Selective oxidation of n-butane to maleic anhydride under oxygen-deficient conditions over V-P-O mixed oxides

The selective oxidation of n-butane to maleic anhydride over V-P-O mixed oxides was studied under oxygen deficient conditions. The mixed oxides were prepared with P/V atomic ratios ranging from 0.7 to 1.0. Catalysts with P/V <1.0 did not show any selectivity to maleic anhydride formation, regardless of whether or not (VO)2P2O7 was present. For catalysts with P/V = 1.0, containing (VO)2P2O7 and/or the so-called. β-phase, the selectivity was strongly influenced by the actual surface V5+/V4+ ratio. This ratio is determined by the temperature, the crystal phases present in the catalyst and the composition of the gas mixture. Optimal selectivity was obtained at 425°C with 15% butane in air and a butane/oxygen ratio of 0.9

О проблемах технического сервиса машин в растениеводческой отрасли

Одним из главных направлений в сохранении и повышении качества производимой продукции является своевременное и качественное техническое и технологическое обслуживание машин и оборудования, используемых во всех отраслях сельского хозяйства. Повышение темпов роста, уровня механизации работ в растениеводстве, требует внедрения новой, более производительной и надежной техники, что невозможно без надлежащей организации их технического обслуживания, ремонта и диагностики, усовершенствования материально- технической базы. Поэтому в снижении объема ремонта, а значит и расхода запасных частей, большую роль может сыграть техническое диагностирование, которое позволит определить действительные потребности машины в ремонте. Оne of the main directions in preservation and improvement of quality of the made production is timely and high-quality technical and technological service of the cars and the equipment used in all branches of agriculture. Increasing the rate of growth of the level of mechanization of works in crop production requires the introduction of new, more productive and reliable equipment, which is impossible without proper organization of their maintenance, repair and diagnosis, improvement of material and technical base. Therefore, in reducing the amount of repair, and hence the consumption of spare parts, a big role can play a technical diagnosis, which will determine the actual needs of the machine in the repair

Vanadium-phosphorous-oxygen industrial catalysts for C4 hydrocarbon selective oxidation to maleic anhydride

The selective oxidation of n-butane to maleic anhydride by vanadium-phosphorus-oxygen (V-P-O) industrial catalysts varying in P-to-V ratio has been studied. V-P-O catalysts have been synthesized, characterized, and the reactivity of these catalysts has been studied in a fixed bed integral reactor system. Catalyst characterization studies including X-ray diffraction, laser Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, and BET surface area measurements were used. A strong effect of P-to-V synthesis ratio on catalyst structure, catalyst morphology, vanadium oxidation state, and reactivity in n-butane selective oxidation was observed. A slight excess of catalyst phosphorus (P/V = 1.1 catalyst) was found to stabilize an active and selective (VO)(,2)P(,2)O(,7) phase. The mechanism of n-butane selective oxidation to maleic anhydride was studied by in situ infrared spectroscopy using n-butane, 1-butene, 1,3-butadiene, crotyl alcohol, maleic acid, crotonic acid, and maleic anhydride feeds. During paraffin selective oxidation, highly reactive olefin species and maleic acid were observed on the surfaces of V-P-O catalysts. Further evidence in support of conjugated or possibly strained olefin and maleic acid reaction intermediates in n-butane and 1-butene partial oxidation to maleic anhydride was gathered

Advanced Materials Center, Battelle

The goal of the Mixed Oxide Program is to determine the results obtained by using microgravity processing on a commercially significant catalyst - V-P-O System. The topics are presented in viewgraph form and include the following: (1) reasons for using microgravity; (2) the synthesis process; (3) novel results of the earth based program; and (4) Dupont interests

Characterisation of vanadium-based oxidation catalysts

Three main research objectives form the basis of the work described in this thesis: i) preparation of highly active and selective supported V-P-O catalysts for the selective oxidation of n-butane to maleic anhydride; ii) characterisation of the structure of the supported V-P-O catalysts and determination of the nature of the active sites and iii) determination of the mechanism of the oxidation reaction. This final chapter deals with a summary of the results described in the preceding chapters of this thesis. Suggestions for further research in this field will be proposed

Synthesis and Characterisation of Vanadium Phosphorous Oxide Catalysts

The V/P/O catalysts were prepared by using (a) organic method (VPO); (b) via dihydrate phase (VPD) and (c) aqueous method (VPA). The effect of calcination time, preparation method and addition of metal cations as dopants to the physico-chemical properties were studied using nitrogen physisorption measurements, scanning electron microscopy (SEM), X-ray diffraction, inductively coupled plasma (ICP) spectroscopy, redox titration, temperature programmed desorption (TPD) and temperature programmed reduction (TPR). Surface areas of these mesoporous vanadium phosphorous oxides were apparently influenced by the length of calcination time, preparation method and incorporation of metal cations. The changes of surface areas were related to the changes of surface and bulk morphologies as evidenced by SEM. X-ray diffraction revealed that while all of the VIP10 were consisted of predominantly v4+p hase of (V0)2P207,m inority v5+p hase which resumed many crystalline forms made up the remaining portion. Addition of metal cations to the basic matrix resulted in slight loss of crystallinity for V/P/O by VPO method but a huge effect to VIP10 by VPD method which also accompanied by a marked increase in lattice strains. Average oxidation state of vanadium (determined by redox titration) can be altered by (i) increase time of calcinations, (ii) predisposed by the preparation method and (iii) incorporation of metal cations. The persistently lowering of the amount of oxygen atoms that were available thermally until stabilisation at around half a monolayer suggests that the catalytic activity, and hence the conversion of hydrocarbon is stabilised after 100 h. From the extra peak that appeared at higher temperature during TPR by HZ for VIP10 calcined for longer duration, it was postulated that the selective nature of equilibrated VPIO is originated from these oxygen atoms. Based on the above argument, it was suggested that the VPD type of preparation would result in VPIO with more active and selective nature than VPO and VPA. The addition of metal cations to bulk VPO was shown to increase the activity in the order of Zn > VPO (bulk) > Cr > Co and selectivity in the order of Co > Cr > Zn > VPO (bulk). While for VPD the activity and selectivity will be in the order of Co > VPD (bulk) > Cr > Zn and Zn > Cr > VPD (bulk) = Co, respectivel

Magnetic interactions and high-field properties of Ag(2)VOP(2)O(7): frustrated alternating chain close to the dimer limit

We report on high-field magnetic properties of the silver vanadium phosphate Ag(2)VOP(2)O(7). This compound has a layered crystal structure, but the specific topology of the V-P-O framework gives rise to a one-dimensional spin system, a frustrated alternating chain. Low-field magnetization measurements and band structure calculations show that Ag(2)VOP(2)O(7) is close to the dimer limit with the largest nearest-neighbor interaction of about 30 K. High-field magnetization data reveal the critical fields \mu_0H_{c1} of about 23 T (closing of the spin gap) and \mu_0H_{c2} of about 30 T (saturation by full alignment of the magnetic moments). From H_{c1} to H_{c2} the magnetization increases sharply similar to the system of isolated dimers. Thus, the magnetic frustration in Ag(2)VOP(2)O(7) bears little influence on the high-field properties of this compound.Comment: 4 pages, 2 figures. A paper for the proceedings of the HFM 2008 conferenc

1-Butanol dehydration and oxidation over vanadium phosphate catalysts

The transformation of 1-butanol into either butenes or maleic anhydride was carried out both with and without oxygen, using V/P/O catalysts. With vanadyl pyrophosphate prepared by coprecipitation, at temperature lower than 240 ◦C and without oxygen, selectivity to butenes was higher than 90%, but a slow deactivation took place. At temperature higher than 300 ◦C and in the presence of air, maleic and phthalic anhydrides were the prevailing products, with selectivity of 60% and 14%, respectively. Catalytic performance was affected by crystallinity and acidity. αI-VOPO4 showed a poor performance in the absence of air, with a quick deactivation due to coke accumulation; but it displayed an excellent selectivity to butenes (close to 98%) at temperatures lower than 320 ◦C in the presence of air, with stable performance. At temperature higher than 360 ◦C, α I-VOPO4 was reduced to vanadyl pyrophosphate and catalyzed the direct oxidation of 1-butanol into maleic anhydride, but with 35% selectivit

Optical, physical and structural studies of vanadium doped P 2O5-BaO-Li2O glasses

Glasses in the compositions (Li2O)25–(BaO)25–(P2O5)50−x–(V2O5)x (with x=0.5,1.0,1.5,2.0,2.5, and 3.0 mol%) have been prepared by the conventional melt quenching technique. X-ray powder diffractrogram show broad peaks which conforms glassy nature of the sample. Differential scanning calorimetry (DSC) thermograms show characteristic glass transition temperature (Tg) and it increases with increasing substitution of V2O5 for P2O5. The measured physical parameters like density, refractive index, ionic concentration and electronic polarizability are found to vary linearly with increasing x. Infrared spectra exhibits few bands, which are attributed to (P=O)AS, (P=O)S, (V=O), (P–O–P)AS,P–O–V, (P–O–P)AS and O–P–O vibrations. The optical absorption spectra of VO2+ ions in these glasses show three bands and are assigned to the 2B2→ 2E,2B2→ 2B1 and 2B2→ 2A1 transitions. Electron paramagnetic resonance spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of Spin-Hamiltonian parameters indicate that the VO2+ ions are present in octahedral sites with tetragonal compression and belong to C4V symmetry