initial sulfur concentration as well as sulfur species on the adsorption performance of MMMs adsorbents have been evaluated. At 4 wt.% zeolites content, adsorption capacity for NaY/PI, AgY/PI and CeY/PI MMMs adsorbents come to 2.0, 7.5 and 7.9 mg S/g, respectively. And the regeneration results suggest that the corresponding spent membranes can recover about 98%, 90% and 70% of the desulfurization capacity, respectively. The distinct adsorption and desorption behavior of MMMs adsorbents with various functional zeolites was markedly related with their various binding force and binding mode with sulfur compounds.