Porous Solid Acid Research Articles

Transesterification of Pistacia chinensis seed oil using a porous cellulose-based magnetic heterogeneous catalyst

ABSTRACTIn the present work, a novel cellulose-based porous heterogeneous solid acid catalyst encapsulation of ferriferous oxide (Fe3O4) and sulfonated graphene (GO-SO3H) into cellulose to form composite porous microspheres catalyst (GO-SO3H/CM@Fe3O4) was synthesized and evaluated for biodiesel production from Pistacia chinensis seed oil. The SEM, EDS and FTIR analysis revealed that the catalyst GO-SO3H/CM@Fe3O4 owned stronger active sites and GO-SO3H dispersed well in porous surface and inside of cellulose support. Under the optimum conditions, microwave-assisted transesterification process was carried out with the best catalyst amount, i.e. 5 wt% GO-SO3H/CM@Fe3O4 (weight ratio of GO-SO3H/cellulose), and conversion yield reached 94%. The prepared catalyst could be easily separated from reaction solution by extra magnetic field and reclaimed at least five runs.

A comparative study on porous solid acid oxides as catalysts in the esterification of glycerol with acetic acid

Abstract Acid catalysts comprising of porous SiAl, as well as molybdophosphoric heteropolyacid, supported SiAl nanotubes were synthesized. The characterizations were through scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), termoprogrammed ammonia desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR). Esterification of glycerol into acetins reaction was evaluated over two series of SiAl-based solids. Both series displayed very good activity as well as selectivity towards the acetins within a short reaction time. However, porous SiAl deactivated due to acid sites leaching in long-term catalytic runs. The tuning of the loadings of the molybdophosphoric amount on SiAl halloysite nanotubes leads to an increase in the selectivity towards the mono, di, and triacetins. These catalysts were also recycled up to three times, and a 17 % of conversion and 100 % of selectivity for triacetin were obtained due to the combination of acidity, stable structure and porosity of the molybdophosphoric supported SiAl nanotubes.

Liquid-phase solvent-less reactions for value addition of glycerol and phenols over nano porous aluminosilicates

The protocol reports an efficient nano porous solid acid catalyst for the effective conversion of bio-waste product glycerol and phenols into valuable chemicals and fuels through acetalization and alkylation reactions respectively. A novel method was adopted for the direct synthesis of the proton form of Aluminosilicate (HAlSi) from alkali-free gel medium for its ready catalytic applications towards bulky molecular reactions producing chemicals and fuels. In the liquid phase phenol alkylation reactions, the catalyst exhibited 83% conversion with 100% selectivity to the alkylated phenols at solvent-less reaction conditions. The catalyst also exhibited more than 90% conversion in glycerol acetalization reaction to produce mono, di and tri-acetalized esters useful for chemicals and fuel industries. Detailed physicochemical characterization of the synthesized material was conducted by XRD, BET, N2-sorption, NH3 TPD, FTIR, Raman, XPS, SEM, TEM, TG/DTA and Si29 NMR spectroscopic techniques. XPS, FTIR, and NMR results indicated the formation of aluminosilicate chemical structure in the material while TPD confirmed the formation of strong acidity, TEM and sorption studies revealed the formation of ∼50 nm size particles of HAlSi material exhibiting nano porous nature make this nano porous material suitable for acid catalysed bulky molecular transformations exemplified by tert- butylation of phenol and glycerol acetylation. The promising performance of the catalyst towards these reactions was ascribed to the presence of nano size pores in the catalyst and the easy accessibility of the acid sites to the reactants and facile diffusion of the bulky product molecules. The catalyst also exhibited high temperature thermal stability in DT/TGA and structural stability of active sites revealed by stable catalyst performance with reaction cycles. Since, glycerol and phenolic compounds obtain from biomass needs to be addressed for effective value addition, the alkylation and esterification reactions catalysed by present catalyst system provides promising processes to produce valuable chemicals and fuels from low value bio-derivatives.

Aqueous Phase Synthesis of 5-Hydroxymethylfurfural from Glucose over Large Pore Mesoporous Zirconium Phosphates: Effect of Calcination Temperature.

For a solid acid-catalyzed dehydration of biomass-derived carbohydrates into useful furan derivatives, a suitable porous solid acid catalyst having an optimum acidic density and its strength is required to avoid cascade reactions in biomass conversion processes. A large-pore mesoporous zirconium phosphate (m-ZrP) was prepared hydrothermally using P123 as a template in water solvent, which resulted in a higher pore diameter (>9 nm) having wormhole-like pore structures with balanced Lewis (L) to Brönsted (B) acid sites. The effects of calcination temperature (500–800 °C) on the textural, acidic/basic, and structural properties of the m-ZrP with its catalytic performance for glucose dehydration to 5-hydroxymethylfurfural (HMF) were investigated in a pure water media as a green and sustainable alternative solvent. The larger number of L and B acid sites and basic sites with their appropriate strengths were clearly related with a better catalytic performance in terms of glucose conversion and HMF yield. The strong L acid and basic sites in the m-ZrP efficiently promoted the glucose isomerization to fructose, which dehydrated exclusively on the weak B acid sites resulting in a maximum conversion of glucose (83.8%) and HMF yield (46.6%). The adjusted acidic and basic sites with large mesopore sizes make the m-ZrP yield a higher reaction rate (2.78 mmol gcat–1 h–1) and turnover frequency (11.68/h) for conversion of glucose to HMF, which showed higher catalytic activity than those of a small-pore m-ZrP and other mesoporous heterogeneous and homogeneous acid catalysts.

Porous zirconium phosphate solid acid catalysts with variable Zr/P ratio for gas phase glycerol dehydration to acrolein

The valuation of glycerol acquired by biodiesel production is an ambitious task. Dehydration of glycerol to acrolein was experimented over porous solid acid catalysts including zirconium phosphate (ZrP) by various Zr/P molar ratios. The different characteristics of the catalysts were probed by different charecterization techniques. All the prepared catalysts were effective for conversion of glycerol (69-100%) to yield of valuable acrolein (selectivity: 26–63%). The superior performance while catalytic activity demonstrated by ZrP:12 catalyst is ascribed to the existences of moderate acidic sites with the most of them Brønsted acidic sites

Super-Hydrophobic, Stable, and Swelling Nanoporous Solid Strong Acid

Super-hydrophobic solid strong acid with superior thermal stability and unique swelling properties has been synthesized by sulfonation of nanoporous polydivinylbenzene (PDVB) with super-acid of trifluoromethanesulfonic acid (TFMSA). The resultant PDVB–HOSO2CF3 has a well developed system of nanopores, superhydrophobic surface character and strong acid sites, and could be used as a highly efficient solid acid for catalyzing production of biodiesel and fine chemicals via transesterification, esterification and acylation. In terms of activity PDVB–HOSO2CF3 is superior to various solid acids such as SBA-15-SO3CF3, Nafion, Amberlyst 15, SBA-15-Ar-SO3H and H form USY. The preparation of PDVB–HOSO2CF3 offers the way to develop new kind of porous solid acid with strong acid strength and regulated wettability.

Sustainable Ammonia and Advanced Symbiotic Fertilizer Production Using Catalytic Multi-Reaction-Zone Reactors with Nonthermal Plasma and Simultaneous Reactive Separation

The theoretical bases of a novel intensified catalytic multi-reaction-zone reactor (M-RZR) system are described. The M-RZR with two reaction zones (RZ-1 and RZ-2) was used for ammonia synthesis. In the catalytic nonthermal plasma reaction zone (RZ-1), ammonia was synthesized and it was immediately sequestrated by a highly porous polymeric solid acid absorbent in the ammonia neutralization reaction zone (RZ-2). The solid acid was a sulfonated cross-linked porous polystyrene foam known as polyHIPE polymer (s-PHP, HIPE = high internal phase emulsion). The s-PHP and its neutralized version (sn-PHP) were previously developed as an advanced symbiotic fertilizer (or synthetic root system) for agro-process intensification for the enhancement (50–300%) of crop yield and nitrogen fixation especially under water and nutrient stress. In this first ever “proof-of-concept” study of the M-RZR system, without any attempt for optimization, it was shown that the ammonia conversion per pass reached ca. 40% and ammonia concentration was ca. 20 vol %. The energy cost of ammonia was 0.76 MJ/g NH3 which was 2 times smaller than optimized systems in which the ammonia concentration in the product stream was ca. 1.5 vol %. Direct conversion of hydrogen enhanced clean syngas (a1CO + a2CO2 + a3H2 + a4N2 + a5CH4) to ammonia and its reversible sequestration by CO2 to form solid ammonium carbamate/carbonate was demonstrated. This method is not only useful for direct conversion of syngas to ammonium carbonate/urea fertilizers but also for obtaining anhydrous ammonia for fuel applications. The reactive in situ air separation was also demonstrated for the generation of nitrogen for ammonia synthesis and oxygen for the gasification of biomass as a sustainable source of hydrogen.

Synthesis of biofuel via levulinic acid esterification over porous solid acid consisting of tungstophosphoric acid and reduced graphene oxide

Reduced graphene oxide (rGO) was synthesized by chemical reduction of graphene oxide with hydrazine hydrate and used as supports to prepare a series of H3PW12O40 (HPW)-based porous solid acids for the first time. Esterification of levulinic acid with ethanol was used to investigate the catalytic properties of the resulting HPW/rGO catalysts. The results showed that the heterogeneous catalysts possessed a porous structure and that their textural characteristics and catalytic activities were influenced by the loading of HPW. Remarkably, they were efficient in the synthesis of ethyl levulinate, with the one with an HPW loading of 45 wt% exhibiting the best efficiency. The conversion of levulinic acid was as high as 96.9%. Meanwhile, the resulting HPW/rGO catalysts also have satisfactory durability. The conversion of levulinic acid still remains at about 53.1% after five cycles under the present conditions. Furthermore, the various catalytic reaction parameters, such as reaction time, ethanol-to-LA molar ratio, and the catalyst dosage, are optimized to maximize the conversion of levulinic acid over 45 wt% HPW/rGO catalysts.

Production of furfural from xylose and corn stover catalyzed by a novel porous carbon solid acid in γ-valerolactone

An efficient catalytic system using S-RFC as catalyst was developed to produce furfural from xylose and corn stover in GVL.

Synthesis and Application of Bifunctional Porous Polymers Bearing Chloride and Sulfonic Acid as Cellulase-Mimetic Solid Acids for Cellulose Hydrolysis

A two-step strategy was demonstrated to synthesize porous polymeric solid acids with bifunctionality (chloride and sulfonic acid) to mimic cellulase for hydrolyzing cellulose. The solid acids were synthesized from aromatic monomers bearing chloride through Friedel-Crafts polymerization and then sulfonated with fuming sulfuric acid to introduce sulfonic acid. The chloride and sulfonic acid were expected to function as the cellulose-binding group (CBG) and the cellulose-hydrolytic group (CHG), respectively. It was found that the synthesized cellulase-mimetic solid acids were more effective in hydrolyzing microcrystalline cellulose (Avicel) than non-cellulase-mimetic solid acid (Amberlyst 15) and sulfuric acid at the same acid loading. Ball-milled Avicel could be hydrolyzed by up to 84.9 % by the cellulase-mimetic solid acids. The performance of the solid acids was supposedly attributed to the synergetic roles of the CBG and the CHG and the porous structure of the synthesized solid acids.

Template-free synthesis of porous carbonaceous solid acids with controllable acid sites and their excellent activity for catalyzing the synthesis of biofuels and fine chemicals

Highly porous carbonaceous solid acids with controllable acidity and enhanced activities for catalyzing biomass transformation have been prepared under template free conditions.

Porous carbonaceous solid acids derived from farm animal waste and their use in catalyzing biomass transformation

We demonstrate here the transformation of waste cow manure into N rich porous carbons (NPC) with large amount of micropores and large Brunauer–Emmett–Teller (BET) surface areas. The transformation process was achieved via carbonization of cow manure in presence of ZnCl2 and FeCl3 additives, without using additional templates. The resultant NPC could be converted into microporous carbonaceous solid acids (NPC-[C4N][X]) by quaternary ammonization of samples with 1,4-butane sultone, and ion exchanging with strong acids such as HSO3CF3 and H2SO4. X-ray diffraction patterns and Raman spectra showed that NPC-[C4N][X] exhibit amorphous carbon network. N2 isotherms and SEM images showed that NPC-[C4N][X] have abundant nanopores with large BET surface areas. XPS, FT-IR and elemental analysis results showed the N rich network in NPC support, has been successfully and homogeneously functionalized with strongly acidic ionic liquid and sulfonic groups. 31P solid NMR spectra confirmed that NPC-[C4N][X] have typical Brønsted acid centers with strong and controllable acidity. Catalytic tests showed that NPC-[C4N][X] exhibits excellent activity and reusability in production of biofuels and fine chemicals through esterifications, transesterifications, and depolymerization of microcrystalline cellulose. This approach may provide a novel and cost effective way to recycle the waste cow manure into efficiently porous carbon based solid acids for heterogeneous acid catalysis.

Synthesis porous carbon-based solid acid from rice husk for esterification of fatty acids

A porous carbon solid acid was synthesized from biomass rice husk by incompletely carbonization, sodium hydroxide leaching and concentrated H2SO4 sulfonation. The solid acid was characterized by XRD, FT-IR, N2 adsorption-desorption and solid-state NMR spectroscopy. The characterization results reveal that the carbon solid acid shows ultra high surface area of 1233 m2/g and stronger acid strength than that of HZSM-5(Si/Al = 38) zeolite. The catalytic performance was tested by the esterification of oleic acid with methanol. The results indicate that this solid acid catalyst is an excellent catalyst compared with other conventional solid acid.

Hypercrosslinked organic polymer based carbonaceous catalytic materials: Sulfonic acid functionality and nano-confinement effect

Porous hypercrosslinked polymers (HCPs) based novel metal-free heterogeneous solid acid catalysts were synthesized via Friedel–Crafts alkylation by self-condensation of bischloromethyl monomers such as α,α′-dichloro-p-xylene and 4,4′-bis(chloromethyl)-1,1′-biphenyl, followed by post-sulfonation process to generate acidic sites. The obtained HCP-based solid acids possessed large amounts of acidic sites homogeneous dispersed over the large surface area of more than 1000m2g−1, and narrow dispersed pores mostly centered at about 2nm, the junction region of micro and mesopores. Assessed in Friedel–Crafts alkylation and Beckmann rearrangement reactions, the obtained HCP-based porous solid acid catalysts demonstrated superior performance and special nano-confinement effect in the reactions. These were due to their acidic property and unique pore structure, thus providing an efficient metal-free carbonaceous catalyst for eco-friendly “carbocatalysis” process and some clues to prepare multi-functional catalysts from HCP-based materials.

Al-coordination polymer-derived nanoporous nitrogen-doped carbon microfibers as metal-free catalysts for oxygen electroreduction and acetalization reactions

Nanoporous nitrogen-doped carbon microfibers were prepared by thermal conversion of Al-DTPA coordination polymers, which could be used as efficient oxygen electroreduction catalysts and to prepare porous solid acid catalysts for the acetalization reaction.

Porous solid acid with high Surface area derived from emulsion templating and hypercrosslinking for efficient one-pot conversion of cellulose to 5-hydroxymethylfurfural

This work addressed efficient one-pot conversion of cellulose to 5-hydroxymethylfurfural by porous solid acid in the presence of [Emim]Cl.

Synthesis of porous clay heterostructures from high charge mica-type aluminosilicates

High charge micas are ideal materials to be used as porous solid acids because of their extraordinarily high content of framework aluminium atoms and their thermal stability. However, all efforts to create porosity in these materials have led to a disordered porous structure, since the full process is compromised by the highly layer attractive forces and hence by the incorporation stage of the porous wall precursors between the clay layers. Thermally stable and ordered mesoporous materials were synthesized for the first time from those swelling brittle micas through a surfactant templating approach. The interlayer space was firstly pre-expanded using alkylammonium cations, giving rise to a homogeneous organic–inorganic hybrid structure, which directs the polymerization step of the silica source. A regular porous structure in the supermicropore to the small mesopore range (15–25 A) together with an exclusive acidity was found after sample calcination. The extraordinary content of framework aluminium is responsible for the large number of acid sites, both in the rare medium and strongly acidic regions. The thermal stability of the new synthesised materials was also tested.

Design and Synthesis of Mesoporous Polymer-Based Solid Acid Catalysts with Excellent Hydrophobicity and Extraordinary Catalytic Activity

Novel excellent hydrophobic- mesoporous- polymer-based solid acid catalysts have been successfully synthesized by copolymerization of divinylbenzene (DVB) with sodium p-styrene sulfonate (H-PDVB-x-SO3H's) under solvothermal conditions. N2 isotherms and TEM images showed that H-PDVB-x-SO3H's have high BET surface areas, large pore volumes, and abundant mesoporosity; CHNS element analysis and acid–base titration technology showed that H-PDVB-x-SO3H's have adjustable sulfur contents (0.31–2.36 mmol/g) and acidic concentrations (0.26–1.86 mmol/g); TG curves showed that H-PDVB-x-SO3H's exhibited much higher stability of the active site (372 °C) than that of the acidic resin of Amberlyst 15 (312 °C); contact angle and water adsorption tests showed that H-PDVB-x-SO3H's exhibited excellent hydrophobic properties. Catalytic tests in esterification of acetic acid with cyclohexanol, esterification of acetic acid with 1-butanol, and condensation of benzaldehyde with ethylene glycol showed that H-PDVB-x-SO3H's were more active than those of Amberlyst 15, SO3H-functionalized ordered mesoporous silicas, and beta and USY zeolites, which were even comparable with that of homogeneous H2SO4. The superior hydrophobicity of solid acid catalysts would be favorable for achieving excellent catalytic performance because water usually acts as a byproduct in various acid-catalyzed reactions, which can easily poison the acid sites and result in opposite reactions. Synthesis of porous solid acid catalysts with good hydrophobicity would be very important for their applications.

Simultaneous Al2O3 Doping and Sulfation in Hierarchically Porous ZrO2 Solid Acids by an One‐pot Synthesis for Enhanced Recycling Catalytic Performances

AbstractAlumina doping and sulfation in hierarchically porous zirconia solid acids have been achieved simultaneously via one‐pot and bi‐surfactant‐assisted self‐assembly process, using aluminum sulfate as both Al and SO42− sources. The prepared composite solid acids showed much enhanced acidity and recycling catalytic activity for an esterification reaction compared with sulfated zirconia without alumina doping and Al‐doped sulfated zirconia without hierarchically porous structure.

Preparation of ethylenediaminetriacetic acid silica-gel immobilised ligand system and its application for trace metal analysis in aqueous samples

This article reports on the preparation of porous solid ethylenediaminetriacetic acid functionalised silica-gel (S-EDTA) of the general formula S-(CH2)3N(CH2COOH)-(CH2)2-N(CH2COOH)2 (where S represents [Si–O] n ). This was prepared by modification of 3-(2-aminoethylaminopropyl)trimethoxysilane with ethyl chloroacetate followed by polycondensation with tetraethylorthosilicate via the sol–gel process. The immobilised ethylenediaminetriacetic acid ligand system (S-EDTA) was characterised by FTIR, 13C CS-MAS NMR and XPS spectroscopic techniques. The resulting functionalised ligand system showed high potential to extract and separate Co2+, Ni2+ and Cu2+ metal ions from aqueous samples. The saturation sorption capacities of Co2+, Ni2+ and Cu2+ metal ions were 77.6, 89.1 and 99.4 mg g−1, respectively. The optimum separation pH values were 4.5 and 4 for Co(II) and Ni(II), respectively, while a solution of 0.1 mol L−1 HNO3 (pH = 1) was used to elute Cu(II).