Solid Superacid Research Articles

An Application of Dunaliella Salina Algae: Biodiesel

Biodiesel has been receiving increasing attention as a potential sustainable fuel. It is used for diesel engines and is becoming well-known as an environmentally friendly fuel due to its non-toxic and biodegradable characteristics. As biodiesel production, Dunaliella salina algae could be an alternative raw material. Due to their high biomass productivity, rapid lipid accumulation, and ability to survive in saline water, algae has been identified as promising feedstocks for industrial-scale production of biodiesel [1]. The oil content of Dunaliella salina algae may exceed to 35%. Using two-step catalytic conversion, algae oil with high free fatty acid and triglyceride content was converted to biodiesel by esterification and transesterification. The conversion rate reached 98% under the ratio of 10:1 at 65°C for 2h,using catalysis with 2% solid superacid.

A high-surface-area mesoporous sulfated nano-titania solid superacid catalyst with exposed (101) facets for esterification: facile preparation and catalytic performance

In this paper, a high-surface-area mesoporous sulfated nano-titania exposed with (101) facets was prepared by a simple hydrothermal method without any template followed by surface sulfate modification. The physicochemical properties of the as-prepared catalyst were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption isotherms, temperature programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and pyridine adsorption infrared spectroscopy. The BET surface area of sulfated nano-titania with exposed (101) facets was 121 m2 g−1. Well dispersed bidentate sulfate groups were linked to the exposed (101) facets of anatase nano-titania. Acid sites with moderate- and superacidic strength formed in the sulfated titania catalyst. Also, the as-prepared sulfated sample possessed both Lewis and Bronsted acid sites. The catalytic activity of sulfated nano-titania with exposed (101) facets was evaluated using the esterification reaction between acetic acid and n-butanol. It was found that the yield of butyl acetate increased to about 92.2% in the presence of the catalyst. Compared with the exposed (001) facets, the exposed (101) facets showed better catalytic activity of sulfated TiO2 in esterification. The effects of different reaction conditions were discussed in detail. Additionally, the as-prepared sulfated sample could be efficiently recycled and regenerated by simple soaking in sulfuric acid followed by calcination.

Optimization and Evaluation of Preparation Process of Activated Carbon Loaded ZrO<sub>2</sub> Catalyst for Oxidative Desulfurization

This paper studied how DBT oxidation was influenced by different preparation conditions of diesel desulfurization catalyst. Fuel oil oxidation and desulfurization technology has been studied by using solid superacid prepared by activated carbon loaded SO42-/ ZrO2 as catalyst instead of the traditional liquid acid, hydrogen peroxide as oxidant, in mild conditions. Impacting factors on removal sulfur have been investigated such as soaking time, burning temperature, burning time, active ingredient content and concentration of sulfuric acid, etc. The results show that soaking time is 6h, burning temperature is 500 °C, burning time is 2.5h, the mass ratio of the active ingredient is 3:100 ZrO2 and activated carbon, sulfuric acid concentration is 0.5mol/L. The desulfurization rate is over 93% and raffinate oil recovery can reach more than 86% under this optimum condition.

ZrO2-modified TiO2 nanorod composite: Hydrothermal synthesis, characterization and application in esterification of organic acid

ZrO2-modified TiO2 nanorod composites were synthesized by using the hydrothermal synthesis approach. The synthesized materials were characterized by XRD, SEM, TEM, Raman, IR, and XPS. It was found that both sizes and morphologies of ZrO2 particles significantly depended on the reaction temperatures and hydrothermal synthesis time. TEM results exhibited that large sized particles of ZrO2 of 50 nm were achieved at low hydrothermal synthesis temperature of 110 °C, while small sized particles of ZrO2 of 20 nm stably deposited on the surface of TiO2 nanorods are generated at high temperature of 200 °C. The ZrO2–TiO2 nanorod composite was further functionalized by sulfate groups and utilized as the solid superacid catalyst for upgrading of bio-oil model compound organic acid by esterification. Both IR and XPS approved the presence of sulfate groups on Zr and Ti adsorption sites. HPLC results for the conversion of model compound levulinic acid to ester showed that 81.2% of levulinic acid converted to ethyl levulinate at 110 °C in 2 h over a 20 wt% ZrO2–TiO2 nanorod composite. GC–MS result displayed that ester was produced as the only product.

Templated fabrication of hierarchically porous Fe–Ti bimetallic solid superacid for efficient photochemical oxidation of azo dyes under visible light

• Hierarchically porous S–Fe 2 − x Ti x O 3 was prepared by critic acid templated method. • Cooperative effect of titanium and sulfate created lots of Lewis acid sites. • Fe–Ti bimetallic solid superacid widened the pH range to 10.0 in Fenton reaction. • Light with wavelength 450–595 nm had significant effect on activity of S–Fe 2 − x Ti x O 3. • Favorable synergetic effect of acid sites and photo improved catalytic activity. A new hierarchically porous solid superacid SO 4 2 - /Fe 2 − x Ti x O 3 was prepared by way of facile citric acid templates and sulfuric acid impregnating strategy. The prepared catalyst exhibited high activity and stability for activation of H 2 O 2 as higher than 90% of organic dyes were decomposed in 30 min at neutral pH under visible light irradiation. UV–vis spectrum and ion chromatography were used to investigate the degradation pathway of dyes. By characterizations, it was found that incorporation of titanium and sulfur had a significant effect on properties and structure of the solid. Large numbers of strong Lewis acid sites were produced on the surface due to cooperative effect of Ti and S, which made significant contributions toward high activity in strong alkaline condition (pH 10.0). Meanwhile, the transition metal doping and oxygen vacancies generation can narrow the band gap of the catalyst and efficiently enhance visible light photocatalytic performance. It was also observed that high catalytic activity can hardly be achieved if acid functionalization or light irradiation was applied individually. This was clearly evidenced that the synergetic effect of acid sites and photo-induced electrons transfer played a crucial role in Fenton reaction, which may be attributed to that the appearance of acid sites (Lewis and Brønsted acidic center) was favorable for the separation of photo-induced electrons and holes and suppressed charge recombination.

Synthesis of Ferric–Manganese Doped Tungstated Zirconia Nanoparticles as Heterogeneous Solid Superacid Catalyst for Biodiesel Production From Waste Cooking Oil

The solid superacid catalyst ferric-manganese doped tungstated zirconia (FMWZ) nanoparticles was prepared by impregnation reaction followed by calcination at 600°C for 3 hr and had been characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), X-ray fluorescence (XRF), transmission electron microscopy (TEM), and Brunner-Emmett-Teller (BET) surface area measurement. The transesterification reaction was used to determine the optimum conditions of methanolysis of waste cooking oil with FMWZ nanoparticles as heterogeneous solid superacid catalyst. The reactions variables such as reaction temperatures, catalyst loading, molar ratio of methanol/oil and reusability were also assessed which effects the waste cooking oil methyl esters (WCOME’s) production yield. The catalyst was reused ten times without any loss in activity and maximum yield of 96% was achieved at the optimized conditions of reaction temperature of 200°C; stirring speed of 600 rpm, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The fuel properties of the WCOME’s were discussed in light of ASTM D6751 biodiesel standard.

Study of Loading SO42- on Sb-SnO2 Nanocrystal and its Calcination Temperature to Make Solid Superacid SO4⊕/Sb-SnO2

SO4 2-/SnO2 were reported to be a solid superacid with an acid strength equal to that of SO4 2-/ZrO2. But papers concerning the SO4 2-/SnO2 catalyst have been quite few, because of difficulty in preparation of the oxide gels from its salts SnCl4. A highly dispersed light yellow powder, Sb-SnO2 nanocrystal, was obtained by the synthesis method of “P-CNAIE” and the drying method of “AD-IAA”. The Sb doping made the energy gap of nano-crystalline SnO2 narrower. A saturated solution of ammonium sulfate was dropped into organic solutions containing a fixed amount of Sb-SnO2 nano-powders in different ratio in order to load Sb-SnO2 powder with ammonium sulfate. This method has an outstanding advantage that is the loading ratio of (NH4)2SO4 to Sb-SnO2 can come to very high and no free water causes the aggregation of Sb-SnO2 nano powder. The methods of Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TG) demonstrated that the working ratio of Sb-SnO2 to (NH4)2SO4 was 1:1.4 to 1:1.6 wt% and the most favorable calcination temperature for the generation of superficially sulfated groups of Sb-SnO2 particles should fall between 380°C and 400°C. The adsorption reaction of indicator reveals that the solid acid, calcined Sb- SnO2 with a bluish color had a H0 ≤ -14.5 at least.

Synthesis of 1-Bromooctane Catalyzed by Solid Super Acid SO4 2–/ZrO2-ZnO

Synthesis of 1-Bromooctane Catalyzed by Solid Super Acid SO4 2–/ZrO2-ZnO

Facile synthesis of mesoporous sulfated Ce/TiO2nanofiber solid superacid with nanocrystalline frameworks by using collagen fibers as a biotemplate and its application in esterification

Collagen fibers, one of the most abundant biomass in the natural world, were used as the biomass template to synthesize cerium-doped mesoporous TiO2 nanofiber (SO42−–Cex/TiO2) solid acid catalysts. The physiochemical properties of the as-prepared catalysts were well characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS). The fibrous morphology of native collagen fibers were found to be well preserved in SO42−–Cex/TiO2, and the acid strength and textural property of the SO42−–Cex/TiO2 were adjustable by changing the doping amount of Ce and the curing temperature. The catalytic properties of as-prepared catalysts were evaluated in the esterification reactions. It was found that the SO42−–Cex/TiO2 exhibited high activity under mild reaction conditions. When reacted at 90 °C for 45 min with a catalyst amount of 2 wt%, the conversion yields of ethyl acetate, butyl acetate, hexyl acetate and ethyl caproate were 99.9%, 97.06%, 94.29% and 86.75%, respectively. Additionally, the SO42−–Cex/TiO2 solid acid catalyst could be reused at least 6 times without significant loss of activity, exhibiting much better reusability as compared with the SO42−–TiO2* catalyst prepared by conventional approach.

γ-Al<sub>2</sub>O<sub>3</sub> Supported SO<sub>4</sub><sup>2&#45</sup>/ZrO<sub>2</sub> Solid Superacid Catalysts for n-Pentane Isomerization

A solid superacid catalyst Pt-SO42-/ZrO2-A12O3 for n-pentane isomerization, was prepared by incipient-wetness impregnation. Preparetion conditions, namely, calcination temperature, concentration of sulfuric acid solution used in impregnation and Al2O3 concentration, were varied to investigate the effects on catalytic performance of Pt-SO42-/ZrO2-A12O3. The results showed that the PtSZA catalyst exhibited excellent catalytic performance for n-pentane isomerization. Under optimized preparation conditions of calcination temperature of 650°C, reaction time for 3 h, concentration of sulfuric acid solution for 0.5 mol/L, 30% of Al2O3 concentration and 0.3% of Pt concentration, the n-pentane conversion and isopentane selectivity of Pt-SO42-/ZrO2-A12O3 could reach up to 62.17% and 91.60%, respectively.

ChemInform Abstract: Highly Efficient Dynamic Kinetic Resolution of Secondary Aromatic Alcohols Using a Low‐Cost Solid Super Acid as a Racemization Catalyst.

AbstractThe dynamic kinetic resolution of alcohols (I) with 4‐chlorophenyl valerate as acyl donor proceeds in the presence of Novozym 435 and sulfated TiO2 as nano solid super acidic racemization catalyst.

Porous Solid Superacid SO42–/Fe2–xZrxO3 Fenton Catalyst for Highly Effective Oxidation of X-3B under Visible Light

Porous solid superacid SO42–/Fe2–xZrxO3 bimetallic oxide was first synthesized by citric acid templated method and impregnated in vitriol solution. The prepared catalyst possessing mesopores and ma...

Study on Catalytic Synthesis of N-Butyl Propionate Using Environmentally Friendly Catalys

The synthesis of butyl propionate from propionic acid and n-butanol with rare earth solid superacid SO42-/TiO2/La3+as environmentally friendly catalyst was studied. The influential factors of reaction were investigated. Results show that the appropriate conditions are: molar ratio of n-butyl alcohol to propionic acid was 3 : 1; Catalyst's weight was 1.2g (the amount of 0.1 molar propionic acid); Cyclohexane is used as water-carrying reagent with 1.0 mL; Reaction time was 1.5 hour. The esterification rate of n-butyl propionate is about 99.08 % .

Preparation of Solid Superacid SO42-/ZnO-TiO2 and Its Action on Synthesis of Dimethyl Carbonate from Urea and Methanol

SO42-/ZnO-TiO2 catalyst was prepared by sulfating ZnO-TiO2 powders with H2SO4 solution. The catalyst was characterized by XRD, IR and Hammett indicator. The catalyst showed strong acidity(H0 ≦-16.0). The optimum conditions are found that the calcination temperature is 823K and the soaked consistency of H2SO4 is 1 mol/dm3. Then SO42-/ZnO-TiO2 was applied as the catalyst in the catalytic synthesis of dimethyl carbonate(DMC) from urea and methanol under the optimum conditions and revealed higher catalytic activity. On condition that the reaction time is 6h, the reaction temperature is 433K, the mass percent of the catalyst used in the reactants is 5wt.%, and the molar ratio of methanol to urea is 14, the yields of DMC can reach 27.9%.

Solid Super Acid Base Co-Catalyzed Transesterification of Soybean Oil Using Ultrasonication

Biodiesel is a renewable, biodegradable, and nontoxic fuel. At present, biodiesel is primarily produced in batch reactors in which the required energy is provided by heating accompanied by mechanical mixing. Alternatively, ultrasonic processing is an effective way to attain required mixing while providing the necessary activation energy. Biodiesel was synthesized by soybean oil using ultrasonication and alkali-acid catalysis method. Its structure was characterized by gas chromatograph, and the effects of various factors on transesterification rate were studied. The results show that a biodiesel yield in excess of 98% can be achieved in 30 min, methanol/oil molar ratio of 6:1, alkali-acid catalysis includes 0.5% of NaOH and 0.5% of solid super acid.

Characterization and Performance of SO<sub>4</sub><sup>2- </sup>/ SnO<sub>2</sub> / MCM-41 for α-pinene Isomerization

Mesoporous MCM-41 molecular sieve was synthesized hydrothermally and selected tetraethoxysilane as silica source. Solid superacid SO42- / SnO2 was supported on MCM-41 by dipping and roasting. The samples were characterized by XRD, TEM, and FT-IR. Solid superacid evenly dispersed on MCM-41 with a good pore structure. Their catalytic activities were evaluated in the isomerization of α-pinene. The results show that samples had a good conversion rate and selectivity.

Highly efficient dynamic kinetic resolution of secondary aromatic alcohols using a low-cost solid super acid as a racemization catalyst

Abstract A new, efficient dynamic kinetic resolution (DKR) of secondary aromatic alcohols using self-made solid super acid TiO 2 / SO 4 2 - as a racemization catalyst was developed. Low-cost and easily produced TiO 2 / SO 4 2 - showed excellent racemization activity. When coupled with the lipase, Novozym 435, good biocompatibility was observed, and optically pure aromatic acetate (>99%) was obtained with a high yield. It is noteworthy that the system could be reused more than 10 times with little loss of yield or reduction in the enantiomeric excess (ee) value of product.

Synthesis of vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) catalyzed by rare earth solid super acid SO42‐/TiO2/Ln3+

AbstractRare earth solid super acids SO42−/TiO2/Ln3+ have been successfully developed to synthesize vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) end‐capped with 1,1,3,3‐tetramethyl‐1,3‐divinyldisiloxane. The features of ring opening polymerization reactions have been investigated in detail. The preferable conditions for the ring opening polymerization of D4 are as follows: [Nd3+] = 0.07 mol L−1 and [SO42−] = 1.85 mol L−1 in the immersing solution; the amount of SO42−/TiO2/Nd3+ calcined at 500 °C was 5 wt% of the amount of D4; polymerization at 80 °C for 1 h. The average molecular weights of the products obtained using various rare earth catalysts were in order Nd > La > Sm > Gd, which shows that the light rare earths were more favorable for higher molecular weight products than the heavy ones. According to the polymerization features, a cationic equilibrium reaction mechanism is proposed. © 2013 Society of Chemical Industry

Zr–La Doped Sulfated Titania with a by Far Better Catalytic Activity and Stability than Pure Sulfated Titania in the Esterification of Acetic Acid and n-Butanol

A novel solid superacid catalyst TiO2–Zr–La/SO4 2− was prepared by doping Zr and La to the bulk of TiO2. The modified TiO2–Zr–La/SO4 2− and the unmodified TiO2/SO4 2− were used to catalyze the esterification of acetic acid and n-butanol, in which these two catalysts were systematically compared in a lost of aspects such as catalytic activity and stability and so on. When a small amount of Zr and La were co-doped into the bulk of TiO2, the modified catalyst obtained a by far better catalytic activity and stability than the unmodified, showing that the modified is more resistive to deactivation than the unmodified. Under the set reaction conditions, the average conversion (of acetic acid) and the 20th-cycle conversion (of acetic acid) are 88.83 and 77.35 % for the modified, 80.83 and 46.15 % for the unmodified, respectively. The two catalysts were characterized by means of FTIR, XRD, BET, SEM, TG, and NH3-TPD methods to find the possible reasons for the superiority of the modified catalyst to the unmodified one. The characteristic results indicated that the incorporation of a small amount of Zr and La into the catalyst was beneficial to the modified catalyst: (1) improving its water-tolerance; (2) increasing its surface sulfate group content; (3) decreasing its crystallinity after calcination by retarding its crystallization from amorphous TiO2 to anatase TiO2; (4) increasing its specific surface area; (5) increasing its acidity including the concentration and acid strength of the surface acidic sites of it. All the above advantageous effects arisen from the two-element-doping are to be responsible for the substantially-improved catalytic performances of the modified catalyst.

Preparation of SO4 2−/ZrO2 solid superacid and oxidative desulfurization using K2FeO4

A catalyst comprising SO4 2–/ZrO2 (SZ) superacid was prepared by impregnation and characterized by FT-IR, FT IR-pyridine desorption, TG/DTA, XRD, SEM, and BET. A novel procedure for oxidative desulfurization (ODS) of simulated light fuel oil and straight-run gasoline using K2FeO4 over the SZ solid superacid was developed. The effects of the support, calcination temperature, impregnation liquid, concentration, and K2FeO4 and SZ amounts on catalyst activity for desulfurization were investigated. The presence of highly dispersed acidic sites over the support, a huge area of catalyst, and the formation of a tetragonal structure play an important role in ODS using K2FeO4. The catalyst subjected to impregnation with 0.8 mol/L H2SO4, supported on ZrO2, and calcined at 600 °C exhibited the best performance. At a temperature of 30 °C, SZ of 0.2 g, K2FeO4 of 0.2 g, and reaction time of 30 min, the straight-run gasoline desulfurization rate reached 89.2 %, and the residual sulfur content was 18.3 mg/L.