Rate Constants For Conversion Research Articles

A pharmacokinetic model for hyperpolarized 13C-pyruvate MRI when using metabolite-specific bSSFP sequences.

Metabolite-specific balanced SSFP (MS-bSSFP) sequences are increasingly used in hyperpolarized [1-13C]Pyruvate (HP 13C) MRI studies as they improve SNR by refocusing the magnetization each TR. Currently, pharmacokinetic models used to fit conversion rate constants, kPL and kPB, and rate constant maps do not account for differences in the signal evolution of MS-bSSFP acquisitions. In this work, a flexible MS-bSSFP model was built that can be used to fit conversion rate constants for these experiments. The model was validated in vivo using paired animal (healthy rat kidneys n = 8, transgenic adenocarcinoma of the mouse prostate n = 3) and human renal cell carcinoma (n = 3) datasets. Gradient echo (GRE) acquisitions were used with a previous GRE model to compare to the results of the proposed GRE-bSSFP model. Within simulations, the proposed GRE-bSSFP model fits the simulated data well, whereas a GRE model shows bias because of model mismatch. For the in vivo datasets, the estimated conversion rate constants using the proposed GRE-bSSFP model are consistent with a previous GRE model. Jointly fitting the lactate T2 with kPL resulted in less precise kPL estimates. The proposed GRE-bSSFP model provides a method to estimate conversion rate constants, kPL and kPB, for MS-bSSFP HP 13C experiments. This model may also be modified and used for other applications, for example, estimating rate constants with other hyperpolarized reagents or multi-echo bSSFP.

Structural enzymology studies with the substrate 3S-hydroxybutanoyl-CoA: bifunctional MFE1 is a less efficient dehydrogenase than monofunctional HAD.

Multifunctional enzyme, type-1 (MFE1) catalyzes the second and third step of the β-oxidation cycle, being, respectively, the 2E-enoyl-CoA hydratase (ECH) reaction (N-terminal part, crotonase fold) and the NAD+-dependent, 3S-hydroxyacyl-CoA dehydrogenase (HAD) reaction (C-terminal part, HAD fold). Structural enzymological properties of rat MFE1 (RnMFE1) as well as of two of its variants, namely the E123A variant (a glutamate of the ECH active site is mutated into alanine) and the BCDE variant (without domain A of the ECH part), were studied, using as substrate 3S-hydroxybutanoyl-CoA. Protein crystallographic binding studies show the hydrogen bond interactions of 3S-hydroxybutanoyl-CoA as well as of its 3-keto, oxidized form, acetoacetyl-CoA, with the catalytic glutamates in the ECH active site. Pre-steady state binding experiments with NAD+ and NADH show that the kon and koff rate constants of the HAD active site of monomeric RnMFE1 and the homologous human, dimeric 3S-hydroxyacyl-CoA dehydrogenase (HsHAD) for NAD+ and NADH are very similar, being the same as those observed for the E123A and BCDE variants. However, steady state and pre-steady state kinetic data concerning the HAD-catalyzed dehydrogenation reaction of the substrate 3S-hydroxybutanoyl-CoA show that, respectively, the kcat and kchem rate constants for conversion into acetoacetyl-CoA by RnMFE1 (and its two variants) are about 10 fold lower as when catalyzed by HsHAD. The dynamical properties of dehydrogenases are known to be important for their catalytic efficiency, and it is discussed that the greater complexity of the RnMFE1 fold correlates with the observation that RnMFE1 is a slower dehydrogenase than HsHAD.

Fast calculation of internal conversion rate constant using the time-dependent formalism

A new method for calculating the internal conversion rate constant, which takes into account all possible vibrational transitions between two adiabatic electronic states, is proposed. The simple analytical form of the correlation function obtained in the harmonic and anharmonic approximations and taking into account the Franck-Condon term makes it possible to perform fast calculations. In addition, the method takes into account temperature effects within harmonic kind, which extends its area of application to explain experimental processes. The approach has been applied to the study of molecules important for organic electronics, such as tetraoxa[8]circulene, free-base porphyrin and poly[n]fluorenes. The method provides valuable information on IC processes and facilitates the design of efficient molecular systems.

Internal conversion induced by external electric and magnetic fields.

We have developed a new methodology for calculating contributions to the rate constants (kIC) of internal conversion that are induced by external electric (kIC-E) or magnetic (kIC-M) fields. The influence of the external electric and magnetic fields on the kIC was estimated for seven representative molecules. We show that the kIC-E contribution calculated at a field strength of 1011 V m-1 is generally as large as the kIC rate constant in the absence of the external field. For indocyanine green, azaoxa[8]circulene, and pyromitene 567, the kIC-E contribution is as large as kIC already at a field strength of 109 V m-1. Such electric-field strengths occur for example in plasmonic studies and in strong laser-field experiments. The induced effect on the kIC rate constant should be accounted for in calculations of photophysical properties of molecules involved in such experiments. The induced effect of an external magnetic field on kIC can be neglected in experiments on Earth because the magnetic contribution becomes significant only at very strong magnetic fields of 104-105 T that cannot be achieved on Earth. However, the magnetic effect on the rate constant of internal conversion can be important in astrophysical studies, where extremely strong magnetic fields occur near neutron stars and white dwarfs.

Intramolecular rate-constant calculations based on the correlation function using temperature dependent quantum Green's functions.

A theoretical method for calculating rate constants for internal conversion (IC), intersystem crossing (ISC) and radiative (R) electronic transitions is presented. The employed method uses temperature-dependent quantum Green's functions, which give the opportunity to consider almost any nth-order polynomial perturbation operator and the influence of external electromagnetic fields on the rate constants. The rate constants of the IC, ISC and R processes are calculated for two important indocyanine molecules namely indocyanine green (ICG) and heptamethine cyanine (IR808) at the Franck-Condon level using the temperature-dependent quantum Green's function approach. Calculations at the time-dependent density functional theory level with the MN15 functional show that ICG and IR808 have only one triplet state below the S1 state. The main deactivation channel of the S1 state is the IC process with a large (kIC(S1 → S0)) rate constant of ∼109-1011 s-1. The estimated quantum yield of fluorescence (φfl) is ∼0.001-0.24 for the two studied molecules, which agrees rather well with experimental values. Thus, the present approach enables calculations of the three kinds of rate constants and the quantum yield of fluorescence using the same computational methodology.

In Situ Quantitative Study of Single-Molecule Photoreduction Activities and Kinetics on 1D-1D Heterostructure.

Understanding the underlying catalytic mechanisms with nanometer resolution is of critical importance to the rational design of 1D heterogeneous catalysts. However, a fundamental investigation of photocatalytic activities and kinetics at their individual sites is still challenging. Herein, in situ single-molecule fluorescence microscopy is employed to study the site-specific catalytic activities and dynamics on 1D-1D heterostructure for the first time. For carbon nanotube (CNT)/CdS nanorod composites, it is found that the CdS end with heterojunction exhibits the highest catalytic conversion rate constant of resazurin photoreduction, which is 30%, 7%, and 19% higher than those of the middle segment and the bare end of CdS, and the CNT end with heterojunction, respectively. A similar trend of adsorption abilities is observed in these structures. Such phenomena can be attributed to the different content of defects in these structures. Regarding the dissociation behaviors, the dissociation rate constants of all structures exhibit an opposite trend to those of adsorption and conversion. The direct and indirect dissociation are found to be predominant on CdS and CNT, respectively. Such investigation provides a deep insight into the understanding of site-specific properties on 1D heterogeneous catalysts and helps construct the "structure-dynamics" correlations at the nanoscale.

Ca/ZSM-5 catalysts for the methanol-to-hydrocarbons reaction: Activity – Selectivity trade-off?

Establishing structure–activity relationships for the methanol-to-hydrocarbons reaction can help to identify better catalysts and optimal reaction conditions. Modification of ZSM-5 catalysts with alkaline-earth cations such as Ca increases the selectivity to C3+ olefins, which has been linked to a change in the effective pore geometry, affecting the formation of particular hydrocarbon pool (HCP) components. To further understand the catalytic properties of Ca/ZSM-5, we estimated the methanol conversion rate constants and deactivation coefficients. The kinetic experiments were carried out at different contact times with and without water in the feed. Ca/ZSM-5 is substantially less active than HZSM-5 and Na/ZSM-5 in a wide range of conditions. The decreased activity can be correlated to a different composition of the HCP due to the presence of Ca, which is supported by step-response IR experiments using various feed mixtures (methanol, methanol + water, water). Ca/ZSM-5 converts methanol significantly slower than HZSM-5 and Na/ZSM-5 but with a higher C3+ olefins selectivity, pointing to the delicate balance between activity and selectivity in these materials.

Preparation of HKUST-1 functionalized porous silica crosslinked sodium alginate composite: Efficient reduction of 4-nitrophenol to 4-aminophenol

In this paper, sodium alginate crosslinked porous silica carrier (SA-SiO2) was introduced by one-pot co-condensation method, and Cu2+ was adsorbed on the carrier by –COOH to in-situ synthesized composite materials (HKUST-1@SA-SiO2). A series of characterizations were carried out by FT-IR, BET, XRD, XPS, SEM, and TEM. The results showed that the carrier SA-SiO2 was successfully cross-linked, HKUST-1 was successfully surface functionalized and the composites was spongy with pores. The catalytic activity and reusability of the compound HKUST-1@xSA-SiO2 were investigated for the reduction of 4-nitrophenol to 4-aminophenol. Among them, HKUST-1@0.15SA-SiO2 had the best catalytic performance and the conversion rate constant was 0.45 min−1, which was better than that of the post-synthesis method. Its catalytic activity did not decrease significantly after five cycles.

Inhibited reactivity of horseradish peroxidase by its conjugated proteins through redox mediated electrochemical interrogation

In this article, a classical redox mediated metal (in this study, Au) indicator electrode approach was revisited for the direct interrogation of ‘slow’ enzymatic redox second-order kinetics of horseradish peroxidase (HRP) for oxidative conversion of the model redox substrates, ferrocenemethanol (FcMeOH) and hydroquinone (H2Q) in low HRP-concentration levels. The presented electroanalysis allowed us to recognize the inhibited enzyme reactivity of HRP for FcMeOH-oxidation by its conjugation to model proteins (streptavidin, avidin, and monoclonal antibody), whereas this effect was negligible for H2Q-oxidation by HRP. From a theoretical investigation using finite element analysis, slow kinetics of HRP can be sensitively recognized through an Au indicator electrode approach in the case where HRP bulk electrolyzes a redox substrate in a solution. Five redox substrates were electrochemically investigated, and FcMeOH and H2Q showed negligible side reactions during mediation between HRP and the indicator electrode. From the chronoamperometric approach, the apparent rate constants for oxidative conversion of FcMeOH by the non-conjugated, free HRP were estimated to be ∼104 M−1s−1 at various pH values, while that of H2Q was roughly two orders of magnitude higher at pH ∼7. The molecular docking simulation revealed the need for a significant conformational change of HRP for FcMeOH access to the heme site, whereas the structural alternation of HRP was negligible for access of the H2Q into the domain of the enzyme. The simulation result indicates that the oxidative conversion rate of FcMeOH by HRP could be more susceptible to recognize additionally induced steric hindrance for access of the redox substrate to the catalytic site of the enzyme than that of H2Q. We experimentally verified that the apparent rate constant for FcMeOH-oxidation by the HRP conjugated to streptavidin was estimated to be ∼5 times smaller than that by the free HRP, and those by other conjugates to avidin and monoclonal antibody were ∼60% of that by the non-conjugated one. In contrast to the case of FcMeOH, the estimated reactivity of H2Q by HRP was barely affected by the conjugated model proteins. The presented study demonstrated that a redox enzymatic reactivity of HRP could be significantly affected by conjugated proteins when access of a redox substrate to a catalytic site of an enzyme is susceptible to conformational changes.

Role of Vibronic Couplings and Energy Gap in the Internal Conversion Process of a Molecule

Abstract An analytical expression for the rate constant of internal conversion (IC) in a molecule was derived based on the crude adiabatic representation. All vibrational modes were considered to be on an equal footing in the rate constant expression. Based on this expression, we investigated the role of vibronic couplings and electronic energy gap in IC processes, using 9-fluorenone as an illustrative example. Vibrational modes with strong off-diagonal vibronic coupling constants (VCCs) give rise to non-radiative transitions. In contrast, vibrational modes with strong diagonal VCCs constitute the final vibronic states that accept the excess electronic energy between the initial and final electronic states. Therefore, vibrational modes are classified into promoting and accepting modes based on their roles. We identified important promoting modes responsible for one-phonon emission/absorption and accepting modes that contribute greatly to the final state. A Franck-Condon envelope, which describes the density of final vibronic states, explains the dependence of the rate constant on the electronic energy gap. VCC can be visualised as a spatial distribution of its density form, i.e., vibronic coupling density (VCD). The VCD concept is expected to facilitate the design of functional molecules with IC processes understood in terms of electronic states and vibrational modes.

Calculation of Excited State Internal Conversion Rate Constant Using the One-Effective Mode Marcus-Jortner-Levich Theory.

In this article, the one-effective mode Marcus-Jortner-Levich (MJL) theory and the classical Marcus theory for electron transfer were applied to estimate the internal conversion rate constant, kIC, of organic molecules and a Ru-based complex, all belonging to the Marcus inverted region. For this, the reorganization energy was calculated using the minimum energy conical intersection point to account for more vibrational levels, correcting the density of states. The results showed good agreement with experimental and theoretically determined kIC, with a small overestimation by the Marcus theory. Also, molecules less dependent on the solvent effects, like benzophenone, presented better results than molecules with an expressive dependence, like 1-aminonaphthalene. Moreover, the results suggest that each molecule possesses unique normal modes leading to the excited state deactivation that does not necessarily match the X-H bond stretching, as previously suggested.

Biomass derived bifunctional catalyst for the conversion of cassava dreg into sorbitol

A biomass derived bifunctional catalyst (Ru/CCD-SO3H) was used for one-pot conversion of cassava dreg and cassava starch into sorbitol. The cassava dreg is mainly composed of residual cassava starch and holocellulose. The highest sorbitol yield of 11.43 % was achieved using cassava dreg as reactant. A synergistic catalytic effect of acid and metal sites of Ru/CCD-SO3H on cassava starch conversion to sorbitol was observed. The maximum sorbitol yield reached 82.51 % using cassava starch as reactant. A kinetic model of cassava starch degradation was performed. The reaction rate constants of cassava starch degradation, glucose conversion and sorbitol generation improved with enhancing temperature. The activation energy of cassava starch hydrolysis is larger than that of glucose hydrogenation, indicating the cassava starch hydrolysis is rate-determining step of cassava starch conversion into sorbitol. This work not only realizes the comprehensive utilization of cassava dreg, but also provides useful guidance for developing kinetic model of polysaccharide conversion.

Surface phase transformation of ZrO2 in VOx/ZrO2 catalysts for boosting propane nonoxidative dehydrogenation

AbstractThe nanocatalysts of VOx deposited on ZrO2 supports with single monoclinic (ZrO2‐M), tetragonal (ZrO2‐T), and binary monoclinic‐tetragonal (ZrO2‐MT) phase were synthesized. VOx/ZrO2‐MT catalysts exhibit better performance during propane nonoxidative dehydrogenation than VOx/ZrO2‐M and VOx/ZrO2‐T catalysts. Among VOx/ZrO2‐MT catalysts, the conversion and deactivation rate constant of VOx/ZrO2‐M31T69 catalyst is 35.2% and 0.22 h−1, respectively. The promoting role of ZrO2‐MT is revealed by experiments and theoretical calculations. The MT‐mixed phase structure in VOx/ZrO2‐MT catalyst improves the structural properties and dispersion of VOx. The tetragonal‐monoclinic transformation on the ZrO2‐MT surface facilitates VOx reduction and produces additional V3+ active sites. The highly dispersed V3+ sites on the ZrO2‐MT surface accelerate CH bond breaking and boost the desorption of propylene, which is the key reason for enhancing activity and stability during the reaction, respectively. Insight into the role of surface phase transformation of ZrO2‐MT is expected to obtain high‐efficient catalysts further.

Internal conversion rate constant calculations considering Duschinsky, anharmonic and Herzberg-Teller effects.

A novel method for calculating rate constants for internal conversion (kIC) that simultaneously accounts for Duschinsky, anharmonic and Herzberg-Teller effects has been developed and implemented. This method has been applied to robust planar molecules like tetraoxa[8]circulene (4B), free-base porphyrin (H2P) and pyrometene (PM567) with small Duschinsky rotation (i.e. with almost identical normal coordinates in the ground and excited states) and to poly[n]fluorenes (P[n]F) (n = 2-14) with a substantial Duschinsky rotation. The obtained results show that the Duschinsky effect is large in the harmonic approximation, whereas it is in general much smaller in the anharmonic approximation. The Duschinsky effect is found to be large for high frequency vibrational modes with energies of ∼3300 cm-1 such as the X-H (X = C, N and O) stretching modes that mix in the S1 → S0 electronic transition. However, even in this case, the increase in kIC due to the Duschinsky effect does not exceed one order of magnitude. The calculations show that anharmonic contributions to kIC are larger than Herzberg-Teller contributions which in turn are larger than contributions from the Duschinsky effect ANH > HT > Du. We also show that an approximation, where only X-H bonds are considered in the kIC calculation, is accurate even for P[n]F (n = 2-14).

Interexcited State Photophysics I: Benchmarking Density Functionals for Computing Nonadiabatic Couplings and Internal Conversion Rate Constants.

We present the first benchmarking study of nonadiabatic matrix coupling elements (NACMEs) calculated using different density functionals. Using the S1 → S0 transition in perylene solvated in toluene as a case study, we calculate the photophysical properties and corresponding rate constants for a variety of density functionals from each rung of Jacob's ladder. The singlet photoluminescence quantum yield (sPLQY) is taken as a measure of accuracy, measured experimentally here as 0.955. Important quantum chemical parameters such as geometries, absorption, emission, and adiabatic energies, NACMEs, Hessians, and transition dipole moments were calculated for each density functional basis set combination (data set) using density functional theory based multireference configuration interaction (DFT/MRCI) and compared to experiment where possible. We were able to derive simple relations between the TDDFT and DFT/MRCI photophysical properties; with semiempirical damping factors of ∼0.843 ± 0.017 and ∼0.954 ± 0.064 for TDDFT transition dipole moments and energies to DFT/MRCI level approximations, respectively. NACMEs were dominated by out-of-plane derivative components belonging to the center-most ring atoms with weaker contributions from perturbations along the transverse and longitudinal axes. Calculated theoretical spectra compared well to both experiment and literature, with fluorescence lifetimes between 7.1 and 12.5 ns, agreeing within a factor of 2 with experiment. Internal conversion (IC) rates were then calculated and were found to vary wildly between 106-1016 s-1 compared with an experimental rate of the order 107 s-1. Following further testing by mixing data sets, we found a strong dependence on the method used to obtain the Hessian. The 5 characterized data sets ranked in order of most promising are PBE0/def2-TZVP, ωB97XD/def2-TZVP, HCTH407/TZVP, PBE/TZVP, and PBE/def2-TZVP.

Investigation of solvent-free esterification of levulinic acid in the presence of tin(IV) complexes

In this study, for the first time, the use of dibutyltin dichloride (Bu2SnCl2), dimethyltin dichloride (Me2SnCl2), butyltin trichloride (BuSnCl3) and butyl stannoic acid (BuSnO(OH)) as catalysts in the esterification of levulinic acid (LA) was investigated through a comparison with reactions performed without the use of a catalyst. The most active system (BuSnCl3) led to 93% conversion of LA in 360 min at 110 °C with an LA:EtOH:CAT molar ratio of 1:5:0.01. The apparent rate constants (kap) for LA conversion confirm these results, and values of 6.2 × 10−3, 12.5 × 10−3 and 19.4 × 10−3 min−1 were obtained at 70, 90 and 110 °C, respectively. The activation energy for LA conversion was determined employing BuSnCl3 and the value was 31.2 kJ mol−1.

Experimental and Modelling Comparison of the Effects of UV Energy on Liquefaction Efficiency in Coal Liquefaction Mechanism

Coal liquefaction process gives very efficient results, especially for value-added chemicals production from low-quality coal. However, when the literature is examined, notably there is not enough scientific study for liquefaction mechanisms. Here, in this study, There are five different liquefaction mechanisms of Beypazarı coals. It includes four different UV light power and a catalyst environment using 180 watts of UV power. Created first-order linear discrete models were proposed and compared with the experimental results. Additionally, the reaction rate constants for each proposed kinetic model were calculated using the Kalman filter method. However, to evaluate the compatibility of the experimental results and the modeling results, the sum of the squared differences of the values calculated from the experimental data and the models was examined. Because of these studies, it has been observed that the rate constants of direct oil formation from coal at 120 and 180 watts of UV power are at least three times greater than the rate constants for the formation of asphaltene and pre-asphaltene from coal. Simultaneously, The results demonstrate that models with reversible and parallel steps are more compatible with experimental data. Experimental data and modeling results are much more compatible with the studies conducted on Beypazarı coals in a 180-watt UV-catalyzed environment compared to a 180-watt catalyst-free environment. In the presence of ZnO catalyst, the rate constants occurring in the conversion reaction from coal to oil were again three times faster than the conversion rate constants from coal to asphaltene and from coal to preasphaltene. In the modeling and experimental results conducted in the catalyst environment, the efficiency was higher than the catalyst-free environment. The best fit was obtained using model that has both reversible (between asphaltene: coal, asphaltene: oil, and asphaltene: preasphaltene) and irreversible (coal: oil, coal: preasphaltene and preasphaltene: oil) reaction steps. The model also evidenced that reversible reactions are critical on the liquefaction of Beypazarı coal.

New insights into humic acid-boosted conversion of bisphenol A by laccase-activated co-polyreaction: Kinetics, products, and phytotoxicity

How humic acid (HA) modifies bisphenol A (BPA) conversion in exoenzyme-activated polyreaction is poorly understood. Herein, the influencing mechanism of HA on laccase-induced BPA self-polymerization was investigated, and the phytotoxicity of the produced BPA self/co-polymers was assessed for the first time. HA prominently boosted BPA elimination, and the rate constants of BPA conversion augmented from 0.61 to 1.43 h−1 as HA level raised from 0 to 50 mg·L−1. It is because the generated BPA-HA co-polymers promptly lowered the yields of long-chain BPA self-oligomers, consequently maintaining laccase activity through opening enzymatic substrate-binding pockets. Notably, a few BPA monomers were re-released from the loosely bound self-polymers and co-polymers, and the releasing amounts respectively were 13.9 − 22.4% and 0.3 − 0.5% at pH 2 − 11. Formation of self/co-polymers was greatly conducive to avoiding BPA biotoxicity. Compared with BPA self-polymers, the phytotoxicity of BPA co-polymers to germinated radish (Raphanus sativus L.) seeds was lower due to these covalently bound products were more complex and stable. It follows that laccase-mediated co-polymerization played a significant role in BPA conversion, contaminant detoxification, and carbon sequestration. These findings are not only beneficial to clarifying exoenzyme-activated the generation mechanism of BPA co-polymers in water, but to reusing these supramolecular aggregates in crop growth.

Theory of Exciton Dynamics in Thermally Activated Delayed Fluorescence

AbstractThermally activated delayed fluorescence (TADF) is an upconversion photophysical process based on the population of a bright excited singlet state from an excited triplet via reverse intersystem crossing (rISC), which might be employed to overcome the statistical limitation of electron‐hole recombination in organic light‐emitting diodes. In this work, we describe the intricacies of TADF dynamics by means of a quantum master equation and through perturbative approaches to rate constants of internal conversion and ISC. Simulation of the time evolution from the lowest excited triplet in systems with small energy gaps allows to disentangle the role of different electronic states mediating the population of the singlet manifold and the importance of various rISC mechanisms. Energy gaps between charge transfer (CT) and local excitons (LE), and interstate (hyperfine, spin‐orbit and vibronic) couplings are key factors tuning the feasibility of rISC. Since in molecules LE/CT spin‐orbit coupling is, in general, larger than hyperfine interactions, the rISC rate is largely increased in those situations where either the direct or mediated triplet‐singlet interconversion between states of different character is energetically available. Interestingly, temperature dependence of rISC rate is stronger for the spin‐vibronic coupling mechanism than via hyperfine interaction.

Ultrasonic-assisted catalytic transfer hydrogenation of cottonseed biodiesel using Raney-Ni catalyst in aqueous environment

The amounts of methyl stearate (C18:0) and trans-methyl oleate (trans-C18:1) increase during the catalytic transfer hydrogenation (CTH) process of biodiesel. Although it could improve the oxidation stability of biodiesel, its low temperature performance would be worsened. As for it, ultrasonic was introduced in the CTH to control the generation of C18:0 and trans-C18:1. In this study, the ultrasonic-assisted CTH was performed using Raney-Ni as catalyst, isopropanol as hydrogen donor and water as solvent. The effect of operating parameters such as reaction temperature, stirring rate, catalyst dosage, isopropanol amount and water amount on hydrogenation process was investigated. It was revealed that the optimum reaction conditions were determined as reaction temperature 80 °C, stirring rate 600 rpm, catalyst dosage 10 wt%, isopropanol amount 32 g and water amount 100 g in the aspect of the iodine value of bioidesel and the yield of C18:0 and trans-C18:1. The process of the ultrasonic-assisted CTH for biodiesel could be well described by pseudo-first order kinetic model. The conversion rate constants from C18:2 to C18:1 (k1) and from C18:1 to C18:0 (k2) were 0.02649 min−1 and 0.00438 min−1, respectively. Ultrasonic field effectively repressed the selectivity of trans-C18:1 and further decreased the iodine value of biodiesel. On the basis of the same iodine value, the yield of C18:0 and hydrogenation time reduced with ultrasonic. Overall, ultrasonic is an effective intensification method for the CTH of biodiesel in the aspect of product selectivity and reaction rate.