BaF(p-BDC)0.5 as the Catalyst Precursor for the Catalytic Dehydrochlorination of 1-Chloro-1,1-Difluoroethane to Vinylidene Fluoride

A BaF(p-BDC)0.5 catalyst was prepared by solid state reaction at room temperature with Ba(OH)2 as precursor, NH4F as F source, and H2(p-BDC) as organic ligand. The calcined samples were used as catalysts for dehydrochlorination of 1-chloro-1,1-difluoroethane to generate vinylidene fluoride (VDF) at 350 °C. Commercial production of VDF is carried out at 600–700 °C. Clearly, pyrolysis of the BaF(p-BDC)0.5 catalyst provided a promising way to prepare VDF at low temperatures. Prior to calcination, the activity of the BaF(p-BDC)0.5 catalyst was low. Following calcination at high temperatures, BaF(p-BDC)0.5 decomposed to BaF2 and BaCO3, and then the catalyst was chlorinated and fluorinated to BaClF, which showed high activity and stable VDF selectivity for dehydrochlorination of 1-Chloro-1,1-Difluoroethane to VDF.

MgF2-Modified Hydrotalcite-Derived Composites Supported Pt-In Catalysts for Isobutane Direct Dehydrogenation

Here, a simple method was developed to prepare an MgF2-modified hydrotalcite-derived composite, which was used as support for the Pt-In catalyst for isobutane direct dehydrogenation. The catalysts, composites, and their precursors were characterized by numerous characterization techniques. The results provided evidence for the MgF2 promoter effect on the physical–chemical properties and dehydrogenation performance of the supported Pt-In catalysts. The catalyst with MgF2 shows exceptional isobutene selectivity that can be stabilized at 95%, and the conversion increases from 50% to 58% during the reaction process. Moreover, the existence of MgF2 plays an important role in the resistance to coke formation and Pt sintering by improving the Pt dispersion, inhibiting the reduction of the In3+ species, and adjusting the acidity of the catalyst.

Facile Preparation of BaClxFy for the Catalytic Dehydrochlorination of 1-Chloro-1,1-Difluoroethane to Vinylidene Fluoride

BaClxFy as well as BaF2 and BaClF catalysts were prepared by solid-state reaction at room temperature with Ba(OH)2 as the precursor and NH4F/NH4Cl as the F and Cl sources. The catalysts were applied for the dehydrochlorination of 1-chloro-1,1-difluoroethane to vinylidene fluoride at 350 °C. The industrial manufacture of vinylidene fluoride (VDF) is carried out at 600–700 °C, whereas the BaClxFy catalysts provided a promising pathway to produce VDF at much lower temperatures. Unfortunately, the selectivity of VDF over BaF2 decreased from 94% to 84% along with the deactivation of the BaF2 catalyst monotonically. In the presence of small amounts of Cl in BaF2, stabilized selectivity was achieved. Over BaCl0.05F0.95, BaCl0.1F0.9 and BaCl0.25F0.75, no decrease in VDF selectivity was observed. Clearly, the presence of small amounts Cl during solid-state preparation inhibited the growth of BaF2 crystalline significantly. Far smaller particles were achieved. The particle size, or more precisely, the crystal size of the barium catalyst played a major role in the catalytic performance. In addition to the crystal growth, the presence of small amounts of Cl during catalyst preparation changed the chemical state of Ba, and therefore the adsorption and activation of the C–Cl bond for HCFC-142b were altered.

Selectivity Dependence of 1,1-Difluoro-1-Chloroethane Dehydrohalogenation on the Metal–Support Interaction over SrF2 Catalyst

SrF2 promotes the dehydrochlorination (DeHCl) of 1,1-difluoro-1-chloroethane, which is the key process for the manufacture of VDF (vinylidene fluoride), one of the most typical fluorinated monomers. However, the selectivity is low as dehydrofluorination (DeHF) to VCF (vinylidene chlorofluoride) competes with the formation of VDF. In this study, SrF2@C (SrF2 embedded in carbon) and SrF2@NC (N-doped carbon) catalysts were fabricated following calcination in N2 with SrC2O4, PVDF (poly vinylidene fluoride) and urea as the precursors. The catalysts were characterized by XRD, SEM, TEM, and XPS. The results show that both the calcination temperature and N-doping play an important role in the conversion of HCFC-142b and the selectivity to VDF and VCF. Calcination at elevated temperatures enhances the Sr-C interaction. For SrF2@C, improved interaction facilitates withdrawing electrons from Sr by the carbon support. By contrast, the strong interaction of Sr with N-doped carbon supply electrons from N species to Sr. The electron deficiency of Sr is favorable for the adsorption of F with higher electronegativity and consequently, DeHF reaction forming VCF. The supply of electrons to Sr by the support improves the formation of VDF (DeHCl). The present work provides a potential strategy for the improvement of selectivity to the target product.

Gravity-driven catalytic nanofibrous membrane with microsphere and nanofiber coordinated structure for ultrafast continuous reduction of 4-nitrophenol

Silver loaded nanofibrous membrane with high catalytic performance for 4-nitrophenol under continuous gravity-driven filtration was developed in this study. A polydopamine (PDA) microsphere and nanofiber coordinated composite structure was fabricated through an in situ PDA synthesis to achieve a high catalyst loading and controllable residence time of 4-nitrophenol. The incorporated PDA microspheres played an important role for the enhancement of catalytic performance due to the increased surface area (23% increase compared with PAN and PAN-PDAs-Ag) and reduced membrane porosity. Silver loading amount and the residence time of 4-nitrophenol was increased by more than 108% (from 1.2 wt% to 2.5 wt%) and 45% (from 0.79 s to 1.15 s) when comparing with PAN-PDAc-Ag and PAN-PDAs-Ag nanofibrous membrane. The conversion rate of 4-nitrophenol in a gravity-driven filtration process was as high as 97% when PAN-PDAs-Ag nanofibrous membrane was used, which was much higher than the PAN-PDAc-Ag membrane (80%). In addition, the PAN-PDAs-Ag nanofibrous membrane exhibited excellent recycle performance, the conversion rate was maintained as high as 93% after five times of reuse. The microsphere and nanofiber coordinated structure with enhanced surface area and controllable residence time of contaminants proposed in this study might advance the real applications of electrospun nanofibrous membrane for catalytic removal of contaminants.

Solution Combustion Synthesis of Cr₂O₃ Nanoparticles and the Catalytic Performance for Dehydrofluorination of 1,1,1,3,3-Pentafluoropropane to 1,3,3,3-Tetrafluoropropene

Cr₂O₃ nanoparticles were prepared by solution combustion synthesis (SCS) with chromium nitrate as the precursor and glycine as the fuel. Commercial Cr₂O₃ and Cr₂O₃ prepared by a precipitation method were also included for comparison. The morphology, structure, acidity and particle size of fresh and spent Cr₂O₃ catalysts were investigated by techniques such as XRD, SEM, TEM, BET and NH₃-TPD. In addition, catalytic performance was evaluated for the dehydrofluorination of 1,1,1,3,3-pentafluoropropane (CF₃CH₂CHF₂, HFC-245fa) to 1,3,3,3-tetra-fluoropropene (CF₃CH=CHF, HFO-1234ze). The catalytic reaction rate of Cr₂O₃ prepared by SCS method is as high as 6 mmol/h/g, which is about 1.5 times and 2 times higher than that of precipitated Cr₂O₃ and commercial Cr₂O₃, respectively. The selectivity to HFO-1234ze for all the catalysts maintains at about 80%. Compared with commercial and precipitated Cr₂O₃, Cr₂O₃-SCS prepared by SCS possesses higher specific surface area and acid amount. Furthermore, significant change in the crystal size of Cr₂O₃ prepared by SCS after reaction was not detected, indicating high resistance to sintering.

Synergistic catalysis of carbon-partitioned LaF3–BaF2 composites for the coupling of CH4 with CHF3 to VDF

Catalytic coupling of CH₄ with potent greenhouse gas CHF₃ to vinylidene fluoride (VDF) was investigated over composite catalysts.

EDTA-assisted hydrothermal synthesis of cubic SrF2 particles and their catalytic performance for the pyrolysis of 1-chloro-1,1-difluoroethane to vinylidene fluoride

Uniform, free-standing and cubic SrF₂ microparticles were fabricated by a facile hydrothermal method with EDTA as the chelating agent.

Fe/hollow nano-MgF2: a green and highly-efficient alternative to classical Cr-based catalysts for the gas-phase fluorination reaction

A green Cr-free catalyst, Fe/hollow nano-MgF₂, was developed for the formation of HFOs via gas-phase fluorination with HF.