Sodium‐based catalysts (such as Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X‐ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometry, and ambient‐pressure X‐ray photoelectron spectroscopy (AP‐XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, have been identified on the outer surfaces at temperatures of ≥800 °C, and these species are useful for various gas‐phase hydrocarbon reactions, including the selective transformation of methane to ethane.

Sodium-based catalysts (sucha sN a 2 WO 4 )w ere proposed to selectively catalyze OH radical formation from H 2 Oa nd O 2 at high temperatures.T his reaction mayp roceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature.T his study provides direct evidence of the molten salt state of Na 2 WO 4 ,which can form OH radicals,using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy( STEM), laser induced fluorescence (LIF) spectrometry,a nd ambient-pressure X-rayp hotoelectron spectroscopy(AP-XPS). As aresult, Na 2 O 2 species,which were hypothesized to be responsible for the formation of OH radicals,h ave been identified on the outer surfaces at temperatures of ! 800 8 8C, and these species are useful for various gasphase hydrocarbon reactions,i ncluding the selective transformation of methane to ethane.Gas-phase radical chemistry involving OH radicals plays acrucial role in the oxidative coupling of methane (OCM), [1] the dehydrogenation of ethane, [2] atmospheric chemistry, [3] and combustion reactions.[4] Thec atalytic generation of OH radicals from O 2 and H 2 Oc an occur on Pt metal and alkali earth oxides at high temperatures (> 700 8 8C).[5] Alkaline metal containing catalysts (that is,N as upported on oxide) enhanced the rate of H 2 Oactivation in the presence of O 2 and enhanced both the CH 4 conversion rate and C 2 selectivity during OCM.[1] Otsuka et al. demonstrated that Na 2 O 2 reacts with CH 4 to form methyl radicals at relatively low temperatures.[6] Recently,k inetic evidence suggests that H 2 Oi s involved in the activation of CH 4 via the quasi-equilibrated formation of OH radicals when aN a-containing catalyst is used.[1] In as imilar context, an in situ Raman spectroscopic study identified Ba species on MgO that formed peroxide ions and was proposed as the active sites.[7] However,d irect evidence of the formation of this sodium peroxide species and an OH radical product are lacking. Here,i nsitu studies performed at high temperatures using different in situ characterization techniques were performed to identify the authentic active species during catalysis responsible for the OCM reaction. We report evidence for the formation of Na 2 O 2 and OH radicals during the catalysis,and these species play asignificant role in high-temperature gas-phase chemistry.Ad etailed kinetic investigation that was focused on the effects of H 2 Oo nt he CH 4 /O 2 reaction was reported in our previous studies.[1] Briefly,the kinetic expression for the CH 4 / O 2 reaction on Na-based catalysts at low conversion levels is given in (1):Thef irst term corresponds to CH 4 activation via surface O (O*), which is quasi-equilibrated with gas-phase O 2 (dry condition). Thes econd term corresponds to CH 4 activation via an OH radical that is formed from O 2 and H 2 Oi nq uasiequilibrated steps (wet condition). Among the studied catalysts,t he Na 2 WO 4 /SiO 2 catalyst exhibited the highest contributi...

Sickle cell disease (SCD) is a group of inherited disorders of hemoglobin synthesis. It is prevalent in different parts of the world, including the Kingdom of Saudi Arabia. The disease is associated with multiple acute and chronic life-threatening complications. Hydroxyurea (HU) is an effective preventive medication; its use has resulted in decreased morbidity and mortality. However, practice variability, including underutilization of HU, has been reported. No local publication has addressed this issue. The aim of this work is to consider the pattern of HU prescription for SCD patients. This is a retrospective study included patients seen in the outpatient clinics in a central hospital. Cases of medications unavailability or patient refusal to take the drug were not included. A total of 152 patients were included, of them 118 were prescribed HU and 34 were not. In 133 (87.5%) patients, the physician’s decision was appropriate. Inappropriate decisions including both under prescription and, to much lesser extent, over utilization had been demonstrated in 19 (12.5%) cases. Impact of raising the healthcare providers’ awareness and improving compliance with the updated SCD management recommendations and guidelines deserve further studying. In our local experience, although the majority of HU prescriptions were appropriate, both under prescription and to a lesser extent, overutilization was demonstrated.

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