01998nas a2200181   4500008004100000022001400041245009600055210006900151260011000220300001400330490000700344520123700351100002501588700002501613700002301638700002801661856012701689       2013                        eng d  a1463-926200aCatalytic dehydration of lactic acid to acrylic acid using calcium hydroxyapatite catalysts0 aCatalytic dehydration of lactic acid to acrylic acid using calci  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a1211-12170 v153 a<p>A series of calcium hydroxyapatite (HAP) catalysts were synthesised with a Ca/P ratio ranging from 1.3 to 1.89 by a co-precipitation method that involved changing the pH of the calcium and phosphorous precursors. The physicochemical characterization by XRD, SEM, BET surface area and CO2 and NH3-TPD techniques confirmed the hydroxyapatite formation. These HAP catalysts were used for the vapour phase dehydration of lactic acid to acrylic acid. The HAP catalyst with a Ca/P ratio of 1.3 was found to be the most efficient catalyst among the synthesised series, which gave 100% conversion of lactic acid and 60% selectivity towards acrylic acid at 375 degrees C when a 50% (w/w) aqueous solution of lactic acid was used. The higher selectivity towards acrylic acid has been correlated to the increased acidity and reduced basicity of the HAP catalyst with a Ca/P ratio of 1.3 compared to the other HAP catalysts. The catalyst was found to be very stable and no deactivation was observed even after 300 h of reaction time. In situ FTIR studies were performed for understanding the mechanistic aspects and showed the formation of calcium lactate as an intermediate species during the dehydration of lactic acid to acrylic acid.</p>1 aGhantani, Vidhya, C.1 aLomate, Samadhan, T.1 aDongare, Mohan, K.1 aUmbarkar, Shubhangi, B.  uhttps://library.ncl.res.in/content/catalytic-dehydration-lactic-acid-acrylic-acid-using-calcium-hydroxyapatite-catalysts-002036nas a2200169   4500008004100000022001400041245013400055210006900189260011000258300001600368490000600384520127900390100002501669700002301694700002801717856012101745       2014                        eng d  a2046-206900aNonstoichiometric calcium pyrophosphate: a highly efficient and selective catalyst for dehydration of lactic acid to acrylic acid0 aNonstoichiometric calcium pyrophosphate a highly efficient and s  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUL  a33319-333260 v43 a<p>Calcium phosphate catalysts were prepared by co-precipitation method using calcium nitrate and mixtures of ammonium and different sodium phosphates as calcium and phosphate precursors, respectively. Depending on the phosphate precursor, the pH of the synthesis mixture changed during the catalyst precipitation. The catalyst characterisation by XRD and ICP revealed the formation of a calcium pyrophosphate structure with varying Ca/P ratio from 1.02 to 0.76 which could be correlated to the different pH of the synthesis solutions. Vapour phase dehydration of lactic acid to acrylic acid was carried out using these calcium pyrophosphate catalysts. Non-stoichiometric calcium pyrophosphate catalyst with Ca/P ratio 0.76 was found to be the most efficient catalyst among the synthesized series with 100% lactic acid conversion and 78% acrylic acid selectivity at 375 degrees C. The higher selectivity for acrylic acid has been correlated to the increased acidity and reduced basicity of non-stoichiometric calcium pyrophosphate compared to other stoichiometric pyrophosphates. In situ FTIR studies showed the formation of a higher amount of calcium lactate on non-stoichiometric compared to stoichiometric pyrophosphate leading to higher selectivity for acrylic acid.</p>1 aGhantani, Vidhya, C.1 aDongare, Mohan, K.1 aUmbarkar, Shubhangi, B.  uhttps://library.ncl.res.in/content/nonstoichiometric-calcium-pyrophosphate-highly-efficient-and-selective-catalyst-0