Selective copolymerization of carbon dioxide with propylene oxide catalyzed by a nanolamellar double metal cyanide complex catalyst at low polymerization temperatures

Traditional cobalt-zinc double metal cyanide complex [Zn-Co(III)DMCC] catalysts could catalyze the copolymerization of carbon dioxide (CO₂) with propylene oxide (PO) to afford poly (propylene carbonate) (PPC) with high productivity. But the molecular weight (MW) of PPC and the polycarbonate selectivity were not satisfied. In this work, by using a nanolamellar Zn-Co(III) DMCC catalyst, the CO₂-PO copolymerization was successfully performed to yield PPC with high molecular weight (M_n: 36.5 kg/mol) and high molar fraction of CO₂ in the copolymer (FCO₂: 74.2%) at low polymerization temperatures (40∼80 °C). Improved selectivity (FCO₂: 72.6%) and productivity of the catalyst (6050 g polymer/g Zn) could be achieved at 60 °C within 10 h. The influences of water content on CO₂-PO copolymerization were quantitatively investigated for the first time. It was proposed that trace water in the reaction system not only acted as an efficient chain transfer agent, which decreased MW of the resultant copolymer, but also strongly interacted with zinc site of the catalyst, which led to low productivity of PPC and more amounts of cyclic propylene carbonate (cPC). These conclusions were also supported by the apparent kinetics of CO₂-PO copolymerization. ESI-MS results showed that all polymers have two end alkylhydroxyl groups. It was thus proposed that the alkylhydroxyl groups came from the initiation reaction of Zn-OH in the catalyst and the chain transfer reaction by H₂O. The proposed mechanism of chain initiation, propagation and chain transfer reaction were proved by the experimental results.     

Alternating copolymerization of carbonyl sulfide and Cyclohexene Oxide catalyzed by zinc–cobalt double metal cyanide complex

This paper describes the first example of alternating copolymerization of carbonyl sulfide (COS) with cyclohexene oxide (CHO) via heterogenous catalysis of a nano-lamellar zinc–cobalt(III) double metal cyanide complex (Zn–Co(III) DMCC), providing an efficient method for converting COS to poly(cyclohexene monothiocarbonate) (PCHMTC) with an alternating degree up to 93%. The number-average molecular weight (M_n) of PCHMTC was 6.5–25.0 kg/mol with polydispersities (PDIs) of 1.6–2.1. The productivity of the catalyst was up to 970 g polymer/g catalyst (5.0 h). The oxygen–sulfur exchange reaction (O/S ER) caused by Zn–Co(III) DMCC was largely suppressed when the reaction was performed at 100–110 °C in the presence of THF or CH₂Cl₂, and thus the selectivity of the monothiocarbonate over carbonate linkages was up to 98%. The mechanisms of the copolymerization and O/S ER were proposed based on the ESI-MS, GC–MS and FT-IR spectra. The obtained PCHMTC is highly transparent and exhibits good solubility in various organic solvents, high T_g of 112 °C, initial decomposition temperature of 214 °C and high refractive index of 1.705.     

Selective production of poly(carbonate–co–ether) over cyclic carbonate for epichlorohydrin and CO2 copolymerization via heterogeneous catalysis of Zn–Co (III) double metal cyanide complex

Epichlorohydrin (ECH), as a cheap raw chemical material, is an ideal monomer for copolymerization with CO₂ to produce biodegradable polycarbonates. This work describes the selective ECH–CO₂ copolymerization via heterogeneous catalysis of nanolamellar zinc–cobalt double metal cyanide complex (Zn–Co (III) DMCC), affording a poly(carbonate–co–ether) with carbonate content up to 70.7%. Remarkably, the cyclic carbonate contents in the product are 5.0%–11.3% at 25–60 °C, better than those from homogeneous catalysis. Moreover, the copolymer with 70.7% carbonate content presents high thermal decomposition temperature of 250 °C and relatively high glass-transition temperature (T_g) of 31.2 °C.     

Copolymerization of epoxides and carbon dioxide by using double metal cyanide complex (DMC) with high crystallinity

Zn₃ [Co(CN)₆]₂ based double metal cyanide complex(Co-Zn DMC) is synthesized and characterized by element analysis, FT-IR, TG-FTIR, XRD and TEM. The composition of Co-Zn DMC summarized by elemental analysis has been confirmed by TG-FTIR. The catalyst has high crystallinity according to strong crystalline peaks shown in XRD and diffraction spot observed by TEM. Copolymerization of epoxides and carbon dioxide are successfully catalyzed by Co-Zn DMC. The efficiency of catalysts is as high as 7488 g polymer/g catalyst for CO₂/propylene oxide (PO), 1100 g polymer/g catalyst for CO₂/ethylene oxide (EO), which are higher than that reported ever before. The effects of various reaction conditions such as amount of the catalyst, reaction time and temperature on the copolymerization are investigated. The results show that insertion of CO₂ into chains is significantly affected by the catalyst quantity and ambient temperature. The weight percentage of byproduct cyclic carbonate can be easily controlled to be less than 5% while the molar fraction of CO₂ in backbone (f_co2) is more than 30%.     

Low-temperature catalytic conversion of lignite: 1. Steam gasification using potassium carbonate supported on perovskite oxide

The catalytic conversion of alkali metal carbonate (K₂CO₃) catalyst supported on perovskite oxide was carefully examined as an effective catalyst for low-temperature catalytic gasification of lignite. It showed much higher activity than K₂CO₃ alone as well as K₂CO₃ supported on γ-alumina under gasification conditions below 800 °C. Furthermore, catalyzed syngas had higher H₂ and lower CO₂ ratios than non-catalyzed syngas. Promisingly, there was also much less tar formation, less than 50 wt.% compared to non-catalyzed gasification. Also, less loss of K₂CO₃ and no coke formation on the catalyst surface were confirmed, comparing to the catalytic gasification with K₂CO₃ supported on γ-alumina.     

Suzuki Cross-Coupling Reaction Catalyzed by the Palladium Complex Pd[N-MorphC(S)NP(O)(OiPr)2-O,S]2

Suzuki cross-coupling reaction between phenyl bromide and phenylboronic acid, catalyzed by the palladium complex Pd[N-MorphC(S)NP(O)(OiPr)₂-1,5-O,S)]₂ in acetonitrile, toluene, THF or DMF has been investigated. Bases employed for the reaction were Na₂CO₃, K₂CO₃ or Cs₂CO₃. Varying largely the experimental conditions we found that excellent yields of the product were obtained using toluene and K₂CO₃ at 100 °C at the catalyst amount of 0.02 mmol.     

The performances of higher alcohol synthesis over nickel modified K2CO3/MoS2 catalyst

Ni modified K₂CO₃/MoS₂ catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H₂/CO (molar radio) = 2.0, GHSV = 3000 h^− 1, and P = 10.0 MPa. Compared with conventional K₂CO₃/MoS₂ catalyst, Ni/K₂CO₃/MoS₂ catalyst showed higher activity and higher selectivity to C₂⁺OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K₂CO₃/MoS₂ was higher, however, it was close to that of K₂CO₃/MoS₂ catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K₂CO₃/MoS₂ catalyst.     

Borane-modified graphene-based materials as CO2 adsorbents

The authors studied the CO₂ adsorption performances of borane modified graphene-based materials (B-rG-O). B-rG-O powder was fabricated by reacting graphene oxide with a borane–THF adduct and showed good CO₂ adsorption capacity (1.82 mmol/g at 1 atm) and recyclability as determined using a CO₂ isotherm and breakthrough experiments respectively. The roles of boron moieties for CO₂ adsorption were studied using theoretical calculation and spectroscopic experiments.     

Impregnated carbon based catalyst for protection against carbon monoxide gas

Activated carbon based palladium impregnated catalyst (Pd/C) was prepared for the reactive removal of carbon monoxide (CO) gas under ambient air conditions. For this, active carbon of 1250 m²/g surface area was impregnated with palladium salt to get Pd/C catalyst, containing palladium from 4.0 to 8.0% (w/w). Catalytic efficiency of the catalyst against CO gas was determined under dynamic conditions by passing CO–air mixture to the fixed bed of the Pd/C catalyst. Results indicated that Pd/C catalyst was continuously adsorbing and actively removing CO gas during the course of the palladium catalyzed reaction, i.e., CO + 1/2 O₂ → CO₂ and was found capable of providing excellent protection against CO gas. Moisture content (humidity) of inlet CO–air mixture indicated it to be an important factor affecting the CO removal efficiency of the catalyst, as an increase in humidity after the CO breakthrough resulted in to the activation of the catalyst due to the generation of hydroxyl groups and enhanced protection by the regeneration of the catalyst. Study indicated that Pd/C catalyst works as a catalytic converter, i.e., the continuous conversion of CO to CO₂ using atmospheric oxygen and moisture. In order to determine the shelf life, the Pd/C catalyst was also evaluated for its performance after accelerated ageing at 70 °C and 50% relative humidity (RH) for 3.75 and 7.5 months. The catalyst was found to be working efficiently for 3.75 months but after 7.5 months it could not provide 100% protection against CO gas, however, the same catalyst started giving 100% protection after regeneration. Hence, studies indicated the Pd/C catalyst to be a promising catalyst for the reactive removal of CO gas in enclosed spaces/compartments, coal mines, fire accidents and for getting the protection for longer duration under ambient air conditions.     

Controlled Synthesis of Statistical Polycarbonates Based on Epoxides and CO2

The controlled synthesis of terpolymer structures is often limited by the intrinsic reactivities of the monomers. For the synthesis of a statistical terpolymer from cyclohexene oxide (CHO) and propylene oxide (PO) with CO₂, an instrumental solution is demanded. Implementing a setup where one monomer can be added to the reaction mixture over the whole course of the reaction, the random distribution of the epoxides over the whole chain is realized. The successful terpolymerization can be determined with diffusion-ordered nuclear magnetic resonance spectroscopy and gel permeation chromatography measurements while the statistical microstructure of the generated polymers is indicated in NMR spectroscopy and differential scanning calorimetry measurements. Furthermore, the concept is transferred to the terpolymerization of limonene oxide with PO and CO₂ underlining the versatility of the setup.     

Upgrading of Lignin-Derived Compounds: Reactions of Eugenol Catalyzed by HY Zeolite and by Pt/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Abstract  

The conversion of eugenol (4-allyl-2-methoxyphenol), a compound derived from the lignin in woody biomass, was catalyzed by HY zeolite at 573 K and atmospheric pressure. The main products were isoeugenol and guaiacol, formed by isomerization and by deallylation, respectively. Substituted guaiacols with saturated side-chains (4-methylguaiacol, 4-ethylguaiacol, and 4-propylguaiacol) were also formed, by hydrogen transfer and alkylation reactions. The pseudo-first-order rate constant for the overall disappearance of eugenol was found to be 12.4 L (g of catalyst)/h. When the catalyst was Pt/γ-Al₂O₃ used in the presence of H₂, significant hydrogenation of the propenyl side-chain took place, accompanied by isomerization, and hydrodeoxygenation. Under similar operating conditions, the reaction catalyzed by Pt/γ-Al₂O₃ in the presence of H₂ gave a higher eugenol conversion (X = 0.70) than the reaction catalyzed by HY zeolite (X = 0.11), primarily because of the dominant hydrogenation observed with the former catalyst. In the absence of H₂ as a co-reactant, the acidic γ-Al₂O₃ support in Pt/γ-Al₂O₃ evidently catalyzed all the classes of reactions catalyzed by HY zeolite.     

Novel coating resins based on polycarbonates and poly(ester-co-carbonate)s made by catalytic chain growth polymerization of epoxides with CO2 and with anhydride/CO2

In this work we describe a possibly new generation of (powder) coating resins of the polycarbonate or poly(ester-co-carbonate) type, synthesized from epoxides like cyclohexene oxide (CHO), anhydrides like phthalic anhydride (PA) and carbon dioxide (CO₂) by chain growth polymerization, catalyzed by a chromium-Salophen complex and using dimethylaminopyridine (DMAP) as a co-catalyst. The molecular structures of the polymers produced were characterized and especially MALDI-ToF-MS yielded important information on the end-groups and other functional groups which are crucial for the curing chemistry of these resins. One special type of copolycarbonate in this study carried pendent vinyl groups, introduced by copolymerization of CHO and CO₂ with 4-vinylcyclohexene oxide (VCHO). This copolycarbonate was first casted from solution, after which the polymer film was successfully cured with a trithiol compound by UV- or thermally induced radical curing chemistry. These cured coatings showed a good acetone resistance (≥75 double rubs) and reversed impact toughness. A powder coating evaluation of this CHO/VCHO-based copolycarbonate showed excellent processability, high pencil hardness (6-8H), value zero in a Gitterschnitt test on aluminum, reasonable appearance in a ‘PCI-smoothness test’ (value 2–3) and good acetone resistance (≥75 double rubs). Most probably due to a too high T_g (85–104 °C) of the cured coating the reverse impact resistance was poor. A similar powder coating evaluation of a poly(ester-co-carbonate) based on CHO, PA and CO₂ showed less promising results due to poor flow properties and foaming above 140 °C.     

Synthesis and Optimization of Ethylene Trimerization Using [Bis-(2-dodecylsulfanyl-ethyl)-amine]CrCl<Subscript>3</Subscript> Catalyst

Abstract  

The bis-(2-dodecylsulfanyl-ethyl)-amine (SNS) ligand was prepared in good yield and high purity using inexpensive reagents and reacted with CrCl₃(THF)₃ at room temperature to give the corresponding SNS/CrCl₃ catalyst in high yield. An ethylene trimerization reaction at 90 °C and 23 bar ethylene, using the SNS/CrCl₃ complex activated by 700 equivalents of MAO, afforded 99.97% 1-C6. Only 0.10% PE was produced and the catalyst activity was 159283 g/g Cr/h.     

Alternating Copolymerization of Carbon Dioxide and Cyclohexene Oxide and Their Terpolymerization with Lactide Catalyzed by Zinc Complexes of N,N Ligands

For the alternating copolymerization of CO₂ and cyclohexene oxide, a variety of zinc acetate complexes with new aminoimidoacrylate ligands has been synthesized and tested as catalysts. All complexes catalyzed the reaction and structure‐activity investigations revealed that the highest activities and selectivities were reached when the ligand’s aromatic rings were 2,6‐substituted by alkyl groups of different size (isopropyl versus methyl) and when the ligand backbone embodied an electron‐withdrawing cyano group. Furthermore, these complexes catalyzed the terpolymerization of CO₂, cyclohexene oxide and lactide to give poly(cyclohexyl carbonate‐co‐lactide) and the composition of the polymer was adjustable by the monomer feed.     

Pd[tBuNH(S)NHP(O)(OiPr)2-S]2Cl2 Complex as Air- and Moisture-Stable Catalyst for Palladium Catalyzed Suzuki Cross-Coupling Reaction

A highly efficient Suzuki cross-coupling reaction between phenyl bromide and phenylboronic acid catalyzed by the palladium complex Pd[tBuNH(S)NHP(O)(OiPr)₂-S]₂Cl₂ in acetonitrile, toluene, THF or DMF has been investigated. The bases we have employed for this reaction were Na₂CO₃, K₂CO₃ or Cs₂CO₃. It was established that using DMF and K₂CO₃ at 100 °C shows excellent yields of the product at the catalyst amount of 0.1 mmol. The cross-coupling reactions of iodo- and chloro-benzene with phenylboronic acid were also investigated. The influence of the halide nature was as expected.     

Effect of H2O on Cu-based catalyst in one-step slurry phase dimethyl ether synthesis

One-step dimethyl ether (DME) synthesis in slurry phase was catalyzed by a hybrid catalyst composed of a Cu-based methanol synthesis catalyst and a γ-Al₂O₃ methanol dehydration catalyst under reaction conditions of 260 °C and 5.0 MPa. It was found that instability of the Cu-based catalyst led to rapid deactivation of the hybrid catalyst. The stability of the Cu-based catalyst under DME synthesis conditions was compared with that under methanol synthesis conditions. The results indicated that harmfulness of water, which formed in DME synthesis, caused the Cu-based catalyst to deactivate at a high rate. Surface physical analysis, elemental analysis, XRD and XPS were used to characterize the surface physical properties, components, crystal structures and surface morphologies of the Cu-based catalysts. It was found that Cu⁰ was the active component for methanol synthesis and Cu₂O might have less activity for the reaction. Compared with methanol synthesis process, crystallite size of Cu became bigger in DME synthesis process, but carbon deposition was less severe. It was also found that there was distinct metal loss of Zn and Al caused by hydrothermal leaching, impairing the stability of the catalyst. In slurry phase DME synthesis, a part of Cu transformed into Cu₂(OH)₂CO₃, causing a decrease in the number of active sites of the Cu-based catalyst. And some ZnO converted to Zn₅(OH)₆(CO₃)₂, which caused the synergistic effect between Cu and ZnO to become weaker. Crystallite size growth of Cu, carbon deposition, metal loss of Zn and Al, formation of Cu₂(OH)₂CO₃ and Zn₅(OH)₆(CO₃)₂ were important reasons for rapid deactivation of the Cu-based catalyst.     

Preparation and Characterization of the Newly Synthesized Metal‐Complexing‐Ligand N‐Methacryloylhistidine Having PHEMA Beads for Heavy Metal Removal from Aqueous Solutions

The aim of this study was to investigate in detail the performance for removal of heavy metal ions of beads composed of poly(2‐hydroxyethyl methacrylate) (pHEMA) to which N‐methacryloylhistidine (MAH) was copolymerized. The metal‐complexing ligand MAH was synthesized by using methacryloyl chloride and histidine. Spherical beads with an average size of 150–200 μm were obtained by the radical suspension polymerization of MAH and HEMA conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, p(HEMA‐MAH) beads had a specific surface area of 17.6 m²/g. The synthesized MAH monomer was characterized by NMR; p(HEMA‐MAH) beads were characterized by swelling studies, FTIR and elemental analysis. The p(HEMA‐MAH) beads with a swelling ratio of 65%, and containing 1.6 mmol MAH/g, were used in the adsorption/desorption experiments. Adsorption capacity of the beads for the selected metal ions, i. e., Cu(II), Cd(II), Cr(III), Hg(II) and Pb(II), were investigated in aqueous media containing different amounts of these ions (10–750 mg/L) and at different pH values (3.0–7.0). Adsorption equilibria were established in about 20 min. The maximum adsorption capacities of the p(HEMA‐MAH) beads were 122.7 mg/g for Cu(II), 468.8 mg/g for Cr(III), 639.4 mg/g for Cd(II), 714.1 mg/g for Pb(II) and 1 234.4 mg/g for Hg(II). pH significantly affected the adsorption capacity of MAH incorporated beads. The chelating beads can be easily regenerated by 0.1 M HNO₃ with high effectiveness. These features make p(HEMA‐MAH) beads a potential candidate for heavy metal removal at high capacity.     

Radical functionalization of poly(butylene succinate-co-adipate): Effect of cinnamic co-agents on maleic anhydride grafting

Maleic anhydride (MAH), trans cinnamic acid (AcCin) and ethyl cinnamate (EtCin) were radically graft onto poly(butylene succinate-co-adipate) (PBSA). Samples were prepared in Brabender at 175 °C by addition of increasing amounts of MAH, AcCin, EtCin and their combinations, i.e. MAH/AcCin and MAH/EtCin, setting DCP content in the 0.2-0.6 wt% range. Monomer grafting was quantitatively determined by FT-IR. MAH grafting degrees (FD_M) resulted up to 1 mol%. Conversely, AcCin grafting degrees (FD_A) were found almost negligible in all cases. EtCin was found grafted in the 0.3-1.0 mol% range when the binary system MAH/EtCin was applied. Same MAH feeds returned almost doubled MAH grafting degrees (FD_M) when AcCin was the stoichiometric co-agent, and even three times higher FD_M when EtCin was the stoichiometric co-agent. On accounts of all the collected results, a kinetic model of the investigated systems is proposed.     

Copolymerization of carbon dioxide and epoxides with a novel effective Zn–Ni double‐metal cyanide complex

A novel double‐metal cyanide complex based on Zn[Ni(CN)₄] was prepared and used as a catalyst for the copolymerizations of carbon dioxide and propylene oxide (PO) and carbon dioxide and cyclohexene oxide (CHO). The copolymers were characterized by IR and ¹H‐NMR, and the effects of temperature, pressure, solvent, and preparative methods for the catalysts on catalytic activity and composition of the copolymer were investigated. The results show that this novel catalyst exhibited its highest catalytic efficiency at about 500 g/g of Zn[Ni(CN)₄] for PO and CO₂, whereas the catalytic efficiency for CHO and CO₂ was merely between 5.6 and 22.5 g/g of Zn[Ni(CN)₄]. The molar fraction of carbonate linkages for PO–CO₂ and CHO–CO₂ copolymers reached about 0.6 and 0.3, respectively. The results show that a lower temperature and a higher CO₂ pressure were favorable for the incorporation of CO₂ into the copolymer, and the nonpolar solvents were better media for copolymerization. As a complexing agent, glycol ether exhibited better promoting effects on catalytic efficiency among those investigated, but the catalysts prepared by different complexing agents showed no significant differences in the compositions of the copolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanism of NO reduction by CO over Pt/SBA-15

The mechanism of the CO + NO reaction catalyzed by Pt/SBA-15 was studied via independent investigations of CO oxidation and NO disproportionation. Below 400 °C, both CO + O₂ and CO + NO reactions approach 100 % conversion, while the catalyst shows negligible activity for NO disproportionation. These results suggest that CO oxidation by atomic oxygen arising from NO dissociation is not a major route for CO₂ formation in the CO + NO reaction. In situ IR spectra reveal the formation of isocyanates (NCO⁻) adsorbed on silica. Their surface concentration changes with the extent of the CO + NO reaction. A mechanism is proposed in which isocyanates are reaction intermediates.