Α-pinene Isomerization Reaction Research Articles

Ti3C2 MXenes-based catalysts for the process of α-pinene isomerization.

In this study, the catalytic performance of Ti3C2 MXene materials in the reaction of α-pinene isomerization was demonstrated. The influence of etching agents (HF, HF/H2SO4, and HF/HCl; weight ratios of mixed acids: 1 : 3, 1 : 4, and 1 : 5) on removing Al atoms from MAX phase, creation of an accordion-like structure typical for MXenes and catalytic activity of the produced samples have been revealed. The MXene HF obtained by MAX phase HF treatment exhibited the highest activity (conversion of α-pinene 74.65 mol%), while materials produced with the mixed acids (HF/H2SO4 and HF/HCl) showed a significant reduction in the conversion of α-pinene (on average about 28-fold). However, these last samples displayed an increase of about 10 mol% in the selectivity to the most desirable product-camphene. The high activity of MXene HF is a result of a high concentration of acid sites (11.62 mmol g-1) - the concentration of acid sites in the samples obtained by MAX phase mixed acids treatment was about 2.5-5.5 times smaller. This work proposes possible mechanisms for the α-pinene isomerization reaction on the MXene HF and on the MXene HF/H2SO4X : Y and MXene HF/HCl X : Y in connection with their structure.

Effective synthesis of limonene over mild alkali-modified 13X catalysts in α-pinene isomerization

The mild alkali-treated 13X was employed in the liquid phase isomerization reaction of α-pinene to increase the yield of limonene. A maximum α-pinene conversion of 100% and limonene yield of 59.1% could be achieved. Crystallinity could be well retained, and the amounts of medium-strong acid sites and the distribution of Brønsted and Lewis acid sites could be changed after the mild alkali treatment for 13X zeolite. Samples with higher micropore specific surface area were easier to obtain higher yields of limonene due to shape-selectivity. A proper amount of the medium-strong acid and the synergistic effect of Brønsted and Lewis acid sites were beneficial to enhance the catalytic activity and the yield of monocyclic product limonene. The main reason for catalyst deactivation could be the decrease in the active sites due to soft coke deposition. For the regeneration process, the conversions of α-pinene were between 95% and 99% during the first seven cycles and the conversion dropped to 90.6% after the eighth cycle, which demonstrated that the ethanol flushing and calcination could be an effective regeneration method for the 13X catalyst used in the α-pinene isomerization reaction.

Isomerization of α-pinene with a hierarchical mordenite molecular sieve prepared by the microwave assisted alkaline treatment

Abstract To develop effective catalysts for α-pinene isomerization reaction is important to get high valuable products. A hierarchical mordenite molecular sieve is prepared using alkaline treatment assisted by the microwave radiation. After the alkaline treatment, the relative crystalline decreases by ~20% and mesopores are introduced in the mordenite molecular sieve. Compared to conventional heating method, microwave assisted alkaline treatment exhibits a selective etching of zeolitic silicon atoms. Aluminum atoms adjacent to silicon atoms are extracted to form Al–OH hydroxyl groups. These extracted aluminum atoms are reconnected to zeolitic silicon atoms. Mordenite after microwave assisted alkaline treatment has a good dispersion of mesopores, higher retention of BrOnsted acid sites in 12-membered rings, and lower concentration of Lewis acid sites. The isomerization reaction of α-pinene suggests that alkaline treatment increases the accessibility of acid sites for α-pinene molecules. The hierarchical porosity increases the conversion of α-pinene from 46.1 to 94.7%. The yields for camphene and limonene increase by 17.0 and 5.4%, respectively. Disproportionation of limonene is inhibited when using microwave assisted alkaline treated mordenite due to a low concentration of Lewis acid sites. These results are important to propose a facile post modification method to realize a selective extraction of zeolitic framework atoms.

Catalytic Activity of Zr4+/ZA on The Isomerization Reaction of α-Pinene and It’s Reusability Test

Production of turpentine oil from pine resin until December 2014<sup>th</sup> was reported to reaching 17.150 tones with the wide of pine forest is 876.992,66 acres. The main component of turpentine oil is α-pinena which isomer products have high value for industrial raw materials. Effects concentration of impregnation and reusability test a best catalyst on α-pinene isomerization reaction using catalysts Zr<sup>4+</sup>/natural zeolite in which modificated with different Zr<sup>4+</sup> concentration were analyzed. Characterization of catalyst included <em>X-ray Fluoroscent </em>for detection of Zr concentration in natural zeolites, <em>Surface Area Analyzer </em> for determine catalyst porosity using BET method, and determination of acidity using vapor ammonia and pyridine base adsorption gravimetric method. Isomerization process used a batch reactor with variation in the concentrations of Zr<sup>4+</sup> impregnations 10, 15, and 20 w/w as well as reusability test used best catalyst. The highest conversion of α-pinene used Zr<sup>4+</sup>/ZA 10% catalyst was 3,89% so as Zr<sup>4+</sup>/ZA 10% catalyst is best catalyst than other catalysts whereas highest conversion of α-pinene used Zr<sup>4+</sup>/ZA 10% regeneration catalyst was 4,26%. The product is produced from isomerization reaction of α-pinene used Zr<sup>4+</sup>/ZA all variations catalysts was camphene and limonene.

A comparative study on the gas-phase and liquid-phase thermal isomerization reaction of α-pinene

In this paper, a method of preparation of ocimene is investigated, which is obtained from isomerization reaction of α-pinene. Two kinds of experimental apparatus are established for the investigation of the thermal isomerization reaction of α-pinene. The behavior of thermal isomerization reaction of α-pinene is respectively discussed in the gas phase and in the liquid phase. Under gas phase conditions, the conversion of α-pinene is 80% and the selectivity of ocimene is 30%–33%. Under liquid phase conditions, the conversion of α-pinene is 60% and the selectivity of ocimene is 50%–54%. According to the kinetic-molecular theory of ideal gases, two kinds of reaction models are proposed to visualize the reaction process. In addition, the mechanism and kinetics of thermal isomerization reaction of α-pinene are respectively discussed. The conclusion is that the gas phase reaction temperature is calculated to be 390–450 °C and the liquid phase reaction temperature is calculated to be 450–550 °C. From a bond dissociation energy point of view, results support the hypothesis that the reaction involves biradical intermediates. Copyright © 2012 John Wiley & Sons, Ltd.

Isomerizaton of α-pinene over H 3PW 12O 40 catalysts supported on natural zeolite

The liquid phase isomerization of α-pinene over a catalyst with 12-tungstophosphoric acid (HPW) supported on natural zeolite rich in clinoptiolite was studied in a batch slurry reactor in a nitrogen atmosphere and at constant temperature of 373 K. The catalysts prepared were characterized by nitrogen adsorption, XRD, SEM, and DSC measurements. The catalytic activity increased from 15% to 99% with the introduction of HPW at 4.25 wt% onto the natural zeolite. However, the catalytic activity decreased with the calcination of the catalyst sample. XRD studies indicated that only the HPW catalyst supported on natural zeolite without calcination was the one where the HPW crystals were formed, no significant HPW crystals were observed in the calcined sample. The main reaction products of the isomerization reaction of α-pinene were camphene and limonene with selectivities of about 40% and 3%, respectively, over the HPW catalyst supported on natural zeolite without heat treatment. One and a half order dependency on α-pinene consumption was observed and activation energy was established to be 65.4 kJ/mol.

Isomerization of Pinene with Al- and Ga-Modified MCM-41 Mesoporous Materials

In recent years the pharmaceutical and cosmetics industries have increased the usage of camphene, an intermediate for the manufacture of, for instance, camphor, anti-swelling drugs and K vitamin. Therefore, recent research efforts have been focused on developing new reaction paths towards a higher selectivity to camphene while avoiding other terpene by-products, such as p-cumene and limonene, which are of little industrial value. The aim of the present work was to study the structure and catalytic performance of Al- and Ga- substituted MCM-41 mesoporous materials for the α-pinene isomerization reaction. Both, Al and Ga, enhance the Brönsted and Lewis acidity of the parental MCM-41 material. At low conversion (± 10%) there was little deactivation, mainly due to the absence of secondary reactions; at higher conversion (± 50%) considerable amount of cyclic products are obtained.

Isomerization of α-Pinene Over Porous Phosphate Heterostructure Materials: Effects of Porosity and Acidity

A series of porous phosphate heterostructure (PPH) samples with different content of silica intercalate were prepared and characterized by XRD, N2 adsorption and SEM. The total and accessible surface acidity of these samples were measured by NH3 and 2,6-di-tert-butyl-pyridine-TPD, respectively. Not the total acid sites but the accessible ones play a crucial role in the α-pinene isomerization reaction. The number of the accessible aid sites is strongly depended on the porosity of PPH samples. 68.1% conversion of α-pinene with 51.9% yield of useful products is achieved at 110 °C.

Theoretical study of chemical reactivity of the main species in the α-pinene isomerization reaction

α-Pinene is an important chemical raw material for products widely used in perfumery, pharmaceutical and other applications. The main industrial processing of pinene is the acidic isomerization reaction to produce camphene. Density functional theory calculations were used to obtain the quantum-chemical descriptors for the theoretical analysis of the reactivity of pinene and its main compounds that are formed under the reaction conditions in order to compare with experimental results and establish new ideas on how to improve the camphene yield. These calculations were done in Gaussian 03W using TPSS/TPSS and 6-31+G (d,p) basis set and PBE/DND with the DMol3 module incorporated in Materials Studio 4.1.

α-Pinene isomerization to campheneEffect of thermal treatment on sulfated zirconia

Abstract The isomerization reaction of α-pinene produces bicyclic and monocyclic compounds and other products. The purpose of this study is to investigate the influence of the pre-treatment temperature of the catalyst on the concentration of Lewis and Bronsted acid sites and the activity and selectivity of the catalyst. Catalyzed reactions in heterogeneous and homogeneous phases were performed. In heterogeneous reaction, sulfated zirconia (SZ) and pre-treated SZ catalyst at several temperatures were used. The thermal treatment affects the ratio between Bronsted and Lewis sites. Results were contrasted with those obtained with SZ catalyst without thermal treatment. In homogeneous reaction the catalyst is sulfuric acid, and in the reaction medium Bronsted sites are only present coming from the H+ of the acid. The ratio between bi/monocyclic compounds for H2SO4, SZ catalyst and pre-treated catalyst at several temperatures, SZ250, SZ350 and SZ500, varies between 0.4 and 4.3. It can be observed that there exists an optimal thermal treatment where the ratio is higher. FT-IR spectra of adsorbed pyridine on catalysts pre-treated thermally show the presence of Lewis and Bronsted acid sites. The amount of acid sites was determined by TPD of adsorbed pyridine.

Isomerization of α-pinene over calcined natural zeolites

In this work, isomerization reaction of α-pinene was studied over several heat-treated natural zeolite catalysts, rich in clinoptilolite, from Balýkesir–Bigadic region in Turkey in a batch slurry reactor under nitrogen atmosphere. Zeolite samples were calcined at different temperatures such as 300, 450 and 600 °C. All catalysts were tested in the isomerization reaction of α-pinene and were characterised by nitrogen adsorption experiments, IR, and XRD measurements. Acidity strength and the distribution of Lewis and Bronsted acid sites of the samples were determined. Selectivities to main reaction products, camphene and limonene, and reaction kinetics were investigated. Catalytic activity, that is total conversion of α-pinene, of heat-treated samples decreased with increasing calcination temperatures. Selectivity to limonene is dependent on α-pinene conversion at high conversion levels while the selectivity to camphene is not. The formation of heavy products increased with treatment temperature. It was seen that α-pinene consumption could be described by a first-order kinetics.

Isomerization of α-pinene over ion-exchanged natural zeolites

Catalysts prepared by ion exchange of clinoptilolite-based natural zeolite tuffs with NH 4 +, Ba 2+ and Pb 2+ were investigated in the isomerization reaction of α-pinene at atmospheric pressure under nitrogen flow. Activity and selectivity to mono-, bi- and tricyclic products were correlated with acidity strength.

On the isomerization of β-pinene: a theoretical study

The β-pinene → α-pinene isomerization reaction was investigated at the HF, MP2 and MP4(SDQ) levels of theory, using the 6-31G, 6-31G(d), 6-31+G(d) and 6-311++G(d,p) basis set. The analysis of the intrinsic reaction coordinate has shown that this reaction takes place through a progressive intramolecular proton transfer. The use of different basis set and the inclusion of the electron correlation effects has little influence on the relative stability of the pinene isomers. Contrary to this, the effects of basis set and electron correlation, affects drastically, the energy barrier for the process, varying by 32.5 kcal/mol on going from HF/6-31G to MP2/6-311++G(d,p) levels of theory. The 6-31G basis set gave a completely different result at both HF and MP2 levels for the relative stability of the isomers. The analysis of the nature of the bonds and charge distribution in the transition state species, is shown in the formation of a π-allylic system with a three-center bond. A mechanism to the isomerization reaction assisted by transition metal compounds is given.

Liquid Phase Isomerization of α-Pinene. Study of the Reaction on Sulfated ZrO2

The α-pinene isomerization reaction was studied on sulfated zirconium oxide catalyst for different experimental conditions. The catalysts are active for producing camphene when they present Bronsted acidity and when zirconium oxide crystallizes in the tetragonal phase. The α-pinene conversion and its selectivity to camphene can be optimised by proper selection of operating conditions such as temperature, catalyst concentration and reaction time. The use of this catalyst in the appropriate conditions can result in selectivity to camphene of about 70%.