Hekzagonal bor nitrür destekli katalizörler varlığında dimetil eter üretimi

Öz

Hekzagonal bor nitrür (hBN), yüksek ısıl iletkenliği, elektriksel yalıtkanlığı, kimyasal ve mekanik dayanıklılığı gibi özellikleriyle son zamanlarda dikkat çeken bir malzemedir. Ayrıca, mezogözenekli yapısı sayesinde alternatif yakıt üretimi reaksiyonlarında destek malzemesi olarak kullanıma da uygundur. Çalışmanın amacı, hBN’nin alternatif yakıt üretimi reaksiyonunda katalizör destek malzemesi olarak kullanımının araştırılması ve metanolün (MeOH) dehidrasyonu ile dimetil eter (DME) üretimi çalışmalarında katalitik aktivite testlerinin gerçekleştirilmesidir. Bu amaçla, hBN yapısına farklı oranlarda (kütlece %1, 4 ve 8) silikotungstik asit (STA) emdirme yöntemiyle yüklenmiş ve malzemenin yüzey asitliği artırılmıştır. Sentezlenen katalizörler X-ışını difraktometresi (XRD), N2 adsorpsiyon/desorpsiyon (BET), endüktif olarak eşleştirilmiş plazma-optik emisyon spektrometrisi (ICP-OES), taramalı elektron mikroskobu-enerji dispersiv spektrum (SEMEDS) ve piridin-adsorplanmış numunelerin difüz yansıma kızılötesi Fourier dönüşüm spektroskopisi (DRIFTS) teknikleri ile karakterize edilmiştir. Katalizörlerin aktivite testleri ise farklı reaksiyon sıcaklıklarında (200-300 °C) ve farklı kütlece saatlik boşluk hızlarında (WHSV, 0,25-0,5 ve 1,0 saat−1) gerçekleştirilmiştir. Böylece reaksiyon sıcaklığının ve akış hızının DME seçiciliğine ve MeOH dönüşümüne etkisi incelenmiştir. Çalışma sonucunda 8STA@hBN katalizörü ile 275°C’de %100 DME seçiciliği elde edilmiştir. Katalizörlerin yapısındaki STA miktarının artmasıyla Bronsted asit siteleri arttığından hBN destekli katalizörler metanolün dehidrasyon reaksiyonunda yüksek aktivite göstermiştir. Ayrıca yüksek reaksiyon sıcaklığı da MeOH dönüşümü ile DME seçiciliğini olumlu etkilemiştir. Çalışmadan elde edilen sonuçlar, STA içerikli hBN katalizörlerinin, alternatif yakıt kaynağı olan dimetil eterin üretimi için uygun bir seçenek olabileceğini göstermiştir.

Anahtar Kelimeler

• Alternatif yakıt
• Dimetil eter
• Hekzagonal bor nitrür
• Metanol

Dimethyl ether production in the presence of hexagonal boron nitride supported catalysts

Öz

Hexagonal boron nitride (hBN) has recently attracted attention due to its properties such as high thermal conductivity, electrical insulation, and chemical and mechanical durability. Moreover, thanks to its mesoporous structure, it is also suitable for use as a support material in alternative fuel production reactions. The aim of the study is to investigate the use of Hbn as a catalyst support material in the alternative fuel production reaction and to perform catalytic activity tests in dimethyl ether (DME) production studies by dehydration of methanol (MeOH). For this purpose, silicotungstic acid (STA) was loaded into the structure of hBN at different rates (1, 4, and 8% by mass) by the impregnation method, and the surface acidity of the material was increased. The synthesised catalysts were characterised by X-ray diffraction (XRD), N2 adsorption/desorption (BET), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDS), and diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) techniques of pyridine-adsorbed samples. Activity tests of the catalysts were carried out at different reaction temperatures (200-300 °C) and different weight hourly space velocity (WHSV, 0.25-0.5 and 1.0 h−1). Thus, the effect of reaction temperature and flow rate on DME selectivity and MeOH conversion was examined. As a result of the study, 100% DME selectivity was achieved with the 8STA@hBN catalyst at 275°C. hBN supported catalysts showed high activity in the dehydration reaction of methanol, as the number of Bronsted acid sites increased with the increase in the amount of STA in the structure of the catalysts. In addition, high reaction temperature positively affected MeOH conversion and DME selectivity. The results obtained from the study showed that STA-containing hBN catalysts may be a suitable option to produce dimethyl ether, an alternative fuel source.

Anahtar Kelimeler

• Alternative fuel
• Dimethyl ether
• Hexagonal boron nitride
• Methanol

Kaynakça

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