Nature and mode of addition of phosphate precursor in the synthesis of aluminum phosphate and its influence on methanol dehydration to dimethyl ether

Copper Phosphinate Complexes as Molecular Precursors for Ethanol Dehydrogenation Catalysts

Nowadays, the production of acetaldehyde heavily relies on the petroleum industry. Developing new catalysts for the ethanol dehydrogenation process that could sustainably substitute current acetaldehyde production methods is highly desired. Among the ethanol dehydrogenation catalysts, copper-based materials have been intensively studied. Unfortunately, the Cu-based catalysts suffer from sintering and coking, which lead to rapid deactivation with time-on-stream. Phosphorus doping has been demonstrated to diminish coking in methanol dehydrogenation, fluid catalytic cracking, and ethanol-to-olefin reactions. This work reports a pioneering application of the well-characterized copper phosphinate complexes as molecular precursors for copper-based ethanol dehydrogenation catalysts enriched with phosphate groups (Cu-phosphate/SiO2). Three new catalysts (CuP-1, CuP-2, and CuP-3), prepared by the deposition of complexes {Cu(SAAP)}n (1), [Cu6(BSAAP)6] (2), and [Cu3(NAAP)3] (3) on the surface of commercial SiO2, calcination at 500 °C, and reduction in the stream of the forming gas 5% H2/N2 at 400 °C, exhibited unusual properties. First, the catalysts showed a rapid increase in catalytic activity. After reaching the maximum conversion, the catalyst started to deactivate. The unusual behavior could be explained by the presence of the phosphate phase, which made Cu2+ reduction more difficult. The phosphorus content gradually decreased during time-on-stream, copper was reduced, and the activity increased. The deactivation of the catalyst could be related to the copper diffusion processes. The most active CuP-1 catalyst reaches a maximum of 73% ethanol conversion and over 98% acetaldehyde selectivity at 325 °C and WHSV = 2.37 h-1.

Pretreatment by recyclable Fe3O4@Mg/Al-CO3-LDH magnetic nano-adsorbent to dephosphorize for the determination of trace F- and Cl- in phosphorus-rich solutions

The magnetic nano-adsorbent Fe3O4@Mg/Al-CO3-LDH (Mg/Al-type layered double hydroxide) with a CO3 2- interlayer anion has been synthesized successfully on Fe3O4 nanoparticles via a urea hydrothermal method. It is confirmed that the nano-adsorbent can adsorb PO4 3- rapidly and efficiently in multi-ion solutions; meanwhile, it did not adsorb any F- and Cl-, even with a high amount of the nano-adsorbent or a longer adsorption time. This behaviour is beneficial for applications to remove PO4 3- in phosphorus-rich solutions, and especially can be utilized to determine trace F- and Cl- anions in phosphorus-rich solutions by physical and chemical analysis methods including ion chromatography without serious interference from PO4 3- for trace determinations. Herein, the hydrothermally synthesized Fe3O4@Mg/Al-CO3-LDH was characterized via SEM, TEM, SAED, XRD, FTIR, magnetic hysteresis loop analysis and adsorption-desorption isotherm analysis. The structure and stability, adsorption mechanism, magnetic saturation value, specific surface area, total pore volume, phosphate adsorption capacity and recyclability are discussed. Using the optimized pretreatment conditions, Fe3O4@Mg/Al-CO3-LDH was utilized successfully to adsorb PO4 3- in real samples and determine trace F- and Cl- accurately by ion chromatography; this would be very beneficial for continuous analysis and on-line tests by physical and chemical analysis methods without interference from PO4 3- in phosphorus-rich samples, leaving F- and Cl- even if in a trace content.

Catalytic performance of Pt/AlPO4catalysts for selective hydrogenolysis of glycerol to 1,3-propanediol in the vapour phase

Glycerol hydrogenolysis to 1,3-propanediol over Pt/AlPO₄catalysts.

Effects of Microwave and Ultrasonic-Assisted Aging on the Synthesis of H-ZSM-5 Nanozeolite and Its Catalytic Performance in Methanol Dehydration

H-ZSM-5 nanozeolite was hydrothermally synthesized under static conditions. Evaluation of hydrothermal synthesis of ZSM-5 was performed by treating the synthesis mixture using different aging processes, consist of ultrasonic, stirring, and microwave-assisted aging, prior to the conventional hydrothermal treatment. The catalytic performances of selected catalysts were studied for the dehydration of methanol to dimethyl ether (DME) in a fixed-bed reactor under the same operating conditions (T = 300°C, P = 1 atm, and WHSV = 26 h−1). The prepared samples were characterized by XRD, SEM, BET, NH3-TPD and FT-IR techniques. The results showed that ultrasonic and microwave-assisted aging shortened the crystallization time and reduced crystal size of the obtained products without having any considerable effects on their catalytic activities.

Removal of boron from wastewater by the hydroxyapatite formation reaction using acceleration effect of ammonia

The mechanism was discussed for the removal of boron by the hydroxyapatite (HAp) formation reaction using Ca(OH)(2) and (NH(4))(2)HPO(4) in room temperature. Time required to remove boron was 20 min by adding Ca(OH)(2) and (NH(4))(2)HPO(4) for the remaining boron to below 1mg/L. The removal rate of boron was controlled by the HAp precipitate formation and the presence of ammonia. From the XRD patterns and SEM images, HAp could be confirmed in the precipitate product. The reaction between borate ions and calcium hydroxide was accelerated by dehydration with ammonia; the borate-calcium hydroxide compound coprecipitated with resulting HAp. Although the removal of boron decreased in the presence of sulfate, phosphate, and aluminum, these effects could be prevented by adding excess Ca(OH)(2). Interference of fluoride ions was eliminated by adding Al(3+). Sodium alpha-olefin sulfonate was the most effective coagulant for HAp precipitation. The proposed boron removal method has several advantages about treating time and ability of boron removal. The method was successfully applied to the real hot spring wastewater.

A CuZnAl-Based Hybrid Material for the Direct Synthesis of Dimethyl Ether from Syngas

A CuZnAl-based hybrid material was prepared by co-precipitation impregnation method using the active components of methanol synthesis material and pseudo-boehmite as the precursors. The as-prepared material was evaluated for the direct synthesis of dimethyl ether (DME) from syngas in a pressurized continuous flow fixed-bed reactor system. It was revealed that the hybrid material showed high activity and selectivity after an induced period, i.e. the CO conversion and DME selectivity reached as high as 81% and 67%, respectively. Moreover, it was observed that there was only slight carbon which could be eliminated rather than graphite carbon deposited on the material after run for 150 h, indicating its good stability for the direct synthesis process .