Abstract:
Increasing concern over greenhouse emission due to depletion of fossil fuels reserves urge
researchers to produce energy from renewable energy sources. The burning of conventional fossil
fuel is considered as one of the main cause of ever-increasing pollution nowadays and hence less
hazardous economic and eco-friendly source of fuel should be sought out. Biodiesel is known as a
best potential replacement for petrodiesel having major advantages like low greenhouse gas
emissions, environment-friendly, and better fuel economy are considered as of biodiesel over
petrodiesel. Biodiesel can be produced by esterification of free fatty acids or by transesterification
of triglyceride obtained from renewable biological sources, in the presence of low molecular
weight chains alcohols and suitable catalysts. Free fatty acids are carboxylic group (-COOH)
containing saturated or unsatureated aliphatic chains. To date, many homogeneous acids & base
catalysts have been reported for esterification and transesterification reactions for the production
of biodiesel. Although these catalysts possess astonishing catalytic activity for trans/esterification
reactions but few serious limitations such as saponification, reusability of catalyst, and
contamination of final products are also attached to these catalysts. These severe limitations of
homogeneous catalysts can be overcome by synthesizing the heterogeneous catalysts for biodiesel
production.
12-Tungstophosphoric acid supported over novel mesoporous silica support KIT-6 was
synthesized and characterized by different analysis techniques such as SEM, BET and FTIR. The
catalytic activity of the various synthesized catalysts was examined for the biodiesel production by
using esterification reaction of oleic acid. Influence of various synthesizing techniques such as
impregnation and sol-gel method on the catalytic activity, reaction parameters like temperature,
wt.% of catalysts with respect to FFA and oil: methanol ratio was examined. For this purpose,
supported HPW synthesised by impregnation as well as a sol-gel method with varying the
percentage of active HPW over support. Catalysts were prepared by impregnation method and
named as 10%-IM, 15%-IM, 20%-IM, 25%-IM and 30%-IM, where 10,15,20,25 and 30 are
assigned to the concentration of active HPW over support. Similarly, sol-gel synthesized catalysts
were named as 10%-SG, 15%-SG, 20%-SG, 25%-SG and 30%-SG. Sulphated KIT-6 was also
synthesized by impregnating the sulfated group over the support. Results revealed the catalytic
activity in this order: Sulfated KIT-6 > 30%-IM > 25%-SG. It also showed that increasing the
amount of catalyst during the reaction increased the product yield. Moreover, synthesized catalysts
also showed higher heterogeneity in the reaction media and can be recycled after simple
10
regeneration method. The sulfated KIT-6, 30%-IM and 25%-SG catalysts showed the good
conversion of FFA i.e 86.5%, 59.68% and 42.6% respectively even at very mild reaction
conditions.
