Organic-inorganic epoxide hydrolase hybrid nanoflowers with enhanced catalytic activity: Hydrolysis of styrene oxide to 1-phenyl-1,2-ethanediol.

Epoxide hydrolases are ubiquitous in nature and are utilized to catalyze the cofactor-independent hydrolysis of epoxides to their corresponding diols. These enzymes have tremendous potential and have been applied in the synthesis of bulk and fine chemical industry and utilized as chiral building blocks. Herein, we report a green, facile, and economical method for immobilization of epoxide hydrolase based on biomimetic mineralization. The organic-inorganic hybrid nanoflowers have received tremendous attention due to their higher catalytic activity and stability. The nanoflowers were synthesized, with the organic component being enzyme epoxide hydrolase and the inorganic component being Ca2+ ions. A unique hierarchical flower-like spherical structure with hundreds of spiked petals was observed. The synthesized nanoflowers were applied for styrene oxide hydrolysis, producing 1-phenyl-1,2-ethanediol. Further, the factors influencing the morphology, catalytic activity, and stability studies were performed to study the activity recovery of the synthesized organic-inorganic hybrid epoxide hydrolase nanoflowers. The findings will have interesting applications.

The production of fuels and chemicals in the new world: critical analysis of the choice between crude oil and biomass vis-à-vis sustainability and the environment.

ABSTRACT: Energy and the environment are intimately related and hotly debated issues. Today's crude oil-based economy for the manufacture of fuels, chemicals and materials will not have a sustainable future. The over-use of oil products has done a great damage to the environment. Faced with the twin challenges of sustaining socioeconomic development and shrinking the environmental footprint of chemicals and fuel manufacturing, a major emphasis is on either converting biomass into low-value, high-volume biofuels or refining it into a wide spectrum of products. Using carbon for fuel is a flawed approach and unlikely to achieve any nation's socioeconomic or environmental targets. Biomass is chemically and geographically incompatible with the existing refining and pipeline infrastructure, and biorefining and biofuels production in their current forms will not achieve economies of scale in most nations. Synergistic use of crude oil, biomass, and shale gas to produce fuels, value-added chemicals, and commodity chemicals, respectively, can continue for some time. However, carbon should not be used as a source of fuel or energy but be valorized to other products. In controlling CO2 emissions, hydrogen will play a critical role. Hydrogen is best suited for converting waste biomass and carbon dioxide emanated from different sources, whether it be fossil fuel-derived carbon or biomass-derived carbon, into fuels and chemicals as well as it will also lead, on its own as energy source, to the carbon negative scenario in conjunction with other renewable non-carbon sources. This new paradigm for production of fuels and chemicals not only offers the greatest monetization potential for biomass and shale gas, but it could also scale down output and improve the atom and energy economies of oil refineries. We have also highlighted the technology gaps with the intention to drive R&D in these directions. We believe  this article will generate a considerable debate in energy sector and lead to better energy and material policy across the world.

Chemoenzymatic Epoxidation of Limonene Using a Novel Surface-Functionalized Silica Catalyst Derived from Agricultural Waste.

Limonene is one of the most important terpenes having wide applications in food and fragrance industries. The epoxide of limonene, limonene oxide, finds important applications as a versatile synthetic intermediate in the chemical industry. Therefore, attempts have been made to synthesize limonene oxide using eco-friendly processes because of stringent regulations on its production. In this regard, we have attempted to synthesize it using a cost-effective and eco-friendly process. Chemoenzymatic epoxidation of limonene to limonene oxide was carried out using in situ generation of peroxy octanoic acid from octanoic acid and H2O2. In this study, agricultural-waste rice husk ash (RHA)-derived silica was surface-functionalized using (3-aminopropyl) triethoxysilane (APTS), which was cross-linked using glutaraldehyde for immobilization of Candida antarctica lipase B. Furthermore, the immobilized enzyme was entrapped in calcium alginate beads to avoid enzyme leaching. Thus, limonene oxide was prepared using this catalyst under conventional and microwave heating. The microwave irradiation intensifies the process, reducing the reaction time under the same conditions. Maximum conversion of limonene to limonene oxide of 75.35 ± 0.98% was obtained in 2 h at 50 °C using a microwave power of 50 W. In the absence of microwave irradiation, the conventional heating gave 44.6 ± 1.14% conversion in 12 h. The reaction mechanism was studied using the Lineweaver-Burk plot, which follows a ternary complex mechanism with inhibition due to peroxyoctanoic acid (in other words H2O2). The prepared catalyst shows high reusability and operational stability up to four cycles.

Synthesis and Application of Novel NiMoK/TS-1 for Selective Conversion of Fatty Acid Methyl Esters/Triglycerides to Olefins.

Methyl palmitate (or triglyceride) was converted into C15 olefin with remarkable selectivity using nickel-molybdenum oxides on the mesoporous titanosilicate support. The olefin has one carbon atom less than the acid portion of the ester. A new catalyst NiMoK/TS-1 was synthesized in which the effect of acidity of supports and molybdenum loading on the decarboxylation conversion along with product selectivity was investigated in methyl palmitate conversion into C15 olefin. The prepared catalysts were analyzed using ammonia-temperature-programmed desorption (NH3-TPD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) techniques. The reaction was carried out using a vapor-phase fixed-bed downflow reactor system at atmospheric pressure. The NiMoK/TS-1 catalyst at a weight hourly space velocity (WHSV) of 5.6/h was found to be selective toward C15 olefin. The catalyst was stable up to 15 h, and it can be regenerated with no considerable decrease in the activity even after fourth reuse. Beyond 653 K, the conversion of methyl palmitate increased but the selectivity for C15 products and C15 olefin was decreased.

Zn- and Ti-Modified Hydrotalcites for Transesterification of Dimethyl Terephthalate with Ethylene Glycol: Effect of the Metal Oxide and Catalyst Synthesis Method.

The activity and selectivity of hydrotalcites (HTs) can be suitably enhanced by the addition of different metal oxides. Zinc and titanium are prospective candidates for such a modification. Transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) using basic catalysts is an industrially important process for the production of bis(2-hydroxyethyl)terephthalate (BHET). BHET is a precursor for polyethylene terephthalate (PET) which is used in production of films, fibers, and molding materials. As against use of polluting liquid bases, solid bases could be employed. In the current work, transesterification of DMT with EG was studied over modified HT base catalysts wherein the HT was activated with the addition of zinc and titanium. These catalysts were prepared by the combustion synthesis using different fuels. The modified HT using Zn and Ti were well characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller surface area analyzer, temperature-programmed desorption, and X-ray diffraction. Effects of several parameters on the rate of reaction and conversion of the limiting reagent were investigated. Zinc-modified HT using glycine as fuel (Zn-HT-glycine) was found to be the most selective, active, and reusable catalyst. The Langmuir-Hinshelwood-Hougen-Watson model was used to establish the reaction mechanism and kinetics. All species were weakly adsorbed leading to a second-order kinetics. Using a mole ratio of 1:2 of DMT to EG and 0.05 g/cm3 Zn-HT-glycine loading resulted in to 64.1% conversion of DMT and 96.1% selectivity to BHET in 4 h at 180 °C. The apparent activation energy was 9.64 kcal/mol. The catalyst was robust and reusable.

Enhancing Activity by Supercritical CO2 Mediated Immobilization of Lipase on Mesocellular Foam in Preparation of Hexyl Laurate.

Hexyl laurate is employed in several cosmetics having great demand. It could be synthesized catalytically like a "natural" perfume using a lipase. The use of mesocellular foam silica (MCF) for immobilization of lipases could be made using supercritical CO2 as a medium to enhance its activity in comparison with the normal techniques. Three different catalysts were supported on MCF such as Candida antractica B (CALB), Amano AYS, and Porcine pancreas (PPL), and their activity was evaluated in the preparation of hexyl laurate from lauric acid and hexyl alcohol. CALB@ MCF was the best among all. A systematic study was conducted to assess the effects of different operating parameters. It was ternary complex mechanism with inhibition by hexyl alcohol. The enzyme was reusable and the process is green.

Single-Step Hydrogenolysis of Furfural to 1,2-Pentanediol Using a Bifunctional Rh/OMS-2 Catalyst.

Hydrogenolysis of biomass-derived furfural (FFA) to 1,2-pentanediol (1,2-PeD) was investigated using a bifunctional catalyst with basic and metallic sites, which was synthesized by the hydrothermal method. The synthesized catalyst consisting of rhodium (Rh) supported on an octahedral molecular sieve (OMS-2) of different loadings, such as 0.5, 1, and 1.5% w/w, was studied, and 1% (w/w) loading gave the best results. This 1% w/w Rh/OMS-2 catalyst showed excellent catalytic activity and selectivity for the hydrogenolysis reaction because of better dispersion of rhodium, later revealed by characterization. Furthermore, 1% Rh/OMS-2 catalyst was well characterized in virgin and reused states using various techniques such as Fourier-transform infrared spectroscopy, NH3-temperature-programmed desorption (TPD), CO2-TPD, temperature-programmed reduction, H2 pulse chemisorption, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, X-ray photoelectron spectroscopy, Raman spectroscopy, and differential scanning calorimetry-thermogravimetry analysis. The catalyst showed a higher surface area of 72 m2/g and the average size of the highly dispersed Rh metal of ∼2 nm. The studies were performed in a batch reactor; the catalyst offered almost 100% conversion of FFA with 87% selectivity to 1,2-PeD at 160 °C and 30 atm hydrogen pressure in 8 h. The reaction mechanism and kinetic model have been developed using a dual-site Langmuir-Hinshelwood-Hougen-Watson mechanism. The activation energies were 12.3 and 27.6 kcal/mol, correspondingly. The catalyst was found to be active, selective, and reusable.

Comparative Studies of White-Rot Fungal Strains (Trametes hirsuta MTCC-1171 and Phanerochaete chrysosporium NCIM-1106) for Effective Degradation and Bioconversion of Ferulic Acid.

Biodegradation of ferulic acid, by two white-rot fungal strains (Trametes hirsuta MTCC-1171 and Phanerochaete chrysosporium NCIM-1106) was investigated in this study. Both strains could use ferulic acid as a sole carbon source when provided with basal mineral salt medium. T. hirsuta achieved complete degradation of ferulic acid (350 mg L-1) in 20 h, whereas P. chrysosporium degraded it (250 mg L-1) in 28 h. The metabolites produced during degradation were distinguished by gas chromatography-mass spectrometry. Bioconversion of ferulic acid to vanillin by P. chrysosporium was also investigated. The optimum experimental conditions for bioconversion to vanillin can be summarized as follows: ferulic acid concentration 250 mg L-1, temperature 35 °C, initial pH 5.0, mycelial inoculum 0.32 ± 0.01 g L-1 dry weight, and shaking speed 150 rpm. At optimized conditions, the maximum molar yield obtained was 3.4 ± 0.1%, after 20 h of bioconversion. Considering that the degradation of ferulic acid was determined by laccase and lignin peroxidase to some extent, the possible role of ligninolytic enzymes in overall bioconversion process was also studied. These results illustrate that both strains have the potential of utilizing ferulic acid as a sole carbon source. Moreover, P. chrysosporium can also be explored for its ability to transform ferulic acid into value-added products.

Synthesis of Geraniol Esters in a Continuous-Flow Packed-Bed Reactor of Immobilized Lipase: Optimization of Process Parameters and Kinetic Modeling.

With increasing demand for perfumes, flavors, beverages, and pharmaceuticals, the various associated industries are resorting to different approaches to enhance yields of desired compounds. The use of fixed-bed biocatalytic reactors in some of the processes for making fine chemicals will be of great value because the reaction times could be reduced substantially as well as high conversion and yields obtained. In the current study, a continuous-flow packed-bed reactor of immobilized Candida antarctica lipase B (Novozym 435) was employed for synthesis of various geraniol esters. Optimization of process parameters such as biocatalyst screening, effect of solvent, mole ratio, temperature and acyl donors was studied in a continuous-flow packed-bed reactor. Maximum conversion of ~ 87% of geranyl propionate was achieved in 15 min residence time at 70 °C using geraniol and propionic acid with a 1:1 mol ratio. Novozym 435 was found to be the most active and stable biocatalyst among all tested. Ternary complex mechanism with propionic acid inhibition was found to fit the data.

Effect of Supercritical CO2 as Reaction Medium for Selective Hydrogenation of Acetophenone to 1-Phenylethanol.

1-Phenylethanol (PhE) is widely employed in the pharmaceutical industry as an anti-inflammatory and analgesic drug, as well as in chewing gums and yogurts as a food additive. In this work, we have investigated the selective synthesis of 1-phenylethanol (PhE) by hydrogenation of acetophenone using supercritical CO2 as a solvent. Supercritical carbon dioxide (scCO2) replaces organic solvent because it is inexpensive, nontoxic, nonflammable, inert, and environmentally benign. Polyurea-based encapsulated mono- and bimetallic catalysts were synthesized and characterized using different characterization techniques. The effects of various reaction parameters, such as co-solvent, catalyst loading, hydrogen pressure, total scCO2 pressure, and temperature, were studied to determine the reaction kinetics.

One-pot synthesis of (R)-1-(pyridin-4-yl)ethyl acetate using tandem catalyst prepared by co-immobilization of palladium and lipase on mesoporous foam: Optimization and kinetic modeling.

The synthesis of (R)-1-(pyridin-4-yl)ethyl acetate was achieved over tandem palladium-lipase catalyst with 100% selectivity using 4-acetyl pyridine as a reactant. The 2% w/w palladium and lipase catalyst was successfully co-immobilized in the microenvironment of the mesocellular foam and characterized by various techniques. The palladium metal from catalyst hydrogenated 4-acetyl pyridine to form 1-(pyridin-4-yl)ethanol. The generated intermediate product then underwent kinetic resolution over lipase and selectively gave (R)-1-(pyridin-4- yl)ethyl acetate. The catalytic conditions were then studied for optimal performance of both steps. The reaction conditions were optimized to 50 °C and toluene as a solvent. Both chemical and enzymatic kinetic models of the reaction were developed for a given set of reaction conditions and kinetic parameters were predicted. At optimal conditions, the obtained selectivity of intermediate (1-(pyridin-4-yl)ethanol) was 51.38%. The final product yield of ((R)-1-(pyridin-4-yl)ethyl acetate) was 48.62%.

The Impending Renaissance in Discovery & Development of Natural Products.

Antibiotics are wonder drugs. Unfortunately, owing to overuse, antibiotic resistance is now a serious problem. Society now finds itself in the post-antibiotic era, and the threat of infectious diseases is on the rise. New antibiotics are sorely needed. There is strong evidence that suggests natural products are an attractive source of new antimicrobials. They posses desirable structural and chemical properties that make them potent thearpeutics. However, steep tehnological challenges associated with screening and manufacturing these molecules has stifled the discovery, development and marketing of new antimicrobials. To this end, two recent scientific developments are poised to redress this situation. The recent development of metagenomics and ancillary high-throughput screening technologies has exponentiated the volume of useful genetic sequence information that can be screened for antimicrobial discovery. These approaches have been instrumental in the discovery of new antibiotics from soil and marine environments. Secondly, a new manufacturing paradigm employing metabolic engineering as its engine has greatly accelerated the path to market for these molecules, in addition to improving the atom and energy economy of antimicrobial manufacturing. We outine these developments in this review, and provide a perspective on integrating next-generation approaches such as metagenomics and metabolic engineering with traditional methodologies for discovering and manufacturing antimicrobial natural products in order to unleash a rennaissance in the discovery and development of antimicrobials.

Arsenic and fluoride contaminated groundwaters: A review of current technologies for contaminants removal.

Chronic contamination of groundwaters by both arsenic (As) and fluoride (F) is frequently observed around the world, which has severely affected millions of people. Fluoride and As are introduced into groundwaters by several sources such as water-rock interactions, anthropogenic activities, and groundwater recharge. Coexistence of these pollutants can have adverse effects due to synergistic and/or antagonistic mechanisms leading to uncertain and complicated health effects, including cancer. Many developing countries are beset with the problem of F and As laden waters, with no affordable technologies to provide clean water supply. The technologies available for the simultaneous removal are akin to chemical treatment, adsorption and membrane processes. However, the presence of competing ions such as phosphate, silicate, nitrate, chloride, carbonate, and sulfate affect the removal efficiency. Highly efficient, low-cost and sustainable technology which could be used by rural populations is of utmost importance for simultaneous removal of both pollutants. This can be realized by using readily available low cost materials coupled with proper disposal units. Synthesis of inexpensive and highly selective nanoadsorbents or nanofunctionalized membranes is required along with encapsulation units to isolate the toxicant loaded materials to avoid their re-entry in aquifers. A vast number of reviews have been published periodically on removal of As or F alone. However, there is a dearth of literature on the simultaneous removal of both. This review critically analyzes this important issue and considers strategies for their removal and safe disposal.

Insight into microwave-assisted lipase catalyzed synthesis of geranyl cinnamate: optimization and kinetic modeling.

Cinnamate esters have gained importance due to their unique antioxidant, flavor, and fragrance properties. Synergism of microwave irradiation and enzyme catalysis was investigated in transesterification of ethyl cinnamate and geraniol. Effects of different operating parameters such as biocatalyst, solvent, and temperature were first studied. An increase in initial rates up to 4.2-fold was observed under microwave irradiation vis-a-vis conventional heating. Further, the Taguchi L16 (4*4) orthogonal array design with four level-four variables and 16 run was employed for the optimization of parameters including enzyme loading, temperature, speed of agitation, and substrate mole ratio. Optimal conditions obtained via the Taguchi approach were as follows: enzyme loading, 60 mg; temperature, 65 °C; speed of agitation, 300 rpm; and substrate mole ratio, 1:2. The analysis of initial rate data established the validity of the ternary complex ordered bi-bi mechanism with inhibition by geraniol. The experimental data fitted very well with the model predictions.

Novelties of combustion synthesized titania ultrafiltration membrane in efficient removal of methylene blue dye from aqueous effluent.

In this study, titania nanoparticles were synthesized by combustion and used to make ultrafiltration membrane. Characteristics of titania membranes such as textural evaluation, surface morphology, pure water permeability and protein rejection were investigated. Titania membrane sintered at 450 °C showed pure water permeability 11 × 10−2 L h−1 m−2 kPa−1 and 76% protein rejection. The membrane presented good water flux and retention properties with regards to protein and methylene blue dye. Ultrafiltration process was operated at lower pressure (100 kPa) and showed 99% removal of methylene blue using adsorptive micellar flocculation at sodium dodecyl sulfate concentration below its critical micellar concentration. Ferric chloride was used as the coagulant. The method of making titania membrane and its use are new. These studies can be extended to other dyes and pollutants.

Lipase-catalyzed kinetic resolution of (±)-1-(2-furyl) ethanol in nonaqueous media.

S-1-(2-Furyl) ethanol serves as an important chiral building block for the preparation of various natural products, fine chemicals, and is widely used in the chemical and pharmaceutical industries. In this work, lipase-catalyzed kinetic resolution of (R/S)-1-(2-furyl) ethanol using different acyl donors was investigated. Vinyl esters are good acyl donors vis-à-vis alkyl esters for kinetic resolution. Among them, vinyl acetate was found to be the best acyl donor. Different immobilized lipases such as Rhizomucor miehei lipase, Thermomyces lanuginosus lipase, and Candida antarctica lipase B were evaluated for this reaction, among which C. antarctica lipase B, immobilized on acrylic resin (Novozym 435), was found to be the best catalyst in n-heptane as solvent. The effect of various parameters was studied in a systematic manner. Maximum conversion of 47% and enantiomeric excess of the substrate (ees ) of 89% were obtained in 2 h using 5 mg of enzyme loading with an equimolar ratio of alcohol to vinyl acetate at 60 °C at a speed of 300 rpm in a batch reactor. From the analysis of progress curve and initial rate data, it was concluded that the reaction followed the ordered bi-bi mechanism with dead-end ester inhibition. Kinetic parameters were obtained by using nonlinear regression. This process is more economical, green, and easily scalable than the chemical processes.

Microwave assisted enzymatic kinetic resolution of (±)-1-phenyl-2-propyn-1-ol in nonaqueous media.

Kinetic resolution of 1-phenyl-2-propyn-1-ol, an important chiral synthon, was studied through trans-esterification with acyl acetate to investigate synergism between microwave irradiation and enzyme catalysis. Lipases from different microbial origins were employed for the kinetic resolution of (R/S)-1-phenyl-2-propyn-1-ol, among which Candida antarctica lipase B, immobilized on acrylic resin (Novozym 435), was found to be the best catalyst in n-hexane as solvent. Vinyl acetate was the most effective among different acyl esters studied. The effect of various parameters was studied in a systematic manner. Definite synergism between microwave and enzyme was observed. The initial rate was improved around 1.28 times under microwave irradiation than conventional heating. Under optimum conditions, maximum conversion (48.78%) and high enantiomeric excess (93.25%) were obtained in 2 h. From modeling studies, it is concluded that the reaction follows the Ping-Pong bi-bi mechanism with dead end alcohol inhibition. Kinetic parameters were obtained by using nonlinear regression. This process is green, clean, and easily scalable as compared to the chemical process.

Insight into microwave irradiation and enzyme catalysis in enantioselective resolution of DL-(±)-3-phenyllactic acid.

Lipase catalyzed kinetic resolution of DL-(±)-3-phenyllactic acid (DL-(±)-3-PLA) was investigated to study the synergistic effect of microwave irradiation and enzyme catalysis. Lipases from different sources were employed for the transesterification of DL-(±)-3-PLA under otherwise similar conditions, among which Novozyme 435 efficiently catalyzed the resolution of DL-(±)-3-PLA to L-(-)-O-acetyl-3-PLA using vinyl acetate as the acyl donor, showing excellent conversion (49%) and enantiomeric excess (>99%). The effect of various parameters affecting the initial rate, conversion and enantiomeric excess of the reaction were studied to establish kinetics and mechanism. There is a synergism between enzyme catalysis and microwave irradiation; an increase in initial rates up to 1.8-fold was observed under microwave irradiation than that under conventional heating. The analysis of initial rate data showed that reaction obeys ternary complex (ordered bi-bi) mechanism with inhibition by DL-(±)-3-PLA. The calculated and simulated rates match very well showing the validity of the proposed kinetic model.

Synergism between microwave irradiation and enzyme catalysis in transesterification of ethyl-3-phenylpropanoate with n-butanol.

Lipase catalyzed transesterification was investigated to study the synergistic effect of microwave irradiation and enzyme catalysis. Transesterification of ethyl-3-phenylpropanoate with n-butanol was chosen as the model reaction using immobilized enzymes such as Novozyme 435, Lipozyme RMIM and Lipozyme TL IM with microwave irradiation. Novozyme 435 was the best catalyst. The effect of various parameters affecting the conversion and initial rates of transesterification were studied to establish kinetics and mechanism. There is synergism between enzyme catalysis and microwave irradiation. The analysis of initial rate data and progress curve data showed that the reaction obeys the Ping-Pong bi-bi mechanism with inhibition by n-butanol. The theoretical predictions and experimental data match very well. These studies were also extended to other alcohols such as 2-phenyl-1-propanol, n-octanol, benzyl alcohol, iso-amyl alcohol, 2-hexanol and 2-pentanol under otherwise similar conditions.

Novel mesoporous solid superacidic catalysts: activity and selectivity in the synthesis of thymol by isopropylation of m-cresol with 2-propanol over UDCaT-4, -5, and -6.

The alkylation of m-cresol with isopropyl alcohol in the presence of novel superacidic catalysts named as UDCaT-4, UDCaT-5, and UDCaT-6 was investigated. The catalysts are modified versions of zirconia showing high catalytic activity, stability, and reusability in the presence of water as compared to conventional sulfated zirconia. The objective of the present investigation was to explore the potential of these catalysts in this alkylation of m-cresol with isopropyl alcohol to thymol, which has widescale applications. The reactions were conducted in liquid phase in the temperature range of 433-473 K. Both, O- and C-alkylated products were obtained at lower temperatures, while at higher temperatures, thymol was the main product of the reaction. The catalytic activity increases in the order UDCaT-5 > UDCaT-6 >UDCaT-4 > sulfated zirconia. Thymol could be efficiently obtained with selectivity reaching up to 79% at an isopropyl alcohol conversion of 92% with UDCaT-5. This process can be a replacement for the existing process based on zeolites where high temperature and pressure are required. Synergistic effects of very high sulfur content present (9% S) and preservation of the tetragonal phase in UDCaT-5, in comparison with sulfated zirconia (4% S), were responsible for higher catalytic activity. A systematic investigation of the effects of various operating parameters was accomplished, and a mathematical model is developed to describe the reaction pathway and validated with experimental results. The reaction was carried out without using solvent, and the process subscribes to the principles of green chemistry.