Page 259 - Biofuels Refining and Performance

238 Chapter Eight

the gasoline portion in the liquid product increased. Considering
propenes, butanes, and i-butenes as gasoline potentials, low rapeseed
oil portions in the FCC feed seem to result in an optimum yield of gaso-
line plus gasoline potentials. Most interestingly, the gasoline fraction
recovered from a 500-h bench scale run using a feed with 30% rapeseed
oil proved suitable for standardized gasoline blending. Calcium con-
centration c(Ca) > 2 ppm gradually decreases FCC catalyst activity.
Oxygen contained in the vegetable oil was mainly converted to water.
Moreover, traces of phenols and carboxylic acid were detected in the
liquid reaction product.

MAT with animal fat. In a laboratory scale, mixtures of vacuum gas oil
and up to 15% of animal fat were converted in a Micro-Activity Test
(MAT) unit [37]. Results are given in Figs. 8.16 and 8.17. Two aspects
are of special interest. First, yields of propene and butene increase with
animal fat as a co-substrate. This is an advantageous finding as C-3 and
C-4 are gasoline potentials. C-3 and C-4 liquefied petroleum gas can be
used for the manufacture of isoparaffins for motor gasoline through
alkylation and polymerization processes.
Second, a higher yield of gasoline fraction is observed. This is a con-
sequence of the high hydrogen:carbon ratio of about 2 and the low het-
eroatom content. For this reason, biomaterials with a hydrocarbon-like
structure are particularly interesting candidates for conversion to low-
molecular-weight fuels or chemical raw materials. Problems to be inves-
tigated are possible calcium and phosphate deposits on the catalyst
particles which may impair catalyst activity and process stability of the
riser. Therefore, the process must include a regeneration step. The
market will decide whether or not animal fat can substitute a bit of non-
renewable resources in petroleum refining.

64
Liquid hydrocarbons [wt.%] 60
62
58
56
54
52
50
0 2 4 6 8 10 12 14 16
Animal fat (%) in VGO
Figure 8.16 Cocatalytic cracking of animal fat and vacuum gas oil (VGO) in MAT
experiments. At around 7% feed component, the maximum yield of liquid hydro-
1
carbons is found; weight–hourly space velocity (WHSV) 2 h .