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The gas-phase deoxydehydration of 2,3-butanediol to butene was investigated in aplug flow reactor over SiO 2 -supported vanadium oxide, g-alumina, P/ZSM-5, andM gO catalysts with acid/bases ites of varying strengths. 5wt% vanadium on SiO 2 (i.e.,5V/SiO 2 )s howedt he best performance with 100 %conversion and up to 45.2 %b utene selectivity.T he combination of weak acid sites and polymericV O x surfaces peciesp rovided the 5V/SiO 2 catalystw ith bifunctional capabilities to achieve both dehydration and transfer hydrogenation, which allowed it to catalyze the deoxydehydration of 2,3-butanediol to butene even in the absence of H 2 .A s2 ,3-butanediol is ac ommon yet underutilized biomassp roduct, this reactionm ay provide av iable route for ab iomass-to-chemicals application for 2,3butanediol.Upgrading of biomass to fuels and chemicals is important for sustainable human development, and intense studiesa re being undertaken to find new technologiest oc onvert the large amount of availablebioderived oxygenates into fuels and chemicals. [1] The vicinal diol 2,3-butanediol (2,3-BDO) is ac ommon biomass product that is synthesized by using bacteria sugars derived from biomass feedstock such as corn starch. [1c] It has great potentialt or eplaces ynthetic 2,3-BDO in the market owing to its cost effectiveness relative to the chemical hydrolysis of 2,3-butene oxide. Whereas its other isomers such as 1,4-butanediola nd 1,3-butanediol have been widely studied for their conversion into other chemicals such as tetrahydrofuran and butyrolactone, [2] these cyclization reactions are not availablef or 2,3-BDO owing to the vicinal positiono fi ts OH groups.T hus, 2,3-BDO is much less studied than 1,4-and 1,3-butanediol, although it could follow multiple oxidation, reduction, and dehydration pathways. [1c,d] The dehydration of 2,3-BDO mainly produces butanone (also knowna sm ethyl ethyl ketone, MEK) and 2-methylpropanal (MPA) through aE 1/E2 mechanism followed by 1,2-rearrangement by hydride and methyl shifts, respectively. [2a] This is readily achieved on acid sites, such as those availablei np hosphate catalysts or zeolites. [3] However,t he doubled ehydration of 2,3-BDO to butadiene is more challenging than that of 1,4-butanediol because the carbonyl compounds MEK and MPAf ormed from 2,3-BDOa re more difficult to dehydrate further than enol compounds such as 3-buten-1-ol, whicha re typically formed from 1,4-butanediol. [4] Alternatively,Z heng et al. recently reported aC u/ZSM5 catalyst that could convert2 ,3-BDOi nto butene in the presence of an excess amount H 2 withoutf urther hydrogenation to butane. [5] In this study,t he gas-phase conversion of 2,3-BDO was performed over SiO 2 -supported vanadium oxide, g-alumina, P/ ZSM-5, and MgO catalysts with acid/base sites of varying strengths. We show that ad eoxydehydration pathway of 2,3-BDO to butene in the absence of H 2 exists that proceeds through ah ydrogen-donor mechanism from 2,3-BDO to MEK over vanadium oxide (VO x )s urfaces ites.The ammonia temperature-programmed d...

In the current study, we have synthesized calcium hydroxyapatite (CaHAP) from different phosphorus sources namely, NH 4 H 2 PO 4 and H 3 PO 4 . The structure of CaHAP was confirmed by XRD, FT-IR, and Raman characterization methods. The CaHAP was further modified with various anions such as WO 4 2− , SO 4 2−, and PO 4 3− with fixed content of 10 wt %. To understand the textural and structural properties, these samples were thoroughly characterized by N 2 physisorption, X-ray diffraction, Fourier transform infrared, Raman and thermogravimetry−differential thermal analysis methods. Ethanol adsorption at various temperatures was studied in detail using diffuse reflectance Fourier transform spectroscopic to unravel the formation and stability of surface species and the interaction of ethanol with CaHAP. The temperature programmed desorption of ethanol (ethanol-TPD) was performed to understand the stability, surface reactivity, and product distribution. The catalytic activity of the above catalysts was tested in ethanol conversion over a temperature range of 300−450 °C.

Nanocrystalline LaP x O y with various starting P to La ratios from 0.5 to 2.0 catalysts were prepared by a sol-gel method using cetyl trimethylammonium bromide (CTAB) as template. The catalysts were thoroughly characterized by N 2 physisorption, powder X-ray diffraction (XRD), temperature programmed desorption (TPD) of NH 3 , solid state 31 P and 1 H nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM) techniques. XRD results indicate the presence of predominantly monazite LaPO 4 with minor amounts of (B3.0 wt%) rhabdophane LaPO 4 phase in the samples with starting P/La ratios of 1.0 and 1.5. NH 3 -TPD results show an increasing trend in the total acidity with increase in P/La ratio. These catalysts were tested in the selective ethanol dehydration in the temperature range between 250 and 400°C. The catalyst activity (lmol/h/m 2 ) is increased with P/La ratio and the catalyst with highest P/La ratio of 2.0 exhibiting the highest ethanol dehydration activity. The ethanol conversion increased with reaction temperature, reaching 100% at 350°C and remains unchanged at higher temperatures. On the other hand, the ethylene selectivity is also increased up to 350°C and then decreased with further increase of reaction temperature. At a P/La ratio of 2, the CTAB templated LaP x O y catalyst showed higher catalytic activities compared to the LaP x O y by hydrothermal method without any template.