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In this study, to enhance the catalytic activity and minimize the carbon/coke formation, cerium incorporated alumina-supported new Ni–Ce–Al catalysts were investigated in dry reforming of biogas. Ni–Ce–Al catalysts were synthesized by the modified one-pot sol-gel method in an inert environment. To determine the effect of the Ce/Al ratio on physicochemical properties of catalysts and their activity, Ni (5 wt %) catalysts with different Ce/Al ratios (0/1, 1/2, 1/1, 2/1 b y wt.) were tested in a fixed-bed flow reactor using an equimolar ratio of CH4/CO2/Ar gas mixture. To explain the correlation between catalytic activity and catalyst properties, characterization studies were carried out by using N2 adsorption-desorption isotherms, XPS, XRD, SEM-EDS, TEM, ICP-OES, DRIFT, O2-TPO and TGA methods before and after activity tests. XRD analysis showed that both CeO2 and γ-Al2O3 crystalline phases with metallic Ni having different peak intensities were separately formed in all the catalysts. Among the catalysts of different Ce/Al ratios, the Ni–1Ce–1Al catalyst containing equal amounts of Al and Ce has the smallest CeO2 crystallite size. This catalyst also has the highest pore diameter and volume. XPS analysis showed that Ce incorporation into the Ni-based Al2O3 catalyst decreased the NiAl2O4 formation. DRIFT analysis indicated that the addition of ceria into the support material decreased the Lewis acidity of alumina. During 25-h long-term activity test, the conversions of CH4 and CO2 obtained with the catalyst Ni–1Ce–1Al (Ce/Al ratio is 1/1) were approximately the same and averaged 76% and 85%, respectively. This behavior of the catalyst indicates its high stability. TGA, XRD and SEM analyzes performed with the used Ni–1Ce–1Al and Ni–Al catalysts show very little carbon formation in the catalyst containing equal weights of Ce and Al compared to the catalyst without Ce. This result shows that the addition of cerium to the catalyst structure prevents carbon deposition due to its special oxygen mobility. This study showed that the crystallite size of CeO2 in the catalyst structure strongly influences preventing carbon accumulation in the dry reforming reaction.

In this study, polymeric composite material production was carried out using palm kernel, an agricultural waste, and its use as wood material was investigated. Urea-formaldehyde resin was used as a polymeric binder. The mechanical strength of the composite material and the non-flammability properties were investigated at different polymer / filler ratios (1/1, 1/2, 1/3 and 1/4). The increase in polymer ratio in the stnicture increased both mechanical strength and fire resistance. Mechanical properties of composite material with equal polymer and filler material were 6.2 MPa and Limit Oxygen Index (LOI) value of 50. It has been observed that mint fiber addition to the stnicture has been improved the strength of the material. An increase in the water absorption capacity was also observed with the increase of the filler material in the composite material. The results show that polymeric composite material prepared by using palm kernel can be an alternative to wood materials.

In this study, Ce-O catalysts were prepared by the modified complexation method and their activities were tested for selective catalytic oxidation of H2S to elementel sulfur. The calcination process, which is the last step of catalyst synthesis, was performed at different temperatures (300 degrees C, 350 degrees C, 400 degrees C ve 450 degrees C) and the effect of calcination temperature on the catalytic activity was investigated. Activity tests with the synthesized catalysts were carried out in a fixed-bed reactor system using different feed ratios of O-2/H2S at 250 degrees C. The XRD patterns of all the catalysts, calcined at different temperatures, show the formation of cerianite phase with non-stoichiometric O-2 (CeO(2-x)) in the bulk phase. The XPS analysis of the Ce-O catalyst supported this result, while most of cerium was in +4 oxidation state, + 3 oxidation state was also observed in Ce-O catalyst. Rather high elemental sulfur selectivity (>= 97%) was achieved with all Ce-O catalysts. However, Ce-O-350 catalyst which was calcined at 350 degrees C gave the longest catalytic activity with an H2S conversion of 69% in selective oxidation of H2S. The decreasing of calcination temperature of the catalysts was resulted in the increase in its catalytic activity. Catalytic activity for longer periods which was achieved with Ce-O catalyst calcined at lower temperatures was due to better oxygen mobility of the catalyst.

İnsan sağlığına ve çevreye ciddi zararlar verebilen H2S gazı, Claus prosesi ile kimya endüstrisinde geniş bir kullanım alanına sahip elementel kükürde dönüştürülmektedir. Claus prosesindeki denge sınırlamaları nedeniyle H2S gazında tam dönüşüm sağlanamaması önemli bir problemdir. H2S'ün seçici katalitik oksidasyon reaksiyonu herhangi bir denge sınırlaması olmadan elementel kükürdün elde edildiği bir reaksiyondur. Bu reaksiyonun başarısı aktivite, kararlılık ve elementel kükürde yüksek seçicilik gibi özellikleri bulunduran katalizörlerin geliştirilmesine bağlıdır. Bu çalışma kapsamında kompleksleştirme yöntemiyle TiO2, Fe2O3, eşmolar Ti-Fe, Ti-Cr ve Ti-Zr, farklı molar oranlarda (1/3 ve 3/1) Ti-Fe katalizörleriyle eşmolar Ti-Fe-Zr katalizörü sentezlenmiş ve H2S'ün elementel kükürde seçici oksidasyon reaksiyonunda aktiviteleri incelenmiştir. Katalizörlerin karakterizasyonları kapsamında azot adsorpsiyon-desorpsiyon, XRD, XPS, SEM, EDS, TPR ve piridin adsorplanmış numunelerin FTIR analizleri gerçekleştirilmiştir. Karakterize edilen katalizörler, farklı sıcaklık (200°C, 250°C ve 300°C) ve gaz karışımlarında (O2/H2S: 0–2) sabit yatak reaksiyon sisteminde FTIR cihazı yardımıyla test edilmişlerdir. Gerçekleştirilen çalışmalar sonucunda eşmolar ve farklı molar oranlarda (1/3 ve 3/1) hazırlanan Ti-Fe, seçici oksidasyon reaksiyonunda en yüksek aktiviteyi gösteren katalizörler olarak tespit edilmiştir. Eşmolar Ti-Fe ve Ti(1)-Fe(3) katalizörlerinin 200°C sıcaklık ve O2/H2S: 0,5 şartlarında gerçekleştirilen deneysel çalışmalar sonucunda % 100 H2S dönüşümü ve elementel kükürt seçiciliği sergiledikleri görülmüştür. En yüksek katalitik aktiviteyi sergileyen Ti-Fe katalizörlerinin redoks özelliği sergilediği ve asidik karakterde olduğu belirlenmiştir. Seçici katalitik oksidasyon reaksiyonunda yüksek aktivite sergileyen Ti-Fe katalizörlerinin yüksek sıcaklıklarda sorbent özellikleri incelenmiştir. Ti-Fe sorbentlerindeki demir metalinin artışının katalizörlerin kükürt tutma kapasitelerini önemli ölçüde artırdığı görülmüştür. H2S gas, which causes serious damages to the environment and human health, can be converted to elemental sulfur, which is an important raw material for the chemical industry with Claus Process. Due to the equilibrium limitations in Claus Process, complete conversion of H2S is not achieved. Selective catalytic oxidation of H2S is a single step reaction in which elemental sulfur is produced without any equilibrium limitation. The success of this reaction depends on the development of catalysts which are active, stable and have high selectivity towards elemental sulfur. In this study, TiO2, Fe2O3, equimolar Ti-Fe, Ti-Cr, Ti-Zr and Ti-Fe in different molar ratios (1/3 ve 3/1) and equimolar Ti-Fe-Zr catalysts were synthesized by complexation method and their activities were investigated for selective oxidation reaction of H2S to elemental sulfur. Catalyst characterizations such as FTIR analysis of the pyridine adsorbed samples, nitrogen adsorption-desorption, XRD, XPS, SEM, EDS, and TPR analysis were carried out. Characterized catalysts were tested in a fixed bed reaction system in different temperatures (200 °C, 250 °C and 300 °C) and using different gas mixtures (O2/H2S: 0-2) by using FTIR. As a result of this study, it was determined that the Ti-Fe catalysts showed the highest activity in the selective catalytic oxidation reaction. Experimental studies which were performed at 200 °C temperature with a feed of O2/H2S molar ratio of 0.5, it was observed that equimolar Ti-Fe and Ti(1)-Fe(3) catalysts showed 100% H2S conversion and elemental sulfur selectivity. It was determined that Ti-Fe catalysts with the highest catalytic activity have redox properties and acidic character. The sorbent properties of Ti-Fe catalysts with the highest catalytic activity in the selective catalytic oxidation reaction were investigated at high temperatures. Sulfur retention capacity of the catalyst increased with an increase in the Fe/Ti ratio. 194

The NOx gases which are released from diesel vehicles can be reduced to N-2 gas with selective catalytic reduction (SCR) reactions. The yield of these reactions are majorly related to the reducing agent. Both urea and its' decomposition/hydrolysis compounds which are isocyanic asid (HNCO) and ammonia (NH3) can be used SCR reactions. Therefore, urea is an attractive reducing agent recently. Ag/Al2O3 catalysts have an important role for NOx reduction. The decomposion and hydrolysis compounds of urea on the %1 Ag/Al2O3 and %2 Ag/Al2O3 catalysts which are prepared by sol-gel method were investigated by using FTIR. The experimental studies were carried out between 100-400 degrees C temperature in the presence of helium. As a result of the analyses of FTIR spectra, NH3, NH4+, -CNO, melamine and CO2 were dedected as the decomposition and hydrolysis compounds of urea on the catalysts. Besides that, OH, CH, NH and C=O stretching vibration bands were also observed. NH4+ compound was not observed at any temperature on the % 1 Ag/Al2O3 catalyst however, it was observed at the temperatures of 100 and 250 degrees C on the % 2 Ag/Al2O3 catalyst. Ammonia, which is a decompositon and hydrolysis compound of urea, was observed on both catalysts at all temperatures and times. Isocyanate (-CNO), which is a decompositon compound of urea, gave its most intensive peak at the temperature of 200 degrees C on %1 Ag/Al2O3 catalyst and at the temperature of 250 degrees C on %2 Ag/Al2O3 catalyst.

Taşıtlardan kaynaklanan hava kirliliğinin önemli bir kısmı dizel araçların egzozlarından salınan NOx gazlarıdır. Bu gazların çevreye zararsız N2 gazına indirgenmesi için kullanılan en etkili yöntemlerden birisi, bir indirgen madde yardımıyla katalizör yüzeyinde gerçekleştirilen seçici katalitik indirgeme (SCR) yöntemidir.Bu çalışmada NOx indirgenmesinde etkin indirgeme maddesi olan ürenin sol-gel yöntemiyle hazırlanan %1 Cu/Al2O3, %2 Cu/Al2O3, %2 Pt/Al2O3, %1 Ag/Al2O3, %2 Ag/Al2O3 ve %5 Ag/Al2O3 katalizörleri yüzeyinde bozunmasıyla meydana gelen bileşikler tespit edilmeye çalışılmıştır. Katalizörlerin kullanılmasıyla hazırlanan tabletlerin üzerine üre çözeltisi damlatılmak suretiyle 100?400°C sıcaklık aralığında FTIR cihazı kullanılarak spektrumlar alınmıştır. Deneysel çalışma sonucunda bütün katalizörlerde ürenin bozunma ve hidroliz bileşikleri olarak OH, NH, CH gerilme bantları görülmüştür. İlave olarak C=O gerilme titreşim bandı, CO2, melamin, amonyak, amonyum ve izosiyanat bileşiklerine ait pikler gözlenmiştir. Bu bileşiklerin yanı sıra üreye ait NH gerilme titreşimi, adsorplanmış ürenin NH2 gerilme titreşimlerine ait pikler de bazı katalizörlerde bozunma bileşiği olarak gözlenmiştir. Ürenin bozunma bileşiklerinden olan izosiyanat bütün katalizörde görülmekle birlikte en şiddetli pikini %2 Cu/Al2O3 katalizörü üzerinde 250°C sıcaklıkta vermiştir. En fazla sayıda bozunma bileşiği %1 Cu/Al2O3 katalizörü üzerinde 100°C sıcaklıkta alınan spektrumda elde edilmiştir.%1 Cu/Al2O3, %2 Ag/Al2O3, %2 Pt/Al2O3 katalizörlerinin maksimum NOx dönüşümü gösterdikleri sıcaklıklarda alınan spektrumlarda izosiyanat bileşiği görülmüştür. Ayrıca çalışılan katalizörlerde ve tüm sıcaklıklarda amonyak bileşiğinin oluştuğunu söylemek mümkündür. Bu katalizörlerde NOx dönüşümünün azaldığı sıcaklıklardaki spektrumlarda ise melamin pikinin şiddetinin yüksek olduğu görülmüştür. Sonuç olarak çalışılan katalizörlerde ürenin bozunması sonucunda NOx dönüşümü için önemli olan amonyak, izosiyanat ve melamin bileşikleri gözlenmiştir. The main part of the air pollution that result from vehicles is the NOx gas that is given with the diesel exhaust. One of the most effective method to reduce these gases to harmless N2 is selective catalytic reduction (SCR) method which took place on the surface of a catalyst with the help of a reducing agent.In this study, the compounds, which are formed by decomposition of the urea (the effective reducing agent in the reduction of NOx) at the surface of the %1 Cu/Al2O3, %2 Cu/Al2O3, %2 Pt/Al2O3, %1 Ag/Al2O3, %2 Ag/Al2O3 and %5 Ag/Al2O3 catalysts that were prepared by the sol-gel method, were tried to be determined. The spectrums were taken by dropping the urea solution on the catalyst tablets and by using the FTIR at temperature betweeen 100?400º C. After the experimental study, it was observed that for all catalysts; there were peaks of OH, NH, CH stretching vibration bands as urea?s decomposition and hydrolysis compounds. Additionally C=O stretching vibration band, CO2, melamine, ammonia, ammonium and isocyanate peaks were observed. It was also observed that there were peaks of NH and adsorbed urea?s NH2 stretching vibration as the decomposition compound for some catalysts. As a decomposition compound of urea, isocyanate seemed in all catalysts but it gave the strongest peak for %2 Cu/Al2O3 at 250ºC. On the spectrum for the %1 Cu/Al2O3 at 100ºC the maximum amount of the decomposition compound was observed.On the spectrums which were taken at the temperatures that the %1 Cu/Al2O3, %2 Pt/Al2O3 and %2 Ag/Al2O3 catalysts gave the maximum NOx conversion, isocyanate was observed. For all catalysts that are mentioned above, it is possible to say that at all temperatures ammonia was formed. For these catalysts, at the spectrums when the conversion of NOX is reduced, the strongest melamine peak seemed. The urea decomposition compounds which were important for NOx conversion to ammonia, isocyanate and melamin were seen on the catalsyts. 153