The most common way to produce biodiesel is by transesterification.
It is, in principle, an alcohol displacing another from an ester,
referred to as alcoholysis. A catalyst is usually used to raise the reaction
rate and yield. The reaction as shown in Eq. (1) is reversible and
hence an excess of alcohol is used to force the equilibrium to the
product side. The excess alcohol promotes the transesterification
and extracts products from the catalyst surface to regenerate catalytic
sites [10]. Methanol is the most frequently used alcohol
because of its low cost and its physical and chemical advantages.
Stoichiometrically, to complete transesterification, a 3:1 ratio of
alcohol to triglycerides is needed. In practice, the ratio needs to be
higher to drive the equilibrium to a maximum ester yield.
Catalysts used for transesterification may be homogeneous or
heterogeneous. Homogeneous transesterification is the easiest
method; however, it involves complexities in the separation of
product and purification steps due to the homogeneous nature of
the mixture (reactant, catalyst and product). It also tends to have
the formation of soap which demands more wash water and leads
to the formation of emulsions in the mixture. All these drawbacks
result in high production costs. Hence, heterogeneous catalysts
are preferred. Heterogeneous transesterification is a cheaper and
less problematic process. It has simpler separation process as the
catalyst is in different phase from the reactants/products and eliminates
the formation of soaps [12].When compared to non-catalytic
process, heterogeneous transesterification is easier to perform
because of the moderate temperature and pressure required in
the process. Heterogeneous catalysts also lower the environmental
impact due to the reduction in process wastes and effluents [13].
The most common way to produce biodiesel is by transesterification.It is, in principle, an alcohol displacing another from an ester,referred to as alcoholysis. A catalyst is usually used to raise the reactionrate and yield. The reaction as shown in Eq. (1) is reversible andhence an excess of alcohol is used to force the equilibrium to theproduct side. The excess alcohol promotes the transesterificationand extracts products from the catalyst surface to regenerate catalyticsites [10]. Methanol is the most frequently used alcoholbecause of its low cost and its physical and chemical advantages.Stoichiometrically, to complete transesterification, a 3:1 ratio ofalcohol to triglycerides is needed. In practice, the ratio needs to behigher to drive the equilibrium to a maximum ester yield.Catalysts used for transesterification may be homogeneous orheterogeneous. Homogeneous transesterification is the easiestmethod; however, it involves complexities in the separation ofproduct and purification steps due to the homogeneous nature ofthe mixture (reactant, catalyst and product). It also tends to havethe formation of soap which demands more wash water and leadsto the formation of emulsions in the mixture. All these drawbacksresult in high production costs. Hence, heterogeneous catalystsare preferred. Heterogeneous transesterification is a cheaper andless problematic process. It has simpler separation process as theในระยะที่แตกต่างจากผลิตภัณฑ์ reactants catalyst และกำจัดการก่อตัวของสบู่ [12] เมื่อเทียบกับไม่มีตัวเร่งปฏิกิริยากระบวนการ บริการเพิ่มคือทำง่ายอุณหภูมิปานกลางและแรงดันที่จำเป็นในกระบวนการ สิ่งที่ส่งเสริมแตกต่างกันนอกจากนี้ยังลดการสิ่งแวดล้อมผลกระทบจากการลดลงในกระบวนการเสียและ effluents [13]
การแปล กรุณารอสักครู่..