Porous Solid Acid Catalyst Research Articles

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

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.

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.

Multimodal Zeolite‐Beta‐Based Catalysts with a Hierarchical, Three‐level Pore Structure

Hole diggers: The hierarchically structured porous solid-acid catalyst described in this report possess a remarkable pore system, encompassing well-defined macrochannels, interconnected mesopores, intracrystalline mesopores, and tunable zeolite micropores. Importantly, the catalyst exhibits very strong acidity and superior catalytic activity for esterification reactions.

The hydrophilic/hydrophobic effect of porous solid acid catalysts on mixed liquid phase reaction of esterification

Abstract The esterification between n-butanol and acetic acid was catalyzed by SBA-15 with a heteropoly acid fixed in the channels, which was synthesized with different hydrophilic/hydrophobic property. In a rigorous sealed batch reactor, the conversions of the reactants surpassed the limit of chemical equilibrium with the hydrophilic catalyst, from which the hydrophobic n-butyl acetate would be rejected. The counter-reaction of hydrolysis was then suppressed. The concept demonstrated in the current work sheds light on the design of practical catalysts and reactors free of complicated separation processes for a reaction in oil/water mixing phase.

N-Pentane isomerization in different phase regions near the critical temperature

The isomerization reaction of n-pentane over porous solid acid catalyst was investigated at 198.0 °C, which is slightly higher than the critical temperature of n-pentane. The pressure of the reactant in the reactor was controlled so that the reaction fluid was in gas, near critical, and supercritical (SC) states. The results showed that the conversion of n-pentane increased sharply with increasing pressure near the critical point. The amount of coke deposition depends strongly on the pressure of the reaction fluid. The main reason for the deactivation of the catalyst was coke deposition on the catalyst. Deactivation of catalyst was repressed at the higher pressure because more coke precursors produced in the reaction was dissolved into the fluid, which increases the stability of the catalyst. UV–vis, IR, thermogravimetric analysis and 1H NMR studies indicated that there were at least two kinds of coke precursors on catalyst surface. The effect of pressure on the properties of the coke was not considerable, although it influences the quantity of the coke deposition on the catalyst significantly. The loss of sulfur can be neglected at reaction temperature and the state of sulfur remains unchanged after reaction. It is advantageous to conduct the isomerization reaction at SC condition.