Sena Yasyerli

Breakthrough Analysis OF H 2 S removal on CU-V-MO, CU-V, and CU-MO mixed oxides

Kinetic studies carried out for the sorption of H 2 S in the presence and absence of hydrogen on Cu-V-Mo, Cu-V, and Cu-Mo mixed oxides gave detailed information about the reaction sequences. Formation of SO 2 even in the presence of hydrogen at the initial stages of the sorption process showed the partial reduction of the metal oxides prior to the sulfidation step. A sorption experiment carried out with Cu-Mo mixed oxide gave incomplete sulfidation of molybdenum, whereas with Cu-V mixed oxide complete sulfidation was obtained. Predictions of the breakthrough curves by the deactivation model showed good agreement with the experimental results.

Kinetics of H2S Sorption on Manganese Oxide and Mn-Fe-Cu Mixed Oxide Prepared by the Complexation Technique

Hydrogen sulfide sorption activities of manganese oxide and Mn-Fe-Cu mixed oxide sorbents were examined in a fixed bed reactor. Sulfur retention capacity of Mn-O sorbent was found to be quite high at 600 °C both in the absence and presence of hydrogen gas (0.17 and 0.14 g S/g sorbent, respectively). This sorbent has a high porosity and a relatively high surface area. Best regeneration temperature of this sorbent was found as 700 °C, with a gas stream containing 6% oxygen in nitrogen. Mn-Fe-Cu mixed oxide sorbent had a lower sulfur retention capacity (0.07 g S/g sorbent). However, both of these sorbents gave quite high initial sorption rate constants, resulting very sharp breakthrough curves. Deactivation model was shown to give good agreement with the experimental H2S breakthrough curves.

The Catalytic Performance of Sol-Gel Alumina Supported Ti-Ce Catalysts for H2S Selective Oxidation to Elemental Sulfur

Abstract In this study, alumina supported Ti-Ce catalysts (10 % by weight and Ti/Ce molar ratio is 4:1) were prepared by using wet impregnation method and their catalytic activities were tested in H2S selective oxidation to elemental sulfur. The support alumina was synthesized by classical (SGC) and modified (SGM) sol-gel methods. The N2 adsorption-desorption, XRD, XPS, EDS and FTIR techniques were used to characterize the synthesized catalysts. The N2 adsorption-desorption isotherms showed that both catalysts have mesoporous structure. Only γ-Al2O3 crystalline phase together with amorphous structure were observed in the XRD patterns. The pyridine adsorbed FTIR analyzes showed that 10 %Ti-Ce@SGC and 10 %Ti-Ce@SGM catalysts have the same Lewis acidity. The activity tests were carried out at 250 °C and with a stoichiometric feed ratio of O2 to H2S being 0.5 for two different reaction times as 150 and 510 min. Complete conversion of H2S was obtained during 180 min. and 330 min. of reaction time over 10 %Ti-Ce@SGC and 10 %Ti-Ce@SGM, respectively. However, all catalysts showed very high sulfur selectivity. Sulfur deposition was detected over 10 %Ti-Ce@SGC catalyst both 150 and 510 min. of reaction time while it was observed after 510 min. of durability test over 10 %Ti-Ce@SGM catalyst. This can be the reason for the earlier loss of catalytic activity 10 %Ti-Ce@SGC than 10 %Ti-Ce@SGM.

H2S’ÜN SEÇİCİ KATALİTİK OKSİDASYONU İLE ELEMENTEL KÜKÜRT ELDESİNDE Ce-O KATALİZÖRLERİ

DOI: Bu çalışmada, modifiye edilmiş kompleksleştirme yöntemi ile Ce-O katalizörleri hazırlanmış ve seçici katalitik oksidasyon ile elementel kükürt eldesindeki aktiviteleri araştırılmıştır. Katalizör sentezinin son basamağı olan kalsinasyon işlemi farklı sıcaklıklarda (300oC, 350oC, 400oC ve 450oC) gerçekleştirilerek kalsinasyon sıcaklığının katalitik aktiviteye etkisi incelenmiştir. Hazırlanan katalizörlerle aktivite testleri 250°C sıcaklık ve farklı O2/H2S oranlarında sabit-yatak reaktör sisteminde gerçekleştirilmiştir. Farklı sıcaklıklarda kalsine edilen bütün katalizörlerin XRD desenlerinde yığın fazın “cerianite” kristal yapısında ve stokiyometrik olmayan oranda O2 bulundurduğu (CeO2-x) gözlenmiştir. Ce-O katalizörlerinin XPS analizi bu sonucu desteklemiş, katalizör yüzeyinde seryumun çoğunlukla +4 ve beraberinde +3 değerlikte bulunduğunu göstermiştir. Bütün Ce-O katalizörleri ile oldukça yüksek elementel kükürt seçiciliği (≥%97) elde edilmiştir. Bununla beraber, H2S seçici oksidasyonunda en uzun süre aktiviteyi (%69 H2S dönüşümü) 350oC’da kalsine edilen Ce-O–350 katalizörü göstermiştir. Katalizörlerin kalsinasyon sıcaklığının düşmesi katalitik aktivitede yükselme ile sonuçlanmıştır. Kalsinasyon sıcaklığının düşmesi Ce-O katalizöründe oksijen hareketliliğini olumlu etkileyerek daha uzun süre katalitik aktivite göstermesine neden olmuştur. 10.17341/gazimmfd.337632