Graphene oxide enhances thermal stability and microwave absorption/regeneration of a porous polymer

Desulfurization of liquid fuels mitigates the amount of noxious sulfur oxides and particulates released during fuel combustion. Existing literature on oxidative-adsorptive desulfurization technologies focus on sulfur-in-fuel removal by various materials, but very little information is presented about their desorption kinetics and thermodynamics. Herein, we report for the first time, the mechanism of sulfur desorption from neutral activated alumina saturated with dibenzothiophene sulfone. Batch experiments were conducted to examine the effects of agitation rate, desorption temperature, sulfur content, and eluent type on sulfur desorption efficiencies. Results show enhanced desorption capacities at higher agitation rate, desorption temperature, and initial sulfur content. Desorption efficiency and capacity of acetone were found to be remarkably superior to ethanol, acetone:ethanol (1:1), and acetone:isopropanol (1:1). Desorption kinetics reveal excellent fit of the nonlinear pseudo-second-order equation on desorption data, indicating chemisorption as the rate-determining step. Results of the thermodynamics study show the spontaneous (ΔG° ≤ -2.08 kJ mol-1) and endothermic (ΔH° = 32.35 kJ mol-1) nature of sulfur desorption using acetone as eluent. Maximum regeneration efficiency was attained at 93% after washing the spent adsorbent with acetone followed by oven-drying. Scanning electron microscopy, Fourier transform infrared, and X-ray diffraction spectroscopy analyses reveal the intact and undamaged structure of neutral activated alumina even after adsorbent regeneration. Overall, the present work demonstrates the viability of neutral activated alumina as an efficient and reusable adsorbent for the removal of sulfur compounds from liquid fossil fuels.

Effect of heat treatment on the pore structure properties of silica gel powders derived from water glass

D-hexagonal mesoporous iron silicate (HMFeS) has been synthesized hydrothermally in the presence of a mixture of an amphiphilic triblock copolymer, pluronic F127 and 1,2,4-trivinylcyclohexane (TVCH) as swelling agent under acidic aqueous conditions. The direct incorporation of iron(III) into 2D-hexagonal silicate framework can be monitored in a optimized molar ratio of water and hydrochloric acid. The mesophase of the materials was investigated by using small-angle powder X-ray diffractions (PXRD), transmission electron microscopy (TEM) image analysis and nitrogen adsorption/desorption studies. TEM image and PXRD revealed that the material had 2D-hexagonal mesoporous architecture. The morphology of the material was investigated by using scanning electron microscope (SEM) and framework bonding by utilizing FT IR spectroscopy. The atomic absorption spectrophotometer (AAS) was used to estimate the incorporated iron sites within the silicate framework. BET surface area (780 m 2 g -1 ) and peak pore size of HMFeS (10.07 nm) is much higher than the pure silica SBA-15 (611 m 2 g -1 and peak pore size of 9.09 nm). This mesoporous material (HMFeS) acts as a very good catalyst in the Friedel Craft benzylation and benzoylation reactions of arenes under optimized reaction condition using benzyl chloride and benzoyl chloride as the bezylating and benzoylating agents, respectively.

Acidic salts of the Keggin-type heteropolytungstic acids prepared through partial neutralization with alkali metal carbonates or ammonium hydroxide had relatively large surface areas, and showed high catalytic efficiency as insoluble solid acid catalysts in Friedel-Crafts alkylation and acylation using benzyl chloride, benzoyl chloride, benzoic anhydride, benzoic acid, acetic anhydride, and acetic acid as electrophiles.

From wood plastic composite waste to high-value aromatics via catalytic pyrolysis over an activated carbon

Porous carbon black-polymer composites for volatile organic compound adsorption and efficient microwave-assisted desorption

The desorption and regeneration of a novel granular bentonite composite adsorbent were investigated in this paper. Copper ions were adsorbed onto the composite adsorbent firstly, then the effects of reagent categories, reagent concentration, desorption time, adsorbed copper ion amount, and temperature on the desorption and regeneration of the adsorbent were studied. The results show that the desorption and regeneration of the composite adsorbent adsorbed copper ions can be carried out by acids, alkalis, or salts. The desorption and regeneration efficiency are closely connected with the experimental conditions and the categories of chemical reagents. Acids have the desorption capacity for composite adsorbent after adsorbing, but they need to be regenerated by other methods. Salts have both desorption and regeneration capacity. Alkalis show the strongest desorption and regeneration capacity.

The growing global demand for energy and environmental concerns have driven the search for renewable fuel sources. This study investigated the production of renewable hydrocarbons through the catalytic pyrolysis of Jatropha curcas L. oil, using the mesoporous material KIT-6 impregnated with cobalt oxide (Co3O4) as the catalyst. The catalysts were characterized using techniques such as X-ray diffraction (XDR), X-ray fluorescence (XRF), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and textural analysis. The catalytic cracking study was carried out through thermogravimetry and analytical pyrolysis. The mesoporous structure of KIT-6 was preserved after impregnation, although there was a reduction in surface area and total pore volume. The pyrolysis tests showed that Co/KIT-6 reduced the reaction temperature, favoring the formation of hydrocarbons in the C10-C18 range, suitable for biofuels such as biokerosene and green diesel. Compared to the thermal process, the use of the catalyst significantly increased the production of hydrocarbons while reducing the formation of undesirable oxygenated compounds. It is concluded that Co/KIT-6 is a promising catalyst for the sustainable production of biofuels from vegetable oils.

Gasification of waste biomass for hydrogen production: Effects of pyrolysis parameters

Physico-chemical characterization of MCM-41 silica spheres made by the pseudomorphic route and grafted with octadecyl chains

The Rh-embedded mesoporous silica (RMS) with a silica-nanosphere pore wall was successfully synthesized using silica nanospheres as a framework and citric acid as a nonsurfactant template. The RMS had a three-dimensionally interconnected and disordered wormhole-like mesostructure, and its pore size was easily controlled by simply changing the citric acid concentration or carrying out the aging treatment. In particular, we have first reported high hydrothermal stability and catalytic activity of the nanosphere-walled mesoporous silica in an ethanol steam reforming reactor at high temperature. As a result, the RMS showed 1.8% and 1.3% reduction of BET surface area and total pore volume after the ethanol steam reforming test for 5 h in the temperature range of 400 °C to 600 °C, whereas Rh-impregnated SBA-15 (RSBA15) showed 31.3% and 14.0% reduction of those. It is well-known that mesoporous materials have not been widely used as catalysts or catalyst supports in industry yet because of their poor hydrothermal stability. Accordingly, we have improved the hydrothermal stability of mesoporous silica through using silica nanospheres as a framework and have confirmed that the high hydrothermal stability of the RMS was attributed to the thermodynamically stable sphere-shaped pore wall, large intra-micropore volume of the silica-nanosphere wall, the thicker pore wall, and the highly branched structure of colloidal silica synthesized under base-catalyzed conditions. Moreover, compared to the RSBA15, the RMS gave a higher catalytic activity for the ethanol steam reforming because of its larger pore size and three-dimensionally interconnected pore structure, which lead to improvement in accessibility of reactants to the catalytic active sites.

Graphene oxide–cellulose acetate (GO–CA) nanocomposite membranes have been successfully prepared via phase inversion method. The GO sheets were firstly well dispersed in formamide, and then the solution was mixed with acetone containing CA so as to confirm the GO sheets well dispersed in the final GO–CA nanocomposite membranes. All the GO–CA nanocomposite membranes are composed of dense skin layer and sponge-like sublayer. With the increase in GO contents (from 0 to 0.01 wt%), the skin layer gradually became thinner and the pore size in the sublayer increased; meanwhile, the contact angle of GO–CA membranes decreased from 70.59° to 53.42° due to better hydrophilicity. All the membranes, except for the nanocomposite membrane containing 0.01 wt% GO, have featured pores at about 0.9 nm. The permeation rate of the membrane containing 0.005 wt% GO was 2.3 times higher than that of the CA membrane (0 wt% GO) with a little decrease (~15%) in salt retention. Compared with CA membrane, the enhanced performance of GO–CA membranes may be attributed to their enhanced structure and hydrophilicity.

Low-cost Scholl-coupling microporous polymer as an efficient solid-phase microextraction coating for the detection of light aromatic compounds

An investigation of the physical structure of MCM-41 novel mesoporous materials using a corrugated pore structure model

The liquid-phase benzylation of toluene with a benzylating agent like benzyl chloride (BC) is an important process for the production of mono-benzylated toluene (MBT), which is an industrially important compound used in pharmaceutical intermediates, fragrances, monomers for polycarbonate resins, heat-transfer fluids, aromatic solvents and fine chemicals. Selective synthesis of MBT by benzylation of toluene with BC over hierarchical micro-mesoporous-H-ZSM-5 (modified zeolite) catalyst was systematically studied for the first time. Hierarchical micro-mesoporous composites of H-ZSM-5 were obtained by treating parent H-ZSM-5 with different alkali (aq. NaOH) concentration. The synthesized catalysts were characterized by powder X-ray diffraction (XRD), BET surface area, TPAD, etc. The 100 % BC conversion with 100 % MBT selectivity was obtained over Hier-HZ-578 (Hierarchical H-ZSM-5) at lower molar ratio (toluene:BC) of 4:1 than 10:1 molar ratio reported, so far. The invented catalyst was also observed to be reusable for six catalytic cycles (one fresh and five recycles). The detailed optimization of process parameters such as molar ratio, catalyst loading and reaction time and temperature is also discussed.