Conversion Of Model Compounds Research Articles

Producing Methyl p-Coumarate from Herbaceous Lignin via a "Clip-Off" Strategy.

As the most abundant renewable aromatic resource on Earth, lignin is a preferred starting material for producing bulk chemicals via a sustainable route. In this study, we provide a novel and efficient "clip-off" approach for producing methyl p-coumarate, an important and versatile fine chemical by selective cleavage of the ester linkage in herbaceous lignin in the presence of commercial metal chlorides. When bagasse lignin was depolymerized at 155 °C for 4 h, a 12.7% yield of aromatic chemicals was obtained in the presence of CuCl2, 71.7% of which was identified as methyl p-coumarate (the yield was 9.1%). Further investigation of the structural evolution of lignin revealed that the ester linkages in lignin were efficiently broken via intensive transesterification with methanol accompanied by the simultaneous weakening of the inter-/intramolecular hydrogen bonds. Moreover, this observation of selective cleavage of ester linkages could be further confirmed by the conversion of model compounds with characteristic bonds under identical reaction conditions. Therefore, this work provides a new insight into the production of value-added chemicals from renewable resources.

Insight into enhanced activation of permanganate under simulated solar irradiation: Rapid formation of manganese species

Herein, permanganate [Mn(VII)] was activated by simulated solar (SS) (SS/Mn(VII)), resulting in rapid degradation of micropollutants in several minutes, with rates of target micropollutants outnumbered those in the Mn(VII) alone and SS. To explore the mechanism in this process, 4-cholorphenol (4-CP), p-hydroxybenzoic acid (p-HBA), and enrofloxacin (ENR) were selected as model compounds. Lines of evidence indicated that reactive manganese species (RMnS) (i.e., Mn(III) and Mn(V)) rather than radicals from Mn(VII) photolysis participated in the conversion of model compounds. Interestingly, roles of RMnS differed among three model compounds, suggesting their selectivity toward micropollutants. Increasing Mn(VII) dosage proved greater micropollutant degradation, while impacts of pH on SS/Mn(VII) performance varied among model compounds. P-HBA and ENR showed the lowest degradation efficiency at alkaline, whereas 4-CP demonstrated the best performance at alkaline, indicating the reactivity of RMnS varied toward micropollutants at different pH values. The quantum yield of Mn(VII) was 8.36 ± 0.03 X 10−6 mol Einstein−1 at pH 7.0. Effects of common co-existing constituents (Cl−, HCO3−, and humic acid (HA)) on micropollutant degradation by SS/Mn(VII) were examined. Specifically, HCO3− positively influenced the 4-CP and p-HBA degradation, whereas ENR was not affected, likely owing to the selectivity of RMnS-HCO3− complexes. HA was conducive to degrade p-HBA due to the production of RMnS-HA complexes, but unfavorable for ENR and 4-CP degradation because of the competitive light absorption and Mn(VII). Furthermore, a number of degradation products of 4-CP, p-HBA, and ENR were identified and possible pathways were proposed accordingly. The effectiveness of this process for micropollutant degradation in real waters, natural sunlight, ultraviolet and visible light via cut-off filtering SS emission was confirmed. This work revealed a great potential of applying SS/Mn(VII) for the marked degradation of micropollutants and facilitated the understandings of Mn(III)/Mn(V) behaviors.

Hydrogen-Free Deoxygenation of Bio-Oil Model Compounds over Sulfur-Free Polymer Supported Catalysts

AbstractHydrotreatment of bio-oil oxygen compounds allows the final product to be effectively used as a liquid transportation fuel from biomass. Deoxygenation is considered to be one of the most promising ways for bio-oil upgrading. In the current work, we describe a novel approach for the deoxygenation of bio-oil model compounds (anisole, guaiacol) using supercritical fluids as both the solvent and hydrogen-donors. We estimated the possibility of the use of complex solvent consisting of non-polar n-hexane with low critical points (Tc = 234.5 ºC, Pc = 3.02 MPa) and propanol-2 used as H-donor. The experiments were performed without catalysts and in the presence of noble and transition metals hydrothermally deposited on the polymeric matrix of hypercrosslinked polystyrene (HPS). The experiments showed that the presence of 20 vol. % of propanol-2 in n-hexane results in the highest (up to 99%) conversion of model compounds. When the process was carried out without a catalyst, phenols were found to be a major product yielding up to 95 %. The use of Pd- and Co-containing catalyst yielded 90 % of aromatic compounds (benzene and toluene) while in the presence of Ru and Ni cyclohexane and methylcyclohexane (up to 98 %) were the main products.

Sustainable Production of Acetonitrile from Microalgae via Catalytic Fast Pyrolysis with Ammonia over Ga/HZSM-5 Catalysts

We report on catalytic fast pyrolysis microalgae under ammonia atmosphere into acetonitrile over Ga/HZSM-5, which provides a long-term sustainable option for acetonitrile production and microalgae valorization. The effect of various catalysts, reaction conditions and species of microalgae on acetonitrile production was explored systematically. Under the optimized conditions, the maximum carbon yield of acetonitrile from Chlorella vulgaris was 23.4%, and the selectivity of acetonitrile in bio-oil was up to 77.2%. The possible reaction pathways were proposed according to the comprehensive experimental investigation on the conversion of model compounds and intermediates (proteins, carbohydrates, lipids, amino acids, carboxylic acids, furans, and amines). High-resolution transmission electron microscopy (TEM) analysis showed that Ga was present mainly at the outer surface of zeolite crystals, and a small amount of Ga was doped into the zeolite crystals.

Investigation of deep catalytic cracking of various model compounds of different classes of light hydrocarbons on a mesoporous catalyst based on ZSM-5 zeolite

The catalytic cracking performance of light hydrocarbon model compounds (1-hexene, n-octane, i-octane, ethylcyclohexane and ethylbenzene) over a mesoporous catalyst based on ZSM-5 zeolite was analyzed and compared using a microscale apparatus with a fixed-bed reactor. The effects of reaction temperature and weight hourly space velocity (WHSV) on feed conversion and the yields of ethene and propene were investigated. The results showed that with increased reaction temperature, the conversion of model compounds increased monotonically, and that of 1-hexene was close to 100% above 660°C; the yield of ethene plus propene of n-octane, i-octane and ethylcyclohexane increased continuously, while that of 1-hexene and ethylbenzene passed through maximum. With increased WHSV, the yield of ethene plus propene of ethylbenzene increased continuously, and that of the other model compounds decreased continuously. Through comprehensive analysis of the data, it is indicated that 1-hexene exhibited the highest cracking performance, followed by n-octane and ethylcyclohexane, whereas i-octane and ethylbenzene exhibited the lowest.

Controlling Acidic Sites to Improve Hydroisomerization Performance of Pt/SAPO-11 Catalysts

SAPO-11 zeolites with different amount of silicon were synthesized to control the acidic sites of Pt/SAPO-11 catalysts. The structure, acidity and hydroisomerization performance of the SAPO-11 zeolites were systematically investigated. The results showed that with increase of silicon amount, the relative crystallinity of SAPO-11 apparently decreased and dominant crystal faces were different. BET surface area and total pore volume of the samples can change by difference of phase crystal structure. Amount of framework silicon controls acidic property of the SAPO-11. The more incorporation of silicon in the framework resulted in more medium acidic sites on the samples. The different acidic property of the samples was ascribed to different coordination mode of silicon. There are SM2 and SM3 substitution in the frameworks of the SAPO-11 zeolites. On catalysts of Pt/SAPO-11, more platinum existed in the pores. Platinum dispersion and reduction property were almost duplication for all the catalysts. The conversion of model compound and isomerization selectivity strongly depended on the acidic property of the catalysts. The results demonstrated that the optimum catalysts for hydrocarbon isomerization should remain the balance between metal sites and acidic sites.

Influence of support and supported phases on catalytic functionalities of hydrotreating catalysts

Different mixed-oxide supports were synthesized using homogeneous co-precipitation methods. Alumina–silica, alumina–titania, and alumina–zeolite supports were prepared and then impregnated with Mo (or W) and Co (or Ni) in order to evaluate their behavior in the dibenzothiophene hydrodesulfurization. Supports and supported catalysts were characterized by atomic absorption and textural properties. The conversion of model compounds (tetralin, 1-methylnaphthalene, and decalin) was investigated with the aim of understanding ring opening reaction over the support in presence of hydrogen. The model test reactions for support as well supported sulfide catalysts were carried out in a batch reactor at 4MPa and 340°C. Conversion of cyclo-compounds showed that decalin had the highest conversion followed by 1-methylnaphthalene and tetralin when using a silica–alumina supported catalyst. The hydrodesulfurization results as a function of support variation indicated that high acidity of support has positive effect on the hydrogenolysis of CS bond breaking. Thus, it is inferred that a balance between metal sites of hydrogenation and cracking of the support is critical in order to synthesize a bifunctional catalyst for deep hydrodesulfurization where sulfur removal as well as cetane improvement are mandatory.

Investigation on the Aqueous-phase Hydrogenation of Bio-oil for Saturated Alcohols Production over Ni-B Amorphous Catalysts

Ni-B amorphous catalysts were prepared by chemical reduction of nickel chloride with potassium borohydride aqueous solution and characterized by X-ray diffraction(XRD), Brunauer-Emmett-Tetter(BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) techniques. The catalytic performances of model compounds and bio-oil to produce saturated alcohols were evaluated in a semi-batch reactor. The results showed that the conversion of model compounds(acetone, furfural and phenol) and the selectivity of saturated alcohols reached 99.99% and 90.00% at 110 degrees C, 4.0 MPa(initial pressure). Under the conditions of 150 degrees C and 4.0 MPa, the yield of saturated alcohols reached 47.54%. High temperature of above 150 degrees C resulted in the transformation of amorphous phase to form crystal, which was attributed to the low catalytic activity. This work provides a new alternative for the production of saturated alcohols from bio-oil.

Thermodynamic analysis of aqueous phase reforming of three model compounds in bio-oil for hydrogen production

Thermodynamic analysis with Gibbs free energy minimization was performed for aqueous phase reforming of methanol, acetic acid, and ethylene glycol as model compounds for hydrogen production from bio-oil. The effects of the temperature (340–660 K) and pressure ratio P sys / P H 2 O (0.1–2.0) on the selectivity of H 2 and CH 4, formation of solid carbon, and conversion of model compounds were analyzed. The influences of CaO and O 2 addition on the formation of H 2, CH 4, and CO 2 in the gas phase and solid phase carbon, CaCO 3, and Ca(OH) 2 were also investigated. With methanation and carbon formation, the conversion of the model compounds was >99.99% with no carbon formation, and methanation was thermodynamically favored over hydrogen production. H 2 selectivity was greatly improved when methanation was suppressed, but most of the inlet model compounds formed solid carbon. After suppressing both methanation and carbon formation, aqueous phase reforming of methanol, acetic acid and ethylene glycol at 500 K and with P sys / P H 2 O = 1.1 gave H 2 selectivity of 74.98%, 66.64% and 71.38%, respectively. These were similar to the maximum stoichiometric hydrogen selectivity of 75.00% (methanol), 66.67% (acetic acid), and 71.43% (ethylene glycol). At 500 K and 2.90 MPa, as the molar ratio of CaO/BMCs increased, the normalized variation in H 2 increased and that for CH 4 decreased. Formation of solid carbon was effectively suppressed by addition of O 2, but this was at the expense of H 2 formation. With the O 2/BMCs molar ratio regulated at 1.0, oxidation and CO 2 capture increased the normalized variation in H 2 to 33.33% (methanol), 50.00% (acetic acid), and 60.00% (ethylene glycol), and the formation of solid carbon decreased to zero.

Conversion of sulphur compounds into light gas oil: I. Kinetics of the conversion of model compounds

The problem of sulfur compounds conversion, particularly heterocyclic compounds, from the middle fraction of crude oil (light gas oil) was analyzed and will be published in several articles in the Chemical Industry Journal. Published data in the literature, covering the conversion of tiophene, benzothiophene and dibenzothiophene are presented in the first paper of this series with the goal of comparing and critically analyzing their usage for reactor calculation.